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Biomedical subjects

D David

Publications and source records attributed to D David.

At least 181 records · Page 10Linked to original sources
PubMed1982

Influence of technical and commercial decamethrin, a new synthetic pyrethroid, on the gonadic germ population in Quail embryos.

Contamination of Quail eggs with the synthetic pyrethroid decamethrin significantly reduced the gonadic germ population in 5 day-old embryos. Technical grade and commercially formulated pesticides were used, the commercial excipient and its main hydrocarbon constituent (xylene) were also tested. Eggs were treated either directly by intravitelline injection (1.25 mg, 0.80 mg or 0.30 mg of active substance by egg) or spraying of the shell (with a 2% aqueous suspension of pesticide) or indirectly through repeated ingestion by the parental birds of feed contaminated with 100 ppm of pyrethroid. Reduction in germ potential was primarily due to the excipient used in the formulation of the commercial product. The xylene, main constituent of the matrix, was responsible of this reductive effect. These chemicals (excipient and xylene) were also chiefly responsible for the high embryo mortality rate observed after injection. Both excipient alone and formulated decamethrin were distinctly less embryolethal when sprayed onto eggs or added to feed.

Animal Feed↗
PubMed1982

[Action of decamethrin, of its commercial solution, of the excipient and of xylene on the quail biotic potential. Effect on the embryonic genital system].

The following products were tested: 1) the purified new synthetic pyrethroid decamethrin; 2) its commercial solution; 3) the excipient of the commercial solution; and 4) the main constituent of the excipient xylene. Eggs were treated either directly by spraying of the shell with 2% and 0.05% aqueous suspensions of commercial decamethrin, excipient and xylene; or indirectly by repeated ingestion by the parental quails of fed contaminated with the four chemicals. All these constituents significantly acted upon the quail biotic potential; they reduced the hatching rate and the embryonic viability and, on the contrary, increased the fecundation rate and the weight of eggs, chickens and adults. Moreover, they reversed the sex-ratio, what brought about the male birds to have the advantage in number. At last, they acted more specifically on the embryonic genital development. The comparative study of effects of both the pesticide and its excipient showed that the later, and more exactly the xylene, was the main responsible factor.

Animals↗
PubMed1981

[Ultrastructure and cytochemistry of primordial germ cells involved in migration in dichlorvos-treated quail embryos].

In dichlorvos-treated quail embryos, the ultrastructural cytochemistry of gonads reveals perturbations in the glycoconjugate distribution. The modifications observed concern the surface and matricial glycoconjugates of tissues involved in the primordial germ cells (PGC) migration. In treated embryos, these cytochemical alterations could explain a delayed migration of PGC to germinal anlage and their disturbed settling into gonads.

Animals↗
PubMed1981

Atrial alternans: experimental echocardiographic and hemodynamic demonstration during programmed pacing.

Simultaneous hemodynamic and echocardiographic recordings were used to demonstrate mechanical atrial alternans during programmed atrioventricular (A-V) pacing in five open chest dogs. Each animal was studied in two stages, first with the A-V conduction system intact (phase I) and later after the experimental induction of complete A-V block (phase II). Atrial alternans was demonstrated during rapid atrial stimulation at cycle lengths ranging from 250 to 120 ms. During phase I, rapid atrial pacing resulted in complex combinations of variable A-V conduction disturbances with superimposed atrial and ventricular alternans. During phase II, atrial alternans could be observed during a programmed prolonged pause in ventricular activity. It is anticipated that this method will facilitate recognition of atrial alternans in various clinical situations and shed further light on its possible hemodynamic significance.

Animals↗
PubMed1981

Exercise cross-sectional echocardiographic diagnosis of coronary artery disease.

To test the feasibility of detecting transient left ventricular regional wall motion abnormalities during exercise-induced myocardial ischemia, 55 patients undergoing diagnostic coronary arteriography were studied in a prospective blinded manner with wide angle cross-sectional echocardiography. The ultrasonic studies were obtained with the patients at rest and during exercise in the supine position using a bicycle ergometer. Cross-sectional echocardiographic studies during exercise were adequate for analysis in 43 (78 percent) of the 55 patients. Forty-one of the 43 manifested either a new regional wall motion abnormality during exercise (20 subjects) or wall motion that remained entirely normal during exercise (21 subjects); in two subjects an abnormal wall motion abnormality at rest did not change with exercise. Nineteen of the 20 patients with a new regional wall motion abnormality had significant coronary artery disease and 15 of these 19 had S-T segment depression during bicycle ergometry. The one patient with a normal coronary arteriogram had an early cardiomyopathy. Ten of the 21 subjects with normal wall motion at rest and during exercise had a normal coronary arteriogram, whereas 11 had evidence of important anatomic coronary artery disease and thus had a false negative echocardiographic findings. Six of these 11 patients had S-T segment depression during exercise. The usefulness of exercise echocardiography to predict coronary artery disease was not altered even when only 26 patients without previous myocardial infarction and with a normal cross-sectional echocardiogram at rest were considered. Thus, new regional wall motion abnormalities during exercise as identified with cross-sectional echocardiography represent a specific finding for the presence of coronary artery disease. However, normal regional wall motion during exercise does not exclude the presence of important anatomic coronary artery disease.

