Incidence Of Sister Chromatid Exchanges Research Articles

Assessment of genome stability in various breeds of cattle.

Chromosomal instability is a type of genome instability involving changes in genetic information at the chromosomal level. The basic tests used to identify this form of instability are sister chromatid exchange (SCE) tests and identification of fragile sites (FS). SCE is the process by which sister chromatids become fragmented as a result of DNA strand breakage and reassembly, followed by exchange of these fragments. FS can be observed in the form of breaks, gaps or constrictions on chromosomes, which often result from multiple nucleotide repeats in DNA that are difficult to replicate. The research material was the peripheral blood of ten breeds of cattle raised in Poland, including four native breeds covered by a genetic resources conservation programme, i.e. Polish Red, Polish Red-and-White, White-Backed, and Polish Black-and-White, as well as Polish Holstein-Friesian, Simmental, Montbéliarde, Jersey, Limousine and Danish Red. Two tests were performed on chromosomes obtained from in vitro cultures: SCE and FS. The average frequency of SCE was 5.08 ± 1.31, while the incidence of FS was 3.45 ± 0.94. Differences in the incidence of SCE and FS were observed between breeds. The least damage was observed in the Polish Red and White-Backed breeds, and the most in Polish Holstein-Friesians. The most damage was observed in the interstitial part of the chromosomes. Age was shown to significantly affect the incidence of SCE and FS. Younger cows showed less damage than older ones (SCE: 4.84 ± 1.25; 5.34 ± 1.24; FS: 3.10 ± 0.88, 3.80 ± 0.92).

Spontaneous sister chromatid exchange in mitotic chromosomes of the chinchilla (Chinchilla lanigera)

Kuchta-Gładysz, M., Wójcik, E., Szeleszczuk, O., Niedbała, P. and Tyblewska, K. 2015. Spontaneous sister chromatid exchange in mitotic chromosomes of the chinchilla (Chinchilla lanigera). Can. J. Anim. Sci. 95: 543–550. The sister chromatid exchange (SCE) test is a cytogenetic tool with applications as a short-term screen. It is used to assess the influence of physical and chemical factors with potential mutagenic and genotoxic properties on the animal organism. The test results make it possible to eliminate mutagens, as well as helping to predict possible genetic consequences in animal cells and assess animal resistance. The mitotic chromosomes were obtained from an in vitro culture of peripheral blood lymphocytes with added bromodeoxyuridine (BrdU), at five different concentrations: 0.25, 0.5, 1.0, 2.5, and 5.0 µg mL−1. The chromosomes were stained according to the FPG method. Our analyses revealed the spontaneous SCE level in the chinchilla at the concentration of 0.5 µg mL−1. Higher concentrations of this substance have a genotoxic effect and cause damage to the DNA structure of the chromosomes by inducing additional SCEs in the chromosomes of this species. The mean SCE/cell incidence in the chinchilla population was 4.34±1.28. We investigated the effects of age on the incidence of SCE and found it significantly affected this phenomenon in both sexes.

Identification of chromosome instability in Japanese quail (Coturnix japonica)

1. A study of the incidence of chromosome instability in the Japanese quail as assessed by sister chromatid exchange (SCE) and fragile site identification in chromosomes was conducted in two parent breeds and their F1 and F2 generations.2. The mean incidence of SCEs was 6.02 ± 0.45 and the frequency of fragile sites was 1.17 ± 0.79.3. There were moderately negative correlations of 0.51–0.64 between chromosome instability and fertility in the F1 and 0.10–0.23 in the F2. The hatch of fertilised eggs was negatively correlated with the number of SCE in male (0.31) and female (0.33) F1 and was lower in P (0.18 and 0.19, respectively), whereas the correlations were similar for the number of fragile sites in both generations (0.51–0.62).

