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Biomedical subjects

N I Shapiro

Publications and source records attributed to N I Shapiro.

At least 37 records · Page 2Linked to original sources
PubMed1984

[Malignant transformation of mouse cultured cells using bovine adenovirus type 3 and modification of this process by MNNG].

It is shown that tumour transformation of cultured mouse cells 10T1/2C3H depends on the time after the infection with virus BAV-3. The maximal number of tumours was observed 3 weeks after infection, then the frequency of tumours was reduced. MNNG modified virus-induced tumour cell transformation differently depending on the time between cell infection and treatment with the chemical agent.

Adenoviridae↗
PubMed1983

The mutational origin of serum independence in Chinese hamster cells in vitro.

The genetic mechanisms determining the ability of transformed cells to grow in a medium with a low serum content (ser+) were studied in a clone of Chinese hamster cells with normal serum requirements. The fluctuation test has shown that serum independence occurs as a random spontaneous event. Its rate of occurrence is about 10(-5). The concomitant study of a gene mutation (resistance to 6-mercaptopurine--6MP) revealed similar characteristics with respect to the distribution of the number of mutants in replicative cultures. N-methyl-N1-nitro-N-nitrosoguanidine (MNNG) and SV40 significantly increased the frequency of ser+ colonies. Induction was detected after an expression time of 3-4 days, which is typical of gene mutations. In 16 out of 18 ser+ clones of independent origin the ser+ character remained stable. The results suggest that the ser+ character originates in most cases from a mutation event.

Animals↗
PubMed1983

[Genetic nature of one of the traits of malignant cell transformation in vitro].

The genetic events controlling the ability of transformed cells to grow in a medium with a low serum content (ser+) were studied. A hypodiploid clone of Chinese hamster cells with normal serum requirements (49a5ser-) was used as starting material. The results of the fluctuation tests have shown that serum-independence is a random spontaneous event. Its rate of occurrence is 1-2 . 10(-5). The concomitant study of a gene mutation (resistance to 6-mercaptopurine) revealed similar characteristics with respect to the distribution of the number of mutants in replicate cultures and the mutation rate. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and the oncogenic SV40 virus significantly increased the frequency of ser+ colonies. In the majority of clones isolated in a medium with 1% serum (11 spontaneous and 7 induced by MNNG), the ser+ character proved to be stable after different periods of cultivation without selective pressure. The degree of serum-independence varied in different clones. The results suggest that the ability to grow in a medium with a low serum content originates, in most cases, from a mutation event.

Animals↗
PubMed1982

The role of the transforming A gene of SV40 in the mutagenic activity of the virus.

The mutagenic activity of the tsA239 mutant of SV40 which synthetizes a defective T antigen at 40 degrees C was investigated in Chinese hamster cells under permissive and nonpermissive temperature. At 33 degrees C the virus increased the yield of 6-mercaptopurine-resistant colonies after 2 days expression time by a factor of 1.6-4 as compared with the control and raised the frequency of aberrant metaphases after the same time by a factor of 1.9-3.4. In the same experiments, with the same initially infected population of Chinese hamster cells, at 40 degrees C tsA SV40 did not induce either gene mutations or chromosome aberrations at the same early stage after infection. Presumably the activity of the A gene of SV40 is necessary not only for the transforming but also for the mutagenic effect of the virus.

Animals↗
PubMed1981

Oncogenic adenovirus as mutagen for chinese hamster cells in vitro.

Oncogenic bovine adenovirus (BAV3) was shown to induce chromosome aberrations and gene mutations to 6-mercaptopurine (6MP) resistance in Chinese hamster cells. BAV3 showed the highest mutagenic effect at the chromosome level 12--24 h postinfection. After 48 h the yield of aberrations dropped to the control level, where it remained after 72 and 96 h. BAV3 showed a highly significant induction of mutations to 6MP resistance 48 h postinfection. The effect of the combined treatment of cells with 5-bromodeoxyuridine (BrdU) and BAV3 on mutagenesis at chromosome and gene levels proved to be synergistic. The mutagenic activity at the gene level of BAV3, along with the earlier established mutagenic effect of SV40, indicates that this property is probably inherent in many DNA-containing oncogenic viruses. The possible mechanisms underlying malignant transformation and mutagenesis are discussed.

Adenoviridae↗
PubMed1981

[Chinese hamster cells mutant for the hypoxanthine-guanine phosphoribosyltransferase locus. II. Characteristics of the hybrids revealing intragenic complementation].

