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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 433 records · Page 24Linked to original sources
PubMed1992

Effects of epidermal growth factor and transforming growth factor-beta on insulin-induced differentiation in rat dental pulp cells.

An established pulp cell line (RPC-C2A) was used to study the regulatory effect of insulin on dentinogenesis. Insulin increased alkaline phosphatase activity and the incorporation of [2,3-3H]-proline into collagenase-digestible protein, whereas [3H]-thymidine incorporation by the cells was inhibited by insulin. The enhancing effect of insulin on alkaline phosphatase activity was inhibited by epidermal growth factor (EGF) or transforming growth factor-beta (TGF-beta). The stimulatory effect of insulin on collagen synthesis was also inhibited when insulin was combined with EGF, but was accelerated by the addition of TGF-beta. Inhibitory effects of insulin on the [3H]-thymidine incorporation were potentiated by EGF, though EGF alone strongly increased the effect; whereas the addition of TGF-beta had no significant effect on the insulin action. These findings suggest that insulin may be concerned with the differentiation of pulp cells in dentinogenesis and that EGF or TGF-beta regulate the insulin effects.

Alkaline Phosphatase↗
PubMed1992

Lack of effect of islet amyloid polypeptide on hepatic glucose output in the in situ-perfused rat liver.

Islet amyloid polypeptide (IAPP), a novel peptide isolated from islet amyloid deposits in patients with insulinoma and non-insulin-dependent diabetes mellitus (NIDDM), has been reported to be cosecreted with insulin from pancreatic beta cells and to inhibit glucose uptake and glycogen synthesis in muscle tissue in vitro. We investigated the effects of the synthesized, rat-amidated form of IAPP on hepatic glucose output, and IAPP extraction, using an in situ flow-through perfusion system in rats to elucidate the actions of IAPP on the liver. The IAPP (10(-8) mol/L) alone had no effects on the hepatic glucose release. Infusion of 6 x 10(-11) mol/L glucagon alone resulted in an expected elevation in glucose production (30.0 +/- 1.7 mumol/35 min/g liver). Insulin (3 x 10(-10) mol/L) submaximally decreased the glucagon-stimulated glucose production to 73% (from 30.0 +/- 1.7 to 22.0 +/- 1.4 mumol/35 min/g liver; n = 7, P less than .01). A simultaneous infusion of 10(-8) mol/L IAPP did not influence the glucagon-stimulated glucose production (27.6 +/- 1.2 mumol/35 min/g liver) or the insulin-dependent inhibition of glucagon-stimulated glucose production (22.6 +/- 1.3 mumol/35 min/g liver). IAPP extraction by the liver in a single passage was minimal, in contrast to approximately 50% hepatic insulin extraction. These results indicate that IAPP does not play any important role in modulating glycogen metabolism in the liver.

Amyloid↗
PubMed1992

Giant basal prolactinoma extending into the nasal cavity.

An unusual case of a giant prolactinoma extending to the nasopharynx and nasal cavity is presented. A 35-year-old man admitted for nasal obstruction and visual disturbances was found to have bilateral anosmia, right homonymous hemianopsia, and a right hemiparesis. The serum prolactin level was 13,300 ng/mL. Radiological examination revealed a large mass invading the skull base and extending into the suprasellar region and the left frontal lobe superiorly and into the nasopharynx inferiorly. Subtotal removal was done through a bilateral orbitofrontal craniotomy, which was followed by radiotherapy and bromocriptine administration. Immunohistochemical analysis confirmed a prolactinoma. The rarity of such a tumor, its location and extension, and the usefulness of magnetic resonance imaging and immunohistochemistry are stressed. Pertinent literature is reviewed.

Adult↗
PubMed1992

Architectural distortion of subcutaneous fascial layer in breast tumors: ultrasonographic evaluation.

