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Biomedical subjects

Z Q Sun

Publications and source records attributed to Z Q Sun.

36 records · Page 2Linked to original sources
PubMed1996

I(to) and action potential notch are smaller in left vs. right canine ventricular epicardium.

Transmural heterogeneities of repolarizing currents underlie prominent differences in the electrophysiology and pharmacology of ventricular epicardial, endocardial, and M cells in a number of species. The degree to which heterogeneities exist between the right and left ventricles is not well appreciated. The present study uses standard microelectrode and whole cell patch-clamp techniques to contrast the electrophysiological characteristics and pharmacological responsiveness of tissues and myocytes isolated from right (RVE) and left canine ventricular epicardium (LVE). RVE and LVE studied under nearly identical conditions displayed major differences in the early repolarizing phases of the action potential. The magnitude of phase 1 in RVE was nearly threefold that in LVE: 28.7 +/- 6.2 vs. 10.6 +/- 4.1 mV (basic cycle length = 2,000 ms). Phase 1 in RVE was also more sensitive to alterations of the stimulation rate and to 4-aminopyridine (4-AP), suggesting a much greater contribution of the transient outward current (I(to) 1) in RVE than in LVE. The combination of 4-AP plus ryanodine, low chloride, or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (chloride channel blocker) completely eliminated the notch and all rate dependence of the early phases of the action potential, making RVE and LVE indistinguishable. At +70 mV, RVE myocytes displayed peak I(to) 1 densities between 28 and 37 pA/pF. LVE myocytes included cells with similar I(to) 1 densities (thought to represent subsurface cells) but also cells with much smaller current levels (thought to represent surface cells). Average peak I(to) 1 density was significantly smaller in LVE than in RVE at voltages more than or equal to +10 mV. Our data point to prominent differences in the magnitude of the I(to) 1-mediated action potential notch in cells at the surface of RVE compared with the LVE and suggest that important distinctions may exist in the response of these two tissues to pharmacological agents and pathophysiological states, as previously demonstrated for epicardium and endocardium. Our findings also suggest that a calcium-activated outward current contributes to the early repolarization phase in RVE and LVE and that the influence of this current, although small, is more important in the left ventricle.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1995

Effects of warm blood cardioplegic solution on myocardial protection.

To evaluate the effects of warm blood cardioplegic solution on myocardial protection, normothermic induction and terminal perfusion of oxygenated blood cardioplegia in combination with intermittent administration of cold blood cardioplegia during ischemia were studied in an isolated working rat heart model. The experimental protocol consisted of a 120 min cardioplegic arrest followed by 45 min normothermic reperfusion. Myocardial content of adenosine triphosphate (ATP), recovery of the left ventricular function, release of creatine phosphokinase (CPK) and ultrastructure of myocardium were assessed before and after ischemia. The results showed that the hearts preserved with warm blood cardioplegic induction and terminal perfusion had significantly higher levels of ATP, better recovery of cardiac function and lower releases and lower releases of CPK than those receiving cold blood cardioplegia alone, with myocardial tissue being of generally normal structure. These findings suggest that warm induction and terminal perfusion of blood cardioplegic solution can accelerate myocardial metabolic and functional recovery, preserve high-energy phosphate, reduce myocardial injury and enhance myocardial protection.

Adenosine Triphosphate↗
PubMed1994

Effects of dihydrexidine, a full dopamine D-1 receptor agonist, on delayed response performance in chronic low dose MPTP-treated monkeys.

Monkeys exposed to low doses of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) over long periods of time develop cognitive deficits without severe parkinsonian motor signs. In the present study we assessed the effects of the selective and full dopamine D-1 receptor agonist dihydrexidine on delayed response deficits in chronic low dose (CLD) MPTP-treated monkeys. Dihydrexidine caused a dose-dependent improvement in task performance, that could be blocked by the D-1 receptor antagonist SCH-23390. In addition to reducing the number of mistakes made during delayed response performance, dihydrexidine also improved task persistence. These data suggest that dihydrexidine may be useful in treating cognitive as well as motor deficits of parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Effects of dopamine agonists on delayed response performance in chronic low-dose MPTP-treated monkeys.

Monkeys exposed to low doses of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) develop difficulty in performing a previously learned delayed response (DR) task. In the present group of animals, performance deficits were manifested as a combination of mistakes or incorrect responses and no response errors, trials on which the animals failed to respond. Methylphenidate and the dopamine D2 receptor agonist LY-171555, at low doses, decreased the number of no-response errors but not mistakes. The partial D1 agonist SKF-38393 had no effects on no-response errors or mistakes. Thus, behavioral deficits associated with decreased task persistence may be amenable to treatment with dopamine agonists, and particularly D2 agonists, while cognitive performance per se may not be improved by such drugs. The similarities between this primate model and the cognitive/behavioral deficits associated with early Parkinson's disease and attention deficit hyperactivity disorder suggest that this may be a useful model for testing hypotheses concerning the pharmacological treatment of these disorders.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Effect of cardiopulmonary bypass on the specific immunity of the host.

T cell subsets and immunoglobulin (Ig) were observed sequentially with the OKT monoclonal antibodies rosette test and the rate scattering turbidimetry in 13 patients who underwent open heart surgery under cardiopulmonary bypass (CPB) for rheumatic heart diseases (RHD) and congenital heart diseases (CHD), before and after operation. Compared with preoperative values, in the early period after CPB, T helper cells, T helper cells to T suppressor cells ratio and IgG decreased significantly; whereas T suppressor cells increased, in RHD and CHD. The T cell subsets returned to the preoperative levels two weeks after CPB in RHD and CHD. The IgG came back to the preoperative levels two weeks after CPB in RHD and only one week after CPB in CHD.

