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排序方式: 共有434条查询结果,搜索用时 15 毫秒
91.
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93.
Ilka M. Kureck Evelien Jongepier Beate Nicolai Susanne Foitzik 《Molecular ecology》2012,21(22):5613-5623
Inbreeding can lead to the expression of deleterious recessive alleles and to a subsequent fitness reduction. In Hymenoptera, deleterious alleles are purged in haploid males moderating inbreeding costs. However, in these haplodiploid species, inbreeding can result in the production of sterile diploid males. We investigated the effects of inbreeding on the individual and colony level in field colonies of the highly inbred ant Hypoponera opacior. In this species, outbreeding winged sexuals and nest‐mating wingless sexuals mate during two separate reproductive periods. We show that regular sib‐matings lead to high levels of homozygosity and the occasional production of diploid males, which sporadically sire triploid offspring. On the individual level, inbreeding was associated with an increased body size in workers. On the colony level, we found no evidence for inbreeding depression as productivity was unaffected by the level of homozygosity. Instead, inbred colonies altered their allocation strategies by investing more resources into sexuals than into workers. This shift towards sexual production was due to an increased investment in both males and queens, which was particularly pronounced in the dispersive generation. The absence of inbreeding depression combined with increased reproductive investment, especially in outbreeding sexuals, suggests that these ants have evolved active strategies to regulate the extent and effects of frequent inbreeding. 相似文献
94.
Poncet D Pauleau AL Szabadkai G Vozza A Scholz SR Le Bras M Brière JJ Jalil A Le Moigne R Brenner C Hahn G Wittig I Schägger H Lemaire C Bianchi K Souquère S Pierron G Rustin P Goldmacher VS Rizzuto R Palmieri F Kroemer G 《The Journal of cell biology》2006,174(7):985-996
Replication of human cytomegalovirus (CMV) requires the expression of the viral mitochondria-localized inhibitor of apoptosis (vMIA). vMIA inhibits apoptosis by recruiting Bax to mitochondria, resulting in its neutralization. We show that vMIA decreases cell size, reduces actin polymerization, and induces cell rounding. As compared with vMIA-expressing CMV, vMIA-deficient CMV, which replicates in fibroblasts expressing the adenoviral apoptosis suppressor E1B19K, induces less cytopathic effects. These vMIA effects can be separated from its cell death-inhibitory function because vMIA modulates cellular morphology in Bax-deficient cells. Expression of vMIA coincided with a reduction in the cellular adenosine triphosphate (ATP) level. vMIA selectively inhibited one component of the ATP synthasome, namely, the mitochondrial phosphate carrier. Exposure of cells to inhibitors of oxidative phosphorylation produced similar effects, such as an ATP level reduced by 30%, smaller cell size, and deficient actin polymerization. Similarly, knockdown of the phosphate carrier reduced cell size. Our data suggest that the cytopathic effect of CMV can be explained by vMIA effects on mitochondrial bioenergetics. 相似文献
95.
There is increasing evidence that the vitamin D metabolite, 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) has endocrine actions. In the current work, we report that an endogenous binding protein for 24,25(OH)2D3 is catalase, based on sequence analysis of the isolated protein. An antibody (Ab 365) generated against equivalent protein recognized bovine catalase and a 64 kDa band in subcellular fractions of chick intestine. A commercially available anti-catalase antibody reduced specific [3H]24,25(OH)2D3 binding in subcellular fractions of chick intestine by greater than 65%, relative to the same fractions treated with an unrelated antibody (Ab 099). The same commercially available anti-catalase was able to block the inhibitory actions of 24,25(OH)2D3 on 32P uptake in isolated intestinal epithelial cell suspensions. We subsequently characterized binding of steroid to commercially available catalase, and found that between 0 and 5 nM of enzyme added to subcellular fraction P2 (20,000g, 10-min post-nuclear pellet) resulted in a linear increase in the amount of [3H]24,25(OH)2D3 specifically bound. Additional studies indicated that 25(OH)D3 was an effective competitor for binding, whereas 1,25(OH)2D3 only poorly displaced [3H]24,25(OH)2D3. Saturation analyses with added catalase yielded a physiologically relevant affinity constant (KD=5.6+/-2.7 nM) and a Bmax=209+/-34 fmols/mg protein, comparable to previous studies using purified basal lateral membranes or vesicular fractions. Moreover, in a study on subcellular fractions isolated from chickens of varying ages, we found that in females, both specific [3H]24,25(OH)2D3 binding and catalase activity increased from 7- to 58-week-old birds, whereas in males, elevated levels of both parameters were expressed in preparations of 7- and 58-week-old birds. The data suggest that signal transduction may occur through modulation of hydrogen peroxide production. 相似文献
96.
