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Biomedical subjects

G B Gerber

Publications and source records attributed to G B Gerber.

At least 37 records · Page 2Linked to original sources
PubMed1995

[Use of the micronucleus test for biological dosimetry in cases of homogeneous or non-homogeneous exposure to ionizing radiations].

The dose effect relationship after homogeneous irradiation and the effect on the Poisson distribution of adding non-irradiated blood and thereby simulating non homogenous accidental exposure were studied for dicentric aberrations and micronuclei in lymphocytes exposed in vitro to 60Co gamma irradiation. The dose effect relationship for both parameters was of the linear quadratic type with the micronuclei responding slightly less to radiation than the dicentrics but a greater number of cells can easily be screened for micronuclei than for dicentrics. Except for one dose level in micronuclei, no deviations from the Poisson distribution were observed, after homogeneous tradition, but such a deviation was evident when non-irradiated blood was added to the irradiated one. With the help of the method of the "contaminated Poisson distribution" the proportion as well as the dose of the exposed blood could be approximately estimated. In order to test the suitability of the micronucleus test in vivo, both dicentrics and micronuclei were determined in patients treated for seminoma to an abdominal field. The data showed a consistent increase in both parameters without a significant difference between patients. The increase of both types of anomalies corresponded about to that expected from the size of the field exposed. The data from micronuclei appear, therefore, about as reliable for biological dosimetry as those from dicentrics for biological dosimetry after homogeneous and non-homogeneous exposure to ionizing radiations.

Adult↗
PubMed1994

Mutagenicity, carcinogenicity and teratogenicity of vanadium compounds.

The mutagenic, carcinogenic and teratogenic effects of vanadium and its compounds are reviewed. It is concluded that vanadium is not clastogenic and only weakly mutagenic; it has marked mitogenic activity affecting the distribution of chromosomes during mitosis and possibly causing aneuploidy. The few positive data on effects of vanadium during development leave it open whether direct effects on the embryo of fetus or physiological disturbances in the mother are responsible. No data exist indicating that vanadium is carcinogenic in animals or man, but since it interferes with mitosis and chromosome distribution, the possibility that vanadium might be carcinogenic under certain conditions cannot be dismissed offhand.

Animals↗
PubMed1994

Chromosome aberrations after treatment with radioactive iodine for thyroid cancer.

The study aimed to investigate whether the determination of chromosome aberrations in circulating blood lymphocytes could be useful to assess whole-body exposure from radioactive iodine released accidentally. Ten patients treated with two doses of 1850 MBq of 131I given 24 h apart for thyroid cancer were studied for chromosome aberrations (dicentrics) in blood samples taken before and at various times after exposure. The increase in the yield of aberrations caused by the exposure to iodine was small but statistically significant. Compared to published values for whole-body doses after such treatment, this increase appears to be somewhat smaller than expected from dose-effect relationships obtained for an acute exposure of lymphocytes in vitro or in vivo, a fact which could be explained by the low dose rate of the 131I exposure. Thus, in situations where a population was exposed as a result of the release of radioactive iodine, a determination of chromosome aberrations in blood lymphocytes would not appear to be very useful to determine exposure from iodine.

Chromosome Aberrations↗
PubMed1993

Effect of age on the ability of rat liver tissues to transform chemical promutagens to mutagens.

Age-related changes in drug metabolism of the liver from male Lou rats were determined by measuring changes in the production of mutagens. Activation of aflatoxin B1 (AFB1), 2-aminoanthracene (2AA) and benzo[a]pyrene (B[a]P) to mutagenic derivatives was assayed using the Ames salmonella test system. The promutagens were incubated with tissue fractions isolated from rats ranging in age from 3 weeks to 18 months. Hepatic activation of AFB1 and 2AA changes with age and is maximal from 4 to 10 months. In contrast, no significant modification with age was observed for the activation of B[a]P. It is concluded that the composition of different cytochrome P-450 fractions is modified with age thereby altering the specific ability to convert different promutagens to mutagens.

Aflatoxin B1↗
PubMed1992

[Study of possible influence of mixed lymphocyte reaction on experimental models used in biological dosimetry].

The study aimed to investigate whether "mixed lymphocyte reactions" could interfere with the results of experiments in which irradiated blood from one person is mixed with non-irradiated blood from another. This experimental model had been designed to simulate, in vitro, non-homogeneous in vivo exposure such as could occur after accidents with ionizing radiation. The results show that the experimental models gives valid results for donors with related blood characteristics.

