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Biomedical subjects

M Kitamura

Publications and source records attributed to M Kitamura.

At least 145 records · Page 8Linked to original sources
PubMed1998

Stimulation of duodenal bicarbonate secretion by carbenoxolone in rats: a comparative study with prostaglandin E2.

1. The effects of carbenoxolone on duodenal HCO3- secretion were examined in anesthetized rats and compared with those of prostaglandin E2 (PGE2). 2. After 18-hr fasting, the duodenal loop (1.7 cm) that was made between the pyloric ring and the area just proximal to the outlet of the common bile duct was perfused with saline (pH 4.5), the pH of perfusate and the transmucosal potential difference (PD) were continuously monitored and HCO3- output was determined by titration with 10 mM HCl. 3. Under these conditions, duodenal pH, PD, and HCO3- secretion were increased in response to PGE2 (0.3 and 1.0 mg/kg) given intravenously as a single injection. Carbenoxolone (0.1-1.0 mg/kg, intravenously) also caused an increase in duodenal pH and HCO3- output in a dose-dependent manner, with a concomitant rise in PD; at 1 mg/kg, the magnitude of HCO3- output was almost equivalent to that induced by PGE2 at 0.3 mg/kg. 4. Prior administration of indomethacin, a cyclooxygenase inhibitor (5 mg/kg, subcutaneously), did not affect the HCO3- stimulatory action of carbenoxolone or PGE2. 5. Duodenal HCO3- secretion was also increased by intravenous injection of dibutylyl adenosine 3',5'-cyclic monophosphate (dbcAMP) but not by isobutylmethyl xanthine (IBMX; 10 mg/kg), an inhibitor of phosphodiesterase, but the former action was significantly potentiated in the presence of IBMX. Likewise, the pretreatment of IBMX significantly enhanced the HCO3- stimulatory action of PGE2 but had no effect on the HCO3- response induced by carbenoxolone. 6. These results suggest that carbenoxolone stimulates duodenal HCO3- secretion in rats, similar to PGE2 and this mechanism does not involve endogenous prostaglandins and is not associated with the intracellular accumulation of cAMP.

Animals↗
PubMed1998

Role of nitric oxide in regulation of gastric acid secretion in rats: effects of NO donors and NO synthase inhibitor.

1. The role of nitric oxide (NO) in the regulation of acid secretion was examined in the anaesthetized rat. 2. A rat stomach was mounted in an ex vivo chamber, instilled with 2 ml of saline every 15 min, and the recovered sample was titrated at pH 7.0 against 0.1 N NaOH by use of an automatic titrator for acid secretion. Gastric mucosal blood flow (GMBF) was measured simultaneously by laser Doppler flowmeter. 3. Intragastric application of NO donors such as FK409 (3 and 6 mg ml[-1]) and sodium nitroprusside (SNP; 6 and 12 mg ml[-1]) as well as i.p. administration of cimetidine (60 mg kg[-1]), a histamine H2-receptor antagonist, significantly inhibited the increase in acid secretion in response to pentagastrin (60 microg kg(-1) h(-1), i.v.), in doses that increased gastric mucosal blood flow (GMBF). 4. Intragastric application of FK409 (6 mg ml[-1]) increased both basal and stimulated acid secretion induced by YM-14673 (0.3 mg kg(-1), i.v.), an analogue of thyrotropin-releasing hormone (TRH), but had no effect on the acid secretory response induced by histamine (4 mg kg(-1) h(-1), i.v.). 5. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME; 10 mg kg(-1), i.v.) did not affect basal acid secretion, but significantly potentiated the increase in acid secretion induced by YM-14673 and slightly augmented the acid secretory response to pentagastrin. 6. Both pentagastrin and YM-14673 increased the release of nitrite plus nitrate (NOx), stable NO metabolites, into the gastric lumen, and these changes were completely inhibited by prior administration of L-NAME (10 mg kg(-1), i.v.). 7. Pentagastrin caused an increase in luminal release of histamine and this response was significantly suppressed by intragastric application of FK409 (6 mg ml[-1]). 8. These results suggest that either exogenous or endogenous NO has an inhibitory action on gastric acid secretion through suppression of histamine release from enterochromaffin-like (ECL) cells.

Animals↗
PubMed1998

Post-translational modification and intracellular localization of a splice product of CD46 cloned from human testis: role of the intracellular domains in O-glycosylation.

