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Biomedical subjects

S Miyoshi

Publications and source records attributed to S Miyoshi.

At least 181 records · Page 10Linked to original sources
PubMed1994

Purification and properties of Saccharomyces cerevisiae cystathionine beta-synthase.

Cystathionine beta-synthase (beta-CTSase), which catalyses cystathionine synthesis from serine and homocysteine, was purified to homogeneity from Saccharomyces cerevisiae. The molecular mass of the enzyme was estimated to be 235 kDa by gel filtration and 55 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, indicating that it is a homotetramer. The N-terminal amino acid sequence of the enzyme perfectly coincided with that deduced from the nucleotide sequence of CYS4, except for the absence of initiation The purified beta-CTSase catalysed cysteine synthesis from serine (or O-acetylserine) and H2S. From this finding, we discuss the multifunctional nature and evolutionary divergence of S-metabolizing enzymes.

Amino Acid Sequence↗
PubMed1994

Structure of vulnibactin, a new polyamine-containing siderophore from Vibrio vulnificus.

A new siderophore named vulnibactin has been isolated from low iron cultures of Vibrio vulnificus, a human pathogen. The structure was established as N-[3-(2,3-dihydroxybenzamido)propyl]-1,3-bis[2-(2-hydroxy-phenyl)- trans-5 - methyl-2-oxazoline-4-carboxamido]propane by a combination of acid hydrolysis, nuclear magnetic resonance spectroscopy and positive fast atom bombardment mass spectrometry. Vulnibactin is characterized as containing one residue of 2,3-dihydroxybenzoic acid as well as two residues of salicylic acid, both of which are involved in the formation of oxazoline rings with L-threonine bound to a norspermidine backbone. In addition, two other compounds with siderophore activity were purified and their structures were also determined. These two compounds provided further support for the structure of vulnibactin.

Amides↗
PubMed1994

Ultrastructure of the main excretory duct epithelium of the female mouse submandibular gland with special reference to sexual dimorphism.

The fine structure of the main excretory duct epithelium (MEDE) of female mouse submandibular gland was investigated by scanning and transmission electron microscopy and the results compared with the previously established structure of male mouse MEDE. A comparative analysis of the subepithelial capillaries of both sexes was also performed. In this pseudostratified epithelium, principal cell-types were observed: types-I, -II, -III and basal cells. This differed significantly from male MEDE, where type-II and -III are absent and type-I cells are the most numerous. The latter cell-type had abundant mitochondria, a few lipid-containing granules, lysosomes in the infra-nuclear cytoplasm and well-developed basal infoldings. These cells were also characterized by abundant glycogen granules throughout the cytoplasm, many profiles of strands of smooth endoplasmic reticulum in the apical region, and lysosomes in the infranuclear region. Type-II cells were the second most numerous. Their most characteristic features were the presence of tubular vesicles which appeared to be invaginated from the plasma membrane, RER, SER, free ribosomes, a few peroxisomes with nucleoids, and primary lysosomes in extremely light cytoplasm. They had many mitochondria throughout the cytoplasm, except in the apical region, a few lipid-containing granules and no basal infoldings. Type-III cells were very few and were characterized by well developed basal infoldings, abundant free ribosomes, RER, SER, vesicles containing moderately dense material, and many lipid-containing granules. They also had many mitochondria throughout the cytoplasm, except apically. Basal cells had a large nucleus and the cytoplasm had few organelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Blockade of ATP-sensitive potassium channels by 5-hydroxydecanoate suppresses monophasic action potential shortening during regional myocardial ischemia.

