Unstable Chromosome Aberrations Research Articles

Mechanisms of Susceptibility to 11q23 MLL Gene Locus Rearrangements in CD34+ Cells Exposed to Etoposide.

Abstract 185Exposure to the topoisomerase II inhibitor etoposide (VP16) is a significant risk factor in the development of t-MDS/AML. VP16 induces a variety of chromosomal lesions, with the most prominent ones involving the Mixed Lineage Leukemia (MLL) gene on chromosome 11q23. The MLL gene is essential for the maintenance of adult hematopoietic stem cells (HSCs) and progenitors. It is not clear whether the high frequency of MLL gene rearrangements in VP16-treated patients represents increased susceptibility of this locus to VP16-induced damage or a growth advantage of MLL-rearranged hematopoietic progenitors. In the present study we investigated the following: i) the sequence of acquisition of chromosomal lesions in normal CD34+ cells following in vitro exposure to VP16; ii) the specific propensity for development of lesions in 11q23 MLL locus; iii) and the fate of these lesions over time. CD34+ cells were selected from peripheral blood stem cell samples obtained from normal donors (n=5); they were exposed to increasing doses of VP16 (0-40 μM) for 4 hours; washed and cultured in serum-free medium containing growth factors; and assessed for apoptosis, colony forming cell (CFC) assay and chromosomal damage. Chromosome painting was performed using whole chromosome probes for chromosomes 1, 5, 7, 11 and 21, covering 25.2% of total genomic DNA with >100 metaphases scored per dose per time point. Evaluations were performed after 72 hours of culture, representing the 1st cell division after VP16 exposure, and after 144 hours representing 3-4 cell divisions. A dose-dependant decrease in colony formation (71.52 ± 0.99% of controls with 5 mM VP16, and 33.62 ± 4.4%%, with 20 mM VP16 at 72h, p<0.001), and increase in apoptosis (9.12 ± 1.67% with 5 mM VP16, and 39.3 ± 5.06 with 20 mM VP16 at 72h, p<0.001) was observed. The percentage of aberrant metaphases at 1st division was 2.4% with 5 μM and 14.9% with 20 μM of VP16. Both stable aberrations (translocations) and unstable (dicentrics, fragments) aberrations were observed. The percentage of aberrant metaphases was reduced after 3-4 cell divisions (1.4% with 5 μM and 8.7% with 20 μM VP16), and only stable aberrations were present whereas unstable aberrations were eliminated. A higher frequency of aberrations was observed in chromosome 11 compared to the other chromosomes. A 1.5- to 4-fold increase in stable lesions of chromosome 11 relative to other chromosomes was seen at the 1st division and a 2- to 3-fold increase relative to other chromosomes was seen after 3-4 divisions. To assess whether the 11q23 MLL locus was specifically affected by VP16 treatment, we performed interphase FISH with a break-apart probe for the MLL gene (11q23). A break-apart probe for the MYC gene (8q24) was studied as a control. Cells were cultured for three weeks. In preliminary experiments we observed that a higher percentage of cells showed 11q23 abnormalities (9.3%) compared with 8q24 abnormalities (5.4%) at the 1st division. 11q23 abnormalities persisted at high levels in cells (9.9%) cultured for 3 weeks. In contrast, 8q24 abnormalities were markedly reduced (0.4%) after 3 weeks of culture, suggesting selective maintenance of MLL-rearranged cells in culture. In conclusion we show that in vitro exposure to VP16 results in a dose-dependent induction of both stable and unstable chromosomal aberrations in CD34+ hematopoietic progenitors. We observe persistence of stable chromosomal aberrations with particular predisposition to aberrations in chromosome 11. Our results suggest a selective predisposition to 11q23 MLL locus rearrangements that appears to be related to enhanced susceptibility to damage to this locus following VP16 exposure as well as selective maintenance of MLL rearranged cells over subsequent cell divisions. These findings are now being applied to understand the relationship between individual susceptibility to acquisition of VP16-induced 11q23 abnormalities in CD34+ cells and risk of development of t-MDS/AML. Disclosures:No relevant conflicts of interest to declare.

