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Biomedical subjects

M Shirakawa

Publications and source records attributed to M Shirakawa.

At least 109 records · Page 6Linked to original sources
PubMed1988

Effects of phenolic dental medicaments on prostaglandin synthesis by microsomes of bovine tooth pulp and rabbit kidney medulla.

Prostaglandin (PG) synthesis from [1-14C]-arachidonic acid by bovine dental pulp microsomes was stimulated by 0.1-0.5 mM concentrations of p-chlorophenol (PCP) and inhibited by more than 3 mM. Dual effects (stimulation and inhibition) of phenol, PCP, o-, m-, p- and tri-cresol on PG synthesis by rabbit kidney medullary microsomes were observed. Of various compounds tested, eugenol, thymol and guaiacol were the most potent inhibitors; the inhibitory action was reversible. Phenolic compounds did not affect the activity of glucose-6-phosphatase, adenosine triphosphatase, or lactate dehydrogenase in rabbit kidney medulla within the range of concentrations that stimulated or inhibited PG synthesis. Thus the analgesic effect of phenolic medicaments in endodontic therapy may be due to inhibition of arachidonic-acid metabolism.

Animals↗
PubMed1988

Prevalence of human immunodeficiency virus (HIV) infection among hemophiliacs in Fukuoka, Japan.

To determine when the hemophiliacs in Fukuoka prefecture, Japan, first became positive for antibodies, we tested human immunodeficiency virus (HIV) antibodies on serum samples obtained from 1976-1987 stored at -30 C. Fifteen out of 64 hemophilia A patients (23.4%), five out of 11 hemophilia B patients (45.5%), but none of 17 patients with von Willebrand's disease (0%) were positive for HIV antibodies. In this series, two with hemophilia A became positive for HIV antibodies for the first time in 1983, and in 1984 another four with hemophilia A and one with hemophilia B became positive.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Base sequence-specific interactions of operator DNA fragments with the lambda-cro repressor coupled with changes in their conformations.

The mechanism of interaction of the operator DNA with the lambda-cro repressor protein was investigated using proton n.m.r. and photo CIDNP. Three kinds of DNA duplexes, the lambda-OR3 17-mer, phi80-OR2 19-mer and CRP binding site 22-mer, were prepared, and all of their imino proton resonances of the complexes with lambda-cro were assigned to individual base pairs. By monitoring the assigned signals of the DNA fragments and lambda-cro, it was found that in the complex of lambda-cro with lambda-OR3, two subunits of the cro dimer bind to the right and left halves of the OR3, respectively, and the bidentate binding induces a structural distortion in the middle of the 17-mer. lambda-cro itself also undergoes a conformational change including loosening of the dimeric form. In the complex of lambda-cro with phi 80-OR2, which has a 6-bp sequence common to that of lambda-OR3, one subunit of the cro dimer seems to bind specifically to the common part. However, there is only a slight conformational change in the cro dimer. In the mixture of the CRP binding site 22-mer and lambda-cro, soft contact without any conformational change was observed between them.

Base Sequence↗
PubMed1987

Susceptibility of diabetic rat aorta to self-deactivation during prostacyclin synthesis.

The ability of aortic rings to produce PGI2 markedly decreased in streptozotocin-induced diabetic rats when compared with age-matched controls. Arachidonic acid dose-dependently stimulated the production of PGI2 both in normal and diabetic rat aorta during 5 min incubation. The deficiency in PGI2 production in diabetic rat aorta was temporarily corrected by the addition of 5-20 microM of arachidonic acid. However, when aortic rings were incubated over a period of 10 min in the presence of arachidonic acid, the ability of PGI2 production in diabetic rats markedly decreased. Repeated exposures of aortic rings to arachidonic acid also markedly reduced PGI2 production in diabetic rats. PGI2 production in diabetic rat aorta was inactivated more readily than in normal rat aorta by pre-incubation with t-butyl hydroperoxide. Phenol had a protective effect on incubation-induced inactivation of PGI2 generating activity in diabetic rat aorta. Serum markedly stimulated PGI2 synthesis in normal and diabetic rat aorta. The serum activity in diabetic rats was less potent than in normal rats. Melittin and dipyridamole were effective in stimulating PGI2 release from diabetic rat aorta. These results suggest that enzymes in the aorta involved in PGI2 synthesis from released arachidonic acid are susceptible to self-inactivation in diabetic rats during the metabolism of arachidonic acid. This may contribute to the defect of PGI2 synthesis in diabetic rat aorta in addition to the decreased availability of the substrate.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

An NMR study on the structure of OR3 in the lambda cro-OR3 complex.

1H-NMR spectra of lambda-OR3 17mer in the complex with lambda-cro has been analysed and the change in its conformation on the complexation has been deduced. The changed conformation is retained until the duplex melts above 55 degrees C. Increase in heat stability of the cro dimer was observed. The result was compared with those of other DNA fragments phi 80-OR2 19 mer and the CRP binding site 22mer mixed with lambda-cro.

Amino Acid Sequence↗
PubMed1985

Photo CIDNP study on the complex formation of lambda cro protein with OR3.

A photo CIDNP spectrum of lambda cro repressor protein showed that one of the three tyrosines and His 35 are quite accessible to the photosensitive dye. For the remaining two tyrosine residues one is slightly accessible, but the other is inaccessible. In comparison with the result of differential nitration at tyrosine side chains followed by the peptide analysis, it can be concluded that Tyr 26 is mostly exposed and Tyr 51 is slightly exposed on the surface of the cro dimer. On the addition of OR3 17mer, His 35 and Tyr 26 are no longer accessible to the dye, which indicates that they are involved in interaction. However, a similar phenomenon was observed by adding CAP binding site 22mer. The interaction mechanism will be discussed.

Bacteriophage lambda↗
PubMed1985

Exposed tyrosine residues of lambda cro repressor protein evidenced by nitration and photo CIDNP experiments.

The tyrosine residues of lambda cro repressor were partially nitrated with tetranitromethane under mild conditions. After digestion by Achromobacter protease I, the extent of nitration was determined by HPLC and amino acid analysis. Tyr 26 was most easily nitrated and Tyr 51 followed it. Tyr 10 was resistant to nitration. By comparison of the proton magnetic resonance spectrum of the partially nitrated cro protein with the above result, the aromatic proton resonances of the tyrosine side chains could be assigned to individual tyrosine residues. The extent of nitration is parallel to the accessibility to a flavin dye as measured by photo CIDNP (chemically induced dynamic nuclear polarization).

Amino Acids↗
PubMed1985

Specificity of the interaction between lambda cro repressor protein and operator DNA fragments.

Cro repressor protein is known to interact with specific sites in the operator DNA. The cro protein of lambda phage was isolated and the mode of its interaction with three different DNA fragment, lambda-OR3 17mer, phi 80-OR2 19mer and CAP binding site 22-mer, were examined by the use of proton NMR. Some of the imino proton resonances of lambda-OR3 shifted and were broadened remarkably on addition of lambda-cro protein, which indicated the induction of conformational change with complexation. In the spectrum of phi 80-OR2 which has a six base pair sequence common to lambda-OR3 the signals of the common base pairs revealed slight shifts on addition of lambda-cro protein. The imino proton signals of the CAP site DNA, however, did not show any change at all on mixing with lambda-cro. Combining the data of photo CIDNP of lambda-cro, we could postulate the mode of interaction between lambda-cro repressor and operator DNA.

Bacteriophage lambda↗