The specific binding of the herbicide acifluorfen 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-~tro~nzoic acid to corn etioplast membranes is competitively inhibited by protoporphyrinogen IX, the substrate of protopotphyrinogen oxidase. Three other peroxidizing molecules, oxadiazon [5-terbutyl-3-(2,4dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-one], LS 82556 [(S)3-N-(methylbenzyl)carbamoyl-5-propionyl-2,6-lutidine], and M&B 39279 [5-amino-4-cyano-l-(2,6-dichloro-4-trifluoromethylphenyl)pyr~ol], also compete with acifluorfen for its binding site. The four herbicides thus bind to the same site, or to closely located sites, on the enzyme protoporphyrinogen oxidase.
S U M M A R YThe herbicide ethofumesate is commonly used in onion fields in Israel. Experiments with four onion cultivars have shown the combination of a pre-emergence treatment with ethofumesate and foliar application of a variety of herbicides to cause a marked decrease in plant fresh weight. This effect of ethofumesate was still evident when post-emergence herbicides were applied as late as the third leaf stage of development. Significantly lower amounts of waxes were extracted with chloroform from the leaves of onion plants treated pre-emergence with ethofumesate, at the rates of 0.2-0.8 kg/ha. SEM micrographs showed considerable changes in the onion epicuticular fine structure following these ethofumesate treatments. Furthermore, a significant increase in the penetration of I4C-labelled compounds into the onion leaves was measured. The possible implications of ethofumesate effects on onion leaf surface fine structure, are discussed. 0 1986 Association of Applied Biologists
Reactive oxygen metabolites have been implicated in gastric mucosal injuries. Superoxide dismutase, a scavenger of superoxide radical, is a key enzyme in gastric mucosal protection against several damaging factors. This study was aimed at investigating the relationship of superoxide dismutase activity to Helicobacter pylori-induced antral gastritis in children. Two groups of 11 children each, one positive and the other negative for Helicobacter pylori, were studied. Biopsies from the antrum and corpus were obtained for evaluation of Helicobacter pylori by CLOtest and histology as well as for superoxide dismutase activity (cytochrome c method). Erythrocytic and serum superoxide dismutase levels were determined as well. Superoxide dismutase activity was significantly higher only in the antrum of children with Helicobacter pylori-induced antral gastritis. There was no significant difference in superoxide dismutase activity in the corpus, erythrocytes, or serum of both groups. These findings may suggest a pathogenic relationship between the presence of Helicobacter pylori and oxygen radicals in inducing antral mucosal injury.
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