Biomedical subjects

J Okuda

Publications and source records attributed to J Okuda.

At least 127 records · Page 7Linked to original sources

PubMed1990

High-yield purification of glucokinase from rat liver.

A rapid and reliable method for the purification of rat liver glucokinase was developed. The procedure consists of DEAE-cellulose ion-exchange chromatography, Phenyl-Sepharose hydrophobic interaction chromatography, DEAE-Affi Gel Blue dye-ligand chromatography, and duplicate steps of glucosamine-Sepharose affinity chromatography. Glucokinase was purified to a specific activity of 290 units/mg protein in a yield of 55% in 6 days. The final enzyme preparations were completely homogeneous in most experiments as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The estimated molecular weight (51,000) and sigmoidal saturation function for glucose of purified glucokinase were in good agreement with published data.

Animals↗

PubMed1990

Hemispatial neglect in a patient with callosal infarction.

Left hemispatial neglect, confined to right-hand and verbal responses, was exhibited by a 56-yr-old right-handed male patient with callosal lesions due to cerebral infarction. Various disconnection signs were also present. His CT and MRI scans disclosed major lesions situated in the posterior half of the genu and the whole trunk of the corpus callosum, as well as in the left medial frontal and temporo-occipital lobes. Left hemispatial neglect was invariably demonstrated in right-hand performance such as copying drawings, line bisection, matching identical figures and copying multiple digit numbers, and in verbal performance such as confrontation naming and reading aloud multiple digit numbers. In contrast, little or no right hemispatial neglect was demonstrated in tasks performed with the left hand. These findings support the hypothesis that the left hemisphere is only concerned with attending to the contralateral hemispace and that the right hemisphere is specialized for attending to both sides of space although the preponderant tendency is for attending to the contralateral hemispace. The neglect symptoms observed in our patient may be a disconnection sign which was attributable to a combination of lesions in the corpus callosum and in the left medial frontal lobe.

Attention↗

PubMed1990

A case of slowly progressive aphasia without generalized dementia in a Japanese patient.

A Japanese patient with a 4-year history of slowly progressive aphasia without generalized dementia is described. From 1985 on, this 61-yr-old right-handed dentist showed insidiously progressive deterioration in his speech and auditory comprehension, but has no memory disturbance, disorientation of space, time or persons, acalculia or other impairments in his behavior. His personality changes are unremarkable. He still treats patients at his clinic. General physical and neurological examinations were normal. CT and MRI (1.5T) scans showed widening of the left sylvian fissure and lateral ventricle without any vascular lesions. A PET scan demonstrated focal hypometabolism restricted to the left temporal lobe. The clinical course and picture of our patient corresponds, well to those of slowly progressive aphasia without generalized dementia, described by Mesulam.

Aphasia↗

PubMed1990

Effects of novel hydantoin derivatives with aldose reductase inhibiting activity on galactose-induced cataract in rats.

Effects of novel aldose reductase inhibitors, M16209 (1-(3-bromobenzo[b]furan-2-ylsulfonyl)hydantoin) and M16287 (1-(3-chlorobenzo[b]furan-2-ylsulfonyl)hydantoin), on galactose-induced cataract formation in rats were investigated. Rats fed a 30% galactose diet developed lenticular opacity in the peripheral region by the 6th day of galactose feeding and showed gradual progression of opacity from the equator to the center of lenses. Histological study on the 15th day showed apparent lens fiber swelling and vacuolation predominantly in the equatorial and anterior cortical regions. Biochemical changes such as accumulation of galactitol, depletion of myo-inositol and decrease in glutathione (GSH) content in lenses preceded the appearance of opacity. Remarkable increase in NADPH content and decrease in NADP+ content, in addition to elevation of the ratio of Na+/K+, in lenses were also observed on the 15th day. Both M16209 and M16287 (10, 30 and 100 mg/kg/day, p.o.) dose-dependently ameliorated these morphological and biochemical changes except that restoration of myo-inositol content was incomplete. These results indicate that M16209 and M16287 can prevent galactose-induced cataract formation through amelioration of metabolic disorders and thus have high potential for clinical use in the treatment of some diabetic complications.

Aldehyde Reductase↗

PubMed1990

Participation of glucokinase inactivation in inhibition of glucose-induced insulin secretion by 2-cyclohexen-1-one.

