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Koichi Sato

Publications and source records attributed to Koichi Sato.

At least 55 records · Page 3Linked to original sources
PubMed2004

A novel, mild, and facile method to prepare 6-methylidene penem derivatives.

A novel and mild method was established to synthesize 6-methylidene penem compounds. This method entails a MgBr(2)/Et(3)N-promoted aldol-type condensation on 6-bromopenem 12 with an appropriately substituted aldehyde to yield the intermediate acetylated bromohydrin, which was smoothly converted to the final product with simultaneous deprotection of C3 carboxylic acid ester using activated zinc dust and phosphate buffer at pH 6.5. This process provides a useful variation of C-C bond formation method for penem derivatives and also serves as a practical synthetic method to prepare 6-exomethylenepenem derivatives without racemization at the C5 position.

Catalysis↗
PubMed2004

TDAG8 is a proton-sensing and psychosine-sensitive G-protein-coupled receptor.

T cell death-associated gene 8 (TDAG8) has been reported to be a receptor for psychosine. Ovarian cancer G-protein-coupled receptor 1 (OGR1) and GPR4, G-protein-coupled receptors (GPCRs) closely related to TDAG8, however, have recently been identified as proton-sensing or extracellular pH-responsive GPCRs that stimulate inositol phosphate and cAMP production, respectively. In the present study, we examined whether TDAG8 senses extracellular pH change. In the several cell types that were transfected with TDAG8 cDNA, cAMP was markedly accumulated in response to neutral to acidic extracellular pH, with a peak response at approximately pH 7.0-6.5. The pH effect was inhibited by copper ions and was reduced or lost in cells expressing mutated TDAG8 in which histidine residues were changed to phenylalanine. In the membrane fractions prepared from TDAG8-transfected cells, guanosine 5'-O-(3-thiotriphosphate) binding activity and adenylyl cyclase activity were remarkably stimulated in response to neutral and acidic pH. The concentration-dependent effect of extracellular protons on cAMP accumulation was shifted to the right in the presence of psychosine. The inhibitory psychosine effect was also observed for pH-dependent actions in OGR1- and GPR4-expressing cells but not for prostaglandin E(2)- and sphingosine 1-phosphate-induced actions in any pH in native and sphingosine 1-phosphate receptor-expressing cells. Glucosylsphingosine and sphingosylphosphorylcholine similarly inhibited the pH-dependent action, although to a lesser extent. Psychosine-sensitive and pH-dependent cAMP accumulation was also observed in mouse thymocytes. We concluded that TDAG8 is one of the proton-sensing GPCRs coupling to adenylyl cyclase and psychosine, and its related lysosphingolipids behave as if they were antagonists against protein-sensing receptors, including TDAG8, GPR4, and OGR1.

Animals↗
PubMed2004

A simple method for the detection of abnormal brain regions in Alzheimer's disease patients using [11C]MP4A: comparison with [123I]IMP SPECT.

We have developed a radiolabeled lipophilic acetylcholine analogue, N-[11C]methylpiperidin-4-yl acetate ([11C]MP4A) to measure brain acetylcholinesterase (AChE) activity by positron emission tomography (PET) in vivo. Aiming to develop a new SPECT tracer similar to MP4A, we first proposed a simple method for diagnosing Alzheimer's disease (AD) using [11C]MP4A PET. We performed [11C]MP4A PET and N-isopropyl [123I]iodoamphetamine ([123I]IMP) SPECT in 13 patients with AD and in 17 normal controls (NC). We calculated the ratio of radioactivity of the cortical region of interest (ROI) to that of the cerebellum measured with [11C]MP4A PET (MP4A ratio) and the ratio of regional cerebral blood flow (rCBF) to that of the cerebellum measured with [123I]IMP SPECT (IMP ratio). Eleven cortical ROIs were placed in the frontal, sensorimotor, temporal, parietal, and occipital cortices in both hemispheres and in the posterior cingulate cortex, and z-score was calculated in each ROI in patients with AD compared with NC. When the z-score was 2 or more in a ROI, it was defined as a positive ROI. When a patient had 3 or more positive ROIs, the patient was diagnosed as having AD. The reduction in the MP4A ratio was greater than that in the IMP ratio in all cortical ROIs except for in the right parietal cortex and cingulate cortex in patients with AD. MP4A ratio method showed 92% sensitivity and the IMP ratio method 69% sensitivity for the diagnosis of AD. These results encourage us to develop a new SPECT tracer similar to MP4A for the diagnosis of AD.

