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ALAIN THIÉRY NICOLAS RABET GABRIEL NÈVE 《Biological journal of the Linnean Society. Linnean Society of London》2007,90(1):55-60
The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60. 相似文献
3.
In a preliminary paper [Decker et al. (1986) Biochem. Biophys. Res. Commun. 136, 1162] we have shown that the antimineralocorticoid spironolactone (SPL) preferentially inactivates dexamethasone (DEX) inducible rat hepatic cytochrome P450p isozymes in a suicidal manner. These findings are now confirmed, and the kinetic characteristics of such a process are detailed. In an effort to elucidate the mechanism of SPL-mediated inactivation of cytochrome P450, we have examined the metabolism of SPL in vitro. Incubation of [14C]SPL and NADPH with liver microsomes prepared from DEX-pretreated rats results in the formation of several polar metabolites separable by HPLC with UV detection. This process is found to be dependent on NADPH, O2, SPL, and enzyme concentration, as well as temperature. Furthermore, metabolite formation was significantly attenuated by P450 inhibitors CO and n-octylamine. Mass spectral analysis (thermospray LC/MS, FAB/MS, and FAB/MS/MS) of the two most prominent polar metabolites indicated that these compounds had molecular weights that corresponded to the sulfinic and sulfonic acid derivatives of deacetyl-SPL (SPL-SH). These findings document the formation of previously unreported polar metabolites of SPL by rat liver microsomes enriched in cytochrome P450p and implicate a role for this isozyme in the oxidation of the thiol moiety of deacetyl-SPL. The detection of such metabolites also implicates a catalytic trajectory that includes the thiyl radical and/or sulfenic acid species as a plausible protagonist in drug-mediated inactivation of cytochrome P450p. 相似文献
4.
Assessing the impact of episodic pollution 总被引:1,自引:0,他引:1
The increased tightening of controls on industrial and municipal wastewater discharges has resulted in steady improvements in the quality of many important rivers over recent years. However, episodic pollution, particularly from farm wastes and combined sewer overflows continues to pose a major problem, and is one of the main causes of poor quality rivers today. Despite our acknowledgement of this continuing problem, very little is known of the mechanistic basis of responses and recovery of aquatic organisms and communities exposed to intermittent pulses of common pollutants. The majority of ecotoxicological studies to date have been concerned with the effects of continuous exposure. Although such studies may provide a means of predicting the impact of episodic pollution events, a more appropriate test design would be to assess toxicity under pulsed and fluctuating exposure. Studies should also include a post-exposure observation period and should consider recovery of individuals and communities. This paper reviews the results of reported studies relevant to the investigation of episodic pollution and pays particular attention to the effects of magnitude, duration and frequency of exposure. Results of field investigations using an in situ bioassay technique are also presented to emphasize the importance of field validation of proposed water quality criteria for intermittent pollution events. 相似文献
5.
Abstract.
- 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
- 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
- 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
- 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.
6.
An important component of the interaction between macroinvertebrates and leaf litter in streams in the extent to which consumers
can differentiate between undecomposed and decomposing leaves. The detritivores Gammarus pulex and Asellus aquaticus fed preferentially on conditioned rather on unconditioned leaf material. Growth in A. aquaticus was significantly reduced when unconditioned leaves were provided, but in G. pulex no significant effect of conditioning on growth was observed. The capacity of G. pulex to tolerate reductions in food quality seems to be a consequence of a compensatory system in which respiration rates change
to compensate for reductions in food quality. In this way a constant growth rate is maintained. Increases in ingestion rates
to compensate for low quality food were not observed. 相似文献
7.
Evolutionary accounts have difficulty explaining why people cooperate with anonymous strangers they will never meet. Recently models, focusing on emotional processing, have been proposed as a potential explanation, with attention focusing on a dual systems approach based on system 1 (fast, intuitive, automatic, effortless, and emotional) and system 2 (slow, reflective, effortful, proactive and unemotional). Evidence shows that when cooperation is salient, people are fast (system 1) to cooperate, but with longer delays (system 2) they show greed. This is interpreted within the framework of the social heuristic hypothesis (SHH), whereby people overgeneralize potentially advantageous intuitively learnt and internalization social norms to ‘atypical’ situations. We extend this to explore intuitive reactions to unfairness by integrating the SHH with the ‘fast to forgive, slow to anger’ (FFSA) heuristic. This suggests that it is advantageous to be prosocial when facing uncertainty. We propose that whether or not someone intuitively shows prosociality (cooperation) or retaliation is moderated by the degree (certainty) of unfairness. People should intuitively cooperate when facing mild levels of unfairness (fast to forgive) but when given longer to decide about another''s mild level of unfairness should retaliate (slow to anger). However, when facing severe levels of unfairness, the intuitive response is always retaliation. We test this using a series of one-shot ultimatum games and manipulate level of offer unfairness (50:50 60:40, 70:30, 80:20, 90:10) and enforced time delays prior to responding (1s, 2s, 8s, 15s). We also measure decision times to make responses after the time delays. The results show that when facing mildly unfair offers (60:40) people are fast (intuitive) to cooperate but with longer delays reject these mildly unfair offers: ‘fast to forgive, and slow to retaliate’. However, for severely unfair offers (90:10) the intuitive and fast response is to always reject. 相似文献
8.
