The isolation and characterization of ngm2, a mutation that affects nitrosoguanidine mutagenesis in yeast

Summary We have isolated and characterized a new mutant of Saccharomyces cerevisiae, carrying a single mutant allele that we designate ngm2-1, which is defective with respect to induced mutagenesis. This mutant was isolated by screening mutagenized clones for reduced frequencies of reversion of the his1-7 allele, induced by N-methyl-N-nitro-N-nitrosoguanidine. As judged by the reversion of his1-7 and ilv1-92, ngm2-1 mutant strains are also deficient with respect to mutability induced by methyl methane sulfonate, ethyl methane sulfonate and, at least partially, by UV. UV-induced reversion of the ochre mutation arg4-17 and the frameshift mutation his4-38 was not much affected by ngm2-1, however. Like rev3 and rev7 mutations, ngm2-1 also has little influence on the reversion of the proline missense allele, cyc1-115. Ngm2-1 mutants are only at best very slightly more sensitive to the toxicity of the four mutagens used, and homozygous diploids sporulate normally.     

CSF distribution of morphine, methadone and sucrose after intrathecal injection

The lumbar to cisternal CSF distribution of morphine and methadone were compared to C-14 sucrose, a standard marker of CSF bulk flow, after lumbar subarachnoid injections in a sheep preparation. Morphine appeared and peaked simultaneously with C-14 sucrose in cisternal CSF at 90 to 190 minutes. The mean peak cisternal CSF morphine concentrations were sustained for 30-40 minutes, and averaged 148 ng/ml, representing 0.3% of the administered dose. Methadone was not detectable in cisternal CSF up to 240-300 minutes after lumbar subarachnoid administration. The C-14 sucrose/morphine ratio was increased an average of 6.7 times in cisternal CSF as compared to the ratio of the two compounds injected into the lumbar subarachnoid space. These studies demonstrate that morphine, a hydrophilic opioid, given intrathecally moves rostrally and appears in cisternal CSF by bulk flow. Furthermore the rostral redistribution of morphine is associated with the clearance of morphine from CSF. Methadone, a lipophilic opioid, appears to be completely cleared from CSF before it reaches the cisterna magna. These pharmacokinetic studies support a contribution of supraspinal sites to the analgesic and adverse effects produced by morphine given by spinal routes of administration. In contrast methadone appears to exert its effects predominantly at spinal sites.     

云南兔Lepus comus G.Allen的分类订正——包括两个新亚种的描记

云南兔Lepus comus G.Allen是云贵高原和滇西山地目前发现的唯一的一种野兔,初由G.M.Allen（1927）根据采自云南西部腾冲的标本命名。其后,国内外学者（包括G.M.Allen本人在内）对云南兔究竟是一独立种或为高原兔Lepus oiostulus（Hodgson）的一个地理亚种意见纷纭（罗泽珣,1981;高耀亭等,1964;Allen,1938;Ellerman et al.,1951;Angermann,1967;Corbet,1978。我们曾对国内有关单位所收藏的这两个类群的100余号标本进行较详细的对比研究。发现云南兔在形态上与高原兔确有明显区别,在分布上又有同域现象,因而主张仍应将云南兔保持其原定种的种级地位;同时,又查对了采于各地的云南兔所有标本,发现云南北部（丽江）至中部（景东、景谷）标本以及云南东部、南部和贵州西部标本都有异于滇西地模标本,且占有不同的地理分布区。经研究,应属两个新的亚种。其中,云南东部,南部和贵州西部的新亚种,为纪念先师彭鸿绶先生毕生献身于云、贵、川的科学考察事业和他的指导与培养,特以彭先生之姓氏命名,以资纪念。     

Roles of the trkB and trkC gene products of Escherichia coli in K+ transport

Mutations at the trkB and trkC loci of Escherichia coli produce an abnormal efflux of K+. The mutations are partially dominant in diploids and revert frequently by what appears to be intragenic suppression to the null state. The mutations can be reverted by insertion of Tn10 into the mutated gene, and spontaneous revertants are fully recessive to the mutant allele in diploids. K+ efflux produced by NEM* and by DNP* persists in strains with presumed null mutations at either locus, indicating neither gene product is the primary target for the effect of these inhibitors on K+ efflux. The results are consistent with the view that trkB and trkC encode independent systems for K+ efflux. Mutations at these loci alter regulation of the process so that K+ efflux occurs inappropriately. A second mutation to the null state abolishes this abnormal K+ efflux. These genes may encode K+/H+ antiporters, an activity postulated to mediate K+ efflux and demonstrated to exist in E. coli and other bacteria.     

