Sister chromatid exchange in patients with viral disease

Sister chromatid exchange (SCE) frequencies were studied in differentially stained chromosomes from lymphocytes of 17 patients with viral disease. The mean SCE score for the patients was 8.7 +/- 2.9 standard deviations. SCE scores were significantly elevated in the patients compared with the controls (p less than 0.01); however, variability in SCE means was observed in the patients. SCE elevations were also present in long term cultured Epstein Barr virus positive human B lymphocytes.     

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.     

Analysis of sister chromatid exchanges in lymphocytes cultured from 71 healthy men

Sister chromatid exchanges (SCE) were analyzed in peripheral blood lymphocytes from a select group of 71 healthy men, 56 nonsmokers and 15 cigarette smokers. In addition to estimating baseline SCE, data were examined to seek relationships of SCE frequencies to age and smoking. The baseline value of 7.53 SCE per cell from the 56 nonsmokers was within the range (5.60 to 9.10 SCE/cell) reported for other human populations. No relationship was found between the mean SCE frequency per cell and age. However, a significant increase in the SCE mean value was observed in smokers as compared to nonsmokers. The results of this study are compared with those of other reports on SCE effects of age and smoking.Abbreviations BUdR 5-bromo,2-deoxyuridine - SCE sister chromatid exchange     

Induction of sister chromatid exchanges (SCE) in G0 lymphocytes by plutonium-238 alpha-particles

Irradiation of human G0 lymphocytes with plutonium-238 alpha-particles and X-rays was performed to investigate the production of sister chromatid exchanges (SCE). Alpha-particles produce a significant increase in SCE and this elevation is more significant when separated lymphocytes are irradiated. X-ray irradiation did not induce any significant increase in SCE. Therefore the relative biological effectiveness (RBE) for the induction of SCE by alpha-particles in this system is undefined and effectively infinite.     

Increased sister chromatid exchange in human lymphocyte cultures infected with mycoplasma

The effects of fermenting, poorly arginine-utilizing Mycoplasma fermentans and arginine-utilizing Mycoplasma salivarium on the frequency of sister chromatid exchange (SCE) in cultured human lymphocytes were examined. M. fermentans caused no apparent mitosis inhibition of lymphocytes and the increase in SCE frequency was dependent on the inoculum size of the mycoplasma. An evident increase in SCE frequency was observed in lymphocytes infected with smaller inoculum sizes of M. salivarium whereas there was mitosis inhibition of lymphocytes infected with larger inoculum sizes of the mycoplasma. In lymphocyte cultures infected with M. salivarium, the addition of arginine to the culture medium reduced mitosis inhibition but did not diminish the increase in SCE frequency, indicating that arginine depletion was not involved in causing the induction of SCEs in mycoplasma-infected lymphocytes. With regard to the genetic effectiveness of SCE, these results suggested that mycoplasmas are capable of inducing cytogenetic changes in infected host cells.     

Sister chromatid exchange frequencies in Progeria and Werner syndrome patients.

An analysis of the baseline and mitomycin-C-induced sister chromatid exchange (SCE) frequencies in peripheral lymphocytes derived from three patients with progeria and three Werner syndrome patients is presented. SCE frequencies did not differ significantly between the two groups of patients and their normal controls.     

Sister chromatid exchange in highly purified human B and T lymphocytes

Summary Sister chromatid exchange (SCE) rates were determined in human peripheral blood B and T lymphocyte populations highly purified by immunologic methods. The purified populations were supplemented with -irradiated unseparated autologous mononuclear cells to restore helper-functions and stimulated with pokeweed mitogen (PWM) and phytohemagglutinin (PHA), respectively. Measured at the different peaks of proliferation after identical bromodeoxyuridine (BrdU) incubation times, T lymphocytes showed significantly higher SCE frequencies than B lymphocytes. In both populations, different proliferation kinetics and a different minimal BrdU concentration for sister chromatid differentiation (SCD) were observed.     

A decreased frequency of sister chromatid exchanges in pregnant women

Sister chromatid exchanges (SCE) and cellular proliferation were studied in lymphocytes from 16 pregnant and 18 non-pregnant women. A lowered SCE frequency was found in lymphocytes obtained from pregnant women (9.41 +/- 0.39 vs. 11.07 +/- 0.42 SCE/metaphase in non-pregnant women). Lower proliferation rates were also common for cultures of pregnant women. Thus, physiological changes occurred in the organism of pregnant women may influence various cytogenetic indices registered in human peripheral blood cultures.     

