DHIAN

allergies

2007-10-26T08:02:00.000-07:00

What Are Allergies?

An allergy is an overreaction of the immune system to a substance that's harmless to most people. But in someone with an allergy, the body's immune system treats the substance (called an allergen) as an invader and reacts inappropriately, resulting in symptoms that can be anywhere from annoying to possibly harmful to the person.

In an attempt to protect the body, the immune system of the allergic person produces antibodies called immunoglobulin E (IgE). Those antibodies then cause mast cells (allergy cells in the body) to release chemicals, including histamine, into the bloodstream to defend against the allergen "invader."

It's the release of these chemicals that causes allergic reactions, affecting a person's eyes, nose, throat, lungs, skin, or gastrointestinal tract as the body attempts to rid itself of the invading allergen. Future exposure to that same allergen (things like nuts or pollen that you can be allergic to) will trigger this allergic response again. This means every time the person eats that particular food or is exposed to that particular allergen, he or she will have an allergic reaction.

Who Gets Allergies?

The tendency to develop allergies is often hereditary, which means it can be passed down through your genes. However, just because you, your partner, or one of your children might have allergies doesn't mean that all of your kids will definitely get them, too. And someone usually doesn't inherit a particular allergy, just the likelihood of having allergies.

But a few kids have allergies even if no family member is allergic. And child who is allergic to one substance is likely to be allergic to others as well.

Common Airborne Allergens

Some of the most common things people are allergic to are airborne (carried through the air):

Dust mites are one of the most common causes of allergies. These microscopic insects live all around us and feed on the millions of dead skin cells that fall off our bodies every day. Dust mites are the main allergic component of house dust, which is made up of many particles and can contain things such as fabric fibers and bacteria, as well as microscopic animal allergens. Present year-round in most parts of the United States (although they don't live at high altitudes), dust mites live in bedding, upholstery, and carpets.
Pollen is another major cause of allergies (most people know pollen allergy as hay fever or rose fever). Trees, weeds, and grasses release these tiny particles into the air to fertilize other plants. Pollen allergies are seasonal, and the type of pollen a child is allergic to determines when symptoms will occur. For example, in the mid-Atlantic states, tree pollination begins in February and lasts through May, grass from May through June, and ragweed from August through October; so people with these allergies are likely to experience increased symptoms during those times.

Pollen counts measure how much pollen is in the air and can help people with allergies determine how bad their symptoms might be on any given day. Pollen counts are usually higher in the morning and on warm, dry, breezy days, whereas they're lowest when it's chilly and wet. Although not always exact, the local weather report's pollen count can be helpful when planning outside activities.
Molds, another common allergen, are fungi that thrive both indoors and out in warm, moist environments. Outdoors, molds may be found in poor drainage areas, such as in piles of rotting leaves or compost piles. Indoors, molds thrive in dark, poorly ventilated places such as bathrooms and damp basements, and in clothes hampers or under kitchen sinks. A musty odor suggests mold growth. Although molds tend to be seasonal, many can grow year-round, especially those indoors.
Pet allergens from warm-blooded animals can cause problems for kids and parents alike. When the animal — often a household pet — licks itself, the saliva gets on its fur or feathers. As the saliva dries, protein particles become airborne and work their way into fabrics in the home. Cats are the worst offenders because the protein from their saliva is extremely tiny and they tend to lick themselves more than other animals as part of grooming.
Cockroaches are also a major household allergen, especially in inner cities. Exposure to cockroach-infested buildings may be a major cause of the high rates of asthma in inner-city kids.

Common Food Allergens

The American Academy of Allergy, Asthma, and Immunology estimates that up to 2 million, or 8%, of kids in the United States are affected by food allergies, and that eight foods account for most of those food allergy reactions in kids: eggs, fish, milk, peanuts, shellfish, soy, tree nuts, and wheat.

Cow's milk (or cow's milk protein). Between 1% and 7.5% of infants are allergic to the proteins found in cow's milk and cow's milk-based formulas. About 80% of formulas on the market are cow's milk-based. Cow's milk protein allergy (also called formula protein allergy) means that the infant (or child or adult) has an abnormal immune system reaction to proteins found in the cow's milk used to make standard baby formulas, cheeses, and other milk products. Milk proteins can also be a hidden ingredient in many prepared foods.
Eggs. One of the most common food allergies in infants and young children, egg allergy can pose many challenges for parents. Because eggs are used in many of the foods kids eat — and in many cases they're "hidden" ingredients — an egg allergy is hard to diagnose. An egg allergy usually begins when kids are very young, but most outgrow the allergy by age 5. Most kids with an egg allergy are allergic to the proteins in egg whites, but some can't tolerate proteins in the yolk.
Seafood and shellfish. The proteins in seafood can cause a number of different types of allergic reactions. Seafood allergy is one of the more common adult food allergies and one that kids don't always grow out of.
Peanuts and tree nuts. Peanuts are one of the most severe food allergens, often causing life-threatening reactions. About 1.5 million people in the United States are allergic to peanuts. (Peanuts are not a true nut, but a legume — in the same family as peas and lentils, although people with peanut allergy don’t usually have cross-reactions to other legumes). Half of those allergic to peanuts are also allergic to tree nuts, such as almonds, walnuts, pecans, cashews, and often sunflower and sesame seeds.
Soy. Like peanuts, soybeans are legumes. Soy allergy is more prevalent among babies than older children; about 30% to 40% of infants who are allergic to cow's milk are also allergic to the protein in soy formulas. Soy proteins, such as soya, are often a hidden ingredient in prepared foods.
Wheat. Wheat proteins are found in many of the foods we eat — some are more obvious than others. As with any allergy, an allergy to wheat can happen in different ways and to different degrees. Although wheat allergy is often confused with celiac disease, there is a difference. Celiac disease is caused by a sensitivity to gluten, which is found in wheat, oat, rye, and barley. It typically develops between 6 months and 2 years of age and the sensitivity causes damage to the small intestine in a different way to the usual allergic reaction.

Other Common Allergens

Insect stings. For most kids, being stung by an insect means swelling, redness, and itching at the site of the bite. But for those with insect venom allergy, an insect bite can cause more severe symptoms. Although some doctors and parents have believed that most kids eventually outgrow insect venom allergy, a recent study found that insect venom allergies often persist into adulthood.
Medicines. Antibiotics — medications used to treat infections — are the most common types of medicines that cause allergic reactions. Many other medicines, including over-the-counter medications, can also cause allergic reactions. If you suspect a medicine allergy, talk to your doctor first before assuming a reaction is a sign of allergy.
Chemicals. Some cosmetics or laundry detergents can cause people to break out in an itchy rash. Usually, this is because someone has a reaction to the chemicals in these products. Dyes, household cleaners, and pesticides used on lawns or plants can also cause allergic reactions in some people.

Some kids also have what are called cross-reactions. For example, kids who are allergic to birch pollen might have reactions when they eat an apple because that apple is made up of a protein similar to one in the pollen. Another example is that kids who are allergic to latex (as in gloves or certain types of hospital equipment) are more likely to be allergic to kiwifruit or bananas.

Signs and Symptoms of Allergies

The type and severity of allergy symptoms vary from allergy to allergy and child to child. Allergies may show up as itchy eyes or an itchy nose, sneezing, nasal congestion, throat tightness, trouble breathing, and even shock (faintness or passing out).

Symptoms can range from minor or major seasonal annoyances (for example, from pollen or certain molds) to year-round problems (from allergens like dust mites or food).

Because different allergens are more prevalent in different parts of the country and the world, allergy symptoms can also vary, depending on where you live. For example, peanut allergy is unknown in Scandinavia, where they don't eat peanuts, but is common in the United States, where peanuts are not only a popular food, but are also found in many of the things we eat.

Airborne Allergy Symptoms

Airborne allergens can cause something known allergic rhinitis, which occurs in about 15% to 20% of Americans. It typically develops by 10 years of age and reaches its peak in the early twenties, with symptoms often disappearing between the ages of 40 and 60.

Symptoms can include:

sneezing
itchy nose and/or throat
nasal congestion
coughing

These symptoms are often accompanied by itchy, watery, and/or red eyes, which is called allergic conjunctivitis. (When dark circles are present around the eyes, they're called allergic "shiners.") Those who react to airborne allergens usually have allergic rhinitis and/or allergic conjunctivitis. If a person has wheezing and shortness of breath, the allergy may have progressed to become asthma.

Food Allergy Symptoms

The severity of food allergy symptoms and when they develop depends on:

how much of the food is eaten
the amount of exposure the child has had to the food
the child's sensitivity to the food

Symptoms of food allergies can include:

itchy mouth and throat when food is swallowed (some kids have only this symptom — called "oral allergy syndrome")
hives (raised, red, itchy bumps)
rash
runny, itchy nose
abdominal cramps accompanied by nausea and vomiting or diarrhea (as the body attempts to flush out the food allergen)
difficulty breathing
shock

Insect Venom Allergy Symptoms

Being stung by an insect that a child is allergic to may cause some of the following symptoms:

throat swelling
hives over the entire body
difficulty breathing
nausea
diarrhea
shock

About Anaphylaxis

In rare instances, if the sensitivity to an allergen is extreme, a child may experience anaphylaxis (or anaphylactic shock) — a sudden, severe allergic reaction involving various systems in the body (such as the skin, respiratory tract, gastrointestinal tract, and cardiovascular system).

Severe symptoms or reactions to any allergen, from certain foods to insect bites, require immediate medical attention and can include:

difficulty breathing
swelling (particularly of the face, throat, lips, and tongue in cases of food allergies)
rapid drop in blood pressure
dizziness
unconsciousness
hives
tightness of the throat
hoarse voice
lightheadedness

Anaphylaxis can happen just seconds after being exposed to a triggering substance or can be delayed for up to 2 hours if the reaction is from a food. It can involve various areas of the body.

Fortunately, though, severe or life-threatening allergies occur in only a small group of kids. In fact, the annual incidence of anaphylactic reactions is small — about 30 per 100,000 people — although those with asthma, eczema, or hay fever are at greater risk of experiencing them. Most anaphylactic reactions — up to 80% — are caused by peanuts or tree nuts.

Diagnosing Allergies

Some allergies are fairly easy to identify because the pattern of symptoms following exposure to certain allergens can be hard to miss. But other allergies are less obvious because they can masquerade as other conditions.

If your child has cold-like symptoms lasting longer than a week or two or develops a "cold" at the same time every year, consult your doctor, who will likely ask questions about the symptoms and when they appear. Based on the answers to these questions and a physical exam, the doctor may be able to make a diagnosis and prescribe medications or may refer you to an allergist for allergy skin tests and more extensive therapy.

To determine the cause of an allergy, allergists usually perform skin tests for the most common environmental and food allergens. These tests can be done in infants, but they're more reliable in kids over 2 years old.

A skin test can work in one of two ways:

A drop of a purified liquid form of the allergen is dropped onto the skin and the area is pricked with a small pricking device.
A small amount of allergen is injected just under the skin. This test stings a little but isn't extremely painful. After about 15 minutes, if a lump surrounded by a reddish area appears (like a mosquito bite) at the injection site, the test is positive.

If reactions to a food or other allergen are severe, a blood test may be used to diagnose the allergy so as to avoid exposure to the offending allergen. Skin tests are less expensive and more sensitive than blood tests for allergies. But blood tests may be required in children with skin conditions or those who are extremely sensitive to a particular allergen.

Even if a skin test and/or a blood test shows an allergy, a child must also have symptoms to be definitively diagnosed with an allergy. For example, a toddler who has a positive test for dust mites and sneezes frequently while playing on the floor would be considered allergic to dust mites.

Treating Allergies

There is no real cure for allergies, but it is possible to relieve symptoms. The only real way to cope with them on a daily basis is to reduce or eliminate exposure to allergens. That means that parents must educate their kids early and often, not only about the allergy itself, but also about what reaction they will have if they consume or come into contact with the offending allergen.

Informing any and all caregivers (from child-care personnel to teachers, from extended family members to parents of your child's friends) about your child's allergy is equally important to help keep allergy symptoms to a minimum.

If reducing exposure isn't possible or is ineffective, medications may be prescribed, including antihistamines (which you can also buy over the counter) and inhaled or nasal spray steroids. In some cases, an allergist may recommend immunotherapy (allergy shots) to help desensitize your child. However, allergy shots are only helpful for allergens such as dust, mold, pollens, animals, and insect stings. They are not used for food allergies, and a person with food allergies must avoid that food.

Here are some things that can help kids avoid airborne allergens:

Keep family pets out of certain rooms, like your child's bedroom, and bathe them if necessary.
Remove carpets or rugs from your child's room (hard floor surfaces don't collect dust as much as carpets do).
Don't hang heavy drapes and get rid of other items that allow dust to accumulate.
Clean frequently.
Use special covers to seal pillows and mattresses if your child is allergic to dust mites.
If your child is allergic to pollen, keep the windows closed when the pollen season is at its peak, change your child's clothing after being outdoors, and don't let your child mow the lawn.
Keep kids who are allergic to mold away from damp areas, such as basements, and keep bathrooms and other mold-prone areas clean and dry.

Injectable Epinephrine

Food allergies usually aren't lifelong (although those to peanuts, tree nuts, and seafood can be). Avoiding the food is the only way to avoid symptoms while the sensitivity persists. Doctors often recommend that caregivers of kids who are extremely sensitive to a particular food, or who have asthma in addition to the food allergy, carry injectable epinephrine (adrenaline) to counteract any allergic reactions. They may also recommend carrying injectable epinephrine for kids who are allergic to insect venom.

Available in an easy-to-carry container that looks like a pen, injectable epinephrine is carried by millions of parents (and older kids) everywhere they go. With one injection into the thigh, the device administers epinephrine to ease the allergic reaction.

An injectable epinephrine prescription usually includes two auto-injectors and a "trainer" that contains no needle or epinephrine, but allows you and your child (if he or she is old enough) to practice using the device. It's essential that you familiarize yourself with the procedure by practicing with the trainer. Your doctor also can provide instructions on how to use and store injectable epinephrine.

Make sure kids 12 years or older keep injectable epinephrine readily available at all times. If your child is younger than 12, talk to the school nurse, your child's teachers, and your child-care provider about keeping injectable epinephrine on hand in case of an emergency.

It's also important to make sure that injectable epinephrine devices are available at your home, as well as at the homes of friends and family members if your child spends time there. Your doctor may also encourage your child to wear a medical alert bracelet. It's also wise to carry an over-the-counter antihistamine, which can help alleviate allergy symptoms in some people. But antihistamines should not be used as a replacement for the epinephrine pen.

Kids who have had to take injectable epinephrine should go immediately to a medical facility or hospital emergency department, where additional treatment can be given if needed. Up to one third of anaphylactic reactions can have a second wave of symptoms several hours following the initial attack, so these kids might need to be observed in a clinic or hospital for 4 to 8 hours following the reaction even though they seem well.

