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Biomedical subjects

M Okada

Publications and source records attributed to M Okada.

At least 1,243 records · Page 69Linked to original sources
PubMed1989

[The anti-mutagenic effects of human saliva investigated by umu-test. Part 1. Effects of filtration and storage at low temperatures].

The anti-mutagenic effects of human saliva were examined by the umu-test. The SOS-inducible DNA-damaging activity of AF-2 was markedly decreased by pre-treatment with human fresh saliva. The anti-mutagenic activity of human saliva was retained even after the filtration (0.45 microns). This activity was also observed after 24 hr-storage at 10 degrees C or -12 degrees C. These results were consistent with previous reports using Ames tests. Significant differences in the activity, however, were observed between sample donors and between experiments with the same sample donor. Further analyses of the effects of the factors contained in saliva as well as the effects of life-styles, including dietary-habits of sample donors will be necessary.

Adult↗
PubMed1989

[Simulation of bone resorption in denture patients using finite element analysis. 1. Application of optimization method].

The purpose of this study was to simulate the process of bone resorption under removable denture bases. Two dimensional finite element models were prepared for the frontal section of a maxillary complete denture with its supporting mucosa and bone in the first molar region. Simulations were performed with the optimization program which could proportionally move the nodal points according to the stress level difference between the actual and the reference stress level. By exerting loads on occlusal table of the model, the bone resorption progressed in the similar manner to reported clinical observations. The location and magnitude of the resorption were highly related to the location and direction of the loads.

Alveolar Bone Loss↗
PubMed1989

A new model of duodenal ulcers induced in rats by diethyldithiocarbamate, a superoxide dismutase inhibitor.

Repeated administration of diethyldithiocarbamate (DDC: 750 mg/kg, s.c.), a superoxide dismutase (SOD) inhibitor, to fed rats induced ulcers in the duodenum with less lesion in the stomach. DDC not only reduced basal acid output but also impaired duodenal alkaline secretion under both basal and acid-stimulated conditions. The duodenal ulcers induced by DDC were significantly prevented by either allopurinol, SOD or dmPGE2 at the doses which significantly reversed the inhibited alkaline responses caused by DDC. The pathogenesis of DDC-induced duodenal ulcers may involve impairment of duodenal alkaline secretion, probably caused by insufficiency of antioxidant machinery in the mucosa.

16,16-Dimethylprostaglandin E2↗
PubMed1989

Increase in negative charge of cytosolic aspartate aminotransferase in vitamin B6 deficiency and during incubation.

Several subforms of cytosolic aspartate aminotransferase (AspATc) in the crude extracts of rat liver and kidney were separated by isoelectric focusing using immunoblotting and staining of activity to detect the enzyme protein and activity, respectively. Vitamin B6-deficiency resulted in decrease in the subforms with higher isoelectric points and increase in those with lower ones both in the liver and in the kidney. When pyridoxal phosphate was added to those preparations from vitamin B6-deficient rats, the isoelectric focusing pattern of kidney was recovered to the similar one to that of the controls. However, the liver preparation was affected only partially by the addition of PLP. The pattern of subforms was altered during in vitro incubation at 37 degrees C for 24 h in both liver and kidney preparations, and their patterns were very similar to that of liver preparation from VB6-deficient rats. The enzyme activity also decreased during this incubation, especially in preparations of the enzyme from the liver of vitamin B6-deficient rats. This loss of enzyme activity was not affected by addition of PLP alone, but was almost completely prevented by addition of substrate. The inactivation was recovered by addition of substrate and pyridoxal phosphate simultaneously. This finding suggests that the inactivation may be related with a conformational change around the catalytic site of the AspATc molecule.

Animals↗
PubMed1989

[Inference engines of expert systems for designing removable partial dentures].

The expert system for designing removable partial dentures has a great potentiality for clinical and educational use. The system sorts out several solutions for clinical problems with the aid of logic and data bases stored in the memory bank. The most important part of this system is the inference engine. Production system and frame system are often used as the inference engine. The purpose of this report was to compare different types of inference engine in practical situations. Following conclusion were obtained. 1) Since each type of inference engine has its own advantages and disadvantages, one has to select most suitable one for the purpose of the system. 2) One must select the inference engine type which will help potential user's understanding.

