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M Ohnishi

Publications and source records attributed to M Ohnishi.

At least 145 records · Page 8Linked to original sources
PubMed1996

A new plasmid-encoded proteic killer gene system: cloning, sequencing, and analyzing hig locus of plasmid Rts1.

A new proteic killer gene system, hig, was identified on the plasmid Rts1. The hig locus consisting of a higA and higB is directly related to the temperature sensitive host cell growth conferred by Rts1. We proved that higB encoding presumably a 92-amino-acid polypeptide inhibited segregation of plasmid free cells, and higA encoding a 104-amino-acid polypeptide suppressed the higB function both in cis and in trans.

Amino Acid Sequence↗
PubMed1996

Elucidation of the subsite structure of bacterial saccharifying alpha-amylase and its mode of degradation of maltose.

The subsite structure of bacterial saccharifying alpha-amylase (BSAm) was elucidated by two methods using a series of maltooligosaccharides labeled with [14C]D-glucose at the reducing end. The rate parameter k0/Km and the cleavage frequency were obtained using the labeled substrates at sufficiently low concentrations to eliminate transglycosylation and condensation. This evaluation showed that the active center is composed of five subsites, with the catalytic site located between the 3rd and the 4th subsites from the nonreducing end. The evaluated affinity values of a subsite varied with the set of data used, which suggests some stimulation factor resulting from the chain length effect. The appearance of a time lag during the digestion of the poor substrate, maltose, was studied using radioactively labeled maltose (81.6 mM). Radioactive oligosaccharides larger than maltose were found at a significant level of more than 2% of the initial substrate in the digests, including a product peculiar to condensation, G-G*-G, as 8-10% of the maltotriose in the digests. This indicates that transglycosylation is a main side reaction (ca. 90%). A degradation pathway for maltose via maltosyl transfer was proposed, in which G3 behaves as a kind of catalyst.

Bacillus subtilis↗
PubMed1996

Role of P-selectin in the early stage of the Arthus reaction.

P-selectin is rapidly translocated to the surface of endothelial cells and platelets following exposure to chemical mediators such as histamine, thrombin and complement factors. The Arthus reaction is caused by vascular injury which is initiated by the local deposition of the immune complex followed by the activation of complement and release of chemical mediators. In this report, the role of P-selectin in the early stage of reverse passive Arthus reaction in rat using monoclonal antibodies (mAbs) against rat P-selectin will be investigated. Intravenous administration of the mAb ARP2-4 significantly attenuated paw edema 1 h after challenging it with antigen by 31.5% (1 mg/kg) and 44.7% (3 mg/kg), respectively. Edema formation was also reduced by sulfatide (73.1%, 50 mg/kg) and inositol hexakisphosphate (InsP6) (72.9%, 30 mg/kg), which have been reported to block P-selectin-mediated neutrophil adhesion. Moreover, neutrophil accumulation into the inflammatory site in the Arthus reaction was inhibited by anti-P-selectin mAb. P-selectin expression was detected along vessel walls prior to neutrophil accumulation, as determined by immunohistochemical staining using the antibody. In addition, the expression of P-selectin mRNA was induced 4 h after deposition of immune complex. From these results, we concluded that P-selectin plays an important role in the pathogenesis of the Arthus reaction especially in the early stage by recruiting neutrophils into sites of inflammation.

Animals↗
PubMed1996

Enhanced expression of the protein kinase substrate annexin in human hepatocellular carcinoma.

Annexin (AX) constitutes a new family of Ca2+-dependent membrane-binding proteins; 13 of them have been described. Among these, annexin-1 (AX-I) has displayed many biological functions in vitro. Its actual role in vivo, however, remains unknown. We already reported that AX-I was expressed in proliferating (regenerating) hepatocytes at both protein and messenger RNA (mRNA) levels. The role of AX-I in human hepatocellular carcinoma (HCC) remains obscure. In this study, the amounts of AX-I at protein and mRNA levels, as well as its localization, have been determined in the normal human liver, chronic hepatitis liver, and nontumorous and tumorous portions of HCC. AX-I was rarely found in normal and chronic liver tissues, whereas it is overexpressed at both the transcriptional and translational levels in tumorous and nontumorous regions of HCC. In addition, more AX-I was expressed in the tumorous portion than the nontumorous portion of HCC. AX-I was present in the hepatocytes and HCC cells, localized mainly in the cytoplasm. AX-I was expressed in poorly differentiated cancer cells. Furthermore, AX-I was tyrosine-phosphorylated in HCC. We also found that some of the AX-I- positive hepatocytes in the nontumorous tissues were derived from a particular subset of parenchymal cells (stem or oval cells). These results indicate that AX-I plays an important role in the malignant transformation process leading to HCC and that it is closely related to the histological grade of HCC. HCC would offer a novel tool with which to study the function of AX-I in malignant transformation.

