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Biomedical subjects

Y Nishida

Publications and source records attributed to Y Nishida.

At least 163 records · Page 9Linked to original sources
PubMed1997

The role of magnetic resonance cholangiopancreatography (MRCP) after resection of the pancreas.

Magnetic resonance cholangiopancreatography (MRCP) was performed in 35 patients to evaluate the feasibility of its use as a postsurgical imaging technique after resection of the pancreas. The surgical procedures performed were: pancreatoduodenectomy in 22 patients, segmental pancreatectomy in 1, distal pancreatectomy in 7, and pyrolus-preserving pancreatoduodenectomy in 5. The pancreatic duct was shown in its entirety in 24 of the 35 patients (68.6%) and was partially visualized in 8 patients (22.9%), but the intrahepatic and extrahepatic bile ducts were visualized completely in all patients. Furthermore, MRCP was able to demonstrate lesions in 3 of 6 patients who had shown clinical evidence of recurrence. The visualization of the pancreatic and bile duct system was satisfactory despite anatomical changes brought about by resection of the pancreas. Thus, we conclude that MRCP is an appropriate follow-up screening test for patients with suspected abnormalities of the biliary and pancreatic duct system.

Aged↗
PubMed1997

Effects of NMDA and its antagonists on ventral horn cholinergic neurons in organotypic roller tube spinal cord cultures.

Neurotoxic effects of excitatory amino acid (EAA) receptor agonist N-methyl-D-aspartic acid (NMDA) and its antagonists on ventral horn cholinergic neurons were studied in organotypic rollertube cultures of spinal cord (OTC-SCs) using biochemical assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity, and AChE histochemistry. NMDA exposure decreased ChAT and AChE activity by 83% and 66%, respectively. Cultures treated with NMDA also showed a marked loss of AChE staining in both dorsal and ventral horns and a significant, dose-dependent decrease in the number of ventral horn AChE-positive neurons (VHANs). NMDA treatment primarily resulted in the loss of small VHANs (< 300 microns2). VHANs with a size and distribution typical of alpha-motoneurons were relatively well preserved. The effects of NMDA on OTC-SCs appeared to be independent of the age of the cultures. The NMDA antagonist DL-AP5 completely prevented the NMDA-induced loss of ChAT activity, but only attenuated the effect of NMDA on ChE activity. The antagonists DL-AP5, D-AP5 and MK-801, used alone, caused significant loss and/or shrinkage of VHANs. These effects appeared to be distinct from the NMDA mediated toxicity. The results indicate that NMDA and its antagonists exert powerful toxic effects on ventral horn cholinergic neurons. The large cholinergic alpha-motoneurons, however, appear to be relatively immune to these toxic effects.

Acetylcholinesterase↗
PubMed1997

Modulation of cardiac interstitial noradrenaline levels through K(ATP) channels during ischemic preconditioning in rabbits: comparison of the effect of anesthesia between pentobarbital and ketamine + xylazine.

In rabbits, both the stimulation of alpha1-adrenoceptors and ischemic preconditioning (PC) reduce infarct size. One candidate for the mechanism of PC is noradrenaline (NA), which stimulates alpha1-adrenoceptors in the myocardium during PC. Opening of the K(ATP) channel is considered to be another candidate for PC, since a K(ATP) channel blocker, glibenclamide, blocks the infarct size-reducing effect of the PC of 5-min ischemia and 5-min reperfusion in rabbits anesthetized with ketamine + xylazine. However, in rabbits anesthetized with pentobarbital, the infarct size-reducing effect of PC was not blocked by glibenclamide. The effect of glibenclamide on the PC effect thus differs depending on the anesthesia used. Therefore, we speculated that the increase in cardiac interstitial NA levels induced by PC may be modified by the anesthesia used, thus regulating the effect of glibenclamide on the PC effect. In open-chest Japanese white male rabbits anesthetized with pentobarbital or ketamine + xylazine, myocardial interstitial NA levels were measured before and during the PC of 5-min ischemia and 5-min reperfusion in the presence or absence of the K(ATP) channel blocker, glibenclamide (0.3 mg/kg, i.v.), using a microdialysis technique. The NA levels were measured using high-performance liquid chromatography coupled with electrochemical detection. The PC of 5-min ischemia and 5-min reperfusion significantly elevated the interstitial NA level. This increase in the NA level was not blocked by glibenclamide under anesthesia with pentobarbital. Under anesthesia with ketamine + xylazine, the PC did not cause an increase in the myocardial interstitial NA level in either the absence or the presence of glibenclamide. In conclusion, PC elevates the myocardial interstitial NA level, and this elevation is not mediated through the opening of the K(ATP) channel under anesthesia with pentobarbital. Under anesthesia with ketamine + xylazine, PC does not cause an increase in the myocardial interstitial NA level. This may explain the discrepancy in the blocking effect of glibenclamide on the infarct size-reducing effect of PC between anesthesia with pentobarbital and ketamine + xylazine.