We obtained a unique CD46 cDNA, STc/CY4, from the human testis, the predicted amino acid sequence of which suggested the presence of a novel isoform of CD46. This message was present predominantly in the testis, and the predicted isoform possessed a short (11 amino acids) transmembrane section (TM) and an unidentified cytoplasmic tail (CY). When expressed in Chinese hamster ovary (CHO) cells, this CD46 isoform underwent no O-glycosylation and was mostly retained in the endoplasmic reticulum. This unusual behaviour of the new isoform was due in part to the short TM and the unusual sequences of the CY. The molecular mass of this isoform was 42,000, approximately 20,000 smaller than conventional CD46. These properties of the STc/CY4 isoform were similar to those of sperm CD46. The only difference between sperm CD46 and the STc/CY4 isoform expressed on CHO cells was that only the latter possessed N-linked sugars of high mannose types. Since the STc/CY4 isoform may behave like sperm CD46 in cellular localization and post-translational modification, studies of sperm-egg interassociation were performed using hamster eggs and CHO cell clones expressing various isoforms including the STc/CY4. Rosette formation was seen most effectively between hamster eggs and STc/CY4-expressing CHO cells. These results infer that O-glycosylation perturbs CD46-mediated sperm-binding to eggs and thus sperm CD46 lacking O-linked sugars can serve as an adhesion molecule. The possible role of CD46 in fertilization and the structural differences between sperm and conventional CD46 are discussed.

Alternative Splicing↗
PubMed1998

Spontaneous apoptosis of podocytes in explanted glomeruli. Technical note.

Despite the extensive use of isolated glomeruli for kidney research, little is understood about whether and how isolation and explantation affect the structure and function of the glomerulus. In this report, we investigate the incidence of apoptosis in explanted, normal rat glomeruli. By using ladder detection assay, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and histological analysis, the present study provides evidence that significant number of resident cells, especially podocytes, spontaneously undergo apoptosis immediately after explantation of glomeruli.

Animals↗
PubMed1998

Three-dimensional matrix primes mesangial cells to down-regulation of alpha-smooth muscle actin via deactivation of CArG box elements.

Prolonged culture of mesangial cells forms multifocal nodular structures, termed "hillocks," composed of cells and extracellular matrix (ECM), which may mimic the situation in the glomerular mesangium. Mesangial cells incorporated in hillocks show repressed expression of alpha-smooth muscle actin, a marker of mesangial cell activation/dedifferentiation. The aim of this study is to elucidate molecular mechanisms involved in this phenomenon, focusing on the activity of CArG box elements located in 5'-flanking region of the alpha-smooth muscle actin gene. Reporter mesangial cells were created to monitor the activity of CArG elements. These clones expressed beta-galactosidase gene (lacZ) under the control of CArG boxes. Within the hillocks, reporter cells showed repressed expression of lacZ as well as alpha-smooth muscle actin compared to the cells in two-dimensional cultures. Consistent with this result, the reporter cells embedded in collagen gel exhibited down-regulation of lacZ and alpha-smooth muscle actin transcripts. Deactivation of CArG box elements by transfection with either a dominant negative mutant of serum response factor or a dominant negative form of ternary complex factor Elk-1 led to depressed expression of alpha-smooth muscle actin gene. These data suggested that three-dimensional ECM primes mesangial cells to down-regulation of alpha-smooth muscle actin via deactivation of CArG box elements.

Actins↗
PubMed1998

Effect of a balanced biventricular bypass system on left ventricular energies.

Left dominant biventricular failure is a common type of heart failure after cardiac surgery. We developed a biventricular bypass (BVB) system for treatment of postcardiotomy ventricular failure, and we previously reported that the clinical results of the BVB system were superior to those obtained with venoarterial bypass (VAB). The purpose of this study was to evaluate the effect of the BVB system on left ventricular (LV) performance in comparison to that of VAB by means of the LV pressure-volume relationship (PVR). Eight adult mongrel dogs (14-21 kg) underwent VAB with right atrial and aortic cannulation. Left atrial cannulation was added for BVB, and both atrial drainage tubes were joined with a Y-shaped connector. The bypass flow was maintained at half of the baseline cardiac output (0.7-1.0 L/min), and the hemodynamic parameters were monitored. A high fidelity microtip catheter and a conductance catheter were used to evaluate LV function. The slope of the LV end-systolic pressure-volume relation (Emax), the slope of the LV end-systolic pressure-stroke-volume relation (Ea), the LV stroke work (SW), LV potential energy (PE), LV pressure-volume area (PVA), the slope of the SW end-diastolic volume relation (PRSW), and an index of the LV energizing charge (ratio of PE/PVA) were assessed during transient occlusion of the inferior vena cava. LV contractility (Emax) showed no significant change during each experiment. Standardized LV work (PRSW) was reduced by BVB in comparison to the baseline and in comparison to VAB. The rate of LV energy charge (PE/PVA) significantly increased only during BVB. These results suggested that the BVB system might be an effective circulatory support for reducing LV work and improving the LV energizing charge in patients with severe heart failure after cardiac operation.

