[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.

[Thyroid and C-cell system function during prolonged rotation (morphobiochemical research)]. / Sostoianie shchitovidnoi zhelezy i sistemy C-kletok pri dlitel'nom vrashchenii (morfobiokhimicheskoe issledovanie).

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. The centrifugation led to a higher activity to C-cells, an increased rate of thyro-calcitonin (TCT) synthesis and excretion, i.e. C-cell degranulation, and a significant (two-fold) increase of TCT in plasma. The stimulation effect of the TCT-producing system persisted during 7-post-rotation days and was very distinct in the animals exposed to 2.0 G. There were no morphological changes in the parathyroid glands or in the PTH concentration in the plasma.

[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.

[Effect of long-term hypokinesia on the C-cell system of the thyroid gland]. / Vliianie dlitel'noi gipokinezii na sistemu C-kletok shchitovidnoi zhelezy.

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). The decline in the function of C-cells during hypokinesia may be one of the factors leading to increased calcium elimination from bones. In conclusion, the state of C-cells in animals exposed to weightlessness and hypokinesia is compared.

[Morphological characteristics of the thyroid glands of Macaca rhesus monkeys normally and in different types of hypokinesia]. / Morfologicheskie osobennosti shchitovidnykh zhelez obez'ian makaka reuz v norme i pri razlichnykh vidakh gipokinezii.

Thyroid glands and C-cells of Macaca rhesus were examined histologically, electron microscopically and morphometrically. The examinations were performed on 6 intact and 7 hypokinetic rhesus monkeys which were kept in a suspension device for 2 months, small cages for 2 months or in a head-down position (7 days in a horizontal position and then 11 days in a head-down position at -6 degrees). The experiment with a diminished motor activity and a normal support function of the lower limbs (maintenance in small cages), in spite of its long duration, produced no structural changes in the parenchyma or C-cells. The 18-day bed rest test was followed by a hypofunction of the thyroid gland, inhibition of hormonal synthesis and secretion without distinct changes in C-cells. Unlike previous experiments, the suspension study led to hyperplasia and hypertrophy of C-cells and increase of their nuclear volume. Activation of C-cells can be regarded as an adaptive reaction aimed at stabilizing bone calcium.

[State of the thyroid gland C-cells in rats after a flight on Kosmos-type biosatellites (based on morphological study data)]. / Sostoianie C-kletok shchitovidnoi zhelezy u krys posle poleta na biosputnikakh tipa "Kosmos" (po dannym morfologicheskogo issledovaniia).

Calcitonin-secreting cells (C-cells) of the thyroid glands from 51 SPF Wistar rats flown for 18.5 to 22 days aboard biosatellites Cosmos-605, 782 and 936 and sacrificed 4.5--13 hours, 1--2 and 25--27 days after recovery were examined histologically and karyometrically. Vivarium (57) and synchronous (58) rats were used as controls. Variations in the nuclear volume of C-cells and their density were shown to depend on the experimental conditions and time interval elapsed after recovery. Morphological changes in C-cells were assumed to be associated with alterations in calcium metabolism during an exposure of rats to weightlessness, artificial gravity and Earth gravity.

[Effect of weightlessness and artificial gravitation on thyroid gland morphology]. / Vliianie nevesomosti i iskusstvennoi gravitatsii na morfologiiu shchitovidnoi zhelezy.

The investigation of the thyroid gland was carried out in Wistar rats, SPF colony 4.5--13 h and 25 days after a 18.5 days flight on board the space biosatellite "Cosmos-936". In animals subjected to weightlessness, moderate symptoms of the thyroid hypofunction were observed, statistically significant decrease in number and volume of the nuclei in calcitonin-secreting cells (C-cells) was especially pronounced during 4.5--9 h after landing. Similar but less pronounced changes were observed in C-cells of the rats subjected to artificial conditions of space flight, besides weightlessness. The similarity of the changes in the animals of both groups made it possible to connect the increasing amount of C-cells and the morphological symptoms of their functional inhibition with the effect of weightlessness and hypokinesia. During the space flight, the animals were kept under the conditions of artificial gravitation on board the biosatellite and therefore morphological peculiarities specific for the earth conditions were preserved in C-cells and the thyroid gland. Thus, it was concluded that artificial gravitation prevented the development of the thyroid changes which appeared under the influence of weightlessness.

[Spermatogenesis in dogs during chronic gamma irradiation over years and in the aftereffect period]. / Spermatogenez u sobak pri mnogoletnem khronicheskom gamma-obluchenii i v periode posledeistviia.

Morphological parameters of spermatogenesis of 60 test and 12 control dogs exposed to a 6-year irradiation with total doses of 21 to 1140 rad were studied. The capacity for reparative regeneration of testes was maintained during the 5-6 years of irradiation at a dose rate of 0.06 and 0.17 rad/day. Early signs of radiation injury of testes were clearly observed during the first years of irradiation at a dose rate of 125 rad/year and progressively developed with an increase in the total dose. Inhibition of spermatogenesis reached maximum (atrophy of the spermatogenic epithelium, depletion of canaliculi) by the end of the first year of combined irradiation (190 rad/year). Spermatogenesis returned to normal in the animals that received a total dose of 570 rad during a 3-year irradiation exposure and were sacrificed 4.5 years after the onset of the experiment.

[State of spermatogenesis in rats exposed on the Cosmos-690 biosatellite]. / Sostoianie spermatogeneza u krys, éksponirovannykh na biosputnike "Kosmos-690".

