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Biomedical subjects

J Ben-David

Publications and source records attributed to J Ben-David.

At least 19 recordsLinked to original sources
PubMed1992

Canine left ventricular hypertrophy predisposes to ventricular tachycardia induction by phase 2 early afterdepolarizations after administration of BAY K 8644.

OBJECTIVES: The purpose of this study was to test the hypothesis that the longer duration of ventricular action potentials in hypertrophied hearts predisposes to the development of early after-depolarizations and triggered ventricular tachyarrhythmias. BACKGROUND: For unknown reasons, the incidence of sudden death is greater in patients with myocardial hypertrophy. METHODS: We measured left ventricular monophasic action potentials in normal dogs and dogs with left ventricular hypertrophy before and after administration of the calcium agonist BAY K 8644 and the potassium channel blocker cesium. RESULTS: We demonstrated longer action potential durations in dogs with than in those without left ventricular hypertrophy. Also, BAY K 8644 produced phase 2 early afterdepolarizations and ventricular tachyarrhythmias more frequently in the dogs with than in those without left ventricular hypertrophy. Phenylephrine, an alpha agonist, further increased the action potential duration in hypertrophied hearts and the propensity to develop early afterdepolarizations and ventricular tachyarrhythmia after administration of BAY K 8644. Control and hypertrophied hearts developed early afterdepolarizations and ventricular tachyarrhythmia equally when exposed to cesium. CONCLUSIONS: Although in vitro studies have shown that fibers of hypertrophied ventricular myocardium can develop triggered activity as a result of both early and late afterdepolarizations, the present study is the first to show in vivo that the hypertrophied ventricular myocardium compared with the normal ventricle is predisposed to develop phase 2 early afterdepolarizations that appear to trigger ventricular tachyarrhythmia. It is possible that such a mechanism contributes to the development of ventricular tachyarrhythmia and sudden cardiac death in patients with left ventricular hypertrophy. If this is shown to be true, specific pharmacologic interventions can be suggested.

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

On the limitation of brainstem auditory evoked potentials for indication of susceptibility to noise.

The efficiency of Brainstem Auditory Evoked Potentials (BAEP) as an indicator of susceptibility to hazardous noise was investigated. In earlier studies, subjects were exposed to very intense occupational noise and temporary threshold shift (TTS) was produced by high intensity noise of 115 dB. Correlations between experimental TTS and the BAEP changes were investigated. BAEP indices, which significant correlations with the eventual hearing loss, were found. Similar criteria, which were found significant in the earlier work, were investigated in 94 industrial workers with normal hearing, without past exposure to noise, using a more moderate TTS-producing noise of 110 dB SPL. Under these conditions, no significant correlation between the noise susceptibility index and BAEP changes during TTS was found. The results of this study demonstrate the limitation of determining individual susceptibility to noise-induced hearing loss using BAEP. TTS-producing noise levels must be high enough. Their predictive value holds only for hearing losses typical of high intensity occupational exposures.

Adolescent↗
PubMed1990

Alpha-adrenoceptor stimulation and blockade modulates cesium-induced early afterdepolarizations and ventricular tachyarrhythmias in dogs.

In 84 open-chest dogs, we studied the effects on early afterdepolarizations (EADs) and ventricular tachyarrhythmias (VTs) induced by cesium chloride (168 mg/kg i.v.) of alpha-adrenoceptor stimulation with phenylephrine (100 micrograms plus 0.25 microgram/kg/min i.v.) and with left ansa subclavia stimulation (LAS; 2 Hz, 4 msec, 2 mA) after propranolol (0.5 mg/kg) administration. We also studied the effects of alpha-adrenoceptor blockade with phentolamine (3 mg/kg), prazosin (25-500 micrograms/kg), yohimbine (10-500 micrograms/kg), WB 4101 (2 mg/kg), and benoxathian (2 mg/kg) during decentralized LAS. EAD amplitude, presented as a percentage of monophasic action potential amplitude, was recorded simultaneously with contact electrodes from the right and left ventricular endocardium. Phenylephrine and LAS plus propranolol increased EAD amplitude (31.5 +/- 8.8% to 47.8 +/- 9.7% and 34.8 +/- 4.1% to 46.1 +/- 6.4%, respectively) and the prevalence of VT (from three to nine of 11 dogs and from the three to five of six dogs, respectively). Prazosin produced a dose-response decrease in EAD amplitude and reduced the prevalence of VT. Yohimbine did not alter the amplitude of EADs or the prevalence of VT. WB 4101 and phentolamine reduced the amplitude of EADs produced by cesium and LAS (from 44.3 +/- 10.2% to 32.6 +/- 9.4% and from 39.8 +/- 6.9% to 30.3 +/- 6.3%, respectively) and the prevalence of VT (from eight to one of 10 dogs and from 13 to 5 of 20 dogs, respectively). Benoxathian did not alter significantly the amplitude of EADs (41.6 +/- 11.4% to 37.5 +/- 9.4%) or the prevalence of VT (from six to five of 10 dogs).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1989

