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Biomedical subjects

M Ohwa

Publications and source records attributed to M Ohwa.

At least 19 recordsLinked to original sources
PubMed1996

Design of a stable charge transfer complex electrode for a third-generation amperometric glucose sensor.

A novel approach to prepare a stable charge transfer complex (CTC) electrode for the direct oxidation of flavoproteins and the fabrication of a third generation amperometric biosensor (Koopal, C.G.J.; Feiters, M.C.; Nolte, R.J.M. Bioelectrochem. Bioenerg. 1992, 29, 159-175) system is described. Tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), an organic CTC, is grown at the surface of a shapable electroconductive (SEC) film (a polyanion-doped polypyrrole film) in such a way that it makes a tree-shaped crystal structure standing vertically on the surface. Glucose oxidase (GOx) is adsorbed and cross-linked with glutaraldehyde to fix at the surface of the CTC structure. The space between crystals is filled with cross-linked gelatin to ensure the stability of the treelike crystal structure as well as the stability of the enzyme. Because of the close proximity and the favorable orientation of the enzyme at the CTC surface, the enzyme is directly oxidized at the crystal surface, which leads to a glucose sensor with remarkably improved performance. It works at a potential from 0.0 to 0.25 V (vs Ag/AgCl). The maximum current density at 0.25 V reaches 1.8 mA/cm2, with an extended linear range. The oxygen in the normal buffer solution has little effect on the sensor output. The current caused by interference contained in the physiological fluids is negligible. The working life as well as the shelf life of the sensor is substantially prolonged. The sensor was continuously used in a flow injection system with a continuous polarization at 0.1 V, and the samples (usually 10 mM glucose) were injected at 30 min intervals. After 100 days of continuous use, the current output dropped to 40% of the initial level. No change in the output of the sensor was observed over a year when the sensor was stored dry in a freezer. The electrochemical rate constants and the effective Michaelis constant of the system are reported.

Biosensing Techniques↗
PubMed1995

[Immunohistochemical analysis of adhesion molecules in directional coronary atherectomy specimens].

Chronic inflammatory cells are key components in the progression of atherosclerotic plaques and restenosis after coronary angioplasty. Adhesion molecules are fundamental in inflammatory processes. Therefore, the distributions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule (VCAM) were investigated in directional coronary atherectomy specimens obtained from 14 patients, in 6 with acute coronary syndromes (myocardial infarction and unstable angina within 1 month), 6 with old myocardial infarction and 2 with stable effort angina. There were eight primary lesions and six restenotic lesions. Atherectomy tissue fragments were snap frozen and cut into 4 microns thick cryostat sections for immunohistochemical staining by avidin-biotin complex immunoperoxidase techniques using adhesion molecule specific monoclonal antibodies BBIG-I1 (ICAM-1) and BBIG-V1 (VCAM). The cells of lesions were characterized in sequential sections by macrophage marker KP1 (CD68), endothelial marker JC/70A (CD31), and smooth muscle cell marker 1A4 (alpha-smooth muscle actin). Four restenotic lesions that had undergone a prior balloon angioplasty within a few months consisted of intimal proliferation and the other lesions were atherosclerotic plaque. Macrophage-rich areas were seen in the lesions from acute coronary syndromes and/or early restenotic lesions. Expression of ICAM-1 or VCAM was strongly associated with macrophage-rich areas, but VCAM staining was weaker than ICAM-1 except in one restenotic lesion. Macrophages that express ICAM-1 and/or VCAM may be important in the unstable plaques and restenotic lesions related to disease activity of ischemic heart disease.

Aged↗
PubMed1993

Study on high-strength plastic teeth. Tooth discoloration.

Conventional plastic teeth (CV teeth) are inferior to porcelain teeth in maintaining an adequate esthetic appearance with wear and discoloration, and thus have a shorter period of durability. Recently, high-strength plastic teeth (HS teeth) have been developed and applied to overcome the wear problems of CV teeth. Since HS teeth made of hard resin are still susceptible to staining with pigments, it has been observed that the esthetics of removable partial dentures made from such plastic teeth are gradually impaired in many patients. To investigate the susceptibility of HS teeth to pigments, we conducted an in vitro study by immersing three types of artificial teeth in three coloring liquids. It was found that the HS teeth tended to be less susceptible to the test pigments than the CV teeth to various degrees. In contrast, they showed markedly stronger susceptibility to the pigments than porcelain teeth. For all three artificial tooth types, daily tooth cleaning with an ultrasonic vibrator had a tendency to reduce the coloration in comparison with their counterparts without ultrasonic cleaning.

Acrylic Resins↗
PubMed1993

Study on the castability of Co-Cr alloy for cast plates. Part 3: Effects of alloy fusion temperature and the heating temperature of the cast ring.

