HPLC separation of 32P-postlabelled DNA adducts formed from dibenz[a,h]anthracene in skin.

Mouse skin and human skin have been treated in vivo or in short-term organ culture with dibenz[a,h]anthracene (DB[a,h]A), the related 3,4- or 5,6-diols or the anti- or syn-3,4-diol 1,2-oxides. DNA hydrolysates have been 32P-postlabelled and the adducts present examined by HPLC using a phenyl-modified reverse phase column and, for comparison, by PEI-cellulose TLC and autoradiography. The adducts formed when the diol-epoxides were reacted with salmon sperm DNA were also examined. The results show that in mouse skin treated in vivo, the major adducts formed from DB[a,h]A and the 3,4-diol were the same and that two of them were more polar than those formed in skin or in DNA that had been treated with the related anti- or syn-diol epoxides. Human skin treated with DB[a,h]A in culture yielded an adduct profile that was qualitatively similar to the profiles obtained with mouse skin.     

Prostaglandin synthesis does not mediate the pulmonary vasodilatory effect of acetylcholine

We wondered if inhibition of hypoxic pulmonary vasoconstriction by acetylcholine was mediated by prostaglandin synthesis. In 5 calves at a simulated altitude of 4,570 m, acetylcholine (10 μg/kg/min) decreased mean pulmonary arterial pressure and total pulmonary resistance by 24 ± 2 and 35 ± 3% before and by 21 ± 2 and 27 ± 4% after the administration of meclofenamate (2 mg/kg). Since there was no difference in the effect of acetylcholine before and after meclofenamate, it was concluded that pulmonary vasodilation by activation of muscarinic receptors was not dependant on prostaglandin synthesis.     

Accumulation of glycosphingolipids in human atherosclerotic plaque and unaffected aorta tissues

We have measured the levels of glycosphingolipids and the activityof glycosphingolipid glycosyltransferases in human aortic intimaand media from patients who died of atherosclerosis. The effectsof lactosylceramide (LacCer) and glucosylceramide (GlcCer) fromplaque intima on smooth muscle cell proliferation were assessed.When the GIcCer data was expressed as (pg GlcCer/mg cholesteroland/mg total phospholipid, a 28-fold and 7-told increase inplaque intima compared to normal intima was observed. Similarly,the level of LacCer was elevated 5-fold and 4-fold, respectively,compared to unaffected intima. The activity of UDPGicCer: ceramideß1     

Genotoxic effects of some organophosphorous pesticides. I. Induction of micronuclei in bone marrow cells in rat

The genotoxic effects of 4 organophosphorous pesticides, i.e. ekatin, fenitrothion, methylparathion and phorate, were examined employing the micronucleus test in bone marrow cells of the rat. Methylparathion and phorate were found to be mutagenic, while ekatin was weakly mutagenic. The frequency of micronuclei induction by fenitrothion did not differ significantly from that noticed in negative control.     

The light : nutrient ratio in lakes: a test of hypothesized trends in bacterial nutrient limitation

The light-to-nutrient hypothesis explores how the balance between energy (as light energy) and nutrients (as total phosphorus) shapes aquatic ecosystem structure and process. The balance of energy and nutrients is thought to regulate ecosystem structure and process such that, in a "high" light-to-nutrient environment, bacteria would probably be driven towards phosphorus (P) limitation, whereas, in a "low" light-to-nutrient environment, bacteria would be driven towards carbon (C) limitation. We assessed the growth limitation of bacteria in two reservoirs of the southern U.S.A. using a mortality-corrected dilution-growth approach. We compared the frequency of P and C growth limitation with the intralake variation in the light-to-nutrient environment. As a metric of the light-to-nutrient environment, we used the ratio of the mean light in the surface mixed layer ( I _m) to the total phosphorus concentration ( TP ). In each lake, bacterial growth was more often P-limited when the I _m :  TP ratio was above the median ratio than below. We believe our data provide the first evidence supporting this aspect of the light-to-nutrient hypothesis.     

How Daphnia cope with algae selected for inedibility in long- running microcosms

Macro video records of restrained feeding Daphnia enabled usto measure simultaneously carapace gape, claw rejection rate,filter limb beat rate, and mandible movement rate. We comparedthe effects of high and low concentrations of highly ediblealgae and of inedible algae, the latter selected by long-termDaphnia grazing in oligotrophic microcosms. Inedible algae slowedthe filtering process and influenced the carapace gape (wideningat low concentration and narrowing at high), but did not affectthe rejection rate.     

Alterations in the coronary circulation of man following ascent to 3,100 m altitude.

Alterations in coronary blood flow associated with adaptation to high altitude were examined. Three normal men native to low altitude were studied, first at sea level, and again after 10 days' sojourn at 3,100 m altitude. During rest at high altitude, a 32% decrease in coronary blood flow was largely offset by a 28% increase in coronary arterial O2 extraction to maintain myocardial O2 delivery. The increase in O2 extraction resulted mainly from a decrease in coronary sinus blood O2 content and saturation. However, coronary sinus O2 tension remained constant, implying a decrease in the affinity of hemoglobin for O2. These observations are consistent with the hypothesis that coronary blood flow is regulated to maintain constant myocardial tissue O2 tension (as reflected here by coronary sinus blood O2 tension). The absence of a decrease in coronary sinus O2 tension or a decrease in myocardial lactate extraction imply that myocardial hypoxia did not develop. Therefore, myocardial hypoxia is not the basis for the decrease in cardiac stroke volume at high altitude reported previously and also observed in the present study.