Biomedical subjects

R Qiao

Publications and source records attributed to R Qiao.

6 recordsLinked to original sources

PubMed1998

Protein kinase C beta regulates heterologous desensitization of thrombin receptor (PAR-1) in endothelial cells.

We studied the effects of protein kinase C (PKC) activation on endothelial cell surface expression and function of the proteolytically activated thrombin receptor 1 (PAR-1). Cell surface PAR-1 expression was assessed by immunofluorescence (using anti-PAR-1 monoclonal antibody), and receptor activation was assessed by measuring increases in cytosolic Ca2+ concentration in human dermal microvascular endothelial cells (HMEC) exposed to alpha-thrombin or phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA). Immunofluorescence showed that thrombin and TPA reduced the cell surface expression of PAR-1. Prior exposure of HMEC to thrombin for 5 min desensitized the cells to thrombin, indicating homologous PAR-1 desensitization. In contrast, prior activation of PKC with TPA produced desensitization to thrombin and histamine, indicating heterologous PAR-1 desensitization. Treatment of cells with staurosporine, a PKC inhibitor, fully prevented heterologous desensitization, whereas thrombin-induced homologous desensitization persisted. Depletion of PKC beta isozymes (PKC beta I and PKC beta II) by transducing cells with antisense cDNA of PKC beta I prevented the TPA-induced decrease in cell surface PAR-1 expression and restored approximately 60% of the cytosolic Ca2+ signal in response to thrombin. In contrast, depletion of PKC beta isozymes did not affect the loss of cell surface PAR-1 and induction of homologous PAR-1 desensitization by thrombin. Therefore, homologous PAR-1 desensitization by thrombin occurs independently of PKC beta isozymes, whereas the PKC beta-activated pathway is important in signaling heterologous PAR-1 desensitization in endothelial cells.

Calcium↗

PubMed1997

Mechanisms of liquid flux across pulmonary alveolar epithelial cell monolayers.

Active transport of sodium by pulmonary alveolar epithelial cells (AEC) is believed to be an important component of edema clearance in the normal and injured lung. Data supporting this premise have come from measurements of sodium movement across AEC monolayers or from perfused lung model systems. However, direct measurement of fluid flux across AEC monolayers has not been reported. In the present work, AEC were studied with an experimental system for the measurement of fluid flux (Jv) across functionally intact cell monolayers. Primary adult rat type II alveolar epithelial cells were cultured on 0.8 micron nuleopore filters previously coated with gelatin and fibronectin. Intact monolayers were verified by high electrical resistance (> 1000 omega) at 4-5 d of primary culture. At the same time interval, transmission electron microscopy revealed cells with type I cell-like morphology throughout the monolayer. These were characterized by both adherens and tight junctional attachments. Fluid flux across the monolayers was measured volumetrically over a period of 2 h in the presence of HEPES-buffered DMEM containing 3% fatty acid-free bovine serum albumin. Flux (Jv) was inhibited 39% by 1 X 10(-4) M ouabain (P < 0.01) and 27% by 5 X 10(-4) M amiloride (P < 0.05). These data support the concept that AEC Na+/K(+)-ATPase and Na+ transport systems are important determinants of AEC transepithelial fluid movement in vitro.

Animals↗

PubMed1996

Tumor necrosis factor decreases thrombin receptor expression in endothelial cells.

We examined the effects of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF alpha) on the expression of proteolytically activated thrombin receptor (PATR) in human umbilical vein endothelial cells (HUVEC). PATR mRNA and protein levels were measured in confluent HUVEC monolayers after challenge with TNF alpha. Northern analysis indicated that TNF alpha treatment resulted in 2- to 3-fold decrease in PATR mRNA in a time- and dose-dependent manner. PATR mRNA level returned to the control level within 6 hr. The nuclear run-on assay indicated that the decreased mRNA signal was due to reduction in the transcription rate. Immunoblotting experiments indicated that the decrease in expression of PATR protein followed in time the decrease in mRNA; the lowest level of protein expression was achieved at 22 hr after TNF alpha treatment. PATR protein returned to basal value within 40 hr after TNA alpha challenge. To assess alterations in endothelial cell function after TNF alpha treatment, we measured thrombin-induced increase in cytosolic Ca2+ ([Ca2+]i) and the cell shape change (measured by decrease in electrical impedance of endothelial cell monolayer). In HUVEC treated with TNF alpha (100 U/ml for 22 hr), the rise in [Ca2+]i after thrombin challenge was approximately 2-fold less than in control thrombin-treated cells. The decrease in electrical impedance of HUVEC monolayers in response to thrombin after TNF alpha treatment was also significantly reduced. However, the rise in [Ca2+]i in response to histamine was not altered by TNF alpha pretreatment. In conclusion, TNF alpha exposure of endothelial cells decreased both mRNA and protein expression of PATR, which explain the decreased activation of thrombin generated signals after the TNF alpha exposure.

