Biomedical subjects

T Sakaguchi

Publications and source records attributed to T Sakaguchi.

At least 73 records · Page 4Linked to original sources

PubMed1999

Flux of the L-serine metabolism in rabbit, human, and dog livers. Substantial contributions of both mitochondrial and peroxisomal serine:pyruvate/alanine:glyoxylate aminotransferase.

L-Serine metabolism in rabbit, dog, and human livers was investigated, focusing on the relative contributions of the three pathways, one initiated by serine dehydratase, another by serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT), and the other involving serine hydroxymethyltransferase and the mitochondrial glycine cleavage enzyme system (GCS). Under quasi-physiological in vitro conditions (1 mM L-serine and 0.25 mM pyruvate), flux through serine dehydratase accounted for only traces, and that through SPT/AGT substantially contributed no matter whether the enzyme was located in peroxisomes (rabbit and human) or largely in mitochondria (dog). As for flux through serine hydroxymethyltransferase and GCS, the conversion of serine to glycine occurred fairly rapidly, followed by GCS-mediated slow decarboxylation of the accumulated glycine. The flux through GCS was relatively high in the dog and low in the rabbit, and only in the dog was it comparable with that through SPT/AGT. An in vivo experiment with L-[3-3H,14C]serine as the substrate indicated that in rabbit liver, gluconeogenesis from L-serine proceeds mainly via hydroxypyruvate. Because an important role in the conversion of glyoxylate to glycine has been assigned to peroxisomal SPT/AGT from the studies on primary hyperoxaluria type 1, these results suggest that SPT/AGT in this organelle plays dual roles in the metabolism of glyoxylate and serine.

Animals↗

PubMed1999

The prognostic significance of amplification and overexpression of c-met and c-erb B-2 in human gastric carcinomas.

BACKGROUND: The c-met and the c-erb B-2 protooncogenes belong to a family of tyrosine kinase growth factor receptors. Abnormalities of these oncogenes and protein products have been reported in several cancers. The authors investigated the correlation between clinical factors and amplification or overexpression of the c-met and/or c-erb B-2 gene in Japanese patients with gastric carcinoma patients, with a focus on prognostic significance. METHODS: Amplification and overexpression of c-met and c-erb B-2 were investigated retrospectively in 128 gastric carcinoma patients by using immunohistochemistry and Southern blot hybridization. Survival analysis was performed with the Kaplan-Meier test, and the log rank test was used for statistical analysis. RESULTS: Overexpression of c-met and c-erb B-2 was observed in 46.1% and 16.4% of gastric carcinoma cases, respectively. Gene amplification of c-met and c-erb B-2 was detected in 10.2% and 11.7% of gastric carcinoma cases, respectively. Amplification and overexpression of c-met were correlated significantly with depth of tumor invasion and lymph node metastasis, whereas amplification and overexpression of c-erb B-2 were correlated significantly with histologic type. The survival rate of patients with amplification and/or overexpression of c-met or c-erb B-2 was significantly poorer than that of patients with no amplification or overexpression. Multivariate analysis revealed that c-met overexpression and lymph node metastasis were independent prognostic factors. CONCLUSIONS: These data suggest that overexpression and/or gene amplification of c-met and c-erb B-2 may be prognostic factors in gastric carcinoma.

Adult↗

PubMed1999

The genome nucleotide sequence of a contemporary wild strain of measles virus and its comparison with the classical Edmonston strain genome.