Adult↗
PubMed1981

The use of the balloon-tipped floating catheter in temporary transvenous cardiac pacing.

The effectiveness and safety of balloon-tipped, flow guided, electrodes for ventricular pacing as opposed to the fluoroscopy-guided semi-rigid bipolar electrodes have never been compared in a controlled study. A prospective study was therefore undertaken to compare both techniques in semi-elective and emergency procedures. Flow guided electrodes were inserted in 67 patients (group A) and semi-rigid electrodes in 44 patients (group B). The results of group A were judged to be superior to those of group B in four aspects: a) shorter time (6'45" vs. 13'30", p less than 0.0005); b) lower incidence of catheter displacement (13.4 vs. 32.0 percent, p less than 0.05); c) longer interval of time between implantation and catheter displacement (4.4 vs. 1.9 days, p less than 0.0005); d) lower incidence of serious ventricular arrhythmias during insertion (1.5 vs. 20.4 percent, p less than 0.005). Threshold at insertion was not significantly different (0.6 +/- 0.3 vs 0.7 +/- 0.2 milliampere). The superiority of flow-guided electrodes over fluoroscopy-guided electrodes persisted in the comparison of semielective insertions in groups A and B. We conclude that the flow-guided insertion technique is safer, more expeditious and more stable than the fluoroscopy-guided technique in semi-elective as well as in emergency insertions.

Adolescent↗
PubMed1981

Mid-systolic click and echocardiographic evidence of mitral valve prolapse during electrical pacing.

A mid-systolic click was present in a patient during three years of follow-up after implantation of a permanent transvenous pacemaker. Echocardiography revealed posterior motion of the anterior leaflet which resembled mitral valve prolapse. Both the click and echocardiographic evidence of prolapse disappeared simultaneously with resumption of sinus rhythm and during supraventricular tachyarrhythmias. Wtih spontaneous change in the position of the electrode three years after initial implantation, both the click and the posterior motion of the mitral valve disappeared. The association of mitral valve prolapse with electrical pacing is most unusual and appears to have a distinct pathophysiological mechanism.

Aged↗
PubMed1981

R-wave amplitude variations during acute experimental myocardial ischemia: an inadequate index for changes in intracardiac volume.

The role of intracardiac volume in controlling electrocardiographic R-wave amplitude changes during acute myocardial ischemia was studied in 24 open-chest dogs. The R-wave amplitude in surface ECG leads 2, V5 and Frank X, Y and Z leads were correlated with hemodynamic, echocardiographic and angiographic changes in a 5-minute circumflex coronary artery ligation and reperfusion model. After coronary ligation, left ventricular end-diastolic diameter and volume increased progressively above control, reached a peak and plateau at 120--130 seconds after ligation and did not return to control levels until more than 5 minutes after release of the occlusion. In contrast, the R-wave amplitude showed a biphasic response to acute ischemia, reaching a nadir (sigma R = 18.2% below control) at 30 seconds after coronary ligation and only subsequently increased to reach a peak (sigma R = 52% above control) at 150 seconds after ligation. In addition, R-wave amplitude returned immediately to control levels within 10 seconds after reperfusion. In six other dogs, both venae cavae were occluded for a 30-second period, beginning 180 seconds after coronary ligation. Although intracardiac volume decreased markedly, R-wave amplitudes increased even more. Thus, the demonstration of discordance between alterations in intracardiac volume and R-wave amplitude in these studies suggests that factors other than intracardiac volume determine R-wave amplitude changes in the course of acute myocardial ischemia.

Acute Disease↗
PubMed1981

Laboratory evaluation of repellent properties against birds of the synthetic pyrethroid decamethrin.

Both technical grade and commercially formulated decamethrin administered in feed has a generally repellent action upon quail, with strong individual variations. The excipient used in the commercial preparation has a similar effect on its own, probably due to its odor. Repellency diminishes after repeated exposure and even becomes reversed in the case of the purified pyrethroid, which attracts intoxicated quail.

Animal Feed↗
PubMed1980

Echocardiographic detection of coronary artery disease. Detection of effects of ischemia on regional myocardial wall motion and visualization of left main coronary artery disease.