The good news is that only a very small group of kids will experience severe or life-threatening allergies. With proper diagnosis, preventive measures, and treatment, most kids can keep their allergies in check and live happy, healthy lives.

thyroid

2007-10-26T07:52:00.000-07:00

Thyroid

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Thyroid

Endocrine system

Thyroid and parathyroid.
Latin	glandula thyroidea
Gray's	subject #272 1269
System	endocinal jubachina system
Artery	superior thyroid artery, inferior thyroid artery,
Vein	superior thyroid vein, middle thyroid vein, inferior thyroid vein, thyreoidea ima
Nerve	middle cervical ganglion, inferior cervical ganglion
Precursor	4th Branchial pouch
MeSH	Thyroid+Gland
Dorlands/Elsevier	g_06/12392768

For other uses, see Thyroid cartilage.

The thyroid is one of the largest endocrine glands in the body. This gland is found in the neck just below the laryngeal prominence. The thyroid controls how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones.

The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T₄) and triiodothyronine (T₃). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Iodine is an essential component of both T₃ and T₄. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.

The thyroid is controlled by the hypothalamus and pituitary. The gland gets its name from the Greek word for "shield", after its shape, a double-lobed structure. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland. Specialists are called Thyroidologists.

[edit] Anatomy

The thyroid is situated on the anterior side of the neck, starting at the oblique line on the thyroid cartilage (just below the laryngeal prominence or Adam's apple), and extending to the 6th Tracheal ring (C-shaped cartilagenous ring of the trachea). It is inappropriate to demarcate the gland's upper and lower border with vertebral levels as it moves position in relation to these during swallowing. It lies over the trachea and is covered by layers of pretracheal fascia (allowing it to move), muscle and skin.

The thyroid is one of the larger endocrine glands - 10-20 grams in adults - and butterfly-shaped. The wings correspond to the lobes and the body to the isthmus of the thyroid. The isthmus overlies tracheal rings 2, 3 and 4. The thyroid may enlarge substantially during pregnancy and when affected by a variety of diseases.

[edit] Embryologic development

Floor of pharynx of embryo between 18 and 21 days.

In the fetus, at 3-4 weeks of gestation, the thyroid gland appears as an epithelial proliferation in the floor of the pharynx at the base of the tongue between the tuberculum impar and the copula linguae at a point latter indicated by the foramen cecum. Subsequently the thyroid descends in front of the pharyngeal gut as a bilobed diverticulum through the thyroglossal duct. Over the next few weeks, it migrates to the base of the neck. During migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct.

Follicles of the thyroid begin to make colloid in the 11th week and thyroxine by the 18th week.

[edit] Histology

At a histological level, there are three primary features of the thyroid:

Feature	Description
Follicles	The thyroid is composed of spherical follicles that selectively absorb iodine (as iodide ions, I^-) from the blood for production of thyroid hormones. Twenty-five percent of all the body's iodide ions are in the thyroid gland. Inside the follicles, colloids rich in a protein called thyroglobulin serve as a reservoir of materials for thyroid hormone production and, to a lesser extent, act as a reservoir for the hormones themselves.
Thyroid epithelial cells (or "follicular cells")	The follicles are surrounded by a single layer of thyroid epithelial cells, which secrete T3 and T4.
Parafollicular cells (or "C cells")	Scattered among follicular cells and in spaces between the spherical follicles are another type of thyroid cell, parafollicular cells, which secrete calcitonin.

[edit] Physiology

The primary function of the thyroid is production of the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin. Up to 80% of the T4 is converted to T3 by peripheral organs such as the liver, kidney and spleen. T3 is about ten times more active than T4.^[1]

[edit] T3 and T4 production and action

Thyroxine is synthesised by the follicular cells from free tyrosine and on the tyrosine residues of the protein called thyroglobulin (TG). Iodine is captured with the "iodine trap" by the hydrogen peroxide generated by the enzyme thyroid peroxidase (TPO)^[2] and linked to the 3' and 5' sites of the benzene ring of the tyrosine residues on TG, and on free tyrosine. Upon stimulation by the thyroid-stimulating hormone (TSH), the follicular cells reabsorb TG and proteolytically cleave the iodinated tyrosines from TG, forming T4 and T3 (in T3, one iodine is absent compared to T4), and releasing them into the blood. Deiodinase enzymes convert T4 to T3.^[3] Thyroid hormone that is secreted from the gland is about 90% T4 and about 10% T3.^[1]

Cells of the brain are a major target for the thyroid hormones T3 and T4. Thyroid hormones play a particularly crucial role in brain development during pregnancy.^[4] A transport protein (OATP1C1) has been identified that seems to be important for T4 transport across the blood brain barrier.^[5] A second transport protein (MCT8) is important for T3 transport across brain cell membranes.^[5]

In the blood, T4 and T3 are partially bound to thyroxine-binding globulin, transthyretin and albumin. Only a very small fraction of the circulating hormone is free (unbound) - T4 0.03% and T3 0.3%. Only the free fraction has hormonal activity. As with the steroid hormones and retinoic acid, thyroid hormones cross the cell membrane and bind to intracellular receptors (α₁, α₂, β₁ and β₂), which act alone, in pairs or together with the retinoid X-receptor as transcription factors to modulate DNA transcription [1].

[edit] T3 and T4 regulation

The production of thyroxine and triiodothyronine is regulated by thyroid-stimulating hormone (TSH), released by the anterior pituitary. The thyroid and thyrotropes form a negative feedback loop: TSH production is suppressed when the T4 levels are high, and vice versa. The TSH production itself is modulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus and secreted at an increased rate in situations such as cold (in which an accelerated metabolism would generate more heat). TSH production is blunted by somatostatin (SRIH), rising levels of glucocorticoids and sex hormones (estrogen and testosterone), and excessively high blood iodide concentration.

[edit] Calcitonin

An additional hormone produced by the thyroid contributes to the regulation of blood calcium levels. Parafollicular cells produce calcitonin in response to hypercalcemia. Calcitonin stimulates movement of calcium into bone, in opposition to the effects of parathyroid hormone (PTH). However, calcitonin seems far less essential than PTH, as calcium metabolism remains clinically normal after removal of the thyroid, but not the parathyroids.

It may be used diagnostically as a tumor marker for a form of thyroid cancer (medullary thyroid adenocarcinoma), in which high calcitonin levels may be present and elevated levels after surgery may indicate recurrence. It may even be used on biopsy samples from suspicious lesions (e.g. swollen lymph nodes) to establish whether they are metastasis of the original cancer.

Calcitonin can be used therapeutically for the treatment of hypercalcemia or osteoporosis.

[edit] Significance of iodine

In areas of the world where iodine (essential for the production of thyroxine, which contains four iodine atoms) is lacking in the diet, the thyroid gland can be considerably enlarged, resulting in the swollen necks of endemic goitre.

Thyroxine is critical to the regulation of metabolism and growth throughout the animal kingdom. Among amphibians, for example, administering a thyroid-blocking agent such as propylthiouracil (PTU) can prevent tadpoles from metamorphosing into frogs; conversely, administering thyroxine will trigger metamorphosis.

In humans, children born with thyroid hormone deficiency will have physical growth and development problems, and brain development can also be severely impaired, in the condition referred to as cretinism. Newborn children in many developed countries are now routinely tested for thyroid hormone deficiency as part of newborn screening by analysis of a drop of blood. Children with thyroid hormone deficiency are treated by supplementation with synthetic thyroxine, which enables them to grow and develop normally.

Because of the thyroid's selective uptake and concentration of what is a fairly rare element, it is sensitive to the effects of various radioactive isotopes of iodine produced by nuclear fission. In the event of large accidental releases of such material into the environment, the uptake of radioactive iodine isotopes by the thyroid can, in theory, be blocked by saturating the uptake mechanism with a large surplus of non-radioactive iodine, taken in the form of potassium iodide tablets. While biological researchers making compounds labelled with iodine isotopes do this, in the wider world such preventive measures are usually not stockpiled before an accident, nor are they distributed adequately afterward. One consequence of the Chernobyl disaster was an increase in thyroid cancers in children in the years following the accident. [2]

The use of iodised salt is an efficient way to add iodine to the diet. It has eliminated endemic cretinism in most developed countries, and some governments have made the iodination of flour mandatory. Potassium iodide and Sodium iodide are the most active forms of supplemental iodine.

[edit] Diseases

[edit] Hyper- and hypofunction (affects about 2% of the population)

Hypothyroidism (underactivity)
- Hashimoto's thyroiditis / thyroiditis
- Ord's thyroiditis
- Postoperative hypothyroidism
- Postpartum thyroiditis
- Silent thyroiditis
- Acute thyroiditis
- Iatrogenic hypothyroidism
Hyperthyroidism (overactivity)
- Thyroid storm
- Graves-Basedow disease
- Toxic thyroid nodule
- Toxic nodular struma (Plummer's disease)
- Hashitoxicosis
- Iatrogenic hyperthyroidism
- De Quervain thyroiditis (inflammation starting as hyperthyroidism, can end as hypothyroidism)

[edit] Anatomical problems

[edit] Tumors

Thyroid adenoma
Thyroid cancer
- Papillary
- Follicular
- Medullary
- Anaplastic
Lymphomas and metastasis from elsewhere (rare)

[edit] Deficiencies

Cretinism

Medication linked to thyroid disease includes amiodarone, lithium salts, some types of interferon and IL-2.

[edit] Diagnosis

[edit] Blood tests

The measurement of thyroid-stimulating hormone (TSH) levels is often used by doctors as a screening test. Elevated TSH levels can signify an inadequate hormone production, while suppressed levels can point at excessive unregulated production of hormone.
If TSH is abnormal, decreased levels of thyroid hormones T4 and T3 may be present; these may be determined to confirm this.
Autoantibodies may be detected in various disease states (anti-TG, anti-TPO, TSH receptor stimulating antibodies).
There are two cancer markers for thyroid derived cancers. Thyroglobulin (TG) for well differentiated papillary or follcular adenocarcinoma, and the rare medullary thyroid cancer has calcitonin as the marker.
Very infrequently, TBG and transthyretin levels may be abnormal; these are not routinely tested.

[edit] Ultrasound

Nodules of the thyroid may or may not be cancer. Medical ultrasonography can help determine their nature because some of the characteristics of benign and malignant nodules differ. The main characteristics of a thyroid nodule on high frequency thyroid ultrasound are as follows:

Possible cancer	Benign characteristics
irregular border	smooth borders
hypoechoic (less echogenic than the surrounding tissue)	hyperechoic
microcalcifications	-
taller than wide shape on transverse study	-
significant intranodular blood flow by power Doppler	-
-	"comet tail" artifact as sound waves bounce off intranodular colloid

Ultrasonography is not always able to separate benign from malignant nodules with complete certainty. In suspicious cases, a tissue sample is often obtained by biopsy for microscopic examination.

[edit] Radioiodine scanning and uptake

Thyroid scintigraphy, imaging of the thyroid with the aid of radioactive iodine, usually iodine-123 (¹²³I), is performed in the nuclear medicine department of a hospital or clinic. Radioiodine collects in the thyroid gland before being excreted in the urine. While in the thyroid the radioactive emissions can be detected by a camera, producing a rough image of the shape (a radiodine scan) and tissue activity (a radioiodine uptake) of the thyroid gland.

A normal radioiodine scan shows even uptake and activity throughout the gland. Irregularity can reflect an abnormally shaped or abnormally located gland, or it can indicate that a portion of the gland is overactive or underactive, different from the rest. For example, a nodule that is overactive ("hot") to the point of suppressing the activity of the rest of the gland is usually a thyrotoxic adenoma, a surgically curable form of hyperthyroidism that is hardly ever malignant. In contrast, finding that a substantial section of the thyroid is inactive ("cold") may indicate an area of non-functioning tissue such as thyroid cancer.

The amount of radioactivity can be counted as an indicator of the metabolic activity of the gland. A normal quantitation of radioiodine uptake demonstrates that about 8 to 35% of the administered dose can be detected in the thyroid 24 hours later. Overactivity or underactivity of the gland as may occur with hypothyroidism or hyperthyroidism is usually reflected in decreased or increased radioiondine uptake. Different patterns may occur with different causes of hypo- or hyperthyroidism.

[edit] Biopsy

A medical biopsy refers to the obtaining of a tissue sample for examination under the microscope or other testing, usually to distinguish cancer from noncancerous conditions. Thyroid tissue may be obtained for biopsy by fine needle aspiration or by surgery.

Needle aspiration has the advantage of being a brief, safe, outpatient procedure that is safer and less expensive than surgery and does not leave a visible scar. Needle biopsies became widely used in the 1980s, but it was recognized that accuracy of identification of cancer was good but not perfect. The accuracy of the diagnosis depends on obtaining tissue from all of the suspicious areas of an abnormal thyroid gland. The reliability of needle aspiration is increased when sampling can be guided by ultrasound, and over the last 15 years, this has become the preferred method for thyroid biopsy in North America.

[edit] Treatment

[edit] Medical treatment

Levothyroxine is a stereoisomer of thyroxine which is degraded much slower and can be administered once daily in patients with hypothyroidism.

Graves' disease may be treated with the thioamide drugs propylthiouracil, carbimazole or methimazole, or rarely with Lugol's solution. Hyperthyroidism as well as thyroid tumors may be treated with radioactive iodine.

Percutaneous Ethanol Injections, PEI, for therapy of recurrent thyroid cysts, and metastatic thyroid cancer lymph nodes, as an alternative to the usual surgical method.

[edit] Surgery

Thyroid surgery is performed for a variety of reasons. A nodule or lobe of the thyroid is sometimes removed for biopsy or for the presence of an autonomously functioning adenoma causing hyperthyroidism. A large majority of the thyroid may be removed, a subtotal thyroidectomy, to treat the hyperthyroidism of Graves' disease, or to remove a goitre that is unsightly or impinges on vital structures. A complete thyroidectomy of the entire thyroid, including associated lymph nodes, is the preferred treatment for thyroid cancer. Removal of the bulk of the thyroid gland usually produces hypothyroidism, unless the person takes thyroid hormone replacement.

If the thyroid gland must be removed surgically, care must be taken to avoid damage to adjacent structures, the parathyroid glands and the recurrent laryngeal nerve. Both are susceptible to accidental removal and/or injury during thyroid surgery. The parathyroid glands produce parathyroid hormone (PTH), a hormone needed to maintain adequate amounts of calcium in the blood. Removal results in hypoparathyroidism and a need for supplemental calcium and vitamin D each day. The recurrent laryngeal nerves provide motor control for all external muscles of the larynx except for the cricothyroid muscle, also runs along the posterior thyroid. Accidental laceration of either of the two or both recurrent laryngeal nerves may cause paralysis of the vocal cords and their associated muscles, changing the voice quality.

[edit] Radioiodine therapy

Large goiters that cause symptoms, but do not harbor cancer, after evaluation, and biopsy of suspicious nodules can be treated by an alternative therapy with radioiodine. The iodine uptake can be high in countries with iodine deficiency, but low in iodine sufficient countries. The 1999 release of rhTSH thyrogen in the USA, can boost the uptakes to 50-60% allowing the therapy with iodine 131. The gland shrinks by 50-60%, but can cause hypothyroidism, and rarely pain syndrome cause by radiation thyroiditis that is short lived and treated by steroids.

