Aberrations In Chinese Hamster Cells Research Articles

Potentiation by hydroxyurea in G2-prophase of thiotepa- and bleomycin-induced chromosomal aberrations in Chinese hamster cells.

The potentiating effect of 5times10-3M hydroxyurea in G2-prophase on chemically induced chromosomal aberrations has been studied in Chinese hamster cells. Hydroxyurea, when given during the last 2 h before fixation, enhanced the frequency of aberrations induced by both S-dependent (thiotepa) and S-independent (bleomycin) agents. The most striking effect was seen on the frequencies of gaps and chromatid breaks but an increase was also found in the number of iso-chromatid breaks of the non-union type. The frequencies of exchanges and iso-chromatid breaks of the sister-union type were comparatively little affected. The results indicate that hydroxyurea inhibits a repair system in G2-prophase involved in the formation of chromosomal aberrations in mammalian cells.

Classification of diverse organic compounds that induce chromosomal aberrations in Chinese hamster cells.

A data set of 297 diverse organic compounds that cause varying degrees of chromosomal aberrations in Chinese hamster lung cells is examined. Responses of an assay are categorized as clastogenic (>10% aberrant cells) and nonclastogenic (<5% aberrant cells). Each of the compounds is represented by calculated structural descriptors that encode topological, geometric, electronic, and polar surface features. A genetic algorithm (GA) employing a k-nearest neighbor (kNN) fitness evaluator is used to iteratively search a reduced descriptor space to find small, information-rich subsets of descriptors that maximize the classification rates for clastogenic and nonclastogenic responses. To further improve modeling, a similarity measure using atom-pair descriptors is employed to create more homogeneous data subsets. Three different data sets are examined. Results for a set of 297 compounds using the GA-kNN method were 86.5% and 80.0% correct classification in the training set and prediction set, respectively. Results for a subset of 279 compounds in model 2 are 85.7% and 85.7% for the training and prediction sets, respectively. Results for a subset of 182 compounds in model 3 are 91.5% and 94.4% for the training and prediction sets, respectively. Creating smaller, more topologically similar data sets result in improved classification rates.

Low molecular weight polyethylene glycol induces chromosome aberrations in Chinese hamster cells cultured in vitro.

The human population is widely exposed to polyethylene glycol (PEG) and its chemical derivatives, which are widely used as vehicles or co-solvents in many pharmaceutical and cosmetic preparations. However, PEG polymers of low molecular weight differ significantly from polymers of higher molecular weight in their physico-chemical properties, biological effects on cell permeability and their absorption and excretion, as well as their higher toxicity and possibly genotoxicity. In the present study we have analysed the induction of chromosome aberrations by the low molecular weight PEG polymers tetraethylene glycol (TEG), PEG 200 and PEG 400 in a Chinese hamster epithelial liver (CHEL) cell line, which retains sufficient metabolic capability to activate different promutagens and procarcinogens. The results indicate that in CHEL cells only TEG and PEG 200 are clastogenic. Parallel experiments performed in CHO cells in the presence and absence of rat liver S9 mix showed significant increases in chromosomal aberrations only in cultures treated with TEG in the presence of rat liver S9, indicating that low molecular weight polymers need to be activated to exert their genotoxic activity.

Analysis of radiation-induced chromosome aberrations in Chinese hamster cells by FISH using chromosome-specific DNA libraries.

The frequencies of chromosome aberrations induced by different doses of X-rays were determined in both splenocytes and primary lung fibroblasts of Chinese hamster by bi-colour FISH using a combination of four chromosome-specific DNA libraries. The results indicate that the X-rays induced more translocations than dicentrics in Chinese hamster cells, in which the karyotype is comprised of both metacentric and acrocentric chromosomes. These results are similar to those reported in human lymphocytes, in which the karyotype contains many metacentric chromosomes. On the contrary, in mouse, which is characterized by acrocentric chromosomes only, the frequencies of translocations and dicentrics are induced in nearly equal proportions by X-rays. The ratio of translocations to dicentrics obtained in Chinese hamster cells was approximately 1.4-1.5, which supports the importance of the karyotypic features of a species in the relative induction of translocations to dicentrics. An analysis was also made on the yield of translocations and dicentrics involving individual chromosomes and the results indicate a non-random involvement of these chromosomes in the formation of aberrations.

