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Biomedical subjects

T Tsuchiya

Publications and source records attributed to T Tsuchiya.

At least 163 records · Page 9Linked to original sources
PubMed1999

Identification of inducible genes at the early stage of adipocyte differentiation of 3T3-L1 cells.

Adipocyte differentiation takes place via a complex series of steps. While PPARgamma2 and C/EBPalpha are known to be master regulators, the events at the earliest stage of adipocyte differentiation are not yet known. In this study, we cloned the genes which are induced at the beginning of differentiation of 3T3-L1 preadipocyte cells. Of 58 clones obtained, only a few were already reported as the genes that are expressed differentially during adipocyte development. More than 30 clones are known but have been newly identified here as differentially expressed genes. Nineteen clones seemed to be unknown genes. The expression of RGS2, HSP105, Rho (TC10), VDR, and HIF-1alpha genes isolated here rapidly increased after the addition of inducers, and after 3-12 h the levels of expression decreased. The expression patterns of these mRNAs were different among growth-arrested and proliferating 3T3-L1 cells and NIH-3T3 cells, strongly indicating that some of the proteins identified here have crucial roles in the program of adipocyte differentiation.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Coactivation of secretogranin-II and BDNF genes mediated by calcium signals in mouse cerebellar granule cells.

In primary culture of mouse cerebellar granule cells, the brain-derived neurotrophic factor (BDNF) gene is activated in an activity-dependent manner, accompanying Ca2+ influx into neurons through voltage-dependent calcium channels (VDCCs). In this study, we investigated the inducibility of secretogranin-II (Sg-II) gene in terms of Ca2+ signals evoked via VDCCs, by a comparison with BDNF and c-fos genes. Deprivation and subsequent induction of membrane depolarization by lowering and reelevating the extracellular concentration of potassium chloride (KCl), respectively, led to an decrease and then an increase in the Sg-II, BDNF and c-fos mRNA expression. The increase in Sg-II mRNA expression was detected as early as but was slower than that of BDNF one. The increase in Sg-II mRNA expression was induced depending upon the extracellular Ca2+ and inhibited by nicardipine, indicating a requirement of Ca2+ influx through VDCCs for the Sg-II as well as BDNF gene induction. Inhibition of de novo protein synthesis by cycloheximide did not affect the Sg-II induction. The response of Sg-II gene to the changes in extracellular KCl concentration was the same as that of BDNF but different from that of c-fos gene. Thus, Sg-II gene is coactivated with BDNF gene in response to the intracellular Ca2+ signals evoked via Ca2+ influx through VDCCs.

Animals↗
PubMed1999

Intestinal synthesis and lymphatic secretion of apolipoprotein A-IV after cessation of duodenal fat infusion: mediation by bile.

We tested whether secretion of apolipoprotein (apo) A-IV depends upon intestinal triglyceride (TG) transport by comparing output kinetics of TG and apo A-IV during and after duodenal lipid infusion in lymph-fistula rats. Lipid infusion (triolein, 40 mumol/h, 8 h) produced increases in lymphatic TG and apo A-IV output. After 8 h, triolein infusate was replaced with glucose-saline; TG output returned to basal levels 4-5 h later. However, apo A-IV output continued at significantly elevated levels until 20 h after the start of the experiment. Bile diversion blocked this continued output of A-IV during the post-lipid period, and resulted in basal TG output that was 75% lower than in bile-intact rats. Return of bile or low-dose triolein infusion (5 mumol/h) into the intestine reversed these effects. There were no differences in hepatic synthesis or filtration of plasma A-IV into lymph between bile-intact and bile-diverted groups. Intestinal A-IV synthesis was elevated in both groups even during the post-lipid period. The results support the hypothesis that intestinal triglyceride transport drives apo A-IV secretion, and suggest the existence of a bile-dependent, post-translational mechanism for the control of lymphatic apo A-IV output.

Animals↗
PubMed1999

Correlation of chromosome abnormalities with presence or absence of WT1 deletions/mutations in Wilms tumor.

Of 40 Wilms tumors with chromosome abnormalities, 6 were hypodiploid, 10 were pseudodiploid, 7 were hyperdiploid with 47 to 49 chromosomes, and 17 were hyperdiploid with 50 or more chromosomes, mostly including +12. WT1 deletions/mutations were found in one hypodiploid, eight pseudodiploid, and one hyperdiploid (47-49 chromosomes) tumor, but in none of the hyperdiploid (> or =50 chromosomes) tumors. Of the 10 tumors with WT1 abnormalities, 6 had a homozygous WT1 deletion, 1 had a nonsense WT1 mutation and loss of heterozygosity at 11p, 1 had an intragenic hemizygous WT1 deletion without detectable WT1 mutation, and 2, which occurred in Wilms tumor-aniridia-genitourinary abnormalities-mental retardation syndrome patients, had a hemizygous deletion and a missense or frameshift mutation of WT1. Six of the nine tumors with homozygous or hemizygous WT1 deletions had chromosome aberrations involving chromosome band 11p13 in one of the two chromosomes 11. While one hypodiploid and one pseudodiploid patient died of the disease, and one hyperdiploid (47-49 chromosomes) patient was alive in nonremission, all hyperdiploid (> or =50 chromosomes) patients had no evidence of disease at the last follow-up. Our data show that chromosome aberrations are closely correlated to WT1 abnormalities and suggest that hyperdiploid (> or =50 chromosomes) Wilms tumors may be characterized by the absence of WT1 abnormalities and possibly also by a favorable prognosis.