Adult↗
PubMed1991

Life-shortening and disease incidence in mice after exposure to gamma rays or high-energy neutrons.

Male C57Bl/Cnb and BALB/c mice were exposed to single and fractionated d(50) + Be neutrons or 137Cs gamma rays at 12 weeks of age and were followed for life-shortening and disease incidence as ascertained by autopsy and histological examinations at the time of spontaneous death. Fractionation schedules used were 10 exposures at 24-h intervals and 8 exposures at 3-h intervals for gamma rays, and 8 exposures at 3-h intervals for neutrons. The data were analyzed by the Kaplan-Meier procedure using as criteria causes of death and possible causes of death. Individual groups were compared by a modified Wilcoxon test according to Hoel and Walburg (J. Natl. Cancer Inst. 49, 361-372 (1972)). No significant difference was found in C57Bl/Cnb and BALB/c male mice between a single gamma-ray exposure and a single neutron exposure. Gamma-ray fractionation was clearly less effective in reducing survival time than a single exposure. In contrast, fractionation of neutrons was slightly, although not significantly, more effective in reducing survival time than a single exposure. The relative biological effectiveness (RBE) for life-shortening for d(50)-Be neutrons compared to gamma rays is of the order of 1 to 2 for a single exposure to neutrons and between 2 and 3 for fractionated neutrons compared to a single exposure to gamma rays. Neutron irradiation caused somewhat more cancer than gamma irradiation, and the RBE for cancer induction may be higher, probably between 2 and 3 in the range of 1 to 3 Gy, although the present data do not allow a more precise assessment.

Animals↗
PubMed1989

Technetium absorption and turnover in monogastric and polygastric animals.

Technetium (Tc) released into the environment can reach animals in various chemical forms: as pertechnetate (TcO-4) in drinking water or deposited on the surface of vegetables and forage plants, or as Tc bioincorporated into plants and associated with various plant constituents. In addition to being influenced by chemical speciation in the diet, absorption, metabolism, and retention of Tc in animals are modified by the treatment that the alimentary bolus undergoes during its passage through the gastrointestinal tract. This behavior differs markedly between polygastric and monogastric animals. We have, therefore, studied the fate of 99mTc given in the diet either as TcO-4 or bioincorporated into maize in rats (as an example of a monogastric animal) and in sheep (as an example of a polygastric animal). Urine and feces were collected and assayed for Tc activity by gamma spectrometry. Animals were sacrificed at different times after contamination, and the Tc content of tissues was determined. The pattern of absorption, excretion and, to a certain degree, of organ distribution and retention depended on animal species and species of Tc administered. Excretion was by feces and urine, and several metabolic components could be discerned. A component of very short half-time in urine suggests that newly absorbed Tc is more readily excreted than that already bound by tissues. The highest tissue concentrations were found in the thyroid. Retention of Tc was, however, most pronounced in bone and skin. Hair contains considerable amounts of Tc and may serve as a bioindicator of Tc contamination.

Administration, Oral↗
PubMed1989

Toxicity of 99Tc: can it represent a risk to man?

The movement through the environment and the toxicity to plants of 99Tc have been studied. However, information is scanty on 99Tc toxicity to mammals even though this is the decisive criterion for assessing the consequences of releases of Tc. A critical tissue could be the thyroid because of its preferential accumulation of Tc and the developing organism because of its greater radiosensitivity; moreover, this toxicity might be enhanced under conditions of a low iodine (I) diet. These questions were studied in rats given large amounts of 99Tc in either a normal or an I-deficient diet for several months starting 2 wk before mating. Newborns were continued on these diets after weaning. The parameters determined were: occurrence of pregnancy and litter size, triiodothyronine and thyroxin in serum, uptake of 131I by the thyroid 24 h after injection, histology of the thyroid and concentration of Tc in tissues of the mothers and their decendants. Thyroid damage, as well as the effects on pregnancy, could be observed after amounts of 10 micrograms Tc g-1 food. Iodine deficiency only slightly influences the 99Tc toxicity. The chemical and radiological toxicity of 99Tc to rats is small. Consequently, it seems unlikely that contamination levels in the environment would ever reach levels that could lead to serious non-stochastic effects, even in the developing organism.

Administration, Oral↗
PubMed1988

Mutagenicity, carcinogenicity and teratogenicity of aluminium.