CYTOGENETIC ANALYSIS OF LYMPHOCYTES WORKERS OCCUPATIONALLY EXPOSED TO IONIZING RADIATION EFFECTS

&amp;lt;p&amp;gt;Occupational exposure is particularly delicate because of chronic exposure to low doses of ionizing radiation and its cumulative effect, where it is important to consider the biological response of body to given conditions of exposure. The objective of this study was the observation of the recovery of the DNA damages in subjects working in the radiation area in twu different intervals. Group I, consisting of 30 subjects, was exposed to ionizing radiation and unstable chromosomal aberrations were identified. Group II included the same, re-examined subjects (30) 9 months later. It was verified that 5 (16.67%) subjects still had unstable chromosomal aberrations, although they had been excluded from radiation area Controls groups (C) consisted of 64 subjects that were not exposed to mutagenic agents.The comparision of the control group with the two studied groups revealed the reduction of the unstable aberrations (p&amp;amp;lt;0.05). The total effective doses , which increased with the years spent in radiation area, reflected the yield of chromosomal aberrations. The presence of chromosomal aberrations in some subjects, after the exclusion from the ionising radiation exposure, suggests that the time needed for the recovery of the DNA damages is different, which indicates the individual differences in radiosensitivity as well as different of the reparatory cellular response.&amp;lt;/p&amp;gt;

Effect of N-metylcarbamate pesticide bendiocarb on cattle lymphocytes afterin vitroexposure

Bendiocarb is a carbamate broad-spectrum insecticide used to control disease vectors such as mosquitoes and flies, as well as household and agricultural pests. Nowadays, only few papers reporting cytogenetic or possible genotoxic effect of this insecticide on mammalian cells are available. In the present study 24-hour exposure to bendiocarbamate at concentrations ranging from 20 to 160 μg/ml was used for investigation of unstable chromosomal aberrations (CA), sister chromatid exchanges (SCE) and stable chromosomal aberration induction in cultured bovine peripheral lymphocytes. The slight but no significant increase of chromatide breaks frequency was observed after the exposure of lymphocytes to 80 μg/ml of bendiocarb. At the highest concentration added to the cell cultures (160 μg/ml) mitotic index decrease was shown in both donors (p < 0.05; p < 0.01). Both statistically significant elevation of SCEs (p < 0.05) and a reduction of proliferative indices (PI) (p < 0.01) were shown at a dose of 80 μg/ml. By means of two fluorescent-labelled whole chromosome-painting probes, stable aberrations such as bovine chromosome 1 and 5 translocation as well as numerical aberrations (polyploidies, heteroploidies) were visualised under fluorescent microscope in some examined metaphases.

Modification of 2-deoxy-D-glucose on radiation-and chemotherapeutic drug-induced chromosomal aberrations

Chemotherapy is the treatment of cancer with drugs, often used as either adjuvant or neoadjuvant or in conjunction with radiation and surgery. Unfortunately, majority of the drugs are toxic to normal tissues, the toxicity being resulting from multidrug protocol used to induce remissions and achieve tumor care. While it has been demonstrated for compounds like the 2-deoxy-glucose (2-DG) used as a modulator for radiation-induced damages, such studies were rarely reported for chemotherapeutic drugs. To study the effect of 2-DG on radiation-and chemotherapeutic drug-induced chromosomal aberrations in normal and tumor cells exposed in vitro. The peripheral blood lymphocytes (PBLs) and BMG-1 cells were exposed to radiation and chemotherapeutic drugs (bleomycin and mitomycin-C) in the presence and absence of 2-DG. The treated cells were cultured for various durations, arrested at either metaphase or cytokinesis stage of the cell cycle. The stable and unstable aberrations were recorded using Giemsa staining and FISH technique. The cell cycle kinetics was studied using fluorescence plus Giemsa (FPG) staining. The presence of 2-DG reduced stable and unstable chromosome aberrations (CA) significantly (P < 0.001), in PBLs induced by radiation, bleomycin and mitomycin-C, when compared to cells treated with radiation or the drugs and increased significantly in BMG cells (P < 0.001). Furthermore, the presence of 2-DG altered the cell cycle kinetics in the PBLs and BMG-1 cells. Thus the overall results showed protection effect on the normal cell damages induced by radiation and chemotherapeutic drugs, while sensitizes the tumor cell. The obtained results suggest that 2-DG in combination with radiotherapy/chemotherapy could lead to an improvement in tumor therapy by sensitizing the tumor cells while protecting the normal cells.