Denture Design↗
PubMed1989

[Clinical application of T-scan System. 1. Sensitivity and reproducibility and its application].

Analyzing occlusal contacts is significant for establishing the occlusal scheme as well as for the diagnosis on dysfunction of stomatognathic system. We tested a new occlusal contact analyzing device (T-Scan: Tekscan Inc. Boston, U.S.A.) for its sensitivity and reproducibility in relation to its clinical application. Following results were obtained. 1) As the modeling of dental arch of this system was not always correct, much care should be needed for identifying the contact location. 2) The minimum amount of load needed for displaying each five step occlusal force increased linear fashion (step 1: 250 g and step 5: 1750 g) when the sensor was vertically pressed on the intersection of force sensitive line. The minimum amount of force changed with the loading condition such as area and direction. Distortion of the sensor could lead the measurement error. 3) Since the time measurement data by this system were shorter than actual length of time and were measured over about 250 g load, light and early occlusal contacts could not be detected.

Dental Arch↗
PubMed1989

[Construction of data base for designing removable partial dentures. 1. Retainer and abutment selection].

In designing removable partial dentures (R.P.D.) for edentulous patients, variety of designs are selected with considering the condition of residual teeth, alveolar ridge, occlusion and other factors. We have been trying to develop the computer consultation system for designing R.P.D. (so called "expert system") to rationalize the processes of R.P.D. design. In developing and expanding this system, the construction and enlargement of the rulebase and database are indispensable. In this report, we analyzed R.P.D. designs in student's clinic ('83-'85), in order to find the logic for design (rulebase) and to construct databases. Following results were obtained. 1) Wire clasps were most frequently used in Kennedy classification I, II in maxilla. Double clasps were mostly used in Kennedy class I, II in mandible. Akers' clasps were mostly used in class III. 2) Canine, first and second premolar were more frequently selected for abutment than other teeth.

Denture Design↗
PubMed1989

[A case of coronary spasm during general anesthesia successfully treated with nitroglycerin and verapamil].

We had a patient without history of angina, who repetitively showed transient elevation of ST-segment during general anesthesia. Coronary spasm was suspected, but no triggering factors could be detected; the spasm being observed under deep and stable anesthesia and at this point no surgical stimulations were interposed. It was treated successfully with intravenous administrations of nitroglycerin and verapamil and no further elevations of ST-segment could be observed.

Aged↗
PubMed1989

Inherited deficiency of functional and free form protein S.

We studied hemostatic function in a family with a history of venous thromboembolic disease. In the propositus, a 36-year-old male, the results of assays for the coagulation, anticoagulation and fibrinolytic factors were almost normal. However, the functional protein S activity in his plasma was less than 5% of normal. Similar laboratory findings were noted in his paternal uncle and two sisters who had recurrent thrombotic episodes and in his asymptomatic father as well. The mean total protein S antigen level in these five patients was 37% (range 19-66%) by conventional Laurell rocket immunoelectrophoresis. However, by crossed immunoelectrophoresis of their plasmas and Laurell rocket immunoelectrophoresis of the polyethyleneglycol 6000-treated plasmas, the free form of protein S was undetectable in their plasmas. The levels of C4b-binding protein in the plasma of three of the five patients were in normal range, and that those in the remaining two were below the normal level. These findings suggest that the recurrent thrombotic disease in this family is due to inherited deficiency of protein S, particularly of the functionally active free form of protein S.

Adult↗
PubMed1989

Affinity labeling of ACTH receptors in bovine adrenal cortex membranes.

Adrenocorticotropin labeled with 125I at Tyr23 [(125I-Tyr23]ACTH) was prepared by radioiodination of ACTH1-39 followed by reverse phase HPLC purification. When incubated with bovine adrenal cortical membranes, the radioligand bound specifically to a 40-kDa membrane protein as revealed by affinity labeling. This result indicates that the bovine adrenal ACTH receptor, whose identification and characterization have proved difficult, has an Mr of about 40,000.