湖北菱科的数量分类研究[Ⅱ]

引言菱科(Trapaceae)植物为一年生水生浮叶草本,常见于湖泊,池塘及沟渠中。全世界约有70余种,主要分布于旧大陆的温带、亚热带地区,亦见于热带地区,如印度,东南亚及非洲,后来被引进美洲大陆和澳大利亚。中国有5至10种及其栽培种。菱科为一单属科。自林奈时期以来,菱科的分类学研究一直是一个富有探索性的问     

Production of auto-anti-idiotypic antibody during the normal immune response: IX. Characteristics of the auto-anti-idiotype antibody and its production

Using hapten-reversible inhibition of plaque formation as an assay for auto-anti-idiotype antibody (anti-Id) and as a means for following idiotype (Id) expression, we have obtained evidence that following immunization with trinitrophenyl (TNP) conjugates (a) there are differences in Id expression in the anti-TNP antibody response to different TNP conjugates although there is some overlap; (b) different strains, although showing some differences in Id expression, tend to produce cross-reactive Ids, thus no obvious allotype linked inheritance of Id expression is observed in this heterogeneous immune response; (c) the auto-anti-Id produced following immunization with TNP-Brucella abortus or TNP-Ficoll tends to be of the IgG_2a and IgG_2b isotypes.     

Structural implications of primary sequences from a family of Balbiani ring-encoded proteins inChironomus

Summary DNA sequencing has revealed an internal, tandemly repetitive structure in the family of giant polypeptides encoded by three types of Balbiani ring (BR) genes, in three different species ofChironomus. Each major BR repeat can be subdivided into two halves: a region consisting of short subrepeats and a more constant region that lacks obvious subrepeats. Comparative predictions of secondary structure indicate that an -helical segment is consistently present in the amino-terminal half of the constant region in all known BR proteins. Comparative predictions, coupled with consideration of the known phosphorylation of serine and threonine residues in BR proteins, suggest that the -helical structure may also extend into the carboxy-terminal half of the constant region, possibly interrupted by -turn(s). However, it is also possible that the structure is variable, and that a -strand is present in that half in some cases. All of the constant regions conserve one methionine and one phenylalanine residue, as well as all four cysteines; these residues presumably play roles in the packing or cross-linking of aligned constant regions. The structure of the subrepeat region is not clear, but the prevalence of a tripeptide pattern (basic-proline-acidic) suggests some type of structural regularity, possibly an extended helix. The possible significance of these conserved molecular features is discussed in the context of how they may serve the elasticity, insolubility, and hydrophilicity of the fibrils and threads formed by the BR polypeptides.     

伊蚊(纷蚊亚属)一新种——功果伊蚊的记述

1979年7月至1980年3月,作者在云南云龙县的功果采集到蚊类标本一批,发现伊蚊属纷蚊亚属(Finlaya)一新种,特记述如下。 功果伊蚊Aedes (Finlaya) gonguoensis,新种 雌蚊 中型黑色蚊虫,翅长3.5—4.2毫米。 头部 头顶前部平覆深褐宽鳞,中央区和后部具白弯鳞;头顶后部和后头有黑色窄竖鳞,并杂有少数白竖鳞;有眶白鳞线;头侧大部平覆白色宽鳞,仅前部有一褐鳞区。触角梗节内侧有淡色鳞。唇基光裸;喙约为前股的1.1倍长,一致暗黑色;触须约为喙     

云南壮异蝽属及娇异蝽属新种记述(半翅目:异蝽科)

云南地区的壮异蝽属(Urochela Dallas)和娇异蝽属(Hrostylis Westwood)截止到目前共记录23种。本文记述了在该省西部地区发现的5新种,现描述如下。模式标本保存于天津南开大学生物系。 钩壮异蝽Urochela hamata,新种(图1,2) 体黄褐色,具黑褐色花斑及黑色刻点。触角第4节中部及第5节基半部为淡黄色;     

Factors affecting the oligomeric structure of yeast external invertase

It has been assumed that yeast external invertase is a dimer, with each subunit composed of a 60-kDa polypeptide chain. We now present evidence that at its optimal pH of 5.0, the predominant form of external invertase is an octamer with an average size of 8 X 10(5) Da. During ultracentrifugation the octamer dissociated to lower molecular weight forms, including a hexamer, tetramer, and dimer. All forms of the enzyme were shown to possess identical specific activities and to contain a similar carbohydrate to protein ratio. Although the monomer subunits (1 X 10(5) Da) were heterogenous in carbohydrate content, each subunit possessed nine oligosaccharide chains. When stained for protein and enzyme activity following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, only the oligomeric form of the enzyme appeared to be active. Thus, on partially inactivating invertase with 4 M guanidine hydrochloride both octamer and monomer were evident on the gels but only the former was active. Similarly, incubating at pH 2.5 in the presence of sodium dodecyl sulfate yielded only inactive monomer. The monomer, unlike the active oligomeric aggregate, was unable to hydrolyze sucrose after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Consistent with the in vitro studies, freshly prepared yeast lysate was shown to contain the octameric species of external invertase as the major active form of this enzyme. From these studies and others which employed deglycosylated invertase, it is concluded that the carbohydrate component of external invertase contributes not only to stabilizing enzyme activity, but also to maintaining its oligomeric structure.