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Biomedical subjects

B N Chiang

Publications and source records attributed to B N Chiang.

At least 109 records · Page 6Linked to original sources
PubMed1988

Coronary spasm complicating sclerotherapy of esophageal varices.

There are rare serious cardiac complications associated with endoscopic examination. An episode of coronary artery spasm developed in a 68-year-old man during endoscopic sclerotherapy for esophageal varices. The coronary artery spasm may have been triggered by a reflex increase in sympathetic discharge under stressful circumstances, and may occur most often in patients with preexisting heart disease. In patients with severe cardiac disease, ECG monitoring during the procedure seems justified.

Aged↗
PubMed1988

Effects of calcium-channel blockers on picrotoxin-induced centrogenic arrhythmias in cats.

Intravenous picrotoxin injection has been established as a model of producing arrhythmias, mainly through enhanced central sympathetic outflow. The effects of calcium-channel blockers, and a beta-blocker on these arrhythmias were tested in chloralose-anesthetized cats. Picrotoxin (10 mg/kg, i.v.) produced mostly ventricular, sometimes supraventricular tachycardias and ectopic beats, as well as a marked elevation of arterial blood pressure. Nifedipine at the doses of 2 micrograms/kg (i.v. or i.c.) and 5 micrograms/kg (i.v.) transiently suppressed the arrhythmias in some of the cats tested. With the dose of 10 micrograms/kg (i.v.), it promptly and consistently abolished the arrhythmias without recurrence and significantly reduced the blood pressure (-62 +/- 8/-59 +/- 8 mmHg, delta systolic pressure/delta diastolic pressure, p less than 0.001, n = 9). A similar degree of blood pressure reduction (-69 +/- 8/-67 +/- 7 mmHg, n = 6) after sodium nitroprusside (4-5 mg/kg, i.v.) injection abolished the arrhythmias in 4 of 6 cats; however, there was marked ECG evidence of myocardial ischemia in 3 cats. Verapamil (50 micrograms/kg, i.v.) transiently abolished the arrhythmias and significantly decreased the blood pressure (7/7 cats), whereas a larger dose (150 micrograms/kg) had a persistent effect (2/4 cats). Propranolol at a dose of 240 micrograms/kg also consistently abolished the arrhythmias without recurrence in all 4 cats. We conclude that nifedipine, verapamil and propranolol are effective in the treatment of picrotoxin-induced arrhythmias. This result indicates that calcium-channel blockers or beta-blockers may be clinically effective in the treatment or prevention of arrhythmias caused by intracranial lesions with enhanced sympathetic outflow.

Animals↗
PubMed1988

The mechanisms of inhibitory effects of liver extract on lymphocyte proliferation: II. Inhibition of DNA, RNA, and protein synthesis and their relationship to the effects of metabolic inhibitors.

The inhibitory effects of liver extract (LEx) on DNA, RNA, and protein synthesis in phytohaemagglutinin (PHA)-stimulated lymphocytes were studied by measuring the incorporation of labelled precursors. DNA, RNA, and protein synthesis were all inhibited by LEx in a dose-related manner. The inhibitory effect of LEx on protein synthesis was additive to the inhibitory effect of puromycin. The inhibitory effect of LEx on DNA synthesis was antagonistic to the inhibitory effect of mitomycin C. In the case of actinomycin D for RNA synthesis, its interactions with LEx were variable, but not additive. LEx may act as an inhibitor of protein synthesis through the mechanism of arginine-depletion.

Animals↗
PubMed1988

Radioimmunoassay of serum IGF-I and IGF-II in patients with chronic liver diseases and hepatocellular carcinoma with or without hypoglycemia.