M mode and cross-sectional echocardiographic studies at rest have been used to detect regional left ventricular wall motion abnormalities as a sign of hemodynamically significant coronary artery disease. These techniques have proved to be fairly specific but not highly sensitive. Detection of new regional wall motion abnormalities with cross-sectional echocardiography during exercise appeared practical in 80 percent of patients in preliminary studies; the finding of such abnormalities is highly specific for the presence of coronary artery disease and, with this approach, the sensitivity of echocardiography is improved. Thus, patients with anatomically severe coronary artery disease on angiography may not manifest an echocardiographic abnormality in regional wall motion even during exercise. The direct noninvasive detection of the left main coronary artery in up to 90 percent of patients studied with cross-sectional echocardiography using the short axis or apical approach, or both, has been well defined. A high sensitivity and specificity of detecting anatomically severe left main coronary artery disease using the criteria of both luminal impingement and the presence of high intensity echoes have been confirmed. Further advances in imaging techniques may allow for better definition of the coronary arterial tree.

Coronary Disease↗
PubMed1980

Echocardiographic features of atrioventricular and ventriculoatrial conduction.

The potential application of diagnostic ultrasound to understanding of the hemodynamic effects of various rhythm and conduction disturbances has not been fully explored. To investigate the change in cardiac function associated with various atrioventricular (A-V) sequencing intervals during cardiac pacing, simultaneous M mode and two dimensional echocardigraphic and hemodynamic studies were performed in 23 dogs. One to one A-V and ventriculoatrial (V-A) sequential pacing at cycle lengths of 400 and 300 ms revealed a stepwise reduction in left ventricular pressure and cardiac output as the A-V interval was changed from +100 to -100 ms. These reductions in cardiac hemodynamics were associated with decreases in left ventricular and increases in left atrial dimensions determined with echocardiography. Mitral valve excursion and the duration of valve opening remained constant over the entire range of A-V intervals. There was angiographic evidence of retrograde blood flow from the left atrium into the pulmonary venous system at an A-V interval of -50 and -100 ms, but no evidence of mitral regurgitation. Thus, correlative echocardiographic and hemodynamic studies can suggest multiple pathophysiologic mechanisms contributing to the decrements in cardiac function observed during tachyarrhythmias with intact A-V conduction as well as those occurring consequent to A-V nodal Wenckebach cycles.

Animals↗
PubMed1980

Permanent overdrive pacing for the suppression of recurrent ventricular tachycardia in a newborn with long QT syndrome.

A newborn with long QT interval and repetitive ventricular tachycardia of the "torsade de pointes" type was seen at the age of one day. The arrhythmia was resistant to lidocaine, propranolol and atropine, but was controlled by isoproterenol infusion. A transvenous pacemaker, inserted at three days of age, suppressed the ventricular tachycardia at stimulation rates above 100/minute. At 19 days of age a permanent pacemaker at pulse rate of 119 beats/minute was implanted. At one year of age the infant was thriving and was completely free of ventricular arrhythmia.

Cardiac Pacing, Artificial↗
PubMed1980

The beneficial effect of the beta blocker timolol in stable agina pectoris.

Timolol is a new beta blocker with cardioselective properties. A single blind controlled study was performed to assess the efficacy of timolol maleate in doses of 10 to 30 mg per day in 20 patients affected by stable angina pectoris. The patients received a placebo for a baseline period of 2 weeks, followed by 12 weeks of timolol. The number of anginal attacks dropped from 14.9 attacks per week in the baseline period to a minimum of 4.6 attacks per week in the sixth week of treatment (P less than 0.01). The number of tablets of nitroglycerin taken per week was reduced from 6.5 during the baseline period to 2.3 in the sixth week of treatment. Resting heart rate decreased from a baseline mean value of 72 beats per minute to 51.7 and 53.7 per minute at weeks 6 and 12 respectively (P less than 0.01). Blood pressure both at rest and during exercise was significantly reduced. The mean work index measured during bicycle ergometry was 127 units before treatment; it increased by 29.4 units and 36.1 units during week 6 and week 12 respectively (P less than 0.05). There was a marked symptomatic improvement in 50% of the patients. Mild fatigue was a common side effect but it disappeared following reduction of dose. We concluded that timolol maleate significantly reduces the number of anginal attacks and increases the work capacity of patients affected by stable angina pectoris

Adrenergic beta-Antagonists↗
PubMed1980

Residual DDT in two successive generations of quail and their eggs.

Gas chromatographic analysis of residual DDT levels following external treatment of parent eggs shows contamination to be present not only in first generation quails but also in second generation eggs laid at the beginning of the laying period and in chicks and adults hatched from them. However, the amount of pesticide detected in second generation eggs laid lately and in all third generation eggs was not significantly higher than that found in control samples.

Animals↗