A morphological examination of sex glands of 30 male rats flown aboard the biosatellite Cosmos-690 was carried out on the 1st-2nd and 26-27th postflight days. A combined exposure to the 20-day space flight and prolonged gamma-irradliation with doses of 220, 800 and 955 rad brought about a significant decrease of the weight of testes, postradiation death of spermatogonia and essential structural changes in the spermatogenic epithelium whose level depended on the radiation dose and the postirradiation time. A comparison of weights and histologies of testes from the flight and synchronous rats did not reveal a modifying effect of weightlessness since no statistically significant differences in the testicular weight, quantitative assay of the occurrence of individual elements of the spermatogenic epithelium and time of manifestation of reparative processes were observed.

State of spermatogenesis in rats flown aboard the biosatellite Cosmos-690.

Testes of 30 rats flown aboard the biosatellite Cosmos-690 for 20.5 d and 30 rats kept in a ground-based experiment, which simulated all flight except weightlessness and accleration, were examined morphologically. On the 10th experimental day the rats were exposed for 24 h to gamma irradiation from a Cs137 source at doses of 220, 800, and 955 rad. Tests from 60 nonirradiated rats that remained in the vivarium were used as controls. On the 1st-2nd and 26-27th post-experimental days the animals showed a significant decrease in the weight of testes, post-radiation death of spermatogonia, and important structural changes in the spermatogenic epithelium, whose level depended on the dose of irradiation and the time elapsed after the exposure. No significant differences in the weight of testes, frequency of occurrence of individual components of the spermatogenic epithelium, and time of emergence of reparative processes were noted. No modifying effect of space flight factors on the development of radiation-induced changes in the spermatogenic epithelium of rats was found.

[Effect of 22-day space flight factors on the state of the sex glands and reproductive capacity of rats]. / Vliianie faktorov 22-sutochnogo kosmicheskogo poleta na sostoianie polovykh zhelez i reproduktivnuiu sposobnost' krys

The paper presents the results of the morphological examination of tests of the Wistar rats flown for 22 days onboard the biosatellite Cosmos-605. Histological, histochemical, electron microscopic and biometric investigations of sex glands carried out 24-48 hours and 26-27 days postflight show that an exposure of the rats to weightlessness and other space flight factors induced no morphological changes in the spermatogenic tissue or disorders in the spermatogenic process of the rats. The offspring of male rats that were exposed to 22-day weightlessness did not differ from the controls with respect to the number of the newborns, their weight at birth, weight gain during the first postnatal month, resistance to hypoxia, etc.

Effect of space flight factors on the mammal: experimental-morphological study.

On the basis of a morphological examination of 27 rats that made a space flight and were sacrificed on the 1st-2nd and 26-27th days postflight, it has been shown that the 22-d space flight has produced no significant changes in the structural organization of vital organs of the animals. However, a space flight exposure is not indifferent for animals and leads to the development of morphologically visible changes in individual organs and systems (musculo-skeletal system, hemopoietic organs, hypothalamic-pituitary-adrenal system, renal juxtaglomerular system). The detected changes are reversible, nonspecific, and develop in animals exposed to ground-based hypokinetic and other stress experiments.

[Morphological effects in rats following a 22-day space flight]. / Morfologicheskie éffekty u krys posle 22-sutochnogo kosmicheskogo poleta

A morphological examination of 27 rats flown onboard the biosatellite and sacrificed on the 1st-2nd and 26-27th postflight days demonstrated no significant changes in the structural organization of the vital organs and systems of the animal body. It was, however, found that the space exposure induced morphologically detectable changes in the musculo-skeletal system, hemo- and lymphopoiesis, hypothalamic-pituitary-adrenal system and the juxtaglomerular apparatus of the kidneys. The changes were reversible and nonspecific, and could be seen in animals exposed to ground-based hypokinetic and other stress experiments. Postflight the animals developed some reactions that were similar to those in humans. This helps to identify the morphological substrate of certain changes in the human body and to investigate their pathogenesis.

[Characteristics of morphological reactions in dog internal organs and endocrine glands during 6-year gamma irradiation]. / Osobennosti morfologicheskikh reaktsii vnutrennikh organov i éndokrinnykh zhelez sobak pri 6-letnem gamma-obluchenii

Dogs were exposed to six-year gamma-irradiation with doses of 21-1140 rad/year; pathomorphological changes were studied in testicles thyroid gland, adrenals, liver and kidneys. The level of morphological changes in the organs during the six-year exposure was dissimilar and depended on the radiosensitivity of a specific organ, dose rate and acute irradiations that were applied during the experiment. In testicles morphological changes (reduction of layers of the spermatogenous epithelium, decrease of the number of spermatozoids in testicular canals) appeared during the first year of irradiation at a dose rate of 0.34 rad/day. Later, these changes progressed and by the end of the six-year exposure were followed by a distinct sclerosis of the interstitial tissue and hyperplasia of Leydig's cells. In the thyroid gland signs of the hypofunctional state were seen by the end of the second year of irradiation at a dose rate of 0.34 rad/day and persisted afterwards. In adrenals hypertrophy of the bundle and glomerular zones were observed during the second-fourth years of irradiation at a dose rate of 0.34 rad/day. As irradiation proceeded hyperplastic processes developed in the thyroid gland and adrenals (adenomatous nodes in the thyroid gland, adenomatous hyperplasia in the adrenal cortex). Vacuolar and fat dystrophy of hepatocytes and disturbed permeability of glomerular capillaries in the kidneys were detected only at the end of the third year of irradiation. During the fifth and, particularly, the sixth year of the exposure sclerotic changes in the liver vessels, hyalinosis of small arteries and nephrosclerotic foci in the kidneys were found.