Aluminium and its salts, which are extensively used in the household and in industry, do not constitute a carcinogenic, mutagenic or teratogenic hazard, except, perhaps, in cases of extremely high exposure. The large majority of the experiments performed to assess the carcinogenicity of aluminium in laboratory animals gave negative results or even suggested some antitumor activity. Moreover, epidemiological studies have not provided clear evidence of a carcinogenic hazard of aluminium to man, and short-term tests made in vitro and in vivo to demonstrate mutagenic activity of A1 were negative except for some experiments in plants. The embryotoxic properties suggested by the studies on birds and mammals could result from the influence of A1 on phosphate and calcium metabolism or from interference with the polymerization of microtubules.

Aluminum↗
PubMed1988

Life-shortening and disease incidence in C57Bl mice after single and fractionated gamma and high-energy neutron exposure.

C57Bl Cnb mice were exposed to single or fractionated d(50)+Be neutrons or 137Cs gamma-ray exposure at 12 weeks of age and were followed for life-shortening and disease incidence. The data were analyzed by the Kaplan-Meier procedure using as criteria cause of death and possible cause of death. Individual groups were compared by a modified Wilcoxon test according to Hoel and Walburg, and entire sets of different doses from one radiation schedule were evaluated by the procedure of Peto and by the Cox proportional hazard model. No significant difference was found in life-shortening of C57Bl mice between a single gamma and neutron exposure. Gamma fractionation was clearly less effective in reducing survival time than a single exposure. On the contrary, fractionation of neutrons was slightly although not significantly more effective in reducing life span than a single exposure. Life-shortening appeared to be a linear function of dose in all groups studied. The data on causes of death show that malignant tumors, particularly leukemias including thymic lymphoma, and noncancerous late degenerative changes in lung were the principal cause of life-shortening after a high single gamma exposure. Exposure delivered in 8 fractions 3 h apart was more effective in causing leukemias and all carcinomas and sarcomas than one delivered in 10 fractions 24 h apart or in a single session. Following a single neutron exposure, leukemias and all carcinomas and sarcomas appeared to increase somewhat more rapidly with dose than after gamma irradiation. No significant difference in the incidence of leukemias and all carcinomas and sarcomas was noted between a single and a fractionated neutron exposure.

Animals↗
PubMed1986

Mutagenicity, carcinogenicity and teratogenicity of zinc.

Zinc is a common element in the human environment and constitutes an important trace element intervening in many biological processes. Toxicity of zinc is low; zinc deficiency represents, however, a hazard for human health. Zinc is not mutagenic and has little, if any, clastogenic properties. Zinc can induce tumours but only following local application, and does not represent a carcinogenic risk to man. It is still uncertain whether zinc can cause malignant transformation but zinc is needed for cellular proliferation of existing tumours and tumour growth is retarded by zinc deficiency. Zinc is not teratogenic; it can, in fact, avert teratogenicity of other agents. Conversely, zinc deficiency may be harmful to the developing organism.

Animals↗
PubMed1985

The transfer of tritium-labeled organic material from grass into cow's milk.

Two lactating cows were given tritiated hay containing organically bound tritium (OBT) only for about 4 weeks. Tritium activity was determined in milk fat, casein, lactose, milk water, and whole milk. In one cow, milk was sampled for approximately 450 days, covering two lactation periods. At steady state, specific tritium activities in casein, lactose, and milk water were 58, 10, and 11%, respectively, of those in milk fat. Some OBT was converted into THO during catabolism and entered the body water pool. This 3H source accounted for nearly 40% of tritium in lactose, but in casein and milk fat about 97% of tritium was derived from ingested OBT. Comparison of the specific activity of milk constituents with the specific activity of ingested hay showed the following values: 0.84 for milk fat, 0.49 for casein, 0.05 for lactose, 0.10 for milk water. About one-half of the tritium transferred to milk was found in organic milk constituents and the other half in milk water. Decrease of tritium activity with time could be represented by three components with different half-lives for the organic milk constituents. Those for milk fat and casein were quite similar, with a slow component of nearly 3 months.

Animals↗
PubMed1984

Metabolism of 51Cr, 54Mn, 59Fe and 60Co in lactating dairy cows.

