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Biomedical subjects

M Irie

Publications and source records attributed to M Irie.

At least 109 records · Page 6Linked to original sources
PubMed1996

Enzymatic activities of several K108 mutants of ribonuclease (RNase) Rh isolated from Rhizopus niveus.

We previously investigated the role of the Lys108 residue of ribonuclease (RNase) Rh from Rhizopus niveus, and suggested that Lys108 probably acts to stabilize the pentacovalent intermediate, and that an Arg residue could replace the role of Lys108. In RNase Le2 from Lentinus edodes, a homologous enzyme of RNase Rh, Lys108 is replaced by Thr. In this paper, the enzymatic properties of a K108T mutant and its analogous enzyme, K108S, were investigated to determine the effect of Thr and its analog, Ser at the 108th position on enzyme activity. The enzymatic properties of these mutant enzymes were compared with those of other mutant enzymes at this position (K108M, K108A, K108L). The results showed that Thr and Ser could replace Lys108 but resulted in only 2-20% of the activity of the native enzyme depending on the substrates used.

Amino Acid Sequence↗
PubMed1996

Base specificity and primary structure of poly U-preferential ribonuclease from chicken liver.

The primary structure and base specificity of chicken liver RNase CL1 which has been reported by Miura et al. [Chem. Pharm. Bull., 32, 4053-4060 (1984)] as poly U-preferential RNase, were extensively studied. The sequence study of this enzyme and comparison of the amino acid sequence of the enzyme with homologous RNases from oyster and Drosophila melanogaster suggested that RNase CL1 consists of three peptides with 17, 19, and 163 amino acid residues. The amino acid sequence of these three peptides were identified. The two small peptides are joined to the large peptide by disulfide bridges. The amino acid sequence of RNase CL1 had 62 (31.2%) and 63 residues (31.6%) identical with oyster RNase and D. melanogaster RNase, respectively, and belongs to the RNase T2 family RNase. Reassessment of the base specificity of RNase CL1 found that it is guanylic acid, then uridylic acid-preferential, and not poly U preferential.

Amino Acid Sequence↗
PubMed1996

Immunohistochemical localization of metallothionein in the olfactory pathway of dogs.

Dogs raised in the open air were used in this study. Metallothionein (MT) immunoreactivity was observed in the nucleus and/or cytoplasm of sustentacular cells of the olfactory epithelium in the nasal mucosa, whereas there was few MT-positive cells in the respiratory epithelium. MT immunoreactivity was also observed in astrocytes in all layers of the the olfactory bulb cortex; glial cells surrounding the glomeruli in the olfactory bulb showed prominent immunoreactivity for MT. Adult dogs exhibited stronger immunoreactivity for MT than young. Northern blot analysis demonstrated substantial levels of MT mRNA in the olfactory mucosa and olfactory bulb. Physiological roles of MT localized in the olfactory pathway of dogs were discussed.

Age Factors↗
PubMed1996

Marginal sealability of resin-modified glass ionomers for base/liner: effect of hygroscopic expansion and bond strength.

The present study investigates the effect of storage in water on hygroscopic expansion and shear bond strength to dentin at periods up to 1 week, of the resin-modified glass ionomers for base/liner, and to analyze the effect on the marginal gaps in dentin cavities. For polishing after storage in water for 1 day, the material indicated significantly smaller marginal gaps both in dentin and in Teflon cavities than in those immediately after light-activation. For the results of after storage in water for 1 day, the material indicated significantly greater bond strength than material immediately after light-activation. The improvement of marginal sealability in dentin cavities may be performed not only by hygroscopic expansion during storage in water but also by greater bond strength after the setting reaction which continues to advance during storage in water.

Analysis of Variance↗
PubMed1996

[Psychosomatic effect of a health program on obese employees].

A 12-week training period including exercise and diet was undertaken to determine the effects of a newly developed health program on the physical and phychological parameters in 24 obese employees of a certain company. The association between a number of somatic parameters and psychological variables, including the attitude toward better health, and the level of mental health (General Health Questionnaire) were analysed before, immediately or 1 year after the program. After the program, significant overall improvements were found in several physical parameters. Those who had higher initial levels of attitudes toward better health showed greater exercising/dieting achievements during the program. Furthermore, these considerable health-related attitudes seemed to be concerned with higher HDL levels preceding the program, and minor improvements in diastolic blood pressure due to the program. The GHQ scores tended to increase in proportion to decreased exercising/ dieting achievements during the program and undesirable lifestyle that ignored any form of exercising.