Mutagenic and clastogenic properties of (3-[3-(6-benzoyloxy-3-cyano-2- pyridyloxycarbonyl) benzoyl]-1-ethoxymethyl-5-fluorouracil) (BOF-A2), a new 5-fluorouracil derivative with anti-tumour activity.

As part of the safety assessment of (3-[3-(6-benzoyloxy-3-cyano-2- pyridyloxycarbonyl)benzoyl]-1-ethoxymethyl-5-fluorouracil) (BOF-A2), a new 5-fluorouracil (5-FU) derivative with anti-tumour activity, its potential genotoxicity was studied in 3 different tests. BOF-A2 was negative in a reverse mutation (Ames) test in strains of S. typhimurium and E. coli. BOF-A2 induced chromosomal aberrations in Chinese hamster cells in vitro especially in the presence of exogenous metabolic activation, and was clastogenic in vivo, inducing micronuclei in mouse bone marrow. The clastogenic activity of BOF-A2 was similar to that of 5-FU.

Radiosensitivity Parameters for Cell Survival in Tradescantia and for Chromosome Aberrations in Chinese Hamster Cells

Abstract Data for the loss of reproductive integrity of Tradescantia stamen hairs irradiated with 250 keV X rays and 0.43 and 5.6 MeV neutrons are fitted with radiosensitivity parameters from track theory, with E0 and m from X ray data while s0 and ? are then found from neutron irradiations. The X ray data display a clear shoulder with 100% survival below 0.18 Gy and a 'linear tail'. Data for abnormal metaphases and chromatid exchanges in Chinese Hamster cells have also been fitted with parameters. Parameters for abnormal metaphases are nearly identical with those obtained years ago for cell killing from data in the same paper, strongly supporting the view that cell killing arises from chromosome aberrations. These dose-response curves are also shouldered with a 'linear tail'.

Radiosensitivity Parameters for Cell Survival in Tradescantia and for Chromosome Aberrations in Chinese Hamster Cells

Radiosensitivity Parameters for Cell Survival in Tradescantia and for Chromosome Aberrations in Chinese Hamster Cells

Effect of surfactants on the induction of chromosomal aberrations in Chinese hamster cells in culture

Effect of surfactants on the induction of chromosomal aberrations in Chinese hamster cells in culture

Chromosome damage induced by decay of 3H and 125I incorporated into DNA of Chinese hamster cells

The present study was undertaken to compare the frequency of chromatid-type aberrations in Chinese hamster cells with previous results on accumulation of unrepaired DNA-strand breaks after incorporation of 3H-TdR or 125IUdR into DNA. A linear-quadratic function was fitted by the weighted-least-square method to the data on yield of chromatid aberrations at different dpm values. Based on a significant linear response at low doses, RBE for 125I in relation to 3H was calculated for (i) chromatid breaks (17 ± 6), (ii) the sum of isochromatid breaks and chromatid exchanges (21 ± 9), and (iii) the total number of chromatid aberrations (18 ± 5). Analogously, the RBE for accumulation of DNA-strand breaks was determined (13 ± 6). Our results are consistent with the assumption that chromosomal aberrations mainly originate from unrepaired DNA-strand breaks.

Berberine: A naturally occurring phototoxic alkaloid

The isoquinoline alkaloid berberine, present in nine different plant families was found to be phototoxic to mosquito larvae. In the presence of near UV the LC50 for acute 24-hr toxicity was 8.8 ppm compared to 250 ppm for dark controls. Mosquito larvae that were treated with 10 ppm berberine plus near UV for 24 hr and then transferred to berberine-free water showed decreased larval survival and resulted in a smaller cumulative number of pupae and adults as compared to controls, during a subsequent 4-week development period. Berberine was found to be a singlet O2 generator in experiments with the chemical trap 2,5-dimethyl furan. A slight increase in chromosome aberrations in Chinese hamster cells was also observed with berberine plus near UV treatment. The significance of the phototoxicity of berberine is discussed in relation to plant-insect relations.