Insulin-like growth factor (IGF) I and IGF-II were measured by radioimmunoassay in the sera of seven patients with acromegaly, 36 normal control subjects, 15 patients with chronic hepatitis, 15 patients with cirrhosis, 25 patients with hepatocellular carcinomas (HCCs) who did not have hypoglycemia, 20 patients with HCCs who did have hypoglycemia, and 10 patients with metastatic liver tumors. Both IGF-I and IGF-II levels decreased as liver disease progressed from the normal control stage to chronic hepatitis and cirrhosis, and both levels reflected the severity of liver disease. Patients with HCCs who had hypoglycemia had relatively higher IGF-II levels in their sera in comparison with those who did not have hypoglycemia (272 +/- 167.5 ng/ml vs 110.4 +/- 85.9 ng/ml [mean +/- SD], p less than 0.0005), despite the fact that those with hypoglycemia had more advanced liver cancer and had lower IGF-I levels in sera (16.7 +/- 14.1 ng/ml vs 46.8 +/- 47.9 ng/ml, p less than 0.002). It is possible that a labile IGF-II material is produced by the cancer cells of patients with hypoglycemia. This factor is reactive to the IGF-II receptor and partially cross-reacts with an antibody to IGF-II; it accounted for the mildly elevated levels of serum IGF-II. Hypoglycemia may be an integral effect of relatively elevated IGF-II like material and an advanced liver cancer. Also, higher serum alpha-fetoprotein (AFP) levels were more frequently found in patients with hypoglycemia who had relatively elevated IGF-II levels and short survivals.

Adolescent↗
PubMed1988

Structural changes in the mouse heart one year after brain exposure to 60Co gamma ray.

This study was conducted to investigate the sequential structural changes in the hearts of C3H male mice 1 to 12 months after brain irradiation. A single brain dose of 8 or 20 60Co gamma Gy was given to the animals at 4 months of age. Degenerative changes in the heart occurred, firstly at 6 months after irradiation, and became progressively more severe at 12 months. The cardiac muscle showed areas of focal myofibrillolysis, myofibrillar degeneration with loss of entire myofibrils, the presence of lysosomal-like bodies, and interstitial fibrosis. Coronary artery degeneration was also found at 12 months after irradiation; the major changes included smooth muscle degeneration with fibrosis, and the accumulation of debris and extracellular matrix. Quantitative analysis indicated that the degeneration of the arterial smooth muscle after 20 Gy irradiation (18.9%) was significantly higher than that of the unirradiated control (13.2%), and shammed control (13.3%) groups, p less than 0.05.

Animals↗
PubMed1988

Effects of verapamil on estimated hepatic blood flow in patients with HBsAg-positive cirrhosis.

Acute and chronic effect of verapamil on estimated hepatic blood flow were investigated in 12 patients with HBsAg-positive cirrhosis and portal hypertension. Acute administration of verapamil results in a significant increase (8%) in estimated hepatic blood flow (p less than 0.05). However, after chronic continued administration of verapamil, the mean value of estimated hepatic blood flow remains unchanged vis-a-vis basal values. Acute and chronic use of verapamil significantly reduced the hepatic venous pressure gradient for about an average of 20% at 1 hr after drug administration (p less than 0.05) and 18% 2 weeks later (p less than 0.05). This drop was associated with a significant reduction in hepatic vascular resistance by 39% at 1 hr later and by 37% 2 weeks later. Furthermore, the drop in hepatic vascular resistance was independent of any verapamil-induced changes in systemic hemodynamics. Verapamil significantly increased the indocyanine green plasma clearance and extraction ratio after acute or chronic use of the drug. We conclude that in patients with HBsAg-positive cirrhosis, the mechanism of verapamil in reducing the hepatic venous pressure gradient is predominantly by inducing a drop in hepatic portal vascular resistance.

Hepatitis B Surface Antigens↗
PubMed1987

Reduction of common carotid resistance upon stimulation of an area dorsal to the facial nucleus of cats.

In chloralose-urethane-anesthetized cats, electrical stimulation and glutamate injection on a small reticular area just dorsal to the facial nucleus (DFA) elicited an ipsilateral reduction in the common carotid resistance (CCR-reduction) with no or minimal change in other cardiovascular parameters. CCR-reduction was mediated via facial and glossopharyngeal nerves, involving partially muscarinic and partially non-muscarinic mechanisms.

Animals↗
PubMed1987

An initial screening of serum lipids and fatty acid profiles of hypertensive and normotensive subjects.

Serum lipids and their acyl group profiles from a group of hypertensive patients with elevated systolic and diastolic pressure were compared with normotensive subjects of matched age, body weight and dietary habits. The level of serum triacylglycerols was elevated in the hypertensive subjects, but the cholesterol level remained normal. The acyl groups of serum triacylglycerols and cholesterylesters from hypertensive subjects indicated a higher proportion of the saturated fatty acids (16:0 and 18:0) and a lower proportion of linoleic acid (18:2) as compared to normal controls. There was no obvious change in the level and acyl group composition of serum phosphatidylcholine between the two groups. Since the hypertensive and normotensive subjects indicated similar dietary habits, the resulting differences in serum lipids reflected an abnormality in the lipolytic process in the hypertensive subjects.

