Search PubMed⌕ Search

Biomedical subjects

R S Chuck

Publications and source records attributed to R S Chuck.

28 records · Page 2Linked to original sources
PubMed1993

Effect of CD4 engagement on CD4-T cell receptor complexes.

To detect the presence of CD4-T cell receptor (TCR) complexes, we previously developed a flow cytometric method for measuring singlet-singlet energy transfer on human T cells labeled with fluorescein isothiocyanate-conjugated anti-CD4 and tetramethylrhodamine isothiocyanate-conjugated anti-TCR. Using the same procedure, we have now studied changes in the expression of CD4, TCR, and CD4-TCR complexes following CD4 engagement. Ligation of the D3 domain with OKT4, or the D1 domain with anti-Leu3a, induced CD4 and TCR down-regulation, while ligation of the D1 domain with gp120 did not. OKT4 caused a transient decrease in CD4-TCR association over 1 hr at 37 degrees C, while anti-Leu3a caused a steady-state decrease. In contrast, gp120 decreased CD4-TCR association mainly at 0 degrees C, rather than at 37 degrees C. Such alteration in CD4-TCR assembly may underly anti-Leu3a- and gp120-mediated inhibition of T cell antigen recognition and account for the negative effect of CD4 ligation on TCR-triggered responses.

Antibodies, Monoclonal↗
PubMed1991

A preliminary study of dye-enhanced laser photosclerosis.

Laser ablation of veins after injection of wavelength-specific dyes to enhance and localize energy absorption could provide a useful adjunct to current treatment options. To enhance the absorption of diode laser energy at 808 nm, ear veins of 41 rabbits were infused with 2 to 3 ml of indocyanine green dye (maximum absorption, 805 nm) and exposed for 2 to 20 seconds. Animals were killed between 0 and 28 days after operation. Discrete time intervals of laser exposure exist during which various-sized vessels can be ablated without significant thermal injury to the overlying tissue. Small vessels (0.2 mm in diameter) blanch after 2 to 3 seconds of exposure, whereas medium-sized vessels (2 mm in diameter) require 8 to 10 seconds. Vessels can be ablated with a power density as low as 11.1 W/cm2. Specimens taken immediately after laser exposure show vessel wall thinning and a reirradiation effect, created as laser energy initially absorbed by dye is reemitted. By the seventh day after operation, a brisk inflammatory response and acanthosis of the overlying epidermal layer develop. The lumen is partially filled by thrombus with cellular invasion. By postoperative day 28, the epidermal thickening and inflammatory reaction have resolved; the vessel walls are fibrotic. The use of low-power, air-cooled diode lasers, in conjunction with wavelength-specific dyes, may provide a simple, viable, and cosmetically appealing alternative to the treatment of superficial varicosities of the extremities.

Animals↗
PubMed1990

Strength of laser vascular fusion: preliminary observations on the role of thrombus.

We hypothesized that autologous clot deposited on the luminal surface of laser vascular welds immediately after creation would produce higher time zero bursting pressures that could be achieved in welds perfused with saline alone. To test this hypothesis, we compared bursting pressures of welds created in isolated rabbit aortic segments 1) with saline perfusion only, 2) with blood perfusion, and 3) with blood perfusion followed by infusion of urokinase. Tissue welds with saline perfusion had a mean bursting pressure of 159 +/- 45 mm Hg; tissue welds following blood perfusion had a mean pressure of 262 +/- 29 mm Hg; tissue welds with blood perfusion followed by urokinase infusion had a mean bursting pressure of 187 +/- 35 mm Hg. The saline and urokinase groups were not significantly different. However, the blood-perfused group was significantly higher than both the saline group and the urokinase group. Thus, the addition of urokinase eliminates the beneficial effects noted after blood reperfusion. These observations suggest that the enhancement of weld strength following exposure to blood is due predominantly to the adherence of fibrin-platelet aggregates at the site of the weld.

Anastomosis, Surgical↗
PubMed1990

CD4-T-cell antigen receptor complexes on human leukemia T cells.

CD4 and T-cell antigen receptor (TCR) comodulate from the surface of human and murine T cells following exposure to monoclonal anti-CD4 or anti-TCR. This comodulation may occur because expression of CD4 and TCR is regulated by similar transmembrane signals or because CD4 and TCR are physically associated. To study multimolecular assemblies on the plasma membrane, we developed a flow cytometric method for detecting singlet-singlet energy transfer between fluorescein isothiocyanate (FITC)- and tetramethylrhodamine isothiocyanate (TRITC)-conjugated monoclonal antibodies as sensitized TRITC emission on intact, single cells. Using this procedure, we detected CD4-TCR complexes on the surface of the transformed human leukemia T cells, HPB-ALL, in the absence of stimulation. More than one CD4 were found in association with one TCR. CD4-TCR complexes were not in rapid equilibrium with free CD4 and free TCR, and they were not induced by the dye-labeled anti-CD4 or anti-TCR.

Antibodies, Monoclonal↗
PubMed1990

Tissue soldering by use of indocyanine green dye-enhanced fibrinogen with the near infrared diode laser.

