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Biomedical subjects

J Nitta

Publications and source records attributed to J Nitta.

At least 55 records · Page 3Linked to original sources
PubMed1991

Effects of pirmenol on electrical induction of sustained ventricular tachycardia in a seven-day-old canine myocardial infarction.

Effects of pirmenol on electrical induction of sustained ventricular tachycardia (VT) were examined in 14 dogs with 7-day-old myocardial infarctions. Before administration of the drug, sustained VT was induced in 8 of 14 dogs. After administration of 3 mg/kg pirmenol, induction of VT was suppressed in 2 dogs but remained inducible in 6 dogs. After cumulative administration of 5 mg/kg pirmenol, VT was no longer inducible in 3 dogs but in the other 3 dogs VTs were still inducible at increased cycle lengths. After 7 mg/kg pirmenol, VT was not inducible in the remaining three dogs. Arrhythmias could not be provoked in any postinfarction dogs after pirmenol administration. Plasma concentrations after sequential and cumulative administration of 3, 5, and 7 mg/kg pirmenol averaged 0.43, 0.65, and 1.15 micrograms/ml, respectively. Administration of pirmenol increased the effective refractory period (ERP) and paced QRS duration in both the normal and infarcted ventricular myocardium. In the infarcted myocardium, prolongation of the ERP for the second and third extrastimuli was greater than for the first one (p less than 0.05). Results indicate that pirmenol is effective for prevention of sustained VT owing to prolongation of both the ERP and conduction time in recent myocardial infarction.

Animals↗
PubMed1991

Giant aneurysms of the horizontal segment of the anterior cerebral artery: report of two cases.

Two cases of giant aneurysm of the horizontal segment of the anterior cerebral artery (A1) are presented. The rare occurrence of a giant aneurysm in this location necessitates evaluation of the cross-flow through the anterior communicating artery when planning surgical strategy. On the basis of angiographic findings, trapping of the A1 on both sides of the aneurysm neck was performed in Case 1, and aneurysmorrhaphy utilizing an angioplastic multiple-clipping method of A1 endarterectomy was accomplished in Case 2. The postoperative courses of both patients were satisfactory.

Aged↗
PubMed1991

Comparative efficacy of subcutaneous mesh and plate electrodes for nonthoracotomy canine defibrillation.

To determine the optimal configuration for the subcutaneous placement of electrodes for the performance of ventricular defibrillation without thoracotomy, internal defibrillation using four different subcutaneous electrodes was performed in 13 anesthetized dogs (7-12 Kg, mean +/- SD: 9.2 +/- 1.5 Kg). An electrode (7 cm2) was positioned transvenously in the superior vena cava with the following electrodes randomly implanted subcutaneously on the left chest: small mesh electrode (14 cm2), large mesh electrode (28 cm2), small titanium plate electrode (14 cm2), and large plate electrode (28 cm2). Ventricular fibrillation was induced by applying alternating current; a monophasic defibrillation wave was administered between the superior vena cava and the subcutaneous electrodes 10 seconds later. The energy level associated with a 50% successful defibrillation, as predicted by logistic regression analysis, was defined as the ED50. After the completion of the defibrillation protocol using the four subcutaneous electrodes, the small mesh electrode was sutured to the epicardium and the ED50 measurements were repeated. Energy ED50s were lower when the superior vena cava electrode was used as the cathode rather than as the anode. Of the subcutaneous electrodes, the large plate electrode showed the lowest energy ED50 (3.3 +/- 0.9 joules). The plate electrodes had lower energy ED50s than the mesh electrodes, and the large electrode had a lower energy ED50 than the small electrodes. Using the epicardium electrode, transient arrhythmias and ST elevation were observed following successful defibrillation; however, no arrhythmias or ST-T changes were observed following defibrillation using the subcutaneous electrodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Two components of use-dependent block of Na+ current by disopyramide and lidocaine in guinea pig ventricular myocytes.

We studied the kinetics of the use-dependent block of the Na+ current (INa) by disopyramide and lidocaine. INa was recorded from isolated guinea pig ventricular myocytes by using the whole-cell patch-clamp technique. The use-dependent block of INa by disopyramide with 20- and 200-msec depolarizing pulses developed in two exponential functions. The degree of the use-dependent block and the amplitude of the fast (Af) and slow (As) components with the short (20-msec) pulse protocol were comparable to those with the long (200-msec) pulse protocol. When pH was raised from 7.3 to 8.0, disopyramide increased Af without a change in As. At pH 6.5, INa block developed with a single exponential function revealing only the slow component. The fast and slow components of INa block by disopyramide could be explained by binding of the uncharged and charged forms, respectively, to the activated state of the channel. Development of INa block by lidocaine also was expressed by two exponentials at all pulse durations (5-200 msec). As pulse durations were prolonged or holding potentials were depolarized, the degree of the use-dependent block and Af increased. When pH was lowered to 6.5, the short pulse produced only the slow component, whereas the long pulse caused two exponentials with decreased Af and increased As. Internal application of QX-314, a permanently charged lidocaine analogue, produced a single exponential block of INa with a very slow onset rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Prognostic significance of sustained monomorphic ventricular tachycardia induced by programmed ventricular stimulation using up to triple extrastimuli in survivors of acute myocardial infarction.

