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Subject: p
Date: Thu, 12 Oct 95 23:34 PDT (429 lines of text)

p24:

1. Within the envelope of the HIV virus is a bullet-shaped core made of another protein, p24, that surrounds the viral RNA. 2. The p24 antigen test looks for the presence of this protein in a patient's blood. 3. A positive result for the p24 antigen suggests active HIV replication. p24 found in the peripheral blood is thought to also correlate with the amount of virus in the peripheral blood. It is believed that there are measurable levels of p24 when first infected with the virus after which there is a strong antibody response to p24 in early disease. Low or unmeasurable levels of p24 may indicate that the virus is in a dormant stage. Spikes in p24 levels may indicate that HIV has begun active replication.

PALLIATIVE:

A treatment that provides symptomatic relief, but not a cure.

PANCREAS:

A gland situated near the stomach that secretes a digestive fluid into the intestine through one or more ducts and also secretes the hormone insulin.

PANCREATITIS:

Inflammation of the pancreas that can produce severe pain and debilitating illness. See also Pancreas.

PANCYTOPENIA:

Deficiency of all cell elements of the blood.

PANDEMIC:

A disease prevalent throughout an entire country, continent or the whole world. See also Epidemic.

PAP SMEAR:

A method for the early detection of cancer and other abnormalities of the female genital tract, especially of the cervix and uterus, employing exfoliated cells (cells that have been shed into vaginal fluid) and a special staining technique for microscopic examination that differentiates diseased tissue. Also known as Papanicolaou Smear after George Papanicolaou, the American cytologist who developed this method and published it in 1943. See also Cervix; Uterus.

PAPILLOMA:

1. A benign tumor (as a wart or condyloma) resulting from an overgrowth of epithelial tissue on papillae of vascularized connective tissue (as of the skin). 2. An epithelial tumor caused by a virus. See also Condyloma; Epithelium.

PARALLEL TRACK:

A system of distributing experimental drugs to patients who are unable to participate in ongoing clinical efficacy trials and have no other treatment options. See also Clinical Trial.

PARASITE:

A plant or animal that lives and feeds on or within another living organism; does not necessarily cause disease.

PARENCHYMA:

The tissue of an organ (as distinguished from supporting or connective tissue).

PARENTERAL:

Not in or through the digestive system. For example, parenteral can pertain to blood being drawn from a vein in the arm or introduced into that vein via a transfusion (intravenous), or to injection of medications or vaccines through the skin (subcutaneous) or into the muscle (intramuscular).

PARESTHESIA:

Any subjective sensation, experienced as numbness, tingling or a "pins-and-needles" feeling.

PATHOGEN:

Any disease-producing microorganism or material.

PATHOGENESIS:

The origin and development of a disease.

PBMC:

See Peripheral Blood Mononuclear Cell.

PCP:

See Pneumocystis carinii Pneumonia.

PCR:

See Polymerase Chain Reaction.

PEER REVIEW:

The process by which new scientific or medical findings, announced by one researcher, are reviewed by other scientists or physicians before these findings are published.

PELVIC INFLAMMATORY DISEASE (PID):

A term used to describe infections of the uterus, the fallopian tubes and the ovaries. PID is usually the result of untreated sexually transmitted disease, primarily chlamydia or gonorrhea. See also Fallopian Tubes; Ovary; Uterus.

PENTAMIDINE:

An approved antiprotozoal drug used for the treatment and prevention of Pneumocystis carinii pneumonia (PCP) infection. It can be delivered intravenously or intramuscularly or inhaled as an aerosol. Aerosolized pentamidine is approved for the prophylaxis of PCP in HIV-positive individuals with CD4+ counts below 200 per cubic millimeter or for those with prior episodes of PCP. The drug is also known under the names Pentam and NebuPent. See also Pneumocystis carinii Pneumonia.

PEPTIDE:

(Also polypeptide). Biochemical formed by the linkage of up to about 50 amino acids to form a chain. Longer chains are called proteins. The amino acids are coupled by a peptide bond, a special linkage in which the nitrogen atom of one amino acid binds to the carboxyl carbon atom of another. Many peptides, such as the hormones vasopressin and ACTH, have physiological or antibacterial activity. See also Amino Acids.

PERIANAL:

Around the anus.

PERINATAL:

Events that occur at or around the time of birth.

