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Biomedical subjects

K Ishikawa

Publications and source records attributed to K Ishikawa.

At least 109 records · Page 6Linked to original sources
PubMed2001

Melatonin's gastroprotective and antistress roles involve both central and peripheral effects.

Systemic administration of melatonin (5 to 20 mg/kg) has been reported to inhibit the induction of acute gastric mucosal lesions by stress or ischemia-reperfusion in rats. We recently demonstrated that intracisternal (i.c.) melatonin at low doses (1 to 100 ng) dose-dependently decreased acid and pepsin outputs in rats. The aim of the present study was to further investigate the peripheral and central roles of melatonin in gastric mucosal defense. Using a radioimmunoassay, we measured melatonin concentrations in the plasma and cerebrospinal fluid (CSF) of the cisterna magna in rats subjected to water immersion restraint stress and given intraperitoneal (i.p.) or i.c. injection of melatonin. Water immersion restraint stress was followed by a significant duration-related increase in peripheral plasma melatonin levels; the stress similarly produced a time-dependent increase in the extent of gastric mucosal lesions. Administration of melatonin (1 or 10 mg/kg, i.p., or 100 ng/10 microl, i.c.) significantly reduced the extent of stress-induced gastric damage, by 46%, 67%, and 54%, respectively. The effective i.c. dose of melatonin was at least 10,000-fold smaller than the effective i.p. dose. Melatonin levels in plasma and CSF after the i.p. injection of melatonin at 10 mg/kg were dramatically higher than those after the i.c. injection of vehicle or 100 ng of melatonin. Our results suggest that the peripheral gastroprotective action of melatonin should be investigated with due regard to these central effects.

Animals↗
PubMed2001

A linkage disequilibrium at the candidate gene locus for 16q-linked autosomal dominant cerebellar ataxia type III in Japan.

We previously mapped the gene responsible for autosomal dominant cerebellar ataxia (ADCA) type III to a 10.9-cM interval between D16S3089 and D16S515 on chromosome 16q. This region, however, was identical to the candidate locus of spinocerebellar ataxia type 4 (SCA4). In this study, we extended our research to refine the gene locus of the disease by applying linkage disequilibrium with 20 microsatellite DNA markers. With 9 markers flanked by D16S3031 and D16S3107, we found that the affected individuals in six families had a common haplotype on their disease chromosomes. Furthermore, linkage disequilibrium was demonstrated with 5 informative markers: D16S3019 (P = 0.013), D16S3067 (P = 0.008), D16S3141 (P = 0.011), D16S496 (P = 0.032), and D16S3107 (P = 0.000). These results indicate that the disease could have originated from a common ancestor harboring a mutation within a less than 3-cM region between D16S3043 and D16S3095. The founder alleles were also observed in other patients with ADCA type III unrelated to the six families.

Aged↗
PubMed2001

Reconstitution of sperm nuclei of zebrafish (Danio rerio) in Xenopus egg extracts.

Cell-free extracts of Xenopus eggs cause cyclic change in permeabilized sperm nucleus, nuclear envelope breakdown, chromosome condensation, and reformation of nuclei. In this study, the ability of cell-free extracts to cause similar changes in zebrafish sperm was examined. When lysolecithin-treated sperm from zebrafish were incubated in Xenopus egg extracts, a series of changes in sperm nuclear morphology were observed periodically. These changes correlated with maturation-promoting factor (MPF) activity. Furthermore, sperm nuclei of zebrafish replicated DNA during reconstitution in Xenopus egg extracts. These results showed that cell-free extracts of Xenopus egg possess the ability to cause cell-cycle-dependent changes in zebrafish sperm, implying the possibility of generating transgenic zebrafish in a similar way to transgenic Xenopus.

Journal Article↗
PubMed2001

Epidemiological study of vancomycin-resistant enterococcus isolated from a single medical university hospital in Japan.

Since 1998 more than 50 reports have described the isolation of high-level vancomycin-resistant enterococci (VRE) in Japan. Here, we report on our clinical isolates of VRE and an epidemiological study carried out using chemical and genetic techniques. VRE isolates were screened for high resistance to vancomycin (VCM) with a cutoff value of 6 microg/ml and VCM-resistant gene was confirmed by polymerase chain reaction (PCR). The epidemiological studies used pulsed-field gel electrophoresis (PFGE) and plasmid analysis. Six strains of VRE were isolated from six different patients on two wards during a 3-months period. All of the isolates possessed vanA on their plasmid, and the isolates were divided into two similar groups. Furthermore, three different patterns were defined by PFGE. Although all of the asymptomatic carriers were hospitalized for more than 3 months, we were able to prevent an outbreak of VRE in our hospital by using our guidelines for infection control, which are stricter than those for methicillin-resistant Staphylococcus aurens. From the results of this epidemiological study, we propose that there was a possibility of contamination in this hospital, and that three of the six isolates may have acquired vanA independently. In this study, we demonstrated that infection control, according to appropriate prevention guidelines, as well as regular surveillance for VRE, are essential for designing interventions to prevent the further spread of VRE.