The only complete genome nucleotide sequences of measles virus (MeV) reported to date have been for the Edmonston (Ed) strain and derivatives, which were isolated decades ago, passaged extensively under laboratory conditions, and appeared to be nonpathogenic. Partial sequencing of many other strains has identified >/=15 genotypes. Most recent isolates, including those typically pathogenic, belong to genotypes distinct from the Edmonston type. Therefore, the sequence of Ed and related strains may not be representative of those of pathological measles circulating at that or any time in human populations. Taking into account these issues as well as the fact that so many studies have been based upon Ed-related strains, we have sequenced the entire genome of a recently isolated pathogenic strain, 9301B. Between this recent isolate and the classical Ed strain, there were 465 nucleotide differences (2.93%) and 114 amino acid differences (2.19%). Computation of nonsynonymous and synonymous substitutions in open reading frames as well as direct comparisons of noncoding regions of each gene and extracistronic regulatory regions clearly revealed the regions where changes have been permissible and nonpermissible. Notably, considerable nonsynonymous substitutions appeared to be permissible for the P frame to maintain a high degree of sequence conservation for the overlapping C frame. However, the cause and the effect were largely unclear for any substitution, indicating that there is a considerable gap between the two strains that cannot be filled. The sequence reported here would be useful as a reference of contemporary wild-type MeV.

3' Untranslated Regions↗

PubMed1999

Contribution of endothelin-1 to microcirculatory impairment in total hepatic ischemia and reperfusion injury.

BACKGROUND: Endothelin (ET)-1 may have a role in hepatic polymorphonuclear leukocyte infiltration as well as microcirculatory disturbance during hepatic ischemia-reperfusion (HIR) injury. This study was conducted to investigate the influence of ET-1 on the hepatic microcirculation after total HIR and to evaluate the effect of a nonselective ET receptor antagonist under these conditions. METHODS: Male rats pretreated with either normal saline (NS group) or TAK-044, a nonselective ET receptor antagonist (TAK group), were subjected to 120 min of total hepatic ischemia with extracorporeal portosystemic shunting. RESULTS: Plasma ET-1 levels increased significantly from 1 to 6 hr after reperfusion in the NS group when compared with the nonischemic control. In the early phase of reperfusion, the NS group showed significantly narrower sinusoids, lower hepatic tissue blood flow, a lower hepatic tissue oxy-hemoglobin concentration, and more hepatic neutrophil infiltration than the TAK group (P<0.05). Pretreatment with TAK-044 improved hepatic microcirculatory derangement, and resulted in significantly better 7-day survival (61.5%) with more bile production after reperfusion when compared with the NS group (P<0.01). CONCLUSIONS: The present study demonstrated that ET-1 is involved in the development of HIR injury by causing deterioration of the hepatic microcirculation. A nonselective ET receptor antagonist successfully ameliorated HIR injury through improvement of hepatic oxygenation and of the microcirculation along with reduced hepatic neutrophil infiltration.

Alanine Transaminase↗

PubMed1999

Participation of platelet-activating factor in the lipopolysaccharide-induced liver injury in partially hepatectomized rats.

Platelet-activating factor (PAF) has been shown to be an important mediator in the pathogenesis of lipopolysaccharide (LPS)-induced liver injury in regenerating rat livers. Both LPS and PAF activate nuclear factor-kappa B (NF-kappaB), a key transcription factor for tumor necrosis factor-alpha (TNF-alpha) and cytokine-induced neutrophil chemoattractant (CINC). The aim of this study is to investigate how PAF participates in the LPS-induced and NF-kappaB-mediated regulation of TNF-alpha and CINC in regenerating rat livers. LPS (1.5 mg/kg) was intravenously administered into 70% hepatectomized rats and sham-operated rats 48 hours postoperatively. LPS administration caused a high mortality rate, scattered necrosis in the liver with infiltration of CINC-positive neutrophils, and a continuous CINC messenger RNA up-regulation and activation of NF-kappaB in the liver only in hepatectomized rats. These phenomena were all effectively prevented by pretreatment and posttreatment with a PAF receptor antagonist, TCV-309. Hepatectomized rats showed NF-kappaB staining in hepatocytes, Kupffer cells, and neutrophils around necrosis 4 hours after the LPS injection, representing the activation of this factor in these cells. Based on these results, we propose that PAF contributes to continuous CINC up-regulation and NF-kappaB activation via accumulation and activation of neutrophils, and thereby is involved in LPS-induced liver injury in regenerating rat livers.

Alanine Transaminase↗

PubMed1999

Acute portal hypertension increases ileal vulnerability to platelet-activating factor in rats.

