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Subject: r
Date: Thu, 12 Oct 95 23:34 PDT (147 lines of text)

RANDOMIZED TRIAL:

A study in which participants are randomly assigned to either a treatment arm or placebo arm of a clinical trial. See also Clinical Trial; Placebo.

REACTOGENICITY:

The capacity to produce adverse reactions.

RECEPTOR:

A molecule on the surface of a cell that serves as a recognition or binding site for antigens, antibodies or other cellular or immunological components. See also Antibodies; Antigen.

RECOMBINANT:

An organism whose genome contains integrated genetic material from a different organism. See also Genome.

RECOMBINANT DNA:

See Biotechnology; Genetic Engineering.

REGULATORY GENES:

As related to HIV:

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

REGULATORY T CELLS:

T cells that direct other immune cells to perform special functions. The chief regulatory cell, the CD4+ T cell or T helper cell, is HIV's chief target. See also CD4 (T4) or CD4+ Cells; T Cells.

REMISSIONS:

The lessening of the severity or duration of outbreaks of a disease, or the abatement (diminution in degree or intensity) of symptoms altogether over a period of time.

RENAL:

Pertaining to the kidneys.

RETICULOENDOTHELIAL CELLS:

A system of interstitial cells that includes all the phagocytic cells, which trap and consume foreign agents, except the leukocytes circulating in the bloodstream. This system forms a network throughout the body and is another of the body's defense systems against invading organisms in the connective tissues of the body. See also Leukocytes; Phagocyte.

RETINA:

Light-sensitive tissue at the back of the eye that transmits visual impulses via the optic nerve to the brain.

RETINITIS:

Inflammation of the retina, linked in AIDS to CMV infection. Untreated, it can lead to blindness. See also Cytomegalovirus; Retina.

RETROVIRUS:

HIV and other viruses that carry their genetic material in the form of RNA and that have the enzyme reverse transcriptase. Like all viruses, HIV can replicate only inside cells, commandeering the cell's machinery to reproduce. Like other retroviruses, HIV uses the enzyme called reverse transcriptase to convert its RNA into DNA, which is then integrated into the host cell DNA. See also DNA; Reverse Transcriptase; Ribonucleic Acid.

REV:

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 nef; tat.

REVERSE TRANSCRIPTASE:

This enzyme of the HIV virus (and other retroviruses) converts the single-stranded viral RNA into DNA, the form in which the cell carries its genes. The antiviral drugs approved in the US for the treatment of HIV infection-AZT, ddC and ddI-all work by interfering with this stage of the viral life cycle. See also AZT; ddC; ddI; DNA; Ribonucleic Acid.

RIBONUCLEIC ACID (RNA):

1. A nucleic acid, found mostly in the cytoplasm of cells, that is important in the synthesis of proteins. The amount of RNA varies from cell to cell. RNA, like the structurally similar DNA, is a chain made up of subunits called nucleotides. In protein synthesis, messenger RNA (mRNA) replicates the DNA code for a protein and moves to sites in the cell called ribosomes. There, transfer RNA (tRNA) assembles amino acids to form the protein specified by the messenger RNA. Most forms of RNA (including messenger and transfer RNA) consist of a single nucleotide strand, but a few forms of viral RNA that function as carriers of genetic information (instead of DNA) are double-stranded. 2. A nucleic acid associated with the control of chemical activities inside a cell. One type of RNA transfers information from the cell's DNA to the protein-forming system of a cell outside the nucleus. Some viruses (e.g., HIV) carry RNA instead of the more usual genetic material DNA. See also Cytoplasm; DNA; Retrovirus.

RIBOSOME:

A cytoplasmic organelle composed of ribonucleic acid and protein that functions in the synthesis of protein. Ribosomes interact with messenger RNA and transfer RNA to join together amino acid units into a polypeptide chain according to the sequence determined by the genetic code. See also Cytoplasm; Ribonucleic Acid.

RNA:

See Ribonucleic Acid.

ROUTE OF ADMINISTRATION:

See Administration.

RYAN WHITE CARE ACT:

The Ryan White Comprehensive AIDS Resources Emergency (CARE) Act of 1990 represents the largest dollar investment made by Congress to date specifically for the provision of services for people with HIV infection. The purpose of the Act is "to improve the quality and availability of care for individuals and families with HIV disease."