RESUMEN
PURPOSE: To determine whether metaphases arising at different times after mitogen stimulation of G0 lymphocytes differ in frequencies of X-ray-induced chromosome aberrations. MATERIALS AND METHODS: Human G0 lymphocytes from peripheral blood exposed to 0, 1.5 or 3.0 Gy X-rays were stimulated to divide with the mitogen phytohaemagglutinin (PHA). First-division metaphases were distinguished from second and third divisions by chromatid labelling with 5-bromodeoxvuridine (BUdR) and staining with Giemsa or DAPI. Cultures harvested 48, 70 and 94 h after mitogen stimulation were analysed for unstable aberrations on Giemsa-stained slides and for stable and unstable aberrations by fluorescence in situ hvbridization (FISH) with painting probes for chromosomes 1, 2 and 4. RESULTS: Frequencies of aberrations declined at the later culture periods, as expected on the basis of unstable aberrations being lost in mitotic division. Whe n scoring was restricted to firstdivision metaphases, however, aberration frequencies were higher in 94-h cultures than in 48-h cultures. CONCLUSIONS: Frequencies of radiation-induced chromosome aberrations in first-division metaphases increase with culture time after mitogen stimulation. Possible explanations for this finding are a delay of damaged cells in mitogenic response or progression through divisions and heterogeneity among lymphocytes in culture kinetics and radiosensitivity. The data argue against the common assumption that all first-division cells are equivalent as indicators of radiation-induced chromosome aberrations.
Asunto(s)
Aberraciones Cromosómicas/efectos de la radiación , Linfocitos/citología , Linfocitos/efectos de la radiación , Metafase/genética , Metafase/efectos de la radiación , Femenino , Humanos , Hibridación Fluorescente in Situ , Técnicas In Vitro , Tolerancia a Radiación , Fase de Descanso del Ciclo Celular/genética , Fase de Descanso del Ciclo Celular/efectos de la radiaciónRESUMEN
The radioprotective aminothiols 2-[(aminopropyl)amino] ethanethiol (WR-1065) and cysteamine (CSM) potentiate the induction of chromosomal damage by the radiomimetic compound bleomycin (BLM) in G0 human lymphocytes. To investigate the mechanism of potentiation, we measured the clastogenic activity of BLM in the cytokinesis-block micronucleus assay in the presence and absence of amines, thiols, and aminothiols. The hydroxy analog of WR-1065, 2-(3-aminopropylamino) ethanol (WR-OH), potentiates BLM only slightly, indicating the critical nature of the thiol group. As thiols, WR-1065 and CSM may donate electrons for the activation of Fe(+2)-BLM or for the regeneration of Fe(+2)-BLM from inactive Fe(+3)-BLM. The amines putrescine, spermidine, and spermine all potentiate BLM, but they are weaker potentiators than the aminothiols, and they are effective only at high concentrations. Their activity, like that of WR-OH, is probably a consequence of conformational alteration of DNA. Dithioerythritol (DTE) and 2-mercaptoethanol (2-ME), thiols lacking an amino group, are less effective potentiators of BLM than are the aminothiols. The thiol group of WR-1065 and CSM is therefore essential, but insufficient, for explaining the strong enhancement of BLM activity. The cationic nature of CSM and WR-1065, conferred by the amino groups, evidently concentrates the active thiol function at the site of BLM action on DNA. As expected on this basis, the diamine WR-1065 is a more effective potentiator of BLM than is the monoamine CSM, whereas cysteine and N-acetylcysteine (NAC), which lack a net positive charge, potentiate BLM only weakly. These studies suggest that potentiation of the clastogenic action of BLM by aminothiols can be explained by the combination of a thiol-mediated redox mechanism and an amine-mediated targeting of the thiol function to DNA.
