Influence of glaciation on divergence patterns of the endemic minnow, Zacco pachycephalus, in Taiwan

The genetic subdivision of the endemic minnow, Zacco pachycephalus, in 12 rivers of Taiwan was studied by allozyme electrophoresis. Among 26 loci surveyed, six were significantly differentiated among sites. Allozyme genotype frequencies within samples accord with Hardy-Weinberg expectations. A highly divergent genetic structure among sites (FST = 0.497) with low genetic variability within samples (H = 0.006-0.062, mean = 0.03) suggests that local populations originated from a small number of founders. UPGMA and Fitch trees derived from Nei's genetic distance and hierarchical analysis of FST values reveal that samples of Z. pachycephalus can be divided into northern, middle, and southern subgroups and that most genetic variation (87%) is distributed among rather than within groups. It is proposed that there were two isolated refugia during the most recent glacial period, and that populations of the southern group (Group I) originated from a southern refugium in Taiwan below the boundary of the Kaoping River, and other groups (Group II), including northern and middle subgroups, originated from a refugium located on the extinct land-bridge between Taiwan and mainland China. The postglacial division between northern and middle subgroups may be due to hydrological differences between these two regions.     

Chronological characterization of diabetes development in male Spontaneously Diabetic Torii rats

To characterize the underlying mechanisms of diabetes development in males of the Spontaneously Diabetic Torii (SDT) rat, a novel spontaneous model for diabetes, we chronologically examined them, focusing on their diabetic features and the pathological changes in the pancreatic islets. Male SDT rats exhibited glucose intolerance with impaired insulin secretion after 14 weeks and developed diabetes with remarkable hyperglycemia and marked hypoinsulinemia after 20 weeks. At prediabetic stage (10-20 weeks), they were normoglycemic, but had significantly lower insulin levels of plasma and pancreas than the normal rats. Their beta-cell volume was already smaller significantly at 10 weeks than that of normal rats. The primary changes of the pancreatic islets were microvascular events such as congestion and hemorrhage at 8-10 weeks. Thereafter, the SDT rat islets were affected with inflammation and progressive fibrosis (at 10-20 weeks), and eventually atrophied with a loss of beta-cells (at 38 weeks). These results indicate that the male SDT rats develop spontaneous diabetes with an absolute decrease in the insulin secretory capacity of the islets.     

The city-fox phenomenon: genetic consequences of a recent colonization of urban habitat

The red fox (Vulpes vulpes) is one of the best-documented examples of a species that has successfully occupied cities and their suburbs during the last century. The city of Zurich (Switzerland) was colonized by red foxes 15 years ago and the number of recorded individuals has increased steadily since then. Here, we assessed the hypothesis that the fox population within the city of Zurich is isolated from adjacent rural fox populations against the alternative hypothesis that urban habitat acts as a constant sink for rural dispersers. We examined 11 microsatellite loci in 128 foxes from two urban areas, separated by the main river crossing the city, and three adjacent rural areas from the region of Zurich. Mean observed heterozygosity across individuals and the number of detected alleles were lower for foxes collected within the city as compared with their rural conspecifics. Genetic differentiation was significantly lower between rural than between rural and urban populations, and highest value of pairwise FST was recorded between the two urban areas. Our results indicate that the two urban areas were independently founded by a small number of individuals from adjacent rural areas resulting in genetic drift and genetic differentiation between rural and urban fox populations. Population admixture and immigration analysis revealed that urban-rural gene flow was higher than expected from FST statistics. In the five to seven generations since colonization, fox density has dramatically increased. Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation over time.     

人脑运动前准备电位（BP）的两种成分

人脑运动前准备电位起始时间之长令研究者费解。本文比较了受指令食指屈曲运动和自我起始食指屈曲运动的ＢＰ。结果显示,ＢＰ在受到指令之前已经开始。显然,指令前那一部分ＢＰ即ＢＰ早期部分与运动无关。本文进一步研究了下意识眨运动,指令眨眼运动和自我起始眨眼运动。发现下意识眨眼运动时,ＢＰ起始时无早期成分,明显较另外两种眨眼运动的ＢＰ为短,表明ＢＰ的早期成分是由于在后两种有意识活动参与的眨眼运动中,心理活动产     

抗虫耐除草剂玉米GH5112E-117C定性PCR检测方法

转基因抗虫耐除草剂玉米GH5112E-117C是由北京奥瑞金公司研发的转mG2-aroA基因和mcry1Ah基因抗虫耐除草剂玉米新品系,对玉米螟、粘虫等鳞翅目害虫具有抗性、耐草甘膦除草剂的转基因玉米,在我国具有重要产业化应用前景。本文研发了GH5112E-117C转基因玉米的定性PCR检测方法,该方法能特异性地检测转基因抗虫耐除草剂玉米GH5112E-117C,在每个反应引物浓度为0.2 μmol/L、Taq DNA 聚合酶0.625 U、DNA模板50 ng,退火温度为58℃的条件下,检测灵敏度可稳定达到0.1%。该方法为转基因抗虫耐除草剂玉米GH5112E-117C的精准检测提供了一种新的技术手段,为农业转基因监管提供技术支撑。     

