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排序方式: 共有419条查询结果,搜索用时 15 毫秒
1.
Josep C. Jiménez-Chillarón Rubén Díaz Débora Martínez Thais Pentinat Marta Ramón-Krauel Sílvia Ribó Torsten Plösch 《Biochimie》2012
Nutrition plays a key role in many aspects of health and dietary imbalances are major determinants of chronic diseases including cardiovascular disease, obesity, diabetes and cancer. Adequate nutrition is particularly essential during critical periods in early life (both pre- and postnatal). In this regard, there is extensive epidemiologic and experimental data showing that early sub-optimal nutrition can have health consequences several decades later. 相似文献
2.
Phylogenetic analyses of primate size evolution: the consequences of sexual selection 总被引:6,自引:0,他引:6
Patrik Lindenfors Birgitta S. Tullberg 《Biological journal of the Linnean Society. Linnean Society of London》1998,64(4):413-447
We have analysed the relationship between primate mating system, size and size dimorphism by utilizing several phylogenetically based methods. An independent contrast analysis of male and female size (log weight) showed that these are tightly correlated and that size dimorphism is not a simple allometric function of size. We found no relationship between mating system and sexual dimorphism in strepsirhines but a strong relationship in haplorhines. By matched-pairs analysis, where sister groups were matched according to whether the mating system predicted higher or lower intrasexual selection for male size, haplorhine species in more polygynous clades (with a predicted higher sexual selection) were significantly more dimorphic, had larger males, and also, but to a lesser degree, larger females. Both independent contrast and matched-pairs analyses are non-directional and correlational. By using a directional test we investigated how a transition in mating system affects size and dimorphism. Here, each observation is the sum of changes in dimorphism or size in a clade that is defined by a common origin of a mating system. Generally, dimorphism, as well as male and female size, increased after an expected increase in sexual selection, and decreased after an expected decrease in sexual selection. The pattern was, however, not significant for all of the alternative character reconstructions. In clades with an expected increase in sexual selection, male size increased more than female size. This pattern was significant for all character reconstructions. The directional investigation indicates that the magnitude of change in haplorhine dimorphism is larger after an increase in sexual selection than after a decrease, and, for some reconstructions, that the magnitude of size increase is larger than the magnitude of size decrease for both sexes. Possible reasons for these patterns are discussed, as well as their implications as being one possible mechanism behind Cope's rule, i.e. general size increase in many phylogenetic lineages. 相似文献
3.
4.
R. C. FISHER 《Biological journal of the Linnean Society. Linnean Society of London》1988,35(4):313-319
The abundance and diversity of insects was the subject of the joint commemorative meeting between the Linnean Society and the Royal Entomological Society of London. This paper gives a brief outline of the foundation and early history of the Entomological Society and its forerunners, and its relations with the Linnean Society at the time. It also shows how the contributions of the founding fellows of the Society, whose interests originated in collecting and insect natural history, laid the foundations of many of the present day fields of entomological research. 相似文献
5.
Serban Iordanescu 《Molecular & general genetics : MGG》1989,217(2-3):481-487
Summary pT181 and pC221 are closely relatedStaphylococcus aureus plasmids with the same genome organization, which is characterized by the overlapping of the origin of replication with the
sequence encoding a protein, Rep, essential for plasmid replication. Former results have shown the lack of in vivo cross-complementation
between these two plasmids, while in vitro studies have revealed the ability of both Rep proteins to act on either origin.
One possible explanation for this difference was based on a previous analysis of the incompatibility expressed by the origin
of replication of these plasmids, showing that the origin embedded in therep gene competes for Rep utilization with the origin of a test plasmid and that changes in the sequence of the origin reduce
its ability to compete. To avoid this problem, in the present work special hybrids were constructed in which the origin of
replication overlapping therep gene was mutationally inactivated, without changing the amino acid sequence of the encoded protein. The level of Rep expression
by these hybrids could be varied by taking advantage of what is presently known about the control of Rep synthesis in plasmid
pT181. The results of complenentation studies conducted using these hybrids have shown that: (i) at the usual level of expression
for a wild-type plasmid each Rep protein can initiate replication strictly from its corresponding origin; (ii) when overproduced,
the pT181 RepC protein could also act efficiently on the pC221 origin; a functional pT181 origin present in the same host
completely prevented this complementation; (iii) in excess, the RepD protein encoded by pC221 could replicate a plasmid carrying
the pT181 origin but could not ensure the hereditary stability of such a plasmid in the absence of another active replication
system; (iv) when overproduced both RepC and RepD could act on the origin of replication of three other related plasmids pS194,
pC223 and pUB112. 相似文献
6.
