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51.
Changes in the abundance and distribution of individual species have been widely documented in Britain and other countries in recent decades, but little has been done to determine changes in community composition over broad geographic areas. Here, we studied species turnover in 51 butterfly assemblages in Britain since 1976, examining extinction and colonisation events together with variation in the abundances of the species. We showed that the species turnover that occurred over 20 years in Britain was associated with colonisation and extinction events and also with variability in the abundance of the species. These changes in community composition differed according to the habitat requirements of the species and their previous distributions, being more evident for habitat specialists and for southerly distributed species. Colonising species often became abundant components of the communities they joined, although this was more evident for generalist than for specialist species. The abundance of species following their arrival, increased with time since colonisation. Species turnover associated with southerly species expanding northwards is consistent with being a response to climate change. The results suggest that climate- and habitat-driven changes in the identity and abundance of species within communities are widespread, and probably ubiquitous. Similar changes are likely to be occurring in other groups of organisms that are similarly undertaking major range shifts associated with climate change.  相似文献   
52.
The origin and diversification of evolutionary novelties-lineage-specific traits of new adaptive value-is one of the key issues in evolutionary developmental biology. However, comparative analysis of the genetic and developmental bases of such traits can be difficult when they have no obvious homologue in model organisms. The finding that the evolution of morphological novelties often involves the recruitment of pre-existing genes and/or gene networks offers the potential to overcome this challenge. Knowledge about shared developmental processes obtained from extensive studies in model organisms can then be used to understand the origin and diversification of lineage-specific structures. Here, we illustrate this approach in relation to eyespots on the wings of Bicyclus anynana butterflies. A number of spontaneous mutations isolated in the laboratory affect eyespots, lepidopteran-specific features, and also processes that are shared by most insects. We discuss how eyespot mutants with disturbed embryonic development may help elucidate the genetic pathways involved in eyespot formation, and how venation mutants with altered eyespot patterns might shed light on mechanisms of eyespot development.  相似文献   
53.
Some properties of the cell-free DNA (cfDNA) of peripheral blood plasma were assessed in 153 employees of atomic industry enterprises. The contents of ribosomal repeat (rDNA) and its concentration in plasma increased in cfDNA of the group of persons in comparison with non-irradiated individuals. The contents of satellite III in cfDNA of donors and of irradiated persons do not differ and less than in DNA nucleus. The correlation between cumulative dose of radiation, contents of rDNA in cfDNA and the frequency of lymphocytes bearing mutations at T-cell receptor (TCR) locus was obtained. The definition of three indications in irradiated persons: the contents of ribosomal genes in cfDNA, TCR-mutant cell frequency and concentration of ribosomal genes in blood plasma--may be useful for revealing individuals in organism of which an intensive cell apoptosis takes place and there is an increased probability of carcinogenesis and of progress of disease of immune system.  相似文献   
54.
Studies of sibling competition within brood hierarchies have rarely assessed simultaneously the effects of sex and rank in the brood hierarchy on traits other than offspring mortality and differential growth. We studied the expression of heat-shock proteins (Hsps) to assess the physiological stress response to different combinations of sex and position within competitive brood hierarchies in the black kite Milvus migrans (Bodd.), a sexually dimorphic raptor showing facultative siblicide. Senior males showed higher stress levels than did senior females and younger siblings of each sex as revealed by Hsp60 values. The analysis of Hsp70 levels indicated that nestlings from broods in which the senior chick was a male showed higher stress levels than did nestlings from broods in which the senior chick was a female. In addition, levels of Hsp60 were related negatively to nutritional condition expressed as levels of plasmatic albumin. This suggests that the sex of senior chicks may be key in determining their stress level and that of their siblings, which is probably associated with sibling competition by fighting within brood hierarchies. The comparatively higher stress levels of senior males (and their siblings) may be a consequence of their ability to exploit their potential advantage from being the head start while avoiding a possible competitive disadvantage from being the smaller sex, independent of environmental conditions determining the probability of brood reduction. Differential stress levels depending on sex and rank in the brood hierarchy may be a consequence of parental control of offspring behaviour through differential resource allocation (e.g. yolk androgens) or it may reflect adaptations of particular chicks (senior males) to enhance their competitive ability within brood hierarchies.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 383–390.  相似文献   
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56.
Oral pathogens have created a menace in recent years due to biofilm formation and antimicrobial drug resistance. The current treatment strategy works well with antibiotics. However, constant use of antibiotics creates a selective pressure, which increases adaptability of the pathogens. Therefore, it is of interest to analyze the potential targets of genistein in dental pathogens using computer aided prediction tools.  相似文献   
57.
A study was made of the effect of cycloheximide on the radioresistant DNA synthesis stimulated by preincubation of cells with 5-fluorodeoxyuridine (FdUrd). It was shown that after the cycloheximide treatment the radioresistant DNA synthesis was absent while in FdUrd-treated cells it did occur. It is assumed that the FdUrd-stimulated radioresistant DNA synthesis is of an inducible nature.  相似文献   
58.
Enzyme immunoassay for ceruloplasmin (CP)*, employing monospecific CP antibodies labeled with horse radish peroxidase was developed. This method permits to determine total content of CP, which is present in Wilson disease patients' blood in enzymatically active and enzymatically inactive forms. The evidence is presented that the method can be used for a direct determination of CP in blood serum. The minimal CP concentration which may be determined by enzyme immunoassay (IEA) is 5.10(-9) g/ml. The method was used for determination of CP concentrations in Wilson disease patients' blood with different disease severity. Analysis of blood samples taken from 6 Wilson disease patients with the use of IEA method revealed similar total CP concentrations. At the same time, the oxidase activities of CP in the blood of different patients varied more than sevenfold.  相似文献   
59.
The comparison of protective effects of native ceruloplasmin (CP) and of preparation CP1 containing carbohydrate fragment GlcNAc(beta(1,4]GlcNAc which specifically binds on RBC (alpha(1,6)Fuc receptors showed that CP1 exhibits much more powerful protective effect on RBC in copper-induced lysis. It was found, however, that CP2 (native CP devoided of CP1) protected RBC as well as CP despite its inability of binding to RBC membrane. CP and CP1 in a similar way decrease copper concentration in RBC. It was shown that copper accumulation and GSH decrease in RBC are two independent and concurrent processes; the copper and GSH concentrations are not the factors determining RBC resistance to hemolysis. CP inhibits the reaction of superoxide radicals generation as a result of Cu interaction with -SH groups of RBC membrane; the effect is more pronounced than the effect of catalase or superoxide dismutase. CP and CP1 preparations equally inhibit this reaction. Apparently CP reception on RBC leads not only to membrane protection from superoxide and hydroxyl radicals but represents a more complex process.  相似文献   
60.
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