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Biomedical subjects

H Okayama

Publications and source records attributed to H Okayama.

At least 199 records · Page 11Linked to original sources
PubMed1979

Effects of verapamil on the contractile force in the glycerinated dog heart muscles.

The effect of Ca-antagonist on the contractile apparatus was investigated in glycerinated cardiac papillary muscle preparations obtained from canine hearts. The results showed that maximal developed tension (P0) was enhanced significantly by 5 mg/liter of verapamil, and the augmentation of contractility was dependent on the concentrations of verapamil. As a conclusion, Ca-antagonist appeared to be a potentiating agent of the contractile force on the contractile apparatus.

Animals↗
PubMed1979

The relationship between the arterial level of angiotensin-converting enzymes and arterial gas tension in bronchial asthma.

To study the mechanism which causes a lowered serum level of angiotensin-converting enzyme (ACE) in asthma patients, the changes in serum ACE in arterial blood gas tension was measured. Serum ACE was also determined in patients with chronic obstructive lung disease (COLD) and fibrosing lung disease (FLD). A reduced level of serum ACE was found in some patients with COLD, similar to that in patients with asthma. A significant relationship existed between the lowered serum ACE level and the degree of arterial hypoxia, especially in asthmatic patients and some patients with COLD. The significance of lowered serum ACE is discussed in relation to the pathogenesis and the mechanism of hypoxemia in patients with asthma, COLD and FLD.

Asthma↗
PubMed1978

Purification of ADP-ribosylated nuclear proteins by covalent chromatography on dihydroxyboryl polyacrylamide beads and their characterization.

Nuclear proteins modified by mono or poly ADP-ribosylation were selectively isolated and purified by covalent chromatography on a dihydroxyboryl polyacrylamide bead column that specifically interacts with cis-diol-containing compounds. From rat liver nuclei that had been incubated with NAD+, histones and some nonhistone proteins were extracted with 0.25 M HCl. Approximately 60% of the ADP-ribose incorporated into 20% trichloroacetic acid-precipitable material was recovered in this extract. The ADP-ribosylated material was then isolated from the extract by covalent chromatography on a borate gel column and further purified by carboxymethylcellulose column chromatography. As judged by electrophoretic mobilities in various gel systems and by amino acid compositions, approximately 50% of the ADP-ribose recovered in the carboxymethylcellulose fractions was associated with several nonhistone proteins with molecular weights of 2-6 x 10(4), while 35% aand 15% were associated with histones H2B and H1, respectively. Since the average chain length of the polymer bound to any of these proteins was less than two ADP-ribos-l units, the percentage distribution reflects the number of ADP-ribosylated sites rather than the chain length.

Animals↗
PubMed1978

Novel enzyme from rat liver that cleaves an ADP-ribosyl histone linkage.

A novel enzyme that splits a bond between ADP-ribose and histone was discovered and partially purified from rat liver cytosol. The 105,000 X g supernatant of rat liver homogenate was precipitated by 45% saturated ammonium sulfate and then chromatographed on a DEAE-cellulose column. The enzyme activity was eluted in a single peak at about 0.2 M NaCl and clearly separated from poly(ADP-ribose) glycohydrolase which came out at 0.13 M NaCl. In contrast to the latter enzyme, this new enzyme catalyzed the spliting of a linkage between ADP-ribose and a protein portion in mono ADP-ribosylated histone H2B but little, if any, of the glycosidic ribosyl(1"-2') ribose bonds within poly(ADP-ribose). Analysis of the reaction product by paper chromatography and Dowex 1 column chromatography indicated that the split product contained the ADP-ribose moiety but was not exactly identical with ADP-ribose. Available evidence suggested that it was either an altered ADP-ribose molecule produced by a structural rearrangement or ADP-ribose itself linked to an unidentified compound. The enzyme had a pH optimum of about 6.0 and was inhibited by 80-90% in the presence of 5 mM ADP-ribose.

Animals↗
PubMed1978

Serum angiotensin converting enzyme level in bronchial asthma.

