Temporal constraints on hydrate-controlled methane seepage off Svalbard.

Methane hydrate is an icelike substance that is stable at high pressure and low temperature in continental margin sediments. Since the discovery of a large number of gas flares at the landward termination of the gas hydrate stability zone off Svalbard, there has been concern that warming bottom waters have started to dissociate large amounts of gas hydrate and that the resulting methane release may possibly accelerate global warming. Here, we corroborate that hydrates play a role in the observed seepage of gas, but we present evidence that seepage off Svalbard has been ongoing for at least 3000 years and that seasonal fluctuations of 1° to 2°C in the bottom-water temperature cause periodic gas hydrate formation and dissociation, which focus seepage at the observed sites.

[Effect and correlation of various risk factors in the development of retinopathy of prematurity. A retrospective study of 338 premature infants]. / Einfluss und Zusammenhang verschiedener Risikofaktoren bei der Entstehung der Retinopathia praematurorum. Eine retrospektive Studie an 338 Frühgeborenen.

The statistical significance of ophthalmological and pediatric findings in the development of retinopathy of prematurity (ROP) was evaluated in a retrospective study of 338 premature infants. Short gestation time, frequent hypoxia, and low birthweight were strongly correlated with advanced stages of ROP. The influence of Vitamin E treatment, duration of oxygen therapy, and need for transfusions was less significant. Neither multiple births nor the infant's sex had any influence on the development of ROP. Cryotherapy appears to reduce ROP, but the number of cases in the present study was too small to permit statistical analysis.

Biological activation of 1,3-butadiene to vinyl oxirane by rat liver microsomes and expiration of the reactive metabolite by exposed rats.

When 1,3-butadiene is incubated with rat liver microsomes and NADPH both enantiomers of vinyl oxirane are formed, the amount of epoxide being dependent on incubation time, microsomal protein, and substrate concentration. Inhibition by SKF 525 A or dithiocarb as well as induction by pretreatment with phenobarbital or 20-methylcholanthrene suggest participation of cytochrome P-450 in this reaction. The amount of epoxide is enhanced by addition of 1,1,1-trichloropropene oxide and reduced by glutathione, especially in the presence of hepatic cytosol. When rats are exposed to 1,3-butadiene in a closed chamber (conditions of maximal metabolism) vinyl oxirane is exhaled and can be quantitatively determined from the gas phase. The concurrent exhalation of acetone is consistent with the idea of biologic action of a reactive metabolite.