Acetates↗
PubMed2004

ATP-dependent chromatin structural modulation by multiprotein complex including HMGB1.

High mobility group box protein 1, HMGB1, is a major nonhistone chromatin component in higher eukaryotic cells. HMGB1 is thought to be involved in the processes of global nuclear events such as transcription, recombination and repair, but the mechanism of these processes is unclear. Here, we show a concrete example of chromatin structural modulation by HMGB1 in HeLa S3 cells. A co-immunopurification experiment with Flag-tagged HMGB1 revealed that a portion of HMGB1 in HeLa S3 cells is included in a large-molecular-weight multiprotein complex. The multiprotein complex including HMGB1 showed ATP hydrolysis and ATP-dependent chromatin structural modulation activities that increased the susceptibility of chromatin to MNase digestion, while HMGB1 alone had no such activity. Thus, HMGB1 in the multiprotein complex is critical for expressing the chromatin structural modulation activity. These results suggest that HMGB1 is involved in chromatin structural modulation in global nuclear events through its interaction with a multiprotein complex in mammalian cells.

Adenosine Triphosphate↗
PubMed2004

Evaluation of simplified kinetic analyses for measurement of brain acetylcholinesterase activity using N-[11C]Methylpiperidin-4-yl propionate and positron emission tomography.

The applicability of two reference tissue-based analyses without arterial blood sampling for the measurement of brain regional acetylcholinesterase (AChE) activity using N-[11C]methylpiperidin-4-yl propionate ([11C]MP4P) was evaluated in 12 healthy subjects. One was a linear least squares analysis derived from Blomqvist's equation, and the other was the analysis of the ratio of target-tissue radioactivity relative to reference-tissue radioactivity proposed by Herholz and coworkers. The standard compartment analysis using arterial input function provided reliable quantification of k3 (an index of AChE activity) estimates in regions with low (neocortex and hippocampus), moderate (thalamus), and high (cerebellum) AChE activity with a coefficient of variation (COV) of 12% to 19%. However, the precise k3 value in the striatum, where AChE activity is the highest, was not obtained. The striatum was used as a reference because its time-radioactivity curve was proportional to the time integral of the arterial input function. Reliable k3 estimates were also obtained in regions with low-to-moderate AChE activity with a COV of less than 21% by striatal reference analyses, though not obtained in the cerebellum. Shape analysis, the previous method of direct k3 estimation from the shape of time-radioactivity data, gave k3 estimates in the cortex and thalamus with a somewhat larger COV. In comparison with the standard analysis, a moderate overestimation of k3 by 9% to 18% in the linear analysis and a moderate underestimation by 2% to 13% in the Herholz method were observed, which were appropriately explained by the results of computer simulation. In conclusion, simplified kinetic analyses are practical and useful for the routine analysis of clinical [11C]MP4P studies and are nearly as effective as the standard analysis for detecting regions with abnormal AChE activity.

Acetylcholinesterase↗
PubMed2004

Antihypertensive effects of long-acting calcium channel blockers on hemodialysis days--a randomized crossover trial between benidipine and nifedipine CR.