Animals↗
PubMed1998

Mechanical circulatory support for severe heart failure after operation.

To evaluate the clinical results of circulatory support for severe heart failure after operation, we examined 62 patients (39 males and 23 females) who underwent circulatory support for postoperative heart failure from 1984 to 1996. Their ages ranged from 22 to 78 (mean 52) years. In 62 patients, 35 had valvular, 25 had ischemic, and 2 had congenital heart disease. Postoperation, 29 patients underwent venoarterial bypass (VAB), 20 had biventricular bypass (BVB), and 8 had left ventricular bypass (LVB). The remaining 5 patients received a pulsatile left ventricular assist device (LVAD). The weaning and discharge rates of the patients by type of support were 51.7% and 31.0% with VAB, 75.0% and 55.0% with BVB, 87.5% and 37.5% with LVB, and 60.0% and 40.0% with LVAD, respectively. The complete results of this series (64.5% weaning rate and 40.3% discharge rate) were acceptable.

Adult↗
PubMed1998

Minimally invasive cardiac surgery in the adult: surgical instruments, equipment, and techniques.

To clarify the special instruments and equipment used for minimally invasive cardiac surgery (MICS), we examined the initial experiences with MICS operations with ministernotomy or minithoracotomy at our institution. Fifty adult patients with congenital, valvular, and/or ischemic heart diseases underwent MICS operations, and all surgical procedures were completed without conversion to full sternotomy. The length of the skin incision was about 10 cm or less in all patients. Postoperative recovery was favorable, and the majority of the patients were discharged from the hospital around the end of the second postoperative week. In this series of patients, an oscillating bone saw, lifting type retractor, 2 blade spreader, cannula with a balloon, and right-angled aortic clamp among other items, were very useful for successfully performing various operations with MICS approaches and techniques. The associated results suggest that MICS with ministernotomy or minithoracotomy was feasible using special instruments and equipment and could be encouraged for adult patients with various cardiovascular diseases.

Adult↗
PubMed1998

Relationship between preoperative assessment of organ function and postoperative morbidity in patients with oesophageal cancer.

OBJECTIVE: To find out if strict assessment of organ function preoperatively predicted morbidity and mortality in patients being operated on for oesophageal carcinoma. DESIGN: Retrospective study. SETTING: Teaching hospital, Japan. SUBJECTS: 178 patients operated on for oesophageal cancer 1989-1993. INTERVENTIONS: Oesophagectomy and reconstruction (using either stomach or colon) in one stage by a right thoracoabdominal approach in 173, and transhiatal resection in 5 with either poor pulmonary reserve or early lesions. MAIN OUTCOME MEASURES: Correlation between preoperative assessment of organ function and postoperative development of complications. RESULT: 79 patients (44%) developed complications and 6 died (3%). Pulmonary dysfunction preoperatively was significantly associated with the development of all complications (p=0.001) and of postoperative pulmonary complications (p=0.04). No other preoperative assessment correlated significantly with the development of postoperative complications. CONCLUSION: Accurate preoperative assessment of pulmonary function is a valuable indicator of postoperative morbidity.

Aged↗
PubMed1998

Well differentiated adult-type fibrosarcoma arising from the occipital subcutaneous tissue in a 17-year-old man: case report with immunohistochemical study.

We report a case of a 17-year-old man with a spindle cell tumor in the occipital subcutaneous tissue. The enucleated tumor, measuring 2.5 x 2.0 x 1.0 cm, had a broad-bean shape and well circumscribed border and was localized to the subcutis without dermal involvement. Microscopically, the tumor was composed of uniform spindle cells showing interlacing bundle formation and a herringbone pattern. The neoplastic cells were separated by collagen fibers in parallel fashion, the amount of which varied with different areas in the tumor. Mitotic figures were eight mitoses per 50 high-power fields in number. The neoplastic cells were positive for vimentin, Factor-XIIIa, alpha-smooth muscle actin and CD34, but negative for desmin, calponin, high molecular weight caldesmon, smooth muscle myosin heavy chain, collagen type IV, laminin and S-100 protein. These immunohistochemical results indicated that the neoplastic cells showed differentiation toward fibroblasts/myofibroblasts/dendritic interstitial cells. Although more than 50% of the neoplastic cells were positive for CD34, the present tumor should be diagnosed as well differentiated fibrosarcoma, adult type, rather than extrapleural solitary fibrous tumor and fibrosarcomatous areas of dermatofibrosarcoma protuberans, on the basis of routine microscopic findings mentioned above.