BACKGROUND: Patients with portal hypertension can easily develop sepsis of enteric origin after suffering severe trauma and hemorrhagic shock. Platelet-activating factor (PAF) is one of the key mediators of such stress. The aim of this study was to investigate whether portal hypertension increases the vulnerability of the ileum to PAF. MATERIALS AND METHODS: Seven days after surgery, PAF (1.5 microg/kg) was intravenously injected into portal stenosis (PS) rats and sham-operated rats. The levels of tumor necrosis factor-alpha (TNF-alpha), cytokine-induced neutrophil chemoattractant (CINC), and endotoxin in portal plasma were determined. The levels of PAF receptor (PAFR), TNF-alpha, and CINC mRNA in the ileum were also investigated. RESULTS: After PAF administration, PS rats showed (1) significantly higher portal plasma levels of TNF-alpha, CINC, and endotoxin; (2) higher histological damage scores in the ileum; (3) more infiltrating neutrophils in the ileum; and (4) a significantly higher mortality rate than sham-operated rats (P < 0.01). However, PAFR mRNA levels were similar in the two groups. The CINC mRNA level in the ileum of PS rats was increased from 1 to 4 h after PAF administration, while that of the sham-operated rats was transiently increased at 1 h. CONCLUSIONS: Portal hypertension increases the vulnerability of the ileum to PAF. These findings suggest that conditions which causes PAF production may be dangerous in patients with portal hypertension.

Acute Disease↗

PubMed1999

Double cancer of the gallbladder and common bile duct associated with an anomalous pancreaticobiliary ductal junction without a choledochal cyst: report of a case.

We report herein the case of a 37-year-old woman found to have double cancer of the gallbladder and common bile duct associated with an anomalous pancreaticobiliary ductal junction (APBDJ) without a choledochal cyst (CC). Abdominal ultrasonography showed an isoechoic mass in the gallbladder, and percutaneous transhepatic biliary drainage tubography revealed incomplete obstruction in the upper portion of the common bile duct and APBDJ. The patient underwent cholecystectomy, partial hepatic resection, pancreatoduodenectomy, and portal vein reconstruction. Pathological examination of the tumors from the gallbladder and bile duct revealed papillary carcinoma and poorly differentiated adenocarcinoma, respectively, and direct continuity was not observed between the tumors. A review of the literature on six cases of multiple primary carcinoma of the biliary tract associated with APBDJ without CC is presented following this case report. Double cancer of the biliary tract was found synchronously in five patients and metachronously in one. Gallbladder cancer showed subserosal invasion in four patients, while bile duct cancer invaded the pancreas in one patient and reached the serosa in two patients. Considering the potential for cancer to arise in the biliary tract and the difficulties associated with monitoring it, cholecystectomy and resection of the extrahepatic common bile duct may be the most appropriate treatment for patients with an APBDJ without a CC.

Adenocarcinoma↗

PubMed1999

The Freestyle stentless bioprosthesis for prosthetic valve endocarditis.

We report a case of methicillin-resistant Staphylococcus aureus-induced prosthetic valve endocarditis, which was successfully treated with aortic valve replacement using the Freestyle stentless bioprosthesis. The total root and stentless design of this bioprosthesis allows for more radical removal of infected tissue and easier treatment for annular abscess, while requiring less prosthetic materials than a conventional prosthesis. This bioprosthesis thus seems to be a valuable option for active endocarditis.

Abscess↗

PubMed1999

Identification of multiple HIV-1 CTL epitopes presented by HLA-B*5101 molecules.

We attempted to identify and characterize HIV-1 CTL epitopes presented by HLA-B51 which is associated with a slow progression to AIDS. HLA-B*5101 stabilization assay showed that 33 out of 172 HIV-1 peptides carrying HLA-B*5101 anchor residues bound to HLA-B*5101. Seven peptides were suggested as HIV-1 CTL epitopes presented by HLA-B*5101 because the specific CTL was induced for these peptides in PBMC from three HIV-1 seropositive individuals carrying HLA-B51 by stimulation with HLA-B*5101 binding peptides. Analysis of these epitopes using the specific CTL clones confirmed that six of seven HIV-1 peptides are epitopes presented by HLA-B*5101. Three epitopes presented by HLA-B*5101 are highly conserved among the clade B strain, suggesting that the specific CTL for these epitopes might play an important role in recognition of HIV-1 infected cells. These epitopes will be useful to analyze CTL responses in HIV-1 infected individuals.

