Biomedical subjects

K Ishihara

Publications and source records attributed to K Ishihara.

At least 55 records · Page 3Linked to original sources

PubMed2002

[Valvular heart surgery in osteogenesis imperfecta].

Osteogenesis imperfecta is a disease in which fragile bones readily cause fracture. Valvular disease concurrently develops. However, the surgery-related mortality rate is approximately 30%. In this study, we report 2 patients with osteogenesis imperfecta who underwent valvular heart surgery. Patient 1 was a 31-year-old male. He had previously been diagnosed as having osteogenesis imperfecta. Echocardiography suggested aortic valve insufficiency, and aortic valve replacement was performed. Patient 2 was a 59-year-old male. During admission, osteogenesis imperfecta was diagnosed. Echocardiography suggested mitral valve insufficiency, and mitral valve plasty was performed. In the 2 patients, intraoperative hemorrhage was marked. However, there were no fatal complications. We also reviewed the literature.

Adult↗

PubMed2001

Enhanced Ca(2+) influx with mossy fiber stimulation in hippocampal CA3 neurons of spontaneously epileptic rats.

This study was performed to determine whether the intracellular Ca(2+) concentration ([Ca(2+)](i)) is increased in hippocampal CA3 neurons of spontaneously epileptic rats (SER) which show both absence-like and convulsive seizures using hippocampal slices loaded with Calcium Green-1 when a weak single stimulation is given to the mossy fiber. [Ca(2+)](i) in the CA3 area was significantly increased after a single stimulus to mossy fibers in SER, while no changes were detected in normal Wistar rats. These findings suggest the existence of an abnormality in the Ca(2+) channel in the SER CA3 region and that this is probably responsible for epileptic seizures.

Action Potentials↗

PubMed2001

Site-directed removal of N-glycosylation sites in BST-1/CD157: effects on molecular and functional heterogeneity.

Cyclic ADP ribose (cADPR) is a novel second messenger that releases calcium from intracellular calcium stores, but works independently of inositol 1,4,5-trisphosphate. In mammals ADP-ribosyl cyclase function is found in two membrane proteins, CD38 and bone marrow stromal cell antigen 1 (BST-1)/CD157. These enzymes are exposed extracellularly and also possess cADPR hydrolase activity, but an intracellular soluble ADP-ribosyl cyclase has been reported in human T-cells. Previously, a soluble form of BST-1/CD157 (sBST-1), which lacked the glycosylphosphatidylinositol-anchored portion, was expressed by a baculovirus-insect-cell system. In this study, we have purified the sBST-1, and it migrated as two major bands by SDS/PAGE, suggesting that it is post-translationally modified. BST-1 contains four putative N-glycosylation sites. Tunicamycin treatment reduced sBST-1 expression in the culture medium, indicating that N-glycosylation is essential for secretion. Site-directed mutagenesis was performed to generate sBST-1 mutants (N1-N4), each preserving a single N-glycosylation site. N1, N3 and N4 were well secreted into the medium, and were each detected as a single band. Although N3 and N4 retained the ADP-ribosyl cyclase activity, the cADPR-hydrolase activity was retained only in N4. We conclude that N-glycosylation of sBST-1 facilitates the folding of the nascent polypeptide chain into a conformation that is conductive for intracellular transport and enzymic activity. Furthermore a crystal has been obtained using the N4 mutant, but not the wild-type sBST-1. Thus the artificial engineering of N-glycosylation sites could be an effective method to generate homogeneous material for structural studies.

ADP-ribosyl Cyclase↗

PubMed2001

Potentiation of 5-HT(3) receptor functions in the hippocampal CA1 region of rats following repeated electroconvulsive shock treatments.