Sister chromatid exchange as an index of chromosome instability in chondrodystrophic chickens (Gallus domesticus)

Commercially bred broiler chickens reared in inadequate breeder-created habitat conditions often suffer from a disease that afflicts their lower limbs, chondrodystrophy. The sister chromatid exchange (SCE) test makes it possible to detect chromosome instability that corresponds with elevated vulnerability of the organism to genotoxic factors of a mutagenic and carcinogenic nature. The frequency of SCE in chromosomes of chondrodystrophic and healthy broilers was analyzed. Chromosome preparations were obtained from our in vitro culture of peripheral blood lymphocytes stained using the fluorescence plus Giemsa technique. The SCE/cell mean of the population under analysis was 6.8 ± 1.6. The SCE/cell mean in the chromosomes of the chondrodystrophic chickens was 8.5 ± 1.0. The healthy chickens had an SCE/cell mean of 5.1 ± 1.3. Statistically significant differences were identified between both chicken groups. Moreover, a higher SCE/cell mean was observed in the males: 6.9 ± 1.7 compared with 6.7 ± 1.7 in the females. However, this difference was not statistically significant. Additionally, SCE incidence in the first 3 biggest autosome pairs (1, 2, 3) was analyzed in detail. The number of identified SCE was proportional to chromosome length. The most exchanges were observed in the proximal region of the chromosomes under analysis.

Dysfunctional telomeres in primary cells from Fanconi anemia FANCD2 patients

BackgroundFanconi anemia (FA) is characterized by sensitivity to DNA cross-linking agents, mild cellular, and marked clinical radio sensitivity. In this study we investigated telomeric abnormalities of non-immortalized primary cells (lymphocytes and fibroblasts) derived from FA patients of the FA-D2 complementation group, which provides a more accurate physiological assessment than is possible with transformed cells or animal models.ResultsWe analyzed telomere length, telomere dysfunction-induced foci (TIFs), sister chromatid exchanges (SCE), telomere sister chromatid exchanges (T-SCE), apoptosis and expression of shelterin components TRF1 and TRF2. FANCD2 lymphocytes exhibited multiple types of telomeric abnormalities, including premature telomere shortening, increase in telomeric recombination and aberrant telomeric structures ranging from fragile to long-string extended telomeres. The baseline incidence of SCE in FANCD2 lymphocytes was reduced when compared to control, but in response to diepoxybutane (DEB) the 2-fold higher rate of SCE was observed. In contrast, control lymphocytes showed decreased SCE incidence in response to DEB treatment. FANCD2 fibroblasts revealed a high percentage of TIFs, decreased expression of TRF1 and invariable expression of TRF2. The percentage of TIFs inversely correlated with telomere length, emphasizing that telomere shortening is the major reason for the loss of telomere capping function. Upon irradiation, a significant decrease of TIFs was observed at all recovery times. Surprisingly, a considerable percentage of TIF positive cells disappeared at the same time when incidence of γ-H2AX foci was maximal. Both FANCD2 leucocytes and fibroblasts appeared to die spontaneously at higher rate than control. This trend was more evident upon irradiation; the percentage of leucocytes underwent apoptosis was 2.59- fold higher than that in control, while fibroblasts exhibited a 2- h delay before entering apoptosis.ConclusionThe results of our study showed that primary cells originating from FA-D2 patients display shorten telomeres, elevated incidence of T-SCEs and high frequency of TIFs. Disappearance of TIFs in early response to irradiation represent distinctive feature of FANCD2 cells that should be examined further.

Abstract 3638: DNA strand breaks induced by 2′-C-cyano-2′-deoxy-nucleoside analogs are repaired by homologous recombination

