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M Miyata

Publications and source records attributed to M Miyata.

At least 73 records · Page 4Linked to original sources
PubMed2000

Local calcium release in dendritic spines required for long-term synaptic depression.

We have used rats and mice with mutations in myosin-Va to evaluate the range and function of IP3-mediated Ca2+ signaling in dendritic spines. In these mutants, the endoplasmic reticulum and its attendant IP3 receptors do not enter the postsynaptic spines of parallel fiber synapses on cerebellar Purkinje cells. Long-term synaptic depression (LTD) is absent at the parallel fiber synapses of the mutants, even though the structure and function of these synapses otherwise appear normal. This loss of LTD is associated with selective changes in IP3-mediated Ca2+ signaling in spines and can be rescued by photolysis of a caged Ca2+ compound. Our results reveal that IP3 must release Ca2+ locally in the dendritic spines to produce LTD and indicate that one function of dendritic spines is to target IP3-mediated Ca2+ release to the proper subcellular domain.

2-Amino-5-phosphonovalerate↗
PubMed2000

What are the appropriate indications for endoscopic mucosal resection for early gastric cancer? Analysis of 256 endoscopically resected lesions.

BACKGROUND AND STUDY AIMS: Although endoscopic mucosal resection (EMR) for early gastric cancer (EGC) without ulceration or scarring has been very popular in Japan and thought to be beneficial, curability by EMR is still lower than that for surgical resection. We investigated patients whose EGCs were resected endoscopically in order to identify the factors affecting curability by EMR. PATIENTS AND METHODS: We investigated retrospectively 256 EGC lesions (251 patients) which were subjected to EMR between 1989 and 1998 with respect to patient profile, macroscopic type, location, maximum diameter of tumors, resection method and histological typing. The prognoses of the patients were also investigated as far as possible. RESULTS: The curative total resection rate for EMR of EGC was 74.2 %. Concerning the factors affecting curability, the size of the lesion (over 15 mm), the method of resection (divisional resection), and histological typing (poorly differentiated) had a statistically significant effect on the complete resection rate. Multivariate analysis of the factors confirmed these results. Submucosal invasion was suspected in 16 patients after EMR, but submucosal cancer was found in only one patient after further surgery. Where there was recurrence, the longest recurrence-free period after EMR of EGC was 48 months, whereas the mean recurrence-free period was 195.4 days. CONCLUSIONS: The appropriate indication for EMR for EGC is thought to be an intramucosal differentiated-type adenocarcinoma without ulceration or scarring, and no more than 15 mm in size regardless of macroscopic type. Periodic follow-up for at least 5 years is necessary.

Adenocarcinoma↗
PubMed2000

Hepatotoxicity of acetaminophen and N-acetyl-p-benzoquinone imine and enhancement by fructose.

1. Although oral administration of 400 mg/kg acetaminophen (APAP) or 1.8-3.4 g/kg sucrose had no effect on serum levels of alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH), their co-administration resulted in 20-fold increases in ALT/SDH activities. APAP alone (1250 mg/kg, p.o.) caused the elevation hepatotoxicity parameters, but the levels were lower than observed with co-administration of APAP (400 mg/kg) and sucrose (2.6 or 3.4 g/kg). 2. Sucrose-associated increase in serum ALT/SDH activities was selective with APAP and not detected with carbon tetrachloride (160 mg/kg, i.p.), D-galactosamine (400 mg/kg, i.p.) or alpha-naphthyl isothiocyanate (100 mg/kg, p.o.). 3. To verify the synergistic mechanism of sucrose, a major reactive intermediate of APAP, N-acetyl-p-benzoquinone imine (NAPQI), was given via the portal vein to rat pretreated with sucrose. Clear elevation of ALT/SDH activities was detected in the co-treated group. These results, together with an allopurinol-inhibition experiment, suggest the involvement of high-dose sucrose at a step(s) occurring after the metabolic activation of APAP. 4. Co-administration of glucose or fructose as well as sucrose elevated APAP-induced hepatotoxicity parameters in rat. Fructose but not glucose elevated APAP- or NAPQI-induced LDH leakage in a primary hepatocyte system. The results suggest the primary role of fructose is on the sucrose enhancement of APAP toxicity in rat.

