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M Sakurada

Publications and source records attributed to M Sakurada.

At least 37 records · Page 2Linked to original sources
PubMed1996

Purification and characteristics of cytosolic chitinase from Piromyces communis OTS1.

A chitinase was purified from the cytosolic fraction of the anaerobic rumen fungus Piromyces communis OTS1 by affinity chromatography using regenerated chitin, gel filtration and chromatofocusing. The chitinase was most active at pH 6.2 and at 60 degrees C in a 20-min assay. The molecular mass of the purified protein was estimated by SDS-PAGE to be 42 kDa and its pI was 4.9. The enzyme activity, which was of the 'endo' type, was inhibited by Ag+, Hg2+ and allosamidin. N-Acetyl-beta-glucosaminidase and 'exo' type chitinase activity were absent from the purified preparation.

Animals↗
PubMed1996

Electrophoretic forms of chitinolytic and lysozyme activities in ruminal protozoa.

Homogenates from a mixed ruminal protozoal population and a ruminal protozoon Entodinium caudatum were analyzed for chitinolytic and lysozyme activities by sodium dodecyl sulfate polyacrylamide gel electrophoresis. For chitinase activity, up to eight bands in mixed protozoa and seven bands in E. caudatum were detected. Estimated molecular mass ranged from 70 to 110 kDa. These enzymes did not display lysozyme activity. N-Acetyl-beta-glucosaminidase activity was also detected in both samples with an estimated molecular mass of 37 kDa. Lysozyme activity in mixed protozoa was present in two major and three minor bands, where one major band displayed the same motility as chicken egg white (CEW) lysozyme, and the other had an approximate molecular mass of 17.5 kDa. The latter remained active even when denatured in the presence of dithiothreitol and renatured under anaerobic conditions. Entodinium caudatum presented one major band coincident with that of CEW lysozyme and a minor band at the 17.5-kDa point. This study showed that protozoal chitinase and lysozyme activities are originated from several enzymes and that none of these enzymes exhibited both activities.

Acetylglucosaminidase↗
PubMed1995

Simple method for cryopreservation of an anaerobic rumen fungus using ethylene glycol and rumen fluid.

The cryopreservation of an anaerobic rumen fungus, Piromyces communis OTS1, was examined at -84 degrees C using dimethyl sulfoxide, propylene glycol or ethylene glycol as cryoprotectants. Ethylene glycol was the most effective agent, combining high survival and low toxicity, followed by dimethyl sulfoxide and propylene glycol. Cell-free rumen fluid in the cryopreservation medium decreased the toxicity of the cryoprotectant agents and also had a protective action per se. A survival of 80% after 1 year storage was obtained when samples with an initial zoospore density of 5 x 10(4) zoospores/ml were equilibrated for 15 min in medium containing 0.64 M ethylene glycol and 5% cell-free rumen fluid, then frozen with dry ice and stored at -84 degrees C.

Animals↗
PubMed1995

Chitinolytic activity of the anaerobic rumen fungus Piromyces communis OTS1.

The anaerobic rumen fungus, Piromyces communis OTS1, was isolated from a fistulated goat. Its chitinolytic activity in the supernatant of media containing different types of chitin was studied. The fungus grew well in our basal medium, with and without colloidal chitin and chitin powder. N-Acetyl-beta-glucosaminidase activity was not detected in any of the culture media. Chitinase activity, however, was detected in the basal medium with and without colloidal chitin and chitin powder. The extracellular chitinase concentrated from the fungal culture's supernatant by ammonium sulfate (80% saturation) showed highest activity at 40 degrees C and at pH 5.5. In the other cell fractions of P. communis OTS1, N-acetyl-beta-glucosaminidase was not detected, but chitinase activity was detected by 4-methylumbelliferyl reagents. Thus, it was found that the rumen fungus P. communis OTS1 has chitinase activity. Chitinases from the extracellular, cytosolic, and the microsomal fractions were mainly of the endo type of chitinase activity.

