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Biomedical subjects

Y Ohta

Publications and source records attributed to Y Ohta.

At least 325 records · Page 18Linked to original sources
PubMed1997

Nonsymmetric leaflet motion of St. Jude Medical mitral valves simulated with a computer-controlled hydraulic mock circulator.

Since the introduction of high-performance prosthetic heart valves, particularly bileaflet valves and monoleaflet valves with larger opening angles, we have observed in vivo complex leaflet motion which has not been experimentally confirmed yet. We developed a computer-controlled hydraulic mock circulator to study the motion of in vivo leaflets. A high speed CCD camera recorded the valve movement. In the mitral position, a standard St. Jude Medical valve was tilted to be horizontal or vertical. The test valve was driven with single- or double-peaked flow. The flow rate was set to 5.0 L/min at 70 bpm with a systole/diastole ratio of 0.3. We found the following results: independent of valve orientation, the valve showed a nonsymmetric leaflet motion; the valve showed unpredictable leaflet position during decreasing flow or absence of flow; and the disc closed temporarily at the lower inflow rate between the 2 flow peaks.

Blood Flow Velocity↗
PubMed1997

Preventive effect of oren-gedoku-to (huanglian-jie-du-tang) extract on progression of carbon tetrachloride-induced acute liver injury in rats.

The effect of oral administration of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15) on the progression of acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). When TJ-15 at a dose of 500 mg/kg body weight (b.w.) was administered to male Wistar rats aged seven weeks 6 hours after i.p. injection of CCl4 (1.0 ml/kg b.w.), an apparent liver injury occurred. Significant prevention against the progression of liver injury was found 24 hours after the injection judging from the activities of serum transaminases and other indices of liver cell damage. An increase in lipid peroxide level and decreases in reduced glutathione level and superoxide dismutase (SOD) activity occurred in the liver at 6 and 24 hours after CCl4 injection. Serum SOD activity increased 24 hours after CCl4 injection. Post-oral TJ-15 administration significantly ameliorated all these changes found at 24 hours after CCl4 injection. An increase in liver triglyceride level and a decrease in serum triglyceride level also occurred 6 and 24 hours after CCl4 injection. Post-oral TJ-15 administration prevented the increase in liver triglyceride level at 24 hours after CCl4 injection. Although the activity of liver tryptophan 2,3-dioxygenase (TDO), a marker of the inhibition of liver protein synthesis by CCl4, decreased 6 and 24 hours after injection of the toxicant, post-oral TJ-15 administration had no effect on this decrease in TDO activity at 24 hours after the injection. These results indicate that oral TJ-15 administration can prevent the progression of acute liver injury in CCl4-injected rats, and suggest that this prevention could be due to the action of TJ-15 to scavenge free radicals formed in the liver and to inhibit triglyceride accumulation in the liver.

Administration, Oral↗
PubMed1997

Comparative study of oral and parenteral administration of sho-saiko-to (xiao-chaihu-tang) extract on D-galactosamine-induced liver injury in rats.

The preventive effect of Sho-saiko-to (Xiao-Chaihu-Tang) extract (TJ-9) on the progression of D-galactosamine (GaIN)-induced liver injury was examined in five week-old male Wistar rats with oral (p.o.) or intraperitoneal (i.p.) administration of the same dose of TJ-9. Rats treated once with GaIN (500 mg/kg body weight, i.p.) received TJ-9 at a dose of 1.0 g/kg body weight (p.o. or i.p.) 2 hours after GaIN treatment at which time an apparent liver injury occurred. Both p.o. and i.p. administration of TJ-9 showed similar significant prevention against the progression of liver injury 24 hours after GaIN injection. Although total protein and albumin concentrations in serum and protein concentration in the liver decreased with the progression of GaIN-induced liver injury, oral or i.p. administration of TJ-9 prevented these decreases in similar degree. However, decreases in serum and liver triglyceride concentration with the progression of liver injury were not attenuated after p.o. or i.p. administration of TJ-9. The activities of liver 5'-nucleotidase and glucose-6-phosphatase, marker enzymes of liver plasma and microsomal membranes, respectively, decreased during the progression of liver injury. A similar preventive effect on the decrease of both enzyme activities was found after p.o. or i.p. administration of TJ-9. These results indicate that the preventive effect on progression of GaIN-induced liver injury by oral or i.p. administration is approximately equal, and that the effect may be through improving the impaired liver protein synthesis and disrupted liver plasma and microsomal membranes in a similar degree.

5'-Nucleotidase↗
PubMed1997

Nuclear magnetic resonance study of lung water compartments in the rat.