Aneuploidy↗
PubMed1999

Transitional change in interaction between HIF-1 and HNF-4 in response to hypoxia.

The roles of the erythropoietin (Epo) 3' enhancer in the activation of gene expression in response to hypoxia were investigated. The enhancer contains hypoxia-inducible enhancer binding site 1 (HIF-1 element) and two direct repeats of hexanucleotide consensus nuclear receptor half site (HNF-4 element). HIF-1, which is a heterodimeric complex of HIF-1 alpha and aryl hydrocarbon receptor nuclear translecator (ARNT), binds to HIF-1 element. HNF-4 binds to HNF-4 element as a homodimeric complex. Studies on mutant reporter plasmids demonstrated that both HIF-1 alpha and HNF-4 elements were necessary for augmentation of the enhancer activity, since mutation of either the HIF-1 or the HNF-4 element caused loss of inducibility under hypoxic conditions. Mammalian two-hybrid experiments in vivo revealed that transitional change took place from the interaction of HNF-4 with ARNT to that with HIF-1 alpha in response to hypoxia. Such interactive domains were identified in amino acids 369-465 containing the C-terminal of HNF-4 and amino acids 1-458 containing basic helix-loop-helix (bHLH) and Per-ARNT-AHR-Sim (PAS) domains of ARNT in normoxia. Also, an extended sequence containing ligand and dimerization domains, and the C-terminal of HNF-4 (amino acids 135-465), and the PAS domain (amino acids 106-526) of HIF-1 alpha were used for the interaction between the two transcription factors in hypoxia. From these data, the functional significance of the transitional change in the augmentation of gene expression by the Epo enhancer in hypoxia is discussed.

Base Sequence↗
PubMed1999

Raman spectroscopic study of changes in fish actomyosin during setting.

Actomyosins (AMs) isolated from tilapia, lemon sole, ling cod, and rock fish were heated at 40 degrees C, and structural changes in AMs were investigated using Raman spectroscopy to elucidate low-temperature gelling phenomenon, that is, "setting", of surimi. The following conformational transitions were observed in lemon sole, ling cod, and rock fish gels during setting: a slow unfolding of alpha-helix and exposure of hydrophobic amino acid residues occurring in long-time incubation at 40 degrees C, thereby forming hydrophobic interactions among AM molecules. In addition, the most frequent conformation in disulfide bonds was gauche-gauche-trans (g-g-t) form in the set gel. On the other hand, tilapia AM did not form a gel with heating at 40 degrees C, its alpha-helical structure in the myosin being far more stable than that of the other species. The heat resistance of the tight alpha-helix may prevent the gelation of tilapia AM. It is, therefore, likely that the unfolding of the alpha-helix of myosin is a prerequisite for gelation of AM during setting.

Actomyosin↗
PubMed1999

Suppression of ethanol-induced apoptotic DNA fragmentation by geranylgeranylacetone in cultured guinea pig gastric mucosal cells.

The purpose of this study was to elucidate the molecular mechanism of action of geranylgeranylacetone, an antiulcer drug. Treatment with ethanol for 8 hr at the optimum concentration (7.5%) caused apoptotic DNA fragmentation in cultured guinea pig gastric mucosal cells. Pretreatment of cells with geranylgeranylacetone suppressed the DNA fragmentation in a dose-dependent manner. The maximum effect was achieved at 10(-6) M, at which concentration the drug was previously shown to induce heat-shock proteins. The suppression required an incubation period longer than 1 hr. Pretreatment of cells with low concentrations of ethanol also prevented DNA fragmentation.

Animals↗
PubMed1999

Displacement and stress distribution in the temporomandibular joint during clenching.

The aim of this study was to analyze biomechanical reactions in the mandible and TMJ during clenching under various restraint conditions. A three-dimensional finite element model of the mandible, including the TMJ, was created for test purposes. The results were as follows: (1) Under any restraint conditions, displacement was greatest on the surface of the condyle and less on the articular disc and the surface of the glenoid fossa, in that order. Resultant stresses followed the same trend. (2) Displacement and stress were greatest when the lower central incisor was restrained and attenuated as the posterior teeth were restrained. Because the biomechanical reaction of the TMJ during clenching was greatest when the lower central incisor was restrained, premature contact of these teeth may be one of the factors involved in the initiation of temporomandibular arthrosis.

Biomechanical Phenomena↗
PubMed1999

Pancreatic endocrine carcinoma with multiple hormone production in a raccoon (Procyon lotor).