Adrenal Cortex↗
PubMed1989

[Long-term survival with Hufnagel ball valve--a case report].

Authors report a 61-year-old female with an aortic aneurysm at the distal end of the Hufnagel ball valve which was implanted surgically for the treatment of aortic insufficiency 23 years previously. The Hufnagel ball valve has been working well for the past 23 years, but the aneurysm was found enlarging in size, therefore the replacement of aneurysm with a 20 mm dacron graft was performed following removal of the well-working Hufnagel ball valve. There were 151 cases with Hufnagel ball valve implantation in the literature and at least 7 cases of them were reported in Japan. Among them, the majority survived only several years after surgery and the cases with long-term survival were very few in number. Our case is unique, because the valve in this case has worked well for 23 years.

Aortic Aneurysm↗
PubMed1989

[Experimental and clinical studies on the laser application in the cardiovascular surgery; analysis of clinical experience of 112 patients].

Since 1980, we have applied lasers experimentally in the following three categories in the fields of cardiovascular surgery. That is, Group 1: New myocardial revascularization in the patients whose coronary arteries are too small or diffuse due to atherosclerosis, Group 2: Laser vascular anastomosis especially for small-caliber vessels, such as coronary artery bypass grafting, Group 3: Laser angioplasty for obstructive arterial disease. Subsequently, efficacy of laser application could be obviously recognized in these fields. On the basis of excellent results of our experimental studies, laser was clinically employed for 112 patients with anginal pain, intermittent claudication and renal failure. They consisted of new myocardial revascularization in one case and vascular anastomosis in 89 cases including 7 cases (LIMA-LAD2, SVG-LAD5) of the coronary artery bypass grafting and laser angioplasty in 22 cases including 5 cases (LAD3, RCA2) of intraoperative laser coronary angioplasty. Optimal conditions of vascular anastomosis were 20-40mW in output and 6-12sec/mm in irradiation time. On the other hand, optimal conditions for laser angioplasty were 6 watts in output and 3sec in irradiation time for each shot. Laser irradiation was carefully repeated according to the grade of atherosclerotic changes. These patients are doing well without any complications throughout laser. Our experimental and clinical experiences of laser application in the fields of the cardiovascular surgery were presented in detail.

Adolescent↗
PubMed1989

[Effect of the intra-aortic balloon pumping on renal function].

The effect of IABP on renal function were studied in 41 patients who underwent cardiac operation. Eight of the 41 patients were acute myocardial infarction (AMI), 4 were unstable angina, and 29 were postoperative low cardiac output syndrome (LOS). In 12 patients with AMI and unstable angina, an IABP was inserted preoperatively. Urinary N-acetyl-beta-D-glucosaminidase (U-NAG) and fractional excretion of beta 2-microglobulin (FE beta 2M) in addition to conventional renal parameters such as creatinine clearance (Ccr) and free water clearance (CH2O) were measured before and during IABP. Patients were divided into three groups according to its responses within 6 to 12 hours of IABP. In Group I (25 cases) which showed the significant improvement of renal and cardiac function, the values of Ccr, CH2O improved to normal range within 6 hours after initiation of IABP. In Group II (4 cases) which showed improved renal functions in spite of insufficient improvement of cardiac functions, renal functions improved 12 hours late, showing 6 hours delay from Group I. In Group III (8 cases) both the renal functions as well as cardiac functions did show no improvement. Retrospective study demonstrated that the patients whose Ccr improved above 50 ml/min/1.48 m2 and CH2O reduced below -0.55 ml/min/1.48 m2 and within 12 hours after initiation of IABP were able to wean from IABP. However, the patients whose Ccr reduced less than 50 ml/min/1.48 m2 and CH2O grown worse above -0.55 ml/min/1.48 m2 for longer than 12 hours could not wean from IABP. And the patients whose U-NAG and FE beta 2M reduced less than 20 U/l and 3.0% during IABP support were able to wean from IABP. In conclusion, IABP was effective therapy for the patients with cardiogenic shock, LOS, and renal dysfunction.