Nuclear magnetic resonance transverse relaxation time (T2) was previously measured in studies of lung water. The T2 decay curves for peripheral lung tissue were found to be multiexponential with two T2 components: T2 fast (T2f) and T2 slow (T2s). This behavior was explained by the compartmentalization of water, in which the protons of water are restricted and do not undergo rapid exchange between the compartments. We investigated the origin of the water for these T2 components using excised rat lungs. The effect of magnetic field inhomogeneity due to air-tissue interfaces was examined by degassing some lungs. The contribution of intravascular water was examined by perfusing the lungs with oil or NaCl solutions. Degassing produced a greater increase in the T2f than the T2s component, indicating that the water in the alveolar walls exposed to air spaces contributed to the T2f. Perfusion with oil decreased the T2s, indicating that intravascular water contributed to the T2s component. The effects of intravascular osmotic pressure on the T2f and T2s components suggest that intracellular water is related to the T2f component.

Air↗
PubMed1997

Effects of active vasoconstriction and total flow on perfusion distribution in the rabbit lung.

We analyzed the effects of hypoxic vasoconstriction and total flow on the distribution of pulmonary perfusion in 38 isolated left rabbit lungs perfused under zone 3 conditions. Lungs were suspended in an upright position, oriented to the apicobasal line. Distributions of regional perfusion rates (RPR) along the vertical and horizontal axes were determined using nonradioactive microspheres labeled with heavy metal elements, which were detectable with X-ray fluorescence spectrometry. Changing the O2 concentration of a respirator and an extracorporeal membrane oxygenator independently, respective influences of active vasoconstriction induced by alveolar hypoxia and pulmonary artery hypoxia (PA hypoxia) on the RPR distribution were examined at a flow rate of 0.4 ml x min(-1) x g wet lung tissue(-1). To analyze the effects of changes in total flow, we investigated the RPR distribution at a perfusion rate of 1.2 ml x min(-1) x g wet lung tissue(-1). The RPR distribution in the absence of hypoxia was inhomogeneous and was augmented in the lower lung fields, whereas alveolar hypoxia shifted the RPR upward and significantly diminished the RPR in the lung base. RPR distributions along the horizontal axes under alveolar hypoxia conditions demonstrated that remarkable hypoxic pulmonary vasoconstriction (HPV) takes place in medial regions at the lung base. PA hypoxia altered the RPR distribution in qualitatively the same manner as alveolar hypoxia. Increased flow rate augmented the RPR in the lung, except in the dorsobasal region. These results suggest that the occurrence of HPV and the vascular conductance are not uniform throughout the lung.

Animals↗
PubMed1997

Rapid response to inhaled frusemide in severe acute asthma with hypercapnia.

We report 7 patients with severe acute asthma unresponsive to standard medication, including sympathomimetic agents, aminophylline and corticosteroids, who responded to inhaled frusemide. All were hypercapneic with a mean PaCO2 of 7.7 kPa (57.7 mm Hg) [range 6.2-8.8 kPa (46.2-66.3 mm Hg)]. Following nebulization of 20 mg frusemide, clinical response was rapid, and the mean PaCO2 fell significantly to 5.4 kPa (40.6 mm Hg) [range 5.0-6.2 kPa (37.5-46.5 mm Hg)] within 20-60 min. No adverse effect was recognized. Inhaled frusemide should be considered for treatment of acute asthma refractory to conventional therapy.

Acute Disease↗
PubMed1997

Involvement of the xanthine-xanthine oxidase system and neutrophils in the development of acute gastric mucosal lesions in rats with water immersion restraint stress.

