Biomedical subjects

Y T Hu

Publications and source records attributed to Y T Hu.

11 recordsLinked to original sources

PubMed2003

Estimating surfactant surface coverage and decomposing its effect on drop deformation.

A novel method is introduced to estimate surface coverage and the equation of state of insoluble surfactant on droplets, involving measurement of interfacial tension on a single parent drop and progressively subdivided generations of daughter drops. This has enabled quantitative decomposition of the dilution, tip-stretching, and Marangoni effects of surfactants on drop deformation. For a small viscosity ratio of 0.09, the Marangoni effect dominates, increasing first and then decreasing with surface coverage, the dilution effect is significant at high, and tip-stretching only at low surface coverage. For a viscosity ratio of 2.3, the dilution effect dominates, and neither Marangoni nor tip-stretching effects play an important role.

Journal Article↗

PubMed1999

Expression of dominant-negative src-homology domain 2-containing protein tyrosine phosphatase-1 results in increased Syk tyrosine kinase activity and B cell activation.

The Src-homology domain 2 (SH2)-containing cytoplasmic tyrosine phosphatase, SHP-1 (SH2-containing protein tyrosine phosphatase-1), interacts with several B cell surface and intracellular signal transduction molecules through its SH2 domains. Mice with the motheaten and viable motheaten mutations are deficient in SHP-1 and lack most mature B cells. To define the role of SHP-1 in mature B cells, we expressed phosphatase-inactive SHP-1 (C453S) in a mature B cell lymphoma line. SHP-1 (C453S) retains the ability to bind to both substrates and appropriate tyrosine-phosphorylated proteins and therefore can compete with the endogenous wild-type enzyme. We found that B cells expressing SHP-1 (C453S) demonstrated enhanced and prolonged tyrosine phosphorylation of proteins with molecular masses of 110, 70, and 55-60 kDa after stimulation with anti-mouse IgG. The tyrosine kinase Syk was hyperphosphorylated and hyperactive in B cells expressing SHP-1 (C453S). SHP-1 and Syk were coimmunoprecipitated from wild-type K46 cells, K46 SHP-1 (C453S) cells, and splenic B cells, and SHP-1 dephosphorylated Syk. Cells expressing SHP-1 (C453S) showed increased Ca2+ mobilization, extracellular signal-regulated kinase activation, and homotypic adhesion after B cell Ag receptor engagement. Thus, SHP-1 regulates multiple early and late events in B lymphocyte activation.

Animals↗

PubMed1995

[Effect of sodium suberogorgin on hemodynamics and myocardial ischemic-reperfused injury in isolated guinea pig working hearts].

AIM: To study the actions of sodium suberogorgin (Sub) on normal- and myocardial ischemic-reperfused-working hearts. METHODS: The isolated guinea pig working hearts were perfused with edetic acid (0.2 mumol.L(-1))-Krebs-Henseleit solution by left pulmonary vein at 37 +/- 0.5 degrees C. The perfusing pressure of left atrium and the afterload of left ventricle were maintained at 1.0 and 7.2 kPa, respectively. During 50-min low-flow global ischemia, coronary flow was maintained at 4.7 +/- 0.2% of normal working hearts via retrograding perfusion. Reperfusion lasted 35 min following ischemia. RESULTS: Before ischemia, the aortic pressure, left ventricular systolic pressure, the maximal rate of left ventricular pressure change (+ dp/dtmax and -dp/dtmax), cardiac output, stroke volume, left ventricular end-diastolic pressure, and heart rate of working hearts treated with Sub 10 mumol.L(-1) for 10 min were increased by 14%, 17%, 17%, 22%, 15%, 32%, -200%, and -11%, respectively. These parameters were reduced when Sub was increased to 50 mumol.L(-1). Reperfusion aggravated the myocardial damages induced by ischemia. Sub 10 mumol.L(-1) used before and during low-flow ischemia completely restored all above parameters except heart rate to the level of preischemia. When Sub was increased to 50 mumol.L(-1), only an attenuation of myocardial damage was observed. CONCLUSION: Sub obviously improved the ischemic-reperfused injury in isolated working hearts.

Animals↗

PubMed1992

[Excitant effect of sodium suberogorgin on isolated rabbit ileum].

Suberogorgin was isolated from Gorgoniae suberogorgia sp from South China Sea. The isolated rabbit ileum contracted in a concentration-dependent manner by suberogorgin-Na (Sub) 2.13 mumol.L-1 or higher. Sub 213 mumol.L-1 had no effect on the relaxation induced by norepinephrine and isoprenaline 10-100 mumol.L-1 on ileum. The stimulation of Sub on ileum was antagonized by atropine 56 mumol.L-1 or indometacin 0.35 mmol.L-1 and was partly blocked by indometacin 0.17 mmol.L-1, but was not affected by diphenhydramine 10 mumol.L-1. On the contracted ileum induced by neostigmine 1.7 mumol.L-1, acetylcholine 0.1 mumol.L-1 increased the tension but Sub 213 mumolL-1 did not. Sub obviously inhibited the acetylcholinesterase (AChE) from mouse brain hemogenates in vitro. Its pI50 (negative logarithm of molar concentration causing 50% inhibition of AChE) was 4.18, while the pI50 of neostigmine was 4.75. The results indicated that the ileum-excitant action of Sub was chiefly related to the inhibition of AChE.

Acetylcholinesterase↗

PubMed1990