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Biomedical subjects

D David

Publications and source records attributed to D David.

At least 127 records · Page 7Linked to original sources
PubMed1989

[Effect of a calcium inhibitor, nicardipine, on aldosterone secretion in primary hyperaldosteronism].

The purpose of the study was to evaluate the effects of a dihydropyridine calcium antagonist, nicardipine (N), on blood pressure (BP) and aldosterone secretion in hypertensive patients (pt) with primary aldosteronism. The study concerned 8 pts, mean age 55.6 +/- 7.7 years, 1 pt with aldosterone-producing adenoma (APA) and 7 pts with idiopathic aldosteronism: plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were respectively 0.30 +/- 0.2 ng/ml/h) and 314 +/- 109 pg/ml. Acute administration of 12 mg of nicardipine during 90 mn (three periods of N infusion during 30 mn: 0.4 mg/mn-5 mn; then 0.08 mg/mn-25 mn) significantly decreased BP, with an increase in heart rate (HR); the levels of PAC were significantly reduced with a slight but not significant increase in PRA, 60 mn after N: (table; see text) N decreased also PAC in the pt with APA [600 to 410 pg/ml] but did not improve hypokalemia (3.1 vs 3.3 mmol/l, n = 8 N.S.). In contrast, PAC levels were not modified 2 hours after acute oral administration of captopril (1 mg/kg): 302 +/- 164 pg/ml vs 332 +/- 191 pg/ml (NS). This study demonstrated the antihypertensive efficacy of acute infusion of nicardipine in primary aldosteronism; the decrease of PAC under this calcium antagonist suggested its potential interest in the management of idiopathic aldosteronism.

Aged↗
PubMed1988

Effect of localized surface cooling of the heart muscle on the high-frequency content of ECG waveforms in dogs.

Hypothermia is known to affect the electrophysiology of the myocardium in various ways. A marked increase in action potential duration, combined with a decrease in rate of depolarization and conduction velocity, has been observed. We studied the effect of localized hypothermia of the ventricular myocardium on the high-frequency (HF) components of the ECG waveform. Signals were obtained from 6 anesthetized dogs using simultaneous recording of three orthogonal body surface leads before, during, and following surface cooling of different areas of the epicardium. Computer analysis included digital averaging and filtering in a frequency range of 150-250 Hz. For each intervention in each animal, the variance of the average nonfiltered QRS complex was used for a quantitative estimate of the total power, whereas the variance of the derived filtered wave (HF QRS complex) expressed the power content in the HF range. The total power increased during localized cooling of the anterior as well as the inferior epicardial surface, while a clear reduction of power was observed in the HF range. This reduction was shown to be lead dependent and nonuniformly distributed during the course of the QRS. In all cases, hypothermia of either anterior or inferior ventricular epicardium produced a zone of reduced amplitude in the HF QRS complex of at least one lead. Thus, typical changes in the morphology of the HF QRS complex are reliable markers for cooling-induced localized electrophysiological (EP) variations. Therefore, the HF analysis of the body surface ECG may provide noninvasive insight into the EP properties of the myocardium.

Animals↗
PubMed1988

Subcostal cross-sectional echocardiographic imaging of patent ductus arteriosus.

A modified subcostal short-axis cross-sectional echocardiographic view for imaging the patent ductus arteriosus (PDA) was studied. A total of 22 newborns with PDA and various associated cardiac anomalies and 16 newborns without PDA were examined. The PDA was imaged in the subcostal view in 19 newborns. In the control group, the absence of the PDA was established in 13 newborns and considered probable in three. The PDA was optimally imaged in the subcostal view in patients with normal or enlarged pulmonary artery, mainly those with the hypoplastic left heart. Among the eight patients with small pulmonary artery (pulmonary atresia or severe tetralogy of Fallot), the PDA was imaged in the subcostal view in three and in the suprasternal view in eight. By combining the suprasternal and the subcostal views, the PDA was imaged in each instance.

Ductus Arteriosus, Patent↗
PubMed1988

Clinical utility of exercise, pacing, and pharmacologic stress testing for the noninvasive determination of myocardial contractility and reserve.

The ability of the left ventricle to modulate its performance is an important and integral component in the cardiovascular system's adaptive response to increased workload. Abnormalities in ventricular contractility can blunt this response and thus significantly limit the patient's functional capacity. The accurate determination and quantitation of cardiac contractility and reserve is a difficult task in the symmetrically contracting ventricle and more so when regional contraction abnormalities are present. Moreover, derangements in other physiologic variables, such as ventricular loading conditions, heart rate, systemic vascular tone, cardiac autonomic function, and pulmonary gas exchange, can diminish cardiopulmonary reserve. This report relates the determinants of myocardial oxygen demand and efficiency to the currently available forms of exercise, pacing, and pharmacologic stress testing. Within this framework, commonly used as well as newer approaches to the noninvasive assessment of stress-induced changes in left ventricular performance and contractility are addressed. In addition, several examples are presented in which noninvasive techniques for assessing intracardiac structures, pressures, and flows (eg, echo/Doppler, radionuclide angiography, rapid acquisition computed tomography, and magnetic resonance imaging) are combined with various cardiovascular stress tests to achieve more reliable measures of myocardial contractility and reserve.

