Gunter Zweig

Separation of chloroplast leaf pigments by thin-layer chromatographer on cellulose sheets☆

Abstract Leaf pigments and saponified leaf pigments were separated by one-dimensional, two-dimensional and radial chromatography on Eastman Chromagram Cellulose sheets. Comparisons with Whatman No. 1 paper and conventional cellulose thin layers on glass plates show the Chromagram sheets to be superior in many systems. Comparative results in sandwich tanks and with columns of cellulose are also presented. The major pigments in leaves were found to be chlorophylls a and b , neoxanthin, violaxanthin, lutein and β-carotene.

Determination of organophosphorus pesticides in water

Increasing use of organic chemicals for agricultural purposes has caused great concern in recent years. Rachel Carson (1962) was one of the first to focus public attention on the possible hazards connected with pesticide use. Because of this concern, much work (Dugan et al. 1963, Anonymous 1964) has been done concerning the possible effects and extent of environmental contamination. Studies are being conducted by the federal government (Nicholson 1959, Dugan and Mcfarland 1967, Green and Love 1967, Johnson et at 1967, Sand et al. 1967, Yobs 1967) concerning pesticide concentrations in the population, in food, and in the entire environment of man.

Membrane damage in human erythrocytes caused by captan and captafol

Abstract Treatment of human erythrocytes with 5 × 10−5 M captan or captafol caused a rapid increase in the efflux of intracellular potassium. Captafol had a more pronounced effect than captan on cation permeability. Captafol also decreased anion permeability whereas captan did not affect this process. Glutathione (5 × 10−4 M) had little effect in reducing potassium efflux when added to the cells after they were incubated for 1 h with captan or captafol, but it was effective in reducing the potassium loss when added to the cells prior to their treatment with the fungicides. Captafol caused an increase in osmotic fragility of the cells. Incubation of the cell membranes with captafol resulted in the liberation of a small fraction of membrane phospholipids, whereas captan produced no effect. Both the fungicides readily reacted with the sulfhydryl groups in the isolated membrane; 31.5 and 45.7% of the membrane sulfhydryl groups had disappeared following treatment with captan and captafol, respectively. It is suggested that the reaction of captan or captafol and/or their reaction products with the sulfhydryl and amino groups of the red cell membrane protein produces changes in the structure of the membrane with consequent alteration in its permeability.

Interaction of dichlone with human erythrocytes. I. Changes in cell permeability.

The uptake of the fungicide dichlone (2,3-dichloro-1,4-naphthoquinone) by human erythrocytes was extremely rapid, reaching a maximum within 5 min of treatment. Most of the dichlone taken up was present in the interior of the cell; only a small fraction of the pesticide (less than 5%) was bound to the cell membrane. Dichlone (3 · 10−5M-10−4M) induced a rapid loss of intracellular potassium from the erythrocytes; the leakage of K+ varied with the fungicide concentration as well as with cell concentration. Pretreatment of the cells with glutathione was able to reduce potassium loss. Cells exposed to dichlone showed increased osmotic fragility. Dichlone also inhibited Na+-K+ ATPase, which is associated with active ion transport. However, the leakage of potassium in dichlone-treated cells does not appear to be related to the interference with active ion transport. An extensive loss of potassium within a relatively short time after treatment suggests that dichlone produces its effect by increasing passive cation permeability, probably as a result of direct action on the membrane structure. Dichlone was able to induce hemolysis, but only at concentrations higher than those which resulted in K+ loss. The loss of hemoglobin appeared to be mainly due to osmotic swelling of the treated cells. Exposure of red cells to dichlone also resulted in a rapid and extensive formation of methemoglobin as well as a denaturation of hemoglobin. Thus, dichlone not only may be capable of lowering the capacity of erythrocytes to transport oxygen but also alters their permeability.

Mode-of-action of photosynthesis inhibitor herbicides

In the commercial development of herbicides during the past 25 years, a relatively few number of classes of chemical compounds have been introduced. Among these are derivatives of halogenated benzoic-, phenoxyalkyl acids, thiocarbamates, aminotriazole, and a series of photosynthesis inhibitors.

Photoreduction of quinones by isolated spinach chloroplasts

Abstract Photoreducibility by isolated spinach chloroplasts of 1,4-benzoquinone, tetrachloro- p -benzoquinone, 2,3-dichloro; 2-chloro-3-amino; 2-methyl, and non-substituted 1,4-naphthoquinones were studied together with oxygen evolution by the Hill reaction. It has been observed by a spectrophotometric method that the naphthoquinones were quantitatively photoreduced to corresponding hydroquinones under anaerobic conditions and readily reoxidized to the original naphthoquinones by molecular oxygen. The naphthoquinones showed no oxygen evolution by the Hill reaction. On the other hand, tetrachloro- p -benzoquinone and p -benzoquinone were photoreduced to hydroquinone under aerobic and anaerobic conditions, and stoichiometric oxygen evolution was observed by the Hill reaction. A possible correlation between the photoreducibility of these quinones and their phytotoxicity was discussed.

