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Biomedical subjects

T Akimoto

Publications and source records attributed to T Akimoto.

At least 181 records · Page 10Linked to original sources
PubMed1992

[Surgical treatment of ventricular tachycardia after total correction of tetralogy of Fallot].

A 38-year-old man with total repair of tetralogy of Fallot at the age of 16 suffered from paroxysmal ventricular tachycardia. His first attack of sustained ventricular tachycardia was recognized at the age of 37 and it was refractory for medical therapy. Electrophysiologic study demonstrated two morphological types of clinical ventricular tachycardias, one originated from the outflow tract of the right ventricle and the other from the area around the patch for closure of ventricular septal defect. He underwent cryosurgical ablation for ventricular tachycardia and patch-closure for residual shunt of ventricular septal defect following the failure of electrical ablation. All of clinical ventricular tachycardias disappeared postoperatively without antiarrhythmic drugs.

Adult↗
PubMed1991

Importance of polymerization initiator systems and interfacial initiation of polymerization in adhesive bonding of resin to dentin.

Although various adhesive resins for dentin have been developed and used clinically, most attention has been directed to adhesion-promoting monomers and pre-treatment agents. The role of polymerization initiator systems in bonding has been overlooked. The purpose of this work was to study the role of initiators from the viewpoint of interfacial initiation of polymerization in dentin bonding. The bond strength between dentin and methyl methacrylate resin was significantly improved by a possible interfacial initiation with (1) the combination of ferric chloride, adsorbed onto dentin, and oxidized tri-n-butylborane (TBBO) and (2) the addition of tertiary butyl peroxymaleic acid (containing a carboxylic acid group, which has an affinity with dentin) to chemically- or light-activated initiator systems.

Acid Etching, Dental↗
PubMed1991

Effects of calcium channel agonists (BAY K 8644, CGP28392 and YC-170) on 45Ca uptake by rat uterine segments.

The characteristics of the stimulating effects of the calcium channel agonists BAY K 8644, CGP28392 and YC-170 on 45Ca uptake by rat uterine segments were investigated. BAY K 8644, CGP28392 and YC-170 caused about 150, 100 and 150% increase, respectively in the 45Ca uptake induced by 20 mM KCl. The ED50 values of BAY K 8644, CGP28392 and YC-170 were 1.8 X 10(-9), 2.5 X 10(-8) and 9.8 X 10(-9) M, respectively. These agonists had little effect on the 45Ca uptake induced by 10(-6) M acetylcholine. They also did not affect the basal 45Ca uptake. Their enhancing effects were blocked by the Ca channel antagonist nitrendipine. We conclude that rat uterine segments have voltage-sensitive Ca channels that are stimulated by Ca channel agonists (BAY K 8644, CGP28392 and YC-170) under depolarizing conditions and that the characteristics of the stimulating effects of CGP28392 and YC-170 on 45Ca uptake by rat uterine segments are qualitatively the same as those of BAY K 8644.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Isolation of Corynebacterium kutscheri from aged Syrian hamsters (Mesocricetus auratus).

Corynebacterium kutscheri was isolated from the oral cavities of 12 male Syrian hamsters (Mesocricetus auratus) which were about 12 months old. At 1, 5, and 9 months after initial isolation of C. kutscheri from the oral cavity, hamsters were euthanatized, and attempts were made to culture C. kutscheri from 13 additional sites. Corynebacterium kutscheri was isolated from nine hamsters, and regardless of the hamsters' ages, the organisms were most frequently isolated from the oral cavity (100%), esophagus (100%), cecal content (100%), and colon and rectum (88.9%). Isolation rates in the nasal cavity were 66.7%, followed by 55.5% in the trachea and 33.3% in the submaxillary lymph nodes. The number of the organisms found in the submaxillary lymph nodes and esophagus was 10(3) to 10(4) CFU/g. The number found in the cecal content and in the colon and rectum was 10(2) to 10(5) CFU/g. The organisms were not isolated from lung, stomach, kidney, spleen, and mesenteric lymph node tissues. The hamsters had neither clinical signs nor lesions. However, 7 of 12 animals had low agglutinating antibody titers. The Syrian hamster can therefore be an asymptomatic carrier of C. kutscheri.