To develop a criterion to evaluate architectural changes of the subcutaneous tissue layer around the breast, 120 patients with histologically proven tumors were studied as to ultrasonographical delineation of the superficial layer (SL) of the superficial fascia. Breast ultrasonography was performed using an electronic-linear scanner with a 5.0 MHz probe. When SL was identified over the tumor, it was classified into 3 types: flat, disrupted, and convergent types. SL was identified in 106 patients (88%). Forty-six were evaluated to be flat type, and 41 (89%) of them had benign tumors. The remaining 60 were subdivided into either disrupted (n = 44) or convergent type (n = 16); 53 (88%) of these 60 cases had cancerous lesions. Histologically, inward retraction of SL was the most common pattern in breast cancer. Thus, the ultrasonographic pattern of SL reflects the histological findings and can be a useful clue to differentiate benign lesions from cancerous ones.

Adult↗
PubMed1992

Equivalence between adenosine and exercise thallium-201 myocardial tomography: a multicenter, prospective, crossover trial.

OBJECTIVES: The study was designed to compare pharmacologic and exercise stress during thallium-201 single-photon tomography in a multicenter prospective crossover trial. BACKGROUND: Both exercise and adenosine myocardial perfusion imaging have high sensitivity and specificity for detection of coronary artery disease. However, few data are available comparing these two stress tests in the same patients. METHODS: The study group consisted of 175 subjects: 55 healthy volunteers and 120 patients with suspected coronary artery disease. All subjects underwent two thallium tomographic tests performed 30 days apart, one during intravenous administration of adenosine (140 micrograms/kg per min for 6 min) and one during exercise stress. All images were computer quantified and interpreted without knowledge of the stress test performed. Interpretation agreement was assessed by kappa and Z statistics. RESULTS: Agreement on the presence of normal or abnormal tomograms by adenosine and exercise scintigraphy was 82.8% by visual analysis with kappa and Z statistics of 0.65 (p less than 0.0001) and 11.1 (p less than 0.00001), respectively. The agreement by computer quantification was 86% with kappa and Z statistics of 0.709 (p less than 0.0001) and 12.2 (p less than 0.00001), respectively. Agreement on localization of the perfusion defect to a specific coronary vascular territory varied from 82.7% to 91.4% with highly significant kappa and Z statistics (p less than 0.0001). There was a good correlation between quantified perfusion defect size by adenosine and exercise (r = 0.80, p less than 0.0001), but the values for defect size were significantly greater by adenosine scintigraphy (p = 0.0073). Adenosine side effects were frequent but transient and ceased spontaneously in most subjects within 1 to 2 min after the infusion was discontinued. CONCLUSIONS: Adenosine thallium-201 scintigraphy provides diagnostic information similar to that of exercise scintigraphy, although values for defect sizes are greater with adenosine.

Adenosine↗
PubMed1992

Effects of acute, transient coronary occlusion on global and regional right ventricular function in humans.

OBJECTIVES: The aim of this study was to investigate the changes in right ventricular function during acute coronary occlusion produced by inflating a coronary angioplasty balloon catheter. BACKGROUND: Alterations in right ventricular function are well known to occur in patients with acute myocardial infarction or ischemic cardiomyopathy. However, the changes in right ventricular function resulting from acute, transient coronary occlusion of each of the major coronary arteries have been scantily studied, perhaps because of serious limitations of currently available technology. METHODS: A newly designed, mobile, multiwire gamma camera, in combination with generator-produced tantalum-178, affords high count rate first-pass radionuclide angiography and is thus ideal for studying right ventricular function at the bedside. Accordingly, 46 patients underwent first-pass radionuclide angiography at baseline and during transient coronary occlusion induced by a coronary angioplasty balloon catheter. RESULTS: A significant, albeit modest, decrease in global right ventricular ejection fraction occurred during occlusion of the left anterior descending (from 42.9 +/- 9.3% to 39 +/- 8.7%, p < 0.05) and left circumflex (from 44 +/- 9.1% to 38.8 +/- 7.9%, p = 0.03) coronary arteries, but diagonal artery occlusion caused no significant change in right ventricular ejection fraction. Occlusion of the right coronary artery proximal (but not distal) to the acute marginal branch caused a significant decrease in right ventricular ejection fraction (from 42.6 +/- 4.7% to 35.7 +/- 7.2%, p < 0.01). Although occlusion of the left anterior descending, left circumflex and proximal right coronary arteries all caused significant deterioration in regional right ventricular function, only proximal right coronary occlusion caused right ventricular dilation (p < 0.005). CONCLUSIONS: Significant impairment of right ventricular function occurs during transient occlusion of the left anterior descending, left circumflex and proximal right coronary arteries, but only occlusion of the latter causes acute right ventricular dilation, probably as a result of ischemia.