Brainstem auditory evoked potentials with increased stimulus rate in patients suffering from systemic lupus erythematosus.

Central nervous system involvement in systemic lupus erythematosus is frequently occult, may be the presenting sign, and is a bad prognostic indicator. At present, there is no reliable, sensitive laboratory test for the evaluation and diagnosis of subclinical central nervous system involvement of the disease. Brainstem auditory evoked potentials with and without increased stimulus rate have been used to diagnose ischemic lesions in the central nervous system. Brainstem auditory evoked potentials, with and without increased stimulus rate, was used to investigate 15 systemic lupus erythematosus patients, 20 normal participants, and 5 patients receiving corticosteroids for bronchial asthma. A significant statistical difference was found in the net effect of increased stimulus rate in comparisons of the systemic lupus erythematosus patients with the normal group. Brainstem auditory evoked potentials, with increased stimulus rate, demonstrated subclinical involvement of the central nervous system in systemic lupus erythematosus, reinforcing the notion that increased stimulus rate measures are sensitive to ischemic changes, in this case, even in neurologically asymptomatic patients.

Acoustic Stimulation↗
PubMed1988

Brainstem auditory evoked potentials to different stimulus rates in parkinsonian patients.

Twenty-five Parkinson's disease (PD) patients were studied by brainstem auditory evoked potentials (BAEP) with increased stimulus rate (ISR) and compared to a control age and hearing matched group. A second comparison was made between L-dopa-treated and untreated PD patients. The results of the study suggest that there is subclinical involvement of the auditory brainstem in PD patients, possibly due to the dopamine influence upon the blood vessels. Our results also indicate that dopamine is probably not involved in the synaptic transmission along the auditory pathway of the brainstem.

Aged↗
PubMed1988

Magnesium suppression of early afterdepolarizations and ventricular tachyarrhythmias induced by cesium in dogs.

The mechanism by which magnesium therapy suppresses some ventricular tachyarrhythmias characterized by a prolonged QT interval (e.g., torsades de pointes) is unknown. Since early afterdepolarizations have been proposed as a cause of the long QT syndrome and the related ventricular tachyarrhythmias, we hypothesized that magnesium therapy would suppress both the early afterdepolarizations and the ventricular arrhythmias. The present study was performed to test that hypothesis. Using monophasic action potentials (MAP) recorded with a contact electrode from the right ventricular endocardium to demonstrate early afterdepolarizations, cesium chloride (168 mg/kg iv) was administered before, during, and 1 to 2 hr after discontinuation of a magnesium infusion (1 to 2 mg/kg/min for 20 to 30 min). Before magnesium infusion, cesium induced early afterdepolarizations that were 49.7 +/- 1.6% (mean +/- SE) of the amplitude of the corresponding monophasic action potential. The amplitude of the early afterdepolarization decreased to 31.2 +/- 3.8% of the MAP amplitude during magnesium infusion (p less than .003) and increased to 48.0 +/- 4.0% 1 to 2 hr after termination of the magnesium infusion (p less than .003). Cesium induced sustained monomorphic ventricular tachycardia, torsades de pointes, or ventricular fibrillation in 12 of 13 dogs before magnesium infusion, and in eight of 11 dogs 1 to 2 hr after stopping infusion, but in only three of 13 dogs during magnesium infusion. Cesium prolonged the corrected QT interval from 338 +/- 16 msec (control) to 387 +/- 14 msec before (p less than .003), 356 +/- 12 msec during (p less than .003), and 406 +/- 16 msec after stopping the magnesium infusion (p less than .003).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1988

Differential response to right and left ansae subclaviae stimulation of early afterdepolarizations and ventricular tachycardia induced by cesium in dogs.