Asunto(s)
Bleomicina/toxicidad , Aberraciones Cromosómicas , Cisteamina/farmacología , Linfocitos/efectos de los fármacos , Mercaptoetilaminas/farmacología , Sinergismo Farmacológico , Humanos , Linfocitos/citología , Pruebas de Micronúcleos , Fase de Descanso del Ciclo Celular , Relación Estructura-ActividadRESUMEN
The induction, distribution, and persistence of chromosome aberrations in human lymphocytes exposed to X-rays in G0 were analyzed in 48-, 70-, and 94-hr cultures by conventional metaphase analysis and painting of chromosomes 1, 2, and 4 by FISH. All cells that had been scored by FISH were relocated to determine by differential staining of chromatids whether they had passed through 1, 2, or > or =3 divisions. FISH revealed a dose-dependent induction of stable and unstable aberrations, while chromatid labeling showed mitotic lag caused by irradiation in G0. Relative to their DNA contents, there was a small but significant overrepresentation of chromosome 4 and underrepresentation of chromosome 2 among the aberrations involving chromosomes 1, 2, and 4. FISH slightly underestimated the genomic frequency of unstable aberrations measured by conventional metaphase analysis. There was a slight excess of translocations relative to dicentrics, but the data are compatible with the 1:1 ratio expected from cytogenetic theory. Many of the translocations were apparently incomplete (i.e., nonreciprocal). Incomplete translocations were more frequent at higher X-ray dose and in first division, suggesting that they may be associated with complex damage and are more apt to be lost in mitosis than complete translocations. Among the incomplete translocations, t(Ab) outnumbered t(Ba) -- a difference ascribable to the FISH technique. Aberration frequencies declined as the cells divided in culture. The overall decline in the frequency of aberrant cells (approximately 29% per cell generation) reflects a rapid decline in dicentrics and fragments (approximately 60% per cell generation) and the relative stability of translocations. The frequency of translocation-bearing cells underwent a modest decline in culture (approximately 13% per cell generation).
Asunto(s)
Aberraciones Cromosómicas , Linfocitos/efectos de la radiación , Mitosis , Fase de Descanso del Ciclo Celular , Células Cultivadas , Humanos , Hibridación Fluorescente in Situ , Linfocitos/citología , Linfocitos/ultraestructura , Rayos XRESUMEN
Studies of workers who were sent to Chernobyl after the 1986 reactor accident are being conducted to provide a better understanding of the effects of chronic low-dose radiation exposures. A crucial component to these investigations is an accurate assessment of the radiation doses received during the cleanup activities. To provide information on biological measurements of dose, fluorescence in situ hybridization (FISH) with whole-chromosome painting probes has been applied to quantify stable chromosome aberrations (translocations and insertions) among a defined cohort of 4,833 cleanup workers from Estonia. Cytogenetic analysis of 48-h lymphocyte cultures from 118 Estonian cleanup workers (10.3 cGy mean recorded dose; 25 cGy maximum), 29 Estonian population controls and 21 American controls was conducted by three laboratories. More than 258,000 painted metaphases were evaluated. Overall, we observed lower translocation frequencies than has been reported in previous studies using FISH among Chernobyl cleanup workers. In our data, a clear association with increased levels of translocations was seen with increasing age at blood drawing. There was no correlation, however, between aberration frequency and recorded measurements of physical dose or any category of potential high-dose and high-dose-rate exposure such as being sent to Chernobyl in 1986, working on the roof near the damaged nuclear reactor, working in special zones or having multiple tours. In fact, the translocation frequency was lower among the exposed workers than the controls, though not significantly so. To estimate the level of effect that would have been expected in a population of men having an average dose of approximately 10 cGy, blood from six donors was exposed to low-LET radiation, and more than 32,000 metaphases were scored to estimate dose-response coefficients for radiation-induced translocations in chromosome pairs 1, 2 and 4. Based on these results, we estimate that had this group of 118 men received an average whole-body dose of 10-11 cGy, as chronic or acute exposures, an increase in the mean frequency of chromosome translocations of more than 40-65% would have been observed in their lymphocytes compared to findings in nonirradiated controls. In spite of evaluating more than a quarter of a million metaphases, we were unable to detect any increase in the mean, median or range in chromosome aberrations in lymphocyte cultures from a group of Estonian men who took part in the cleanup of the Chernobyl nuclear power site and those who did not. We conclude that it is likely that recorded doses for these cleanup workers overestimate their average bone marrow doses, perhaps substantially. These results are consistent with several negative studies of cancer incidence in Chernobyl cleanup workers and, if borne out, suggest that future studies may not be sufficiently powerful to detect increases in leukemia or cancer, much less distinguish differences between the effects of chronic compared to brief radiation exposures.
