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Biomedical subjects

T Hirata

Publications and source records attributed to T Hirata.

At least 325 records · Page 18Linked to original sources
PubMed1992

Interactive effects of verapamil and sympathetic nerve stimulation on the sinus and AV nodes in the canine hearts.

The interactive effects of verapamil and sympathetic nerve stimulation on the sinus and atrioventricular (AV) nodes were studied in 33 bilaterally stellectomized and vagotomized dogs. Sinus cycle length (SCL) and AV nodal conduction time (AH) at a constant drive cycle length (600 msec) were recorded. Sympathetic nerve stimulation (SNS) was performed for 40 sec by electrical stimulation of the right stellate ganglion. Several doses of verapamil (0.5-2.0 microgram/ml, 1.0 ml) were injected directly into the sinus and AV node arteries at 20 sec of SNS. In addition, SNS was repeated at two different intensities after verapamil administration. Verapamil significantly increased the SCL and the AH in a dose dependent fashion, which was reduced by SNS. The reductions of SCL and AH by the SNS were attenuated in the presence of verapamil when the stimulation intensity was weak, but not when the stimulation intensity was strong. It is concluded that verapamil and sympathetic nerve activity interact antagonistically on the sinus node automaticity and AV nodal conduction.

Animals↗
PubMed1992

Electroencephalographic changes during piano playing and related mental tasks.

Theta activity in EEG was found to be augmented in the frontal midline area in 5 young women while they played classical piano pieces and during related mental tasks. This activity was considered to be a frontal midline theta rhythm with the maximal amplitude mostly in Fz and of the frequency ranging from 5 to 7.5 Hz. This theta activity was observed to increase depending on the degree of the subjects' concentration on piano playing or related tasks. In bilateral parietal derivations, increases in the power value of alpha activity were observed in some subjects while they were listening to music, suggesting that alpha activity was involved in appreciation of music.

Adolescent↗
PubMed1992

[Evaluation of endoscopic mucosal resection (EMR) as a curative therapy against early gastric cancer].

This study investigated the effectiveness of EMR as a curative therapy against early gastric cancer, comparing with that of radical operation. In 256 radical operation cases, five year survival rates were 97.5% in m-cancer and 93.2% in sm-cancer. In these cases, postoperative complications occurred in 7.8%, with operative mortality being 0.78%. In 56 EMR cases, nine encountered slight bleeding, which was controlled by ethanol injection under endoscopy. Regarding prognosis of EMR, cancer recurrences occurred in 45.8% of cases with stump involvement in the resected mucosa (stump (+)). In cases without stump involvement in the resected mucosa (stump (-)), no recurrence were found except one case, in which distance from the cancer edge to the stump was only 0.6 mm, suggesting that enough distance (2mm) to the stump is required for curative EMR. Stump (-) rate was high (81.2%) in cases of small cancer less than 1 cm in diameter, but was low in cases of cancer greater than 2 cm and those located in upper body or lesser curvature. To establish EMR as a curative therapy, it must be performed by single collection to check remaining cancer. In conclusion, although radical operation is still the standard curative therapy, EMR should be considered as an alternative therapy.

Aged↗
PubMed1992

[Mechanism of synergism and clinical results of sequential methotrexate and 5-fluorouracil in the treatment of gastric cancer].

Mechanism of synergism and clinical results of methotrexate and 5-fluorouracil (MTX/5-FU) combination therapy for gastric cancer were studied. The response rate against poorly differentiated gastric cancers was 35% in this treatment. This treatment also showed a remarkable effect against cases with pleural and abdominal effusion caused by cancerous disseminations. A promising result was obtained by this treatment as neoadjuvant and postoperative chemotherapy against Borrmann type 4 gastric cancer. A greater dependence on the de novo pathway of pyrimidine synthesis against poorly differentiated gastric carcinoma, which was estimated by the fact that the thymidylate synthetase/thymidine kinase ratio was significantly higher in poorly differentiated gastric cancer than in well differentiated cancer, may potentiate therapeutic results of this treatment.

Adult↗
PubMed1991

Requirement for the beta,gamma-pyrophosphate bond of ATP in a stage between transcription initiation and elongation by Escherichia coli RNA polymerase.

