Susceptibility of human diploid fibroblast strains to transformation by SV40 virus

A quantitative system has been developed for the study of transformation of human diploid fibroblasts in culture by two oncogenic viruses, SV40 and the E46 strain of adeno 7-SV40 "hybrid" virus. Seven of the eleven cell strains derived from human skin biopsies when infected with SV40 (10(9) tissue culture infective doses per milliliter) gave rise to transformed colonies with approximately the same frequency (0.03 percent). Two strains derived from patients with Fanconi's anemia, an autosomal recessive disease associated with a high incidence of chromosome abnormalities and spontaneous neoplasms, gave values more than ten times higher. Two strains from persons heterozygous for this gene were also considerably more susceptible to viral transformation.     

Unwinding of duplex DNA from the SV40 origin of replication by T antigen

The T antigen specified by SV40 virus is the only viral-encoded protein required for replication of SV40 DNA. T antigen has two activities that appear to be essential for viral DNA replication: specific binding to duplex DNA at the origin of replication and helicase activity that unwinds the two DNA strands. As judged by electron microscopy, DNA unwinding is initiated at the origin of replication and proceeds bidirectionally. Either linear or circular DNA molecules containing the origin of replication are effective substrates; with closed circular DNA, a topoisomerase capable of removing positive superhelical turns is required for an efficient reaction. Presence of an origin sequence on duplex DNA and a single-strand DNA-binding protein appear to be the only requirements for T antigen to catalyze unwinding. This reaction mediated by T antigen defines a likely pathway to precise initiation of DNA replication: (i) the sequence-specific binding activity locates the origin sequence, (ii) the duplex DNA is unwound at this site, and (iii) the DNA polymerase and primase begin DNA replication. A similar pathway has been inferred for the localized initiation of DNA replication by bacteriophage lambda and by Escherichia coli in which a sequence-specific binding protein locates the origin and directs the DnaB helicase to this site. Observations with the SV40 system indicate that localized initiation of duplex DNA replication may be similar for prokaryotes and eukaryotes.     

SV40 virus transformation of mouse 3T3 cells does not specifically enhance sugar transport

The apparent enhancement of 2-deoxy-D-glucose uptake by mouse 3T3 cells accompanying transformation by SV40 virus is not due primarily to an effect on the transport process but to enhanced phosphorylation of the sugar by intracellular kinases. Moreover, the effect is not specifically a function of the presence of the viral genome, but is a reflection of the overall growth rate and physiological state of the cell.     

Encapsidation of free host DNA by simian virus 40: a simian virus 40 pseudovirus

Under specified growth conditions, simian virus 40 encapsidated host DNA in a noncircular form free of viral DNA. Two bands of virus particles were present in cesium chloride equilibrium density centrifugation. The host DNA species contained in the upper band was of a lower molecular weight than the DNA present in the mature virus in the lower band.     

Neoplastic transformation of hamster astrocytes in vitro by simian virus 40 and polyoma virus

Astrocytes in cultures of brain cells from fetal or newborn hamsters undergo neoplastic transformation after infection with simian virus 40 or polyoma virus. Subcutaneous or intracerebral inoculation of the transformed brain cells into newborn or adult hamsters produces progressively enlarging astrocytomas at the sites of injection. Astrocytomas produced by polyomatransformed cell lines are histologically better differentiated, but grow more rapidly and metastasize more frequently, than astrocytomas produced by cell lines transformed by simian virus 40. These observations make available in vitro models of virus-induced oncogenesis in astrocytes and provide simple techniques for obtaining astrocytoma cell lines suitable for screening studies of chemical agents effective against astrocytomas.     

Neoplastic transformation in vitro of hamster lens epithelium by simian virus 40

Hamster lens epithelium infected with simian virus 40 underwent transformation in vitro and produced tumors when injected into homologous hosts. Undisturbed lens epithelium in man and experimental animals has not been observed to undergo neoplastic change. The virus-induced tumors contained undifferentiated cells that were either polygonal or spindle-shaped. Their origin from lens epithelium seems certain since it is possible to isolate this unique structure free of connective tissue and blood vessels.     

