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Biomedical subjects

T Tateishi

Publications and source records attributed to T Tateishi.

At least 127 records · Page 7Linked to original sources
PubMed1993

The effects of age and gender on the stereoselective pharmacokinetics of verapamil.

The effects of age and gender on the pharmacokinetics of verapamil stereoisomers were examined. Eighty milligrams of racemic verapamil was given orally to 12 young and 12 elderly healthy subjects, half of whom were women. The area under the plasma concentration-time curves (AUC) of (S)- and (R)-verapamil were greater in the elderly group than in the young group [(S)-/(R)-verapamil (mean +/- SD), 214.4 +/- 123.0/1582.2 +/- 763.0 and 50.4 +/- 36.5/584.9 +/- 252.4 ng.hr/ml for the elderly and young groups, respectively (p < 0.001/p < 0.001)]. Conversely, the apparent oral clearance values of (S)- and (R)-verapamil were significantly smaller in the elderly group than in the young group [(S)-/(R)-verapamil (mean +/- SD), 4.8 +/- 3.0/0.53 +/- 0.21 and 22.5 +/- 21.3/1.30 +/- 0.67 L/hr/kg for the elderly and young groups, respectively (p < 0.01/p < 0.001)]. The ratio of apparent oral clearance of (S)- to (R)-verapamil was significantly smaller in the elderly group than in the young group. As a consequence, the negative chronotropic and dromotropic effect of verapamil was observed in the elderly group. This study suggests that the effect of age on metabolism was greater for (S)-verapamil than for (R)-verapamil.

Adult↗
PubMed1993

Viscoelastic properties of stiff joints: a new approach in analyzing joint contracture.

The purpose of this study was to analyze the joint stiffness after immobilization in a rat's lower extremity model. Rat knee joints were surgically immobilized in a full flexed position for periods of up to 7 weeks with or without intra-articular intervention. The biomechanical analysis was assessed by measuring the bone-joint-bone sample as a cantilever. Measurement was performed with (a) knee flexion angle with gravity, (b) fast Fourier transform analysis of time-dependent mechanical noise with random frequencies, and (c) dynamic stiffness and loss tangent with sinusoidal vibration at a certain frequency. The results showed that the conventional static mechanical test could not detect the intraarticular changes of the whole knee joint. The measurement of the viscoelastic properties covering wide frequencies revealed that an accurate change occurred.

Animals↗
PubMed1993

Mechanical properties of artificial teeth.

In selecting the teeth for fabrication of complete or partial dentures, each patient's anatomic and physiologic requirements and the properties of the artificial teeth themselves should be taken into consideration. The purpose of this study was to evaluate the mechanical properties of the artificial teeth by the static compression test and the impact test. Specimens were the lower first molar porcelain and resin teeth (Livdent FB-20 teeth by G. C. Co., Tokyo, Japan). All were of the same shape. In the static compression test, the fracture load and deformation of the artificial teeth were measured with an Instron-type universal testing machine at a cross-head speed of 1.0 mm/min. Elastic modulus, ultimate strength and absorbed energy were calculated. In the impact test, the acceleration of a falling impactor was measured with a drop impact apparatus. The load applied to the specimen was equivalent to 300N. Absorbed energy and deformation were calculated. The resin teeth showed a lower elastic modulus, higher fracture toughness and shock-absorbing ability than the porcelain teeth. Resin teeth should be selected when the first requisite is high shock-absorbing ability, and porcelain teeth should be selected when the first requisite is high masticating efficiency.

Dental Porcelain↗
PubMed1992

Nocturnal blood pressure monitored by ambulatory blood pressure measurement in elderly hypertensive patients.

This study was designed to characterize the nocturnal fall of blood pressure (NFBP) of elderly hypertensive patients (EH), with or without cerebrovascular disease or diabetes mellitus, as measured by automated blood pressure (BP) monitoring. Systolic and diastolic BP and heart rate was measured every 15 minutes in 133 hospitalized patients with nearly similar schedules and diets. The patients were divided into five groups: I, normotensive elderly patients over age 65: II, EH without cardiovascular diseases, controlled without medication: III, EH with cerebral infarction, chronic stage: IV, EH with noninsulin-dependent diabetes mellitus: and V, hypertensives under age 65, without cardiovascular diseases. A significant NFBP was observed in the patients of groups I and V, a significant but smaller NFBP in the hypertensives of groups II and IV, and no NFBP in the patients of group III. Administration of the antihypertensive drugs, enalapril and nifedipine, tended to augment the NFBP. These preliminary observations showed that NFBP did occur in elderly hypertensives but the fall was smaller than that observed in younger hypertensives or elderly normotensives. Although the ambulatory BP measurements were useful in the overall clinical evaluation of elderly patients, NFBP in elderly patients was affected by hypertensive drugs and therefore NFBP should be interpreted with caution.