Animals↗
PubMed1995

Viability of partial liver graft from living donor in pigs.

For evaluation of the viability of partial liver graft from a living donor, we investigated energy production of mitochondria and radical scavenging enzyme activities in partial and whole liver transplantation in pigs. The values of adenosine triphosphate (ATP) and total adenine nucleotide (TAN) of the partial liver graft were higher than those of the whole liver graft, whereas the hypoxanthine of the partial liver graft was lower than that of the whole liver graft. There was no statistical difference in the radical scavenging enzyme activities between the two groups. The values of respiratory control ratio (RCR) in both groups were above 3.0 and there was no statistical difference. The survival rates of pigs received partial liver and whole liver graft with 2 to 3 hr cold preservation was 71% and 91%, respectively and there was no statistical difference between two groups. These results suggest that viabilities of the partial liver graft from the living donor are satisfactory enough, compared with those of whole liver graft from a cadaver.

Adenine Nucleotides↗
PubMed1995

[Results of emergency coronary artery bypass surgery after failed coronary angioplasty].

In the past 7 years, 9 emergent or urgent coronary artery bypass operations after failed percutaneous transluminal angioplasty (PTCA) were performed among 947 (PTCA). Since the introduction of coronary perfusion catheter system for the support of coronary perfusion during PTCA we could reduce the number of emergent cases and these patients could be operated on semi-emergently and securely without endangering co-medical staffs in a hurry. It is also unnecessary to be on standby all the time when the PTCA is being undertaken. Two acute myocardial infarction cases died in the early phase of this study (operative mortality 22%) and none after the introduction of coronary perfusion system during PTCA.

Aged↗
PubMed1994

Pituitary adenylate cyclase activating polypeptide is an extraordinarily potent intra-pancreatic regulator of insulin secretion from islet beta-cells.

Insulin secretion from pancreatic islets is controlled by peptides as well as by nutrients. We report here a novel, extraordinarily potent peptidergic regulation of insulin secretion. A 27-residue form of pituitary adenylate cyclase activating polypeptide (PACAP27) as low as 10(-14) to 10(-13) M stimulated insulin release from rat islets in a glucose-dependent manner. PACAP27 also increased cytosolic free Ca2+ concentration ([Ca2+]i) in islet beta-cells. Nitrendipine, a blocker of the L-type Ca2+ channel, abolished both [Ca2+]i and insulin responses. Vasoactive intestinal peptide, a peptide exhibiting 68% amino acid homology with PACAP, also increased [Ca2+]i in beta-cells but only at concentrations in the nanomolar range, indicating that PACAP27 is 4 logs more potent. A 38-residue form of the peptide (PACAP38) stimulated insulin release and increased beta-cell [Ca2+]i in a manner similar to that of PACAP27. PACAP-like immunoreactivity was demonstrated in pancreatic nerve fibers, islets, and capillaries. The results indicate that PACAP is a physiologically occurring peptide in pancreas and that PACAP, in a glucose-dependent manner, activates beta-cells presumably via a high affinity PACAP-selective receptor, raises [Ca2+]i by increasing the activity of L-type Ca2+ channels, and consequently stimulates insulin release. PACAP appears to be by far the most potent insulinotropic peptide known.

Animals↗
PubMed1994

Presence in rumen bacterial and protozoal populations of enzymes capable of degrading fungal cell walls.

