The European Radiobiology Archives (ERA)--content, structure and use illustrated by an example.

The European Radiobiology Archives (ERA), supported by the European Commission and the European Late Effect Project Group (EULEP), together with the US National Radiobiology Archives (NRA) and the Japanese Radiobiology Archives (JRA) have collected all information still available on long-term animal experiments, including some selected human studies. The archives consist of a database in Microsoft Access, a website, databases of references and information on the use of the database. At present, the archives contain a description of the exposure conditions, animal strains, etc. from approximately 350,000 individuals; data on survival and pathology are available from approximately 200,000 individuals. Care has been taken to render pathological diagnoses compatible among different studies and to allow the lumping of pathological diagnoses into more general classes. 'Forms' in Access with an underlying computer code facilitate the use of the database. This paper describes the structure and content of the archives and illustrates an example for a possible analysis of such data.

Usefulness and limits of biological dosimetry based on cytogenetic methods.

Damage from occupational or accidental exposure to ionising radiation is often assessed by monitoring chromosome aberrations in peripheral blood lymphocytes, and these procedures have, in several cases, assisted physicians in the management of irradiated persons. Thereby, circulating lymphocytes, which are in the G0 stage of the cell cycle are stimulated with a mitogenic agent, usually phytohaemagglutinin, to replicate in vitro their DNA and enter cell division, and are then observed for abnormalities. Comparison with dose-response relationships obtained in vitro allows an estimate of exposure based on scoring: Unstable aberrations by the conventional, well-established analysis of metaphases for chromosome abnormalities or for micronuclei; So-called stable aberrations by the classical G-banding (Giemsa-Stain-banding) technique or by the more recently developed fluorescent in situ hybridisation (FISH) method using fluorescent-labelled probes for centromeres and chromosomes. Three factors need to be considered in applying such biological dosimetry: (1) Radiation doses in the body are often inhomogeneous. A comparison of the distribution of the observed aberrations among cells with that expected from a normal poisson distribution can allow conclusions to be made with regard to the inhomogeneity of exposure by means of the so-called contaminated poisson distribution method; however, its application requires a sufficiently large number of aberrations, i.e. an exposure to a rather large dose at a high dose rate. (2) Exposure can occur at a low dose rate (e.g. from spread or lost radioactive sources) rendering a comparison with in vitro exposure hazardous. Dose-effect relationships of most aberrations that were scored, such as translocations, follow a square law. Repair intervening during exposure reduces the quadratic component with decreasing dose rate as exposure is spread over a longer period of time. No valid solution for this problem has yet been developed, although, in theory, both deterministic damage and aberrations might be repaired to a similar degree; a comparison of aberrations following a linear dose relationship might also help when the doses have been sufficiently large. (3) Investigations might have been possible only a certain time after the exposure. The relatively rapid disappearance of lymphocytes carrying unstable aberrations limits their use in retrospective dosimetry, years after exposure. Scoring stable aberrations, thought to persist in the circulating lymphocytes, might appear more appropriate in such situations. However, the examination of a representative number of cells by G-banding is extremely laborious, and the FISH method is not only expensive but has not yet been fully validated in different laboratories. In conclusion, biological dosimetry has serious limitations exactly for situations where the need for information is most urgent. It renders its most useful results when an individual has been exposed to a rather homogeneous high-level radiation over a short time interval, i.e. accidents at high-intensity radiation devices. On the other hand, it yielded less satisfactory information even when the most recent techniques were used for situations, where a low level, low dose rate exposure has occurred at some time in the past, for example for persons living in areas contaminated from the Chernobyl accident. Such negative experiences should be kept in mind in order to avoid futile and expensive investigations in the case of populations exposed from radioactivity and, notably, also from potentially clastogenic chemical agents.

The European Radiobiology Archives (ERA), present state and future developments.

The European Radiobiology Archives (ERA) aims to collect most of the information still available in Europe on long-term animal experiments--including some selected human studies suitable for comparison with animal data--and to make them available to the scientific community for further analysis. ERA cooperates with the US (National Radiobiology Archives, NRA) and Japan (Japanese Radiobiology Archives, JRA) in the International Radiobiology Archives (IRA).

