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G Decat

Publications and source records attributed to G Decat.

At least 19 recordsLinked to original sources
PubMed1991

An appraisal of the value of the contaminated Poisson method to estimate the dose inhomogeneity in simulated partial-body exposure.

The situation in which inhomogeneous radiation exposure is likely to occur with accidental overexposure was simulated by studying chromosome aberrations in mixtures of male irradiated and female nonirradiated lymphocytes. The data were evaluated by means of the contaminated Poisson method. For X-ray doses from 1 to 10 Gy and ratios of irradiated to nonirradiated blood from 1:1 to 1:19, a good agreement was found between calculated and applied radiation doses and fractions exposed.

Accidents↗
PubMed1990

[Cytogenetic effects produced by an in vitro exposure of human lymphocytes to ultrasounds with intensity levels of 1 W/cm2 to 3 W/cm2].

Peripheral blood from four human male donors have been exposed to ultrasounds delivered at intensity levels of 1, 2 or 3 W/cm2. Cytogenetic observations performed after in vitro culture of blood samples in Ham's medium did not reveal a significant increase of structural chromosome aberrations nor of sister chromatid exchanges in the lymphocytes.

Chromosome Aberrations↗
PubMed1990

Chromosome aberrations in patients treated with telecobalt therapy for glioblastoma.

The yield of dicentric chromosomes has been recorded in peripheral blood lymphocytes of patients undergoing telecobalt therapy for glioblastoma. Blood samples were taken by venipuncture, prior to the first radiotherapy session and 24 h after 10, 20 and 30 Gy to the tumor volume. On the basis of the maximum likelihood method, the yield of chromosome aberrations was best fitted by a linear quadratic dose-response relationship. According to this relationship, the dose inducing ten dicentrics at the target volume is 58 Gy, a value considerably higher than those found after radiotherapy for mammary carcinoma (15 Gy) or for pelvic tumors (5.62 Gy). Our results indicate that, in the case of fractionated exposures, confined to a small volume of the body, it is not possible to estimate the total dose administered and that the method only provides an estimate of the proportion of the lymphocytes irradiated.

Brain Neoplasms↗
PubMed1990

Chromosome aberrations induced in vitro in human lymphocytes by monoenergetic 2.5 MeV neutrons and 60Co gamma rays.

The aim of the present experiments was to evaluate the relative biological effectiveness (RBE) of monoenergetic 2.5 MeV neutrons, in view of the scarcity of data on the RBE of neutrons in this energy range. Human peripheral blood lymphocytes from two donors were exposed to doses of neutrons ranging from 0.005 Gy to 0.5 Gy. Gamma rays produced by a telecobalt therapy unit were used as reference radiation. RBE values were of the same order of magnitude, whatever was the model of the dose-response curve chosen for the neutrons (linear or linear-quadratic). As expected, RBE increased markedly with decreasing doses and went beyond 30 at a dose level of 0.2 Gy. The present results, compared with RBE values obtained with neutrons of higher energy (6.5, 14 and 21 MeV), confirm that low energy neutrons are more effective in producing genetic effects, especially at low doses.

Adult↗
PubMed1988

Chromosome aberrations in mixed cultures of in vitro irradiated and unirradiated human lymphocytes.

Human whole blood samples were exposed to different doses (1, 2, 4, 6 or 10 Gy) of gamma-radiation and mixed with different volumes of non-irradiated blood before culturing to simulate partial body irradiations. Chromosome aberrations were analysed and the frequency of dicentrics was found to be lower than expected, particularly when irradiated blood was mixed with large volumes of non-irradiated blood and after exposure to high radiation doses. For the mixtures of irradiated and unirradiated blood the deviation from the Poisson distribution depends on the respective proportions and on the doses. The results can be correlated to in vivo aberration frequencies in case of therapeutical treatments, but the yields of aberrations are generally underestimated in vitro.

Chromosome Aberrations↗
PubMed1987

[Chromosome aberrations induced in the lymphocytes of rabbits by ultrasounds of 1MHz alone or followed by treatment with 5-bromo-2'-deoxyuridine].

Rabbit lymphocytes were treated in Go with therapeutical ultrasound waves (1 W/cm2; 1 MHz; continuous wave mode) alone or followed by an additional exposure to 5-bromo-2'-deoxyuridine (BrdU). Doses in the Fresnel zone ranged from 120 to 960 J/cm2; no refrigeration was provided, and temperature increased from 37 degrees C to 45 degrees C. In the Fraunhofer zone, only an ultrasound dose of 960 J/cm2 was used, and the temperature of the insonated blood sample was maintained at 37 degrees C. For the sequential treatment, BrdU (10 micrograms/ml medium) was added immediately after the ultrasound treatment and was left in contact with the lymphocytes for 48 hours. Ultrasound alone did not induce chromosome aberrations, but ultrasound followed by the BrdU exposure resulted in an increased number of abnormal cells.

