RESUMO
Space radiation and microgravity (µG) are two major environmental stressors for humans in space travel. One of the fundamental questions in space biology research is whether the combined effects of µG and exposure to cosmic radiation are interactive. While studies addressing this question have been carried out for half a century in space or using simulated µG on the ground, the reported results are ambiguous. For the assessment and management of human health risks in future Moon and Mars missions, it is necessary to obtain more basic data on the molecular and cellular responses to the combined effects of radiation and µG. Recently we incorporated a µGâ»irradiation system consisting of a 3D clinostat synchronized to a carbon-ion or X-ray irradiation system. Our new experimental setup allows us to avoid stopping clinostat rotation during irradiation, which was required in all other previous experiments. Using this system, human fibroblasts were exposed to X-rays or carbon ions under the simulated µG condition, and chromosomes were collected with the premature chromosome condensation method in the first mitosis. Chromosome aberrations (CA) were quantified by the 3-color fluorescent in situ hybridization (FISH) method. Cells exposed to irradiation under the simulated µG condition showed a higher frequency of both simple and complex types of CA compared to cells irradiated under the static condition by either X-rays or carbon ions.
Assuntos
Radioisótopos de Carbono/efeitos adversos , Aberrações Cromossômicas/efeitos da radiação , Fibroblastos/efeitos da radiação , Simulação de Ausência de Peso/efeitos adversos , Raios X/efeitos adversos , Sobrevivência Celular/efeitos da radiação , Células Cultivadas , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 2/efeitos da radiação , Cromossomos Humanos Par 4/efeitos da radiação , Pontos de Checagem da Fase G2 do Ciclo Celular/efeitos da radiação , Humanos , Hibridização in Situ FluorescenteRESUMO
Chromosomal translocations arise from misrejoining of DNA double strand breaks (DSBs) between loci located on two chromosomes. One current model suggests that spatial proximity of potential chromosomal translocation partners influences translocation probability. Ionizing radiation (IR) is a potent inducer of translocations. Accumulating evidence demonstrates that particle irradiation more frequently causes translocations compared with X-ray irradiation. This observation has led to the hypothesis that the high frequency of translocations after particle irradiation may be due to the formation of DSBs at chromosome boundaries along the particle track, because such DSBs can be misrejoined between distinct chromosomes. In this study, we simultaneously visualized the site of IR-induced DSBs and chromosome position by combining Immunofluorescence and fluorescence in situ hybridization. Importantly, the frequency of γH2AX foci at the chromosome boundary of chromosome 1 after carbon-ion irradiation was >4-fold higher than that after X-ray irradiation. This observation is consistent with the idea that particle irradiation generates DSBs at the boundaries of two chromosomes along the track. Further, we showed that resolution of γH2AX foci at chromosome boundaries is prevented by inhibition of DNA-PKcs activity, indicating that the DSB repair is NHEJ-dependent. Finally, we found that γH2AX foci at chromosome boundaries after carbon-ion irradiation contain DSBs undergoing DNA-end resection, which promotes repair utilizing microhomology mediated end-joining during translocation. Taken together, our study suggests that the frequency of DSB formation at chromosome boundaries is associated with the incidence of chromosomal translocations, supporting the notion that the spatial proximity between breaks is an important factor in translocation formation. © 2016 Wiley Periodicals, Inc.
Assuntos
Quebras de DNA de Cadeia Dupla/efeitos da radiação , Reparo do DNA por Junção de Extremidades/efeitos da radiação , Histonas/genética , Translocação Genética/efeitos da radiação , Radioisótopos de Carbono , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Dano ao DNA/efeitos da radiação , Reparo do DNA/efeitos da radiação , Fibroblastos/efeitos da radiação , Humanos , Hibridização in Situ Fluorescente , Radiação Ionizante , Raios XRESUMO
High-resolution multicolour banding FISH (mBAND) and multiplex FISH (mFISH) were used to analyse the aberrations of chromosome 1 in irradiated-AG01522 human primary fibroblasts. The cells were exposed to 1Gy of a panel of radiation of different qualities, such as X-rays, low-energy protons (28keV/µm), helium-ions (62keV/µm) and carbon-ions (96 and 252keV/µm). mBAND and mFISH analysis in calyculin-A G2-condensed chromosome spreads allowed us to detect intra- and interchromosome aberrations involving chromosome 1, including simple and complex-type exchanges, inversions (both para- and pericentric ones), deletions and rings. The data indicate that the induction of chromosomal exchanges was influenced by both Linear energy transfer (LET) and particle types. Moreover, the complex-to-simple exchanges ratio (C-ratio) and interchromosome to intrachromosome exchanges ratio (F-ratio) were evaluated by mFISH and mBAND techniques, respectively. Our results indicate that the C-ratio is a more reliable marker of radiation quality, with values that increased linearly in an LET-dependent manner. In addition, by means of mBAND analysis, the distribution of radiation-induced breakpoints along chromosome 1 was analyzed and compared with the expected distributions of the breaks. The expected values were calculated assuming a random distribution of the breakpoints. The data indicate that, irrespective of the radiation that was used, the breakpoints were non-randomly distributed along chromosome 1. In particular, breaks in the pericentromeric region were encountered at a higher frequency than expected. A deeper analysis revealed that breaks were not located in the constitutive heterochromatin (G-bands 1p11/1q11 and 1q12), but rather in a region comprised between 1p11.2 and 1p22.1, which includes G-light and G-dark bands.