BACKGROUND/AIMS: Since antihypertensive effects of most calcium channel blockers largely depend on their plasma concentrations, a rapid increase in blood pressure may occur as circulating levels of such blockers decrease after hemodialysis. Thus, the effects of benidipine and nifedipine CR (extended-release coated tablets, Adalat CR), which are long-acting calcium channel blockers, on post-hemodialytic blood pressures were investigated. METHODS: A randomized crossover trial was carried out with 10 hypertensive patients on chronic maintenance hemodialysis. Patients were assigned to receive benidipine (4-8 mg/day) or nifedipine CR (20-40 mg/day), and after 4 weeks, 24-hour ambulatory blood pressure monitoring was performed on the day of hemodialysis and blood samples were obtained before and after hemodialysis to measure plasma concentrations of the blockers. The calcium channel blockers were then exchanged in each patient and the same protocol was repeated. RESULTS: The pattern of fluctuation of blood pressure differed markedly between the treatment with benidipine and nifedipine CR. Under treatment with nifedipine CR, rapid increase in blood pressure was observed after hemodialysis, while blood pressure remained at favorable levels with benidipine. Plasma concentrations of the blockers were significantly decreased by hemodialysis. CONCLUSION: Benidipine exerts more sustained antihypertensive effects than expected from its disposition in plasma. The stable depressor effects of benidipine even after hemodialysis may contribute to favorable control of blood pressure in this population.

Aged↗
PubMed2004

Enhancement of sphingosine 1-phosphate-induced phospholipase C activation during G(0)-G(1) transition in rat hepatocytes.

We previously reported that sphingosine 1-phosphate (S1P) induces inhibition of adenylyl cyclase and activation of phospholipase C via independent G protein-coupled receptors in adult rat hepatocytes. Although S1P activation of phospholipase C and subsequent increase of intracellular Ca(2+) concentration were enhanced during the primary culture of hepatocytes, S1P inhibition of adenylyl cyclase remained unchanged. Here, we addressed whether enhancement of S1P-induced actions is dependent on change of status from the differentiated (G(0)) phase to proliferating (G(1)/S) phase in hepatocytes. By employing cell-density-dependency of the transition (G(0)-G(1)) of hepatocytes in primary culture in vitro, it was found that the enhancement of phospholipase C activation by S1P was dependent on cell density and correlated to the G(0)-G(1) transition. The correlation was further confirmed in vivo by 70% hepatectomy as a proliferating hepatocytes model. Northern blot analysis suggested an enhanced expression of S1P(2) receptor in proliferating hepatocytes.

Animals↗
PubMed2004

Role of actin microfilaments in canine distemper virus replication in vero cells.

Several studies have indicated that viruses require a specific cytoskeletal structure for replication in host cells. In this study, we examined the role of actin fiber in the replication of canine distemper virus (CDV), belonging to the Morbillivirus genus of the family Paramyxoviridae. For this purpose, we used two actin depolymerizing agents, cytochalasin-D (C-D) and mycalolide-B (ML-B). In Vero cells, C-D disrupted actin fibers distributed in the cytosol, but peripheral actin fibers remained intact. On the other hand, ML-B completely disrupted the actin fibers distributed in both areas. Treatment of Vero cells with C-D or ML-B inhibited the replication of CDV. Double staining of CDV-infected Vero cells with antibody to N-protein and rhodamine-phalloidin revealed the presence of N-protein in mid-cytoplasm. However, the N-protein was specifically localized at the submembrane region in the presence of C-D, whereas it was clustered in the presence of ML-B. Viral mRNA levels of N- and H-proteins were rather increased by treatment with C-D or ML-B. The treatment with ML-B strongly inhibited N-protein expression, whereas C-D only slightly inhibited N-protein expression. These results suggest that actin microfilaments distributed in the cytoplasm and on the membrane region in host cells may have a different role in the process of CDV replication.

Actin Cytoskeleton↗
PubMed2004

Usefulness of dual 67Ga and 99mTc-sestamibi single-photon-emission CT scanning in the diagnosis of cardiac sarcoidosis.