Chromosomal Aberrations in Subjects Exposed to Ionizing Radiation

Occupational exposure to low doses of ionizing radiation is a particularly delicate subject for investigation, due to the cumulative effects of chronic exposure. It is extremely important to consider and to measure the biological response to given conditions of exposure. The aim of this study was to establish possible recovery from DNA damage in subjects professionally exposed to radiation in their working area by examinations for chromosomal aberrations (CA) at two different times. The first group (I) was composed of 30 professionally exposed subjects in whom unstable CA (dicentrics, ring, acentric fragments, chromatid, chromosomal breaks, and chromatid interchanges) were identified at time zero. After removal from the radiation area, they were re-examined 9 months later. The second group (II) contained 64 healthy individuals, not professionally exposed to ionizing radiation or other known mutagenic agents. In the group of exposed individuals, five (16.67%) subjects exhibited permanent unstable CAs, even after 9 months absence from the radiation. When the nonexposed and exposed groups were compared, an increase of unstable aberrations (p < 0.05) was observed in the exposed group. Nevertheless, a statistically significant decrease of dicentrics, acentric fragments, and ring frequencies was observed in exposed individuals after 9 months away from the radiation area. However, chromatid and isochromatid break frequencies increased slightly but not significantly after 9 months. The detected CAs corresponded to the total effective doses of radiation measured in our subjects. The existence of CAs in some individuals even after absence from the radiation area suggests that the time necessary for the damaged DNA to recover is extremely variable and indicates interindividual differences in radiosensitivity as well as differences in the cellular-reparation response.

Seventeen-year follow-up study on chromosomal aberrations in five victims accidentally exposed to several Gy of 60Co γ-rays

On 25 June 1990, a radiation accident occurred in a (60)Co source radiation unit in Shanghai, due to violations in operation regulations. This accident resulted in the exposure of seven individuals to acute high-dose and dose-rate whole-body external irradiation. Conventional chromosomal aberration analysis, G-banding automatic karyotype analysis and/or fluorescent in situ hybridization (FISH) painting methods were used to analyze chromosomal aberrations in peripheral blood lymphocytes from five of the victims 24 h to 17 years after accidental exposure to 1.9-5.1 Gy of (60)Co gamma-rays. The frequency of unstable chromosomal aberrations (dicentrics and rings) remained at constant levels 1 month after exposure. Three months after exposure, the frequency was reduced by 20-40% in three victims, while no reduction was seen in the other two victims. Twelve years after exposure, the number of dicentrics and rings decreased by more than 90%, and did not reveal a dose-dependent relationship. However, even at 12-17 years after exposure, stable chromosome aberrations, dominated by translocations, remained at a high level in a dose-dependent manner. The frequency of stable chromosomal aberrations detected by FISH showed a similar dose-dependent relationship as that detected by karyotype analysis of G-banding chromosomes. The G-banding analysis also suggested that the pattern of chromosome breakpoints is random. The FISH data showed a decreasing tendency with time for chromosome translocation frequency in the peripheral lymphocytes, and the rate of reduction varied among different individuals. It is likely that the higher dose the victim received, the lesser the translocation frequency decreased with time. The G-banding data also showed that the rate of reduction of translocations is different among individuals. From 5 to 17 years after accidental irradiation, a very small reduction (approximately 10%) of translocation frequency was observed in victims C and D, while there was about a 35% reduction (the highest among the victims) for victim G who received the smallest dose (1.9 Gy). These observations can be used to validate the existence of chromosomal aberrations in peripheral blood lymphocytes as a biological dosimeter for radiation exposures.

