Evaluation of cardiac anoxia and ischemia models in the rat using calcium antagonists.

The effects of severe global ischemia on cardiac high energy phosphate (HEP) stores were investigated in an in vitro rat model. The heart was removed from the rat in this model, sealed in a plastic bag and incubated for varying times and temperatures (20-45 degrees C). The rat, in the in vivo anoxic model, was subjected to cervical dislocation which resulted in respiratory arrest. In both models the hearts were removed and analyzed for HEP at appropriate times following the onset of anoxia or ischemia. Verapamil and nifedipine, administered intravenously 10 minutes before the start of the experiments, preserved HEP stores in both models. The degree of protection provided by the Ca+2 blockers was related to both the dose of drug and the duration of the ischemia/anoxia. Verapamil was more active than nifedipine in both models.

Field concentrations and persistence of polybrominated biphenyls in soils and solubility of PBB in natural waters.

Soil samples were collected from 28 fields which had received manure from Michigan's most highly contaminated dairy herds. The number of fields in each concentration range of PBB in soil were: 2, not detectable; 15, 0.0 to 8.0 ppb; 6, 14-102 ppb, and 5, 153 to 371 ppb. Plant tissue sampled from the 10 most highly contaminated fields contained no detectable PBB. No evidence of significant degradation of PBB was noted after 1 year incubation in soil. When 14C hexabromobiphenyl and heptabromobiphenyl isomers were incubated in soil less than 0.2% of the 14C was volatilized. Also gas chromatographic analysis of soil extracts showed no difference in recovery of the six major PBB isomers between sterilized and nonsterilized soil. Analysis of these extracts by thin layer chromatography and autoradiography showed no 14C-PBB intermediates. Photodegradation products of the major hexa- and heptabromobiphenyl isomers showed more but still minor (approximately 3%) biodegradation in soil. Much of the photodegradation products appeared bound to soil, since these products could not be extracted from soil. Photodegradation does not appear to be a significant fate of PBB in manures spread on fields since no change was noted in the relative concentrations of isomers in soil samples from our field survey. Studies with distilled, tap, river, and soil waters showed that PBB solubility was markedly influenced by water composition.

Absence of plant uptake and translocation of polybrominated biphenyls (PBBs).

Studies of polybrominated biphenyl (PBB) uptake by plants have been conducted in hydroponic solutions and in greenhouse experiments with soil. Autoradiograms of corn and soybean seedlings grown in hydroponic solutions showed no translocation of 14C-PBB from 14C-PBB-treated solutions to plant tops or within the leaf from 14C-PBB-treated spots on the upper leaf surface. A significant portion of the 14C-PBB associated with the roots was removed when the roots were dipped in acetone. Three root crops (radishes, carrots, and onions) were grown in two soils, each treated with a mixture of FireMaster BP-6 (PBB) and 14C-PBB to achieve final concentrations of 100 ppm and 100 ppb. All roots showed more PBB when grown in the soil with the lower clay and organic matter content than they did when grown in the soil with more clay and organic matter. In the latter soil (clay loam) no PBB was detected in any roots from the 100 ppb treatment. More PBB was associated with roots of carrot than of radish or onion. Corn leaf whorls containing dust from a PBB contamination soil and washed radishes from a heavily contaminated garden showed no PBB.