Abstract CNDAC [2′-C-cyano-2′-deoxy-1-β-D-arabino-pentofuranosyl-cytosine], which is undergoing clinical trials, and its congener CNDAG [9-(2-C-cyano-2-deoxy-1-β-D-arabino-pentofuranosyl) guanine] likely share the unique action mechanism of inducing single strand breaks (SSBs) through β-elimination which generates the chain-terminating analog CNddC(G) following incorporation into DNA. We postulate that subsequent processing or DNA replication across the unrepaired nicks would generate double strand breaks (DSBs). Cellular responses to these 2′-C-cyano-2′-deoxy-nucleoside analogs are concentration dependent. Cells were arrested in G2 or S- phase when exposed to high concentrations of CNDAC(G), while at lesser concentrations cells could progress into a second S-phase. This study used cytogenetic approaches to define the mechanisms of DSB formation and damage repair in the above biological context. First, metaphase chromosomal aberrations (including breaks and gaps) were measured in Chinese hamster ovary line AA8 and its mutant UV41, which is sensitized to CNDAC(G) due to lack of XPF, a key endonuclease in the nucleotide excision repair (NER) pathway. The mean values of chromosomal aberrations increased 6(7)-fold and > 6(3)-fold in AA8 and UV41 cells, respectively, after exposure to CNDAC(G) for two population doubling times, compared to those treated for only one population doubling time (n>50). These data clearly demonstrate that SSBs induced by CNDAC(G) in the first S-phase can be converted into one-ended DSBs during the second S-phase when replication forks encountering unrepaired SSBs. Second, the frequencies of sister chromatid exchanges (SCEs) in AA8 cells incubated with CNDAC(G) for two cell cycles (mean 14.2-17.6 per metaphase) were 2-fold of those exposed for one cell cycle (mean 7.4-8.4 per metaphase, n>20, p<0.001), the latter greater than control (mean 6 per metaphase, p<0.05). Since homologous recombination (HR) is considered the mechanism for SCE, these results indicate that CNDAC(G)-caused DNA damage is repaired by HR. Third, spontaneous chromosomal alterations in UV41 cells were 7-fold greater than those in parental AA8 cells, suggesting genetic instability conferred by XPF deficiency. The increase in chromosomal aberrations after CNDAC(G) exposure, regardless of length of time, was greater in UV41 cells compared to the wild-type. This suggests that XPF is likely needed to remove CNddC(G) preceding HR in the first cell cycle. Thus, NER and HR may work in concert to repair CNDAC(G)-induced damage. In addition, UV41 cells presented greater incidence of SCE after treatment with CNDAC for one population doubling time (n=30, p<0.01), suggesting nuclease(s) other than XPF may function in removal of CNddC. Together these results demonstrate that HR is responsible for repair of CNDAC(G)-induced DSBs generated during the second replication across initial SSBs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3638.

Sister chromatid exchanges in human bone marrow cells I. Control subjects and patients with leukaemia

The number and position of sister chromatid exchanges (SCE) in bone marrow cells was determined in 8 haematologically healthy subjects, 4 patients with chronic myeloid leukaemia (CML), 4 patients with acute myeloid leukaemia (AML), 4 patients with refractory idiopathic sideroblastic anaemia (pre-leukaemia), and 1 patient with malignant histiocytosis. The number of SCE in haematologically healthy subjects varied from 3.9 to 6.0 per metaphase and in the leukaemia groups from 3.6 to 7.4 per metaphase, the incidence being lowest in a patient with CML in chronic phase and highest in a patient with CML in blastic crisis. One of the patients with AML, who had as few SCE (4.4) as the controls in the bone marrow cells, had a fourfold SCE score (15.0) in his cultured lymphocytes. Both in controls and in patients with leukaemia the exchanges were, in general, fewer than expected in E, F and G group chromosomes and more frequent than expected in chromosome 2 and the B group chromosomes. Thus, the incidence of SCE in bone marrow cells was lower than in cultured lymphocytes, and in most cases of CML and AML, did not seem to be altered.

Protective effect of curcumin on γ-radiation-induced sister chromatid exchanges in human blood lymphocytes

The present work evaluates the radioprotective effect of curcumin on γ-radiation-induced genetic toxicity. The DNA damage was analysed by the frequencies of Sister Chromatid Exchanges (SCEs). Human lymphocytes were treated in vitro with 5.0 γg/ml of curcumin for 30 min at 37°C then exposed to 1, 2 and 4 Gy γ-radiation. The lymphocytes were cultured in (RPMI) 1640 tissue culture medium and autologous serum (20%). Phytohemagglutinin and 5-bromodeoxyuridine (10 pM) were added upon the initiation of culture and harvesting was done 72 h after culture initiation. The SCEs were counted and compared with the control lymphocytes, which were untreated with curcumin and exposed to the same γ-radiation doses. At 0 and 4 Gy no significant difference in the frequency of SCEs was found between the control lymphocytes and the lymphocytes pretreated with curcumin. Moreover, at 1 and 2 Gy the incidence of SCEs decreased in the pretreated lymphocytes with curcumin but not in the control lymphocytes. From the results obtained, it can be concluded that curcumin could effectively reduce the clastogenic effects of radiation with a dose of 1?2 Gy in human lymphocytes in vitro. However, further studies are needed to clarify the mechanism of action.

