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Biomedical subjects

R Yamada

Publications and source records attributed to R Yamada.

At least 271 records · Page 15Linked to original sources
PubMed1984

"In vivo" inhibition of murine liver aspartate aminotransferase by isoniazid.

Intraperitoneal administration of isoniazid (IN), an antituberculous agent, to mice or rats at a dose of 100 mg/kg body weight resulted in remarkable and rapid inhibition of liver cytosolic aspartate aminotransferase (AAT); inhibition was less marked with other antivitamin B6 compounds; AATs in other tissues and other aminotransferases in liver were less effectively inhibited by IN. The inhibition of liver cytosolic AAT was apparently irreversible in vivo; it was reversed only a little by gel filtration and dialysis to remove excess IN in vitro, although treatment with pyridoxal phosphate or 5'-deoxypyridoxal slowly restored the full activity. Attempts to inhibit the enzyme by in vitro treatments showed that IN itself was not an effective inhibitor, while the liver extracts from IN treated mice contained some strongly inhibitory substance. In addition, the extracts were shown to contain only trace amounts of IN. These results suggest that IN is metabolized to some other form which is markedly inhibitory to murine liver cytosolic AAT, and the metabolite binds to the coenzyme moiety of enzyme in a manner not readily dissociable.

Animals↗
PubMed1983

Indications for endoscopic Nd-YAG laser surgery in the trachea and bronchus.

Nd-YAG laser surgery via the fiberoptic bronchoscope can vaporize lesions causing airway obstruction or stenosis located from the trachea to segmental bronchi with minimized danger of bleeding, and improve ventilatory disturbances. 35 lesions in the trachea and bronchus consisting of 27 malignant lesions and 8 benign lesions were treated with endoscopic Nd-YAG laser surgery. The procedures were performed under local anesthesia, and no significant side effects were recognized. The lesions was irradiated with 20-80 W. power. In most cases a continuous wave was used, but in cases of early stage squamous cell carcinoma intermittent irradiation of 0.5 second laser spots were used. In 21 of 35 cases effective results were obtained. The non-effective results obtained in 14 cases were considered to be due to inexact preprocedural evaluation of the extent of the lesions. Effective results were obtained in 11 of 13 lesions located in the trachea, in 3 of 5 lesions in the trachea and bronchus and in 7 of 17 lesions in the bronchus. Tumor in the trachea with severe ventilatory disturbance is a good indication for Nd-YAG laser surgery to rapidly alleviate symptoms. But in cases of lung cancer, indications even as a palliative procedure are limited to those cases in which the lung parenchyma distal to the stenotic portion is viable. However, the indications for this procedure as a curative modality are extremely limited.

Adult↗
PubMed1983

Hepatic artery embolization in 120 patients with unresectable hepatoma.

Transcatheter hepatic artery embolization was performed in 120 patients with unresectable hepatoma. The cumulative one-year survival rate was 44%. In most cases follow-up angiography revealed the selective disappearance of tumor vessels, and computed tomography demonstrated a marked decrease in tumor density without any changes in the surrounding liver parenchyma. Histologic examination in 14 cases confirmed these findings.

Adult↗
PubMed1983

Segmental obstruction of the hepatic inferior vena cava treated by transluminal angioplasty.

Five patients with segmental obstruction of the hepatic inferior vena cava associated with Budd-Chiari syndrome were successfully treated by percutaneous transluminal angioplasty using Grüntzig balloon catheters. Three or four balloons were used simultaneously to achieve sufficient dilatation. Long-term patency was obtained in all 5 cases without serious complications. This procedure may be applicable to other portions of the venous system as well.

Adult↗
PubMed1983

Basic and clinical reevaluation of tyramine and histamine tests for the investigation of adrenomedullary sympathetic functions.

In vitro and in vivo studies using histamine and tyramine tests were carried out to investigate adrenomedullary sympathetic functions. Administration of 10(-3) M tyramine enhanced catecholamine release from both the perifused swine adrenal medulla and human pheochromocytoma tissue, whereas histamine did not show this effect. Tyramine also induced release of catecholamine from the isolated catecholamine granules in vitro, but histamine did not. The tyramine or histamine test was performed in vivo on groups of 16 subjects, respectively, consisting of healthy adults and hypertensive patients. In all cases, a rise in blood pressure was observed after loading with either tyramine or histamine. On the other hand, when urinary catecholamine output was examined during the first 2 h after loading, a significant increase was not observed in 4/16 after tyramine administration, and in 6/16 after histamine loading. Thus, using an in vitro system, we showed a difference between tyramine and histamine in the mode of direct action on adrenal medulla. We also conclude that urinary catecholamine output is of less significance than the blood pressure response as an index of tyramine or histamine test.

Adrenal Gland Neoplasms↗
PubMed1983

Effect of acebutolol on plasma catecholamine concentrations in anesthetized dogs with ouabain-induced arrhythmias and its direct actions in vitro on the adrenal medulla.

We have performed studies on blood hormone dynamics following intravenous administration of acebutolol, a newly synthesized beta-blocker, and its direct action on the adrenal medulla in vitro. Intravenous injection of acebutolol into anesthetized dogs almost doubled the plasma adrenaline and noradrenaline concentrations within 5 to 15 minutes, while renin activity was reduced to approximately two-thirds of the pre-administration level. When arrhythmia was induced in dogs with ouabain, the plasma adrenaline and noradrenaline levels increased to 220 +/- 109 and 392 +/- 84 pg/ml, respectively, from the basal levels of 44 +/- 24 and 140 +/- 43 pg/ml. The restoration of sinus rhythm following the administration of acebutolol was accompanied by a further increase in the plasma adrenaline and noradrenaline levels to 797 +/- 364 and 1226 +/- 263 pg/ml, respectively. A perifusion experiment indicated that acebutolol directly accelerated catecholamine release from the adrenal medulla in pigs.

Acebutolol↗