Biomedical subjects

G Voigt

Publications and source records attributed to G Voigt.

At least 55 records · Page 3Linked to original sources

PubMed1996

Long-term behavior of radiocesium in dairy herds in the years following the Chernobyl accident.

The longterm behavior of 137Cs in milk of a Bavarian farm (farm A) deposited as a consequence of the Chernobyl accident has been followed from April 1986 until August 1994. On the basis of activity measurements in milk and feed, transfer coefficients for the different seasons have been estimated in order to see any changes in transfer behavior (aging effect) of 137Cs with time. The influence of different grazing regimes has been tested by comparison of activity concentrations in milk and pasture grass in one farm (farm A with rotational grazing regime) with that of a nearby farm (farm B with continuous grazing regime) over a complete grazing season by frequent measurements in 1993. Though the farms are located only 4 km apart, have similar soils, and were contaminated to the same extent by the Chernobyl fallout, tenfold lower 137Cs activity concentrations in milk have been observed in farm B. This finding seems to be partly due to the influence of a different grazing intensity.

Animals↗

PubMed1996

A review of countermeasures to reduce radioiodine in milk of dairy animals.

The most effective countermeasure for radioiodine contamination of milk is to provide dairy animals with uncontaminated feed, with the added advantage that it will be effective for other radionuclides in the fallout. Another effective response is to process the milk into storable dairy products for an appropriate length of time to allow for physical decay. The use of additives given to ruminants to reduce radioiodine in milk is an alternative countermeasure which could be effective. Stable iodine administration is a practically feasible option which has the potential to reduce radioiodine levels in milk by at most a factor of three. Stable iodine supplementation should be at sufficiently high rates to be effective (and at least 1 g d-1 for dairy cows), particularly for ruminants already receiving high amounts of iodine in the diet. Currently available data are inadequate to recommend a suitable stable iodine administration rate for different species of ruminants. Other compounds, such as perchlorate and thiocyanate, also reduce the transfer to radioiodine to milk (and thyroid). Some of these compounds seem to be potentially equally as effective as stable iodine. However, currently there is inadequate information on their effectiveness and possible toxicity to both ruminants and humans for these compounds to be considered as suitable countermeasure additives.

Animals↗

PubMed1996

The feasibility of using 129I to reconstruct 131I deposition from the Chernobyl reactor accident.

Radioiodine released to the atmosphere from the accident at the Chernobyl nuclear power station in the spring of 1986 resulted in large-scale thyroid-gland exposure of populations in Ukraine, Belarus, and Russia. Because of the short half life of 131I (8.04 d), adequate data on the intensities and patterns of iodine deposition were not collected, especially in the regions where the incidence of childhood-thyroid cancer is now increasing. Results are presented from a feasibility study that show that accelerator-mass-spectrometry measurements of 129I (half life 16 x 106 y) in soil can be used to reconstruct 131I-deposition density and thus help in the thyroid-dosimetry effort that is now urgently needed to support epidemiologic studies of childhood-thyroid cancer in the affected regions.

Cesium Radioisotopes↗

PubMed1996

Modeling the dynamics of radioiodine in dairy cows.

A metabolically based model of radioiodine transfer in cows was applied to previously collected data. The model required some modification and reparameterization before it could describe the measured data satisfactorily. In particular, significant fecal excretion of radioiodine needed to be considered. The model was used to predict the effect of dietary intake of stable iodine on the transfer of radioiodine to milk. Increased dietary intake asymptotically increased the proportion of radioiodine excreted via milk.

Animals↗

PubMed1996

Estimation of 131I thyroid doses for the evacuees from Pripjat.