Annexin A1↗
PubMed1996

Inhibitory effects of d-limonene on the development of colonic aberrant crypt foci induced by azoxymethane in F344 rats.

The modifying effect of the monoterpenoid d-limonene in drinking water on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) was investigated in male F344 rats. The effects of d-limonene intake on ornithine decarboxylase (ODC) activity and on the silver stained nucleolar organizer region protein (AgNOR) count in the colonic mucosa were also estimated. Animals were given 3 weeks s.c. injections of AOM (15 mg/kg body wt) to induce ACF. These rats were treated with or without 0.5% d-limonene in the drinking water, starting 1 week before the first dosing with AOM. All rats were killed 2 weeks after the last AOM injection, to measure the number of ACF, ODC activity and AgNOR count/nucleus in the colon. In rats given AOM and d-limonene the frequencies of ACF and aberrant crypts/colon, and aberrant crypts/focus were significantly decreased compared with those of rats given AOM alone (P < 0.01, P < 0.001 and P < 0.001 respectively). Number of AgNOR counts/nucleus of rats treated with AOM and d-limonene was significantly smaller than that of rats treated with AOM alone (P < 0.001). These results suggest that the monoterpenoid d-limonene might be a chemopreventive agent for colonic carcinogenesis in rats.

Animals↗
PubMed1996

Occurrence of deoxyribonucleic acid fragmentation during prolactin-induced structural luteolysis in cycling rats.

We determined whether fragmentation of genomic DNA, one of the hallmarks of apoptosis, occurs during structural luteolysis in cycling rats. Corpora lutea (CL) were collected from rats at each estrous cycle stage (1800 h), and fragmented DNA was extracted. Only CL from rats at the proestrous stage showed distinct DNA fragmentation. To determine the period of occurrence of DNA fragmentation, CL were collected at several points between 1200 h on the day of proestrus and 0600 h on the day of estrus. Distinct DNA fragmentation was observed from 1800 h (proestrus) to 2400 h (proestrus), and the extent was significantly lower at 0600 h (estrus). It is known that prolactin (PRL) induces structural luteolysis in rats. To examine the role of PRL in luteal DNA fragmentation, 2-bromo-alpha-ergocryptine (BE) was used to suppress the PRL surge on the day of proestrus. CL collected at 1800 h from BE-treated rats did not show distinct DNA fragmentation, and PRL injection offset the effect of BE. Histochemical analysis with a 3'-end labeling technique confirmed the occurrence of DNA fragmentation in luteal tissue. These results suggest that apoptotic cell death occurs during PRL-induced structural luteolysis.

Animals↗
PubMed1996

Chemopreventive effects of taurine on diethylnitrosamine and phenobarbital-induced hepatocarcinogenesis in male F344 rats.

Modifying effects of taurine, a naturally occurring organosulfur compound, on diethylnitrosamine (DEN) and phenobarbital (PB)-induced hepatocarcinogenesis were examined in rats. Male F344 rats, 5 weeks old, were divided into 8 groups. Rats of groups 1 through 5 were given i.p. injections of DEN (100 mg/kg body weight) once a week for 3 weeks from one week after the start of the experiment. Of them, animals of group 2 received taurine mixed in a basal diet at a concentration of 2000 ppm for the initial 4 weeks, and those of groups 3 and 5 were given the agent starting 4 weeks after the beginning of the experiment until the end (24 weeks). Rats in groups 1, 4, 7 and 8 were kept on the basal diet throughout the experiment (24 weeks). Group 6 was given taurine throughout the experiment and group 8 was treated as a vehicle control. Animals of groups 1,2, 3 and 7 received PB in drinking water at a dose of 500 ppm from one week after the end of carcinogen or vehicle treatment. Liver neoplasms were recognized only in DEN-treated groups. The incidence and average number of liver neoplasms of group 3 were significantly lower than those of group 1. The number of glutathione S-transferase placental form (GST-P)-positive foci of group 2 or 3 was significantly smaller than that of group 1 (P < 0.01 or P < 0.005). The average and unit areas of GST-P-positive foci in groups 2 and 3 were also significantly smaller than those in group 1 (P < 0.005 and P < 0.0001 and P < 0.0001, respectively). In this study, the level of ornithine decarboxylase activity in non-neoplastic liver tissue was reduced by taurine treatment in both the initiation and postinitiation phases. These results suggest that taurine could be a chemopreventive agent for liver neoplasia.