Co-Cr alloy is used more frequently than Ni-Cr alloy as a non-precious alloy for cast plates in Japan. However, since the melting temperature of Co-Cr alloy is very high, about 1300 degrees C, and since it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reduced atmosphere has recently been developed. Using this machine, the effects of fusion temperature and the heating temperature of the cast ring on the Co-Cr alloy were studied. It was found that in the vacuum-pressure casting method, both the fusion temperature of the Co-Cr alloy and the heating temperature of the cast ring had a significant effect (p < 0.01) on the castability of the Co-Cr alloy.

Chromium Alloys↗
PubMed1992

Wear of denture teeth by use of metal plates. Part 2: Abrasive wear of posterior teeth.

An in vitro study was conducted to evaluate the abrasive wear resistance of high-strength denture teeth (HS teeth). Eight types of specimen were used in the experiments; 3 types of HS teeth, 3 types of conventional plastic denture teeth (PL teeth), porcelain teeth and metal teeth. Sliding-induced wear tests were conducted by sliding the samples on a metal plate. The abrasive wear resistance of the samples was evaluated in terms of wear depth, weight loss and SEM observation. Comparison of wear depth showed that abrasive wear resistance of HS teeth was 4.7 times that of PL teeth, 0.7 times that of porcelain teeth and 8.3 times that of metal teeth. In terms of weight loss, the corresponding values were 3.3-fold, 0.2-fold and 11.4-fold, respectively.

Dental Porcelain↗
PubMed1992

Wear of denture teeth by use of metal plates. Part 3: Abrasive wear of posterior teeth and wear of opposing metal plates.

An in vitro evaluation of abrasive wear resistance of high-strength denture (HS) teeth and wear of metal plates (Pd alloy) on the opposing side was conducted. A total of 8 types of teeth were used in the experiments including 3 types of HS teeth, 3 types of conventional plastic denture (PL) teeth, porcelain teeth and metal teeth (Pd alloy). Sliding-induced wear tests were conducted by sliding these teeth over the metal plates. Abrasive wear resistance of the teeth was evaluated in terms of wear depth and weight loss. A comparison of wear depth showed that the abrasive wear resistance of HS teeth was 4.7 times that of PL teeth, 0.7 times that of porcelain teeth and 8.3 times that of metal teeth. Weight loss showed that the abrasive wear resistance of HS teeth was 3.3 times that of PL teeth, 0.2 times that of porcelain teeth and 11.4 times that of metal teeth. The weight loss of the metal plates was minimal when they slid over HS teeth, but increased in the order PL teeth, porcelain teeth and metal teeth.

Dental Alloys↗
PubMed1991

[CABG in 2 patients with severe left ventricular dysfunction].

Coronary artery bypass grafting was performed in two patients with left ventricular dysfunction (EF 16%). In both cases they had chest pain at rest and ischemic myocardium were detected by the SPECT. We considered them candidate for the operation regardless of LV dysfunction. They were eventful in the postoperative course. One case was discharged and is free from chest pain now, but another unfortunately died for multiple organ failure.

Coronary Artery Bypass↗
PubMed1990

Wear of artificial denture teeth by use of toothbrushes. Part 1: Abrasive wear of anterior teeth.

High-strength denture teeth (HS teeth) were developed in order to improve the hardness and wear resistance of conventional plastic denture teeth (PL teeth), while retaining their feature of easy occlusal adjustment. The objective of this study was to evaluate the abrasive wear resistance of HS teeth. We conducted wear tests and measured surface roughness using six types of anterior artificial teeth, i.e., three types of HS teeth and three types of PL teeth, the latter serving as the control. The results of the toothbrush abrasion test revealed that the HS teeth had about 5 times greater wear resistance than the PL teeth. It was also found that the type of artificial teeth and the number of abrasive wear-testing strokes had a significant (P less than 0.05) influence on the surface roughness of artificial teeth.

Dental Stress Analysis↗
PubMed1990

[Acute myocardial infarction due to blunt chest trauma: a case report].

A 32-year-old man who suffered from acute myocardial infarction due to blunt chest trauma was admitted to our hospital. The first coronary angiography was performed on the 38th day after admission. We found aneurysmal dilatation, intimal flap and subintimal hematoma, so coronary dissection of the left anterior descending branch was suspected. When the second coronary angiography was performed 11 months later, those findings had disappeared.

Adult↗
PubMed1987

[Noninvasive measurement of cardiac output using two-dimensional Doppler echocardiography and analysis of sources of error].