The thyroid doses of 49,360 inhabitants of Pripjat evacuated after the accident at Chernobyl were reconstructed. During their evacuation most of the evacuees passed through highly contaminated territories. The evaluation of a large-scale public survey showed that only about 50% of the evacuees had left the contaminated areas within 5 days and that 30% of them stayed there for more than 30 days. As a first step, the model of dose estimations was improved, and thyroid doses were assessed for the group of evacuees for whom the 131I activity in the thyroids was measured. The 131I incorporation during the first 5 days after the accident was described by a single-intake model (inhalation); later incorporations were assumed to be proportional to the radioiodine activity in milk. As a second step, the correlation between the calculated doses and individual parameters (place of residence in Pripjat, intake of stable iodine, and age at the time of the accident) was described by an empirical equation. This equation was applied to all evacuees who completed the questionnaires of the public survey. Previous dose assessments were found to overestimate the thyroid doses especially for the younger evacuees. On the basis of these estimations, collective doses and the resulting radiation risks for thyroid cancer were assessed for different age groups.

Adolescent↗

PubMed1994

Distribution of radiocaesium activities in the waters of a Bavarian chain of lakes.

The procedure to extract caesium from seawater developed by Mann and Casso (1984) has been slightly modified and applied to the determination of radiocaesium originating from the Chernobyl accident in the waters of a Bavarian chain of lakes. Activity concentrations and estimated water inventories are given for 15 lakes 5 years after the accident, and depth profiles of the 137Cs activity concentration in the water column of three selected lakes are presented. The activity concentrations in water of the different lakes show a high variability from 1.2 to 93 mBq l-1. The calculated inventory of dissolved radiocaesium has decreased over the 5 years to 0.03% and 2% of the deposited activity, respectively.

Cesium Radioisotopes↗

PubMed1994

Influence of stable iodine on the transfer of 131I into cows' milk.

The effect of supplying three different stable iodine levels (about 70, 80, and 160 mg day-1) in the daily feed of four dairy cows has been studied for the excretion pattern of 131I. None of the different treatments had a statistically significant effect. A mean milk transfer coefficient of 0.015 +/- 0.001 d l-1 was determined for all iodine supply levels investigated.

Animals↗

PubMed1993

Chemical methods to reduce the radioactive contamination of animals and their products in agricultural ecosystems.

After major nuclear accidents the most effective action to reduce activity levels in animal products is to provide uncontaminated feed or feed diluted with uncontaminated material. However, uncontaminated feed may not always be available in such situations. Therefore other effective procedures are needed to reduce activity levels which must be easy to apply, low in cost and have no side effects on animals and their products. Chemical substances administered as feed additive to housed or grazing animals act by influencing gut absorption or increasing the rate of excretion from blood and organs. The main chemical methods used are: (1) dilution of radionuclides by stable isotopes or analogous inactive elements; and (2) natural or artificial binding agents. In this paper a summary and critical review of the different chemical methods described in the literature is given.

Accidents↗

PubMed1993

Countermeasures for reducing radioactive contamination of farm animals and farm animal products.

A summary is given of the range and effectiveness of different available countermeasures which can reduce the radiation dose arising from the radioactive contamination of food products from animals. The choice of which countermeasure is suitable for each particular situation will depend on many factors. Consideration should be given not only to the effectiveness of each countermeasure in terms of reduction of radionuclide content, but also to its practicality and cost, particularly where deposition levels are high or where high contamination levels in animal food products persist for a long period of time. Effective countermeasures which can reduce radiocaesium contamination of milk and meat from farmed animals by more than a factor of 10 have been developed, tested and used during the last 30 years. Less progress has been made in identifying effective binders for reducing levels of the other important contaminating radionuclides, such as I and Sr, in animal food products.

Animal Feed↗

PubMed1993

Environmental behaviour of radionuclides deposited after the reactor accident of Chernobyl and related exposures.

Several radioecological experiences with isotopes of ruthenium, iodine, caesium and barium, obtained after the reactor accident of Chernobyl, are reported. It was found that for a wet deposition barium was the element with the highest retention on grass. The retention of caesium was lower by a factor of 1.6, retention of iodine by a factor of 2.4 and retention of ruthenium by a factor of 3.5. Former data on the caesium transport in cereals from leaves to grain were confirmed. Depending on the conditions the iodine transfer factor for milk varied between 0.002 and 0.007 d.kg-1. The caesium transfer factor for milk was (0.003 +/- 0.0006) d.kg-1 and was found to be relatively constant in the years 1986-1988. In 1991, the values were higher by a factor of 2-5. Radioecological model results of whole-body burdens in Southern Bavaria showed a reduction of the caesium ingestion doses due to countermeasures and spontaneous changes of consumption habits in the first 2 months by a factor of 5 and till the end of 1987 by a factor of 1.5. The model results agree well with the range of measured whole-body burdens. One month after the deposition, the external exposures in urban environments due to ruthenium, caesium and barium isotopes were found to be reduced by a factor of 2, compared with open lawns, in the case of iodine the reduction was even a factor of 2.5. External exposures of a population group from the Munich area were determined by thermoluminescence dosimetry. The results are in accordance with the spectral measurements of external dose rates in urban environments.

