The rate of sister chromatid exchange in normal human bone marrow cells

Summary A ring chromosome 22 is described in a 6-year-old mentally retarded boy, who presented a dysmorphic syndrome. The ring chromosome 22 was inherited from the mother, in whom a 46,XX/46,XX,r(22)/45,XY,-15,-22,+t(15;22)(p11;q11) mosaic karyotype was found, indicating a high degree of instability of the chromosome(s) 22 in this woman.     

Aging and sister chromatid exchange : I. The effect of aging on mitomycin-C induced sister chromatid exchange frequencies in mouse and rat bone marrow cells in vivo

Utilizing the differential staining of chromatids containing BUdR, it was demonstrated that frequencies of mitomycin-C induced sister chromatid exchanges decline with age. The concomitant increase in chromosomal aberrations suggest an altered response to DNA damage with aging.     

The frequency of sister chromatid exchanges in cultured cells of mouse blood, bone marrow and spleen

Analysis of factors leading to the increase of SCE in vitro is presented. Frequency of SCE is the same in the blood, spleen, marrow cell culture and does not influence upon the time of culture and BDU or BDC concentration. The authors consider that procedure preparation of the culture leads to an increase of SCE in vitro as compared to in vivo.     

Aging and sister chromatid exchange. IV. Reduced frequencies of mutagen-induced sister chromatid exchanges in vivo in mouse bone marrow cells with aging.

Induction of sister chromatid exchanges (SCE's) was examined in bone marrow cells of young and old C57BL/6J mice exposed to three different DNA-damaging agents (cyclophosphamide, mitomycin C, and doxorubicin). At low concentrations of all three mutagens, the levels of induced SCE's were similar in young and old cell populations. However, at higher mutagen concentrations, SCE induction was significantly reduced in old cell populations. Studies of mice aged 5 to 32 months revealed that induced SCE frequencies remain stable during early adulthood (5 to 12 months) and then begin to decline as a function of age. These results indicate that with aging there exists a gradual alteration of cellular response to DNA damage.     

Effect of pretreatment with cysteamine on gamma-radiation-induced sister chromatid exchanges in mouse bone marrow cells in vivo

The effect of pretreatment with cysteamine on gamma-radiation-induced sister chromatid exchanges (SCEs) and on the mitotic index and average generation time was determined. Groups of mice were treated in one of the following regimens: (1) irradiated, (2) treated with cysteamine and irradiated, (3) treated with cysteamine only, or (4) left untreated. Intraperitoneal administration of cysteamine preceding gamma-radiation exposure protected against SCE induction. However, radioprotection was not reflected by change in the mitotic index or in the average generation time. The results suggest that, under the experimental conditions of this study, the SCEs are caused by free radicals produced by gamma radiation, but not the additional damage indices measured.     

Increased sister chromatid exchange in bone marrow and blood cells from Bloom's syndrome.

Bone-marrow cells from a patient with Bloom's syndrome cultured for 48 h in the presence of BudR exhibited a striking increase in the number of sister chromatid exchanges (SCEs) in comparison to that in the marrow cells of a patient with treated polycythemia vera (PV). Thus, it appears that an increased incidence of SCE in Bloom's syndrome occurs in various differentiated types of cells, not just blood lymphocytes, and constitutes the syndrome's most characteristic cytogenetic feature. In contrast, the incidence of SCE was not increased in marrow cells and lymphocytes of the particular PV patient studied here, whose cells did exhibit increased numbers of chromatid and chromosome gaps and breaks, presumably as result of the patient's earlier treatment. An increased frequency of SCE was demonstrated in Bloom's syndrome lymphocytes using both a technique based on BudR incorporation and one based on labeling with tritated deoxycytidine. This observation constitutes evidence against the increase of SCE being due to an unusual reaction to BudR. By conventional cytogenetic techniques, chromosome instability, including chromatid and chromosome breaks, but no homologous chromatid interchanges were also recognized in Bloom's syndrome bone-marrow cells incubated in vitro (without BudR) for either 1.k or 16 h. This observation points to the existence of chromosome instability in vivo.     