Amino Acid Sequence↗

PubMed1996

[Methodology for controlling healthy worker effect on coal miners' mortality].

This paper reports how to control the healthy worker effect (HWE) in a mortality study of coal miners. We used four methods, namely (1) age-specific corrective coefficient, (2) proportional mortality ratio (PMR), (3) corrective standarized mortality ratio (CSMR), and (4) a control group composed of factory workers. The results showed that all these methods could control HWE, and the total mortality in the coal miner group was significantly higher than that of the general population group (P < 0.05). However, the best way for controlling HWE awaits further studies.

Adult↗

PubMed1994

Removal of albumin microinjected in rat lung perimicrovascular space.

We used a microinjection approach to assess hydraulic properties of lung perimicrovascular adventitia (interstitial cuff surrounding microvessels). Isolated blood-perfused rat lungs held at constant airway pressure were microscopically viewed to identify subpleural venules (20 microns diam). Venular adventitia were microinjected with 20 nl of fluorescent albumin (4 g/dl), and then adventitial fluorescence was quantified at the injection site by either photometery or imaging. Nonlinear decay of adventitial fluorescence indicated liquid flux from the injection site into normal interstitium. In some experiments, we determined that the adventitial fluorescence flowed longitudinally along the venule length and filled single lymphatics. The fluorescence decay at the injection site was best described by equations of convective but not diffusive transport. The decay time constant (time to 37% initial), which relates inversely to hydraulic conductivity, increased 10-fold above baseline on lung expansion with airway pressure from 5 to 15 cmH2O (P < 0.05). However, presence or absence of blood flow, increase in filtration pressure, and tissue edema were all without effect on the time constant. Our estimate of the lower limit of baseline adventitial hydraulic conductivity was 5 x 10(-6) ml.cm-2.s-1.cmH2O-1. We conclude that hydraulic conductivity of perimicrovascular adventitia is not augmented by edema but that it is decreased by lung expansion.

Albumins↗

PubMed1993

Albumin and Ricinus communis agglutinin decrease endothelial permeability via interactions with matrix.

We studied the effects of albumin and the lectin Ricinus communis agglutinin (RCA) on hydraulic conductivity (Lp) of bovine pulmonary microvascular endothelial cell monolayers (BPMVEC) because of the evidence that albumin and RCA can interfere with transendothelial albumin permeability (Siflinger-Birnboim, A., J. Schnitzer, H. Lum, F. Blumenstock, C. Shen, P. Del Vecchio, and A. Malik. J. Cell. Physiol. 149: 575-584, 1991). BPMVEC were seeded on microporous polycarbonate filters, and the liquid flux was measured by collecting effluent into a tubing of known inner diameter at transendothelial hydrostatic pressures (P) ranging from 5 to 20 cmH2O. Lp was calculated as the slope of the relationship of liquid flux per unit surface area (Jv) vs. P. Addition of RCA (50 micrograms/ml) or albumin (5 mg/ml) to the endothelial cell medium containing albumin-free Hanks' balanced saline solution (HBSS) decreased total Lp (expressed x 10(-6) cm.s-1 x cmH2O-1) from 17.2 +/- 3.6 during HBSS to 4.7 +/- 0.9 during albumin and 5.7 +/- 1.6 during RCA (P < 0.01 for both). The RCA effect, but not that of albumin, was prevented by the addition of D-galactose (0.1 M) (the cognate hapten monosaccharide of RCA). We determined the contribution of the extracellular matrix (ECM) in decreasing the Lp by obtaining ECM after treatment of the monolayers with 0.025 M NH4OH to detach endothelial cells from the ECM. Basal ECM Lp (expressed x 10(-6) cm.s-1 x cmH2O-1) was 57.0 +/- 15.3, and it decreased to 19.7 +/- 4.3 and 17.5 +/- 2.9 during RCA and albumin, respectively (P < 0.01 for both). In contrast, RCA and albumin did not alter the filter Lp values. Another lectin, Ulex europaeus agglutinin, and the protein immunoglobulin G had no effect on Lp values.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