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Biomedical subjects

D David

Publications and source records attributed to D David.

At least 145 records · Page 8Linked to original sources
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↗
PubMed1986

The role of animal models in electrophysiologic studies of life-threatening arrhythmias.

Animal models have made substantial contributions to the understanding of basic electrophysiologic principles and arrhythmia mechanisms, as well as to the development of antiarrhythmic drugs, devices and procedures. The field of clinical electrophysiology has progressed very dramatically and there have also been advances in the basic laboratory that bear relevance to the methods, design and interpretation of clinical electrophysiologic testing, and to the application of new, potential antiarrhythmic interventions.

Animals↗
PubMed1986

Diastolic 'locking' of the mitral valve: possible importance of diastolic myocardial properties.

The effects of pharmacologically induced changes in myocardial properties on diastolic mitral valve mechanics were studied in five open-chest dogs. After the induction of complete atrioventricular block, the dogs were subjected to a protocol of programmed pacing. During prolonged diastolic pauses, programmed atrial contractions were induced at progressively increasing coupling intervals. Echocardiographically determined mitral valve reopening time was established for each coupling interval in the control state as well as under the influence of calcium or verapamil. Compared with control, calcium caused an increase in myocardial tension from 23.8 +/- 3.0 to 30.0 +/- 4.6 g/cm2 (mean +/- SD, p less than .005) as well as an increase in mean septal contraction and relaxation velocities from 142 +/- 25.9 and 144 +/- 15.2 mm/sec to 188 +/- 21.7 and 174 +/- 19.5 mm/sec, respectively (each p less than .001). Conversely, verapamil caused a decrease in mean myocardial tension from 23.8 +/- 3.0 to 19.4 +/- 5.3 g/cm2 (p less than .001) and in mean septal contraction and relaxation velocities from 142 +/- 25.9 and 144 +/- 15.2 mm/sec to 112 +/- 32.7 and 112 +/- 21.6 mm/sec, respectively (each p less than .001). At every coupling interval, calcium significantly (p less than .01 to .001) prolonged, whereas verapamil significantly shortened (p less than .01 to .001), mitral reopening time compared with the control state. These pharmacologically induced changes in mitral valve mechanics occurred despite variations in left ventricular volume, as well as left ventricular and left atrial pressures that under normal conditions exert opposite effects on mitral valve mechanics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Self-stabilizing osteotomy for frontal bar advancement.

This technique is simple, quick to perform, and produces a rigid block against posterior relapse of the advanced frontal bar in surgery for bicoronal synostosis. This stability is achieved without the need to place a bone graft across the craniectomy site in small infants with rapidly expanding brains. Finer and fewer interosseous wires are required, decreasing the chance of transcutaneous palpation, and this principle can be incorporated into most osteotomy patterns around the orbits.

Craniosynostoses↗
PubMed1985

[Critical study of the stress electrocardiogram after aortocoronary bypass, based on 95 coronary angiographic correlations].

This paper studies the correlations between the stress electrocardiogram and the angiographic findings after aorto-coronary bypass grafts. 95 correlations were established in 75 patients (coronary angiography and stress tests were performed on two occasions after the operation in 20 patients). 32 patients had a past history of myocardial infarction. The stress test was positive when the ST depression was equal to or greater than 1 mm, over more than 80 milliseconds. Four groups could be defined on the basis of the angiography: patient graft(s) with no residual stenosis; old or new coronary lesions; occlusion of one or more grafts; malfunction of the graft(s). The stress test and the coronary angiography were separated by a mean delay of 4.6 days. The stress test was positive in 43 cases, due to the residual postoperative stenoses in 63% of cases, due to occlusion of the graft(s) in 25% of cases and due to malfunction of the graft(s) in 9% of cases. In 3% of cases, the signs of ischaemia were due to an old infarct. The stress test was negative in 52 cases. This negative result corresponded to the 66% of cases with complete revascularisation of the coronary system; in 34% of cases, there were persistent angiographic abnormalities, consisting of uncorrectable coronary stenoses in half of the cases. When the coronary revascularisation was complete, the stress test was negative in every case. Residual coronary lesions were associated with a positive stress test in 66% of cases and with a negative test in 34% of cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1985

Asynchronous intraventricular recovery as a basis for apparent 'supernormality'.