Assuntos
Aberrações Cromossômicas , Bandeamento Cromossômico/métodos , Pontos de Quebra do Cromossomo , Cromossomos Humanos Par 1/efeitos da radiação , Fibroblastos/efeitos da radiação , Hibridização in Situ Fluorescente/métodos , Carbono , Linhagem Celular , Cromossomos Humanos Par 1/genética , Íons Pesados , Hélio , Humanos , Transferência Linear de Energia , Prótons , Raios XRESUMO
PURPOSE: This paper briefly summarizes the research on increased radiosensitivity in breast cancer patients measured by the micronucleus test (MNT) and its association to genetic variants in DNA repair genes. More preliminary data are presented on the distribution of chromosomes and chromosome fragments in micronuclei (MN) in order to gain more information on clastogenic and aneugenic effects and better understand the phenotype of increased radiosensitivity. MATERIAL AND METHODS: Reports of relevant studies obtained from a search of PubMed and studies referenced in those reports were reviewed. In four patients with high MN frequency (three cancer patients, one control) and four probands with low MN frequency, the presence of chromosome fragments or whole chromosomes in MN was determined by fluorescence in situ hybridization analysis for chromosomes 1, 7, and 17. RESULTS: An increased MN frequency in breast cancer patients compared to controls has consistently been reported with high significance. Higher MN frequencies were observed in 20-50% of breast cancer patients. Chromosomal fragments of chromosome 17, but not of chromosomes 1 and 7 were more frequent in the probands with high MN frequency than in those with low frequency (p = 0.045). CONCLUSION: The MNT detects a cellular phenotype common to a portion of sporadic breast cancer patients. This phenotype is very likely to be genetically determined. For the genetic dissection of breast cancer susceptibility this phenotype may turn out to be more efficient than breast cancer itself. Additional parameters which can be measured simultaneously with the MN frequency may be able to further enhance its usefulness.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/radioterapia , Reparo do DNA/genética , Predisposição Genética para Doença/genética , Testes para Micronúcleos , Tolerância a Radiação/genética , Aneuploidia , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 17/genética , Cromossomos Humanos Par 17/efeitos da radiação , Cromossomos Humanos Par 7/genética , Cromossomos Humanos Par 7/efeitos da radiação , Análise Mutacional de DNA , Feminino , Variação Genética/genética , Humanos , Hibridização in Situ Fluorescente , FenótipoRESUMO
BACKGROUND: WHO grade II gliomas are often approached by radiation therapy (RT). However, little is known about tumor response and its potential impact on long-term survival. PATIENTS AND METHODS: Patients subjected to RT were selected from the own database of WHO grade II gliomas diagnosed between 1991 and 2000. The volumetric tumor response after RT was assessed based on magnetic resonance imaging and graded according to standard criteria as complete, partial (PR, >or= 50%), or minor (MR, 25% to <50%). RESULTS: There were 24 astrocytomas and three oligoastrocytomas. 21 patients (78%) were dead at follow-up (mean survival 74 months). None of the patients had chemotherapy. Objective response occurred in 14 patients (52%, five PR and nine MR) but was not associated with overall survival. The vast majority of the tumors had no loss of heterozygosity (LOH) 1p and/or 19q (86%). CONCLUSION: Approximately 50% of patients with astrocytic WHO grade II gliomas respond to RT despite the absence of LOH for 1p/19q. The potential predictive factors for response and the impact of response on overall survival remain unclear.
