Biomedical subjects

T Ishihara

Publications and source records attributed to T Ishihara.

At least 91 records · Page 5Linked to original sources

PubMed2000

Characterization of Ce-atl-1, an ATM-like gene from Caenorhabditis elegans.

An ATM-like gene was identified in the genome of Caenorhabditis elegans. The putative product of the gene, termed Ce-atl-1 (C. elegans ATM-like 1) consists of 2514 amino acid residues. The C-terminal sequence, which contains a PI-3 kinase-like domain, showed good homology with the products of the gene MEC1/ESR1 from budding yeast, the rad3+ gene of fission yeast and mammalian ATM (ataxia-telangiectasia and rad3+ related) genes. The results of RNA-mediated interference indicated that the major phenotype associated with repression of Ce-atl-1 was lethality (approximately 50-80%) during early embryogenesis. Among the surviving progeny, males (XO animals) arose at a high frequency (2-30%). In addition, 5% of oocyte chromosomes demonstrated aneuploidy due to a defect in pre-meiotic chromosomal segregation. Gene expression analyses indicated that Ce-atl-1 mRNA was expressed in all larval stages and that its level increased about fivefold in the adult stage. The adult expression level was decreased in the glp-4 mutant, which is defective in germ line proliferation. Ce-atl-1 was strongly expressed in both the mitotic and meiotic cells of adult gonads. In summary, Ce-atl-1 appears to be important for early embryogenesis, and loss of its function results in a defect in chromosome segregation, similar to what has been observed for AT-related proteins.

Amino Acid Sequence↗

PubMed2000

Recent advances in bilirubin metabolism research: the molecular mechanism of hepatocyte bilirubin transport and its clinical relevance.

Bilirubin is taken up from blood into hepatocytes by sinosuidal membrane transporters and then excreted into bile through the bile canalicular membrane mainly as bilirubin glucuronides. (1) Mechanism of bilirubin uptake into hepatocytes: many organic anions are incorporated into hepatocytes by organic anion transporting polypeptides (rat, oatp1, oatp2, oatp3; human, OATP), liver-specific transporter (rlst/HLST), and/or by organic anion transporters (OAT2, OAT3). Oatp1 and HLST transport bilirubin monoglucuronide. However, a transporter of unconjugated bilirubin in the sinusoidal membrane has not as yet been identified. Unconjugated bilirubin may also go across the hepatocyte sinusoidal membrane by a diffusion process. (2) Intrahepatic transport and conjugation of bilirubin: ligandin carries bilirubin to the endoplasmic reticulum (ER) of hepatocytes. In the ER, bilirubin is conjugated by bilirubin uridine diphosphate (UDP)-glycosyltransferase (bilirubin UGT; UGT1A1) to form mono- and diglucuronides of bilirubin. (3) Transport mechanism of bilirubin glucuronides across the hepatocyte canalicular membrane: at the canalicular membrane, bilirubin glucuronides are excreted into bile by multidrug resistance-associated protein 2 (MRP2), a member of the ATP-binding cassette transporter family. (4) Regurgitation of bilirubin glucuronides into blood: MRP3, which is located in the lateral membrane, transports bilirubin glucuronides into blood under conditions of impaired biliary bilirubin excretion.

Anion Transport Proteins↗

PubMed2000

Long-term outcome of endoscopic papillotomy for choledocholithiasis with cholecystolithiasis.

BACKGROUND: Although endoscopic papillotomy is now considered established treatment for choledocholithiasis, therapeutic results of endoscopic papillotomy alone without subsequent cholecystectomy in patients with cholecystolithiasis have not been well evaluated. The aim of this study was to assess the long-term outcome of endoscopic papillotomy for these patients. METHODS: Patients admitted with choledocholithiasis and cholecystolithiasis from 1976 to 1993 were studied retrospectively. Of 385 patients in whom the bile duct was cleared by endoscopic papillotomy and endoscopic stone extraction, 371 patients (195 men and 176 women; mean age 65.4 years) were followed. Predisposing risk factors for late complications were analyzed. RESULTS: The mean duration of follow-up was 7.7 years. Cholecystitis and recurrence of choledocholithiasis as late complications occurred in 22 cases (5.9%) and 36 cases (9.7%), respectively. Cholecystitis, including 1 severe case, resolved with conservative treatment. Recurrent choledocholithiasis was successfully treated endoscopically except in 1 case. No significant risk factors were identified for cholecystitis. The presence of pneumobilia (p = 0.0016) and the need for lithotripsy (p = 0.0342) were found to be significant risk factors for the recurrence of choledocholithiasis. CONCLUSIONS: Long-term outcome of endoscopic papillotomy in patients with choledocholithiasis and cholecystolithiasis was found to be relatively favorable. Cholecystectomy after endoscopic papillotomy is not always necessary in the management of cholecystolithiasis.

