SOMATOTROPIN INFLUENCE ON THE THYMUS IN AGING

免疫功能随着年龄的增长而下降，这一点可以通过与年龄相关的 增加对感染、肿瘤疾病的易感性， 自身免疫性疾病 免疫系统衰老的原因 还不为人所知，但很可能，在很大程度上， 由于胸腺的退化和 血液中的胸腺激素浓度，开始于性行为后 成熟，并通过老年的进展。 已经观察到 垂体分泌的生长激素也随着年龄的增长而减少 生长激素具有促胸腺作用 这些观察导致 这一假设可能是通过减少生长激素的产生， 腺垂体在胸腺体积的进行性减小中起作用 以及胸腺激素的分泌。 拟议研究的目的是进一步表征 生长激素对小鼠胸腺和免疫系统的影响 老狗 具体目的是：1）在正常犬中确定 胸腺激素胸腺素α 1和胸腺素的血清浓度 β 4从出生到老年; 2）测定血清胸腺素α 1， 中年犬在治疗前、治疗中和治疗后的胸腺素β 4浓度 生长激素给药; 3）观察胸腺细胞超微结构 在年轻狗和中年狗的上皮细胞之前和之后 生长激素治疗 如果对老龄犬给予生长激素会刺激胸腺， 增加其生产的胸腺激素，它可能会产生影响， 与免疫系统衰老有关的疾病的发病率或严重程度 系统 在拟议的实验中获得的信息将 为生长激素的进一步实验提供基础 给药至具有自发发生的自身免疫性或 肿瘤条件。

Immune function decreases with age as evidenced by the age-correlated increase in susceptibility to infections, neoplastic diseases, and autoimmune diseases. The causes of the senescence of the immune system aren't understood but it is associated with and, probably, in large part, due to the involution of the thymus gland and the decrease in the concentration of thymic hormones in the blood which begins after sexual maturation and progresses through old age. It has been observed that growth hormone secretion by the pituitary also decreases with advancing age and that growth hormone has a thymotrophic effect. These observations lead to the hypothesis that perhaps decreasing production of growth hormone by the adenohypophysis plays a role in the progressive decrease in thymus size and the secretion of thymus hormones with age. The objective of the proposed research is to further characterize the influence of growth hormone on the thymus gland and immune system of the aging dog. The specific aims are to: 1) determine in normal dogs the serum concentration of the thymus hormones thymosin alpha 1 and thymosin beta 4 from birth through old age; 2) determine serum thymosin alpha 1 and thymosin beta 4 concentration in middle-aged dogs before, during and after growth hormone administration; and 3) evaluate the ultrastructure of thymic epithelial cells in young dogs and in middle-aged dogs before and after growth hormone treatment. If growth hormone administration to aging dogs will stimulate the thymus to increase its production of thymus hormones, it may have an impact on the incidence or severity of diseases associated with senescence of the immune system. The information gained in the proposed experimentation would provide the basis for further experimentation on growth hormone administration to aging dogs with spontaneously occurring autoimmune or neoplastic conditions.