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Biomedical subjects

I Yamaguchi

Publications and source records attributed to I Yamaguchi.

At least 343 records · Page 19Linked to original sources
PubMed1977

Characteristics of sinoatrial conduction in patients with coronary artery disease.

Electrophysiologic studies were performed in 32 patients with angiographically documented coronary artery disease (CAD). Group I was composed of ten patients (31%) with severe stenosis (greater than or equal to 75%) proximal to the origin of the sinus node artery (SNA); group II was composed of five patients (16%) with moderate (50--75%) proximal stenosis; and group III was composed of 17 patients (53%) with insignificant (0--50%) proximal stenosis. The mean sinoatrial conduction time (SACT) for group I was 119 +/- 18 msec; group II was 84+/- 16 msec; and group III was 72 +/- 5 msec. The SACT was significantly longer in group I than in group III (P less than 0.005). In conclusion 1) in patients with CAD, SACT greater than 72 +/- 5 msec is abnormal; 2) the results suggest a pathogenetic role of CAD in the development of sinus node dysfunction; 3) the SACT is a more sensitive indicator of subtle sinus node dysfunction in CAD patients than is heart rate, sinus node response to artrial extrastimuli, or sinus node recovery time; and 4) the ability to diagnose sinus node dysfunction in its early stages and recognition that coronary artery disease is an etiologic factor may allow for the elucidation of the natural history of the sick sinus syndrome.

Adult↗
PubMed1977

Effect of diltiazem on insulin secretion. I. Experiments in vitro.

Effect of diltiazem on glucose-induced insulin secretion was investigated in the rat islets of Langerhans isolated by a collagenase digestion technique. It was found that B-cells, main constituents of isolated islet preparations, had a well-preserved ultrastructural appearance immediately following isolation or after incubation with glucose or glucose and diltiazem. The islets released a large amount of insulin upon stimulation with glucose and CaCl2. Diltiazem (10(-6)-10(-4) M) produced a dose-related inhibition of glucose-induced insulin secretion and this effect was antagonized by the increase in extracellular concentration of CaCl2. The inhibitory effect of diltiazem on the insulin secretion was also counteracted by dibutyryl-3',5'-cyclic AMP or by theophylline. Among calcium-antagonists tested, nifedipine produced the most powerful inhibitory action on the insulin secretion, while the effect of verapamil was similar to or somewhat stronger than that of diltiazem. It was suggested that diltiazem may reduce the intracellular concentration of free calcium ion, thus causing an inhibitory effect on the glucose-induced insulin secretion by the isolated islets of Langerhans.

Animals↗
PubMed1977

Wolff-Parkinson-White syndrome. Alterations in electrophysiologic characteristics of the bypass tract secondary to ischemia.

Accurate electrocardiographic diagnosis of myocardial ischemia or infarction is difficult in patients with the Wolff-Parkinson-White syndrome; however, myocardial ischemia may also have profound effects on the electrophysiologic characteristics of the bypass tract in these patients. Comparison of studies performed during and two months following an episode of significant myocardial ischemia demonstrated substantial prolongation of the refractoriness of the bypass tract during the period of ischemia. Bypass refractoriness was prolonged by 196 msec, yet atrioventricular nodal refractoriness was not significantly different from normal. These studies, therefore, suggest that, on occasion, the presence of acute myocardial ischemia may, in fact, obscure the electrocardiographic diagnosis of the Wolff-Parkinson-White syndrome.

Aged↗
PubMed1977

Central and peripheral adrenergic mechanisms regulating gastric secretion in the rat.

Subcutaneous injection of sympathomimetic agents reduced gastric secretion in pylorus-ligated rats, and the decreasing order of activity was: isoproterenol, norepinephrine, naphazoline and phenylephrine. The effect of naphazoline and phenylephrine was antagonized with 4 mg/kg s.c. of phentolamine, and that of isoproterenol with 4 mg/kg s.c. of propranolol. Thus there exist separate, alpha and beta adrenergic receptors which control gastric secretion in the rat. Intracerebroventricular (i.c.v.) injection of the sympathomimetic agents also reduced secretion, naphazoline being the most potent. The ED50 of i.c.v. naphazoline was 12.3 times less than that of s.c. dose. The antisecretory effect of i.c.v. naphazoline was antagonized with i.c.v. phentolamine (0.016 and 0.064 mg/kg), but not with propranolol. These results suggest that naphazoline stimulates central alpha adrenergic receptors which has a tonic inhibiting role in rat gastric secretion. Analogous to the results with naphazoline, i.c.v. phentolamine, but not propranolol, blocked an antisecretory effect of chlorpromazine. Phentolamine administered s.c. also reduced the antisecretory activity, but the dose required for the antagonism was 250 times that of i.c.v. phentolamine. An antisecretory effect of imipramine was not blocked by phentolamine or propranolol. These results suggest that an activation of central alpha adrenergic receptors is important for the antisecretory effect of chlorpromazine.

Animals↗
PubMed1976

Recurrent reciprocating tachycardias in the Wolff-Parkinson-White syndrome; control by the use of a scanning pacemaker.

Frequent episodes of arrhythmias in patients with the Wolff-Parkinson-White syndrome are sometimes unresponsive to medical management. Recent emphasis has been placed on the role of surgery as a means of effectively controlling these patients' tachyarrhythmias; however, in some patients the use of permanent pacing has been espoused as an effective means of controlling arrhythmias. This report documents the efficacy of a new pacemaker with rate-scanning features, which offers significant technical advantages. Subsequent follow-up has documented the efficacy of this unit in the management of a young woman with type-A Wolff-Parkinson-White syndrome and previously intractable arrhythmias.

Adult↗
PubMed1975

Oplophorus oxyluciferin and a model luciferin compound biologically active with Oplophorus luciferase.

The luciferin of the bioluminescent decapod shrimp, Oplophorus gracilorostris, was purified and studied with respect to u.v. spectrum, fluorescence spectrum, mass spectrum and luminescent cross-reaction with the enzyme luciferase of the bioluminescent ostracod, Cypridina hilgendorfii. On the basis of these results, an empirical formula C10H13N3O3 and an imidazo [1,2-a]pyrazin-3-one structure are proposed for luciferin. Of three model luciferin compounds, 3-hydroxy-2-methylimidazo[1,2-a]pyridine is biologically active with both Oplophorus and Cypridina luciferase, indicating that a pyrazine structure is not essential for biological activity with Cypridina luciferase.

Animals↗
PubMed1975

Isolation and purification of blasticidin S deaminase from Aspergillus terreus.

An enzyme catalyzing the deamination of the cytosine moiety of blasticidin S was extracted from a fungal strain that belongs to Aspergillus terreus. The enzyme was purified with ammonium sulfate fractionation, Sephadex G-100 column and DEAE cellulose column chromatography, followed by preparative polyacrylamide gel electrophoresis. Blasticidin S deaminase could be separated easily from co-existing cytidine deaminase by DEAE column chromatography or gel electrophoresis, and preliminary study on the substrate specificity showed that this enzyme acts on blasticidin S derivatives, such as cytomycin and acetylblasticidin S, but not on cytosine, cytidine, purine bases or their nucleosides. Blasticidin S deaminase could be induced by the addition of blasticidin S to the culture, and sulfhydryl compounds, such as mercaptoethanol, were effective in protecting the enzyme from inactivation. The homogeneity of the enzyme was examined by both sedimentation analysis and polyacrylamide gel electrophoresis. The molecular weight and isoelectric point were found to be around 30,000 and 4.35, respectively. Some other properties were also examined.

Aminohydrolases↗