Aged↗

PubMed2000

Pathogenic factors of glucose intolerance in obese Japanese adolescents with type 2 diabetes.

We attempted to identify the pathogenic factors involved in the progression to type 2 diabetes in obese Japanese adolescents. Subjects included 18 nondiabetic obese adolescents, 12 obese adolescents with type 2 diabetes on diet therapy, 10 obese adolescents with type 2 diabetes manifesting ketosis at onset or with a history of treatment with hypoglycemic agents, and 26 non-obese adolescent control subjects. The first-phase insulin response (FPIR), glucose disappearance constant (Kg), glucose effectiveness (Sg), and insulin sensitivity (S(I)) were obtained using an insulin-modified frequently sampled intravenous glucose tolerance test (FSIGT) and a minimal model analysis. The disposition index (DI, by FPIR x S(I)) was determined to assess any endogenous insulin effect. The results showed that Kg was decreased significantly (P = .0006) with the progression to severe diabetes in the obese groups. Although S(I) and Sg did not differ significantly among the 3 obese groups, both parameters were significantly lower in each obese group versus the non-obese controls. As a result of the significant decrease in FPIR (P < .0001), the DI decreased (P = .0006) with the progression to severe diabetes in the obese groups. In conclusion, an early manifestation of type 2 diabetes with occasional ketosis at onset may result from beta-cell dysfunction to glucose stimulation. This finding is demonstrated by the relatively low FPIR to decreased S(I) in obese Japanese adolescents, as well as the low Sg as a synergic role in glucose intolerance. The present findings from a Japanese population for pathogenic factors aside from obesity may help us to gain a better understanding of the progression to adolescent, early-onset, obese type 2 diabetes and its severity.

Adolescent↗

PubMed2000

Identification of a myofibril-bound serine proteinase (MBSP) in the skeletal muscle of lizard fish Saurida wanieso which specifically cleaves the arginine site.

A myofibril-bound serine proteinase (MBSP) from the skeletal muscle of lizard fish (Saurida wanieso) was purified to homogeneity by a heating treatment followed by a series of column chromatographies on DEAE-Sephacel, Sephacryl S-200, Q-Sepharose, Hydroxyapatite and Benzamidine-Sepharose 6B, and characterized enzymatically. On SDS-poly-acrylamide gel electrophoresis (SDS-PAGE), the purified enzyme showed a band with molecular mass of approximately 29 kDa under reducing conditions, while 60 kDa under non-reducing conditions. The optimum temperature of the enzyme was 50 degrees C using t-butyloxycarbonyl-Phe-Ser-Arg-4-methylcoumaryl-7-amide (Boc-Phe-Ser-Arg-MCA) as a substrate. Substrate specificity analysis both using MCA-substrates and peptides showed that MBSP specifically cleaved at the carboxyl side of the arginine residue. Inhibitor susceptibility analysis revealed that MBSP was inhibited effectively by Pefabloc SC, soybean trypsin inhibitor (STI) and aprotinin, indicating the characteristic of a serine proteinase. When myofibril was incubated with the enzyme, it optically degraded myosin heavy chain at 55-60 degrees C, while alpha-actinin and actin were not at all hydrolyzed as detected by immunoblotting. The N-terminal amino acid sequence of MBSP was partially determined as IVGGAEXVPY- and was very homologous to other serine proteases.

Amino Acid Motifs↗

PubMed2000

Polygonum tinctorium extract suppresses nitric oxide production by activated macrophages through inhibiting inducible nitric oxide synthase expression.

