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G Zweig

Publications and source records attributed to G Zweig.

At least 37 records · Page 2Linked to original sources

Analytical determination of N-nitroso compounds in pesticides by the United States Environmental Protection Agency--a preliminary study.

Lijinsky, Eisenbrand and others have demonstrated the formation of N-nitroso derivatives of certain secondary amine pesticides under specified experimental conditions. Partly based on these studies and on reports of the industrial discharge of N-nitrosos compounds from several chemical manufacturing facilities the Environmental Protection Agency (EPA) has issued several reports on the nitroso problem, including a report by a special ad hoc committee under the Administrator's Science Advisory Board (1976). Unexpectedly high N-nitrosoalkylamine residues found in several pesticide products (Fine et al., 1976) have prompted EPA to conduct a survey, initially of approximately 70-80 pesticides that potentially were representative of the following three routes of contamination: 1. industrial process formation and carryover; 2. in situ (container) nitrosation and 3. utilization of contaminated amines in the manufacturing process. Environmental formation was not studied in this survey. Duplicate samples were analysed by two different laboratories using GC and HPLC interfaced with Hall, UV and chemiluminescent (TEA) detectors. Results of some analyses of this continuing survey are presented. Based partly on the results of this study, the Agency has decided to conduct risk-benefit analyses on pesticides suspected of containing N-nitroso contaminants, with special consideration given to oncogenic and mutagenic potential. The analytical results of the study are discussed, as is the cooperative effort within the Agency.

Chromatography, Gas↗

Alteration in cell permeability as a mechanism of action of certain quinone pesticides.

The permeability of the Chlorella pyrenoidosa membrane was studied by following the efflux of (14)C-intracellular material from cells which had been allowed to incorporate (14)CO(2) photosynthetically. It was observed that the efflux increased upon treatment with low concentrations (3-30 muM) of 2, 3-dichloro-1, 4-naphthoquinone (dichlone), 2-amino-3-chloro-1, 4-naphthoquinone (06K-quinone), and 2, 3, 5, 6-tetrachloro-1, 4-benzoquinone (chloranil). Dichlone caused a greater loss of intracellular material than chloranil or 06K-quinone. The rate of loss as well as the total loss of (14)C increased with an increase in the concentration of the quinones. In the dichlone-treated cells, the leakage was observed within 1 minute of the addition of the chemical and the effect on cell permeability was irreversible. Cells exposed to dichlone in the light or under anaerobic conditions released significantly greater amounts of (14)C-material than cells treated in the dark or under aerobic conditions. The aqueous ethanol-soluble fraction of the cell was found to be the source of the released material. The proportion of the ethanol-soluble (14)C that leaked out of the cell varied with the time of (14)C-assimilation prior to treatment with dichlone. In the dichlone-treated cells, practically all the (14)C-sucrose, alanine, glutamine, serine, and glycine leaked out, whereas glutamic, aspartic, succinic, and fumaric acids were lost only partially. Essentially no (14)C-lipids were lost from the cells during dichlone treatment.The extreme rapidity of the effect of dichlone on permeability and the low concentrations at which dichlone acted suggest that the cell membrane may be a primary site of action of dichlone, and that the metabolic changes observed in dichlone-treated Chlorella may be due to the changes in the cell membrane structure.

Journal Article↗

Studies on Effect of Certain Quinones: I. Electron Transport, Photophosphorylation, and CO(2) Fixation in Isolated Chloroplasts.

The effect of quinone herbicides and fungicides on photosynthetic reactions in isolated spinach (Spinacia oleracea) chloroplasts was investigated. 2,3-Dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), and 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited ferricyanide reduction as well as ATP formation. Benzoquinone had little or no effect on these reactions. The two reactions showed a differential sensitivity to these inhibitors. Dichlone was a strong inhibitor of both photosystems I and II; photosystem I was more sensitive to 06K-quinone than was photosystem II, whereas the reverse was true of chloranil. Chloranil and 06K-quinone inhibited ferricyanide reduction and the coupled photophosphorylation to the same extent, whereas dichlone affected photophosphorylation to a greater extent than the ferricyanide reduction.CO(2) fixation was inhibited by all the quinones to varying degrees. In chloroplasts treated with 06K-quinone or benzoquinone, CO(2) fixation was inhibited to a greater extent than the photoreduction of ferricyanide or ATP formation, indicating the possibility that the two quinones may also inhibit certain reactions in the carbon reduction cycle. The effect of dichlone and chloranil, but not of 06K-quinone, was overcome by the addition of reduced glutathione. The quinones caused an increase in the proportion of (14)C incorporated into 3-phosphoglyceric acid and a reduction in the amount of glycolic acid.

Journal Article↗

Studies on Effects of Certain Quinones: II. Photosynthetic Incorporation of CO(2) by Chlorella.

The effects of various quinone herbicides and fungicides on the photosynthetic (14)CO(2) fixation and the incorporation of (14)C among the products of photosynthesis in Chlorella pyrenoidosa was investigated. Addition of 30 mum 2,3-dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), or 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited CO(2) fixation, whereas 1,4-benzoquinone had no effect. Treatment with 3 mum or higher concentrations of dichlone, 06K-quinone or 1,4-benzoquinone also produced marked changes in the pattern of (14)C distribution. A noticeable effect was an increase in the proportion of (14)C in sucrose and glycine accompanied by a reduction in (14)C lipids and glutamic acid. These changes appear to occur as a result of shifts in the flow of carbon along various biosynthetic pathways of photosynthetic CO(2) fixation. It is suggested that inactivation of coenzyme A and shortage of reduced triphosphopyridine nucleotide in the quinone-treated cells inhibited the synthesis of lipids and glutamic acid, thereby diverting more carbon into sucrose and glycine.

Journal Article↗

Chromatography.

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Animals↗

Effect of diquat (1,1'-ethylene-2,2'-dipyridylium dibromide) on the photosynthetic growth of Rhodospirillum rubrum.

Diquat (2 x 10(-4)m) inhibited both aerobic and anaerobic growth of Rhodospirillum rubrum. With photosynthetic cultures, diquat affected the synthesis of bacteriochlorophyll more readily than cell mass (turbidity). Diquat retarded the synthesis of bacteriochlorophyll and some protein more readily than that of other cellular constituents such as ribonucleic acid, deoxyribonucleic acid, and cell mass. With cells deficient in phosphate, diquat inhibited the uptake-conversion of inorganic phosphate completely only when 3-(3,4-dichlorophenyl)-1,1'-dimethyl urea and ascorbate were also present.

DNA, Bacterial↗