981 resultados para DEVELOPMENTAL EVOLUTION


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Recent studies showed that nonhuman primate TRIM5 alpha can efficiently block HIV-1 infection in human cell lines. It can also restrict other retroviruses, therefore, suggested as a general defender against retrovirus infection. Here, we present an evolutionary analysis of TRIM5 alpha in primates. Our results demonstrated that TRIM5a has been evolving rapidly in primates, which is likely caused by Darwinian positive selection. The SPRY domain of TRM5 alpha, which may be responsible for recognition of incoming viral capsids showed higher nonsynonymous/synonymous substitution ratios than the non-SPRY domain, indicating that the adaptive evolution of TRIM5a ill primates might be an innate strategy developed in defending retrovirus infection during primate evolution. In addition, the comparative protein sequence analysis suggested that the amino acid substitution pattern at a single site (344R/Q/P) located in the SPRY domain may explain the differences in Susceptibilities of HIV-1 infection in diverse primate species. (c) 2005 Elsevier B.V. All rights reserved.

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A transmembrane protein gene, c1orf37-dup, was identified as a young gene specific to humans. It was derived from the conserved c1orf37 gene through retroposition after the divergence of human and chimpanzee. This gene has evolved rapidly driven by positi

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Early developmental stages of two Secutor species, Secutor insidiator (Bloch) (11.9-36.0 mm standard length, SL) and Secutor ruconius (Hamilton-Buchanan) (14.0-33.0 mm SL) collected by ichthyoplankton net from the Bak-khali river estuary of the Bay of Bengal, Cox's Bazar, Bangladesh are described and illustrated. All of the fins with supporting spines and rays were present in the smallest collected sizes of both species. With growth of the specimens, significant changes in melanophore patterns were found. S. insidiator is similar to S. ruconius in having upward protracting mouth parts and body colouration, but can be distinguished easily by its more elongate body shape (body depth 38-47% of SL compared with 46-52% of SL in Secutor ruconius). Both the species occurred round the year from August 1998 to July 1999. The surface water temperature and salinity during the study period varied from 22.0-32) C and 10-37 ppt respectively.

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In order to study the early developmental stages of Nandus nandus an experiment was conducted, where eggs and milt were obtained from the laboratory reared N nandus by stripping after 15 hours of 150 mg/kg body weight of carp PG extract injection. Then the eggs were fertilized in the laboratory and subsequent developmental stages were studied. First cleavage (two cell), four cell, eight cell, sixteen cell and multi cell stages were found 30, 50, 70, 105 and 160 minutes after fertilization respectively. Morula, early gastrula, middle gastrula, late gastrula and yolk plug stages were found 5, 8, 9, 11 and 13 hours after fertilization respectively. Hatching occurred within 20±2 hours after fertilization, and larvae were measured 1.60 mm in diameter. After one hour of hatching two melanophore bands were found at the caudal region of the body of the larvae. Eyes were first observed in l 0 hours, pectoral and pelvic fin buds appeared in 22 hours and well developed in 38 hours old larvae. Mouth cleft and brain lobes were visible when the larvae were 34 and 38 hours old respectively. Myomeres partially appeared in 16 hours, which were clearly visible in 74 hours old larvae. Larvae started wandering and searching for food after 56 hours of hatching. The yolk sac was completely absorbed when larvae became 62 hours old.

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Effects of age and season on the developmental capacity of oocytes from unstimulated and FSH-stimulated rhesus monkeys were examined, Immature cumulus-oocyte complexes were matured in vitro in modified CMRL-1066 medium containing 20% bovine calf serum and

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Dalai-lamae (Ovis ammon dalai-lamae), Gobi (O. a. darwini), Kara Tau (O. a. nigrimontana) and Tibetan (O. a. hodgsoni) argali share a 2n = 56 diploid chromosome number and a karyotype consisting of 2 pairs of biarmed and 25 pairs of acrocentric autosomes, a large acrocentric X and a minute Y chromosome. The Giemsa-banding patterns of the largest pair of biarmed chromosomes were identical to those of the largest biarmed chromosomes in all wild sheep and domestic sheep of the genus Ovis. The banding patterns of the second pair of biarmed chromosomes (metacentric) were identical to the third pair of biarmed chromosomes in Ovis with 2n = 54 and to the third largest pair of chromosomes in the 2n = 52 karyotype of Siberian snow sheep (O. nivicola). The G-banded karyotypes of dalai-lamae, darwini, hodgsoni and nigrimontana are consistent with all subspecies of argali (O. ammon), except that the Y chromosome is acrocentric instead of metacentric as typical of the argaliform wild sheep and Ovis. The Dalai-lamae and Tibetan argali specimens exhibit the light-colored, long-haired ruffs and body coloration typical of argalis from the Tibetan Plateau. The Gobi argali, from the extreme western Gobi, is similar to the dark phase argali.