Assuntos
Astrocitoma/genética , Astrocitoma/radioterapia , Cromossomos Humanos Par 19/efeitos da radiação , Cromossomos Humanos Par 1/efeitos da radiação , Irradiação Craniana , Perda de Heterozigosidade/efeitos da radiação , Neoplasias Supratentoriais/genética , Neoplasias Supratentoriais/radioterapia , Sobreviventes , Adulto , Idoso , Astrocitoma/mortalidade , Astrocitoma/patologia , Feminino , Seguimentos , Humanos , Estimativa de Kaplan-Meier , Imageamento por Ressonância Magnética , Masculino , Repetições de Microssatélites , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Dosagem Radioterapêutica , Estudos Retrospectivos , Neoplasias Supratentoriais/mortalidade , Neoplasias Supratentoriais/patologia , Análise de SobrevidaRESUMO
In interphase, chromosomes occupy defined nuclear volumes known as chromosome territories. To probe the biological consequences of the described nonrandom spatial positioning of chromosome territories in human lymphocytes, we performed an extensive FISH-based analysis of ionizing radiation-induced interchanges involving chromosomes 1, 4, 18 and 19. Since the probability of exchange formation depends strongly on the spatial distance between the damage sites in the genome, a preferential formation of exchanges between proximally positioned chromosomes is expected. Here we show that the spectrum of interchanges deviates significantly from one expected based on random chromosome positioning. Moreover, the observed exchange interactions between specific chromosome pairs as well as the interactions between homologous chromosomes are consistent with the proposed gene density-related radial distribution of chromosome territories. The differences between expected and observed exchange frequencies are more pronounced after exposure to densely ionizing neutrons than after exposure to sparsely ionizing X rays. These experiments demonstrate that the spatial positioning of interphase chromosomes affects the spectrum of chromosome rearrangements.
Assuntos
Aberrações Cromossômicas/efeitos da radiação , Posicionamento Cromossômico/fisiologia , Células Cultivadas , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 18/genética , Cromossomos Humanos Par 18/efeitos da radiação , Cromossomos Humanos Par 19/genética , Cromossomos Humanos Par 19/efeitos da radiação , Cromossomos Humanos Par 4/genética , Cromossomos Humanos Par 4/efeitos da radiação , Humanos , Interfase/efeitos da radiação , Linfócitos/metabolismo , Linfócitos/efeitos da radiaçãoRESUMO
For a retrospective dose estimation of human exposure to ionising radiation, a partial genome analysis is routinely used to quantify radiation-induced chromosome aberrations. For this purpose, fluorescence in situ hybridisation (FISH) with whole chromosome painting probes for selected chromosomes is usually applied covering about 20% of the whole genome. Since genome-wide screening techniques like spectral karyotyping (SKY) and multiplex FISH (mFISH) have been developed the detection of radiation-induced aberrations within the whole genome has now become feasible. To determine the correspondence between partial and whole genome analysis of radiation-induced chromosome aberrations, they were measured comprehensively in this study using in vitro irradiated blood samples from three donors. We were able to demonstrate that comparable results can be detected with both approaches. However, complex aberrations might be misinterpreted by partial genome analysis. We therefore conclude that whole genome analysis by SKY is useful especially in the high dose range to correct aberration data for complex exchange aberrations.
Assuntos
Aberrações Cromossômicas/efeitos da radiação , Genoma Humano/efeitos da radiação , Hibridização in Situ Fluorescente , Cariotipagem Espectral , Raios X , Adulto , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 12/efeitos da radiação , Cromossomos Humanos Par 4/efeitos da radiação , Feminino , Humanos , Linfócitos/efeitos da radiação , Masculino , MatemáticaRESUMO
PURPOSE: To study chromosomal abnormalities in 49 patients with Hodgkin's lymphoma (HL), before and after treatment and at several times during a 2-year period. METHODS AND MATERIALS: Simple chromosomal aberrations (CAs) and complex chromosomal rearrangements (CCRs) were counted in peripheral lymphocytes by painting of chromosomes 1, 3, and 4 (fluorescence in situ hybridization). A control population was composed of 20 healthy donors and 69 untreated cancer patients who had undergone various radiologic scans. RESULTS: A greater frequency (p < 10(-4)) of spontaneous cytogenetic abnormalities was observed in untreated HL patients compared with the control populations. CCRs were observed exclusively in the HL population (p < 10(-4)). Chemotherapy was associated with a significant increase in the frequency of CAs (p < 10(-4)), according to the chemotherapy regimen (p = 0.002). Immediately after radiotherapy, a significant increase (p < 10(-4)) was observed in CAs according to the size of the irradiation field. Conversely, the significant increases in the frequency of CCRs observed after treatment did not correlate with the chemotherapy regimens, radiotherapy dose, or size of the irradiation field. The evolution of CAs vs. CCRs over time was also dissociated: during the follow-up of these patients, a significant decrease was observed in the frequency of CAs at 6 months and 1 and 2 years. In contrast, after an initial decrease for up to 6 months after treatment, the frequency of CCRs remained constant for up to 2 years. CONCLUSION: Increased cytogenetic abnormalities were observed in untreated HL patients compared with the control populations. The greater frequency of cytogenetic abnormalities persisted in some patients. The presence of CCRs supports the concept of a unique genetic environment in HL patients that persists in response to potentially noxious treatments.
