Search PubMed⌕ Search

Biomedical subjects

I Watanabe

Publications and source records attributed to I Watanabe.

At least 73 records · Page 4Linked to original sources
PubMed2000

Effect of casting method on castability of titanium and dental alloys.

Titanium, once considered to be difficult to cast because of its relatively high melting point (1670 +/- 50 degrees C) and strong chemical affinity, can now be acceptably cast using newly developed casting apparatus. The objectives of this study were to examine the castability of commercially pure (CP) titanium using an ultra high-speed centrifugal casting machine and a pressure difference-type casting unit and to compare the castability of titanium with that of conventional dental casting alloys. To determine castability, two types of patterns were used: a mesh pattern of 22 x 24 mm cut polyether thread sieve, and a saucer pattern (24 mm diameter) perforated to create four T-shaped ends. The casting equipment significantly affected the mold filling of both patterns (p < 0.001). The castability indices obtained from both patterns of CP titanium cast in the centrifugal casting machine were significantly (p < 0.05) better than the indices of the castings produced in the pressure-difference casting unit. The radiographs of the saucer pattern cast in the centrifugal casting machine showed some pores that were fewer and smaller in size than the pores found in castings made in the pressure-difference unit. When the ultra high-speed centrifugal casting machine was used with the manufacturer's recommended mold material, the castability of titanium was similar to that of gold alloy or Ni-Cr alloy cast by conventional means.

Journal Article↗
PubMed2000

Dynorphins directly inhibit neuronal nicotinic acetylcholine receptors in PC12 cells.

The authors have previously reported that dynorphin A (1-17), an endogenous kappa opioid agonist, inhibits the current mediated through neuronal nicotinic acetylcholine receptors (nAChRs) without the involvement of opioid receptors or G-proteins. We have further characterized this action to elucidate the mechanisms. The nicotine-induced current was studied in PC12 cells using patch-clamp techniques. In the whole-cell configuration, four kinds of dynorphins with different lengths, dynorphin A (1-17) (1-13) (2-13) and (1-8), similarly inhibited the nicotine-induced inward current at 1 microM and accelerated the current decay. The inhibition by dynorphin A (1-17) was not antagonized by the increasing concentrations of nicotine. The current-voltage relationship revealed that dynorphin's inhibition was voltage independent at the membrane potentials from -30 to -70 mV. The inhibition was not affected by pretreatment with pertussis toxin (PTX) or inclusion of staurosporine into the pipette solution. The inhibitory effect of dynorphin A (1-17) was well preserved in the outside-out patch configuration. Analysis of the nicotine-induced noise and single-channel kinetics revealed that dynorphin A(1-17) reduced open time without changing the amplitude of the unitary current. We found that the inhibitory effect on neuronal nAChRs is shared by all four dynorphins studied. The inhibition appears to be non-competitive and voltage independent. The outside-out recording together with other experiments indicated that a major part of this inhibition is not mediated through cytoplasmic messengers, but based on the direct action of dynorphins on neuronal nAChRs leading to the reduction of open time.

Animals↗
PubMed2000

Complete recovery of consciousness in a patient with decorticate rigidity following cardiac arrest after thoracic epidural injection.

A 46-yr-old man with dysaesthesia (burning sensation) following herpes zoster in the left upper chest region was treated with a single thoracic (T2/T3) epidural injection (1.0% lidocaine 3 ml + 0.125% bupivacaine 3 ml) as an outpatient. Twenty minutes after the injection, a nurse noticed the patient to be unconscious with dilated pupils, apnoea and cardiac arrest. Following immediate cardiopulmonary resuscitation, the patient was treated with an i.v. infusion of thiamylal sodium 2-4 mg kg-1 h-1 and his lungs were mechanically ventilated. When the patient developed a characteristic decorticate posture, mild hypothermia (oesophageal temperature, 33-34 degrees C) was induced. On the 17th day of this treatment, after rewarming (35.5 degrees C) and discontinuation of the barbiturate, the patient responded to command. Weaning from the ventilator was successful on the 18th day. About 4 months after the incident, the patient was discharged with no apparent mental or motor disturbances. We suggest that mild hypothermia with barbiturate therapy may have contributed to the successful outcome in this case.

Analgesia, Epidural↗
PubMed2000

The effects of nicardipine on dynamic cerebral autoregulation in patients anesthetized with propofol and fentanyl.

