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Biomedical subjects

D Roy

Publications and source records attributed to D Roy.

At least 343 records · Page 19Linked to original sources
PubMed1982

Effect of isoproterenol on the anterograde refractory period of the accessory pathway in patients with the Wolff-Parkinson-White syndrome.

To evaluate the effect of beta adrenergic stimulation on the duration of the anterograde refractory period of the accessory pathway, isoproterenol was infused in seven patients with the Wolff-Parkinson-White syndrome. In two patients the effect of isoproterenol was studied during long-term oral amiodarone administration. To avoid rate-related changes induced by isoproterenol, the anterograde refractory period of the accessory pathway was determined using the single test stimulus method at identical basic cycle lengths. Isoproterenol shortened the anterograde refractory period of the accessory pathway in six of the seven patients studied. In two of the three patients with an initial anterograde refractory period of the accessory pathway of equal to or less than 290 ms, shortening measured 30 ms. In three patients having an anterograde refractory period of the accessory pathway of more than 290 ms, isoproterenol abbreviated these values by 30, 60 and 80 ms, respectively. The greatest amount of shortening was observed in patients having the longest initial values for the anterograde refractory period of their accessory pathway. In the two patients receiving oral amiodarone therapy, isoproterenol shortened the anterograde refractory period of the accessory pathway by 180 and 60 ms, respectively, indicating that the effect of isoproterenol can not be prevented by long-term oral amiodarone administration. Our observations may be of importance in patients with the Wolff-Parkinson-White syndrome and atrial fibrillation. They suggest that beta adrenergic stimulation induced by hypotension or anxiety may result in shortening of the anterograde refractory period of the accessory pathway, leading to increased ventricular rates during atrial fibrillation.

Adult↗
PubMed1982

Termination of ventricular tachycardia: role of tachycardia cycle length.

The mode of termination of ventricular tachycardia (VT) and its relation to tachycardia cycle length was evaluated in 139 patients. Tachycardia was terminated by programmed stimulation in 110 patients (79%) and cardioversion was required in 29 patients (21%). Single, double, and triple ventricular extrastimuli terminated the tachycardia in 23 of 85 (27%), 39 of 62 (63%), and 7 of 16 patients (44%), respectively. In all patients requiring 1 extrastimulus, in 35 patients (90%) requiring 2 extrastimuli, and in 6 patients (86%) requiring 3 extrastimuli, the tachycardia cycle length exceeded 300 ms. Rapid ventricular pacing terminated tachycardia in 41 of 54 patients (76%). In 21 (51%) of these patients the tachycardia cycle length exceeded 300 ms. However, rapid ventricular pacing caused acceleration of the arrhythmia in 19 patients (35%). The ability of procainamide to modify the termination of VT was studied in 23 patients. In 7 of these patients (30%) procainamide increased the tachycardia cycle length by 49 +/- 42 ms (p less than 0.01) and did not modify the mode of termination. In 6 patients (26%) procainamide increased cycle length by 142 +/- 108 ms (p less than 0.01), but termination was more difficult. In 10 patients (44%) procainamide increased the cycle length by 138 +/- 110 ms (p less than 0.001) and termination was easier. We conclude that termination of VT by timed extrastimuli requires a tachycardia cycle length longer than 300 ms. Rapid pacing or cardioversion is usually required when the cycle length is less than 300 ms. Although procainamide slows tachycardia, it can unpredictably make termination more difficult in 1 of 4 patients.

Adolescent↗
PubMed1982

Inter- and intraatrial dissociation during spontaneous atrial flutter: evidence for a focal origin of the arrhythmia.

Programmed electrical stimulation of the heart was performed in 2 patients with spontaneous atrial flutter. Patient 1 was a young man with paroxysmal atrial flutter that had proved resistant to drug therapy and who was studied during an episode of sustained flutter. In this patient rapid atrial pacing from the coronary sinus at a critical rate faster than the intrinsic flutter rate provoked local atrial fibrillation in the mid and low right atrium which persisted after termination of pacing. In spite of persistent local fibrillation in these regions, atrial flutter continued in the left atrium and the high right atrium. A second burst of pacing resulted in restoration of sinus rhythm. Patient 2 was an elderly woman with probable sick sinus syndrome who developed spontaneous atrial flutter during the course of an electrophysiologic investigation. During flutter intracavitary recordings from multiple sites in the atria revealed a pattern of 3:2 Wenckebach conduction between the left atrium and the high right atrium, with block of every third atrial depolarization at the latter site. These results indicate that atrial flutter may exist at some sites in the atria which are functionally dissociated from the remainder of the atrial tissue, thus supporting the hypothesis that flutter in some patients may be focal in origin.