Aging↗
PubMed1991

[Orthotopic heart transplantation with sinus venosus incision of right atrium in dogs--preservation of sinus node and original right atrium].

Orthotopic heart transplantation with sinus venosus incision of right atrium was aimed to preserve the sinus node, terminal crista, sinus node artery and whole right atrial muscle of the transplanted heart. This transplant procedure was performed in eight mongrel dogs and electrocardiogram was followed up to five postoperative months. Direct cross circulation technique was employed as an alternative of cardiopulmonary bypass. Donors and recipients were 6 to 8 kg mongrel puppies, and 19 to 25 kg adult dogs supported the cross circulation. Myocardial protection of the donor heart was carried out by low-flow continuous potassium cardioplegia and topical cooling. Right atrial incision of the donor heart was made longitudinally in the posterior wall of sinus venosus. After a median sternotomy, ascending aorta and superior and inferior venae cavae of the recipient were cannulated and connected respectively with carotid artery and jugular vein of the cardiopulmonary support dog. Electrocardiogram, arterial pressure and central venous pressure of the recipient were monitored, and an electro-magnetic flow meter was employed for measuring the blood flow of direct cross circulation. The native heart was resected after aortic cross-clamping, and left atrium and atrial septum were sutured continuously. Sinus venosus incision of the donor heart was anastomosed to the recipient's right atrium. Ascending aorta and pulmonary trunk were reconstructed in the standard fashion. Aortic cross-clamp time was less than one hour and sinus rhythm of the transplanted heart was continued in all cases. Five of the eight dogs were alive postoperatively for one week to five months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[The automatic implantable cardioverter defibrillator--clinical experience in patients with life-threatening ventricular tachyarrhythmias].

Five patients (pts) with life-threatening ventricular tachyarrhythmias (idiopathic VF; 2 pts, Torsade de pointest; 1 pt, VT/VF after valve replacement; 2 pts) underwent surgical treatment of the automatic implantable cardioverter defibrillator (AICD). Implantation of an AICD was indicated for patients who survived circulatory arrest due to documented VT and/or VF. The patient should be medically refractory or medical treatment precluded by hemodynamic instability; other surgical treatment should not be possible. We selected myocardial electrode for sensing and small and large patch electrodes for defibrillating. VF/VT was induced 1 to 6 times for the measurement of defibrillation threshold (DFT). In all of our pts, the AICD appropriately discharged at postoperative EPS. In three of pts, the AICD discharged within the postoperative hospital phase, in two because of sinus tachycardia during treadmill test and restored sinus rhythm after non-sustained VT. As for complications, in one pt. with severe LV dysfunction, incessant form of VT/VF occurred after DFT testing and LV assist circulation and IABP were needed. In two pts, inappropriate discharge and in two, pericarditis were recognized postoperatively. It was considered that this system was effective for the treatment of life-threatening ventricular tachyarrhythmias but strict indication was necessary because of unsolved problems.

Adult↗
PubMed1990

Characterization of immobilized hepatocytes as liver support.

Hepatocytes isolated from rat liver were immobilized within Ca-alginate. Immobilized hepatocytes could remove ammonia and other toxic substances causing hepatic coma, such as indole, phenol, bilirubin, and short chain fatty acids. Although free hepatocytes lost those activities within 2 days, immobilized hepatocytes maintained those activities for more than 7 days. Immobilized hepatocytes induced tyrosine aminotransferase (TAT) in the presence of dexamethasone and dibutyryl-cAMP and retained the ability to induce TAT for more than 7 days. Biologically active form of coagulation factor II, prothrombin could be synthesized and secreted into medium by immobilized hepatocytes. Moreover, immobilized hepatocytes produced glucose from lactate, alanine, fructose, and galactose. Like adult rat liver, growth-related function and liver-specific function in immobilized hepatocytes were reciprocally controlled by cell density. There are both alpha-, and beta-adrenergic receptors in membrane of liver cells, and the adrenergic action of epinephrine is alpha-predominant in adult rat liver. Monolayer-cultured hepatocytes can not maintain alpha-adrenergic response. However, immobilized hepatocytes maintained alpha-adrenergic response as shown in vivo. Those characteristics of immobilized and three-dimensionally cultured hepatocytes are regarded almost the same as liver cells in vivo. Furthermore, therapeutic effect of immobilized hepatocytes on the hepatic failure were confirmed in the experiment using hepatocytes damaged with D-galactosamine. Therefore, it is suggested that immobilized hepatocytes could be applied to a hybrid artificial liver support.