Adult↗
PubMed1992

Quantification of left ventricular performance during transient coronary occlusion at various anatomic sites in humans: a study using tantalum-178 and a multiwire gamma camera.

To study the functional significance of transient coronary occlusion on systolic and diastolic left ventricular function relative to the anatomic site of occlusion, first-pass radionuclide angiography with a mobile multiwire gamma camera using tantalum-178 (dose activity less than or equal to 84 mCi/elution) was performed in 46 patients undergoing balloon coronary angioplasty. First-pass images were acquired immediately before angioplasty and during the last 30 s of a 60-s balloon inflation in 23 left anterior descending arteries, 18 right coronary arteries, 8 circumflex arteries and 3 diagonal coronary arteries. Occlusion of the left anterior descending artery resulted in significant decreases in left ventricular ejection fraction (54.6 +/- 12.7% to 32.3 +/- 10.6%, p = 0.0001) and peak filling rate (2.48 +/- 0.68 to 1.75 +/- 0.64 end-diastolic volumes/s, p = 0.0001), accompanied by severe abnormalities in regional function and left ventricular dilation. Right coronary artery occlusion caused inferior hypokinesia, but did not significantly change left ventricular ejection fraction (48.5 +/- 12.4% vs. 45.8 +/- 12.5%, p = NS) or peak filling rate (2.05 +/- 0.81 vs. 2.09 +/- 0.81 end-diastolic volumes/s, p = NS). Circumflex artery occlusion resulted in mild wall motion deterioration and a borderline decrease in ejection fraction (54.7 +/- 11.4% to 50.5 +/- 12%, p = 0.057). Diagonal artery occlusion did not cause significant changes in left ventricular ejection fraction or filling rate. The decrease in left ventricular ejection fraction during coronary occlusion was 9 +/- 25% and 27 +/- 22%, respectively, in those arteries with and without collateral supply (p = 0.052). These data provide strong evidence for the critical importance of the left anterior descending artery and the secondary role of the other coronary arteries in maintaining global systolic and diastolic left ventricular function and suggest a protective role of collateral vessels during coronary occlusion.

Angioplasty, Balloon, Coronary↗
PubMed1992

Protection of DNA damage by dietary restriction.

Dietary restriction is known to retard the aging processes and delay the onset of age-related neoplastic diseases. The mechanisms underlying these remarkable actions of nutritional intervention are not known in spite of recently intensified research efforts. However, the last couple of years' research on dietary restriction produced strong evidence indicating that its effective antiaging actions might be related to its ability to modulate free radical damage. In the present study, DNA damage and attenuation of the damage by dietary restriction were assessed by measuring 8-hydroxydeoxyguanosine 8-OH dG) in both nuclear DNA (nuDNA) and mitochondrial DNA (mitDNA) fractions. The data show that substantially more damage (approximately 15 times) occurred in mitDNA compared to nuDNA. More interestingly, the DNA damage was significantly attenuated in dietarily restricted rats.

Animals↗
PubMed1992

Zonisamide blocks T-type calcium channel in cultured neurons of rat cerebral cortex.