A linear fragment of DNA was fixed to acrylamide or agarose beads by its ends. When a fragment containing the lambda PR promoter is immobilized and transcribed, the RNA products are unchanged from those obtained on the unfixed DNA. Transcription from the immobilized fragment can be interrupted by diluting the reaction mixture into a large volume of the same buffer. Brief centrifugation allows isolation of the transcription complex with the immobilized DNA. If interruption occurs during elongation, the elongation can be resumed upon a second addition of substrates. If ATP is replaced by a beta, gamma-unhydrolyzable analogue in the second addition, the elongated products are similar to those obtained when the substrate contain ATP. When ATP is replaced by the analogue at the initiation step, however, the yield of elongated products is decreased to less than one-sixth and that of short abortive products is increased. Thus the ATP analogues are good substrates once elongation has been established in the presence of ATP, but not good enough to get past a stage just after initiation in the absence of ATP. We conclude that the beta, gamma-pyrophosphate bond of ATP is important for preparation of efficient elongation.

Adenosine Triphosphate↗
PubMed1991

Improved delineation of the gallbladder wall with ultrasonography: its value in assessment of the depth of carcinoma invasion.

We examined 30 surgically removed gallbladders with ultrasound using a 10 MHz transducer in a water bath. The sonographic structure of gallbladder wall was imaged as 5 layers. The layer 3, a well-defined hyperechoic zone, was confirmed histologically as corresponding to the boundary between subserosa and muscularis. Since the spreading of gallbladder carcinoma beyond the muscle coat is an important prognostic indicator, high resolution images may well be used to advantage in assessing gallbladder wall penetration intraoperatively, enabling the surgeon to choose the proper operative procedure.

Adenocarcinoma, Papillary↗
PubMed1991

The A5 antigen, a candidate for the neuronal recognition molecule, has homologies to complement components and coagulation factors.

The A5 antigen is a neuronal cell surface protein of Xenopus presumed to be involved in the neuronal recognition between the optic nerve fibers and the visual centers. Analyses of cDNA clones revealed that the A5 antigen is a class I membrane protein containing two different internal repeats in the extracellular segment. The first repeat bears homology to domain III of complement components C1r and C1s, and the second repeat is homologous to the C1 and C2 domains of coagulation factors V and VIII. The mRNA for the A5 antigen was present in retinal ganglion cells and visual center neurons. Nonneuronal cells in the peripheral and central nervous systems did not express the mRNA for the A5 antigen.

Amino Acid Sequence↗
PubMed1991

Synthesis and biological evaluation of quinocarcin derivatives: thioalkyl-substituted quinones and hydroquinones.

Varieties of thioalkyl-containing quinone and hydroquinone analogues of quinocarcin (1a) were prepared effectively, by addition of mercaptan to 3a-c, which were derived from 1a via DX-52-1 (1b). Antitumor activities of these analogues were preliminarily evaluated by growth inhibition of HeLa S3 cells (in vitro) and increased life span of P388 implanted mice (in vivo). Bis(alkylthio)quinones 4a-d and 5a-d, and corresponding hydroquinones 9b-d exhibited high activities both in vitro and in vivo. They were superior to 1a especially in single administration. Selected compounds 4a, 4d, 5a, 5d, and 9b were subjected to further evaluation, and bis(methylthio)quinone 5a was revealed to possess broad-spectrum activity toward human xenographted carcinomas MX-1, Co-3, St-4, and LC-06.

Animals↗
PubMed1991

Correlation between magnetic resonance imaging and histopathology of intracranial glioma.

Postmortem histopathology of eight gliomas was studied in correlation with magnetic resonance imaging (MRI) and computed tomography (CT) findings. MRI demonstrated the lesions more clearly and widely than CT. Also, T2-weighted images (T2WI) had a greater ability to depict the lesion than T1-weighted images (T1WI). The areas in which neoplastic cells had invaded corresponded to the high intensity areas on T2WI in four cases of glioblastoma multiforme. In the case of a grade II astrocytoma, neoplastic cells were scattered beyond the region corresponding to the high intensity area on T2WI. In the case of a grade III astrocytoma, neoplastic cells did not come up to the line corresponding to the margin of the high intensity area on T2WI. In the remaining two cases, although the high intensity areas on T2WI were depicted as being larger than the areas in which neoplastic cells were seen histopathologically, the high intensity regions corresponding to the outside zones of the tumour-infiltrated area were thought to be a radiation necrosis in one case and a 'periventricular high intensity' in the other. The high cellularity of the glioma was seen mainly as a low intensity area on T1WI and as an isointensity or a slightly high intensity area on T2WI. However, the signal intensities of glioma on MRI, reflecting T1 or T2 values of the tumour tissues, did not correlate with the malignancy of the tumour.

