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Biomedical subjects

D M Becker

Publications and source records attributed to D M Becker.

At least 91 records · Page 5Linked to original sources
PubMed1988

Effects of chronic beta-blockade on beta-receptors and adenylate cyclase activity in the canine heart.

To test the hypothesis that beta-receptors 'up-regulate' during chronic beta-blockade, myocardial beta-receptor density, affinity and functional sensitivity were examined in dogs before and after chronic beta-blockade. Membrane preparations from the left ventricle and right atrium were assayed for beta-receptors in 8 control dogs, and 8 dogs given oral nadolol (4 mg/kg) twice a day for 3 weeks. Beta-receptor density and affinity of membrane fractions were determined using 3H-dihydroalprenolol (0.5-20 nM), and Scatchard analysis. Beta-receptor densities after chronic beta-blockade were 419 +/- 28 (mean +/- SEM) and 436 +/- 47 fmol/mg protein in membranes from the left ventricle and right atrium respectively. These values were not significantly different from the left ventricle (412 +/- 25) or the right atrium (413 +/- 25) in control dogs. Beta-receptor affinities were 5.6 +/- 0.5 nM (left ventricle) and 8.5 +/- 1.1 nM (right atrium) after chronic beta-blockade, and not significantly different from control (6.9 +/- 0.7 nM, ventricle; 11.3 +/- 0.9 nM, atrium). Beta-receptor sensitivity was determined in membrane fractions from the left ventricle by analysis of the dose-response relationship between isoproterenol and the formation of c-AMP (pmol/min/mg protein). The concentration of isoproterenol that resulted in 50% of the maximal response was not significantly altered by chronic beta-blockade. Maximally stimulated adenylate cyclase with Gpp(NH)p or NaF was also unchanged by beta-blockade. These results suggest that in the canine heart, chronic beta-blockade does not lead to 'up-regulation' of beta-receptors nor catecholamine supersensitivity.

Adenylyl Cyclases↗
PubMed1988

Calf deep venous thrombosis. A wolf in sheep's clothing?

To determine the natural history of calf deep venous thrombosis (C-DVT), an analytic review of the 20 relevant English-language papers published since 1942 was performed. Remarkably little methodologically sound research on this subject was found. However, available evidence suggests that C-DVT propagates to the thigh in up to 20% of cases and that propagation invariably occurs before embolization. No fatal emboli were reported in patients presenting with isolated C-DVT. Traditional anticoagulation treatment with heparin sodium and warfarin sodium of symptomatic patients with C-DVT appears to prevent extension, embolization, and early recurrence. There is no convincing evidence that C-DVT leads to chronic venous insufficiency or whether the risks of anticoagulation exceed the risks of no treatment. As an option to anticoagulation, physicians may choose to follow patients with C-DVT with serial impedance plethysmography, treating only if there is evidence of proximal extension.

Heparin↗
PubMed1988

Hypercholesterolemia in patients undergoing coronary bypass surgery: are they aware, under treatment, and under control?

Hypercholesterolemia is an important determinant of progressive atherosclerosis in both vein grafts and native vessels after coronary artery bypass surgery. We demonstrated that nearly half of all patients admitted for coronary bypass have elevated cholesterol levels before surgery. Of these, half are unaware of the elevations in cholesterol level, and few are undergoing any treatment. The results suggest that lipids should be measured before coronary bypass surgery to optimize postoperative risk reduction education.

Adult↗
PubMed1988

The costs of employee smoking. A computer simulation of hospital nurses.

A computer simulation model of the economic impact of employee smoking on an employer was developed with a population of hospital nurses as the example. Net economic impact was calculated by estimating cumulative costs borne by the employer under various scenarios and comparing them with projected costs estimated from baseline data. The model included the following: baseline number of staff, baseline percentage of smokers, annual employee turnover rate, number of smokers interested in quitting, the cost of a smoking cessation program, expected success rate of a voluntary cessation program, smokers quitting spontaneously without a program, and employer-borne costs related to employee smoking. A variety of scenarios were constructed to generate a range of employer net economic impact figures and resulting percentages of smoking employees. Results showed that the benefits of a cessation program would be eliminated over several years, unless the prevalence of smoking in incoming employees was reduced. The most favorable scenario, combining a hospital cessation program and reduced smoking among new employees, generated cumulative savings, discounted at 5%, of $358,000 to $684,000 over an eight-year period.