Adult↗
PubMed1996

Role of Kupffer cell-derived reactive oxygen intermediates in alcoholic liver disease in rats in vivo.

The pathophysiology of alcoholic liver disease (ALD) remains largely unknown. In this work, we have developed an experimental rat model to elucidate the mechanism of liver injury, including ALD, in which Kupffer cell-derived reactive oxygen intermediates (ROIs) might be involved. Groups of male Wistar rats were pair-fed on a liquid high-fat diet containing ethanol (36% of total calories) or isocaloric carbohydrate with or without dietary carbonyl iron (0.5% w/v) for 3 weeks. In this rat model, we investigated Kupffer cell-derived ROI generation, which affected hepatocellular injury and hepatic fibrosis in ALD. The production of ROIs in Kupffer cells isolated from the iron-fed, the ethanol-fed, and the ethanol plus iron-fed rats were significantly increased, compared with that in Kupffer cells isolated from control rats (iron > ethanol+iron > ethanol > > control). However, hepatic vitamin E content in the ethanol plus iron-fed rats was decreased rather than that in the iron-fed rats. Then, lipid peroxidation of isolated microsomes was assessed as malondialdehyde equivalents determined by thiobarbituric acid assay. Compared with controls, the malondialdehyde equivalents were elevated in experimental groups (ethanol+iron > ethanol > iron > control). Serum ALT levels were greatly elevated in rats fed a diet containing both ethanol and iron (ethanol+iron > iron > ethanol > control). Hepatic content of hydroxyproline was significantly increased in ethanol plus iron-fed rats, compared with rats other than the ethanol plus iron-fed group (ethanol+iron > iron > ethanol > control). These results suggested that the enhanced Kupffer cell-derived ROI generation could itself contribute to the increased susceptibility to lipid peroxidation, which might cause hepatocellular injury and lead to hepatic fibrosis in ALD.

Animals↗
PubMed1995

[A study on the usefulness of stress assessment based on the THP health measurement--comparison with the general health questionnaire].

Although the "Total Health Promotion Plan (THP)" drawn up by the Labor Ministry includes a self-administered stress checklist (THP-SC) as a health measurement, THP-SC has not been utilized in the way that it had been planned. Hence, we studied the usefulness of this list by comparing it with the General Health Questionnaire (GHQ). We made a questionnaire that included both THP-SC and the 60-item GHQ, and collected answers from 261 white-collar workers (male, average age 43.7). The GHQ was evaluated using the Goldberg's method. When analyzing THP-SC, the number of answers indicating stress was counted, and the respondents were divided into two groups based on the cut-off points of 75 percentile or 90 percentile. In the 60-item GHQ, 48 respondents out of 243 with valid answers had a higher score than the cut-off point, and in the 12-item GHQ, 77 out of 256 had a higher score. The average number of THP-SC was 5.67 +/- 3.19. Concerning the relationship with GHQ, many items of the 'A' section of THP-SC were significant. The comparison also suggested that four or more items checked in 'A' section or seven or more items checked in the whole list would mean that a respondent may be under stress.

Adult↗
PubMed1995

Nucleotide sequence of hepatitis B virus isolated from subjects without serum anti-hepatitis B core antibody.

The nucleotide sequences of the precore/core and X open reading frames (ORFs) of hepatitis B virus (HBV) were studied in four subjects who were serologically negative for anti-hepatitis B core antibody. These subjects were positive for serum hepatitis B surface antigen and were considered to be asymptomatic HBV carriers. Sequencing of the precore/core ORF revealed precore wild type and 3 to 8 nucleotide substitutions (replacing 0 to 2 amino acids) in the core region compared with the sequence of subtype adr. These substitutions were not considered to have changed the epitope of the core antigen, resulting in the absence of anti-HBc as determined by a conventional diagnostic kit. The X ORF showed 1 to 5 nucleotide substitutions (replacing 1 to 3 amino acids) and the structure of the X protein and the core promoter/enhancer II complex appeared to be conserved. These findings strongly suggest that the absence of serum anti-HBc is not due to mutation of the HBV DNA but to an aberrant immune reaction of the host to HBV.

