Biomedical subjects

S Okabe

Publications and source records attributed to S Okabe.

At least 91 records · Page 5Linked to original sources

PubMed1999

EP4 receptor mediation of prostaglandin E2-stimulated mucus secretion by rabbit gastric epithelial cells.

Prostaglandin (PG) E receptors are divided into four subtypes (EP1-EP4). We investigated the EP receptor subtype involved in PGE2-stimulated mucus secretion by rabbit gastric epithelial cells. Northern blot analysis revealed that epithelial cells express EP3 and EP4 receptor mRNAs, but neither EP1 nor EP2 receptor mRNAs were detected. PGE2, 11-deoxy-PGE1 (an EP3/EP4/EP2 agonist) and 16,16-dimethyl-PGE2 (an EP3/EP2/EP4 agonist) concentration-dependently promoted mucus secretion. In contrast, 17-phenyl-PGE2 (an EP3/EP1 agonist), sulprostone (an EP3/EP1 agonist), and butaprost (an EP2 agonist) failed to stimulate secretion. The effective concentrations of PGE2, 11-deoxy-PGE1, and 16,16-dimethyl-PGE2 were associated with their affinities for the EP4 receptor. In addition, PGE2, 11-deoxy-PGE1, and 16,16-dimethyl-PGE2 increased cyclic AMP (cAMP) production, but the other prostanoids had no effect. SQ22536 [9-(tetrahydro-2'-furyl)adenine; an adenylate cyclase inhibitor] inhibited both the increased cAMP production and mucus secretion induced by PGE2, 11-deoxy-PGE1, and 16,16-dimethyl-PGE2. H-89 (N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinoline sulfonamide; a protein kinase A inhibitor) also abolished the stimulatory effects of the prostanoids on mucus secretion, but calphostin C (a protein kinase C inhibitor) did not. These results indicate that PGE2 promotes mucus secretion by rabbit gastric epithelial cells, mediated through EP4 receptor stimulation and the subsequent activation of protein kinase A.

16,16-Dimethylprostaglandin E2↗

PubMed1999

Inhibitory effect of macrophage-derived factors on the recovery of wounds induced in rat gastric epithelial monolayers.

The effect of macrophage supernatant on the recovery of wounds induced in rat gastric epithelial RGM1 monolayers was investigated. The repair of wounds induced in the monolayers of RGM1 cells was accelerated time-dependently by 10 ng/mL of transforming growth factor-alpha (TGF-alpha). TGF-alpha also significantly stimulated DNA synthesis in RGM1 cells for 24 hr. Upon treatment of the cells with the macrophage supernatant, spontaneous and TGF-alpha-stimulated restoration was inhibited in a time- and concentration-dependent manner. After 24 hr, TGF-alpha-enhanced restoration was eliminated completely by the supernatant at 10(6) cells/mL. Similarly, the macrophage supernatant suppressed the spontaneous and TGF-alpha-stimulated DNA syntheses in a concentration-dependent manner. The macrophage supernatant at 10(6) cells/mL contained 0.4 ng/mL of interleukin-1beta (IL-1beta). Interleukin-1 receptor antagonist (IL-1RA) reversed the inhibition induced by the macrophage supernatant in a concentration-dependent manner. Nonetheless, pretreatment with IL-1RA had no effects on the spontaneous and TGF-alpha-stimulated DNA syntheses. Reverse transcription-polymerase chain reaction analysis revealed that RGM1 cells express mRNA for IL-1 receptor type 1, but not for type 2. These results indicate that macrophages can inhibit the spontaneous and TGF-alpha-stimulated recovery of wounds induced in gastric epithelial monolayers. The inhibitory effects of the supernatant are suggested to be partially mediated through a IL-1beta/IL-1 receptor type 1 pathway.

Animals↗

PubMed1999

Hypothesis--origin of parietal cells: transfer of the H+K+-ATPase gene from parasitic microorganisms to Cnidaria?

