Thymosin: Thymosin. A family of heat-stable, polypeptide hormones secreted by the thymus gland. Their biological activities include lymphocytopoiesis, restoration of immunological competence and enhancement of expression of T-cell characteristics and function. They have therapeutic potential in patients having primary or secondary immunodeficiency diseases, cancer or diseases related to aging.Thymus Hormones: Humoral factors secreted by the thymus gland. They participate in the development of the lymphoid system and the maturation of the cellular immune response.Thymus Extracts: Extracts of the thymus that contain specific, but uncharacterized factors or proteins with specific activities; three distinct substances are already known: thymotoxin, thymin and thymosin.Actins: Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle.