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Biomedical subjects

E R Arbel

Publications and source records attributed to E R Arbel.

10 recordsLinked to original sources
PubMed1983

Somatostatin-like immunoactivity and biological activity is present in a human pheochromocytoma.

Somatostatin (SRIF)-like immunoreactivity (SRIF-LI) has previously been demonstrated immunohistochemically in sympathetic nerves and ganglia and in adrenal medullary cells. Studies were therefore performed to determine whether SRIF-LI was present in an adrenal pheochromocytoma. Acetic cid extracts of pheochromocytoma tissue contained high SRIF-LI concentrations (5.52 micrograms/g wet wt). On Sephadex G-75 gel filtration, the major peak of pheochromocytoma SRIF-LI coeluted with synthetic SRIF. SRIF-LI of a larger molecular size was also present in the tumor. Pheochromocytoma SRIF-LI coeluted with synthetic SRIF on reverse phase high pressure liquid chromatography. Pheochromocytoma SRIF-LI purified by high pressure liquid chromatography was equipotent to synthetic SRIF in inhibiting (Bu)2cAMP-stimulated GH release by rat pituitary cells in monolayer culture. Serum SRIF-LI was elevated in the patient before surgery and was restored toward normal after removal of the tumor. Serum levels of GH, TSH, and insulin were not obviously different before and after tumor removal. The results indicate that SRIF-LI is produced in excessive quantities by a pheochromocytoma. The immunological, chromatographic, and biological properties of the pheochromocytoma SRIF-LI suggest that it is indistinguishable from synthetic SRIF. This finding extends the list of peptides produced by pheochromocytoma and may provide an additional serum marker for the tumor in man.U

Adrenal Gland Neoplasms↗
PubMed1979

A perfused canine right bundle branch-septal model for electrophysiological studies.

UNLABELLED: As documented in the literature, isolated ventricular muscle preparations perfused with protein-free media become edematous and deteriorate. We hypothesized that the addition of colloid oncotic pressure to the perfusion medium might affect favorably the electrical characteristics and survival of an isolated right bundle branch-septal muscle preparation perfused via the anterior septal artery. Perfusion with protein-free Tyrode solution produced edema formation and a loss of transmembrane potential of Purkinje and muscle cells within 5.9 +/- 0.40 h. Addition of bovine albumin, 4 g/100 ml, to the Tyrode solution or perfusion with horse serum greatly reduced the formation of edema. Furthermore, intact electrical activity continued for more than 9 +/- 0.31 h (P less than 0.001). The preparations showed a greater diastolic potential and action potential amplitude during perfusion than during superfusion with Tyrode solution. IN CONCLUSION: 1) a viable, perfused septal muscle preparation was developed for electrophysiological studies, and 2) colloid oncotic pressure in the perfusion medium is essential to preserve the integrity of the capillary circulation and to eliminate edema formation and tissue death.

Animals↗
PubMed1979

Effects of veratrine on the in situ dog heart: evidence for increased ventricular fibrillation threshold.

The present work studied the effect of veratrine on electrical stability of the mammalian ventricles. In a group of anesthetized open-chest dogs we determined the effects of veratrine (0.001-0.3 mg/kg) on the threshold for ventricular fibrillation (VFT), both during sinus rhythm (SR) and during atrial drive (AD) at 166 +/- 7 beats/min. Veratrine (0.3 mg/kg) increased the VFT during SR from control levels of 33 +/- 5 mA to 56 +/- 4 mA (P less than .05) and during AD from 34 +/- 6 to 57 +/- 9 mA (P less than .05). VFTs after infusion of veratrine were higher than in a control group of dogs given the saline diluent in which VFT during SR was 26 +/- 3 mA (P less than .001) and during AD was 24 +/- 3 mA (P less than .005). The increase in VFT during SR was independent of the decrease in heart rate, which fell from 147 +/- 8 to 106 +/- 6 beats/min (P less than .001). It was associated, however, with an increase in the QT interval during SR from control values of 254 +/- 13 to 308 +/- 19 msec (P less than .02) and during AD from 238 +/- 8 to 267 +/- 8 msec (P less than .005). We conclude that small doses of veratrine increase the electrical stability of the ventricles in the normal dog heart.

Animals↗
PubMed1978

Successful treatment of drug-resistant atrial tachycardia and intractable congestive heart failure with permanent coupled atrial pacing.

Temporary coupled atrial stimulation slowed the ventricular rate by nearly 50% in an adolescent patient with intractable congestive heart failure and focal repetitive atrial tachycardia that was resistant to drug treatment. Because of the success with the temporary pacemaker, a specially designed permanent pacemaker was implanted to provide coupled atrial stimulation. The necessary electrophysiologic conditions for ventricular slowing by coupled atrial pacing are: (1) an atrial effective refractory period shorter than that of the atrioventricular junction, and (2) depolarization of the ectopic atrial pacemaker by the responses to coupled atrial stimulation. During a 4 year follow-up period the treatment resulted in elimination of the tachycardia, followed by return of the heart size to normal and complete clinical recovery. Coupled atrial stimulation can provide effective treatment in selected patients with disabling drug-resistant atrial tachycardia in whom this mode of therapy is shown to be effective by careful electrophysiologic studies.

Adolescent↗
PubMed1977

Attenuation of cardiac sympathetic drive in experimental myocardial ischemia in dogs.

Sympathetic discharges to the heart were recorded from the left inferior cardiac nerve of 16 dogs. Inferior cardiac nerve activity (ICNA) under normal conditions consisted of grouped discharges, synchronous with the cardiac cycle and modulated by respiration. After ligation of the circumflex branch of the left coronary artery, ICNA declined concomitant with a decline in heart rate and mean aortic pressure. After 30 minutes, when arterial pressure tended to recover toward control values (six dogs), ICNA remained low; in contrast, when arterial pressure dropped to shock levels (three dogs), ICNA increaed. When aortic pressure fell precipitously as a result of ventricular fibrillation, even during the first 30 minutes of ischemia (seven dogs), ICNA immediately increased greatly. The results of this study suggest that acute coronary occlusion produces a cardiocardiac depressor reflex with attenuation of sympathetic discharge to the heart. This reflex, under the experimental conditions studied, gives way to the baroreceptor reflex when aortic pressure drops to critically low levels.

Animals↗
PubMed1977

Electrophysiological and anatomical observations on the heart of the African lungfish.

Electrophysiological and histological observations were made on the heart of the African lungfish. Impulse origin and propagation were studied using simultaneously recorded epicardial and pericardial electrograms. The primary pacemaker site in the lungfish was found to be at the sinus venosus at its junction with the left cardinal vein. Under a variety of circumstances, pacemaker function shifted to other sites. In response to stress, probably under vagal influence, the regular and rapid sinus venosus rate was generally superseded by an irregular and slower atrial pacemaker. Heart rate and sinoatrial and atrioventricular conduction times varied with changes in temperature [Q10=3.77, 2.55, and 5.46, respectively]. Although alterations in impulse formation and conduction did occur, the site of impulse formation and the patterns of conduction between heart chambers were usually fixed, implying the existence of an organized conduction system. Nonetheless, extensive histological study failed to disclose either organized nodal structures or specialized conduction pathways.

Africa, Central↗
PubMed1977

Tachycardia and bradycardia-dependent bundle branch block alternans: clinical observations.

Eleven patients with tachycardia-dependent, bradycardia-dependent, or "pseudobradycardia-dependent" bundle branch block (BBB) alternans were studied. This classification is based on the following criteria: 1) When alternans is initiated by a sudden acceleration in ventricular rate, or it appears with aberration of the second beat after a pause, the alternans is tachycardia-dependent and results from a 2:1 bidirectional block in the affected bundle branch. 2) When alternans begins with the aberrant complex terminating a pause it is bradycardia-dependent; such an alternans results from alternating bundle branch cycle lengths and refractoriness, possibly produced by alternating transseptal retrograde penetration of the affected bundle branch. 3) In cases referred to as "pseudobradycardia-dependent BBB" alternans, a change from alternans to persiscardia-dependent BBB" alternans, a change from alternans to persistent BBB occurs as the cycle lengthens; however, the disappearance of BBB with further increase of the cycle length proves the tachycardia-dependence of the conduction defect.

Aged↗
PubMed1976

Tachycardias and electrical pacing.

Techniques of electrical pacing for the treatment of tachycardias are multiple. The choice of a suitable method for a particular tachycardia depends upon understanding the mechanism of the tachycardia and the pacing characteristics that will lead to interruption or suppression of the tachycardia, or to ventricular slowing. Electrical pacing is indicated for tachycardias when drug therapy alone has failed or cannot be initiated or continued, and only for those tachycardias that are likely to respond to this type of electrical stimulation. In either the circus movement type or the ectopic pacemaker type an ectopic tachycardia is more likely to be suppressed if the pacing site is near the site of origin of the tachycardia. Pacing more rapidly than the basic rate in order to prevent or abolish tachycardias is termed overdrive suppression. The mechanisms responsible for this phenomenon may be associated with release of acetylcholine, release of potassium, activation of an electrogenic sodium pump, increase in cardiac output and coronary flow, decrease in size of the heart with a consequent decrease in wall tension, and decrease in the inhomogeneity of recovery of excitability that occurs at more rapid rates in the non-ischemic heart. All of these effects of pacing suppress accelerated pacemaker activity or prevent emergence of conditions favorable for development of circus movement tachycardias. Paired, coupled, or rapid atrial pacing may improve ventricular performance or slow ventricular rate, or both, without abolishing the ectopic pacemaker activity. Atrial pacing with pacing sites located at endocardial, epicardial, coronary sinus, trans-septal, or esophageal locations may interrupt or prevent rapid supraventricular or ventricular arrhythmias. Similarly, ventricular pacing at endocardial, epicardial, myocardial, or transthoracic sites may be equally effective. Artificial pacing has abolished almost every type of tachycardia. Ventricular fibrillation always, and atrial fibrillation usually, require countershock if electrical treatment is to be employed, although defibrillation of the atria by rapid pacing has been reported once. Unipolar or bipolar pacemakers may be used temporarily, or permanently after implantation. Pacing rates used to abolish supraventricular tachycardias range from single premature beats to alternating current atrial pacing at 3600 cycles per minute. Artificial electrical stimulation of the heart may be on demand, or may be competitive (fixed rate). External magnets, induction coil coupling, and radio frequency signals allow competitive pacing to be used intermittently, with permanently implanted pacemakers. Thus, electrical pacing of the heart is a technique of major importance for the control of rapid heart rates.

Action Potentials↗
PubMed1975

Effects of veratrine on repolarization in the canine right bundle branch.

Superfusion of Purkinje fibers in the canine right bundle branch with Tyrode solution containing veratrine, less than or equal to 1 mug/ml, prolonged repolarization phases 2 and 3 and induced a long-lasting negative after-potential that ended in some experiments with a slightly hyperpolarized resting transmembrane potential. The alterations in repolarization time were reversed by washout with veratrine-free Tyrode solution or by adding tetrodotoxin to the veratrine-containing Tyrode solution to a concentration of 0.1 and 1 mug/ml. The effect of veratrine on the repolarization time was more prominent at slower driving rates. Its effect on repolarization of ventricular muscle cells was smaller than that on the repolarization of Purkinje fibers. In the concentrations used, veratrine did not induce multiple responses.

Action Potentials↗