Gene amplification at a locus encoding a putative Na+/H+ antiporter confers sodium and lithium tolerance in fission yeast.

We have identified a new locus, sodium 2 (sod2) based on selection for increased LiCl tolerance in fission yeast, Schizosaccharomyces pombe. Tolerant strains have enhanced pH-dependent Na+ export capacity and sodium transport experiments suggest that the gene encodes an Na+/H+ antiport. The predicted sod2 gene product can be placed in the broad class of transporters which possess 12 hydrophobic transmembrane domains. The protein shows some sequence similarity to the human and bacterial Na+/H+ antiporters. Overexpression of sod2 increased Na+ export capacity and conferred sodium tolerance. Osmotolerance was not affected and sod2 cells were unaffected for growth in K+. In a sod2 disruption strain cells were incapable of exporting sodium. They were hypersensitive to Na+ or Li+ and could not grow under conditions that approximate pH7. The sod2 gene amplification could be selected stepwise and the degree of such amplification correlated with the level of Na+ or Li+ tolerance.     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

自发性高血压大鼠血管α1肾上腺素受体亚型的改变

本工作在离体与整体条件下比较易卒中型自发性高血压(SHRSP)大鼠与WKY大鼠血管中α_1受体的两种亚型。在离体灌流的主动脉、肾动脉与肠系膜动脉,50μmol/L氯甲基可乐定(CEC)预温育30min可使α_1受体激动时引起的最大收缩张力在SHRSP与WKY大鼠分别降为对照时的31.4±8.3％与35.2±2.9％,68.4±8.2％与80.1±7.3％,68.4±6.3％与55.4±7.0％,两者间均无显著性差别。但10μmol/L硝苯吡啶对α_1受体收缩效应的阻断作用则在SHRSP大鼠大大超过WKY大鼠,最大收缩张力分别降为对照时的3.1±1.5％与56.5±4.8％(P<0.01),9.0±4.1％与23.6±3.5％(P<0.05),5.9±2.5％与28.0±0.8％(P<0.01)。整体动物实验也显示硝苯吡啶的降血压作用及对苯肾上腺素升血压效应的阻断作用在SHRSP大鼠都较WKY大鼠显著增强。离体主动脉a_1受体激动时的快速相与持续相收缩均主要由α_(1B)亚型激动引起,硝苯吡啶对快速相收缩的阻断作用在SHRSP与WKY大鼠无显著性差别,但对持续相收缩的阻断作用则在SHRSP大鼠显著强于WKY大鼠。上述结果提示SHRSP大鼠血管α_1受体两种亚型的分布没有显著改变,但α_(1B)受体激动时继发性细胞外Ca~(2+)进入的途径由非双氢吡啶敏感性钙通道转变为双氢吡啶敏感性钙通道。     

NMDA受体在海马CA_3区习得性LTP保持中的作用

在大鼠明暗分辨学习的建立和巩固过程中,通过与记录电极一起慢性埋植于海马CA_3区的注药管微量注射NMDA受体的特异性拮抗剂2-amino-5-phosphonovaleric acid(APV),观察对海马CA_3区突触效应及与之相关的习得性行为的影响。结果如下:(1)在动物经训练PS峰幅值刚增大至最高水平后,即在习得性LTP刚好形成后,每实验单元先于CA_3区注射AFV 1μl(2mmol/L),然后在药物有效作用时间内再进行训练,则PS峰值不能随训练而保持在最高水平,相反经8个实验单元,PS峰值降至实验前水平;相应地动物的正确反应率不能随训练而巩固,反而下降至10％以下。(2)在动物习得性LTP已形成并经一单元训练PS保持在最高水平后,于每实验单元训练前注射APV 1μl(2mmol/L),PS峰值同样不会随训练而保持在最高水平,经14个实验单元注药和训练,PS峰值逐渐降至实验前水平,相应地动物行为的正确反应率也降至10％以下,习得性行为消退,不过其消退速度比前一情况的动物为慢,说明习得性LTP发展情况不同,APV的作用效率有差别。结果表明:NMDA受体在习得性LTP的巩固中起着重要作用。     

一个拖延了半个多世纪的研究课题的总结汇报

本文是汤佩松教授为北京植物生理学会1992年年会准备的发言稿,并以庆祝中国植物生理学会成立30周年。后“北京年会”因故未开,本刊应汤老要求按原样发表于此(并附英文摘要),以飨读者。     