The purpose of this study was (1) to analyze the factors responsible for errors in the two-dimensional Doppler echographic measurements of cardiac output (C.O.) and (2) to establish a noninvasive method for measuring C.O. The subjects were 50 cardiac patients who had neither aortic valve disease nor intracardiac shunts. The C.O. was calculated using the following formula: C.O. (l/min) = mean flow velocity (cm/sec) x pi(aortic ring diameter/2)2 (cm2) x 60/10(3) Left ventricular ejection flow velocity was recorded in the center of the aortic ring from the apical approach. Mean velocity was calculated by integration of instantaneous mean velocity in the ejection phase divided by the cardiac cycle length, and was corrected by the Doppler incident angle. The inner diameter of the aortic ring was measured in the parasternal long-axis view at the time of the maximum ejection flow velocity. The following results were obtained: 1. Sources of error in the measurement of cardiac output. 1) Accuracy of instantaneous mean velocity calculating circuit: This calculating circuit was accurate in model experiments using pulsatile flow. 2) Effect of high-pass filter: In model circuits, application of high-pass filter overestimated flow velocity. The higher the cut-off frequency of the high-pass filter, the larger the overestimation. This was probably due to the parabolic flow velocity profile in the circuit. 3) Flow velocity profile in the aortic ring: The flow velocity profile seemed to be flat in the aortic ring except near the anterior aortic wall. Therefore, the effect of the high-pass filter was considered to be negligible in case of clinical application. 4) The effects of shift and size of sample volume: The location of sample volume relative to the aortic valve ring shifted about 7 mm during systole. However, the shift and size of sample volume seemed to have little effect on the measured C.O., because the flow velocity profile was nearly flat in the aortic ring. 5) Ultrasound beam incident angle: From a practical viewpoint, it was necessary to set an incident angle of less than 50 degrees for minimizing the error. We were able to set the angle within 50 degrees in all but one of patients. 6) Diameter of the aortic ring: Two-dimensional echographic measurement of the aortic ring diameter was not so accurate; it seemed to become a major source of error in the calculation of C.O.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

[Mitral regurgitation: detection and quantitative evaluation by two-dimensional Doppler echocardiography].

Mitral regurgitation was detected and quantitatively evaluated using two-dimensional Doppler-echocardiography. The subjects consisted of 74 cases having a variety of heart diseases, who underwent left ventriculography within one week before or after the Doppler study. Among 50 patients with mitral regurgitation confirmed by left ventriculography, the Doppler study detected mitral regurgitant flow signals in 46, for a sensitivity of 92%. Minimal mitral regurgitation in four cases could not be detected by Doppler studies. Twenty-four patients had no mitral regurgitation according to left ventriculography; all but one also had no mitral regurgitation by Doppler study, for a specificity of 96%. In one false positive case, typical mitral regurgitant flow signals were detected in an area localized within the left atrial cavity near the mitral valve orifice. The possibility remains that left ventriculography missed this minimal regurgitation. For quantitative assessment of mitral regurgitation, the following two methods were used. Three long-axis views through the lateral, middle and medial parts of the mitral valve, and a short-axis view at the level of the mitral orifice were imaged via the parasternal approach. The area where mitral regurgitant flow signals were detected was mapped on each cross-sectional echocardiogram, then the distance attained by the regurgitant flow from the mitral valve and the area covered by the regurgitant flow were determined. The maximal distance among the three long-axis views and the sum of the distances in these views was parallel to the severity of mitral regurgitation as assessed by left ventriculography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

[Noninvasive determination of the ratio of pulmonary to systemic blood flow with two-dimensional Doppler echocardiography: efficacy and limitation].

Noninvasive determination of the ratio of the pulmonary to systemic blood flow (Qp/Qs) was attempted in 31 cases with intracardiac shunt using two-dimensional pulsed Doppler echocardiography. The Qp/Qs of these cases was ranged from 0.99 to 4.55 with an average of 2.63 by cardiac catheterization. Technical problems in the measurement were also studied. Seventeen cases with no shunt were served as controls. Systemic and pulmonary flow volumes, Qp and Qs (ml/min), were calculated by the following equation: Q (ml/min) = mean flow velocity (cm/sec) X cross sectional area of the semilunar valve ring (cm2) X 60 Here, the sample volume was set in the center of the valve ring at the phase when the flow velocity attained its peak in a pulse period. The mean velocity was obtained by dividing the integration of instantaneous mean frequency in the sample volume for a pulse period by RR interval. The ultrasonic incident angle was measured on the echocardiogram. The velocity profile at the valve ring was assumed to be a plane wave. The diameter (D) of the valve ring was measured on the echocardiograms of the long-axis view of the outflow tract. To make a correction referring to the value obtained by angiocardiography, 0.22 cm was added to the value obtained on the echocardiogram (D). The cross sectional area of the valve ring was calculated according to the following formula: Cross sectional area (cm2) = pi X [(D + 0.22/2)]2 The Qp/Qs ratio by the Doppler method in the cases with no intracardiac shunt was 1.11 (S.D. = 0.21) on an average and the Qp/Qs in the cases with an intracardiac shunt was well correlated with that by catheterization (r = 0.82). These results suggested the feasibility of the clinical application of the Doppler method for noninvasive determination of Qp/Qs. In 17 cases, pulmonary and systemic flow volumes measured by the direct Fick method were compared with those by the Doppler method, respectively. Considerable differences were observed between them. There was a tendency that both pulmonary and systemic flow volumes were under-estimated by the Doppler method in cases with a large shunt.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Circulation↗