Ruminal bacteria and protozoa, and cell-free rumen fluid, were tested for the presence of enzymes involved in the degradation of the fungal cell wall. Protozoal homogenate obtained by ultrasonication showed chitinase (EC 3.2.1.14) and N-acetyl-beta-glucosaminidase (EC 3.2.1.52) activities when assayed with fluorogenic 4-methylumbelliferyl substrates. The chitinase activity was predominantly of the 'exo'-type. Lysozyme (EC 3.2.1.17) and 1,3-beta-glucanase (EC 3.2.1.39) activities were also present in this fraction. All these activities, except lysozyme activity, were recovered mainly in the supernatant fraction of the homogenate (approximately 85% of the total activity). Lysozyme showed the same amount of activity in the precipitate and supernatant fractions. Bacterial homogenates had N-acetyl-beta-glucosaminidase activity in both supernatant and precipitate fractions. The specific activity was one-third that of the protozoa. Bacteria able to grow in a medium with chitin as the sole carbon source were recognized and counted. Cell-free rumen fluid was unable to degrade any of the substrates tested.

Acetylglucosaminidase↗
PubMed1994

Effects of ruminal protozoa on cellulose degradation and the growth of an anaerobic ruminal fungus, Piromyces sp. strain OTS1, in vitro.

An anaerobic rumen fungus, Piromyces sp. strain OTS1, was incubated in the presence or absence of a mixed, A-type, protozoal population obtained from a goat, in a medium containing filter paper cellulose as energy source and antibiotics to suppress bacterial growth. Fermentation end products, cellulose degradation, and chitin as an indicator of fungal biomass were examined. In the presence of protozoa, total volatile fatty acids, notably propionate and butyrate, increased, and lactate decreased. In fungus-protozoan coincubations, formate was not detected at the end of the experiment and the amount of reducing sugars remained low throughout the incubation period. The fungal growth in the coincubations was negatively affected. While protozoal predation on zoospores was one mechanism of inhibition, mature fungal cells were also affected. Total cellulose degradation was greater in fungal monocultures, but the amount of cellulose degraded per unit of fungal biomass was 25% larger in the coincubations. The negative effects that the protozoal predatory activity had on the fungal growth and subsequently on the amount of cellulose degraded by Piromyces sp. strain OTS1 were partially attenuated by the protozoal fibrolytic activity or by an enhanced fungal activity due to a more favorable environment.

Anaerobiosis↗
PubMed1994

The importance of prevention of sinusoidal endothelial cell injury during cold preservation of liver graft.

We investigated adenosine triphosphate (ATP) synthesis, lipid peroxidation, and activities of radical scavenging enzymes in mitochondria, as well as the ultrastructural morphological changes during cold preservation of swine liver grafts (n = 6) with either Euro Collins (EC) or University of Wisconsin (UW) solutions. The liver, harvested by a standard procedure, was preserved in one of the solutions at 4 degrees C. The values of the total adenine nucleotide and mitochondrial respiratory control ratio (RCR), an index of ATP synthesis, decreased gradually for up to 24 hr during preservation with either of the two solutions and there was no statistical difference between them. Chemiluminescence of mitochondria, an index of lipid peroxidation, in the graft preserved with EC solution or UW solution decreased, and after 24 hr there was no significant difference between the two solutions. Activities of radical scavenging enzymes were well maintained in any of the two solutions. Transmission electron microscopy (TEM) findings showed that the sinusoidal endothelial cells were preserved much better with UW solution than with EC solution even after 12 hr preservation. We concluded that UW solution, more effective for the protection against injuries of the sinusoidal endothelial cells during cold preservation, leads to better results in clinical transplantation, but this solution has no protective effects on energy production, nor radical scavenging enzyme activities of mitochondria. In the maintenance of liver graft viability, protection of the sinusoidal microcirculatory disturbance is more important than that of the mitochondrial function.

Adenosine↗
PubMed1993

Relation between glucose-stimulated insulin secretion and intracellular calcium accumulation studied with a superfusion system of a glucose-responsive pancreatic beta-cell line MIN6.

