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Biomedical subjects

J Rantanen

Publications and source records attributed to J Rantanen.

At least 73 records · Page 4Linked to original sources
PubMed1976

Urinary mandelic acid concentration after occupational exposure to styrene and its use as a biological exposure test.

Excretion of mandelic acid from workers in the reinforced polyester plastic industry was studied with the determination of urinary mandelic acid concentrations. The styrene exposure level at the workplaces was evaluated with measurements of the styrene concentration in the ambient air. Three different groups (I, II and III) were studied. In group I [n=9, median of the time-weighted average (TWA) of exposure = 23 ppmof styrene, postexposure observation period = 64 h] two excretion slopes were observed, the first with a median half-time of 9.4 h (postexposure period 0--18 h) and a second with a median half-time of 16.6 h (postexposure period 19--64 h). For group II (n=9, median TWA exposure = 248 ppm, postexposure observation period = 15 h) a half-time of 6.4 h was found. These results suggest that the excretion rate of mandelic acid is dependent on the styrene exposure level. In addition the mandelic acid concentrations of 29 workers (group III) before and after the work shift were analyzed. The urinary mandelic acid concentrations of groups I, II and III, sampled immediately after the 8-h work shift, correlated with the 8-h TWA of styrene exposure (n=47, r=0.93). Accordingly about 2,300 mg of mandelic acid per gram of creatinine corresponded to 100 ppm of styrene.

Air Pollutants, Occupational↗
PubMed1975

Determination of toxic metals in blood by x-ray fluorescence spectrometry.

An application of X-ray fluorescence spectrometry for the analysis of various toxic metals (lead, cadmium, manganese, chromium, nickel, vanadium) in whole blood was studied, and two techniques for sample preparation (vacuum drying and nitric acid combustion) were compared. The acid combustion method appeared to be superior on the basis of the accuracy and precision of the determinations. The tungsten-target X-ray tube was suitable for determining manganese, nickel, and vanadium, the lowest limits of detection being 0.021 mug/ml, 0.035 mug/ml and 0.017 mug/ml, respectively, and the precisions being between 4.25 and 6.92%. The sensitivity and reproducibility for lead, cadmium, and chromium were unsatisfactory. A comparison between the recoveries of X-ray fluorescence and atomic absorption analyses demonstrated that the X-ray method is suitable for determining manganese, vandium, nickel, cadmium, and lead. The poor sensitivity of the X-ray method, however, restricts its practical use. For vandium the results obtained by X-ray fluorescence were superior to those measured by a colorimetric method. No significant differences were observed between the results of single component and multicomponent analyses at the metal concentrations usual in physiological and toxicological cases.

Animals↗
PubMed1975

Collagen metabolism in rat lungs during chronic intermittent exposure to oxygen.

Collagen metabolism was studied in rat lungs during prolonged intermittent exposure to oxygen. After an initial of 2-d exposure to oxygen, the rats alternately breathed air and oxygen in 24-h periods up to 30 d. Lung histology showed perivascular edema as an early sign of oxygen toxicity. Increased capillary permeability was followed by a marked perivascular leukocytosis that was prominent between the 5th and 11th d of the treatment. During the further course of the experiment, the inflammatory response gradually diminished, and finally a network of collagen fibres filled the perivascular areas. The inflammatory process elevated the amounts of DNA and RNA in lung tissue, and the ratio of RNA to DNA was maximal on the 5th day. Studies on metabolism of lung collagen with intraperitoneally injected 3H-proline as label showed that, after the initial inflammatory reaction, both synthesis and degration of collagen were increased in oxygen-treated lungs. The increase in synthesis exceeded the rise in degradation and, therefore, collagen was accumulated. The activation of lung collagen synthesis coincided in time with a rise in the activity of lung protocollagen proline hydroxylase.

Animals↗
PubMedDate not supplied

Radiation carcinogenesis.

In radiation-induced carcinogenesis the stages of initiation, transformation, and promotion can be identified. Radiation carcinogenesis is a stochastic phenomenon that does not exhibit any threshold in the dose-response relationship. The most important risk to be controlled is that of the population--either industrial or medical--exposed to radiation at low levels and low dose rates. Despite the expanding use of radiation, the average doses in most industrialized societies have not been increasing during the last few years. However, sensitive subpopulations with high cancer risks are included within the present low-level average exposure figures.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Effects of nonsteroidal antiinflammatory medication on satellite cell proliferation during muscle regeneration.

Previous experimental studies have indicated delayed muscle regeneration after nonsteroidal antiinflammatory drug therapy. Successful regeneration of muscle after injury requires activation of normally dormant satellite cells that share the basal laminae with adjacent muscle cells. In the presence of adequate capillary ingrowth, satellite cells proliferate into myotubes and eventually form new muscle cells. In this study, the onset and extent of satellite cell and fibroblast proliferation as well as the production of myotubes and capillaries were analyzed with immunohistochemical methods after contusion injuries to rats' gastrocnemius muscles. Two groups of animals received daily doses of an intramuscular nonsteroidal antiinflammatory drug (naproxen) starting 6 hours and 3 days after injury, respectively. Treated animals were compared with similarly injured untreated animals. Satellite cell and fibroblast proliferation were unaffected by the treatment, and there were no significant differences in myotube or capillary production between treated and control animals. We conclude that naproxen treatment does not compromise the basic process of myofiber regeneration after injury.

Animals↗