Accidents↗

PubMed1993

137Cs transfer after Chernobyl from fodder into chicken meat and eggs.

The distribution and the biological half-lives of 137Cs in poultry after continuous intake of foodstuffs contaminated by the Chernobyl fallout were studied in order to determine transfer coefficients to yolk, albumen, and shell of eggs as well as transfer coefficients to chicken meat. Mean values for laying hens were found to be 0.2 d kg-1 (whole consumable egg), 1.2 d kg-1 (leg meat), and 1.6 d kg-1 (breast meat) when radiocesium was fed in contaminated grass pellets, and about twice as large [i.e., 0.4 d kg-1 (whole consumable egg), 2.8 d kg-1 (leg meat), and 3.0 d kg-1 (breast meat)] when radiocesium was fed in contaminated wheat. Reducing effects of the feed additive ammonium-ferric-cyano-ferrate in concentrations of 0.66 g kg-1 of feed mixture on the contamination of hen products were quantified to be a factor of 3 to 4 (whole consumable egg and meat after grass pellet feeding) and 8 to 14 (whole consumable egg and meat after wheat feeding). A drastically higher reduction with an ammonium-ferric-cyano-ferrate dose twice as large (1.33 g kg-1) was achieved. For broiler chickens, activity concentration ratios of meat to feed were derived for various fattening periods, with mean values of about 0.3 (leg), 0.4 (breast), and 0.2 (liver). The addition of ammonium-ferric-cyano-ferrate reduced the activity concentrations in meat by factors of more than 6.

Accidents↗

PubMed1992

137Cs uptake with cafeteria food after the Chernobyl accident.

After the Chernobyl accident, the activity concentrations of radiocesium were measured in both the meals served at the cafeteria of a research center and in the employees eating there. The time-dependent means of monthly 137Cs activities in meals and people show a similar distribution pattern with highest values between March and July 1987, i.e., only 1 y after the accident. In meals, the highest activities were found when the menu consisted of pork, milk, or milk products. The 50-y cumulative effective dose calculated from the whole-body measurements is 0.21 mSv for male and 0.15 mSv for female employees. Cafeteria food contributed only a small share to this exposure.

Accidents↗

PubMed1991

Experiments on the seasonality of the cesium translocation in cereals, potatoes and vegetables.

The translocation of cesium from leaves into the edible parts after foliar deposition at different stages of growth has been determined for cereals, potatoes, green beans and carrots in field experiments. For all the plant species investigated a significant seasonality of the cesium translocation was observed. The highest translocation factors were determined after foliar contamination 50 to 60 days before harvest for cereals, and 70 to 90 days and 15 days before harvest for potatoes and green beans, respectively. The variations among the different experiments can be reduced when the translocation is normalized to the yield. This facilitates the application in probabilistic models due to the implicit consideration of the relationship between translocation and yield. The seasonality of the cesium translocation can be described with gaussian functions being consistent with the physiological development of cereals and potatoes. The uncertainty of these approaches is a factor of 3 and 4 for cereals and potatoes, respectively.

Biological Transport↗

PubMed1990

Stress-related changes of saliva cortisol in VDU operators.