Cardiac Pacing, Artificial↗
PubMed1988

Post-traumatic stress disorder following myocardial infarction.

The evaluation of Post-Traumatic Stress Disorder (PTSD) following myocardial infarction in four patients is described. The authors outline principles of the therapeutic interventions performed to alter the disorder and alleviate patients' incapacitation. Also discussed are the reasons that may be at the root of the omission of the diagnosis of PTSD for this patient population.

Abreaction↗
PubMed1988

Extracellular potassium dynamics in the border zone during acute myocardial ischemia in a canine model.

Bifunctional intramyocardial potassium ion (K+)-sensitive and bipolar wire electrodes were used to evaluate extracellular K+ dynamics and electrophysiologic changes during acute myocardial ischemia in the border zone, ischemic zone (5 to 7 mm from the border), central ischemic zone (15 to 25 mm from the border) and normal myocardium in 11 open chest dogs during a 30 min ligation of the left anterior descending coronary artery. At the end of this period, the hearts were injected with rhodamine dye and quickly frozen. Ultraviolet NADH (nicotinamide adenine dinucleotide) rhodamine fluorescence photography was used to localize the border between normally perfused and ischemic tissue and determine the site of electrodes in relation to this border. Before coronary ligation, extracellular K+ ranged from 4.0 +/- 0.3 to 4.3 +/- 0.3 mM in these four zones. After ligation, extracellular K+ accumulated in the ischemic and central ischemic zones in a pattern characterized by an initial rapid increase for approximately 5 min, followed by a slowly rising plateau phase, reaching maximal levels of 9.8 +/- 2.0 and 14.4 +/- 4.4 mM, respectively. In contrast, K+ dynamics in the border zone showed a biphasic response, with an initial rapid increase to a maximal level of 7.5 +/- 2.4 mM at approximately 9 min after coronary ligation, followed by a gradual decrease to a level of 5.3 +/- 1.2 mM by the end of the 30 min ligation period. No significant changes in K+ occurred in the normal zone throughout the ischemic period. The correlation of K+ electrode, electrophysiologic and postmortem NADH-rhodamine fluorescence data indicated the existence of a well defined border zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Bopindolol in the treatment of moderate hypertension: a dose-response study.

To determine the optimal antihypertensive dose of bopindolol, we performed a randomized double-blind study in parallel groups. After 15 days of placebo single-blind, 115 hypertensive patients received daily for 28 days one of 4 doses: 0 mg (placebo), 0.5 mg, 1.0 mg, 2.0 mg. The reduction of supine diastolic blood pressure (BP) did not exhibit the pattern of a dose-effect relationship. The effect of 0.5 mg belonged to the plateau of the dose-effect curve (P = 0.1, analysis of variance). The reduction of heart rate (HR) followed a typical dose-effect curve, with a plateau beginning with 1 mg (P = 0.02). A trend toward an increase in the incidence of side-effects with dosage was observed (P = 0.3). Thus, the optimal antihypertensive dose may be 0.5 mg or less. Previous studies not using parallel randomized groups suggested an antihypertensive dose ranging from 2 to 4 mg. This study confirms that the dose-effect curves of beta blockers on HR and BP are dissociated. The dose-effect curve of HR seems unsuitable for assessing the optimal antihypertensive dose of a beta blocker.

Adrenergic beta-Antagonists↗
PubMed1988

Transtelephonic electrocardiographic monitoring for the detection and treatment of cardiac arrhythmias.

TTEM as a means for ambulatory arrhythmia detection and management of cardiac patients has demonstrated the potential for considerable clinical utility. Because it is easy to use, relatively inexpensive, and highly effective in aiding in the diagnosis of various cardiac arrhythmias, it may be a preferred mode of surveillance for a number of cardiac patients of all ages. TTEM is presently used most widely for pacemaker followup. TTEM can be used alone and in conjunction with Holter monitoring in the management of cardiac arrhythmias, and has lately become a recognized tool in the followup of patients with ischemic heart disease, especially post-myocardial infarction patients. It is important to emphasize that TTEM is only one part of an overall approach to ambulatory monitoring that also includes Holter monitoring and exercise testing. It must be noted, however, that the studies comparing the efficacy of TTEM with that of other surveillance methods are few and consist of only a relatively small number of patients. Therefore, it would be premature to draw conclusions regarding the ultimate role of TTEM and its comparative value in the routine management of most cardiac arrhythmia problems. However, available data do support an increasing role for these systems in the future.

Anti-Arrhythmia Agents↗
PubMed1988

[Donor artificial insemination. Psychological survey of 830 couples].