Aged↗
PubMed2001

Thiazolidinedione derivative improves fat distribution and multiple risk factors in subjects with visceral fat accumulation--double-blind placebo-controlled trial.

BACKGROUND: It has been clarified that visceral fat accumulation leads to atherosclerosis through multiple risk factors such as insulin resistance, glucose intolerance, hyperlipidemia and hypertension. So far, it has been reported that a thaizolidinedione derivative, troglitazone, improves the insulin resistance in subjects with diabetes, glucose intolerance and obesity. However, it has not been reported yet that troglitazone affects fat distribution in subjects concomitant with visceral fat accumulation and multiple risk factors. METHODS: Twenty-nine subjects with visceral fat accumulation who had at least two risk factors including glucose intolerance, hyperlipidemia and hypertension were investigated. They were randomly assigned to receive either 200 or 400 mg per day of troglitazone or placebo for 12 weeks. A 75 g oral glucose tolerance test (OGTT) was performed before and after the treatment for 12 weeks. Fasting plasma glucose, insulin, HbA(1c), total serum cholesterol (T-chol), triglyceride (TG), HDL-cholesterol (HDL-C), and blood pressure, as well as the number of risk factors were measured periodically during the treatment. The change of the abdominal fat distribution was evaluated using computed tomographic scanning (CT scan) at the umbilicus level. RESULTS: After the treatment for 12 weeks, the area under the curve (AUC) of plasma glucose from a 75 g OGTT decreased dose-dependently. HbA(1c) and TG decreased significantly in the high-dose troglitazone group (400 mg per day) compared with the placebo group (P<0.05). Systolic blood pressure was significantly lower in subjects with hypertension in the pooled troglitazone group than in the placebo group (P<0.05). Therefore, the number of risk factors decreased with the troglitazone treatment. The ratio of visceral fat area (VFA) to subcutaneous fat area (SFA) (V/S ratio) decreased in the troglitazone groups due to decreased VFA and increased SFA. CONCLUSION: These results suggest that thiazolidinedione derivative may be a useful drug to improve multiple risk factors by changing the fat distribution in subjects with visceral fat accumulation.

Adipose Tissue↗
PubMed2001

Extracellular glutamate changes in rat striatum during ischemia determined by a novel dialysis electrode and conventional microdialysis.

Our newly developed method using a dialysis electrode has made it possible to perform real time monitoring of extracellular glutamate concentration ([Glu]e) utilizing the oxygen-independent reaction with glutamate oxidase and ferrocene. In this study, we therefore, investigated [Glu]e changes during brain ischemia using both the conventional microdialysis method and the dialysis electrode method. A comparison between our newly developed dialysis electrode and conventional microdialysis methods provided the following results. When the conventional microdialysis method was employed: (1) the elevation of [Glu]e during complete global ischemia was delayed; and (2) the elevation of concentration and reuptake of glutamate were delayed during 10-min transient ischemia, and the elevation of [Glu]e reached a maximum later using conventional microdialysis than using our dialysis electrode. (3) The biphasic [Glu]e elevation of glutamate concentration detected using the dialysis electrode method was not observed using the conventional microdialysis method. It was additionally investigated why the conventional microdialysis method provides inferior time resolution. In this study, we also demonstrated with the chromatographic SMART procedure coupled to UV detection that biogenic substances, i.e. low molecular weight proteins and peptides, are released during ischemic injury, and they may cause a delay in the time resolution in the microdialysis method.

Animals↗
PubMed2001

Endogenous 5-HT tonically inhibits spontaneous firing activity of dorsal hippocampus CA1 pyramidal neurons through stimulation of 5-HT(1A) receptors in quiet awake rats: in vivo electrophysiological evidence.