The concept that cytosolic free calcium is the primary signal for insulin secretion is generally accepted, but studies with intact pancreatic beta-cells of the cytosolic free calcium concentration-insulin secretion relationship have produced contradictory and sometimes confusing data. We designed a superfusion system of a pancreatic beta-cell line, MIN6, loaded with fura-2, which allowed simultaneous measurement of cytosolic free calcium concentration and insulin secretion. MIN6 cells released insulin in response to high glucose, thus resembling events in normal islet cells. Cytosolic free calcium concentration and insulin secretion rapidly increased, and the increase was suppressed by mannoheptulose or by sodium azide. This increase was suppressed by lowering the temperature of the medium. Cytosolic free calcium concentration and the insulin secretion induced by leucine were not influenced by mannoheptulose but were inhibited by sodium azide. In RINm5F cells, cytosolic free calcium concentration and insulin release were slightly suppressed by glucose but were increased by ionomycin. There was a close relation between the rise in cytosolic free calcium concentration and insulin secretion in all cases. Our findings provide a direct evidence that a rise in cytosolic free calcium concentration depends on glucose metabolism and is a primary signal for insulin secretion.

Animals↗
PubMed1993

Efficacy of carbon monoxide laser in selectively intimal thermal welding--implications for laser balloon angioplasty.

Excessive vascular damage causes excessive vascular repair, which results in restenosis. To limit the thickness of the coagulation layer in laser balloon angioplasty, we used a carbon monoxide (CO) laser, which has high tissue absorption, as a therapy laser source instead of a Nd: YAG laser. To investigate the benefit of short-penetration CO laser light to vascular tissue, excised human abdominal aorta was irradiated with a CO laser through a 30 microns polyethylene membrane. The temperature of the vascular tissue was continuously monitored during irradiation. CO laser irradiation of 20 W/cm2 was performed in either a continuous mode or an intermittent mode with various duty ratios (exposure/interval duration). With a total fluence of 200 J/cm2, the adventitial temperature decreased as the duty ratio was reduced. The adventitial temperature at a duty ratio of 1:2 was 43 degrees C. Microscopic examination of aorta which had been intermittently irradiated duty ratio of 1:2 showed thermal coagulation localized within the intima and a flattened intimal surface. These results suggest that intermittent laser irradiation with a CO laser can be used to limit the depth of thermal coagulation, and can selectively weld the intima without excessive thermal damage. Laser balloon angioplasty using a CO laser may help to prevent restenosis.

Angioplasty, Balloon, Laser-Assisted↗
PubMed1992

Exploratory eye movements and neuropsychological tests in schizophrenic patients.

Exploratory eye movements in schizophrenic and nonschizophrenic subjects were examined with an eye mark recorder while the subjects viewed geometric figures. Elementary components of eye movements and the responsive search score (RSS), a function of the number of sections on which the subjects fixated, were measured by means of an eye movement analyzer and slow motion replay. The schizophrenic group and the depressed patient group had fewer eye fixations than the normal control group and the obsessive-compulsive disorder group. The schizophrenic group had a lower RSS average than patients with depression, patients with obsessive-compulsive disorders, or subjects in the normal control group. These results in conjunction with those of our previous studies suggest that a low RSS is specific to schizophrenia. We examined the relationship between these eye movements and neuropsychological tests and also investigated the relation between the eye movements and clinical symptoms by means of the Brief Psychiatric Rating Scale, Schedule for Affective Disorders and Schizophrenia, and the Scale for the Assessment of Negative Symptoms. The RSS correlated positively with the performance IQ and Wechsler's Maze test, but not with the Wisconsin Card Sorting Test or the verbal IQ result. The RSS also correlated negatively with negative symptoms. These results suggest that the RSS has two characteristic features: it is strongly associated with the interpersonal response and it may be connected with visuospatial and visuomotor functions including attention.

Adult↗
PubMed1992

[Mitochondrial energy synthesis during cold preservation and after reperfusion in liver transplantation].

