铃兰族rbcL基因的PCR—RFLP分析

本文用7属9种铃兰族Tribe convallarieae植物的叶绿体DNA中rbcL基因片段的PCR产物的RFLP结果进行聚类分析。结果表明:开口箭属与蜘蛛抱蛋属关系密切,夏须草属与族内其余各属亲缘关系稍远,与外部器官形态、核型和孢粉学资料所得出的结论基本一致。此外,本文对铃兰属的系统位置也进行了讨论。     

Calcium binding to the subunit c ofE. coli ATP-synthase and possible functional implications in energy coupling

The 8-kDa subunit c of theE. coli F₀ ATP-synthase proton channel was tested for Ca⁺⁺ binding activity using a⁴⁵Ca⁺⁺ ligand blot assay after transferring the protein from SDS-PAGE gels onto polyvinyl difluoride membranes. The purified subunit c binds⁴⁵Ca⁺⁺ strongly with Ca⁺⁺ binding properties very similar to those of the 8-kDa CF₀ subunit III of choloroplast thylakoid membranes. The N-terminal f-Met carbonyl group seems necessary for Ca⁺⁺ binding capacity, shown by loss of Ca⁺⁺ binding following removal of the formyl group by mild acid treatment. The dicyclohexylcarbodiimide-reactive Asp-61 is not involved in the Ca⁺⁺ binding, shown by Ca⁺⁺ binding being retained in twoE. coli mutants, Asp61Asn and Asp61Gly. The Ca⁺⁺ binding is pH dependent in both theE. coli and thylakoid 8-kDa proteins, being absent at pH 5.0 and rising to a maximum near pH 9.0. A treatment predicted to increase the Ca⁺⁺ binding affinity to its F₀ binding site (chlorpromazine photoaffinity attachment) caused an inhibition of ATP formation driven by a base-to-acid pH jump in whole cells. Inhibition was not observed when the Ca⁺⁺ chelator EGTA was present with the cells during the chlorpromazine photoaffinity treatment. An apparent Ca⁺⁺ binding constant on the site responsible for the UV plus chlorpromazine effect of near 80–100 nM was obtained using an EGTA-Ca⁺⁺ buffer system to control free Ca⁺⁺ concentration during the UV plus chlorpromazine treatment. The data are consistent with the notion that Ca⁺⁺ bound to the periplasimic side of theE. coli F₀ proton channel can block H⁺ entry into the channel. A similar effect occurs in thylakoid membranes, but the Ca⁺⁺ binding site is on the lumen side of the thylakoid, where Ca⁺⁺ binding can modulate acid-base jump ATP formation. The Ca⁺⁺ binding to the F₀ and CF₀ complexes is consistent with a pH-dependent gating mechanism for control of H⁺ ion flux across the opening of the H⁺ channel.This work was supported in part by grants from the Department of Energy and the U.S. Department of Agriculture.On leave from the Institute of Soil Science and Photosynthesis, Russian Academy of Science, Pushchino, Russia.     

48例原发性闭经患者的细胞遗传学分析

本文报告对48例原发闭经患者的临床和细胞遣传学分析,共发现染色体异常17例,占35.4%,其中包括45,X,7例;45,X/46,XX,2例;X染色体结构异常5例;核型中有Y染色体3例。讨论了原发闭经的细胞遗传学病因及异常核型与表型的关系。     

Gene conversion plays the major role in controlling the stability of large tandem repeats in yeast.

The genomic stability of the rDNA tandem array in yeast is tightly controlled to allow sequence homogenization and at the same time prevent deleterious rearrangements. In our study, we show that gene conversion, and not unequal sister chromatid exchange, is the predominant recombination mechanism regulating the expansion and contraction of the rDNA array. Furthermore, we found that RAD52, which is essential for gene conversion, is required for marker duplication stimulated in the absence of the two yeast type I topoisomerases. Our results have implications for the mechanisms regulating genomic stability of repetitive sequence families found in all eukaryotes.     

人巨细胞病毒小鼠模型的建立

采用HCMV-AD_(169)株实验感染昆明系和BALB/C系小鼠,攻毒后感染急性期BALB/C系小鼠的死亡率(28.57％)高于昆明系小鼠(5.26％)。两种不同品系小鼠的临床症状和HCMV导致的病理损害脑钙化无明显差异。昆明小鼠的发病率(94.74％)高于BALB/C小鼠。     

我国仓贮昆虫病原芽孢杆菌的研究

对９５１个样品分离鉴定,有７４７个样品含芽孢杆菌,有菌率为７８．５５％．共分离得到芽孢杆菌１１３８株,其中苏云金杆菌（Ｂａｃｉｌｌｕｓｔｈｕｒｉｎｇｉｅｎｓｉｓ,简称Ｂ．ｔ）１４３株,占１２．５％;球形芽孢杆菌（Ｂａｃｉｌｌｕｓｓｐｈａｅｒｉｃｕｓ,简称Ｂ．ｓ）１１株,占０．９７％;其他芽孢杆菌９８４株,占８６．４０％．从芽孢杆菌中选出产生晶体、苏云金素或磷酸酯酶Ｃ（ＰｈｏｓｐｈａｌｉｐａｓｅＣ,简称ＰＬＣ）的毒素菌株１６８株,其中Ｂ．ｔ占１４３株,Ｂ．ｓ有５株,其他芽孢杆菌１０株．在产毒素菌株中,经测定有１２０株菌对供试昆虫毒性达标．占７７．９２％．不同菌株的杀虫毒素、杀虫范围和毒力各异,认为这种差异取决于毒素和虫种两方面的特异性．     

多年生黑麦草草地生态系统中放牧强度对草地结构及组织转化的影响

研究了放牧强度对多年生黑麦草人工草地蘖的形态、密度、草地生产率及组织转化的影响。结果表明,重牧条件下蘖密度大于轻牧,而轻牧的单株蘖重大于重牧。重牧划地净生产率大于轻牧,主要是由于轻和手条件下,草地的高的生长率被更高的枯死率所抵消。春夏之交,采用灵活的管理措施,转换放牧强度可以提高草地的生产率。     

RELATIONSHIP BETWEEN INCLUSION IN THE RAPE CROP-QINGYOU Ⅱ AND ALATE RATIO OF MYZUS PERSICAE

AlateratioofMyzuspersicaeSulzerwasgreatlycloserinrelationshiptocertaininclusionintherapecrop-QingyouⅡ,suchastryptophan,ratioofcontentsofsolublesugartoproteinandmeancrowdingnessunderconditionsofvariedmateproportionoffertilizers-N,P,K.Thefollowinginclusionintherapecropwerealsorelatedtotheratioofalatate:asperticacid,troeoninie,serine,glutancicacid,phenylalanine,lysine,histidine,valine,methionine,isoleucine,leucine,solublesugarandwater-solubleprotein.     

造礁石珊瑚群落结构研究的概况,问题和前景

造礁石珊瑚作为珊瑚礁生态系统中的关键生物类群,其群落结构是珊瑚礁系统研究中的一个重 要方面。本文回顾了20余年以来世界各国对造礁石珊瑚群落结构研究所取得的主要进展和认识,指出了目前研究中存在的问题并分析了不同空间范围研究结论之间的缺乏一致性和中等干扰假说的不足。 最后,结合珊瑚礁生态系统基础理论和应用发展的需求,本文探讨了造礁石珊瑚群落结构研究的前景。