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S N Yang

Publications and source records attributed to S N Yang.

64 records · Page 4Linked to original sources
PubMed1991

Gel electrophoresis of reacting macromolecules. Rate-limited self-association.

Prompted by experimental sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis (PAGE) patterns of an oligomerizing 73-residue peptide, PAGE and gradient PAGE patterns were simulated numerically for two rate-limited, reversible self-associating systems, viz., monomer-dimer and monomer-dimer-tetramer interactions. A wide range of values for rate constants and other relevant parameters was examined. The cardinal result for interactions with half-times comparable to the time of electrophoresis is that the number of peaks in the pattern can exceed the number of interacting species. Since peaks of intermediate migration velocities are composed of interconverting monomer and oligomers, molecular weights corresponding to individual species cannot be assigned to them.

Computer Simulation↗
PubMed1990

Regulation of cytosolic sodium ion activity in frog sartorius.

To explore the regulation of cytosolic sodium ion activity in the frog sartorius, we used Na(+)-selective microelectrodes to monitor intracellular sodium ion activity in situations of lowering external sodium concentration and elevating external potassium concentration. Reductions of 20%, 40%, 60% and 80% in extracellular sodium concentration produced slight but statistically insignificant changes in the membrane potential of the muscle. However, cytosolic sodium ion activity decreased significantly from 10.0 +/- 1.1 mM to 7.8 +/- 1.1 mM, 7.1 +/- 1.4 mM, 6.5 +/- 1.2 mM and 5.9 +/- 1.1 mM, respectively. In addition, elevation of the external potassium concentration from 2 mM to 12 mM, 32 mM and 62 mM caused respective stepwise depolarization of membrane potential from -87.2 +/- 1.6 mV to -62.4 +/- 3.6 mV, -45.4 +/- 3.0 mV, -27.2 +/- 1.8 mV. Under these conditions, the cytosolic sodium ion activity decreased from 10.5 +/- 1.4 mM to 7.3 +/- 1.6 mM, 6.4 +/- 1.1 mM and 5.2 +/- 0.8 mM, respectively. The results illustrate that the net sodium flux is out of cell either in the reduction of sodium chemical gradient or in the potassium depolarization across the cell membrane.

Animals↗
PubMed1990

[The functional connection of rat habenular nucleus and lateral hypothalamic area in the regulation of cardiovascular activities].

The electrical stimulation of the lateral hypothalamic area (LH) in the rat elicited an obvious rise of the arterial pressure and increase in the heart rate. After the microinjection of lidocaine hydrochloride into the habenular nucleus (Hb) on the same side of the electrode, the vasopressor effect elicited by the electrical stimulation of the LH was blocked by 38.9% and the effect on heart rate was reduced by 44.4%. After the microinjection of lidocaine hydrochloride into the bilateral Hb, the vasopressor effect elicited by the electrical stimulation of the LH was blocked by 40.7% and the effect on heart rate was reduced by 41.2%. After the microinjection of the artificial cerebrospinal fluid into the unilateral or bilateral Hb, the cardiovascular effect elicited by the electrical stimulation of the LH was not affected. The electrical stimulation of the Hb in the rat elicited an obvious rise of the arterial pressure, but the heart rate was not changed significantly. After the microinjection of lidocaine hydrochloride into the LH on the same side of the electrode the vasopressor effect elicited by the electrical stimulation of the Hb was blocked by 63.2%. After the microinjection of lidocaine hydrochloride into the bilateral LH the vasopressor effect elicited by the electrical stimulation of Hb was blocked by 62.6%. After the microinjection of the artificial cerebrospinal fluid into the unilateral or bilateral LH, the cardiovascular effect elicited by the electrical stimulation of the Hb was not affected. The present study shows that the Hb and LH exert synergistic action in the regulation of the cardiovascular activities.

Animals↗
PubMed1989

The electrophysiological and mechanical effects of atrial natriuretic peptide and acetylcholine on guinea pig ventricular papillary muscle.