Cytogenetic investigations on Werner's syndrome, Acrogeria and Keratosis Palmo-Plantaris

The frequencies of sister chromatid exchanges and of aspecific chromosome aberrations have been investigated in the lymphocytes from a Werner patient, from an Acrogeria patient and from three members of a family with Keratosis Palmo-Plantaris. These investigations point out that: 1) the SCE frequency is significatively enhanced in Werner as in KPP lymphocytes, 2) the frequency of aspecific chromosome aberrations is increased only in Werner lymphocytes, without evidence of variegated translocation mosaicism. The findings confirm that SCE and chromosome aberrations do not necessarily result from the same genetic damage and that SCE may represent the cytological evidence of unexcised non fatal DNA lesions, which occasionally may be responsible for carcinogenesis.     

Effect of deoxycytidine on the frequency of sister chromatid exchanges in human lymphocytes detected by using 5-bromdeoxyuridine

The frequency of sister chromatid exchanges (SCE) was studied in cultivated blood lymphocytes of three normal individuals under elimination of DNA synthesis inhibiting action of 5-bromodeoxyuridine (BrdUrd 0.05 mM) with deoxycytidine (Cdr 0.1 and 0.01 mM). The frequency of SCE was significantly increased in the presence of 0.1 mM Cdr. In parallel with SCE frequency, Cdr elevated the percentage of metaphases of the second division. The increase of SCE in the presence of Cdr may be connected with normalization of the DNA replication under its action.     

Increased frequency of sister-chromatid exchange and chromatid breaks in lymphocytes after treatment of human volunteers with therapeutic doses of paracetamol

Paracetamol was given to 10 healthy human volunteers in 3 doses of 1 g each during a period of 8 h. Blood samples for lymphocyte cultures were taken before and 24 h after paracetamol administration. A small but significant increase was found in the frequency of sister-chromatid exchanges (SCE) after intake of paracetamol (0.187 +/- 0.030 per chromosome before and 0.208 +/- 0.024 per chromosome after). After exposure the mean frequency of chromatid breaks per 100 cells was significantly increased (2.16 +/- 1.33 versus 0.33 +/- 0.50 before exposure). Exposure of human lymphocytes in vitro showed that concentrations of paracetamol above 0.1 mM induced inhibition of replicative DNA synthesis. Increased SCE was found in lymphocytes exposed to 1-10 mM paracetamol for 2 h. Furthermore, 0.75-1.5 mM paracetamol exposure for 24 h increased the frequency of chromatid and chromosome breaks in the lymphocytes. The paracetamol-induced SCE and chromosome aberrations may be secondary effects of paracetamol-induced inhibition of DNA synthesis or due to covalent binding of paracetamol metabolite(s) to DNA.     

Differential fluorescence of sister chromatids with 4'-6-diamidino-2-phenylindole.

Differential fluorescence of sister chromatids and sister chromatid exchanges (SCE) in chromosomes from human lymphocytes grown two replication cycles in medium containing 5-bromodeoxyuridine can be detected by fluorescence microscopy after staining with 4'-6-diamidino-2-phenylindole (DAPI). The DAPI fluorescence appears to be more stable than that of the dye 33258 Hoechst and may provide a more sensitive method for the detection of SCE.     

Sister chromatid exchanges in cultured peripheral lymphocytes from twins

Summary Sister chromatid exchange points (SCE points) on individual chromosomes were studied in cultured lymphocytes from 11 monozygotic (MZ) and nine dizygotic (DZ) same-sexed pairs by means of sequential Q-banding and BUdR-Giemsa techniques. No statistically significant variation between unrelated individuals with respect to SCE points on specific chromosomes was found. Intrapair differences in the number of SCE points on specific chromosomes were not significantly smaller between MZ twin partners as compared with DZ partners. The results suggest that genetic factors do not play any major role in the frequency and distribution of SCE in normal subjects.     

Sister chromatid exchange in lymphocytes in myelodysplastic syndrome

Sister chromatid exchange (SCE), percentage of first, second, third mitoses, blastic transformation index and mitotic index in patients with myelodysplastic syndrome (MDS) (3 with refractory anaemia, 2 with refractory anaemia with sideroblasts, 1 with refractory anaemia with excess of blasts, 4 with refractory anaemia with excess of blasts in transformation) and in 15 healthy volunteers were estimated. Three types of lymphocytes cultures were set up: first with phytohemaglutinin (PHA), second with PHA and bromodeoxyuridine (BRdU), third with BRdU. In healthy persons the SCE frequency was negatively correlated to proliferating rate index, but in MDS such correlation was not found. The lymphocytes cell cycle duration based on percentage of mitoses was longer in MDS patients than in controls. The results of our studies show the disturbances of lymphocytes during cell cycle division resulting in higher SCE frequency and lower proliferating rate compared to controls.     