We investigated the effect of zonisamide, a new antiepileptic drug, on voltage-dependent Ca2+ currents in cultured neurons of rat cerebral cortex. Whole-cell voltage-clamp recordings demonstrated at least two distinct voltage-dependent Ca2+ currents: (1) a low-threshold, rapidly inactivating component, T-type Ca2+ current, which is sensitive to 100 microM Ni2+, and (2) a high-threshold, slowly inactivating (long-lasting) component, L-type Ca2+ current. Zonisamide, a new anticonvulsant effective against maximal electroshock (MES) seizures in mice reduced T-type Ca2+ current in a dose-dependent manner. The mean percentage of reduction was 59.5 +/- 7.2% at 500 microM, but zonisamide had no effect on L-type Ca2+ current. A methylated analog of zonisamide, which is ineffective against MES seizures in mice, was tested at a concentration of 500 microM, and reduced neither T-type nor L-type Ca2+ current. These findings suggest that the effects of zonisamide against MES seizures might occur through the reduction of T-type Ca2+ current. Because drugs that are effective against MES seizures are thought to prevent seizure discharge spread, T-type Ca2+ channels could underlie a cellular mechanism of spreading activity in epileptic seizures.

Action Potentials↗
PubMed1992

Mutations in transmembrane domain of c-erbB-2 gene in human malignant tumours of the central nervous system.

Point mutations in the transmembrane domain of c-erbB-2 gene in human brain tumours were studied by DNA amplification with the polymerase chain reaction method. Amplified gene fragments in M13 phage vector were cloned, and subsequent nucleotide sequences were determined. Studied specimens were 10 human malignant and 3 human benign tumours of the central nervous system, and a normal human placenta. In malignant tissues, Val-to-Glu mutation that induces transforming activity of c-erbB-2 did not appear to codon 659 of c-erbB-2. In malignant tissues, many other types of mutations appeared in low frequency, either at codon 659 or other positions of the transmembrane domain of c-erbB-2. The ratio of mutated genes to normal genes was very low in all specimens of malignant tumours. The point mutations were not observed in benign brain tumour or normal human placental tissues. The transmembrane domain of c-erbB-2 may have several highly mutable hot spots, where brain tumour tissues show a predilection for point mutation.

Amino Acid Sequence↗
PubMed1992

1H-NMR assignment and secondary structure of human insulin-like growth factor-I (IGF-I) in solution.

Human insulin-like growth factor-I (IGF-I) was studied by two-dimensional 1H-NMR spectroscopy. Resonance assignments were obtained for all the backbone protons and almost all of the sidechain protons of the total 70 amino acid residues, using sequence-specific assignment procedures. The secondary structure elements of human IGF-I were identified by investigation of the sequential and medium range NOEs as a preliminary step in determining the three-dimensional structure of this protein by means of distance geometry calculations. The typical NOEs of d alpha beta(i,i + 3) and d alpha N(i,i + 3), as well as the successive strong NOEs of dNN connectivities and slowly exchanging amide protons confirmed the presence of three helical segments corresponding to the sequence regions, Ala8-Cys18, Gly42-Cys48, and Leu54-Cys61, and the existence of a beta-turn in the Gly19-Gly22 region. Our results definitely indicate that the secondary structure of human IGF-I in solution is consistent with that of insulin in the crystalline state.

Amino Acid Sequence↗
PubMed1992

Clinical application of an active electrode using an operational amplifier.

An active electrode (d10 mm, t6 mm) is presented, that functions as an impedance transformer (an input impedance > 10 G omega, an output impedance < 1 omega) by means of which we can derive surface EMG without any skin preparation and paste. This electrode was compared with a conventional one, and it was ascertained that the electrode could be replaced with the conventional one, and, moreover, it was preferable because it required less preparation time, and was less affected by environmental noise.

Amplifiers, Electronic↗
PubMed1992

Ubiquitous presence in mammalian cells of enzymatic activity specifically cleaving 8-hydroxyguanine-containing DNA.

