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321.
A sample of 55 South African cheetahs (Acinonyx jubatus jubatus) from two geographically isolated populations in South Africa were found to be genetically monomorphic at each of 47 allozyme (allelic isozyme) loci. Two-dimensional gel electrophoresis of 155 abundant soluble proteins from cheetah fibroblasts also revealed a low frequency of polymorphism (average heterozygosity, 0.013). Both estimates are dramatically lower than levels of variation reported in other cats and mammals in general. The extreme monomorphism may be a consequence of a demographic contraction of the cheetah (a population bottleneck) in association with a reduced rate of increase in the recent natural history of this endangered species. 相似文献
322.
Lewis RS Parker RG Danehower DA Andres K Jack AM Whitley DS Bush LP 《Journal of agricultural and food chemistry》2012,60(25):6454-6461
Tobacco-specific nitrosamine (TSNA) formation in tobacco is influenced by alkaloid levels and the availability of nitrosating agents. Tobacco types differ in their potential for TSNA accumulation due to genetic, agronomic, and curing factors. Highest TSNA concentrations are typically measured in burley tobaccos. One of the main genetic differences between burley and all other tobacco types is that this tobacco type is homozygous for recessive mutant alleles at the Yellow Burley 1 (Yb(1)) and Yellow Burley 2 (Yb(2)) loci. In addition, burley tobacco is typically fertilized at higher nitrogen (N) rates than most other tobacco types. This study utilized nearly isogenic lines (NILs) differing for the presence of dominant or recessive alleles at the Yb(1) and Yb(2) loci to investigate the potential influence of genes at these loci on TSNA accumulation. Three pairs of NILs were evaluated at three different nitrogen fertilization rates for alkaloid levels, nitrogen physiology measures, and TSNA accumulation after air-curing. As previously observed by others, positive correlations were observed between N application rates and TSNA accumulation. Recessive alleles at Yb(1) and Yb(2) were associated with increased alkaloid levels, reduced nitrogen use efficiency, reduced nitrogen utilization efficiency, and increased leaf nitrate nitrogen (NO(3)-N). Acting together, these factors contributed to significantly greater TSNA levels in genotypes possessing the recessive alleles at these two loci relative to those carrying the dominant alleles. The chlorophyll-deficient phenotype conferred by the recessive yb(1) and yb(2) alleles probably contributes in a substantial way to increase available NO(3)-N during curing and, consequently, increased potential for TSNA formation. 相似文献
323.
PCB dechlorination in Hudson River sediment 总被引:1,自引:0,他引:1
324.
Transcutaneous ultrasound over the right flank to diagnose mid- to late-pregnancy in the dairy cow 总被引:1,自引:1,他引:0
Objective To investigate the practical application and image quality of transcutaneous ultrasonography across the right flank for the diagnosis of mid- to late-gestation in cattle.
Procedure Dairy cows of known pregnancy status were used to establish criteria for the identification of mid- to late-stage pregnancy by transcutaneous ultrasonography. Factors involved in the practical application of transcutaneous ultrasound for routine use in pregnancy diagnosis in dairy cattle were also examined.
Results Transcutaneous ultrasound, using a 3.5-MHz sector transducer applied over the caudodorsal right flank fold, allowed rapid and detailed visualisation of bovine pregnancy (i.e. fetus, fetal fluids, placentomes and/or fetal membranes) and could be used to establish criteria for the diagnosis of pregnancy. The commonly available cattle holding facilities of the herringbone dairy, rotary herringbone dairy, AI race or crush, and walk-through dairy all allow safe access to the right flank of a dairy or beef cow. However, transcutaneous scanning over the right flank is difficult in modern rotary turnstile dairies.