Animals↗
PubMed1996

Chemopreventive effect of a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate, on rat oral carcinogenesis.

The effect of a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate (ACA), on 4-nitroquinoline 1-oxide (4-NQO)-induced oral carcinogenesis was investigated in male F344 rats. All rats except those in the ACA-alone and untreated groups were given 4-NQO (20 ppm) In the drinking water for 8 weeks to induce oral cancer. Starting 1 week before the 4-NQO exposure, animals were fed diet containing 100 ppm or 500 ppm ACA for 10 weeks, followed by the basal diet without ACA for 22 weeks. Other groups were fed the diet containing ACA at 100 ppm or 500 ppm for 22 weeks, starting 1 week after the cessation of 4-NQO exposure. The remaining groups consisted of rats given 500 ppm ACA alone or untreated rats. At the termination of the experiment (32 weeks), the incidences of tongue neoplasms and preneoplastic lesions, polyamine levels in the tongue tissue, and cell proliferation activity estimated in terms of 5-bromodeoxyuridine (BrdU)-labeling index and by morphometric analysis of silver-stained nucleolar organizer regions' protein (AgNORs) were compared among the groups. Feeding of ACA at the two doses during initiation or postinitiation significantly decreased the development of tongue carcinoma (93-100% reduction, P < 0.001) and preneoplasia (43-50% reduction for hyperplasia and 34-48% reduction for dysplasia, P < 0.05). There were no such lesions in rats fed ACA alone or those in the untreated control group. The number of AgNORs per cell nucleus was significantly decreased by feeding of ACA at a high dose (500 ppm) (29% inhibition, P < 0.05). The BrdU-labeling index was also reduced by dietary administration of ACA (23-32% inhibition, P < 0.01). In addition, ACA feeding reduced tongue polyamine levels (35-40% inhibition, P < 0.05). These results indicate that ACA inhibited rat oral carcinogenesis, and such inhibition might be related to suppression of cell proliferation in the oral mucosa by the xanthine oxidase inhibitor.

4-Nitroquinoline-1-oxide↗
PubMed1996

Inhibitory effect of chlorophyllin on diethylnitrosamine and phenobarbital-induced hepatocarcinogenesis in male F344 rats.

Modifying effects of chlorophyllin (CHL) on the diethylnitrosamine (DEN)-phenobarbital (PB) hepatocarcinogenesis model were examined in rats. Five-week-old male F344 rats were divided into 8 groups. Groups 1 through 5 were given i.p. injections of DEN (100 mg/kg body weight) once a week for 3 weeks beginning one week after the start of the experiment, while groups 6 through 8 received vehicle treatment. Groups 1, 2, 3 and 7 received drinking water with 500 ppm PB from one week after the end of carcinogen or vehicle treatment. CHL-containing diet (2000 ppm) was given to group 2 during the initiation phase and to groups 3 and 5 during the promotion and the post-initiation phase, respectively. Group 6 was given the experimental diet alone throughout the experiment (24 weeks). Liver neoplasms were present in DEN-treated groups and PB treatment promoted liver tumorigenesis. The incidences of adenoma in groups 2 and 3 were significantly smaller than in group 1 (P<0.05 and P<0.02), although the reductions in the incidences of liver cell cancer were not significant. The average numbers of liver neoplasms/rat in group 2 were significantly smaller than in group 1 (P<0.05-P<0.005). Glutathione S-transferase placental form-positive foci were also significantly decreased by CHL treatment (P<0.05 and P<0.001). DEN and PB exposure increased liver ornithine decarboxylase activity and this increase was significantly inhibited by feeding of CHL during the initiation phase (P<0.001). These results suggest that CHL is a chemopreventive agent for liver neoplasia.

Animals↗
PubMed1996

A glucocorticoid antagonist, mifepristone affects anti-Candida activity of murine neutrophils in the presence of prednisolone in vitro and experimental candidiasis of prednisolone-treated mice in vivo.

The effects of a glucocorticoid-antagonist, mifepristone on the suppressive action of prednisolone for anti-Candida activity of murine neutrophils were examined. Prednisolone suppressed inhibitory activity of neutrophils to mycelial growth of Candida albicans. This suppression was cancelled in the presence of 10(-7)-10(-6) M of mifepristone in vitro. Corresponding to this in vitro action, mifepristone protected prednisolone-treated mice from lethal C. albicans infection in vivo. These results suggest that glucocorticoid-induced vulnerability to Candida infection may be recovered or normalized by application of mifepristone.