The present study was performed to examine an overall effect of endogenous serotonin (5-HT) on the spontaneous firing activity of the dorsal hippocampus CA1 pyramidal neurons in quiet awake rats. A selective 5-HT(1A) antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xanecarboxamide (WAY-100635: 0.03-0.2 mg/kg, s.c.) significantly increased the firing activity. A depletion of 5-HT with parachlorophenylalanine (PCPA: 500 mg/kg/day x 3 days) completely abolished this increasing effect of WAY-100635. The baseline spike frequency of the PCPA-treated rats (3.90 +/- 0.39 Hz) was significantly higher than that of the vehicle-treated rats (2.09 +/- 0.19 Hz). A 5-HT(2A) antagonist ritanserin (1 mg/kg, i.p.) and a 5-HT(3/4) antagonist 2-methoxy-4-amino-5-chloro benzoic acid 2-(diethylamino) ethyl ester (SDZ-205557: 3 mg/kg, s.c.) did not modify the firing activity and the increasing effect of WAY-100635. These results suggest that, in quiet awake rats, endogenous 5-HT would tonically inhibit the spontaneous firing activity of the CA1 pyramidal neurons mainly through stimulating 5-HT(1A) receptors.

Action Potentials↗
PubMed2001

Immunoreactivity to monoclonal antibody, Hep Par 1, in human hepatocellular carcinomas according to histopathological grade and histological pattern.

We evaluated the immunoreactivity to monoclonal antibody for hepatocyte (Hep Par 1) and determined the cellular distribution of the antigen in hepatocellular carcinoma (HCC), based on the histopathological grade and histological pattern. The pathological material included 100 areas selected at random in 61 tissue sections from 12 autopsy livers with HCC. Immunoreactivity was classified into four categories; strongly positive (>90% of the area showed positive staining), moderately positive (5-90% of the area), weakly positive (<5% of the area), and negative (completely negative). All 19 (100%) well-differentiated, trabecular type HCC areas were strongly positive for Hep Par 1. Among 11 well-differentiated, pseudoglandular type HCC areas, 2 (18%) were strongly positive, 5 (46%) were moderately positive, 2 (18%) were weakly positive, and 2 (18%) were negative. Among 36 moderately differentiated, trabecular type HCC areas, 6 (17%) were strongly positive, 17 (47%) were moderately positive, 9 (25%) were weakly positive, and 4 (11%) were negative. None of the four moderately differentiated, pseudoglandular type HCC areas were strongly positive, 3 (75%) were moderately positive, 0 was weakly positive, and 1 (25%) was negative. Among 25 poorly differentiated, compact or trabecular type HCC areas, 15 (60%) were weakly positive and 10 (40%) were negative. All 5 (100%) undifferentiated HCC areas were negative for Hep Par 1. Our results indicate that immunoreactivity to Hep Par 1 in HCC decreases with reduced differentiation of the tumor, suggesting that Hep Par 1 monoclonal antibody is useful as a marker for the diagnosis and differentiation of HCCs.

Journal Article↗
PubMed2001

Tissue responses to anti-washout apatite cement using chitosan when implanted in the rat tibia.

The tissue response to anti-washout apatite cement using chitosan (aw-AC(chi)) was evaluated by implanting aw-AC(chi) into bone defects of rat tibiae using conventional apatite cement (c-AC) as a control material. During the experimental period up to 16 weeks, the only difference between aw-AC and c-AC was found at two weeks in the tissue response of soft tissue. At two weeks, c-AC showed a moderate inflammatory response; small particles of c-AC were scattered in the cutaneous tissue and many foreign body giant cells were collected around the scattered c-AC, whereas aw-AC showed only a slight inflammatory response and few foreign body giant cells. We found no difference between aw-AC(chi) and c-AC with respect to bone tissue response. Both AC were almost completely surrounded by mature bone at eight weeks. No promotion or reduction of osteoconductivity was observed by chitosan even though it is considered to promote bone formation. We concluded, therefore, that enhancement of bone formation cannot be expected by employing chitosan to obtain anti-washout properties, at least in the concentration used in this study, even though aw-AC(chi) is much more useful than c-AC.

Journal Article↗
PubMed2001

Cell lineage analysis during liver development using the spf(ash)-heterozygous mouse.