Adult↗
PubMed1995

Crystallization and preliminary crystallographic analysis of a 2,3-dihydroxybiphenyl dioxygenase from Pseudomonas sp. strain KKS102 having polychlorinated biphenyl (PCB)-degrading activity.

Crystals have been obtained for a 2,3-dihydroxybiphenyl dioxygenase (conventionally called BphC) from a polychlorinated biphenyl (PCB)-degrader, Pseudomonas sp. strain KKS102. The crystals were grown using both ammonium sulfate and MPD as the precipitating agents. The crystals belonged to a tetragonal space group (I422) and diffracted to 2.5 A.

Crystallization↗
PubMed1995

Role of Lys108 in the enzymatic activity of RNase Rh from Rhizopus niveus.

In order to elucidate on the mechanism of action of RNase Rh from Rhizopus niveus, we investigated the role of Lys108, which is conserved among the RNase T2 family RNases except for two cases. The RNase activities of Lys108 mutant RNases, RNase RNAP K108R and K108L, are about 33.5 and 3.1% of that of the wild type enzyme, respectively. The relative rates of cleavage of dinucleoside phosphates by these two mutant enzymes were comparable to those with RNA as a substrate. The kinetic parameters of RNases RNAP K108R and K108L towards XpGs (where X is one of A, G, U, and C) were measured. The data indicated that the Km values of the two mutant enzymes are similar to those of the wild-type enzyme. The rates of release of the four nucleotides from RNA by digestion with the mutant enzymes were in the order A > G > U > C, which is qualitatively the same as that of the wild-type enzyme. From these data, we concluded that the Lys108 residue participates in the catalytic process, but not in the binding, and the positive charge of Lys108 is indispensable for the catalytic process, that is, the positive charge of Lys108 may stabilize the pentacoordinated intermediate in the transition state as proposed in the case of Lys41 in RNase A, or may polarize the phosphate moiety of the substrate.

Amino Acid Sequence↗
PubMed1995

Purification, and properties of a base non-specific acid ribonuclease from bullfrog (Rana catesbeiana).

An acid ribonuclease (RNase RCL2) was purified to homogeneity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) from a homogenate of bullfrog liver (Rana catesbeiana). The apparent molecular weight estimated from SDS-PAGE was ca. 25kDa. The pH optimum of the RNase was 5.0. The RNase released mononucleotides from RNA in the order of 3'-UMP, 3'-GMP and 3'-AMP. The N-terminal amino acid sequence of RNase RCL2 was determined up to the 20th residue, and it was found to have a 5 residue sequence homology with that of oyster acid RNase [H. Watanabe et al. J. Biochem. (Tokyo), 114, 800 (1993)]. Thus, RNase RCL2 seems to be a member of the RNase T2 family RNases. This is the first evidence of the RNase T2 family RNase in amphibians.

Amino Acid Sequence↗
PubMed1995

Purification and characterization of the 2nd 5'-nucleotide-forming nuclease from Lentinus edodes.

The 2nd endonuclease (nuclease Le3) which hydrolyzes both RNA and heat denatured DNA to 5'-nucleotides was purified from the fruit bodies of Lentinus edodes to a homogeneous state by SDS PAGE. The nuclease was different from the nuclease Le1 previously characterized [H. Shimada et al. Chem. Pharm. Bull., 39, 2633-2637 (1991)] in molecular weight, optimal pH and N-terminal amino acid sequence. The N-terminal amino acid sequence of nuclease Le3 analyzed up to the 20th residue showed that 50% of the amino acid residues are identical to nuclease Le1.

Amino Acid Sequence↗
PubMed1995

Base non-specific acid ribonuclease from Irpex lacteus, primary structure and phylogenetic relationships in RNase T2 family enzyme.

