The German uranium miners cohort study: feasibility and first results.

In Germany, the largest single cohort study on uranium miners to date is being conducted. The cohort includes about 64,000 workers of the former Wismut company in eastern Germany. Inclusion criteria were: a date of employment between 1946 and 1989, a minimum period of employment of 180 days, and complete information on working history. Due to poor working conditions in the late 1940s and early 1950s, miners were exposed to high levels of radiation, while later radiation exposure was significantly reduced. The aim of the cohort study is to evaluate the risk of lung cancer and other cancers associated with several indicators of exposure to radon and its progeny, with particular attention to low levels of radiation. Radon exposure will be estimated by a detailed job- exposure matrix. Some information about smoking, dust and arsenic is already available. About 49,000 miners are defined as exposed (underground or processing), while the internal control group (surface only) consists of 15,000 workers. A total of 1,436 lung cancer deaths among cohort members have been reported. The first mortality follow-up will be finished early in 2002, and a total of about 3,000 lung cancer deaths are expected by then.

Inhibition of x-ray-induced protection of Escherichia coli K-12 cells against the lethal effects of ultra-violet light by nitrofurantoin.

Wild-type cells of E. coli K-12 showed increasing U.V. resistance if they were X-irradiated and incubated at 37 degrees C in growth medium before the U.V. exposure. Development of higher U.V. resistance could be inhibited by incubating the X-irradiated cells either at temperatures below 15 degrees C, or in the presence of 0.01 M KCN. Nitrofurantoin (NF), which was recently found specifically to inhibit inducible enzyme synthesis, had only a transient inhibitory effect on X-ray-induced U.V. resistance. Cells grown in glucose medium showed less inhibition by NF of X-radiation-induced resistance to U.V.-radiation than did cells grown in glycerol, or in glucose medium with added cyclic AMP. It is suggested that X-ray-induced U.V. resistance requires active cellular metabolism, but it is not subject to catabolite repression. The following hypothesis is offered to explain the action of NF: Under de-repressed conditions (without catabolite repression by glucose) nitrofurantoin could counteract the radiation-induced inhibition of a repair inhibitor (such as post-irradiation DNA degradation).

[A new radiation protection dose limit for occupationally exposed personnel in the Federal Republic of Germany]. / Ein neuer Strahlenschutz-Grenzwert für beruflich strahlenexponierte Personen in der Bundesrepublik Deutschland.

In the Federal Republic of Germany, as in most other countries, the dose limit is 50 mSv per year for occupationally exposed persons, as recommended by the International Commission on Radiological Protection (ICRP). A reduction in the annual dose limit was recently considered in connection with a discussion of a higher estimation of radiation risk. In the recent amendment of the German Radiological Protection Ordinance, however, the dose limit of 50 mSv per year was retained and additionally a new occupational lifetime dose limit of 400 mSv was introduced. The possible consequences of the 400 mSv dose limit will be discussed on the basis of the previous results of dose monitoring in the Federal Republic of Germany.

W-reactivation of phage lambda in X-irradiated mutants of Escherichia coli K-12.

The survival of UV irradiated phage lambda was increased on X-irradiated E. coli K-12 host cells over that on unirradiated cells. The frequency of c mutants among the surviving phages was to a similar extent increased by the X-ray exposure of the host cells as by UV light. This W-reactivation of phage lambda occurred in uvrA, polA, and recB mutants besides the wild type at about equal X-ray doses, however, at a reduced reactivation efficiency compared with the wild type. W-reactivation was undetectable in recA mutants. While maximal UV induced W-reactivation occurred 30 min after irradiation, the maximal X-ray induced reactivation was found immediately after irradiation. Chloramphenicol (100 micrograms/ml) and nitrofurantoin (50 micrograms/ml) inhibited W-reactivation of phage lambda if added before irradiation of the host cells, indicating the necessity of protein synthesis for W-reactivation.

Inactivation of bacteriophage lambda by combined X-ray and U.V.-light exposure.

Extracellular phage lambda has been successively exposed to X-rays and U.V. light. The plaque-forming ability of the irradiated phages was determined on host cells with different repair capacities. No change in sensitivity was found with a pre-treatment of one type of radiation to lethal damage inflicted by the other. This indicates that a prerequisite for an interaction of different types of radiation is either an active metabolism or repair process occurring during the two radiation exposures.