Biomedical subjects

S Takehana

Publications and source records attributed to S Takehana.

At least 19 recordsLinked to original sources

PubMed2000

Effects of a novel vesamicol receptor ligand, m-(iodobenzyl)trozamicol, on the canine isolated, blood-perfused atrioventricular node preparation.

m-(Iodobenzyl)trozamicol (MIBT) is a recently discovered vesamicol analogue. It has been shown that radiolabelled [125I]MIBT can be used as a marker of cholinergic innervation in the heart as well as in the brain. The purpose of this study was to analyze the direct effects of MIBT on the atrioventricular and intraventricular conduction in addition to the coronary blood flow using the canine isolated, blood-perfused atrioventricular node preparation. Intracoronary administration of MIBT suppressed the atrioventricular and intraventricular conduction, while it increased the coronary blood flow. The effect and duration of action on the intraventricular conduction was less pronounced compared with other effects. Moreover, the doses of MIBT needed to cause negative dromotropic and coronary vasodilator effects in this study was much greater than those needed for imaging the cardiac cholinergic innervation. Pretreatment of the preparations with a muscarinic receptor antagonist, atropine, did not block these effects of MIBT, suggesting that MIBT may possess muscarinic receptor-independent ion channel activity in the cardiac conduction system and coronary arteries.

Animals↗

PubMed1999

Negative chronotropic and inotropic effects of class I antiarrhythmic drugs assessed in isolated canine blood-perfused sinoatrial node and papillary muscle preparations.

The present study was designed to assess the negative chronotropic and inotropic effects of 10 class I antiarrhythmic drugs, using isolated canine blood-perfused sinoatrial node and papillary muscle preparations. Each drug showed negative chronotropic and inotropic effects in a dose-related manner. The potency of the suppressive effect on the sinoatrial automaticity was in the order of aprindine, quinidine, flecainide, lidocaine, mexiletine, cibenzoline, disopyramide, procainamide, tocainide, and phenytoin, while the effect on the ventricular contraction was in the order of aprindine, flecainide, cibenzoline, lidocaine, mexiletine, disopyramide, tocainide, phenytoin, quinidine, and procainamide. The differences in the suppressive effects could not necessarily be explained by their subclassification, based either on action potential duration or kinetic properties of dissociation or association with sodium channels. On the other hand, we found a good correlation between the negative inotropic effects of class I drugs in this study and the canine antiarrhythmic plasma concentrations for the digitalis- and coronary ligation-induced ventricular arrhythmia models in our previous studies. However, the negative chronotropic effects of the drugs showed a poor correlation with the antiarrhythmic plasma drug concentrations. The data shown in this paper may provide a convenient guideline for predicting acute cardiosuppressive effects of antiarrhythmic drugs, especially in patients with reduced cardiac function.

Animals↗

PubMed1999

Cardiovascular effects of optical isomers of cibenzoline, assessed in the canine isolated, blood-perfused papillary muscle and sinoatrial node preparations.

A clinically available racemic mixture of the optical isomers of cibenzoline possesses a potent sodium channel-blocking action in addition to the moderate calcium channel-blocking action. It has been reported that the S(-)-isomer inhibits sodium channels more potently than calcium channels, whereas the R(+)-isomer suppresses the sodium channels as well as calcium channels, and that the calcium channel-blocking potency of these isomers is similar. This study was designed to assess the effects of each optical isomer of cibenzoline on ventricular contraction, coronary blood flow, and sinus node automaticity by using the canine isolated, blood-perfused papillary muscle and sinoatrial node preparations. Each isomer showed negative inotropic and chronotropic effects as well as coronary vasodilator action in a dose-dependent manner. The negative inotropic effect of S(-)-cibenzoline was 1.8 times more potent than that of R(+)-cibenzoline, whereas there was no significant difference between the isomers in the negative chronotropic and coronary vasodilator effects. These results suggest that the difference of the inotropic effects between the optical isomers of cibenzoline is mainly derived from the extent of the sodium channel-blocking action, whereas the vasodilator and negative chronotropic effects may chiefly depend on the calcium channel inhibition.

