Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity compared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcription factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only microgravity-induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis.

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PCR-SSCP was applied to analyze the polymorphisms of CXCR2 gene and its relationships with milk quality and mastitis in 160 cattle samples including Holstein dairy cow, Simmental dairy cow and Tongjiang cattle. The results showed that there were 3 SNP loci in CXCR2 gene, which located at 684 bp, 777 bp, 861 bp, respectively. Five alleles (A, B, C, E and F) were determined based on the 3 SNP loci. The genotypes for each locus were BC and CC, AA and AB, CC and BC at 685 bp, 777 bp and 861 bp, respectively. Results also demonstrated that genotypes BC, CC and FF were probably relevant with mastitis, but AA, BB and EE may resist the mastitis of cattle. The genotypes AA, AB and EE may have better milk quality (extremely significant difference or significant difference) than other genotypes.