Aged↗
PubMed1992

The influence of diltiazem versus cimetidine on propranolol metabolism.

The present study was undertaken to examine whether the inhibitory effect of diltiazem on the metabolism of propranolol differs from that of cimetidine. Six healthy male volunteers received a single oral dose of 20 mg propranolol with pretreatment with placebo, 60 mg diltiazem, or 400 mg cimetidine three times daily for 4 days. Diltiazem and cimetidine increased the area under the concentration (AUC) of propranolol and its glucuronide. Cimetidine also increased the urinary excretion of propranolol glucuronide. There were no significant differences in the AUC of 4-hydroxypropranolol (4OHPPL) and its conjugates or the urinary excretion of conjugated 4OHPPL. Diltiazem increased the AUC of naphthoxylactic acid (NLA) and the urinary excretion to NLA. After cimetidine pretreatment, there was the trend toward a decrease in the partial metabolic clearance to 4OHPPL and a significant decrease in that of NLA. These results suggest that diltiazem and cimetidine inhibit the oxidation pathways of propranolol in different manners. Cimetidine might inhibit both oxidative pathways to 4OHPPL and NLA, whereas diltiazem might not inhibit the pathway to NLA.

Adult↗
PubMed1992

Effect of diltiazem on the pharmacokinetics of MPC-1304, a new calcium channel blocker.

The effect of diltiazem pretreatment on the pharmacokinetics and pharmacodynamics of MPC-1304, a new calcium channel blocker, were evaluated in six healthy male volunteers. Placebo or diltiazem 60 mg was given orally three times daily for 3 days in a double-blind crossover method. MPC-1304 10 mg was administered orally two times at an interval of four weeks as a washout period. Diltiazem significantly increased the maximum plasma level (Cmax) and the area under the plasma concentration-time curve (AUC) of MPC-1304 from control values (3.0 +/- 1.5 to 10.2 +/- 4.8 ng/ml, p less than 0.05, and 11.0 +/- 3.8 to 36.0 +/- 15.6 ng.h/ml, p less than 0.01, respectively) without any changes of t1/2. In the case of the major active metabolite, side chain reduced form (MI), Cmax, AUC, and t1/2 were significantly increased by diltiazem as follows: Cmax, 60.7 +/- 21.1 to 171.4 +/- 73.6 ng/ml, p less than 0.05; AUC, 317.6 +/- 62.6 to 1,334.9 +/- 563.6 ng.h/ml, p less than 0.01; t1/2, 2.8 +/- 0.7 to 3.9 +/- 0.6 h, p less than 0.01. Diltiazem pretreatment slightly, but not significantly decreased blood pressure after MPC-1304 dosing. The inhibition of hepatic metabolism on MPC-1304 may explain the significant changes in pharmacokinetics of MPC-1304 after diltiazem pretreatment.

Administration, Oral↗
PubMed1991

Probing the role of lysines and arginines in the catalytic function of cytochrome P450d by site-directed mutagenesis. Interaction with NADPH-cytochrome P450 reductase.

To identify amino acids of cytochrome P450d (P450d) which participate in the interaction with NADPH-cytochrome P450 reductase, we changed conserved ionic amino acids of P450d to others by site-directed mutagenesis. Turnover numbers (0.032-0.008 min-1) of purified mutants Lys94-Glu, Lys99-Glu, Lys105-Glu, Lys440-Glu, Lys453-Glu, Arg455-Glu, and Lys463-Glu toward 7-ethoxycoumarin were much lower than that (0.380 min-1) of the wild type at 25 degrees C. Reduction rates (less than 0.054 s-1) of the heme of all mutants (0.1 microM) in the presence of NADPH and the reductase (0.3 microM) were much lower than that (5.9 s-1) of the wild type. Furthermore, a turnover number (0.042 min-1) of a microsomal triple mutant (Arg135-Leu + Arg136-Leu + Arg137-Leu) of a conserved Arg cluster was much lower than that (0.674 min-1) of the wild type at 37 degrees C. Thus, we suggest that Lys94, Lys99, Lys105, Lys440, Lys453, Arg455, Lys463, and perhaps the Arg cluster Arg135-Arg136-Arg137 of P450d will participate in the intermolecular electron transfer process by forming ionic bridges between the two proteins and/or by orienting appropriate geometry for electron transfer on the interfacial surface between the two proteins.