Modulation of serotonin (5-HT)(3)-receptor function by repeated electroconvulsive shock (ECS) treatment was investigated to elucidate the mechanism underlying the effectiveness of electroconvulsive therapy (ECT) which is clinically used for drug-resistant depression. ECS (100 V, 1 s) was applied once a day for 14 days via an electrode placed on the ears of rats (ECS group). For controls, rats were handled similar to the ECS-treated group except for the stimulation. Hippocampal slices (thickness, 450 microm) were prepared 24 h after the final ECS treatment when rats were 5-6 weeks old. Intracellular recordings were made from the neurons in the CA1 pyramidal cell layer. Activation of 5-HT(3) receptors increased spontaneous postsynaptic potentials (sPSP). Increased sPSP was mainly mediated by GABA. The 5-HT(3) receptor mediated increase in sPSP was potentiated in the ECS group compared with the control group. These findings suggest that the 5-HT(3) receptor function is potentiated by repeated ECS.

Action Potentials↗

PubMed2001

Solar 8B and hep neutrino measurements from 1258 days of Super-Kamiokande data.

Solar neutrino measurements from 1258 days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0-20.0 MeV. The measured solar neutrino flux is 2.32+/-0.03(stat)+0.08-0.07(syst)x10(6) cm(-2) x s(-1), which is 45.1+/-0.5(stat)+1.6-1.4(syst)% of that predicted by the BP2000 SSM. The day vs night flux asymmetry (Phi(n)-Phi(d))/Phi(average) is 0.033+/-0.022(stat)+0.013-0.012(syst). The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a 90% C.L. upper limit of 40x10(3) cm(-2) x s(-1), which is 4.3 times the BP2000 SSM prediction.

Journal Article↗

PubMed2001

Constraints on neutrino oscillations using 1258 days of Super-Kamiokande solar neutrino data.

We report the result of a search for neutrino oscillations using precise measurements of the recoil electron energy spectrum and zenith angle variations of the solar neutrino flux from 1258 days of neutrino-electron scattering data in Super-Kamiokande. The absence of significant zenith angle variation and spectrum distortion places strong constraints on neutrino mixing and mass difference in a flux-independent way. Using the Super-Kamiokande flux measurement in addition, two allowed regions at large mixing are found.

Journal Article↗

PubMed2001

High-performance liquid chromatographic assay with fluorescence detection for the determination of cephaeline and emetine in human plasma and urine.

A high-performance liquid chromatographic assay method for the quantitation of ipecac alkaloids (cephaeline and emetine) in human plasma and urine is described. Human plasma or urine was extracted with diethylether under alkaline conditions following the addition of an internal standard. Concentrations of alkaloids and internal standard were determined by octadecylsilica chromatographic separation (Symmetry C18 columns, plasma analysis; 15 cmx4.6 mm I.D., 5 microm particle size, urine analysis; 7.5 cmx4.6 mm I.D., 5 microm particle size). The mobile phase consisted of buffer (20 mmol/l 1-heptanesulfonic acid sodium salt, adjusted to pH 4.0 with acetic acid)-methanol (51:49, v/v). Eluate fluorescence was monitored at 285/316 nm. The lowest quantitation limits of cephaeline and emetine were 1 and 2.5 ng/ml, respectively, in plasma, and 5 ng/ml in urine. Intra- and inter-day relative standard deviations were below 15%. The assay is sensitive, specific and applicable to pharmacokinetic studies in humans.

Chromatography, High Pressure Liquid↗

PubMed2001

Possible participation of a JAK2 signaling pathway in recombinant rat interleukin-5-induced prolongation of rat eosinophil survival.