The prognostic significance of sustained monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation using up to 3 extrastimuli was evaluated in 133 consecutive survivors of acute myocardial infarction (AMI) at a mean interval of 1.8 +/- 1.1 months after onset. This was compared with hemodynamic and angiographic abnormalities shown by cardiac catheterization and ventricular ectopic activity detected by Holter monitoring. Sustained monomorphic VT was induced in 25 (19%) patients, sustained polymorphic VT in 11 (8%) patients, nonsustained monomorphic VT (greater than or equal to 10 beats) in 12 patients (9%) and nonsustained polymorphic VT in 9 patients (7%). Multivariate logistic regression analysis of clinical, angiographic, hemodynamic and electrocardiographic variables showed that the presence of a left ventricular aneurysm (p = 0.005) and Lown grade 4B ventricular ectopic activity (p less than 0.001) were independent predictors of inducibility of sustained monomorphic VT. During a mean follow-up of 21 +/- 13 months, there were 8 (6%) sudden cardiac deaths and 3 (2.3%) spontaneous occurrences of life-threatening sustained VT. The 2-year probability of freedom from sudden cardiac death or sustained ventricular tachyarrhythmias was 53 +/- 13% for patients with inducible sustained monomorphic VT, 70 +/- 10% for those with a left ventricular ejection fraction less than 40% and 58 +/- 13% for those with Lown grade 4B ventricular ectopic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Arrhythmogenic right ventricular dysplasia with sick sinus syndrome and atrioventricular conduction disturbance.

Although arrhythmogenic right ventricular dysplasia (ARVD) is believed to involve primarily the right ventricle, left ventricular abnormalities have also been described. We report a case of ARVD with abnormalities of the sinus node, right atrium and atrioventricular node. The biopsies taken from the right atrium and the right ventricle showed replacement of myocardium by fibrous tissue. The pathologic changes of this disease process may extend into the atrium and atrioventricular node.

Atrioventricular Node↗
PubMed1990

Usefulness of electrophysiologic study and endomyocardial biopsy in differentiating arrhythmogenic right ventricular dysplasia from idiopathic right ventricular tachycardia.

Fifteen patients with right ventricular tachycardia without evidence of coronary artery disease or dilated or hypertrophic cardiomyopathy were evaluated, by means of electrophysiologic study and right ventricular endomyocardial biopsy. Six cases were diagnosed as definite arrhythmogenic right ventricular dysplasia (ARVD), while 2 cases without characteristic findings of ARVD by noninvasive studies and angiography were diagnosed as probable ARVD on the basis of their electrophysiologic and histopathologic data. In conclusion, ARVD is relatively common as an etiology of right ventricular tachycardia, and detailed electrophysiologic study and endomyocardial biopsy appear to be useful for diagnosis of ARVD.

Adolescent↗
PubMed1989

[Study on metabolism of pyridonecarboxylic acid II. Determination of metabolites of (+-)-7-(3-amino-1-pyrrolidinyl)-6-fluoro-1-(2,4-difluorophenyl)- 1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid p-toluenesulfonate hydrate (T-3262) in blood, urine, bile, and feces].

The fate of (+-)-7-(3-amino-1-pyrrolidinyl)-6-fluoro-1-(2,4-difluorophenyl-1,4- dihyro-4-oxo-1,8-naphthyridine-3-carboxylic acid p-toluenesulfonate hydrate (T-3262) was studied using T-3262 and 14C-T-3262 in various animals. 1. Metabolites in serum and urine were assayed for mouse, rat, rabbit, dog and monkey following oral administration of T-3262. In serum, besides unchanged T-3262 base, T-3262A (N-acetylated) was detected in rat, rabbit and monkey; T-3262B (deamino-hydroxylated) was detected in monkey. In urine, unchanged T-3262 base was excreted mainly. But a few of metabolites (T-3262A, T-3262B, T-3262 glucuronide, T-3262A glucuronide, T-3262B glucuronide, and unknown compound M-1) were detected, and species difference existed in types of metabolites. 2. Metabolites in bile and feces were assayed for mouse and rat following oral administration of T-3262 and 14C-T-3262. Metabolites in bile were similar to the urine, but the volume of T-3262A and T-3262A glucuronide was larger than in urine. In feces, the excreted compounds mainly consisted of unchanged T-3262 base. 3. p-Toluenesulfonic acid, which is the counter acid for T-3262 base, was absorbed following the oral administration of T-3262, and excreted in urine in the unchanged form.