In the field of work physiology, catecholamines and cortisol are used as strain indicators, because their production is increased in stressing work situations. Short-term stress cannot be ascertained by measuring catecholamines in urine. We studied the excretion of cortisol in saliva during short-term stress. We examined 77 healthy subjects who worked at a video display unit (VDU) for 30 min. They had to carry out a task with high speed and accuracy demands. Saliva specimens were taken before and after VDU work. Saliva cortisol levels were determined by means of a sensitive enzyme immunoassay (EIA). Additionally physiological parameters (heart rate, blood pressure, respiratory rate) and task performance were measured, and the subjects were asked about their feelings of stress and psychovegetative disorders. Saliva cortisol concentrations were significantly increased after 30 min of VDU work. Heart rate, blood pressure and respiratory rate were also increased during the task. In persons with high heart rate and blood pressure levels saliva cortisol increased significantly stronger during VDU work than in persons with lower heart rate and blood pressure levels. The results indicate that saliva cortisol is a useful strain indicator in short-term stress situations.

Adult↗

PubMed1990

[Task specificity and reproducibility of the psychophysiologic reaction pattern].

This paper presents results from investigations of physiological activation processes concerning two subjects. Firstly: Different tasks cause different reactions of the activation variables. In our experiment the heart rate raised stronger in the mental arithmetic task than in the trakking task. Conversely, blood pressure and respiratory frequency showed higher values in the tracking task. Secondly: By analyzing the stabilities for repeated investigations we obtained the following results: a) The reliability of the physiological strain variables is higher than that of the difference values. b) Habitual values are predicted best by the second investigation. c) If the experiment is often repeated, one can determine intraindividual correlations between activation variables for every single person.

Adult↗

PubMed1989

Weathering of 134/137Cs following leaf contamination of grass cultures in an outdoor experiment.

After spraying grass cultures with rainwater collected after the Chernobyl reactor accident, the time-dependence of the weathering of leaf contamination of 134/137Cs was determined. Hereby the influence of rain and of biomass increase due to growth was considered. Two effective half-lives were found of 6 d and more than 60 d in rain-protected grass for the activity per area (corresponding to 8 d and more than 60 d when related to the activity per dry weight) and 2 d and 30 d in rain-exposed grass for the activity per area (3 d and 23 d when activity per dry weight is considered). These half-lives represent the initially rapid (for about 90% of the activity) and later slow (for the residual about 10%) decrease of the Cesium content in grass. They might be due to different weathering mechanisms whereby the translocation of the radionuclides from the leaf surface into the plant interior and the loss of wax particles might be of importance.

Accidents↗

PubMed1989

Effect of ketotifen on the distribution and degranulation of uterine eosinophils in estrogen-treated rats.

Eosinophil leukocytes migrate from the blood to the uterus under estrogen stimulation, redistribute through uterine extravascular compartment, degranulate in the organ, and release agents that are involved in several parameters of estrogen action. Agents that induce blood eosinopenia, block their migration to the uterus, interfere with their redistribution within the organ or modify their degranulation, selectively interfere with eosinophil-mediated responses to estrogen. The present study investigated whether ketotifen, an antiallergic agent that inhibits allergen-induced eosinophil degranulation, interferes with estrogen-induced eosinophil migration to the uterus and their subsequent degranulation. Ketotifen does not interfere with estrogen-induced eosinophil accumulation in the uterus, but decreases the proportion of eosinophils located in endometrium and inhibits their degranulation. These results suggest that neither histamine, calcium or slow reacting substance of anaphilaxis are involved in eosinophil migration to the uterus. The inhibition by ketotifen of eosinophil degranulation may diminish eosinophil migration through extravascular compartment via a decrease in the release from degranulating eosinophils of enzymes required for this migration. It is possible that the inhibition by ketotifen of both, eosinophil degranulation and eosinophil motility through uterine extravascular compartment, interfere with eosinophil-mediated responses to estrogen or with other functions of these cells.

Animals↗

PubMed1989

The influence of the feeding practice and the season on the contamination of animal food products after a single deposition of radionuclides.

After accidental releases of radionuclides to the atmosphere, the activity concentration in animal food products are dependent on the month in which the release occurs. In most cases the highest contamination of milk or meat can be expected in that month in which the main feedstuff of the ration is harvested. The integral activity concentrations due to foliar uptake in the first year are much greater than the integral activity concentrations over 50 years root uptake.

Animal Feed↗