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61.
Little is known about the major histocompatibility (Mhc) genes of birds in different taxonomic groups or about how Mhc genes may be organized in avian species divergent by evolution or habitat. Yet it seems likely that much might be learned from birds about the evolution, organization, and function of this intricate complex of polymorphic genes. In this study a close relative of the chicken, the ring-necked pheasant (Phasianus colchicus), was examined for the presence and organization of Mhc B-G genes. The patterns of restriction fragments revealed by chicken B-G probes in Southern hybridizations and the patterns of pheasant erythrocyte polypeptides revealed in immunoblots by antisera raised against chicken B-G polypeptides provide genetic, molecular, and biochemical data confirming earlier serological evidence for the presence of B-G genes in the pheasant, and hence, the presence of a family of B-G genes in at least a second species of birds. The high polymorphism exhibited by the pheasant B-G gene family allowed genetic differences among individuals within the small experimental population in this study to be detected easily by restriction fragment patterns. Further evidence was found for the organization of the pheasant Mhc class I and class II genes into genetically independent clusters. Whether these gene clusters are fully comparable to the B and Rfp-Y systems in the chicken or whether yet another organization of Mhc genes has been encountered in the pheasant remains to be determined. 相似文献
62.
Aflatoxin and cyclopiazonic acid production by a sclerotium-producing Aspergillus tamarii strain. 总被引:1,自引:0,他引:1
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The production of aflatoxins B1 and B2 by Aspergillus tamarii (subgenus Circumdati section Flavi) is reported for the first time. The fungus was isolated from soil collected from a tea (Camellia sinensis) field in Miyazaki Prefecture, Japan. Three single-spore cultures, NRRL 25517, NRRL 25518, and NRRL 25519, were derived from subcultures of the original isolate 19 (MZ2). Each of these single-spore cultures of A. tamarii produced aflatoxins B1 and B2 and cyclopiazonic acid, as well as black, pear-shaped sclerotia. The demonstration of aflatoxin production by A. tamarii is examined in connection with A. tamarii phylogenetic relationships, chemical ecology, and potential use in food fermentations. 相似文献
63.
Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine. 相似文献
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Previous studies have demonstrated that developing hamster embryos are very sensitive to visible light. In order to elucidate why visible light exerts a toxic effect on hamster embryos, we examined the effect of visible light on the production of hydrogen peroxide (H(2)O(2)) within individual embryos, using a fluorimetric method. In addition, we examined the H(2)O(2) generating capacity of other factors which are known to be related to the in vitro developmental capacity of hamster embryos. One-cell hamster embryos were cultured with 2',7'-dichlorodihydrofluorescin diacetate, and the fluorescence emissions of the H(2)O(2)-dependent oxidative product in the embryos were measured using an Olympus microscopic photometry system. When embryos were exposed to visible light (14,000 lux) for a specified period (0, 0.5, 1, 2 or 3 min) prior to measurement, the fluorescence emissions from embryos increased with the time of exposure to visible light. An exposure of even 0.5 min resulted in a significant increase in hydrogen peroxide. This increase was more rapid in embryos cultured under 20% O(2) than in those cultured under 5% O(2), and the response was quicker than that observed in mouse embryos. The fluorescence emissions from embryos cultured under 5% O(2) were significantly (P<0.001) lower than those from embryos cultured under 20% O(2) in TLP medium. However, the effects of different oxygen tensions on fluorescence emissions were medium-dependent, and were not significant in embryos cultured in HECM-1 medium. The addition of L-cysteine to or elimination of phenol red from the media decreased the fluorescence emissions from embryos (P<0.001), but glucose and phosphate did not affect them. These results suggest that the toxic effect of visible light on the in vitro development of hamster embryos might be due to increased generation of reactive oxygen species, induced by the visible light. This could be one of the explanations for the strict conditions required for overcoming the in vitro developmental block. It is also suggested that the promotive effects of low oxygen culture and L-cysteine on embryo development seem to be derived from their ability to reduce reactive oxygen species. 相似文献
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Takeo Yoshimura Takuro Kobayashi Shuichiro Goda Ikuo Goto 《Neurochemical research》1994,19(6):735-741
The repetitive passages of a Schwann cell culture results in the appearance of immortalized cells. In order to investigate the direct effects of cyclic AMP (cAMP) on Schwann cell proliferation, we used the immortalized Schwann cells because the responses of a short-term Schwann cell culture to agents increasing the intracellular cAMP are more complicated and it does not seem that all of them are due to the direct effects of cAMP. By adding up to 200 M of forskolin, an adenylate cyclase activator, to the culture medium, Schwann cell proliferation was inhibited and the intracellular 1,2-diacylglycerol (DG) level was decreased in a dose-dependent manner to 44 and 53% of the control values, respectively. The protein phosphorylation activity in the cytosol from the cell treated with 100 M forskolin, assayed with myelin basic protein as the acceptor, decreased to 78% and this inhibition was then reversed by the addition of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeable DG, to the assay mixture. The cell proliferation inhibited by forskolin was also restored by the addition of OAG. These data suggest that cAMP inhibits both the activity of protein kinase C (PKC) and consequently cell proliferation through suppression of intracellular DG level, an activator of PKC. Since the inositol 1,4,5-triphosphate level and the hydrolysis of phosphatidylcholine to DG and phosphorylcholine were not affected, forskolin therefore appears to suppress the de novo synthesis of DG. 相似文献
68.
Suzuki Y Murakami T Kawakubo K Haruna Y Takenaka K Goto S Makita Y Ikawa S Gunji A 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1994,1(1):P57-P58
To this day, many studies have suggested that prolonged bed rest (BR) affects on muscle mass and strength not only in gravity muscles but also in ungravity muscles. However, it is still unclear whether the decrease in regional muscle strength after BR is due to the alterations in the corresponding muscle mass, or not. On the other hand, if BR decreases the mass of antigravity muscles (UGM) as well as muscle strength and then increases tissue compliance of the antigravity muscles, orthostatic tolerance capacity will be decreased by the reduction in cardiac output (CO) in spite of the increase in myocardial contractility because the more decrease in venous return due to the more increase in blood pooling within the compliant tissues of the lower body. However, this is also unclear. To make these questions clear, the present study investigated the regional muscle mass and strength and orthostatic tolerance capacity before and after 20 days of bed rest in young subjects. 相似文献
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