Frequencies of stable and unstable chromosomal aberrations in lymphocytes of workers employed in carbamate production

Frequencies of stable and unstable chromosomal aberrations in lymphocytes of workers employed in carbamate production

Cytogenetic damage in preimplantation mouse embryos generated after paternal and parental γ-irradiation and the influence of vitamin C

Cytogenetic damage expressed as micronuclei (MN) in 4-8-cell embryos generated after irradiation of male or male and female mice in the absence and presence of vitamin C was investigated. Male NMRI mice were whole body exposed to 4 Gy gamma-rays and mated with non-irradiated superovulated female mice in 6 successive weeks after irradiation in a weekly interval. In experiments involving irradiation of both male and female mice, irradiated male mice for 6 weeks post irradiation were mated with female mice irradiated after induction of superovulation. Effect of 100 mg/kg vitamin C (ascorbic acid) on the frequency of MN was also studied. Pregnant animals were euthanized and embryos flushed from the oviducts and fixed on slides. The rate of MN observed in embryos generated from irradiated male compared with control group dramatically increased (P<0.01). Frequency of MN in this group decreased dramatically after vitamin C treatment (P<0.01). Frequency of MN in embryos generated by mating both male and female irradiated mice was higher than that observed for those embryos generated by irradiated male mice alone. However, a considerable modifying effect of vitamin C was observed for this group too (P<0.05). Results indicate that irradiation of gonads during spermatogenesis and preovulatory stage oocytes may lead to unstable chromosomal aberrations and probably stable chromosomal abnormalities affecting pairing and disjunction of chromosomes in successive preimplantation embryos expressed as MN. The way vitamin C reduces clastogenic effects of radiation on germ cells leading to reduced frequency of MN in pre-embryos might be due to its antioxidation and radical scavenging properties.

Influence of hOGG1 genotype on the frequencies of stable and unstable chromosome aberrations in radiation-exposed individuals

Influence of hOGG1 genotype on the frequencies of stable and unstable chromosome aberrations in radiation-exposed individuals

Mechanism of adaptive response: Estimation of human lymphocyte adaptive response to radiation using various criteria

Blood lymphocytes of 15 healthy donors have been investigated for their ability to reduce radiosensitivity after low-dose irradiation-radio-induced adaptive response (AR). The frequency of unstable chromosome aberrations was used to evaluate cell radiosensitivity after the irradiation of cells in low adaptive (5 cGy) and high challenge (1 Gy) doses in comparison with the effect of challenge irradiation only. Three indexes have been used, i.e., (A) the frequency of cells with aberrations per total analyzed cell, (B) the number of chromosome aberrations per one cell, (C) and the number of chromosome aberrations per one aberrant cell. It was found that the donors can be divided in the four following groups: 1. AR was not estimated any of the indexes used; 2. AR was estimated with indexes A and B, but not C; 3. AR was shown by indexes B and C; 4. AR was evident with all three indexes. The generally accepted AR repair model only explains the appearance of group-3 and-4 donors, but not group-2. For the purpose of understanding the AR mechanisms and the difference in AR estimations with various criteria, the metaphase distribution by the number of chromosome aberrations has been analyzed for each donor. It was shown that, in group-2 donors, the number of cells without aberrations after adaptive and challenge irradiations was significantly higher than after irradiation with a challenge dose only. Thus, in this group, AR is formed as a result of the changed frequency of cells in the 0 class (population shift). A similar shift is observed in the metaphase distribution in the donors of group 4, but not in group 3. The data obtained show that AR is probably a result of several processes, including the activation of the reparation of premutational genome damages, population shifts evident in the frequency of undamaged cells, and, possibly, the activation of apoptotic cell death. The complex character of AR is reflected to different degrees in each criterion of radiosensitivity.