Recombinant rat interleukin (IL)-5-induced prolongation of rat eosinophil survival in culture was inhibited in a concentration-dependent manner by the protein synthesis inhibitor cycloheximide, the DNA-dependent RNA synthesis inhibitor actinomycin D, and the tyrosine kinase inhibitor herbimycin A when examined 96 h after incubation. The MEK-1 inhibitor PD98059 inhibited IL-5-induced phosphorylation of both p44 and p42 MAP kinases, but the IL-5-induced prolongation of eosinophil survival was not inhibited. In contrast, the JAK2 inhibitor AG490 inhibited the IL-5-induced prolongation of eosinophil survival. Treatment of eosinophils with IL-5 resulted in phosphorylation of STAT5 but not STAT1, and the IL-5-induced phosphorylation of STAT5 was inhibited by AG490. These findings suggest that the activation of JAK2 tyrosine kinase and protein synthesis are required for the prolongation of rat eosinophil survival induced by recombinant rat IL-5. STAT5 phosphorylation might also participate in the IL-5-induced survival of rat eosinophils.

Animals↗

PubMed2001

Simultaneous determination of byak-angelicin and oxypeucedanin hydrate in rat plasma by column-switching high-performance liquid chromatography with ultraviolet detection.

A simple and sensitive column-switching HPLC method was developed for the simultaneous determination of two furocoumarin compounds, byak-angelicin and oxypeucedanin hydrate, which are the main components of hot water extract of Angelica dahurica root (AE), in rat plasma. Plasma sample was simply deproteinated with perchloric acid. After centrifugation, the supernatant was injected into a column-switching HPLC system consisting of a clean-up column (Symmetry Shield RP 8, 20x3.9 mm I.D.) and analytical column (Symmetry C18, 75x4.6 mm I.D.) which were connected with a six-port switching valve. The flow-rate of the mobile phase (acetonitrile-water, 20:80) was maintained at 1 ml/min. Detection was carried out at wavelength 260 nm with a UV detector. The column temperature was maintained at 40 degrees C. The calibration curves of byak-angelicin and oxypeucedanin hydrate were linear over the ranges 19.6 to 980 ng/ml (r2>0.997). The accuracy of these analytes was less than 4.4%. The intra- and inter-day relative standard deviations of byak-angelicin and oxypeucedanin hydrate were within 12.0% and 12.7%, respectively. The present method was applied for the analysis of plasma concentration from rats after administration of AE.

Animals↗

PubMed2001

Shared antigenicity between Helicobacter pylori and periodontopathic Campylobacter rectus strains.

Periodontopathic Campylobacter rectus strains possess 41- and 68-kDa proteinaceous antigens which share antigenicity with antigens of Helicobacter pylori strains. H. pylori strains have a 54-kDa antigen which reacts with C. rectus strains. We found that the salivary IgA levels against H. pylori were correlated with those against C. rectus. These cross-reactive antigens of C. rectus may affect the serological diagnosis of H. pylori infections, especially when saliva is used. It is possible that these cross-reacting antigens may relate to the induction of immunopathological responses against both microorganisms.

Antigens, Bacterial↗

PubMed2001

Epigenetic mark sequence of the H19 gene in human sperm.

We have investigated the epigenetic mark in the human H19 gene. The H19 promoter is methylation-free in human sperm, but it is methylated in the paternally derived allele of most adult tissues. Consequently, the H19 gene is exclusively transcribed from the maternal allele. It was demonstrated that the differentially methylated region (DMR) located 2 kb upstream from mouse H19 is essential for the imprinting of H19. A 39 bp sequence in DMR has a high degree of similarity between humans, mice and rats. The highly conserved 15 bp core region of the consensus sequence contains four methylatable sites, and thus has been proposed as a potential imprinting mark region. In this study, fine epigenetic sequencing analysis was performed on the sperm DNA in comparison with other adult organs. Interestingly, the conserved sequence of the potential mark region was methylated in almost all the sperm genomes analyzed. Furthermore, the single dinucleotide CpG, whose methylation affects the accessibility of the element to CTCF, was methylated in the conserved core in the human sperm. These results suggest that the human core sequences may act as an imprinting center in the reciprocal monoallelic expression of H19.

Adult↗

PubMed2001

Inhibition by L-3,4-dihydroxyphenylalanine of hippocampal CA1 neurons with facilitation of noradrenaline and gamma-aminobutyric acid release.