Adenosine Triphosphatases↗
PubMed1997

Effect of lipoproteins on cultured human mesangial cells.

It was recently reported that low-density lipoprotein (LDL) promotes mesangial cell proliferation, and oxidized LDL is cytotoxic for mesangial cells. However, there have been few studies about the effects of other lipoproteins on mesangial cells. Accordingly, we investigated the effect of various lipoproteins on cultured human mesangial cells using 3H-thymidine (3H-TdR) incorporation and cell counting assays. We also investigated the levels of several cytokines in mesangial cell culture supernatants after stimulation by the lipoproteins. Addition of very-low-density lipoprotein (VLDL) at concentrations up to 100 micrograms/mL, intermediate-density lipoprotein (IDL) at up to 50 micrograms/mL, and LDL at up to 50 micrograms/mL induced the proliferation of cultured human mesangial cells, whereas cell growth was inhibited at higher concentrations. Oxidized LDL caused a concentration-dependent decrease of 3H-TdR incorporation. High-density lipoprotein (HDL) had no proliferative effective effect at any concentration. Exposure to VLDL, IDL, LDL, or a high concentration of HDL enhanced the secretion of interleukin-6, platelet-derived growth factor, and transforming growth factor-beta by mesangial cells, whereas tumor necrosis factor-alpha secretion was stimulated by oxidized LDL. These finding indicate that triglyceride (TG)-rich lipoproteins (VLDL and IDL) promote mesangial cell proliferation as well as LDL, whereas oxidized LDL has the reverse effect. These effects of lipoproteins may be related to modulation of various cytokines. Accordingly, TG-rich lipoproteins, LDL, and oxidized LDL may be involved in mesangial cell proliferation and injury in patients with mesangial proliferative glomerulonephritis.

Analysis of Variance↗
PubMed1997

Conditional immortalization of hair cells from the inner ear.

The aim of this work was to culture conditionally immortalized cells that possess the potential to differentiate into mechanosensory hair cells. Utricular epithelia at embryonic stage E16 were cultured from the vestibular system of the H2kbtsA58 transgenic mouse (Immortomouse) that carries a conditionally expressed immortalizing gene derived from the simian virus 40. Immunolabelling showed that the immortalizing transgene product, the T antigen (Tag), was expressed in utricular cells under permissive conditions and that it was inactivated under non-permissive conditions. Several morphologically distinct cell types proliferated when Tag was expressed, including those that resembled fibroblasts, nerve cells and epithelial cells. Mixed cultures of cells from the utricle, passaged up to 50 times every 3-4 days over a period of 5 months, were subsequently allowed to differentiate for 10 days by transferring them to non-permissive conditions. Monoclonal antibody markers were used to locate expression of hair cell specific antigens. One antibody that normally labels stereociliary bundles from postnatal stage P4-6 labelled cellular projections from a population of spheroid cells that were distributed across the culture surface. A second antibody that normally labels stereociliary bundles did not label the same structures. We conclude that utricular hair cell progenitors can be derived from the H2kbtsA58 transgenic mouse but that under the experimental conditions used they do not follow the normal pattern of differentiation.

