[Histological and histomorphometric examination of tibiae of Mongolian gerbils Meriones unguiculatus of different age as possible objects in space experiments].

Histological and histomorphological examinations of tibiae taken from young (body mass = 27 g) and adult (body mass = 73 g) male Mongolian gerbils Meriones unguiculatus was fulfilled. Tibial bones of Mongolian gerbils have a hockey-stick form and are extremely thin. Morphologically the gerbil's tibial bone is very similar to that of rat.

[Histological study of the visceral organs of Mongolian gerbil Meriones unguiculatus as a subject in spaceflight experiments].

Survey histological study of the heart, lung, liver, kidney, pancreas, adrenals, thymus, spleen, testicles of the Mongolian gerbil Meriones unguiculatus with a body mass of about 27 g showed their macro- and microscopic similarity with the organs of laboratory rats and mice notwithstanding some slight differences. For instance, the ascending knee of Hengle's loop in the gerbil kidney is much better developed and forms in whole a kind of a singular cortical fiber bordering the medulla. It is the well-developed parts of Hengle's ascending loop in gerbil that ensures a more complete water reabsorption decrease the quantity of urine and sharply reduce the amount of exogenous fluid vitally important for animals in arid areas.

[Role of insufficient hormone production in development of osteopenia in consequence of physical loads defficiency].

Experiments with rats deprived of support loading on hind limbs by tail-suspension showed that injection of hormones participating in bone metabolism impeded the development of tibial spongy osteopenia; also, normalization of longitudinal bone growth was observed in several cases. Investigations were aimed to evaluate the effectiveness of growth hormone, sex hormones, thyreoid hormones, calcitonin, CNS stimulating ephedrine and strychnine, and graded support loads. The best results were obtained after injection of calcitonin combined with sinestrol (synthetic analog of estradiol) and graded support loads which acted as initiators and amplifiers of hormonal effects.

[Action of estradiol, calcitonin and weight-loading on the development of osteopenia in tail-suspended female rats].

Experiments with tail-suspended female rats demonstrated that injection of sinestrol (synthesized estradiol) and myocalcic (sermon calcitonin) on a background of graded weight bearing (suspension interruption for 2 hrs. a day) prevented osteopenia in the spongy metaphyses of the shin-bone deprived of loading.

[Dynamics of the structural recovery of the rat's tibia from suspension-produced osteopenia].

The qualitative histomorphometric techniques were used to study the dynamics of tibia structural recovery from osteopenia in 30 female rats previously suspended by tail for 30 days. The suspension was found to have caused osteopenia in the tibial proximal metaphysis that was fully gone only after 60 day; in other words, readaptation took twice as much time as the osteopenia development. This fact should be taken into consideration by designers of rehabilitative methods.

[Muscle atrophy in microgravity and during its simulation].

Summarized are the results of comparative analysis of morphological changes in rat's skeletal muscles after microgravity and its simulation. On completion of space flight, hindlimb muscles of rats exhibited atrophy developed in space microgravity in consequence of the lack of weight-bearing loads and changes solely in the slow anti-g muscles due to the hemodynamic disorders appearing after space flight. Immobilization combined with clinostatting cannot be a veridical laboratory model of microgravity, as horizontally positioned animals still possess weight and, besides, experience severe chronic stress of immobilization.

[Histomorphometry of primate's iliac bones following head-down tilting and "dry" immersion].

Histomorphometry of the iliac bone in Macaca mulatta males was performed in experiments with 30-d head-down tilting (HDT, n = 6) and 8-10-d "dry" immersion (DI, n = 6). The iliac crest was sampled two weeks before DI or a month prior to HDT, and immediately after completion of the experiments. HDT was shown to provoke osteopenia in the bone spongy manifested by losses in the volume of spongiosa, number of trabeculae, and growth of the space in-between.

[Morpho-functional endocrine glands changes in male and female rats under deficiency of functional loading].

Histomorphometric and immunocytochemical methods were employed in comparative morphofunctional analysis of the endocrine glands of female and male rats deprived of support loads on the hind limbs by tail suspension. It was shown that pituitary somatotrophs, pancreatic insulocytes and thyroid calcitonin-producing cells in females and males react to deficiency of support loading equally by reducing the functional activity. Blood testosterone decreases in the tail-suspended rats and concurrent hyperplasia of Leydig's cells in testicles are suggestive of an abnormal testosterone synthesis/secretion by these cells in consequence of resticle displacement toward the abdomen.

[Effects of ibandronate on the osteopenia process in tail-suspended rats].

Histological and histomorphometric effects of ibandronate on the metaphyseal spongiosis in tibia were studied in tail-suspended rats and their controls in a 30-d experiment. Ten- to twenty-day course of ibandronate at a dose of 6 micrograms/kg of the body mass per diem altered the architectonics of metaphyseal spongiosis and increased materially the total spongiosis volume no matter whether those were suspended rats or controls. Spongiosis growth was a result of a sharp deterioration of resorption and spongy bone remodelling due to ibandronate.

[Comparative histomorphometric studies of shin bones of male and female rats following tail suspension].

In a 30-d experiment with tail-suspension of male and female rats histomorphometric studies were performed to compare impacts of deficient weight loading on the tibial spongy tissue. The 30-d suspension was found to slow down the body and adrenal mass gain irrespective of sex; however, this effect was more pronounced in male rats suggesting a greater stress to males as compared to females. Also, suspension caused tibial osteopenia in either of sexes.

[Morphofunctional changes in the endocrine system of male rats during microgravity and suspension].