Adult↗
PubMed1991

Arrhythmogenic properties of the ventricular myocardium in cardiomyopathic Syrian hamster, BIO 14.6 strain.

STUDY OBJECTIVE: Incidence of spontaneous cardiac arrhythmias and inducibility of ventricular arrhythmias in the cardiomyopathic hamster, BIO 14.6 strain, were examined. DESIGN: A 3 min electrocardiogram (ECG) was recorded weekly to 50 weeks of age. Programmed ventricular stimulation was then performed with single and double ventricular premature stimuli during both sinus rhythm and ventricular pacing, and with brief bursts of ventricular pacing to induce ventricular arrhythmias. EXPERIMENTAL MATERIAL: 19 male cardiomyopathic and 10 age matched normal hamsters from 16 to 50 weeks were used for recording the 3 min ECG; 11 cardiomyopathic and 10 normal hamsters aged 50 to 55 weeks were used for the induction of ventricular arrhythmias. MEASUREMENTS AND MAIN RESULTS: Spontaneous and sporadic ventricular premature contractions were documented in 8.3% of 218 ECGs from the cardiomyopathic hamsters between the ages of 30 and 46 weeks, whereas no ventricular arrhythmia was recorded in normal hamsters throughout the entire follow up period. Non-sustained ventricular tachycardia (NSVT) was induced in 7/11 cardiomyopathic hamsters by single ventricular premature stimulus. Either NSVT or ventricular fibrillation was induced in all cardiomyopathic hamsters with a significantly prolonged intraventricular conduction delay and refractory period. In contrast, neither NSVT nor ventricular fibrillation was induced in normal hamsters. CONCLUSION: This study provides the first evidence of the high arrhythmogenicity of the ventricles in cardiomyopathic hamsters.

Animals↗
PubMed1991

Influence of sympathetic nerve activity on ventricular arrhythmogenicity in the dog with chronic hypokalemia.

To examine the influence of sympathetic nerve activity on ventricular arrhythmogenicity in the dog with chronic hypokalemia, an electrophysiologic study was performed before and after bilateral stellectomy (BS) in 10 dogs with chronic hypokalemia (2.8 +/- 0.1 mEq/L), which was created by feeding a low-potassium diet and by administering furosemide over a four-week period, and the results were compared with those obtained from 10 dogs with normokalemia (4.7 +/- 0.3 mEq/L) from being fed an ordinary diet over a four-week period. Before BS the incidence of electrically induced ventricular arrhythmias was higher in the hypokalemic than in the normokalemic dogs. After BS it was decreased considerably in the hypokalemic but not in the normokalemic dogs. Heterogeneity of effective refractory period (delta ERP), which was determined as the difference between the longest and shortest effective refractory periods in three sites of the right and left ventricles, was greater in the hypokalemic than in the normokalemic dogs before BS. The delta ERP decreased slightly in the two groups both before and after BS. There was, however, no significant difference in delta ERP in the two groups both before and after BS. Ventricular fibrillation threshold (VFT) was significantly lower in the hypokalemic dogs than in the normokalemic dogs before BS (p less than 0.005). VFT was elevated in the two groups after BS. Percent increase in VFT after BS was significantly greater in the hypokalemic than in the normokalemic dogs. In conclusion, sympathetic nerve activity may play an important role in the increase in ventricular arrhythmogenicity in the presence of chronic hypokalemia.

Animals↗
PubMed1991

Studies on cardiotonic agents. V. Synthesis of 1-(6,7-dimethoxy-4-quinazolinyl)piperidine derivatives carrying various 5-membered heterocyclic rings at the 4-position.

A series of 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying various 5-membered heterocycles at the 4-position was synthesized and examined for cardiotonic activity in anesthesized dogs. The (4-oxo-2-thioxo-3-imidazolindinyl)amino derivatives showed the most potent inotropic activity. Marked loss of activity was observed in the 2,4-dihydro-3-thioxo-3H-1,2,4-triazolyl, the 2,4-dihydro-3-oxo-3H-pyrazolyl and the (2,3-dihydro-2-thioxo-3H-1,3,4-thiadiazol-5-yl)amino derivatives. The synthesis and structure-activity relationships are discussed.

