Effect of nucleotides on translocation of sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate into Golgi apparatus vesicles

Recent studies from this laboratory have suggested that rat-liver Golgi apparatus derived membranes contain different proteins which can translocate in vitro CMP-N-acetylneuraminic acid, GDP-fucose and adenosine 3'-phosphate 5'-phosphosulfate from an external compartment into a lumenal one. The aim of this study was to define the role of the nucleotide, sugar and sulfate moieties of sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate in translocation of these latter compounds across Golgi vesicle membranes. Indirect evidence was obtained suggesting that the nucleotide (but not sugar or sulfate) is a necessary recognition feature for binding to the Golgi membrane (measured as inhibition of translocation) but is not sufficient for overall translocation; this latter event also depends on the type of sugar. Important recognition features for inhibition of translocation of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate were found to be the type of nucleotide base (purine or pyrimidine) and the position of the phosphate group in the ribose. Thus, UMP and CMP were found to be competitive inhibitors of translocation of CMP-N-acetylneuraminic acid, while AMP did not inhibit. Structural features of the nucleotides which were less important in inhibition of translocation (and thus presumably in binding) of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate were the number of phosphate groups in the nucleotide (CDP and CMP inhibited to a similar extent), the presence of ribose or deoxyribose in the nucleotide, a replacement of hydrogen in positions 5 of pyrimidines or 8 in purines by halogens or an azido group. The sugar or sulfate did not inhibit translocation of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate into Golgi vesicles and therefore appear not to be involved in their binding to the Golgi membrane.     

Correlation of cotylenol with the aglycone of fusicoccin

The stereostructure of cotylenol, the aglycone of the cotylenins, has been confirmed by chemical correlation with the aglycone of fusicoccin A.     

Isolation of cytochalasins A and B fromAscochyta lathyri

The possible presence of toxic metabolites in the culture extracts of 24Ascochyta strains, grown on autoclaved wheat, was ascertained by the use of the biological assay on brine shrimps (Artemia salina). Only in the culture extract ofA lathyri, that showed a very high toxicity, the presence of cytochalasins A and B was revealed by tlc,¹H nmr and fab-mass spectra. SinceA heteromorpha, previously described as the firstAscochyta species to produce cytochalasins, has been reclassified asPhoma exigua varheteromorpha, this is therefore the first report on the cytochalasin production by a trueAscochyta species.     

Enhancement by levamisole of the contractions induced by prostaglandin E2 in the guinea-pig isolated ileum

The effect of levamisole on prostaglandin E₂ (PGE₂)-evoked contractions was studied on guinea-pig isolated ileum. Addition of levamisole (10 μg/ml) to the organ bath produced a pronounced increase in the amplitude of the PGE₂-evoked responses. Levamisole (10 μg/ml) also sensitized the guinea-pig isolated ileum to 5-hydroxytryptamine and bradykinin, but not to histamine. The effect of the levamisole was not due to stimulation of autonomic ganglia or cholinergic activity since it was unaffected by hexamethonium or atropine, but it was prevented by indomethacin.     

Safety of ethanolic kava extract: Results of a study of chronic toxicity in rats

BACKGROUNDS: Recently, potential liver toxicity was discussed with the intake of kava extract preparations (Piper methysticum) as anxiolytic drugs. The aim of this study was to test chronic toxicity in rats by oral application of an ethanolic kava full extract. METHODS: Wistar rats of both sexes were fed 7.3 or 73 mg/kg body weight of ethanolic kava extract for 3 and 6 months. The animals were examined for changes in body weight, hematological and liver parameters, and macroscopical and microscopical histological changes in the major organs. RESULTS: No signs of toxicity could be found. CONCLUSIONS: The results are in accordance with the medical experience regarding the use of kava preparations and the long tradition of kava drinking in the South Pacific island states. Specifically, the results do not back the suspicion of potential liver toxicity.