[edit] History

There are several findings that evidence a great interest for thyroid disorders just in the Medieval Medical School of Salerno (XII Century). Rogerius Salernitanus, the Salernitan surgeon and author of "Post mundi fabricam" (around 1180) was considered at that time the surgical text par excellence all over Europe. In the chapter "De bocio" of his magnus opum he describes several pharmacological and surgical cures, some of which nowadays are reappraised quite scientifically effective.^[6]

In modern times, the thyroid was first identified by the anatomist Thomas Wharton (whose name is also eponymised in Wharton's duct of the submandibular gland) in 1656.^[7]

Thyroid hormone (or thyroxin) was only identified in the 19th century.

[edit] Additional images

	Section of the neck at about the level of the sixth cervical vertebra.	Muscles of the neck. Anterior view.	The arch of the aorta, and its branches.
Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.	Diagram showing common arrangement of thyroid veins.	Sagittal section of nose mouth, pharynx, and larynx.	Muscles of the pharynx, viewed from behind, together with the associated vessels and nerves.
The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.	Section of thyroid gland of sheep. X 160.	The thymus of a full-term fetus, exposed in situ.	Thyoid histology

transfer RNA

2007-10-26T07:50:00.001-07:00

Transfer RNA

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Transfer RNA

Transfer RNA (abbreviated tRNA), first hypothesized by Francis Crick, is a small RNA chain (73-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has a 3' terminal site for amino acid attachment. This covalent linkage is catalyzed by an aminoacyl tRNA synthetase. It also contains a three base region called the anticodon that can base pair to the corresponding three base codon region on mRNA. Each type of tRNA molecule can be attached to only one type of amino acid, but because the genetic code contains multiple codons that specify the same amino acid, tRNA molecules bearing different anticodons may also carry the same amino acid.

[hide]

1 Structure
2 Anticodon
3 Aminoacylation
4 tRNA genes
5 History
6 References
7 See also
8 External links

[edit] Structure

Structure of tRNA. CCA tail in orange, Acceptor stem in purple, D arm in red, Anticodon arm in blue with Anticodon in black, T arm in green.

tRNA has primary structure, secondary structure (usually visualized as the cloverleaf structure), and tertiary structure (all tRNAs have a similar L-shaped 3D structure that allows them to fit into the P and A sites of the ribosome).

The 5'-terminal phosphate group.
The acceptor stem is a 7-bp stem made by the base pairing of the 5'-terminal nucleotide with the 3'-terminal nucleotide (which contains the CCA 3'-terminal group used to attach the amino acid). The acceptor stem may contain non-Watson-Crick base pairs.
The CCA tail is a CCA sequence at the 3' end of the tRNA molecule. This sequence is important for the recognition of tRNA by enzymes critical in translation. In prokaryotes, the CCA sequence is transcribed. In eukaryotes, the CCA sequence is added during processing and therefore does not appear in the tRNA gene.
The D arm is a 4 bp stem ending in a loop that often contains dihydrouridine.
The anticodon arm is a 5-bp stem whose loop contains the anticodon.
The T arm is a 5 bp stem containing the sequence TΨC where Ψ is a pseudouridine.
Bases that have been modified, especially by methylation, occur in several positions outside the anticodon. The first anticodon base is sometimes modified to inosine (derived from adenine) or pseudouridine (derived from uracil).

[edit] Anticodon

An anticodon ^[1] is a unit made up of three nucleotides that correspond to the three bases of the codon on the mRNA. Each tRNA contains a specific anticodon triplet sequence that can base-pair to one or more codons for an amino acid. For example, one codon for lysine is AAA; the anticodon of a lysine tRNA might be UUU. Some anticodons can pair with more than one codon due to a phenomenon known as wobble base pairing. Frequently, the first nucleotide of the anticodon is one of two not found on mRNA: inosine and pseudouridine, which can hydrogen bond to more than one base in the corresponding codon position. In the genetic code, it is common for a single amino acid to occupy all four third-position possibilities; for example, the amino acid glycine is coded for by the codon sequences GGU, GGC, GGA, and GGG.

To provide a one-to-one correspondence between tRNA molecules and codons that specify amino acids, 61 tRNA molecules would be required per cell. However, many cells contain fewer than 61 types of tRNAs because the wobble base is capable of binding to several, though not necessarily all, of the codons that specify a particular amino acid^[2].

[edit] Aminoacylation

Aminoacylation is the process of adding an aminoacyl group to a compound. It produces tRNA molecules with their CCA 3' ends covalently linked to an amino acid.

Each tRNA is aminoacylated (or charged) with a specific amino acid by an aminoacyl tRNA synthetase. There is normally a single aminoacyl tRNA synthetase for each amino acid, despite the fact that there can be more than one tRNA, and more than one anticodon, for an amino acid. Recognition of the appropriate tRNA by the synthetases is not mediated solely by the anticodon, and the acceptor stem often plays a prominent role.

Reaction:

amino acid + ATP → aminoacyl-AMP + PPi
aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP

[edit] tRNA genes

Organisms vary in the number of tRNA genes in their genome. The nematode worm C. elegans, a commonly used model organism in genetics studies, has 19,000 genes in its nuclear genome, of which 659 code for tRNA^[3]. The budding yeast Saccharomyces cerevisiae has 275 tRNA genes in its genome. In the human genome, which according to current estimates has about 25,000 genes in total, there are about 2000 non-coding RNA genes, which include tRNA genes. There are 22 mitochondrial tRNA genes^[4]; 497 nuclear genes encoding cytoplasmic tRNA molecules and there are 324 tRNA-derived putative pseudogenes.^[5]

Cytoplasmic tRNA genes can be grouped into 49 families according to their anticodon features. These genes are found on all chromosomes, except 22 and Y chromosome. High clustering on 6p is observed (140 tRNA genes), as well on 1 chromosome.^[5]

tRNA molecules are transcribed (in eukaryotic cells) by RNA polymerase III, unlike messenger RNA which is transcribed by RNA polymerase II.

[edit] History

Significant research on structure was conducted in the early 1960s by Alex Rich and Don Caspar, two researchers in Boston, the Jacques Fresco group in Princeton University and a United Kingdom group at King's College London.^[6] A later publication reported the primary structure in 1965 by Robert W. Holley. The secondary and tertiary structures were derived from X-ray crystallography studies reported independently in 1974 by American and British research groups headed, respectively, by Alexander Rich and Aaron Klug.

[edit] References

^ Felsenfeld G, Cantoni G. "Use of thermal denaturation studies to investigate the base sequence of yeast serine sRNA". Proc Natl Acad Sci U S A 51: 818-26. PMID 14172997.
^ Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). Molecular Biology of the Cell. WH Freeman: New York, NY. 5th ed.
^ Hartwell LH, Hood L, Goldberg ML, Reynolds AE, Silver LM, Veres RC. (2004). Genetics: From Genes to Genomes 2nd ed. McGraw-Hill: New York, NY. p 264.
^ Ibid. p 529.
^ ^a ^b Lander E. et al. (2001). "Initial sequencing and analysis of the human genome". Nature 409 (6822): 860-921. PMID 11237011.
^ Brian F.C. Clark (October 2006). "The crystal structure of tRNA". J. Biosci. 31 (4): 453-7. PMID 17206065.

[edit] See also

[edit] External links

v • d • e Major families of biochemicals
Peptides \| Amino acids \| Nucleic acids \| Carbohydrates \| Lipids \| Terpenes \| Carotenoids \| Tetrapyrroles \| Enzyme cofactors \| Steroids \| Flavonoids \| Alkaloids \| Polyketides \| Glycosides
Analogues of nucleic acids:	Types of Nucleic Acids	Analogues of nucleic acids:
Nucleobases:	Purine (Adenine, Guanine) \| Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides:	Adenosine/Deoxyadenosine \| Guanosine/Deoxyguanosine \| Uridine \| Thymidine \| Cytidine/Deoxycytidine
Nucleotides:	monophosphates (AMP, UMP, GMP, CMP) \| diphosphates (ADP, UDP, GDP, CDP) \| triphosphates (ATP, UTP, GTP, CTP, GTPgammaS) \| cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides:	monophosphates (dAMP, TMP, dGMP, dCMP) \| diphosphates (dADP, TDP, dGDP, dCDP) \| triphosphates (dATP, TTP, dGTP, dCTP)
Ribonucleic acids:	RNA \| mRNA \| piRNA \| tRNA \| rRNA \| ncRNA \| gRNA \| shRNA \| siRNA \| snRNA \| miRNA \| snoRNA
Deoxyribonucleic acids:	DNA \| mtDNA \| cDNA \| plasmid \| Cosmid \| BAC \| YAC \| HAC
Analogues of nucleic acids:	GNA \| PNA \| TNA \| Morpholino \| LNA

Retrieved from "http://en.wikipedia.org/wiki/Transfer_RNA"

Categories: RNA | Protein biosynthesis | Non-coding RNA

cell

2007-10-26T07:42:00.000-07:00

Cell (biology)

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Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word "cell" being used to describe the smallest unit of a living organism

Cells in culture, stained for keratin (red) and DNA (green)

The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is sometimes called the building block of life.^[1] Some organisms, such as bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 10¹⁴ cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an ostrich egg. In 1837 before the final cell theory was developed, a Czech Jan Evangelista Purkyňe observed small "granules" while looking at the plant tissue through a microscope. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells. All cells come from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

The word cell comes from the Latin cellula, meaning, a small room. The descriptive name for the smallest living biologial structure was chosen by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.^[2]

Preamble

Each cell is at least somewhat self-contained and self-maintaining: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities.

Mouse cells grown in a culture dish. These cells grow in large clumps, but each individual cell is about 10 micrometres across

All cells have several different abilities:^[3]

Reproduction by cell division: (binary fission/mitosis or meiosis).
Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and ribosomes.
Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is derived from metabolic pathways.
Response to external and internal stimuli such as changes in temperature, pH or nutrient levels.
Cell contents are contained within a cell surface membrane that contains proteins and a lipid bilayer.

Some prokaryotic cells contain important internal membrane-bound compartments,^[4] but eukaryotic cells have a highly specialized endomembrane system characterized by regulated traffic and transport of vesicles.^[5]

Anatomy of cells

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are usually found in multicellular organisms.

Prokaryotic cells

Main article: Prokaryote

Diagram of a typical prokaryotic cell

Prokaryotes are distinguished from eukaryotes on the basis of nuclear organization, specifically their lack of a nuclear membrane. Prokaryotes also lack most of the intracellular organelles and structures that are characteristic of eukaryotic cells (an important exception is the ribosome, which are present in both prokaryotic and eukaryotic cells). Most functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella and pili — proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. Other differences include:

The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment and serves as a filter and communications beacon.
Most prokaryotes have a cell wall (some exceptions are Mycoplasma (a bacterium) and Thermoplasma (an archaeon)). It consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from "exploding" (cytolysis) from osmotic pressure against a hypotonic environment. A cell wall is also present in some eukaryotes like plants (cellulose) and fungi, but has a different chemical composition.
A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance.

Eukaryotic cells

Main article: Eukaryote

Diagram of a typical eukaryotic cell, showing subcellular components. Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles within centrosome

Eukaryotic cells are about 10 times the size of a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell's DNA. It is this nucleus that gives the eukaryote its name, which means "true nucleus". Other differences include:

The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles also contain some DNA.
Eukaryotes can move using cilia or flagella. The flagella are more complex than those of prokaryotes.

**Table 1: Comparison of features of prokaryotic and eukaryotic cells**
	Prokaryotes	Eukaryotes
Typical organisms	bacteria, archaea	protists, fungi, plants, animals
Typical size	~ 1-10 µm	~ 10-100 µm (sperm cells, apart from the tail, are smaller)
Type of nucleus	nucleoid region; no real nucleus	real nucleus with double membrane
DNA	circular (usually)	linear molecules (chromosomes) with histone proteins
RNA-/protein-synthesis	coupled in cytoplasm	RNA-synthesis inside the nucleus protein synthesis in cytoplasm
Ribosomes	50S+30S	60S+40S
Cytoplasmatic structure	very few structures	highly structured by endomembranes and a cytoskeleton
Cell movement	flagella made of flagellin	flagella and cilia made of tubulin, lamellipodia
Mitochondria	none	one to several thousand (though some lack mitochondria)
Chloroplasts	none	in algae and plants
Organization	usually single cells	single cells, colonies, higher multicellular organisms with specialized cells
Cell division	Binary fission (simple division)	Mitosis (fission or budding) Meiosis

**Table 2: Comparison of structures between animal and plant cells**
	Typical animal cell	Typical plant cell
Organelles	Nucleus Nucleolus (within nucleus) Rough endoplasmic reticulum (ER) Smooth ER Ribosomes Cytoskeleton Golgi apparatus Cytoplasm Mitochondria Vesicles Lysosomes Centrosome Centrioles Vacuoles	Nucleus Nucleolus (within nucleus) Rough ER Smooth ER Ribosomes Cytoskeleton Golgi apparatus (dictiosomes) Cytoplasm Mitochondria Vesicles Chloroplast and other plastids Central vacuole(large) Tonoplast (central vacuole membrane) Peroxisome (e.g. Glyoxysome) Vacuoles
Additional structures	Plasma membrane Flagellum Cilium	Plasma membrane Flagellum (only in gametes) Cell wall Plasmodesmata

Subcellular components

The cells of eukaryotes (left) and prokaryotes (right).

All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. This article will list these primary components of the cell, then briefly describe their function.

Cell membrane: A cell's defining boundary

Main article: Cell membrane

The cytoplasm of a cell is surrounded by a plasma membrane. The plasma membrane in plants and prokaryotes is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of lipids (hydrophobic fat-like molecules) and hydrophilic phosphorus molecules. Hence, the layer is called a phospholipid bilayer. It may also be called a fluid mosaic membrane. Embedded within this membrane is a variety of protein molecules that act as channels and pumps that move different molecules into and out of the cell. The membrane is said to be 'semi-permeable', in that it can either let a substance (molecule or ion) pass through freely, pass through to a limited extent or not pass through at all. Cell surface membranes also contain receptor proteins that allow cells to detect external signalling molecules such as hormones.

Cytoskeleton: A cell's scaffold

Main article: Cytoskeleton

The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis, the uptake of external materials by a cell, and cytokinesis, the separation of daughter cells after cell division; and moves parts of the cell in processes of growth and mobility. The eukaryotic cytoskeleton is composed of microfilaments, intermediate filaments and microtubules. There is a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. The prokaryotic cytoskeleton is less well-studied but is involved in the maintenance of cell shape, polarity and cytokinesis.^[6]

Genetic material

Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms use DNA for their long-term information storage, but some viruses (e.g., retroviruses) have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence. RNA is also used for information transport (e.g., mRNA) and enzymatic functions (e.g., ribosomal RNA) in organisms that use DNA for the genetic code itself.

Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the cytoplasm. Eukaryotic genetic material is divided into different, linear molecules called chromosomes inside a discrete nucleus, usually with additional genetic material in some organelles like mitochondria and chloroplasts (see endosymbiotic theory).

A human cell has genetic material in the nucleus (the nuclear genome) and in the mitochondria (the mitochondrial genome). In humans the nuclear genome is divided into 46 linear DNA molecules called chromosomes. The mitochondrial genome is a circular DNA molecule separate from the nuclear DNA. Although the mitochondrial genome is very small, it codes for some important proteins.