UNLABELLED: We investigated the effects of nicardipine on dynamic cerebral pressure autoregulation in 13 normal adult patients undergoing gynecologic or orthopedic surgery. Anesthesia was induced and maintained with propofol and fentanyl. Hypotension to a mean arterial pressure of 60-65 mm Hg was induced and maintained with a continuous infusion of nicardipine. Time-averaged mean blood flow velocity in the right middle cerebral artery was measured continuously by using transcranial Doppler ultrasonography. The cerebral autoregulatory responses were activated by releasing thigh cuffs. The actual blood flow velocity in the right middle cerebral artery response to acute change in mean arterial pressure was fitted to 1 of 10 computer-generated curves to determine the dynamic rate of cerebral autoregulation (dRoR), and the best fitting curve was used. The autoregulation test was repeated until two values of dRoR were obtained at baseline and during induced hypotension. Nicardipine significantly reduced dRoR values of 13.1% +/- 3.6%/s at baseline to 8.3% +/- 2.6%/s during hypotension (P: < 0.01). During deliberate hypotension induced by nicardipine, the cerebral dynamic autoregulatory response is impaired in normal adult patients. IMPLICATIONS: During deliberate hypotension induced by nicardipine, the cerebral dynamic autoregulatory response is impaired in normal adult patients.

Adjuvants, Anesthesia↗
PubMed2000

Nonstereoselective inhibition of neuronal nicotinic acetylcholine receptors by ketamine isomers.

UNLABELLED: We have found that racemic ketamine strongly inhibits the current mediated through neuronal nicotinic acetylcholine receptors (nAchRs) in PC12 cells, a rat pheochromocytoma cell line. Ketamine stereoisomers have different potencies for the anesthetic action, with the S-enantiomer being about 3 times as potent as the R-enantiomer. The purpose of this study was to clarify if the inhibitory effects of ketamine on neuronal nAchRs contribute to their anesthetic effect. We compared potencies of ketamine enantiomers for neuronal nAchR inhibition with those for the anesthetic action. S(+) and R(-) ketamine inhibited the nicotine-induced whole-cell current in a dose-dependent manner at the membrane potential of -60 mV. They accelerated the current decay, resulting in the larger effects on the nondesensitized current than on the peak current. There was no significant difference in the concentrations for 50% inhibition between the stereoisomers. The ketamine isomers exerted the same effects on single-channel properties estimated from analysis of the nicotine-induced current noise. These results indicate that the inhibitory action of ketamine isomers on neuronal nAchRs is not stereoselective. Although our findings do not deny possible involvement of these receptors in ketamine anesthesia, they suggest that inhibition of neuronal nAchRs is not primarily responsible for the anesthetic action of this anesthetic. IMPLICATIONS: We found that inhibition of neuronal nicotinic acetylcholine receptors by ketamine is not stereoselective in PC12 cells. The result suggests that this effect does not directly correlate with the anesthetic action of ketamine.

Algorithms↗
PubMed2000

Prognostic significance of p27(kip1) protein expression and spontaneous apoptosis in patients with colorectal adenocarcinomas.

Tumor cell apoptosis, proliferation and p27 expression using an in situ apoptosis detection kit, anti-Ki67 antibody and anti-p27 antibody were investigated in 171 colorectal adenocarcinoma specimens, together with the assessment of mutated p53 expression. No apparent association was observed among p27 expression, mutated p53 accumulation, the Ki67 labeling index and the apoptotic index (AI). In the multivariate analysis using the median values as the cut-off points (46.8% for p27 expression and 0.89% for AI), p27 expression was identified as an independent and significant predictor for overall survival. When the present series of patients were dichotomized by these cut-off points to categorize the cases into 4 subgroups, the patients in the group with low p27 expression and a low AI had the poorest prognosis. The assessment of p27 expression and AI therefore may prove valuable in identifying patients with colorectal adenocarcinoma who may have a poor prognosis.

Adenocarcinoma↗
PubMed2000

Nematocidal activity of quassinoids against a species of Diplogastridae.

The nematocidal activity of 38 quassinoids, C19 or C20 compounds isolated from Simaroubaceae, was measured using a species of Diplogastridae (Nematoda) to develop lead parasiticides. Of the various quassinoids tested, samaderines B and E displayed the most potent nematocidal activity with a minimum lethal concentration (MLC) of 2.0 x 10(-5) M. The nematocidal activities of samaderines B and E were 15-fold greater than that of albendazole (3.0 x 10(-4) M), 10-fold greater than that of thiabendazole (2.0 x 10(-4) M) and 7.5-fold greater than that of avermectin (1.5 x 10(-4) M). Thus, samaderines B and E may eventually be used as lead parasiticides. In light of the relationship between the structures of quassinoids and their nematocidal activities, those with potent nematocidal activity may require the elements mentioned. These results should help to further our understanding of nematocidal activity.