Anastomoses welded by laser have been strengthened by applying a solder of fibrinogen combined with a laser energy absorbing dye (indocyanine green, maximum absorbance 805 nm) to the anastomotic site before continuous-wave diode laser exposure (808 +/- 1 nm, 4.8 W/cm2). Immediately after creation, the bursting pressures of welds created without fibrinogen (262 +/- 29 mm Hg, n = 11) were significantly less than repairs with fibrinogen (330 +/- 75 mm Hg, n = 11) (p less than 0.05). When repairs performed with fibrinogen were exposed to urokinase (25,000 IU) the bursting pressures were not significantly different from baseline (290 +/- 74 mm Hg, n = 5). Aortotomies closed by suture did not burst but leaked at pressures significantly below those of vessels closed by laser (165 +/- 9 mm Hg, n = 11) (p less than 0.01). Twenty-two repairs soldered with fibrinogen were incorporated into survival studies in rabbits and examined from 1 to 90 days after operation. No anastomotic ruptures, thromboses, or aneurysms were identified. Soldered sites rapidly regenerated a new intimal surface and healed by myofibroblast proliferation. No significant foreign body response was identified; the fibrinogen was resorbed. Laser soldering with exogenous fibrinogen is feasible without topical administration of additional clotting agents, significantly improves the bursting strength of primary laser welded anastomoses, and appears to result from urokinase-resistant fibrinogen cross-linking.

Anastomosis, Surgical↗
PubMed1989

Welding of gallbladder tissue with a pulsed 2.15 microns thulium-holmium-chromium:YAG laser.

Percutaneous endoscopic approaches to cholelithiasis would be facilitated by methods for welding gallbladder tissues. We evaluated the bursting pressure and histologic appearance of canine gallbladder tissue welded with a thulium-holmium-chromium:YAG (THC:YAG) laser producing a 2.15 microns pulsed output. The tissue absorption characteristics at this wavelength as well as the pulsed nature of the output permit tissue welding with limited collateral thermal damage. The THC:YAG is compatible with a flexible fiberoptic delivery system. Bursting strengths of the welded junctions averaged 42 mm Hg, which is above physiologically encountered pressures. Histologic sections of the bonded tissues revealed tissue fusion and limited thermal injury to the surrounding tissue. We feel that THC:YAG laser welding may be a useful technique in the clinical development of percutaneous endoscopic biliary surgery.

Animals↗
PubMed1989

In vitro comparison of thulium-holmium-chromium: YAG and argon ion lasers for welding of biliary tissue.

Laser welding offers several potential advantages over suture closure, including improved healing, lack of a nidus for stone formation, and greater speed and ease. We examined in vitro gallbladder cystic duct welds created by two different systems, the thulmium-holmium-chromium (THC):YAG (2,150 nm) and argon ion (488-514 nm) lasers, in an effort to define suitable parameters for tissue fusion. Mean bursting pressures for argon welds were 95 mm Hg at 1.5 W CW and 26 mm Hg at 1.5 W, 50 msec chopped delivery. For the THC:YAG laser, the mean bursting pressure for welds created with 300 mJ pulses was 45 mm Hg. Full-thickness tissue fusion and limited collateral thermal damage were observed histologically for both the CW argon and pulsed THC:YAG welds. Examination of the suggested mechanisms of tissue fusion for these photothermal lasers suggests that increased duration of tissue heating at the appropriate temperature results in more extensive collagen crosslinking and a stronger weld.

Animals↗
PubMed1989

Dye-enhanced laser tissue welding.

For vascular anastomosis, use of topical photosensitizing dye enhances selective delivery of laser energy to target tissue, thus reducing the amount of collateral thermal injury and threshold power required for welding. For fluorescein isothiocyanate (FITC)--stained rabbit aorta in vitro, the threshold for tissue blanching was 15 seconds of 100 mW exposure of cw argon ion laser compared with 15 seconds at 300 mW for unstained tissue. The threshold power density needed for argon laser welding of abdominal aortotomies in rabbits in vivo was 3.8 W/cm2 with FITC and 7.6 W/cm2 without the dye. However, bursting pressures for the two groups (164 mm Hg with FITC, 147 mm Hg without FITC) were not significantly different. Histology revealed decreased collateral thermal damage in FITC-enhanced welds. Use of photosensitizing dyes for tissue welding is feasible and may allow arterial welding with lower power laser systems and cause less thermal trauma by lowering threshold power levels.

Animals↗
PubMed1989

Comparison of methods for transcatheter fragmentation of gallstones.

Alternative methods have been considered for treating cholelithiasis. Compared to extracorporeal shockwave lithotripsy (ESWL), a percutaneous endoscopic approach would be more invasive, but would offer the advantage of immediate stone removal without the need for subsequent drug therapy. We performed an in vitro comparison of three methods of transcatheter cholecystolithotripsy with regard to effectiveness of stone fragmentation, damage to the gallbladder mucosa, and compatibility with percutaneous delivery systems. The three devices used for cholecystolithotripsy were the ultrasonic lithotriptor (UL), the electrohydraulic lithotriptor (EHL), and the thulium-holmium-chromium: YAG laser (THC:YAG). The UL effectively fragmented all types of stones studied, although it is necessary to hold the stone against the tip of the probe. The EHL quickly fragmented noncalcified and pigment stones simply by placing the tip in the vicinity of the stone, but calcified stones had to be held in position near the electrode. The THC:YAG was effective at fragmenting each type of stone, but the number of pulses required was quite large, corresponding to 7 min for some stones. The EHL had the most capacity for mucosal damage, followed by the THC:YAG laser. The UL produced no mucosal damage at the exposure times tested. The UL is not compatible with flexible endoscopes while the EHL and the THC:YAG are. Because of the specific advantages and disadvantages of each device, a combination of devices may be required for successful clinical cholecystolithotripsy.

Catheterization↗