After polyethylene glycol treatment of GPRT- mutant cells, 12 clones were isolated on the ATG medium showing intragenic complementation. Karyological analysis confirmed the hybrid nature of the clones isolated. The GPRT activity in the hybrid clones, as assessed in vitro, exceeded the sum of parental activities. In vivo incorporation of 14C-hypoxanthine showed the GPRT activity in the hybrids to be an order of magnitude higher than in the mutant parental cells. Moreover, the GPRT activity in the hybrid clones was found to increase considerably during cultivation on the ATG medium; hence, their ability to multiply on this selective medium. All hybrid cells surviving and multiplying on the ATG medium were shown to maintain a high enough resistance to 8-AG, 6-MP and, to somewhat less extent, to 6-TG. The frequency of complementation was determined for the cells of mutant clones selected on media with different purine base analogues. The complementation map for the GPRT locus was constructed and proved to be linear. Five groups of complementation were specified.

Animals↗
PubMed1981

[Characteristics of preparations of typhoid antigens obtained by ultrafiltration].

The properties of the preparations of the total typhoid antigens isolated by various methods, purified and concentrated by ultrafiltrations, were studied, and the technique of the preservation of their high solubility on drying (the neutralization and removal of disperse components prior to drying) was developed. Preparations obtained by ultracentrifugation were characterized by lower ash content and, when compared with alcohol tryptic preparations, had better antigenic properties, inducing the synthesis of not only O- and Vi-, but also H-antibodies in high titers.

Animals↗
PubMed1980

The synergistic effects of SV40 and BUdR on induction of gene mutations and chromosomal aberrations in Chinese hamster cells.

The induction of chromosomal aberrations and gene mutations was studied in Chinese hamster cells after separate and combined treatment with BUdR and SV40. Separate treatment of cells with BUdR or virus infection increased the yield of chromosomal aberrations and reversions from glutamine requirement, expressed at 40 degrees C (a ts mutant), to prototrophy. The combined effect of the incorporation of BUdR into one DNA strand, and a subsequent infection by SV40 was additive as regards the percentage of aberrant metaphases. The integration of the analogue into both DNA strands followed by SV40 treatment resulted in a statistically significant increase in the frequency of aberration carrying metaphases, as compared with the frequency expected if the two agents had acted additively. The same phenomenon was detected when the frequency of reversions to glutamine independence was studied. Hence, the effect of the joint treatment by BUdR incorporated into both DNA strands and SV40 was synergistic. This is known to characterize the effect of BUdR on virus-induced transformation. Therefore, obviously the agent that enhances the malignant transformation of cells by the virus similarly modifies its mutagenic activity. The results obtained are presumed to confirm the previously advanced hypothesis that the same events following infection might control both the integration of viral DNA into the host-cell chromosome (and hence cell transformation) and virus-induced mutagenesis. The role of repair processes in the synergistic effect of BUdR and SV40 in the yield of reversions to glutamine independence is discussed.

Animals↗
PubMed1980

[Postreplicative DNA repair in UV-sensitive Chinese hamster cell clones].

The postreplication repair (PRR) of DNA has been studied in UV-irradiated (10 J/m2) and carcinogen (7-bromomethylbenz(alpha)anthracene -- BMBA) treated (1.65-3.3) 10(-6) M Chinese hamster clones with different UV-sensitivity. Ultracentrifugation in alkaline sucrose gradients has been used. Compared to the UV-resistent clone V-79, the UV-sensitive clone CHS2 displayed a lower effectivity of PRR of DNA after both UV-irradiation and carcinogen treatment, by 6 and 10 times, resp. Thus, there is a positive correlation between lethal and mutagenic effects of UV-irradiation and the effectivity of PRR of DNA. The same conclusion is apparently true in the case of carcinogen 7-BMBA treated Chinese hamster cells.

Animals↗
PubMed1978

[Stimulation of nonspecific resistance in mice with high- and low-molecular fractions of endotoxin on 2 models of Shigella infection].

The capacity of S. paratyphi B endotoxin and its high molecular (HMF) and low molecular (LMF) fractions to stimulate the resistance of mice to shigella infection in intraperitoneal and intranasal challenge was investigated. The HMF developed high activity after the intraperitoneal injection (efficiency index--EI = 2.8). All the preparations were less active on the lung model (EI = 1.6--1.7). Materials of this work lead to the conclusion that in studying the phenomenon of nonspecific resistance induction conditions providing antitoxic and antiinfectious resistance should be considered separately.

Animals↗
PubMed1978

[Study of the structure and function of endotoxins with the aid of enzymes. 2. Modification of Salmonella paratyphi B endotoxin with lysozyme and lipase].

Endotoxin preparations from the S. paratyphi B cultures, isolated by various methods, were treated with lysozyme (splitting of beta-1,4-glycoside links of lipid A) and lipase of the pancreas (splitting of complex ester links of glycerophosphatides). Lysozyme and, to a lesser extent, lipase, were capable of partial depression of the toxic endotoxin function. The process of enzymatic detoxication coursed selectively, without influencing the serological and immunological activity of the preparations. Suppositions are put forward on the complicated nature of the toxic endotoxin function manifestation and possibility of provision of detoxication effect by specific actions differing by the point of application.

Antitoxins↗