Assuntos
Aberrações Cromossômicas , Coloração Cromossômica , Doença de Hodgkin/genética , Doença de Hodgkin/radioterapia , Linfócitos/efeitos da radiação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Estudos de Casos e Controles , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 3/genética , Cromossomos Humanos Par 3/efeitos da radiação , Cromossomos Humanos Par 4/genética , Cromossomos Humanos Par 4/efeitos da radiação , Feminino , Doença de Hodgkin/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-Idade , Estatísticas não ParamétricasRESUMO
The purpose of this study was to assess the cytogenetic effects of the X ray irradiation used during a CT scan in order to estimate the mean absorbed dose in circulating lymphocytes. Chromosomal aberrations were scored in blood lymphocytes of ten patients undergoing CT scans, by applying fluorescence in situ hybridisation (FISH) to metaphase cells and premature chromosome condensation (PCC) with chromosomes 1, 3 and 4 painting probes immediately after exposure. This generated a dosimetric index that reflects the dose to the circulating lymphocytes. By using PCC a significant increase in the frequency of chromosomal fragment was observed immediately after a CT scan. However, no significant increase in chromosomal aberration was detected in metaphase cells. The mean dosimetric index immediately after exposure was 0.057 Gy (95% CI: 0.052-0.082 Gy). This dosimetric index depends essentially on the size of the examined and exposed blood volumes. This dose is in close agreement with the dose length product (DLP) (Gy cm) (R = 0.80). It should be kept in mind when justifying requests for diagnostic CT scan especially in young patients. The presence of chromosomal fragments after a CT scan indicated the cytogenetic effect of a low dose. PCC associated with chromosome painting is a method for detecting the cytogenetic effect of a low dose immediately after exposure.
Assuntos
Aberrações Cromossômicas , Coloração Cromossômica , Cromossomos Humanos/efeitos da radiação , Linfócitos/efeitos da radiação , Tomografia Computadorizada por Raios X/efeitos adversos , Adulto , Animais , Sangue/efeitos da radiação , Células CHO/efeitos da radiação , Carcinoma/diagnóstico por imagem , Quebra Cromossômica , Cromossomos/efeitos da radiação , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 1/ultraestrutura , Cromossomos Humanos Par 3/efeitos da radiação , Cromossomos Humanos Par 3/ultraestrutura , Cromossomos Humanos Par 4/efeitos da radiação , Cromossomos Humanos Par 4/ultraestrutura , Cricetinae , Cricetulus , Relação Dose-Resposta à Radiação , Feminino , Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Humanos , Interfase , Linfócitos/ultraestrutura , Masculino , Metáfase , Pessoa de Meia-Idade , Mitose/efeitos da radiação , Imagens de Fantasmas , Radiometria/instrumentação , Neoplasias da Glândula Tireoide/diagnóstico por imagem , Translocação Genética , Neoplasias Urológicas/diagnóstico por imagemRESUMO
The most important stage in the making of mutations is a reparation of different DNA damage, including the more deleterious double-strand DNA breaks (DSB). The first stage of adaptive response--fundamental antimutagenic cell reaction, purposeful to reparation for induced DSB repair--is investigated in present work. Non-radioactive in situ hybridization of biotin-labeled DNA probe was used to mark chromosome 1 pericentromeric regions (PR) in G0 human lymphocytes. It was shown that under 3-10 cGy (X-radiation, 160 kV) PR become displaced from a nucleus periphery to inner territory of a nucleus. The moving process realizes during several hours after an irradiation. As far as some non-specific gene repressors are co-localized with chromosome centromeric regions it is possible hypothesizes that the displacement cause changing expression of some genes. It is possible to propose that an absence of radiation induced chromosome locus displacement may be one of causes DSB repair disturbance. This hypothesis was tested by the model. It is assumed that one consequence of the underlying defect may be inappropriate involvement of cell's recombination machinery in the repair of DSB. We studied lymphocytes of patients with hereditary BRCA2 mutation. It is thought that this gene takes part in DSB repair. The significant differences of the PR moving between control samples and the cases were revealed under 10 cGy. Similar results were observed on lymphocytes of patients with Fanconi syndrome. Thus, abnormal moving of interphase nucleus chromosomes conditioned by low-dose irradiation may suggest on imperfect machinery of DSB repair, i.e. genetic risk. We realize that further investigations are needed for definitive conclusion.
