排序方式: 共有45条查询结果,搜索用时 15 毫秒
41.
M‐J Sánchez‐Calabuig C López‐Fernández E Martínez‐Nevado JF Pérez‐Gutiérrez J de la Fuente SD Johnston D Blyde K Harrison J Gosálvez 《Reproduction in domestic animals》2014,49(5):761-768
Over the last two decades, there have been significant advances in the use of assisted reproductive technology for genetic and reproductive management of captive dolphin populations, including evaluation of sperm DNA quality. This study validated a customized sperm chromatin dispersion test (SCDt) for the bottlenose dolphin (Tursiops truncatus) as a means of assessing sperm DNA damage both in the field and in the laboratory. After performing the SCDt, two different sperm morphotypes were identified: (i) sperm with fragmented DNA showed large haloes of dispersed DNA fragments emerging from a compact sperm nucleoid core and (ii) sperm containing non‐fragmented DNA displayed small compact haloes surrounded by a dense core of non‐dispersed DNA and protein complex. Estimates of sperm DNA fragmentation by means of SCDt were directly comparable to results obtained following a two‐tailed comet assay and showed a significant degree of correlation (r = 0.961; p < 0.001). This investigation also revealed that the SCDt, with minor modifications to the standard protocol, can be successfully conducted in the field using a LED florescence microscopy obtaining a high correlation (r = 0.993; p = 0.01) between the data obtained in the laboratory and in the field. 相似文献
42.
RW Graham EL Lundelius MA Graham EK Schroeder RS Toomey E Anderson AD Barnosky JA Burns CS Churcher DK Grayson RD Guthrie CR Harington GT Jefferson LD Martin HG McDonald RE Morlan HA Semken SD Webb L Werdelin MC Wilson 《Science (New York, N.Y.)》1996,272(5268):1601-1606
Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene. 相似文献
43.
Male Esterase 6 Catalyzes the Synthesis of a Sex Pheromone in Drosophila melanogaster Females 总被引:1,自引:0,他引:1
Esterase 6, a component of the seminal fluid of Drosophila melanogaster males, hydrolyzes cis-vaccenyl acetate, a lipid made only by males, to cis-vaccenyl alcohol. This reaction occurs in the female reproductive tract and is virtually complete within 6 hours after copulation. Both the alcohol and the acetate decrease the number of matings among pairs of virgin flies in which the female is treated topically with these substances. Although females tested 10 minutes after copulation elicit less courtship than virgin females, females tested 6 hours after copulation stimulate even less courtship if they received active esterase 6 in the seminal fluid of their respective mates. Either the alcohol or a derivative appears to be an antiaphrodisiac that decreases courtship elicited by inseminated females and thus reduces the probability of further mating. Thus the activity of the pheromone depends on a final reaction which occurs in the female, using both substrate and enzyme provided by the male. 相似文献
44.
Klein RJ Zeiss C Chew EY Tsai JY Sackler RS Haynes C Henning AK SanGiovanni JP Mane SM Mayne ST Bracken MB Ferris FL Ott J Barnstable C Hoh J 《Science (New York, N.Y.)》2005,308(5720):385-389
Age-related macular degeneration (AMD) is a major cause of blindness in the elderly. We report a genome-wide screen of 96 cases and 50 controls for polymorphisms associated with AMD. Among 116,204 single-nucleotide polymorphisms genotyped, an intronic and common variant in the complement factor H gene (CFH) is strongly associated with AMD (nominal P value <10(-7)). In individuals homozygous for the risk allele, the likelihood of AMD is increased by a factor of 7.4 (95% confidence interval 2.9 to 19). Resequencing revealed a polymorphism in linkage disequilibrium with the risk allele representing a tyrosine-histidine change at amino acid 402. This polymorphism is in a region of CFH that binds heparin and C-reactive protein. The CFH gene is located on chromosome 1 in a region repeatedly linked to AMD in family-based studies. 相似文献
45.
Demand for the fabric wipes is growing continuously. Wipes in industry are used for cleaning purpose. Cleaning involves rubbing
action, so it is very important to know how much frictional force is encountered during the cleaning action. In this study
the effects of normal load, sliding speed on frictional characteristics of nonwoven and woven wipes, both dry and wetted with
different liquids, against glass and floor tile surfaces have been reported. With the increase in the normal load the coefficient
of friction goes on decreasing for both nonwoven and woven wipes and this trend is observed in both dry and wet wipes. The
coefficient of friction of both nonwoven and woven wipes against glass surface is in general higher than the floor tile surface.
The wipes wetted with water shows an increase in coefficient of friction as compared to dry sample, but there is reduction
in the coefficient of friction when the wipe samples are wetted with vegetable oil. In case of dry wipes, the coefficient
of friction in case of nonwoven wipe is higher than the woven wipe. In case of woven wipes, the ranges of coefficient of friction
either due to change in liquid type, normal load or sliding speed are in general smaller than that in case of nonwoven fabrics. 相似文献