Antigen Presentation↗

PubMed1999

Protection of excitotoxic neuronal death by gluconate through blockade of N-methyl-D-aspartate receptors.

Excitotoxic neuronal death is mediated primarily by the N-methyl-D-aspartate receptor. N-methyl-D-aspartate induces two forms of excitotoxicity in CA1 pyramidal neurons of cultured rat hippocampal slices: the rapidly developing form that depends on external Na+ and Cl-, and the delayed form that requires external Ca2+ but not Cl-. Consistent with this notion, replacement of external Cl- with glucuronate, isethionate or methylsulfate attenuated or delayed selectively the rapid excitotoxicity. However, gluconate substituting for Cl- blocked both rapid and delayed forms of excitotoxicity. Gluconate also reduced N-methyl-D-aspartate-induced membrane currents recorded from CA1 neurons in a dose-dependent manner. This dose-dependence was remarkably similar to that observed for protection of N-methyl-D-aspartate-induced neuronal death by gluconate. Although gluconate chelated Ca2+ most strongly among the four Cl- substitutes examined, excitotoxic neuronal death could be protected by 7 mM gluconate without Ca2+ chelating action. The voltage-dependent Mg2+ block of N-methyl-D-aspartate receptors was not affected by gluconate. Gluconate suppressed the N-methyl-D-aspartate component of excitatory synaptic currents evoked in CA1 neurons. We conclude that protection of excitotoxic neuronal death by gluconate at low doses (<20 mM) is due to its antagonistic action on N-methyl-D-aspartate receptors. Gluconate is a widely used substitute for Cl-. Our unexpected findings give a warning that the results of any of the experiments concerning excitotoxicity or glutamate receptors obtained by gluconate substituting for Cl- must be interpreted with caution.

Animals↗

PubMed1999

Allograft transduction of IL-10 prolongs survival following orthotopic liver transplantation.

Interleukin-10 (IL-10) is an ideal candidate cytokine for suppressing the alloimmune response in transplantation. To determine whether genetic modulation of the hepatic graft with IL-10 could prolong survival following orthotopic liver transplantation, we constructed a replication-deficient adenovirus vector expressing human IL-10 (AdCMVhIL-10). Intraportal injection of this vector into a donor rat 24-48 h before grafting resulted in efficient release of IL-10 into the circulation of a recipient rat after transplantation. Moreover, levels of hIL-10 from the suprahepatic vena cava were significantly (1.48-fold) higher than those from the infrahepatic vena cava (P = 0.013), indicating local IL-10 production within the transduced hepatic graft. AdCMVhIL-10 induced a prolongation of median survival to more than 87 days, with two of five transduced grafts showing more than 100 days of ongoing survival, when compared with 11 days for grafts transduced with a control adenovirus vector carrying the E. coli beta-galactosidase gene (P = 0.0021) and 11 days for untreated grafts (P = 0.0021). Pathological findings occurring in the AdCMVhIL-10-transduced hepatic grafts revealed no evidence of progressive rejection reaction resulting in graft failure. These results demonstrate that hepatic grafts modulated by IL-10 gene transfer make local and effective immunosuppression feasible in the transplantation setting.

Adenoviridae↗

PubMed1999

Combined transfrontal and endonasal endoscopic surgery of epidural abscess following frontal sinusitis. A case report.

A large epidural abscess secondary to frontal sinusitis in a previously healthy 19-year-old man was successfully treated with a small eyebrow incision using combined transfrontal and endonasal endoscopic technique. The abscess was resolved with concomitant pneumatization of the paranasal sinuses. The present case illustrates the promising use of endoscopy in the merging fields of neurosurgery and otorhinolaryngology.