Conclusion A 3.5-MHz sector transducer applied over the caudodorsal right flank fold allows detailed visualisation of the bovine fetus in most types of cattle-holding facilities. Further investigation of the sensitivity and specificity of this technique over the entire gestation period and its possible use in ageing of the bovine fetus is merited. 相似文献
Procedure Dairy cows of known pregnancy status were used to establish criteria for the identification of mid- to late-stage pregnancy by transcutaneous ultrasonography. Factors involved in the practical application of transcutaneous ultrasound for routine use in pregnancy diagnosis in dairy cattle were also examined.
Results Transcutaneous ultrasound, using a 3.5-MHz sector transducer applied over the caudodorsal right flank fold, allowed rapid and detailed visualisation of bovine pregnancy (i.e. fetus, fetal fluids, placentomes and/or fetal membranes) and could be used to establish criteria for the diagnosis of pregnancy. The commonly available cattle holding facilities of the herringbone dairy, rotary herringbone dairy, AI race or crush, and walk-through dairy all allow safe access to the right flank of a dairy or beef cow. However, transcutaneous scanning over the right flank is difficult in modern rotary turnstile dairies.
Conclusion A 3.5-MHz sector transducer applied over the caudodorsal right flank fold allows detailed visualisation of the bovine fetus in most types of cattle-holding facilities. Further investigation of the sensitivity and specificity of this technique over the entire gestation period and its possible use in ageing of the bovine fetus is merited. 相似文献
325.
Ying’an Zhu ShiJun Wu Jianmin Xu Zhaohua Lu Guangyou Li Yang Hu Xueyan Yang David Bush 《Euphytica》2017,213(7):142
An inter-specific hybrid breeding program involving Eucalyptus urophylla (U) and Eucalyptus camaldulensis (C) was implemented in order to provide genotypes better adapted to southern China with improved growth rate, stem-straightness and wind-resistance. A trial involving 36 reciprocal crosses from six parents each of C and U that had been preselected for superior growth and stem-straightness was established at a site in Luokeng in Guangdong province. Ten, pure-species families using the hybrid parents as open-pollinated female parents were included as controls. Survival and growth traits at ages 2 and 8.3 years and stem-straightness at age 2 years were assessed. Inter-specific hybrids generally performed better than the pure species in terms of survival, growth traits and stem-straightness. Female U by male C crosses generally outperformed those involving male U and female C. Further indication of the significant reciprocal effect was supported by negative and low correlations between paired groups of full-sibs that differed only in the direction of the cross. Components of female additive genetic variance and narrow-sense heritability calculated from this estimate (\(\sigma_{\rm Af}^{2}\) and \(h_{\rm f}^{2}\)), respectively) were generally higher than those of the male \(\left( {\sigma_{\rm Am,}^{2} h_{\rm m}^{2} } \right)\), providing evidence for maternal effects. The narrow-sense heritability (h2) estimates based on general hybridizing ability for growth traits and stem-straightness were generally low at both ages, and of low precision at 8.3 years. The ratio of hybrid additive-to-dominance variance \(\left( {{{\sigma_{\rm A}^{2} } \mathord{\left/ {\vphantom {{\sigma_{\rm A}^{2} } {\sigma_{\rm D}^{2} }}} \right. \kern-0pt} {\sigma_{\rm D}^{2} }}} \right)\) was of little practical consequence at age 2 years and had further decreased by age 8.3 years. Trait-trait genetic correlations amongst hybrids were generally positive and moderate to high. Hybrid vigour, gauged by comparison with the performance of the pure species progeny was significant, though correlations between pure species and hybrid progeny-based estimates of parental performance were weak, indicating that making parental selections in pure species trials may not be a successful strategy. 相似文献
326.
Mertens Arne Bawin Yves Vanden Abeele Samuel Kallow Simon Swennen Rony Vu Dang Toan Vu Tuong Dang Minh Ho Thi Panis Bart Vandelook Filip Janssens Steven B. 《Genetic Resources and Crop Evolution》2022,69(7):2515-2534
Genetic Resources and Crop Evolution - Collection and storage of crop wild relative (CWR) germplasm is crucial for preserving species genetic diversity and crop improvement. Nevertheless, much of... 相似文献