Animals↗
PubMed1996

Altered vasoreactivity in lungs isolated from rats exposed to nitric oxide gas.

A rebound phenomenon (severe arterial desaturation and pulmonary vasoconstriction) has been observed in some patients with pulmonary hypertension after sudden discontinuation of nitric oxide (NO) inhalation therapy. The mechanism responsible for this phenomenon is unknown. It has recently been reported that NO synthase (NOS) can be inhibited by NO as a negative feedback mechanism. We therefore hypothesized that this rebound phenomenon might be attributable to reduced endogenous NO production due to inhibition of pulmonary endothelial NOS (eNOS) activity by inhaled NO. To test this hypothesis, vasoreactivities were compared in isolated perfused lungs from rats exposed to 40 ppm NO gas and room air for 2 days. The pressor responses to angiotensin II and hypoxia of lungs from rats exposed to NO were markedly potentiated and their depressor response to bradykinin was considerably impaired, whereas that to sodium nitroprusside was preserved, compared with the responses of those exposed to room air. This altered pulmonary vasoreactivity was also induced by lower concentrations of inhaled NO (as low as 1 ppm) and was completely reversed by discontinuation of NO inhalation for several (< 8) hours. The expression of eNOS mRNA by lungs isolated from rats exposed to 40 ppm NO and room air for 2 days did not differ. These results suggest that pulmonary endogenous NO production is reversibly reduced after relatively short-term NO inhalation, which probably inhibits eNOS activity directly. We speculate that reduced production of pulmonary endogenous NO by exogenous (inhaled) NO could be the mechanism responsible for this rebound phenomenon.

Administration, Inhalation↗
PubMed1996

Lack of inhibitory effect of benzyl isothiocyanate on 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in rats.

Modifying effects of benzyl isothiocyanate (BITC), a glucosinolate compound, were investigated on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in female SD rats. One hundred twenty five female rats were divided into 4 groups. Starting at 6 weeks of age, rats were fed high fat diet containing 23.5% corn oil (Groups 1 and 4) or the experimental diet (high fat diet with 400 ppm BITC) (Groups 2 and 3). At 7 weeks of age, Groups 1 and 2 were given PhIP (100 mg/kg body weight, 8 times for 16 days) by intragastric tube. One week after the final PhIP treatment, the experimental diet for Groups 2 and 3 switched to high fat diet. At the termination (31 weeks after the start of experiment), mammary adenocarcinomas were recognized in Group 1 (PhIP alone) and Group 2 (PhIP + BITC). The incidence of neoplasms was 74.2% in Group 1, and 62.5% in Group 2. The multiplicity of them was 1.71 +/- 1.70 in Group 1, and 1.91 +/- 2.94 in Group 2. Mean sizes of tumors were 9.9 +/- 7.1 mm in Group 1, and 10.8 +/- 6.8 mm in Group 2. But no significant differences for tumors were available between the two groups. These results imply that the glucosinolate compound does not have clear inhibitory effects on PhIP-induced mammary carcinogenesis in rats.

Animals↗
PubMed1995

Clustering of the trp genes in Burkholderia (formerly Pseudomonas) cepacia.

Chromosomal location of trp genes of a strain Burkholderia cepacia (formerly Pseudomonas cepacia) has been determined by transduction using a generalized transducing phage CP75 and by molecular analysis for a cosmid plasmid clone with trp genes isolated from a genomic gene library of the strain. The trp genes were classified into three linkage groups and they all were closely linked on a short chromosomal region probably in the order (trpA, trpB, trpF)-(trpC, trpD)-trpE.

Bacteria↗
PubMed1995

Chemoprevention of azoxymethane-induced colon carcinogenesis by dietary feeding of S-methyl methane thiosulfonate in male F344 rats.

