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Biomedical subjects

T Okabe

Publications and source records attributed to T Okabe.

At least 307 records · Page 17Linked to original sources
PubMed1989

[Normalizing method for determining the mode of crack-propagation in amalgams and composite resins].

A normalizing method for determining the mode of crack-propagation in a phase or component of a dental amalgam or composite resin was devised. The results calculated using the method were found to be satisfactory when the method was applied to the materials. Furthermore, details of the mode of crack-propagation in the materials which cannot be seen using pictures of the cross-section structure of the materials are revealed using the method.

Composite Resins↗
PubMed1989

[Theoretical patterns of the panel D-15 test in congenital dichromatic color vision defects].

In order to study the theoretical patterns of the panel D-15 test for congenital dichromatic color vision defects, the spectral reflectance for the 16 color caps of the panel D-15 test was measured with a spectro-photometer. Then, the chromaticity-coordinates of each color cap were calculated using the spectral distribution of standard illuminant C. The theoretical patterns of the panel D-15 test for dichromats were obtained based on the confusion lines. For this procedure, the slope of the line between the color cap and the convergence point on the CIE chromaticity diagram was obtained first. Then, the order of the arrangement was decided starting with the slope having the smallest cap number and continuing progressively. For the chromaticity coordinates of the convergence points the following values were used; x = 0.7465, y = 0.2535 for protanopia, x = 1.08, y = -0.08, x = 1.40, y = -0.40, and x = 1.70, y = -0.70 for deuteranopia, and x = 0.171, y = 0.000 for tritanopia. The results show a very clear similarity between the orientation axis obtained by simulation and the actual data. Therefore, it was confirmed that dichromats arrange the color caps in the order of the slope of the line between the color cap and the convergence point, when performing the panel D-15 test. Furthermore, it was suggested that the patterns of the panel D-15 test differ by the convergence points among dichromats even of the same type.

Color Perception↗
PubMed1989

[Theoretical patterns of the panel D-15 test in congenital red-green dichromats as a function of the chromaticity coordinate of the convergence points].

In order to determine whether or not the patterns of the panel D-15 test for congenital red-green dichromats change when the convergence point is changed, a simulation experiment was attempted assuming that dichromats arrange the color caps in the order of the slope of the line between the chromaticity coordinates of the color cap and the convergence point. For this procedure, chromaticity coordinates of the color cap were calculated using both the spectral distribution of standard illuminant C and the daylight fluorescent lamp (Toshiba-EDL). For this prediction, the chromaticity coordinates of the convergence points were changed according to y = 1-x. The results show several different patterns for both protanopia and deuteranopia under both illuminants. The range of the x chromaticity coordinates common to both illuminants was 0.6868 to 0.8552 when the protanopic patterns were obtained, while the range of the x chromaticity coordinates common to both illuminants for deuteranopic patterns was 1.0878 to infinity and minus infinity to -1.8153. As a result, it was suggested that the patterns of the panel D-15 test for red-green dichromats change according to the convergence points. Therefore, it was considered that this test cannot be used as a dependable measurement for color discrimination ability in cases showing dichromatic patterns.

Color Perception↗
PubMed1989

Effects of streptozotocin-induced diabetes on glucose utilization that was stimulated by various agents in rat thymocytes.

Post receptor insulin resistance has been demonstrated in insulin sensitive tissues from streptozotocin induced diabetic animals. Insulin deficiency itself or metabolic derangements of diabetes seem to contribute to this insulin resistant state. However, the mechanism is presently unknown. Using largely insulin insensitive rat thymocytes, we have studied glucose oxidation stimulated by agents that mimic insulin action but that work independently of the insulin receptor. Glucose oxidations stimulated by these agents were markedly diminished in the thymocytes from streptozotocin induced diabetic rats. These findings as well as our finding that the thymocytes from diabetic rats possess a normal complement of insulin receptor provide further evidence that post insulin receptor impairment of glucose metabolism occurs in streptozotocin diabetes. Thus although thymocytes are not sensitive to insulin, they are useful for the investigation of the impaired glucose metabolism.

Animals↗
PubMed1989

[A case of thoracic kidney].

An asymptomatic 37-year-old woman visited our outpatient clinic for evaluation of an abnormal shadow of the right thorax detected by a mass roentgenographic survey. P-A chest roentgenogram showed a round homogeneous mass with a convex superior margin in the posterior portion of the right thorax. The CT with contrast enhancement and intravenous pyelography demonstrated the ectopic high location of the right kidney. Renal arteriography showed the right renal artery originated from the abdominal aorta at a normal level. Renal function tests showed no abnormality.

Adult↗
PubMed1988

Radioimmunotherapy of transplanted small cell lung cancer with 131I-labelled monoclonal antibody.