Adolescent↗
PubMed1998

Cloning and expression of the gene encoding flavodoxin from Desulfovibrio vulgaris (Miyazaki F).

The gene encoding a flavodoxin of Desulfovibrio vulgaris (Miyazaki F) was cloned, and overexpressed in Escherichia coli. A 1.6-kbp DNA fragment, isolated from D. vulgaris (Miyazaki F) by double digestion with SalI and EcoRI, contained the flavodoxin gene and its regulatory region. An expression system for the flavodoxin gene under control of the T7 promoter was constructed in E. coli. The purified protein was soluble and exhibited a characteristic visible absorption spectrum. HPLC analysis of the recombinant flavodoxin revealed the presence of an identical FMN to that found in the native D. vulgaris flavodoxin, and its dissociation constant with FMN was determined to be 0.38 nM. In vitro H2 reduction analysis indicated that the recombinant flavodoxin is active, and its redox potential was determined to be E1 = -434 and E2 = -151 mV using methyl viologen and 2-hydroxy-1,4-naphthoquinone, respectively. Its redox behavior was also examined with the recombinant flavodoxin adsorbed onto a graphite electrode. The mutant, A16E, was also produced, which revealed the feature of a conserved Glu residue at the surface of the molecule.

Base Sequence↗
PubMed1998

Expression of selenoprotein-P messenger ribonucleic acid in the rat testis.

It has been suggested that a plasma protein, selenoprotein P, functions as an antioxidant and that its mRNA is expressed ubiquitously, including in the testis. To determine its physiological function, we have investigated the expression of selenoprotein-P mRNA in the rat testis. Northern blot analysis showed that selenoprotein P was exclusively expressed in the Leydig cell fraction. In situ hybridization experiments further supported this observation. Testes of rats administered ethylene dimethane sulfonate (EDS) were also examined by Northern blot analysis. Selective degeneration of Leydig cells by EDS treatment resulted in disappearance of selenoprotein-P mRNA from the testis. Furthermore, upon recovery, in association with regenerative differentiation of Leydig cells, reappearance of the selenoprotein-P mRNA was observed. These results indicated that selenoprotein-P mRNA was predominantly expressed in the interstitial Leydig cells.

Animals↗
PubMed1998

A prospective comparative trial of a gonadotropin-releasing hormone analogue with clomiphene citrate for the treatment of oligoasthenozoospermia.

BACKGROUND: We undertook a prospective trial to compare the efficacy and adverse effects of a gonadotropin releasing-hormone analogue (GnRHa) and clomiphene therapy for idiopathic normogonadotropic oligoasthenozoospermia (INOA). METHODS: Between January and December 1995, 44 newly-diagnosed INOA patients were randomly allocated to treatment with GnRHa or clomiphene citrate. Efficacy was assessed by measuring changes in semen parameters prior to and after 3 months of treatment. Twenty-three INOA patients underwent GnRHa therapy with 15 microg of diluted buserelin acetate given once a day intranasally, and 21 INOA patients were treated with 50 mg of clomiphene citrate daily by oral administration. RESULTS: The mean sperm density in the GnRHa group increased from 16.1 x 10(6)/mL to 26.9 x 10(6)/mL (P < 0.05), while the mean sperm density did not change significantly in the group treated with clomiphene. Similarly, the mean sperm motility increased from 35.9% to 43.9% in the GnRHa group (P < 0.05), but did not significantly change in the clomiphene group. No adverse effects were observed in either group. CONCLUSION: This GnRHa treatment protocol can be administered as an outpatient and is hoped to benefit INOA patients.

Administration, Intranasal↗
PubMed1998

Regulation of invasive potential of human prostate cancer cell lines by hepatocyte growth factor.

BACKGROUND: The growth and progression of prostate cancer depends on the stromal-epithelial interaction which is under paracrine control. Hepatocyte growth factor (HGF), produced by mesenchymal cells, is a multifunctional growth factor stimulating the movement and growth of epithelial cells including cancer cells. We therefore assessed the relationship between the invasive potential of prostate cancer and HGF in vitro. METHODS: Three human prostate cancer cell lines were used including PC-3 and DU145 (androgen-independent), and LNCaP (androgen-dependent). We studied the expression of the HGF receptor c-met proto-oncogene (c-met) by Western blot analysis, and also determined the effects of HGF on cell scattering, and the mechanisms of invasion and proliferation, by microscopic observation, the matrigel invasion chamber assay, and the MTT assay. RESULTS: c-met was detected in PC-3 and DU145 cells, but not in the LNCaP cells. There was increased cell motility in the scatter assay and an increased cell invasive potential in the matrigel invasion chamber assay by stimulation with HGF only with DU145 cells. CONCLUSION: HGF plays an important role in the invasion and metastasis of the DU145 cell line through a paracrine mechanism mediated by the c-metreceptor. In the PC-3 cell line, the lack of downstream signal transduction after the c-met receptor is suggested.

