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N I Shapiro

Publications and source records attributed to N I Shapiro.

At least 55 records · Page 3Linked to original sources
PubMed1977

[Hybridization of Chinese hamster cells sensitive to ultraviolet irradiation].

Resistance to UV-light was studied in two UV-sensitive aneuploid Chinese hamster cell clones to different origin and degree of sensitivity, their respective polyploids and somatic cell hybrids. The karyotype of the parental clones, cell hybrids and polyploids was analyzed in parallel. A great variability of karyotypes was detected in hybrid cells. Serial cultivation of hybrids was accompanied by chromosome loss. Soon after fusion the hybrid clones proved to be more resistant to UV than the parental sensitive cells. However, their sensitivity increased with passages. The comparison of UV-sensitivity with data on karyotype analysis allowed to assume that the increase in sensitivity was correlated with the loss of particular chromosomes or chromosome regions. The results obtained indicated the existence of a polygenic control of UV-sensitivity, the multiple genes being assigned to different chromosomes. A reverse effect of ploidy was detected, i.e. a decrease in the resistance to the lethal action of UV-light in polyploids as compared to the parental clones.

Animals↗
PubMed1977

[Rate of spontaneous chromosome aberration occurrence in cultured Chinese hamster cells].

The spontaneous chromosome mutation rate was studied in cultured aneuploid Chinese hamster cells (clone 237(1)) using the method of slowing down the rate of cell division in a limiting medium containing 0.1% of serum. It was shown that during one cell generation (which lasted 14 days in limiting medium) the accumulation of chromosome aberrations with time took place. The data obtained are in keeping with the assumption of a linear dependence of this accumulation on time. The spontaneous chromosome rearrangement rate was 1.2 X 10(-2) mutations per cell per 24 hours. Proceeding from this value the spontaneous chromosome aberration rate in cells with a normal duration of the cell cycle was 0.6 X 10(-2) per cell per generation.

Animals↗
PubMed1976

[Development of spontaneous mutations in somatic mamalian cells and DNA replication. II. Expression of gene mutations in cultured cells].

The dependence of spontaneous rate and phenotypic expression of 6-mercaptopurine resistance mutations of DNA replication synthesis was studied in cultured Chinese hamster cells. Spontaneous mutations arising with a constant rate per cell per time unit independently on DNA replication rate were shown to be expressed only in the course of subsequent cell divisions. The frequency of N-nitrosomethylurea induced mutations in cells with reduced and normal DNA replication rate is approximately the same. However, DNA replication synthesis is necessary for the phenotypic expression of both induced and spontaneous mutations. The causes of the phenotypic lag are discussed.

Animals↗
PubMed1976

[New principles for obtaining protective antigens from deep cutlures of enterobacteria].

A model of S. typhi submerged culture was used; application of the principle of sparing extraction of surface protective antigens by the action of sublethal concentrations of two damaging agents differing by the mechanism of inhibition of the processes of vital activity of the microorganisms was founded. The principle is based on regularities characteristic of cells of bacterial pupulations: a) nonhomogeneity of individual cells of the population by the resistance to the damaging agents, and b) independence of distribution in the population cells of resistance to different damaging agents. The following typhoid antigens were obtained by combined action of sublethal concentrations of hydrogen peroxide (0.25%) and formalin (0.1%): antigens with a full antigenic structure (inducing formation of O-, Vi- and H-antibodies), of low toxicity (V50 - 0.65+/-19 mg) and highly immunogenic (AU50- 0.45+/-0.25 mug) in experiments on mice.

Animals↗
PubMed1976

[Trial of the new chemical sorbed typhoid monovaccine P in a strictly controlled experiment].

A comparative study of the reactogenicity and immunologial activity of a new chemical sorbed typhoid monovaccine II, reference-vaccine (chemical sorbed monovaccine from tryptic antigens) and placebo-sorbent (hydroxy aluminium gel) was made under conditions of strictly gested monovaccine II, an equal capacity to induce formation of O- and Vi-antibodies, and also an accumulation of H-antibodies not induced by refrence-vaccine.

Adolescent↗
PubMed1976

[Rate of the spontaneous mutation process in mammalian somatic cells and several related questions].

Various criteria are considered according to which newly arising hereditary changes in somatic mammalian cells can be classified as mutations. The analysis of experimental data reveals that the similarity of spontaneous mutation rates in somatic and germinal cells per generation, implies drastic differences in the probability of their arising per time unit: the mutation rate per time unit is considerably higher in somatic than in germ cells. This phenomenon is discussed from the viewpoint of the spontaneous mutation rate level as an adaptive character of species. The role of spontaneous mutations in ontogenesis is considered.

Animals↗
PubMed1976

[Use of Soviet semipermeable acetate-cellulose membranes for concentration and purification of typhoid antigens].

A study was made of a possibility of using Soviet made membranes "Vladipor" with a pore diameter of 16--17 nm for the purpose of concentration and purification of antigenic extracts from stab cultures of S. typhi obtained by the action of typsin, hydrogen peroxide and detergents. Preparations, complete by antigenic structure, were obtained by ultrafiltration, with a good yield. The maximal rate of ultrafiltration was noted in case of "peroxide" antigenic preparations. The use of diafiltration provided a significant reduction of the ash content in the end products.

Acetates↗
PubMed1975

[Characteristics of the hydrodynamic and biological properties of flagellar preparations isolated from submerged cultures of S. typhi].

A study was made of the hydrodynamic and biological properties of the flagella from the S. typhi 4446 cultures, isolated by the methods of differential centrifugation, in crude condition and following depolimerization and denaturing by the action of chemical and physical agents. Molecular parameters of the slow and rapid components of the flagella and subunits of the flagellin were compared. The greatest antigenic activity was possessed by the high molecular fraction of the flagella isolated in the 60% sucrose density gradient.