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Comparative studies of the efficiency of 32 m bulged belly, long wing and four panel trawls have shown that the bulged belly trawl to be superior to the other nets in catching bottom fishes and column fishes. 40% of the bottom fishes and 48% of the column fishes were caught by the bulged belly trawl. However, for prawn catch, the long wing trawl appears to be better as it landed 52% of the total prawn catch of the three nets. Bulged belly trawl was found to be next only to long wing trawl in this respect.

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Design work involves uncertainty that arises from, and influences, the progressive development of solutions. This paper analyses the influences of evolving uncertainty levels on the design process. We focus on uncertainties associated with choosing the values of design parameters, and do not consider in detail the issues that arise when parameters must first be identified. Aspects of uncertainty and its evolution are discussed, and a new task-based model is introduced to describe process behaviour in terms of changing uncertainty levels. The model is applied to study two process configuration problems based on aircraft wing design: one using an analytical solution and one using Monte-Carlo simulation. The applications show that modelling uncertainty levels during design can help assess management policies, such as how many concepts should be considered during design and to what level of accuracy. © 2011 Springer-Verlag.

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Theory suggests that spatial structuring should select for intermediate levels of virulence in parasites, but empirical tests are rare and have never been conducted with castration (sterilizing) parasites. To test this theory in a natural landscape, we co

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Explaining "Tragedy of the Commons" of evolution of cooperation remains one of the greatest problems for both biology and social science. Asymmetrical interaction, which is one of the most important characteristics of cooperative system, has not been sufficiently considered in the existing models of the evolution of cooperation. Considering the inequality in the number and payoff between the cooperative actors and recipients in cooperation systems, discriminative density-dependent interference competition will occur in limited dispersal systems. Our model and simulation show that the local but not the global stability of a cooperative interaction can be maintained if the utilization of common resource remains unsaturated, which can be achieved by density-dependent restraint or competition among the cooperative actors. More intense density dependent interference competition among the cooperative actors and the ready availability of the common resource, with a higher intrinsic contribution ratio of a cooperative actor to the recipient, will increase the probability of cooperation. The cooperation between the recipient and the cooperative actors can be transformed into conflict and, it oscillates chaotically with variations of the affecting factors under different environmental or ecological conditions. The higher initial relatedness (i.e. similar to kin or reciprocity relatedness), which is equivalent to intrinsic contribution ratio of a cooperative actor to the recipient, can be selected for by penalizing less cooperative or cheating actors but rewarding cooperative individuals in asymmetric systems. The initial relatedness is a pivot but not the aim of evolution of cooperation. This explains well the direct conflict observed in almost all cooperative systems.

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GATA基因在脊椎动物和非脊椎动物的发育中行使重要的功能,该家族的成员在进化上也足非常保守的.脊椎动物的GATA基因分为两个亚群:GATA1/2/3和GATA4/5/6.通过生物信息分析,在文吕鱼的基因缓中找到了3个GATA基因:一个GATA1/2/3业家族基因,两个GATA4/5/6亚家族基因:还找到一个类GATA基因.还克隆了白氏文昌鱼(Branchiostoma belcheri)GATA123的一段序列,并研究了它在早期胚胎发育中的表达图式.结果表明GATA123在原肠胚的中内胚层表达,而在神经胚晚期和幼体早期,GATA123在脑泡和消化道中部区域表达.这种表达模式与头部发育的重要基因Otx相类似.结果提示在文吕鱼脑泡的发育过程中GATA123和Otx很可能共同发挥着重要的作用.

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The evolutionarily conserved Nkx6 family transcription factors play important roles in the patterning of the central nervous system (CNS) and pancreas in vertebrates. In this study, we describe the cloning and expression patterns of the three Nkx6 family

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Vertebrate RACK1 plays a key role in embryonic development. This paper described the cloning, phylogenetic analysis and developmental expression of AmphiRACK1, the RACK1 homologous gene in amphioxus. Phylogenetic analysis indicated that amphioxus RACK1 wa