Assuntos
Cromossomos Humanos Par 1/efeitos da radiação , Interfase/efeitos da radiação , Dano ao DNA , Reparo do DNA , Relação Dose-Resposta à Radiação , Humanos , Hibridização In Situ , Linfócitos/efeitos da radiação , Linfócitos/ultraestruturaRESUMO
PURPOSE: To study the impact of radiation quality on the spectrum of chromosome exchange aberrations in human lymphocytes using chromosome arm-specific and telomeric probes. The analysis is focused on: (1) incomplete exchanges, (2) interstitial fragments, (3) interarm intrachanges and (4) the complexity of the aberration patterns. The present data after neutron exposure are compared with previously obtained data after X-irradiation. MATERIALS AND METHODS: Isolated human lymphocytes from three donors were irradiated with 1 MeV fast neutrons (0.25, 0.5, 1.0, 1.5, 2.0 Gy). Analysis was performed on first post-irradiation metaphases with arm-specific probes for chromosome 1 in combination with a pan-centromeric probe, or with telomeric and centromeric PNA probes. RESULTS: In comparison with X-rays, exposure to neutrons leads to: (1) similar frequencies of incomplete exchanges or terminal deletions, (2) a significantly higher induction of both inter- and intraarm intrachanges, (3) a higher proportion of complex aberrations, and (4) aberrations with a higher degree of complexity, i.e. derived from more chromosome breaks which interact more frequently in a non-reciprocal fashion. Essentially no dose dependence was found for the yield ratios between the various types of chromosomal aberrations. CONCLUSIONS: Despite the reduced rejoining deficiency of DNA double-strand breaks induced by high-LET radiation, exposure to neutrons does not lead to enhanced levels of unrejoined chromosome breaks that can be observed as incomplete exchanges in cells that have reached mitosis. Proximity effects are more pronounced after densely ionizing radiation than after sparsely ionizing radiation. Clustered damage produced by neutron tracks results in a high proportion of complex aberrations and in non-reciprocal interactions of chromosome breaks. Most of the exchanges occur within one neutron track and little interaction seems to take place between the breaks formed in different tracks.
Assuntos
Aberrações Cromossômicas , Cromossomos Humanos/genética , Cromossomos Humanos/efeitos da radiação , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Dano ao DNA , Sondas de DNA , Relação Dose-Resposta à Radiação , Nêutrons Rápidos , Humanos , Hibridização in Situ Fluorescente , Técnicas In Vitro , Transferência Linear de Energia , Ácidos Nucleicos Peptídicos , Troca de Cromátide Irmã/efeitos da radiação , Telômero/genética , Telômero/efeitos da radiação , Raios XRESUMO
G0 human lymphocytes were exposed in vitro to plutonium-239 alpha-particles, with doses ranging from 0 to 1.62 Gy, to provide a dose response curve and to compare complex rearrangements produced by high LET radiation with low LET data from previous work. Metaphase chromosomes 1 and 2 were painted using fluorescence in situ hybridization (FISH) whole chromosome probes. All unstable and stable aberrations involving the painted chromosomes were scored. The whole genome corrected alpha-coefficient for dicentrics was 0.244 +/- 0.023 and for total translocations 0.346 +/- 0.032, when considering simple and complex exchanges. The ratio of bicoloured total translocations to bicoloured dicentrics was 1.21 +/- 0.15 and the ratio of 2-way to 1-way translocations was 1.73 +/- 0.27 for apparently simple exchanges only. A correlation was noted between the distributions of dicentrics and translocations and this applied even when the complex rearrangements were removed. 20% of the observed rearrangements were complex and this observation was independent of dose. Qualitatively, following irradiation with alpha-particles the complex rearrangements observed were of a greater complexity than seen after X- or gamma-rays. Using the Savage and Simpson system to classify the complex rearrangements, the higher order complexes were found to be the most common type observed. However the insertion type increased while the 2F + 2G types decreased when complex rearrangements induced by alpha-particles were compared to those formed after X- or gamma-irradiation.
Assuntos
Partículas alfa/efeitos adversos , Aberrações Cromossômicas/efeitos da radiação , Hibridização in Situ Fluorescente , Linfócitos/citologia , Linfócitos/efeitos da radiação , Plutônio/efeitos adversos , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 2/efeitos da radiação , Humanos , Masculino , Plutônio/sangue , Radiação Ionizante , Radioisótopos/efeitos adversos , Radioisótopos/sangue , Translocação Genética/efeitos da radiaçãoRESUMO
The constitutively heterochromatic 1q12 band and the primarily euchromatic 17cen-p53 region comprise a similar size in terms of percentage of the total human genome but have a completely distinguishable chromatin structure. The aim of this study is to unravel whether this structural difference has an impact on the formation and processing of radiation-induced chromosome aberrations. To do so, we have analysed the initial induction and the long-term persistence of radiation-induced (3 Gy gamma-rays) chromosomal aberrations with breakpoints in either the 1q12 band or the 17cen-p53 region in comparison with the behaviour of the overall genome. The fusigenic potential of euchromatic and heterochromatic ends was also compared. This time course experiment was performed in a human lymphoblastoid cell line with sampling times at 1, 3, 7, 14 and 56 days after irradiation. The outcome of this study, with 68 000 metaphases studied by multicolour FISH, with centromeric (1cen and 17cen), paracentric (1q12) and locus specific (p53 gene) probes, revealed: (i) a similar radiosensitivity of all regions analysed irrespective of their chromatin configuration; (ii) a possible enhanced fusigenic potential of heterochromatic chromosome ends; (iii) a rapid decline of 1q12 translocations; and (iv) a similar long-term behaviour of translocations involving 1q12 and 17cen-p53. The implications of these findings in biomonitoring studies are discussed.