Here we report the finding of enzymatic activity that specifically cleaves DNA containing 8-hydroxyguanine (oh8Gua) residues in various mammalian cells. To detect this activity, we used a synthetic double-stranded DNA containing a single oh8Gua at a defined position as the substrate, and analyzed the products of enzymatic digestion by polyacrylamide gel electrophoresis. Two cleavage sites near the oh8Gua residue were detected with partially purified fractions from cow brain and rat liver, and also with preparations from all mammalian tissues examined. These results suggest that enzymatic activity for the removal of oh8Gua from DNA is widely distributed in mammalian cells.

Animals↗
PubMed1992

Possible regulation of caffeine-induced intracellular Ca2+ mobilization by intracellular free Na+.

To gain some understanding of the regulatory mechanism involved in caffeine-induced Ca2+ release in adrenal chromaffin cells, we took advantage of the paradoxical observation that removal of divalent cations potentiated the secretory response to caffeine. We measured the concentration of cytosolic free Ca2+ ([Ca]in) in isolated cat chromaffin cells, by fura-2 microfluorometry, to see whether there was any correlation between the secretory response and the rise in [Ca]in. The caffeine-induced [Ca]in rise and catecholamine secretion were increased by treatment of cells with a divalent cation-deficient solution. These potentiated responses were strongly inhibited either by pretreatment with ryanodine, by the reduction of the external Na+ concentration, or by the addition of Ca2+ channel blockers. Removal of divalent cations caused a large rise in the cytosolic free Na+ concentration ([Na]in), which was measured using SBFI microfluorometry. This rise in [Na]in was reduced either by adding Ca2+ channel blockers or by reducing the external Na+ concentration. These results show a good correlation between caffeine-induced Ca2+ release and [Na]in at the time of stimulation, suggesting that caffeine-induced Ca2+ release is regulated by [Na]in.

Animals↗
PubMed1992

Prolongation of canine epidural anesthesia by liposome encapsulation of lidocaine.

The purpose of our study was to produce a long-acting lidocaine by using a liposome that would entrap the drug. Egg yolk phosphatidylcholine and cholesterol were used as liposome materials. After epidural administration, the pharmacodynamics and pharmacokinetics of liposomal and free lidocaine were studied in 20 dogs. Two percent liposomal or free lidocaine (3.0 mL) was injected into the lumbar epidural space. Nerve blocking effects were estimated by measuring somatosensory evoked potentials. Recovery time from the epidural block in the liposomal lidocaine group (170 +/- 49.5 min) was approximately three times longer than that in the free lidocaine group (61 +/- 18.1 min). The areas under the drug concentration-time curves (AUC0-infinity) and time to maximal concentration (Tmax) in the liposomal lidocaine group were significantly larger than those in the free lidocaine group. These results suggest that the prolongation of epidural blockade by liposomal lidocaine is caused by a slow release of the drug from liposomes. The present study suggests that liposomal lidocaine can be used as a long-acting local anesthetic.

Amines↗
PubMed1992

In vitro replication study of modified bases in ras sequences.

DNA templates containing a modified base (O6-methylguanine, 8-hydroxyguanine, xanthine or hypoxanthine) which was located in nucleotide sequences corresponding to the 12th or 61st codon of a ras gene were synthesized and deoxynucleotide incorporation opposite the lesions was investigated. The templates were replicated by Taq DNA polymerase, recombinant rat DNA polymerase beta and mouse DNA polymerase alpha-primase complex. Sequence analysis of the replicated products indicated selective incorporation of nucleotide(s) opposite a modified base, depending on the kind of base and of DNA polymerase. This system is very useful to obtain results of in vitro replication of modified bases in ras sequences.

Animals↗
PubMed1992

A novel cDNA clone for acid invertase in tomato fruit.

The sequence of a novel cDNA clone, Aiv-1, for tomato acid invertase was similar to that of TIV1 (Klann et al., 1992) for the enzyme except for a unique intron-like insertion. It is considered that Aiv-1 is derived from either an alternatively spliced mRNA for an isozyme or a pre-mRNA of TIV1.

Amino Acid Sequence↗