Animals↗
PubMed1997

Dominant mutations of Drosophila MAP kinase kinase and their activities in Drosophila and yeast MAP kinase cascades.

Eight alleles of Dsor1 encoding a Drosophila homologue of mitogen-activated protein (MAP) kinase kinase were obtained as dominant suppressors of the MAP kinase kinase kinase D raf. These Dsor1 alleles themselves showed no obvious phenotypic consequences nor any effect on the viability of the flies, although they were highly sensitive to upstream signals and strongly interacted with gain-of-function mutations of upstream factors. They suppressed mutations for receptor tyrosine kinases (RTKs); torso (tor), sevenless (sev) and to a lesser extent Drosophila EGF receptor (DER). Furthermore, the Dsor1 alleles showed no significant interaction with gain-of-function mutations of DER. The observed difference in activity of the Dsor1 alleles among the RTK pathways suggests Dsor1 is one of the components of the pathway that regulates signal specificity. Expression of Dsor1 in budding yeast demonstrated that Dsor1 can activate yeast MAP kinase homologues if a proper activator of Dsor1 is coexpressed. Nucleotide sequencing of the Dsor1 mutant genes revealed that most of the mutations are associated with amino acid changes at highly conserved residues in the kinase domain. The results suggest that they function as suppressors due to increased reactivity to upstream factors.

Alleles↗
PubMed1997

Demonstration of ras and p53 gene mutations in carcinomas in the forestomach and intestine and soft tissue sarcomas induced by N-methyl-N-nitrosourea in the rat.

The presence of ras family and p53 gene mutations in rat forestomach, intestine and liver tumors and soft tissue sarcomas induced by N-methyl-N-nitrosourea (MNU) was examined using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) followed by direct sequencing analysis. In the forestomach squamous cell carcinomas (SCC), Ha-ras and p53 mutations were detected in 2 (40%) and 4 (80%) of 5 cases, respectively. The figures for Ki-ras and p53 gene mutations in adenocarcinomas of the large and small intestines were 3 (18.8%) and 5 (31.3%) of 16 cases. Soft tissue sarcomas in different sites were found to have mutations of Ki-ras in 7 (23.3%) and of p53 in 9 (30%) of 30 cases. One forestomach SCC and 2 soft tissue sarcomas had double p53 mutations in different exons. Single cases of forestomach SCC and intestinal adenocarcinoma had mutations in both Ki-ras and p53 genes. No mutations were found in counterpart benign tumors or hepatocellular adenomas. The p53 mutation spectrum revealed preferential clustering within exon 8 for the forestomach SCCs, and exons 5 and 8 for the intestinal adenocarcinomas, whereas the distribution was evenly spread through exons 5 to 8 in soft tissue sarcomas. All the detected ras or p53 mutations were G:C to A:T transitions. These results indicate firstly that specific Ki-ras, Ha-ras and p53 gene mutations in MNU-induced lesions are related to particular alkylation sites (G:C to A:T transitions) and secondly, although not essential, Ki-ras, Ha-ras or p53 gene mutations may be involved in the progression stage of forestomach, intestine and soft tissue neoplasms induced by MNU.

Adenocarcinoma↗
PubMed1997

Low-density lipoprotein apheresis for focal glomerular sclerosis.

We report on a 22-year-old female with focal glomerular sclerosis and hyperlipidemia who did not respond to long-term steroid or immunosuppressant therapy. When low-density lipoprotein (LDL) apheresis was performed, her total daily protein excretion decreased, serum albumin increased, total cholesterol decreased from 1,052 mg/dl to 148 mg/dl after 3 months, and the serum lipoprotein(a) level also decreased from 117.8 mg/dl to 9.1 mg/dl. After this therapy, her clinical course was well maintained. By controlling hyperlipidemia, including oxidized low-density lipoprotein and lipoprotein(a), low-density lipoprotein apheresis may produce clinical improvement in focal glomerular sclerosis.