Sister chromatid exchange in chromosomes of cattle from three different breeds reared under similar conditions

A homogeneous group (same sex, age and environmental conditions) of 35 Italian cattle of the Podolian, Friesian, and Romagna breeds was investigated concerning the spontaneous incidence of sister chromatid exchange (SCE). The mean values of SCEs/cell were 7.9 +/- 3.4, 7.1 +/- 3.3, and 7.3 +/- 3.2 in the Podolian, the Friesian, and the Romagna breeds, respectively, with significant differences between the Podolian and the Friesian breeds. Simultaneous disclosure of SCEs and fluorescent G-bands in the lighter chromatid made possible the identification of chromosome 1, in addition to the biarmed X and Y chromosomes. The inter-chromosomal SCE-distribution revealed a nonrandom pattern due to significantly increased values of SCEs in chromosomes 1 and X, particularly in the Romagna breed.

Modulation of SCE frequencies in cell lines derived from human B and T lymphocytes.

The frequency of sister chromatid exchanges (SCEs) in correlation to the concentration of bromodeoxy-uridine (BrdUrd) was studied in rosetting and non-rosetting human peripheral lymphocytes, EBV-lymphoid and lymphoma cell lines, T-lymphoid and lymphoma cell lines. An euploid T-cell line and the rosetting cells had a higher mean frequency of SCEs than the euploid B-cell lines and the non-rosetting cells. In the B-cell lineage, but not in the T-cell derived lines, the yield of SCEs was increased by the addition of deoxycytidine. This hints at an epigenetic difference in the DNA precursor metabolism that also might be the underlying reason for the overall level of SCEs in the two cell types. A higher incidence of SCEs is not an inevitable consequence of malignancy and aneuploidy; an increased level seems to be a property only of malignant cells of the B-cell lineage.

Genotoxic effects of environmental estrogen-like compounds in CHO-K1 cells

Some environmental estrogen-like compounds, such as bisphenol A (BPA), 4-nonylphenol (NP), 4-octylphenol (OP), propyl p-hydroxybenzoate (P-PHBA), and butyl p-hydroxybenzoate (B-PHBA), synthetic estrogen, diethylstilbestrol (DES), and natural estrogen, 17β-estradiol (E2), were studied for their genotoxicity in CHO-K1 cells using sister-chromatid exchange (SCE), chromosome aberration (CA), and DNA strand break (comet) assays. Six of the chemicals, excluding E2, caused DNA migration in the comet assay and induced SCEs at one or more of the highest doses. Among the chemicals, OP produced an especially high incidence of SCEs. Structural CA was induced by five of the chemicals, excluding OP and NP, and BPA, E2, and DES also induced aneuploid cells. E2 and DES particularly increased the rate of polyploidy at high doses. The incidence of colchicine-mitosis-like (c-mitotic) figures suggesting spindle disrupting effects was also detected with five of the chemicals, excluding OP and NP, and six of the chemicals, excluding E2, caused endoreduplication (ERD), a form of nuclear polyploidization induced by block of cell cycle at G2 phase, at one or more high doses. Our present results suggest that OP and NP cause repairable DNA damage, including SCEs, and do not result in CA, while the damage caused by DES, BPA, P-PHBA, and B-PHBA results in the induction of CAs together with SCEs probably because of imperfect repair. We are unable to explain the observation that the DNA damage caused by E2 resulted in CA induction but not DNA migration or SCE induction, except for speculating that the DNA damage is different from that caused by DES and the estrogen-like chemicals. Our findings also suggest that E2, DES and BPA have aneuploidogenic properties, and that the former two of chemicals also are polyploidy-inducing agents.