Carcinogenicity, mutagenicity and teratogenicity of manganese compounds.

Manganese, an essential trace element, is one of the most used metals in the industry. Recently, several new manganese compounds have been introduced as fungicide, as antiknock agent in petrol and as contrasting agent in nuclear magnetic resonance tomography. Manganese displays a somewhat unique behaviour with regard to its toxicity. It is relatively non-toxic to the adult organism except to the brain where it causes Parkinson-like symptoms when inhaled even at moderate amounts over longer periods of time. Relatively high doses of manganese affect DNA replication and repair in bacteria and causes mutations in microorganism and mammalian cells although the Ames test does not appear to be particularly responsive to manganese. In mammalian cells, manganese causes DNA damage and chromosome aberrations. Information on organic manganese derivatives is still insufficient. Large amounts of manganese affect fertility in mammals and are toxic to the embryo and foetus. The fungicide MANEB and the contrasting agent MnDPDP also can be embryotoxic, but the latter only at doses much higher than those clinically employed. Information on the anti-knock agent MMT is inadequate. On the other hand, manganese deficiency can also affect fertility and be teratogenic. Information on cancer due to manganese is scanty but the results available do not indicate that inorganic manganese is carcinogenic. More information is desirable with regard to the organic manganese derivatives. It may surprise that an agent that causes mutations is not also carcinogenic. The experience with manganese shows that conclusions with regard to carcinogenicity of an agent based on the observation of mutations are subject to uncertainties. Altogether, it appears that, because of the very high doses at which positive effects have been found, manganese would not represent a significant carcinogenic risk to the population and workers. Care must, however, be exercised with respect to central-nervous symptoms after chronic exposure and with respect to effects on the embryo. Pregnant women should not be exposed to manganese at the work place.

International radiobiology archives of long-term animal studies: structure, possible uses and potential extension.

Animal experiments have contributed a great deal to our information on effects and risks arising from exposure to radionuclides. This applies, in particular, to alpha-emitting radionuclides where information from man is limited to thorotrast, 224Ra and 226Ra. The late C.W. Mays was the first to suggest that animal data in conjunction with epidemiological data could allow estimates of human risks for radionuclides - predominantly from actinides - where information in man is scarce. The 'International Radiobiology Archives of Long-term Animal Studies' were created through the combined efforts of European, American and Japanese scientists and aim to safeguard the large amount of existing data on long-term animal experiments and make them available for, among others, an improved assessment of risks from alpha-emitting radionuclides. This paper summarizes the structure of the archives and reviews their present status and future plans. It also demonstrates the extensive information available in these archives on alpha-emitting radionuclides which is suitable for further analysis. Also, the structure of the animal archives could - in a slightly modified form - accommodate the epidemiological data available on 224Ra and thorotrast and, thus, facilitate a direct comparison of data from man, dogs and rodents.

Mutagenicity, carcinogenicity, and teratogenicity of acrylonitrile.