Amino Acid Sequence↗
PubMed1991

The effect of diltiazem on hepatic drug oxidation assessed by antipyrine and trimethadione.

The effect of pretreatment for 3 days with diltiazem 60 mg three times a day on the pharmacokinetics of 500-mg antipyrine and 250-mg trimethadione was studied in six healthy male subjects. Diltiazem decreased the total body clearance from 34.0 +/- 8.0 to 28.6 +/- 6.1 mL/min (P less than .01), and prolonged the elimination half-life from 12.6 +/- 3.0 to 14.3 +/- 2.5 hours (P less than .01) of antipyrine without any changes in volume of distribution. The cumulative renal excretion (% dose) of antipyrine was significantly increased from 2.23 +/- 0.73 to 2.78 +/- 0.83% (P less than .05). Clearances of production for three major antipyrine metabolites, norantipyrine (4.31 +/- 1.64 to 3.50 +/- 1.28 mL/min, P less than .01), 3-hydroxymethylantipyrine (4.67 +/- 1.63 to 3.82 +/- 1.34 mL/min, P less than .01) and 4-hydroxyantipyrine (10.47 +/- 3.41 to 8.16 +/- 2.82 mL/min, P less than .01) were reduced significantly by diltiazem. On the other hand, diltiazem did not produce any significant changes in pharmacokinetic parameters of trimethadione and plasma concentration ratio, oxidative major metabolite of trimethadione to trimethadione itself. These results suggest that other drugs metabolizing the same hepatic oxidative pathways as antipyrine, may be influenced by diltiazem.

Adult↗
PubMed1991

[Gastric xanthomas in the elderly].

Gastric xanthomas are single or multiple yellowish-white small nodules or plaques in the gastric mucosa. Microscopically they consist of macrophage-derived foam cells full of lipids. However, because of their benign nature, there are few reports of gastric xanthomas in the literature and their clinical significance still remains unknown. In this study, we studied 131 elderly cases (42 males and 89 females) with the average age of 75.6 +/- 12.3 (S.D.) years old who were examined gastroendoscopically. The endoscopic finding of gastric xanthomas was observed in 17 males (40.5%) and in 23 females (25.8%). Gastric xanthomas tended to increase with age, and the frequency was highest in the seventies (40.0%). Of the xanthoma cases, 42.5% had a solitary xanthoma, and 17.5% had more than 5 xanthomas. More than 70% of xanthomas were observed in antral and pyloric regions. There was no difference in serum lipids between the cases with and without xanthomas. Gastric mucosa biopsied from around xanthomas showed moderate to severe atrophic change of gastric glands in most cases (89%). Hyperplasia of gastric-pit epithelia and intestinal metaplasia were also often observed. However, there was no correlation between gastric xanthomas and small round cell infiltration in the gastric mucosa. It was concluded that gastric xanthomas in the elderly arise from the mucosa with atrophic change in most cases, which may have a disturbance of local lipid metabolism, and that the presence of gastric xanthomas may be a marker of the pathological aging change of gastric mucosa.

Age Factors↗
PubMed1991

[Effect of a direct electric current on modification of bone and ligament repair processes--experimental investigation of a rabbit model].

Investigations of the effect of direct current on 1) fracture healing, and 2) ligament healing was conducted by applying 10 microA to 1) the defect of the fibula, and 2) that of the patellar ligament of adult rabbits. After time periods for stimulation all specimens were tested with combinations of roentgenological, histological, biomechanical and biochemical methods. The results were analyzed and compared with the non-stimulated, opposite side and with the normal tissue. The electricity produced 1) a more massive callus with normal histological features in an early stages at the fracture site, and 2) higher tensile stiffness and earlier change of the collagen types in the newly-formed tissue, though no significant differences were observed as to 1) the mechanical parameters of callus and bone material, and 2) histological findings of repairing tissue. Electrical stimulation was indicated not only on bone tissue but also on non-osseous tissues and their components.

