Effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic acetylcholine receptors on transmembrane potentials and currents in guinea pig ventricular myocytes

The effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic receptor on transmembrane potentials and currents in guinea pig single ventricular cells were analyzed using whole-cell patch clamp technique. These effects were compared with those of the muscarinic receptor agonists carbachol and acetylcholine. The antibodies shortened the action potential duration in a dose-dependent manner. By using a ramp or step rectangular pulse protocol, it was found that the antibodies increased the outward K⁺ current and decreased the inward basal I Ca significantly. The reversal potential of both carbachol-and antibody-induced extra currents were close to –80 mV, being in proximity to the calculated E_k of –90 mV. A -adrenergic receptor agonist, isoprenaline, prolonged the action potential and increased the overshoot which could be inhibited by both antibody and carbachol. Isoprenaline increased inward I_ca and outward I_k simultaneously. Both antibody and carbachol could significantly reduce the isoprenaline-stimulated I_Ca but not the isoprenaline-stimulated I_k. The antibody- or carbachol-induced outward K⁺ current and the depressant effects of antibody and carbachol on isoprenaline-stimulated I_ca were partially antagonized by atropine. These results suggest that the anti-M2 muscarinic receptor antibodies display a stimulatory activity similar to muscarinic receptor agonist on the receptor-mediated electrophysiological events.     

中国沿海代表性河口地区鳗苗群体形态特征的比较研究

本文报道了１９９２—１９９４年连续３年采自海南至辽宁（包括台湾）沿海７个代表性河口地区鳗苗群体的主要形态特征比较研究结果。４项计数性状和３项度量性状,差异系数分析结果未达到亚种差异水平;判别函数显示,大多数群体间存在显著差异,这种差异应源于遗传变异。各年差异变化无规律,可能与鳗苗漂游分布的随机性有关。     

An abscisic acid analog inhibits abscisic acid-induced freezing tolerance and protein accumulation, but not abscisic acid-induced sucrose uptake in a bromegrass (Bromus inermis Leyss) cell culture

The application of abscisic acid (ABA), either as a racemic mixture or as optically resolved isomers, increases freezing tolerance in a bromegrass (Bromus inermis Leyss) cell culture and induces the accumulation of several heat-stable proteins. Two stereoisomers of an ABA analog, 23 dihydroacetylenic abscisyl alcohol (DHA), were used to study the role of ABA-induced processes in the acquisition of freezing tolerance in these cells. Freezing tolerance was unchanged in the presence of (–) DHA (LT₅₀ -9°C), and no increase in heat-stable protein accumulation was detected; however, the (+) enantiomer increased the freezing tolerance (LT₅₀ -13°C) and induced the accumulation of these polypeptides. All three forms of ABA increased freezing tolerance in the bromegrass cells, although (–) ABA was less effective than either (+) or (±) ABA when added at equal concentrations. Cells pretreated with 20 or 50 M (–) DHA displayed lower levels of freezing tolerance following the addition of 2.5, 7.5 or 25 M (±) ABA. Full freezing tolerance could be restored by increasing the concentration of (±) ABA to > 25 M. Pretreatment of cells with (–) DHA (20 or 50 M) had no effect on freezing tolerance when 25 M (+) ABA was added. The induction of freezing tolerance by 25 M (–) ABA was completely inhibited by the presence of 20 M (–) DHA. The accumulation of ABA-responsive heat-stable proteins was inhibited by pretreatment with 20 M (–) DHA in cells treated with 2.5 or 7.5M (+) ABA, and in cells treated with 25 M (–) ABA. The accumulation of these polypeptides was restored when (±) or (+) ABA was added at a concentration of 25 M. The analysis of proteins which cross-reacted with a dehydrin antibody revealed a similar inhibitory pattern as seen with the other ABA-responsive proteins. The effects of the various isomers of ABA and DHA on cell osmolarity and sucrose uptake was also investigated. In both cases, (±) and (+) ABA had pronounced effects on the parameters measured, whereas (–) ABA treated cells gave substantially different results. In both sucrose uptake and cell osmolarity, DHA had no significant effect on the results obtained following (±) or (+) ABA treatment. Maximum freezing tolerance was only observed in cells when both heat-stable protein accumulation and sucrose uptake were observed.Abbreviations ABA abscisic acid - DHA 2,3 dihydroacetylenicabscisyl alcohols - DMSO dimethyl sulfoxide - LT₅₀ temperature at which 50% of cells are killed The authors would like to acknowledge the technical assistance of Angela Bollman, Bruce Ewan and Angela Shaw. This work was supported by grants from the Natural Science and Engineering Research Council of Canada to L.V.G. and N.H.L., and a grant from the University of Saskatchewan to R.W.W.     