Acetaminophen↗
PubMed2000

Structure and photodimerizations of 1-alkylthymines in single crystals.

1-Alkylthymine gave four kinds of crystals depending on the solvents used. Photodimerizations of 1-alkylthymine in single crystals were found to depend on the crystal structure. In inactive crystals, the terminal methyl group of alkyl chains approached to the double bond of thymine, and inhibited rotation of thymine bases during photodimerization.

Alkylation↗
PubMed2000

Hepatic lymphocyte transplantation in hyperbilirubinemic gunn rats.

Hepatic lymphomyeloid cells (HLCs) are thought to contain liver stem cells. We investigated whether HLCs generated enzyme-producing cells in vivo. HLCs from normal Wistar/Shi rats and rats in which liver ischemia was induced using a portal clamp 4 days previously were studied histopathologically and characterized using flow cytometry. Splenic lymphocytes obtained from these animals were compared as a control. The proliferative activity of HLCs and splenic cells from both groups was also tested by stimulation with concanavalin A. HLCs contained a significantly higher number of NK-T cells and OV6+ cells compared with the splenic cells. The HLCs from rats in which liver ischemia was induced tended to have greater proliferative activity than those from normal rats, while the proliferative activity of splenic lymphocytes was impaired by liver ischemia. The HLCs obtained from Wistar/Shi rats with liver ischemia were then injected into hereditary hyperbilirubinemic Gunn rats to determine whether the HLCs generated enzyme-producing cells. After injection of these stimulated HLCs, the titer of serum bilirubin in the recipient rats was markedly reduced over a long time course (6.80+/-0.93 to 4.87+/-0.22 mg/dl after 1 month and 3.52+/-1.33 mg/dl after 6 months). The results of the present study indicate that HLCs have different populations than splenic cells, and ischemia-reperfusion of the liver increased their proliferative activity. HLC transplantation successfully reduced high bilirubin levels over a long time course.

Animals↗
PubMed2000

Tamoxifen inhibits lipoprotein activity: in vivo and in vitro studies.

Tamoxifen, a nonsteroidal antiestrogenic antitumor agent, has weak estrogen-like effects on lipid metabolism, however, the mechanism remains unknown. We previously reported that tamoxifen decreases the activity of lipoprotein lipase (LPL), a key enzyme in triglyceride metabolism, in patients with breast cancer. This study evaluated the effect of tamoxifen on LPL activity in vitro and in vivo. In experiment 1, total cholesterol, triglyceride, adipose tissue weight, and LPL activity of post-heparin plasma were measured in ovariectomized female rats with and without tamoxifen treatment. In experiment 2, purified very-low-density lipoprotein (VLDL) and purified LPL were incubated with and without tamoxifen or estrogen, and the triglycerides in VLDL were measured using an enzymatic method. In experiment 1, total cholesterol and adipose tissue weight decreased significantly in tamoxifen-treated rats (p < 0.001 and p < 0.01, respectively). Triglyceride measurements were not significantly different between the two groups, however, the LPL activity was lower in tamoxifen-treated rats (p < 0.005). In experiment 2, triglycerides in VLDL were significantly higher after VLDL and LPL were incubated with tamoxifen and estrogen (p < 0.005). We concluded that tamoxifen inhibits the hydrolytic activity of LPL in vivo and in vitro. This mechanism may explain the elevated serum triglyceride levels in some patients treated with tamoxifen.

Animals↗
PubMed2000

Athymic nude rats develop severe pulmonary hypertension following monocrotaline administration.