High frequency of telomeric associations and chromatid exchanges and breaks in human ovarian carcinoma

Cytogenetic analysis of an unselected series of twenty human serous adenocarcinomas and undifferentiated carcinomas of the ovary revealed the presence of telomeric associations (tas) and unstable chromosomal aberrations, including chromatid-type exchanges (cte) and breaks (ctb) in high proportion of tumors studied. Tas and cte & ctb were present in 75% and 55% of tumors, respectively. Involvement of different chromosome telomeres in tas seemed to be random. This is the first report describing telomeric associations in ovarian cancer. Our findings suggest that the frequency of extensive spontaneous chromosome breakage in ovarian carcinoma may be higher than that reported in the literature.

BIOLOGICAL ESTIMATION OF DOSE IN HEMI-BODY IRRADIATION OF CANCER PATIENTS BY CYTOGENETIC ANALYSIS

The objective of this study was to estimate equivalent whole body dose and dose to the irradiated region in hemi-body irradiation of cancer patients using chromosome aberrations and micronuclei techniques. The frequency of unstable chromosome aberrations and micronuclei was studied in peripheral blood lymphocytes of cancer patients before and after hemi-body irradiation. The mean estimated equivalent whole body dose was 3.74 +/- 0.16 Gy and 4.07 +/- 0.15 Gy from dicentrics and micronuclei frequency in lymphocytes after hemi-body irradiation. The mean dose to the irradiated region from unstable chromosome aberrations was estimated to be 6.85 +/- 0.2 Gy and 6.79 +/- 0.26 Gy using Dolphin's contaminated Poisson dispersion analysis and the Qdr method, respectively. The mean dose to the irradiated region from micronuclei frequency was 7.04 +/- 0.25 Gy by Dolphin's method. There was a slight underestimation of mean dose to the irradiated part in vivo. The percentage of irradiated blood and fraction of the cells exposed could be estimated using the contaminated Poisson method.

The impact of the bystander effect on the low-dose hypersensitivity phenomenon

The aim of this study was to investigate the possible relationship between the bystander effect and the low-dose hypersensitivity/increased radio-resistance phenomenon in BJ fibroblast cells taking as response criteria different end points of radiation damage such as cell survival, chromosomal damage (as detected by using micronucleus assay) and double strand breaks (DSBs) of the DNA. Although gamma-H2AX foci were observed in confluent bystander BJ cells, our data suggest that X-irradiation does not lead to a significant rate of DSBs in bystander cells. Thus, neither bystander effect induced unstable chromosomal aberrations nor bystander effect induced DSBs are sufficiently pronounced to explain the apparent relationship between bystander effect and low-dose hypersensitivity. The experiments described here suggest that the hyper-radiosensitivity phenomenon might be related to bystander factor induced cell inactivation in the low-dose region (lower than 1 Gy).

The Continuous Observation by Chromosome Aberration Elimination at Irradiated Persons