We tested 5-hydroxydecanoate (5-HD), a specific blocker of ATP-sensitive potassium channels (IK.ATP), to determine if mitigates electrophysiologic changes produced by regional myocardial ischemia in vivo. A sequence of 5-minute occlusion of the distal LAD and 30-minute reperfusion was repeated while recording the monophasic action potential (MAP) and bipolar electrogram (EG) from the epicardial center of the ischemic myocardium in anesthetized dogs. 5-HD (30 mg/kg, i.v.) or glibenclamide (0.15 or 0.3 mg/kg, i.v.) was administered before the third occlusion, and the data were compared to the second occlusion data. 5-HD did not affect baseline MAP duration at 90% and 50% repolarization (APD90, APD50) before LAD occlusion but suppressed occlusion-induced shortening of APD90 (16 +/- 2% during the second occlusion vs. 5 +/- 3% during the third occlusion, n = 8, p < 0.01) and APD50 (16 +/- 3% vs. 10 +/- 3%, n = 8, p < 0.05). Pretreatment with glibenclamide also suppressed occlusion-induced MAP shortening and eliminated an additional effect of 5-HD (n = 3). 5-HD did not affect the occlusion-induced increase in duration and activation time of EG. 5-HD, as well as glibenclamide, suppressed regional ischemia-induced MAP shortening, probably by blocking activation of IK.ATP, without affecting conduction delay. These differential effects of 5-HD on repolarization and conduction during the early phase of regional ischemia might have the potential to suppress reentrant ventricular arrhythmias.

Action Potentials↗
PubMed1994

A study of electrical promontory stimulation in tinnitus patients.

Electrical promontory stimulation relieved tinnitus in 74 (57.4%) of 129 ears (112 patients). There was no significant difference in etiology of tinnitus, age, average audiogram, or tinnitus frequency between patients who responded to electrical stimulation and those who did not. Most patients who did not respond to the initial stimulation trial did not respond to the subsequent trials, suggesting that the initial response to treatment predicts the subsequent response. Patients who did not respond to repetitive treatment were supposed to be under severe stress.

Adolescent↗
PubMed1994

Existence of a novel hemagglutinin having no protease activity in Vibrio mimicus.

The protease elaborated by Vibrio mimicus is known to possess hemagglutinating ability to chicken erythrocytes, the well-known HA/protease. A non-protease hemagglutinin (HA) with strong agglutinating ability towards rabbit erythrocytes was obtained from 32 hr culture supernatant of a pathogenic environmental strain of V. mimicus. This HA (V. mimicus HA: VMHA) appeared stable at relatively higher temperature and agglutinated the erythrocytes from rabbit, guinea pig and mouse but not the erythrocytes from chicken, bovine, horse and sheep. Simple sugars, metal ions and chelating agents failed to inhibit the activity of VMHA. The activity of VMHA was found to be sensitive to digestion by proteolytic enzymes including HA/protease. These results provide evidence for the existence of novel HA other than HA/protease in V. mimicus.

Animals↗
PubMed1994

[Electroconduction system for implantable tinnitus suppressor].

The purpose of this study was to introduce the electroconduction system for an implantable tinnitus suppressor. This system is a modification of the extracochlear implant system, which was developed at Hokkaido University. This system consists of a stimulator and two coils. One of the coils is implanted inside the temporal bone and its size, including the current limiter, is 9 mm long, 6.4 mm wide and 6 mm thick. Another is contained in the plastic case which is used for hearing aids. The efficacy of conduction depends on the wave frequency. The most effective frequency was about 30 kHz. The maximum current required to relieve tinnitus is 100 microA when using this system. The heat emitted from the coil inside the case is so minimal at an intensity of 100 microA as to be negligible systemically. The electromagnetic coupling system works well for more than 4 months in saline.

Cochlear Implants↗
PubMed1994

[A tinnitus case with an implanted electrical tinnitus suppressor].

An electrical tinnitus suppressor, which was developed at Hokkaido University, was implanted in a female tinnitus patient. She had suffered from bilateral chronic otitis media and her bilateral hearing was seriously impaired. The electrical tinnitus suppressor consists of a stimulator, a coil inside the plastic hearing aid case and an implanted coil in the mastoid. The auditory nerve is stimulated at home twice. Using the system, her hearing ability and emotion improved in addition to tinnitus suppression. Her hearing level and tinnitus also improved in the ear contralateral to the stimulated side.

