Bruno Buys

In vivo experimental evaluation of skin remodeling by using an Er:Glass laser with contact cooling

Selective dermal remodeling consists of inducing collagen tightening, neocollagen synthesis, or both, without damage to the overlying epidermis. This experimental study aimed to evaluate an Er:Glass laser emitting at 1.54 μm combined with contact cooling to target the upper dermis while protecting the epidermis.

Inhaled nitric oxide modulates leukocyte kinetics in the mesenteric venules of endotoxemic rats.

Objective: to determine whether inhaled nitric oxide (NO) would alter leukocyte kinetics in the septic microvasculature. Design: Randomized, controlled trial. Setting: Experimental laboratory. Subjects: Male Sprague Dawley rats. Interventions: Rats were treated with either saline or endotoxin (10 mg/kg, iv) and then allowed to breathe either air or air plus NO (10 ppm). Measurements and Main Results: After a 4‐hr period, rolling, firm adhesion, and emigration of leukocytes and endothelial dysfunction were monitored in mesenteric venules by using intravital videomicroscopy. Compared with controls, endotoxemic rats exhibited a profound influx in mesenteric venule rolling leukocytes (55 ± 17 vs. 70 ± 19 leukocytes/min; p < .05), associated with a reduction of leukocyte rolling velocity (83 ± 14 vs. 34 ± 3 μm/sec; p < .05). In endotoxemic rats, venular endothelium leukocyte firm adhesion (1.15 ± 0.32 vs. 4.08 ± 0.96 leukocytes/100 μm; p < .05) and emigration (0.84 ± 0.47 vs. 4.23 ± 1.2 leukocytes/100 μm; p < .05) increased compared with controls. Inhaled NO had no effect on leukocyte kinetics in control rats. Inhaled NO significantly attenuated endotoxin‐induced venular endothelium leukocyte adhesion (4.08 ± 0.96 vs. 1.86 ± 0.76 leukocytes/100 μm; p < .05) and emigration (4.23 ± 1.2 vs. 1.68 ± 0.72 leukocytes/100 μm; p < .05). Compared with control rats, macromolecular (FITC‐dextran) vascular leakage, expressed as the perivenular/intravenular fluorescence intensity ratio, increased in endotoxemic rats (0.56 ± 0.02 vs. 0.81 ± 0.05; p < .01). Endotoxin‐induced macromolecular vascular leakage increases were partially prevented by inhaled NO (0.66 ± 0.01 vs. 0.56 ± 0.02; p < .05). Conclusion: These observations suggest that inhaled NO reduces leukocyte adhesion and the degree of vascular permeability dysfunction in mesenteric venule of endotoxemic rats.

In Vivo Application of Intestinal pH Measurement Using 2,7‘‐Bis(carboxyethyl)‐5,6‐carboxyfluorescein (BCECF) Fluorescence Imaging

Measurement of gastrointestinal intramucosal pH (pH,m) has been recognized as an important factor in the detection of hypoxia‐induced dysfunctions. However, current pH measurement techniques are limited in terms of time and spatial resolutions. A major advance in accurate pH measurement was the development of the ratiometric fluorescent indicator dye, 2′,7′‐bis(carboxyethyl)‐5,6‐car‐boxyfluorescein (BCECF). This study aimed to set up and validate a fluorescence imaging technique to measure in vivo the intramucosal pH (pHim) of the intestine. The intestine was inserted into an optical chamber placed under a microscope. Animals were injected intravenously with the pH‐sensitive fluorescent dye BCECF. Fluorescence was visualized by illuminating the intestine alternately at 490 and 470 nm. The emitted fluorescence was directed to an intensified camera. The ratio of emitted fluorescence at excitation wavelengths of 490 and 470 nm was measured, corrected and converted to pHim by constructing a calibration curve. The pHim controls were performed with a pH microelectrode and were correlated with venous blood gas sampling. Results show that pHim is determined with an accuracy of ± 0.07 pH units and a response time of I min. In conclusion pHim mapping of rat intestine can be obtained by fluorescence imaging using BCECF. This technology could be easily adapted for endoscopic pH measurements.

Zirconium fluoride glass fiber radiometer for low temperature measurements

Infrared signal transmission through zirconium fluoride glass fibers is used for noncontact temperature measurement. A radiometer was developed for temperature measurement between 30 degrees C and 150 degrees C. The dependence of the radiometer signal on the black-body temperature is presented. Experimental and theoretical results are compared. >

In-vivo experimental evaluation of nonablative skin remodeling using a 1.54-μm laser with surface cooling