BLM is required for faithful chromosome segregation and its localization defines a class of ultrafine anaphase bridges

Mutations in BLM cause Bloom's syndrome, a disorder associated with cancer predisposition and chromosomal instability. We investigated whether BLM plays a role in ensuring the faithful chromosome segregation in human cells. We show that BLM-defective cells display a higher frequency of anaphase bridges and lagging chromatin than do isogenic corrected derivatives that eptopically express the BLM protein. In normal cells undergoing mitosis, BLM protein localizes to anaphase bridges, where it colocalizes with its cellular partners, topoisomerase IIIalpha and hRMI1 (BLAP75). Using BLM staining as a marker, we have identified a class of ultrafine DNA bridges in anaphase that are surprisingly prevalent in the anaphase population of normal human cells. These so-called BLM-DNA bridges, which also stain for the PICH protein, frequently link centromeric loci, and are present at an elevated frequency in cells lacking BLM. On the basis of these results, we propose that sister-chromatid disjunction is often incomplete in human cells even after the onset of anaphase. We present a model for the action of BLM in ensuring complete sister chromatid decatenation in anaphase.

Genotoxic effects in human lymphocytes exposed to arsenic and vitamin A

Arsenic is a ubiquitous trace element and a well-established human carcinogen. In search for an ‘antidote’ to this global poison, this work was undertaken to study the probable beneficial effect of vitamin A upon arsenic induced genotoxicity. Peripheral blood lymphocyte culture was carried out to study the effects of arsenic at three different dose levels (0.5, 1 and 2 μg) for 24 h prior to harvesting. In addition, mutagenic in vitro effect of ethyl methanesulphonate was studied as a positive control. Genotoxic variables presented here are sister chromatid exchanges (SCE), cell cycle proliferative index/replicative index (CCPI/RI), average generation time (AGT) and population doubling time (PDT). Inevitably, arsenic treatment showed dose-dependent augmentation in the incidences of SCE and CCPI/RI together with AGT and PDT. However, vitamin A supplemented arsenic cultures demonstrated remarkable resurgence in the described genotoxic parameters. This data shows that vitamin A might be a useful interventional treatment in arsenic poisoning.

A Comparison of Sister Chromatid Exchanges in Lymphocytes of Anesthesiologists to Nonanesthesiologists in the Same Hospital

An increased incidence of sister chromatid exchanges (SCEs) in peripheral lymphocytes of operating room personnel exposed to waste anesthetic gases has been reported. We investigated whether the increase of SCEs in anesthesiologists was reversible. Twenty-five anesthesiologists exposed to waste anesthetic gases such as sevoflurane and nitrous oxide were compared with nonexposed internists working in the same hospital. The concentrations of sevoflurane and nitrous oxide in the operating rooms were measured. The incidence of SCE was measured in lymphocytes cultures of anesthesiologists before and after a 2-mo leave from the operating room. These values of SCE were compared with those of nonexposed physicians. Occupational exposure to sevoflurane and nitrous oxide in the operating rooms were above the threshold values. There was a significant difference in SCE values of the anesthesiologists compared with the nonexposed physicians (11.9 +/- 4.4 versus 4.2 +/- 1.1, P < 0.001). After a 2-mo leave from the operating room, the SCE values of the anesthesiologists were significantly lower compared with those taken before the leave (4.8 +/- 1.8 and 11.9 +/- 4.4, respectively, P < 0.001). We conclude that the increase of SCE in anesthesiologists exposed to increased environmental concentrations of waste anesthetics gases, such as sevoflurane and nitrous oxide, are reversible if they work free from exposure for 2 mo.

Eugenol Causes Melanoma Growth Suppression through Inhibition of E2F1 Transcriptional Activity