The direct effects of atrial natriuretic factor (ANF) and acetylcholine (ACh) on isolated guinea pig ventricular papillary muscle were studied. ANF (3 x 10(-9) - 3 x 10(-7) M), a cardiogenic hormone, had no significant electrical or mechanical effects on guinea pig papillary muscle driven at a frequency of 60 beats/min in normal (4 mM) and high [K]0 (27 mM) Tyrode solutions. On the other hand, ACh (3 x 10(-8) - 3 x 10(-7) M) caused a significant shortening of action potential duration and the contractile force showed no change or a slight decrease. At high concentration (5 microM), ACh reduced action potential durations at 50% and 90% repolarization (APD50 and APD90) by 10.5 +/- 2.1% and 12.4 +/- 1.8%, respectively, but the contractile force was slightly increased by 9.8 +/- 1.2%. In eleven of twenty-six preparations, spontaneous activity occurred and intermingled with driven activity. The ectopic rhythms were suppressed by ACh (1-5 microM). The changes in electrical but not mechanic activity induced by ACh were suppressed in the presence of five micromolar atropine. These results reveal that, in guinea pig papillary muscle, ANF had no direct chronotropic or inotropic effect. ACh may reduce APD and spontaneous discharges through an activation of muscarinic receptors but enhance twitch tension through other mechanisms.

Acetylcholine↗
PubMedDate not supplied

Muscarinic activation causes biphasic inotropic response and decreases cellular Na+ activity in canine cardiac Purkinje fibers.

In this study, the effects of carbachol (CCh) on twitch tension, intracellular Na+ activity (aiNa), and action potential were simultaneously measured in canine cardiac Purkinje fibers in order to examine the regulation of inotropy through muscarinic receptors and its relation to aiNa. In fibers driven at 1 Hz, CCh (10 microM) initially and transiently decreased and then increased the twitch tension by 36 +/- 8%. The action potential showed a significant elevation of the plateau and a significant shortening of the duration at 90% repolarization (APD90), from 403 +/- 7 to 389 +/- 7 ms. The aiNa decreased from 7.4 +/- 0.4 to 6.7 +/- 0.3 mM (n = 23, p < 0.05). Atropine (1 microM) decreased the twitch tension by 21 +/- 6% (n = 7, p < 0.05) without significant effects on the action potential and aiNa, and inhibited the effects of CCh. Cs+ (20 mM) increased the plateau height and APD90, enhanced the twitch tension by 66 +/- 24%, but decreased aiNa from 7.3 +/- 0.3 to 6.3 +/- 0.4 mM (n = 6, p < 0.05). In the presence of 20 mM Cs+, some fibers generated slow responses. The addition of 10 microM CCh further increased the twitch tension and APD90, and decreased aiNa from 6.3 +/- 0.4 to 5.3 +/- 0.3 mM. Ouabain (0.3 microM) increased the twitch tension and aiNa, and inhibited the CCh-induced decrease of aiNa. In the presence of ouabain, 20 mM Cs+ depolarized the fiber and generated slow responses with a decreased aiNa. The addition of 10 microM CCh enhanced the slow action potential, and increased aiNa although there was a transient decrease during early exposure. These results suggest that activation of muscarinic receptors in canine Purkinje fibers results in an enhancement of the Na+-K+ pump activity and a biphasic inotropic response, probably via different receptor subtypes. The inhibitory effect, most likely through M2 receptors, is associated with the activation of K+ channels. The stimulatory effect, on the other hand, is probably due to the action on the M1 receptors, resulting in increases in Ca2+ currents.

Action Potentials↗
PubMedDate not supplied

Differentiating benign and malignant pulmonary lesions with FDG-PET.

The purpose of this retrospective study was to evaluate the efficacy of positron emission tomography (PET) with 18F-fluoro-2-deoxyglucose (FDG) to differentiate benign from malignant pulmonary lesions. Fifty-five patients, suspected of having primary pulmonary neoplasm based on chest radiographic findings, underwent FDG-PET scanning. Pathological diagnoses were obtained in 41 patients with a total of 43 pulmonary lesions. The other 14 patients (14 lesions) were followed-up clinically for at least four months. The standard uptake value (SUV) was determined in each patient. The SUV of the 15 benign and 40 malignant pulmonary lesions were 1.60+/-0.42 and 6.14+/-2.67, respectively. If SUV was > 2.50, the pulmonary lesion was considered as a malignant pulmonary lesion. FDG-PET could correctly detect 34 true-positive and 15 true-negative pulmonary lesions. However, 6 false-positive and one-false negative pulmonary lesions were misdiagnosed by FDG-PET. The sensitivity, specificity and accuracy of FDG-PET to differentiate between benign and malignant pulmonary lesions were 94%, 71% and 86%, respectively. FDG-PET can accurately detect malignant pulmonary lesions with a high sensitivity. However, false-positive FDG-PET findings caused by some inflammatory processes may decrease its specificity.

Adult↗