Asunto(s)
Hibridación Fluorescente in Situ , Linfocitos/efectos de la radiación , Exposición Profesional , Centrales Eléctricas , Dosis de Radiación , Liberación de Radiactividad Peligrosa , Translocación Genética , Adulto , Relación Dosis-Respuesta en la Radiación , Estonia/etnología , Humanos , Linfocitos/ultraestructura , Persona de Mediana Edad , Análisis de Regresión , Fumar , UcraniaRESUMEN
Thorotrast, a colloidal suspension of the long-lived radionuclide, thorium-232, was widely used as a radiographic contrast medium for several decades. Due to the poor excretion of the sol, however, Thorotrast would deposit in the liver, bone marrow and other tissue, and patients would receive alpha-particle irradiation for life. To gauge the cumulative genetic damage to hematopoietic stem cells due to chronic exposure to alpha particles, we conducted a multi-end-point evaluation in a 72-year-old man who had been administered a 32-ml bolus of Thorotrast during cerebral angiography performed over 40 years ago in 1950. Peripheral T lymphocytes were cultured to quantify the frequencies and cellular distributions of asymmetrical and symmetrical types of chromosome aberrations in first-division metaphases and micronuclei in cytokinesis-arrested interphase II cells. Aberrations were scored using classical chromosome group analysis methods and chromosome painting techniques. Assays of glycophorin-A (GPA) mutations in red blood cells were also performed to obtain a relative measurement of damage sustained by the erythroid stem cell population. Results revealed that approximately 30% of the lymphocytes in this patient contained one or more chromosome aberrations, the majority of which were of the "stable" type. About one-third of the lymphocytes with chromosome damage carried multiple aberrations, suggesting that significant numbers of stem cells survive exposures to alpha-particle radiation that induce complex genomic alterations. Increased frequencies of GPA mutations were observed, demonstrating that genomic damage is also induced in erythroid progenitors. The numbers of micronuclei in lymphocytes were only moderately increased compared to expected values for persons of comparable age, and thus this end point was not useful for quantifying exposure level. Despite the relatively severe burden of somatic cell damage induced by 40 years of internal alpha-particle irradiation, the patient remains surprisingly free of any serious illness.
Asunto(s)
Partículas alfa , Aberraciones Cromosómicas , Células Madre Hematopoyéticas/efectos de la radiación , Dióxido de Torio/efectos adversos , Células Cultivadas , Glicoforinas/genética , Células Madre Hematopoyéticas/ultraestructura , Humanos , Micronúcleos con Defecto CromosómicoRESUMEN
Thyroid examinations, including palpation, ultrasound and, selectively, fine-needle aspiration biopsy, were conducted on nearly 2,000 Chernobyl cleanup workers from Estonia to evaluate the occurrence of thyroid cancer and nodular thyroid disease among men with protracted exposure to ionizing radiation. The examinations were conducted in four cities in Estonia during March-April 1995, 9 years after the reactor accident. The study population was selected from a predefined cohort of 4,833 cleanup workers from Estonia under surveillance for cancer incidence. These men had been sent to Chernobyl between 1986 and 1991 to entomb the damaged reactor, remove radioactive debris and perform related cleanup activities. A total of 2,997 men were invited for thyroid screening and 1,984 (66%) were examined. Estimates of radiation dose from external sources were obtained from military or other institutional records, and details about service dates and types of work performed while at Chernobyl were obtained from a self-administered questionnaire. Blood samples were collected for assay of chromosomal translocations in circulating lymphocytes and loss of expression of the glycophorin A (GPA) gene in erythrocytes. The primary outcome measure was the presence or absence of thyroid nodules as determined by the ultrasound examination. Of the screened workers, 1,247 (63%) were sent to