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191.
The Zic genes are the vertebrate homologues of the Drosophila pair rule gene odd-paired. It has been proposed that Zic genes play several roles during neural development including mediolateral segmentation of the neural plate, neural crest induction, and inhibition of neurogenesis. Initially during mouse neural development Zic2 is expressed throughout the neural plate while later on expression in the neurectoderm becomes restricted to the lateral region of the neural plate. A hypomorphic allele of Zic2 has demonstrated that in the mouse Zic2 is required for the timing of neurulation. We have isolated a new allele of Zic2 that behaves as a loss of function allele. Analysis of this mutant reveals two further functions for Zic2 during early neural development. Mutation of Zic2 results in a delay of neural crest production and a decrease in the number of neural crest cells that are produced. These defects are independent of mediolateral segmentation of the neurectoderm and of dorsal neurectoderm proliferation, both of which occur normally in the mutant embryos. Additionally Zic2 is required during hindbrain patterning for the normal development of rhombomeres 3 and 5. This work provides the first genetic evidence that the Zic genes are involved in neural crest production and the first demonstration that Zic2 functions during hindbrain patterning.  相似文献   
192.
Protecting species and their habitats through the designation and management of protected areas is central to present biodiversity conservation efforts in Europe. Recent awareness of the importance of ecosystem dynamics in changing environments and of human needs for the sustainable provision of ecosystem services expose potential weaknesses in current European conservation management strategies and policy. Here we examine these issues in the light of information gained from reviews, workshops, interviews and discussions undertaken within the RUBICODE project. We present a new conceptual framework that joins conventional biodiversity conservation with new requirements. The framework links cultural and aesthetic values applied in a static environment to the demands of dynamic ecosystems and societal needs within social–ecological systems in a changing Europe. We employ this framework to propose innovative ways in which ecosystem service provision may be used to add value to traditional conservation approaches by supporting and complementing present European biodiversity conservation strategy and policy while remaining within the guidelines of the Convention on Biological Diversity.  相似文献   
193.
Selecting thresholds of occurrence in the prediction of species distributions   总被引:15,自引:0,他引:15  
Transforming the results of species distribution modelling from probabilities of or suitabilities for species occurrence to presences/absences needs a specific threshold. Even though there are many approaches to determining thresholds, there is no comparative study. In this paper, twelve approaches were compared using two species in Europe and artificial neural networks, and the modelling results were assessed using four indices: sensitivity, specificity, overall prediction success and Cohen's kappa statistic. The results show that prevalence approach, average predicted probability/suitability approach, and three sensitivity-specificity-combined approaches, including sensitivity-specificity sum maximization approach, sensitivity-specificity equality approach and the approach based on the shortest distance to the top-left corner (0,1) in ROC plot, are the good ones. The commonly used kappa maximization approach is not as good as the afore-mentioned ones, and the fixed threshold approach is the worst one. We also recommend using datasets with prevalence of 50% to build models if possible since most optimization criteria might be satisfied or nearly satisfied at the same time, and therefore it's easier to find optimal thresholds in this situation.  相似文献   
194.
Oncogenic signaling stimulates the dynamic remodeling of actin microfilaments and substrate adhesions, essential for cell spreading and motility. Transformation is associated with increased expression of beta1,6GlcNAc-branched N-glycans, products of Golgi beta1,6-acetylglucosaminyltransferase V (Mgat5) and the favored ligand for galectins. Herein we report that fibronectin fibrillogenesis and fibronectin-dependent cell spreading are deficient in Mgat5(-/-) mammary epithelial tumor cells and inhibited in Mgat5(+/+) cells by blocking Golgi N-glycan processing with swainsonine or by competitive inhibition of galectin binding. At an optimum dosage, exogenous galectin-3 added to Mgat5(+/+) cells activates focal adhesion kinase (FAK) and phosphatidylinositol 3-kinase (PI3K), recruits conformationally active alpha5beta1-integrin to fibrillar adhesions, and increases F-actin turnover. RGD peptide inhibits PI3K-dependent fibronectin matrix remodeling and fibronectin-dependent cell motility, while galectin-3 stimulates and overrides the inhibitory effects of RGD. Antibodies to the galectin-3 N-terminal oligomerization domain stimulate alpha5beta1 activation and recruitment to fibrillar adhesions in Mgat5(+/+) cells, an effect that is blocked by disrupting galectin-glycan binding. Our results demonstrate that fibronectin polymerization and tumor cell motility are regulated by galectin-3 binding to branched N-glycan ligands that stimulate focal adhesion remodeling, FAK and PI3K activation, local F-actin instability, and alpha5beta1 translocation to fibrillar adhesions.  相似文献   
195.