Structural and functional changes in mouse fibroblast cells treated with 2,3-dichloro-1,4-naphthoquinone (dichlone)

Abstract When strain L mouse fibroblasts were treated with the substituted quinone pesticide dichlone (2,3-dichloro-1,4-naphthoquinone), a rapid loss of intracellular potassium, ATP, and protein with a concomitant increase in intracellular water and volume occurred. Electron microscopic examination showed a nonreversible swelling of the cells associated with the formation of large protruding blebs. The findings indicate that dichlone can alter the permeability of the cell membrane which may be one of the sites of action of the pesticide in the fibroblast cells. Menadione (2-methyl-1,4-naphthoquinone), a synthetic vitamin K, also a substituted quinone, was found to be less effective in short-term incubation at corresponding concentrations, althought it did produce loss of K + ions and protein from the cell. The action of dichlone was compared with that of model compounds which are known to act on plasma membranes ( p -chloromercuribenzene sulfonate—PCMBS) and those which interfere with intracellular energy metabolism (combination of antimycin A plus iodoacetate). From the results reported in this paper it appears that dichlone acts in most respects, like PCMBS, by a direct interaction with membrane components, but unlike PCMBS, dichlone enters the cell rapidly and stimulates oxygen uptake probably by constituting a bypass of electron transfer.

Ultrastructural changes in isolated spinach chloroplasts and in Chlorella pyrenoidosa chick (Emerson strain) treated with dichlone

Abstract Isolated spinach chloroplasts and Chlorella cells treated with dichlone (2,3-dichloro-1,4-naphthoquinone) exhibited morphological changes which appeared to be consistent with an alteration of protein elements in the cell. The stroma of dichlone-treated chloroplasts appeared less structured and more homogeneous than that of the control. The cell membrane in dichlone-treated Chlorella cells shrank from the cell wall and exhibited much invagination while the outer membrane of Chlorella chloroplasts appeared wavy. The changes in the cytoplasm of treated Chlorella cells closely reflected those noted in the chloroplast stroma.

Effect of certain quinone pesticides on acetate photometabolism and dark CO2 fixation in Chlorella

Abstract The effect of dichlone (2,3-dichloro-1,4-naphthoquinone), 06K-quinone (2-amino-3-chloro-1,4-naphtoquinone), and chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone) on photometabolism of acetate and on dark 14 CO 2 fixation by Chlorella was studied. Treatment of the cells with 3 × 10 −6 M or higher concentrations of these pesticides reduced acetate assimilation. Lower quinone concentrations did not appreciably change the pattern of 14 C distribution among the products resulting from acetate assimilation, although acetate incorporation was markedly inhibited. At higher concentrations, quinones decreased the proportion of 14 C incorporated in lipids and increased the proportion of 14 C incorporated in glutamic and citric acids. The data suggest that higher concentrations of quinones preferentially inhibited lipid synthesis resulting in the availability of more acetate for the intermediates of the tricarboxylic acid cycle. The above quinones also inhibited 14 CO 2 fixation in the dark and significantly altered the distribution of 14 C; both 06K-quinone and chloranil caused a decrease in the percent of 14 C incorporated in glutamic acid and an increase in 14 C-citric acid. The cells treated with chloranil also showed an increase in the proportion of 14 C-malic acid accompanied by a decrease in 14 C-aspartic acid. Possible explanations are given to account for the changes in the distribution of carbon in the metabolic products resulting from acetate assimilation and dark CO 2 fixation in the treated cells. Our findings indicate that the quinone pesticides act at a number of sites in the cell and their inhibitory effect is not restricted to photosynthetic reactions.

Effect of certain substituted naphthoquinones on growth and respiration of Rhodospirillum rubrum

Abstract The effect of dichlone (2,3-dichloro-1,4-naphthoquinone) on photoautotrophic, photoheterotrophic and heterotrophic growth, and respiration of Rhodospirillum rubrum (a nonsulfur purple bacterium) was studied to elucidate the mechanism of action of this toxicant on photosynthetic bacteria. The photosynthetic growth with malate or with hydrogen and CO 2 was inhibited by dichlone. Light respiration of photoheterotrophically grown cells, unlike their dark respiration, was found to be insensitive to dichlone. Although dichlone caused an inhibition of the respiration of dark-grown cells, such cells were able to grow in the presence of dichlone after a lag. Light-dependent 14 C-substrate incorporation by photoheterotrophic or photoautotrophic cells was found to be relatively more sensitive to dichlone than oxidative substrate incorporation by heterotrophic cells. Short-term exposure of the light-grown cells to dichlone resulted in an irreparable loss of their ability to grow photosynthetically and photoassimilate 14 C-substrates. Menadione (2-methyl-1,4-naphthoquinone), a synthetic vitamin K, failed to affect these reactions to a significant extent at comparable concentrations. The findings suggest that dichlone causes an irreversible damage to some primary photosynthetic reaction in chromatophores, whereas the damage caused to the dark heterotrophic metabolism of the cell is less severe and repairable. The inhibitory action of dichlone does not appear to be via the formation of semiquinone free radicals.