Parietal cells present in the stomach and terminal ileum secrete a highly-concentrated hydrochloric acid into the lumen. The cells are characterized by the enzyme P-type H+K+-ATPase, which has an alpha-subunit with a high homology (>85%) for the amino acid sequences of frog, mouse and pig stomachs. Gastric H+K+-ATPase also exhibits a high homology to H+-ATPase in yeast and Na+K+-ATPase in many tissues, suggesting origination from a common ancestral ATPase. It is known that parietal cells first appeared in fish and were later expressed in evolutionarily-higher organisms. Primitive organisms, such as Cnidaria and Ctenophora, that possessed digestive organs, but not parietal cells, were abundant in the ocean more than 600 million years ago (Pre-Cambrian period). The author thus hypothesized that the genes of either H+-ATPase or H+K+-ATPase that were present in parasitic microorganisms, such as yeast, were transferred to the interstitial cells of host organisms, such as Cnidaria, eventually leading to the evolution of parietal cells. It appears that although parietal cells in the stomach developed by chance, such cells have greatly contributed to the evolution of advanced organisms, including humans, by affording safe ingestion of a large volume of various foods.

Animals↗

PubMed1999

Alternative splicing of the C-terminal domain regulates cell surface expression of the NMDA receptor NR1 subunit.

Subcellular localization of the NMDA receptor NR1 splice forms was studied by expressing individual splice variants and their epitope-tagged derivatives in mouse fibroblasts and in hippocampal neurons. When NR1 splice variants were expressed in fibroblasts, the amount of NR1 molecules expressed on the cell surface varied among forms with different C-terminal cytoplasmic domains. The splice forms with the longest C-terminal cytoplasmic tail (NR1-1a and NR1-1b) showed the lowest amount of cell surface expression, and the splice forms with the shortest C-terminal cytoplasmic tail (NR1-4a and NR1-4b) showed the highest cell surface expression. Cell surface expression of NR1 was enhanced by the coexpression of the NR2 subunit. We measured the glutamate-induced increase of calcium concentration in fibroblasts expressing one of the NR1 splice forms and the NR2B subunit. The increase of calcium concentration after glutamate application had a positive correlation with the amount of NR1 splice forms expressed on the cell surface. When epitope-tagged NR1 splice variants were expressed in primary hippocampal neurons using recombinant adenoviruses, we also observed the differential expression on the cell surface between splice variants. These results suggest that the splicing of the C-terminal domain of the NR1 subunit regulates the cell surface expression of the functional NMDA receptors.

3T3 Cells↗

PubMed1999

Essential role of tumor necrosis factor alpha (TNF-alpha) in tumor promotion as revealed by TNF-alpha-deficient mice.

To examine the hypothesis that tumor necrosis factor (TNF) alpha is an essential cytokine in carcinogenesis, we conducted two-stage carcinogenesis experiments with an initiator, 7,12-dimethylbenz(a)anthracene (DMBA), plus either of two tumor promoters, okadaic acid and 12-O-tetradecanoylphorbol-13-acetate (TPA), on the skin of TNF-alpha-deficient (TNF-/-) mice. TNF-/- mice treated with DMBA plus okadaic acid developed no tumors for up to 19 weeks, and at 20 weeks, the percentage of tumor-bearing TNF-/- mice was 10%, whereas the percentage of tumor-bearing TNF+/+ mice was 100%. In TNF-/- mice treated with DMBA plus TPA, tumor onset was delayed 4 weeks, and the time to development of small tumors in 100% of mice was 9 weeks later than that seen in TNF+/+ CD-1 mice. The average number of tumors in TPA-treated TNF-/- mice was 2.8, compared with 11.8 for TNF+/+ CD-1 mice. To understand the residual tumor-promoting activity in TNF-/- mice, we also investigated the possible significance of interleukin (IL) 1 as an additional cytokine in tumor promotion. A single application of TPA and okadaic acid increased IL-1alpha and IL-1beta gene expression in TNF-/- mice. All of our results demonstrate that TNF-alpha is the key cytokine for tumor promotion in mouse skin and, very possibly, for carcinogenesis in humans as well.

