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1.
Cypripediumlichiangense S.C.Chen & P.J.Cribb (Orchidaceae),endemic to China,is an endangered species according to I UCN Red List criteria (IUCN,2001:I UCN Red List Categories and Criteria,Version 相似文献
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In vitro fertilization of mouse ova by spermatozoa exposed isothermally to radio-frequency radiation
Mouse spermatozoa were exposed in vitro for 1 h to 27- or 2,450-MHz CW RF radiation at SARs of 0 to 90 W/kg under isothermal (37 +/- 0.2 degrees C) conditions. Exposure at either frequency to RF radiation at SARs of 50 W/kg or greater resulted in a statistically significant reduction in the ability of irradiated sperm to fertilize mouse ova in vitro (P less than .05). Over the range of SARs there was no apparent difference in the effects of 27- vs. 2,450-MHz RF radiation. There were no readily detectable exposure effects on spermatozoan morphology, ultrastructure, or capacitation. The reduction of in vitro fertilization is attributed to a direct effect of RF radiation on spermatozoa rather than to heating. 相似文献
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Exchange rates and numbers of annular lipids for the calcium and magnesium ion dependent adenosinetriphosphatase 总被引:3,自引:0,他引:3
A spin-labeled phospholipid is used to study lipid-protein interactions in the (Ca2+,Mg2+)-ATPase of sarcoplasmic reticulum from muscle. A novel null method is used to decompose composite electron spin resonance spectra into two components, characteristic of immobilized and mobile environments. Calculations based on a random mixing model suggest that protein-protein interactions will be relatively rare in these systems and that the immobilized lipid does not represent lipid trapped between proteins but rather represents annular phospholipid at the lipid-protein interface of the adenosinetriphosphatase. The apparent decrease in the amount of immobilized lipid with increasing temperature is shown to be consistent with lipid exchange between bulk and annulus, characterized by an exchange time of 10(-7) s at 37 degrees C. A minimum number of annular phospholipid sites of 32 and 22 are calculated at 0 and 37 degrees C, respectively. 相似文献
5.
Diacylglycerol kinase (DGK) of Escherichia coli has been reconstituted into a variety of phospholipid bilayers and its activity determined as a function of lipid headgroup structure and phase preference. The anionic phospholipids dioleoylphosphatidic acid, dioleoylphosphatidylserine, and cardiolipin were all found to support activities lower than that supported by dioleoylphosphatidylcholine. In mixtures of dioleoylphosphatidylcholine and 20 mol % anionic phospholipids, the presence of anionic phospholipids all resulted in lower activities than in dioleoylphosphatidylcholine, except for dioleoylphosphatidylglycerol whose presence had little effect on activity. In some cases, the low activity in the presence of anionic phospholipid followed from a decrease in v(max); in some cases, it followed from an increase in the K(m) for diacylglycerol, and in the case of dioleoylphosphatidic acid, it followed from both. Activities in mixtures containing 80 mol % dioleoylphosphatidylethanolamine were lower than in dioleoylphosphatidylcholine at temperatures where both lipids adopted a bilayer phase; at higher temperatures where dioleoylphosphatidylethanolamine preferred a hexagonal H(II) phase, the differences in activity were greater. These experiments suggest that the presence of lipids preferring a hexagonal H(II) phase leads to low activities. Activities of DGK are low in a gel phase lipid. 相似文献
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We have developed a procedure for the reconstitution of Escherichia coli diacylglycerol kinase (DGK) into phospholipid bilayers containing diacylglycerol substrate. When DGK is reconstituted into a series of phosphatidylcholines containing monounsaturated fatty acyl chains, activity against dihexanoylglycerol (DHG) as a substrate was found to be markedly dependent on the fatty acyl chain length with the highest activity in dioleoylphosphatidylcholine [di(C18:1)PC] and a lower activity in bilayers with shorter or longer fatty acyl chains. Low activities in the short chain phospholipid dimyristoleoylphosphatidylcholine [di(C14:1)PC] followed from an increase in the K(m) value for DHG and ATP, with no effect on v(max). In contrast, in the long chain lipid dierucoylphosphatidylcholine [di(C24:1)PC], the low activity followed from a decrease in v(max) with no effect on K(m). In mixtures of two phosphatidylcholines with different chain lengths, the activity corresponded to that expected for the average chain length of the mixture. Cholesterol increased the activity in di(C14:1)PC but slightly decreased it in di(C18:1)PC or di(C24:1)PC, effects that could follow from changes in bilayer thickness caused by cholesterol. 相似文献
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Yeying Sun a b Quanqi Zhang a Jie Qi a Yanjie Chen a Qiwang Zhong a Chunmei Li a Yan Yu a Shuo Li a Zhigang Wang a a Key Laboratory of Marine Genetics Breeding Ministry of Education Qingdao China b College of Pharmacy Binzhou Medical University Yantai China 《Acta Genetica Sinica》2010,(2)
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Wenyi Yan a bc Shenghai Ye b Qingsheng Jin b Longjun Zeng c Yu Peng c Dawei Yan c Weibing Yang c Donglei Yang c Zuhua He c Yanjun Dong a Xiaoming Zhang b a College of Life Environment Sciences Shanghai Normal University Shanghai China b Institute of Crop Nuclear Technology Utilization Zhejiang Academy of Agricultural Sciences Hangzhou China c Institute of Plant Physiology & Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai China 《Acta Genetica Sinica》2010,(1)
Plant senescence plays diverse important roles in development and environmental responses.However,the molecular basis of plant senescence is remained largely unknown.A rice spontaneous mutant with the character of early senescence and male sterility (sms) was found in the breeding line NT10-748.In order to identify the gene SMS1 and the underlying mechanism,we preliminarily analyzed physiological and biochemical phenotypes of the mutant.The mutant contained lower chlorophyll content compared with the wild t... 相似文献