We assessed our speculation that 2-cyclohexen-1-one (CHX) impairs glucose-induced insulin secretion through inactivation of glucokinase. Treatment of pancreatic islets with CHX at concentrations (0-5 mM) that caused a dose-dependent inactivation of glucokinase activity similarly inhibited glucose-induced insulin secretion. Another glucose-phosphorylating enzyme (hexokinase) in pancreatic islets was little affected by CHX. CHX-induced inactivation of glucokinase was blocked by the presence of its substrates (glucose and mannose) and an inhibitor (N-acetylglucosamine), all of which also protected against the inhibitory effect of the drug on glucose-induced insulin secretion. CHX also impaired insulin secretion induced by D-glyceraldehyde and dimethyl succinate, which are believed to stimulate the release of the hormone by being directly oxidized by glyceraldehyde-3-phosphate dehydrogenase, by entering the midstream of the glycolytic pathway as glyceraldehyde 3-phosphate, or by entering the tricarboxylic acid cycle in mitochondria after intracellular hydrolysis. The inhibitory effect of CHX on glucose-induced insulin secretion, however, was far more marked than that on insulin secretion evoked by D-glyceraldehyde and dimethyl succinate at any CHX concentrations used. Our study revealed that the inhibitory action of CHX on glucose-induced insulin secretion is exerted mainly, but not solely, through inactivation of glucokinase. This conclusion supports the view that glucokinase is a key enzyme in the recognition of glucose as an insulin secretagogue in pancreatic islets.

Animals↗

PubMed1990

Evidence for the presence of rat liver glucokinase in the nucleus as well as in the cytoplasm.

Subcellular distribution of glucokinase was studied in rat liver. With an immunohistochemical procedure, glucokinase immunoreactivity was clearly shown in the nucleus of parenchymal cells of rat liver, but faintly in the cytoplasm. Nuclei, cytosol (extranuclear fraction in the strict sense), and homogenate prepared in nonaqueous medium, i.e. glycerol, were analyzed for glucokinase by both immunoblotting and activity measurement. Such analyses demonstrated that glucokinase concentration was far higher in the nuclei than in the cytosol when compared on the basis of total protein content and that total glucokinase activity in the cytosolic fraction was about 1.8 times that in the nuclear fraction. These results indicate that hepatocyte glucokinase is present in the nucleus as well as in the cytoplasm in contradiction to the widespread belief of its exclusive localization in the cytoplasm.

Animals↗

PubMed1989

Mechanism of inhibition of erythrocyte glutathione reductase by mitomycin-C.

Mitomycin-C (MT-C) inhibits human erythrocyte glutathione reductase (EGR). We found that Km values of EGR for GSSG, NADPH, and FAD were 1.3 X 10(-4) mol/l, 2.3 X 10(-5) mol/l, and 3.9 X 10(-7) mol/l respectively, and that EGR was inhibited by MT-C non-competitively with respect to both the substrate GSSG (Ki = 4.8 X 10(-5) mol/l) and the cofactor NADPH (Ki = 2.2 X 10(-4) mol/l), and competitively with respect to FAD (Ki = 4.2 X 10(-5) mol/l). On the other hand, we demonstrated that FAD makes a complex with MT-C, the dissociation constant (K = 6.5 X 10(-5) mol/l) of which was obtained from fluorescence quenching of FAD with MT-C. It also became clear that spectra wf FAD at around 375 nm changes with increasing MT-C concentration. So, the data strongly suggest that the mechanism of inhibition of EGR by MT-C is mainly due to complex formation of the co-enzyme FAD with MT-C.

Erythrocytes↗

PubMed1989

Hemispheric asymmetry of processing temporal aspects of repetitive movement in two patients with infarction involving the corpus callosum.

Two right-handed patients with infarction involving the forebrain commissural fibres produced irregular but rapid repetitive movements with their left hands while producing normal movements with their right hands as well as having normal oral expression. The abnormality was more conspicuous when producing slow tapping patterns. When required to reproduce rapid tapping patterns of around 5 beats/sec, one of the patients produced a comparatively regular tapping pattern. Thus, we believe that both hemispheres are equipped with the faculty to produce rapid repetitive patterns and that only the left hemisphere is responsible for the temporal processes involved in producing required repetitive patterns.

Aged↗

PubMed1989

Tactile extinction to simple (elementary) and complex stimuli.

Thirty patients with cerebrovascular disease and 85 control subjects were examined using both the classical tactile extinction test and a modified Quality Extinction Test (modified QET) in order to investigate the so-called tactile extinction phenomenon to complex stimuli from the qualitative standpoint. As a result, 1) the patients with tactile extinction to simple (elementary) stimuli also manifested extinction to complex tactile stimuli in the modified QET; 2) there were patients who exhibited extinction only to complex tactile stimuli. Our results provide support for the concept that the so-called tactile extinction phenomenon could result from competition between tactile stimuli presented to both hands at at least 2 different levels of tactile processing, i.e. the process of perception and the process of recognition. When discussing the phenomenon of extinction to complex tactile stimuli, therefore, one should consider these 2 forms of extinction separately.

Adult↗

PubMed1989

Improvement of nerve conduction velocity in mutant diabetic mice by aldose reductase inhibitor without affecting nerve myo-inositol content.