3T3 Cells↗

PubMed1999

Green tea and cancer chemoprevention.

Worldwide interest in green tea as a cancer preventive agent for humans has increased, because it is non-toxic and it is effective in a wide range of organs. (-)-Epigallocatechin gallate (EGCG) is the main constituent of green tea; the others are (-)-epicatechin gallate, (-)-epigallocatechin and (-)-epicatechin (EC). This paper reports the results of our latest pharmacological and biochemical studies with 3H-EGCG, along with studies on human subjects. The study on bioavailability of 3H-EGCG in mice revealed the wide distribution of radioactivity in multiple organs. Specifically, radioactivity was found in all reported target organs of EGCG and green tea extract (digestive tract, liver, lung, pancreas, mammary gland and skin) as well as other organs (brain, kidney, uterus and ovary or testes) in mice. Recently, we demonstrated that EC enhanced incorporation of 3H-EGCG into human lung cancer cell line PC-9 cells. EC along with another cancer preventive agent sulindac also synergistically enhanced apoptosis in PC-9 cells induced by EGCG. Moreover, a case-control study on breast cancer patients revealed that high daily consumption of green tea was associated with a lower recurrence rate among Stages I and II patients. All the results suggest that consumption of green tea is a practical and effective cancer preventive both before cancer onset and after cancer treatment.

3T3 Cells↗

PubMed1999

Synergistic effects of (--)-epigallocatechin gallate with (--)-epicatechin, sulindac, or tamoxifen on cancer-preventive activity in the human lung cancer cell line PC-9.

The study on incorporation of [3H](-)-epigallocatechin gallate (EGCG) into human lung cancer cell line PC-9 indicated that the [3H]EGCG incorporation was significantly enhanced by (-)-epicatechin, an inert tea polyphenol without a galloyl moiety. (-)-Epicatechin enhanced apoptosis, growth inhibition of PC-9 cells, and inhibition of tumor necrosis factor-alpha release from BALB/c-3T3 cells by EGCG and other tea polyphenols with a galloyl moiety in a dose-dependent manner. Moreover, the effects of EGCG on induction of apoptosis were also synergistically enhanced by other cancer-preventive agents, such as sulindac and tamoxifen. This paper reports significant evidence that whole green tea is a more reasonable mixture of tea polyphenols for cancer prevention in humans than EGCG alone and that it is even more effective when it is used in combination with other cancer preventives.

3T3 Cells↗

PubMed1999

Endosonography during endoscopic mucosal resection to enhance its safety: a new technique.

BACKGROUND: We have performed endoscopic mucosal resection of the esophagus (172 cases), stomach (102 cases), and colon (28 cases) using a transparent plastic cap. Because the lesion-bearing mucosa is suctioned up inside the cap under endoscopic suction, the mucosa should be dissected sufficiently from the proper muscle layer to prevent perforation. METHODS: To avert the risk of perforation, we introduced endosonographic assessment of submucosal dissection (47 cases). In all cases, just keeping the ultrasonic probe on the surface of the mucosa allowed us to evaluate whether the mucosal lesion was lifted up sufficiently from the proper muscle layer after local saline injection. RESULTS: It was possible to confirm that the muscle layer was kept outside the strangulating snare by the same procedure (32 of 37 cases, 86.5%). CONCLUSIONS: We experienced five muscular resections in cases without the ultrasonic probe and no muscular resection with the ultrasonic probe. Thus we recommend endosonographic assessment during endoscopic mucosal resection to enhance its safety.

Colonic Neoplasms↗

PubMed1999

The role of Bcl6 in mature cardiac myocytes.

