[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"]. / Morfologiia shchitovidnoi zhelezy i soderzhanie tireoidnykh gormonov v krovi u krys v éksperimentakh na biosputnikakh "Kosmos-1667" i "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 above structural and functional changes in the thyroid gland and hormonal status are characteristic of a moderate stress-reaction and reflect variations of the early and intermediate stages of adaptation to microgravity during 7- and 13-day space flights.

[The C-cell system of the thyroid in rats following a flight on the Kosmos 1667 biosatellite]. / Sistema C-keltok shchitovidnoi zhelezy u krys posle poleta na biosputnike "Kpsmos-1667".

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. These observations together with the results obtained in prolonged animal flights suggest that in microgravity the synthesis and excretion of the hormone calcitonin diminish. In combination with other factors, the functional decline of C-cells inhibits bone neoformation and enhances bone resorption.

[Structural characteristics of the thyroid and parathyroid C cells of monkeys during head-down tilt hypokinesia]. / Strukturnye osobennosti C-kletok shchitovidnoi zhelezy i parashchitovidnykh zhelez obez'ian pri antiortostaticheskoi gipokinezii.

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. By day 19 most C cells were in the secretion stage. Morphological signs of an increased functional activity of the thyroid gland were seen on experimental day 7 and those of the parathyroid gland on day 19, both in light and electron microscopies. Taking into account the antagonism of C cells and parathyroid glands, it can be assumed that the hypocalcemic effect of calcitonin plays a part in the stimulation of parathyroid glands during head-down tilt.

[Ultrastructural localization of thyrocyte acid phosphatase in the presence of thyrocyte hyperfunction in rats]. / Ul'trastrukturnaia lokalizatsiia kisloi fosfatazy v tireotsitakh pri giperfunktsii shchitovidnoi zhelezy krysy.

Acid phosphatase was found by electron microscopy in the lysosomes which appeared in great numbers in the follicular cells of rat hyperplastic thyroid gland. The other types of granules (mature secretory granules and lipids) whose amounts were also greatly increased in cases of functional thyrocyte strain were also nonreactive. The lysosomes were subdivided into three main groups according to distribution of the reaction product: the lysosomes with dense homogeneous deposit and with deposit in the form of densely or loosely packed dark round granules. The lysosome heterogeneity was apparently connected with their different functions also found within the colloid droplets in the form of inclusions of rarely located dark granules. The authors believe such granules to be the result of the merging of the colloid droplets and lysosomes. The acid phosphatase of the latter participated in the hydrolysis of the product of cell secretion with the formation of active substances.

[Electron-cytochemical and morphometric study of the activity of several enzymes in thyrocyte metochondria during malignant degeneration]. / Elektronno-tsitokhimicheskoe i morfometricheskoe issledovanie aktivnosti nekotorykh fermentov v mitokhondriiakh tireotsitov v protesesse malignizatisii

Cytochrome oxidase and succinic dehydrogenase activities were studied in the mitochondria of rat thyroid cell during experimental malignization by means of the electron-cytochemical and morphometric methods. The activity of these enzymes in the mitochondria changed depending on the stage of malignization: at the early stages it approached the normal activity, and at the later stages (precancer)--it decreased and approached the mitochondrial activity of cancer cells. A sharp decrease in the activity of the enzymes under study in the morphologically changed mitochondria of cancer cells may characterize their qualitative changes.