Animals↗

PubMed1999

Direct cardiac effects of a novel vesamicol receptor ligand, m-iodobenzyl-trozamicol, assessed in the canine isolated, blood-perfused heart preparations.

MIBT, m-(iodobenzyl)trozamicol, is a recently discovered vesamicol analogue that can be used as a functional marker of cholinergic activity in the heart as well as the brain. The purpose of this study was to assess the effects of MIBT on sinus node automaticity, ventricular contraction, and coronary blood flow in addition to the action-potential duration of the ventricle by using canine isolated, blood-perfused sinoatrial node and papillary muscle preparations. Intracoronary administration of MIBT (1-300 microg) exerted negative chronotropic, inotropic, and coronary vasodilator effects in a dose-related manner. Pretreatment of the preparations with the muscarinic receptor antagonist atropine did not change these effects of MIBT. Moreover, MIBT had little effect on the repolarization phase of the ventricular action potential. Because the doses of MIBT needed for imaging cardiac cholinergic function were much lower than those affecting the cardiovascular system, MIBT may be used safely in future clinical applications.

Action Potentials↗

PubMed1999

Pharmacological evaluation of a new laser blood flowmeter for measuring coronary blood flow, assessed in the canine isolated, blood-perfused ventricular tissue preparation in comparison with an electromagnetic flowmeter.

A new portable-type laser blood flowmeter was recently developed for measuring the blood flow in vessels. The sensitivity and specificity of the laser flowmeter was assessed in comparison with the well-established electromagnetic flowmeter using a canine isolated, blood-perfused ventricular tissue preparation. The laser flowmeter can record the phasic pattern of the coronary blood flow like the electromagnetic flowmeter. The extent of the changes after intracoronary administration of ACh and angiotensin II as well as coronary occlusion was almost identical between these two methods. These results suggest that the new laser flowmeter may possess potential utilities in both basic experimental and clinical practices.

Acetylcholine↗

PubMed1998

Clarification of the binding mode of teleocidin and benzolactams to the Cys2 domain of protein kinase Cdelta by synthesis of hydrophobically modified, teleocidin-mimicking benzolactams and computational docking simulation.

Phorbol esters (12-O-tetradecanoylphorbol 13-acetate; TPA) and teleocidins are known to be potent tumor promoters and to activate protein kinase C (PKC) by binding competitively to the enzyme. The relationship between the chemical structures and the activities of these compounds has attracted much attention because of the marked structural dissimilarities. The benzolactam 5, with an eight-membered lactam ring and benzene ring instead of the nine-membered lactam ring and indole ring of teleocidins, reproduces the active ring conformation and biological activities of teleocidins. Herein we describe the synthesis of benzolactams with hydrophobic substituents at various positions. Structure-activity data indicate that the existence of a hydrophobic region between C-2 and C-9 and the steric factor at C-8 play critical roles in the appearance of biological activities. We also computationally simulated the docking of teleocidin and the modified benzolactam molecules to the Cys2 domain structure observed in the crystalline complex of PKCdelta with phorbol 13-acetate. Teleocidin and benzolactams fitted well into the same cavity as phorbol 13-acetate. Of the three functional groups hydrogen-bonding to the protein, two hydrogen-bonded with protein atoms in common with phorbol 13-acetate, but the third one hydrogen-bonded with a different protein atom from that in the case of phorbol 13-acetate. The model explains well the remarkable difference in activity between 5 and its analogue having a bulky substituent at C-8.

Binding Sites↗

PubMed1997

Photoaffinity labeling of tumor promoter-binding protein (CN-TPBP) and preparation of affinity sorbent gels.