Animals↗
PubMed1987

Chromosome aberrations in patients irradiated for pelvic tumours.

Peripheral blood lymphocytes of patients undergoing radiation therapy for pelvic tumours have been examined for the presence of dicentric and centric ring chromosomes. Blood samples were taken, by venipuncture, prior to the first radiotherapy session and 24 h after radiotherapy sessions to allow the mixing of the irradiated lymphocytes in the circulating blood. The yield of dicentrics and centric rings was best fitted by a straight line which, according the maximum likelihood method, corresponds to Y = 1.77 +/- 0.0003 10(-2) D. On this basis the dose inducing ten dicentrics or rings is 5.62 Gy at the target volume and, thus, is intermediate between the doses at the target volumes displaying the same effects in patients treated for mammary carcinoma (15 Gy) or for ankylosing spondylitis (2 Gy).

Adenocarcinoma↗
PubMed1985

Effect of an enhanced natural radioactivity on mammal fertility.

Male and female mice of the BALB/c strain were placed on the floor of a hut built at a site of the Permian Basin of Lodève (Southwest France) where the dose rate of gamma radiation amounts to about 10 mrad/h. In previous experiments such high natural radioactivity was shown to induce point mutations in plant material as well as chromosome aberrations in somatic cells of experimental mammals. Controls were kept near the radioactive site under comparable conditions. After the exposure period, the animals were mated in our laboratory, with control mice of the same strain. Due to the high radiosensitivity of mouse oocytes, the fertility of the exposed females was drastically reduced in spite of the fact that the dose received did not exceed 13.8 rad. The fertility of the males exposed to 13 rad, 15 rad or to 45 rad was increased above the control values but was reduced for the animals receiving 63 rad. Analysis of the results show that the differences in fertility are mainly due to a decrease in the number of sterile pairs when males have been exposed to doses upto 45 rad and to an inverse effect when animals received 63 rad. Since histology and weight of the testes suggest that the germ cell population was normal, one has to conclude that the variations in fertility result from physiological effects.

Animals↗
PubMed1985

[Chromosome analysis of the lymphocytes of wild rats living close to waterways contaminated with effluents from nuclear plants].

Chromosomes of peripheral lymphocytes of wild rats living in the vicinity of a water stream contaminated by radioactive liquid releases from nuclear stations were studied. Our observations show that the quantities of radionuclides accumulated in different organs of the exposed rats were in some animals slightly but not significantly higher than in the control ones. Such low internal radioactivity does not result in an enhancement of the yield of structural chromosome aberrations. Since the radiosensitivity of rat chromosomes is roughly comparable to that of human chromosomes one has to conclude that our results can be extrapolated to human beings.

Animals↗
PubMed1984

[In vitro study of the cytogenetic effects produced by ultrasound used in medical therapy and administered alone or in combination with X-rays].

Rabbit peripheral blood lymphocytes have been exposed in vitro in Go to therapeutic ultrasound (1 MHz continuous wave mode) alone or in combination with 50 rads of X-rays. The results demonstrate that ultrasound doses ranging from 0 to 960 J/cm2 delivered at intensity levels of 0.5 or 1 W/cm2 do not interfere with the cell kinetics of PHA stimulated cells and do not enhance the frequencies of sister chromatid exchanges above the control levels.

Animals↗
PubMed1983

[Effect of elevated levels of natural radioactivity on the fecundity of male mice].

Male mice of the BALB/c strain were placed on the floor of a hut built at a site of Southwest France where the dose rate of gamma radiation amounts to about 10 mrad/h. Controls were kept near the radioactive site under comparable conditions. The doses of gamma rays received during a seven month period ranged from 0.1275 rad for the controls to 45 rad and 63 rad for the exposed animals. Due, possibly, to an effect on the libido exposure to 45 rad increased the fertility whereas the animals given 63 rad produced less offspring than the controls.

Animals↗
PubMed1982

Radiosensitivity and life span of dog peripheral blood lymphocytes.