Two base non-specific acid RNases (RNase Irp1 and RNase Irp2) were purified from a commercial enzyme, "Driselase" (Irpex lacteus) in a homogenous state on SDS-PAGE by several steps of chromatographic separations. RNAse Irp2 was a simple polypeptide with 235 amino acid residues and RNase Irp1 was a glycopeptide with 248 amino acid residues. The amino acid sequences of both RNases were identified by Edman degradation of the peptides derived from these RNAses. RNase Irp1 was composed of the RNase Irp2 and extra C-terminal 13 residues of peptide. The phylogenetic relation of these RNases with the other fungal RNases already known was discussed. The sequence of RNase Irp2 was very highly homologous (67.5%) with that of RNase Le2 from Lentinus edodes.

Amino Acid Sequence↗
PubMed1995

Effect of immersion in water on linear expansion and strength of three base/liner materials.

The purpose of this study was to characterize three base/liner materials in the initial stage of setting, i.e., dual-cured (light-activated glass ionomer), light-cured (light-activated glass ionomer analogue), and chemically-cured (conventional glass ionomer) materials. Changes in dimension, weight and flexural strength were examined from immediately after setting to the end of one week following immersion in water. The results obtained from these three types of material differed from each other, and showed a statistically significant correlation between changes in dimension and weight. This may be attributed to hygroscopic expansion. They also showed different flexural strength, indicating differences in the polymerization system. From these results, it appeared that marginal gaps following setting would be compensated for by hygroscopic expansion during immersion in water for one day or more. Physical properties would be favourably improved following the setting process which continues to advance during immersion in water.

Absorption↗
PubMed1994

pH profile of kinetic constants of RNase Rh from Rhizopus niveus and its mutant enzymes towards UpU, and possible mechanisms of RNase Rh.

In order to elucidate the mechanism of action of Rhizopus niveus RNase Rh, we investigated the pH profiles of the kinetic parameters of RNase RNAP Rh, a derivative of RNase Rh, and its mutant enzymes, i.e., RNase RNAP Rh H104F, RNase RNAP Rh E105Q, and RNase RNAP Rh D51N. Based on comparisons of their profiles we concluded that protonation of His104 is indispensable for the enzymatic activity and Glu105 accelerates the enzymatic activity, especially at acid pH centered at pH 3.5. Based on these data and the previous data on the chemical modification and enzymatic properties of other mutant enzymes, we propose the following as a possible mechanisms of RNase Rh action. (i) His109 participates in enzymatic action as a general base catalyst which removes the hydrogen of the 2'-OH of the ribose moiety. (ii) His46 participates in the reaction as a general acid catalyst which interacts with the 5'-oxygen atom of the scissile phosphodiester bond and becomes a proton donor to the departing nucleoside or nucleotide. (iii) His104 interacts with phosphate anion and its protonation is favorable for the enzymatic activity. (iv) Since the protonated form of Glu105 is more favorable for activity, we postulate two possible roles for Glu105: (a) its stabilizes the intermediate, and (b) it interacts with the oxygen atom of P = O and polarizes the phosphorus atom.

Dinucleoside Phosphates↗
PubMed1994

Purification and primary structure of a new guanylic acid specific ribonuclease from Pleurotus ostreatus.

A guanine nucleotide-specific RNase (RNase Po1) was isolated from caps of the fruit bodies of Pleurotus ostreatus. RNase Po1 is most active towards RNA at pH 8.0. The effect of heating on the molar ellipticity at 210 nm of RNase Po1 showed that RNase Po1 is more stable than RNase T1. The primary structure of RNase Po1 was determined to be < ETGVRSCNCAGRSFTGTDVTNAIRSARAGGSGNYPHVYNNFEGFSFSCTPTFFEFPVFRGSVYSGGSPG ADRVIYD- QSGRFCACLTHTGAPSTNGFVECRF. It consisted of 101 amino acid residues, with a molecular weight of 10,760. RNase Po1 has relatively higher sequence homology with RNase T1 family RNase. It contains 6 half cystine residues. The locations of four of them are superimposable on those of RNase U1 and RNase U2. The amino acid residues forming the active site of RNase T1 were well conserved in this RNase. Therefore, RNase Po1 is a unique member of the RNase T1 family in respect of the location of one disulfide bridge, and its stability.

Amino Acid Sequence↗