PERIPHERAL BLOOD MONONUCLEAR CELL (PBMC):

Cells in the bloodstream with one nucleus. See also Nucleus.

PERSISTENT GENERALIZED LYMPHADENOPATHY (PGL):

Chronic, diffuse, noncancerous lymph node enlargement. Typically it has been found in those with immune system disturbances who develop frequent and persistent bacterial, viral and fungal infections.

PGL:

See Persistent Generalized Lymphadenopathy.

PHA:

See Phytohemagglutinin.

PHAGOCYTE:

A cell that is able to ingest and destroy foreign matter, including bacteria.

PHAGOCYTOSIS:

The process of ingesting and destroying a virus or other foreign matter by phagocyte. See also Macrophage; Monocyte.

PHARMACOKINETICS:

The processes (in a living organism) of absorption, distribution, metabolism and excretion of a drug or vaccine.

PHS:

See Public Health Service.

PHYTOHEMAGGLUTININ (PHA):

A plant chemical used to stimulate the multiplication of white blood cells.

PITUITARY GLAND:

Small, oval endocrine gland that lies at the base of the brain. It is called the master gland because the other endocrine glands depend on its secretions for stimulation. The pituitary has two distinct lobes, anterior and posterior. The anterior lobe secretes at least six hormones:

human growth hormone, which stimulates overall body growth; ACTH(adrenocorticotropic hormone), which controls steroid hormone secretion by the adrenal cortex; thyrotropic hormone, which stimulates the activity of the thyroid gland; and three gonadotropic hormones, which control growth and reproductive activity of the gonads (ovaries and testes). The posterior lobe secretes antidiuretic hormone, which causes water retention by the kidneys, and oxytocin, which stimulates the mammary glands to release milk and also causes uterine contractions. An overactive pituitary during childhood can cause gigantism; during adulthood, it can cause acromegaly. Dwarfism results from pituitary deficiency in childhood. See also Acromegaly.

PLACEBO:

An inactive substance against which investigational treatments are compared for efficacy. See also Placebo Controlled Study.

PLACEBO CONTROLLED STUDY:

A method of investigation of drugs in which an inactive substance (the placebo) is given to one group of patients, while the drug being tested is given to another group. The results obtained in the two groups are then compared.

PLACEBO EFFECT:

A physical or emotional change occurring after a substance is taken or administered that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the patient and, often, the expectations of the person giving the substance.

PLASMA:

That 10 percent of the blood that contains nutrients, electrolytes (dissolved salts), gases, albumin, clotting factors, wastes and hormones.

PLASMA CELLS:

Large antibody-producing cells that develop from B cells. See also Antibodies; B Lymphocytes.

PLASMAPHERESIS:

The selective removal of certain proteins or antibodies from the blood (followed by reinjection of the blood). This process is sometimes used in the treatment of some peripheral neuropathies and is an integral part of passive immunotherapies for HIV. See also Neuropathy.

PLATELETS:

Active agents of inflammation when damage occurs to a blood vessel. They are not actually cells, but fragments released by megakaryocyte cells. Megakaryocyte is a large cell in the bone marrow whose function is to produce platelets. When vascular damage (i.e., damage to blood vessels) occurs, the platelets stick to the vascular walls, forming clots to prevent the loss of blood. Thus, it is important to have adequate numbers of normally functioning platelets to maintain effective coagulation of the blood. There are drugs that can potentially alter the platelet count, making it necessary to monitor the count. Also, some people with HIV infection develop thrombocytopenia (a condition characterized by a platelet count of less than 100,000 platelets per cubic millimeter of blood). The normal value for men is 154,000-354,000 platelets per cubic millimeter of blood. For women, it is 162,000-380,000 platelets per cubic millimeter of blood.

PML:

See Progressive Multifocal Leukoencephalopathy.

PNEUMOCYSTIS CARINII PNEUMONIA (PCP):

1. A protozoal infection of the lungs. 2. A life-threatening lung infection that can affect people with weakened immune systems, such as those infected with HIV. More than three-quarters of all people with HIV disease will develop PCP if they do not receive treatment to prevent it. The standard treatment for people with PCP is either a combination of trimethoprim and sulfamethoxazole (TMP/SMX, also called Bactrim or Septra) or pentamidine. See also Pentamidine; Protozoa.

