Simulated space environmental factors of weightlessness, noise and low atmospheric pressure differentially affect the diurnal rhythm and the gut microbiome.

The circadian clock extensively regulates physiology and behavior. In space, astronauts encounter many environmental factors that are dramatically different from those on Earth; however, the effects of these factors on circadian rhythms and the mechanisms remain largely unknown. The present study aimed to investigate the changes in the mouse diurnal rhythm and gut microbiome under simulated space capsule conditions, including microgravity, noise and low atmospheric pressure (LAP). Noise and LAP were loaded in the capsule while the conditions in the animal room remained constant. The mice in the capsule showed disturbed locomotor rhythms and faster adaptation to a 6-h phase advance. RNA sequencing of hypothalamus samples containing the suprachiasmatic nucleus (SCN) revealed that microgravity simulated by hind limb unloading (HU) and exposure to noise and LAP led to decreases in the quantities of differentially expressed genes (DEGs), including circadian clock genes. Changes in the rhythmicity of genes implicated in pathways of cardiovascular deconditioning and more concentrated phases were found under HU or noise and LAP. Furthermore, 16S rRNA sequencing revealed dysbiosis in the gut microbiome, and noise and LAP may repress the temporal discrepancy in the microbiome community structure induced by microgravity. Changes in diurnal oscillations were observed in a number of gut bacteria with critical physiological consequences on metabolism and immunodefense. We also found that the superimposition of noise and LAP may repress normal changes in global gene expression and adaptation in the gut microbiome. Our data demonstrate that in addition to microgravity, exposure to noise and LAP affect the robustness of circadian rhythms and the community structure of the gut microbiome, and these factors may interfere with each other in their adaptation to respective conditions. These findings are important for furthering our understanding of the alterations in circadian rhythms in the complex environment of space.

Time-Domain NMR Applied to Sitophilus zeamais Motschulsky/Wheat Detection.

Time-domain nuclear magnetic resonance (NMR) is used for the characterization of wheat infested with Sitophilus zeamais. NMR parameters (T21, T22, P21, P22, and A21/22) were achieved by biexponential analysis combined with a discrete method. Sound wheat, S. zeamais, and S. zeamais/wheat binary mixture are all explored by this method to find the changes in the process of the number increase and growth stage. Based on different sets of NMR parameters, the classification and quantification of the stage and number are made by linear discriminant analysis and partial least squares regression with very high accuracy. The weight and moisture content information lack will make the misclassification rate increase but not by more than 7%. This NMR-based hidden-insect detection method, with fast and nondestructive advantages, was confirmed by X-ray and had a high potential to be equipped in the online analysis system.

[A simulation facility for low temperature water surface environment].

OBJECTIVE: To simulate the water environment during floating status after astronauts returned and splashed down on the sea because of space capsule emergency in the launching stage. METHOD: Environmental temperature in the laboratory and water-temperature in the tank were auto-controlled individually according to heat charge calculation. To meet the need of maintaining the uniformity of water-temperature, the structure of the water circulation pipeline was specially designed to increase thread-conflux and laminar flow effect. RESULT: It was proved that the experimental system satisfied the requirements for medical research and evaluation by its high precision and uniformity which even exceeded the design requirements. After acceptance, its performance was further proved in the field experiment of "the medical evaluation of the soak and cold resisting garment." CONCLUSION: The equipment provides satisfactory experimental condition for medical evaluation of the space suit used in the "Shenzhou" space capsule and simulated the low-temperature water environment for studies of human reaction in the floating status and medical evaluation of relative products in the area of aerospace.