830 couples who had asked for Artificial Insemination by Donor (AID) were questioned using separate questionnaires for the husband and for the wife. The questions were directed to the reactions that followed in succession to discovery of the sterility, the psychological conditions that led to choosing AID, their attitude as far as secrecy was concerned and finally their contribution to finding donors of sperm. Overall the husband-wife replies corresponded to one another. Frequently the reaction to the news that the man is sterile is a depressive one and to a lesser degree followed by troubles in sexual performance. The choice of AID is usually a decision of both members of the couple. Most couples express themselves as hesitant about adoption. Most of them said that secrecy about the procedure was an essential condition. It appears that, above all, male sterility had to be hidden from the circle in which they associated and from the child. It is this position as far as secrecy is concerned that makes it difficult for the couples to help in recruiting sperm donors.

Attitude↗
PubMed1987

Acute hemodynamic effects of intravenous nicardipine in patients treated chronically with propranolol for coronary artery disease.

Intravenous nicardipine, 5 mg, was infused over 5 minutes in 2 comparable groups of 8 patients with chronic coronary artery disease but no clinical signs of heart failure. Eight patients had received no previous treatment and served as a control group; 8 other patients had received long-term treatment with large doses of propranolol. The hemodynamic responses to nifedipine were similar in the 2 groups, but was greater in patients taking propranolol. At 10 minutes, systemic vascular resistance decreased by 47% in patients taking propranolol and by 39% in the control group; mean aortic pressures decreased by 25% and 10%; heart rate increased by 23% and 19%; and cardiac index increased by 45% in both groups. At 20 minutes, left ventricular end-systolic volume index decreased by 20% in patients taking propranolol and 15% in the control patients; angiographic stroke index increased by 19% and 8%; left ventricular ejection fraction increased by 22% and 11%; and mean circumferential fiber velocity increased by 46% and 32%. Intravenous nicardipine infusion (5 mg) did not induce negative inotropic effects in patients with chronic coronary heart disease, and no evidence of congestive heart failure was seen, even in patients receiving large doses of propranolol. Nicardipine counteracted the potential deleterious effects of propranolol; increased peripheral vascular resistance and left ventricular stroke work and decreased cardiac output.

Adult↗
PubMed1987

Detection of human cytomegalovirus DNA in human tonsillar lymphocytes.

The human cytomegalovirus (HCMV) was first isolated in cell cultures from the oropharynx, which is thought to be a site of primary infection. Although HCMV can be recovered from the oropharynx during reactivation phases, its exact site of latency is not known. In the present study we demonstrated evidence suggesting the presence of latent HCMV in this anatomic region--in the palatine tonsils. Samples from 30 tonsils obtained by tonsillectomy were screened for the presence of HCMV. Out of the 30 tonsil donors, 23 were seropositive for HCMV. Three methods were used in attempts to demonstrate HCMV's presence in the tonsils: (1) viral isolation attempts on various cell cultures, (2) immunohistochemical staining--immunoperoxidase method--designed to detect viral antigens, and (3) DNA dot hybridization with a HCMV-DNA probe designed to detect viral DNA. Neither infectious HCMV nor other viruses were isolated in cell cultures. No viral antigens were detected by immunoperoxidase staining in the tonsillar tissue. Four out of the 30 tonsils studied were found to contain viral DNA. In one case in which the tonsillar mononuclear (MN) fraction was separated from the polymorphonuclear (PMN) fraction, only the first fraction contained the viral DNA.

Adolescent↗
PubMed1987

Ontogenetical study of the chick embryo subcommissural organ by lectin-histofluorescence and electronmicroscopy.

The secretory activity of the subcommissural organ (SCO) was studied during embryogenesis of the chick (Gallus gallus) using two lectins labelled with fluorescein isothiocyanate, concanavalin A (Con A) and wheat-germ agglutinin (WGA). While WGA labels the apical or ventricular border of the organ, Con A labels both, the apical and vascular poles of the cells. Glycoproteinaceous secretory products, visualized by Con A appear early, at 5 days, in the ependymal epithelium and expand progressively in a rostrocaudal direction. A correlation is established between histofluorescence and the ultrastructural aspects of the ependymocytes. This throws light on the role of the endoplasmic reticulum in the synthesis, storage and transport of the material produced by the SCO, and points to the existence of two poles of exchange between the secretory cells and the extracellular medium, i.e., the ventricular and the vascular one. WGA reactivity at the apical border is linked up with the formation of Reissner's fibre and shows that the secretory product of the SCO cells undergoes at least partly modifications during its intracytoplasmic transport preceding apical discharge.

Animals↗
PubMed1986

The organization of the human HPRT gene.

The organization of the X-linked gene for human hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8.) has been determined by a combination of restriction endonuclease mapping, heteroduplex analysis and DNA sequence analysis of overlapping genomic clones. The entire gene is 42 kilobases in length and split into 9 exons. The sizes of the 7 internal exons and the exon-intron boundaries are identical to those of mouse HPRT gene. The 5' end of the gene lacks the prototypical 5' transcriptional regulatory sequence elements but contains extremely GC-rich sequences and five GC hexanucleotide motifs (5'-GGCGGG-3'). These structural features are very similar to those found in the mouse HPRT gene and to some of the regulatory signals common to a class of constitutively expressed "housekeeping" genes. Several transcriptional start sites have been identified by nuclease protection studies. Extensive sequence homology between the mouse and human genes is found in the 3' non-coding portion of the gene.

Animals↗