In liver transplantation, primary graft nonfunction (PGN) occurred 5 to 10% in all cases. For preventing PGN it is necessary to elucidate a reliable assessment procedure for graft function before transplantation. In addition, methods of harvest or preservation which can maintain good viability of the graft are also needed. The purpose of this study is to clarify whether mitochondrial respiratory ratio (RCR), which is ability of ATP synthesis, is a reliable marker of the graft viability and whether a harvesting method with an artificial heart and lung is effective for keeping high energy synthesis of mitochondria or not. Pigs were used for this study. In a standard harvest method RCR decreased gradually during cold preservation. Grafts with values of RCR more than 3.0 had good function after transplantation. RCR depended on mitochondrial ATP, not tissue ATP. Grafts harvested with artificial heart and lung kept RCR more than 4.0 at 12 hours after preservation. Five of 6 pigs transplanted 12 hours preserved liver harvested from the donor with an artificial heart and lung survived more than 5 days. These results suggested that mitochondrial ATP synthesis has strong relation to PGN and RCR is a reliable marker for graft viability.

Adenosine Triphosphate↗
PubMed1991

Angioscopic coronary macromorphology in patients with acute coronary disorders.

To investigate the pathogenesis of acute coronary disorders and to clarify what type of plaque precedes these disorders, percutaneous transluminal coronary angioscopy, by means of a new angioscope, was carried out during catheterisation in 100 consecutive patients anatomically suitable for such investigations. The quality of the angioscopic image was good enough for analysis in 84 patients (14 with acute myocardial infarction [within 8 h of onset], 16 with recent myocardial infarction [3 days-2 months since onset], 24 with old myocardial infarctions, 10 with unstable angina, and 20 with stable angina). Thrombi were observed in most patients with acute coronary disorders (all 14 with acute myocardial infarction, 9 of 10 with unstable angina). Occlusive thrombi were more common in patients with acute myocardial infarction than in those with unstable angina (11 [79%] vs 1 [10%]; p less than 0.001), whereas mural (non-occlusive) thrombi were more common in the unstable angina than in the acute myocardial infarction group (8 [80%] vs 3 [21%]; p less than 0.001). Xanthomatous ulcerated plaques or ragged irregular surfaces were seen in patients with acute coronary disorders and in those with recent myocardial infarction. Xanthomatous plaques were more common in patients with acute coronary disorders (50%) than in those with stable angina (15%) or old myocardial infarction (8%). By contrast white and smooth plaques were seen in cases of stable angina and old myocardial infarction. Angioscopy could display the intracoronary lumen more precisely than could coronary arteriography. This angioscopic study suggested that, although a thrombus overlying a rupture in the lining of the plaque was common in both unstable angina and acute myocardial infarction, the character of the thrombus may differ between these disorders, and lipid-rich xanthomatous plaque may precede rupture.

Acute Disease↗
PubMed1991

Fluctuating CPAP (F-CPAP) versus conventional CPAP (C-CPAP) in dogs with blood aspiration.

Fluctuating CPAP(F-CPAP) is a combination of spontaneous ventilation and fluctuating PEEP, in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with localized lung injury induced by the aspiration of non-heparinized blood (2 ml.kg(-1) body weight), we carried out a comparative study of the effects of F-CPAP in which the EEP was cyclically changed from 4 to 12 cmH(2)O with periods of 10 min and those of conventional CPAP with a fixed EEP of 8 cmH(2)O (C-CPAP), on hemodynamics and pulmonary oxygenation. The blood aspiration produced significant increases in the intrapulmonary shunt (Qsp/Qt), the alveolar-arterial difference of partial pressure of oxygen (A-aD o(2)), and the respiratory rate (RR). Although both F-CPAP and C-CPAP reduced Qsp/Qt and A-aD o(2) and RR, 7 dogs treated with F-CPAP showed a significantly greater recovery of Qsp/Qt and A-aD o(2) than 7 dogs treated with C-CPAP. There were no significant differences in hemodynamic variables between the two groups. These results suggest that F-CPAP is more useful in the treatment of some kinds of hypoxic respiratory failure due to uneven distribution of lung injury.

Journal Article↗