OBJECTIVE: The Bcl6 gene encodes a sequence-specific transcriptional repressor and is ubiquitously expressed in adult murine tissues including heart muscle. The objective of this study was to examine the role of Bcl6 in cardiac myocytes. METHOD: We developed Bcl6-deficient (Bcl6-/-) mice and histologically examined hearts from these mice. RESULTS: Massive myocarditis with eosinophilic infiltration occurred in Bcl6-/- mice after 4-6 weeks of age. Since expression of the Bcl6 gene was induced in normal cardiac myocytes after 2 weeks of age and thereafter detected through adulthood, loss of Bcl6 in mature cardiac myocytes may be related to the induction of eosinophilic myocarditis. To examine the effects of eosinophils from Bcl6-/- mice on normal hearts, bone marrow cells from Bcl6-/- mice were adoptively transferred into sublethally irradiated RAG1-deficient mice. Although massive eosinophilic infiltration was detected in conjunctivas and spleens from the chimeric mice, myocarditis was never observed. Electron microscopic analysis of cardiac myocytes from Bcl6-/- mice revealed a spectrum of degenerative changes prior to eosinophilic infiltration. CONCLUSION: Bcl6 maynot be essential for the maturation of cardiac myocytes but may play a role in protecting mature cardiac myocytes from eosinophilic inflammation.

Adoptive Transfer↗

PubMed1999

Colon-specific delivery of R68070, a new thromboxane synthase inhibitor, using chitosan capsules: therapeutic effects against 2,4,6-trinitrobenzene sulfonic acid-induced ulcerative colitis in rats.

The objective of this study was to estimate the therapeutic effects of R68070, a new thromboxane synthase inhibitor, on 2,4,6-trinitrobenzenesulfonic acid sodium salt (TNBS)-induced ulcerative colitis in rats. We also examined the acceleration of the healing effect of R68070 with chitosan capsules to achieve its colon-specific delivery. The colonic injury and inflammation were assessed by measuring the myeloperoxidase (MPO) activities, colon wet weight/body weight (C/B) ratio and the damage score, respectively. These markers were decreased by the oral administration of R68070 with chitosan capsules and carboxymethyl-cellulose (CMC) suspension. The therapeutic effects of R68070 against ulcerative colitis were observed in both dosage forms in a dose dependent manner. In addition, its therapeutic effects were increased by the use of chitosan capsules, compared with CMC suspension. These results suggest that chitosan capsule might be a very useful dosage form for the colon-specific delivery of R68070 as an anti-inflammatory drug and for the therapy of ulcerative colitis.

Animals↗

PubMed1999

Thrombopoietin induces an SH2-containing protein, CIS1, which binds to Mpl: involvement of the ubiquitin proteosome pathway.

The interaction of thrombopoietin (TPO) with its receptor, Mpl, triggers growth and differentiation of megakaryocytes and their progenitors. The Mpl cytoplasmic domain controls this process through src homology 2 (SH2)-containing target molecules and their receptor docking sites. A novel cytokine inducible SH2-containing protein, CIS1, has been isolated. CIS1 is induced by interleukin-2 (IL-2), IL-3, GM-CSF, and erythropoietin (EPO), but not by IL-6, granulocyte colony-stimulating factor (G-CSF), or stem cell factor. To investigate the functional domains of Mpl for induction of CIS1, we examined FDCP-2 cell lines expressing seven carboxyl truncations of the human Mpl cytoplasmic domain. We found that the box1 and box2 regions of Mpl were necessary for induction of CIS1 after TPO stimulation. CIS1 was degraded very quickly and was found to be involved in the ubiquitin-proteosome pathway. A 4-hour depletion of TPO almost completely eliminated CIS1 protein; within 1 hour after TPO stimulation, CIS1 protein reappeared as 37- and 32-kDa proteins in the wild type Mpl-expressing FDCP-2 cells. Further, CIS1 was stably associated with tyrosine-phosphorylated Mpl. The SH2 domains of CIS1, constructed as glutathione S-transferase fusion protein, bound to activated Mpl in vitro. These results suggest that CIS1 may be an important signaling component downstream of Mpl and may regulate the proliferation and differentiation of hematopoietic cells.

Animals↗

PubMed1999

28-deacetylbelamcandal, a tumor-promoting triterpenoid from Iris tectorum.