Biliary epithelial cells differentiate from periportal hepatoblasts during fetal mouse liver development. It remains to be determined whether each hepatoblast is equivalent for differentiation into hepatocytes and biliary epithelial cells in normal liver development. To resolve this question, the mosaic pattern of ornithine transcarbamylase (OTC) expression was analyzed in the hepatoblast population of spf(ash) (sparse-fur with abnormal skin and hair)-heterozygous fetal mouse livers, in which random inactivation of either the X chromosome carrying the spf(ash) gene (causing OTC deficiency) or its wild-type gene occurs. Aggregates (patches) of OTC-positive hepatoblasts showed very complex patterns, and their shapes and size distributions were similar in sections from periportal regions and nonperiportal regions of the fetal liver in which bile duct differentiation by periportal hepatoblasts occurred. Average sizes of periportal patches were larger than those of nonperiportal patches because of the presence of more hemopoietic cells in the latter region. The OTC mosaicism in periportal bile duct progenitors and hepatoblast islands of other liver parenchyma was also similar. These results suggest that the growth patterns of hepatoblasts are similar in both periportal and nonperiportal regions. Isolated three-dimensional patches comprising hepatoblasts giving rise to only biliary epithelial cells or hepatoblasts giving rise to both hepatocytes and biliary epithelial cells were observed in periportal regions. In nonperiportal regions, patches consisting of hepatoblasts differentiating into hepatocytes were also seen. Thus, it is likely that there are three lineages for the developmental fates of hepatoblasts: hepatoblasts giving rise to only biliary epithelial cells, hepatoblasts giving rise to only hepatocytes, and hepatoblasts giving rise to both of them.

Animals↗
PubMed2001

Identification of rab7 as a melanosome-associated protein involved in the intracellular transport of tyrosinase-related protein 1.

The melanosome is a unique secretory granule of the melanocyte in which melanin pigments are synthesized by tyrosinase gene family glycoproteins. Melanogenesis is a highly regulated process because of its inherent toxicity. An understanding of the various regulatory mechanisms is important in delineating the pathophysiology involved in pigmentary disorders and melanoma. We have purified and analyzed the total melanosomal proteins from B16 mouse melanoma tumors in order to identify new proteins that may be involved in the control of the melanogenesis process. Melanosomal proteins were resolved by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis, a predominant spot (27 kDa with isoelectric point 5.8-6.4) was excised and digested with cyanogen bromide, and the fragments were sequenced. Synthetic oligonucleotide primers were synthesized corresponding to the peptide sequences, and reverse transcriptase polymerase chain reaction amplification of total RNA from B16 cells was carried out. Sequencing of one of the polymerase-chain-reaction-mediated clones demonstrated 80%-97% sequence homology of 200 bp nucleotide with GTP-binding proteins at the 3'-untranslated region. GTP-binding assay on two-dimensional gels of melanosomal proteins showed the presence of several (five to six) small GTP-binding proteins, suggesting that small GTP-binding proteins are associated with the melanosome. Among the known GTP-binding proteins with similar molecular weight and isoelectric point ranges, rab3, rab7, and rab8 were found to be present in the melanosomal fraction by immunoblotting. Confocal immunofluorescence microscopy showed that rab7 is colocalized with the tyrosinase-related protein 1 around the perinuclear area as well as, in part, in the perikaryon, thereby suggesting that rab7 might be involved in the intracellular transport of tyrosinase-related protein 1. Tyrosinase-related protein 1 transport was blocked by the treatment of B16 cells with antisense oligonucleotide to rab7. We suggest (i) that rab7 is a melanosome-associated molecule, (ii) that tyrosinase-related protein 1 is present in late-endosome delineated granules, and (iii) that rab7 is involved in the transport of tyrosinase-related protein 1 from the late-endosome delineated granule to the melanosome.

Animals↗
PubMed2001

Effects of plaque control on the patency and occlusion of dentine tubules in situ.

To elucidate the nature of dentine hypersensitivity, the effects of plaque control on the patency and occlusion of dentinal tubules were investigated systematically in situ using human dentine slabs embedded in partial dentures. The dentine slabs were divided into three groups. In group I, the dentine slabs were kept in an oral cavity without plaque control. In group II, plaque was removed mechanically by brushing. Plaque control was carried out chemically using chlorhexidine in group III. After being kept in the oral cavities for 1, 2 and 3 weeks, the slabs were removed from the partial denture, followed by SEM observation to determine the morphological changes of the dentinal tubules. When no attempt was made to remove plaque, the diameter of tubule orifices increased to 390% of the original values within 3 weeks. In contrast, dentinal tubules were found to be occluded, i.e. the tubule orifices became <20% of the original value within 1 week when plaque control efforts were made, using either method of plaque control. We conclude that plaque control plays one of the key roles in the patency versus occlusion of dentinal tubules, and thus in the aetiology and natural reparative process of dentine hypersensitivity.

Adult↗
PubMed2001

A trial study of RhinoSleep for the diagnosis of sleep apnea.

RhinoSleep was developed to diagnose obstructive sleep apnea (OSA). The RhinoSleep consists of a soft catheter, a measuring probe, and a computer. The soft catheter is inserted through the naris into the esophagus. The catheter is connected to the measuring probe, which creates and sends a continuous noise signal into the catheter. When the catheter is compressed during an obstruction, the sound reflections change, making it possible to identify both the level and the duration of the obstruction. Sixteen OSA patients were examined using RhinoSleep and daytime polysomnography simultaneously. With RhinoSleep, we successfully examined 13 cases. This trial study identified problems with RhinoSleep, such as vomiting of the catheter, hardware instability, and the criteria decision for the analysis of OSA.