Cytosolic-nuclear tumor promoter-specific binding protein (CN-TPBP) was photoaffinity-labeled with a specific ligand, 3beta,5alpha-dihydroxycholestan-6-one (YS-64). Analysis by ODS-HPLC of peptide fragments obtained from the labeled CN-TPBP by trypsinization indicated the existence of a single specifically labeled site. Affinity gels for the purification of CN-TPBP were then prepared. As ligands for the affinity gels, 12-O-tetradecanoylphorbol 13-acetate (TPA), a typical phorbol-type tumor promoter, and benzolactam-V8-310 (BL-V8-310), a structural/biological mimic of teleocidin-class tumor promoters, were adopted. The use of these gels afforded a protein that showed a single band of 58 kDa on SDS-PAGE.

Affinity Labels↗

PubMed1997

High-level expression of the chemically synthesized gene for microbial transglutaminase from Streptoverticillium in Escherichia coli.

We developed a novel approach for the high-level production of a microbial transglutaminase (TGase) from Streptoverticillium in E. coli. The direct expression of the TGase gene in E. coli cells did not cause overproduction, probably due to the harmful influence of TGase activity, which introduces covalent crosslinks between proteins. Therefore, we fused the chemically synthesized TGase gene coding for the entire 331 amino acid residues at the amino terminus to a bacteriophage T7 gene 10 leader peptide (260 amino acids) using an inducible expression vector. The TGase gene was expressed as inclusion bodies in the E. coli cytoplasm. Restoring 15 amino acid residues upstream of the amino terminus of the mature TGase by a two-step deletion of the fusion sequence facilitated solubilization and subsequent proteolytic cleavage, thus releasing mature TGase. Although the mature form had less TGase activity than native TGase, because of the poor refolding rate, these results suggest that this system is suitable for the efficient production of TGase.

Amino Acid Sequence↗

PubMed1994

Chemical synthesis of the gene for microbial transglutaminase from Streptoverticillium and its expression in Escherichia coli.

The gene coding for microbial transglutaminase (TGase) from Streptoverticillium, which consists of 331 amino acids, was chemically synthesized. The codons have been substituted for those mainly favored in yeast. Our strategy involved the construction of the TGase gene in five sections (54 oligomers) that contained unique restriction enzyme sites at both ends, which could readily be ligated to form the full-length product. The chemically synthesized gene was inserted downstream from the ompA signal peptide of the E. coli expression vector, pIN-III-ompA, which carries lpp and lac promotors. The resultant plasmid directed the expression of TGase, with the activity being secreted mainly into the periplasmic space of E. coli. The induced gene product was identical with native TGase in size and in immunological properties, though the enzyme activity was low.

Amino Acid Sequence↗

PubMed1991

Palpation as a method for evaluating occlusal discrepancies.

In this study, 30 dentists were surveyed about their methods of palpating teeth for the evaluation of premature contacts. Thirty-eight dentists were then tested to determine their ability to discriminate degrees of prematurity using each of two different methods of palpation. The degree of digital pressure used by each dentist during palpation was also measured. The majority of dentists chose the same method for palpation: a single forefinger overlaying the facial surfaces of the central incisors being evaluated. In the discrimination test, the majority of dentists were able to identify reliably occlusal interference of greater than or equal to 50 microns regardless of the palpation method used.

Adult↗

PubMed1991

Application of balance index standards.

The Balance Index is a list of standards by which instructors can assess the postures and position in the clinical performance of dental students. The purpose of this study was to examine the basic reliability of clinical instructors' understanding and application of the Balance Index. Certain reference Balance Index standards (Back Vertical, Head Position, Elbow/Arm Position and Wrist Bend) were learned and applied by eighteen clinical instructors, and the effectiveness of one instructor training method was evaluated. The results indicated that a simple graphic and numerical presentation of the Balance Index can be a useful tool to help clinical instructors learn how to assess postural and positional balance. It was also found that a feedback exercise using measured, graded variations of performance imbalances is likely to promote higher intra-rater (and inter-rater) reliability for evaluation of certain postural/positional components of dental clinical performance.