One from a problem of biological dosimetry is the dose evaluation in remote time after irradiation. This takes place in certain percent of cases of acute irradiation, for ex-ample, when patient entrance in hospital is delayed. The retrospective dose evaluation is necessary for confirmation of irradiation fact and determination of quantity of possible absorbed dose in aims of medical social examination and potential judicial trials which are associated with requirements of a compensation of damage caused by health. There-fore the investigation of chromosome aberration rate dynamics of patients injured in a result of Chernobyl accident is very important. In this situation the fact of presence of primary cytogenetic analysis results of peripheral blood lymphocyte cultures established in nearest days and weeks after irradiation for many number of injured patients is espe-cially essential. It allows to make the comparison between primary and repeated investi-gations. Chernobyl patients (73 humans investigated in during 12 years after irradiation) were divided by three groups depending on primarily evaluated dose by medium dicen-tric frequency: patients irradiated by 0,2-2,4 Gy (30 individuals, 90 cultures); patients ir-radiated by 2,6-4,4 Gy (28 individuals, 117 cultures) and patients irradiated by 4,6-9,8 Gy (15 individuals, 64 cultures). The cytogenetic analysis was produced by FPG-method. Also the cytogenetic data of nearest time after irradiation testified to relatively uniform irradiation of basic body mass for almost all injured patients. We used double exponential model how in the article IAEA (1998) for Goiania pa-tients for the mathematical description of elimination of dicentrics and unstable chromo-some aberrations. A speed of decrease of frequency of dicentrics in cells with dicentrics in middle was more than for frequencies of dicentrics and unstable aberrations by 100 analyzed cells. In all cases the elimination speeds of cytogenetic indexes of unstable aberrations was the more the more primary absorbed dose. High individual variability of this process was observed. Qdr index which is often proposed for retrospective dose indication sub-mitted these principles also. The middle speed of its decrease was less than for frequen-cies of dicentrics and unstable aberrations by 100 analyzed cells but more than for fre-quency of dicentrics in cells with dicentrics. As against dicentrics and other unstable ab-errations atypical chromosomes frequency in whole was approximately constant in dur-ing 12 years of observation in spite of high individual variability. However in late period atypical chromosomes were contained mainly in stable cells but not unstable cells.

A comparison of different cytological stains for biological dosimetry

Purpose: This paper examines the relative accuracy of analysis of unstable chromosomal aberrations (dicentrics, rings and fragments) in lymphocyte metaphases using four microscope slide staining options, widely used to assess radiation overdose or to survey occupationally exposed subjects.Materials and methods: Peripheral blood lymphocytes from a healthy donor were irradiated with 1.5 and 3.0 Gy of X-rays at a dose rate of 0.715 Gy/min. Dicentrics were scored by different cytological stains in order to compare block staining: Giemsa and 4′, 6-Diamidine-2′-phenylindole dihydrochloride (DAPI); with techniques that highlight centromeres: C-banding and Centromere Multiplex Fluorescence in situ Hybridization (CM-FISH).Results: At each of the two doses, the values for dicentrics per cell observed with each staining method were compared. In terms of dose estimation, no statistical difference was observed between the evaluated methods (χ2 p: 0.27 and 0.64, respectively; analysis of variance – ANOVA, p > 0.99). Therefore, the evidence of centromeres by C-banding and CM-FISH did not promote an increased discovery of dicentrics. On the other hand, when confirmation of unequivocal identification of dicentrics is needed, C-banding and CM-FISH can be a suitable method to confirm its presence. Economical and social factors must be taken into account in the decision of method as well.Conclusion: For routine use where several hundreds of cells need to be reliably processed and analyzed daily, processing slides by block staining with Giemsa and DAPI is preferable. However, to assist in resolving the minority of images that are ambiguous, C-banding and CM-FISH provide a better identification of suspected dicentrics.

Automatic detection of dicentrics chromosomes in biodosimetry

In case of large scale accidental overexposure to ionizing radiation, a rapid triage of the population exposed is needed first, followed by an accurate dose estimation for each individual. Currently, these two steps are performed by scoring unstable chromosomal aberrations (dicentrics, rings and fragments) in peripheral blood lymphocytes after Giemsa staining. For the triage step, only 50 metaphases are currently manually analysed. This is rapid but not accurate and may introduce false negative dose classification. For the second step, 500 metaphases are currently manually analysed. This is very accurate but very long. To improve the method, we have studied the automatic dicentrics detection by Metafer 4 software (MetaSystems) on accidental overexposure victims of the Dakar accident (Africa). The study has been performed firstly by the manual scoring of dicentrics on 50 metaphases (50 MS) used for a population triage, secondly by the manual scoring of dicentrics on 500 metaphases (standard approach; 500 MS) and thirdly by the automatic scoring of dicentrics (ADS). The comparison between dose classification obtained by 50MS and obtained by 500MS methods shows 54.2% (32 on 59 individuals) correlation however there is 45.8% (27 on 59 individuals) of underestimation. Moreover, comparisons of dose classification between the results obtained by ADS and 500MS show 95.7% (44 on 46 individuals) of correlation and 4.3% (2 on 46 individuals) of underestimation. In addition, the mean doses obtained by ADS method are near to the mean doses obtained by 500MS. To conclude, ADS method is faster and more accurate than the manual scoring of 50 cells and could be used in case of triage. In addition, ADS method could also be used instead of 500MS in case of individual dose estimation as it is as accurate and much faster.