Cardiac sarcoidosis is potentially fatal and hence requires a precise diagnosis. We performed dual (67)Ga (Ga)-(99m)Tc-sestamibi (Tc) single-photon emission CT (SPECT) scans by superimposing a Ga-SPECT image on the myocardial outline traced with Tc. The usefulness of this imaging technique in the diagnosis of cardiac sarcoidosis was studied. The subjects in this study were 14 patients with sarcoidosis (mean [+/- SD] age, 52 +/- 16 years; 5 men and 9 women). An IV dose of Tc (74 MBq per 2 mL) was injected into patients 72 h after an IV dose of Ga (111 MBq per 3 mL) was injected. The dual SPECT scan was performed 30 min after the Tc dose was administered. The energy used for collection was 93 keV for Ga and 140 keV for Tc. The myocardial outline was successfully traced in all subjects, allowing us to check for myocardial Ga uptake and to identify its location. Abnormal Ga uptake in the myocardium was observed in 9 of the 14 subjects. In seven of these nine subjects, the location of the abnormal myocardial Ga uptake was identical to the location of reduced Tc uptake. Abnormal Ga uptake disappeared in all cases following steroid therapy. Of the five subjects who were free of abnormal Ga uptake, two showed reduced Tc uptake, and these two subjects had been receiving steroid therapy. These results suggest that dual SPECT scanning using Ga and Tc represents a very useful diagnostic imaging technique since it improves the diagnostic capability of Ga-SPECT to allow the highly specific diagnosis of cardiac sarcoidosis.

Adult↗
PubMed2004

Cognitive event-related potentials: useful clinical information in Alzheimer's disease.

Cognitive event-related potentials (ERPs) have been used as a marker of cognitive function in patients with psychiatric and neurological disorders. In particular, the P300 potential has been widely utilized to study dementia and aging, because the P300 ERP component is easily observed and reflects attention and memory processing. However, the relationship between parameters of the P300 potential and the severity or type of cognitive impairment in patients with Alzheimer's disease (AD) remains controversial. Because specific and effective anti-dementia treatments have recently become available for AD, more useful information is needed about the clinical aspects of this disease, including methods of making an accurate and early diagnosis, differentiation from vascular dementia and other degenerative dementias, assessment of severity, assessment of disease progression, evaluation of the response to treatment, and prediction of the prognosis. This mini-review described new discoveries on recent clinical application of ERPs in AD with respect to the above-mentioned areas. Although the definition of normal ERP values and the most appropriate method of ERP recording in AD patients have not been well defined, recent findings suggest that ERP analysis may be a clinically useful, inexpensive, noninvasive, and reliable method of assessing AD.

Alzheimer Disease↗
PubMed2004

[A case of primary squamous cell carcinoma of the lung with a metastatic thyroid tumor improved following chemotherapy].

Metastatic thyroid tumor is rarely diagnosed clinically. We report here a case of a 59-year-old male of a primary squamous cell carcinoma of the lung with metastatic thyroid tumor diagnosed by an ultrasonography-guided aspiration cytology. A squamous cell carcinoma of the lung (c-T4N3M1 stage IV) was diagnosed in March 2001, and so chemotherapy using carboplatin and paclitaxel was tried initially. A partial response was obtained. Then, he was re-admitted to our hospital because his thyroid gland was swollen. Ultrasonography-guided aspiration cytology of the thyroid tumor was performed and revealed a metastatic squamous cell carcinoma from the lung cancer. The patient was given chemotherapy using gemcitabine and docetaxel as second line chemotherapy. This reduced the thyroid tumor size and improved the symptoms.

Antimetabolites, Antineoplastic↗
PubMed2003

Lysophosphatidic acid (LPA) in malignant ascites stimulates motility of human pancreatic cancer cells through LPA1.

Cytokines and growth factors in malignant ascites are thought to modulate a variety of cellular activities of cancer cells and normal host cells. The motility of cancer cells is an especially important activity for invasion and metastasis. Here, we examined the components in ascites, which are responsible for cell motility, from patients and cancer cell-injected mice. Ascites remarkably stimulated the migration of pancreatic cancer cells. This response was inhibited or abolished by pertussis toxin, monoglyceride lipase, an enzyme hydrolyzing lysophosphatidic acid (LPA), and Ki16425 and VPC12249, antagonists for LPA receptors (LPA1 and LPA3), but not by an LPA3-selective antagonist. These agents also inhibited the response to LPA but not to the epidermal growth factor. In malignant ascites, LPA is present at a high level, which can explain the migration activity, and the fractionation study of ascites by lipid extraction and subsequent thin-layer chromatography indicated LPA as an active component. A significant level of LPA1 receptor mRNA is expressed in pancreatic cancer cells with high migration activity to ascites but not in cells with low migration activity. Small interfering RNA against LPA1 receptors specifically inhibited the receptor mRNA expression and abolished the migration response to ascites. These results suggest that LPA is a critical component of ascites for the motility of pancreatic cancer cells and LPA1 receptors may mediate this activity. LPA receptor antagonists including Ki16425 are potential therapeutic drugs against the migration and invasion of cancer cells.

