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Biomedical subjects

H T Tien

Publications and source records attributed to H T Tien.

At least 37 records · Page 2Linked to original sources
PubMed1986

Action of calcium channel and beta-adrenergic blocking agents in bilayer lipid membranes.

The action of beta-adrenergic blockers (propranolol, exprenolol, metoprolol, sotalol, atenolol, timolol) and calcium-channel blockers (verapamil, diltiazem) on the electrical properties and fluidity of bilayer lipid membranes (BLM and liposomes) has been investigated. When antibiotic ionophore substances were used as a probe, the electrical measurements showed that many of the drugs inhibited the cation transport across the membrane facilitated by the mobile carrier valinomycin, while having no significant effect on the cation transport through channels formed by gramicidin. The ability of the drugs to decrease the carrier-dependent membrane conductance was correlated to their partition into the lipid bilayer and the magnitude of transmembrane potential induced by them. In the TEMPO ESR spectral measurements, a number of beta-adrenergic and calcium blockers showed the fluidizing effect on liposomes composed of different lipids. The drug concentration required for a detectable change in TEMPO spectra parameter (f) was rather high (0.01 M verapamil), and the variation of pH from 6.5 to 3.0 did not affect the fluidizing effect of the drugs.

Adrenergic beta-Antagonists↗
PubMed1986

Cell-mediated tumor-killing effect studied by using bilayer lipid membranes.

The bilayer lipid membrane (BLM) system was used to investigate the tumor killing effect of natural killer (NK) cells under various experimental conditions. It was found that NK cells interact specifically with BLMs made from lipids and proteolipids isolated from target K562 cells inducing an increase of the membrane conductance. This effect was more pronounced when the NK cells were pretreated with interferon. A similar effect was observed when NK cells were pretreated with sodium selenite. The results suggest that changes in membrane conductance and permeability are involved in the mechanism of the tumor-killing effect mediated by NK cells.

Cell Membrane↗
PubMed1985

Intermembrane linkage mediated by tubulin.

Two membranes from brain lipids were formed in the presence of brain tubulin and their electrical potentials were simultaneously measured. When electrical pulses were applied across one of them, displacements of the potential of the other membrane were found even when the membranes were not in contact. This effect was observed only in the presence of polymerized tubulin. It was not found in the presence of depolymerized tubulin or in other control experiments. The findings suggest that the microtubule fiber networks may serve as an interconnecting system between membranes or membrane bounded compartments.

Animals↗
PubMed1985

Application of voltammetric techniques to membrane studies.

The application of voltammetric methods to planar bilayer lipid membranes (BLM) studies is described. BLM-compound interaction experiments lead to the measurement of the membrane current underlying transport phenomena. From measurements of current/voltage of BLM in unstirred solutions as a function of scan rates, it is possible to obtain both thermodynamic and kinetic information. In past years, a variety of techniques have been used to study the electrical properties of BLMs, but in terms of versatility, the cyclic voltammetric technique is outstanding. Cyclic voltammetry is the definitive means of characterizing the redox process of electroactive membranes.

Electric Conductivity↗
PubMed1984

A voltammetric investigation of TCNQ-containing bilayer lipid membranes.

Cyclic voltammetry (CV) is a useful tool for investigating electrochemical redox reactions. A number of bilayer lipid membranes containing TCNQ (7,7,8,8-tetracyanoquinodimethane) have been studied by the CV technique. The results indicate electron movement across the lipid bilayer and redox reactions at the membrane/solution interfaces.

Coloring Agents↗
PubMed1984

Antigen-antibody-complement reaction studies on micro bilayer lipid membranes.

The ion permeability of lipid membranes formed on Millipore and Nuclepore filters has been found to exhibit stepwise reductions in electrical resistance in the presence of Forssman antigen, appropriate antiserum and complement. The results appear to support the "hydrophobic doughnut" or transmembrane channel hypothesis, which envisions several polypeptide chains anchoring from more than one terminal complement component to interact with one another within the lipid bilayer. Channel formation in these artificial membranes is believed to be due to the insertion of complement proteins. Concentrations and temperature studies were carried out to ascertain that the electrical responses were owing to the generation of stable channels by complement across the membrane. The diameter of these channels was estimated to be in the order of 100 A.

Animals↗
PubMed1980

Photoelectrospectrometry of bilayer lipid membranes.

These different bilayer lipid membrane systems were studied under visible and ultraviolet illumination. The first system consisted of a bilayer lipid membrane formed with a mixture of phospholipids and cholesterol, to one side of which purple membrane fragments from Halobacterium halobium were added. The second system consisted of a membrane formed from spinach chloroplast extract. When either of these membrane systems was illuminated with ultraviolet and visible radiation, photopotentials were observed and photoelectric action spectra were recorded (the technique is termed photoelectrospectrometry). Each spectrum had a definite structure which was characteristic of each of the modified membranes. The third system studied consisted of an otherwise photoinactive membrane formed with a mixture of phospholipids and cholesterol, to one side of which chymotrypsin was added. When the membrane was illuminated with visible light no photoresponse was observed. On the other hand, a photopotential which increased with incubation time was observed when the membrane was illuminated with ultraviolet light. Since, in our systems, the photoresponses have been observed to be due to certain species incorporated into the membrane, it appears that photoelectrospectrometry is a useful tool for studying lipid-protein interactions, constituent organization and energy transfer in membranes.

Bacteriorhodopsins↗
PubMed1978

Bilayer lipid membranes (BLM) study of antigen-antibody interactions.

Previous work of del Castillo and co-workers has shown that bilayer lipid membranes (BLM) can be used as transducers for detection of antigen-antibody reactions. The present experiments extend the previous work by incorporating complement into the BLM system. The results indicate that the antigen-antibody complex or the complement has no ability to affect the BLM system separately, but when carefully combined they will destabilize the BLM as a tool for investigating immunological reactions is suggested.

Antibodies↗