Adult↗
PubMed1989

[Superplastic forming of titanium alloy denture base].

Ti-6Al-4V alloy has both excellent biocompatibility and superior mechanical properties. This Ti-6Al-4V can be deformed greatly and easily at the superplastic temperature of 800 degrees C to 900 degrees C. The superplastic forming of Ti-6Al-4V was made to apply to fabrication of denture base. Almost the same procedure as for dental casting mold was employed in producing the superplastic forming die by the improved phosphate bonded investment. In the pressure vessel of heat resistant alloy, Ti-6Al-4V plate was formed superplastically on the die by argon gas pressure at 850 degrees C. The fit of superplactic forming Ti-6Al-4V denture base was better than that of casting Co-Cr alloy denture bases. The Ti-6Al-4V alloy might react a little with the die. Because micro Vikers hardness of the cross-section did not go up too much near the surfaces. Even just after being formed, the surfaces were much smoother than that of Co-Cr alloy casting. The tensile strength and yield strength of superplastic forming Ti-6Al-4V were higher than those of Co-Cr castings. The elongation was about 10%. These results show that superplastic forming of Ti-6Al-4V would be suitable for a denture base.

Dental Alloys↗
PubMed1989

[Current topics on coronary artery surgery: clinical experience of laser application].

In recent years, laser has been gradually utilized in cardiovascular surgery. Since 1980, we have applied lasers experimentally in the following three categories in the fields of cardiovascular surgery. That is, Group 1: new myocardial revascularization in the patients for whom coronary artery bypass surgery can not be performed, because of small or diffuse coronary arteries, Group 2: laser vascular anastomosis especially for small-caliber vessels, Group 3: laser angioplasty for obstructive arterial disease. Subsequently, efficacy of laser application could be obviously recognized in these fields. On the basis of good results of our experimental studies, laser was clinically employed for 112 patients with anginal pain, intermittent claudication or renal failure. Optimal conditions of vascular anastomosis were 20-40 mW in output and 6-12 sec/mm in irradiation time. They consisted of new myocardial revascularization in 1 case and vascular anastomosis including 7 cases of coronary artery bypass surgery in 89 cases and laser angioplasty with 5 cases of intraoperative laser coronary angioplasty in 22 cases. Optimal conditions for laser angioplasty were 6 watts in output and 3 sec in irradiation time for each shot. Laser irradiation was carefully repeated according to the grade of atherosclerotic changes. Vascular endoscopy was useful to keep safe procedures. These patients are doing well without complications throughout laser. Our clinical experience of laser application in the cardiovascular surgery is presented in detail.

Adolescent↗
PubMed1989

[Prediction of coronary artery disease using post exercise T wave change].

In the evaluation of the exercise stress test, conventional electrocardiographic criteria using 1 or 2 mm ST segment depression below the isoelectric line yields many false positive results and is not so useful to predict the severity of coronary artery disease. In this study, we have attempted to predict the presence and the severity of coronary artery disease from the post exercise T wave change. Fifty-six patients who had positive treadmill exercise test results by conventional ST segment criteria and underwent selective coronary arteriography were studied. T wave change was defined as inversion or biphasic change in one or more of leads aVF, V4, V5, V6 during the recovery phase, and in the cases who showed T wave changes, T wave configuration were also analysed. Seventeen of 28 patients with and 11 of 28 patients without significant coronary artery disease showed post exercise T wave changes. This difference was not statistically significant. But in the cases who showed T wave changes, the maximum amplitude of the negative component of T wave was significantly greater in the true positive group than in the false positive group. And the development of deeply negative component (more than 1.5 mm) indicated the presence of multivessel coronary artery disease. In the cases who showed the negative component of T wave less than 1 mm, the characteristics of T wave configuration including the amplitude, height of positive component, and the depth from the isoelectric line were different between the 2 groups. These results suggest that careful observation of T wave during the recovery phase is useful to improve the diagnostic accuracy of the exercise electrocardiogram.

Adult↗