Adult↗

PubMed1991

[A study of the adhesive resins used in adhesion bridges].

UNLABELLED: We suspected that the composition of stiffened adhesive resins may cause adhesion bridges to drop out. In this study, by using a scanning type electron microscope, we observed the breaking sides of the adhesive resin after the tension test. We also examined the surfaces of the resin that we cut and ground after it had hardened, and the surfaces of the adhesion bridges that dropped out. RESULTS: 1) RESULTS of the tension test. No significant differences between the adhesive resins were observed. We noticed no significant differences between the metal surface treatment methods. 2) Observations of the breaking side after the tension test. When we examined Panavia EX, we observed flaking of the metallic side and the tooth enamel. We noticed that the surface was smooth regardless of the method of preprocessing the metal. But the surface of the adhesive resin was bumpy, and we found bubbles of different sizes on the resin surfaces. When we examined Super-Bond C&B, we observed flaking of the metallic side and the tooth enamel, and the surfaces were smooth regardless of the method of preprocessing the metal. Unlike Panavia EX, however, we found various hollows, big and small, like the bubbles on the smooth surfaces of Super-Bond C&B. 3) Observations of the abrasive surface of stiffened adhesive resins. With an ambient temperature of 15 and 28 degrees, we found many minute hollows like bubbles on the abrasive surfaces of Panavia EX and Super-Bond C&B. 4) Observations of the surface of the bonding materials of the adhesion bridges which dropped out. We found bumpy surfaces on the adhesive resin which remained on the metallic side of the adhesion bridges, whichever position the adhesion bridges dropped out of.

Boron Compounds↗

PubMed1990

[A study on the outer shape of full cast crown. 1. Au-Pd-Ag alloy].

Recently, as the result of much research, cast crowns with a very accurate fit are being produced, and even on the clinical level satisfactory results have been achieved. Few reports, however, have been made on the outer shapes of full cast crowns and no clear results have been obtained in this field of research. In a previous report a newly developed apparatus and method were introduced by means of which the outer shapes of wax patterns and the casting made from them can be compared and evaluated, and the apparatus and method were shown to be very accurate. In the present study, the difference in the shapes of wax patterns and castings made from them was investigated using 12% Au-Pd-Ag alloy, the alloy used for restorations as stipulated by the National Health Insurance. Also, dry and wet asbestos was used to see if this affected the shape of the castings. The results are given below: 1. When day asbestos was used, the casting were the same size as the wax patterns at the marginal areas but became smaller towards the occlusal surface. The upper surface of the castings were lower than the wax patterns, being much closer to the occlusal surface itself. 2. When the asbestos was immersed in water before using it, the diameter of the casting above the marginal area was even smaller but at the occlusal surface the height of the casting was almost the same as the wax pattern. 3. It appears that better results may be obtained by using dry asbestos because of the possibility of reducing the space between the cast crown and occlusal surface of the tooth.

Asbestos↗

PubMed1990

[The physical properties of silicone impression materials with hydrophilicity and hydrophobicity. Wetting, water absorption, surface structure of dental stone and dimensional change on stone dies].

In order to compare the physical properties of the silicone impression materials with regard to their hydrophilicity and hydrophobicity, wetting and water absorption, the surface structure and dimensional changes of stone dies were investigated. The evaluation of wetting was performed on one kind of addition-type material with hydrophilicity, five kinds of addition-type materials with hydrophobicity and one kind of condensation-type silicone impression material. One kind of addition-type silicone impression material with hydrophilicity and hydrophobicity was used in other research. Wetting was assessed by measuring the contact angle between water and the impression materials. Water absorption was assessed by the change in weight of the impression materials after immersion in water. The surface structure of the dental stone was observed by SEM. The dimensional changes of stone dies were measured by means of an apparatus designed in this department. The results were as follows: 1. Wetting: The addition-type impression material with hydrophilicity had a 51.4 +/- 1.3 degree contact angle, and other impression materials varied from 84.6 +/- 6.1 degrees to 97.7 +/- 4.4 degrees. 2. Water absorption: The amount of water absorption of the hydrophilic type was greater than that of the hydrophobic type. 3. The surface structure of dental stone: In the case of Vermix stone, which was poured into water-immersed hydrophilic type material, the stone crystals became large, but Fujirock showed no change. 4. The dimensional change on stone dies: No difference was apparent between the hydrophilic type and the hydrophobicity type. 5. Hydrophilicity may affect the surface structure of the dental stone slightly but this is possible within the permissible clinical limits.