Acoustics↗
PubMed2001

Uvulopalatopharyngoplasty for obstructive sleep-related breathing disorders: one-year follow up.

The effectiveness of uvulopalatopharyngoplasty was evaluated in 28 patients (25 men and three women; mean age 47.6 years) with obstructive sleep apnea by comparing preoperative daytime polysomnography with those carried out 6 months and 1 year postoperatively. The mean apnea plus hypopnea index (AHI) in the supine position decreased from 51.0/h to 23.0/h 6 months postoperatively and 57.1% of patients showed a 50% or more reduction of AHI. By changing the sleep position from supine to lateral, 71.4% of the 28 patients indicated a 50% or more reduction in AHI before surgery, which increased to 92.3% of 26 patients 6 months postoperatively. The positive results of uvulopalatopharyngoplasty were maintained at least until 1 year after surgery.

Body Mass Index↗
PubMed2001

Can the proximal isovelocity surface area method calculate stenotic mitral valve area in patients with associated moderate to severe aortic regurgitation? Analysis using low aliasing velocity of 10% of the peak transmitral velocity.

To assess the ability of the proximal isovelocity surface area (PISA) method to accurately measure the stenotic mitral valve area (MVA), and to assess whether aortic regurgitation (AR) affects the calculation, we compared the accuracy of the PISA method and the pressure half-time (PHT) method for determining MVA in patients with and without associated AR by using two-dimensional echocardiographic planimetry as a standard. The study population consisted of 45 patients with mitral stenosis. Seventeen of the 45 patients had associated moderate-to-severe AR. The PISA method was performed using low aliasing velocity (AV) of 10% of the peak transmitral velocity, which provided the most accurate estimation of MVA when compared with planimetry. The maximal radius r of the PISA was measured from the orifice to blue-red aliasing interface. Using the PISA method, MVA was calculated as (2pir(2)) x theta / 180 x AV/Vmax, where theta was the inflow angle formed by mitral leaflets, AV was the aliasing velocity (cm/sec), and Vmax was the peak transmitral velocity (cm/sec). MVA by the PISA method correlated well with planimetry both in patients with AR (r = 0.90, P < 0.001, SEE = 0.17 cm(2)) and without AR (r = 0.92, P < 0.001, SEE = 0.16 cm(2)). However, MVA by the PHT method did not correlate as well with planimetry (r = 0.57, P < 0.05, SEE = 0.37 cm(2)) in patients with associated AR, and the PHT method produced a significant overestimation (24%) of MVA obtained by planimetry in these patients. We conclude that the PISA method allows accurate estimation of MVA and is not influenced by AR.

Adult↗
PubMed2001

Acute effects of cigarette smoking on platelet-dependent thrombin generation.

AIMS: Thrombin is an important factor in the pathogenesis of thrombotic diseases. To clarify whether smoking has an effect in platelet-dependent thrombogenesis, we studied the acute effects of smoking on platelet-dependent thrombin level in smokers. METHODS AND RESULTS: Subjects consisted of ten smokers and nine non-smokers. Platelet-dependent thrombin level measured after overnight fasting was greater in smokers than in non-smokers (smokers vs non-smokers, 121 +/- 47 vs 56 +/- 5 mIU. ml(-1), P < 0.01). When subjects in the smokers group smoked two cigarettes containing 0.9 mg of nicotine per cigarette, platelet-dependent thrombin levels showed a transient three-fold increase in blood samples obtained immediately after smoking (365+/-76 mIU. ml(-1), P < 0.001). Thrombin levels in the blood samples obtained 10 min and 30 min after smoking were less than that in the samples obtained immediately after smoking ceased, but were not significantly different from those in the samples obtained before smoking. Blood nicotine level increased significantly immediately after smoking (P < 0.001), and plasma protein C activity decreased significantly 30 min after smoking (P < 0.05). When nicotine or cotinine was added to the platelet-rich plasma of non-smokers ex vivo, the platelet-dependent thrombin level increased significantly (P < 0.002). CONCLUSION: Platelet-dependent thrombin level is enhanced in smokers, even when not smoking, when compared with non-smokers and increases immediately after smoking. Increases in nicotine and cotinine levels caused by smoking induced a prothrombotic state in smokers via increased platelet-dependent thrombogenesis.

Adult↗