Biocompatible Materials↗
PubMed1998

Establishment and characterization of a human Epstein-Barr virus-associated gastric carcinoma in SCID mice.

A transplantable human Epstein-Barr virus-associated gastric carcinoma (EBVaGC), designated KT, was propagated in severe combined immunodeficiency (SCID) mice for 12 passages. Mucin and cytokeratin expression and the Alu sequence in tumor DNA confirmed that the KT tumor was derived from human epithelial tissue. The identity of clonal EBV in the original and KT tumors was demonstrated by terminal repeat analysis of EBV DNA. The pattern of latency gene expression of EBV was the same in both tumors. EBER1 was presented similarly in tumor cell nuclei by in situ hybridization. Reverse transcription-PCR analysis also demonstrated Q-promoter-driven EBNA1 expression but not BZLF1, EBNA2, or LMP1 expression. Thus, the transplantable human EBVaGC KT retains the original EBV with the same latency gene expression and can serve as a model for this unique type of gastric carcinoma.

Adenocarcinoma↗
PubMed1998

Wnt-1 induces growth, cytosolic beta-catenin, and Tcf/Lef transcriptional activation in Rat-1 fibroblasts.

Genetic evidence suggests that regulation of beta-catenin and regulation of Tcf/Lef family transcription factors are downstream events of the Wnt signal transduction pathway. However, a direct link between Wnt activity and Tcf/Lef transcriptional activation has yet to be established. In this study, we show that Wnt-1 induces a growth response in a cultured mammalian cell line, Rat-1 fibroblasts. Wnt-1 induces serum-independent cellular proliferation of Rat-1 fibroblasts and changes in morphology. Rat-1 cells stably expressing Wnt-1 (Rat-1/Wnt-1) show a constitutive up-regulation of cytosolic beta-catenin, while membrane-associated beta-catenin remains unaffected. Induction of cytosolic beta-catenin in Rat-1/Wnt-1 cells is correlated with activation of a Tcf-responsive transcriptional element. We thus provide evidence that Wnt-1 induces Tcf/Lef transcriptional activation in a mammalian system. Expression of a mutant beta-catenin (beta-CatS37A) in Rat-1 cells does not result in a proliferative response or a detectable change in the cytosolic beta-catenin protein level. However, beta-CatS37A expression in Rat-1 cells results in strong Tcf/Lef transcriptional activation, comparable to that seen in Wnt-1-expressing cells. These results suggest that Wnt-1 induction of cytosolic beta-catenin may have functions in addition to Tcf/Lef transcriptional activation.

Animals↗
PubMed1998

The requirement of intercellular adhesion molecule-1 for neutrophil respiratory burst in the pulmonary circulation of rats infused with endotoxin.

Recently, we demonstrated direct evidence of respiratory burst of the neutrophil in the pulmonary circulation of the endotoxin-infused rat (Am. J. Respir. Crit. Care Med. 1995;152:348-354). To determine the role of intercellular adhesion molecule-1 (ICAM-1) in this model, we neutralized ICAM-1 using antirat ICAM-1 monoclonal antibody (mAb) 1A29. We observed and measured the number of sticking leukocytes and the amount of hydrogen peroxide (H2O2) in the pulmonary circulation of the endotoxin-infused rat by means of a fluoro-imaging technique. The rats received 4.5 mg/kg/h of endotoxin for 2 h. Ten rats received 2 mg/kg of mAb 1A29 20 min before the intravenous infusion of endotoxin. Although the pretreatment with mAb 1A29 did not reduce the number of leukocytes sticking to the pulmonary capillaries, it almost completely inhibited the H2O2 production of leukocytes in the rat lung infused with endotoxin. We confirmed that the leukocytes that produced H2O2 were neutrophil by an electron microscopic cerium technique. We conclude that, although ICAM-1 is not necessary for neutrophil to stick to the capillary in the rat pulmonary circulation infused with endotoxin, ICAM-1 is required for neutrophil H2O2 production in this model.

Animals↗