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Biomedical subjects

K Fujimura

Publications and source records attributed to K Fujimura.

At least 145 records · Page 8Linked to original sources
PubMed1983

Calcium cation regulation of glycoprotein IIb-IIIa complex formation in platelet plasma membranes.

The regulating effect of Ca2+ on the association and dissociation of the glycoprotein IIb-IIIa complex from human platelet membranes was determined both for detergent-solubilized and intact plasma membranes. Glycoproteins IIb and IIIa were solubilized from isolated membranes with 0.5% Triton X-100 and incubated in buffers containing ionized calcium, which resulted in the formation of the glycoprotein IIb-IIIa complex. With the addition of EGTA to reduce the ionized calcium content of the solution, the glycoprotein IIb-IIIa complex dissociated. This dissociation was measured by comparing the sedimentation properties of the glycoproteins and by observing the susceptibility of glycoprotein IIb to thrombin-catalyzed hydrolysis. With 10(-3) M Ca2+, glycoproteins IIb and IIIa were resistant to hydrolysis at thrombin concentrations up to 2.4 X 10(-5) M. When the Ca2+ concentration was decreased to less than 10(-4) M by chelation with EDTA or EGTA, glycoprotein IIb was cleaved by thrombin. This increased susceptibility to thrombin hydrolysis at decreasing Ca2+ levels correlated with the increased dissociation of the glycoprotein IIb-IIIa complex as determined by sucrose density centrifugation. Susceptibility to thrombin hydrolysis was also used as a probe to determine the extent to which Ca2+ regulates the formation of the glycoprotein IIb-IIIa complex within membranes. At more than micromolar levels of Ca2+, less than 10% of the membrane-bound glycoprotein IIb was cleaved by thrombin. Increased hydrolysis was observed at decreasing concentrations of Ca2+. Resistance to thrombin hydrolysis was partially regained upon the readdition of Ca2+ to dissociated glycoproteins. These data indicate that micromolar concentrations of Ca2+ exert a direct effect on platelet plasma membrane structure by regulating the intramembranous interactions of glycoprotein IIb.

Blood Platelets↗
PubMed1982

Method for determination of angiotensin-converting enzyme activity in blood and tissue by high-performance liquid chromatography.

A simplified method for an angiotensin-converting enzyme activity assay in biological samples was developed. Samples were incubated with hippurylhistidylleucine, an artificial substrate of angiotensin-converting enzyme. The reaction was terminated by the addition of metaphosphoric acid and liberated hippuric acid in the supernatant was quantitated directly by reversed-phase high-performance liquid chromatography. Tissues were homogenized in the presence of Nonidet-P40, a detergent, and the resulting supernatant was used for the assay of tissue angiotensin-converting enzyme activity by high-performance liquid chromatography. The present procedure made it possible to determine angiotensin-converting enzyme activity in whole blood and the total activity in tissues. A comparative study of angiotensin-converting enzyme activity in plasma, kidney and lung of five experimental animals showed a high degree of variation from species to species.

Animals↗
PubMed1982

Studies on heterogeneity of Taka-amylase A: isolation of an amylase having one N-acetylglucosamine residue as the sugar chain.

Crystalline Taka-amylase A, prepared from Takadiastase, was fractionated into four fractions by DEAE-Sephacel and Concanavalin A-Sepharose column chromatography. The relative weight ratio of the fractions was 90 : 4 : 4 : 2. They had similar molecular weights (51,000), amino acid compositions, and hydrolytic activity against soluble starch, but different phenyl maltosidase activities and electrophoretic mobilities on polyacrylamide gel electrophoresis. Three of the fractions mainly had the high mannose type sugar chain with the sugar composition of Man5-GlcNAc2, but the other fraction had only one N-acetylglucosamine residue as the sugar chain. These results suggested that Taka-amylase A was heterogeneous both in the sugar portions and in the polypeptide portions.

Acetylglucosamine↗
PubMed1982

[Experimental studies on cryochemotherapy (author's transl)].

The combination effect of chemotherapy and cryosurgery on solid tumor have been evaluated using Ehrlich tumor implanted in hind-limbs of ddN mice. Following regimens were performed. 1) Mitomycin C (MMC) lmg/kg i.p. as a chemotherapeutic agent. 2) cryosurgery -60 degree C for 1.5 minutes. 3) various combination of MMC and cryosurgery. Each average life-span was A) without therapy: 23.8 +/- 4.3 days, B) MMC: 28.0 +/- 4.0 days, C) cryosurgery: 29.5 +/- 6.1 days. Combination therapy which cryosurgery was first performed and then MMC was administered was most effective among various combinations. And the life-span was significantly extended to 38.7 +/- 5.2 days compared with that of each single therapy. When PSK, a immunopotentiator, was added to this regimen, the life-span was extended to 45.0 +/- 9.3 days. The immunological aspects of these regimens were examined by radioisotopic foot-pad assay. Transient increase of cellular immunity was observed in cryosurgery group. The effect of cryosurgery on uptake of anti-tumor agent into tumor tissue were also studied using 3H-labelled 5FU and 14C-labelled 5FU. It was revealed that the uptake rate was significantly increased in tumor margin, but not in tumor center. When the uptake in tumor margin was examined at serial time after cryosurgery, peak of increased uptake was observed at 6 and 12 hours after cryosurgery. Satisfactory response was obtained in clinical application of cryochemotherapy based on these experimental findings.U

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