4-Quinolones↗
PubMed1988

Effects of procainamide and lidocaine on electrically inducible ventricular tachycardia studied with programmed ventricular stimulation in post myocardial infarction.

The effects of procainamide and lidocaine, representative of class IA and IB antiarrhythmic agents, on electrically inducible ventricular tachycardia (VT) were studied using programmed ventricular stimulation in 47 post myocardial infarction patients at an average of 1.5 months after the onset. The mean doses of administered procainamide and lidocaine were 1050 mg and 161 mg, and their mean plasma concentrations were 7.5 micrograms/ml and 3.1 micrograms/ml respectively. The induction of sustained VT was suppressed in 15 of 29 patients (52%) by procainamide, but in none by lidocaine. The induction of nonsustained VT was suppressed in 6 of 18 patients (33%) by procainamide, and in 1 of 8 patients (13%) by lidocaine. The efficacy rate of procainamide was significantly higher than that of lidocaine in suppression of VT induction (21/47 vs 1/14 p less than 0.01). Procainamide significantly prolonged the effective refractory period of the right ventricle as well as the HV and QRS interval, however lidocaine did not affect them significantly. On the other hand, the worsening effect which changed nonsustained VT inducible in the baseline into sustained VT inducible post drug administration was demonstrated in 8 of 18 procainamide cases (44%), and in 3 of 8 lidocaine cases (38%). Between the procainamide effective and ineffective or worsening patients, there were no differences found in the electrophysiologic variables either in the baseline or post procainamide administration. We concluded that procainamide was more effective than lidocaine for the prevention of potential life-threatening VT induction in post myocardial infarction patients, although its efficacy was considerably limited, and to confirm the effectiveness and exclude the worsening effects of the class IA and IB antiarrhythmic agents, drug testing using programmed ventricular stimulation appeared to be valuable.

Cardiac Pacing, Artificial↗
PubMed1987

Dynamics of membrane structure of frog erythrocyte ghosts measured with a nanosecond fluorometer.

The dynamics of membrane microstructure was studied as molecular motions of phospholipids for bullfrog erythrocyte ghosts by the DPH fluorescence depolarization technique with a nanosecond fluorometer. The bullfrog erythrocyte ghosts were obtained by hypotonic lysis and collagenase treatment. The constituents of membrane proteins were confirmed by the disk gel electrophoresis. The viscosity of erythrocyte membrane ghosts was estimated to be 3.3 +/- 1.0 at 10 degrees C, and 2.1 +/- 0.1 at 20 degrees C and 1.3 +/- 0.2 at 30 degrees C in the unit of poise and the wobbling angle of lipid molecule was 35 +/- 1, 41 +/- 1 and 43 +/- 1 degree at the respective temperatures on an average and +/- S.D. The viscosity is lower than that of human erythrocytes. The relatively low viscous phospholipid bilayer may be one of the factors for the deformability of bullfrog erythrocytes.

Animals↗
PubMed1986

Viscosity and order in erythrocyte membranes studied with nanosecond fluorometry.

The viscosity and the order in the interior of human erythrocyte membranes were investigated by the fluorescence depolarization technique in the nanosecond region with 1,6-diphenyl-1,3,5-hexatriene (DPH). After pulsed excitation with a polarized light, the fluorescence anisotropy ratio of DPH in membranes rapidly decreased and gave a final value (r infinity). The rate of initial decrease and the value of r infinity related to the viscosity in the interior of the membranes and a wobbling angle of DPH which reflects a size of range for the phospholipid motion relating to the order of membrane structure. For normal human erythrocyte membranes the viscosity and the wobbling angle were obtained to be 0.82 poise and 42 degrees, at 37 degrees C. Similar values were obtained for spectrin-free membranes. Hardened membranes by the cross-linking of the cytoskeletal proteins with glutaraldehyde showed a small wobbling angle of 37 degrees, but the viscosity of them was unchanged.

Blood Viscosity↗
PubMed1984

A grating laser microscope for measurements of blood flow velocity in microvessels.

A velocimeter for measurements of blood flow velocity in microvessels was constructed with a microscope, a grating, a photomultiplier and a wave-period measuring circuit. A differential detection system seemed to be useful when the probing area was extremely small. A pulsating flow velocity contour and the velocity reduction caused by an application of noradrenaline were on-line recorded in an arteriole of foot web of frogs.

Animals↗