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排序方式: 共有424条查询结果,搜索用时 15 毫秒
421.
Begum NA Kinoshita K Kakazu N Muramatsu M Nagaoka H Shinkura R Biniszkiewicz D Boyer LA Jaenisch R Honjo T 《Science (New York, N.Y.)》2004,305(5687):1160-1163
Activation-induced cytidine deaminase (AID) is required for the DNA cleavage step in immunoglobulin class switch recombination (CSR). AID is proposed to deaminate cytosine to generate uracil (U) in either mRNA or DNA. In the second instance, DNA cleavage depends on uracil DNA glycosylase (UNG) for removal of U. Using phosphorylated histone gamma-H2AX focus formation as a marker of DNA cleavage, we found that the UNG inhibitor Ugi did not inhibit DNA cleavage in immunoglobulin heavy chain (IgH) locus during CSR, even though Ugi blocked UNG binding to DNA and strongly inhibited CSR. Strikingly, UNG mutants that had lost the capability of removing U rescued CSR in UNG-/- B cells. These results indicate that UNG is involved in the repair step of CSR yet by an unknown mechanism. The dispensability of U removal in the DNA cleavage step of CSR requires a reconsideration of the model of DNA deamination by AID. 相似文献
422.
Daisuke Yamanaka Kazumi Sakuramoto Naoki Suzuki Tohru Nagasawa 《Fisheries Science》2007,73(4):837-844
Catch forecasting and the relationship between water temperature and catch in the snow crab Chionoecetes opilio in the western Sea of Japan were investigated. Catch was used as an index of abundance on the basis of high correlations
between catch per unit effort for the period when the latter data were available. The pattern of fluctuations, in catches
and index coincided well with each other. Therefore, catch data were regarded as an index of abundance and the correlation
coefficient between catch and water temperature was calculated at several depths from 1964 to 1999. Catch forecasting models
were composed using significantly correlated variables with the following results: (i) in April and September, the catch showed
high positive correlation with water temperatures (depth 50, 100, and 200 m, time lag 4–6 years); and (ii) a model using water
temperatures in April alone (depth 100 m, time lag 4–7 years) forecasted the catches with a coefficient of determination of
0.504, where models using more variables (water temperatures in the 2 months and catches) showed a coefficient of 0.587 at
most. Environmental conditions during the early life stages of the snow crab are thought to deeply influence the fluctuations,
in abundance. 相似文献
423.
Kazufumi Osako Akihiko Fujii Yaowalux Ruttanapornvareesakul Naoki Nagano Koichi Kuwahara Akira Okamoto 《Fisheries Science》2007,73(3):660-667
ABSTRACT: For the purpose of clarifying the differences of taste components between the testis and ovary of the sea urchin Anthocidaris crassispina , variations in free amino acid composition in gonadal extract during gonadal development were investigated using chemical and histopathological methods. Sea urchins were collected at Iki Island, Nagasaki, Japan between 30 April and 5 June 2003, and maturation stages and the free amino acid compositions were determined. The sweet amino acids threonine (Thr), glycine (Gly), and alanine (Ala), the umami amino acid glutamic acid (Glu), and the bitter amino acids lysine (Lys) and arginine (Arg) were the main constituents accounting for more than 80% of total free amino acids. In the testis and ovary, Gly levels were the highest among them and increased with gonadal development. The other free amino acids consisted mainly of bitter amino acids and either showed no variation or decreased with gonadal development. These variations in free amino acid composition were observed more clearly in the ovary than the testis. These findings indicate the possibility of differences in the flavor of sea urchin gonad by sex and gonadal development stages. 相似文献
424.
ABSTRACT: Research on ghost fishing became active in the late 1980s. Ghost fishing has been confirmed for traps, gillnets, trammel-nets and small seine nets. Some lost traps are functional for a long period of time, even in shallow waters. Consequences for gillnets after loss depend on seabed conditions. The ghost fishing function of gillnets remaining on flat seabeds declines rapidly with decreasing heights and increasing visibility. Gillnets left tangled around an artificial reef, for example, three-dimensionally maintain the initial magnitude of ghost fishing for a long period of time, even after badly fouled. There are increasing numbers of researches working on the total number of mortality per gear after gear loss for gillnets and trammel-nets. It has become also possible to estimate the total number of mortality for a unit period of time in a certain fishing sector. This paper reviews research which has provided evidence and quantitative data on ghost fishing, and proposes five items important for future studies on ghost fishing. 相似文献