Biomedical subjects

Yuehong Tong

Publications and source records attributed to Yuehong Tong.

5 recordsLinked to original sources

PubMed2006

Monitoring in real time with a microelectrode the release of reactive oxygen and nitrogen species by a single macrophage stimulated by its membrane mechanical depolarization.

Macrophages are key cells of the immune system. During phagocytosis, the macrophage engulfs a foreign bacterium, virus, or particle into a vacuole, the phagosome, wherein oxidants are produced to neutralize and decompose the threatening element. These oxidants derive from in situ production of superoxide and nitric oxide by specific enzymes. However, the chemical nature and sequence of release of these compounds is far from being completely determined. The aim of the present work was to study the fundamental mechanism of oxidant release by macrophages at the level of a single cell, in real time and quantitatively. The tip of a microelectrode was positioned at a micrometric distance from a macrophage in a culture to measure oxidative-burst release by the cell when it was submitted to physical stimulation. The ensuing release of electroactive reactive oxygen and nitrogen species was detected by amperometry and the exact nature of the compounds was characterized through comparison with in vitro electrochemical oxidation of H2O2, ONOO-, NO*, and NO2(-) solutions. These results enabled the calculation of time variations of emission flux for each species and the reconstruction of the original flux of production of primary species, O2*- and NO*, by the macrophage.

Animals↗

PubMed2006

Variable coding sequence protein A1 as a marker for erectile dysfunction.

OBJECTIVE: To investigate whether variable coding sequence protein A1 (Vcsa1) is down-regulated in rat models of diabetes and ageing, and to investigate the role of Vcsa1 in erectile function, as Vcsa1 is the most down-regulated gene in the corpora of a rat model of neurogenic erectile dysfunction (ED). MATERIALS AND METHODS: Quantitative reverse-transcriptase polymerase-chain reaction was used to determine Vcsa1 expression in the corpora of rats in three models of ED, i.e. streptozotocin-induced diabetes, retired breeder (old), and neurogenic (bilaterally ligated cavernosal nerves), and in control rats. To confirm a physiological role of Vcsa1 in erectile function, we carried out gene transfer studies using a plasmid in which Vcsa1 was expressed from a cytomegalovirus promoter (pVAX-Vcsa1). This plasmid was injected intracorporally into old rats, and the effect on physiology of corporal tissue was analysed by intracorporal/blood pressure (ICP/BP) measurement and histological analysis, and compared with the effects of a positive control plasmid (pVAX-hSlo, which we previously reported to restore erectile function in diabetic and ageing rats) and a negative control plasmid (pVAX). RESULTS: In each rat model of ED there was a significant down-regulation of the Vcsa1 transcript of at least 10-fold in corporal tissue. Remarkably, intracorporal injection with 80 microg pVAX-Vcsa1 caused priapism, as indicated by visible prolonged erection, histological appearance, and elevated resting ICP/BP. Lower doses of pVAX-Vcsa1 (5 and 25 microg) increased ICP/BP over that in untreated controls. CONCLUSION: These results show that Vcsa1 has a role in erectile function and might be a molecular marker for organic ED. The role of Vcsa1 in erectile function suggests that it could represent a novel therapeutic target for treating ED.

Aging↗

PubMed2003

Characterization and property of DNA incorporated bilayer lipid membranes.

Calf-thymus DNA-incorporated bilayer lipid membranes supported on a glassy carbon (GC) electrode was prepared by making layers of phosphatidylcholine dimyristoyl (DMPC) on GC electrode. DNA in the BLM was characterized by cyclic voltammetry, IR and AFM, and lipid layers formed on the GC electrode were demonstrated to be a bilayer lipid membrane by electrochemical impedance experiment. In IR and AFM experiments the findings indicated that DNA was incorporated into BLM. The ion channel of bilayer lipid membranes incorporated was studied. The result showed that the ion channel was opened in the presence of the stimulus quinacrine. In the absence of quinacrine the channel was switched. The process can repeat itself many times. The impedance spectroscopy measurements demonstrate that the stimulus quinacrine opens the channel for permeation of marker ion. The mechanism of forming an ion channel was investigated.

Animals↗

PubMed2002

Study of electron transfer across the liquid/ice-like matrix interface by scanning electrochemical microscopy.

In this work, we report the findings of a study on scanning electrochemical microscopy (SECM) to investigate the interfacial electron-transfer (ET) reaction between the 7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ*-) in 1,2-dichloroethane and ferricyanide in an ice-like matrix (a mixture of insulting ice and conductive liquid) under low temperatures. Experimental results indicate that the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to a liquid/liquid interface at temperatures above -20 degrees C. Furthermore, imaging data show that the surface of the ice-like matrix is microscopically flat and physically stable and can be applied as either a conductive or an insulting substrate for SECM studies. Perchlorate ion was selected as the common ion in both phases, the concentrations of which controlled the interfacial potential difference. The effect of perchlorate concentration in the DCE phase on interfacial reactions has been studied in detail. The apparent heterogeneous rate constants for TCNQ*- oxidation by Fe(CN)6(3-) in another phase under different temperatures have been calculated by a best-fit analysis, where the experimental approach curves are compared with the theoretically derived relationships. Reaction rate data obey Butler-Volmer formulation before and after the freezing point, which is similar to most other known cases of ET reactions at liquid/liquid interfaces. However, there is a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition. At temperatures below -20 degrees C, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrix became an insulating one, which indicates that the aqueous phase is really a frozen phase.

Journal Article↗

PubMed2002

Electrochemical study of ion channel behavior in incorporated poly L-glutamate bilayer lipid membranes.

The lipid layer membranes were fabricated on the glassy carbon electrode (GC) and demonstrated to be bilayer lipid membranes by impedance spectroscopy. The formation of incorporated poly L-glutamate bilayer lipid membrane was achieved. The ion channel behavior of the incorporated poly L-glutamate membrane was determined. When the stimulus calcium cations were added into the electrolyte, the ion channel was opened immediately and exhibited distinct channel current. Otherwise, the ion channel was closed. The cyclic voltammogram at the GC electrode coated with incorporated poly L-glutamate DMPC film response to calcium ion is very fast compared with that at the GC electrode coated only with DMPC film. Ion channel current is not dependent on the time but on the concentration of calcium. The mechanism of the ion channel formation was investigated.

Calcium↗