Quantitative morphological investigations on smooth muscle cells in vascular surgical specimens and their clinical importance.

A distinct distribution of activated SMC could be demonstrated in atherosclerotic plaques and the neighbouring media of human beings. An increased proliferation was found in the younger age group and generally in the marginal regions of the plaques. The occurrence of activated SMC is thought to be a sequel of metabolic hypoxic damages. A high frequency of activated SMC is a bad prognostic sign in surgical specimens indicating a tendency for proliferation and occlusion.     

Pleiotropic scaling of gene effects and the 'cost of complexity'

As perceived by Darwin, evolutionary adaptation by the processes of mutation and selection is difficult to understand for complex features that are the product of numerous traits acting in concert, for example the eye or the apparatus of flight. Typically, mutations simultaneously affect multiple phenotypic characters. This phenomenon is known as pleiotropy. The impact of pleiotropy on evolution has for decades been the subject of formal analysis. Some authors have suggested that pleiotropy can impede evolutionary progress (a so-called 'cost of complexity'). The plausibility of various phenomena attributed to pleiotropy depends on how many traits are affected by each mutation and on our understanding of the correlation between the number of traits affected by each gene substitution and the size of mutational effects on individual traits. Here we show, by studying pleiotropy in mice with the use of quantitative trait loci (QTLs) affecting skeletal characters, that most QTLs affect a relatively small subset of traits and that a substitution at a QTL has an effect on each trait that increases with the total number of traits affected. This suggests that evolution of higher organisms does not suffer a 'cost of complexity' because most mutations affect few traits and the size of the effects does not decrease with pleiotropy.     

Host specificity of Lepidoptera in tropical and temperate forests

For numerous taxa, species richness is much higher in tropical than in temperate zone habitats. A major challenge in community ecology and evolutionary biogeography is to reveal the mechanisms underlying these differences. For herbivorous insects, one such mechanism leading to an increased number of species in a given locale could be increased ecological specialization, resulting in a greater proportion of insect species occupying narrow niches within a community. We tested this hypothesis by comparing host specialization in larval Lepidoptera (moths and butterflies) at eight different New World forest sites ranging in latitude from 15 degrees S to 55 degrees N. Here we show that larval diets of tropical Lepidoptera are more specialized than those of their temperate forest counterparts: tropical species on average feed on fewer plant species, genera and families than do temperate caterpillars. This result holds true whether calculated per lepidopteran family or for a caterpillar assemblage as a whole. As a result, there is greater turnover in caterpillar species composition (greater beta diversity) between tree species in tropical faunas than in temperate faunas. We suggest that greater specialization in tropical faunas is the result of differences in trophic interactions; for example, there are more distinct plant secondary chemical profiles from one tree species to the next in tropical forests than in temperate forests as well as more diverse and chronic pressures from natural enemy communities.     

基于场景的软构件自动化测试模型研究

随着软构件技术的快速发展,聚集软构件设计复杂软件系统的软件开发方法日趋成熟.如何利用系统架构和软构件的可靠性分析软件系统的可靠性成为一个亟待解决的问题.提出了一种基于场景的软构件自动化测试模型,给出基于统一建模语言UML的顺序图构造测试场景具体方法,并对基于UML顺序图构造测试场景方法的有效性进行了分析.     

xnd-1 regulates the global recombination landscape in Caenorhabditis elegans

Meiotic crossover (CO) recombination establishes physical linkages between homologous chromosomes that are required for their proper segregation into developing gametes, and promotes genetic diversity by shuffling genetic material between parental chromosomes. COs require the formation of double strand breaks (DSBs) to create the substrate for strand exchange. DSBs occur in small intervals called hotspots and significant variation in hotspot usage exists between and among individuals. This variation is thought to reflect differences in sequence identity and chromatin structure, DNA topology and/ or chromosome domain organization. Chromosomes show different frequencies of nondisjunction (NDJ), reflecting inherent differences in meiotic crossover control, yet the underlying basis of these differences remains elusive. Here we show that a novel chromatin factor, X non-disjunction factor 1 (xnd-1), is responsible for the global distribution of COs in C. elegans. xnd-1 is also required for formation of double-strand breaks (DSBs) on the X, but surprisingly XND-1 protein is autosomally enriched. We show that xnd-1 functions independently of genes required for X chromosome-specific gene silencing, revealing a novel pathway that distinguishes the X from autosomes in the germ line, and further show that xnd-1 exerts its effects on COs, at least in part, by modulating levels of H2A lysine 5 acetylation.