[Studies of the morphology of the thyroid gland and thyroid hormone levels in the blood of rats in experiments on "Kosmos-1667" and "Kosmos-1887"].

Using histological, electron microscopic, and biochemical (measurement of total thyroxine, free thyroxine and triiodothyronine in plasma) method, thyroid glands of 17 male rats of the Wistar SPF strain flown for 7 days on Cosmos-1667 and for 13 days on Cosmos-1887 were investigated. It was found that a longer exposure to space flight effects (for 13 days) led to a thyroid activity decline (significant reduction of thyrocyte size and nuclear area, accumulation of colloid drops in the cytoplasm, decrease of iodinated thyroglobulins in the colloid, etc.) together with a substantial decrease of T4 and T3 in plasma.

[The C-cell system of the thyroid in rats following a flight on the Kosmos 1667 biosatellite].

Histological, electron-microscopic and morphometric investigations of the thyroid gland of Wistar SPF male rats (aged 3 months) flown for 7 days on Cosmos-1667 showed that its parenchyma was functionally active and changed but little as compared to the controls. However, at an acute stage of adaptation to microgravity C-cells showed morphological signs of their functional decline: the number of low activity cells and cells whose cytoplasm contained secretory granules increased, the volume of nuclei decreased significantly (by 16.2% as compared to the control), and dystrophic changes seen ultrastructurally appeared.

[Thyroid and C-cell system function during prolonged rotation (morphobiochemical research)].

The thyroid and parathyroid glands of 65 Wistar rats centrifuged for 30 days at 1.1 and 2.0 G were examined histologically and biochemically.

[Structural characteristics of the thyroid and parathyroid C cells of monkeys during head-down tilt hypokinesia].

Eight monkeys Macaca rhesus were exposed to head-down tilt for 7 days and to clinostatic hypokinesia for 7 days with subsequent 12-day head-down tilt. C cells of the thyroid gland and the parathyroid glands of 5 control and 8 experimental monkeys were investigated histologically, morphometrically and electron-microscopically. On the 7th tilt day the C cell population increased, their nuclei grew significantly, synthesis activated, and secretory granules accumulated.

[Effect of long-term hypokinesia on the C-cell system of the thyroid gland].

The state of C-cells of the thyroid gland of Wistar rats during prolonged (30-165 days) hypokinesia was examined. Histo- and morphometric data pointed to a gradual decline in the function of C-cells during hypokinesia and its return to normal after 2-month readaptation. The decline was most distinct by hypokinesia day 90 (significant decrease in the number and size of nuclei, prevalence of small cells with densely packed granules in the cytoplasm).