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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 667 records · Page 37Linked to original sources
PubMed1982

Diacetyl derivative of nadolol. I. Ocular pharmacology and short-term ocular hypotensive effect in glaucomatous eyes.

On topical application to rabbit eyes, the diacetate ester of nadolol was more easily absorbed into ocular tissue than nadolol and was enzymatically hydrolyzed to nadolol within the eye. In a 24-hour clinical study, the ocular hypotensive activities of 0.5% diacetyl nadolol, 2% diacetyl nadolol, 2% nadolol, and 0.5% timolol maleate in subjects with open-angle glaucoma or ocular hypertension were compared. Both concentrations of diacetyl nadolol significantly reduced intraocular pressure during the first six hours. Two percent diacetyl nadolol was as effective as 0.5% timolol maleate during the first eight hours. During the remainder of the testing period, timolol showed greater IOP control. Two percent diacetyl nadolol and 2% nadolol showed similar ocular hypotensive effects both in magnitude and duration in this short-term study.

Absorption↗
PubMed1982

Effects of beta-bungarotoxin and phospholipase A2 from Naja naja atra snake venom on ATPase activities of synaptic membranes from rat cerebral cortex.

Non-neurotoxic phospholipase A2 of Formosan cobra venom possessed higher hydrolytic activity on phosphatidylcholine vesicles and also had higher inhibitory action on Na+-K+-ATpase and Mg2+-ATPase of the rat synaptic membrane than neurotoxic beta-bungarotoxin of Formosan Krait Venom. Na+-K+-ATPase was more susceptible than Mg2+-ATPase to the inhibitory action of toxins, especially in the presence of Triton X-100. The inhibition of ATPases by toxins followed the Michaelis-Menton equation. It is interesting that various phospholipids and ions influenced phospholipase A2 and beta-bungarotoxin inhibition of ATPases. Sphingomyelin antagonized phospholipase A4 more profoundly than beta-bungarotoxin, while egg lecithin had the reverse effect. Both phosphatidylethanolamine and phosphatidylserine protected Na+-K+-ATPase from the inhibitory action of phospholipase A2 but not that of beta-bungarotoxin. High K+ (30 mM) did not affect, while Ca2+ (0.2 mM) decreased, the inhibitory action of phospholipase A2 on Na+-K+-ATPase; in contrast, high K+ reversed, and Ca2+ increased, that of beta-bungarotoxin. These findings imply that phospholipase A2 and beta-bungarotoxin may have different substrate specificities and prefer different conformational states of the membrane for binding. This may explain, at least in part, why beta-bungarotoxin is neurotoxic, while phospholipase A2 is not.

Adenosine Triphosphatases↗
PubMed1982

Immediate diagnosis of acute myocardial infarction by two-dimensional echocardiography.

To define the role of portable two-dimensional echocardiography (2-D echo) in the immediate diagnosis of acute chest pain syndrome, 80 consecutive patients were studied. Adequate 2-D echo studies were obtained in 65 (81%). Thirty-three patients had clinical evidence of transmural or nontransmural acute myocardial infarction (AMI), 18 of whom had nondiagnostic initial ECGs. Thirty-two did not have a clinical AMI. Thirty-one of the 33 (94%) patients with clinical AMI had regional wall motion abnormalities on the initial 2-D echo; the other two had uncomplicated nontransmural AMIs, diagnosed only by ECG in one and by ECG and moderate elevation of CK-MB isoenzyme in the other. Twenty-seven of the 32 patients without clinical AMI had normal regional wall motion on the initial 2-D echo and none had a complication (severe arrhythmia, recurrent pain, heart failure or death) during the hospital course. Conversely, 10 of the 36 patients with initial 2-D echo regional wall motion abnormalities had a complication (p less than 0.05). Thus, in patients with acute chest pain syndrome, an initial 2-D echo that shows no regional wall motion abnormality suggests that such patients will not develop an AMI or clinical complication during the hospital course. An initial 2-D echo with regional wall motion abnormality identifies a high-risk group of patients who are likely to have AMI and important cardiac complications and may, therefore, benefit from admission to an intensive care unit.

Adult↗
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

Numerical simulation of the transient transport of inert gases in lung tissue.