There has long been interest in determining if mass ivermectin administration for onchocerciasis has 'unknowingly' interrupted lymphatic filariasis (LF) transmission where the endemicity of the two diseases' overlaps. We studied 11 communities in central Nigeria entomologically for LF by performing mosquito dissections on Anopheline LF vectors. Six of the communities studied were located within an onchocerciasis treatment zone, and five were located outside of that zone. Communities inside the treatment zone had been offered ivermectin treatment for two-five years, with a mean coverage of 81% of the eligible population (range 58–95%). We found 4.9% of mosquitoes were infected with any larval stage of W. bancrofti in the head or thorax in 362 dissections in the untreated villages compared to 4.7% infected in 549 dissections in the ivermectin treated villages (Mantel-Haenszel ChiSquare 0.02, P = 0.9). We concluded that ivermectin annual therapy for onchocerciasis has not interrupted transmission of Wuchereria bancrofti (the causative agent of LF in Nigeria).  相似文献   
196.
Given the concern about biodiversity loss, there are a number of arguments used for biodiversity conservation ranging from those emphasising the intrinsic value of biodiversity to those on the direct use value of ecosystems. Yet arguing the case for biodiversity conservation effectively requires an understanding of why people value biodiversity. We used Q methodology to explore and understand how different conservation practitioners (social and natural science researchers, environmental non-Governmental organisations and decision-makers) in nine European countries argue for conservation. We found that there was a plurality of views about biodiversity and its conservation. A moral argument and some arguments around the intrinsic and ecological value of biodiversity were held by all stakeholder groups. They also shared the view that species valuation does not justify the destruction of nature. However, there were also some differences within and between the groups, which primarily reflected the espousal of either ecocentric or anthropocentric viewpoints. Our findings suggest that moral arguments and those around biodiversity’s intrinsic and ecological value could potentially serve as a starting point for building consensus among conservation practitioners.  相似文献   
197.
Research on social learning may be of use in the conservation of primates, especially great apes, through (a) promoting their public image, (b) identifying specific adaptations, and (c) devising reintroduction training programs. We surveyed all the instigated social learning studies in primates published since 1950 in order to assess their usefulness to devise reintroduction training programs. We identified 99 publications containing 130 data sets from 27 species of primates. Great apes produced significantly more positive social learning effects than either cercopithecines or cebids. There was also an enhanced social learning effect when skilled demonstrators were used. Our survey indicates that the scientific understanding of many aspects of primate social learning relevant to conservation, including its function, learning spatial route plotting, food and sleeping site location, predator avoidance and detection, and the effect of model and tutee status, would benefit from greater research. Future instigated studies on primate social learning would be most informative for reintroduction if they included ecologically valid tasks presented to 2 similarly composed social groups, one of which functioned as a control, i.e., without being exposed to a model.  相似文献   
198.
Relationships between leaf wettability and surface physicochemicalcharacteristics were examined in two genotypes of tobacco (Nicotianatabacum L. cv. Samsun) grown under controlled conditions atthree different levels of biologically effective ultraviolet-B(UV-BBE; 280–320 nm) radiation; 0 (control), 4.54 and5.66 kJ m–2d–1. Leaf wettability, assessed by measuringleaf-water droplet contact angles, was positively correlatedwith epicuticular wax chemical composition and trichome density,but not the amount of wax on the surface of leaves. Tobaccowax comprised a mixture of C19–C33 n-alkanes (59%) withhomologues containing an odd number of carbon atoms predominating,C28–C32 br-alkanes (38%), and a small quantity (3%) offree Cl6–C18 fatty acids. Significant effects of UV-Bradiation upon wax production and chemical composition wererestricted to the adaxial surface of leaves. Enhanced UV-B radiationreduced the quantity of epicuticular wax in the more sensitivegenotype [GR32-3], assessed from effects on dry matter accumulation,partitioning and changes in leaf morphology, and resulted inmarked changes in wax composition and homologue distributionsin both genotypes. UV-B-induced increases in branching, andshifts toward the synthesis of shorter-chain homologues providedevidence for a fundamental effect of UV-B radiation on wax biosynthesis,with the observed effects consistent with a highly specificand direct effect of UV-B radiation on microsomal-based elongasesin the epidermis. UV-B radiation also reduced the density oftrichomes on the adaxial leaf surface, whilst increasing thenumber of trichomes on the abaxial leaf surface. Changes inwax composition and trichome density induced by UV-B radiationwere associated with increases in leaf surface wettability whichwere particularly pronounced on the adaxial surface. The subtle,though possibly far-reaching, physiological consequences ofsuch UV-B-induced changes in surface wettability are discussedin the light of other recent findings. Key words: Epicuticular wax chemistry, wax quantity, leaf wettability, trichome density, ultraviolet-B radiation  相似文献   
199.
A series of α7 nicotinic acetylcholine receptor full agonists with a 1,3,4-oxadiazol-2-amine core has been discovered. Early lead 1 was found to have a limited therapeutic index with respect to its potential for cardiovascular side effects. Further optimisation of this series led to the identification of 22 a potent full agonist showing efficacy at a dose of 0.1mg/kg in the novel object recognition model of cognition enhancement. Comparison of 1 with 22 demonstrated the latter to have an improved oral pharmacokinetic profile and cardiovascular therapeutic index.  相似文献   
200.
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