Electrophysiological studies were performed to elucidate whether L-3,4-dihydroxyphenylalanine (L-DOPA) acted on hippocampal CA1 neurons, since this drug has been reported to act as a neurotransmitter in the hypothalamus and striatum. Hippocampal slices (450 microM thick) obtained from male Wistar rats (4-7 weeks of age) were placed in a bath (maintained at 30+/-1 degrees C) continuously perfused with artificial cerebrospinal fluid. The population spikes elicited by electrical stimuli applied to the Schaffer collateral/commissural fibers were recorded in the hippocampal CA1 region, using a glass micropipette filled with 3 M NaCl. Drugs were applied in the bath through a perfusion system. The population spikes were inhibited by L-DOPA (1 nM-10 microM) with a bell-shaped concentration-response curve (n=7-15). Maximum inhibitory effects were obtained at 100 nM. L-DOPA cyclohexyl ester, a putative L-DOPA recognition site antagonist, antagonized the L-DOPA-induced inhibition of population spike. However, the inhibition remained unaffected in the presence of 3-hydroxybenzylhydrazine, an aromatic amino acid decarboxylase inhibitor. Furthermore, bath application of either phentolamine, an alpha-adrenoceptor antagonist, or bicuculline, a GABA(A) receptor antagonist, antagonized the inhibitory effects of L-DOPA on population spikes. In addition, bicuculline (1 microM) antagonized the inhibition of population spike induced by 6-fluoronorepinephrine (10 microM), an alpha-adrenoceptor agonist, while phentolamine (10 microM) did not affect the muscimol (1 microM)-induced inhibition. These results suggested that L-DOPA itself acted on L-DOPA recognition sites to release noradrenaline, and that the latter facilitates gamma-aminobutyric acid (GABA) release via alpha-adrenoceptors located on the GABA-containing cells and/or their nerve terminals, thereby inhibiting the population spikes in the hippocampal CA1 field.

Action Potentials↗

PubMed2001

Preservation of platelet function on 2-methacryloyloxyethyl phosphorylcholine-graft polymer as compared to various water-soluble graft polymers.

The chemical structures of water-soluble polymers grafted onto PE surfaces affect platelet function when the platelets contact the polymer surfaces. To improve our understanding of this effect, this study sought to control the blood/materials interaction on the surfaces of polyethylene (PE) by grafting with various water-soluble polymers. Such polymers as poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(acrylamide) (PAAm), poly(N-vinylpyrrolidone) (PVPy), and poly[monomethacryloyl poly(ethylene glycol)] (PMPEG) were grafted on low-density PE sheets by photoinduced graft polymerization. Both the PE bags modified with water-soluble polymers and those nonmodified were prepared by heat processing. Activation of platelets after storage in the PE bags was evaluated by measuring the cytoplasmic free calcium ion concentration ([Ca(2+)]i). The concentration of [Ca(2+)]i of platelets in contact with the PE surface grafted with PMPC was the same as that of native platelets and significantly less than that in contact with other PE surfaces grafted with water-soluble polymers. The number of adherent platelets was effectively decreased on PE surfaces grafted with PMPC and PMPEG, as compared with nontreated PE. The aggregation ability of platelets was also measured after storage of platelet-rich plasma in the PE bags. The PE surface grafted with PMPC effectively maintained aggregation ability as compared with both the nontreated PE and with PE grafted with PAAm, PVPy, and PMPEG. It was concluded that for preserving platelet function, PMPC was the most effective of these water-soluble polymers used for surface modification.

Animals↗

PubMed2001

Electroosmosis injection of blood serum into biocompatible microcapillary chip fabricated on quartz plate.