Computer Simulation↗
PubMed1988

Lack of effect of warfarin on uric acid concentration.

Uric acid concentrations reportedly are increased in patients being treated with warfarin. We measured uric acid in 40 patients before and during warfarin administration. The mean pre- and post-warfarin uric acid concentrations for our patients were 0.39 mmol/L and 0.40 mmol/L, respectively, not a significant difference. Further observations of hyperuricemic patients started on warfarin are needed to prove that their risk of gout is not increased.

Adult↗
PubMed1987

Cancer among Haitians in Florida.

Data on cancer rates from West Indian populations are scarce, and to the authors' knowledge there are no published data on cancer rates and distributions among Haitians. Proportional distributions of cancers among three groups of patients living in Florida were compared: Haitian born blacks, United States born blacks, and non-Haitian Caribbean born blacks. The incidence rate of cancer of the cervix among the Haitian and United States born black groups was also compared. Increased rates of certain malignancies associated with viral infection or immunodeficiency were found in the Haitian group. These tumors were hepatocellular carcinoma, nasopharyngeal carcinoma, reticulum cell sarcoma, Kaposi's sarcoma, and carcinoma of the uterine cervix. The age-adjusted incidence rate of carcinoma of the cervix was especially high among Haitian women even with a liberal estimate of the female Haitian population from whom the cases were drawn. Except for cancer of the cervix, the numbers of cancers of interest were small, and age-adjusted incidence rates were not calculated. Continued epidemiological study of larger numbers of patients is needed to evaluate these findings further.

Adult↗
PubMed1987

Prevention of deep venous thrombosis in patients with acute spinal cord injuries: use of rotating treatment tables.

A randomized clinical trial of 15 patients with acute spinal cord injuries was performed to test the hypothesis that rotating treatment tables prevent deep venous thrombosis in this population. Four of 5 control (nonrotated) patients developed distal and proximal thrombi, assessed by 125I fibrinogen leg scans and impedance plethysmography. In comparison, only 1 of 10 treated (rotated) patients developed both distal and proximal thrombosis (P = 0.007). These results suggest but do not prove that rotating treatment tables prevent the development of proximal deep venous thrombosis in spinal cord-injured patients. Larger clinical trials are needed to confirm this heretofore undocumented benefit of rotating treatment tables.

Beds↗
PubMed1986

Smoking behavior and attitudes toward smoking among hospital nurses.

We examined smoking prevalence, smoking behavior, and attitudes toward smoking in hospitals in 1,380 respondents among 1,719 registered nurses in a large urban teaching hospital. In this group, current prevalence of smoking in hospital nurses (22 per cent) was less than women in the general population (29 per cent). Smoking nurses were more likely than nonsmokers to hold attitudes which potentially reduce their efficacy in helping patients to stop smoking.

Adult↗
PubMed1985

Ventricular fibrillation during coronary angiography: an analysis of mechanisms.

To investigate the mechanisms of ventricular fibrillation (VF) during coronary angiography, we assessed ventricular automaticity, local QT intervals, local conduction characteristics, and the ability to induce arrhythmias with premature ventricular stimulation in 30 dogs after intracoronary injections of 4 to 6 cc of Renografin 76 (RG 76). Ventricular automaticity was measured in six dogs as the idioventricular escape rate following intense vagal stimulation and was unchanged (51 +/- 6 vs 52 +/- 6 bpm, p greater than 0.05) with 6 cc of RG 76. In addition, 8 of 10 injections of 6 cc of RG 76 produced VF at a heart rate of 200 bpm compared to only 2 of 10 injections at a heart rate of 80 bpm (p less than 0.05). Composite and bipolar plunge electrodes were placed in the region perfused by the left anterior descending coronary artery (LAD) and circumflex coronary artery to assess QT intervals and conduction characteristics. RG 76, 4cc, produced a 116 +/- 18 msec increase in the QT intervals recorded from the region perfused by the LAD, resulting in a marked dispersion in repolarization. Both local bipolar and composite electrograms showed minimal conduction delay, which rarely extended beyond the QRS of a lead II ECG during atrial paced rhythm. As premature beats (spontaneous or induced) conducted through the region of QT prolongation, marked conduction delay was recorded from bipolar electrograms, while composite electrograms recorded continuous fractionated electrical activity spanning the diastolic interval at the onset of VF.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1985

Decision to adopt new medical technology: a case study of thrombolytic therapy.

