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Biomedical subjects

C H Cheng

Publications and source records attributed to C H Cheng.

At least 145 records · Page 8Linked to original sources
PubMed1991

Stoichiometry of maltodextrin-binding sites in LamB, an outer membrane protein from Escherichia coli.

We have directly measured the stoichiometry of maltodextrin-binding sites in LamB. Scatchard plots and computer fitting of flow dialysis (rate-of-dialysis) experiments clearly establish three independent binding sites per LamB trimer, with a dissociation constant of approximately 60 microM for maltoheptaose. The current model for LamB's function as a specific pore is discussed with respect to the symmetry in LamB's kinetic properties and the implications of our results.

Bacterial Outer Membrane Proteins↗
PubMed1991

Cardiac pacemaking in Hong Kong: report of a survey of general practitioners and internists.

A questionnaire study was carried out among cardiologists, internists, general practitioners, and final year medical students in Hong Kong concerning cardiac pacemaking. The response rate was 11.2%. Salient results include the misconception on the part of 40% and 12% of physicians, that general anesthesia and thoracotomy respectively, are commonly required for permanent pacing and that the procedure is associated with significant mortality (14.2% of physicians). Most would offer permanent pacing to patients with symptomatic complete atrioventricular block, but advanced age appeared to be considered as a barrier to permanent pacemaking. There was confusion about the need to pace asymptomatic sick sinus syndrome and bundle branch conduction diseases. Oral isoprenaline was still used to treat bradycardia by 16.6% of physicians. A similar deficiency in knowledge was found among the students. It is suggested that misunderstanding of cardiac pacing is common and may be a reflection of the lack of emphasis in undergraduate teaching. This deficiency may have prevented some patients from receiving the benefits of permanent pacing.

Adult↗
PubMed1991

Venous gangrene (phlegmasia caerulea dolens) complicating heart failure from severe mitral stenosis--a case history.

Gangrene of the left upper limb was found to complicate severe mitral stenosis presenting with heart failure in a sixty-eight-year-old woman with a documented left atrial thrombus. Arterial obstruction as the cause of gangrene was excluded by Doppler-assisted assessment of the peripheral pulses. Venous gangrene can complicate severe mitral stenosis and must be distinguished from arterial embolization, in which urgent surgical treatment is imperative.

Acute Disease↗
PubMed1990

Usefulness of labetalol in chronic atrial fibrillation.

Beta-adrenergic blocking agents are useful in controlling excessive ventricular rate in chronic atrial fibrillation (AF) but often reduce exercise capacity. To investigate the advantage of labetalol--a unique beta blocker with alpha-blocking property--in chronic AF, 10 patients without underlying structural heart disease were studied with treadmill test, 12-minute walk and 24-hour ambulatory electrocardiographic monitoring. Patients were randomized and crossed over to receive 4 phases of treatment (placebo, digoxin, digoxin with half-dose labetalol, and full-dose labetalol). Exercise durations were 14.1 +/- 1.5, 14.2 +/- 1.5, 16.1 +/- 1.1 and 15.6 +/- 1.1 minutes, respectively, indicating that labetalol did not reduce exercise tolerance. Although digoxin had no advantage over placebo in controlling maximal heart rate (177 +/- 2 vs 175 +/- 3 beats/min), labetalol, both as monotherapy or as an adjunct to digoxin, was advantageous (156 +/- 4 vs 177 +/- 2 beats/min, p less than 0.01, and 154 +/- 4 vs 177 +/- 2 beats/min, p less than 0.01, respectively). The rate-pressure product was consistently lowered by labetalol at rest and during exercise. At peak exercise, the addition of labetalol to digoxin reduced the maximal rate-pressure product achieved from 30,900 +/- 1300 to 24,100 +/- 2,000 mm Hg/min (p less than 0.01) and the maximal rate-pressure product was lowest with full-dose labetalol (22,300 +/- 1,600 mm Hg/min). During submaximal exercise on treadmill or during the 12-minute walk, the combination of labetalol and digoxin produced the best heart rate control, whereas labetalol monotherapy was comparable to digoxin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗
PubMed1990

Doxorubicin for unresectable hepatocellular carcinoma. A prospective study on the addition of verapamil.