Chernobyl in 1986, including 603 (30%) sent in April or May, soon after the accident. Workers served at Chernobyl for an average of 3 months. The average age was 32 years at the time of arrival at Chernobyl and 40 years at the time of thyroid examination. The mean documented radiation dose from external sources was 10.8 cGy. Biological indicators of exposure showed low correlations with documented dose, but did not indicate that the mean dose for the population was higher than the average documented dose. Ultrasound examinations revealed thyroid nodules in 201 individuals (10.2%). The prevalence of nodules increased with age at examination, but no significant associations were observed with recorded dose, date of first duty at Chernobyl, duration of service at Chernobyl, building the sarcophagus or working on the roof of neighboring buildings or close to the damaged reactor. Nodularity showed a nonsignificant (p(1) = 0.10) positive association with the proportion of lymphocytes with chromosome translocations, but associations with the frequency of variant erythrocytes in the GPA assay were weak and unstable (p(1) > or = 0.46). The majority of fine-needle biopsies taken on 77 study participants indicated benign nodular disease. However, two cases of papillary carcinoma and three benign follicular neoplasms were identified and referred for treatment. Both men with thyroid cancer had been sent to Chernobyl in May of 1986, when the potential for exposure to radioactive iodines was greatest. Chernobyl cleanup workers from Estonia did not experience a markedly increased risk of nodular thyroid disease associated with exposure to external radiation. Possible reasons for the apparent absence of effect include low radiation doses, the protracted nature of the exposure, errors in dose measurement, low sensitivity of the adult thyroid gland or the insufficient passage of time for a radiation effect to be expressed.
Asunto(s)
Neoplasias Inducidas por Radiación/etiología , Exposición Profesional , Centrales Eléctricas , Liberación de Radiactividad Peligrosa , Neoplasias de la Tiroides/epidemiología , Nódulo Tiroideo/epidemiología , Adenocarcinoma Folicular/epidemiología , Adenocarcinoma Folicular/etiología , Adenocarcinoma Folicular/patología , Adulto , Biopsia con Aguja , Carcinoma Papilar/epidemiología , Carcinoma Papilar/etiología , Carcinoma Papilar/patología , Cromosomas Humanos/efectos de la radiación , Estudios de Cohortes , Membrana Eritrocítica/química , Estonia/epidemiología , Glicoforinas/genética , Humanos , Linfocitos/ultraestructura , Masculino , Persona de Mediana Edad , Neoplasias Inducidas por Radiación/diagnóstico por imagen , Neoplasias Inducidas por Radiación/epidemiología , Neoplasias Inducidas por Radiación/patología , Vigilancia de la Población , Prevalencia , Monitoreo de Radiación , Glándula Tiroides/efectos de la radiación , Neoplasias de la Tiroides/diagnóstico por imagen , Neoplasias de la Tiroides/etiología , Neoplasias de la Tiroides/patología , Nódulo Tiroideo/diagnóstico por imagen , Nódulo Tiroideo/etiología , Nódulo Tiroideo/patología , Translocación Genética , Ucrania , UltrasonografíaRESUMEN
Cytogenetic end-points have been successfully used in epidemiological studies for many years. Conventional end-points are now being replaced by procedures that utilize molecular methods, with greatly increased sensitivity, specificity and precision. In this paper we briefly review the most common cytogenetic assays that are useful in epidemiological settings, including structural chromosome aberrations, micronuclei, sister chromatid exchanges and analysis of interphase cells for aneuploidy. We describe new developments of each assay, where applicable, and discuss the strengths and weaknesses of the assays for detecting exposures and estimating risks. Finally, pertinent information concerning each of the assays that is useful in designing epidemiological studies is summarized in a table. It is hoped that the information presented here will be useful to individuals who are interested in applying biomarkers to studies of human environmental exposure and disease.
