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Biomedical subjects

J R Beall

Publications and source records attributed to J R Beall.

At least 19 recordsLinked to original sources

Low-level exposures: some implications for the U.S. Department of Energy.

The U.S. Department of Energy (U.S. DOE) maintains several programs to study and understand the health and environmental effects of exposure to low levels of energy-related agents. These programs include research to understand the mechanisms of action of agents of concern and to assess the risks associated with exposures of people and ecological systems to these agents. They also include implementing appropriate occupational safety and health standards and remediating waste sites to environmental standards. These programs require that the U.S. DOE pursue a realistic understanding of the effects of exposures to small amounts of energy-related agents. The largest of these programs involves hazardous waste remediation and includes potentially harmful exposures to low levels of numerous agents. The U.S. DOE conducts research to establish the scientific bases for the realistic assessment of risks of exposure to such wastes. As part of the U.S. DOE efforts to understand the risks of low-level exposures to hazardous waste, the Office of Health and Environmental Research and the Office of Environmental Management recently launched a broad cooperative program. It is comprised of research projects in nine general scientific areas and includes research on the health impacts and risk estimation of exposure to low levels of hazardous wastes. Projects for this new cooperative research program were selected from 610 applications and totaled approximately $47 million in fiscal year 1996. This program marks a new approach by using basic research to reduce cleanup costs and to develop scientific foundations for advances in environmental technologies. The research will also examine the effects of exposure to low levels of chemical and radiological wastes.

Hazardous Waste↗

Formaldehyde and hepatotoxicity: a review.

Exposure to formaldehyde appears to be associated with hepatoxicity in many species, including humans, following injection, ingestion, or inhalation. Macroscopic, microscopic, and biochemical manifestations in the liver include alterations in weight, centrilobular vacuolization, focal cellular necrosis, and increased alkaline phosphatase concentrations. Time-related changes in the pattern of the effects are suggested as one goes from acute exposure by inhalation at greater concentrations to repeated exposure at lesser concentrations. Although the hepatic changes are generally not extensive and can be reversible following acute exposure, the potential exists for them to progressively become more serious with repeated exposures. There are several possible mechanisms for the toxicity. Depending on the route of exposure could include direct effects on hepatocytes and/or indirect effects through the circulatory and immune systems. The catabolism of formaldehyde includes conversion to CO2 by reactions involving glutathione. Many hepatotoxic chemicals require glutathione for detoxification. Formaldehyde may then have the potential to cause additive toxicity with such chemicals in some circumstances.

Alkaline Phosphatase↗

Occurrence and distribution of sucrose-metabolizing enzymes in oral streptococci.

Specific growth rates, growth yields, and the level and cellular distribution of three sucrose-metabolizing enzyme activities were determined for seven oral streptococci (Streptococcus mutans strains E49, BHT, 10449, SL-1, and LM-7, S. sanguis 10558, and S. salivarius 25975). Cultures were grown in a fermentor at pH 6 with either 20 mM glucose or 10 mM sucrose. Generation times varied between 21 and 70 min. Whereas some strains grew 10 to 50% more slowly with sucrose than with glucose, others did not. Growth was always logarithmic, and the growth yields were similar. Glcosyl transferase (EC 2.4.1.5) was largely extracellular; in sucrose cultures it was appreciably lower, but no major shift to a cell-associated form was found. In glucose cultures, the activity varied between 4 and 140 IU per 6-liter culture. The glucan formed was mostly or exclusively water insoluble. Glcosyl transferase was stimulated weakly (60% or less) by various dextrans. Fructosyl transferase (EC 2.4.1.10) was primarily extracellular (except in glucose cultures of S. salivarius) and varied between 0 and 337 IU/culture. In S. salivarius, the extracellular fructosyl transferase was induced by sucrose. In all S. Mutans cultures, the total fructosyl transferase activity was lower after growth with sucrose. All strains had extra- and intracellular invertase (EC 3.2.1.26) activity. Total levels varied between 210 and 3,500 IU/culture. Less extracellular activity was present in sucrose cultures. Only S. salivarius had appreciable activity in the cellular particulate fraction. Invertase activity was significantly higher than the combined glucosyl and fructosyl transferase activities in all cultures.

Fructose↗

Griseofulvin: a teratogenic study.

Griseofulvin, a fungistatic agent, was administered in oral doses of 125 to 1500 milligrams per kilogramn per day to pregnant rats during organogenesis. Evaluation of the offspring from dams treated with the largest doses, 63 and 75 times a therapeutic dose in man, indicated decreased survival rates and a syndrome of malformations.

Abnormalities, Drug-Induced↗