In rats subjected to water immersion restraint (WIR) stress for 1, 3, and 6 h, gastric mucosal lesions developed time-dependently with an increase in lipid peroxide (LPO) levels and a decrease in nonprotein sulfhydryl levels in the gastric mucosa. The gastric mucosal xanthine oxidase (XO) activity significantly increased with the conversion of xanthine dehydrogenase (XD) to XO at 6 h of WIR (3.2-fold that of the control group without WIR). A significant increase in myeloperoxidase (MPO) activity, an index of neutrophil infiltration, occurred in the gastric mucosa at 3 and 6 h of the WIR (2.2- and 3.3-fold that of the control group without WIR, respectively). In contrast, superoxide dismutase, catalase, and glutathione peroxidase activities in the gastric mucosa did not change during the WIR period. Pretreatment with either allopurinol (AP), an inhibitor of XO, or soybean trypsin inhibitor (STI), a serine protease inhibitor, attenuated the lesion development at 6 h of WIR, but not at 3 h. In the gastric mucosa of rats pretreated with AP, enhancements of LPO formation, sulfhydryl oxidation, and XO activity found at 6 h of WIR were prevented with inhibition of XD plus XO activity, while in the gastric mucosa of rats pretreated with STI, these enhancements were prevented with inhibition of the conversion of XD to XO. In the gastric mucosa of rats pretreated with anti-polymorphonuclear leukocyte antiserum, the lesion development and enhanced LPO formation and sulfhydryl oxidation found at 3 and 6 h of WIR were prevented with a decrease in increased MPO activity. These results indicate that in the gastric mucosa of rats with WIR stress, the progression of lesions is mainly related to enhanced LPO formation and sulfhydryl oxidation which depend on an increased generation of oxygen free radicals via the xanthine-XO system and neutrophils rather than the change in the oxygen free radical-scavenging activity of antioxidant enzymes. The present results also suggest that increased gastric mucosal LPO formation and sulfhydryl oxidation found at 3 h of WIR could be mainly due to neutrophil-derived oxygen free radicals, while enhanced gastric mucosal LPO formation and sulfhydryl oxidation found at 6 h of WIR could be due to both neutrophil- and XO-derived oxygen free radicals.

Allopurinol↗
PubMed1997

Cerebral metabolism in sleep apnea. Evaluation by magnetic resonance spectroscopy.

Repeated apneic episodes during sleep may lead to cerebral damage in patients with obstructive sleep apnea (OSA). We performed proton magnetic resonance (MR) spectroscopic studies to examine cerebral metabolism in patients with OSA. We studied 15 healthy subjects and 23 patients with OSA who displayed no anatomical abnormalities on MR imaging. The patients were classified into two groups based on the results of polysomnography: mild OSA (11 patients) or moderate to severe OSA (12 patients). All the subjects were examined with two-dimensional chemical shift imaging. The N-acetylaspartate (NAA)/choline (Cho), NAA/creatine (Cre), and Cho/Cre ratios for cerebral cortex and white matter were calculated separately. A statistically significant intergroup difference was found for the NAA/Cho ratio in cerebral white matter (p < 0.005). This ratio was significantly lower in patients with moderate to severe OSA than in patients with mild OSA (p < 0.01) and healthy subjects (p < 0.01). Our findings indicate that cerebral metabolic changes occur in normal-appearing brain tissue in patients with moderate to severe OSA. The findings of a decreased NAA/Cho ratio suggests the presence of cerebral damage, probably caused by repeated apneic episodes. Proton MR spectroscopy may be useful for evaluating cerebral damage in patients with OSA.

Adult↗
PubMed1997

Laryngeal adjustment in whispering magnetic resonance imaging study.

Previous studies confirmed that during whispering the glottis is kept open to prevent vocal fold vibration and the supraglottal structures are constricted. However, there has been no study exploring the exact contour of the laryngeal lumen in the frontal dimension during the production of whispering. In order to further elucidate the nature of the laryngeal adjustments regarding the contour of the laryngeal lumen in whispering, and the role of supraglottal constriction in particular, we conducted a physiological study using magnetic resonance imaging. According to the results, the supraglottal structures were not only constricted but also shifted downward, attaching to the vocal fold to prevent vocal fold vibration completely during whispering. The results suggested the underlying mechanism of suppression of vocal fold vibration during the production of whispering.

Humans↗
PubMed1997

Purification and characterization of N-acetylneuraminate synthase from Escherichia coli K1-M12.

N-Acetylneuraminate (NeuAc) synthase, which catalyzes NeuAc synthesis by condensation of N-acetyl-D-mannosamine (ManNAc) and phosphoenolpyruvate (PEP), was purified from a cell extract of Escherichia coli K1-M12 to electrophoretically homogeneity by serial column chromatographies. The molecular weight of native enzyme was estimated to be 106,000 by gel filtration. After denaturation in sodium dodecyl sulfate, the molecular weight was reduced to 52,000, indicating the existence of 2 identical subunits. The optimum pH was 7.5 and the stable pH range was 7.0 to 10.0. The enzyme was thermostable up to 30 degrees C. No metal ion was required for the enzyme activity. SH-inhibitors such as p-chloromercuribenzoic acid and mercury chloride were potent inhibitors. The K(m) for ManNAc and PEP were 5.6 mM and 0.04 mM, respectively.

Chloromercuribenzoates↗
PubMed1997

Cellular hypertrophy and calcification of embryonal carcinoma-derived chondrogenic cell line ATDC5 in vitro.