The sciatic motor nerve conduction velocity of mutant diabetic C57BL/Ks mice was significantly improved from 30.0 +/- 1.4 to 38.0 +/- 4.6 m/s by treatment with the aldose reductase inhibitor 1-[(beta-naphthyl)sulfonyl]hydantoin (30 mg/kg/d) for 2 weeks. The treatment, however, did not cause any significant change in myo-inositol concentration in the sciatic nerve. The results indicate that the ameliorating effect of the aldose reductase inhibitor on nerve conduction velocity in mutant diabetic mice is not due to alteration of myo-inositol content in the nerve.

Aldehyde Reductase↗

PubMed1989

[Endoscopic treatment of early gastric cancer in patients undergoing chronic hemodialysis].

Endoscopic treatment of early gastric cancer (type Ila in all patients) was performed in four patients undergoing chronic hemodialysis. Surgical treatment was contraindicated because of various risk factors in these patients. Endoscopic treatment was performed by concomitant use of YAG laser irradiation, local ethanol injection and mucosal resection. After endoscopic treatment, stomach biopsy revealed no cancer in four patients. In one patient who is alive now, no sign of cancer recurrence has been noted for about two years after endoscopic treatment. This patient has undergone hemodialysis on outpatient department. The remaining three patients died from diseases other than gastric cancer. When one of them was autopsied, no gastric cancer demonstrated. Taking the prognosis related to life in to consideration, endoscopic treatment should be used positively when surgical treatment of early gastric cancer cannot be performed in patients undergoing chronic hemodialysis.

Aged↗

PubMed1988

Analysis of sorbitol, galactitol, and myo-inositol in lens and sciatic nerve by high-performance liquid chromatography.

Accumulation of sorbitol or galactitol and depletion of myo-inositol in hyperglycemic conditions such as diabetes and galactosemia involve the activity of aldose reductase and are implicated in hyperglycemia-induced complications such as cataract and neuropathy. A high-performance liquid chromatographic method has been developed for the measurement of polyols in the lens and sciatic nerve of rats. This method comprises polyol extraction from tissues, lyophilization of extracts, derivatization of polyols by the reaction with phenylisocyanate, and HPLC of derivatives with detection at 240 nm. The time needed for each run is less than 25 min, which allows the testing of a large number of samples per day. Sensitivity is very high: as low as 0.5 nmol each of sorbitol, galactitol, and myo-inositol in lyophilized extracts of tissues can be determined. The present method offers a reliable tool to evaluate the in vivo activities of aldose reductase and its inhibitors.

Animals↗

PubMed1988

[Transfer of injected sulbactam/cefoperazone into burn blister fluid].

Transfer of sulbactam/cefoperazone (SBT/CPZ) into the burn blister fluid was studied in 10 burn patients after one shot intravenous injection of 50 mg/kg SBT/CPZ (CPZ 25 mg/kg, SBT 25 mg/kg). CPZ and SBT concentrations in serum and burn blister fluid were determined using bioassay and high performance liquid chromatography (HPLC). The concentration of CPZ in serum reached 109.5 +/- 9.2 micrograms/ml (mean +/- S.E.) at 0.25 hour after injection, and decreased to 6.8 +/- 2.3 micrograms/ml after 8 hours. The concentration of CPZ in burn blister fluid peaked at 4 hours and reached 28.2 +/- 8.0 micrograms/ml. The concentration of SBT in serum reached 75.7 +/- 8.3 micrograms/ml at 0.25 hour after injection, and decreased to 2.3 +/- 0.7 micrograms/ml after 8 hours. The peak concentration of SBT in burn blister fluid was 13.5 +/- 1.8 micrograms/ml at 3 hours. The data obtained were analysed pharmacokinetically. Cmax of CPZ and SBT levels in burn blister fluid were calculated to be 30.4 micrograms/ml and 13.6 micrograms/ml, respectively. The AUC0-8 hrs. (area under the burn blister fluid concentration of drug-time curve between 0 and 8 hours after injection), absorption rate constant (ka) and therapeutic AUC (AUC where drug concentrations were above minimum effective concentration) of CPZ were calculated to be 194.0 micrograms.hr/ml, 1.52 hr-1 and 97.1 micrograms.hr/ml (0.3-11.1 hours), respectively. The AUC0-8 hrs. and ka of SBT were also calculated as 68.3 micrograms.hr/ml and 0.62 hr-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blister↗

PubMed1988

Asymmetric transport of D-glucose anomers across the human erythrocyte membrane.

