Heat shock proteins within the mammalian cell cycle: relationship to thermal sensitivity, thermal tolerance, and cell cycle progression

We have measured endogenous and induced rates of 70-kD, 89-kD, and 110-kD heat shock proteins in highly pure G1-, S-, or G2-M phase fractions of Chinese hamster fibroblasts (CHO) separated by fluorescence-activated cell sorting (FACS). Relative rates of synthesis of all three polypeptides as measured by two-dimensional gel electrophoresis were similar throughout the cell cycle, and therefore, endogenous levels were unlikely to explain the thermal sensitivity of S-phase cells. Distinct heterogeneity in induced rates of these polypeptides was noted in all phase fractions. Enhanced rates of 70-kD polypeptide were measured in S and G2-M as compared to G1 following heat shock. Little increase in either the 89-kD or 110k-kD heat shock proteins was observed in heated G1 cells. This heterogeneity in induced rates of synthesis was in contrast to the similarity in thermal tolerance expression kinetics between each phase. Finally, enhanced synthesis of these polypeptides appeared unrelated to regulation of either heat-induced cell cycle delay or to the resumption of phase-specific progression after heat shock as measured by simultaneous flow cytometric measurement of incorporated BrdUrd and DNA content.     

Unique sequence, ski, in Sloan-Kettering avian retroviruses with properties of a new cell-derived oncogene.

The Sloan-Kettering viruses (SKVs) are a group of transforming retroviruses that were isolated from chicken embryo cells which had been infected with the avian leukosis virus transformation-defective Bratislava 77 (tdB77). Each of the SKV isolates was shown to contain multiple genomes of different sizes indicating the presence of several viruses in addition to tdB77. To identify and characterize the putative transforming gene(s) of the SKVs, we used hybridization selection to isolate the fraction of a representative cDNA which was SKV specific. Both solution and blot hybridization studies with viral RNAs showed that the specific probe contained a sequence, ski, that was at least partially held in common by the multiple SKV genomes. This conclusion was confirmed by the observation that a molecularly cloned ski probe also hybridized to each of the multiple SKV genomes. Southern blots of chicken DNA revealed homologs of ski (c-ski) which were not associated with endogenous viral loci. Results showing that c-ski was expressed in polyadenylated cytoplasmic RNA of uninfected chicken cells indicated that it is a functional gene. Other data showed that c-ski was conserved in avian and mammalian evolution, suggesting a functional role for the gene in species other than chickens. Using ski cDNA in solution hybridizations with viral RNAs and in Southern blot hybridization with cloned retroviral oncogenes, we did not detect any relationship between ski and any of 15 previously identified oncogenes.     

Isolation and characterization of the TRM1 locus, a gene essential for the N2,N2-dimethylguanosine modification of both mitochondrial and cytoplasmic tRNA in Saccharomyces cerevisiae

The trm1 mutation of Saccharomyces cerevisiae is a single nuclear mutation that affects a specific base modification of both cytoplasmic and mitochondrial tRNA. Transfer RNA isolated from trm1 cells lacks the modified base N2,N2-dimethylguanosine, and extracts from these cells do not have detectable N2,N2-dimethylguanosine-specific tRNA methyltransferase activity. As part of our efforts to determine how this mutation affects enzyme activities in two different cellular compartments we have isolated the TRM1 locus by genetic complementation. The TRM1 locus restores the N2,N2-dimethylguanosine modification to both cytoplasmic and mitochondrial tRNA in trm1 cells. An open reading frame in this TRM1 gene is essential for complementation of the trm1 phenotype. Expression of this open reading frame in Escherichia coli converts the organism from one that neither makes N2,N2-dimethylguanosine nor has N2,N2-dimethylguanosine-specific tRNA methyltransferase activity into one that does. This result suggests that the TRM1 locus is the structural gene for the tRNA modification enzyme and that both nuclear/cytoplasmic and mitochondrial forms of the methyltransferase are produced from the same gene.     