Adult↗
PubMed1997

Fos induction in rat brain neurons after stimulation of the hepatoportal Na-sensitive mechanism.

Responses of hepatic afferent nerves to intraportal bolus injection of hypertonic solutions were examined in anesthetized rats. Hepatic afferent nerve activity increased in response to an intraportal injection of 0.75 M NaCl or NaHCO3 but did not respond to a similar injection of 1.5 M mannitol, 0.75 M LiCl, or 0.15 M NaCl, implying that nerves in the hepatoportal area are sensitive to increases in Na concentrations and that this leads to stimulation of hepatic afferent nerve activity. To study central activation in response to stimulation of the hepatic Na-sensitive mechanism, c-fos induction was monitored. After electrical stimulation of hepatic afferent nerves, neurons containing Fos-like immunoreactivity (Fos-li) were found in the area postrema, nucleus of the solitary tract, paraventricular hypothalamic nucleus, and supraoptic nucleus at 90 min after stimulation. Induction of Fos-li was also studied after simultaneous infusion of 0.45 M NaCl into the portal vein and distilled water into the inferior vena cava in conscious rats so as to keep the total amount of solution introduced into the systemic circulation isotonic, thus avoiding changes in mean arterial pressure, plasma osmolality, and plasma NaCl concentrations. Fos-li-containing neurons were found in the same regions in which they were found after electrical stimulation. However, few, if any, Fos-li-containing cells were found if the rats were hepatically denervated or if they received an intraportal infusion of hypertonic LiCl or mannitol. These data provide evidence for involvement of the brain stem and forebrain structures in NaCl regulatory functions induced by stimulation of the hepatoportal Na-sensitive mechanism. However, stimulation of the hepatoportal osmosensitive mechanism does not activate these central structures.

Afferent Pathways↗
PubMed1997

Long-term effects of AVP-induced neurohumoral interaction via area postrema on body fluid and blood pressure.

Arginine vasopressin (AVP) has been known to interact with the central nervous system via the area postrema (AP), resulting in suppression of renal sympathetic outflow in short-term studies. We hypothesize that if this sympathoinhibitory effect lasts long, then the neurohumoral interaction would enhance urinary output because of the suppression of neurogenic reuptake of sodium (Na+) and water. Intact (Int) and AP-lesioned (APX) rabbits were chronically catheterized and housed in metabolic cages. AVP was intravenously infused (0.1 mU.kg-1.min-1) for 5 consecutive days. Urine volume and urinary Na+ excretion rates in Int rabbits were lower than those in APX rabbits during AVP infusion. This smaller urinary output in Int rabbits was reconfirmed either from the daily balance of water and Na+ or from the body weight, plasma Na+ concentration, and plasma osmolality data. This result contradicted the hypothesis. Mean arterial pressure was not altered in either group of rabbits while heart rate was suppressed in the Int rabbits. These data suggest that AP-mediated long-term action of AVP augments water retention and sustains bradycardia.

Animals↗
PubMed1997

Remnant-like particle cholesterol may indicate atherogenic risk in patients on chronic hemodialysis.

Recently, involvement of remnant-like particle cholesterol (RLP-C) in atherosclerosis was reported, but this parameter has not been adequately investigated in hemodialysis (HD) patients. The present study investigated the relationship between the RLP-C level and total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), lipid peroxides (malone dialdehyde, MDA), apolipoprotein (Apo) A-I, and ApoB. In addition, the fractions of very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), LDL, and HDL in serum lipoproteins were determined by disk polyacrylamide gel electrophoresis. The relationship between the RLP-C level and three atherogenic indices was also studied. The RLP-C level in HD patients (8.2 +/- 6.7 mg/dl) was significantly higher than that in normal controls (2.7 +/- 1.3 mg/dl). The RLP-C level showed a significant positive correlation with the levels of TC, TG, LDL-C, MDA, ApoB, VLDL(%), and IDL(%), as well as a negative correlation with HDL(%). However, there was no correlation with age or the duration of HD. RLP-C also showed significant positive correlations with the (TC -HDL-C)/HDL-C ratio and the (VLDL + LDL)/HDL ratio, as well as a negative correlation with the ApoA-I/ApoB ratio. These results suggest that RLP-C may be a potential indicator of atherogenic risk in HD patients.