植物单宁对烟草花叶病毒的抑制活性

测试了从11种植物提取的单宁对烟草花叶病毒(TMV)的抑制活性.结果表明:(1)任一植物的单宁质量浓度为5.000或2.500mg·mL-1时,与TMV混合10min后接种,其抑制率均达80%以上.(2)单宁质量浓度为5.000mg·mL-1时,与TMV混合后立即接种,其抑制率也均达80%以上,表明单宁与病毒粒体作用时间很短.(3)TMV与单宁混合,透析3d后,可恢复大部分侵染力;混合3d但未作透析处理,与混合10min的处理相比,抑制率下降,表明部分植物的单宁体外稳定性可能较差,与TMV粒体作用能力下降.(4)这11种植物的单宁对TMV体内抑制复制效果不明显.(5)大飞扬、杠板归、虎杖3种植物的单宁,在接种前先喷施心叶烟再接种TMV,可抑制病毒的初侵染;在接种前先喷施普通烟草K326再接种TMV,烟株发病期推迟3-8d.     

平菇DNA两种提取方法的比较研究

用两种不同方法从平菇菌丝体中提取DNA,结果表明,在两种不同DNA提取方法中,CTAB提取法比SDS提取法提取的DNA片段降解少,DNA纯度高,可以满足进一步遗传分析的要求。     

Staurosporine 对人低分化鼻咽癌细胞系细胞周期和 DNA 倍体含量影响的动态观察

目的：探讨蛋白激酶Ｃ（ＰＫＣ）抑制剂Ｓｔａｕｒｏｓｐｏｒｉｎｅ（ＳＴ）诱导ＣＮＥ－２Ｚ细胞凋亡时,对细胞周期的选择性和对ＤＮＡ含量及细胞周期的动态影响。方法：以ＰＫＣ催化区抑制剂ＳＴ作用于ＣＮＥ－２Ｚ细胞不同时间后,收集细胞进行ＰＩ染色和流式细胞仪检测。结果：ＳＴ以２×１０－６ｍｏｌ／Ｌ终浓度分别作用至３,６,１２,２４ｈ后,发现Ｇ２期百分比分别为３０．４３±７．１６、３０．８３±６．２５、４２．４３±３．９８和７１．８０±７．５５,均较对照组１２．０８±３．４９增高明显。比较差异有显著性（Ｐ＜０．０１）;而Ｇ１期在３,６,１２,２４ｈ分别为３４．７０±１．５６,３７．０３±６．４７,１６．６３±１．７７和１５．３０±５．４６,均较对照组６２．５６±６．５７明显降低,比较差异有显著性（Ｐ＜０．０１）。亚二倍体峰百分比在１２、２４ｈ分别为３７．１０±７．２１和４３．７２±６．７３,均较对照组９．８１±１．７８显著增加（Ｐ＜０．０１）;而１２ｈ以前该峰增加不明显。结论：ＳＴ在终浓度为２×１０－６ｍｏｌ／Ｌ诱导ＣＮＥ－２Ｚ细胞至１２ｈ后即可出现明显的ＤＮＡ含量降低的凋亡细胞,对Ｇ２期细胞敏感而使之逐渐阻滞,且存在     

Human monoclonals from antigen-specific selection of B lymphocytes and transformation by EBV

Hybridoma technology has made it possible to prepare monoclonal antibodies with the use of murine lymphocytes. Attempts to extend this technology to the human level, however, have met with difficulties. A method has been developed for making human monoclonal antibodies of predetermined specificity. Biotinylated antigens (human thyroglobulin or tetanus toxoid) were incubated with human B lymphocytes from peripheral blood. The lymphocytes to which the antigens bound were selected by fluorescence-activated cell sorting. Positively selected (high fluorescence) and negatively selected (low fluorescence) cells were then transformed with Epstein-Barr virus (EBV) and grown in microculture wells. All wells from the positively selected fraction produced antigen-specific antibody (95 to 1800 nanogram-equivalents per milliliter), whereas fewer than 6% of the wells from negatively selected fraction made any detectable antibody (less than 10 nanogram-equivalents per milliliter). When the positively selected EBV-transformed cells were cultured in limiting dilution, clones were obtained that made antigen-specific monoclonal antibodies. By this method, monoclonal antibodies to both foreign antigens and autoantigens can be prepared from the normal human B-cell repertoire.     