Abscess↗

PubMed1999

Purification and characterization of cold-active L-glutamate dehydrogenase independent of NAD(P) and oxygen.

L-Glutamate dehydrogenase (GLDH) independent of NAD(P) and oxygen was first obtained from the psychrotrophic bacterium Aeromonas sp. L101, originally isolated from the organs of salmon (Oncorhynchus keta). GLDH was purified by a series of chromatography steps on DEAE-Sepharose, Superdex 200pg, Q-Sepharose, CM-Sepharose, and Phenyl-Sepharose. The purified protein was determined to have a molecular mass of 110 kDa and a pI of 5.7. Maximum activity was obtained at 55 degrees C and pH 8.5. The activity of GLDH at 4 and 20 degrees C was 38 and 50%, respectively, of that at 50 degrees C. GLDH was coupled to cytochrome c and several redox dyes including 1-methoxy-5-methylphenazinium methylsulfate (1-Methoxy PMS), 2, 6-dichlorophenylindophenol (DCIP), 9-dimethylaminobenzo[alpha]phenoxazin-7-ium chloride (meldola's blue), 3,3'-[3,3'-dimethoxy-(1,1'-biphenyl)-4, 4'-diyl]-bis[2-(4-nitrophenyl)-5-phenyl-2H tetrazolium chloride] (nitroblue tetrazolium; NBT), and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H tetrazolium (INT). The presence of NAD(P) and oxygen gave no oxidation activity to GLDH. Spectroscopic profile and ICP data indicated a b-type cytochrome containing iron.

Aeromonas↗

PubMed1999

Comparison of substrate specificities against the fusion glycoprotein of virulent Newcastle disease virus between a chick embryo fibroblast processing protease and mammalian subtilisin-like proteases.

The fusion (F) protein precursor of virulent Newcastle disease virus (NDV) strains has two pairs of basic amino acids at the cleavage site, and its intracellular cleavage activation occurs in a variety of cells; therefore, the viruses cause systemic infections in poultry. To explore the protease responsible for the cleavage in the natural host, we examined detailed substrate specificity of the enzyme in chick embryo fibroblasts (CEF) using a panel of the F protein mutants at the cleavage site expressed by vaccinia virus vectors, and compared the specificity with those of mammalian subtilisin-like proteases such as furin, PC6 and PACE4 which are candidates for F protein processing enzymes. It was demonstrated in CEF cells that Arg residues at the -4, -2 and -1 positions upstream of the cleavage site were essential, and that at the -5 position was required for maximal cleavage. Phe at the +1 position was also important for efficient cleavage. On the other hand, furin and PC6 expressed by vaccinia virus vectors showed cleavage specificities against the F protein mutants consistent with that shown by the processing enzyme of CEF cells, but PACE4 hardly cleaved the F proteins including the wild type. These results indicate that the proteolytic processing enzymes of poultry for virulent NDV F proteins could be furin and/or PC6 but not PACE4. The significance of individual contribution of the three amino acids at the -5, -2 and +1 positions to cleavability was discussed in relation to the evolution of virulent and avirulent NDV strains.

Animals↗

PubMed1999

Antitumor effect on human gastric cancer and induction of apoptosis by vascular endothelial growth factor neutralizing antibody.

Induction of apoptosis by antiangiogenic therapy has been suggested as a new anticancer strategy. To clarify the mechanism of the antitumor effect achieved by inhibition of vascular endothelial growth factor (VEGF), which is a major mediator of angiogenesis, we used an orthotopic transplantation model of human gastric carcinoma line (MT2) treated with a monoclonal VEGF neutralizing antibody (VEGF Ab). We histologically examined the microvessel density (MVD) and the apoptotic index (AI) in this model. Transplanted tumor growth was significantly inhibited by the VEGF Ab (P = 0.03), and there was a significant decrease in the number of mice with liver metastasis (P = 0.004). The MVD detected by immunohistochemical staining with ER-MP12 antibody was 33.6 +/- 8.0 in the control group and 21.1 +/- 5.4 in the treated group, and the difference was significant (P < 0.0001). The AI values of the control and treated groups were 4.73 +/- 1.11 and 7.26 +/- 1.62, respectively, and this difference is also significant (P < 0.0001). However, the expression of VEGF mRNA in transplanted tumors did not show a significant difference between the control and treated groups. These results suggest that the antitumor effect of the VEGF Ab on human gastric carcinoma is exerted by inducing mild hypoxia followed by apoptosis, which does not influence VEGF mRNA expression in the carcinoma.