In vivo sister chromatid exchange in cells of various organs of the mouse

In vivo sister chromatid exchange (SCE) in mouse cells derived from various organs was studied by infusing BrdU from the tail vein. It was found that at BrdU concentrations ranging from 2.2–13.5 g/g/h, the SCE frequency in bone marrow cells seemed to stay at a constant level (1.5–2/cell/two cell cycles) whereas it started to rise as the BrdU dose exceeded this dose range. When BrdU within this dose range was infused continuously from the tail vein for appropriate hours to label chromosomes in various organs, the average SCE frequencies per cell were found to be 1.64 in bone marrow cells, 1.82 in spermatogonia, 1.99 in splenic cells, 2.89 in intestinal cells and 3.69 in cells from adjuvant stimulated lymph nodes. It is suggested that the spontaneous level of the in vivo SCE frequency might be about 1.5–2/cell/two cell cycles in the mouse. In cells derived from intestine and adjuvant stimulated lymph node, some unknown factors might work as a inducer of SCEs resulting in a significant increase in the SCE frequency in these organs.     

Automatic measurement of sister chromatid exchange frequency.

An automatic system for detecting and counting sister chromatid exchanges in human chromosomes has been developed. Metaphase chromosomes from lymphocytes which had incorporated 5-bromodeoxyuridine for two replication cycles were treated with the dye 33258 Hoechst and photodegraded so that the sister chromatids exhibited differential Giemsa staining. A computer-controlled television-microscope system was used to acquire digitized metaphase spread images by direct scanning of microscope slides. Individual objects in the images were identified by a thresholding procedure. The probability that each object was a single, separate chromosome was estimated from size and shape measurements. An analysis of the spatial relationships of the dark-chromatid regions of each object yielded a set of possible exchange locations and estimated probabilities that such locations corresponded to sister chromatid exchanges. A normalized estimate of the sister chromatid exchange frequency was obtained by summing the joint probabilities that a location contained an exchange within a single, separate chromosome over the set of chromosomes from one or more cells and dividing by the expected value of the total chromosome area analyzed. Comparison with manual scoring of exchanges showed satisfactory agreement up to levels of approximately 30 sister chromatid exchanges/cell, or slightly more than twice control levels. The processing time for this automated sister chromatid exchange detection system was comparable to that of manual scoring.     

Effect of 5-bromodeoxyuridine concentration on sister chromatid exchange frequency in consecutive replication cycles

A yield of single and twin sister chromatid exchanges (SCE) in Chinese hamster cells incubated at different concentrations of 5'-bromodeoxyuridine (BrdUrd) has been studied. The ratio of SCEs formed in the second and in the first cycle has been discovered to be dependent on the dose of BrdUrd; it is 1.5:1 for the high concentration of BrdUrd and 1:1 for the lowest one. The authors arrived at a conclusion that the observed level of SCEs--0.1 per chromosome per cycle for the lowest concentration is spontaneous.     

Effect of cyclosporin A and tacrolimus on sister chromatid exchange frequency in renal transplant patients

Long-term use of Cyclosporin A (CsA) and Tacrolimus is known to yield serious untoward side effects including nephrotoxicity, neurotoxicity, and malignant tumor formation. Sister chromatid exchange (SCE) is used to assess the genotoxic potential of various agents. A total of 37 postrenal transplant patients receiving either CsA (n = 20) or Tacrolimus (n = 17) were included in this study. The genotoxic effects of CsA and Tacrolimus were assessed by determination of SCE frequency. In patients receiving CsA, SCE frequency was increased significantly compared to that in the control group (p = 0.001), whereas Tacrolimus did not yield such a significant change (p = 0.801). SCE frequency was not correlated with drug dosage (p > 0.05). Our results indicate that the use of CsA, but not Tacrolimus 506, is associated with an increased genotoxic effect in postrenal transplant patients.     