Foreign genetic material (most commonly DNA) can also be artificially introduced into the cell by a process called transfection. This can be transient, if the DNA is not inserted into the cell's genome, or stable, if it is.

Organelles

Main article: Organelle

The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs," called organelles, that are adapted and/or specialized for carrying out one or more vital functions. Membrane-bound organelles are found only in eukaryotes.

Cell nucleus (a cell's information center) The cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes, and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spherical in shape and separated from the cytoplasm by a double membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or copied into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.
Mitochondria and Chloroplasts (the power generators) Mitochondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. As mitochondria contain their own genome that is separate and distinct from the nuclear genome of a cell, they play a critical role in generating energy in the eukaryotic cell, they give the cell energy by the process of respiration, adding oxygen to food (typicially pertaining to glucose and ATP) to release energy. Organelles that are modified chloroplasts are broadly called plastids, and are often involved in storage. Since they contain their own genome, they are thought to have once been separate organisms, which later formed a symbiotic relationship with the cells. Chloroplasts are the counter-part of the mitochondria. Instead of giving off CO₂ and H₂O Plants give off glucose, oxygen, 6 molecules of water (compared to 12 in respiration) this process is called photosynthesis.
Endoplasmic reticulum and Golgi apparatus (macromolecule managers) The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that will float freely in the cytoplasm. The ER has two forms: the rough ER, which has ribosomes on its surface, and the smooth ER, which lacks them. Also the Golgi apparatus's ends "pinch" off and become new vacuoles in the animal cell.
Ribosomes (the protein production centers in the cell) The ribosome is a large complex, composed of many molecules, in prokaryotes only exist floating freely in the cytosol, whereas in eukaryotes they can be found either free or bound to membranes.
Lysosomes and Peroxisomes (of the eukaryotic cell) The cell could not house such destructive enzymes if they were not contained in a membrane-bound system. These organelles are often called a "suicide bag" because of their ability to detonate and destroy the cell.
Centrosome (the cytoskeleton organiser) The centrosome produces the microtubules of a cell - a key component of the cytoskeleton. It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in the animal cells. They are also found in some fungi and algae cells.
Vacuoles Vacuoles store food and waste. Some vacuoles store extra water. They are often described as liquid filled space and are surrounded by a membrane. Some cells, most notably Amoeba, have contractile vacuoles, which are able to pump water out of the cell if there is too much water. Cell functions Cell growth and metabolism Main articles: Cell growth and Metabolism Between successive cell divisions, cells grow through the functioning of cellular metabolism. Cell metabolism is the process by which individual cells process nutrient molecules. Metabolism has two distinct divisions: catabolism, in which the cell breaks down complex molecules to produce energy and reducing power, and anabolism, in which the cell uses energy and reducing power to construct complex molecules and perform other biological functions. Complex sugars consumed by the organism can be broken down into a less chemically-complex sugar molecule called glucose. Once inside the cell, glucose is broken down to make adenosine triphosphate (ATP), a form of energy, via two different pathways. The first pathway, glycolysis, requires no oxygen and is referred to as anaerobic metabolism. Each reaction is designed to produce some hydrogen ions that can then be used to make energy packets (ATP). In prokaryotes, glycolysis is the only method used for converting energy. The second pathway, called the Krebs cycle, or citric acid cycle, occurs inside the mitochondria and is capable of generating enough ATP to run all the cell functions. An overview of protein synthesis. Within the nucleus of the cell (light blue), genes (DNA, dark blue) are transcribed into RNA. This RNA is then subject to post-transcriptional modification and control, resulting in a mature mRNA (red) that is then transported out of the nucleus and into the cytoplasm (peach), where it undergoes translation into a protein. mRNA is translated by ribosomes (purple) that match the three-base codons of the mRNA to the three-base anti-codons of the appropriate tRNA. Newly-synthesized proteins (black) are often further modified, such as by binding to an effector molecule (orange), to become fully active. Creation of new cells Main article: Cell division Cell division involves a single cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms. Prokaryotic cells divide by binary fission. Eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis. A diploid cell may also undergo meiosis to produce haploid cells, usually four. Haploid cells serve as gametes in multicellular organisms, fusing to form new diploid cells. DNA replication, or the process of duplicating a cell's genome, is required every time a cell divides. Replication, like all cellular activities, requires specialized proteins for carrying out the job. Protein synthesis Main article: Protein biosynthesis Cells are capable of synthesizing new proteins, which are essential for the modulation and maintenance of cellular activities. This process involves the formation of new protein molecules from amino acid building blocks based on information encoded in DNA/RNA. Protein synthesis generally consists of two major steps: transcription and translation. Transcription is the process where genetic information in DNA is used to produce a complementary RNA strand. This RNA strand is then processed to give messenger RNA (mRNA), which is free to migrate through the cell. mRNA molecules bind to protein-RNA complexes called ribosomes located in the cytosol, where they are translated into polypeptide sequences. The ribosome mediates the formation of a polypeptide sequence based on the mRNA sequence. The mRNA sequence directly relates to the polypeptide sequence by binding to transfer RNA (tRNA) adapter molecules in binding pockets within the ribosome. The new polypeptide then folds into a functional three-dimensional protein molecule. Cell movement or motility Cell has the ability to move spontaneously during the process of wound healing, immune response and cancer metastasis. The fastest moving cells in the human body are the spermaculi, which enter and exit through the penis. This was proven when Professor Julia Ertmann of UCLA observed changes in the reproductive spermaculi in a lab environment (circa 2005). For wound healing to occur, white blood cells and cells that ingest bacteria move to the wound site to kill the microorganisms that cause infection. A the same time fibroblasts (connective tissue cells) move there to remodel damaged structures. In the case of tumor development, cells from a primary tumor move away and spread to other parts of the body. Cell motility involves many receptors, crosslinking, bundling, binding, adhesion, motor and other proteins.^[7] The process is divided into three steps - protrusion of the leading edge of the cell, adhesion of the leading edge and deadhesion at the cell body and rear, and cytoskeletal contraction to pull the cell forward. Each of these steps is driven by physical forces generated by unique segments of the cytoskeleton. ^[8]^[9] Origins of cells Main article: Origin of life The origin of cells has to do with the origin of life, and is one of the most important steps in the theory of evolution. The birth of the cell marked the passage from prebiotic chemistry to biological life. Origin of the first cell For more information RNA world hypothesis In a gene-centered view of evolution, life is regarded in terms of replicators—that is DNA molecules in the organism. In this paradigm, cells satisfy two fundamental conditions: protection from the outside environment and confinement of biochemical activity. The former condition is needed to maintain the stability of fragile DNA chains in a varying and sometimes aggressive environment, and may have been the main reason for which cells evolved. The latter is fundamental for the evolution of complexity. If freely-floating DNA molecules that code for enzymes are not enclosed in cells, the enzymes that benefit a given replicator (for example, by producing nucleotides) may do so less efficiently, and may in fact benefit competing replicators. If the entire DNA molecule of a replicator is enclosed in a cell, then the enzymes coded from the molecule will be kept close to the DNA molecule itself. The replicator will directly benefit from its encoded enzymes. Biochemically, cell-like spheroids formed by proteinoids are observed by heating amino acids with phosphoric acid as a catalyst. They bear many of the basic features provided by cell membranes. Proteinoid-based protocells enclosing RNA molecules may have been the first cellular life forms on Earth. Some amphiphiles have the tendency to spontaneously form membranes in water. A spherically closed membrane contains water and is a hypothetical precursor to the modern cell membrane composed of proteins and phospholipid bilayer membranes.^[10] Origin of eukaryotic cells The eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. It is almost certain that DNA-bearing organelles like the mitochondria and the chloroplasts are what remains of ancient symbiotic oxygen-breathing proteobacteria and cyanobacteria, respectively, where the rest of the cell seems to be derived from an ancestral archaean prokaryote cell – a theory termed the endosymbiotic theory. There is still considerable debate about whether organelles like the hydrogenosome predated the origin of mitochondria, or viceversa: see the hydrogen hypothesis for the origin of eukaryotic cells. Sex, as the stereotyped choreography of meiosis and syngamy that persists in nearly all extant eukaryotes, may have played a role in the transition from prokaryotes to eukaryotes. An 'origin of sex as vaccination' theory suggests that the eukaryote genome accreted from prokaryan parasite genomes in numerous rounds of lateral gene transfer. Sex-as-syngamy (fusion sex) arose when infected hosts began swapping nuclearized genomes containing coevolved, vertically transmitted symbionts that conveyed protection against horizontal infection by more virulent symbionts.^[11]

Blood pressure

2007-10-26T07:35:00.000-07:00

Blood pressure

From Wikipedia, the free encyclopedia

(Redirected from Home blood pressure monitoring)

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See Hypertension for information about recognition and treatment of high blood pressure.

A sphygmomanometer, a device used for measuring arterial pressure.

Blood pressure (strictly speaking: vascular pressure) refers to the force exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as blood moves through arteries, arterioles, capillaries, and veins; the term blood pressure generally refers to arterial pressure, i.e., the pressure in the larger arteries, arteries being the blood vessels which take blood away from the heart. Arterial pressure is most commonly measured via a sphygmomanometer, which uses the height of a column of mercury to reflect the circulating pressure (see Non-invasive measurement). Although many modern vascular pressure devices no longer use mercury, vascular pressure values are still universally reported in millimetres of mercury (mmHg).

The systolic arterial pressure is defined as the peak pressure in the arteries, which occurs near the beginning of the cardiac cycle; the diastolic arterial pressure is the lowest pressure (at the resting phase of the cardiac cycle). The average pressure throughout the cardiac cycle is reported as mean arterial pressure; the pulse pressure reflects the difference between the maximum and minimum pressures measured.

Typical values for a resting, healthy adult human are approximately 120 mmHg (16 kPa) systolic and 80 mmHg (11 kPa) diastolic (written as 120/80 mmHg, and spoken as "one twenty over eighty"), with large individual variations. These measures of arterial pressure are not static, but undergo natural variations from one heartbeat to another and throughout the day (in a circadian rhythm); they also change in response to stress, nutritional factors, drugs, or disease. Hypertension refers to arterial pressure being abnormally high, as opposed to hypotension, when it is abnormally low.

[hide]

1 Measurement
2 Normal values
3 Physiology
- 3.1 Regulation
4 Pathophysiology
- 4.1 High arterial pressure
- 4.2 Low arterial pressure
5 Influential factors
- 5.1 Low arterial pressure
6 Venous pressure
7 See also
8 References
9 External links

[edit] Measurement

Arterial pressures can be measured invasively (by penetrating the skin and measuring inside the blood vessels) or non-invasively. The former is usually restricted to a hospital setting.

[edit] Non-invasive measurement

The non-invasive auscultatory (from the Latin for listening) and oscillometric measurements are simpler and quicker than invasive measurements, require less expertise in fitting, have virtually no complications, and are less unpleasant and painful for the patient. However, non-invasive measures may yield somewhat lower accuracy and small systematic differences in numerical results. Non-invasive measurement methods are more commonly used for routine examinations and monitoring.

[edit] Auscultatory methods

Auscultatory method aneroid sphygmomanometer with stethoscope

Mercury manometer

The auscultatory method uses a stethoscope and a sphygmomanometer. This comprises an inflatable (Riva-Rocci) cuff placed around the upper arm at roughly the same vertical height as the heart, attached to a mercury or aneroid manometer. The mercury manometer, considered to be the gold standard for arterial pressure measurement, measures the height of a column of mercury, giving an absolute result without need for calibration, and consequently not subject to the errors and drift of calibration which affect other methods. The use of mercury manometers is often required in clinical trials and for the clinical measurement of hypertension in high risk patients, including pregnant women.

A cuff of appropriate size is fitted and inflated manually by repeatedly squeezing a rubber bulb until the artery is completely occluded. Listening with the stethoscope to the brachial artery at the elbow, the examiner slowly releases the pressure in the cuff. When blood just starts to flow in the artery, the turbulent flow creates a "whooshing" or pounding sound (first Korotkoff sounds). The pressure at which this sound is first heard is the systolic blood pressure. The cuff pressure is further released until no sound can be heard (fifth Korotkoff sound), at the diastolic arterial pressure. Sometimes, the pressure is palpated (felt by hand) to get an estimate before auscultation. With a mercury manometer this is simple technology which gives accurate pressure readings without issues of calibration.

[edit] Oscillometric methods

Oscillometric methods are sometimes used in the long-term measurement and sometimes in general practice. The equipment is functionally similar to that of the auscultatory method, but with an electronic pressure sensor (transducer) fitted in to detect blood flow, instead of using the stethoscope and the expert's ear. In practice, the pressure sensor is a calibrated electronic device with a numerical readout of blood pressure. To maintain accuracy, calibration must be checked periodically, unlike the inherently accurate mercury manometer. In most cases the cuff is inflated and released by an electrically operated pump and valve, which may be fitted on the wrist (elevated to heart height), although the upper arm is preferred. They vary widely in accuracy, and should be checked at specified intervals and if necessary recalibrated.

Oscillometric measurement requires less skill than the auscultatory technique, and may be suitable for use by untrained staff and for automated patient home monitoring.

The cuff is inflated to a pressure initially in excess of the systolic arterial pressure, and then reduces to below diastolic pressure over a period of about 30 seconds. When blood flow is nil (cuff pressure exceeding systolic pressure) or unimpeded (cuff pressure below diastolic pressure), cuff pressure will be essentially constant. It is essential that the cuff size is correct: undersized cuffs may yield too high a pressure, whereas oversized cuffs yields too low a pressure. When blood flow is present, but restricted, the cuff pressure, which is monitored by the pressure sensor, will vary periodically in synchrony with the cyclic expansion and contraction of the brachial artery, i.e., it will oscillate. The values of systolic and diastolic pressure are computed, not actually measured from the raw data, using an algorithm; the computed results are displayed.

Oscillometric monitors may produce inaccurate readings in patients with heart and circulation problems, that include arterial sclerosis, arrhythmia, preeclampsia, pulsus alternans, and pulsus paradoxus.

In practice the different methods do not give identical results; an algorithm and experimentally obtained coefficients are used to adjust the oscillometric results to give readings which match the auscultatory as well as possible.^[1] Some equipment uses computer-aided analysis of the instantaneous arterial pressure waveform to determine the systolic, mean, and diastolic points. Since many oscillometric devices have not been validated, caution must be given as most are not suitable in clinical and acute care settings.

The term NIBP, for Non-Invasive Blood Pressure, is often used to describe oscillometric monitoring equipment.

[edit] Invasive measurement

Arterial blood pressure (BP) is most accurately measured invasively. Invasive arterial pressure measurement with intravascular cannulae involves direct measurement of arterial pressure by placing a cannula needle in an artery (usually radial, femoral, dorsalis pedis or brachial). This is usually done by an anesthesiologist or surgeon in a hospital.

The cannula must be connected to a sterile, fluid-filled system, which is connected to an electronic pressure transducer. The advantage of this system is that pressure is constantly monitored beat-by-beat, and a waveform (a graph of pressure against time) can be displayed. This invasive technique is regularly employed in human and veterinary intensive care medicine, anesthesiology, and for research purposes.