Despite its beneficial role in host defense mechanisms, excessive nitric oxide (NO) production by activated macrophages has been implicated in several inflammatory diseases. To clarify the mechanisms of anti-inflammatory activities of Polygonum tinctorium, we evaluated whether extracts of P. tinctorium could modulate the production of NO by activated macrophages. An AcOEt extract of P. tinctorium markedly inhibited NO synthesis by interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages and the macrophage-like cell line RAW 264.7 in a dose-dependent manner. Inhibition of NO synthesis was achieved by reducing inducible NO synthase (iNOS) expression at protein and mRNA levels. However, the AcOEt extract of P. tinctorium failed to inhibit NO synthesis when iNOS was already expressed following stimulation with IFN-gamma and LPS. The AcOEt extract also exhibited inhibitory activity on iNOS expression in human lung epithelial A549 cells stimulated with a combination of IFN-gamma, TNF-alpha and IL-1 beta without affecting the expression of constitutive isoforms of NOS. Furthermore, in vivo injection of the AcOEt extract of P. tinctorium into LPS-treated mice significantly reduced NO synthesis by peritoneal exudate cells under ex vivo conditions. These results suggest that P. tinctorium extract may be a potential therapeutic modulator of NO synthesis in various pathological conditions.

Animals↗

PubMed2000

Temporal profile of CRE DNA-binding activity in the rat hippocampus following a kindling stimulation.

This study was designed to establish a role for cAMP-responsive element (CRE) binding protein (CREB) in signal transduction cascade in the hippocampus associated with kindling. Male Sprague-Dawley rats were kindled from the left amygdala until they exhibited Racine's class 5 generalized seizures [Racine (1972). EMBO J. 11, 3337-3346] Nuclear proteins were extracted from dorsal hippocampi obtained from 0 to 24 h after final kindling stimulation. From these, we evaluated the temporal pattern of CRE DNA-binding activity by use of a gel mobility-shift assay with a 32P-labeled CREB oligonucleotide probe. CRE-binding activity in the hippocampus was enhanced significantly at 2 h and returned to baseline level within 4 h after the stimulation. Our results suggest that CREB may be involved in the hippocampal signal transduction pathway of rats activated in response to a kindling stimulation to the amygdala. However, the transient elevation of CRE-binding activity following a seizure in a kindled animal also suggests that persistent activation of CREB may not be required for maintenance of the kindling phenomenon.

Animals↗

PubMed2000

Identification and characterization of the high-affinity choline transporter.

In cholinergic neurons, high-affinity choline uptake in presynaptic terminals is the rate-limiting step in acetylcholine synthesis. Using information provided by the Caenorhabditis elegans Genome Project, we cloned a cDNA encoding the high-affinity choline transporter from C. elegans (cho-1). We subsequently used this clone to isolate the corresponding cDNA from rat (CHT1). CHT1 is not homologous to neurotransmitter transporters, but is homologous to members of the Na+-dependent glucose transporter family. Expression of CHT1 mRNA is restricted to cholinergic neurons. The characteristics of CHT1-mediated choline uptake essentially match those of high-affinity choline uptake in rat brain synaptosomes.

Amino Acid Sequence↗

PubMed2000

YM-53601, a novel squalene synthase inhibitor, reduces plasma cholesterol and triglyceride levels in several animal species.

The aim of this study was to evaluate the potency of YM-53601 ((E)-2-[2-fluoro-2-(quinuclidin-3-ylidene) ethoxy]-9H-carbazole monohydrochloride), a new inhibitor of squalene synthase, in reducing both plasma cholesterol and triglyceride levels, compared with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor and fibrates, respectively. YM-53601 equally inhibited squalene synthase activities in hepatic microsomes prepared from several animal species and also suppressed cholesterol biosynthesis in rats (ED(50), 32 mg kg(-1)). In guinea-pigs, YM-53601 and pravastatin reduced plasma nonHDL-C (=total cholesterol - high density lipoprotein cholesterol) by 47% (P<0.001) and 33% (P<0.001), respectively (100 mg kg(-1), daily for 14 days). In rhesus monkeys, YM-53601 decreased plasma nonHDL-C by 37% (50 mg kg(-1), twice daily for 21 days, P<0.01), whereas the HMG-CoA reductase inhibitor, pravastatin, failed to do (25 mg kg(-1), twice daily for 28 days). YM-53601 caused plasma triglyceride reduction in hamsters fed a normal diet (81% decrease at 50 mg kg(-1), daily for 5 days, P<0.001). In hamsters fed a high-fat diet, the ability of YM-53601 to lower triglyceride (by 73%, P<0.001) was superior to that of fenofibrate (by 53%, P<0.001), the most potent fibrate (dosage of each drug: 100 mg kg(-1), daily for 7 days). This is the first report that a squalene synthase inhibitor is superior to an HMG-CoA reductase inhibitor in lowering plasma nonHDL-C level in rhesus monkeys and is superior to a fibrate in significantly lowering plasma triglyceride level. YM-53601 may therefore prove useful in treating hypercholesterolemia and hypertriglyceridemia in humans.