Animals↗
PubMed1975

[Design of new types of chemical vaccines for the prevention of intestinal infections and problems of their qualitative evaluation. Report 2. Immunochemical characteristics of the experimental preparations].

A study was made of chemical composition and immunochemical properties of 36 samples of the antigenic preparations from typhoid, paratyphoid (A and B) and dysentery (Flexner and Sonne) cultures obtained at the Leningrad, Moscow and Tashkent Institutes of Vaccine and Sera by various methods. The preparations isolated by the method of tryptic proteolysis had a polysaccharide-protein nature, and preparations isolated by the action of chemical reagents (hydroxylamine, hydrogen peroxide, detergents) -- a protein-polysaccharide one. The former contained more nucleic acids, this indicating the presence of components of cytoplasmic and nuclear origin. The preparations were characterized by molecular heterogeneity and contained high- and low-molecular components. The preparations had complex antigenic spectra by the immunodiffusion data; the preparations obtained had complex antigenic spectra by the immunodiffusion data; the preparations obtained had complex antigenic spectra by the immunodiffusion data; the preparations obtained by different method displayed identity reactions, and group specificity was expressed in some of them.

Antigens, Bacterial↗
PubMed1975

[A further study of the mutation process in Chinese hamster cells in vitro].

Spontaneous mutagenesis and mutagenesis induced by chemical mutagens in culture Chinese hamster cells were investigated. Appearance of mutations controlling the resistance to 6-mercaptopurine (6M) and reverse mutations to sensitivity was studied. The rate of spontaneous mutations of 6M resistance in cells studied was found to be sufficiently stable: it was independent on the repeated freezing of these cells and the duration of their cultivation. 5-bromodeoxyuridine (BUdR) has been shown to induce mutations to 6M resistance in cells of the 237i clone; the rate of induced mutations in some experiments as compared to the rate of spontaneous mutations was 1-2 orders higher. No clear-cut delay of phenotypic expression of BUdR-induced mutations was found. Seven independently arisen mutant clones were isolated. Five of them appeared spontaneously and two clones were induced by BUdR. Three spontaneously arisen clones were found to be reversible to sensitivity. The rate of reverse mutations in cells of the other four clones, did not exceed (2,3-3,5)-10(-6) per cell per generation. The rate of spontaneous reverse mutations in these clones was less at least one order lower as compared to the rate of spontaneous mutations to 6M-resistance. The attempts to induce reverse mutations to sensitivity by N-nitrosomethylurea in spontaneously reversible resistant cells and by BUdR in mutant cells arisen as a result of the treatment with the same agent proved unsuccessful. A method of estimation of experiment's resolving power is described for cases, when no expected events (in our study reverse mutations) were observed.

Animals↗
PubMed1975

[DNA replication and the development of spontaneous mutations in the somatic cells of mammals. I. The relationship between the outcome of gene mutations and the duration of cell life].

The reduction of serum concentration in culture medium to 0,1% was proposed as a method of slowing division and DNA replication in Chinese hamster cells in vitro. Under these conditions the rate of DNA replication was reduced by more than one order of magnitude, while cell viability remained high enough (about 10%) for a long period up to 30 days. The spontaneous mutation rate to 6-mercaptopurine resistance, as calculated per day in cells with reduced DNA replication rate, was comparable to that in normally dividing cells [(1,2 +/- 0,3) X 10(-5) and (3,1 +/- 0,5) X 10(-5) per cell per day respectively]. This proves that a considerable fraction of spontaneous mutants arise independently on DNA replicative synthesis.

Animals↗
PubMed1975

Induction of gene mutations and chromosomal aberrations by simian virus 40 in cultured mammalian cells.

Induction of gene mutations by SV40 was studied in aneuploid human and Chinese hamster cells. In Chinese hamster cells SV40-induced chromosome aberrations were also studied. SV40 penetrated into the cells of both lines and induced synthesis of the T antigen. The efficiency of infection in Chinese hamster cells was tested additionally by their ability to form colonies in medium lacking the serum growth factor. The maximal number of cells with serum growth factor independence was observed on the first day after infection. When hamster cells had been maintained in "factor-free medium" for the first two passages after infection a sub-line was isolated, which synthesized T antigen 60 days after exposure to SV40. This was considered to be an indirect proof of the integration of viral genome into host chromosome. A significant increase in the frequency of chromosomal aberrations was detected in SV40-infected Chinese hamster cells. It was observed on the first and second days after treatment. The most numberous were the chromosome and chromatid breaks, which were distributed randomly in 5 morphological groups according to the chromosome length. SV40-induced mutations of resistance to 8-AG and 6-MP in human and Chinese hamster cells respectively were detected, when cells were plated in selective medium one to five days after infection. Induction was detected in all the 4 experiments with human cells and in 9 out of 11 experiments with Chinese hamster cells. Induction was highly significant according to the Wilcoxon test (P greater than 0.99), when the results of all experiments carried out in human and Chinese hamster cells were summarized. Resistance was stable after prolonged cultivation of 13 isolated clones under non-selective conditions. It is suggested that viral genome integration, gene mutations and chromosomal aberrations may have common molecular mechanisms. The role of gene mutations in virus-induced carcinogenesis is discussed.

Aneuploidy↗
PubMed1975

[Present problems of somatic cell genetics].

A review of recent advances in genetics of somatic cells is given in the article. It contains three sections: 1) hybridization of somatic cells and its application to the mapping of genes and to the study of gene action; 2) relation of somatic cell genetics to genetic engineerings; 3) progress and perspectives of higher plant somatic cell genetics.

Animals↗