A comparison of sister chromatid exchange frequencies in peripheral lymphocytes and bone marrow cells of Fischer 344 and Sprague-Dawley rats

We have investigated spontaneous sister chromatid exchange (SCE) frequencies in peripheral lymphocytes and bone marrow cells explanted from two strains of the laboratory rat, Fischer 344 and Sprague-Dawley. A small, but significant difference was noted for both cell types, with the Fischer 344 rat being consistently higher. Other cell parameters, such as the mitotic index and the replicative index, were similar in the two strains. SCE levels in cultured peripheral lymphocytes after intraperitoneal administration of the alkylating drug cyclophosphamide (10 mg/kg) were similar for the two strains. Fischer 344 rats are known to have approximately a 10-fold higher incidence of spontaneous leukemia than do Sprague-Dawley rats. Since SCE frequency is a sensitive measure of DNA damage, our observations suggest that high leukemia incidence in the Fischer 344 rat may be related to a higher level of spontaneous DNA damage.     

Distribution of the frequency of sister chromatid exchange among Leningrad inhabitants

Peculiarities of frequency variations in sister chromatid exchanges (SCE) were studied in a group of healthy Leningrad citizens who are not engaged in health-risk industries. No relations were found between the SCE frequency and sex, age and smoking habit (10 cigarettes per day as much). The statistical processing of the data obtained was made taking into account the errors in individual measurements of the SCE frequency. Repeated measurements revealed systematic and statistically significant variations in the rate of SCE.     

Effect of high-density extremely low frequency magnetic field on sister chromatid exchanges in mouse m5S cells

The induction of sister chromatid exchanges (SCEs) was evaluated in the cultured mouse m5S cells after exposure to extremely low frequency magnetic field (ELFMF; 5, 50 and 400 mT). Exposure to 5 mT and 50 mT ELFMF led to a very small increase in the frequency of SCEs, but no significant difference was observed between exposed and unexposed control cells. The cells exposed to 400 mT ELFMF exhibited a significant elevation of the SCE frequencies. There was no significant difference between data from treatments with mitomycin-C (MMC) alone and from combined treatments of MMC plus ELFMF (400 mT) at any MMC concentrations from 4 to 40 nM. These results suggest that exposure to highest-density ELFMF of 400 mT may induce DNA damage, resulting in an elevation of the SCE frequencies. We suppose that there may be a threshold for the elevation of the SCE frequencies, that is at least over the magnetic density of 50 mT.     

Effect of high-density extremely low frequency magnetic field on sister chromatid exchanges in mouse m5S cells

The induction of sister chromatid exchanges (SCEs) was evaluated in the cultured mouse m5S cells after exposure to extremely low frequency magnetic field (ELFMF; 5, 50 and 400 mT). Exposure to 5 mT and 50 mT ELFMF led to a very small increase in the frequency of SCEs, but no significant difference was observed between exposed and unexposed control cells. The cells exposed to 400 mT ELFMF exhibited a significant elevation of the SCE frequencies. There was no significant difference between data from treatments with mitomycin-C (MMC) alone and from combined treatments of MMC plus ELFMF (400 mT) at any MMC concentrations from 4 to 40 nM. These results suggest that exposure to highest-density ELFMF of 400 mT may induce DNA damage, resulting in an elevation of the SCE frequencies. We suppose that there may be a threshold for the elevation of the SCE frequencies, that is at least over the magnetic density of 50 mT.     