OBJECTIVE: To investigate the significance of the presence or absence of the thymus in the development of pulmonary hypertension (PH) following monocrotaline (MCT) administration, the degree of MCT-induced PH (MCT-PH) in athymic nude (F344/N Jcl-rnu) rats was compared with that in their euthymic (rnu/+) littermates. METHODS: Histopathological studies of the lung in terms of interstitial edema, congestion, thickening of the alveolar wall, inflammatory cell infiltration and degeneration of arteries were performed by staining with hematoxylin-eosin (HE), elastin van Gieson and Masson's trichrome. The medial wall thickness of the small pulmonary arteries and the weight ratio of the right ventricular free wall (RV) to that of the left ventricle plus septum [RV/(LV + S) weight ratio] were used as indices of the degree of PH. Toluidine blue staining was performed to estimate the number of the mast cells in the lung interstitium. RESULTS: Interstitial edema was significantly severer in MCT- injected euthymic rats than in MCT-injected athymic nude rats (p < 0.01); in contrast, the thickening of the alveolar wall was severer in MCT-injected athymic nude rats than in MCT-injected euthymic rats (p < 0.05). The degree of MCT-PH, as determined by the medial wall thickness of the small pulmonary arteries and RV/(LV + S) weight ratio in MCT-injected athymic nude rats, was significantly severer than in MCT-injected euthymic rats (p < 0.05 and p < 0.01, respectively). The number of mast cells was significantly greater in MCT-injected athymic nude rats than in MCT-injected euthymic rats (p < 0.01). The degree of the medial wall thickness of the small pulmonary arteries was significantly correlated with RV/(LV + S) weight ratio (p < 0.05) as well as with the number of mast cells in MCT-injected rats. CONCLUSIONS: Athymic nude rats developed severer PH than euthymic rats along with a greater number of mast cells and severer histopathological changes, such as thickening of the alveolar wall. Mast cell proliferation was considered to play a pivotal role in the development of PH in MCT-PH.

Animals↗
PubMed2000

Sjögren's syndrome with primary biliary cirrhosis, complicated by transverse myelitis and malignant lymphoma.

A 53-year-old woman with Sjögren's syndrome (SS) and primary biliary cirrhosis (PBC) complicated by transverse myelitis (TM) and malignant lymphoma (ML) is reported. TM has been described only in seven cases of primary SS, including three with PBC and four without PBC. The features of SS associated with PBC and complicated by TM were less typical compared with those seen in SS without PBC complicated by TM. This case is the first report of a case with SS, PBC, TM and ML. SS in association with PBC is, in general, overlooked, but such cases must be investigated with great caution for extraglandular complications.

Abdomen↗
PubMed2000

Magnetic resonance imaging findings in primary amyloidosis-associated arthropathy.

The MRI findings of amyloid arthropathy associated with primary amyloidosis are presented here possibly for the first time in the literature. Two types of lesions are noted: (1) capsular and tendon lesions; these regions are thickened, hypointense and enhanced by gadolinium (Gd) on T1 weighted imaging (T1WI), and hyperintense on T2 weighted imaging (T2WI), and (2) periarticular and osseous lesions; these regions appear to be tumor-forming and hypointense on both T1WI and T2WI and are not enhanced by Gd. It is necessary to differentiate these findings from other diseases such as chondrosarcoma, rhabdomyosarcoma and chronic inflammatory lesions such as tuberculosis.

Amyloidosis↗
PubMed2000

Takayasu's arteritis in a 69 year-old woman.

Takayasu's arteritis and temporal arteritis share many clinical and pathological features. The most discriminatory feature between the two diseases is the age at onset; the mean age at onset of the disease was reported as being 26 years for Takayasu's arteritis and 69 years for temporal arteritis. Here we report a 69-year-old woman who presented with a weak right radial artery pulse. The ethnic background and the presence of vascular insufficiency of the right upper extremity and the absence of clinical signs such as shoulder stiffness and tender scalp indicate that her diagnosis is Takayasu's arteritis. It must be emphasized that the two conditions could be differentiated based on the clinical findings even in a patient as old as 69 years old.

Age of Onset↗
PubMed2000

Primary antiphospholipid syndrome presenting with cerebral ischemia, thrombocytopenia, anemia and proteinuria successfully treated with warfarin potassium.

A 30-year-old woman with primary antiphospholipid syndrome (PAPS) presented with cerebral ischemia, thrombocytopenia, anemia and proteinuria. Administration of warfarin potassium, without concomitant corticosteroid administration, significantly improved all of these symptoms along with a decrease in the titers of antiCL-beta2-GP-I antibodies and a shortening of prolonged APTT. Therefore, the antiphospholipid antibodies in this patient could have been evoked by vitamin-K-dependent coagulation factors or plasma proteins which are assumed to undergo conformational changes exposing cryptic epitopes. This case report provides clues to the mechanisms underlying the production of antiphospholipid antibodies in patients with PAPS.

