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91.
Marie Salomonsson Bo Carlsson Johan Hggblad 《The Journal of steroid biochemistry and molecular biology》1994,50(5-6):313-318
It is generally accepted that the Kd for hormone binding to estrogen receptors in extracts ranges between 0.1–1 nM and that binding displays positive cooperativity due to formation of homodimers. After carefully optimizing assay procedures, to diminish ligand depletion phenomena and to fully control recoveries, we find a single class of non-interacting high affinity hormone binding sites with a Kd of approx. 10 pM. Ligand depletion was avoided by decreasing receptor concentrations to 5–8 pM. We were therefore obliged to employ radioiodinated estradiol as a probe as the specific radioactivity of tritiated estradiol was too low to maintain the accuracy of the binding assay. Human estrogen receptor extracted from the MCF7 cell line and recombinantly produced (in yeast) wild-type human receptor have identical equilibrium hormone binding characteristics. 相似文献
92.
Per Putkonen Charlotta Nilsson Kerstin Hild Reinhold Benthin Martin Cranage Anne Marie Aubertin Gunnel Biberfeld 《Journal of medical primatology》1993,22(2-3):100-103
Several groups have reported protection against experimental SIV infection in macaques immunized with a whole inactivated virus vaccine. The aim of the current study was to investigate whether five macaques vaccinated with whole inactivated SIV and previously shown to be protected against challenge with two divergent strains of SIV grown on human cells could resist challenge with a subsequent homologous SIV grown on macaque cells. We show here that this same vaccine did not protect when the challenge virus was grown on primary cells of monkey origin. 相似文献
93.
Marie J. Richard Veronique Ducros Michel Rorêt Josiane Arnaud Charles Coudray Michèle Fusselier Alain Favier 《Biological trace element research》1993,39(2-3):149-159
In six chronic dialyzed uremic patients, an intravenous sodium selenite (Se 50 μg during 5 wk and then 100 μg) and zinc gluconate
(Zn 5 mg) supplementation was performed during 20 wk at each dialysis session three times weekly. Before supplementation,
plasma Se and Zn, plasma and erythrocytes (RBC) antioxidant metalloenzymes glutathione peroxidase (GPX), and superoxide dismutase
(SOD) were significantly decreased, whereas lipid peroxidation (as thiobarbituric acid reactants TBARs) was increased. To
obtain a significative change in plasma selenium, we had to use an Se dose of 100 μg/dialysis session. Then, treatment-increased
plasma Se (from 0.58 ±0.09 to 0.89±0.16 μmol/L) led to a repletion of RBC-GPX (from 29.6±6 to 43±5.8 U/g Hb) and increased
plasma GPX levels (from 62±13 to 151±43 U/L). Plasma Zn and RBC-SOD did not vary significantly. The change of TBARs was not
observed between wk 1 and 4. They decreased significantly between wk 4 (4.80±0.21μmol/L) and wk 20 (4.16±0.26 μmol/L). We
noted a low correlation between TBARs and plasma GPX. A strong correlation was observed between Se and plasma GPX. The reversal
of Se deficiencies should reduce oxidative damage observed in these patients. 相似文献
94.
Arlette Pesty Brigitte Lefvre Jacek Kubiak Grard Graud Jan Tesarik Bernard Maro 《Molecular reproduction and development》1994,38(2):187-199
The incubation of mechanically denuded mouse oocytes in medium containing LiCl delayed both germinal vesicle breakdown (GVBD) and polar body extrusion in a dose-dependent and reversible manner. When myo-inositol alone was added to the culture medium, we observed that it accelerated GVBD and increased the rate of polar body extrusion, whereas, when combined with LiCl, the normal timing of GVBD was recovered. In the same way, when inositol trisphosphate (InsP3) was microinjected into the ooplasma, we observed an important improvement of the rate of GVBD, as compared to control oocytes, and prevention of lithium inhibition. However, neither myo-inositol nor InsP3 were able to rescue totally the oocytes from the negative effect of lithium on polar body extrusion. Moreover, lithium induced some important changes in microtubule and chromosome organizations. Before extrusion of the first polar body, the reduction of the spindle size or the appearance of short individualized chromosomes dispersed around a large aster of microtubules were often observed, whereas, after polar body extrusion, the spindle appeared smaller and chromosomes were often trapped in the midbody. Thus lithium affects mouse oocyte maturation at two different levels: GVBD and polar body extrusion. Whereas the former seems to be affected via polyphosphoinositide turnover, the latter is InsP3-independent and seems to be influenced negatively via underdevelopment of microtubular structures. © 1994 Wiley-Liss, Inc. 相似文献
95.