Adult↗
PubMed1997

Absence of myocardial 123I-BMIPP uptake in the presence of a normal coronary angiogram and normokinetics on a left ventriculogram.

We present the case of a 44-year-old man with abnormal myocardial fatty acid metabolism who exhibited no myocardial uptake of 123I-beta-methyl- iodophenyl pentadecanoic acid (123I-BMIPP). This patient presented to our hospital with an ECG abnormality detected during a medical check-up. He felt no chest discomfort, but a 12-lead ECG at rest showed flat T-waves in leads I, V5, and V6 with no marked ischemic changes during exercise. A left ventriculogram and coronary angiograms were normal. Thallium-201 single photon emission computed tomography imaging revealed a normal myocardial uptake, but 123I-BMIPP imaging showed no such uptake. However, 18F-labelled fluorodeoxyglucose positron emission tomography imaging after an overnight fast showed a marked increase in myocardial uptake. It appears that myocardial uptake of 123I-BMIPP was totally lacking and that energy production by the myocardium during fasting depended on the metabolism of glucose rather than of fatty acids.

Adult↗
PubMed1997

Bioavailability of ruminally protected sulfamethoxazole after oral administration in ruminating calves.

Bioavailabilities of oral rumen-protected and non-protected formulations of sulfamethoxazole (SMS) were compared in ruminating calves, since in vitro degradation of SMX in ruminal fluid was confirmed. The coated with a gastric-acid-soluble polymer and uncoated formulations were administered to 3 calves through a catheter. Neither formulation could produce sufficient blood concentration of the drug, though the bioavailability of SMX for the coated formulation was higher than that for the uncoated formulation. It was suggested that the rumen-protected drug could improve the bioavailability by escaping from degradation in the rumen, but scarcely attain the effective levels in blood.

Administration, Oral↗
PubMed1997

Occurrence of subtypes of gustatory cells in cat circumvallate taste buds.

Transmission-electron microscopy of cat taste buds confirmed that, as in other mammals, each taste bud comprised four distinct types of cells: Type I, Type II, Type III (gustatory), and Type IV (basal) cells. Gustatory cells made synaptic contacts with nerves to which synaptic vesicles were gathered. The following are the main findings on the cat gustatory cells: 1) The synaptic vesicles of gustatory cells were essentially all dense-cored in type; small clear vesicles, which usually are intermingled in other mammals, could not be found. 2) The vesicles were accumulated not only in the synaptic area but also in the basal cytoplasm. This implies endocrine and paracrine functions. 3) On the basis of the fine structure of the vesicles, two subtypes of gustatory cells were discriminated. A large part of the cells contained vesicles measuring about 180 nm in diameter, while a small part had smaller ones of about 100 nm in diameter. This is the first demonstration of a dual population of gustatory cells in mammals, suggesting different messenger substances utilized.

Animals↗
PubMed1997

[Emergency coronary artery bypass grafting using the internal thoracic artery graft after percutaneous transluminal coronary angioplasty in a patient with left main coronary artery disease associated with acute myocardial infarction].

A 66-year-old woman suffering acute myocardial infarction developed cardiogenic shock during urgent coronary angiography, which demonstrated a subtotal occlusion of the left main coronary artery and the triple-vessel coronary artery disease. The patient survived, after prompt percutaneous transluminal coronary angioplasty for the left main coronary artery disease, followed by emergency triple-vessel coronary artery bypass grafting using the internal thoracic artery graft for the left anterior descending artery. Postoperative angiography demonstrated well patent bypass grafts with good preservation of left ventricular function.

Aged↗