Observations made after 48 h of cultivation show that 52% of dog lymphocytes are already in M2 and 17% in M3 at that fixation time. Evidently, the large discrepancy observed between man and dog with respect to the yield of dicentric chromosomes induced by an exposure to 200 rad of X-rays and observed after a culture time of 48 h does not correspond to a difference in chromosomal radiosensitivity. There is, indeed, no statistically significant difference between the yield of dicentrics observed in M1 human lymphocytes (32.0 per 100 cells) and that in dog lymphocytes after correction of the values obtained at 48 h (28.6 per 100 cells). From the observations performed on whole-body irradiated dogs one can estimate that the half-time of dog lymphocytes carrying chromosome aberrations is less than 30 days.

Animals↗
PubMed1982

The lymphocytes of small mammals. A model for research in cytogenetics?

The influence of nuclear characteristics such as chromosome number, chromosome arm number or amount of R-band material on the yield of radiation-induced chromosome aberrations has been re-evaluated on the basis of some recent experiments with the harlequin-staining method to distinguish the first from subsequent divisions. The results obtained up to now show that differences in cell kinetics of stimulated peripheral blood lymphocytes, causing a different distribution of first and following mitoses at the time of observation, can result in an underestimate of the incidence of unstable chromosome aberrations such as dicentric chromosomes when the observations are performed at a standardized fixation time without taking into account the cell generation. If, however, only first-division mitoses are considered, the radiosensitivity of the cells appears to be independent on nuclear characteristics. Furthermore, observations on whole-body irradiated animals show that, owing to the very short survival time of lymphocytes carrying chromosome aberrations, mammals generally available for such experiments represent inappropriate models when cytogenetic effects in somatic cells are to be followed for long periods of time after an acute exposure to ionizing radiation or after a chronic exposure.

Animals↗
PubMed1982

Chromosome aberrations as a measure of mutagenesis: cytogenetic extrapolation from animal to man.

A reevaluation of the factors considered to affect the chromosomal sensitivity of mammalian peripheral blood lymphocytes has been made on the basis of some recent experiments using the harlequin-staining method to distinguish the first from subsequent divisions. Observations on human lymphocytes show that the mixing up of first and second or third cell cycle cells cannot explain all the variability between the experiments performed without bromodeoxyuridine labeling. Establishing a uniform methodology is also not likely to eliminate all causes of variation. Similar heterogeneity is observed for other mammalian species. Provided comparisons are restricted to results obtained within the same laboratory, some estimation of the relative sensitivity of chromosomes from different species is, however, possible.

Animals↗
PubMed1982

[Cell kinetics and chromosome radiosensitivity of lymphocytes from 4 Cercopithecus species].

The harlequin-staining technique has been used to study the cell kinetics and the radiosensitivity of PHA-stimulated lymphocytes from Cercopithecus nictitans. C. aethiops var. cynosorus, C. irus, and C. ascanius. At 48 hours, the fixation time normally used for human lymphocytes, a large heterogeneity appears between the four species, with respect to the incidence of cells in first, second or third mitoses. If analysis of lymphocytes is restricted to Ml dividing cells, the yield of radiation-induced chromosome aberrations does not differ significantly from the incidence observed in irradiated human lymphocytes.

Animals↗
PubMed1981

Biological effects observed in mammals maintained in an area of vey high natural radioactivity.

Male rabbits (Oryctolagus cuniculus) were maintained for a 28-month period on the floor of the hut built at a site in southwestern France where the dose rate from natural radioactivity amounts to about 8 mrad/h. Male and female BALB/c mice (Mus musculus) were also placed in the hut during the summer period. The observations performed on those animals demonstrate that exposure to high natural radiation can increase the frequency of chromosome aberrations in somatic cells and indicate also the fertility in males and females is affected in an inverse manner. Model experiments with radon exposure of laboratory rabbits under controlled conditions have shown that the chromosome aberrations observed in somatic cels cella are not due to the radon exposure but essentially to gamma irradiation.

Animals↗
PubMed1980

Lymphocyte lifetime in the rabbit measured by the decline in radiation-induced chromosome damage.

The life span of rabbit lymphocytes carrying radiation-induced chromosome aberrations has been studied by following the decline in aberration frequency as a function of the time after irradiation. Female rabbits were given a whole body X-ray dose of 300 rad. The day before exposure and at 2 hours, 14, 28, 42, 56, 84, 140, 250 and 500 days thereafter, blood samples were taken from a marginal ear vein of each animal. A plot of log abnormalities against time suggests an exponential decline for dicentrics and fragments up to 140 days, the half time for dicentrics and fragments being 70 and 46 days respectively. The results of the present investigation thus demonstrate that because of their shorter life span, in vivo observations on aberrations in rabbit lymphocytes are not suitable for extrapolation of information on chronic exposure to man.

Animals↗