Isospin effect in pi * 14C elastic scattering at 50 MeV.
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Biomedical subjects
K Gotow
Publications and source records attributed to K Gotow.
Light-Induced Alkalinization of the Suspending Medium of Guard Cell Protoplasts from Vicia faba L.
The light-dependent pH changes in the suspending medium of guard cell protoplasts (GCP) from Vicia faba were studied. Upon illumination, the medium was initially slightly alkalinized and then acidified. The extent of alkalinization was lower in CO(2)-free air than in normal air. This initial alkalinization was inhibited by DCMU. Acidification in CO(2)-free air became observable in shorter duration of light exposure than that in normal air. The rate of acidification was higher in CO(2)-free air than in normal air. The CO(2) level of the medium decreased in the light, and increased in the dark. (14)CO(2) uptake was enhanced 2- to 3-fold by light, but not in the presence of DCMU. These results indicate that photosynthetic CO(2) fixation does take place in GCP and that the initial alkalinization is due to this photosynthetic CO(2) uptake. Diethylstilbestrol, a nonmitochondrial membrane-bound ATPase inhibitor, inhibited the acidification, suggesting that the acidification resulted from H(+) extrusion by GCP. The acidification in light was also prevented by KCN, and partly by DCMU. Possible mechanisms of alkalinization and acidification are discussed in relation to guard cell metabolism.
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Light Activation of NADP-Malate Dehydrogenase in Guard Cell Protoplasts from Vicia faba L.
Light-induced swelling of guard cell protoplasts (GCP) from Vicia faba was accompanied by increases in content of K(+) and malate. DCMU inhibited the increase of K(+) and malate, and consequently swelling.Effect of light on the activity of selected enzymes that take part in malate formation was studied. When isolated GCP were illuminated, NADP-malate dehydrogenase (NADP-MDH) was activated, and the activity reached a maximum within 5 minutes. The enzyme activity underwent 5- to 6-fold increase in the light. Upon turning off the light, the enzyme was inactivated in 5 minutes NAD-MDH and phosphoenolpyruvate carboxylase (PEPC) were not influenced by light. The rapid light activation of NADP-MDH was inhibited by DCMU, suggesting that the enzyme was activated by reductants from the linear electron transport in chloroplasts. An enzyme localization study by differential centrifugation indicates that NADP-MDH is located in the chloroplasts, NAD-MDH in the cytosol and mitochondria, and PEPC in the cytosol. After light activation, the activity of NADP-MDH in guard cells was 10 times that in mesophyll cells on a chlorophyll basis. The physiological significance of light-dependent activation of NADP-MDH in guard cells is discussed in relation to stomatal movement.
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