The anomeric preference in the influx and efflux of D-glucose across the human erythrocyte membrane was studied. beta-D-Glucose was transported 1.5 times faster than alpha-D-glucose into the cells, when washed cells were incubated at 20 degrees C in medium containing either alpha- or beta-D-glucose (100 mM). On the other hand, no difference between half-times of efflux of the two anomers was distinguishable. The result demonstrates the presence of influx-efflux asymmetry in anomeric preference in D-glucose transport across the human erythrocyte membrane, and is consistent with the view (Barnett et al., Biochem. J. 145, 417-429, 1975) that the C-1 hydroxyl group of D-glucose interacts with the D-glucose transport protein only in the influx, but not in the efflux.

Erythrocyte Membrane↗

PubMed1987

Development of potent aldose reductase inhibitors having a hydantoin structure.

Seventeen hydantoin derivatives were tested as inhibitors of aldose reductase, an enzyme believed to participate in the initiation of diabetic complications. Nine compounds with high inhibitory activities (IC50 values against purified rat lens aldose reductase less than or equal to 1.06 X 10(-6)M) were tested further for their abilities to prevent sorbitol accumulation induced by exposure of excised rat lens and sciatic nerve to a high glucose concentration (50 mM). Seven active compounds among them inhibited sorbitol accumulation by about 50% or more at a concentration of 10(-5)M. These seven compounds were given orally to streptozotocin-induced diabetic rats at a dose of 50 mg/kg/day and were assessed for their abilities to prevent both sorbitol accumulation in two tissues (lens and sciatic nerve) and myo-inositol depletion in the sciatic nerve. 1-[(2,4,5-Trichlorophenyl)sulfonyl]hydantoin, 1-[(2,5-dichlorophenyl)sulfonyl]hydantoin, and 1-[(beta-naphthyl)sulfonyl]hydantoin were found to be the most effective: they inhibited sorbitol accumulation in the sciatic nerve completely and that in the lens by more than 92%. It is conceivable from this study that the three compounds are promising for further investigation targeted to the treatment of diabetic complications.

Aldehyde Reductase↗

PubMed1987

Determination of pseudo-alpha- and pseudo-beta-DL-glucose by gas-liquid chromatography, high-performance liquid chromatography, and enzymatic colorimetry with glucose 2-oxidase.

Three methods have been developed for measuring pseudo-alpha- and pseudo-beta-DL-glucose (pseudo-beta-D-glucose), synthetic compounds in which the ring oxygens of alpha- and beta-DL-glucose (beta-D-glucose) have been replaced by a methylene group. Moderate sensitivity in the determination of these pseudo-glucoses dissolved in human serum was obtained by GLC (0.1 nmol) and HPLC (0.5 nmol). The colorimetric determination with glucose 2-oxidase, peroxidase, and 2,2'-azino-di-(3-ethylbenzothiazoline-6-sulfonic acid) was satisfactory for the assay of pseudo-alpha- and pseudo-beta-DL-glucose (respective sensitivities: 25 and 5 nmol). The addition of hexokinase to the colorimetric assay system made it possible to eliminate glucose present in the sample, such as serum, and the remaining pseudo-alpha- or pseudo-beta-DL-glucose in the sample solution could then be measured by a colorimetric method using glucose 2-oxidase. The methods described can be used for biochemical studies involving pseudo-alpha- and pseudo-beta-DL-glucose.

Chromatography, Gas↗

PubMed1987

Anomeric specificity of glucose effect on cAMP, fructose 1,6-bisphosphatase, and trehalase in yeast.

The addition of beta-D-glucose (final concentration, 50 mM) to a cell suspension of Saccharomyces cerevisiae in stationary phase caused a rapid 4-fold increase in the concentration of cAMP, while a 2-fold increase of cAMP was observed by the addition of alpha-D-glucose. beta -D-Glucose was also more effective than alpha-D-glucose in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase. These results, taken together with the previous report that alpha-D-glucose is transported more rapidly than beta-D-glucose in Saccharomyces cerevisiae, do not support the view currently proposed by some investigators that cotransport of D-glucose with protons causes the depolarization of the cell membrane, resulting in the activation of adenylate cyclase. The present data, however, provides supporting evidence for the view that cAMP-dependent protein kinase is implicated in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase.

Cyclic AMP↗

PubMed1987

Optimal conditions for injection of tobramycin and cefmenoxime into burn patients.

The concentrations of tobramycin (TOB) or cefmenoxime (CMX) in serum and burn blister fluid of 51 burn patients (21 for TOB, 30 for CMX) after an i.v. or i.m. injection were determined to find the optimal administration of TOB (2 mg/kg) or CMX (50 mg/kg). Among the various protocols tested, we found from the values of tAUC for TOB that a bolus i.v. injection, or 1-h drip infusion, or i.m. injection are recommended for systemic sepsis, however, the 1-h drip infusion is strongly suggested for treating wound surface infection. It has also been found that with CMX a bolus i.v. injection with a long period of efficacy is recommended for treating systemic sepsis, while a 1-h drip infusion or bolus i.v. injection was the best method for treating wound-surface infection.

Adult↗