[Experiments using rats on Kosmos biosatellites: morphologic and biochemical studies]. / Eksperimenty s krysami na biosputnikakh "Kosmos": morfologicheskie i biokhimicheskie issledovaniia.

Results of morphological and biochemical investigations of rats flown on Cosmos biosatellites are discussed. It is emphasized that most changes occurring during exposure to microgravity are directly or indirectly related to lower musculoskeletal loads which in turn produce deconditioning of different physiological systems and organism as a whole. It is concluded that this deconditioning is associated with both metabolic and structural changes.

[Experiments on rats exposed in the Cosmos 1667 biosatellite (goals, protocols, results)]. / Eksperiment na krysakh, éksponirovannykh na biosputnike "Kosmos-1667" (osnovnye zadachi, usloviia provedeniia i rezul'taty).

Morphobiochemical investigations of the rats flown on the biosatellite Cosmos-1667 have shown that the 7-day space flight produces shifts in different systems, organs and tissues which reflect adaptive processes to microgravity. Early signs of structural, functional and metabolic rearrangement can be detected in the musculoskeletal apparatus, hemopoietic system, lymphoid organs, neurohormonal systems, i.e., in the systems and organs that develop changes during long-term flights. The rates of adaptation to microgravity are different not only in various systems and organs but also within the same tissues. Most shifts that emerge at an early stage of adaptation to microgravity progress with flight time but some of them develop to a full extent after the 7-day flight. The specific feature of the early stage of adaptation to microgravity is the lack of significant changes in blood biochemistry in the presence of structural and metabolic changes in tissues. This fact gives evidence that the mechanisms maintaining homeostasis at the organism level are not as yet disrupted during 7 days of flight.

[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.

[Head-down tilt hypokinesia in monkeys: a morphological study]. / Antiortostaticheskaia gipokineziia u obez'ian: morfologicheskoe issledovanie.

Morphological examinations of rhesus monkeys (Macaca mulatta) exposed to head-down tilt for 7 and 19 days are summarized. The major changes detected in various systems, organs and tissues are described. The changes are thought to be of different origin and caused by blood redistribution, hypokinesia per se and concomitant stress. It is emphasized that head-down tilt is one of the most adequate methods for simulating effects of zero-g in monkeys.

[Adrenal reactions of monkeys to antiorthostatic hypokinesia]. / Osobennosti reaktsii nadpochechnikov obez'ian v usloviiakh antiortostaticheskoi gipokinezii.

The following experiments were performed to study the morphology of the adrenals of male rhesus monkeys: six monkeys were exposed to clinostatic hypokinesia for 7 days and then to head-down tilt at -6 degrees for 12 days; two monkeys were exposed only to head-down tilt for 7 days and 5 monkeys were used as controls. The adrenals exhibited changes of three types: stress-reaction manifestations, activation of the glomerular area of the cortex, and synchronization of the medullary matter to noradrenaline production. All these changes reflect adaptive reactions of the animal body to head-down tilt.

[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.

[Morphometric study of the adrenal medulla of rats in long-term hypokinesia]. / Morfometricheskoe issledovanie mozgovogo veshchestva nadpochechnikov krys pri dlitel'noi gipokinezii.

Using Wood's differential staining, norepinephrine- and epinephrine-secreting cells of the adrenal medulla of 36 Wistar male rats exposed to 1 to 5.5-month hypokinesia were measured karyometrically. After 2 month hypokinesia the nuclear volume of norepinephrine-secreting cells increased significantly. After 5.5-month hypokinesia no dystrophic changes were seen in the adrenal medulla.

[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.

[Morphological effects of weightlessness and their pathogenesis]. / Morfologicheskie éffekty nevesomosti i ikh patogenez.

The paper summarizes the results of morphological and histochemical investigations of rats flown onboard the Soviet biological satellites of the Cosmos series. The changes in different functional systems and organs have been found to be related. The paper contains hypotheses concerning the pathogenesis of the changes detected. It is emphasized that most changes are induced by a reduction of load upon the musculoskeletal system in weightlessness.

[Effect of weightlessness and artificial gravitation on morphological manifestations of the adrenal cortex reaction in rats after space flight on board the biosatellite "Cosmos-936"]. / Vliianie nevesomosti i iskusstvennoi sily tiazhesti na morfologicheskie proiavleniia reaktsii kory nadpochechnikov krys posle poleta na biosputnike "Kosmos-936".

Comparing the changes revealed in the adrenals of rats subjected to weightlessness and artificial gravitation, it has been stated that rotation of the animals in the centrifuge, while flying (with an acceleration of lg), prevents development of morphological stress reaction as a response to landing. After the effect of weightlessness, return to normal gravitation is accompanied with definite signs of an acute stress-reaction in the rat adrenal cortex. Differences in the adrenal reaction of the animals of the groups compared speak in favour of the fact that application of artificial gravitation in an orbital space flight contributes to level the changes resulting from weightlessness and, hence, increase the organism's stability to stress effects, while returning to the Earth.

[Reactions of the adrenal cortex to immobilization stress in intact animals and against a background of hypokinesia]. / Ob osobennostiakh reaktsii kory nadpochechnikov na immobilizatsionnyi stress u intaktnykh zhivotnykh i na fone gipokinezii.

