Journal of Aeronautic Dentistry

The objective of this study was to valid a water immersion model for microgravity and to study the effects of simulated condition on salivary cortisol and a-amylase.Increased activity of stress systems is reported during space flight, but unchanged or decreased activity during simulated microgravity. We here investigated the impact of head-out water immersion on the activity of the hypothalamus-pituitary-adrenal axis and the sympathetic-adrenal-medullary system. The healthy young men were exposed to a nine -hour water immersion in a thermo neutral bath and a control condition. Saliva samples were taken before, during, and after interventions to assess cortisol as an index for hypothalamus-pituitary-adrenal axis activity, and salivary a amylase as  an index for sympathetic-adrenal-medullary system activity. Cortisol and Amylase levels uniformly increased during simulated conditions. In conclusion, Both systems activity shows initial increased during water immersion. 

Key words: Simulated microgravity, salivary cortisol, salivary a-amylase, water immersion model.

Microgravity is associated with an increase of peroxidative damage. The effect is more pronounced after long-duration space flight and can even last for several weeks after landing. The extensive research is going on preventation of peroxidative damge due to microgravity. It have been evidence that curcumin (diferuloylmethane), a yellow pigment in curry powder, exhibits antioxidant, anti-inflammatory, and proapoptotic activities. To determine preventive effect of curcumin on peroxidative damage due to two bed rest conditions. 20 healthy male volunteers equally divided into two groups ( 10 with curcumin and 10 without curcumin ) were studied in condition before , during, and just bed rest conditions -6° head-down-tilt (HDT) bed rest and bed rest position (BD) for 10 days. We measured the salivary and serum oxidative markers such as Malonaldehyde, 8-hydroxydeoxyguanosine, vitamin C and E just before HDT & BD, during HDT & BD experiment, and in recovery in with curcumin and without curcumin group. The value of serum and salivary Vitamin C & E showed statistically significant decrease in both bed rest conditions condition as compared to before and in recovery stage , however levels were decreased less in curcumin groups as compared to without curcumin groups ( Table-1&2, P<0.05) .MDA and 8-OHdG levels showed significant increase in simulating microgravity and Zero gravity condition as compared to before and in recovery stage , however levels were low in curcumin grops as compared to without curcumin groups ( Table-1& 2, P<0.05). Serum and salivary correlation analysis revealed strong and highly significant correlation for MDA, Vitamin C & E and 8 dihydro-2 deoxyguanosine (8-OHdG) in before , during and recovery in both bed rest conditions. Since, saliva can be easily collected, non-invasive and measurement of salivary markers levels may prove to useful in space research. Hence, curcumin prevent peroxidative damage in both bed rest condition. Further study is required on antioxidation action of curcumin in space microgravity condition. 

Key Words- Curcumin, Serum, Saliva, oxidative stress, two bed rest position, space microgravity. 

The objective of this study was to valid a ground-based model for microgravity and zero gravity and to study the effects of simulated condition salivary cortisol. Because 6° head-down tilt (HDT)and bed rest position (HB) an established method to mimic low gravity and zero gravity on earth, the aim of the present study was to determine the effects of 20-day HDT &HB on salivary cortisol levels in 10 healthy male volunteers. The cortisol was measured in saliva. During HDT and HB, all volunteers the diurnal rhythm of cortisol  secretion was significantly increased in simulated conditions. Thus 6° HDT & HB appears to be a valid model to induce psychic stress due to increased levels of cortisol, changes that might also be encountered by astronauts and marsonaunts during long-duration spaceflights.

Key words: Head-down tilt, Bed rest position, cortisol, saliva.

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