Metastatic malignant melanoma is an extremely aggressive cancer, with no currently viable therapy. 4-Allyl-2-methoxyphenol (eugenol) was tested for its ability to inhibit proliferation of melanoma cells. Eugenol but not its isomer, isoeugenol (2-methoxy-4-propenylphenol), was found to be a potent inhibitor of melanoma cell proliferation. In a B16 xenograft study, eugenol treatment produced a significant tumor growth delay (p = 0.0057), an almost 40% decrease in tumor size, and a 19% increase in the median time to end point. More significantly, 50% of the animals in the control group died from metastatic growth, whereas none in the treatment group showed any signs of invasion or metastasis. Eugenol was well tolerated as determined by measurement of bodyweights. Examination of the mechanism of the antiproliferative action of eugenol in the human malignant melanoma cell line, WM1205Lu, showed that it arrests cells in the S phase of the cell cycle. Flow cytometry coupled with biochemical analyses demonstrated that eugenol induced apoptosis. cDNA array analysis showed that eugenol caused deregulation of the E2F family of transcription factors. Transient transfection assays and electrophoretic mobility shift assays showed that eugenol inhibits the transcriptional activity of E2F1. Overexpression of E2F1 restored about 75% of proliferation ability in cultures. These results indicate that deregulation of E2F1 may be a key factor in eugenol-mediated melanoma growth inhibition both in vitro and in vivo. Since the E2F transcription factors provide growth impetus for the continuous proliferation of melanoma cells, these results suggest that eugenol could be developed as an E2F-targeted agent for melanoma treatment.

Sister chromatid exchange in patients with joint prostheses

The evaluation of sister chromatid exchanges (SCE) is used to establish the cytogenic damage in subjects exposed to toxic substances. The test is considered to be 1 of the most sensitive and accurate indicators of damage and responds to toxic chemicals at low doses. We evaluated the incidence of SCE in peripheral lymphocytes of patients with articular prostheses. Subjects with prostheses made of titanium-aluminium-vanadium alloys presented a significantly higher SCE number than the control population (6.3±2.3 vs 4.4±1.3; P =.0128), whereas subjects with prostheses made of chrome-cobalt alloy or mixed prostheses presented a higher SCE value than the controls but not significantly different. The presence of high-frequency cells was alarming only in 5 patients, 4 of whom had titanium alloy prostheses, whereas none belonged to the control group. The number of SCE was not affected by the presence of bone-cement used in prosthesis fixation or by the implant duration. The indication of possible cytogenic damage in patients with titanium alloy prostheses that emerged from this study should be considered carefully, even though the sample population was small.

Sister chromatid exchanges and ion release in patients wearing fracture fixation devices.

The quantification of sister chromatid exchange (SCE) during mitosis is a useful index for evaluating genotoxic effects in subjects occupationally or incidentally exposed to potentially toxic substances. The authors investigated the hypothesis that ions released by corrosion from prosthetic components of fracture fixation devices are associated with change in SCE incidence. In the present study, ten patients with implants were examined, and fifteen subjects with no implants were used as controls. SCE and high frequency cell (HFC) numbers were evaluated in circulating lymphocytes. In addition, nickel (Ni) and chromium (Cr) ion values in the serum were measured because, after iron, these metals are major components of stainless steel. A significant increase in SCE numbers was observed in patients compared to the control population (4.9 +/- 1.3 vs. 3.5 +/- 1.4). Ni concentration was 1.71 +/- 1.49 ng/mL in patients and 0.72 +/- 0.52 ng/mL in control subjects; Cr concentration was, respectively, 1.01 +/- 0.77 ng/mL and 0.19 +/- 0. 27 ng/mL. The increase of serum Cr and Ni was statistically significant. No correlation was found between the increased Cr concentrations and SCE number while Cr ion levels were found to be significantly correlated to HFC. An inverse correlation between Ni level and SCE numbers was observed. Our findings suggest that Cr release by stainless steel implants could have a genotoxic effect; thus it would be useful to carefully monitor implanted subjects with regard to serum ion dosage, SCE analysis, and HFC evaluation. In any case, it would be appropriate to remove the implant when fracture fixation is reached.

Genotoxicity of the anticonvulsant drug phenytoin (PHT): A follow-up study of PHT-untreated epileptic patients. I. Sister chromatid exchange (SCE) analysis