Alginates↗
PubMed1990

New method of treatment for dentin hypersensitivity by precipitation of calcium phosphate in situ.

The hydrodynamic theory is generally accepted as an explanation of hypersensitive dentin and suggests that occlusion of exposed dentinal tubules should result in a reduction of hypersensitivity. We tried to block tubules by in situ precipitation of insoluble calcium phosphate. Calcium phosphate crystals precipitated in situ on patent dentin surfaces and formed in the tubules immediately upon serial application of sodium phosphate and calcium chloride solutions, thus occluding the tubules. The size of crystals, their degree of coverage, and the thickness of the precipitate depended on the method of application and concentration of the solutions. The application of 5% disodium phosphate solution followed by rubbing with 10% calcium chloride solution resulted in immediate relief from dental hypersensitivity in 84% of patients treated.

Adult↗
PubMed1990

WBN/Kob rats. A new spontaneously occurring model of chronic pancreatitis.

Chronic pancreatitis-like lesions are observed in 100% of male Wistar Bonn/Kobori rats. At 3 mo of age, histopathologic examinations of the pancreas revealed a distinct infiltration of inflammatory cells with interstitial edema in the acini. At the same time, periductal and interstitial fibrosis and adenomatous hyperplasia of the ductular epithelium were observed. Extensive fibrotic exudation developed rapidly with age, and irregular destruction of the parenchyma was noted. The only abnormality, prior to the appearance of glycosuria, that could be detected clinically was lower levels, compared to Wistar rats, of BT-PABA excreted in the urine after oral ingestion. These lower levels indicate a decrease in enzyme secretion in WBN/Kob rats. Ultrastructural observations in histologically normal areas at 2 mo of age showed a swelling of mitochondria, indicating that ischemia was associated with the early pancreatic lesions. Serial pancreatographies were performed at 2-8 mo of age. Irregular widenings of the main pancreatic duct and dilations of the smaller ducts were observed already at 2 mo of age, suggesting a stasis of pancreatic juice in the early stages of the disease. It seems that male WBN/Kob rats are a useful model of human chronic pancreatitis, with an unknown mechanism regulated by the sex hormones.

Amylases↗
PubMed1990

[Experimental studies on the combined effect of radiation and UFT: 2. fractionated treatments combining UFT and X ray radiation].

The combined effects of fractionated radiation and UFT, which is a mixture of tegafur (FT) and uracil, have been studied using C3H mouse mammary carcinoma. The tumor was implanted in the right hind legs of and irradiated with 300R daily for either 10 or 15 days. UFT (FT 15mg/kg + uracil 33.6mg/kg) was intra-gastrically administered 2 hr. before irradiation. Dose modifying factor (DMF) of UFT obtained from the tumor growth delay assay was 1.52 for 10 fractions (3,000R) and 1.27 for 15 fractions (4,500R). The continuous administrations of UFT for one month after combination treatment suppressed the tumor regrowth. It is suggested that UFT is a useful radiosensitizer for concurrent fractionated radiation and useful adjuvant agent after radiation therapy.

Animals↗
PubMed1990

[Study on adhesion mechanism of MMA-TBBO resin to dentin. A model experiment using decalcified dentin].