A spiroiridal-type triterpenoid, 28-deacetylbelamcandal (1), was isolated from the rhizomes of Iris tectorum as an active principle that stimulated differentiation of human promyelocytic leukemia (HL-60) cells, a short-term screening method for 12-O-tetradecanoylphorbol 13-acetate (TPA)-type tumor promoters. In the same manner as TPA, compound 1 bound to protein kinase C (PKC) and activated PKC, and induced tumor necrosis factor-alpha release from HL-60 cells. In an in vivo study, groups treated with 100 microg 7, 12-dimethylbenz[a]anthracene plus 400 nmol of 1 showed 64.3% tumor incidence by week 20. It has thus been demonstrated that 1 represents a new structural class of mouse skin-tumor promoters.

Animals↗

PubMed1999

Antisecretory and ulcer healing effects of S-0509, a novel CCK-B/gastrin receptor antagonist, in rats.

The effects of a novel CCK-B/gastrin receptor antagonist, S-0509, on gastric acid secretion and the healing of acetic acid ulcers in rats were examined. S-0509, orally administered 1, 6, and 12 hr prior to a 3-hr pylorus ligation, significantly inhibited basal gastric acid secretion in both normal rats and rats with gastric ulcers. The inhibition was nearly dose-related, persisted for more than 15 hr, and proved to be more potent in rats with ulcers than in normal rats. In addition, S-0509 markedly inhibited pentagastrin- and carbachol-stimulated acid secretion in both normal rats and rats with ulcers, but failed to inhibit histamine-stimulated secretions. In chronic gastric fistula rats, S-0509 also significantly inhibited pentagastrin- and carbachol-stimulated gastric acid secretion in a dose-related manner, but had no effect on histamine-stimulated secretion. These effects were largely similar to those observed with famotidine, although famotidine also inhibited histamine-stimulated secretion. A two-week treatment with S-0509 markedly enhanced the spontaneous healing of acetic acid ulcers and prevented the delay in ulcer healing caused by indomethacin. Gastric secretion was significantly inhibited and the plasma gastrin level was increased in the animals studied. It is concluded that S-0509 is a promising new antisecretory drug for the treatment of peptic ulcers.

Animals↗

PubMed1999

Cytokine-induced neutrophil chemoattractants in healing of gastric ulcers in rats: expression of >40-kDa chemoattractant in delayed ulcer healing by indomethacin.

We examined the roles of cytokine-induced neutrophil chemoattractants (CINCs) in neutrophil infiltration of ulcerated gastric tissue in rats. Neutrophil chemotactic and myeloperoxidase (MPO) activities were negligible in the normal mucosa but were markedly elevated by ulceration. The activities decreased with spontaneous ulcer healing, but remained quite high when the healing was prevented by indomethacin. Neither CINC-1 nor CINC-2alpha was detected, and CINC-3 was negligible in the normal mucosa. The expression of these CINCs was also promoted by ulceration, but the expression patterns during ulcer healing were apparently different among them. The change in net content of CINCs was well associated with those in chemotactic and MPO activities during spontaneous healing. The chemotactic activity due to the net CINCs was equivalent to most parts of the activity extracted from the tissue. On the other hand, indomethacin did not affect CINC expression, compared with that in spontaneous healing, but induced the expression of high-molecular-weight (>40-kDa) chemoattractant when ulcer healing was impaired. The chemotactic activity due to >40-kDa chemoattractant was equivalent to the activity extracted from the tissue. We conclude that CINCs play crucial roles in neutrophil infiltration of ulcerated gastric tissue in the spontaneous healing in rats and that the expression of CINCs might be differentially regulated. Furthermore, the >40-kDa chemoattractant might be the predominant contributor to the increased neutrophil infiltration in the delayed healing by indomethacin.

Animals↗

PubMed1999

Healing of Helicobacter pylori-induced gastric ulcers in Mongolian gerbils: combined treatment with omeprazole and clarithromycin.

