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101.
The gametogenic cycle of Kefersteinia cirrata (Polychaeta: Hesionidae) is described for a population in north-east England. Gametogenesis begins in September with previtellogenic and prespermiogenic phases of gametogenesis accumulating until December. Vitellogenesis and spermiogenesis are initiated in January and gravid animals are present in May. Breeding with an unmodified behavioural epigamy takes place in June and July. The effects of environmental temperature and day-length on oocyte growth rates have been determined. There is a synergism between the accelerating effects of long day-length and elevated temperature, the day-length effect being dominant. 相似文献
102.
Background
Coronary Heart Disease and Cerebrovascular Disease share many predisposing, modifiable risk factors (hypertension, abnormal blood lipids and lipoproteins, cigarette smoking, physical inactivity, obesity and diabetes mellitus). Lifestyle interventions and pharmacological therapy are recognised as the cornerstones of secondary prevention. Cochrane review has proven the benefits of programmes incorporating exercise and lifestyle counselling in the cardiac disease population. A Cochrane review highlighted as priority, the need to establish feasibility and efficacy of exercise based interventions for Cerebrovascular Disease. 相似文献103.
Laura A. Mike Jacob E. Choby Paul R. Brinkman Lorenzo Q. Olive Brendan F. Dutter Samuel J. Ivan Christopher M. Gibbs Gary A. Sulikowski Devin L. Stauff Eric P. Skaar 《PLoS pathogens》2014,10(3)
Two-component signaling systems (TCSs) are one of the mechanisms that bacteria employ to sense and adapt to changes in the environment. A prototypical TCS functions as a phosphorelay from a membrane-bound sensor histidine kinase (HK) to a cytoplasmic response regulator (RR) that controls target gene expression. Despite significant homology in the signaling domains of HKs and RRs, TCSs are thought to typically function as linear systems with little to no cross-talk between non-cognate HK-RR pairs. Here we have identified several cell envelope acting compounds that stimulate a previously uncharacterized Bacillus anthracis TCS. Furthermore, this TCS cross-signals with the heme sensing TCS HssRS; therefore, we have named it HssRS interfacing TCS (HitRS). HssRS reciprocates cross-talk to HitRS, suggesting a link between heme toxicity and cell envelope stress. The signaling between HssRS and HitRS occurs in the parental B. anthracis strain; therefore, we classify HssRS-HitRS interactions as cross-regulation. Cross-talk between HssRS and HitRS occurs at both HK-RR and post-RR signaling junctions. Finally, HitRS also regulates a previously unstudied ABC transporter implicating this transporter in the response to cell envelope stress. This chemical biology approach to probing TCS signaling provides a new model for understanding how bacterial signaling networks are integrated to enable adaptation to complex environments such as those encountered during colonization of the vertebrate host. 相似文献
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Leavy O 《Nature reviews. Immunology》2011,11(4):234-235
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Gellon L Razidlo DF Gleeson O Verra L Schulz D Lahue RS Freudenreich CH 《PLoS genetics》2011,7(2):e1001298
Expansion of DNA trinucleotide repeats causes at least 15 hereditary neurological diseases, and these repeats also undergo contraction and fragility. Current models to explain this genetic instability invoke erroneous DNA repair or aberrant replication. Here we show that CAG/CTG tracts are stabilized in Saccharomyces cerevisiae by the alternative clamp loader/unloader Ctf18-Dcc1-Ctf8-RFC complex (Ctf18-RFC). Mutants in Ctf18-RFC increased all three forms of triplet repeat instability--expansions, contractions, and fragility--with effect over a wide range of allele lengths from 20-155 repeats. Ctf18-RFC predominated among the three alternative clamp loaders, with mutants in Elg1-RFC or Rad24-RFC having less effect on trinucleotide repeats. Surprisingly, chl1, scc1-73, or scc2-4 mutants defective in sister chromatid cohesion (SCC) did not increase instability, suggesting that Ctf18-RFC protects triplet repeats independently of SCC. Instead, three results suggest novel roles for Ctf18-RFC in facilitating genomic stability. First, genetic instability in mutants of Ctf18-RFC was exacerbated by simultaneous deletion of the fork stabilizer Mrc1, but suppressed by deletion of the repair protein Rad52. Second, single-cell analysis showed that mutants in Ctf18-RFC had a slowed S phase and a striking G2/M accumulation, often with an abnormal multi-budded morphology. Third, ctf18 cells exhibit increased Rad52 foci in S phase, often persisting into G2, indicative of high levels of DNA damage. The presence of a repeat tract greatly magnified the ctf18 phenotypes. Together these results indicate that Ctf18-RFC has additional important functions in preserving genome stability, besides its role in SCC, which we propose include lesion bypass by replication forks and post-replication repair. 相似文献
110.
Gérard Lescoat Lucie Gouffier Isabelle Cannie Olive Lowe Isabelle Morel Sylvie Lepage Martine Ropert Olivier Loréal Pierre Brissot François Gaboriau 《Molecular and cellular biochemistry》2013,378(1-2):205-215
Natural polyamines such as putrescine (Put), spermidine (Spd), and spermine (Spm), which are present in the human diet in large amounts, associated with their active transporter, are assumed to play a role in non-heme iron uptake and iron bioavailability from nutrients. Enterocytes and hepatocytes play pivotal roles in the regulation of body iron homeostasis. In this study, we report the effects of natural polyamines on iron transport in the Caco-2 cell line. In enterocyte-like Caco-2 cells, polyamines did not significantly modulate the transepithelial iron flux across the cell monolayer cultured on permeable membranes. In contrast, Spd, Spm, and to a lesser extent, Put were shown to activate Caco-2 cell iron uptake and to induce an increase in the ferritin level. This iron co-transport in enterocytes, which involved an interaction between iron and polyamine then cell uptake of the polyamine–iron complexes by the polyamine transport system, was more pronounced in proliferating than in differentiated Caco-2 cells. Moreover, it was observed at physiological concentrations of both polyamines and iron. It could thus play a role in the rapid renewal of enterocytes. These data suggest the involvement of polyamines as components of the pool of transferrin-independent iron-chelating vectors. Further investigations are needed to demonstrate their biological relevance in physiological situations. 相似文献