Modifying effects of dietary exposure of S-methyl methane thiosulfonate (MMTS) isolated from cauliflower Brassica oleracea L. var. botrytis on rat colon carcinogenesis induced by azoxymethane (AOM) and on the expression of cell proliferation biomarkers were investigated in two experiments. In experiment 1, male F344 rats were given three s.c. injections of AOM (15 mg/kg body weight) and fed 100 ppm MMTS for 5 weeks, starting 1 week before the first dose of AOM. The frequency of colonic aberrant crypt foci was determined at 5 weeks after the start. Feeding of 100 ppm MMTS for 5 weeks significantly decreased the number of aberrant crypt foci/colon. Colonic mucosal ornithine decarboxylase activity and the number of silver-stained nucleolar organizer regions per nucleus in colonic epithelium were significantly decreased by MMTS treatment compared with those of AOM alone. In experiment 2, effects of dietary feeding of MMTS at two doses (20 and 100 ppm) during the postinitiation phase on intestinal tumorigenesis initiated with AOM were investigated by using a long-term experiments in male F344 rats. Incidence of intestinal neoplasms of rats fed MMTS-containing diets after AOM exposure were reduced in a dose-dependent manner. Feeding of MMTS during the postinitiation phase decreased the number of aberrant crypt foci/colon, colonic ornithine decarboxylase activity, 5-bromodeoxyuridine-labeling index in colonic epithelium, and polyamine level in blood compared with those of AOM alone. These results suggest that MMTS might be a possible chemopreventive agent for intestinal neoplasia.

Animals↗
PubMed1995

Chemoprevention of rat oral carcinogenesis by naturally occurring xanthophylls, astaxanthin and canthaxanthin.

The chemopreventive effects of two xanthophylls, astaxanthin (AX) and canthaxanthin (CX) on oral carcinogenesis induced by 4-nitroquinoline 1-oxide (4-NQO) was investigated in male F344 rats. Rats were given 20 ppm of 4-NQO in their drinking water for 8 weeks to induce oral neoplasms or preneoplasms. Animals were fed diets containing 100 ppm AX or CX during the initiation or postinitiation phase of 4-NQO-induced oral carcinogenesis. The others contained the groups of rats treated with AX or CX alone and untreated. At the end of the study (week 32), the incidences of preneoplastic lesions and neoplasms in the oral cavity of rats treated with 4-NQO and AX or CX were significantly smaller than those of rats given 4-NQO alone (P < 0.001). In particular, no oral neoplasms developed in rats fed AX and CX during the 4-NQO exposure and in those given CX after the 4-NQO administration. Similarly, the incidences of oral preneoplastic lesions (hyperplasia and dysplasia) in rats treated with 4-NQO and AX or CX were significantly smaller than that of the 4-NQO-alone group (P < 0.05). In addition to such tumor inhibitory potential, dietary exposure of AX or CX decreased cell proliferation activity in the nonlesional squamous epithelium exposed to 4-NQO as revealed by measuring the silver-stained nucleolar organizer regions protein number/nucleus and 5'-bromodeoxyuridine-labeling index. Also, dietary AX and CX could reduce polyamine levels of oral mucosal tissues exposed to 4-NQO. These results indicate that AX and CX are possible chemopreventers for oral carcinogenesis, and such effects may be partly due to suppression of cell proliferation.

Animals↗
PubMed1995

Molecular cloning and expression of mouse mg(2+)-dependent protein phosphatase beta-4 (type 2C beta-4).

A full-length complementary DNA (cDNA) clone (pTK-3) encoding an isoform of Mg(2+)-dependent protein phosphatase beta (MPP beta-4) was isolated for the first time from a mouse melanocyte cDNA library. It was strongly suggested that the mRNA corresponding to the pTK-3 insert was a splicing variant of a single pre-mRNA that also encodes MPP beta-1 and -2 (T. Terasawa, T. Kobayashi, T. Murakami, M. Ohnishi, S. Kato, O. Tanaka, H. Kondo, H. Yamamoto, T. Takeuchi, and S. Tamura, 1993, Arch. Biochem. Biophys. 307, 342-349). The amino acid sequence of MPP beta-4 differed from those of MPP beta-1 and -2 only at the carboxyl terminal region. Analysis by reverse transcriptase polymerase chain reaction (RT-PCR) revealed that MPP beta-4 mRNA was expressed only in testis and intestine and not in other mouse tissues tested. Specific expression of the mRNA signals of two other isoforms of MPP beta, MPP beta-3 and -5 (a novel isoform), in testis and intestine was also demonstrated by the RT-PCR. The carboxyl terminal region of MPP beta-5 was found to have a chimera structure composed of part of MPP beta-1 and part of MPP beta-3. The recombinant MPP beta-3 and -4 and the putative MPP beta-5 expressed in Escherichia coli cells exhibited Mg(2+)-dependent and okadaic acid-insensitive protein phosphatase activities. It was demonstrated that the mRNA expression levels of MPP beta-3, -4, and -5 alter according to the maturation of mouse testis. These results suggest that the complex structure of MPP beta isoforms and their tissue- and developmental stage-specific expression reflect the variety of their physiological functions.

Alternative Splicing↗