Asunto(s)
Biomarcadores de Tumor , Citogenética/métodos , Neoplasias/epidemiología , Aneuploidia , Animales , Aberraciones Cromosómicas/genética , Diseño de Investigaciones Epidemiológicas , Humanos , Micronúcleos con Defecto Cromosómico/genética , Neoplasias/genética , Medición de Riesgo , Intercambio de Cromátides Hermanas/genéticaRESUMEN
Procedures are described for the in vitro culture of human lymphocytes, which have been concentrated by density gradient centrifugation, and for a modified slide-making technique for the fixed cells. The method yields improved percentages of mitotic cells which are largely synchronized at harvest. Controlled placement of fixed cells on slides produces well-spread metaphase preparations with little background material to interfere with fluorescence in situ hybridization (FISH) probe procedures. The FISH reagents and microscope scanning time required are minimized by concentrating cells in a defined area of the slide.
Asunto(s)
Técnicas de Cultivo de Célula/métodos , Hibridación Fluorescente in Situ/métodos , Linfocitos/citología , Metafase , Coloración y Etiquetado/métodos , Criopreservación , Humanos , Índice Mitótico , Reproducibilidad de los Resultados , Manejo de Especímenes , Factores de TiempoRESUMEN
The blood beryllium lymphocyte proliferation test (BeLPT) is a modification of the standard lymphocyte proliferation test that is used to identify persons who may have chronic beryllium disease. A major problem in the interpretation of BeLPT test results is outlying data values among the replicate well counts (approximately 7%). A long-linear regression model is used to describe the expected well counts for each set of Be exposure conditions, and the variance of the well counts is proportional to the square of the expected count. Two outlier-resistant regression methods are used to estimate stimulation indices (SIs) and the coefficient of variation. The first approach uses least absolute values (LAV) on the log of the well counts as a method for estimation; the second approach uses a resistant regression version of maximum quasi-likelihood estimation. A major advantage of these resistant methods is that they make it unnecessary to identify and delete outliers. These two new methods for the statistical analysis of the BeLPT data and the current outlier rejection method are applied to 173 BeLPT assays. We strongly recommend the LAV method for routine analysis of the BeLPT. Outliers are important when trying to identify individuals with beryllium hypersensitivity, since these individuals typically have large positive SI values. A new method for identifying large Sls using combined data from the nonexposed group and the beryllium workers is proposed. The log(SI)s are described with a Gaussian distribution with location and scale parameters estimated using resistant methods. This approach is applied to the test data and results are compared with those obtained from the current method.
Asunto(s)
Beriliosis/diagnóstico , Activación de Linfocitos/efectos de los fármacos , Enfermedad Crónica , Humanos , Funciones de Verosimilitud , Control de Calidad , Análisis de RegresiónRESUMEN
The cancer chemotherapy drug bleomycin (BLM) is a potent inducer of genetic damage in a wide variety of assays. The radioprotectors cysteamine (CSM) and WR-1065 have been shown in previous studies to potentiate the induction of micronuclei and chromosome aberrations by BLM in Go human lymphocytes. By contrast, WR-1065 is reported to reduce the induction of hprt mutations by BLM in Chinese hamster cells. To elucidate the basis for these interactions, we examined the effects of CSM and WR-1065 on the induction of mitotic gene conversion by BLM in the yeast Saccharomyces cerevisiae. Treatment with BLM causes a dose-dependent increase in the frequency of mitotic gene conversion and gene mutations. Unlike its potentiation of BLM in Go lymphocytes, WR-1065 protected against the recombinagenicity of BLM in yeast. CSM was also strongly-antirecombinagenic under, some conditions, but the nature of the interaction depended strongly on the treatment conditions. Under hypoxic conditions, cysteamine protected against BLM, but under oxygen-rich conditions CSM potentiated the genetic activity of BLM. The protective effect of aminothiols against BLM may be ascribed to the depletion of oxygen required for the activation of BLM and the processing of BLM-induced damage. Aminothiols may potentiate the effect of BLM by acting as an electron source for the activation of BLM and/or by causing conformational alterations that make DNA more accessible to BLM. The results indicate that aminothiols have a strong modulating influence on the genotoxicity of BLM in yeast as they do in other genetic assays. Moreover, the modulation differs markedly depending on physiological conditions. Thus, yeast assays help to explain why aminothiols have been observed to potentiate BLM in some genetic systems and to protect against it in others.