Assuntos
Aberrações Cromossômicas , Cromossomos Humanos Par 17/efeitos da radiação , Cromossomos Humanos Par 1/efeitos da radiação , Eucromatina/efeitos da radiação , Heterocromatina/efeitos da radiação , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 17/genética , Dano ao DNA/efeitos da radiação , Eucromatina/genética , Heterocromatina/genética , Humanos , Hibridização in Situ Fluorescente , Fatores de Tempo , Células Tumorais CultivadasRESUMO
Werner syndrome (WS) is a rare autosomal disorder characterized by premature aging exhibiting chromosome instability and predisposition to cancer. Cells derived from WS patients show a variety of constitutionally stable chromosomal aberrations as detected by conventional chromosome banding techniques. We have employed the fluorescence in situ hybridization (FISH) technique using painting probes for 12 different chromosomes to detect stable chromosome exchanges in three WS cell lines and three control cell lines. WS cell lines showed increased frequencies of both stable and unstable chromosome aberrations detected by FISH and Giemsa staining, respectively. One WS lymphoblastoid cell line (KO375) had a 5/12 translocation in all the cells and approximately 60% of the cells had an additional translocated chromosome 12. A high frequency of aneuploid cells was found in all the WS cell lines studied. Though WS cells are known to be chromosomally unstable, unlike other chromosome instability syndromes they are not sensitive to mutagenic agents. We studied the frequencies of X-ray-induced chromosomal aberrations in two WS cell lines and found an approximately 60% increase in the frequencies of fragments and no consistent increase in the frequencies of exchanges.
Assuntos
Aberrações Cromossômicas , Cromossomos/efeitos da radiação , Cromossomos/ultraestrutura , Hibridização in Situ Fluorescente/métodos , Síndrome de Werner/genética , Linhagem Celular , Células Cultivadas , Coloração Cromossômica , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 12/efeitos da radiação , Cromossomos Humanos Par 4/efeitos da radiação , Cromossomos Humanos Par 5/efeitos da radiação , Relação Dose-Resposta à Radiação , Humanos , Microscopia de Fluorescência , Translocação Genética , Raios XRESUMO
PURPOSE: To determine the exact location of radiation-induced chromosomal breakpoints along the euchromatic or heterochromatic regions: G-light and G-dark bands, respectively. MATERIALS AND METHODS: The distribution of radiation-induced chromosomal breakpoints was scored in human lymphocytes irradiated in vitro with 3 Gy of gamma-radiation. Image analysis was applied to combine G-banded and FISH-painted images of the human chromosome 1. RESULTS: A total of 195 chromosomal breakpoints in 176 cells with structural chromosomal aberrations was used for the present analysis. Radiation-induced breakpoints were found to be distributed randomly with respect to the p or q arms of chromosome 1 and specific band or band length, but more breakpoints were mapped to G-light than to G-dark bands, the difference being statistically significant. CONCLUSIONS: The results can well be interpreted in terms of concepts of existing models of nuclear architecture, chromatin structure and transcriptional activities of the chromatin, which can influence the induction of primary chromosomal aberrations by gamma-rays. Differential repair of randomly produced primary aberrations may also explain the non-random distribution of radiation-induced breakpoints.