PHYLOGENY OF THE SUBFAMILIES OF THE FAMILY BRACONIDAE (HYMENOPTERA: ICHNEUMONOIDEA): A REASSESSMENT

Abstract— The recently published phylogeny of Braconidae by Quicke and van Achterberg is reassessed. Character-state definitions and character polarities are evaluated, and more rigorous methods are suggested. Our results indicate that there are many more parsimonious solutions to their data set, the consensus of which differs substantially from their results. Based on our reassessment, little can be said about the relationships among braconid subfamilies. Consensus trees show the cyclostomes as a largely unresolved basal grade. The two other major lineages which have been proposed, the helconoids and microgastroids, are somewhat better resolved, but not consistently so. Relationships among the helconoids vary considerably depending on the parameters used for parsimony analysis.     

The fate of female donor blastodermal cells in male chimeric chickens.

In previous experiments in our laboratories, chickens that are chimeric in their gamete, melanocyte, and blood cell populations have been produced by injection of dispersed stage X blastodermal donor cells into the subgerminal cavity of stage X recipient embryos. In some experiments, donor cells were transfected with reporter gene constructs prior to injection as a preliminary step in the production of transgenic birds. Chimerism was assessed by test mating, observation of plumage, and DNA fingerprinting. Methods were sought that would provide a relatively rapid analysis of the spatial distribution of descendants of donor cells in chimeras to assess the efficacy of various methods of chimera construction. To date, the sex of donor and recipient embryos was not known and, therefore, numerous mixed sex chimeras must have been constructed by chance, since donor cells were usually collected from several embryos rather than from individual embryos. The presence of female-derived cells was determined by in situ hybridization using a W-chromosome-specific DNA probe, using smears of washed erythrocytes from 16 phenotypically male chimeric chickens ranging in age from 4 days to 42 months posthatching. The proportion of female cells detected in the erythrocyte samples was zero (eight samples) or very low (0.020-0.083%), although 1% of the erythrocytes from a phenotypically male chick that was killed 4 days after hatch were female-derived. The low proportions of female-derived cells were surprising, considering that most of these chimeras had been produced by the injection of cells pooled from several donor embryos and most recipients had been exposed to gamma irradiation prior to injection, thus dramatically enhancing the level of incorporation of donor cells into the resulting chimeras. By contrast, 0-100% of the erythrocytes were female-derived in blood samples taken at 10 days of incubation from the chorioallantois of seven phenotypically normal male embryos that resulted from the injection of blastodermal cells pooled from five embryos into irradiated recipient embryos. Approximately 70% of the erythrocytes in a blood sample from a phenotypically normal female chimeric embryo were female-derived, and 100% of the erythrocytes examined from an intersex embryo bearing a right testis and a left ovary were female-derived. These results indicate that female-derived cells can contribute to the formation of erythropoietic tissue during the early development of what will become a phenotypically male chimeric embryo. It would appear, therefore, that female-derived cells are blocked in development or destroyed, or certain male-female combinations of cells may be lethal prior to hatching.(ABSTRACT TRUNCATED AT 400 WORDS)     

Identification of a lysA-like gene required for tabtoxin biosynthesis and pathogenicity in Pseudomonas syringae pv. tabaci strain PTBR2.024.

Pseudomonas syringae pv. tabaci strain PTBR2.024 produces tabtoxin and causes wildfire disease on tobacco and green bean. PTBR7.000, a Tn5 mutant of PTBR2.024, does not produce tabtoxin, is nonpathogenic on tobacco, and is prototrophic. A 3-kb fragment from a genomic library of the parent strain PTBR2.024 complemented both mutant phenotypes. This 3-kb fragment contains two open reading frames (ORFs), ORF1 and ORF2, and two truncated ORFs, ORF3 and ORF4. The Tn5 insert in PTBR7.000 was mapped to ORF2, and complementation studies showed that an intact ORF2 was sufficient to restore tabtoxin production and pathogenicity. The deduced amino acid sequences of ORF2 and truncated ORF3 contain significant homology to bacterial lysine biosynthetic enzymes, diaminopimelate decarboxylase, and delta 1-piperidine-2,6-dicarboxylate succinyl transferase, respectively. ORF2, however, is not required for lysine biosynthesis. We designated the sequence corresponding to ORF2 as gene tabA and propose that the product of tabA is an enzyme in the tabtoxin biosynthetic pathway that recognizes a substrate analogue of a compound in the lysine biosynthetic pathway.