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Subject: n
Date: Thu, 12 Oct 95 23:34 PDT (246 lines of text)

NATIONAL AIDS CLEARINGHOUSE:

See CDC National AIDS Clearinghouse.

NATIONAL CANCER INSTITUTE (NCI):

An NIH institute with the overall mission of conducting and supporting research, training and disseminating health information with respect to the causes, diagnosis and treatment of cancer. NCI also performs these functions for HIV infections and associated diseases. See also National Institutes of Health.

NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES (NIAID):

An NIH institute that conducts and supports research to study the causes of allergic, immunologic and infectious diseases, and to develop better means of preventing, diagnosing and treating illnesses. NIAID is responsible for the federally funded, national basic research program in AIDS. See also National Institutes of Health.

NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN DEVELOPMENT (NICHD):

An NIH institute that conducts and supports research on the reproductive, developmental and behavioral processes that determine the health of children, adults, families and populations. Thus, NICHD supports clinical research related to the transmission of HIV from infected mothers to their offspring, the progression of disease in HIV-infected infants and children, and the testing of potential therapies and preventatives for this population. See also National Institutes of Health.

NATIONAL INSTITUTES OF HEALTH (NIH):

A multi-institute agency of the Public Health Service, NIH is the federal focal point for health research. It conducts research in its own laboratories and supports research in universities, medical schools, hospitals and research institutions throughout this country and abroad. See also Public Health Service.

NATIONAL LIBRARY OF MEDICINE (NLM):

An NIH institute, NLM is one of three US national libraries. It is the world's largest research library in a single scientific and professional field (i.e., medicine). NLM provides (among others) electronic and print information services relating to HIV/AIDS, including AIDSLINE, AIDSTRIALS, AIDSDRUGS and the AIDS Bibliography. See also AIDS Bibliography; AIDSDRUGS; AIDSLINE; AIDSTRIALS; National Institutes of Health.

NATURAL HISTORY STUDY:

Study of the natural development of something (such as an organism or a disease) over a period of time.

NATURAL KILLER CELLS:

(NK cells). A type of lymphocyte that does not carry the markers to be B cells or T cells. Like cytotoxic T cells, they attack and kill tumor cells and protect against a wide variety of infectious microbes. They are "natural" killers because they do not need additional stimulation or need to recognize a specific antigen in order to attack and kill. Persons with immunodeficiences such as those caused by HIV infection have a decrease in "natural" killer cell activity. See also Antigen; B Lymphocytes; Cytotoxic; Lymphocyte; Null Cell; T Cells.

NCI:

See National Cancer Institute.

NEBULIZED:

See Aerosolized.

NECROLYSIS:

Shedding of surface components of tissue, such as cells from internal body surfaces, due to death of a portion of tissue.

NEF:

One of the regulatory genes of the HIV virus. Three HIV regulatory genes-tat, rev and nef-and three so-called auxiliary genes-vif, vpr and vpu-contain information necessary for the production of proteins that control the virus's ability to infect a cell, produce new copies of the virus or cause disease. See also rev; tat.

NEONATAL:

Concerning the first four weeks of life after birth.

NEOPLASM:

An abnormal and uncontrolled growth of tissue; a tumor.

NEPHROTOXIC:

Poisonous to the kidneys.

NEURALGIA:

A sharp, shooting pain along a nerve pathway.

NEUROLOGICAL COMPLICATIONS OF AIDS:

See Central Nervous System (CNS) Damage.

NEUROPATHY:

The name given to a group of disorders involving nerves. Symptoms range from a tingling sensation or numbness in the toes and fingers to paralysis. It is estimated that 35 percent of people with HIV disease have some form of neuropathy. A "peripheral neuropathy" refers to the peripheral nerves outside the spinal cord.

NEUTRALIZATION:

The process by which an antibody binds to specific antigens, thereby "neutralizing" the microorganism. See also Antibodies; Antigen.