Phenytoin (PHT) is a widely prescribed antiepileptic drug. Its potential to interact with genetic material was investigated in a set of 30 epileptic patients (age 10-30 years) prior to and following the administration of PHT over a period of 9 months (grouped in a multiple of 3 months) and 40 control subjects in relation to age, sex, duration of drug therapy, and plasma concentration of PHT, using the sister chromatid exchange (SCE) frequency assay. Plasma levels of the phenytoin were measured by biochemical assay in epileptic patients before and after the PHT therapy. The peripheral blood lymphocytes were cultured and harvested at 72 h. The frequency of SCE was significantly higher (P < 0.001) in both age groups (10-20 and 21-30 years) for PHT-treated epileptics compared to PHT-untreated and control subjects. However, there were no considerable variations in SCE finding between the control and PHT-untreated patients. Between the two age groups, a significantly higher SCE frequency was observed in PHT-treated patients (P < 0.01) in the older age group (21-30 years). Mean SCE frequency did not differ between the male and female in the controls, PHT-untreated, or treated epileptics. Correlation between the plasma concentration of PHT and the incidence of SCE among 30 patients was insignificant. PHT monotherapy appears to have genotoxic effect as expressed by the induction of increased SCE rates in treated epileptics, while disease does not play any role in inducing genetic damage as shown by no difference in SCE frequencies between control subjects and PHT-untreated epileptic patients.

Genotoxicity of the anticonvulsant drug phenytoin (PHT): A follow‐up study of PHT‐untreated epileptic patients. I. Sister chromatid exchange (SCE) analysis

Phenytoin (PHT) is a widely prescribed antiepileptic drug. Its potential to interact with genetic material was investigated in a set of 30 epileptic patients (age 10–30 years) prior to and following the administration of PHT over a period of 9 months (grouped in a multiple of 3 months) and 40 control subjects in relation to age, sex, duration of drug therapy, and plasma concentration of PHT, using the sister chromatid exchange (SCE) frequency assay. Plasma levels of the phenytoin were measured by biochemical assay in epileptic patients before and after the PHT therapy. The peripheral blood lymphocytes were cultured and harvested at 72 h. The frequency of SCE was significantly higher (P < 0.001) in both age groups (10–20 and 21–30 years) for PHT-treated epileptics compared to PHT-untreated and control subjects. However, there were no considerable variations in SCE finding between the control and PHT-untreated patients. Between the two age groups, a significantly higher SCE frequency was observed in PHT-treated patients (P < 0.01) in the older age group (21–30 years). Mean SCE frequency did not differ between the male and female in the controls, PHT-untreated, or treated epileptics. Correlation between the plasma concentration of PHT and the incidence of SCE among 30 patients was insignificant. PHT monotherapy appears to have genotoxic effect as expressed by the induction of increased SCE rates in treated epileptics, while disease does not play any role in inducing genetic damage as shown by no difference in SCE frequencies between control subjects and PHT-untreated epileptic patients. Teratogenesis Carcinog. Mutagen. 19:61–72, 1999. © 1999 Wiley-Liss, Inc.

Investigations on the in vitro and in vivo genotoxic potential of 5-vinyl-2-norbornene.

5-Vinyl-2-norbornene (VNB: CAS no. 3048-64-4), an industrial chemical that produces hyaline droplet nephropathy in the male rat with associated alpha2u-globulin increases, was investigated in vitro and in vivo for its genotoxic potential. A Salmonella typhimurium reverse mutation assay (strains TA98, 100, 1535, 1537, 1538) was negative both without (dose range 0.003-0.3 mg per plate) and with (0.003-0.3 mg per plate) metabolic activation. A forward gene mutation test in Chinese Hamster Ovary (CHO) cells (HGPRT locus) did not show any significant concentration-related increases in mutation frequencies in the absence (0.01-0.1 mg ml[-1]) or presence (0.005-0.1 mg ml[-1]) of metabolic activation. In a sister chromatid exchange (SCE) test, VNB did not produce statistically significant or dose-related increases in the incidence of SCEs in the absence (0.02-0.06 mg ml[-1]) or presence (0.005-0.03 mg ml[-1]) of metabolic activation. A bone marrow chromosome aberration test was conducted in groups of 10 male and 10 female Sprague-Dawley rats exposed for 6 hr/day for 5 consecutive days to mean (+/- SD) VNB vapor concentrations of 0 (air control), 48.1 +/- 1.29, 146 +/- 9.2, or 336 +/- 8.5 ppm. Marrow was collected 6 and 24 hr after the final exposure. No statistically significant or dose-related increases in chromosomal aberrations occurred in the VNB-exposed animals. 5-Vinyl-2-norbornene did not show any potential for genotoxic activity with this in vitro-in vivo battery of tests.