Rupert A. Collins Giulia Trauzzi Katherine M. Maltby Thomas I. Gibson Frances C. Ratcliffe Jane Hallam Sophie Rainbird James Maclaine Peter A. Henderson David W. Sims Stefano Mariani Martin J. Genner 《Journal of fish biology》2021,99(4):1446-1454
The accuracy and reliability of DNA metabarcoding analyses depend on the breadth and quality of the reference libraries that underpin them. However, there are limited options available to obtain and curate the huge volumes of sequence data that are available on public repositories such as NCBI and BOLD. Here, we provide a pipeline to download, clean and annotate mitochondrial DNA sequence data for a given list of fish species. Features of this pipeline include (a) support for multiple metabarcode markers; (b) searches on species synonyms and taxonomic name validation; (c) phylogeny assisted quality control for identification and removal of misannotated sequences; (d) automatically generated coverage reports for each new GenBank release update; and (e) citable, versioned DOIs. As an example we provide a ready-to-use curated reference library for the marine and freshwater fishes of the U.K. To augment this reference library for environmental DNA metabarcoding specifically, we generated 241 new MiFish-12S sequences for 88 U.K. marine species, and make available new primer sets useful for sequencing these. This brings the coverage of common U.K. species for the MiFish-12S fragment to 93%, opening new avenues for scaling up fish metabarcoding across wide spatial gradients. The Meta-Fish-Lib reference library and pipeline is hosted at https://github.com/genner-lab/meta-fish-lib . 相似文献
9.
S. A. F. Bonnett M. S. A. Blackwell R. Leah V. Cook M. O'Connor E. Maltby 《Geobiology》2013,11(3):252-267
Soils are predicted to exhibit significant feedback to global warming via the temperature response of greenhouse gas (GHG) production. However, the temperature response of hydromorphic wetland soils is complicated by confounding factors such as oxygen (O2), nitrate () and soil carbon (C). We examined the effect of a temperature gradient (2–25 °C) on denitrification rates and net nitrous oxide (N2O), methane (CH4) production and heterotrophic respiration in mineral (Eutric cambisol and Fluvisol) and organic (Histosol) soil types in a river marginal landscape of the Tamar catchment, Devon, UK, under non‐flooded and flooded with enriched conditions. It was hypothesized that the temperature response is dependent on interactions with ‐enriched flooding, and the physicochemical conditions of these soil types. Denitrification rate (mean, 746 ± 97.3 μg m?2 h?1), net N2O production (mean, 180 ± 26.6 μg m?2 h?1) and net CH4 production (mean, 1065 ± 183 μg m?2 h?1) were highest in the organic Histosol, with higher organic matter, ammonium and moisture, and lower concentrations. Heterotrophic respiration (mean, 127 ± 4.6 mg m?2 h?1) was not significantly different between soil types and dominated total GHG (CO2eq) production in all soil types. Generally, the temperature responses of denitrification rate and net N2O production were exponential, whilst net CH4 production was unresponsive, possibly due to substrate limitation, and heterotrophic respiration was exponential but limited in summer at higher temperatures. Flooding with increased denitrification rate, net N2O production and heterotrophic respiration, but a reduction in net CH4 production suggests inhibition of methanogenesis by or N2O produced from denitrification. Implications for management and policy are that warming and flood events may promote microbial interactions in soil between distinct microbial communities and increase denitrification of excess with N2O production contributing to no more than 50% of increases in total GHG production. 相似文献
10.
Keatinge-Clay AT Maltby DA Medzihradszky KF Khosla C Stroud RM 《Nature structural & molecular biology》2004,11(9):888-893
The synthesis of aromatic polyketides, such as actinorhodin, tetracycline and doxorubicin, begins with the formation of a polyketide chain. In type II polyketide synthases (PKSs), chains are polymerized by the heterodimeric ketosynthase-chain length factor (KS-CLF). Here we present the 2.0-A structure of the actinorhodin KS-CLF, which shows polyketides being elongated inside an amphipathic tunnel approximately 17 A in length at the heterodimer interface. The structure resolves many of the questions about the roles of KS and CLF. Although CLF regulates chain length, it does not have an active site; KS must catalyze both chain initiation and elongation. We provide evidence that the first cyclization of the polyketide occurs within the KS-CLF tunnel. The mechanistic details of this central PKS polymerase could guide biosynthetic chemists in designing new pharmaceuticals and polymers. 相似文献