A numerical simulation of the transport of xenon gas into healthy and oedematous lung tissue is described. The lung is modelled as four parallel tissue layers; alveolar membrane, interstitial fluid, capillary membrane, and blood, surrounded by a uniform air space. Using a finite difference representation of the governing diffusion equations, the concentration distribution of Xe gas in each of the layers of tissue is obtained for a step change in the Xe concentration in the air space. The effect of a thickening of the interstitial fluid layer, found in pulmonary oedema, on the kinetics of Xe transport is also considered. Computational findings indicate that a good approximation to the steady state profiles for Xe in the layers of tissue can be obtained simply by assuming that instantaneous equilibrium exists (as described by Henry's Law) between the lung tissue and surrounding air space. This same finding is documented even when the thickness of the interstitial fluid layer is increased by a factor of 40 above baseline values. The results suggest that the reduction in gas exchange which occurs in pulmonary oedema is caused by fluid flow into the alveoli, rather than a true diffusion deficit caused by a thicker alveolar-capillary barrier. The relationship of the present findings to those which would be obtained for more physiological input functions of Xe gas into the air space in also discussed.

Biological Transport↗
PubMed1981

Towards an evaluation of the accuracy of ventilatory rate constants derived from dynamic computer-assisted tomographic measurements.

Dynamic computer-assisted tomographic (CT) measurements using non-radioactive xenon gas have recently been employed along with a simple model of pulmonary transport to derive ventilation rate constants (K) in small tissue volumes. Inherent in the model description is the assumption that instantaneous diffusion equilibrium occurs between inhaled Xe gas and lung tissue. The validity of this assumption as it relates to the accuracy of the derived values of K has been considered for both normal and oedematous tissue, the latter characterised by a severe widening of the interstitial fluid space. It was found that only a small error in the predicted values for K results, when the simple model is applied to the dynamic cT measurements of xenon enhancement.

Models, Structural↗
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

Derealization syndrome and the outcome of schizophrenia: a report from the international pilot study of schizophrenia.

Eighty-five schizophrenic patients were found to have worse two-year follow-up outcome (history of remission, clinical course, improvement in psychotic symptoms, general treatment result) than 39 non-schizophrenic psychotic patients. The outcome of 36 schizophrenic patients with derealization at initial evaluation, especially when nine hebephrenics were excluded, was better than that of 49 schizophrenic patients without derealization but similar to that of 39 non-schizophrenic patients. The hebephrenics with derealization demonstrated similar outcomes to schizophrenic patients without derealization. In non-schizophrenic patients, derealization had no prognostic significance.

Adolescent↗
PubMed1981

Apical cross-sectional echocardiography. Standard for the diagnosis of idiopathic mitral valve prolapse syndrome.

In light of the nonspecificity of left ventricular angiography and physical examination, and the limitations of M-mode echocardiography to define the presence of mitral valve prolapse syndrome, we evaluated left ventricular longitudinal and apical four-chamber tomographic views of cross sectional echocardiography in 19 subjects with normal left ventricular cineangiography and in 5 patients with congestive cardiomyopathy. None had auscultatory findings suggestive of mitral valve prolapse syndrome. In all 24 control subjects, the apical view demonstrated the coaptation point and the leaflets of the mitral valve to lie inside the left ventricular cavity. A retrospective analysis of 900 consecutive cross sectional echocardiographic studies revealed 105 subjects with no evidence of structural heart disease other than the presence of the mitral valve leaflets in the left atrium in systole defining the existence of idiopathic mitral valve prolapse syndrome. Both mitral leaflets were prolapsed in 90 percent of the involved populations, and the apical tomographic cross sectional echocardiographic view was superior to the left ventricular longitudinal view for the detection of anterior leaflet prolapse. These data suggest that the apical cross sectional view may be the single best technique to define the presence of idiopathic mitral valve prolapse syndrome.

Adolescent↗
PubMed1981

Tricuspid valve prolapse diagnosed by cross-sectional echocardiography.

Cross-sectional echocardiography utilizing the apical and longitudinal right ventricular inflow tract views was used to investigate the tricuspid valve in 64 patients with mitral valve prolapse and 16 controls who had no angiographic or echocardiographic evidence of mitral valve prolapse. The tricuspid valve leaflets and their coaptation point in systole were found to be below (towards the right ventricular apex) the level of the tricuspid valve ring in systole in all controls. Tricuspid valve prolapse, defined as the leaflet(s) of the tricuspid valve lying above the tricuspid valve ring level within the right atrium, was seen in 31/64(48 percent) of patients with mitral valve prolapse. The right ventricular inflow tract view demonstrated tricuspid valve prolapse most readily compared to the apical view, and 29 of the 31 patients with tricuspid valve prolapse had prolapse of at least two leaflets of the tricuspid valve. The 31 patients with both mitral and tricuspid valve prolapse, when compared to the 33 patients with mitral valve prolapse alone, had more symptomatology and abnormal physical findings.

Adult↗