Cannulation for invasive vascular pressure monitoring is infrequently associated with complications such as thrombosis, infection, and bleeding. Patients with invasive arterial monitoring require very close supervision, as there is a danger of severe bleeding if the line becomes disconnected. It is generally reserved for patients where rapid variations in arterial pressure are anticipated.

Invasive vascular pressure monitors are pressure monitoring systems designed to acquire pressure information for display and processing. There are a variety of invasive vascular pressure monitors for trauma, critical care, and operating room applications. These include single pressure, dual pressure, and multi-parameter (i.e. pressure / temperature). The monitors can be used for measurement and follow-up of arterial, central venous, pulmonary arterial, left atrial, right atrial, femoral arterial, umbilical venous, umbilical arterial, and intracranial pressures.

Vascular pressure parameters are derived in the monitor's microcomputer system. Usually, systolic, diastolic and mean pressures are displayed simultaneously for pulsatile waveforms (i.e. arterial and pulmonary arterial). Some monitors also calculate and display CPP (cerebral perfusion pressure). Normally, a zero key on the front of the monitor makes pressure zeroing extremely fast and easy. Alarm limits may be set to assist the medical professional responsible for observing the patient. High and low alarms may be set on displayed temperature parameters.

[edit] Home monitoring

Up to 25% of patients diagnosed with hypertension do not suffer from it, but rather from white coat hypertension (elevated arterial pressure specifically during medical exams, probably as a result of anxiety). Thus, well-performed, accurate home arterial pressure monitoring can prevent unnecessary anxiety, as well as costly and potentially dangerous therapy in many millions of people worldwide. Home arterial pressure monitoring provides a measurement of a person's arterial pressure at different times and in different environments, such as at home and at work, throughout the day. Home arterial pressure monitoring may assist in the diagnosis of high or low arterial pressure. It may also be used to monitor the effects of medication or lifestyle changes taken to lower or regulate arterial pressure levels.

The 2003 US Joint National Committee recommends the use of self monitoring of arterial pressure, before considering the more expensive ambulatory monitoring of arterial pressure, to improve hypertension management.^[2] Both the Joint National Committee and the 2003 guidelines from the European Society of Hypertension and the European Society of Cardiology suggest that self monitoring might also be used as an alternative to ambulatory monitoring for the diagnosis of white coat hypertension.^[3]

A study published in the May 2006 American Journal of Hypertension^[4] compared home and ambulatory blood pressure monitoring methods in the adjustment of antihypertensive treatment. The study showed home arterial pressure monitoring is as accurate as a 24 hour ambulatory monitoring in determining arterial pressure levels. Researchers at the University of Turku, Finland studied 98 patients with untreated hypertension. They compared patients using a home arterial pressure device and those wearing a 24hr ambulatory monitor. Researcher Dr. Niiranen said that, "home blood pressure measurement can be used effectively for guiding anti-hypertensive treatment". Dr. Stergiou added that home tracking of arterial pressure, "is more convenient and also less costly than ambulatory blood pressure monitoring".

A clinical study published in the May 2007 edition of The American Journal of Hypertension^[5] compared the accuracy of 3 different methods of taking arterial pressure in indicating cardiovascular health. The study aim was to assess the accuracy of home blood pressure monitoring (HBP), 24hr ambulatory blood pressure monitoring (ABP) and arterial pressure readings taken in a doctor’s office (OBP). The arterial pressure tests were compared to the left-ventricular mass index (LVMI). The LVMI was calculated from an echocardiogram of the heart and indicates cardiovascular organ damage, an indicator of arterial pressure. Researchers at The Columbia University Medical Center, New York found that home arterial pressure monitoring, over a 10 week period was a significant independent predictor of LVMI even after adjusting for age, sex and BMI (body mass index). They found that home monitoring over time is a better indicator of cardiovascular health than ambulatory readings or readings taken at the doctors’ office. The value of home monitoring increases over time with a number of measurements taken.

The June 2007 AMNews; Newspaper for America's Physicians^[6] released a study which showed arterial pressure readings taken in a doctors office are often unreliable. The American Medical Association newspaper quoted Prof Norman Kaplan from the University of Texas Southwestern Medical Center who said, "Of all the procedures done in a doctor's office, measurement of blood pressure is usually the least well performed but has the most important implications for the care of the patient." The paper explained that arterial pressure readings taken in a Doctors office can be falsely raised or lowered. This can be due to the presence of a Doctor or clinician which results in the patient experiencing white coat hypertension.

The American Heart Association website^[7] states, "You may have what's called 'white coat hypertension'; that means your blood pressure goes up when you're at the doctor's office. Monitoring at home will help you measure your true blood pressure and can provide your doctor with a log of blood pressure measurements over time. This is helpful in diagnosing and preventing potential health problems."

Those using home arterial pressure monitoring devices are increasingly also making use of arterial pressure charting software. These charting methods provide print outs for the patients physician and reminders on how often to check arterial pressure.^[8]

[edit] Normal values

While statistically normal values for arterial pressure could be computed for a given population, it needs to be remembered that, not only does arterial pressure vary from person to person, it also varies in individuals from moment to moment. Additionally, since there's no guarantee the norm of the population in question should even be considered healthy, the relevance of such values would be questionable.

In children the observed normal ranges are lower; in the elderly, they are often higher, largely because of reduced flexibility of the arteries. Factors such as age, gender and race influence blood pressure values. Pressure also varies with exercise, emotional reactions, sleep, digestion and time of the day.

In the U.S., the optimal arterial pressure (sometimes referred to as the ‘gold standard’) targets are:^[9]^[10]^[11]

Systolic: less than 120 mmHg (2.32 psi or 15 kPa)
Diastolic: less than 80 mmHg (1.55 psi or 10 kPa)

Levels above 120 but below 140 mmHg in systolic pressure, or above 80 but below 95 mmHg in diastolic pressure, are referred to as "prehypertensive" and often progress to frankly hypertensive levels. However studies already extant reveal that there are fewer complications at, e.g., 115 mmHg systolic than 120, and in fact arterial pressure is a continuum with decreasing pathology associated with lower levels to well within the current "optimum" range.^[12] "Some data indicates that 115/75 mm Hg should be the gold standard. Once arterial pressure rises above 115/75 mm Hg, the risk of cardiovascular disease begins to increase. Prehypertension is now considered to be a systolic pressure ranging from 120 to 139 or a diastolic pressure ranging from 80 to 89." (Excerpts from Mayo Clinic website). In the past, hypertension was only diagnosed if secondary signs of high arterial pressure were present, along with a prolonged high systolic pressure reading over several visits. In the U.S., this reactive stance has been soundly rejected in the light of recent evidence.

In the UK, mirroring abandoned earlier U.S. practice, nursing students continue to be taught that their patients’ readings should be considered ‘normal’ if in the range:

Systolic: 110 - 140mmHg
Diastolic: 70 - 90 mmHg

Clinical trials demonstrate that people who maintain arterial pressures at the low end of these pressure ranges have much better long term cardiovascular health. The principal medical debate is the aggressiveness and relative value of methods used to lower pressures into this range for those who don't maintain such pressure on their own. Elevations, more commonly seen in older people, though often considered normal, are associated with increased morbidity and mortality. The clear trend from double blind clinical trials (for the better strategies and agents) has increasingly been that lower arterial pressure is found to result in less disease.^{[citation needed]}

[edit] Physiology

The mean arterial pressure (MAP) is the average pressure measured over one complete cardiac cycle.

The up and down fluctuation of the arterial pressure results from the pulsatile nature of the cardiac output. The pulse pressure is determined by the interaction of the stroke volume versus the resistance to flow in the arterial tree.

The larger arteries, including all large enough to see without magnification, are low resistance (assuming no advanced atherosclerotic changes) conduits with high flow rates that generate only small drops in pressure. For instance, with a subject in the supine position, blood travelling from the heart to the toes typically only experiences a 5 mmHg drop in mean pressure.

Modern physiology developed the concept of the vascular pressure wave. This wave is created by the heart during the systole and originates in the ascending aorta. Much faster than the stream of blood itself, it is then transported through the vessel walls to the peripheral arteries. There the pressure wave can be palpated as the peripheral pulse. As the wave is reflected at the peripheral veins it runs back in a centripetal fashion. Where the crests of the reflected and the original wave meet, the pressure inside the vessel is higher than the true pressure in the aorta. This concept explains why the arterial pressure inside the peripheral arteries of the legs and arms is higher than the arterial pressure in the aorta.^[13]^[14]^[15]

[edit] Regulation

The endogenous regulation of arterial pressure is not completely understood. Currently, three mechanisms of regulating arterial pressure have been well-characterized:

Baroreceptor reflex: Baroreceptors in various organs can detect changes in arterial pressure, and adjust the mean arterial pressure by altering both the force and speed of the heart's contractions, as well as the total peripheral resistance.

Renin-angiotensin system (RAS): This system is generally known for its long-term adjustment of arterial pressure. This system allows the kidney to compensate for loss in blood volume or drops in arterial pressure by activating an endogenous vasoconstrictor known as angiotensin II.

Aldosterone release: This steroid hormone is released from the adrenal cortex in response to angiotensin II or high serum potassium levels. Aldosterone stimulates sodium retention and potassium excretion by the kidneys. Since sodium is the main ion that determines the amount of fluid in the blood vessels by osmosis, aldosterone will increase fluid retention, and indirectly, arterial pressure.

These different mechanisms are not necessarily independent of each other, as indicated by the link between the RAS and aldosterone release. Currently, the RAS system is targeted pharmacologically by ACE inhibitors and angiotensin II receptor antagonists. The aldosterone system is directly targeted by spironolactone, an aldosterone antagonist. The fluid retention may be targeted by diuretics; however, the antihypertensive effect of diuretics is not due to its effect on blood volume. Generally, the baroreceptor reflex is not targeted in hypertension because if blocked, individuals may suffer from orthostatic hypotension and fainting.

[edit] Pathophysiology

[edit] High arterial pressure

Main article: Hypertension

The diagnosis of abnormalities in arterial pressure may require serial measurement. Since arterial pressure varies throughout the day, measurements should be taken at the same time of day to ensure the readings taken are comparable. Suitable times are:

immediately after awakening (before washing/dressing and taking breakfast/drink), while the body is still resting,
immediately after finishing work.

It is sometimes difficult to meet these requirements at the doctor's office; also, some patients become nervous when their arterial pressure is taken at the office, causing readings to increase (this phenomenon is called white coat hypertension). Taking blood pressure levels at home or work with a home blood pressure monitoring device may help determine a person's true range of arterial pressure readings and avoid false readings from the white coat hypertension effect. Long term assessments may be made with an ambulatory blood pressure device that takes regular arterial pressure readings every half an hour throughout the course of a single day and night.

Aside from the white coat effect, arterial pressure readings outside of a clinical setting are usually slightly lower in the majority of people. The studies that looked into the risks from hypertension and the benefits of lowering the arterial pressure in affected patients were based on readings in a clinical environment.

Arterial pressure exceeding normal values is called arterial hypertension. In itself it is only an acute problem; see hypertensive crisis. But because of its long-term indirect effects (and also as an indicator of other problems) it is a serious worry to physicians diagnosing it.

All levels of arterial pressure put mechanical stress on the arterial walls. Higher pressures increase heart workload and progression of unhealthy tissue growth (atheroma) that develops within the walls of arteries. The higher the pressure, the more stress that is present and the more atheroma tend to progress and the heart muscle tends to thicken, enlarge and become weaker over time.

Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure, arterial aneurysms, and is the leading cause of chronic renal failure. Even moderate elevation of arterial pressure leads to shortened life expectancy. At severely high pressures, mean arterial pressures 50% or more above average, a person can expect to live no more than a few years unless appropriately treated.^[16]

In the past, most attention was paid to diastolic pressure; but nowadays it is recognised that both high systolic pressure and high pulse pressure (the numerical difference between systolic and diastolic pressures) are also risk factors. In some cases, it appears that a decrease in excessive diastolic pressure can actually increase risk, due probably to the increased difference between systolic and diastolic pressures (see the article on pulse pressure).

[edit] Low arterial pressure

Main article: Hypotension

Blood pressure that is too low is known as hypotension. The similarity in pronunciation with hypertension can cause confusion.

Low arterial pressure may be a sign of severe disease and requires urgent medical attention.

When arterial pressure and blood flow decrease beyond a certain point, the perfusion of the brain becomes critically decreased (i.e., the blood supply is not sufficient), causing lightheadedness, dizziness, weakness and fainting.

However, people who function well, while maintaining low arterial pressures have lower rates of cardiovascular disease events than people with normal arterial pressures.^{[citation needed]}

[edit] Influential factors

The physics of the circulatory system, as of any fluid system, are very complex. That said, there are many physical factors that influence arterial pressure. Each of these may in turn be influenced by physiological factors, such as diet, exercise, disease, drugs or alcohol, obesity, excess weight and so-forth.

In cardiac physiology, the rate and volume of flow are accounted for in a combined fashion by cardiac output which is the heart rate (the rate of contraction) multiplied by the stroke volume (the amount of blood pumped out from the heart with each contraction). It represents the efficiency with which the heart circulates blood throughout the body.

Some physical factors are:

Rate of pumping. In the circulatory system, this rate is called heart rate, the rate at which blood (the fluid) is pumped by the heart. The higher the heart rate, the higher (potentially, assuming no change in stroke volume) the arterial pressure.
Volume of fluid or blood volume, the amount of blood that is present in the body. The more blood present in the body, the higher the rate of blood return to the heart and the resulting cardiac output. There is some relationship between dietary salt intake and increased blood volume, potentially resulting in higher arterial pressure, though this varies with the individual and is highly dependent on autonomic nervous system response.
Resistance. In the circulatory system, this is the resistance of the blood vessels. The higher the resistance, the higher the arterial pressure. Resistance is related to size (the larger the blood vessel, the lower the resistance), as well as the smoothness of the blood vessel walls. Smoothness is reduced by the buildup of fatty deposits on the arterial walls. Substances called vasoconstrictors can reduce the size of blood vessels, thereby increasing blood pressure. Vasodilators (such as nitroglycerin) increase the size of blood vessels, thereby decreasing arterial pressure. Some types of omega-6 fatty acids, particularly from olive oil, have been known to increase vascular smoothness.^{[citation needed]}
Viscosity, or thickness of the fluid. If the blood gets thicker, the result is an increase in arterial pressure. Certain medical conditions can change the viscosity of the blood. For instance, low red blood cell concentration, anemia, reduces viscosity, whereas increased red blood cell concentration increases viscosity. Viscosity also increases with blood sugar concentration—visualize pumping syrup. It had been thought that aspirin and related "blood thinner" drugs decreased the viscosity of blood, but studies found^[17] that they act by reducing the tendency of the blood to clot instead.

In practice, each individual's autonomic nervous system responds to and regulates all these interacting factors so that, although the above issues are important, the actual arterial pressure response of a given individual varies widely because of both split-second and slow-moving responses of the nervous system and end organs. These responses are very effective in changing the variables and resulting blood pressure from moment to moment.