POLYMERASE:

Any of several enzymes that catalyze the formation of DNA or RNA from precursor substances in the presence of preexisting DNA or RNA acting as templates (i.e., patterns). See also DNA; Enzyme; Ribonucleic Acid.

POLYMERASE CHAIN REACTION (PCR):

1. A laboratory process that selects a DNA segment from a mixture of DNA chains and rapidly replicates it; used to create a large, readily analyzed sample of a piece of DNA. It is used in DNA fingerprinting and in medical tests to identify diseases from the infectious agent's DNA. See also DNA. 2. As related to HIV:

A sensitive laboratory technique that can detect and quantify HIV in a person's blood or lymph node.

POLYNEURITIS:

Inflammation of many nerves at once.

POLYVALENT VACCINE:

A vaccine that is active against multiple viral strains.

PRECURSOR CELLS:

Cells from which other cells are formed by natural processes.

PREVALENCE:

A measure of the proportion of people in a population affected with a particular disease at a given time.

PROCTITIS:

Inflammation of the rectum.

PRODROME:

A symptom that indicates the onset of a disease.

PROGENITOR:

Parent or ancestor.

PROGRESSIVE MULTICOCAL LEUKOENCEPHALOPATHY (PML):

An opportunistic infection resulting from reactivation or new infection with the JC virus. See also Opportunistic Infection.

PROPHYLAXIS:

Treatment that helps to prevent a disease or condition before it occurs or recurs.

PROTEASE:

An enzyme that hydrolyzes (i.e., breaks down) proteins to their component peptides. See also Enzyme; Peptide; Proteins.

PROTEASE INHIBITORS:

HIV protease is an aspartyl enzyme essential to the replicative life cycle of HIV. The three-dimensional molecular structure of the HIV protease has been fully determined. Pharmaceutical developers are therefore able to rationally design compounds to inhibit it and thus interfere with replication of the virus. In the US, five peptide-based protease inhibitors (saquinavir, Roche; A-80987, ABT-538, Abbott Laboratories; L735,524, Merck; KNI-272, NCI) are in clinical development. All compounds inhibit HIV-1 in vitro in nanomolar concentrations. In Europe, two peptide-based compounds (ABT-987, Abbott Laboratories; AG-1343, Agouron Pharmaceuticals, Inc.) are currently in development. See also In Vitro.

PROTEINS:

Any of the group of highly complex organic compounds found in all living cells. Protein is the most abundant class of all biological molecules, comprising about 50 percent of cellular dry weight. Classified by biological function, proteins include the enzymes, which catalyze cellular reactions; collagen, keratin and elastin, which are structural, or support, proteins; hemoglobin and other transport proteins; casein, ovalbumin and other nutrient proteins; antibodies, which are necessary for immunity; protein hormones, which regulate metabolism; and proteins such as actin and myosin, the contractile muscle proteins that perform mechanical work. Structurally, proteins are large molecules composed of one or more chains of varying amounts of the same 22 amino acids, which are linked by peptide bonds. Each protein is characterized by a unique and invariant amino acid sequence. Protein chains may contain hundreds of amino acids; some proteins also incorporate phosphorus or such metals as iron, zinc and copper. The amino acid sequence also determines the molecule's three-dimensional structure; this so-called native state is required for proper biological function. The information for the syntheses of the specific amino acid sequences from free amino acids is carried by the cell's nucleic acid. See also Peptide; Ribonucleic Acid.

PROTOCOL:

The detailed plan for a clinical trial that states the trial's rationale, purpose, drug or vaccine dosages, length of study, routes of administration, who may participate and other aspects of trial design. See also Clinical Trial; Inclusion/Exclusion Criteria.

PROTOPLASM:

Fundamental material composing all living things. Protoplasm, which exists in all plants and animals in the small units called cells, is mainly (85-90 percent) water and also contains proteins, fatty substances and inorganic salts. It is always enclosed by a thin surface membrane that controls the passage of materials into and out of the cell. It displays the general properties associated with life-the capacity to respond to stimuli and the ability to perform the essential physiological functions.

PROTOZOA:

A group of one-celled animals. Some protozoa can cause human disease.

PSEUDOVIRION:

A virus-like particle.

PUBLIC HEALTH SERVICE (PHS):

A multi-agency organizational component of the US Department of Health and Human Services. See also Centers for Disease Control and Prevention; Health Resources and Services Administration; National Institutes of Health.

PULMONARY:

Pertaining to the lungs.