Acrylonitrile (AN) is an important intermediary for the synthesis of a variety of organic products, such as artificial fibres, household articles and resins. Although acute effects are the primary concern for an exposure to AN, potential genotoxic, carcinogenic and teratogenic risks of AN have to be taken seriously in view of the large number of workers employed in such industries and the world-wide population using products containing and possibly liberating AN. An understanding of the effect of acrylonitrile must be based on a characterization of its metabolism as well as of the resulting products and their genotoxic properties. Tests for mutagenicity in bacteria have in general been positive, those in plants and on unscheduled DNA synthesis doubtful, and those on chromosome aberrations in vivo negative. Wherever positive results had been obtained, metabolic activation of AN appeared to be a prerequisite. The extent to which such mutagenic effects are significant in man depends, however, also on the conditions of exposure. It appears from the limited data that the ultimate mutagenic factor(s), such as 2-cyanoethylene oxide, may have little opportunity to act under conditions where people are exposed because it is formed only in small amounts and is rapidly degraded. The carcinogenic action of AN has been evaluated by various agencies and ranged from 'reasonably be anticipated to be a human carcinogen' to 'cannot be excluded', the most recent evaluation being 'possibly carcinogenic to humans'. Animal data that confirm the carcinogenic potential of AN have certain limitations with respect to the choice of species, type of tumors and length of follow up. Epidemiological studies which sometimes, but not always, yielded positive results, encounter the usual difficulties of confounding factors in chemical industries. Exposure of workers to AN should continue to be carefully monitored, but AN would not have to be considered a cancer risk to the population provided limitations on releases from consumer products and guidelines on AN in water and air are enforced. AN is teratogenic in laboratory animals (rat, hamster) at high doses when foetal/embryonic (and maternal) toxicity already is manifest. Pregnant workers should not be exposed to AN. In view of the small concentrations generally encountered outside plants, women not professionally exposed would appear not to be at risk of teratogenic effects due to AN. Future research should concentrate on the elucidation of the different degradation pathways in man and on epidemiological studies in workers including pregnant women, assessing also, if possible, individual exposure by bio-monitoring.

No evidence for radiation-induced clastogenic factors after in vitro or in vivo exposure of human blood.

Experiments were performed with human plasma irradiated in vitro or in vivo in order to evaluate the extent to which clastogenic factors might disturb the adaptive response to DNA-damaging factors currently studied in our laboratory. The studies were carried out with plasma isolated from whole blood given 4 Gy of X-rays in vitro and with plasma from people receiving local radiotherapy at a total dose of about 60 Gy gamma rays. Addition of irradiated plasma to culture medium did not result in a statistically significant increase in structural aberrations in chromosomes of non-irradiated normal blood.

Adaptive response to DNA-damaging agents: a review of potential mechanisms.

The study of the adaptive response, i.e. a reduced effect from a higher challenging dose of a stressor when a smaller inducing dose had been applied a few hours earlier, has opened many new vistas into the mechanisms by which cells can adapt to hazardous environments. Although the entire chain from the initial event, supposedly the presence of DNA damage, to the end effect, presumably improved DNA repair, has not been fully elucidated, many individual links have been postulated. Initial elements--following the still unknown signal for the presence of radiation damage--are various kinases (protein kinase C and stress-activated protein kinases), which, in turn, induce early response genes whose products initiate a cascade of protein-DNA interactions that regulate gene transcription and ultimately result in specific biological responses. These responses include the activation of later genes that can promote production of growth factors and cytokines, trigger DNA repair, and regulate progress through the cell cycle. Indeed, there appears to be a relation between the induction of the adaptive response and the effects of radiation and cytostatic agents on the cell cycle, although these effects, especially the G1 delay, occur at much higher doses than the adaptive response, and one may not indiscriminately extrapolate mechanisms responsible for cell cycle changes observed at high doses, e.g. for radiation in the order of grays, to those involved in the adaptive responses at much lower doses, i.e. some tens of milligrays.

Mutagenicity, carcinogenicity and teratogenicity of thallium compounds.

The paper reviews the information available concerning the mutagenic, carcinogenic and teratogenic effects of thallium. Data on mutagenic and carcinogenic risks of thallium and its compounds are extremely scanty but what is available does not indicate that thallium could be mutagenic or carcinogenic. At any rate, such risks, if they exist, would be submerged by the general high toxicity of thallium. On the other hand, thallium has some teratogenic properties, especially on cartilage and bone formation, although this seems to be more prominent in chicks than in mammals. Nevertheless, pregnant women should not be exposed to doses of thallium which might produce toxic symptoms; exposure to lower doses such as might occur near thallium-emitting plants is probably not embryotoxic.

Mutagenicity, carcinogenicity and teratogenicity of germanium compounds.

The metalloid germanium has found widespread application in electronics, nuclear sciences and in medicine. General toxicity of germanium is low, except for the tetrahydride germane, and few observations on toxicity of germanium in man exist. Germanium is not carcinogenic and even appears to inhibit cancer development and, in the form of the organic germanium compound, spirogermanium, to destroy cancer cells. Germanium compounds have no mutagenic activity and may, under certain conditions, inhibit the mutagenic activity of other substances. High doses of germanium may result in an increased embryonic resorption, but possible malformations have been reported only after administration of dimethyl germanium oxide to pregnant animals. Germanium may thus be considered an element of rather low risk to man.

