H. Oku, S. Ouchi, T. Shiraishi
1976
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18
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Journal name not available for this finding
Abstract
Phytoalexins, post inf ectional anti-fungal compounds, have been isolated from various diseased plant tissues and discussed in relation to defense reaction of plants against fungal infection. However, their role in disease specificity and the mode of their f ungistatic or f ungicidal action remained undetermined, although recent findings in our laboratory indicate that phytoalexins play a significant part in hostparasite specificity at least in some powdery mildew diseases.l)-3) Pisatin, a phytoalexin of pea (Pisum sativum L.), was found to injure the plasma membrane of cells of pea plants at a concentration of 3.00 ppm which is about the concentration that accumulates in leaves 4 days after infection by powdery mildew, and is enough to cause wilting of the infected leaves.4) No report seems to have appeared on the toxicity of phytoalexins to animal cells other than the one report on the haemolytic activity of phaseollin, a phytoalexin of bean (Phaseolns vulgaris L.).(5) This communication deals with results of experiments on the toxicity of pisatin to human red blood cells and on uncoupling of oxidative phosphorylation by rat liver mitochondria. A solution of pisatin was added to human blood diluted with physiological saline to give final concentrations of 100 or 300 ppm and morphological changes of erythrocytes were observed under a light or interference phase contrast microscope. The shape of erythrocytes became undetectable by light microscopy within a few minutes when treated with 300 ppm of pisatin. Interference phase contrast microscopy, however, showed that erythrocytes were replaced by ghost-like spherical structures. The detailed study of this haemolytic process is under way. Erythrocytes were deformed to crenated sphere (echinocytes), or cup-shape (stomatocytes) immediately after treatment at 100 ppm (Fig. 1). The effect of pisatin on the function of erythrocyte membrane