Genotoxic potential of cyclosporin A in patients with renal transplantation

We analyzed the induction of sister chromatid exchange (SCE) by cyclosporin A (CsA) as a marker of genotoxic potential. In 30 patients undergoing renal transplantation, SCE induction was tested before the introduction of CsA and 3 months later. We found that SCE frequency increased significantly at the end of 3 months. To our knowledge, this is the first study demonstrating in vivo induction of SCE by CsA in humans. We conclude that CsA has a genotoxic potential on human lymphocytes.     

Genetic aspects of nonchromaffin paraganglioma

Summary Sister chromatid exchanges (SCE) and structural chromosome aberrations were analyzed in peripheral blood lymphocytes of 100 individuals, and correlated to age and sex. No correlation was found between the frequency of SCE and age, but older individuals had significantly more structural aberrations than younger. Females had significantly more SCE as well as structural chromosome aberrations than males. The positive correlations of SCE and structural aberrations to age and sex were also significant when these factors, as well as smoking habits, were taken into consideration in an analysis of covariance.     

The correlation between the frequency of sister chromatid exchanges and the kinetics of human lymphocyte proliferation: the dependence on the sex of the donor

Sister chromatid exchanges (SCE) and average generation time (AGT) were studied in lymphocytes from 35 donors (23 females and 12 males). A higher SCE frequency was found in lymphocytes from females than from males. Smoking increased SCE frequency in lymphocytes of males, but not of females. No differences in AGTs between males and females were found. Partial correlation coefficients between SCE frequency, AGT values, donor's age and smoking were determined. A statistically significant correlation (r = 0.650, P less than 0.01) between SCE frequency and AGT was found in lymphocytes obtained from females. In lymphocytes from males statistically significant partial correlation coefficients were detected between SCE frequency and AGT (r = -0.696, P less than 0.05), SCE frequency and donor's age (r = 0.770, P less than 0.01), SCE frequency and smoking intensity (r = 0.697, P less than 0.01), AGT value and donor's age (r = 0.882, P less than 0.01), and AGT value and smoking (r = 0.634, P less than 0.05). Thus, considerable differences in number of indices between males and females exist. The present observations together with other studies (D'Souza et al., 1988) suggest that considerations for population monitoring using cytogenetic techniques (ICPEMC Publication No 14) may be supplemented with the recommendation to use (whenever it possible) only males as donors in population studies.     

Genotoxicity testing of fluconazole in vivo and in vitro

The genotoxic effects of the antifungal drug fluconazole (trade name triflucan) were assessed in the chromosome aberration (CA) test in mouse bone-marrow cells in vivo and in the chromosome aberration, sister chromatid exchange (SCE) and micronucleus (MN) tests in human lymphocytes. Fluconazole was used at concentrations of 12.5, 25.0 and 50.0 mg/kg for the in vivo assay and 12.5, 25.0 and 50.0 microg/ml were used for the in vitro assay. In both test systems, a negative and a positive control (MMC) were also included. Six types of structural aberration were observed: chromatid and chromosome breaks, sister chromatid union, chromatid exchange, fragments and dicentric chromosomes. Polyploidy was observed in both the in vivo and in vitro systems. In the in vivo test, fluconazole did not significantly increase the frequency of CA. In the in vitro assays, CA, SCE and MN frequencies were significantly increased in a dose-dependent manner compared with the negative control. The mitotic, replication and cytokinesis-block proliferation indices (CBPI) were not affected by treatments with fluconazole. According to these results, fluconazole is clastogenic and aneugenic in human lymphocytes, but these effects could not be observed in mice. Further studies should be conducted in other test systems to evaluate the full genotoxic potential of fluconazole.     

Influence of diethylenetriamine (DETA) and sodium nitroprusside (NaNP) on sister chromatid exchange frequency and cell kinetics in cultured human lymphocytes

Diethylenetriamine (DETA) and Sodium Nitroprusside (NaNP), the exogenous NO-generating compounds, were tested for their genotoxicity in human lymphocytes in vitro using the sister chromatid exchange (SCE) technique. Both compounds were found to be inactive in inducing SCE in concentrations from 0.3 to 30 pM. However both compounds displayed an inhibiting effect on cell kinetics.     

Ratio of the frequency of chromosome aberrations and sister chromatid exchanges to the dose of the mutagenic exposure to cyclophosphamide in vivo and in vitro

Cyclophosphamide (CP) and its metabolites were used to compare the rate of chromosomal aberrations (CA) and sister chromatid exchange (SCE) in the rabbit lymphocytes in vivo and in vitro. The dose-dependent increase of cytogenetic effects rate appeared to be of linear and exponential dependence for SCE and CA, respectively, both in vivo and in vitro. The regression equation coefficients coincided in in vivo and in vitro experiments.