Body Weight↗
PubMed1987

Endomyocardial fibrosis with massive endocardial calcific deposits.

Massive endocardial calcific deposits in the left ventricular chamber is such an uncommon lesion that only three cases have been reported previously. This report describes an apparently asymptomatic patient with endomyocardial fibrosis and massive endocardial calcific deposits. The results of electrocardiography, echocardiography, angiography, and endomyocardial biopsy findings are presented, and the pathogenesis of massive endocardial calcification is speculated upon. The interesting point is that the clinical history and manifestation of this patient suggests that endomyocardial fibrosis may occur in a benign form and long-term survival may be expected.

Biopsy↗
PubMed1987

Modulatory effects of corticotropin-releasing factor on the delayed corticosteroid feedback in humans: implications of feedback sites.

We recently demonstrated the presence of a delayed phase of glucocorticoid feedback on nonstress-induced ACTH secretion in normal volunteers. In this study, we investigate the effects of corticotropin-releasing factor (CRF) on that delayed feedback pathway with an attempt to determine the sites on which glucocorticoid exerts its delayed feedback effects. Thirty normal subjects were subjected to study and each subject received a single midnight dosage of 30 mg/kg BW metyrapone before each test. The whole experiment was divided into two studies. In study I, we found that ovine CRF (oCRF) 1 microgram/kg BW alone as an IV bolus injection caused an increase in the plasma ACTH level, which persisted for at least 120 minutes. Continuous infusion of cortisol 25 mg/h alone for two hours produced a significant decrease in the plasma ACTH level; this fall of ACTH began 30 minutes after the onset of cortisol administration. When IV bolus injection of oCRF 1 microgram/kg BW and the continuous infusion of cortisol 25 mg/h for two hours were both given, the plasma ACTH level increased firstly and then decreased 60 minutes after the onset of cortisol administration, progressing thereafter to the end of the study. Study II showed in those who received the IV bolus injection of human CRF (hCRF) 100 micrograms and the continuous infusion of cortisol 25 mg/h for two hours, the plasma ACTH level increased firstly and began to decline 45 minutes after the onset of cortisol administration, progressing thereafter to the end of the test.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Arrhythmogenic effects of theophylline in human atrial tissue.

We studied the effects of theophylline on the transmembrane action potential and the contractile force of human atrial fibers obtained from the hearts of 15 patients, undergoing corrective open-heart surgery. Atrial fibers were perfused with Tyrode solution and driven electrically at a constant rate of 60 beats per min. Theophylline (0.1-1 mM) steepened the diastolic depolarization, increased the amplitude of oscillatory potential during diastole and facilitated the development of spontaneous slow response action potentials. These arrhythmogenic effects of theophylline were suppressed after diltiazem (0.1-0.3 microM) pretreatment. The present findings provide the electrophysiologic evidence that abnormal atrial automaticity as a result of triggered activity may be the underlying cause for atrial ectopic activity and multifocal atrial tachycardia in patients taking theophylline.

Adult↗
PubMed1987

Left ventricular diastolic function in hypertrophic cardiomyopathy: assessment by radionuclide angiography.

Diastolic left ventricular function was studied in 20 patients with obstructive hypertrophic cardiomyopathy, 10 with apical hypertrophic cardiomyopathy, and 20 control subjects. The left ventricular time-activity curve was filtered using Fourier expansion with 4 harmonics. The first and second derivatives of the filtered curve were used to define various parameters of the left ventricle. Isovolumic relaxation period and time to peak filling rate were prolonged in obstructive hypertrophic cardiomyopathy and apical hypertrophic cardiomyopathy (101.56 +/- 44.81 msec, 105.19 +/- 45.27 versus 72.19 +/- 29.36 (CS) P less than 0.05; 169.70 +/- 50.73 msec, 173.83 +/- 50.53 versus 138.02 +/- 29.54 (CS) P less than 0.05, respectively). Rapid filling period, diastasis, atrial contraction period, time to peak filling rate-isovolumic relaxation period, and filling fraction of diastasis were not significantly different in these groups. Fasting filling fraction was 11% lower in hypertrophic groups than in control subjects. The filling fraction of atrial contribution was 12% higher in hypertrophic groups. We conclude: Isovolumic relaxation period, rapid filling phase, and diastasis atrial contraction period can be clearly defined by this technique. Impaired relaxation is an important determinant of decreased left ventricular filling in patients with obstructive hypertrophic cardiomyopathy and apical hypertrophic cardiomyopathy. Prolonged time to peak filling rate is mainly due to increased isovolumic relaxation period in hypertrophic patients. Atrial contraction contributes to more stroke volume in patients with hypertrophic cardiomyopathy.

