Biomedical subjects

S L Wung

Publications and source records attributed to S L Wung.

4 recordsLinked to original sources

PubMed1997

Restriction mapping of genes by capillary electrophoresis with laser-induced fluorescence detection.

Restriction mapping is one of the essential steps in gene analysis and molecular biology studies. Slab gel electrophoresis is the traditional way to separate DNA fragments for restriction mapping. However, slab gel electrophoresis does not provide sufficient resolution as required in many mapping applications, and the use of radioisotopes in traditional mapping methods creates health hazards. In the present study, capillary electrophoresis coupled with laser-induced fluorescence detection and a modified partial digestion mapping procedure was developed to map DNA fragments. By using capillary electrophoresis, a restriction map of genomic lambda phage clone of human interleukin 5 receptor alpha chain (IL5R alpha) gene was constructed. The IL5R alpha gene was analyzed to have five XbaI enzyme cutting sites at locations 1370, 2290, 2950, 5430, and 9330. The system was further characterized by using pBluescript SK(+) phagemid DNA as a model. Using a sequence-derived map as a reference, the pBluescript SK(+) restriction map constructed by capillary electrophoresis had an accuracy greater than 90%.

DNA↗

PubMed1994

Humic acid induces expression of tissue factor by cultured endothelial cells: regulation by cytosolic calcium and protein kinase C.

Blackfoot disease is a thrombotic peripheral vascular disease causally related to the fluorescent humic acid (HA) found in the drinking water of wells in endemic areas in Taiwan. In this study we examined the effect of HA on tissue factor (TF) expression by vascular endothelial cells. Incubation of cultured human umbilical vein endothelial cells (HUVEC) with HA isolated from endemic area drinking water or with a synthetic humic acid polymer (SHA), resulted in enhanced cell surface expression of TF activity by HUVEC. The intracellular calcium level ([Ca2+]i) was measured using a calcium-specific fluorescent probe, fura 2. Changes in [Ca2+]i level were followed and quantitatively analyzed by spectrofluorometric microscopy, after incubation of the fura 2-loaded HUVEC with HA or SHA in a medium containing 1.8 mM CaCl2. Both HA and SHA increased [Ca2+]i in the presence of extracellular calcium ions, but not in their absence, indicating that influx of extracellular Ca2+ occurred during incubation of HUVEC with HA or SHA. Verapamil, a potent calcium channel blocker, did not abolish the enhancement of [Ca2+]i induced by HA or SHA, indicating that specific calcium channels may not be involved in the HA/SHA-induced elevation of [Ca2+]i. The elevated [Ca2+]i level induced by HA or SHA returned to basal level following removal of HA or SHA and incubation of the washed cells in medium containing 1.8 mM CaCl2. All these changes occurred in the absence of significant cytotoxic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1993

Mechanical models of pseudopod formation.

The active locomotion of polymorphonuclear leukocytes into a glass pipette has been recently reported using formyl-methionyl-leucyl-phenylalanine (fMLP) as a chemoattractant. The frontal portion of the leukocyte appears clear and free of granules as observed in pseudopod formation. Three possible mechanisms for pseudopod formation are considered: (1) pressure-flow generated by actin-myosin contraction at the rear of the cell or at the base of the pseudopod; (2) osmotic pressure generated at the cell membrane, interior to the cell; and (3) actin polymerization of the cell membrane at the leading edge of the pseudopod. Experimental data on the movement of F-actin toward the rear of the cell, away from the front, favors polymerization of G-actin to F-actin at the leading edge. The active role of osmotic pressure and contraction at the base of the pseudopod are possible but not yet proven.

Actins↗

PubMed1992

Locomotion forces generated by a polymorphonuclear leukocyte.

There have been very few studies which have measured the physical forces generated by cells during active movements. A special micropipette system has been designed to make it possible to observe cell motion within the pipette and to apply a pressure to counter the chemotactic migration of the cell. This provides a direct measure of the locomotion force generated by the cell. The average velocity of forward motion is 0.33 microns/s in the absence of counter-pressure. The application of a positive counter-pressure (C-P) causes a decrease in the velocity of the forward motion of the cell. At 17 cm H2O of C-P, the cell velocity drops to zero and even moves backward with a higher C-P. The results show that the decrement of velocity is linearly related to the magnitude of the C-P with a complete stoppage at a pressure of 17 cm H2O which corresponds to a force of 0.003 dyn. The maximum work rate of the cell is approximately 2.5 x 10(-8) erg/s.

Biomechanical Phenomena↗