Effects of a recent founding event and intrinsic population dynamics on genetic diversity in an ungulate population

Maintenance of genetic diversity has recently become a management goal for a number of species, due to its importance for present and future population viability. Genetic drift, primarily through differential reproductive success and inbreeding, can accelerate the loss of genetic diversity in recently recovered populations. We attempt to quantify the consequences of these factors on the genetic diversity contained in a small, recently founded wood bison (Bison bison athabascae) population by examining the genetic variation in this conservation herd, the calves born therein, and its large source population. The Hook Lake Wood Bison Recovery Project was initiated to found a disease-free herd of wood bison containing a representative amount of the genetic diversity present in the Wood Buffalo National Park metapopulation. Levels of diversity in the Hook Lake Wood Bison Recovery Project founders are higher than in previous salvage attempts. To examine the effects of differential reproductive success on this population, we monitored parentage of the calves born in the Hook Lake Wood Bison Recovery Project for 3 years since the founders reached sexual maturity. Two of the male founders sired over 90% of the offspring born in this population, which has led to a reduction in diversity in their calves. Monitoring of reproductive success, and incorporation of selective breeding strategies will be required to reduce the rate at which genetic diversity is lost from this small, isolated population. These steps should occur in other recovery projects, particularly when a small number of individuals are capable of dominating reproduction.     

Bayesian inferences on predictors of conception probabilities

Reproductive scientists and couples attempting pregnancy are interested in identifying predictors of the day-specific probabilities of conception in relation to the timing of a single intercourse act. Because most menstrual cycles have multiple days of intercourse, the occurrence of conception represents the aggregation across Bernoulli trials for each intercourse day. Because of this data structure and dependency among the multiple cycles from a woman, implementing analyses has proven challenging. This article proposes a Bayesian approach based on a generalization of the Barrett and Marshall model to incorporate a woman-specific frailty and day-specific covariates. The model results in a simple closed form expression for the marginal probability of conception, and has an auxiliary variables formulation that facilitates efficient posterior computation. Although motivated by fecundability studies, the approach can be used for efficient variable selection and model averaging in general applications with categorical or discrete event time data.     

Nonparametric and semiparametric trend analysis for stratified recurrence times

Recurrent event data are frequently encountered in longitudinal follow-up studies when the occurrences of multiple events are considered as the major outcomes. Suppose that the recurrent events are of the same type and the variable of interest is the recurrence time between successive events. In many applications, the distributional pattern of recurrence times can be used as an index for the progression of a disease. Such a distributional pattern is important for understanding the natural history of a disease or for confirming long-term treatment effect. In this article, we discuss and define the comparability of recurrence times. Nonparametric and semiparametric methods are developed for testing trend of recurrence time distributions and estimating trend parameters in regression models. The construction of the methods is based on comparable recurrence times from stratified data. A real data example is presented to illustrate the use of methodology.     

Increase of genetic variation over time in a recently founded population of great reed warblers (Acrocephalus arundinaceus) revealed by microsatellites and DNA fingerprinting

Genetic similarity within pairs of individuals was examined using both 10 polymorphic microsatellite loci and multi-locus DNA fingerprinting profiles in a semi-isolated population of great reed warblers at Lake Kvismaren, south Central Sweden, in 1987-1993. The population was founded by a few individuals in 1978, followed by a gradual increase in numbers until 1988, since when the population has remained relatively stable with about 60 breeding birds. We have previously found that high genetic similarity between pair-mates in the population during the early part of the study period reduced egg hatching success, and hence reproductive success. The measures of pairwise genetic similarity, microsatellite allele sharing and DNA fingerprinting band sharing, were highly correlated with pedigree-based relatedness. Both microsatellite and DNA fingerprinting similarities between pair-mates declined significantly over the study period, and the pattern was most pronounced in the DNA fingerprinting data. Analyses restricted to the microsatellite data showed that the average annual microsatellite similarity between pairwise combinations of individuals, as well as individual homozygosity in males, declined significantly over the study period, and that several immigrants carrying novel alleles entered the population during the study. Hence, the temporal decline in genetic similarity of mates in the population is probably a consequence of increased immigration, facilitated by the recent expansion of the species in the region. These results suggest that the population has now recovered genetically, or is in the process of recovering, from a recent founder event.