Alteration of peripheral blood T-reg cells and cytokines production in angiography personnel exposed to scattered X-rays.

Angiocardiography is an X-ray examination of the blood vessels or chambers of the heart. Cardiologists and staff members applying this procedure are exposed to high levels of scattered radiation. In our previous study the incidence of unstable chromosomal aberrations and cytokinesis-blocked micronuclei were found to be significantly higher in exposed individuals than the age and sex matched controls. In the present study we assessed cytokine production by peripheral blood mononuclear cells of the above cases and the percentage of Treg cells. According to film dosimeter analysis, personnels received 0.25-15 mSv during the previous year (average of 3 mSv/y). Isolated PBMCs from the test and control groups were stimulated with Phorbol Myristate Acetate/ Ionomycin (PMA/I). Cytokine production was measured in the supernatants of cultured lymphocytes. The percentage of Treg cells was studied by flow cytometry. The production of IL-10 and IL-5 was significantly down-regulated in the test group compared to the control group. In contrast, IL-12 was up-regulated. Yet, no statistically significant difference was found for IFN- gamma between two groups. In addition, we found higher percentage of CD4+CD25+(bright) Treg cells in the study group compared to the controls. Taken together, it was shown that low doses of scattered X-rays could skew cytokine profile of peripheral blood mononuclear cells in favour of inflammatory response causing the increase of Treg cells.

The Chernobyl Nuclear Catastrophe: Unacknowledged Health Detriment

The Chernobyl Nuclear Catastrophe: Unacknowledged Health Detriment

Biodosimetry using chromosome aberrations in human lymphocytes

In vitro dose-response calibration curves for (60)Co gamma rays have been established for unstable chromosome aberrations in human peripheral blood lymphocytes. The observed dose-response data were fitted to a linear quadratic model. The calibration curve parameters were used to estimate the equivalent whole-body dose and dose to the irradiated region in partial body irradiation of cancer patients. The derived partial body doses and fractions of lymphocytes irradiated were in agreement with those estimated from the radiotherapy regimes.

A comparative analysis of bleomycin‐induced incomplete chromosome elements in two mammalian cell lines using a telomeric PNA probe

Fluorescence in situ hybridization (FISH) with a telomeric peptide nucleic acid probe was employed to analyze the induction of incomplete chromosome elements (ICE; i.e., incomplete chromosomes and terminal fragments) by bleomycin (BLM) in two mammalian cell lines. Chinese hamster embryo cells (CHE cell line, average 2n = 23) and domestic rabbit cells (CPC cell line, average 2n = 44) were treated with 2.5 micro g/ml BLM; after 18 hr of incubation, first-division metaphases were stained with the telomeric probe, and ICE and other unstable chromosomal aberrations were scored. BLM induced ICE, dicentrics, and interstitial acentric fragments in CHE cells, but only ICE in CPC cells. About 50% of the metaphases in BLM-treated CHE cells contained one or more pairs of ICE, while only 20% of treated CPC cells contained ICE. Almost 100% of the BLM-induced ICE in both cell lines consisted of pairs formed by an incomplete chromosome and a terminal fragment. Our results confirm that ICE are the most frequent type of unstable chromosomal aberration induced by BLM in mammalian cells. Moreover, the present study shows that an increase in the chromosome number does not necessarily result in an increase in the frequency of BLM-induced ICE. The results also show that the difference in the chromosomal sensitivity to BLM in CHE and CPC cells is due to differences in the absolute frequency but not in the pattern (i.e., type and proportion) of ICE.