The Induction of Micronuclei in Human Lymphocytes by<i>in Vitro</i>Irradiation with Alpha Particles from Plutonium-239

Here we compared the effectiveness of neutrons ( = 5.5 MeV) versus 60Co gamma-rays in producing micronuclei (MN) in human lymphocytes. To obtain dose-response data, blood samples of six donors were irradiated with doses ranging from 0.1 to 5 Gy for gamma-rays and 0.1-3 Gy for neutrons. A linear dependence of MN yield with dose was found for fast neutrons while for gamma-rays a nonlinear dependence existed. For both radiation qualities no significant interindividual differences were found. Derived relative biological effectiveness values decreased with increasing dose. The MN frequency distributions were overdispersed with respect to the Poisson distribution, with neutrons showing higher dispersion values than with gamma-rays. To compare the repair kinetics of both radiation qualities split-dose experiments were performed. A dose of 4 Gy gamma-rays (3 Gy neutrons) was delivered either as a single exposure or in two equal fractions separated by time intervals ranging from 30 min to 10 h (30 min to 7 h for neutrons). The data showed for gamma-rays a significant decline (30% +/- 10%) in MN yield with interfraction time due to repair of DNA damage. This repair is a continuous process starting almost immediately after the first of the two doses and lasting 3-5 h. For fast neutrons no decline was observed indicating irreparable damage.

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“…1989, Thierens et al 1991, Vral et al . 1992 and for MN exposed to high LET a particles (Bilbao et al . 1989) .…”

Section: Resultsmentioning

confidence: 98%

Micronuclei Induced by Fast Neutrons Versus⁶⁰Co γ-rays in Human Peripheral Blood Lymphocytes

Vral

Verhaegen

Thierens

et al. 1994

International Journal of Radiation Biology

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“…The quality factor for alpha radiation is assumed to be 20 in personal dosimetry, but the Relative Biological Effectiveness of alpha radiation with respect to micronucleus induction may be different. A number of studies suggest that it is in fact smaller, say around 4 (Bilbao et al 1989, Yamada et al 2002, which would mean our alpha doses could be a factor of 5 too high, and our finding of an increase of micronucleus frequency with dose would be even more surprising. On the other hand, the alpha dose to circulating lymphocytes, which should mainly stem from exposure in the tracheobronchial tract and the lungs, may be quite different from the effective dose calculated in personal dosimetry, but the exact relationship remains to be established (Harley andRobbins 2009, Little et al 2009).…”

Section: Resultsmentioning

confidence: 71%

Enhanced frequency of micronuclei in lymphocytes from current as opposed to former uranium miners

et al. 2011

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Micronuclei can be used as markers of past radiation exposure, but few pertinent studies have dealt with alpha radiation. Here we report on micronuclei in lymphocytes from uranium miners, comparing some that are currently active and others that retired 15-20 years ago. Their radiation exposure is assumed to come mainly from radon and its decay products in the air breathed at the work place. Current miners showed a greater micronucleus frequency than former miners. This can be attributed to their recent radiation exposure, while the lower frequency in the former miners probably results from the disappearance of potentially micronucleus containing lymphocytes from the peripheral blood, which is known to occur with a half-life of about one year. For current miners there is a significant correlation between micronucleus frequency and effective dose received over the last 12 months. The dose at which a doubling of the micronucleus frequency is observed is around 10 mSv. This is a much smaller dose than would usually be expected to be detectable with this test, and raises a number of questions about the induction of micronuclei by alpha radiation from radon and its decay products.

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“…Thus, the beta term obtained from fitting MN data to the linearquadratic model is significantly lower than those obtained for dicentrics. Two, not mutually exclusive, hypotheses could explain such an observation: that two or more aberrations in a cell might coalesce to produce fewer MN [43] or that with increasing radiation doses, the likelihood that MN could be included in one of the main daughter nuclei increases [44]. Uncertainty remains as to what objects become micronuclei after high-LET irradiation.…”

Section: Discussionmentioning

confidence: 99%

Chromosome aberrations, micronuclei, and activity of superoxide dismutases in human lymphocytes after irradiation in vitro

Joksić¹,

Pajović²,

Stanković³

et al. 2000

Cellular and Molecular Life Sciences (CMLS)

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The goal of this study was to provide data on the dose-dependent production of dicentrics and micronuclei in human lymphocytes irradiated with 22.6 MeV protons and to estimate the possible contribution of intracellular superoxide dismutases (SOD) to the relative biological effectiveness (RBE) of protons. For the dose-response study, heparinized whole blood of a healthy volunteer was irradiated with protons and X-rays employing radiation doses of 0.5-4 Gy. Three biological endpoints were analyzed: chromosomal aberrations, micronuclei, and specific activity of cytosolic (CuZnSOD) and mitochondrial (MnSOD) superoxide dismutases in harvested human blood cells. Dicentric dose-response curves fit a linear-quadratic form (alpha = 0.094 +/- 0.006, beta = 0.032 +/- 0.001) induced with X-rays and (alpha = 0.119 +/- 0.057, beta = 0.029 +/- 0.014) for 22.6 MeV protons. Protons were more effective than X-rays in producing exchanges, particularly at 0.5 and 1 Gy. In contrast to X-ray irradiated samples where a significant increase in the specific activity of MnSOD was recorded (up to a radiation dose of 1 Gy), irradiation with protons markedly reduced its activity. As a consequence of the reduced activity of MnSOD, the chromosomal dose-response curve became quadratic. The RBE for dicentrics varies with dose (from 2.2 to 1.01) and reduced activity of MnSOD is an important contributor to the RBE of protons. SODs, particularly MnSOD, play an important role in defending DNA from reactive oxygen species. A reduced activity of SOD, particularly MnSOD, is an important contributor to the RBE of protons.

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The Induction of Micronuclei in Human Lymphocytes byin VitroIrradiation with Alpha Particles from Plutonium-239

Cited by 29 publications

References 11 publications

Micronuclei Induced by Fast Neutrons Versus⁶⁰Co γ-rays in Human Peripheral Blood Lymphocytes

Micronuclei Induced by Fast Neutrons Versus⁶⁰Co γ-rays in Human Peripheral Blood Lymphocytes

Enhanced frequency of micronuclei in lymphocytes from current as opposed to former uranium miners

Chromosome aberrations, micronuclei, and activity of superoxide dismutases in human lymphocytes after irradiation in vitro

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The Induction of Micronuclei in Human Lymphocytes byin VitroIrradiation with Alpha Particles from Plutonium-239

Cited by 29 publications

References 11 publications

Micronuclei Induced by Fast Neutrons Versus60Co γ-rays in Human Peripheral Blood Lymphocytes

Micronuclei Induced by Fast Neutrons Versus60Co γ-rays in Human Peripheral Blood Lymphocytes

Enhanced frequency of micronuclei in lymphocytes from current as opposed to former uranium miners

Chromosome aberrations, micronuclei, and activity of superoxide dismutases in human lymphocytes after irradiation in vitro

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Product

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Micronuclei Induced by Fast Neutrons Versus⁶⁰Co γ-rays in Human Peripheral Blood Lymphocytes

Micronuclei Induced by Fast Neutrons Versus⁶⁰Co γ-rays in Human Peripheral Blood Lymphocytes