Morphological investigation of the rat adrenal cortex and corticosterone contents in the blood plasma demonstrated certain peculiarities in the adrenal reaction to the primary and repeated immobilization stress in intact animals and after hypokinesia. It has been stated that morphological manifestation to an acute stress reaction kinesia is less pronounced than at an analogous single effect. Investigation on corticosterone content in blood plasma revealed certain functional peculiarities in the adrenal cortex reactions in different variants of the experiments. Five hours after the beginning of the stress, corticosterone content was increased only at the initial immobilization, while at repeated stimulations during the same time it did not differ from the control. Changes in functional possibilities of the adrenal cortex in response to a repeated stimulation and in response to a new stimulation in animals previously adapted to another type of stress are discussed.

[Functional state of the posterior lobe of the neurohypophysis of rats exposed aboard the biosatellite "Cosmos-936" (according to the results of morphologic studies)]. / O funktsional'nom sostoianii zadnei doli neirogipofiza krys, éksponirovannykh na biosputnike "Kosmos-936" (po dannym morfologicheskogo issledovaniia).

A comparative evaluation on some morphological indices of functional state of the posterior neurohypophysis was performed in rats subjected to weightlessness and artificial gravitation for 18.5 days on board the biosatellite "Cosmos-936". The data of the investigation were compared to those obtained on the test animals used for terrestial series of the experiment where all the factors of space flight, except weightlessness were imitated. As the analysis of morphological data demonstrated, a prolonged effect of weightlessness results in a considerable decrease in the number of the neurosecretory cumulative corpuscles (Herring's bodies), in decreasing volume of nuclei and size of pituicytes. A suggestion is made on decreasing basal level of functional activity of the hypothalamo-hypophyseal neurosecretory system under the conditions of weightlessness. Administration of artificial gravitation (lg) levels partly the changes produced by weightlessness and ensure a higher level of functioning in the neurosecretory system.

[Morphological study of the adrenals of rats exposed on the Kosmos-690 satellite]. / Morfologicheskoe issledovanie nadpochechnikov krys, éksponirovannykh na sputnike "Kosmos-690".

Adrenals of 12 rats flown aboard the biosatellite Cosmos-690 and 30 rats used in the ground-based experiments Control-1 and Control-2 were studied morphologically. The animals were sacrificed on the 2nd and 27th days after completion of the experiments (i. e., on the 12 and 37th days after irradiation at a total dose of 800 rad). A comparative study of morphological changes in the adrenals of flight and control rats did not show any distinct differences. It is therefore concluded that space flight factors did not produce a significant effect on the adrenal response to irradiation at a dose of 800 rad.

[Morphologic study of rat adrenals following flight aboard biosatellites "Cosmos-605" and "Cosmos-782"]. / Morfologicheskoe issledovanie nadpochechnikov krys posle poleta na biosputnikakh "Kosmos-605" i "Kosmos-782".

Dynamics of morphological changes of the rat adrenals was investigated on the first day and 25--27 days after a prolonged exposure to weightlessness. Analysing the general histological picture of the adrenal cortex during the first hours of the flight (presence of a subglomerular sudanophilic layer and distinct zones in other cortical parts), it is possible to conclude that by the completion of the flight the cortical substance has reached a definite degree of normalization, hence the animals have adopted to the flight conditions. Morphological signs of elevated functional cortical activity 9--11 h after the flight, such as enlarged nuclear volume of the fascicular zone cells and delipoidization of the internal parts of the cortex could be treated as manifestation of an acute stress-reaction developing in the animals after landing. Evaluating morphological manifestation of the acute stress-reaction observed in animals at transition from weightlessness to the earth level of gravitation, it is possible to conclude that there are no signs of depletion in the adrenal cortical function and hence, adaptive possibilities in the organism are preserved after a prolonged exposure to weightlessness.

[Combined action of weightlessness and ionizing radiation on the body of rats (based on data from morphological studies)]. / O sochetannom deistvii nevesomosti i ioniziruiushchego izlucheniia na organizm krys (po dannym morfologicheskikh issledovanii).

The combined effect of weightlessness and ionizing radiation (24 hour exposure to Cs-137 at a total dose of 800 rad) was investigated morphologically in Cosmos-690 flight, synchronous and vivarium rats. Irradiation-induced lesions prevailed in both groups of rats. Comparative study of changes in flight and control rats showed that weightlessness and other space flight factors did not induce any new, previously unknown effects as compared with the exposure on the Earth; they did not exert a significantly aggravating effect on the development of radiation-induced lesions.

[Morphological manifestations of the functional shifts in the hypothalamo-hypophyseal neurosecretory system and kidneys of rats exposed to the action of space flight factors]. / Morfologicheskie proiavleniia funktsional'nykh sdvigov v gipotalamo-gipofizarnoi neirosekretornoi sisteme i pochkakh krys pri deistvii faktorov kosmicheskogo poleta.

The hypothalamic-pituitary neurosecretory system and the kidneys of rats flown for 22 days and sacrified on the R+1 and R+26 days were studied morphologically. By histological, histochemical and morphometric measurements an increased activity of the hypothalamic-pituitary neurosecretory system and the juxtaglomerular apparatus of the kidneys was shown. The changes were reversible and by the R+26 day returned to normal. The above changes can be induced not only by space flight effects but also by readaptation to 1 g.