Animals↗

PubMed2000

The conserved nuclear receptor Ftz-F1 is required for embryogenesis, moulting and reproduction in Caenorhabditis elegans.

BACKGROUND: Nuclear receptors are essential players in the development of all metazoans. The nematode Caenorhabditis elegans possesses more than 200 putative nuclear receptor genes, several times more than the number known in any other organism. Very few of these transcription factors are conserved with components of the steroid response pathways in vertebrates and arthropods. Ftz-F1, one of the evolutionarily oldest nuclear receptor types, is required for steroidogenesis and sexual differentiation in mice and for segmentation and metamorphosis in Drosophila. RESULTS: We employed two complementary approaches, direct mutagenesis and RNA interference, to explore the role of nhr-25, a C. elegans ortholog of Ftz-F1. Deletion mutants show that nhr-25 is essential for embryogenesis. RNA interference reveals additional requirements throughout the postembryonic life, namely in moulting and differentiation of the gonad and vulva. All these defects are consistent with the nhr-25 expression pattern, determined by in situ hybridization and GFP reporter activity. CONCLUSIONS: Our data link the C. elegans Ftz-F1 ortholog with a number of developmental processes. Significantly, its role in the periodical replacement of cuticle (moulting) appears to be evolutionarily shared with insects and thus supports the monophyletic origin of moulting.

Animals↗

PubMed2000

The inhibitory effects of carvedilol against arrhythmias induced by coronary reperfusion in anesthetized rats.

BACKGROUND: Previous study has shown the antiarrhythmic effects of carvedilol on isolated rat hearts, but little is known about the mechanism of this protective action. This article examines the inhibitory effect of carvedilol against arrhythmias induced by reperfusion in anesthetized rats. In addition, the results are compared with those with propranolol, superoxide dismutase (SOD) plus catalase, and a combination of both in order to elucidate the mechanism of the protective actions. METHODS AND MATERIALS: Ninety percent of the rats in the control group showed lethal ventricular fibrillation (VF). Carvedilol at the doses of 0.03, 0.1, and 0.3 mg/kg significantly reduced the incidence of lethal VF to 0%, 0%, and 10%, respectively (P <.05). In contrast, propranolol at the doses of 0.3, 1.0, and 3.0 mg/kg and SOD (35,000 units/kg) plus catalase (400,000 units/kg) did not reduce the incidence of lethal VF (80%, 60%, 70%, and 70%, respectively). However, administration of a combination of propranolol (1.0 mg/kg) and SOD plus catalase completely inhibited the occurrence of lethal VF to 0% (P<.05). CONCLUSION: These results indicate that carvedilol has the inhibitory effect against reperfusion arrhythmias in rats and suggest that the mechanism of action of this compound is related to the combined effects of beta-blocking and antioxidant.

Adrenergic beta-Antagonists↗

PubMed2000

Peroral pancreatoscopy in the diagnosis of mucin-producing tumors of the pancreas.

