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Biomedical subjects

B Holmberg

Publications and source records attributed to B Holmberg.

18 recordsLinked to original sources
PubMed1978

Extrapolation of carcinogenic risk from animal experiments in man.

When estimating the absolute risk of cancer, the shape of the dose--response curve in the region of doses where actual exposure of man occurs is of crucial importance. This shape is equally important for the determination of relative risks, as in the comparison of risks from alternative energy sources. Experimental and epidemiological studies are, for various reasons, unable to give sufficiently exact information concerning the dose response in the low dose region. Therefore, the discussion concerning dose--response relationships also has to consider biologically reasonable mechanisms for the origin of tumors.

Animals↗
PubMed1977

Variations in the blood concentration of 1,1,2-trichloroethane by percutaneous absorption and other routes of administration in the guinea pig.

The blood concentration of 1,1,2-trichloroethane was studied after epicutaneous application, by an intracutaneous, subcutaneous or intraperitoneal injection. An equation with three exponential terms was necessary for a satisfactory description of the experimental data in the case of intraperitoneal injection. Subcutaneous and intracutaneous injections seem to give essentially the same king of blood concentration curves as for intraperitoneal injection. In the case of percutaneous absorption an equation with three exponential terms and a constant was necessary to account for the experimental data. The complex toxicokinetics of 1,1,2-trichloroethane by percutaneous absorption was assumed to be associated with progressive skin damage observed in previously reported experiments, a damage apparently involving a change in barrier function.

Administration, Topical↗
PubMed1977

Morphological lesions in guinea pigs during skin exposure to 1,1,2-trichloroethane.

Guinea pigs were exposed to 1,1,2-trichloroethane applied directly on the skin of the back for periods between 15 minutes and twelve hours under anaesthesia. Morphological changes could be observed in the epidermis after 15 minutes and continued to progress during continuing exposure. The changes consisted of pyknotic nuclei, perinuclear oedema of basal and suprabasilar cells as well as a focal separation of the epidermis from the corium with vesicle formations. The liver tissue showed reduction of glycogen content as well as hydropic changes in the centrilobular areas six hours after the start of exposure. The liver changes were less marked 12 hours after exposure and absent in nonanaesthetized animals. No morphological changes were observed in the kidney or the brain.

Animals↗
PubMed1977

A study on the distribution of methylchloroform and n-octane in the mouse during and after inhalation.

The distribution of methylchloroform and n-octane, respectively, in the blood, liver, kidney, and brain of mice was studied at different inspired air concentrations and after different exposure times. The air concentration varied between 10 and 10,000 ppm; and the exposure time, between 0.5 and 24 h. The resulting solvent concentrations in kidney and brain were about the same, but the liver concentrations were usually somewhat higher for both solvents. There was a linear dependence between inspired air concentration and tissue concentrations at fixed exposure times. A correlation between blood and organ concentrations was observed in animals exposed at different inhalation air concentrations but not in animals exposed only at one fixed concentration. The ratios between the concentrations of the solvents in the organs and blood were higher for n-octane than for methylchloroform. The ratios increased as the exposure concentration increased for all organs studied in the case of n-octane but only for the liver in the case of methylchloroform. When the exposure dose, i.e., inspired air concentration X time, was generated in different ways, a high concentration during a short exposure resulted in a ten times higher organ concentration than a low concentration during a long exposure. The liver, kidney, and brain concentrations generally did not differ more than twice between methylchloroform and n-octane after exposure of the same concentration and duration. The blood concentration, however, was much less in n-octane exposed animals than in methylchloroform exposed ones. A pharmacokinetic model with both uptake and elimination of the first order fitted the empirical data better for methylchloroform than a model with zero order uptake and first order elimination. Postexposure concentrations of methylchloroform were linear in a semilog graph. A one-compartment pharmacokinetic model was in accordance with the experimental data for methylchloroform. For n-octane, however, at least a two-compartment model must be assumed.

Aerosols↗
PubMed1977

Occupational health standards. An international comparison.

The background for establishing standards for toxic agents is reviewed, and the standards of 14 different countries, including Sweden, are compared with special reference to criteria and organizational aspects. The differences among countries in the numerical limit values for toxic substances are largely due to differences in definitions, biomedical criteria, technical feasibility and sociopolitical judgements.

Air Pollutants↗
PubMed1976

Biological effects of vinyl chloride: an experimental study.

Plasma activities of alkaline phosphatase, (AP), transaminases and total lactate dehydrogenase (LDH) with isoenzymes were determined in mice inhaling 50 and 550 ppm vinyl chloride (VC). The animals were also autopsied and the tissue pathology was studies. The total LDH activity was elevanted in both dose groups along with a shift to cathodic enzymes. AP was increased in animals exposed to 500 ppm and transaminases were not at all changed. Enzyme changes occurred after the appearance of tumors. Alveologenic adenomas occurred in all animals at the higher dosage and in about half of the animals inhaling the lower dose. Subperitoneal and subcutaneous hemangiosarcomas were frequent in both dose groups; but especially among 50 ppm animals. Only one animal had a hemangiosarcoma of the liver. No liver fibrosis was seen. All primary subperitoneal and subcutaneous tumors were located in fat tissue. Telangiectasis was observed in two animals in the 500 ppm series. The importance of blood vessel changes in the toxicology of vinyl chloride is discussed.

Abdominal Neoplasms↗
PubMed1976

Recent achievements and research initiated in the Swedish plastics and rubber industry.

The improvement in exposure conditions in the Swedish vinyl chloride producing industry is reported. The article comments on the technology and control methods by which the vinyl chloride concentration has been lowered to less than 1 ppm vinyl chloride. Two epidemiological retrospective cohort studies are presently under way on workers in PVC-utilizing industries and in the rubber industry.

Air Pollutants, Occupational↗