J?rg Oehlmann Ulrike Schulte-Oehlmann Werner Kloas Oana Jagnytsch Ilka Lutz Kresten O. Kusk Leah Wollenberger Eduarda M. Santos Gregory C. Paull Katrien J. W. Van Look Charles R. Tyler 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2009,364(1526):2047-2062
This review provides a critical analysis of the biological effects of the most widely used plasticizers, including dibutyl phthalate, diethylhexyl phthalate, dimethyl phthalate, butyl benzyl phthalate and bisphenol A (BPA), on wildlife, with a focus on annelids (both aquatic and terrestrial), molluscs, crustaceans, insects, fish and amphibians. Moreover, the paper provides novel data on the biological effects of some of these plasticizers in invertebrates, fish and amphibians. Phthalates and BPA have been shown to affect reproduction in all studied animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations. Molluscs, crustaceans and amphibians appear to be especially sensitive to these compounds, and biological effects are observed at environmentally relevant exposures in the low ng l−1 to µg l−1 range. In contrast, most effects in fish (except for disturbance in spermatogenesis) occur at higher concentrations. Most plasticizers appear to act by interfering with the functioning of various hormone systems, but some phthalates have wider pathways of disruption. Effect concentrations of plasticizers in laboratory experiments coincide with measured environmental concentrations, and thus there is a very real potential for effects of these chemicals on some wildlife populations. The most striking gaps in our current knowledge on the impacts of plasticizers on wildlife are the lack of data for long-term exposures to environmentally relevant concentrations and their ecotoxicity when part of complex mixtures. Furthermore, the hazard of plasticizers has been investigated in annelids, molluscs and arthropods only, and given the sensitivity of some invertebrates, effects assessments are warranted in other invertebrate phyla. 相似文献
97.
98.
Ilka E. Bauer Jagtar S. Bhatti Christopher Swanston R. Kelman Wieder Caroline M. Preston 《Ecosystems》2009,12(4):636-653
Peatland-margin habitats with organic matter accumulation of 40–150 cm make up a significant but poorly quantified portion
of Canada’s boreal forest region. Spanning the transition between non-wetland forest and fen proper, these ecosystems represent
a zone of complex environmental and vegetation change, yet little is known about their ecological function or development.
We here use vegetation and macrofossil analysis, traditional 14C, bomb-spike 14C, and 210Pb dating to investigate the development, organic matter accumulation, and recent vegetation history of peat margin communities
at two sites in central Saskatchewan, Canada. Although similar in general shape, bomb-spike 14C and 210Pb chronologies show limited agreement in three of the four profiles examined, with 210Pb generally producing younger ages than 14C. Peat initiation and long-term organic matter accumulation at the Old Black Spruce (OBS) transect were probably driven mainly
by the dynamics of Sphagnum, whereas at the Sandhill Fen (SF) transect, they were controlled by water level fluctuations in the neighboring fen. Bryophyte
macrofossils suggest a recent drying of the vegetation surface at both sites, most likely triggered by regional drought in
the late 1950s and 1960s. At OBS, the shift from Sphagnum- to feather moss-dominated communities continued in the 1990s, possibly reflecting effects of direct disturbance on local
drainage patterns. Overall, our results suggest that community composition and C dynamics of peat-margin swamps respond dynamically
to climatic and hydrologic fluctuations. However, uncertainties regarding the reliability of different chronologies limit
our ability to link observed community changes to specific causal events.
Author Contributions IEB conceived/designed study, performed research, analyzed data, wrote paper. JSB conceived/designed study, wrote paper. CS
performed research, analyzed data, wrote paper. RKW performed research and analyzed data. CMP performed research and wrote
paper. 相似文献
99.
Ilka Wittig Bjoern Meyer Heinrich Heide Mirco Steger Lea Bleier Zibiernisha Wumaier Michael Karas Hermann Schägger 《BBA》2010,1797(6-7):1004-1011
Here we study ATP synthase from human ρ0 (rho zero) cells by clear native electrophoresis (CNE or CN-PAGE) and show that ATP synthase is almost fully assembled in spite of the absence of subunits a and A6L. This identifies subunits a and A6L as two of the last subunits to complete the ATP synthase assembly. Minor amounts of dimeric and even tetrameric forms of the large assembly intermediate were preserved under the conditions of CNE, suggesting that it associated further into higher order structures in the mitochondrial membrane. This result was reminiscent to the reduced amounts of dimeric and tetrameric ATP synthase from yeast null mutants of subunits e and g detected by CNE. The dimer/oligomer-stabilizing effects of subunits e/g and a/A6L seem additive in human and yeast cells. The mature IF1 inhibitor was specifically bound to the dimeric/oligomeric forms of ATP synthase and not to the monomer. Conversely, nonprocessed pre-IF1 still containing the mitochondrial targeting sequence was selectively bound to the monomeric assembly intermediate in ρ0 cells and not to the dimeric form. This supports previous suggestions that IF1 plays an important role in the dimerization/oligomerization of mammalian ATP synthase and in the regulation of mitochondrial structure and function. 相似文献
100.
Transfer RNA (tRNA) molecules are highly conserved in length, sequence and structure in order to be functional in the ribosome. However, mostly in archaea, the short genes encoding tRNAs can be found disrupted, fragmented, with permutations or with non-functional mutations of conserved nucleotides. Here, we give an overview of recently discovered tRNA maturation pathways that require intricate processing steps to finally generate the standard tRNA from these unusual tRNA genes. 相似文献