Animals↗
PubMed1990

Effects of diltiazem on the pharmacokinetics of nifedipine.

To evaluate the effect of diltiazem pretreatment (60 mg three times a day for 3 days) on pharmacokinetics and pharmacodynamic effect of nifedipine, six healthy subjects received 20 mg nifedipine orally on two occasions using a double-blind cross-over, placebo-controlled method. Diltiazem induced a marked increment of the area under the plasma concentration-time curve (AUC) for nifedipine by a mean of 140% and reduced the total body clearance (Cl) from 0.0043 +/- 0.0019 to 0.0017 +/- 0.0006 ml/min/kg (p less than 0.05, mean +/- SD). The biological half-life (t1/2) of nifedipine was prolonged from 2.46 +/- 0.65 to 3.21 +/- 0.92 h (p less than 0.05) without any changes in indocyanine green (ICG) clearance. Diltiazem did not produce significant changes of AUC, Cl, and t1/2 for the acid metabolite of nifedipine. Blood pressure (BP) after nifedipine administration with diltiazem pretreatment was more decreased than that without diltiazem. Both a decreased hepatic clearance and an increased bio-availability of nifedipine by diltiazem probably explain the significant changes in pharmacokinetics and hemodynamics of nifedipine. A clinically important drug interaction may occur with nifedipine when diltiazem is administered concurrently.

Adult↗
PubMed1990

Circadian rhythm in recognition threshold of salt taste in healthy subjects.

The circadian rhythm in recognition threshold of salt taste was examined in six healthy young subjects. Plasma aldosterone (PA) and cortisol concentrations, plasma renin activity (PRA), salivary sodium concentration, and salt recognition thresholds were measured every 3 h for a 24-h period. The salt recognition threshold and salivary sodium concentration exhibited similar circadian rhythms, with the lowest values recorded in the afternoon. Positive correlations were observed between the recognition threshold and salivary sodium (P less than 0.001) and between cortisol and PA (P less than 0.001). There was no correlation between PRA and PA. A negative correlation was observed between PA and salivary sodium concentration (P less than 0.01). These data indicate that the recognition threshold for salt taste has a circadian rhythm in young healthy subjects. This rhythm appears to be related to daily variations in the plasma aldosterone concentration and its subsequent effects on salivary sodium concentration.

Adult↗
PubMed1990

[Application of the thermoelastic stress imaging method to prosthodontics. (2) Basic study of the stress field of artificial molar teeth, in which the existence of saliva was considered].

A basic study was conducted utilizing a thermoelastic stress imaging method for stress analysis of model of simplified artificial molars based on an interocclusal contact relationship. This involved examining the effect of artificial saliva application on a stress field in a situation where occlusal pressure was applied in a dynamic sliding movement. As a result, the following conclusions were obtained. 1. The thermoelastic stress imaging method allowed the stress field to be determined artificial saliva application at distributed load due to plane contact in dynamic sliding movement. 2. Compared with the case of non-saliva application, in a squaremodel having a sliding movement and to which artificial saliva was applied, the pattern of the high compressive stress area was found to be a circle or an ellipsoid. This showed a slight dispersion trend at 10 degrees, with the contact plane as the boundary, and the dispersion of stress concentration began to become clearer at 20; stress concentration on the contact plane tended to disappear at 30 degrees, and sliding was conspicuous and determination impossible at 45 degrees. 3. Results showed that 10 degrees was a transition angle at which a different aspect was shown, representing a trend in a stress field pattern change accompanying an increase in the facet bevel angle when artificial saliva was applied. 4. From the results of stress analysis using the square-shape sliding movement model to which artificial saliva was applied, 10 degrees to 20 degrees of facet bevel of artificial molars was considered preferable in consideration of the presence of saliva.

Bite Force↗
PubMed1990

[Biological age and longitudinal study of aging].