Cochlear Implants↗
PubMed1994

Two components of GABA-induced currents in catfish retinal horizontal cells.

In cone-driven horizontal cells dissociated from the catfish retina, we recorded GABA-induced currents by using a whole-cell voltage-clamp technique. The current consisted of two components. The major component was blocked by picrotoxin, but not by bicuculline, and was identified as a current flowing through the GABAC receptor channel. The second minor component was identified as a current carried by an electrogenic GABA transporter.

Animals↗
PubMed1993

Chemical modification of Vibrio vulnificus metalloprotease with activated polyethylene glycol.

Vibrio vulnificus, an opportunistic human pathogen causing septicemia, produces a metalloprotease which is suspected to be a virulence determinant, but which is labile in vivo due to inactivation by alpha-macroglobulin. To obtain a derivative which is stable in vivo, the metalloprotease was modified with activated monomethoxy polyethylene glycol. The modified protease retained full activity to a peptide substrate and 10-20% activity to protein substrates, and was resistant to entrapment by alpha-macroglobulin because of the increased molecular size (approx. 90 kDa). These findings suggest that the modified protease is stable in vivo and may be used to investigate the pathological actions of the protease in the bloodstream.

Bacteremia↗
PubMed1993

Specificity for various imino-acid-residues of a proline-specific dipeptidylcarboxypeptidase from a Streptomyces species.

A proline-specific dipeptidylcarboxypeptidase, which removes diproline from the C-terminus of the proline-containing peptides, such as Boc-Pro-Pro-Pro-Pro and Leu-Pro-Pro-Pro-Pro-Pro, has recently been purified from a Streptomyces sp. The specificity of the enzyme for various imino acid-containing synthetic peptide substrates was further studied. The peptides with proline, hydroxyproline, or dehydroproline at the P2' position were found to be good substrates, while those with pipecolic acid, D-proline or other usual amino acids at the P2' position were scarcely hydrolyzed. The peptides with proline, dehydroproline, pipecolic acid, or N-methyl-alanine at the P1' position were well-hydrolyzed, while those with hydroxyproline or D-proline at the P1' position were not hydrolyzed. Utilizing this high specificity for imino acids, Boc-Pro-Pro-Pro-Pro was synthesized by the enzyme using Boc-Pro-Pro as the acidic component and Pro-Pro as the basic component.

Amino Acid Sequence↗
PubMed1993

Fine structure and subepithelial capillaries of the main excretory duct epithelium of the submandibular gland of the Japanese monkey, Macaca fuscata.

The fine structure and subepithelial capillaries of the main excretory duct epithelium (MEDE) of the submandibular gland in the Japanese monkey, Macaca fuscata were investigated by light, scanning, and transmission electron microscopy. Capillaries found beneath the MEDE were all fenestrated ones. Some of them had elevated endothelium known as pored domes. The capillary density (number of capillaries per 200 microns length of MEDE) was 6.05 +/- 1.36, and the number of fenestrae per 10 microns length of available endothelium was 11.62 +/- 3.82. The MEDE was pseudostratified, and consisted of four cell types: Type I and II, which were columnar cells without basal infoldings, basal and goblet cells. The most characteristic feature was the presence of well-developed lateral interdigitations between Type I and II cells.

Animals↗
PubMed1993

Cystathionine gamma-lyase of Saccharomyces cerevisiae: structural gene and cystathionine gamma-synthase activity.