Adult↗
PubMed1987

Somatostatin effects in isolated human atrial fibres.

Effects of hypothalamic hormone somatostatin on the action potential and contractile force of 54 human atrial preparations obtained at cardiac surgery were studied with standard microelectrode techniques. In the atrial fibres responding to electrical stimuli with fast response action potentials in 4 mM [K]0 Tyrode solution (maximum rate of phase 0 depolarization greater than 50 V/s), somatostatin (10(-7) to 10(-6) M) reduced slightly the duration of action potential and decreased twitch force dose-dependently. In spontaneously active atrial fibres, somatostatin (10(-7) to 10(-6) M) abolished the action potentials in the preparations with low maximal diastolic potential (MDP, -48 +/- 2.8 mV), but induced only mild suppressive effect in the preparations with high MDP (-70 +/- 2.4 mV). When the fibres were depolarized in 27 mM [K]0 Tyrode solution, somatostatin decreased the maximum rate of depolarization and amplitude of the slow response action potentials induced by electrical stimuli. The delayed afterdepolarizations or triggered action potentials induced by high-frequency electrical drive in the presence of epinephrine were also suppressed by somatostatin. The above findings suggest that somatostatin may suppress the abnormal automaticity and the triggered activity in human atrial fibres through a reduction of cellular calcium.

Action Potentials↗
PubMed1987

Lack of effects of nifedipine on hepatic hemodynamics in patients with HBsAg-positive cirrhosis.

The acute effects of Nifedipine on hepatic venous pressure gradient (HVPG) and estimated hepatic blood flow (EHBF) were investigated in six patients with HBsAg-positive cirrhosis and portal hypertension by simultaneous hepatic venous catheterization. The mean arterial pressure significantly decreased by 18% at 1 h after sublingual administration of 10 mg Nifedipine. Significant increases in heart rate (13%) and cardiac output (20%) were also demonstrated in our patients 1 h after administration of Nifedipine. However, there were no significant changes in HVPG and EHBF after Nifedipine. We conclude that in patients with HBsAg-positive cirrhosis who receive Nifedipine, EHBF is maintained despite a substantial change in systemic hemodynamics, and that Nifedipine is not effective in acutely reducing HVPG.

Female↗
PubMed1987

The spermicidal potency of Coca-Cola and Pepsi-Cola.

The inhibitory effect of Old Coke, caffeine-free New Coke, New Coke, Diet Coke and Pepsi-Cola on human sperm motility was studied with a trans-membrane migration method. None of them could decrease sperm motility to less than 70% of control within one hour. A previous study which claimed a marked variation of spermicidal potencies among different formulations of Coca-Cola could not be confirmed. Even if cola has a spermicidal effect, its potency is relatively weak as compared with other well-known spermicidal agents.

Beverages↗
PubMed1987

The mechanisms of inhibitory effects of liver extract on lymphocyte proliferation. I. The extracellular mechanism of the inhibition.

Liver aqueous extract (LEx) can powerfully inhibit phytohaemagglutinin (PHA)-induced lymphocyte proliferation. The extracellular mechanism of inhibition by LEx was studied. There are three possibilities. (1) The possibility of extracellular inactivation of PHA by LEx was excluded by incubating cells with PHA first, followed by washing, and then incubating cells with LEx. The result was that LEx was still able to inhibit cell proliferation completely. (2) The possibility of competition for cell surface PHA receptors by LEx was excluded by the above experiments plus the use of N-acetyl-D-galactosamine to remove surface-bound PHA. Following this treatment, LEx was still able to inhibit cell proliferation completely. (3) The possibility of arginase-induced arginine depletion resulting in lymphocyte suppression was supported by the following experiments. Cells were incubated in media in which arginine was depleted either by reacting with LEx, and the media were afterwards bound with anti-arginase antibody, or by amino acid constituted media without arginine. The degrees of proliferation inhibition were similar in both treatments. These results indicate the important role of arginine-depletion by LEx, and may account for the LEx-induced lymphocyte inhibition.

Animals↗