New medical technologies are adopted by practising physicians at varying rates. Thrombolytic therapy is an example of a technological advance that many physicians have seemed reluctant to employ. A random sample of board certified internists was surveyed by mail to study factors that influence decisions to use thrombolytic agents. Variables important in predicting use were identified by discriminant analysis. In general users and non-users had similar assumptions about the risks and benefits of this technology. Among the important predictor variables were a perception of having patients suitable for treatment, availability of the agents and self-rating of knowledge about this therapy. Among questions related to type of practice and education, only subspecialization and textbook reading were important discriminators. These results suggest that decisions to adopt new technologies do not follow simply from risk-benefit assessments.

Adult↗
PubMed1985

Differential responses accompanying sequential stimulation and ablation of vagal branches to dog heart.

Electrical excitation of small thoracic vagal branches elicited highly localized responses in the canine heart. Specific pathways to the sinoatrial nodal (SAN) regions were identified from negative chronotropic responses to stimulation (20 Hz, 5.0 ms, 3.0-5.0 V) of these branches. Pathways to the atrioventricular nodal (AVN) region were determined from changes in A-H interval (His bundle electrogram) and incidence of heart block as vagal branches were stimulated during concurrent atrial pacing. A few small branches influenced a single cardiac function (atrial rate, contractile force, or AV conduction). More commonly, activation of such branches elicited simultaneous chronotropic and dromotropic effects. However, many branches failed to elicit any detectable cardiac change. The major outflow from the left vagus to SAN and AVN regions is by way of cardiac branches from the recurrent laryngeal nerve at its reflection around the aorta. Activation of the left recurrent nerve reduced atrial rate by 43% and doubled A-H interval 84 to 167 ms. The right thoracic vagus or its branches induced A-H prolongation from 78 to 131 ms. H-V intervals remained constant at a mean of 35 ms. Outflows from the right thoracic vagus to SAN and/or AVN regions originated just below the middle cervical ganglion and at all levels down to the azygos vein.

Animals↗
PubMed1984

Plasma fibronectin in medical ICU patients.

Plasma fibronectin levels in 66 medical ICU (MICU) patients were measured daily. Mean values of initial levels were significantly higher in survivors (266 +/- 14 mg/L) than nonsurvivors (179 +/- 13 mg/L; p less than .0003). There was extensive overlap between survivors and nonsurvivors. The clinical categories of sepsis, disseminated intravascular coagulation (DIC), adult respiratory distress syndrome (ARDS), and hepatic failure with GI bleeding were associated with low fibronectin levels. Within all diagnostic categories the mean initial fibronectin level of the survivors was higher than that of nonsurvivors. This difference was significant only in the septic group (p less than .02). Patients with minimum fibronectin levels less than 195 mg/L had a 65% mortality rate; patients with minimum levels greater than or equal to 195 mg/L had a 17% mortality rate. Fibronectin, via its role in reticuloendothelial system (RES) function, may have a pathophysiologic role in a variety of medical illnesses.

Adolescent↗
PubMed1983

Opportunistic infections and Kaposi's sarcoma among Haitians: evidence of a new acquired immunodeficiency state.

Twenty Haitian patients, hospitalized from 1 April 1980 to 20 June 1982, had Pneumocystis carinii pneumonia, central nervous system toxoplasmosis, esophageal candidiasis, cryptococcosis, disseminated cytomegalovirus, progressive herpes simplex virus, chronic enteric coccidiosis, or invasive Kaposi's sarcoma. Ten patients died. Opportunistic infections were frequently multiple and were recurrent in three patients. In seven patients disseminated tuberculosis preceded the other infections by 2 to 15 months. There was no evidence of an underlying immunosuppressive disease, and no history of homosexuality or intravenous drug abuse. At least three patients probably acquired the syndrome in Haiti. Lymphadenopathy was common. Seventeen patients tested had anergy, and 18 had lymphopenia. Monoclonal antibody analysis of peripheral-blood T-cell subsets done on 11 patients showed a marked decrease in T-helper cells and an inversion of the normal ratio of T-helper cells to T-suppressor cells. This syndrome among heterosexual Haitians is strikingly similar to the syndrome of immunodeficiency described recently among American homosexuals.

Acquired Immunodeficiency Syndrome↗