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Biomedical subjects

M Okuma

Publications and source records attributed to M Okuma.

At least 271 records · Page 15Linked to original sources
PubMed1977

Solubilization and resolution of thromboxane synthesizing system from microsomes of bovine blood platelets.

The thromboxane synthetase system of the microsomes of bovine blood platelets was solubilized by the treatment with Triton X-100. The solubilized preparation was separated into two enzyme fractions by DEAE-cellulose chromatography. One catalyzed the formation of prostaglandin H2 from arachidonic acid in the presence of heme and tryptophan. The other fraction converted prostaglandin H2 to thromboxane B2 and 12L-hydroxy-5,8,10-heptadecatrienoic acid. However, incubation of the latter fraction with prostaglandin H2 at lower temperature produced an unstable compound with platelet-aggregating activity, which was presumably thromboxane A2 and which decomposed readily to thromboxane B2 and 12L-hydroxy-5,8,10-heptadecatrienoic acid.

Animals↗
PubMed1977

Human platelet aggregation induced by prostaglandin endodisulfide.

The effect on human platelet functions of 9,11-dithio analogues of prostaglandin endoperoxide was investigated. Methyl (5Z, 9alpha, 11alpha, 13E, 15S)-9,11-epidithio-15-hydroxyprosta-5,13-dienoate induced platelet aggregation, while the 9beta,11beta-epimer was inactive. The platelet aggregation caused by the 9alpha,11alpha-dithio analogue was associated with serotonin release from platelets, and was inhibited by methyl ester of prostaglandin I2 (prostacyclin) but not by indomethacin.

Blood Platelets↗
PubMed1976

Antagonism of 5-hydroxykynurenamine against serotonin action on platelet aggregation.

Serotonin induced an aggregation of human platelets, whereas 5-hydroxykynurenamine, produced from serotonin by the action of indoleamine 2,3-dioxygenase, did not cause any significant degree of platelet aggregation. 5-Hydroxykynurenamine specifically inhibited both a serotonin-induced aggregation of platelets and the potentiation of the ADP-induced platelet aggregation by serotonin. It did not, however, alter the profiles of the platelet aggregation induced by ADP, collagen, or adrenaline. The degree of inhibition was proportional to the time of preincubation of platelets with 5-hydroxykynurenamine, and to the concentration of 5-hydroxykynurenamine used. Available evidence indicated that 5-hydroxykynurenamine completed with serotonin for the same receptor sites. Studies with analogues of 5-hydroxykynurenamine indicated that the substitutions of 0-amino-benzyl moiety with hydroxy or methoxy groups were somewhat tolerated, whereas the masking of alkylamine moiety with N-acetylation completely lost the inhibitory activity.

Adenosine Diphosphate↗
PubMed1976

Studies on some lipogenic enzymes of cultured myeloid leukemic cells.

The microsomal fraction of M1 cells (an established cell line of myeloid leukemia) was capable of catalyzing acylation of sn-glycerol 3-phosphate by long-chain fatty acyl-CoA thioesters. The principal lipid product formed was identified as phosphatidic acid. Palmityl-CoA, stearyl-CoA, and oleyl-CoA were more effective acyl donors than linoleyl-CoA and arachidonyl-CoA. M1 cells and macrophages differentiated from them exhibited similar levels of sn-glycerol 3-phosphate-acylating activity, which were approximately one-half that in mouse liver and approximately four times that in peritoneal macrophages. The levels of acetyl-CoA carboxylase activity in M1 cells and macrophages differentiated from them were not significantly different from each other and were comparable to those in mouse liver, whereas no activity was detected in peritoneal macrophages. These results indicated that differentiation of the myeloid leukemic cells, which results in loss of leukemogenicity and mitotic activity, is not associated with changes in the activities of these lipogenic enzymes, although the cultured cells exhibited remarkably higher activities than freshly harvested peritoneal macrophages. Furthermore, the present study supports the view that the glycerophosphate pathway makes an essential contribution to the de novo synthesis of phospholipids in M1 cells, as well as in both types of macrophages.

Acetyl-CoA Carboxylase↗