Animals↗
PubMed1991

Effects of sympathetic and parasympathetic stimulation on the induction of atrial flutter in dogs with aseptic pericarditis.

To study the effects of sympathetic stimulation (SS) and vagal stimulation (VS) on the induction of atrial flutter (AF) and its cycle length, aseptic pericarditis was produced surgically in 17 adult mongrel dogs. Programmed atrial stimulation was used to induce AF and to determine the effective refractory periods (ERP) and maximum conduction delay (maxCD) of the atrium. These tests were performed before and during stimulation of the right cervical vagus nerve and the right stellate ganglion. Results showed: (1) AF could be induced in animals with short ERP and large maxCD before SS; (2) ERP was significantly shortened, maxCD was significantly increased by VS; (3) During SS, ERP was slightly shortened, but there were no changes in maxCD and the induction rate of AF; (4) The cycle length of AF was shortened by SS, however, the cycle length of AF was shortened more notably by VS than by SS. From these findings, a shortening of the ERP and an increase in maxCD appear to be related to an increased AF induction rate by VS.

Animals↗
PubMed1991

Intraoperative radiation therapy for malignant glioma.

Intraoperative radiation therapy (IORT) was used as part of the initial therapy for malignant glioma in 32 of 73 patients with histologically verified anaplastic astrocytoma (grade III astrocytoma) and glioblastoma multiforme. The initial treatment for all cases was subtotal or total tumor resection combined with external irradiation and chemotherapy. IORT was performed 1 week after tumor resection, with doses of 10-50 Gy (mean 26.7 Gy) in one session. Fourteen of 32 cases had IORT two times because of tumor recurrence. The IORT patients had survival rates at 24 and 36 months after initial treatment of 57.1 and 33.5% (median survival 26.2 months). The other 41 patients had 23.6 and 13.1% survivals (median survival 20.7 months), which were significantly lower (p less than 0.01). Tumor recurrence within the original lesion site was suspected because of clinical condition, computed tomography, and magnetic resonance imaging studies in 65.6% of the IORT group (21 cases) 12 months after initial treatment. Twenty cases of death in the IORT group, including five autopsy cases, demonstrated regional tumor recurrence with a high incidence of intraventricular tumor invasion. The authors consider IORT is beneficial for selected malignant glioma patients, including tumor recurrence, because of prolonged survival.

Adolescent↗
PubMed1991

Compensatory process of vestibular neuronitis. From findings of combined galvanic test and caloric test.

The compensatory process of vestibular neuronitis in 7 patients was followed up and evaluated using the Combined Galvanic Test (CGT) and other neuro-otological data. CGT is the simultaneous recording of both galvanic eye movement (GEM) and galvanic body sway (GBS), and has proved to be reliable in the diagnosis of retrolabyrinthine disorders. The results were as follows: The subjective symptoms remained in 3 cases from 1 month to 1 year. The recovery of the GBS response was seen earlier than that of both GEM and caloric responses. The recovery of GEM and caloric responses was observed at almost the same time. We observed the favorable recovery process of caloric response and GEM response in some cases which had recovery of GBS response within 4 weeks and suggest that the system of GBS response is different from that of GEM and caloric response. However, the systems of the latter two may be the same. We assume that the recovery of GBS response is earlier than that of GEM and caloric responses because the otolithic system recovers more easily than the semicircular canal system. The CGT and caloric test were reliable in examining the compensatory process of vestibular neuronitis.

Adult↗
PubMed1991

[Role of combined pulmonary resection during descending thoracic aortic aneurysmectomy].

Between April, 1982 and December 1990, five of 98 patients who underwent aneurysm repair for the thoracic aorta received combined resection of the descending thoracic aortic aneurysm and the lung because of marked adhesion between the aneurysm and the lung. Partial resection of the upper lobe of the lung was performed in all of five patients with auto-suture device. Three of the five patients needed no homologous blood transfusion during the surgery. Neither operative death nor pulmonary complication related to lung injury and bleeding was noticed. Our results indicate that partial resection of the lung is beneficial for avoiding intra-operative rupture of the aneurysm as well as lung injury in patients with descending thoracic aortic aneurysm severely adherent to the lung.

Aged↗