Elena B. Rodriguez de Turco Marie Therese Droy-Lefaix Nicolas G. Bazan 《Journal of neurochemistry》1993,61(4):1438-1444
Abstract: The effect of Ginkgo biloba extract (EGb 761) treatment (100 mg/kg/day, per os, for 14 days) on electroconvulsive shock (ECS)-induced accumulation of free fatty acids (FFA) and diacylglycerols (DAG) was analyzed in rat cerebral cortex and hippocampus. EGb 761 reduced the FFA pool size by 33% and increased the DAG pool by 36% in the hippocampus. These endogenous lipids were unaffected in cerebral cortex. During the tonic seizure (10 s after ECS) the fast accumulation of FFA, mainly 20:4, was similar in sham- and EGb 761 -treated rats, in both the cerebral cortex and hippocampus. However, further accumulation of free 18:0 and 20:4, observed in the hippocampus of sham-treated rats during clonic seizures (30 s to 2 min after ECS), did not occur in EGb 761-treated animals. The rise in DAG content triggered in the cortex and hippocampus by ECS was delayed by EGb 761 treatment from 10 s to 1 min, when values similar to those in sham animals were attained. Moreover, in the hippocampus the size of the total DAG pool was decreased by 19% during the tonic seizure. At later times, DAG content showed a faster decrease in EGb 761-treated rats. By 2 min levels of all DAG acyl groups decreased to values significantly lower than in sham animals in both cortex and hippocampus. This study shows that EGb 761 treatment affects, with high selectivity, lipid metabolism and lipid-derived second messenger release and removal in the hippocampus, while affecting to a lesser extent the cerebral cortex. 相似文献
96.
In the Baltic Sea area, the cladoceran Daphnia magna is commonly found in brackish water rockpools and it has been suggested that salinity is one of the niche dimensions that affects the distribution of the species. The salinity tolerance of D. magna was studied both in physiological and life history experiments. The experimental salinities were freshwater, 4S and 8S. The highest respiration and ammonium excretion rates were measured in the freshwater treatment with decreasing respiration and ammonium excretion rates at higher salinities. The lowest O/N ratio (oxygen consumption to ammonium excretion), describing the metabolic status of an organism, was obtained at 8S, although the only significant differences were detected when comparing to 4S treatments. Individual growth rate, reproductive output and population growth rate were highest at 4S. At 8S growth and reproduction were reduced as compared to freshwater and 4S. The life history parameters in the performed experiments indicated higher fitness (expressed as r) as well as more favourable conditions for growth and reproduction at 4S, whereas the O/N ratio was more difficult to interpret and, in this case, gave a less clear picture of the salinity influence. 相似文献
97.
Marie Arnaud Stefan Krause Richard J. Norby Thuong Huyen Dang Nezha Acil Nicholas Kettridge Vincent Gauci Sami Ullah 《Global Change Biology》2023,29(12):3256-3270
Mangroves are among the most carbon-dense ecosystems worldwide. Most of the carbon in mangroves is found belowground, and root production might be an important control of carbon accumulation, but has been rarely quantified and understood at the global scale. Here, we determined the global mangrove root production rate and its controls using a systematic review and a recently formalised, spatially explicit mangrove typology framework based on geomorphological settings. We found that global mangrove root production averaged ~770 ± 202 g of dry biomass m−2 year−1 globally, which is much higher than previously reported and close to the root production of the most productive tropical forests. Geomorphological settings exerted marked control over root production together with air temperature and precipitation (r2 ≈ 30%, p < .001). Our review shows that individual global changes (e.g. warming, eutrophication, drought) have antagonist effects on root production, but they have rarely been studied in combination. Based on this newly established root production rate, root-derived carbon might account for most of the total carbon buried in mangroves, and 19 Tg C lost in mangroves each year (e.g. as CO2). Inclusion of root production measurements in understudied geomorphological settings (i.e. deltas), regions (Indonesia, South America and Africa) and soil depth (>40 cm), as well as the creation of a mangrove root trait database will push forward our understanding of the global mangrove carbon cycle for now and the future. Overall, this review presents a comprehensive analysis of root production in mangroves, and highlights the central role of root production in the global mangrove carbon budget. 相似文献
98.