Assuntos
Aberrações Cromossômicas , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos/efeitos da radiação , Bandeamento Cromossômico , Quebra Cromossômica , Cromossomos/genética , Dano ao DNA/efeitos da radiação , Raios gama , Humanos , Hibridização in Situ Fluorescente , Linfócitos/efeitos da radiação , Metáfase/efeitos da radiaçãoRESUMO
Ionizing radiation is a well-known risk factor for sarcoma development. To investigate whether radiation-associated sarcomas are characterized by chromosome aberrations that distinguish them from de novo sarcomas, we identified those patients in our series of more than 500 cytogenetically abnormal sarcomas that fulfilled the following criteria: (1) each patient should have been irradiated for another malignancy at least 3 years prior to the sarcoma diagnosis, and (2) the sarcoma should have developed within the field of radiation. Ten patients fulfilling these criteria could be retrieved (median age at sarcoma diagnosis was 55 years, range 17-79; median latency period between primary tumor and radiation-associated sarcoma was 9 years, range 4-30). The diagnoses were typical for radiation-associated sarcomas: 2 each of malignant fibrous histiocytoma, leiomyosarcoma, and pleomorphic sarcoma, and 1 each of osteosarcoma, fibrosarcoma, myxofibrosarcoma, and spindle cell sarcoma. All 10 cases had relatively complex karyotypes with multiple, mostly unbalanced, structural rearrangements, similar to what has been reported in de novo sarcomas of the corresponding histologic subtypes. The only cytogenetic features that were unusually frequent among the radiation-associated sarcomas were the finding of unrelated clones in 3 cases, and loss of material from chromosome arm 3p, in particular 3p21-3pter, in 8 cases. Loss of the same chromosome segment has been described in 4 of the 8 previously published cases of radiation-associated sarcomas that have been analyzed after short-term culturing, which makes this imbalance significantly (P < 0.001) more frequent among radiation-associated sarcomas (12 of 18 cases) than among unselected cases of the corresponding histologic subtypes (74 of 282 cases). In contrast to the cytogenetic results, no 3p deletions were detected among the 6 cases of the present series that could be analyzed by comparative genomic hybridization (CGH). The most frequent imbalance detected by CGH was gain of 15cen-q15 (3 cases), followed by loss of chromosome 13 and gain of 5p, and 7cen-q22, each detected in 2 cases.
Assuntos
Aberrações Cromossômicas/genética , Cromossomos Humanos Par 3/efeitos da radiação , Neoplasias Induzidas por Radiação/genética , Sarcoma/genética , Adolescente , Adulto , Idoso , Transtornos Cromossômicos , Cromossomos Humanos Par 1/genética , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 3/genética , Feminino , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Pessoa de Meia-Idade , Hibridização de Ácido Nucleico , Cromossomo X/genética , Cromossomo X/efeitos da radiaçãoRESUMO
The aim of the present work was to examine in human lymphocytes, firstly, whether in vitro gamma-rays as compared with X-rays also induce chromatid malsegregation and at higher frequencies than chromosome loss and, secondly, whether the cytokinesis-blocked micronucleus assay combined with fluorescence in situ hybridization might be useful for the biomonitoring of individuals exposed to ionizing radiation. After irradiation, the relative frequencies of centromere-positive micronuclei decreased from 39.2% at 0.1 Gy to 21. 63% at higher doses. There was no statistically significant increase in MNCen+ frequencies at doses below 1 Gy (0.1, 0.25 and 0.5 Gy), but a statistically significant increase at 1 (P < 0.05) and 2 Gy (P < 0.001) was observed for all the donors. No significant differences in baseline and gamma-ray-induced non-disjunction frequencies for chromosomes 1 (P = 0.9) and 17 (P = 0.8) between individuals were detected. For radiation-induced non-disjunction, lower doses (0.1, 0. 25 and 0.5 Gy) of gamma-rays did not induce a statistically significant increase in non-disjunction frequencies whereas 1 Gy and above clearly induced a statistically significant increase in the total non-disjunction frequencies for all the donors (P < 0.05 at 1 Gy and P < 0.0001 at 2 Gy). The aneugenic effect of radiation is less clearly dose dependent at the lower doses, suggesting an apparent threshold below which no change could be demonstrated. At high radiation doses the major mechanism for gamma-ray-induced aneuploidy is related to chromosome loss through non-disjunction, as has been demonstrated using X-rays, and not through the formation of micronuclei.