A pancreatic endocrine carcinoma with lung metastases was found in a 15-year-old male raccoon. This tumour was characterized by great variation in cell size and production of multiple polypeptide hormones. Endocrine markers expressed by the neoplastic cells were, in descending order of frequency, chromogranin A, pancreatic polypeptide (PP), glucagon, somatostatin and insulin. Co-expression of PP and glucagon, somatostatin or insulin was demonstrated immunohistochemically with consecutive sections, and cells with both glucagon and insulin were also observed. The pattern of co-expression was similar to that in the earliest stages of murine pancreatic development. Amyloid deposits in the islets of Langerhans, which reacted with antibody to islet amyloid polypeptide, were thought to be associated with age.

Animals↗
PubMed1999

Purification and characterization of a novel isoform of myosinase from spear squid liver.

A novel isoform of myosinase was purified to homogeneity from liver of spear squid by sequential chromatographies using SP Sephadex, hydroxylapatite, Zn/Co chelating affinity, and TSK-gel G2000SW columns. Myosinase activity was detected as a single peak of 45-kDa protein by gel filtration. The novel isoform of myosinase specifically hydrolyzed a rabbit skeletal muscle myosin heavy chain into products of 120 and 100 kDa in the presence of Co(2+) ions, and the cleavage site in the myosin heavy chain was quite different from those of two known myosinase isoforms, I and II. Therefore, we named the novel isoform myosinase III. Myosinase III was also distinguishable from myosinase I by its amino-terminal sequence. The sequence showed similarity to an internal sequence of the astacin family.

Amino Acid Sequence↗
PubMed1999

Dynamic light-scattering and preliminary crystallographic studies of the sensor domain of the haem-based oxygen sensor FixL from Rhizobium meliloti.

FixL is a transmitter protein in a two-component system which acts as an oxygen sensor when the symbiotic Rhizobia resides in root nodules of host plants. The oxygen-sensor domain of Rhizobium meliloti FixL (RmFixLH) was purified by His-tag affinity and isoelectronic focusing chromatographies, without the use of gel-filtration chromatography. Dynamic light-scattering measurements of RmFixLH thus obtained revealed it to be monodispersive and present as a homodimer in solution. A single crystal of RmFixLH in the met (Fe3+) form was grown in 100 mM acetic acid/NaOH buffer at pH 4.6 in the presence of 200 mM ammonium acetate, using 40%(w/v) PEG 4000 as a precipitant. A crystal of the ferrous CO form of RmFixLH was also prepared by reduction of the met crystal with Na2S2O4 in an atmosphere of CO. The crystals (0.2 x 0.05 x 0.01 mm) belong to the monoclinic system (C2) with unit-cell parameters a = 60.94, b = 37.44, c = 54.14 A, beta = 115.29 degrees and diffract X-rays to 1.7 A resolution at station BL44B2 of SPring-8, Japan. Bijvoet difference Patterson maps show a clear peak corresponding to the haem iron in RmFixLH.

Bacterial Proteins↗
PubMed1999

Atrial ectopy originating from the posteroinferior atrium during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia.

Atrial ectopy sometimes appears during RF ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examine these issues, we analyzed 67 consecutive patients with AVNRT (60 with slow-fast AVNRT and 7 with fast-slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patients. During successful RF ablation, junctional ectopy with the activation sequence showing H-A-V at the His-bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A-H-V at the His-bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 patients) or without junctional ectopy (5 patients). Before RF ablation, retrograde slow pathway conduction induced during ventricular burst and/or extrastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.001). Successful ablation site in group A was distributed between the His-bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coronary sinus ostium. In group B, atrial ectopy also appeared in 21% of the unsuccessful RF ablations. In conclusion, atrial ectopy is relatively common during slow pathway ablation and observed in 8% of RF applications overall and 22% of RF applications that successfully eliminated inducible AVNRT. Atrial ectopy appears to be closely related to successful slow pathway ablation among patients with manifest retrograde slow pathway function.

Adult↗
PubMed1999

Expression in Escherichia coli of a new multidrug efflux pump, MexXY, from Pseudomonas aeruginosa.

Two new genes (mexXY) similar to mexAB, mexCD, and mexEF and mediating multidrug resistance were cloned from the chromosome of Pseudomonas aeruginosa. Elevated ethidium extrusion was observed with Escherichia coli cells harboring the plasmid carrying mexXY. This MexXY system confers higher resistance to fluoroquinolones than the MexAB and MexCD systems, and E. coli ToIC or P. aeruginosa OprM is necessary for the function of the MexXY system.

Bacterial Outer Membrane Proteins↗
PubMed1999

Marked reduction in the minimum inhibitory concentration (MIC) of beta-lactams in methicillin-resistant Staphylococcus aureus produced by epicatechin gallate, an ingredient of green tea (Camellia sinensis).

We found that epicatechin gallate, a constituent of an extract of tea leaves (green tea) markedly lowered the minimum inhibitory concentration (MIC) of oxacillin and other beta-lactams, but not of other antibacterial agents tested, in strains of methicillin-resistant Staphylococcus aureus. The antibacterial action of epicatechin gallate plus oxacillin was a bactericidal one.

Anti-Bacterial Agents↗