Using hippuryl-L-histidyl-L-leucine as a substrate analogue, serum angiotensin converting enzyme (ACE) was spectrophotometrically estimated in patients with bronchial asthma. The mean level of asthmatic patients was significantly lower than that of the control subjects. The reduced serum ACE activities did not change during an acute asthmatic attack. Significantly lower levels of serum ACE occurred in patients with chronic asthma than in those who only suffered with occasional asthma. Serum ACE activity was not reduced when the patients were taking steroids. Serum ACE activity could not be correlated with either the systolic blood pressure or the diastolic blood pressure of our asthmatic patients. However, serum ACE activity was correlated with the serum beta-globulin fraction in asthmatic patients.

Asthma↗
PubMed1977

Purification and properties of poly(adenosine diphosphate ribose) synthetase.

Poly(ADP-ribose) synthetase has been purified approximately 5000-fold from rat liver nuclei. The activity of the purified enzyme is absolutely dependent upon the presence of native or synthetic DNA, and the further addition of histone(s) stimulates the activity 3- to 5-fold. When the ADP-ribosylated material synthesized in the absence or presence of various histones is analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the major product in all cases migrates between histones H1 and H3-H2B with the same RF value of 0.58 relative to the marker dye. No ADP-ribose was found to co-electrophorese with any of thehistones. The addition of histones does not affect the chain number of the poly(ADP-ribose) synthesized but does result in an increase in the average chain length of the polymer. In the presence of histones, the Km for NAD+ decreases from 80 micron to 25 micron and the Vmax doubles. These results indicate that, in the purified poly(ADP-ribose) synthetase system, histones are not ADP-robosylated but act as allosteric activators.

Animals↗
PubMed1976

Characterization of the NAD+ glycohydrolase associated with the rat liver nuclear envelope.

The localization of NAD+ glycohydrolase [EC 3.2.2.5] (NADase) in purified rat liver nuclei has been examined. Subnuclear fractionation revealed that at least 70% of the NADase in nuclei was associated with the nuclear envelope fraction. The nuclear envelope fraction was practically free of microsomal contamination as judged by electron microscopic morphometry and assays of microsomal marker enzymes. Therefore, NADase was found to be an integral component of the nuclear envelope. The enzymological properties of the nuclear envelope NADase were compared with those of the microsomal enzyme. The nuclear envelope NADase was identical to the microsomal enzyme in its Km for NAD+ (60 muM), pH optimum (pH 6.5), ratio of transglycosidase activity to NADase activity (about 0.5), thermal stability and sensitivity to various inhibitors. Thus, NADase is a common enzymic component of both the nuclear envelope and the endoplasmic reticulum.

Animals↗
PubMed1975

Nicotinamide adenine dinucleotide glycohydrolase from rat liver nuclei. Isolation and characterization of a new enzyme.

A new type of nicotinamide adenine dinucleotide glycohydrolase (NADase) has been isolated from rat liver nuclei. When partially purified chromatin is passed through a Sephadex G-200 column in the presence of 1 M NaCl, enzyme activities catalyzing the liberation of nicotinamide from NAD elute in two peaks. One, which appears in the void volume fraction, hydrolyzes the nicotinamide-ribose linkage of NAD to produce nicotinamide and ADP-ribose in stoichiometric amounts. This activity is not inhibited by 5 mM nicotinamide. The other, which elutes much later, catalyzes the formation of poly(ADP-ribose) from NAD and is completely inhibited by 5 mM nicotinamide. The former, NADase, is DNase-insensitive and thermostable, has a pH optimum of 6.5 to 7, a Km for NAD of 28 muM, and a Ki for nicotinamide of 80 mM, and hydrolyzes NADP as well as NAD. The latter, poly(ADP-ribose) synthetase, is sensitive to DNase treatment and heat labile, has a pH optimum of 8 to 8.5, a Km for NAD of 250 muM and a Ki for nicotinamide of 0.5 mM and is strictly specific for NAD. Further, the former NADase is shown to lack transglycosidase activity, which has been documented to be a general property of NADases derived from animal tissues. These results indicate that the NAD-hydrolyzing enzyme newly isolated from nuclei is a novel type of mammalian NADase which catalyzes the hydrolytic cleavage of the nicotinamide-ribose linkage of NAD.

Animals↗