During the process of endochondral bone formation, proliferating chondrocytes give rise to hypertrophic cells, which then deposit a mineralized matrix to form calcified cartilage prior to replacement by bone. Previously, we reported that a clonal cell line, ATDC5, undergoes efficient chondrogenic differentiation through a cellular condensation stage. Here we report that the differentiated ATDC5 cells became hypertrophic at the center of cartilage nodules, when the cells ceased to grow. Formation of hypertrophic chondrocytes took place in association with type X collagen gene expression and a dramatic elevation of alkaline phosphate (ALPase) activity. After 5 weeks of culture, mineralization of the culture could be discerned as Alizarin red-positive spots, which spread throughout the nodules even in the absence of beta-glycerophosphate. Electron microscopy and electron probe microanalysis revealed that calcification was first initiated at matrix vesicles in the territorial matrix and that it advanced progressively along the collagen fibers in a manner similar to that which occurs in vivo. The infrared spectrum of the mineralized nodules indicated two absorption doublets around 1030 cm-1 and 600 cm-1, which are characteristic of apatitic mineral. Calcifying cultures of ATDC5 cells retained responsiveness to parathyroid hormone (PTH): PTH markedly inhibited elevation of ALPase activity and calcification in the culture in a dose-dependent manner. Thus, we demonstrated that ATDC5 cells keep track of the multistep differentiation process encompassing the stages from mesenchymal condensation to calcification in vitro. ATDC5 cells provide an excellent model to study the molecular mechanism underlying regulation of cartilage differentiation during endochondral bone formation.

Alkaline Phosphatase↗
PubMed1997

The mechanism of respiratory rhythm generation during constant flow assisted mechanical ventilation in the decerebrated dog.

In awake human subjects input from the forebrain has significant effects on the respiratory pattern during assisted (AMV) and controlled (CMV) mechanical ventilation. The hypothesis in this animal study was that if the influence from the forebrain is eliminated, the respiration during AMV and that during CMV is controlled by the same mechanism. Fifteen decerebrated and tracheostomized dogs were subjected to CMV with a variety of combinations of tidal volume and frequency. The respiratory rhythm during CMV was simulated by a mathematical model composed of the central respiratory activity and inputs from pulmonary receptors. During AMV, the respiratory cycle duration was prolonged, and this was found to be the summated effect of prolonged Ttg (ventilator trigger period) and shortened Tinf (lung inflation period). When these changes in Ttg and Tinf were included, the model for CMV predicted respiratory changes during AMV. We concluded that the basic mechanism controlling AMV and CMV may be the same.

Animals↗
PubMed1997

Abnormal cerebral blood flow associated with antiphospholipid antibody syndrome--four case reports.

Patients with antiphospholipid antibody syndrome manifesting as neurological symptoms (one patient with twice repeated cerebral ischemic symptoms in the left parietal and frontal lobes, and the other patient with cerebral infarction of the right temporal lobe) and non-neurological symptoms (one patient with occlusion of the superior mesenteric artery and the other patient with thrombophlebitis) underwent cerebral blood flow (CBF) studies using xenon-enhanced computed tomography. The patients with neurological symptoms had decreased CBF at the affected sites. The patients with non-neurological symptoms had decreased CBF in the left parietal and temporal lobes and/or corona radiata. Subtle preclinical thrombosis may cause chronic cerebral hypoperfusion in patients with antiphospholipid antibody syndrome.

Adult↗
PubMed1997

Stroboscopic observation of the larynx after radiation in patients with T1 glottic carcinoma.

We studied laryngeal video stroboscopy (LVS) system for evaluation of patients with glottic carcinoma (T1N0M0) before and after radiotherapy. There were 10 patients with T1 glottic squamous cell carcinoma (9 men and 1 woman) who received radiotherapy at the Hitachi General Hospital. We performed LVS before and after radiotherapy. The presence or absence of mucosal waves (MW) was particularly noted. No MW were present before radiotherapy but at 1-6 months after, MW gradually appeared. One year after radiotherapy all patients showed MW on LVS. In patients with glottic carcinoma MW recovered after radiation therapy. LVS may be useful for the clinical follow-up of post-radiation patients for early detection of recurrence of glottic carcinoma.

Carcinoma, Squamous Cell↗
PubMed1997

Furosemide given by inhalation ameliorates acute exacerbation of asthma.