A chip which allows the detection of various human health markers from a trace amount of blood has been studied. As a goal, a microcapillary with a 30 x 30 microm cross-section was fabricated using all-dry etching technologies on a 2 x 2 cm SiO2 chip. The coating of the biocompatible 2-methacryloyloxyethylphosphorylcholine (MPC) polymer on the inner quartz wall of the microcapillary demonstrated a sufficiently long adsorption suppression of proteins in the serum on the quartz surface, while rapid stopping occurred for serum injected into the microcapillary with a bare quartz surface. The latter rapid stopping corresponded well to fast electroosmosis flow due to the negatively increasing zeta-potential by the adsorption of proteins on the quartz surface. The electroosmosis pump arranged a downstream of the microcapillary was also developed to inject serum into it. As a preliminary application, a given concentration-standard solution was injected into the ion-sensitive field-effect transistor (ISFET) embedded in the chip, employing the electroosmosis pump arranged downstream of the sensor position. Hence, the pH and Na+ and K+ cation concentrations were measured.

Blood Chemical Analysis↗

PubMed2001

A serine protease inhibitor, N-alpha-tosyl-l-lysine chloromethyl ketone, prolongs rat hepatic allograft survival.

BACKGROUND: Serine protease inhibitors have profound suppressive effects on cellular and humoral immune responses. We investigated the effect of a serine protease inhibitor, N-alpha-tosyl-l-lysine chloromethyl ketone (TLCK), on hepatic allograft survival in rats. Methods. Orthotopic hepatic transplantation was performed in an ACI (RT1(a))-to-LEW (RT1(1)) rat combination. TLCK was administered continuously at a dose of 4.4 mg/kg/day using an osmotic subcutaneous infusion minipump. RESULTS: TLCK prolonged hepatic allograft survival. Histologic staging of acute rejection based on Banff criteria in TLCK-treated hepatic allografts was significantly lower than in untreated allografts. TLCK significantly reduced serum concentrations of interferon (IFN)-gamma and tumor necrosis factor (TNF) alpha in allograft recipients. TNF-alpha mRNA levels in TLCK-treated allografts were significantly lower than in untreated allografts. TLCK also decreased perforin mRNA levels in hepatic allografts. Hepatic infiltrates eluted from TLCK-treated allografts showed significantly lower cell-mediated lympholytic activity against donor Con A blast cervical lymph node cells than those from untreated allografts. In vitro, TLCK suppressed interleukin-2 production and [(3)H]thymidine incorporation into an allogeneic mixed lymphocyte reaction. CONCLUSION: TLCK suppressed acute allograft rejection, suggesting a novel immunosuppressive strategy for therapy of acute organ rejection.

Animals↗

PubMed2001

Differential splenic migration of dendritic cells after immunologic unresponsiveness in rat hepatic allografts induced by pretransplant donor-specific transfusion.

BACKGROUND: Donor dendritic cells migrate into the recipient spleen after hepatic transplantation. We previously reported that immunologic unresponsiveness to rat hepatic allografts can be induced by prior donor-specific blood transfusion (DST). We investigated the phenotype and splenic distribution of donor dendritic cells after allografting and DST. METHODS: Donor dendritic cells were identified with anti-rat dendritic cell (OX-62) and anti-donor class II MHC (RT1B(a)) (OX-76) antibodies. The phenotype of dendritic cells was determined with antibodies to CD45RC, CD62L, and the maturation markers CD80 (B7-1) and CD86 (B7-2). The cytokine profile of sorted CD45RC(+) OX-62(+) and CD45RC(-) OX-62(+) dendritic cells was analyzed by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Pretransplant DST significantly prolonged rat hepatic allograft survival. Immunostaining revealed OX76(+)/OX-62(+) cells in the splenic red pulp of animals receiving pretransplant DST and in the white pulp of untreated animals after transplantation. The ratio of splenic CD45RC(-) OX-62(+) cells to CD45RC(+) OX-62(+) cells was significantly higher in DST recipients than in untreated animals. CD62L, CD80, and CD86 were lower on CD45RC(-) OX-62(+) than CD45RC(+) OX-62(+) cells. RT-PCR revealed that sorted CD45RC(-) OX-62(+) cells expressed interleukin (IL)-4 and IL-10. In contrast, sorted CD45RC(+) OX-62(+) cells expressed only IL-2 and interferon gamma (IFN-gamma). CONCLUSION: Differential splenic migration of CD45RC(-) dendritic cells is associated with immunologic unresponsiveness to rat hepatic allografts.