Early afterdepolarizations (EADs) are depolarizing potentials that occur before complete repolarization. They may be important in the acquired and possibly the idiopathic long QT syndrome and associated ventricular tachycardia (VT). The purpose of these experiments was to study in 20 open-chest dogs the effects of sympathetic stimulation on EADs and VT produced with cesium chloride (84 mg/kg i.v.) alone or combined with left (LAS), right (RAS), or bilateral (BAS) ansae subclaviae stimulation (2 Hz, 4 msec, 2 mA). We compared the EAD amplitude and area as a percentage of monophasic action potential amplitude and area, respectively, recorded simultaneously with contact electrodes from right (RV) and left ventricular (LV) endocardium and recorded the prevalence of VT induction during each intervention. Both LAS and BAS produced left ventricular EADs with larger amplitudes and areas than did RAS or cesium alone. BAS and LAS produced larger EADs recorded from the LV than from the RV. Cesium produced VT in six of 20 dogs, RAS in three of 20, BAS in 12 of 20, and LAS in 16 of 20. Norepinephrine (0.1-1.5 micrograms/kg/min) caused VT in all dogs by producing a dose-related increase in EAD amplitude that was similar in RV and LV, suggesting that the response of RV and LV EADs to catecholamine stimulation was not intrinsically different. During stimulation of left ansae subclaviae at increasing frequencies (1, 2, 4, and 6 Hz), EADs were significantly larger in LV than in RV at all stimulus frequencies, and the amplitude of EADs in both ventricles increased with increasing stimulus frequencies. Based on the increased LV amplitude and area of cesium chloride-induced EADs during LAS and BAS, with EAD amplitude dependent on the frequency of LAS but with an equal RV and LV EAD amplitude during norepinephrine infusion, it is possible that more norepinephrine released into the LV during LAS and BAS compared with RAS causes larger amplitude LV EADs that reach threshold to cause VT more often. Thus, quantitative differences between the effects of left and right stellate ganglia stimulation rather than qualitative differences or imbalance may account for the arrhythmogenic potential of the left stellate ganglion.

Action Potentials↗
PubMed1988

Comparative pharmacokinetic analysis of novel sustained-release dosage forms of pentoxifylline in healthy subjects.

The pharmacokinetics and relative bioavailability of pentoxifylline, from a new sustained-release formulation (Oxopurin) and from a standard sustained-release formulation (Trental-400), were compared in 8 healthy adult male volunteers. After a single oral dose of 400 mg Oxopurin, a mean maximal plasma concentration (Cmax) of 164 +/- 62 micrograms/l was obtained after 2.2 h (tmax). After an identical dose of Trental-400, a peak plasma concentration of 123 +/- 33 micrograms/l was obtained after 2.4 h. Plasma levels of pentoxifylline were determined by a new HPLC assay which was developed as part of this study and makes possible monitoring plasma levels of pentoxifylline for 14 h after a single dose. The mean relative bioavailability of pentoxifylline from Oxopurin was 1.30 +/- 0.19 relative to that of Trental-400. As the rate and the extent of absorption of pentoxifylline was not significantly different after the administration of the two investigated formulations, it can be concluded that Oxopurin is bioequivalent to Trental-400.

Adult↗
PubMed1988

Comparative pharmacokinetic analysis of a novel sustained-release dosage form of diclofenac sodium in healthy subjects.