[edit] Low arterial pressure

Sometimes the arterial pressure drops significantly when a patient stands up from sitting. This is known as postural hypotension; gravity reduces the rate of blood return from the body veins below the heart back to the heart, thus reducing stroke volume and cardiac output.

When people are healthy, the veins below their heart quickly constrict and the heart rate increases to minimize and compensate for the gravity effect. This is carried out involuntarily by the autonomic nervous system. The system usually requires a few seconds to fully adjust and if the compensations are too slow or inadequate, the individual will suffer reduced blood flow to the brain, dizziness and potential blackout. Increases in G-loading, such as routinely experienced by acrobatic jet pilots "pulling Gs", greatly increases this effect. Repositioning the body perpendicular to gravity largely eliminates the problem.

Other causes of low arterial pressure include:

Sepsis
Hemorrhage - blood loss
Toxins including toxic doses of blood pressure medicine
Hormonal abnormalities, such as Addison's disease

Shock is a complex condition which leads to critically decreased perfusion. The usual mechanisms are loss of blood volume, pooling of blood within the veins reducing adequate return to the heart and/or low effective heart pumping. Low arterial pressure, especially low pulse pressure, is a sign of shock and contributes to and reflects decreased perfusion.

If there is a significant difference in the pressure from one arm to the other, that may indicate a narrowing (for example, due to aortic coarctation, aortic dissection, thrombosis or embolism) of an artery.

[edit] Venous pressure

Venous pressure is the vascular pressure in a vein or in the atria of the heart. It is much less than arterial pressure, with common values of 5 mmHg in the right atrium and 8 mmHg in the left atrium. Measurement of pressures in the venous system and the pulmonary vessels plays an important role in intensive care medicine but requires an invasive central venous catheter.

[edit] See also

[edit] References

^ http://www.braun.com/medical/bloodpressure/downloads

Pneumonia

2007-10-26T06:51:00.000-07:00

DEFINISI

Pneumonia adalah peradangan paru yang disebabkan oleh infeksi bakteri, virus maupun jamur.

PENYEBAB

Penyebab pneumonia adalah:

Bakteri (paling sering menyebabkan pneumonia pada dewasa):
- Streptococcus pneumoniae
- Staphylococcus aureus
- Legionella
- Hemophilus influenzae
Virus: virus influenza, chicken-pox (cacar air)
Organisme mirip bakteri: Mycoplasma pneumoniae (terutama pada anak-anak dan dewasa muda)
Jamur tertentu.

Adapun cara mikroorganisme itu sampai ke paru-paru bisa melalui:
- Inhalasi (penghirupan) mikroorganisme dari udara yang tercemar
- Aliran darah, dari infeksi di organ tubuh yang lain
- Migrasi (perpindahan) organisme langsung dari infeksi di dekat paru-paru.

Beberapa orang yang rentan (mudah terkena) pneumonia adalah:

Peminum alkohol
Perokok
Penderita diabetes
Penderita gagal jantung
Penderita penyakit paru obstruktif menahun
Gangguan sistem kekebalan karena obat tertentu (penderita kanker, penerima organ cangkokan)
Gangguan sistem kekebalan karena penyakit (penderita AIDS).

Pneumonia juga bisa terjadi setelah pembedahan (terutama pembedahan perut) atau cedera (terutama cedera dada), sebagai akibat dari dangkalnya pernafasan, gangguan terhadap kemampuan batuk dan lendir yang tertahan.
Yang sering menjadi penyebabnya adalah Staphylococcus aureus, pneumokokus, Hemophilus influenzae atau kombinasi ketiganya.

Pneumonia pada orang dewasa paling sering disebabkan oleh bakteri, yang tersering yaitu bakteri Streptococcus pneumoniae (pneumococcus).
Pneumonia pada anak-anak paling sering disebabkan oleh virus pernafasan, dan puncaknya terjadi pada umur 2-3 tahun. Pada usia sekolah, pneumonia paling sering disebabkan oleh bakteri Mycoplasma pneumoniae.

Pneumonia dikelompokkan berdasarkan sejumlah sistem yang berlainan. Salah satu diantaranya adalah berdasarkan cara diperolehnya, dibagi menjadi 2 kelompok, yaitu "community-acquired" (diperoleh diluar institusi kesehatan) dan "hospital-acquired" (diperoleh di rumah sakit atau sarana kesehatan lainnya).
Pneumonia yang didapat diluar institusi kesehatan paling sering disebabkan oleh Streptococcus pneumoniae.
Pneumonia yang didapat di rumah sakit cenderung bersifat lebih serius karena pada saat menjalani perawatan di rumah sakit, sistem pertahanan tubuh penderita untuk melawan infeksi seringkali terganggu. Selain itu, kemungkinannya terjadinya infeksi oleh bakteri yang resisten terhadap antibiotik adalah lebih besar.

GEJALA

Gejala-gejala yang biasa ditemukan adalah:
- batuk berdahak (dahaknya seperti lendir, kehijauan atau seperti nanah)
- nyeri dada (bisa tajam atau tumpul dan bertambah hebat jika penderita menarik nafas dalam atau terbatuk)
- menggigil
- demam
- mudah merasa lelah
- sesak nafas
- sakit kepala
- nafsu makan berkurang
- mual dan muntah
- merasa tidak enak badan
- kekakuan sendi
- kekakuan otot.

Gejala lainnya yang mungkin ditemukan:
- kulit lembab
- batuk darah
- pernafasan yang cepat
- cemas, stres, tegang
- nyeri perut.

DIAGNOSA

Pada pemeriksaan dada dengan menggunakan stetoskop, akan terdengar suara ronki.
Pemeriksaan penunjang:

Rontgen dada

Pembiakan dahak

Hitung jenis darah

Gas darah arteri.

PENGOBATAN

Kepada penderita yang penyakitnya tidak terlalu berat, bisa diberikan antibiotik per-oral (lewat mulut) dan tetap tinggal di rumah.

Penderita yang lebih tua dan penderita dengan sesak nafas atau dengan penyakit jantung atau paru-paru lainnya, harus dirawat dan antibiotik diberikan melalui infus. Mungkin perlu diberikan oksigen tambahan, cairan intravena dan alat bantu nafas mekanik.

Kebanyakan penderita akan memberikan respon terhadap pengobatan dan keadaannya membaik dalam waktu 2 minggu.

PENCEGAHAN

Untuk orang-orang yang rentan terhadap pneumonia, latihan bernafas dalam dan terapi untuk membuang dahak, bisa membantu mencegah terjadinya pneumonia.

Vaksinasi bisa membantu mencegah beberapa jenis pneumonia pada anak-anak dan orang dewasa yang beresiko tinggi:

Vaksin pneumokokus (untuk mencegah pneumonia karena Streptococcus pneumoniae)

Vaksin flu

Vaksin Hib (untuk mencegah pneumonia karena Haemophilus influenzae type b).

Kelainan Katup Jantung

2007-10-26T06:39:00.000-07:00

DEFINISI

Jantung memiliki empat ruangan, 2 ruangan kecil di atas (atrium) dan 2 ruangan besar di bawah (ventrikel).

Setiap ventrikel memiliki satu katup masuk searah dan satu katup keluar searah.
Katup trikuspidalis membuka dari atrium kanan ke dalam ventrikel kanan, dan katup pulmonalis membuka dari ventrikel kanan ke dalam arteri pulmonalis.
Katup mitral membuka dari atrium kiri ke dalam ventrikel kiri, dan katup aorta membuka dari ventrikel kiri ke dalam aorta.

Katup-katup jantung bisa mengalami kelainan fungsi baik karena kebocoran (regurgitasi katup) atau karena kegagalan membuka secara adekuat (stenosis katup).
Keduanya dapat mempengaruhi kemampuan jantung untuk memompa darah.
Kadang-kadang satu katup mempunyai kedua masalah tersebut.

Beberapa jenis kelainan katup jantung:

Regurgitasi Katup Mittral
Prolaps Katup Mitral
Stenosis Katup Mitral
Regurgitasi Katup Aorta
Stenosis Katur Aorta
Regurgitasi Katup Trikuspidalis
Stenosis Katup Trikuspidalis
Stenosis Katup Pulmoner.

PENYEBAB

GEJALA

Depresi

2007-10-26T06:38:00.001-07:00

DEFINISI

Depresi adalah suatu perasaan sedih yang sangat mendalam, yang bisa terjadi setelah kehilangan seseorang atau peristiwa menyedihkan lainnya, tetapi tidak sebanding dengan peristiwa tersebut dan terus menerus dirasakan melebihi waktu yang normal.

Sekitar 10% orang yang mengunjungi dokter untuk keluhan psikisnya sesungguhnya menderita depresi.
Depresi mulai timbul pada usia 20, 30 atau 40 tahun.

Suatu episode depresi biasanya berlangsung selama 6-9 bulan, tetapi pada 15-20% penderita bisa berlangsung sampai 2 tahun atau lebih.
Episode depresi cenderung berulang sebanyak beberapa kali.

Depresi situasional adalah depresi yang terjadi setelah suatu peristiwa traumatik, seperti kematian orang yang dicintai.
Holiday blues adalah depresi yang terjadi ketika sedang berlibur atau merayakan sesuat, bersifat sementara.
Depresi endogenous adalah depresi tanpa penyebab yang pasti.

PENYEBAB

Penyebab depresi belum sepenuhnya dimengerti.
Sejumlah faktor dapat menyebabkan seseorang cenderung menderita depresi:
- Faktor keturunan
- Efek samping dari obat-obatan tertentu
- Kepribadian introvert
- Peristiwa emosional (terutama kehilangan).

Depresi bisa terjadi atau semakin memburuk tanpa disertai stres kehidupan yang nyata ataupun berarti.

Wanita dua kali lebih mudah terkena depresi, meskipun alasannya belum diketahui dengan jelas.
Penelitian jiwa memperlihatkan bahwa wanita cenderung memberikan respoon terhadap kesengsaraan dengan cara menarik diri dan menyalahkan dirinya sendiri. Sebaliknya, pria cenderung menolak atau mengalihkannya ke dalam berbagai kegiatan.

Faktor biologis yang paling banyak terlibat adalah faktor hormonal.
Perubahan kadar hormon pada wanita memegang peranan penting; perubahan suasanan hati bisa terjadi sesaat sebelum menstruasi (ketegangan pre-menstruasi) dan setelah persalinan (depresi post-partum). Perubahan hormon serupa bisa terjadi pada wanita pemakai pil KB yang mengalami depresi.
Kelainan fungsi tiroid, yang sering terjadi pada wanita, juga merupakan faktor yang berperan dalam terjadinya depresi.

Depresi juga bisa terjadi karena atau bersamaan dengan sejumlah penyakit atau kelainan fisik.
Kelainan fisik bisa menyebabkan depresi secara:
- Langsung, misalnya ketika penyakit tiroid menyebabkan berubahnya kadar hormon, yang bisa menyebabkan terjadinya depresi.
- Tidak langsung, misalnya ketika penyakit artritis rematoid menyebabkan nyeri dan cacat, yang bisa menyebabkan depresi.
Ada pula kelainan fisik yang menyebabkan depresi secara langsung dan tidak langsung. Misalnya AIDS; secara langsung menyebabkan depresi jika virus penyebabnya merusak otak; secara tidak langsung menyebabkan depresi jika menimbulkan dampak negatif terhadap kehidupan penderitanya.

Berbagai obat yang diresepkan (terutama obat yang digunakan untuk mengatasi tekanan darah tinggi) bisa menyebabkan depresi.

Sejumlah kelainan jiwa bisa menyebabkan penderitanya mengalami depresi (misalnya penyakit kecemasan, alkoholisme dan penyalahgunaan zat-zat lainnya, skizofrenia dan stadium awal demensia).

Kelainan Fisik yang Dapat Menyebabkan Depresi

Efek samping obat-obatan
- Amfetamin
- Obat anti-psikosa
- Beta bloker
- Simetidin
- Pil KB
- Sikloserin
- Indometasin
- Air raksa
- Metildopa
- Reserpin
- Talium
- Vinblastin
- Vinkristin
Infeksi
- AIDS
- Influenza
- Mononukleosis
- Sifilis (stadium lanjut)
- Tuberkulosis
- Hepatitis virus
- Pneumonia virus
Kelainan hormonal
- Penyakit Addison
- Penyakit Cushing
- Hiperparatiroidisme
- Hipotiroidisme dan hipertiroidisme
- Hipopituitarisme
Penyakit jaringan ikat
- Artritis rematoid
- Lupus eritematosus sistemik
Kelainan neurologis
- Tumor otak
- Cedera kepala
- Sklerosis multipel
- Penyakit Parkinson
- Tidur apneu
- Stroke
- Epilepsi lobus temporalis
Kelainan gizi
- Pellagra (kekurangan vitamin B6)
- Anemia pernisiosa (kekurangan vitamin B12)
Kanker
- Kanker perut (indung telur, usus besar)
- Kanker yang menyebar ke seluruh tubuh.

GEJALA

Gejalanya muncul secara bertahap selama beberapa hari atau minggu.
Penderita tampak tenang dan sedih atau mudah tersinggung dan cemas.

Pada depresi vegetatif, penderita cenderung menarik diri, jarang berbicara, tidak mau makan dan tidak mau tidur.
Sedangkan penderita depresi agitasi tampak sangat gelisah, meremas-remas tangannya serta banyak berbicara.

Banyak penderita yang tidak dapat merasakan emosi duka cita, gembira dan senang secara normal; dunia tampak semakin suram, tidak ada kehidupan dan mati.
Berfikir, berbicara dan kegiatan umum lainnya semakin berkurang, sehingga aktivitas volunter terhenti sama sekali.

Fikirannya dipenuhi oleh perasaan bersalah dan memiliki gagasan untuk menghancurkan dirinya sendiri, serta tidak dapat berkonsentrasi dengan baik.
Mereka sering bimbang dan menarik diri, merasa tak berdaya dan putus asa serta berfikir tentang kematian dan bunuh diri.

Penderita mengalami sulit tidur dan seringkali terbangun, terutama pada dini hari.
Gairah dan kenikmatan seksualnya hilang.
Nafsu makan yang buruk dan penurunan berat badan kadang menyebabkan penderita menjadi kurus dan siklus menstruasinya berhenti (pada wanita).

Pada depresi yang lebih ringan, penderitanya makan sangat banyak dan terjadi penambahan berat badan.

Pada sekitar 20% penderita, gejalanya lebih ringan tetapi berlangsung selama bertahun-tahun bahkan berpuluh-puluh tahun.
Depresi disritmik ini seringkali muncul pada awal kehidupan dan berhubungan dengan perubahan kepribadian yang nyata.
Penderita tampak muram, pesimis, tidak suka bercanda atau tidak mampu merasakan kesenangan; pasif dan letargis; introvert; curiga, suka mengkritik dan sering menyesali dirinya sendiri.
Fikiran penderita dipenuhi dengan kekurangan, kegagalan dan peristiwa negatif, kadang sampai menikmati kegagalan mereka sendiri.

