Rats subjected to various accelerations (+G) exhibited increased levels of plasma epinephrine (EPI), norepinephrine (NE), and corticosterone. However, the collection of blood was performed after a centrifugation finished, and therefore the levels could be affected by the process of deceleration. The aim of this study was to evaluate plasma EPI, NE, and corticosterone levels in blood collected directly during centrifugation after reaching different G (2-6), using newly developed remote-controlled equipment. Animals placed into the centrifuge cabins had inserted polyethylene tubing in the tail artery, which was connected with a preprogrammed device for blood withdrawals. Plasma EPI, NE, and corticosterone levels were measured at different time intervals of hypergravity of 2-6G. Plasma EPI levels showed a huge, hypergravity-level-dependent increase. After the last blood collection was completed during hypergravity, the centrifuge was turned off and another blood sampling was performed immediately after the centrifuge stopped (10 min). In these samples, plasma EPI showed significantly lower levels compared to centrifugation intervals. Plasma NE levels were significantly increased after 6G only. The increase in plasma corticosterone was dependent on level of G, however after the centrifuge stopped, corticosterone levels remained elevated. Thus, our data show that hypergravity highly activates the adrenomedullary and hypothalamo-pituitary-adrenocortical systems, whereas the sympathoneural system is activated only at high hypergravity. Immediately after centrifugation is over, EPI levels quickly return to control values. Our technique of blood collection during centrifugation allows assessment of the real hormonal levels at the particular hypergravity value.

Hypodynamy is a method to simulate weightlessness in the earth laboratory conditions. The objective of this study was to study the effects of hypodynamy on the growth of the body and of the right leg of female Japanese quail chicks reared under these conditions from day 2 after hatching to 56 days of age. Therefore, body weight, food consumption, food conversion and length of femur, tibiotarsus and tarsometatarsus of the quail chicks were recorded at weekly intervals.The effect of hypodynamy on these indices was significant (p < 0.001). The mean body weight of the test group after the 56-day hypodynamy was about 34% less than that of the age-matched control. The food consumption in both groups increased with age but in the hypodynamy quails it was 17% lower compared to control. Similarly, the food conversion of test birds was affected until day 42 of age except for day 14. The size of the femur in the hypodynamy group was reduced (by 0.7 mm) compared to the age-matched control at 56 days. The tibiotarsus and tarsometatarsus of hypodynamy quails were shorter by 4.41 mm and 3.35 mm, respectively, at the end of experiment.Our results show that Japanese quail female chicks are capable to grow and develop under conditions of prolonged simulated weightlessness. Based on these results a similar experiment under conditions of real weightlessness in space may be considered.

The goal of this study was to assess the influence of simulated microgravity (hypodynamy) on morphological characteristics and mineral content of the long bones of the right leg of female Japanese quail chicks from 3 to 56 days of age. Femur and tibiotarsus were collected at 14, 28, 42 and 56 days; the variables studied were: weight (g), length and width (mm), bone index (ash weight/bone length in mg·mm -1 ), bone breaking strength (N) and calcium, phosphorus and magnesium content (mg·g -1 dry bone).All variables increased with bird age. However, the effect of hypodynamy on the examined variables was frequently large and significant. The tibiotarsus mean weight was significantly (P < 0.001) reduced by 0.154 g, although the femur mean weight in hypodynamy reared quails was almost identical to that of the age-matched control at 56 days. Similarly, there was significantly decreased tibiotarsus mean length (P < 0.01) by 3.16 mm and tibiotarsus mean width (P < 0.001) by 0.44 mm by 56 days. Similarly, bone index and bone breaking strength of both bones in birds reared under hypodynamy were significantly lower (P < 0.001) than those of control. Moreover, hypodynamy significantly (P < 0.01) decreased the calcium content in femur and tibiotarsus at 42 days; phosphorus content in tibiotarsus was reduced significantly at 14 and 42 days (P < 0.001; P < 0.05, respectively) and magnesium content was decreased at 42 days (P < 0.01). On the contrary, magnesium content in both long bones of test quails was increased significantly (P < 0.01) at 14 days. Other differences in femur and tibiotarsus mineral content between test and control group were not significant. These findings suggest that, although hypodynamy reduce bone growth of test birds, the long bones of the right leg of female Japanese quail were able to develop under conditions of simulated microgravity.

The model for studying the effects of simulated microgravity on the bird organism is hypodynamia. The aim of this study was to investigate the influence of chronic hypodynamia on the structure of the vestibular apparatus in Japanese quail by light microscopy. Morphological changes in the sensory epithelium of chicks reared under hypodynamia from 1 to 42 days of age were evaluated. The differences of shape and arrangement of hair cells in sensory epithelium macula utriculi and the dilatations on their basal parts were found in birds exposed to hypodynamia on day 14 and 42 compared to control.The results confirmed that hypodynamia has specific impact on developmental processes in Japanese quail and indicated that similar damage of inner ear sensory epithelium could be developed in chicks hatched and reared in conditions of real weightlessness during the space flight. Simulated weightlessness, inner ear, sensory epitheliumVestibular apparatus is the sensory system which contributes to balance and spatial orientation of animals. It detects head movements and gravitational stimuli which are transferred upon the mechanosensory hair cells of the inner ear. The hair cells transduce these stimuli into electrical signals which are transmitted to brain (Colclasure and Holt 2003). The development and structural organization of the vestibular receptors under earthly conditions was described (Money et al. 1974;Fermin et al. 1998). However, fewer data are available from the studies of the influences of real microgravity on structure of vestibular apparatus in birds (Lychakov et al. 1993;Kenyon et al. 1995;Fermin et al. 1996), and therefore further information may be provided by the ground-based model of simulated weightlessness (hypodynamia). The first experiment to examine the effects of hypodynamia on the organism of Japanese quail was carried out on adult birds (Juráni et al. 1983). The aim of this experiment was to study the effect of simulated weightlessness on the development of structure of the vestibular apparatus in Japanese quail chicks reared under hypodynamia from 1 to 42 days of age. Materials and MethodsTen healthy 1-day-old male Japanese quail chicks (Laying Line 01 Ivanka pri Dunaji) were randomly divided into experimental group (n = 5) and control (n = 5). The birds of experimental group were exposed to hypodynamia and those of control were placed on the floor in rearing box as described by Škrobánek et al. (2004). The care and use animals were in accordance with laws and regulations of the Slovak Republic and were approved by the Ethics Committee of the Institute of Animal Biochemistry and Genetics, SASci, Ivanka pri Dunaji.At days 1, 5, 14 and 42 of age, one bird of each group was decapitated and sample of tissues of inner ear was taken for histological analysis of vestibular apparatus. Excisions were fixed by immersion in 3% glutaraldehyde in cacodylate buffer (pH 7.2), decalcified in Chelatone, post-fixed in 1% OsO 4 , dehydrated in acetone and propyloxide and embedded into Durcupan ACM. For light ...