Monoclonal antibody TFS-4 has previously been shown to react selectively with human small cell lung cancer (SCLC). We evaluated the use of 131I-labelled TFS-4 for the treatment of established human SCLC transplanted in nude mice. The specific accumulation of the antibody in the transplanted tumour was recorded by both scintigraphic and biodistribution studies. Administration of 200 microCi 131I-labelled TFS-4 inhibited tumour growth when compared with the same radiation dose of the control monoclonal antibody. The therapeutic effect was dose-dependent and complete disappearance of the tumour was observed transiently in one out of the three animals following the administration of 500 microCi 131I-labelled TFS-4.

Adenocarcinoma↗
PubMed1988

Measurement of angiotensin-converting enzyme activity in intact human alveolar macrophages and effect of smoking.

Serum angiotensin-converting enzyme (ACE) activity is known to be elevated in various granulomatous conditions such as sarcoidosis, whose characteristic epithelioid cells are thought to belong to the macrophage series. It was recently shown that alveolar macrophages had ACE activity in their sonicated and homogenate forms. We investigated ACE activity of human alveolar macrophages in the intact form using a sensitive radioimmunoassay of generated angiotensin II. We also investigated the effect of smoking on ACE activity of alveolar macrophages using this method. Alveolar macrophages generated angiotensin II (218 +/- 106 pg/20 min/10(5) cells). More angiotensin II was generated in smokers (246 +/- 119 pg/20 min/10(5) cells) than in nonsmokers (160 +/- 50 pg/20 min/10(5) cells) (p less than 0.05). These data showed that ACE activity of macrophages is higher in smokers than nonsmokers.

Angiotensin I↗
PubMed1988

Cytotoxicity of amalgams.

The purpose of this study was to compare the relative cytotoxicity of amalgams and to determine whether their toxicity depends upon composition and aging time, by means of a rapid and sensitive in vitro cell culture test. Zinc-containing amalgams showed higher cytotoxicity than did any other amalgams. High-copper amalgams had the same cytotoxicity as did the low-copper amalgam. The addition of selenium did not reduce the cytotoxicity of amalgam. Moreover, excessive additions of selenium increased the cytotoxicity of amalgam compared with that of a similar selenium-free material. The cytotoxicity of amalgam was decreased with aging time, possibly due to the combined effects of surface oxidation and further amalgamation.

Cells, Cultured↗
PubMed1988

Recurrent attacks of vomiting, hypertension and psychotic depression: a syndrome of periodic catecholamine and prostaglandin discharge.

A syndrome of periodic catecholamine and prostaglandin E2 discharge is described in 2 patients aged 17 and 3 years. They had recurrent attacks of vomiting, hypertension and psychotic depression for several years with a fixed periodicity. At initiation of the attack, plasma ACTH, AVP, norepinephrine and prostaglandin E2 were markedly elevated, whereas dopamine was undetectable. This resulted in hypercortisolemia, hyponatremia and oliguria, which were completely normalized when the attack subsided. Dopaminergic inhibition by metoclopramide injection induced a sustained rise in plasma bicyclo-prostaglandin E2 in the patients, a transient rise in 4 controls, and no response in 8 control children. The 4 control responders had significantly higher plasma norepinephrine levels and aldosterone responses than the non-responders (P less than 0.001). There was a linear correlation between peak values of bicyclo-prostaglandin E2 and basal norepinephrine levels (r = 0.990, P less than 0.001). The patients released bicyclo-prostaglandin E2 and aldosterone more easily than the control responders in terms of plasma norepinephrine and dopamine levels. Treatment of the patient with clonidine was partially effective, whereas administration of indomethacin completely suppressed recurrence of the attacks for 1 year. These results suggest the etiologic possibility that the patients have a decreased dopaminergic inhibition of prostaglandin E2-mediated norepinephrine secretion, which causes periodic discharge of norepinephrine and concomitant release of ACTH and AVP.

Adolescent↗
PubMed1988

Mechanism of action of lactoquinomycin A with special reference to the radical formation.

Lactoquinomycin A (LQM-A), an antibiotic containing a quinone moiety in the molecule, inhibited biosyntheses of DNA, RNA and protein to a similar extent in doxorubicin-resistant mouse leukemia L5178Y cells at concentrations higher than 0.08 micrograms/ml. The antibiotic caused cell death in a short period of incubation and the degree of cell death correlated with that of the inhibition of macromolecular syntheses, suggesting that the inhibition of macromolecular syntheses was not a primary effect of LQM-A. LQM-A served as a good electron acceptor, when cytochrome c reductase was used as a quinone reductase. The treatment of the cells with LQM-A significantly reduced cellular NADH and ATP levels. The generation of superoxide radical by LQM-A in cell lysate was observed by reduction of nitro blue tetrazolium, and the production of hydroxyl radical was confirmed by electron spin resonance. The importance of radical formation for the cytotoxicity of LQM-A is discussed.

Adenosine Triphosphate↗