Absorption↗

PubMed1990

[A study of how to distinguish the side on which TMJ noise is occurring].

Many patients with TMJ dysfunction suffer from TMJ noise. The measurement of TMJ noise is an important factor in assessing the state of the TMJ dysfunction. Consequently we measured the TMJ noise using electrical techniques in order to make an accurate record. However, determining the side on which the noise occurs is not always easy in auscultation or when picking up the noise electrically, because the sound is carried across the bony structure and picked up on both sides. To solve this problem, we used a three-directional accelerometer, measuring the sound on both sides in the hope that a difference in measurements would allow us to identify the side of the noise. In this study, we vibrated one side of the TMJ with pulse waves, and we compared the vibrated side to the unvibrated side. The height of the pulses was held at 4 volts. In addition, we changed the rising time from 0 volt to 4 volts within a range of 0.6-2.0 msec. The following results were obtained. 1. The time difference between the peaks of the three directions was from 0.32 msec to 3.22 msec on the vibrated side, and from 2.92 msec to 18.2 msec on the unvibrated side. 2. Whenever the time was increased within the selected range, the time difference between the peaks of the three directions on the vibrated side was shorter than that on the unvibrated side. 3. These results suggest that the use of a three-directional accelerometer is a reliable method of distinguishing on which side the TMJ noise is occurring.

Acceleration↗

PubMed1989

Epithelial dysplasia produced by carcinogen pretreatment and subsequent wounding.

Golden hamsters in which the tongues were pretreated with DMBA for 4 weeks, subsequently excised, and either received no treatment or received additional postexcisional applications of acetone or DMBA for 9 to 13 days exhibited histologic evidence of epithelial dysplasia; these dysplastic lesions stained positive for papillomavirus genus-specific antigens. Conversely, animals in which the tongues received the same pretreatment yet had no excision failed to show any dysplastic changes, even though the tongues received additional applications of DMBA. Furthermore, papillomavirus genus-specific antigens were not demonstrable. The animals in which the tongues received no pretreatment with DMBA for 4 weeks followed by excisional wounding showed normal healing, even though the tongues were post-treated with DMBA. Papillomavirus genus-specific antigens could not be demonstrated in this last group.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1989

Verruciform xanthoma of the gingiva: report of three cases.

Forty-seven English and Japanese cases (including three new cases) of verruciform xanthoma of the gingiva were analyzed. Males were affected more frequently than females, and the average age of the patients was 40.9 years. Both maxillary and mandibular gingivae were affected. The most frequent site of involvement in both jaws was the premolarmolar gingiva. Simple surgical excision was the treatment of choice.

Adolescent↗

PubMed1989

[A study of how to distinguish the occurring side of TMJ noise--multiple click].

Patients with TMJ dysfunction often suffer from TMJ noise. However, determining the side at which the noise occurs is not always easy in auscultation or when picking up the noise electrically, because the sound is carried across the bony structure and picked up on both sides. To solve this problem, we utilized a three-directional accelerometer, measuring the sound on both sides in the hope that a difference in measurements would identify the side of the noise. We discovered that time difference between the acceleration peaks for the side originating the sound was shorter than that of the other side. Our report also contains a few observations on the result of this study on patients with plural TMJ noises occurring during one movement of the mandible.

Auscultation↗