Pancreatic neoplasia induced by SV40 T-antigen expression in acinar cells of transgenic mice

Three lines of transgenic mice were produced that develop pancreatic neoplasms as a consequence of expression of an elastase I-SV40 T-antigen fusion gene in the acinar cells. A developmental analysis suggests at least a two-stage process in the ontogeny of this disease. The first stage is a T antigen-induced, preneoplastic state characterized by a progression from hyperplasia to dysplasia of the exocrine pancreas, by an increased percentage of tetraploid cells, and by an arrest in acinar cell differentiation. The second stage is characterized by the formation of tumor nodules that appear to be monoclonal, because they have discrete aneuploid DNA contents. The cells within the nodules as compared to normal pancreatic tissue have less total RNA by a factor of 5, less pancreas-specific messenger RNA by a factor of about 50, and increased levels of T-antigen messenger RNA. A tumor cell line has been derived that retains both pancreatic and neoplastic properties.     

Human insulin from recombinant DNA technology

Human insulin produced by recombinant DNA technology is the first commercial health care product derived from this technology. Work on this product was initiated before there were federal guidelines for large-scale recombinant DNA work or commercial development of recombinant DNA products. The steps taken to facilitate acceptance of large-scale work and proof of the identity and safety of such a product are described. While basic studies in recombinant DNA technology will continue to have a profound impact on research in the life sciences, commercial applications may well be controlled by economic conditions and the availability of investment capital.     

ROS-generating mitochondrial DNA mutations can regulate tumor cell metastasis

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (ND6). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.     

Cellular transformation by human papillomavirus DNA in vitro

Molecularly cloned DNA's of human papillomaviruses HPV-5 and HPV-l induced morphological transformation of mouse C127 cells in culture. Single-cell clones of cells transformed by papillomavirus contained multiple persistent episomal copies of the transfected DNA species and were analyzed for growth characteristics indicating malignant potential.     

Identity of HeLa cell determinants acquired by vesicular stomatitis virus with a tumor antigen

Growth of vesicular stomatitis virus (VSV) in HeLa cells results in progeny containing non-VSV antigens with a molecular weight around 75,000. The non-VSV antigens were detected by antiserums to HeLa cell determinants. These antiserums precipitate whole virions but do not neutralize them. Because one of the antiserums is directed to a tumor-specific surface antigen of HeLa cells, it appears that VSV specifically acquires such antigens during its passage through human tumor cells.     

Polysomes extracted from Escherichia coli by freeze-thaw-lysozyme lysis

Polysomes can be extracted from Escherichia coli by freezing and thawing in the presence of lysozyme, followed by treatment with sodium deoxycholate. The method is simple and convenient; the yields consistently high.     

高效液相色谱法测定红甘蓝中矢车菊色素含量

试验建立了红甘蓝提取物中矢车菊色素含量的高效液相色谱测定方法。采用资生堂C18色谱柱(4.6mm×250mm);以甲醇:甲酸水(1:10)=40:60(v/v)作流动相分析矢车菊色素;流速为1.0mL·min-1;柱温为室温;检测波长为530nm。结果表明,红甘蓝提取物中的矢车菊色素含量为0.11‰,平均回收率为104.5%,相对标准偏差(RSD)为0.5%(n=5)。该方法快速、准确、重复性好。     

二倍体、四倍体苹果矮化砧木SH40抗寒性的比较研究

采用电导法(EL法)和电阻抗图谱法(EIS法)测定了二倍体和离体加倍获得的四倍体苹果矮化砧木SH40一年生枝条的半致死温度,并对二者的与抗寒性相关的几个生理指标进行了比较。结果表明:四倍体的半致死温度比二倍体高,无论抗寒锻炼前期,还是抗寒锻炼后期,四倍体的可溶性蛋白质、可溶性糖和脯氨酸含量均极显著低于二倍体,苹果矮化砧木SH40染色体加倍后抗寒性降低。