Adult↗
PubMed2003

Chronic treatment with interleukin-1beta attenuates contractions by decreasing the activities of CPI-17 and MYPT-1 in intestinal smooth muscle.

Interleukin-1beta (IL-1beta) is a proinflammatory cytokine that plays a central role in inflammatory bowel disease (IBD). In order to elucidate the mechanism of motility disorders frequently observed in IBD, we investigated the long term effects of IL-1beta on rat ileal smooth muscle contractility by using an organ culture system. When ileal smooth muscle strips were cultured with IL-1beta (10 ng/ml), contractions elicited by high K+ and carbachol were inhibited in a time-dependent manner. IL-1beta more strongly inhibited the carbachol-induced contractions than high K+ with decreasing myosin light chain phosphorylation. In the alpha-toxin-permeabilized ileal muscle, carbachol with GTP or guanosine 5'-3-O-(thio)triphosphate increased the Ca2+ sensitivity of contractile elements, and this G protein-coupled Ca2+ sensitization was significantly reduced in the IL-1beta-treated ileum. Among the functional proteins involved in the smooth muscle Ca2+ sensitization, CPI-17 expression was significantly reduced after the culture with IL-1beta, whereas the expressions of RhoA, ROCK-I, ROCK-II, MYPT-1, myosin light chain kinase, and myosin phosphatase (PP1) were unchanged. The phosphorylation level of CPI-17 by carbachol was low in accordance with the decrease in CPI-17 expression due to IL-1beta treatment. In contrast, constitutively phosphorylated MYPT-1 was also decreased in the IL-1beta-treated muscles. These results suggest that long term treatment with IL-1beta decreases either CPI-17 expression or MYPT-1 phosphorylation, which may result in an increase in myosin phosphatase activity to reduce force generation. Based on these findings, we consider IL-1beta to be an important mediator of gastrointestinal motility disorders in IBD, and CPI-17 and MYPT-1 are key molecules in the decreased smooth muscle contractility due to IL-1beta.

Animals↗
PubMed2003

High-density lipoprotein stimulates endothelial cell migration and survival through sphingosine 1-phosphate and its receptors.

OBJECTIVE: Plasma high-density lipoprotein (HDL) level is inversely correlated with the risk of atherosclerosis. However, the cellular mechanism by which HDL exerts antiatherogenic actions is not well understood. In this study, we focus on the lipid components of HDL as mediators of the lipoprotein-induced antiatherogenic actions. METHODS AND RESULTS: HDL and sphingosine 1-phosphate (S1P) stimulated the migration and survival of human umbilical vein endothelial cells. These responses to HDL and S1P were almost completely inhibited by pertussis toxin and other specific inhibitors for intracellular signaling pathways, although the inhibition profiles of migration and survival were different. The HDL-stimulated migration and survival of the cells were markedly inhibited by antisense oligonucleotides against the S1P receptors EDG-1/S1P1 and EDG-3/S1P3. Cell migration was sensitive to both receptors, but cell survival was exclusively sensitive to S1P1. The S1P-rich fraction and chromatographically purified S1P from HDL stimulated cell migration, but the rest of the fraction did not, as was the case of the cell survival. CONCLUSIONS: HDL-induced endothelial cell migration and survival may be mediated by the lipoprotein component S1P and the lipid receptors S1P1 and S1P3.

Cell Adhesion↗
PubMed2003

Decrease in activity of smooth muscle L-type Ca2+ channels and its reversal by NF-kappaB inhibitors in Crohn's colitis model.

