Monoclonal antibody detection of transformation associated protein (TAP) in ts110 Moloney murine sarcoma virus transformed 6M2 cells that are different from the mos gene product

By the use of a highly specific monoclonal antibody (designated MC), we were able to detect three radiolabeled bands with molecular weights of 60,000, 63,000, and 66,000 daltons in the ts-110 Moloney murine sarcoma virus mutant-transformed rat kidney cells known as 6M2. Expression of transformation properties as well as these three bands in 6M2 cells was found to be temperature sensitive. Therefore, MC detected factors that are apparently associated with the transformation of 6M2 cells. These factors are tentatively referred to as transformation associated proteins. These transformation proteins were found in two other Moloney murine sarcoma virus-transformed rat cell lines. These proteins were found to differ from known gene products of the ts-110 Moloney murine sarcoma virus mutant and do not have kinase activity. The transformation associated proteins may represent rat cellular factors activated during the transformation of rat cells by Moloney murine sarcoma virus.     

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.     

Folic acid and chromosome breakage. III. Types and frequencies of spontaneous chromosome aberrations in proliferating lymphocytes

The types and frequencies of spontaneous chromosome aberrations were studied in human lymphocytes cultured for 96 h in minimal essential medium (MEM) or MEM without folic acid (MEM-FA). In both media, the most frequent aberrations were chromatid gaps, isochromatid gaps and chromatid breaks. Chromosome (isochromatid) breaks and dicentrics were seen less frequently. Neither of these less frequent aberrations was seen in 4000 cells from MEM, but both were seen in 4000 cells from MEM-FA.     

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。     

钙通道阻断剂异搏定对缺氧性肺动脉高压形成的影响

为考察Ca~( )在缺氧性肺动脉高压形成中的作用,我们观察了钙通道阻断剂异搏定对慢性连续性缺氧大鼠肺动脉压及左右心功能的影响。将动物置于模拟海拔5000m高原的低压舱内,腹腔注射异搏定,剂量为4mg/kg BW,每日两次。实验结果表明:异搏定可以减弱缺氧15天所引起的肺动脉压升高和右心功能加强的程度,对颈动脉压及左心功能无明显影响,提示Ca~( )的跨膜内流是构成缺氧性肺动脉高压形成的重要基础之一。我们还比较了异搏定对缺氧持续时间不同(15天、10天、5天)的大鼠肺循环的影响,并讨论了异搏定发生作用的机制。     

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。     

苜蓿二磷酸核酮糖(RuBP)羧化酶体内活化作用的调节

苜蓿RuBP羧化酶的初活性和活化作用在不饱和光强下与光合速率一样随光强增加而增加。缺硫培养苜蓿叶片的光合速率和RuBP羧化酶的含量、初活性及总活性均比对照有不同程度的降低,其中酶的初活性与光合速率两者减少的趋势比较接近,说明RuBP羧化酶的初活性可能在光合CO_2固定作用中具有决定作用。然而,缺硫植株中酶的活化作用比对照明显增高。酶的活化作用与叶片中的叶绿素,6-PG,NADPH及ATP相对酶含量的比值成正比,与体内的酶量成反比。     

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。