BACKGROUND: Mucin-producing tumor of the pancreas is an increasingly recognized clinical entity. However, the differentiation of benign from malignant mucin-producing tumors of the pancreas is challenging. Peroral pancreatoscopy as recently developed may have potential for the diagnosis of mucin-producing tumors of the pancreas. METHODS: The subjects were 41 patients with clinically diagnosed mucin-producing tumors of the pancreas, 40 of whom underwent surgical resection. Autopsy findings were available in another patient with unresectable disease. Histologically, hyperplasia was identified in 3 patients, mildly atypical adenoma in 11, severely atypical adenoma in 16, and adenocarcinoma in 11. Peroral pancreatoscopy was performed before surgery or pathologic examination. The findings were retrospectively evaluated and compared with the histopathologic diagnosis. RESULTS: Pancreatoscopic observation was successful in 30 patients (73.2%). Elevated lesions were identified in 22 (73.3%). Villous or vegetative elevations and red color markings were frequently found in severely atypical adenoma or adenocarcinoma. Tumor location (main or branch duct type) did not correlate with survival after resection. Partial resection was performed in 7 of 30 patients with nonmalignant tumors and resulted in favorable outcomes. CONCLUSION: Peroral pancreatoscopy can be used to differentiate benign mucin-producing tumors of the pancreas (hyperplasia and mildly atypical adenoma) from the more dysplastic lesions (severely atypical adenoma and adenocarcinoma) and may provide useful information for determining the type of surgery to be performed.

Adenocarcinoma↗

PubMed2000

Long-term follow-up after treatment of Mirizzi syndrome by peroral cholangioscopy.

BACKGROUND: The standard treatment for Mirizzi syndrome is surgical, although endoscopic and percutaneous management have also been described. The aim of this study was to evaluate the usefulness of shock wave lithotripsy combined with peroral cholangioscopy and its long-term outcome in patients with Mirizzi syndrome. METHODS: The records of 25 patients with Mirizzi syndrome who underwent endoscopic treatment between April 1990 and November 1998 were retrospectively reviewed. Shock wave lithotripsy was performed under direct vision with a "mother-baby" endoscope system in 2 patients with type I and 23 with type II Mirizzi syndrome (12 men and 13 women, mean age 60 years). Follow-up data were obtained from clinical records or through telephone interviews. RESULTS: In the two patients with type I, the cholangioscopic approach failed and both patients underwent open cholecystectomy. The 23 patients with type II were all successfully treated with shock wave lithotripsy alone. The cholangioscopic approach was unsuccessful in the treatment of residual gallbladder stones. Follow-up data were obtained in all but one patient (mean 43.6 months, range 4 to 103 months). Of the 23 patients with type II, 12 with no gallbladder stones had remained asymptomatic during the follow-up period. Of the 6 patients with type II with large residual gallbladder stones, 4 had acute cholangitis due to stone migration 6, 9, 28, and 34 months after endoscopic treatment. Two patients died during the follow-up period, one of non-biliary causes and the other of coexistent gallbladder carcinoma. CONCLUSIONS: Endoscopic treatment of Mirizzi syndrome using peroral cholangioscopy is a safe and effective alternative to surgery, especially in patients with the type II syndrome. A favorable long-term outcome depends on the absence of large residual gallbladder stones.

Adult↗

PubMed2000

Effect of imidapril in dipper and nondipper hypertensive patients: comparison between morning and evening administration.

The purpose of the study was to identify differences in the patterns of efficacy and duration of effects of imidapril administered at different times of the day (morning versus evening) in dipper and nondipper hypertensive patients. Twenty patients with untreated hypertension were classified into two groups: dippers (n = 9) and nondippers (n = 11). Imidapril (10 mg) was given at 07:00 or 18:00 for 4 weeks in a crossover fashion. Blood pressure (BP) and heart rate (HR) were monitored before and after morning and evening treatment every 30 min for 48h by ambulatory BP monitoring (ABPM). In dipper hypertension, the mean 48h BP was reduced with both doses. The decrease in the diurnal BP was stronger when the drug was administered in the evening than morning, but without significant difference. In nondipper hypertension, the systolic BP decreased at night with both doses, but the extent of the nocturnal reduction in systolic BP was greater after morning therapy. There were no significant differences in the decrease in BP during the day or night between the morning and evening administrations. When imidapril was administered in the morning, its serum concentration reached a maximum at 16:00, and when the drug was administered in the evening, it reached a maximum at 6:00. In dipper hypertension, the time taken for the blood concentration of imidapril to reach a maximum changed depending on its time of administration, and the time when the maximum antihypertensive effect of the drug appeared was different. In nondipper hypertension, decreases in the BP were confirmed at night regardless of the time of administration; this might be caused by angiotensin converting enzyme (ACE) inhibitors effectively blocking the BP from increasing by activating the parasympathetic nervous system. Therefore, when assessing the effectiveness of antihypertensive agents, factors such as the various patterns of BP before therapy and administration time must be considered.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2000

Chlamydia pneumoniae in atherosclerotic and nonatherosclerotic tissue.