Various mechanisms have been postulated for the supernormal phase of intraventricular conduction where relatively early impulses are conducted with normal intraventricular conduction and relatively late impulses with abnormal intraventricular conduction. The cases presented here illustrate how asynchronous recovery of conducting tissue may result in fortuitous momentary synchrony early on in the recovery phase with asynchronous conduction properties in the later phases of recovery. This will facilitate potential synchronous conduction early on in the cycle which would result in a normal QRS complex, and potential asynchronous conduction in the later phases which would manifest with a bundle branch block QRS complex.

Aged↗
PubMed1985

An electromyographic study of elbow motion during postexercise muscle soreness.

Postexercise muscle soreness was induced in the elbow flexors of human volunteer subjects through the use of a regimen of eccentric contractions. Physical examination before and 48 h after the exercise included measurements of range of elbow motion at the elbow and of arm diameter. Electromyographic (EMG) observations, utilizing fine wire electrodes introduced into each of the elbow flexors, were carried out before and 48 h after the exercise. These observations included resting EMG levels, EMG activity under various isometric loads, and activity during active and passive extensions. The soreness induced was accompanied by a reduction in resting elbow angle while the subjects stood with arms relaxed at their sides, decreased range of both flexion and extension of the elbow, and swelling of the arm. EMG measurements showed no increase in EMG activity as the sore arms were extended passively at the elbow, indicating that the extra resistance to extension associated with the soreness was not a result of stretch receptor-induced activity in the flexors. The results rule out the possibility that neuromuscular activity is responsible for the restriction of motion and are consistent with the idea that edematous changes within the perimuscular connective tissue alter the elastic behavior of the muscles and cause restriction of motion.

Adult↗
PubMed1985

[Clinical and electrophysiological aspects of median intra-His bundle block with normal electrocardiogram at rest].

The clinical and electrophysiological features and the natural history of median intra-His block with a normal resting electrocardiogram were studied: 11 patients had a fixed split H1-H2 potential with a spontaneous or induced block between H1 and H2. The patients (5 men and 6 women) were aged 17 to 70 years (average 53 years). Associated pathology included 2 cases of aortic stenosis (1 severe), 1 case of ischaemic heart disease (effort angina), 1 case of mitral valve prolapse and 2 cases of hypertension. The presenting symptoms were syncope (4 cases), dizziness (2 cases), effort angina (1 case) and tiredness (3 cases); 1 patient was asymptomatic. Holter monitoring (24 hours) was performed in 8 patients and s-owed paroxysmal conduction defects in 6 cases; 4 Mobitz II 2nd degree AV block, 1 3rd degree AV block with narrow QRS complexes and 1 case of blocked atrial extrasystoles at coupling intervals longer than 480 ms and sinus cycle lengths of over 800 ms. Exercise testing by bicycle ergometry (4 patients) was normal in 1 case and revealed Mobitz II 2nd degree AV block in 3 cases. Baseline electrophysiological studies showed an A-H1 interval ranging from 60 to 100 ms (average 78 ms), a H1-H2 interval of 20 to 40 ms (average 31 ms) and a H2-V interval of 30 to 50 ms (average 32 ms). Block between H1 and H2 was observed: "spontaneously" during electrophysiological investigation in 6 cases, after IV atropine in 1 case, during overdrive atrial pacing at rates slower than 150/min in 7 cases, after atrial extrastimulus with a functional intra-His refractory period of over 420 ms in 7 cases, after ajmaline in 3 of the 4 cases in which this test was performed. A cardiac pacemaker was implanted in 10 patients in whom the initial symptoms have all regressed; the remaining patient considered to be "epileptic" had another syncopal attack under therapy and was finally paced. This series demonstrates that the diagnosis of median intra-His block depends on precise electrophysiological criteria and should be looked for even when the presenting symptoms are atypical; some of our patients complained only of tiredness. The value of Holter monitoring and careful endocavitary investigation is emphasised. Median intra-His block should be distinguished from longitudinal and functional His bundle dissociation.

Adolescent↗