斯氏狸殖吸虫螺类宿主新记录:洪山拟钉螺新种记述

本文报道斯氏狸殖吸虫新的螺类宿主——洪山拟钉螺Tricula hongshanensis sp. nov.的特点:螺壳较宽而短,体螺层较高大,壳口上缘成锐角,触角伸展时较长,收缩吋有环状皱褶,雄性阴茎较粗短,末端钝圆,齿舌公式不同于其它拟钉螺。     

B淋巴细胞在多向造血祖细胞生长中的地位

小鼠骨髓细胞在体外培养中,加入用流式自由电泳法分离所得的高纯度正常B淋巴细胞,可使多向祖细胞(CFU-mix)集落增加至5倍;加入小鼠B淋巴瘤细胞株的条件培基(M_(12.4.1)-CM)时,CFU-mix数也可增加至4倍。单集落形态学分析结果表明M_(12.4.1)-CM可加强CFU-GEMm及p-BFU-E等早期造血祖细胞的增殖与分化。小鼠高纯度B细胞样品在体外培养中加入1000 rad照射的骨髓细胞可出现CFU-mix集落,如果再加入适量的小鼠肺条件培基,则CFU-mix数量比对照大15倍,其集落性质为CFU-GEMm,GMm及p-BFU-E。在此培养中加不同稀释度抗小鼠IgM血清,结果CFU-mix的产率与抗IgM血清的浓度成直线反比关系,当加入1:10抗小鼠IgM血清时,CFU-mix为0。作者假设在一定培养条件下,IgM阳性的部分B细胞可返祖转化为CFU-mix。     

纪念蒋英教授

蒋英教授是著名的植物分类学家。他从事中国夹竹桃科、萝藦科、番荔枝科植物的专门研究和教育事业有五十四年历史,为祖国科学事业奋斗一生,作出了重大贡献。本文详细地介绍了他的生平、艰苦创业的经过、严谨治学精神、培养人才的经验,并总结了他一生的科研成就和八十多篇著作名录,供后人参考。     

Immunocytochemical diagnosis of acute leukemia with pleural involvement

Cytologic examination of the pleural effusion from a patient with acute leukemia, leukocytosis and bleeding revealed the presence of many leukemic cells, "lymphocytes" and erythrocytes. The significance of these cellular changes was investigated by simultaneous study of blood and effusion leukocytes by morphologic, cytochemical and immunochemical methods. Both the leukemic blasts and the "lymphocytes" in the effusion and the blood were found to be neoplastic and contained antigens characteristic of both myeloid cells (OKM-1) and lymphoblasts (C-ALLA, common acute lymphoblastic leukemia antigen). These results, when analyzed in the context of the clinical findings, were indicative of acute leukemia with pleural involvement. Such a clinically oriented approach may further enhance the potential of cytodiagnosis in patients with serous effusions.     

Chemical transformation of eremofortin C into PR toxin.

The natural products of both eremofortin C (EC) and PR toxin are secondary metabolites of Penicillium roqueforti. Because the chemical structures of EC and PR toxin are closely related to each other and differ only by a hydroxyl functional group in EC and an aldehyde functional group in PR toxin at the C-12 position, the chemical transformation of EC into PR toxin was investigated. Oxidation with a chromic anhydride-pyridine complex was found to be the most satisfactory method.     

Structure of an antifreeze polypeptide and its precursor from the ocean pout, Macrozoarces americanus

Serum antifreeze polypeptides (AFP) from Newfoundland ocean pout have been resolved by ion exchange chromatography and reverse phase high performance liquid chromatography into at least 12 components. The protein sequences of three of the AFP were determined using a combination of protein Edman degradation and cDNA sequencing. The AFP precursor protein encodes for a preprotein of 87 amino acids with no obvious prosequences. Two of the AFP (SP1-A and SP1-C) were separate gene products with minor amino acid sequence differences. The protein structure of SP1-C precursor is MKSVILTGLLFVLLCVDHMTASQSVVAT QLIPINTALTPAMMEGKVTNPIGIPFAEMSQIVGKQVNTPVAKGQTLMPNMVKTYVAGK. The third AFP (SP1-B) is a post-translation modification product of SP1-C. These experiments indicate that the ocean pout AFP are a multigene family with protein structure different from any other known polypeptide antifreezes.     

Comparative research on erythrocyte anionic adenosine triphosphatase in vertebrates

Studies have been made on the level of activity of anion ATPase and its sensitivity to anions in erythrocytic membranes from fishes, amphibians, reptiles, birds and mammals. Significant variations in these properties of the ATPase were found among the species investigated. Protein composition of erythrocytic membranes was also investigated by means of disc-electrophoresis in polyacrylamide gel in men, rabbit, rat, mouse, hamster, tortoise, crow and starling.