Asunto(s)
Bleomicina/farmacología , Cisteamina/farmacología , Conversión Génica/efectos de los fármacos , Mercaptoetilaminas/farmacología , Saccharomyces cerevisiae/genética , Alelos , Antibióticos Antineoplásicos/farmacología , Bleomicina/metabolismo , Cisteamina/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulación Fúngica de la Expresión Génica/genética , Mercaptoetilaminas/metabolismo , Mitosis , Mutagénesis/genética , Oxígeno/farmacología , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/metabolismoRESUMEN
The aminothiol cysteamine enhances the induction of micronuclei by bleomycin in G0 human lymphocytes. The potentiation of bleomycin (12.5, 25, 50, or 100 micrograms/ml) increased with cysteamine concentration from 5 to 20 mM in a 2-h treatment before culturing the cells for the cytokinesis-block assay. The maximum clastogenic activity of bleomycin in the presence of cysteamine was more than 10-fold greater than that of the same dosage of bleomycin alone. Both the thiol and amine functions of aminothiols seem to contribute to the potentiation of bleomycin.
Asunto(s)
Bleomicina/metabolismo , Cisteamina/farmacología , Linfocitos/efectos de los fármacos , Adulto , Células Cultivadas , Cromosomas Humanos/efectos de los fármacos , Sinergismo Farmacológico , Humanos , Masculino , Pruebas de MicronúcleosRESUMEN
The advent of chromosome painting has brought the realization that structural aberrations can be far more complicated than previously imagined. Various investigators have devised their own nomenclature systems to deal with this difficulty, with the result that the terminology has become inconsistent and confusing. Recently, an international group of cytogeneticists experienced in chromosome painting gathered to address this issue. Results of the meeting are presented in this report, which provides a nomenclature system capable of describing chromosome aberrations that occur between painted and unpainted chromosomes, as well as aberrations involving only painted chromosomes. The nomenclature is flexible enough to describe accurately even the extensively rearranged chromosomes. As a consequence of this flexibility, the scheme upon which the nomenclature is based differs substantially from other systems of aberration classification. We call this system the Protocol for Aberration Identification and Nomenclature Terminology (PAINT).
Asunto(s)
Aberraciones Cromosómicas , Hibridación Fluorescente in Situ/métodos , Sondas de ADN , Reordenamiento Génico/genética , Humanos , Translocación GenéticaRESUMEN
Excess leukemias have occurred after partial-body radiotherapy for cervical cancer and benign gynecological disease (BGD). However, the level of risk is nearly the same in both groups, about twofold, despite a tenfold difference in average dose to active bone marrow (8 Gy vs 0.7 Gy, respectively). High-dose cell killing has been postulated as one explanation for this apparent inconsistency. To examine whether chromosome aberration rates observed in lymphocytes many years after exposure might serve as population markers of cancer risk, blood samples were taken from 60 women treated for BGD (34 with radiation) and cytogenetic data compared with previous results from 96 women irradiated for cervical cancer. Remarkably, the rate of stable aberrations, which reflects nonlethal damage in surviving stem cells, was only slightly higher among the cancer patients. Thus the lower-dose regimens to treat benign disorders resulted in much higher aberration yields per unit dose than those for cervical cancer. Assuming that the fraction of cytogenetically aberrant stem cells that survive radiotherapy contributes to the leukemogenic process, these data are then consistent with the epidemiological observations of comparable overall leukemia risks seen in these two irradiated populations. Accordingly, for patient populations given partial-body radiotherapy, stable aberrations at a long time after exposure appear to serve as biomarkers of effective risk rather than as biomarkers of radiation dose received.