Robert G. Rutledge Thérèse Quellet Jiro Hattori Brian L. Miki 《Molecular & general genetics : MGG》1991,229(1):31-40
Summary The Brassica napus rapeseed cultivar Topas contains an acetohydroxyacid synthase (AHAS) multigene family consisting of five members (AHAS 1–5). DNA sequence analysis indicate that AHAS1 and AHAS3 share extensive homology. They probably encode the AHAS enzymes essential for plant growth and development. AHAS2 has diverged significantly from AHAS1 and AHAS3 and has unique features in the coding region of the mature polypeptide, transit peptide and upstream non-coding DNA, which raises the possibility that it has a distinct function. AHAS4 and AHAS5 have interrupted coding regions and may be defective. The complexity of the AHAS multigene family in the allotetraploid species B. napus is much greater than reported for Arabidopsis thaliana and Nicotiana tabacum. Analysis of the presumptive progenitor diploid species B. campestris and B. oleracea indicated that AHAS2, AHAS3 and AHAS4 originate from the A genome, whereas AHAS1 and AHAS5 originate from the C genome. Further variation within each of the AHAS genes in these species was found. 相似文献
7.
Eville Gorham 《Biogeochemistry》1991,13(3):199-239
The history of how aspects of biology, geology and chemistry came together over the past three centuries to form a separate discipline known as biogeochemistry is described under four major headings: metabolic aspects, geochemical aspects, biogeochemical cycles, and the origin of life. A brief chronology of major conceptual advances is also presented. 相似文献
8.
JON MALLATT 《Zoological Journal of the Linnean Society》1984,82(3):261-272
Based on protochordates and extant fish, the earliest Palaeozoic vertebrates were microphagous suspension-feeding animals that pumped food-carrying water very slowly and thus required highly concentrated suspensions. Such conditions exist in benthic (not open water) aquatic environments. Feeding modes which on the basis of extant fish are closely related to benthic microphagous suspension feeding include deposit feeding, epilithic algal scraping, and macrophagous suspension feeding; early jawless vertebrates are predicted to have included all these feeding types. The gnathostome condition is predicted to have followed an initial switch from feeding on suspensions to taking tiny individual food particles (microphagous suspension-feeding → microphagous particulate-feeding → macrophagous particulate-feeding). 相似文献
9.
J. J. Burdon 《Evolution; international journal of organic evolution》1994,48(5):1564-1575
The genetic basis of resistance in wild flax (Linum marginale) to its host-specific pathogen Melampsora lini was investigated in seven lines collected from a single population growing at Kiandra, New South Wales and in an additional ten lines collected more widely across southeastern Australia. All lines showed different phenotypic patterns of resistance and susceptibility. Genetic analyses indicated the presence of single dominant genes for race-specific resistance in all but one of these lines. That particular line appeared to carry two linked dominant genes for resistance. Intercrosses between lines in each of these groups of L. marginale detected substantially more linkage between the resistance genes in the Kiandra population sample than between those in the broader geographic collection. This result is interpreted to indicate a possible mechanism whereby resistance genes are generated in natural populations. 相似文献
10.
Nancy Minugh-Purvis 《American journal of physical anthropology》1993,92(4):449-461
Reexamination of the immature Upper Pleistocene hominid maxilla from Mugharet el-'Aliya (Tangier), Morocco is undertaken in light of new evidence on the growth and development of Upper Pleistocene hominids. Metric and qualitative comparisons were made with 17 immature Upper Pleistocene maxillae, and with a recent Homo sapiens sapiens sample. No unambiguous criteria for aligning the maxilla with Neandertals were found, although one character, the degree of maxillary flexion on the zygoma, strongly suggests that this child could be a representative of H. s. sapiens. The probable lack of a canine fossa in Mugharet el-'Aliya 1, the primary criterion used previously to align it with Neandertals, cannot be accurately extrapolated to its adult form from this juvenile. The present evidence suggests that it is inappropriate to refer to this fossil as “Neandertal-like” or as a North African “neandertaloid.” Thus, the Tangier maxilla should not be cited as evidence for the presence of Neandertal facial features in North Africa during the Upper Pleistocene. © 1993 Wiley-Liss, Inc. 相似文献