NEUTRALIZING ANTIBODY:

An antibody that keeps a virus from infecting a cell, usually by blocking receptors on the cell or the virus. See also Antibodies; Receptor.

NEUTRALIZING DOMAIN:

The section of the HIV envelope protein gp120 that elicits antibodies with neutralizing activities. See also Antibodies; gp120.

NEUTROPENIA:

An abnormal decrease in the number of neutrophils (the most common type of white blood cells) in the blood. The decrease may be relative or absolute. Neutropenia is associated with acute leukemia, infection, rheumatoid arthritis and other conditions.

NEUTROPHIL:

Also called polymorphonuclear neutrophil (PMN). A white blood cell that plays a central role in defense of a host against infection. Neutrophils engulf and kill foreign microorganisms.

NIAID:

See National Institute of Allergy and Infectious Diseases.

NICHD:

See National Institute of Child Health and Human Development.

NIH:

See National Institutes of Health.

NLM:

See National Library of Medicine.

NON-HODGKIN'S LYMPHOMA:

See Lymphoma.

NSAID:

Nonsteroidal anti-inflammatory (i.e., counteracting inflammation) drug.

NUCLEIC ACID:

Organic substance, found in all living cells, in which the hereditary information is stored and from which it can be transferred. Nucleic acid molecules are long chains that generally occur in combination with proteins. The two chief types are DNA (deoxyribonucleic acid), found mainly in cell nuclei, and RNA (ribonucleic acid), found mostly in cytoplasm. Each nucleic acid chain is composed of subunits called nucleotides, each containing a sugar, a phosphate group, and one of four bases:

adenine (symbolized A), guanine (G), cytosine (C) and thymine (T). RNA contains the sugar ribose instead of deoxyribose and the base uracil (U) instead of thymine. The specific sequences of nucleotides constitute the cell's genetic information:

Each three-nucleotide DNA sequence specifies one particular amino acid. The long sequences of DNA nucleotides thus correspond to the sequences of amino acids in the cell's proteins. In order to be expressed as protein, the genetic information is carried to the protein-synthesizing machinery of the cell, usually in the cell cytoplasm. Forms of RNA mediate this process. DNA not only provides information, but also specifies its own exact replication. The cell replicates its DNA by making a complementary copy of its exact nucleotide sequence:

T for every A, C for every G, G for every C, A for every T. Although the triplet nucleotide code seems to be universal, the actual sequences of the nucleotides vary according to the species and individual. See also Gene; Genetic Engineering; Mutation.

NUCLEOLI:

Bodies in the nucleus that become enlarged during protein synthesis and contain the DNA template for ribosomal RNA. See also Ribonucleic Acid; Ribosome.

NUCLEOSIDE ANALOG:

Nucleosides are related to nucleotides, the subunits of nucleic acids; however, they do not carry the phosphate groups of the nucleotides. Nucleoside analogs generally are synthetic compounds similar to one of the components of DNA or RNA; a general type of antiviral drug (e.g., acyclovir and AZT). See also Acyclovir; AZT; Nucleic Acid.

NUCLEUS:

1. The central controlling body within a living cell, usually a spherical unit enclosed in a membrane and containing genetic codes for maintaining the life systems of the organism and for issuing commands for growth and reproduction. 2. The nucleus of a cell is an organelle (i.e., a cellular organ) that is essential to such cell functions as reproduction and protein synthesis. It is composed of nuclear sap and a nucleoprotein-rich network from which chromosomes and nucleoli arise and is enclosed in a definite membrane. See also Nucleoli.

NULL CELL:

A lymphocyte that develops in the bone marrow and lacks the characteristic surface markers of the B and T lymphocytes. Null cells represent a small proportion of the lymphocyte population. Stimulated by the presence of antibody, null cells can attack certain cellular targets directly and are known as "natural killer" or NK cells. See also Lymphocyte.