The positivity rate and localization of Chlamydia pneumoniae were investigated in atherosclerotic and nonatherosclerotic tissues by immunohistochemistry, polymerase chain reaction, and cell culture. In total, 67 atheromatous plaques from Japanese symptomatic patients and 110 nonatherosclerotic tissues and organs were evaluated. Of these, 62% of atherosclerotic plaques from symptomatic patients were infected with C. pneumoniae compared with just 2% of nonatherosclerotic tissues. Immunohistochemically stained C. pneumoniae were found most often in smooth muscle cells, less often in macrophages, and in a few endothelial cells.

Adult↗

PubMed2000

Triplex formation using ODN conjugates with polycation comb-type copolymer.

Polycation comb-type copolymer that is composed of polylysine backbone and dextran side chains (PLL-g-Dex) has previously been shown to stabilize duplex and triplex DNAs quite effectively. In this study, we have conjugated PLL-g-Dex with oligonucleotides (ODN) aiming to increase the triplex stabilizing efficiency of the copolymer. Here we have demonstrated that the copolymer-TFO conjugates selectively stabilize triplex DNA. Also its potential to form triplex DNA was found to be greater than PLL-g-Dex/ODN mixture.

Base Sequence↗

PubMed2000

Acceleration of DNA strand exchange by polycation comb-type copolymer.

The accelerating effect of cationic substances on DNA strand exchange reaction between 20 bp DNA duplex and its complementary single strand was studied. A comb-type polycationic copolymer which is composed of poly (L-lysine) backbone and dextran graft chain (PLL-g-Dex) and known to stabilize triplex DNA expedites the strand exchange reaction under physiological relevant conditions. Electrostatically small excess of the copolymer increased DNA strand exchange rate by 300-fold while large excess of spermine or cethyltrimethylammonium bromide, cationic detergent known to promote markedly hybridization of complementary DNA strands, showed slight effect. It should be noted that the copolymer promotes the strand exchange reaction while it stabilizes double stranded DNA.

Animals↗

PubMed2000

Acute effects of a single low oral dose of pimobendan on left ventricular systolic and diastolic function in patients with congestive heart failure.

A recent long-term multicenter trial has shown that pimobendan is more effective when administered in low doses. However, no data are available concerning the effect of a low dose of pimobendan on the systolic and diastolic pressure-volume relations in patients with heart failure. Therefore we examined the effects of a single low dose of oral pimobendan, a calcium sensitizer, on systolic and diastolic hemodynamics in patients with cardiomyopathy and congestive heart failure. We measured the left ventricular (LV) pressure-volume relations using a conductance catheter with a micromanometer tip in 10 patients with chronic congestive heart failure resulting from idiopathic cardiomyopathy before and 45 and 90 min after administration of a single oral dose of 2.5 mg of pimobendan. End-systolic elastance was used as an index of LV contractility and was measured during transient occlusion of the inferior vena cava. End-systolic elastance increased significantly by 25% at 45 min (p < 0.05) and by 55% at 90 min (p < 0.01) without an increase in myocardial oxygen consumption. The inotropic effect was accompanied by improved ventriculoarterial coupling. This effect was attenuated in patients with severely impaired myocardial contractility. LV relaxation, assessed by the time constant of isovolumic pressure decay (T(1/2)), was significantly shortened at 90 min (from 47.7 +/- 1.9 to 41.2 +/- 1.7 ms; p < 0.01), although it remained unchanged at 45 min. The diastolic pressure-volume relation showed a leftward and downward shift in all patients. These results indicate that low-dose oral pimobendan had favorable short-term inotropic and lusitropic effects in patients with congestive heart failure caused by idiopathic dilated cardiomyopathy, and may thus be a useful alternative to traditional agents. Further study in a large-scale trial is merited.

Administration, Oral↗