We investigated the mechanisms of dysmotility of the colonic circular muscle of the Crohn's disease rat model. Contractions induced by KCl, carbachol, and Bay K 8644 were decreased in circular smooth muscles isolated from 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis rat colon. However, the absolute force and Ca2+ sensitivity of contractile proteins were not affected as assessed in alpha-toxin permeabilized smooth muscle. The current density of the L-type Ca2+ channel in circular smooth muscle cells was significantly decreased in the TNBS-treated colonic cells. However, expressions of the L-type Ca2+ channel mRNA and protein did not differ between control and TNBS-treated preparations. Pretreatment with the NF-kappaB inhibitors pyrrolidinedithiocarbamate and sulfasalazine partially recovered the decreased contractility and current density of the L-type Ca2+ channel by TNBS treatment. These results suggest that the decrease in the contraction of circular smooth muscle isolated from TNBS-induced colitis rat colon, which may be related to gut dysmotility in Crohn's disease, is attributable to the decreased activity of the L-type Ca2+ channel. The dysfunction of the L-type Ca2+ channel may be mediated by NF-kappaB-dependent pathways.

Animals↗
PubMed2003

Assessment of the role of sphingosine 1-phosphate and its receptors in high-density lipoprotein-induced stimulation of astroglial cell function.

It has been suggested that lipoproteins in the central nervous system are involved in the regulation of several neural functions independent of cholesterol metabolism as well as those related to lipid metabolism. We recently demonstrated that lipoproteins are carriers for sphingosine 1-phosphate (S1P). This raised the possibility that S1P mediates the neural cell functions induced by lipoproteins. In the current study, we examined the effects of plasma high-density lipoprotein (HDL) on astroglial cell functions, focusing especially on the role of the lipoprotein-associated S1P. In rat type I astrocytes or C6 glioma cells, similar to S1P, HDL stimulated DNA synthesis and mRNA expression of fibroblast growth factor-2, a potent neurotrophic factor, which was associated with the activation of extracellular signal-regulated kinase (ERK) in a pertussis toxin-sensitive manner. The data from fractionation studies of HDL indicated that S1P may be a major component for the activation of ERK. In C6 glioma cells, HDL also induced phospholipase C-dependent intracellular Ca(2+) mobilization. Desensitization of the C6 glioma cells with S1P abolished these HDL-induced actions. Furthermore, overexpression of S1P receptors in C6 glioma cells led to a significant enhancement of HDL-induced ERK activation and Ca(2+) mobilization. Thus, at least some HDL-induced actions may be mediated by cell-surface S1P receptors in astroglial cells. These results imply that S1P might partially mediate lipoprotein-induced cholesterol metabolism-independent neural cell functions in the central nervous system.

Animals↗
PubMed2003

A case of triple synchronous cancers occurring in the gallbladder, common bile duct, and pancreas.

We report a 74-year-old man with triple synchronous cancers occurring in the gallbladder, common bile duct, and pancreas. The patient had consulted a nearby physician because of epigastralgia and icterus. On September 30, 1997, the patient was admitted to our department for further evaluation and treatment. Abdominal computed tomography (CT) showed dilatation of the common bile duct, cystic duct, and intrahepatic bile duct, and swelling of the gallbladder. On CT, the wall of the distal common bile duct was thick and a low-density mass was detected on the left side. Cholangiography, performed via percutaneous transhepatic cholangiodrainage (PTCD), revealed stenosis of the distal common bile duct. Endoscopic retrograde pancreatography (ERP) showed marked dilatation of the main pancreatic duct. On October 17, 1997, pancreatoduodenectomy was performed under the diagnosis of carcinoma of common bile duct and pancreas. Histopathological examination revealed poorly differentiated tubular adenocarcinoma of the common bile duct, well-differentiated tubular adenocarcinoma of the gallbladder, and mucinous cystadenocarcinoma of the pancreas. These three tumors were histopathologically different. Moreover, p53-positive nuclei were recognized only in the pancreas tumor. These findings suggested that the oncogenic mechanisms of multiple synchronous cancers were not the result of only abnormal DNA reparative mechanisms.

Adenocarcinoma↗