A gene at 59 minutes on the Escherichia coli chromosome encodes a lipoprotein with unusual amino acid repeat sequences.

We report a 1.432-kb DNA sequence at 59 min on the Escherichia coli chromosome that connects the published sequences of the pcm gene for the isoaspartyl protein methyltransferase and that of the katF or rpoS (katF/rpoS) gene for a sigma factor involved in stationary-phase gene expression. Analysis of the DNA sequence reveals an open reading frame potentially encoding a polypeptide of 379 amino acids. The polypeptide sequence includes a consensus bacterial lipidation sequence present at residues 23 to 26 (Leu-Ala-Gly-Cys), four octapeptide proline- and glutamine-rich repeats of consensus sequence QQPQIQPV, and four heptapeptide threonine- and serine-rich repeats of consensus sequence PTA(S,T)TTE. The deduced amino acid sequence, especially in the C-terminal region, is similar to that of the Haemophilus somnus LppB lipoprotein outer membrane antigen (40% overall sequence identity; 77% identity in last 95 residues). The LppB lipoprotein binds Congo red dye and has been proposed to be a virulence determinant in H. somnus. Utilizing a plasmid construct with the E. coli gene under the control of a phage T7 promoter, we demonstrate the lipidation of this gene product by the incorporation of [3H]palmitic acid into a 42-kDa polypeptide. We also show that treatment of E. coli cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 46-kDa precursor. We thus designate the protein NlpD (new lipoprotein D). E. coli cells overexpressing NlpD bind Congo red dye, suggesting a common function with the H. somnus LppB protein. Disruption of the chromosomal E. coli nlpD gene by insertional mutagenesis results in decreased stationary-phase survival after 7 days.     

Map locations of mouse hepatitis virus temperature-sensitive mutants: confirmation of variable rates of recombination.

Using standard genetic recombination techniques, studies in our laboratory suggest that recombination rates are very high and vary in different portions of the mouse hepatitis virus (MHV) genome. To determine the actual recombination frequencies in the MHV genome and localize the nucleotide boundaries of individual viral genes, we have sequenced temperature-sensitive and revertant viruses to identify the location of specific mutant alleles. Complementation group F RNA+ ts mutants (LA7, NC6, and NC16) each contained a unique mutation which was tightly linked to the ts phenotype and resulted in a conservative or nonconservative amino acid change in the MHV S glycoprotein gene. In agreement with previous recombination mapping studies, the mutation in LA7 and NC6 mapped within the S1 domain while NC16 mapped within the S2 domain. To determine the map coordinates of the MHV polymerase genes, several RNA- mutants and their revertants belonging to complementation groups C (NC3 and LA9) and E (LA18 and NC4) were also sequenced. Mutations were identified in each virus that were tightly linked to the ts phenotype and resulted in either a conservative or nonconservative amino acid change. The group C allele spanned the ORF 1a/ORF 1b junction, while the group E mutants mapped at the C terminus of ORF 1b about 20 to 22 kb from the 5' end of the genome. Mutation rates, calculated from the reversion frequencies of plaque-purified ts viruses requiring a single nucleotide alteration for reversion, approached 1.32 (+/- 0.89) x 10(-4) substitutions per nucleotide site per round of template copying. Detailed recombination mapping studies across known distances between these different ts alleles has confirmed that homologous recombination rates approached 25% and varied within different portions of the MHV genome.     

银杏扦插繁殖试验

本文报道银杏扦插繁殖技术。采用不同插穗、机械处理、不同激素及浓度处理进行扦插繁殖试验．扦插成活率可达９０—１００％。     

边界层阻力在叶片气体交换过程中的作用

作者对现有的气体交换法的叶室作了改进。从实验上检验了作者根据电学类比分析和模拟检验得到的结论：在已有的气体交换测定装置中,空气流速不变,叶片的边界层导度也固定不变,所得到的结论用于边界层导度变化的情形时,会造成比较大的误差。现加一障碍物使得流过叶片的风速减小,从而改变叶片的边界层导度。通过测量在不同边界层导度下同一叶片的光强曲线可以考察不同边界层导度下的气孔导度、光合速率、蒸腾速率以及它们之间的相互关系。实验结果与作者以前的电学类比分析和模拟得到的结论是基本一致的     

沈阳西部污灌水中有机污染物的分析

沈阳西部污灌水中有机污染物的分析刘海玲,张丽珊,姚家彪,于殿臣,朱岩,可夫,姜萍（中国科学院沈阳应用生态研究所,１１００１５）ＡｎａｌｙｓｉｓｏｆＯｒｇａｎｉｃＰｏｌｌｕｔａｎｔｓｉｎＩｒｒｉｇａｔｅｄｓｅｗａｇｅＩｎＷｅｓｔｅｒｎＳｈｅｎｙａｎｇ．...