Mutagenicity, carcinogenicity and teratogenicity of antimony compounds.

The paper reviews the information available concerning the mutagenic, teratogenic and carcinogenic effects of antimony. A claim that antimony compounds could have mutagenic properties is based on insufficient and not particularly relevant data. Additional experiments, particularly with organic antimony compounds, would be desirable, but from what we know already, one may be confident that antimony is less a mutagenic risk than many other metals such as As, Cr, Ni, among others. Evidence for a carcinogenic risk of antimony in experimental animals was judged by the IARC sufficient for antimony trioxide and limited for antimony trisulfide. In man, IARC considered antimony trioxide as possibly carcinogenic. However, exposure in all studies on which these conclusions are based also involved other proven or likely carcinogenic compounds. Studies with pure antimony compounds, especially those used in therapy, need to be performed to clarify the situation. Although some indications exist that antimony trioxide could interfere with embryonic and fetal development, the studies seem not entirely conclusive. It is regrettable that, at least to our knowledge, the outcome of pregnancy in women treated with antimony compounds for leishmaniasis has not been studied. In conclusion, it appears that mutagenic, carcinogenic and teratogenic risks of antimony compounds, if they exists at all, are not very important.

Survival and diseases in C57BL mice exposed to X rays or 3.1 MeV neutrons at an age of 7 or 21 days.

Survival and causes of mortality were studied in 7- or 21-day-old male C57BL/Cnb mice exposed to 0.5, 1 or 3 Gy of 250 kVp X rays or 0.125, 0.25, 0.5 or 1 Gy of accelerator neutrons (modal energy 3.1 MeV). A total of 1287 animals were used in the experiments. Survival of irradiated animals was reduced significantly only in the mice receiving the highest doses (1 Gy neutrons, 3 Gy X rays ). Mice exposed to the lowest doses (0.125 Gy neutrons, 0.5 Gy X rays) lived significantly longer than controls, apparently reflecting a reduction in non-neoplastic lung and liver diseases. All malignant tumors increased significantly from (and including) doses of 0.5 Gy neutrons and 1 Gy X rays. Hepatocellular carcinoma was the principal contributor to the increase in tumor incidence, at least after exposure to neutrons. No significant increase in hepatocellular carcinoma was seen in 21-day-old mice exposed to X rays. An increase, especially after 3 Gy X rays, was also observed for all leukemias. Controls in the present study lived significantly longer than those in our earlier studies of irradiated adult mice, making a direct comparison of the radiation-induced effects in adult and infant mice difficult. Based on percentage life shortening, it appears that exposure during infancy does not shorten total survival or survival from cancer much more than exposure of adults, although such exposure, especially to neutrons, causes more hepatocellular carcinoma. Due to the nonlinearity of the dose-effect relationships, it is difficult to calculate the RBE of neutrons. For survival time at higher doses an RBE of about 3 is obtained. When the incidence of all malignant tumors and of hepatocellular cancer is fitted to a linear or a linear-quadratic function, an RBE from 5 to 8 is obtained. No RBE can be estimated for hepatocellular carcinoma in mice of an age of 21 days because exposure to X rays does not seem to cause this tumor at that age.

Long-term effects on tumour incidence and survival from 241Am exposure of the BALB/c mouse in utero and during adulthood.

