Cystic Fibrosis

-
Cystic Fibrosis is incurable hereditary disorder that causes the body to secrete an abnormally thick, sticky mucus that clogs the pancreas and the lungs, leading to problems with breathing and digestion, infection, and ultimately, death. Three decades ago most babies born with cystic fibrosis died in early childhood, but advances in diagnosing and treating the disease have significantly improved its prognosis.

Cystic fibrosis is caused by a defect in the gene responsible for manufacturing cystic fibrosis transmembrane conductance regulator (CFTR), a protein that controls the flow of chloride ions into and out of certain cells. In healthy people, CFTR forms a channel in the plasma membrane through which chloride ions enter and leave the cells lining the lungs, pancreas, sweat glands, and small intestine. In people with cystic fibrosis, malfunctioning (or absent) CFTR prevents chloride from entering or leaving cells, resulting in production of a thick, sticky mucus that clogs ducts or tubes in these organs. In the lungs, this mucus blocks airways and impedes natural infection-fighting mechanisms, eventually turning the body’s immune system against its own lung tissue. Similar blockage prevents crucial digestive enzymes produced in the pancreas from reaching the intestines, impairing the ability to break down certain foods. In healthy people most of the chloride in sweat is reabsorbed, but in people with cystic fibrosis, sweat glands cannot take up chloride ions, enabling excessive amounts of salt to escape in the sweat.

Depending on the disease’s severity, symptoms may be apparent soon after birth, or they may escape detection for months or years. In nearly 20 percent of all cases, the first symptom is meconium ileus, intestinal blockage in newborns. In other babies, the first evidence of cystic fibrosis is bulky stool, poor weight gain, flabby muscle tone, or slow growth, all products of low levels of digestive enzymes in the intestines.

The earlier a diagnosis is made the better so that early treatment can slow the progression of lung damage caused by infection. Prenatal tests are available to determine if a baby will be born with cystic fibrosis. In newborns, blood tests indicating high levels of digestive enzymes suggest cystic fibrosis, but a certain diagnosis requires a sweat test to determine the amount of salt in the sweat. Sweat tests provide a valid diagnosis in babies over 24 hours old, and this test is also used to confirm diagnosis in older children and adults.

Cystic fibrosis remains incurable; existing treatments aim to relieve discomfort and delay the devastating and inevitable effects of the disease. Meconium ileus, the intestinal obstruction occurring in newborns, may require surgery. Patients with pancreatic blockage must take pancreatic enzymes with meals. Even with such enzymes, people with cystic fibrosis must consume adequate amounts of protein, vitamins, and higher-than-normal amounts of fat to ensure growth. Those with respiratory infections are treated with antibiotics, often in aerosol form. When inhaled, these medicated vapors fight infection and relieve constriction of the airways. Using a procedure called chest physical therapy or postural drainage, caregivers of people with cystic fibrosis repeatedly and vigorously pound on the patient’s back and chest to dislodge mucus obstructing the airways. Increasingly, cystic fibrosis patients with severe, irreparable lung damage turn to lung transplantation surgery (see Medical Transplantation).

Comments

Post a Comment

Popular posts from this blog

Cream, Butter, and Ice Cream

-
. In order for a product to be labeled as cream, it must contain 18 percent milk fat or more. Light whipping cream must contain at least 30 percent fat, and 36 percent fat is the minimum fat content for heavy whipping cream. Half-and-half, an equal mixture of both milk and cream, must have at least 10.5 percent fat. The various grades of cream are valued for their smooth, thick texture. They are often used in cooking instead of milk, because they are less likely to form a skin when heated and can be whipped into a stiff foam. When chilled cream is churned gently, the fat globules gather together to form butter, leaving buttermilk as the by-product. Butter contains at least 82.5 percent fat. In the past, before the advent of widespread refrigeration, salt was added to butter to retard bacterial spoilage; now salt is added mainly for flavor. Ice cream, a popular frozen dessert, is made of milk, cream, sugar, and flavoring. The mixture is slowly beaten while chilled until it is partially
Read more

How HIV Causes Infections

-
HIV transmission occurs when a person is exposed to body fluids infected with the virus, such as blood, semen, vaginal secretions, and breast milk. The primary modes of HIV transmission are (1) sexual relations with an infected person (see Sexually Transmitted Infections ); (2) sharing hypodermic needles or accidental pricking by a needle contaminated with infected blood; and (3) transfer of the virus from an infected mother to her baby during pregnancy, childbirth, or through breast-feeding. When HIV enters the body, it infects lymphocytes, which are a type of white blood cell in the immune system . HIV uses its glycoproteins to attach itself to receptors on the surface of a lymphocyte. The outer envelope of HIV then fuses with the lymphocyte, enabling the HIV capsid to enter the lymphocyte itself. HIV commandeers the genetic material of the lymphocyte, instructing the cell to replicate more viruses. The newly formed viruses break free from the host, destroying the cell in the process
Read more

Deoxyribonucleic Acid

-
Deoxyribonucleic Acid (DNA), genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct protein synthesis and replication. Protein synthesis is the production of the proteins needed by the cell or virus for its activities and development. Replication is the process by which DNA copies itself for each descendant cell or virus, passing on the information needed for protein synthesis. In most cellular organisms, DNA is organized on chromosomes located in the nucleus of the cell .
Read more