Atmospheric dispersion of vapors: are molecular properties unimportant?

Vapor profiles of pesticide mixtures over fallow agricultural fields reveal consistent rapid shifts in the relative proportions of the components in air. These relative concentration changes are correlated with molecular weight and size and reveal a significant molecular contribution to dispersion in turbulent air. Atmospheric studies that rely upon tracer gases, or use calculations that assume the equality of eddy dispersion coefficients, may be in serious error.     

Reverse diel vertical migration: an escape from invertebrate predators

The marine copepod Pseudocalanus sp. exhibits an unusual reverse diel vertical migration in Dabob Bay, Washington, concurrently with a normal vertical migration by nocturnal invertebrate predators. Reduced spatial overlap with predators appears to decrease mortality rate of adult female Pseudocalanus. A life table analysis suggests that the demographic disadvantage associated with daily migration across a thermal gradient can be overcome if mortality is reduced by as little as 16 percent.     

Sucrose: a constitutive elicitor of phytoalexin synthesis

Extracts of seeds and leaves of the tropical legume Cajanus cajan (L.) Millsp. (the pigeon pea) elicited the accumulation of three phytoalexins when applied as droplets to superficially wounded leaves of the plant. The active component was purified and identified as sucrose. Phytoalexin accumulation was proportional to the logarithm of the concentration of sucrose applied, with maxima ranging from 338 to 455 micrograms per gram (fresh weight) of leaf tissue. The sucrose concentrations required to elicit half these amounts ranged from 20 to 35 micrograms per milliliter, but other sugars had little effect even at 1000 micrograms per milliliter. The elicitor activity of sucrose was abolished by actinomycin D, puromycin, and cycloheximide at a concentration of 10 micrograms per milliliter or greater, suggesting that gene derepression is required for expression of the phytoalexin response.     

Reduced nicotinamide-adenine dinucleotide phosphate oxidase: activity enhanced by ethanol consumption

Prolonged consumption of ethanol enhances the activities of the hepatic microsomal ethanol oxidizing system and of reduced nicotinamide-adenine dinucleotide phosphate oxidase, but not of catalase. The oxidase-catalase system is not part of the microsomal ethanol oxidizing system since catalase inhibitors dissociate ethanol oxidation by the two pathways. Enhanced reduced nicotinamide-adenine dinucleotide phosphate oxidase activity may contribute to liver injury, possibly by favoring lipoperoxidation.     

Enzyme replacement in Fabry's disease, an inborn error of metabolism

Two patients with Fabry's disease were infused with normal plasma to provide active enzyme (ceramide trihexosidase) for hydrolysis of the plasma substrate, galactosylgalactosylglucosylceramide. Maximum ceramide trihexosidase activity occurred 6 hours after infusion of the plasma, attaining a level approximately 150 percent of that in normal plasma; enzymatic activity was detectable for 7 days. The amount of accumulated substrate in the plasma of these recipients decreased about 50 percent on day 10 after infusion. Thus, periodic replacement of ceramide trihexosidase activity in the plasma of patients with Fabry's disease might lead to consistently lower amounts of substrate in the plasma and a decrease in its rate of accumulation in tissues.     

Specific inhibition of nuclear RNA polymerase II by alpha-amanitin

alpha-Amanitin, a toxic substance from the mushroom Amanita phalloides, is a potent inhibitor of DNA-dependent RNA polymerase II (the nucleoplasmic form) from sea urchin, rat liver, and calf thymus. This compound exerts no effect on the activity of polymerase I (nucleolar form) or polymerase III (also nucleoplasmic). The inhibition is due to a specific interaction with polymerase II or with a complex of DNA and polymerase II.