Selective dermal remodeling using diode or 1.32 micrometer Nd:YAG lasers has been recently proposed for skin rejuvenation. This new technique consists in inducing collagen tightening and/or neocollagen synthesis without significant damage of the overlying epidermis. Such an approach requires (1) a cooling system in order to target dermal collagen with relatively good protection of the epidermal layer, (2) a specific wavelength for confining the thermal damage into the upper dermis (100 to 400 micrometer). Based on previous studies, demonstrating a better water absorption and a reduced melanin absorption at 1.54 micrometer compared to the 1.32 micrometer, this experimental study aimed to evaluate a new laser (co-doped Yb-Er:phosphate glass material, Aramis, Quantel-France) emitting at 1.54 micrometer. This laser was used in combination with the Dermacool system (Dermacool, Mableton, USA) in order to achieve epidermis cooling before, during and after irradiation. Male hairless rats were used for the study. Pulse train irradiation (1.1 J, 3 Hz, 30 pulses) and different cooling temperatures (+5 degree(s)C, 0 degree(s)C, -5 degree(s)C) were screened with clinical examination and histological evaluation at 1, 3, and 7 days after laser irradiation. The clinical effects showed that pulse train irradiation produced reproducible epidermal preservation and confinement of the thermal damage into the dermis. The different cooling temperatures did not provide detectable differences in terms of size and depth of thermal damage. New collagen synthesis was confirmed by a marked fibroblastic proliferation, detected in the lower dermis at D3 and clearly seen in the upper dermis at D7. This new laser appears to be a promising new tool for the treatment of skin laxity, solar elastosis, facial rhytids and mild reduction of wrinkles.

Laser preconditioning of calvarial bone prior to an X-ray radiation injury: a preliminary in vivo study of the vascular response.

Thermal preconditioning prior to injury induces a cytoprotective effect on soft tissues and promotes their recovery. Lasers are an adequate tool to generate controlled and reproducible heat. X‐ray irradiation induces a chronic antiangiogenic effect on bone, affecting its healing and remodeling processes. The aim of this study was to investigate the effect of laser preconditioning on the re‐vascularization of X‐ray irradiated bone.

Effect of a Laser irradiation on the vascularisation of safety and X-ray radiated bone

Thermal preconditioning induces a cytoprotective effect and promotes tissue recovering. Laser is an appropriated method to generate a controlled and reproducible heating. Bone healing, a crucial challenge in medicine, is affected by X- ray radiation which induces a chronic antiangiogenic effect. So, this study aims to investigate the role of laser preconditioning on the vascularisation of bone after X-ray radiation. An optical bone chamber allowed the study of the vascularization process. The vascular density (VD) was determined using image processing. A longitudinal study was performed on 20 rabbits divided in four groups: #1: control group (n=5); #2: laser irradiation alone (diode laser 810 nm, fluence= 48 J/cm2) (n=5). #3: X-ray radiation (18.75 Gy) alone (n=5), #4: laser preconditioning 24 hours before a X-ray radiation (n=5). VD remained stable during 12-week follow up for groups #1 and #2. X-ray radiation lead to an important decrease of the superficial bone vascularization in group #3. The decrease of the vascularization was limited in group #4 highlighting a different evolution between group #3 and #4. Those results were confirmed by histological analysis. Our preliminary findings show that laser preconditioning preserves vascularization in X-ray radiated bone site, outlining a novel approach for the bone healing in which the vascular supply has been injured.

New directions in Medical laser concept: role of laser-tissue interaction modelization and feedback control

Thermal lasers are used in many specialties. Clinical use of lasers is complicated by variations in tissue characteristics or hazards such as movement. Pionners in this field, relying on experimental work, have mastered the therapeutic use of lasers. Nevertheless, teaching such poorly defined technique has proved to be very difficult. To widespread the use of lasers, it is necessary to work in new directions. The goal is to give the practitioner a real medical tool, which should be cheap, easy and safe to use.

Adaptive control of a medical Nd:YAG laser for tissue coagulation

Adaptive control is proposed as a useful process for an improvement of Nd:YAG laser treatments. A computer-controlled Nd:YAG laser system with a closed-loop capability has been developed. Infrared radiometry provided noncontact temperature measurement for real-time coagulation and ablation control. The controller design is based on the predicted response, defined by mathematical models. Deviations of the actual response beyond an established tolerance causes the Nd:YAG laser system to adjust its parameters automatically.<<ETX>>

Intravital fluorescence microscopic study of the behavior of long-circulating liposomes during microvascular thrombosis

Treatment of thrombosis depends on the selectivity of thrombolytic agents to the clot. It has been already demonstrated that liposomes can provide a better selectivity of such agents to the clot site. We have recently shown that intravital fluorescence microscopy is a powerful tool to image in situ and in real time the labeling of leukocytes by long circulating liposomes. The aim of this study was to monitor the in vivo behavior of such liposomes in a clot site. Carboxyfluorescein-loaded long circulating liposomes were prepared and characterized in term of size and permeability. The liposomes suspension was injected intravenously to golden hamsters. The skin microcirculation was observed using a dorsal skin-fold chamber by fluorescence microscopy. Thrombosis were obtained as the consequence of the inflammatory response due to the surgery. Using this model, fluorescent dots were observed at the site of the clot. Liposomes accumulate at the clot site whatever the mechanism (passive deposition or uptake). There is a period of latency and 30 seconds after the blood flow stop, fluorescence increases very rapidly and a bright fluorescent spot is observed at the site of the clot. Further studies are needed to determine the exact localization of liposomes in the clot and the mechanism of interaction.