The pharmacokinetics and relative bioavailability of diclofenac sodium from a new sustained-release formulation (Effekton-100) and from a standard sustained-release formulation (Voltaren-Retard) were compared in 11 healthy adult male volunteers. After a single oral dose of 100 mg Effekton-100, a mean maximal plasma concentration (Cmax) of 497 +/- 120 ng/ml was obtained after 7.4 h (tmax). After an identical dose of Voltaren-Retard, a peak plasma concentration of 654 +/- 329 ng/ml was obtained after 6.4 h. Plasma levels of diclofenac were determined by a new HPLC assay which was developed as part of this study and makes possible monitoring plasma levels of diclofenac for 24 h after a single dose. The mean bioavailability of diclofenac from Effekton-100 was 0.97 +/- 0.28 relative to that of Voltaren-Retard. As the rate and the extent of absorption of diclofenac sodium was not significantly different after the administration of the two investigated formulations, it can be concluded that Effekton-100 is bioequivalent to Voltaren-Retard.

Adult↗
PubMed1987

Prediction of atrial and ventricular fibrillation complicating myocardial infarction from admission data: a prospective study.

This study set out to examine prospectively two logistic formulae based on admission clinical data to predict ventricular or atrial fibrillation complicating acute myocardial infarction. A prospective study of 87 consecutive patients with acute transmural myocardial infarction was conducted. The formula for predicting ventricular fibrillation from the diastolic blood pressure, degree of ST-segment elevation, and QTc had a sensitivity of 93%, specificity of 83%, and a predictive value for an abnormal test of 62% (13 of 14 patients who developed ventricular fibrillation were identified). The formula for predicting atrial fibrillation from the age of the patient, a history of heart failure, systolic blood pressure, and four electrocardiographic parameters had a sensitivity of 78%, specificity of 85%, and a predictive value of 67% (14 of 18 patients identified). Our study shows that patients with myocardial infarction who are liable to develop ventricular or atrial fibrillation can be identified on admission from simple clinical data.

Atrial Fibrillation↗
PubMed1987

Brainstem auditory evoked potentials with and without increased stimulus rate as diagnostic tool in brainstem minor transient changes.

Two clinical groups of patients - 25 with Parkinson's disease and 17 with migraine - were evaluated using brainstem auditory evoked potentials (BAEP) to regular (10/s) and increased (55/s) stimulus rates. Each group of patients had an age-matched control group. The BAEP data were statistically evaluated, comparing the data of migraine patients during and between migraine spells, and the parkinsonian patients before and after L-dopa treatment. We believe that when group data are compared BAEP to an increased stimulus rate is an efficient tool for detecting even minor transient reversible physiologic changes of the brainstem.

Adolescent↗
PubMed1987

Quix test.

Explore the source record for details and available documents.

Equipment Design↗
PubMed1986

Auditory brain stem evoked potentials in patients suffering from peripheral facial nerve palsy and diabetes mellitus.

Forty-two patients affected by acute idiopathic peripheral facial palsy (AIPFP) underwent auditory brainstem evoked potential (ABEP) investigation in order to further our understanding of the nature of facial palsy. Twenty-two of these patients suffered from diabetes mellitus. Our results indicate that the AIPFP of the diabetic person may be considered as a preliminary sign of diabetic peripheral neuropathy.

Adult↗
PubMed1985

Treatment of Meniere's disease by intratympanic injection with lidocaine.

Intratympanic injection of lidocaine hydrochloride was used to alleviate distressing symptoms of tinnitus and vertigo in 28 patients with Meniere's disease. Of the 28 patients, 82% found an immediate improvement in vertigo, and there was an improvement in tinnitus in 67.8%. There was no change in complaints of tinnitus or vertigo in five patients with Meniere's disease who were each injected with a similar amount of saline into the middle ear, and who acted as a control group. An intratympanic injection of lidocaine alleviated the disabling symptoms of tinnitus and vertigo in some of the patients with Meniere's disease who had not reacted well to medical treatment. The procedure is without the hazards of the intravenous injection of lidocaine, and can be done by every otologist, even in clinic practice.

Adult↗
PubMed1985

Eosinophilic granuloma of the temporal bone.

Involvement of the temporal bone by eosinophilic granuloma is rare. Four cases are presented here and the pertinant literature is reviewed. This disease must be kept in mind by the otolaryngologist because of the diagnostic and therapeutic problems that may arise. Direct injection of methyl-prednisolone sodium succinate is suggested as a treatment of eosinophilic granuloma in the temporal bone.

Bone Diseases↗