Adenocarcinoma↗

PubMed1999

Orally administered Panax ginseng extract decreases platelet adhesiveness in 66% hepatectomized rats.

The effect of oral administration of Panax ginseng extract (GE) on platelet adhesiveness was examined in 66% hepatectomized rats. A significant decrease in platelet adhesiveness was obtained when 125 mg/kg/day GE was administered for 6 days before and after hepatectomy. The total cholesterol concentration in the serum was also decreased by GE administration. Food intake was unaffected by GE administration. Serum parameters indicating liver and kidney function were unchanged after GE administration except for lipid metabolic parameters. Because enhanced platelet adhesiveness and hyperlipidemia induces atherosclerosis, these results suggest that orally administered GE is capable of improving the atherosclerotic condition associated with hepatectomy.

Animals↗

PubMed1999

Physiological effects of sudden change in illuminance during dark-adapted state.

To derive an optimal illuminance of nighttime illumination, we conducted an experiment with 7 healthy young individuals and 7 healthy elderly individuals as subjects. After 20 minutes of adaptation to darkness, subjects were exposed to illumination under 5 conditions comprising 0.5 lx, 1 lx, 3 lx, 10 lx, or 30 lx vertical illuminance of the facial region, and heart rate variability (HRV) and electroencephalogram (EEG) were measured, and discomfort was evaluated by subjective report. Results of LF/(LF + HF) (LF = low frequency, HF = high frequency) demonstrated a V-shaped trend for the young groups beginning during exposure and ending post exposure, with 3 lx conditions representing the minimum value, a value markedly lower than that for 30 lx conditions. From these results we inferred that approximately 3 lx illuminance could best suppress physiological stress. Evaluation of discomfort by subjective report also demonstrated an increase in discomfort evaluation scores under high illuminance conditions. The alpha-wave proportion of EEG during exposure fell markedly on 3 lx or higher illuminance conditions, and we inferred that visual sensory information and cortical activity level were adequately attained in 3 lx or higher illuminance conditions. These results suggest that the optimal illuminance of nighttime illumination is approximately 3 lx.

Adult↗

PubMed1999

Effect of illuminance and color temperature on lowering of physiological activity.

To investigate how illuminance and color temperature in illumination affect the autonomic nervous system and central nervous system in conditions tending to lower physiological activity, and with an ordinary residential setting in mind, we performed an experiment on 8 healthy male subjects. The experimental conditions consisted of 4 conditions provided by a combination of 2 levels of color temperature (3000 K, 5000 K) and 2 levels of illuminance (30 lx, 150 lx). Physiological measurement was carried out during a process of 22 minutes of light exposure followed by 20 minutes of sleep in darkness. Heart rate variability (HRV) was used as an index of the autonomic nervous system, and alpha attenuation coefficient (AAC) and mean frequency of EEG were used as indices of the central nervous system. Subjective evaluation of drowsiness during the experiment was also carried out immediately following the 20 minutes sleep. No effect on HRV from illumination was noted, but significantly (p < 0.05) lower values for AAC were obtained under 3000 K conditions than 5000 K conditions in measurements during the first half of light exposure (Session 1). During alpha attenuation testing, significantly (p < 0.05) lower values for mean frequency in the theta-beta EEG bandwidth were also obtained under 3000 K conditions than 5000 K conditions, but that pattern persisted in measurement during the second half of light exposure (Session 2). Subjective drowsiness was also higher under 3000 K conditions than 5000 K conditions. These results suggest that low color temperature light creates a smooth lowering of central nervous system activity, and that low color temperature illumination can be used effectively in a bedroom or other such environment where it is desirable to facilitate lowered physiological activity.

Adult↗