We assessed the biological aging status by multiple regression analysis of clinical parameters. Estimated ages of external appearance, physiological function, physical strength and general biological status were calculated. The aging grade was defined as the percent estimated age to chronological age. The aging grade was lower in the managers, and in nonsmokers. It was lower in subjects who drank a small amount of alcohol than in those who drank a large amount of alcohol or those who did not drink alcohol. We also studied the longitudinal changes of 27 clinical parameters. Physical, hematological and blood biochemical data were annually recorded for a 10-year period. Age-time matrix was made for each parameter and was analyzed in terms of aging, cohort and time, by utilizing [1] longitudinal, [2] cross-sectional and [3] time series approaches. The parameters that were considered to be affected by aging were right grip strength (reduced), and sedimentation rate (increased).

Adolescent↗
PubMed1989

Dose dependent effect of diltiazem on the pharmacokinetics of nifedipine.

The effect of diltiazem pretreatment on the pharmacokinetics of nifedipine were determined in six healthy male volunteers. Placebo or diltiazem (30 mg and 90 mg) was given orally three times daily for 3 days in a double-blind, Latin square method. On the fourth day, a 20-mg nifedipine was given orally 1 hour after the last dose of placebo or diltiazem. The mean elimination half-life of nifedipine prolonged significantly following diltiazem (2.54 hours on placebo vs 3.40 hours on 30 mg diltiazem and 3.47 on 90 mg diltiazem, both P less than .01). The mean AUC of nifedipine increased during diltiazem (1726.6 nmol X hr/ml on placebo vs 3838.0 on 30 mg diltiazem, and 5370.0 on 90 mg diltiazem, both P less than .05, 30 mg vs 90 mg, 0.1 less than P less than .05). The ratio of the AUC of primary metabolite (nitropyridine form) to the AUC of nifedipine was reduced by diltiazem pretreatment in a dose-dependent manner. ICG clearance was not influenced following diltiazem. These results indicate that diltiazem dose-dependently alters the pharmacokinetic profiles of nifedipine. The ICG clearance test showed that the liver blood flow did not decrease during diltiazem therapy, therefore, the reduction in the metabolic clearance of nifedipine might be caused by inhibiting effect of diltiazem on the activity of drug oxidizing enzymes.

Adult↗
PubMed1989

Effect of diltiazem on the pharmacokinetics of propranolol, metoprolol and atenolol.

The pharmacokinetic interaction between diltiazem and three beta-adrenoceptor blockers propranolol, metoprolol and atenolol was investigated in healthy volunteers given diltiazem 30 mg or placebo t.d.s. for 3 days, followed by a single dose of propranolol 20 mg, metoprolol 40 mg or atenolol 50 mg. The AUCs of propranolol and metoprolol were significantly increased after diltiazem and it significantly prolonged the elimination half-life of metoprolol. In contrast, it did not significantly affect the pharmacokinetics of atenolol. Propranolol significantly decreased the resting pulse rate after diltiazem pretreatment as compared to placebo. The results indicate that diltiazem impaired the clearance of propranolol and metoprolol, which are principally metabolized by an oxidative pathway, and that the kinetic interaction between diltiazem and propranolol may partly be related to the significant reduction in the pulse rate produced by the latter.

Adult↗
PubMed1989

Effects on autonomic function of a new angiotensin converting enzyme inhibitor, ramipril.

To investigate the effects of ramipril, a new angiotensin converting enzyme inhibitor, on autonomic function, autonomic function tests were performed in eight healthy male subjects, aged 22-26 years, after single oral administration of 5 mg of ramipril or placebo, in a randomized, double-blind, crossover design. Measurements of heart rate variability and diving reflex test were performed as indices of parasympathetic tone. Forearm isometric exercise (handgrip test) and cold pressor test were carried out to evaluate sympathetic nervous reactivity. Supine systolic blood pressure was decreased significantly after ramipril (F = 11.16, p less than 0.01), but diastolic blood pressure was not. Heart rate at rest did not significantly differ between ramipril and placebo. Heart rate variability was significantly increased 120 min after ramipril [5.5 +/- 0.7% (SEM) on ramipril and 3.7 +/- 0.2% on placebo; F = 7.13, p less than 0.05]. However, reflex bradycardia during the diving test was not enhanced after ramipril. Plasma norepinephrine concentrations before and after handgrip test were not influenced by ramipril. Increments of mean blood pressure and heart rate during handgrip or cold pressor test did not significantly differ between ramipril and placebo, either. These results suggest that ramipril may enhance cardiac vagal tone without affecting sympathetic nervous activity. Enhanced parasympathetic activity could be related to an absence of reflex tachycardia following the administration of ramipril.

Adult↗