Purification of Saccharomyces cerevisiae cystathionine gamma-lyase (gamma-CTLase) was hampered by the presence of a protein migrating very close to it in various types of column chromatography. The enzyme and the contaminant were nevertheless separated by polyacrylamide gel electrophoresis. N-terminal amino acid sequence analysis indicated that they are coded for by CYS3 (CYI1) and MET17 (MET25), respectively, leading to the conclusion that CYS3 is the structural gene for gamma-CTLase and that the contaminant is O-acetylserine/O-acetylhomoserine sulfhydrylase (OAS/OAH SHLase). Based on these findings, we purified gamma-CTLase by the following strategy: (1) extraction of OAS/OAH SHLase from a CYS3-disrupted strain; (2) preparation of antiserum against it; (3) identification of a strain devoid of the OAS/OAH SHLase protein using this antiserum; and (4) extraction of gamma-CTLase from this strain. Purified gamma-CTLase had cystathionine gamma-synthase (gamma-CTSase) activity if O-succinylhomoserine, but not O-acetylhomoserine, was used as substrate. From this notion we discuss the evolutional relationship between S. cerevisiae gamma-CTLase and Escherichia coli gamma-CTSase.

Amino Acid Sequence↗
PubMed1993

Malignant schwannoma of the intrathoracic vagus nerve: report of a case.

We report herein the case of a 48-year-old man with malignant schwannoma of the intrathoracic vagus nerve associated with von Recklinghausen's disease. Malignant intrathoracic vagal tumors are extremely rare and to our knowledge, only four other cases have been documented in the literature, none of which were associated with von Recklinghausen's disease.

Cranial Nerve Neoplasms↗
PubMed1993

Influence of temperature of flushing solution on lung preservation.

For lung transplantation the technique of flushing the donor pulmonary vascular bed may provide advantages in lung preservation such as rapid cooling and washout of blood. However, rapid cooling of the ischemic lung may also produce adverse effects. The aim of this study was to compare methods of cold flushing and topical cooling, and to evaluate the effect of temperature of the flushing solution on lung preservation. A total of 25 rabbit lungs were studied. Using an ex vivo rabbit lung model, postischemic function was assessed by the ability of the lung to oxygenate perfused blood and by measurement of pulmonary artery and airway pressures. The lungs in group I were preserved with simple immersion at 10 degrees C for 30 hours. The lungs in groups II through V were flushed with solution containing phosphate-buffered dextran (LPD) at different temperatures (groups II and IV, 10 degrees C; groups III and V, 23 degrees C) and stored at 10 degrees C for various ischemic periods (groups II and III, 30 hours; groups IV and V, 36 hours). Pulmonary vascular resistance during flushing at 10 degrees C was significantly higher than that at 23 degrees C (p < 0.001). Flushing resulted in better preservation than topical hypothermia. Flushing at 23 degrees C resulted in superior postischemic function compared with flushing at 10 degrees C. We conclude that in lung preservation, uniform flushing with LPD solution improves the ischemic tolerance as compared with topical hypothermia, and that flushing with solutions at too low temperatures may have adverse effects on lung preservation.

Animals↗
PubMed1993

Midbrain tegmentum as an intermediate relay station of the periaqueductal-facial pathway in the cat.

Iontophoretic injection of horseradish peroxidase (HRP) into the medial part of the facial nucleus resulted in retrograde labeling in the lateral midbrain tegmentum contralaterally which corresponded to the paralemniscal zone (PL). Further experiments in which HRP was injected iontophoretically into the PL revealed heavy retrograde labeling in the lateral portion of the ipsilateral periaqueductal gray (PAG). These light microscopic studies indicated the possibility of the pathway from the PAG to the facial nucleus via the midbrain PL. The electron microscopic observations were carried out on the lateral midbrain tegmentum containing the PL after kainic acid, and wheat germ agglutinin conjugated HRP injections were made into the PAG and the contralateral facial nucleus in the same animal, respectively. Although in the neuropil many degenerating PAG fibers and retrogradely labeled neurons were observed, it was of particular interest that the degenerating fibers made synaptic contacts with HRP-labeled somata and dendrites.

Animals↗