Assuntos
Aneuploidia , Segregação de Cromossomos/efeitos da radiação , Raios gama , Linfócitos/efeitos da radiação , Adulto , Divisão Celular/fisiologia , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 17/efeitos da radiação , Citocalasina B/farmacologia , Feminino , Humanos , Hibridização in Situ Fluorescente , Técnicas In Vitro , Linfócitos/citologia , Linfócitos/ultraestrutura , Masculino , Micronúcleos com Defeito Cromossômico/efeitos da radiação , Pessoa de Meia-Idade , Não Disjunção GenéticaRESUMO
We report the results of a study of chromosome translocations in 126 Russian subjects who participated in the cleanup activities at Chernobyl and another 53 subjects, from other places in Russia, who were not exposed at Chernobyl. In agreement with our earlier study, we find increased translocation frequencies among the exposed compared to Russian controls. We describe statistical methods for estimating the dose of ionizing radiation determined by scoring chromosome translocations found in circulating lymphocytes sampled several years after exposure. Two statistical models were fitted to the data. One model assumed that translocation frequencies followed an overdispersed Poisson distribution. The second model assumed that translocation frequencies followed a negative binomial distribution. In addition, the effects of radiation exposure were modeled as additive or as multiplicative to the effects of age and smoking history. We found that the negative binomial model fit the data better than the overdispersed Poisson model. We could not distinguish between the additive and the multiplicative model with our data. Individual dose estimates ranged from 0 (for 43 subjects) to 0.56 Gy (mean 0.14 Gy) under the multiplicative model and from 0 to 0.95 Gy (mean 0.15 Gy) under the additive model. Dose estimates were similar under the two models when the number of translocations was less than 4 per 100 cells. The additive model tended to estimate larger doses when the number of translocations was greater than 4 per 100 cells. We also describe a method for estimating upper 95% tolerance bounds for numbers of translocations in unexposed individuals. We found that inclusion of data on age and smoking history was important for dose estimation. Ignoring these factors could result in gross overestimation of exposures, particularly in older subjects who smoke.
Assuntos
Exposição Ocupacional , Centrais Elétricas , Doses de Radiação , Liberação Nociva de Radioativos , Fumar , Translocação Genética/efeitos da radiação , Adulto , Fatores Etários , Idoso , Calibragem , Células Cultivadas , Distribuição de Qui-Quadrado , Cromossomos Humanos Par 1/efeitos da radiação , Cromossomos Humanos Par 2/efeitos da radiação , Cromossomos Humanos Par 4/efeitos da radiação , Relação Dose-Resposta à Radiação , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Distribuição de Poisson , Federação Russa , UcrâniaRESUMO
One of the health consequences of the Chernobyl nuclear power plant accident was a radioactive iodine-related increase in the incidence of thyroid cancer in exposed children. This radioisotope is used in the treatment of thyroid cancer and hyperthyroidism patients providing a convenient opportunity to study cytogenetic damage induced by known doses of radioactive iodine in treated patients. We used pancentromeric FISH on micronuclei and chromosome 1 tandem labelling FISH to monitor overall chromosome breakage and loss, 1q12 breakage and decondensation and chromosome 1 numerical abnormalities in buccal cells from 31 radioactive iodine-exposed hyperthyroidism and thyroid cancer patients. The overall outcome of the study, with 250,000 buccal cells analysed, is that there was no radioactive iodine-related increase in the frequency of micronuclei, 1q12 breakage, 1q12 decondensation or chromosome 1 numerical abnormalities. In addition, neither age nor gender, health status nor radioactive iodine dose modulated the frequency of the above cytogenetic end points. Although several uncertainties of these emerging molecular cytogenetic methodologies will require further experimentation, we conclude that, at the reported exposure levels, radioactive iodine did not induce detectable chromosome damage in buccal cells from treated patients.
Assuntos
Centrômero/genética , Aberrações Cromossômicas/genética , Cromossomos Humanos Par 1/efeitos da radiação , Hipertireoidismo/genética , Radioisótopos do Iodo/efeitos adversos , Micronúcleos com Defeito Cromossômico/efeitos da radiação , Neoplasias da Glândula Tireoide/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Quebra Cromossômica/genética , Transtornos Cromossômicos , Cromossomos Humanos Par 1/genética , Feminino , Humanos , Hipertireoidismo/radioterapia , Hibridização in Situ Fluorescente/métodos , Radioisótopos do Iodo/uso terapêutico , Masculino , Micronúcleos com Defeito Cromossômico/química , Pessoa de Meia-Idade , Mucosa Bucal/efeitos da radiação , Neoplasias da Glândula Tireoide/radioterapiaRESUMO
PURPOSE: To examine the distribution of radiation-induced breakpoints in chromosomes 1, 2 and 4 both in relation to their DNA content and by localization of the breaks along each chromosome. MATERIAL AND METHODS: The work consisted of two studies, one with chromosomal aberrations found in persons after accidental exposure in Estonia in 1994 and another involving aberrations seen in in vitro-irradiated lymphocytes. Localization of breakpoints in painted chromosomes involved in complete exchange-type aberrations was conducted by applying a computerized measuring system on stored image-files. RESULTS AND CONCLUSIONS: The yield of exchanges in chromosomes 1, 2 and 4 in both studies was equal to that expected from their DNA content. In contrast, the breakpoint location of complete exchanges within these chromosomes was not random. Chromosomes 1 and 4 contained more breaks in the middle parts of the p and q arms, whereas breaks were observed more uniformly along chromosome 2. Complete exchanges, however, were very rare in the terminal regions of all three chromosomes, most probably resulting from limitations in the resolution of small painted pieces.