Animals↗
PubMed2000

Quantitative structure-activity relationship study of N-(3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carbonyl)guanidines as potent Na/H exchange inhibitors.

We have previously reported that N-(4-isopropyl-2,2-dimethyl-3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-6-car bonyl)guanidine (4b) methanesulfonate salt (KB-R9032) is a potent and highly water-soluble Na/H exchange inhibitor. In a series of studies on Na/H exchange inhibitors, we designed and synthesized N-(3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carbonyl)guanidines (5) as more potent inhibitors with high water-solubility. The design strategy for 5 was based on a quantitative structure-activity relationship (QSAR) study, involving the proportional relationship between the biological activity and hydrophobicity of the ring structure of compounds 4. As expected, compounds 5 showed more potent activity than 4. It was found by using the QSAR analysis that 5 were about five-fold more potent than 4. The increase in potency of compounds 5 well agreed with our previous QSAR analysis result. The most potent derivative was the methanesulfonate salt 5d of the 4-isopropyl derivative (IC50=0.0091 microM). And in addition to the in vitro study, 5d showed significant protective activity against a rat acute myocardial infraction model.

Animals↗
PubMed2000

Electrophysiological effect of adenosine triphosphate and adenosine on atrial and ventricular action potential duration in humans.

Bolus injection of adenosine triphosphate (ATP) or adenosine is widely used clinically for terminating supraventricular tachycardia. However, bolus injection of these drugs has been reported to provoke atrial fibrillation (Afib). The effects of ATP and adenosine on the monophasic action potential duration (MAPD) of atrial and ventricular muscle was investigated, as well as the changes in the spatial distribution of atrial functional refractoriness caused by adenosine. Bolus injection of ATP and adenosine shortened atrial MAPD; no change was observed in the ventricle. Because local f-f intervals during atrial fibrillation correlate with the atrial refractory period, changes in mean f-f intervals in the right atrial appendage, His bundle region, coronary sinus ostium and distal coronary sinus were compared before and after injection of adenosine during induced Afib. Maximal shortening of f-f intervals was observed in the right atrial appendage. Inhomogeneous shortening of atrial refractoriness may account for the Afib following bolus injection of ATP or adenosine.

Action Potentials↗
PubMed2000

Radiofrequency catheter ablation of ventricular tachycardia from the anterobasal left ventricle.

Ventricular tachycardia (VT) in coronary artery disease arises mostly from endocardial sites. However, little is known about the site of origin in other diseases. We report two patients who had VT originating from an anterior aspect of the left ventricle just below the mitral annulus, adjacent to the left ventricular outflow tract. The QRS configuration of VT showed an inferior axis and monophasic R waves in all the precordial leads. Radiofrequency current delivered to this site from the endocardial site successfully ablated the tachycardia in both.

Adult↗
PubMed2000

Recurrent hemoptysis in tuberculosis with non-cavitary lung disease as a symptom of mild hemophilia A in a young adult.

Hemoptysis in patients with tuberculosis is usually associated with smear-positive and cavitary lung disease. The present case describes a patient suffering from recurrent hemoptysis associated with tuberculosis who had smear-negative and non-cavitary lung disease, and who was subsequently diagnosed as having mild hemophilia A. Although mild hemophilia A sometimes escapes detection until adolescence, there has been no reported case of mild hemophilia A detected by recurrent hemoptysis due to pulmonary tuberculosis. Here, we report a rare case of recurrent hemoptysis in a patient with tuberculosis who had smear-negative and non-cavitary lung disease and who was finally shown to have hemophilia A.

Adolescent↗
PubMed2000

The effects of long-acting nitrates on 5-year cardiac events of patients with coronary thrombolytic therapy for acute myocardial infarction.

OBJECTIVE: A retrospective study was performed to evaluate the effects of using long-term long acting nitrates without a dose-free interval in treating patients undergoing thrombolytic therapy for acute myocardial infarction (MI). PATIENTS AND METHODS: A total of 297 patients taking prescribed medication for secondary prevention of the MI were selected for the study. They were divided into a nitrate group consisting of 222 patients who had continuously received long-acting nitrates without a dose-free interval, and a control group consisting of 75 patients who were not able to use the long-acting nitrates because of adverse effects. The primary endpoint was cardiac events, either cardiac death or a nonfatal MI, in five years. RESULTS: The incidence of primary endpoint in five years was 13.4 percent in the nitrate group and 6.2 percent in the control group, a 2.2-fold increase in risk. However, the difference was not significant. After adjustment for age, there was no statistically significant difference between the incidence of primary endpoint in the nitrate group (9.8%) and that in the control group (5.7%). A Cox proportional-hazards regression analysis revealed that the long-acting nitrates were not related to the incidence of primary endpoint (p=0.23). CONCLUSION: The administration of long-term long-acting nitrates without a dose-free interval had no benefit of reducing the incidence of cardiac events of patients undergoing thrombolytic therapy for acute MI.