As a model experiment to understand the mechanism of adhesion of the MMA-TBBO resin to dentin, MMA-TBBO was polymerized using a decalcified dentin sheet treated with aqueous citric acid (CA) solutions of copper fluoride (CF), ferric fluoride (FF), or ferric chloride (FC), which are usually used as treating agents in the bonding of the resin to dentin. The curing time for MMA-TBBO resin was considerably reduced on the decalcified dentin sheet treated with FC-CA, CF-CA or FF-CA at an appropriate concentration. Polymerization of MMA-TBBO resin was accelerated in the presence of a fluoride ion. Molecular weight of PMMA depended on the site of polymerization; PMMA polymerization inside the decalcified dentin sheet gave the highest and that outside gave the lowest molecular weight in the presence of an appropriate amount of ferric or cupric ion. These results suggested that ferric compounds adsorbed to decalcified dentin are involved in the polymerization of MMA and thus will influence the bond strength of the MMA-TBBO resin to dentin.

Acrylic Resins↗
PubMed1990

[Adhesion mechanism of MMA/TBBO resin containing 4-META to decalcified dentin].

As a model experiment to understand the mechanism of adhesion of the 4-META-MMA/TBBO resin to dentin, 4-META-MMA/TBBO was polymerized in the presence of decalcified dentin sheet treated with citric acid (CA) aqueous solution containing ferric chloride (FC). Curing time of MMA/TBBO resin was reduced by the addition of 4-META to MMA. Addition of 4-META increased molecular weight of PMMA. PMMA polymerized inside the decalcified dentin sheet was insoluble in acetone. PMMA obtained from the monomer liquid used in commercial Super-Bond C & B was all insoluble and no soluble fraction was obtained. These results suggested that 4-META accelerated polymerization of MMA-TBBO resin in the presence of ferric ion and was effective to enhance molecular weight of PMMA. These effects seemed to be related to high bond strength of Super-Bond with dentin.

Acrylic Resins↗
PubMed1990

[Successful surgical treatment of automatic atrial tachycardia].

A 3-year-old boy had chronic repetitive atrial tachycardia. The tachycardia could not be induced neither terminated with rapid atrial pacing nor atrial extrastimuli. Overdrive suppression and warm-up phenomenon were demonstrated. These electrophysiological features suggested atrial ectopic automaticity. Endocardial and epicardial mapping determined the origin of tachycardia at the left atrial appendage. The LA appendage was excised and the tachycardia was completely terminated. The patient is asymptomatic without medication and echocardiographic indices of left ventricular function returned to normal over 1 year follow-up period.

Child, Preschool↗
PubMed1989

[Experimental studies on the combined effect of radiation and UFT 1. Radiosensitizing effect of UFT under single X-ray exposure].

The combined effects of X-ray and UFT, which is a mixture of tegafur (FT) and uracil, were studied using C3H mouse mammary carcinoma. Tumors were irradiated with a single dose of 1,000 R, 2,000 R one week after intramuscular transplantation. UFT (FT 15mg/kg+Uracil 33.6mg/kg) was intragastrically administered 2 hours before irradiation. In the group treated by combination of UFT and 1,000 R, the dose modifying factor (DMF) of UFT was 1.28 on the tumor growth delay and 1.64 on the survival time. A decrease in pulmonary metastases was found in the group treated by combination of UFT and radiation. It is suggested that UFT is a useful oral drug for combined treatment with radiation.

Animals↗
PubMed1989

[Effect of fluoride of copper and iron on polymerization of MMA/TBBO resin and adhesion to dentin].

As a model experiment to understand the mechanism of adhesion of the MMA/TBBO resin to dentin, polymerization of MMA/TBBO was investigated in the presence of a collagen sheet treated with the aqueous citric acid (CA) solutions of copper fluoride (CF), ferric fluoride (FF), or ferric chloride (FC), which is usually used as a treating agent in bonding of the resin to dentin. The curing time of MMA/TBBO resin was considerably reduced in the presence of collagen treated with CF-CA or FF-CA solutions when compared to that with FC-CA solution. Molecular weight of PMMA depended on the site of polymerization; PMMA polymerized inside the collagen sheet was the highest and that polymerized outside was the lowest. Bond strength to dentin treated with CF-CA, FF-CA solutions was as strong as that treated with FC-CA solution. Treatment of dentin with CF-CA or FF-CA was as effective as that with FC-CA in bonding the MMA/TBBO resin. These results suggested that ferric compounds adsorbed to collagen are involved in polymerization of MMA and thus influence bond strength of the MMA/TBBO resin to dentin.

Adhesiveness↗