Adult↗
PubMed2000

[Chemotherapy for unresectable recurrent or metastatic squamous cell carcinomas of the head and neck].

The efficacy of chemotherapy for unresectable recurrent or metastatic squamous cell carcinomas of the head and neck can not be proved by survival periods. However, the efficacy of chemotherapy has been observed in some select patients. We investigated the effect of chemotherapy for unresectable recurrent squamous cell carcinomas of the head and neck. Four patients with a good performance status (PS) were treated with high-doses of leucovorin (LV), cisplatin (CDDP), and 5-fluorouracil (5-FU). The regimen consisted of 25 mg/m2 of CDDP on days 1-5; 600 mg/m2 of 5-FU of days 2-6; and 200 mg/m2 of LV on days 1-6. Patients received 3 cycles of this regimen at 28-day intervals. Ten patients with a poor PS were treated with low-doses of CDDP and tegafur.uracil upon admission. The regimen of seven poor PS patients consisted of 8 mg/m2 of CDDP on days 1-5 and 8-12, and 400 mg/body of tegafur.uracil administered orally on days 1-14. The other three patients received chemotherapy on an outpatient basis for ten weeks. The weekly regimen consisted of 7.5 mg/m2 of CDDP on days 3 and 6 and 400 mg/body of tegafur.uracil administered orally on days 1-7. With respect to the LV + CDDP and 5-FU treatment, complete remission was obtained in one patient. Two patients showed no change (NC), while one patient developed a progressive disease (PD). This regimen is highly toxic, has severe side effects including myelosuppression, oral mucositis, and diarrhea, and has a survival period of between 16 and 32 weeks. The low-dose CDDP + tegafur.uracil treatment produced a partial response in three patients, NC in three patients, and four patients developed a PD. This regimen doses not have any severe side effects and has a survival period of between 4 and 67 weeks.

Aged↗
PubMed2000

Enantioresolution of aliphatic alcohols by lithocholamide.

Lithocholamide (LCAM) forms inclusion compounds with aliphatic alcohols involving over five carbon atoms. Enantioresolution of the racemic alcohols was studied in channels of the inclusion compounds. X-ray crystallographic study clarified that host assemblies exhibit guest-dependent polymorphism. In each polymorphic crystal, the more longer or bulkier groups the alcohols have, the effective the resolutions become. The inclusion spaces were analyzed by a computed tomographic method, explaining the chiral recognition mechanism from a stereochemical viewpoint.

Alcohols↗
PubMed2000

Differential display of ethanol-induced gene in N18TG2 cells.

BACKGROUND: Recent advances in molecular biology, such as polymerase chain reaction (PCR) differential display, have enabled the screening of mRNAs transcriptionally regulated by chronic ethanol treatment. Screening of gene expression after ethanol exposure will be the most needed for new biological insights into alcoholism. METHODS: We used PCR differential display to detect differentially expressed RNAs in N18TG2 cells treated for 4 days with physiologic concentrations of ethanol (25 mM). RESULTS: We succeeded in identifying two differentially expressed RNAs in the ethanol-treated cells. The increase in the expression of the two RNAs was verified by Northern hybridization analysis. Sequence analyses and searches of the sequence databases revealed that one of the RNAs was that of the heat shock cognate protein 73 (HSC73) gene and that the other was the product of a novel gene. The increase in the level of HSC73 mRNA after ethanol administration was consistent with similar reports from other laboratories, and indicated that our assay system would be applicable to the screening of up-regulated gene expression during ethanol treatment. Rapid amplification of cDNA 5'-ends (5'-RACE) allowed us to determine the upstream sequence of the uncharacterized mRNA that would code for a protein of 113 amino acids. A homology search by MPsrch indicated very low homology to the calcium channel L-type alpha I subunit. CONCLUSIONS: The function of this new gene product is presently unknown, but our results indicate that an investigation of the pathophysiological significance of the gene in alcoholism would be worthwhile. Identification of genes that are influenced by chronic ethanol will certainly increase of the molecular mechanisms underlying physiologic dependence.

Animals↗