Comparisons of in vivo BrdU labeling methods and spontaneous sister chromatid exchange frequencies in regenerating murine liver and bone marrow cells

BrdU and BrdC have been employed as DNA labeling agents for differentiation of sister chromatids and for extension of sister chromatid exchange (SCE) methods to regenerating murine liver cells in vivo. Comparisons were made between bone marrow and liver cells isolated simultaneously from mice following DNA labeling with either BrdC or BrdU. Although the total mitotic yield of bone marrow cells was considerably greater than in liver, a higher percentage of second division metaphases was observed in liver cell preparations. The percentages of second division c-metaphase cells observed were 31.5% in bone marrow and 73% in liver cell preparations. Utilizing either BrdU or BrdC, no significant difference in percentage of second division metaphases was discerned. The number of spontaneous SCEs per cell was distributed according to the Poisson probability function. No significant differences in mean numbers of SCEs per cell were found in comparisons of bone marrow (1.40) and liver cells (1.65) or of cells which had incorporated BrdU or BrdC.     

A family study of spontaneous sister chromatid exchange frequency.

The frequency of spontaneous sister chromatid exchanges (SCEs) was determined in PHA-stimulated peripheral lymphocytes of 52 individuals, comprising 12 complete 2-generation pedigrees. Neither intraindividual variation between replicate cultures established from the same blood sample nor variation among samples from the same individual initiated at different times was significant. However, familial factors affecting mean SCE frequencies were indicated by detection of significant differences among, but not within, families. Although sample sizes were small, a genetic contribution to the SCE frequency was suggested by the observed pattern of familial correlations.     

Fenvalerate-induced chromosome aberrations and sister chromatid exchanges in the bone marrow cells of mice in vivo

To investigate whether subjects with low-acid states are exposed to increased genetic risk with respect to controls, we evaluated mutagenicity and presence of clastogenic factors (CF) in the gastric juice of chronic atrophic gastritis and omeprazole-treated patients. Mutagenic gastric juice was found in 8/15 (53%) chronic atrophic gastritis patients, 8/11 (73%) omeprazole-treated patients, and 2/13 (15%) healthy control subjects. The mean mutagenicity ratio of omeprazole-treated patients (1.52+/-0.48/0.1 ml gastric juice) was significantly higher than those of either controls (1.07+/-0.15; P<0.01) or chronic atrophic gastritis patients (1.16+/-0.21; P<0.05). Only chronic atrophic gastritis patients showed an increased clastogenic index with respect to healthy controls (2.67+/-2.13 versus 0.38+/-0.51; P<0.001). These findings expand our knowledge of gastric disease risk factors, and indicate that there may well be a risk of mucosal DNA damage arising from the presence of mutagenic and CF in the gastric juice.     

Fenvalerate-induced chromosome aberrations and sister chromatid exchanges in the bone marrow cells of mice in vivo

Fenvalerate, a synthetic pyrethroid insecticide, is commonly used in agriculture and other domestic applications due to its high insecticidal activity and low mammalian-, avian- and phyto-toxicities. However, the genotoxic effect of fenvalerate is highly equivocal. In the present study the genotoxic effects of fenvalerate was evaluated using structural chromosome aberration (CA) and sister chromatid exchange (SCE) assays in mice. Out of the three doses (5, 10 and 20 mg/kg) tested, statistically significant increase in CA was found following intra peritoneal (i.p.) treatment of 20 mg/kg of fenvalerate for 24 h (P<0.01) and 48 h (P<0.05) only. Neither the acute doses of 5 and 10 mg/kg, nor the sub-acute dose (5×4 mg/kg) of fenvalerate could induce any significant effect. All the three acute doses induced significant increase in the frequency of SCEs (P<0.01) in the bone marrow cells, which showed a significant dose-response correlation (r=0.9541, P<0.05). With certain reservations to possible impurities, from the present findings technical grade fenvalerate may be considered as a weak clastogen and a potent inducer of SCEs in mice.     

Gene mutation and sister chromatid exchange in Chinese hamster cells

The mutation in hypoxanthine phosphoribosyl transferase gene and the induction of sister chromatid exchange (SCE) were comparatively studied treating Chinese hamster ovary cells with the mutagens ethylmethanesulphonate. N-methyl-N'-nitro-N-nitrosoguanidine, Mitomycin C and X-ray. All the agents exerted strong mutagenic effects and showed a dose-dependent relationship for the induction of SCEs.