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Biomedical subjects

T Kagawa

Publications and source records attributed to T Kagawa.

194 records · Page 11Linked to original sources
PubMed1973

Enzymes of phospholipid metabolism in the endoplasmic reticulum of castor bean endosperm.

The intracellular location of several enzymes concerned with phospholipid metabolism was investigated by examining their distribution in organelles separated on sucrose gradients from total homogenates of castor bean (Ricinus communis var. Hale) endosperm. The enzymes phosphatidic acid phosphatase, CDP-diglyceride-inositol transferase, and phosphatidyletha-nolamine-l-serine phosphatidyl transferase were all primarily or exclusively confined to membranes of the endoplasmic reticulum. These results and those reported previously on lecithin synthesis establish a major role of the endoplasmic reticulum in phospholipid and membrane synthesis in plant tissues.

Journal Article↗
PubMed1972

Intracellular distribution of enzymes of the cytidine diphosphate choline pathway in castor bean endosperm.

The occurrence and subcellular distribution of enzymes of the cytidine diphosphate choline pathway of lecithin synthesis have been examined. Choline kinase (EC 2.7.1.32) was completely soluble, while phosphorylcholine-cytidyl transferase (EC 2.7.7.15) and phosphorylcholine-glyceride transferase (EC 2.7.8.2) were associated with particulate fractions. Although components sedimenting at 10,000 to 100,000 x g contained both enzymes, phosphorylcholine-cytidyl transferase and particularly phosphorylcholine-glyceride transferase were present in the 10,000 x g pellet, which contained the major organelles, mitochondria, and glyoxysomes. When the crude homogenate was centrifuged on a sucrose density gradient, four major bands of particulate protein were recovered. A band at density 1.24 g/cm(3) contained the glyoxysomes and was devoid of phosphorylcholine-cytidyl transferase and phosphorylcholine-glyceride transferase activity. Enzyme activity was barely detectable in the mitochondria, at density 1.18 g/cm(2). Phosphorylcholine-glyceride transferase was found almost exclusively in a sharp band at density 1.12 g/cm(3), and phosphorylcholinecytidyl transferase was found in the uppermost band at density 1.08 g/cm(3). Thus, for the synthesis of lecithin in their membranes, the glyoxysomes and mitochondria depend on enzymes elsewhere in the cell; the final two steps in lecithin formation occur, apparently exclusively, in separate particulate cell components.

Carbon Isotopes↗
PubMedDate not supplied

Positive and negative tropic curvature induced by microbeam irradiation of protonemal tip cells of the moss Ceratodon purpureus.

The photoreceptor phytochrome mediates tropic responses in protonemata of the moss Ceratodon purpureus. Under standard conditions the tip cells grow towards unilateral red light, or perpendicular to the electrical vector of polarized light. In this study the response of tip cells to partial irradiation of the apical region was analysed using a microbeam apparatus. The fluence response curve gave an unexpected pattern: whereas a 15-min microbeam with light intensities around 3 micro mol m (-2) s (-1) induced a growth curvature towards the irradiated side, higher light intensities around 100 micro mol m (-2) s (-1) caused a negative response, the cells grew away from the irradiated side. This avoidance response is explained by two effects: the light intensity is high enough to induce photoconversion into the active Pfr form of phytochrome, not only on the irradiated but also on the non-irradiated side by stray light. At the same time, the strong light on the irradiated side acts antagonistically to Pfr. As a result of this inhibition, the growth direction is moved to the light-avoiding side. Such a Pfr-independent mechanism might be important for the phototropic response to distinguish between the light-directed and light-avoiding side under unilateral light.

Bryopsida↗
PubMedDate not supplied

Myocardial protection during open-heart surgery: preservation of myocardial metabolism and ultrastructure by cold coronary perfusion.

Myocardial protection by means of selective, continuous coronary perfusion with cold oxygenated blood of low flow rate and of low perfusion pressure is an excellent procedure both clinically and experimentally. This method should be particularly useful in poor-risk patients, for whom a maximal preservation of the myocardium is imperative.

Animals↗