Previous studies have suggested that inhaled furosemide may have a protective effect against a wide variety of bronchoconstrictor agents, but a therapeutic effect has not been established in acute exacerbation of asthma. The purpose of this study was to investigate whether inhaled furosemide would exhibit any therapeutic benefit in acute asthma. We conducted a double-blind, placebo-controlled, randomized study in 40 patients with acute mild or moderate exacerbation of asthma. All patients received intravenous (i.v.) aminophylline 250 mg for 90 min and i.v. hydrocortisone 100 mg at entry. After randomization, 3 patients were excluded from the final analysis. At 30 min after starting i.v. aminophylline, 20 patients were given inhaled furosemide 20 mg and 17 patients received normal saline as placebo-control. Both inhalations were given by a jet nebulizer. The baseline forced expiratory volume at 1 sec (FEV1), peak expiratory flow rate (PEFR), and serum concentration of theophylline did not differ between the two groups. An increase in FEV1 in the furosemide group by 28.2 +/- 5.9% (mean +/- SE) was noted at 60 min, and this was significantly higher than in the control group. PEFR at 60 min was also significantly higher in the furosemide group than in control group. We conclude that inhaled furosemide has a bronchodilator effect on mild to moderate exacerbation of asthma when it is used with i.v. theophylline. Inhaled furosemide may benefit certain acute asthma patients, especially those suffering complications from the adverse effects of beta 2-agonists.

Acute Disease↗
PubMed1997

Attenuation of disrupted hepatic active oxygen metabolism with the recovery of acute liver injury in rats intoxicated with carbon tetrachloride.

In this study, we examined how disrupted hepatic active oxygen metabolism at a progressed stage of carbon tetrachloride (CCl4)-induced acute liver injury is attenuated with the recovery of the injury in fed rats. When the progression and recovery of liver injury were assessed by measuring the activities of serum transaminases, indexes of liver cell damage, at 2, 24, 48, and 72 h after a single intraperitoneal injection of CCl4 (1.0 ml/kg body weight), an apparent liver injury was found at 2 h, the most progressed liver injury occurred at 24 h, and the progressed liver injury fairly recovered at 72 h. Hepatic superoxide dismutase and catalase activities decreased with the progression of liver injury but both decreases were maintained during the recovery of the injury. Hepatic glutathione peroxidase activity did not change with the progression and recovery of liver injury. Hepatic glutathione reductase activity decreased with the progression of liver injury and the decreased activity was returned up to the original level with the recovery of the injury. Hepatic glucose-6-phosphate dehydrogenase activity increased with the progression and recovery of liver injury but this increased activity was reduced at a late stage of the recovery. Hepatic reduced glutathione and ascorbic acid contents decreased with the progression of liver injury but both decreased contents were returned up to the original levels with the recovery of the injury. Hepatic vitamin E content decreased at an early stage of liver injury but this decreased vitamin E content increased over the original level with the progression of the injury and this increased vitamin E content was maintained during the recovery of the injury. Hepatic lipid peroxide content increased with the progression of liver injury and this increased content was returned near the original level with the recovery of the injury. These results indicate that in rats intoxicated once with CCl4, disrupted hepatic active oxygen metabolism at a progressed stage of liver injury is attenuated with the recovery of the injury mainly through the improvement of hepatic active oxygen metabolism mediated by the glutathione redox cycle and ascorbic acid.

Alanine Transaminase↗
PubMed1997

Expression of intercellular adhesion molecule-1 and lymphocyte function-associated antigen-1 on alveolar macrophages in the acute stage of radiation-induced lung injury in rats.

We investigated the expression of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) on alveolar macrophages and on lung tissue in the early stage of radiation-induced lung injury. Cells in the bronchoalveolar lavage and lung tissue were obtained from rats at various times between 1 and 8 weeks after 20 Gy of 60Co gamma irradiation of a hemithorax. These specimens were stained immunohistochemically with anti-ICAM-1 and anti-LFA-1alpha monoclonal antibodies. The expression of these factors was compared with that of a control group. The total number of alveolar macrophages in the bronchoalveolar lavage was significantly reduced from 1 to 3 weeks, and the number of neutrophils was significantly increased 2 and 3 weeks after irradiation. ICAM-1 and LFA-1 expression on alveolar macrophages was significantly increased starting 1 week after irradiation. The expression of ICAM-1 and LFA-1 on lung tissue was not elevated up to 8 weeks after irradiation. In conclusion, the increased expression of ICAM-1 and LFA-1 on alveolar macrophages as early as 1 week after irradiation suggests that adhesion molecules play a role in the development of radiation-induced lung injury.

Analysis of Variance↗