A prospective study was conducted to assess the safety and efficacy of the addition of oral verapamil to intravenous Adriamycin (doxorubicin) for the management of patients with unresectable hepatocellular carcinoma (HCC). All 28 patients studied had histologically verified disease, and cirrhosis was present in 20 of the 21 patients with adequate tissue sampling. The overall median survival was 57 days. Chemotherapy was terminated in seven patients after one course of treatment. Partial response and complete response were noted in four patients (19%) and one patient (4.8%), respectively, among the 21 patients evaluated. Side effects related to the chemotherapy were present in all patients studied. Death from fulminating sepsis occurred in three of the 13 patients with leukopenia. Symptomatic myocardial dysfunction developed in one patient. The addition of verapamil apparently did not potentiate the tumoricidal effect of systemic Adriamycin on HCC but probably did increase its complications.

Carcinoma, Hepatocellular↗
PubMed1990

A new pacing method for rapid regularization and rate control in atrial fibrillation.

In 15 patients with atrial fibrillation (AF), a single right ventricular extrastimulus (intercalated pacing) was delivered after every sensed conducted beat resulting in a reduction in rate. This method was used in 10 patients with lone AF and the average success rate of inducing coupling was 86 +/- 14% (range 64 to 100), using a mean coupling interval of 232 +/- 28 ms (range 175 to 290). During intercalated pacing, the pulse rate of AF was reduced (from 137 +/- 26 to 75 +/- 14 beats/min, p less than 0.001). Intercalated pacing resulted in enhancement of mean stroke volume (28 +/- 6 vs 44 +/- 10 ml in AF, p less than 0.0001), pulse pressure and the pulse-to-pulse regularity. Both the systolic and diastolic arterial pressures were regularized. The reduction in pulse rate during intercalated pacing was determined by the coupling interval, and the induction of concealed ventriculoatrial conduction (82 +/- 44 ms). Myocardial lactate extraction was similar during AF and short-term intercalated pacing (28 +/- 10 vs 25 +/- 9%, difference not significant). In 5 patients with severe mitral stenosis in AF, intercalated pacing resulted in an improvement in the cardiac output (3.1 +/- 0.2 vs 3.4 +/- 0.2 liters/min, p less than 0.04), a reduction in the gradient across the mitral valve (16 +/- 8 vs 10 +/- 5 mm Hg, p less than 0.02), and a reduction in pulmonary arterial and wedge pressures. This new pacing method thus achieved rapid temporary control of rate, regularity and cardiac hemodynamics during AF, which were more prominent in patients with mitral stenosis and restricted left ventricular filling.

Adult↗
PubMed1990

Fatal massive pulmonary hemorrhage complicating mitral stenosis.

Mitral stenosis is a well known cause of hemoptysis; however, sudden death due to fatal massive pulmonary hemorrhage is an extremely rare complication. In this report, we describe a 28-year-old female with severe mitral stenosis who died suddenly due to such complication. A review of the literature shows such complication is extremely rare and unpredictable. We recommend that patients with severe mitral stenosis and history of hemoptysis be considered as candidates for early surgical intervention.

Adult↗
PubMed1990

Aneurysmal coronary sinus associated with severe valvular heart disease.

We report a case of aneurysmal coronary sinus complicating severe valvular disease with severe tricuspid regurgitation. Injection in the left superior vena cava outlines the aneurysmal coronary sinus with stasis of the contrast. As this anomaly carries special surgical implication in patients requiring open heart surgery, a correct preoperative diagnosis is mandatory.

Adult↗
PubMed1990

Hypocalcemic myocardial dysfunction: short- and long-term improvement with calcium replacement.