Beberapa penderita mengeluhkan penyakit fisik, berupa sakit dan nyeri atau ketakutan akan musibah atau menjadi gila.
Penderita lainnya berfikir bahwa mereka menderita penyakit yang tidak dapat disembuhkan atau yang memalukan (misalnya kanker atau penyakit menular seksual), dan mereka menularkannya kepada orang lain.

Sekitar 15% penderita (terutama pada depresi berat), mengalami delusi (keyakinan yang palsu) atau halusinasi, yaitu melihat atau mendengar benda yang sesungguhnya tidak ada.
Mereka yakin bahwa mereka melakukan dosa atau kejahatan yang tidak dapat dimaafkan, atau mereka mendengar suara-suara yang menuduh mereka telah melakukan berbagai perbuatan yang tidak senonoh atau suara-suara yang mengutuk mereka supaya mati.
Kadang penderita membayangkan bahwa mereka melihat peti mati dan orang-orang yang sudah meninggal.
Perasaan tidak aman dan tidak berharga bisa menyebabkan depresi yang sangat berat pada penderita yang yakin bahwa mereka diawasi dan dihukum.
Depresi yang disertai dengan delusi dinamakan depresi psikotik.

Gejala depresi yang paling serius adalah pemikiran tentang kematian.
Banyak penderita yang ingin mati atau merasa mereka sangat tidak berguna sehingga mereka sepantasnya mati.
Sebanyak 15% penderita menunjukkan perilaku bunuh diri.
Rencana bunuh diri merupakan keadaan yang gawat, dan penderitanya harus dirawat dan diawasi secara ketat, sampai keinginannya untuk bunuh diri hilang.

DIAGNOSA

Diagnosis biasanya ditegakkan berdasarkan tanda-tanda dan gejalanya.
Riwayat depresi sebelumnya atau riwayat keluarga dengan depresi bisa memperkuat diagnosis.

Untuk membantu menentukan beratnya depresi kadang digunakan pertanyaan standar berikut:
- Skala Penilaian Depresi Hamilton, pertanyaan diarahkan secara verbal oleh penanya
- Kuosioner Depresi Beck, pertanyaan diisi sendiri oleh penderita.

Pemeriksaan darah bisa membantu menentukan penyebab depresi.
Hal ini terutama dilakukan pada penderita wanita, dimana faktor hormonal bisa menyebabkan terjadinya depresi.

Pada kasus-kasus yang sulit, bisa dilakukan pemeriksaan lainnya untuk memperkuat diagnosa.
Gangguan tidur adalah gejala depresi yang khusus. Ensefalogram tidur bisa dilakukan guna mengukur waktu yang diperlukan penderita untuk sampai pada tahap tidur REM (periode tidur selama terjadinya mimpi).
Dalam keadaan normal diperlukan waktu sekitar 90 menit, pada penderita depresi biasanya hanya diperlukan waktu 70 menit atau kurang.

PENGOBATAN

Pada saat ini pengobatan depresi tidak memerlukan perawatan di rumah sakit.
Penderita yang harus dirawat di rumah sakit adalah penderita yang:
- memiliki kecenderungan bunuh diri atau merencanakan tindakan bunuh diri
- terlalu lemah karena berat badannya turun
- memiliki resiko terjadinya kelainan jantung karena penderita sangat gelisah.

Pemberian obat-obatan merupakan langkah utama dalam mengobati depresi sekarang ini.
Pengobatan lainnya adalah psikoterapi dan terapi elektrokonvulsif.
Kadang digunakan kombinasi dari ketiga terapi tersebut.

Obat-obatan.

Tersedia beberapa jenis obat-obatan yang harus diminum secara teratur minimal selama beberapa minggu sebelum obat mulai bekerja.

Anti-depresi trisiklik.
Sering menimbulkan efek samping berupa mengantuk dan penambahan berat badan.
Obat ini juga menyebabkan peningkatan denyut jantung, penurunan tekanan darah ketika penderita berdiri, pandangan kabur, mulut kering, linglung, sembelit, kesulitan untuk memulai berkemih dan orgasme yang tertunda. Efek ini disebut efek antikolinergik, yang lebih sering terjadi pada usia lanjut.
Anti-depresi yang mirip dengan trisiklik memiliki efek samping yang berbeda:
- Venlafaksin bisa menyebabkan kenaikan tekanan darah yang ringan
- Trazodon menyebabkan priapisme (nyeri ketika ereksi)
- Maprotilin dan bupropion bisa menyebabkan kejang.
Selective serotonin reuptake inhibitors (SSRIs).
Efek sampingnya lebih sedikit dan biasanya lebih aman digunakan pada penderita depresi yang disertai kelainan jiwa.
Efek samping yang terjadi berupa mual, diare dan sakit kepala; yang sifatnya ringan dan akan segera menghilang jika pemakaian obat dilanjutkan.
SSRIs efektif digunakan pada depresi yang disertai oleh kelainan jiwa berikut:
- Distimia, yang memerlukan pemberian jangka panjang
- Penyakit obsesif-kompulsif
- Penyakit panik
- Fobia sosial
- Bulimia.
Kerugian utama dari SSRIs adalah sering menyebabkan kelainan fungsi seksual.
Monoamine oxidase inhibitors (MAOIs).
Penderita yang meminum obat golongan MAOIs harus menjalani sejumlah pengaturan diet dan larangan tertentu.
Mereka sebaiknya tidak mengkonsumsi makanan atau minuman yang mengandung tiramin, misalnya bir, anggur merah (termasuk sherry), kopi manis, makanan yang terlalu matang, salami, keju tua, ekstrak jamur dan kecap.
Mereka harus menghindari obat-obatan seperti fenilpropanolamin dan dekstrometorfan, yang menyebabkan pelepasan adrenalin dan menyebabkan peningkatan tekanan darah yang hebat secara tiba-tiba. Obat lainnya yang juga harus dihindari adalah anti-depresi trisiklik, SSRIs dan meperidin (pereda nyeri).
Penderita yang meminum MAOIs biasanya diharuskan membawa obat penawar (misalnya klorpromazin atau nifedipin) setiap saat. Jika timbul nyeri kepala berdenyut dan hebat, maka obat penawar ini harus diminum dan segera pergi ke rumah sakit terdekat.
MAOIs jarang digunakan karena menimbulkan kesulitan dalam pembatasan diet dan larangan tertentu, sehingga hanya diberikan kepada penderita yang tidak menunjukkan perbaikan dengan anti-depresi lainnya.
Psikostimulan (perangsang psikis).
Contohnya adalah metilfenidat, yang biasanya diberikan kepada penderita yang menarik diri, tenang dan mengalami kelelahan atau penderita yang tidak menunjukkan perbaikan pada pemberian obat anti-depresi lainnya.
Psikostimulan cenderung bekerja dengan cepat (dalam 1 hari), sehingga kadang diberikan kepada penderita depresi usia lanjut yang baru menjalani pembedahan atau menderita penyakit yang berkepanjangan.

Psikoterapi.
Psikoterapi yang dijalankan bersamaan dengan pemberian anti-depresi memberikan hasil yang lebih baik.

Psikoterapi individual maupun kelompok bisa membantu penderita secara bertahap untuk memulai kembali tanggung jawabnya yang dahulu dan menyesuaikan diri dengan tekanan kehidupan yang normal.
Pada psikoterapi interpersonal, penderita menerima dukungan untuk menyesuaikan diri dengan perubahan dalam hidupnya.

Terapi kognitif bisa membantu merubah fikiran negatif dan rasa putus asa.

Untuk depresi yang lebih ringan, psikoterapi saja bisa sama efektifnya dengan terapi obat-obatan.

Terapi Elektrokonvulsif.

Terapi elektrokonvulsif (ECT) digunakan untuk mengatasi depresi berat, terutama pada:
- penderita psikotik
- penderita yang mengancam akan melakukan bunuh diri
- penderita yang tidak mau makan.

Terapi ini biasanya sangat efektif dan bisa segera meringankan depresi.

Elektroda dipasang di kepala dan aliran listrik diberikan untuk merangsang kejang di dalam otak. Untuk alasan yang tidak dimengerti, kejang ini menyebabkan berkurangnya depresi.
Pengobatan dilakukan sebanyak 5-7 kali.
Aliran listrik bisa menyebabkan kontraksi otot dan nyeri, sehingga penderita dibius total selama pengobatan.
ECT bisa menyebabkan hilangnya ingatan untuk sementara waktu.

PROGNOSIS

Jika tidak diobati, depresi bisa berlangsung sampai 6 bulan atau lebih.
Gejala yang ringan bisa menetap, tetapi fungsi penderita cenderung kembali normal.

Sebagian besar penderita mengalami episode depresi berulang, sekitar 4-5 kali sepanjang hidupnya.

Diagnosis Kanker

2007-10-26T06:37:00.000-07:00

Diagnosis Kanker

DEFINISI

PENYARINGAN KANKER

Tes penyaringan kanker dimaksudkan untuk mengetahui kemungkinan terjadinya kanker.
Tes ini dapat mengurangi jumlah kematian akibat kanker, karena jika kanker ditemukan pada stadium paling dini, biasanya dapat diobati sebelum menyebar lebih jauh.

Tes penyaringan tidak pasti, hasilnya diperkuat atau disangkal oleh pemeriksaan dan tes lanjutan.

Meskipun tes penyaringan dapat menyelamatkan hidup seseorang, tetapi biayanya mahal dan kadang menimbulkan reaksi psikis atau fisik.
Biasanya tes penyaringan memberikan sejumlah besar hasil positif palsu, dimana diduga terjadi kanker padahal sesungguhnya tidak.
Tes penyaringan juga bisa memberikan hasil negatif palsu, dimana tidak ditemukannya bukti dari suatu kanker padahal telah terjadi kanker.

Hasil positif palsu bisa menimbulkan stres psikis yang tidak semestinya dan bisa mengarah kepada dilakukannya tes lain yang mahal dan berbahaya.
Hasil negatif palsu bisa melenakan seseorang dalam perasaan aman yang palsu.
Karena itu praktisi medis harus secara seksama mempertimbangkan apakah perlu dilakukan tes penyaringan atau tidak.

2 tes penyaringan yang paling banyak digunakan pada wanita adalah tes Papanicolau (Pap smear) untuk menemukan kanker leher rahim dan mamografi untuk menemukan kanker payudara.
Kedua tes ini telah berhasil mengurangi angka kematian akibat kanker-kanker tersebut.

Tes penyaringan yang sering dilakukan pada pria adalah pengukuran kadar PSA (prostate-spesific agent) dalam darah.
Pada penderita kanker prostat, kadar PSA ini tinggi, tetapi kadarnya juga meningkat pada pria dengan pembesaran prostat yang jinak.
Kekurangan dari tes ini adalah biayanya yang tinggi dan seringnya ditemukan hasil positif palsu.

Tes penyaringan lainnya yang sering digunakan adalah memeriksa darah yang tersermbunyi (occult blood) dalam tinja.
Occult blood tidak dapat terlihat dengan mata telanjang, harus dilakukan pemeriksaan terhadap contoh tinja.

Ditemukannya occult blood dalam tinja merupakan pentunjuk ada sesuatu yang tidak beres di usus besar. Mungkin suatu kanker, meskipun penyakit lainnya juga bisa menyebabkan ditemukannya sejumlah kecil darah dalam tinja.

Beberapa tes penyaringan dapat dilakukan di rumah.
Misalnya melakukan pemeriksaan payudara sendiri setiap bulan sangat berharga dalam membantu wanita menemukan kanker payudara.
Secara teratur memeriksa buah zakar dapat membantu pria menemukan kanker buah zakar, salah satu bentuk kanker yang paling dapat disembuhkan jika ditemukan pada stadium awal.
Secara teratur memeriksa adanya luka terbuka di mulut bisa membantu menemukan kanker mulut dalam stadium awal.

Tes Penyaringan Kanker Yg Dianjurkan

Prosedur	Frekuensi
Kanker Paru-paru
Rontgen dada	Tidak dianjurkan pada pemeriksaan rutin
Sitologi dahak	Tidak dianjurkan pada pemeriksaan rutin
Kanker Rektum & Usus Besar
Pemeriksaan tinja untuk occult blood	Setiap tahun setelah usia 50 tahun
Pemeriksaan rektum	Setiap tahun setelah usia 40 tahun
Pemeriksaan sigmoidoskopi	Setiap 3-5 tahun setelah usia 50 tahun
Kanker Prostat
Pemeriksaan rektum & pemeriksaan darah untuk PSA	Setiap tahun setelah usia 50 tahun
Kanker leher rahim, rahim dan indung telur
Pemeriksaan panggul	Setiap 1-3 tahun pada usia 18-40 tahun, setiap tahun setelah usia 40 tahun
Kanker leher rahim
Pap Smear	Setiap tahun pada usia 18-65 tahun Setelah 3 kali/lebih berturut² hasilnya normal, bisa dilakukan lebih jarang Tidak terlalu sering dilakukan diatas usia 65 tahun
Kanker payudara
Pemeriksaan payudara sendiri	Setiap bulan setelah usia 18 tahun
Pemeriksaan fisik payudara	Setiap 3 tahun pada usia 18-40 tahun, setiap tahun setelah usia 40 tahun
Mamografi	Pemeriksaan dasar awal pada usia 35-40 tahun, setiap 1-2 tahun pada usia 40-49 tahun, setiap tahun setelah usia 50 tahun

DIAGNOSIS KANKER

Karena jenis kanker dan pengobatannya bervariasi, maka mendiagnosis adanya kanker dan menentukan jenisnya merupakan hal yang sangat penting.
Hal ini hampir selalu memerlukan pengambilan contoh jaringan kanker untuk diperiksa dibawah mikroskop.
Sejumlah tes khusus terhadap contoh jaringan kanker mungkin diperlukan untuk menggambarkan lebih jauh mengenai kanker yang ditemukan.

Bila jenis kankernya diketahui, akan membantu dokter dalam menentukan pemeriksaan yang akan dilakukan, karena setiap kanker cenderung untuk mengikuti suatu pola pertumbuhan dan penyebaran tertentu.

Pada 7% penderita, pemeriksaan dilakukan untuk menemukan metastase (penyebaran) sebelum kanker asalnya diobservasi.
Kadang kanker asalnya tidak dapat ditemukan.

Dokter biasanya dapat menentukan jenis tumor utamanya dengan melakukan biopsi dari kanker yang bermetastase dan memeriksanya dibawah mikroskop.
Namun identifikasi kanker tidak selalu mudah dan pasti.

MENENTUKAN STADIUM KANKER

Jika ditemukan kanker, pemeriksaan penentuan stadium (staging) kanker membantu dokter dalam merencanakan pengobatan yang tepat dan menentukan prognosisnya.

Serangkaian pemeriksaan digunakan untuk menentukan lokasi tumor, ukurannya, pertumbuhannya ke jaringan di sekitar dan penyebarannya ke bagian tubuh yang lain.

Staging bisa dilakukan dengan menggunakan:

Scan (misalnya scan hati atau tulang)
Pewarnaan
CT (computed tomography) atau MRI (magnetic resonance imaging)
Mediastinoskopi
Biopsi sumsum tulang.