BALB/c mice were given 100, 500 or 1500 Bq/g 241Am at day 14 of pregnancy. The offspring were separated from the mothers at birth and followed until death. In addition, adult females and one group of males were also studied for the effects of 241Am following treatment with 45-213 Bq/g. Adults treated with 241Am showed significantly shortened survival and increased incidence of osteosarcoma (to 40 - 50%). The data also suggest that the female mouse is more susceptible to induction of osteosarcoma than the male. There was also a significant increase in osteosarcoma, all bone tumours, all sarcomas, and all leukaemias in the offspring from the contaminated mothers, although this appeared to occur independently of dose. Calculations of the number of osteosarcomas induced per Gy varied for contamination of adult mice between 0.2 and 0.01 and for the offspring between 6 and 0.6. Thus, offspring seemed to be about 10 times more at risk if osteosarcomas induced per mouse Gy are compared. Surprisingly, offspring from mothers treated with 241Am displayed a longer survival time than controls, possibly due to fewer deterministic lung diseases appearing early in life.

Mutagenicity, carcinogenicity and teratogenicity of lithium compounds.

This paper reviews the information available concerning the mutagenic, teratogenic and carcinogenic effects of lithium. Such effects would be highly unlikely in an occupational setting but might be a risk to the considerable percentage of the population treated for manic-depressive disorders. It is concluded that lithium compounds have no significant clastogenic and, based on studies on microorganisms, only a doubtful mutagenic activity. Information on teratogenic effects is contradictory. While some observations in man and a few animal studies suggest that lithium in concentrations in the order of those given to patients may cause malformations, other observations do not support this claim and the risk with a carefully controlled therapy is probably small. Until more information becomes available from ongoing lithium data registries, it is probably prudent to exercise caution in treating pregnant women with lithium during the period of cardiac organogenesis. No information is available on cancer caused by treatment with lithium, and it is highly unlikely that lithium is carcinogenic.

Dose-effect relationship for in vivo and in vitro induction of dicentric aberrations in blood lymphocytes of children.

Chromosome aberrations induced in vivo were studied in nine children 5-12 years old treated with total-body high-energy photon irradiation (pulsed exposure from a LINAC) for different types of malignant diseases. Dose-effect relationships were obtained for each child by taking blood at different times during exposure. In vitro dose-effect relationships for chromosome aberrations in children and adults were obtained by exposing blood under the same conditions as the children. Exposure in vivo and in vitro yielded similar linear-quadratic dose-effect relationships for dicentric aberrations. The response in vitro was slightly greater than in vivo, but the difference was not very large. It is concluded that the dose-effect relationship for dicentric chromosome aberrations obtained in vitro for adults can be used for biological dosimetry in irradiated children. Some of the children displayed a high number of "rogue cells" before exposure; this may be due to the malignant disease as it was not found in the healthy controls.

The role of cooked food mutagens as possible etiological agents in human cancer. A critical appraisal of recent epidemiological investigations.

The paper reviews the epidemiological studies that investigate the relationships between dietary protein intake and the risk of some cancer and that have been published since 1980. A comparison of these reports is complicated because of many confounding factors that could obscure the conclusions (e.g. choice of controls) and because it is difficult to distinguish the consumption of fat from that of animal proteins. The 75 examined publications deal with the influence of food intake on different cancers: colo-rectal (42), stomach (8), breast (7), ovarian (4), endometrium (3), prostate (4), pancreas (2), urothelium (1), bladder (2), brain (1), lymphoma (1). From these studies in parallel with information from other sources, it is concluded that pyrolysis products generated by heat treatment of protein-rich food could be responsible factors for, at least, colo-rectal cancer.

[Study of the relation between dose of ionizing radiation and level of chromosome abnormalities in an adult patient following total body irradiation]. / Etude de la relation entre la dose de rayonnements ionisants et le taux d'anomalies chromosomiques chez une personne adulte irradiée in toto.

The dose-effect relationship for dicentric chromosome aberrations and centric rings was studied in a female patient exposed to whole-body gamma irradiation for myeloid leukaemia. Samples were taken before and at different times during the exposure. The dose-effect relationship is on the linear-quadratic type and practically identical with those found earlier when the blood from adults and children was irradiated in vitro and only slightly above that of children irradiated in vivo.

[Use of the micronucleus test for biological dosimetry in cases of homogeneous or non-homogeneous exposure to ionizing radiations]. / Utilisation du test des micronoyaux comme dosimètre biologique en cas d'exposition homogène ou non homogène aux radiations ionisantes.

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.

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.