O6-methylguanine, but not N7-methylguanine or N3-methyladenine, induces gene mutations, sister-chromatid exchanges and chromosomal aberrations in Chinese hamster cells

Induction of mutations to 6-thioguanine resistance, sister-chromatid exchanges (SCEs) and chromosomal aberrations were studied in V79 cells grown for 24 h in medium containing either O 6-MeG, N7-MeG, N3-MeA, guanine or adenine. N7-MeG and N3-MeA, at least in the concentration range tested, did not significantly increase the frequency of mutations, SCEs or aberrations. Exposure of cells to O 6-MeG within the concentration range of 1–12 μg/ml reduced cell survival and induced mutations and SCEs. The mutation frequency increased exponentially with dose, whereas the yield of SCEs increased linearly with dose. O 6-MeG also induced chromosomal aberrations, however relatively high concentrations and long periods between treatment and fixation were necessary to obtain a reasonable yield. With O 6-MeG concentrations up to 40 μg/ml, not more than 25% of the cells showed aberrations, but chromosomes were frequently uncoiled and showed a large number of gaps. Guanine and adenine induced neither mutations nor SCEs. Only adenine proved to be slightly clastogenic. The results indicate that O 6-MeG may be incorporated into DNA and give rise to promutagenic and SCE-inducing lesions. Differences of dose-response relationship, however, indicate that mutations and SCEs are not directly related and that different factors are involved in mutation induction and SCE formation after exposure to O 6-MeG. Furthermore, the results suggest that the probability that O 6-MeG will produce chromosomal aberrations is low as compared with the induction of mutations and SCEs.

Mutagenicity tests and in vitro transformation assays on triethanolamine

Triethanolamine has been widely used as a neutralizer in cosmetics and toilet preparations. A significant increase in the incidence of malignant tumors has been reported in female mice fed on diets containing triethanolamine throughout life. The possible mutagenicity and cell-transforming activity of triethanolamine were examined by measuring the reactivity of triethanolamine with DNA by rec assay, its mutagenicity in S. typhimurium and E. coli test systems, its ability to produce chromosomal aberrations in Chinese hamster cells and its ability to induce transformation of hamster embryo cells. The four test systems showed no evidence of induction of DNA damage, gene mutation, chromosomal aberration or cell transformation in prokaryotic or eukaryotic cells treated with triethanolamine. Neither diethanolamine nor monoethanolamine induced transformation of hamster embryo cells. These results suggest that triethanolamine may not produce so-called genotoxic effects by reaction with DNA, and consequent induction of changes in DNA structure and function. The increased incidence of tumors induced by triethanolamine may be a secondary or indirect result of some specific cytotoxic effect.

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.

UNUSUALLY HIGH INCIDENCE OF SPONTANEOUS CHROMOSOMAL ABERRATIONS IN MOUSE PRIMARY CELL CULTURE

Fibroblast cultures established from mouse embryos showed an abnormally high incidence of spontaneous chromosomal aberrations at early passages. The aberration frequency reached a peak (39.5%) at the 4th passage (13 days after initiation of the cultures), and then declined gradually. Culture media collected from the mouse cultures were found to be capable of inducing chromosomal aberrations in Chinese hamster cells. This indicates that some chromosome-damaging substances had evolved in the mouse primary cultures and were secreted into the culture medium. These substances seemed to affect cells very rapidly, since the production of chromosomal aberrations was detected as early as 2h after Chinese hamster cells were exposed to the conditioned medium derived from the mouse cultures. The substances appeared to be heat-labile, as the mouse conditioned medium lost its chromosome-damaging effect when it was prewarmed at 37°C for 24h. The nature of these toxic substances is, however, yet unknown. Preliminary studies on the primary cultures derived from other mammals imply that the phenomenon reported here is specific to certain groups of mammals except primates.

The enhancement by caffeine of alkylation-induced cell death, mutations and chromosomal aberrations in Chinese hamster cells, as a result of inhibition of post-replication DNA repair

Summary It can be convincingly argued that alkylation of DNA is a causal event in the death of alkylated mammalian cells. However, there are numerous chemical, biochemical and biological observations which indicate that mammalian cells can recover from the otherwise lethal effects of DNA alkylations which therefore implies the existence of a mechanism for repairing alkylation lesions in mammalian cell DNA. Various indications of “excision” or “cut and patch” repair can be detected in mammalian cells following alkylation by both mono- and difunctional alkylating agents. However, manifestations of excision repair do not correlate with the sensitivities of different cell types to various chemical agents, which suggests that an alternative DNA repair mechanism is also present in mammalian cells. Evidence has been adduced that this could be related to that proposed for the repair of UV-irradiation damage to DNA, in which lesions are by-passed during DNA replication. Caffeine has been found to potentiate the lethal action of alkylating agents and it appears that this results from inhibition of this proposed alternative form of DNA repair. MNU has been found to increase the yield of mutations to 8-azaguanine resistance in Chinese hamster cells and the relationships between the increase in induced mutation frequency and the extent of methylation of DNA and the effect of MNU, on cellsurvival, have been determined. Mutations were only observed with concentrations of MNU which produced some cell killing. Caffeine increased the alkylation-induced mutation frequency in a manner which did not support the concept that caffeine inhibits an error-prone repair mechanism. The number of MNU-induced chromosomal aberrations in Chinese hamster cells has been found to be dramatically increased when alkylated cells were grown subsequently in medium containing a non-toxic concentration of caffeine, which on its own failed to produce any chromosomal damage. It is proposed therefore that there are common steps in the repair of alkylation damage to cellular DNA which is responsible for the lethal, mutagenic and chromosomal effects of alkylating agents in mammalian cells. Moreover it seems likely that the common mechanism involves the repair of post-replication lesions in DNA.

