Genus of non-oncogenic retroviruses which establish persistent infections in many animal species but are considered non-pathogenic. Its species have been isolated from primates (including humans), cattle, cats, hamsters, horses, and sea lions. Spumaviruses have a foamy or lace-like appearance and are often accompanied by syncytium formation. SIMIAN FOAMY VIRUS is the type species.

A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.

Synthetic or natural materials, other than DRUGS, that are used to replace or repair any body TISSUES or bodily function.

The testing of materials and devices, especially those used for PROSTHESES AND IMPLANTS; SUTURES; TISSUE ADHESIVES; etc., for hardness, strength, durability, safety, efficacy, and biocompatibility.

Family of RNA viruses that infects birds and mammals and encodes the enzyme reverse transcriptase. The family contains seven genera: DELTARETROVIRUS; LENTIVIRUS; RETROVIRUSES TYPE B, MAMMALIAN; ALPHARETROVIRUS; GAMMARETROVIRUS; RETROVIRUSES TYPE D; and SPUMAVIRUS. A key feature of retrovirus biology is the synthesis of a DNA copy of the genome which is integrated into cellular DNA. After integration it is sometimes not expressed but maintained in a latent state (PROVIRUSES).

Retroviruses that have integrated into the germline (PROVIRUSES) that have lost infectious capability but retained the capability to transpose.

The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.

Virus diseases caused by the RETROVIRIDAE.