The effects of short- and long-term calcium replacement on myocardial function in six asymptomatic patients (age 48 +/- 3, mean +/- SEM) with hypocalcemia complicating surgical hypoparathyroidism were studied. Cardiac output was determined by ascending aortic continuous wave Doppler assessment and was measured as minute distance. During intravenous calcium replacement at rest, ascending aortic minute distance increased from 6.75 +/- 1.10 to 9.17 +/- 1.29 m as the calcium level rose from 1.76 +/- 0.08 to 2.06 +/- 0.19 mmol/L without changes in heart rate and blood pressure (p less than 0.01). The peak velocity and acceleration of blood flow derived from Doppler measurement showed a similar rise during calcium infusion. Symptom-limited cycle ergometry was performed before and 3 months after normalization of calcium by long-term oral therapy. Although the resting cardiac output was unchanged, the maximum cardiac output at peak exercise also increased from a minute distance of 11.58 +/- 1.84 to 15.37 +/- 2.28 m (p less than 0.05), together with an increase of maximum heart rate from 136 to 149 beats/min (p less than 0.05). Exercise duration was also prolonged from 11.9 +/- 2.9 to 13.0 +/- 2.8 minutes. Thus hypocalcemia impairs cardiac performance, but this impairment is reversible with calcium replacement.

Calcium↗
PubMed1990

Doppler echocardiographic evaluation of left ventricular diastolic function in patients with systemic lupus erythematosus.

Subclinical myocardial involvement frequently occurs in patients with systemic lupus erythematosus (SLE). In this study, left ventricular diastolic function was assessed in 58 patients (54 female and 4 male; mean age 32 +/- 11 years) and in 40 sex-matched and age-matched healthy control subjects (37 female and 3 male; mean age 33 +/- 9 years) by means of pulsed Doppler echocardiography. All subjects had no clinical evidence of overt myocardial disease or abnormal left ventricular systolic function. Compared with the control group, patients with SLE had significantly prolonged isovolumic relaxation time (62 +/- 12 vs 80 +/- 14 msec; p less than 0.01), reduced peak early diastolic flow velocity (peak E) (82 +/- 18 vs 76 +/- 16 cm/sec; p less than 0.05), increased peak late diastolic flow velocity (peak A) (45 +/- 7 vs 53 +/- 8 cm/sec; p less than 0.01), reduced E/A ratio (1.81 +/- 0.32 vs 1.46 +/- 0.29; p less than 0.001), and lower deceleration rate of early diastolic flow velocity (EF slope) (489 +/- 151 vs 361 +/- 185 cm/sec2; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Delayed decline in plasma atrial natriuretic peptide levels after an abrupt reduction in atrial pressures: observation in patients with dual-chamber pacing.

The effect of an abrupt reduction in atrial pressures on atrial natriuretic peptide (ANP) secretion was studied in four patients with complete atrioventricular block with a dual-chamber pacemaker when the pacing mode was changed from the VVI to the DVI mode at an equal rate of 70/min. Simultaneous continuous hemodynamic monitoring was performed using a balloon-tipped thermodilution catheter. With DVI pacing, there was an immediate decrease of right atrial pressure from 4.5 +/- 0.9 to 1.8 +/- 1.1 mm Hg, and a reduction of pulmonary arterial wedge pressure from 7 +/- 0.8 to 4.5 +/- 0.9 mm Hg, together with a rise in cardiac output from 3.1 +/- 0.2 to 3.7 +/- 0.2 L/min. However, despite a constant hemodynamic status after dual-chamber pacing, the arterial ANP level steadily decreased from 151 +/- 26 pg/ml to a steady low level of 78 +/- 15 pg/ml after 20 minutes of dual-chamber pacing (percentage reduction- 48 +/- 8%, p less than 0.05). This persisted until the end of the study at 60 minutes. The time-dependent decay in ANP secretion after an abrupt and constant change in hemodynamic status should be considered when interpreting ANP levels.