David W. Kikuchi William L. Allen Kevin Arbuckle Thomas G. Aubier Emmanuelle S. Briolat Emily R. Burdfield-Steel Karen L. Cheney Klára Daňková Marianne Elias Liisa Hämäläinen Marie E. Herberstein Thomas J. Hossie Mathieu Joron Krushnamegh Kunte Brian C. Leavell Carita Lindstedt Ugo Lorioux-Chevalier Melanie McClure Callum F. McLellan Iliana Medina Viraj Nawge Erika Páez Arka Pal Stano Pekár Olivier Penacchio Jan Raška Tom Reader Bibiana Rojas Katja H. Rönkä Daniela C. Rößler Candy Rowe Hannah M. Rowland Arlety Roy Kaitlin A. Schaal Thomas N. Sherratt John Skelhorn Hannah R. Smart Ted Stankowich Amanda M. Stefan Kyle Summers Christopher H. Taylor Rose Thorogood Kate Umbers Anne E. Winters Justin Yeager Alice Exnerová 《Journal of evolutionary biology》2023,36(7):975-991
Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies. 相似文献
99.
Donald H. Burke Linda A. Raubeson Marie Alberti John E. Hearst Elizabeth T. Jordan Susan A. Kirch Angela E. C. Valinski David S. Conant Diana B. Stein 《Plant Systematics and Evolution》1993,187(1-4):89-102
We examinedchlL (frxC) gene evolution using several approaches. Sequences from the chloroplast genome of the fernPolystichum acrostichoides and from the cyanobacteriumSynechococcus sp. 7002 were determined and found to be highly conserved. A complete physical map of the fern chloroplast genome and partial maps of other vascular plant taxa show thatchlL is located primarily in the small single copy region as inMarchantia polymorpha. A survey of a wide variety of non-angiospermous vascular plant DNAs shows thatchlL is widely distributed but has been lost in the pteridophytePsilotum and (presumably independently) within the Gnetalean gymnosperms.The namefrxC was originally used to denote a gene encoding a product with probable Fe : S cluster binding activity. This activity was postulated due to the amino acid sequence similarity between this product and the Fe : S-binding nitrogenase iron proteinnifH. Fe : S-binding is a property shared by ferredoxins, which are denoted by the prefix frx. However, this gene does not encode a ferredoxin. It is much larger than any known ferredoxin, it binds its Fe : S cluster between two halves of a homodimer (Fujita & al. 1989,Burke & al. 1993 a, c) instead of within a single subunit, and it lacks the pattern of clustered cysteines present in all ferredoxins (Meyer 1988). Therefore, we use the namechlL to recognize the sequence and functional similarities to the bacterial PChlide reductase subunit,bchL. Similar usage has been adopted for this (Suzuki & Bauer 1992) and other (Choquet & al. 1992,Burke & al. 1993b) PChlide reductase subunits. 相似文献
100.
Juliette Gaëtan Sébastien Halary Maxime Millet Cécile Bernard Charlotte Duval Sahima Hamlaoui Amandine Hecquet Muriel Gugger Benjamin Marie Neha Mehta David Moreira Fériel Skouri-Panet Cynthia Travert Elodie Duprat Julie Leloup Karim Benzerara 《Environmental microbiology》2023,25(3):751-765
The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments. 相似文献