Different radionuclides which can be released by nuclear installations (Na2(51) CrO4 , 54MnCl2 , 59FeCl3 and 60CoCl2 ) were given to lactating dairy cows either orally or by intravenous (i.v.) injection. Excretion into feces and urine as well as secretion into milk were followed for several weeks. Distribution of activity in organs was determined at sacrifice 102 days after oral and 70 days after i.v. administration. After ingestion, excretion of chromate followed a three-term exponential function with half-lives of 0.88, 3.7 and 26 days. Intestinal absorption was on the order of 0.1-0.2%. About 63% of injected chromate was excreted into urine, about 18% into feces and about 3.6% into milk. Orally administered chromate was concentrated in liver, intestine and spleen. The transfer coefficient into milk was about 1 X 10(-5) days/1. Less than 1% of an ingested dose of manganese was absorbed. Excretion occurred mainly into feces and followed a three-term exponential function. Very little manganese was excreted into urine or secreted into milk. Manganese is concentrated in brain, pancreas, kidney and heart but the differences in concentration are small. The body burden is, therefore, mainly determined by manganese in muscle, skin and bone. The transfer coefficient of manganese into milk is about 3 X 10(-5). Excretion of iron into feces after oral administration follows a three-term exponential function with a small component having a half-life of 72 days. Intestinal absorption is on the order of 0.5-2% of the dose. After i.v. administration, 7% of the dose is excreted in the feces displaying two components of turnover. Very little iron is excreted into urine. Secretion into milk also follows a two-term exponential function. The transfer coefficient of iron into milk is about 3 X 10(-5). About 0.6% of an oral and about 94% of an i.v. dose were recovered from the cows at sacrifice. Most activity was present in blood, liver and spleen. Excretion of radiocobalt into feces after oral administration is described by a three-term exponential function, while excretion into milk and urine is described by two-term exponential functions. Long-lived components in urine and milk represent about 5-10% of the activity absorbed. Only 1-2% of an oral cobalt dose is absorbed and 0.05% of an oral and 5.85% of an i.v. dose is recovered from the cow at sacrifice where concentrations are highest in kidney and thyroid. The body burden depends mainly on cobalt in muscle, skin and bone. The transfer coefficient of cobalt into milk is about 7.5 X 10(-5).

Animals↗
PubMed1984

The effect of X irradiation on cardiac beta-adrenergic receptors in the rabbit.

Cardiac beta receptors in rabbits were studied at different times following lethal (5 Gy) or supralethal (10 Gy) whole-body X irradiation. Using the radioactive ligand [125I]iodocyanopindolol, it was found that the maximal binding capacity, as determined from the Scatchard plot, decreased from 298.2 +/- 13.2 fmole/mg protein in controls to 142.4 +/- 5.5 fmole/mg 3 days after 10 Gy whole-body X irradiation, whereas the dissociation constant was only little affected. Three days after an exposure to 5 Gy, maximal binding capacity was reduced slightly and tended toward control values at Day 7. Local irradiation of the cardiac region with 10 Gy reduced cardiac beta receptors to 218 +/- 7 fmole/mg (73% of control) after 3 days. The latter observation suggests that about half the effect of radiation on cardiac beta receptors originates from a direct action of radiation on the heart tissue, the rest being due to abscopal systemic reactions.

Animals↗
PubMed1983

The metabolism of tritium and water in the lactating dairy cow.

Two lactating Friesian cows received tritiated water (19 nCi of tritium per ml) to drink for 25 days. Urine and milk samples were collected and analyzed for tritium content. Plateau levels in milk water, and in milk fat, lactose and casein were reached in about 18 days. Tritium concentration in milk water and urine water was about 82% that in drinking water, indicating dilution with water from food and metabolic processes, and as a result of exchange through lungs and skin. At steady state, tritium activity in milk fat, lactose and casein was about 30, 28 and 15% of that in drinking water on a weight basis; at this time, about 1.5% of the daily ingested tritium appeared in one litre of milk in both animals. Comparison of the specific activity of the various milk constituents with the specific activity of the body water showed that the highest tritium incorporation occurred in lactose (0.58), followed by milk fat (0.36) and casein (0.27). Tritium incorporation in milk dry matter (0.45) is considerably higher than in most tissue components of several mammalian species after continuous ingestion of THO as reported in the literature. Tritium levels fell rapidly in milk and urine after the administration of THO was stopped, with half-times of around 4 days for the rapid components in all milk constituents. A slow component of 44 days, 225 days and 24 days half-time was found in milk water, milk fat and casein respectively.

Animals↗
PubMed1983

Lymphocyte chromosome aberrations in patients undergoing radiation therapy for mammary carcinoma.

Patients undergoing radiation therapy for mammary carcinoma have been cytologically examined for the presence of polycentric chromosomes in their peripheral blood lymphocytes. The mean values of the observed yields can be fitted to a quadratic function. Due probably to a lower number of lymphocytes exposed the curve now obtained gives a smaller aberration yield than the dose effect curves published earlier for patients given telecobalt therapy.

Adult↗