Helicobacter pylori can colonize the stomachs of Mongolian gerbils and subsequently induce penetrating ulcers five months later. Using this gerbil model, the effects of both combined treatment with omeprazole and clarithromycin, as well as treatment with each drug separately, on the healing of H. pylori-induced gastric ulcers, and the effects of the cessation of the drug treatment on healed ulcers were examined. Beginning five months after H. pylori (NCTC11637) inoculation, omeprazole (four weeks), clarithromycin (two weeks), their combination, or the vehicle was orally administered once daily. These drugs, in combination or separately, markedly enhanced ulcer healing and lowered the increased myeloperoxidase (MPO) activity. While omeprazole had no effect on viable H. pylori, clarithromycin and the drug combination significantly reduced viable H. pylori. The degree of bacterial eradication was much higher in the case of the drug combination compared to clarithromycin alone. Four months after cessation of the treatment, visible ulcers, hypertrophic gastritis and increased MPO activity were found in the control animals (all H. pylori-positive). Nonetheless, only one of the eight gerbils subjected to the drug combination developed a small ulcer, although no hypertrophic gastritis was exhibited. It is concluded that: (1) the gerbil model of H. pylori infection is useful for the study of ulcer healing; (2) combined treatment with omeprazole and clarithromycin enhances the ulcer healing in infected gerbils; and (3) healed ulcers do not relapse, despite cessation of the drug treatment.

Animals↗

PubMed1999

Continual remodeling of postsynaptic density and its regulation by synaptic activity.

A postsynaptic density (PSD) protein, PSD-95, was tagged with green fluorescent protein (GFP-PSD-95) and expressed in cultured hippocampal neurons using recombinant adenoviruses. GFP-PSD-95 was selectively localized to excitatory postsynaptic sites. Time-lapse fluorescence imaging of hippocampal neurons revealed that >20% of GFP-PSD-95 clusters turned over within 24 hours. The appearance rate of clusters was higher than the disappearance rate, and this difference accounted for the gradual increase of the cluster density observed in culture. Dynamics of PSD-95 clusters were also inhibited by blockers of excitatory synaptic transmission. Continual PSD turnover and its regulation by synaptic activity may be important in activity-dependent remodeling of neuronal connections.

2-Amino-5-phosphonovalerate↗

PubMed1999

Volume-pressure properties of the upper airway in normal subjects and patients with obstructive sleep apnoea.

The aim of this study was to examine the volume-pressure (V-P) characteristics of isolated upper airways in normal subjects and patients with obstructive sleep apnoea (OSA) and to ascertain whether an increase in upper airway muscle activity affects these characteristics. We studied upper airway pressure changes during volume changes by inflation and deflation of air volumes of 5, 10, 15 and 20 mL without and with submental electrical stimulation, during voluntary closing of the glottis, in seven normal subjects and 13 OSA patients. Volume-pressure properties of the upper airway were assessed by elastance (Euaw) which was obtained from the slope of the regression line of the V-P relationships. Euaw in OSA patients was 0.52 +/- 0.08 cmH2O/mL, which was greater than in normal subjects (0.26 +/- 0.06 cmH2O/mL). Submental stimulation increased Euaw in both OSA patients and normal subjects (0.70 +/- 0.11 cmH2O/mL and 0.41 +/- 0.11 cmH2O/mL, respectively). These results suggest that upper airways of OSA patients during wakefulness are less collapsible than those of normal subjects, and that, in both groups, submental stimulation may stiffen the upper airway.

Adult↗

PubMed1999

Suppression of epileptogenesis by modification of N-methyl-D-aspartate receptor subunit composition.

The effects of altered N-methyl-D-aspartate (NMDA) receptor subunit composition on seizure development in kindling epilepsy were assessed in transgenic mice expressing high neuronal levels of NR2D under control of the calcium/calmodulin kinase II alpha subunit (alphaCaMKII) promoter. The NR2D subunit is normally present at very low levels in the mature forebrain. Transgenic mice showed a marked reduction of amygdala kindling development. Spread of epileptic activity was retarded and generalized seizures appeared later in animals overexpressing NR2D compared with wild-type mice. The progressive lengthening of epileptiform activity, which normally occurs in kindling, was also dampened in transgenic animals. We conclude that NMDA receptor subunit composition determines the progression of experimental epilepsy.

Animals↗