Aged↗
PubMed1990

Presence of prolactin receptors in kidney and large intestine of the snake Ptyas mucosa.

125I-labeled ovine prolactin was used to test for the presence of prolactin receptors in membranes prepared from tissues of the common rat snake Ptyas mucosa. High levels of specific binding were found in kidney and large intestine membranes prepared from snakes of both sexes. The binding was time, temperature, and protein dependent. The presence of Ca2+ in the incubation medium enhanced the binding, with optimal concentrations at 10-20 mM. Specificity of binding was established by employing different hormones as the displacing species in the radioreceptor assay. The results suggested the presence of lactogenic receptors in snake kidney and large intestine membranes. Scatchard analysis of the binding data indicated the presence of a single class of binding sites in snake kidney membranes with a dissociation constant of 0.83 nM. The present study is the first report of the presence of prolactin receptors in snake kidney and large intestine membranes.

Animals↗
PubMed1990

Cardiac abnormalities in systemic lupus erythematosus: a prospective M-mode, cross-sectional and Doppler echocardiographic study.

A prospective M-mode, cross-sectional and Doppler echocardiographic study was performed on 75 patients with systemic lupus erythematosus and 60 sex- and age-matched control subjects. Compared with the control group, patients with lupus had an increased prevalence of echocardiographic abnormalities. These included pericardial effusion and/or thickening (37%), left ventricular hypertrophy (12%), global left ventricular hypokinesis (5%), segmental abnormalities of left ventricular wall motion (4%), right ventricular enlargement (4%), focal verrucous valvar thickening (12%), gross valvar thickening and dysfunction (8%), mitral regurgitation (25%) and aortic regurgitation (8%). Two patients with gross mitral valvar thickening and dysfunction subsequently underwent valvar replacement. Correlation between echocardiographic abnormalities and clinical parameters showed that pericardial effusion was significantly associated with pericardial pain (P less than 0.05) and active disease (P less than 0.001), and left ventricular hypertrophy with systemic hypertension (P less than 0.05). Thus, there was a high prevalence of cardiac abnormalities, especially pericardial and valvar lesions, in patients with systemic lupus erythematosus. Echocardiography is invaluable in identifying these abnormalities and should be used routinely for cardiac evaluation of these patients.

Adolescent↗
PubMed1990

Improvement in exercise performance and hemodynamics by labetalol in patients with idiopathic dilated cardiomyopathy.

Labetalol, a combined alpha- and beta-blocking agent, was administered to 12 patients (mean age 55 years) with idiopathic dilated cardiomyopathy to examine its effects on symptomatology and exercise performance. Studies were performed before treatment, after 8 weeks of placebo, and after 8 weeks of labetalol therapy in a randomized, crossover, double-blind design. The mean (+/- SEM) dose of labetalol for the group was 275 +/- 29 mg. Compared to treatment with placebo, the maximum duration of symptom-limited exercise was significantly prolonged with labetalol (580 +/- 72 seconds to 683 +/- 71 seconds; p less than 0.005). Both the resting and peak exercise heart rate and systolic blood pressure were significantly reduced. Ascending aortic blood flow velocity was also measured by continuous-wave Doppler technique during exercise. Compared to placebo, treatment with labetalol conferred no significant change in cardiac output at rest but significantly improved cardiac output at maximum exercise (14 +/- 3%; p less than 0.001). Doppler-derived peak aortic flow velocity, acceleration, and flow velocity integral were also significantly improved at maximum exercise. Systemic vascular resistance, as derived from mean blood pressure/cardiac output, was reduced by 12 +/- 3% and 16 +/- 3% at rest and at maximum exercise, respectively. New York Heart Association functional class was improved (3.2 +/- 0.2 to 2.2 +/- 0.3; p less than 0.005). No major side effects from labetalol were encountered. Thus labetalol improves symptomatology, exercise capacity, and exercise hemodynamics and reduces systemic vascular resistance in patients with idiopathic dilated cardiomyopathy.

Cardiomyopathy, Dilated↗