Adult↗
PubMed1992

[Photodynamic therapy of nasopharyngeal carcinoma by argon or dye laser--an analysis of 137 cases].

137 cases of nasopharyngeal carcinoma were treated by photodynamic therapy (PDT). Forty-eight and 72 hours after iv administration of 3-5 mg/kg HpD, laser treatment with either argon or dye laser was given. Dye laser (630 nm) with over 350 mw output transmitted through quartz fiber was given to 57 patients. Argon laser (488 nm and 514.5 nm) was delivered to 80 patients. The results were: complete response 76 cases (55.47%) and marked response 47 cases (34.31%), with an over-all marked response rate of 89.78% (123/137). The efficacy and indication of photodynamic therapy for nasopharyngeal carcinoma using various light sources (argon and dye laser) are discussed.

Adult↗
PubMed1991

The role of G-protein in matrix-mediated motility of highly and poorly invasive melanoma cells.

Membranes from 2 K1735 murine melanoma clones of high invasive capacity show increased amounts of pertussis toxin (PT) substrate when compared to a weakly invasive cellular counterpart. Using a panel of specific G-protein antibodies, we identified Gi alpha 2 as the PT-sensitive G-protein uniquely abundant in highly invasive cells. In addition, RNA hybridization results confirm the immunoblot observations that Gi alpha 2 is present at higher levels in strongly invasive cells. This result suggests that the elevated expression of Gi alpha 2 in highly invasive cells is not entirely due to differences in either translational efficiency or protein degradation but is related to altered RNA transcriptional initiation, processing and/or degradation. ADP-ribosylation of Gi alpha-subunits by PT inhibited the fibronectin, laminin and collagen type-IV-stimulated motility of the 2 highly invasive clones, while PT treatment of cells from a poorly invasive clone resulted in little or no reduction of the fibronectin, laminin or collagen type-IV-stimulated lower motility. Furthermore, PT treatment of highly or poorly invasive K1735 clones does not result in any alteration in cellular cAMP accumulation, suggesting that the PT substrate is not linked with the adenylyl cyclase enzyme complex. The data suggest that a PT-sensitive G-protein, probably Gi alpha 2 regulates second messenger pathways that contribute to elevated motility in highly invasive K1735 cells.

Adenylate Cyclase Toxin↗
PubMed1990

Transmission of a Gaussian scanning beam through circular, square, and slit apertures: Part II. Experimental results for transmission through a circular aperture.

To perform an analysis of the hazards associated with scanned laser radiation to determine compliance with either federal or user standards, it is usually necessary to determine the amount of energy entering a specified aperture. A mathematical model has recently been developed that may simplify the hazard analysis. Experimental data and the mathematical model were compared for stationary and scanning Gaussian laser beams transmitted through a stationary 7-mm-diameter circular aperture, representing the dilated pupil of the human eye. Data were obtained for three values of laser beam diameter. The data and the mathematical model were found to agree within the estimated experimental error when the laser beam was concentric with the aperture, the situation typically encountered in compliance measurements. For two of the three laser beam diameters studied, as the eccentricity of the laser beam with respect to the center of the aperture was increased, the difference between the data and the mathematical model was found to increase. At the higher degrees of eccentricity, the percentage errors were shown to be highly sensitive to the errors in the determination of relative position.

Energy Transfer↗
PubMed1990

[Hematoporphyrin derivative (HPD) plus laser photodynamic therapy for nasopharyngeal carcinoma--analysis of 57 cases].

Fifty-seven cases of nasopharyngeal carcinoma treated by photodynamic therapy in our hospital from 1984 to 1986 are reported. Forty-eight to 72 hours after 5 mg/kg HPD injection, 630 nm laser with over 300 mW output transmitted through quartz fiber was given. Of 57 cases, 25 (43.9%) achieved complete response, 25 (43.9%) marked response and 7 (12.2%) mild response. The indications of photodynamic therapy for nasopharyngeal carcinoma are discussed.

Adult↗
PubMed1989

G-protein involvement in matrix-mediated motility and invasion of high and low experimental metastatic B16 melanoma clones.

Membranes from a B16 murine melanoma clone of high experimental metastatic capacity show increased amounts of pertussis toxin (PT) substrate when compared to a low metastatic counterpart. Using specific antibodies, we identified Gi2 as the PT-sensitive G-protein uniquely abundant in highly metastatic cells. ADP ribosylation of a G-protein alpha subunit by PT decreased both the migration of tumor cells through Matrigel (Collaborative Research, Bedford, MA) and the fibronectin-, laminin-, and collagen type IV-mediated motility of a high metastatic clone. Treatment of cells from a low metastatic clone with PT did not alter either the relatively low invasive capacity or lower motility of these cells. While cholera toxin treatment of cells resulted in decreased invasion and motility of both high and low metastatic clones, there were significant qualitative and quantitative differences, when compared to the PT effects, which indicated that the two toxins were acting on different second messenger systems. PT treatment of B16 clones of high or low experimental metastatic capacity does not result in any alteration in cellular cyclic AMP accumulation suggesting that the PT substrate is not linked with the adenylyl cyclase enzyme complex. The data suggest that a PT-sensitive G-protein, possibly Gi2, regulates second messenger pathways that contribute to the metastatic capacity of B16 melanoma cells.

1-Methyl-3-isobutylxanthine↗