Incomplete chromosome exchanges are not fingerprints of high LET neutrons.
ABSTRACT A new fluorescence in situ hybridisation (FISH) technique combining whole chromosome specific DNA libraries with pan-centromeric DNA and telomeric PNA probes was introduced to investigate the induction of chromosome exchanges in human lymphocytes after exposure to low (4 Gy X rays) and high (1 Gy neutrons) linear energy transfer radiation. This combination of probes allowed accurate detection of exchange aberrations involving the painted chromosomes and an unambiguous discrimination between complete and incomplete exchanges, as well as terminal and interstitial deletions. Data obtained in the present study using combined FISH assay with telomeres detection showed no differences between two types of radiation regarding the induction of incomplete exchanges.
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ABSTRACT: Fluorescence in situ hybridization (FISH) with a telomeric peptide nucleic acid (PNA) probe was employed to analyze the induction of incomplete chromosome elements (ICE, i.e., unjoined or "open" chromosome elements with telomeric signal at only one end) and excess acentric fragments (i.e., in excess of fragments resulting from the formation of dicentric and ring chromosomes) by the methylating agent streptozotocin (STZ) in a Chinese hamster embryo (CHE) cell line. CHE cells were treated with 0-4 mM STZ and chromosomal aberrations were analyzed in the first mitosis after treatment using the telomeric probe. Centric (incomplete chromosomes) and acentric (terminal fragments) ICE were the only unstable chromosome-type aberrations induced by STZ in CHE cells. The induction of these aberrations exhibited a curvilinear concentration-response relationship. About 40% of the metaphases present in cell cultures treated with STZ contained one or more pairs of ICE. In STZ-treated cells, ICE were always observed as pairs consisting of an incomplete chromosome and a terminal fragment. Moreover, all of the excess acentric fragments induced by STZ were of terminal type. These results indicate that chromosomal incompleteness is a very common event following exposure to STZ and suggest that all of the excess acentric fragments induced by STZ originate from terminal deletions.Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 04/2005; 570(2):237-44. DOI:10.1016/j.mrfmmm.2004.11.008 · 4.44 Impact Factor
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ABSTRACT: Low energy neutrons (< 1 MeV) are known to induce complex chromosome aberrations due to their high radiobiological effectiveness (RBE). These complex chromosome aberrations normally escape detection by conventional giemsa staining methods. Data on the RBE of low energy neutrons is required in order to estimate risks, provide protection measures for nuclear workers, air and space crew personnel and also assign realistic dose estimates among survivors of the atomic bombings at Hiroshima and Nagasaki. In the present study, lymphocytes from five healthy donors were irradiated in vitro with mono-energetic neutrons of energies 2.3, 1.0, 0.79, 0.57, 0.37 and 0.186 MeV, using the Hiroshima University Radiobiological Accelerator (HIRRAC). Cultures were stimulated and cells arrested at metaphase were hybridised with FISH probes and analysed for chromosome aberrations. Many metaphase spreads were found to contain complex chromosomal rearrangements involving 3 or more breaks in 2 or more chromosomes. A wide variety of aberrations including dicentrics, simple translocations, centric and acentric rings, insertions and chromatid type aberrations were observed. A significant number of acentric fragments were indicative of a greater failure to repair chromosomal damage induced by neutrons. Analysis of the various types of aberrations indicate that insertions appear to be produced in significant numbers by neutrons and can be used to determine the neutron energy of maximum LET. Observations made in the present study suggest that the I ratio (ratio of translocation to insertions) is a potential fingerprint for determining the RBE of low energy neurons and other high LET radiations. The present study also indicates that neutrons induce sister chromatid fusions in lymphocytes irradiated in G0 state.
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ABSTRACT: We investigated the induction of incomplete chromosome elements (ICEs; i.e., elements with a telomeric signal at only one terminal end) and interstitial fragments induced by the antibiotic streptonigrin (SN) in a Chinese hamster embryo (CHE) cell line using FISH with a telomeric peptide nucleic acid probe. CHE cells were treated with 0-250 ng/ml SN and chromosomal aberrations were analyzed in the first mitosis after treatment using the telomeric probe. Exposure of CHE cells to SN resulted in a linear concentration-related increase in all of the aberration types analyzed (P < 0.05) except ring chromosomes. Depending on the SN concentration employed, 33-68% of the metaphases contained one or more pairs of ICEs (an incomplete chromosome accompanied by a terminal fragment or two incomplete chromosomes accompanied by a compound fragment). Pooled data from all SN concentrations revealed that 77.8% of the acentric fragments were terminal fragments, 18.8% interstitial fragments, and 3.4% compound fragments. Furthermore, it was estimated that about 80% of excess acentric fragments induced by SN originated from incomplete exchanges or terminal deletions and 20% from complete exchanges (interstitial deletions). These results show that incomplete chromosomes and terminal fragments are the most frequent asymmetrical chromosomal aberrations induced by SN and indicate that true incompleteness is a very common event following exposure to SN.Environmental and Molecular Mutagenesis 01/2004; 44(4):277-82. DOI:10.1002/em.20051 · 2.55 Impact Factor