Enhancement by caffeine of N-methyl- N-nitrosourea-induced mutations and chromosome aberrations in chinese hamster cells

N-Methyl- N-nitrosourea (MNU) increased the induction of mutations to 8-azaguanine resistance in Chinese hamster cells in a dose-dependent manner. Mutations were only observed with toxic concentrations of MNU. Since a plot of the fraction of cells surviving alkylation against the extent of methylation of DNA exhibited a shoulder it followed that there was a threshold level of DNA reaction which did not lead to mutations possibly due to efficient repair of DNA damage. Post-alkylation incubation in medium containing caffeine decreased cell survival while at the same time it increased the induced mutation frequency. Mutation frequency was increased whether caffeine was present for 48 h or for a further 12 days in the presence of the selective agent 8-azaguanine. MNU caused chromatid aberrations in Chinese hamster cells and these reached a value of 15% of the treated cells by 48 h after methylation. Post-alkylation incubation in caffeine increased the percentage of cells showing chromosomal damage to a maximum of 86% of treated cells by 40 h after alkylation. A large proportion of cells exhibited completely fragmented or shattered chromosomes. The proportion of cells showing the presence of micronuclei also dramatically increased following incubation of methylated cells in caffeine. These results are discussed in terms of the possibility that damage to DNA is responsible for the lethal, mutagenic and cytological effects of MNU in Chinese hamster cells, and that there is a caffeine sensitive step(s) in the repair of the DNA damage which is responsible for these effects.

The effect of caffeine on alkylation-induced cell death, mutations and chromosomal aberrations in Chinese hamster cells : Roberts, J. J., Chester Beatty Research Institute, Institute of Cancer Research, Pollards Wood Research Station, Chalfont St. Giles, Buckinghamshire (Great Britain)

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases in humans characterized by the loss of photoreceptor cells leading to reduction of the peripheral visual field (known as tunnel vision) and eventually to blindness. N-Methyl-N-nitrosourea (MNU) is an alkylating agent that exhibits its toxicity by transferring its methyl group to nucleobases in nucleic acids. A single systemic administration of MNU causes retinal degeneration in various animal species. The retinal degeneration is highly reproducible, and the photoreceptor cell loss occurs within a week when a suitable dose of MNU is administered. Photoreceptor cell loss occurs via apoptosis, which resembles human RP. Decreased levels of basal autophagy concomitantly occur during the course of apoptosis progression. The time-course progression of the disease, the molecular mechanisms of the disease, and the therapeutic trials against MNU-induced photoreceptor cell apoptosis are described.

Differential response of constitutive and facultative heterochromatin in the manifestation of mitomycin induced chromosome aberrations in Chinese hamster cells in vitro.

The distribution of chromatid aberrations induced by mitomycin C among the individual chromosomes of female and male Chinese hamster cells in vitro was studied. The aberrations were found to be non-randomly distributed. Among the autosomes, the chromosomes possessing constitutive heterochromatin were more often involved in aberrations as well as in homologous exchanges. The inactivated X chromosomes in the female cells offer a situation where the short arm is facultatively heterochromatic and the long arm constitutively heterochromatic, thus enabling an analysis of their response for aberration formation. The short arm was seldom found to be involved in the aberration. The long arm of the inactivated X was more often affected (5 to 10 times) than the long arm of the functional X though both are constitutively heterochromatic. The possible role of (a) structure of heterochromatin, (b) the chromocenter formation and their association, (c) allocycly, and (d) the qualitative differences in the DNA of different types of heterochromatin are discussed in relation to the formation of chromatid aberrations.