Coronary Vessels↗
PubMed2000

[Effect of cholesterol reducing therapy with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor on secondary prevention after myocardial infarction in Japanese patients].

Lowering the blood cholesterol level is a safe method to improve survival for primary and secondary prevention of coronary heart disease. However, there is no evidence for any effectiveness in Japanese. This study was designed to evaluate the effect of cholesterol lowering therapy with 3-hydroxy-3-methylglutaryl coenzyme A(HMG-CoA) reductase inhibitor on cardiac events(death and reinfarction) in Japanese patients after myocardial infarction. A total of 290 patients after myocardial infarction were studied retrospectively. The patients were divided into 2 groups with or without HMG-CoA reductase inhibitor therapy for lowering blood cholesterol levels. The cumulative cardiac events and percentage change of cholesterol levels[total cholesterol and low-density lipoprotein (LDL) cholesterol level] were compared between the 2 groups. HMG-CoA reductase inhibitor therapy lowered plasma cholesterol levels significantly (total cholesterol level--11 +/- 20%, LDL cholesterol level--23 +/- 26%) in patients with hypercholesterolemia, whereas there was no change(total cholesterol level 4.3 +/- 22%, LDL cholesterol level--7.2 +/- 24%) in patients without hypercholesterolemia. HMG-CoA reductase inhibitor therapy reduced cardiac events significantly compared in patients with hypercholesterolemia(p = 0.0008), but there was no benefit in patients without hypercholesterolemia. We suggest that treatment with HMG-CoA reductase inhibitor therapy for lowering cholesterol levels was effective for secondary prevention after myocardial infarction in Japanese patients with hypercholesterolemia.

Anticholesteremic Agents↗
PubMed2000

[Simulation of night myopia in pseudophakic eyes].

PURPOSE: Eyes with an intraocular lens (IOL) implanted that have no accommodative ability are likely to have night myopia caused by Purkinje's shift and chromatic aberration. We evaluated the changes in retinal images caused by night myopia in various IOL-implanted eyes by simulation using model eyes. METHODS: A polymethylmethacrylate (PMMA) IOL, soft acrylic IOLs, and high-refractive-index silicone IOLs were prepared, and inserted into the model eye. The image plane of the model eye was determined as the line image at which a slit light of 560 nm was best focused, which was regarded as emmetropic condition under photopic vision. A slit light of 505 nm was then directed into the model eye. Its line image on the image plane was blurred, which was regarded as myopic condition under scotopic vision. Under each condition, the modulation transfer functions (MTF) were calculated and the line images were photographed. RESULTS: The degree of reduction of MTF and blurring of the line image under the night myopic condition was in the order of PMMA < soft acrylic < high refractive index silicone IOL. CONCLUSION: Eyes with a soft acrylic or high-refractive-index silicone IOL may have more intense night myopia caused by chromatic aberration.

Cataract↗
PubMed2000

Intersectional gene flow between insular endemics of Ilex (Aquifoliaceae) on the Bonin Islands and the Ryukyu Islands.

Hybridization and introgression play important roles in plant evolution, and their occurrence on the oceanic islands provides good examples of plant speciation and diversification. Restriction fragment length polymorphisms (RFLPs) and trnL (UAA) 3'exon-trnF (GAA) intergenic spacer (IGS) sequences of chloroplast DNA (cpDNA), and the sequences of internal transcribed spacer (ITS) of nuclear ribosomal DNA were examined to investigate the occurrence of gene transfer in Ilex species on the Bonin Islands and the Ryukyu Islands in Japan. A gene phylogeny for the plastid genome is in agreement with the morphologically based taxonomy, whereas the nuclear genome phylogeny clusters putatively unrelated endemics both on the Bonin and the Ryukyu Islands. Intersectional hybridization and nuclear gene flow were independently observed in insular endemics of Ilex on both sets of islands without evidence of plastid introgression. Gene flow observed in these island systems can be explained by ecological features of insular endemics, i.e., limits of distribution range or sympatric distribution in a small land area.

Journal Article↗