Kadang perlu dilakukan pembedahan untuk menentukan stadium kanker.
Misalnya suatu laparotomi (pembedahan perut) memungkinkan ahli bedah untuk mengangkat atau mengobati kanker usus besar sambil menentukan penyebaran kanker ke kelenjar getah bening terdekat.
Analisa kelenjar getah bening yang diangkat dari ketiak pada saat dilakukan mastektomi, membantu menentukan seberapa jauh kanker payudara telah menyebar dan apakah diperlukan terapi paska pembedahan.
Splenektomi dilakukan untuk mengangkat limpa dan membantu menentukan stadium dari penyakit Hodgkin.

Skening ultrasonik merupakan prosedur non-invasif dan tidak menimbulkan nyeri, yang menggunakan gelombang suara untuk menunjukkan struktur organ dalam.
Pemeriksaan ini membantu dalam menentukan ukuran kanker tertentu, terutama kanker ginjal, hati, panggul dan prostat.

CT scan digunakan untuk menemukan kanker di otak, paru-paru dan organ perut, termasuk kelenjar adrenal, kelenjar getah bening, hati dan limpa.

Limfangiogram adalah suatu pemeriksaan dimana zat warna disuntikkan ke dalam kaki lalu dilakukan pemotretan rontgen.
Pemeriksaan ini membantu menemukan kelainan dalam kelenjar getah bening perut dan menentukan stadium dari penyakit Hodgkin dan kanker buah zakar.

Dengan prosedur MRI bisa menemukan kanker otak, tulang dan korda tulang belakang.

Pemeriksaan untuk staging kanker

Organ Yg Terkena	Jenis Biopsi Yg Dilakukan	Pemeriksaan Lainnya
Payudara	Biopsi jarum atau biopsi seluruh benjolan	Mammogram Skening hati & tulang CT scan otak Pemeriksaan reseptor estrogen & progesteron pada contoh biopsi,/td>
Saluran Pencernaan	Jaringan untuk biopsi diambil dengan endoskopi atau dengan jarum melalui kulit menuju ke hati, pankreas atau organ lainnya	Rontgen dada Rontgen barium Ultrasonik CT scan Skening hati Pemeriksaan darah untuk enzim hati
Paru-paru	Biopsi paru-paru & mungkin biopsi pleura Mediastinoskopi	Rontgen dada CT scan Sitologi dahak
Sistem Limfatik	Biopsi kelenjar limfa Biopsi sumsum tulang	Rontgen dada Hitung jenis sel darah Ultrasonik CT scan Radioisotop scan Pembedahan eksplorasi Splenektomi
Prostat	Biopsi jarum	Pemeriksaan darah untuk asam fosfatase & PSA (prostate-specific antigen) Ultrasonik
Buah Zakar	Pengangkatan buah zakar untuk biopsi	Rontgen dada CT scan
Rahim, leher rahim, indung telur	Jaringan untuk biopsi diambil selama pembedahan eksplorasi	Pemeriksaan panggul Ultrasonik CT scan Barium enema

PENYEBAB

Demam Hemoragik

2007-10-26T06:34:00.000-07:00

Di beberapa bagian dunia, infeksi yang secara khusus ditemukan pada binatang, bisa mengenai manusia.
Infeksi ini berhubungan dengan tempat hidup dan vektor virus untuk penyebarannya.

Beberapa virus menyebabkan infeksi hebat yang berakibat fatal, ditandai dengan demam hemoragik, perdarahan yang meluas dan kegagalan berbagai organ.
Yang termasuk ke dalam infeksi ini adalah demam hemoragik Bolivia & Argentina serta demam Lassa.

Demam Lassa merupakan infeksi arenavirus yang ditularkan dari binatang pengerat kepada manusia atau dari manusia ke manusia, yang menyebabkan demam, muntah-muntah dan perdarahan.
Kasus ini sangat fatal dan penderita harus diisolasi secara ketat.
Penyakit ini terutama terjadi di Afrika Barat.

VIRUS EBOLA & VIRUS MARBURG

Virus Ebola dan Virus Marburg merupakan dua jenis virus di Afrika yang termasuk ke dalam kelompok filovirus.
Kedua virus tersebut menyebabkan demam hemoragik yang hebat pada manusia.

Virus Ebola mungkin berasal dari monyet. Sering ditularkan kepada manusia melalui darah atau jaringan tubuh yang terinfeksi.

Infeksi akan menyebabkan demam, diare, perdarahan dan penurunan kesadaran.
Sering berakibat fatal, tetapi spesies virus yang tidak mematikan juga ada, yaitu di Afrika Timur, Selatan dan Tengah.

Virus Marburg didapat dari pemaparan terhadap jaringan primata terinfeksi.
Virus ini sangat infeksius, menyebabkan penyakit berat pada beberapa organ.
Kematian hampir selalu tidak dapat dihindarkan.
Sumber virus ini tampaknya hanya berada di Afrika Tengah.

Penyakit Sel Sabit

2007-10-26T06:20:00.000-07:00

Penyakit Sel Sabit

DEFINISI

Penyakit Sel Sabit (sickle cell disease adalah suatu penyakit keturunan yang ditandai dengan sel darah merah yang berbentuk sabit dan anemia hemolitik kronik.

Pada penyakit sel sabit, sel darah merah memiliki hemoglobin (protein pengangkut oksigen) yang bentuknya abnormal, sehingga mengurangi jumlah oksigen di dalam sel dan menyebabkan bentuk sel menjadi seperti sabit.
Sel yang berbentuk sabit menyumbat dan merusak pembuluh darah terkecil dalam limpa, ginjal, otak, tulang dan organ lainnya; dan menyebabkan berkurangnya pasokan oksigen ke organ tersebut.

Sel sabit ini rapuh dan akan pecah pada saat melewati pembuluh darah, menyebabkan anemia berat, penyumbatan aliran darah, kerusakan organ dan mungkin kematian.

PENYEBAB

Penyakit sel sabit hampir secara eksklusif menyerang orang kulit hitam.

Sekitar 10% orang kulit hitam di AS hanya memiliki 1 gen untuk penyakit ini (mereka memiliki rantai sel sabit) dan tidak menderita penyakit sel sabit.
Sekitar 0,3% memiliki 2 gen dan menderita penyakit sel sabit.

GEJALA

Penderita selalu mengalami berbagai tingkat anemia dan sakit kuning (jaundice) yang ringan, tetapi mereka hanya memiliki sedikit gejala lainnya.

Berbagai hal yang menyebabkan berkurangnya jumlah oksigen dalam darah, (misalnya olah raga berat, mendaki gunung, terbang di ketinggian tanpa oksigen yang cukup atau penyakit) bisa menyebabkan terjadinya krisis sel sabit,yang ditandai dengan:
- semakin memburuknya anemia secara tiba-tiba
- nyeri (seringkali dirasakan di perut atau tulang-tulang panjang)
- demam
- kadang sesak nafas.
Nyeri perut bisa sangat hebat dan bisa penderita bisa mengalami muntah; gejala ini mirip dengan apendisitis atau suatu kista indung telur.

Pada anak-anak, bentuk yang umum dari krisis sel sabit adalah sindroma dada, yang ditandai dengan nyeri dada hebat dan kesulitan bernafas.
Penyebab yang pasti dari sindroma dada ini tidak diketahui tetapi diduga akibat suatu infeksi atau tersumbatnya pembuluh darah karena adanya bekuan darah atau embolus (pecahan dari bekuan darah yang menyumbat pembuluh darah).

Sebagian besar penderita mengalami pembesaran limpa selama masa kanak-kanak.
Pada umur 9 tahun, limpa terluka berat sehingga mengecil dan tidak berfungsi lagi.

Limpa berfungsi membantu melawan infeksi, karena itu penderita cenderung mengalami pneumonia pneumokokus atau infeksi lainnya.
Infeksi virus bisa menyebabkan berkurangnya pembentukan sel darah, sehingga anemia menjadi lebih berat lagi.

Lama-lama hati menjadi lebih besar dan seringkali terbentuk batu empedu dari pecahan sel darah merah yang hancur.
Jantung biasanya membesar dan sering ditemukan bunyi murmur.

Anak-anak yang menderita penyakit ini seringkali memiliki tubuh yang relatif pendek, tetapi lengan, tungkai, jari tangan dan jari kakinya panjang.
Perubahan pada tulang dan sumsum tulang bisa menyebabkan nyeri tulang, terutama pada tangan dan kaki.

Bisa terjadi episode nyeri tulang dan demam, dan sendi panggul mengalami kerusakan hebat sehingga pada akhirnya harus diganti dengan sendi buatan.

Sirkulasi ke kulit yang jelek dapat menyebabkan luka terbuka di tungkai, terutama pada pergelangan kaki.
Kerusakan pada sistem saraf bisa menyebabkan stroke.

Pada penderita lanjut usia, paru-paru dan ginjal mengalami penurunan fungsi.
Pria dewasa bisa menderita priapisme (nyeri ketika mengalami ereksi).

Kadang air kemih penderita mengandung darah karena adanya perdarahan di ginjal.
Jika diketahui bahwa perdarahan ini berhubungan dengan rantai sel sabit, maka penderita tidak boleh menjalani pembedahan eksplorasi dengan jarum.

DIAGNOSA

Anemia, nyeri lambung dan nyeri tulang serta mual-mual pada seorang kulit hitam merupakan tanda yang khas untuk krisis sel sabit.

Pada pemeriksan contoh darah dibawah mikroskop, bisa terlihat sel darah merah yang berbentuk sabit dan pecahan dari sel darah merah yang hancur.

Elektroforesis bisa menemukan adanya hemoglobin abnormal dan menunjukkan apakah seseorang menderita penyakit sel sabit atau hanya memiliki rantai sel sabit.
Penemuan rantai sel sabit ini penting untuk rencana berkeluarga, yaitu untuk menentukan adanya resiko memiliki anak yang menderita penyakit sel sabit.

PENGOBATAN

Dulu penderita penyakit sel sabit jarang hidup sampai usia diatas 20 tahun, tetapi sekarang ini mereka biasanya dapat hidup dengan baik sampai usia 50 tahun.
Penyakit sel sabit tidak dapat diobati, karena itu pengobatan ditujukan untuk:
- mencegah terjadinya krisis
- mengendalikan anemia
- mengurangi gejala.

Penderita harus menghindari kegiatan yang bisa menyebabkan berkurangnya jumlah oksigen dalam darah mereka dan harus segera mencari bantuan medis meskipun menderita penyakit ringan, misalnya infeksi virus.

Penderita memiliki resiko tinggi terhadap terjadinya infeksi, sehingga harus menjalani imunisasi dengan vaksin pneumokokus dan Hemophilus influenzae.

Krisis sel sabit membutuhkan perawatan di rumah sakit.
Penderita mendapatkan sejumlah besar cairan lewat pembuluh darah (intravena) dan obat-obatan untuk mengurangi rasa nyeri.
Diberikan transfusi darah dan oksigen jika diperkirakan aneminya cukup berat sehingga bisa menimbulkan resiko terjadinya stroke, serangan jantung atau kerusakan paru-paru.
Keadaan yang mungkin menyebabkan krisi, misalnya infeksi, harus diobati.

Obat-obatan yang mengendalikan penyakit sel sabit (misalnya hidroksiurea), masih dalam penelitian.
Hidroksiurea meningkatkan pembentukan sejenis hemoglobin yang terutama ditemukan pada janin, yang akan menurunkan jumlah sel darah merah yang berubah bentuknya menjadi sabit.
Karena itu obat ini mengurangi frekuensi terjadinya krisis sel sabit.

Kepada penderita bisa dicangkokkan sumsum tulang dari anggota keluarga atau donor lainnya yang tidak memiliki gen sel sabit.
Pencangkokan ini mungkin bisa menyembuhkan, tetapi resikonya besar dan penerima cangkokan harus meminum obat yang menekan kekebalan sepanjang hidupnya.

Terapi genetik, yang merupakan teknik penanaman gen normal ke dalam sel-sel prekursor (sel yang menghasilkan sel darah), masih dalam penelitian.

Hipoglikemia

2007-10-26T06:11:00.000-07:00

Hipoglikemia

DEFINISI

Hipoglikemia adalah kadar gula darah (glukosa) yang rendah.

PENYEBAB

Hipoglikemia biasanya terjadi jika seorang bayi pada saat dilahirkan memiliki cadangan glukosa yang rendah (yang disimpan dalam bentuk glikogen).
Penyebab lainnya adalah:

Prematuritas

Post-maturitas

Kelainan fungsi plasenta (ari-ari) selama bayi berada dalam kandungan.

Hipoglikemia juga bisa terjadi pada bayi yang memiliki kadar insulin tinggi.
Bayi yang ibunya menderita diabetes seringkali memiliki kadar insulin yang tinggi karena ibunya memiliki kadar gula darah yang tinggi; sejumlah besar gula darah ini melewati plasenta dan sampai ke janin selama masa kehamilan. Akibatnya, janin menghasilkan sejumlah besar insulin.
Peningkatan kadar insulin juga ditemukan pada bayi yang menderita penyakit hemolitik berat.

Kadar insulin yang tinggi menyebabkan kadar gula darah menurun dengan cepat pada jam-jam pertama kehidupan bayi setelah dilahirkan, dimana aliran gula dari plasenta secara tiba-tiba terhenti.

GEJALA

Banyak bayi yang tidak menunjukkan gejala. Sedangkan bayi yang lainnya bisa menunjukkan gejala berikut:
- lesu
- tidak kuat menghisap
- ototnya kendur
- pernafasannya cepat atau terjadi apneu (henti nafas)
- kadang timbul kejang.

DIAGNOSA

Diagnosis ditegakkan berdasarkan gejala, hasil pemeriksaan fisik dan hasil pemeriksaan kadar gula darah.

PENGOBATAN

Diberikan glukosa, baik melalui mulut maupun melalui infus, tergantung kepada beratnya hipoglikemia.

DHIAN

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What Are Allergies?

Who Gets Allergies?

Common Airborne Allergens

Common Food Allergens

Other Common Allergens

Signs and Symptoms of Allergies

Airborne Allergy Symptoms

Food Allergy Symptoms

Insect Venom Allergy Symptoms

About Anaphylaxis

Diagnosing Allergies

Treating Allergies

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[edit] Anatomy

[edit] Embryologic development

[edit] Histology

[edit] Physiology

[edit] T3 and T4 production and action

[edit] T3 and T4 regulation

[edit] Calcitonin

[edit] Significance of iodine

[edit] Diseases

[edit] Hyper- and hypofunction (affects about 2% of the population)

[edit] Anatomical problems

[edit] Tumors

[edit] Deficiencies

[edit] Diagnosis

[edit] Blood tests

[edit] Ultrasound

[edit] Radioiodine scanning and uptake

[edit] Biopsy

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[edit] Medical treatment

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[edit] Radioiodine therapy

[edit] History

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[edit] Anticodon

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[edit] History

[edit] References

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Contents

Preamble

Anatomy of cells

Prokaryotic cells

Eukaryotic cells

Subcellular components

Cell membrane: A cell's defining boundary

Cytoskeleton: A cell's scaffold

Genetic material

Organelles

Cell functions

Cell growth and metabolism

Creation of new cells

Protein synthesis

Cell movement or motility

Origins of cells

Origin of the first cell

Origin of eukaryotic cells

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