Asunto(s)
Aberraciones Cromosómicas , Leucemia Inducida por Radiación/epidemiología , Linfocitos/efectos de la radiación , Neoplasias Inducidas por Radiación/epidemiología , Radioterapia/efectos adversos , Neoplasias del Cuello Uterino/radioterapia , Enfermedades Uterinas/radioterapia , Anciano , Anciano de 80 o más Años , Médula Ósea/efectos de la radiación , Células Cultivadas , Femenino , Estudios de Seguimiento , Humanos , Leucemia Inducida por Radiación/etiología , Neoplasias Inducidas por Radiación/etiología , Valores de Referencia , Factores de Riesgo , Factores de TiempoRESUMEN
The aminothiol radioprotector WR-1065 potentiates the induction of chromosome aberrations and micronuclei by the chemotherapy drug bleomycin in G(0) human lymphocytes. Potentiation by 5 mM WR-1065 was observed at bleomycin concentrations from 0.1 to 100 micrograms/ml in a 2-h treatment. The frequencies of micronuclei induced by bleomycin in the presence of WR-1065 reached that of 500-fold higher concentrations of bleomycin alone. The potential therapeutic implications of these findings are discussed.
Asunto(s)
Bleomicina/toxicidad , Daño del ADN , Mercaptoetilaminas/toxicidad , Protectores contra Radiación/toxicidad , Adulto , Células Cultivadas , Aberraciones Cromosómicas , Sinergismo Farmacológico , Humanos , Interfase , Linfocitos/citología , Linfocitos/efectos de los fármacos , Masculino , Pruebas de MicronúcleosRESUMEN
Radiation-induced chromosome aberrations were used as biomarkers to compare G0, mid-G1, and methotrexate (MTX)-arrested lymphocytes. The ratio of chromosome-type to chromatid-type aberrations in MTX-arrested cells was consistent with that predicted when postreplicative chromosomes are exposed to ionizing radiation and supports the premise that MTX arrests cells in late S/G2 of the cell cycle.
Asunto(s)
Ciclo Celular/efectos de los fármacos , Cromosomas/efectos de la radiación , Metotrexato/farmacología , Células Cultivadas , Aberraciones Cromosómicas , Cromosomas/efectos de los fármacos , Humanos , Linfocitos/efectos de los fármacos , Linfocitos/efectos de la radiaciónAsunto(s)
Bleomicina/toxicidad , Mercaptoetilaminas/farmacología , Mutágenos/toxicidad , Mutación/efectos de los fármacos , Protectores contra Radiación/farmacología , Aberraciones Cromosómicas , Sinergismo Farmacológico , Transferencia de Energía , Humanos , Mercaptoetilaminas/toxicidad , Pruebas de Micronúcleos , Protectores contra Radiación/toxicidadRESUMEN
The cytokinesis-block micronucleus assay was used to investigate the induction of chromosomal damage by bleomycin in G0 human lymphocytes. A dose-dependent increase in the frequency of micronuclei was observed in binucleate cells, and the frequency approached 0.5 micronuclei per cell at the highest dosage tested. The distribution of micronuclei among cells was overdispersed, rather than fitting a Poisson distribution. Even at the highest dosage, more than two-thirds of the cells did not contain micronuclei, while some cells were highly damaged, containing more than 4 micronuclei per cell.
Asunto(s)
Bleomicina/toxicidad , Linfocitos/efectos de los fármacos , Pruebas de Micronúcleos , Fase de Descanso del Ciclo Celular , Adulto , Relación Dosis-Respuesta a Droga , Humanos , Linfocitos/citología , Masculino , Distribución de Poisson , Reproducibilidad de los ResultadosRESUMEN
Dimethylsulfoxide (DMSO) and WR-1065 are radioprotectors, in that they reduce the effectiveness with which ionizing radiation causes genetic damage. Unlike their protective effects with radiation, these agents potentiate the induction of micronuclei by bleomycin in the cytokinesis-block assay in G0 human lymphocytes. High concentrations of DMSO (1 M) are required to cause potentiation. In contrast, WR-1065 causes dose-dependent potentiation at relatively low concentrations (1.25 to 10 mM). Cytogenetic analysis supports the results from the micronucleus assay, showing higher levels of genetic damage induced by the combination of bleomycin with DMSO or WR-1065 than by bleomycin alone. Possible mechanisms of potentiation are proposed.