Morphofunctional changes in somatotrophs and gonadotrophs of the adenohypophysis and Leydig's cells in the testicles were investigated histologically and hystomorphometrically in male rats following microgravity or tail-suspension. Deficient loading of the musculoskeletal system in microgravity was shown to suppress the functional activity of somatotrophs, gonadotrophs and, seemingly, Leydig's cells. As a consequence, blood levels of the growth hormone and testosterone reduced in the space-flown rats.

[Healing fibular bone fracture in rats during extended suspension ].

Healing of peroneal bone fracture was studied histologically and histomorphologically in rats exposed to a 30-d tail-suspension. To fracture bones, anesthetized rats were operated on day 15 of suspension. Hind limb deprivation of the support loading for a period of 30 days minimizes healing processes in fractured peroneal bones as was evidenced by undersized callus and lowered strength of bone consolidation.

[Functioning of endocrine glands controlling calcium turnover in microgravity].

Presented are literary and authors' data on functioning of the endocrine glands involved in the control of calcium turnover in microgravity. On analysis of research findings the conclusion has been made that exposure to microgravity stimulates functional activity of the parathyroid and suppresses thyroid C-cells producing the parathyroid hormone and calcitonin, respectively. Shifts in the calcium-controlling endocrine systems are considered to be adaptive and play an important role in pathogenesis of disorders in calcium turnover in microgravity.

[Bioethics of research on humans and animals in aviation, space and marine medicine].

The article includes excerpts from The Bioethic Rules of Research With Humans and Animals that have established on analysis of national and international bioethic guidelines for biomedical research with the use of humans and animals and are a part of the ISS human use guidelines.

[Stimulation of bone fracture healing in rats under the support load deficit].

Experiment with rats the hind limbs of which were deprived of support loads (tail suspension) for two weeks following operational fracture of fibular bones evidenced inhibited callus formation and lowered strength of bone fragments consolidation. Injection of anabolic steroid retabolite to the traumatized animals together with limited support loading was favorable to the bone callus formation and consolidation of fragments. This measure also distinctly increased the functional activity of adenohypophysial somatotrophs (growth hormone producers) and thyroid C-cells (calcitonine producers).

[Age-related characteristics of osteopenia in rats caused by deficient support loads on hind limbs].

Progress of osteopenia in 40-, 100-, and 220-d old rats who had been suspended by tails to release support loading on their hind limbs for 30 days was compared. Deficient support loading was shown to inhibit the longitudinal growth of tibia and produce osteopenia of the proximal metaphysis spongiosis in all groups of rats. Humerus of the rats whose front limbs were still partially loaded, suffered same changes as tibia though much less pronounced.

[Ethics of space life science research with animals].

The authors present a historical sketch on the ethics of use of animals in life sciences experiments. Experiments with animals are necessary to expand knowledge in the field of life sciences including the space ones, and health service. It is emphasized that these experiments must be performed with observance of certain moral rules and utilize minimum animals suffice to obtain statistically significant data.

[Effect of gravitation loading and retabolil on development of atrophy in muscles and bones of rats due to suspension].

In a 3-wk experiment with tail-suspended rats histological and histomorphometric methods were used to determine the effects of graded gravitational loading (GGL) and anabolic steroid retabolil (nortestosterone decanoate) on the course of atrophy in soleus m. (SM), gastrocnemius m. (GM), tibia and humerus, and functioning of somatotrophic hormones (STH) of the pituitary and thyrocytes of the thyroid.

[The effect of support loads and CNS stimulants on the development of the atrophic process in the muscles of suspended rats].

The histomorphometric method there was used to study effects of ephedrine, strychnine, and support loads on the atrophy of m. soleus and m. gastrocnemius in rats with load-deprived lower extremities (14-day tail-suspension).

[Role of growth hormone underproduction and support load deficit in development of muscle atrophy and osteopenia in tail-suspended rats].

In a 20-day experiment with tail-suspended male rats histological and histomorphometric techniques were used to study the effects of growth hormone, thyroxin, and graded support loads on the progress of atrophy in soleus and gastrocnemius m.m., tibial metaphyses spongiosis, and growth of tibiae.

[Comparative analysis of changes in rats organisms exposed to microgravity and head-down suspension].

Comparative analysis of metabolic and structural shifts in rats following 14 days of microgravity aboard biosatellite Cosmos-2044 and their tail-suspended synchronous controls gave evidence that suspension-induced deprivation of hind limbs of support loading yields inherent to microgravity shifts the endocrine control of energy, plastic, and mineral metabolism. The conclusion has been drawn that tail-suspension can be used as a model of the microgravity effects on the musculoskeletal apparatus and the endocrine systems controlling metabolism in muscles and bones.

[Effects of support++ loads and stimulation of CNS on functional activity of somatotrops and thyreocytes in suspended rats].

In the 14-day experiment with suspended rats there investigated the effect of support loads and stimulated of CNS (ephedrine and strychnine) on functional activity of somatotrops of adenohypophysis and thyrocytes of the thyroid gland. It is shown that the support loads and stimulators of the CNS increase the functional activity of somatotrops and thyreocytes. As this takes place, the loads of support give rise to the elevation of production and secretion of the growth hormone and thyroid hormones whereas ephedrine induces mainly the secretion of growth hormone.

[Effect of ephedrine and support loads on development of osteopenia and growth of shin bones in suspended rats].

Effects of graded support loads and stimulators of the central nervous system (ephedrine and strychnine) on growth of bones and the volume of spongy bone tissue in the proximal metaphyses of the shin bones were studied in the 14-day experiment with rats suspended by tail in the orthostatic position. It is indicated that the support loads in combination with ephedrine injection prevent the suspension-induced inhibition of bone growth and development of osteopenia of spongiosa of metaphyses. The preventive effect of support loads and ephedrine relates with their stimulating influence on the functional activity of the STH-cells of adenohypophysis producing the growth hormone.