Animals↗

PubMed2001

Survival and sinus rhythm maintenance after modified Cox/maze procedure and mitral valve operation in patients with chronic atrial fibrillation.

OBJECTIVE: Sinus rhythm gained after the Cox/maze procedure concomitant with mitral valve operation has demonstrated long-term attrition during the follow-up, no information exists on whether the type of mitral valve operation--(repair vs. replacement)--affects this sinus rhythm maintenance rate. We retrospectively studied patients undergoing concomitant mitral valve operation and Cox/maze procedure to answer this question. METHODS: Between April 1993 and August 1995, 87 consecutive patients--35 men and 52 women (mean age: 59.3 years)--with chronic atrial fibrillation and mitral valve disease underwent the modified Cox/maze procedure and concomitant mitral valve operation, with 56 having mitral valve repair (repair group) and 31 mitral valve replacement (replacement group). Patients were followed up and changes in rhythm studied retrospectively. RESULTS: Follow-up for a mean 51.3 +/- 11.6 months was completed in 82 of 83 long-term survivors (99%). Repair group surgery survival was 98.1 +/- 1.9% at 1 year and 94.2 +/- 3.2% at 5 based on the Kaplan-Meier method. Replacement group surgery survival was 85.7 +/- 5.9% at 1 year and 82.9 +/- 6.4% at 5. Probability in sinus rhythm maintenance for the repair group at 1 year was 88.6 +/- 5.4% and at 5 years was 67.6 +/- 9.1%. Probability in sinus rhythm maintenance for the replacement group at 1 year was 95.7 +/- 4.3% and at 5 years was 65.0 +/- 11.1%. CONCLUSIONS: Medium-term results after the Cox/maze III procedure concomitant with mitral valve operation are good. The attrition of sinus rhythm maintenance appears similar by the completion of 5-year follow-up.

Atrial Fibrillation↗

PubMed2001

Aortic valve repair in dominant aortic regurgitation.

OBJECTIVE: We studied immediate and mid-term results after aortic valve repair. METHODS: Immediate and mid-term results were studied in 63 patients undergoing aortic valve repair, calculating survival and reoperation free rates. RESULTS: Subjects were 49 men and 14 women aged 15 to 76 years (mean: 53 +/- 17 years). Mean preoperative aortic regurgitation grading of 1 to 4 was 3.2 +/- 0.7. Mean preoperative New York Heart Association functional class was 1.9 +/- 0.8. Two in-hospital deaths occurred. (3.2%) Mean aortic regurgitation grade at discharge was 1.3 +/- 0.8 (p < 0.0001; vs preoperative grade) and functional class was 1.1 +/- 0.2 (p < 0.0001; vs preoperative class),--significantly improved. Overall follow-up was 98.4%, and mean follow-up continued 41.4 +/- 22.1 months. Mean functional class at follow-up was 1.2 +/- 0.4 (n = 49), improved from preoperative class (p < 0.0001). Mean aortic regurgitation grading at follow-up was 1.8 +/- 0.8 (n = 41), improved from preoperative grading (p < 0.0001). Five-year survival was 95.1 +/- 2.8%. One-year reoperation freedom was 96.6 +/- 2.4% and 5-year 77.9 +/- 6.9%. CONCLUSIONS: Survival after surgery was good, while reoperation was comparable to other reports but less satisfactory compared to reoperation freedom after aortic valve replacement. Based on reoperative findings, a change in indication was made. We believe technical refinements could improve postoperative results.

Adolescent↗