Adult↗
PubMed1982

Lens plasma membrane: isolation and biochemical characterization.

Lens plasma membrane from different animal lenses has been prepared by the acylation procedure. Using three different criteria: heat aggregation of intrinsic membrane polypeptides, immunochemistry and solubilization of intrinsic proteins at low (40 mM) LIS concentration, it has been shown that these preparations are essentially free of cytoplasmic contaminants. Using the results obtained with acylated membrane as the reference of purity, it has been shown that both sucrose gradient centrifugation of bovine WI protein and urea washing of old human lenses give impure membrane preparations. The main intrinsic polypeptides (mol. wt 26 000 and 22 000) of human lens membrane have been purified and characterized. It has been shown by enzymatic digestion and amino terminal analysis of the residual membrane-bound fragments that the amino terminal halves of the polypeptides are embedded in the lipid bilayer and are probably blocked at their amino terminal sites. Lipid analyses of human and bovine lens membranes suggest that the protein to total lipid ratio is 1:1. Carbohydrate analyses of chromatographically separated intrinsic membrane polypeptides indicate the presence of 1 mol glucose/1 mol protein.

Amino Acids↗
PubMed1982

"Sawfish" systolic narrowing of the left anterior descending coronary artery: an angiographic sign of hypertrophic cardiomyopathy.

The morphologic characteristics at coronary arteriography of systolic narrowing of the left anterior descending coronary artery (LAD) were evaluated in 14 patients. Six patients had systolic narrowing of the LAD not associated with other cardiac abnormalities (group A) and eight patients had systolic narrowing of the LAD associated with hypertrophic cardiomyopathy (group B). Patients in group A showed a smooth and progressive constriction of the vessel up to the point of maximal stenosis, giving it a "rat-tail" appearance. There was no systolic narrowing of septal branches or of other epicardial vessels in this group. In patients of group B, systolic narrowing of the LAD had a "saw-fish" appearance. Seven patients had systolic narrowing of the septal branches, and five had systolic narrowing of other epicardial vessels. These data indicate that systolic narrowing of the LAD in patients with hypertrophic cardiomyopathy differs angiographically from systolic narrowing due to an intramural course of a part of the vessel (as in group A patients). We postulate that in patients with hypertropic cardiomyopathy, fiber hypertrophy and disarray in the vicinity of the coronary vessels is responsible for the morphology and the widespread distribution of systolic narrowing.

Adolescent↗
PubMed1982

[Dying with dignity : an open debate.].

"Dying with dignity" is little more than a slogan until its meaning is spelled out in guidelines facilitating medical decisions that honor a patient's needs and wishes. The attempt to do this shifts "dying with dignity" to the center of a debate, as yet unfinished, on a series of issues. When should efforts to prolong or save a patient's life be stopped? On what moral basis should these decisions be made? How is the responsibility to take such decisions to be shared? If it is morally justifiable to let a patient die, why is it not morally justifiable to hasten a patient's death? These and other questions are still challenging society and professional communities to work out a defensible consensus to resolve difficult moral dilemmas in medicine today.

English Abstract↗
PubMed1981

Biochemical evidence for membrane disintegration in human cataracts.

Biochemical evidence is presented for the disintegration of the lens fiber plasma membrane in human cataracts. The intrinsic membrane proteins are found in both the water-soluble and water-insoluble nonmembrane fractions of the cataract lens but not in the normal tissue. Furthermore, in contrast to the normal lens, not all of the lipid found in the cataractous lens is isolated with the membrane fraction. In cataracts, both the membrane and membrane fragments are involved in covalent high molecular weight aggregates with an extrinsic membrane protein (43,000 daltons) and a cytoplasmic protein (gamma-crystallin).

Amino Acid Sequence↗
PubMed1981

The antidepressant efficacy of zimelidine and maprotiline.

In a double-blind group comparison study of 39 patients with primary depressive illness zimelidine in a dose of 200 mg at night demonstrated the same order of antidepressant efficacy as maprotiline in a dose of 150 mg at night after either two or four weeks treatment measured by the amelioration or final score on the Hamilton Rating Scale (HRS) and on the Montgomery & Asberg Depression Rating Scale (MADRS). Both zimelidine and maprotiline demonstrated significant antidepressant activity at 2 weeks compared with 2 weeks prior treatment with placebo measured by amelioration on HRS (paired t 4.1 P less than 0.001, t 2.7 P less than 0.02) or MADRS (paired t 3.5 P less than 0.005, t 5.1 P less than 0.001). An item analysis of the MADRS showed significantly better sleep and appetite in the maprotiline-treated group compared with the zimelidine-treated group which is in accord with the pharmacology of the two compounds.

Adult↗