Brownfields Rejuvenation
The rejuvenation of brownfields--abandoned industrial sites with proven or suspected environmental contamination--is one of the few success stories where everyone involved seems to win. The Focus article looks at what is involved in the federal government's ambitious project to clean up these unused commercial sites, turning urban blight into urban might.
For the Children's Sake
Children's environmental health is getting close attention from politicians and regulatory agencies who are looking for ways to improve the protection afforded these vulnerable members of our society. The Spheres of Influence examines why improved environmental protection for children is so crucial and outlines some of the advances being made in this area.
Oxidative Metabolites from Macrophages
Rat lung alveolar macrophages were loaded with fluorescent dye and exposed to 10-15 µm long erionite mineral fibers. Long et al. examined in vitro generation of reactive oxygen metabolites during phagocytosis and were able to monitor events on a single cell basis over time.
Cadmium Toxicity in Human Fetal Lung Cells
Yang et al. evaluated effects of cadmium on human fetal lung fibroblast cells by measuring lipid peroxidation, reactive oxygen species, and mitochondrial membrane potential. The in vitro responses suggested that lipid peroxidation by hydrogen peroxide was one of the main pathways of cytotoxicity, although mitochondrial damage was also involved. The data indicate that oxidative damage of lung cells may be closely associated with the pulmonary toxicity of cadmium.
Brain Asymmetry from TCDD Exposure
An animal model was used by Henshel et al. to investigate whether TCDD, suspected of causing left-right interhemispheric differences in brain symmetry in wild bird species, was the causal environmental contaminant. Chicken eggs were injected with parts per trillion doses of TCDD and the brains were examined after sequential development. Brain assysmetry was similar to that in wild birds exposed to mixtures of TCDD-related contaminants, the responses were dose-related, and the toxic developmental effects were a direct effect of TCDD on the brain rather than on the braincase.
Aging and Heat Stress on Rat Liver Enzymes
A variety of adaptive metabolic systems in aging rats was compromised by exposure to increasing temperatures as high as 40°C for up to 42 days. Ando et al. showed that 7-week and 12-month-old rats were also adversely affected by heat stress, but not to the same extent as rats aged 17 or 25 months old, suggesting similar consequences might occur in aged humans.
Recombinant Yeast Cell Estrogen Screen
Yeast cells transformed with plasmids encoding the human estrogen receptor and an estrogen responsive promoter linked to a reporter gene were used by Coldham et al. to screen compounds for estrogenic activity. Relative sensitivity to estrogens was calibrated with 17ß-estradiol and by reference to responses in MCF-7 human breast cancer cells and the prepubertal mouse uterotrophic assay. The yeast assay was about 2 to 5 orders of magnitude more sensitive to 17ß-estradiol than the other two assays. The estrogenic potency of 53 chemicals was measured. Maximum sensitivity, lack of biotransformation of test compounds, ease of use, and potential for measurement of antiestrogenic activity are valuable attributes for the yeast cell estrogen screen.
Magnesium Inhibits Nickel-Induced Genotoxicity
In vitro studies of cytotoxicity and genotoxicity induced by nickel compounds were conducted by Hong et al. . Nickel inhibited cell proliferation and increased micronuclei formation, DNA-protein crosslinking, and peroxide-induced 8-hydroxy-deoxyguanosine formation. Nickel exhibited intracellular accumulation 80-fold above controls. All responses were attenuated by magnesium, suggesting that this metal functions by either reducing intracellular nickel concentration or reactive oxygen formation.
Structure-Activity Relationships, PAHs, and Endometriosis
Johnson et al. used endometriosis in mice as an endpoint to assess structure- activity relationships of TCDD and related polyhalogenated aromatic hydrocarbons that have varying degrees of affinity for the Ah receptor. Animals were gavaged 5 times with 3 weeks between doses, and endometriosis was surgically induced at the second dose. The data were consistent with the hypothesis that endometriosis promoted by these compounds was mediated by the Ah receptor.
Last Update: August 1, 1997 |