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PubMed1990

Molecular surgery of the basement membrane by the argon laser.

Although the argon laser is used successfully to weld a number of different tissues, the underlying chemical and cellular mechanisms for this process are not precisely defined. Consequently, a biochemical model has been developed in vitro using the well-defined extracellular matrix from the murine Engelbreth-Holm-Swarm (EHS) sarcoma. Control and experimental samples of EHS basement membranes were irradiated with a Trimedyne argon laser at 500-3,000 Joules/cm2 at 0 degrees C. The samples were diluted into cold phosphate-buffered saline and allowed to gel at 35 degrees C. The time course of the gelation reaction was followed in a spectrophotometer at 360 nm. Irradiation reduced the absorbance 7.5-15% compared to controls and was independent of the dilution over a 10-fold range. Gelation was also measured by determining the amount of protein by the Bradford assay that could be collected by centrifugation at 10,000g for 10 minutes. Argon-irradiated samples had 30-40% less protein in the precipitate than the controls. The addition of 5 mM beta-mercaptoethanol to the EHS extract blocked the effect of the laser on the gelation reaction. In addition, when gelation was carried out in the absence of calcium and magnesium, there were no differences between laser-treated samples and controls. The basement membrane proteins were separated by electrophoresis through polyacrylamide gels under denaturing plus reducing or denaturing and non-reducing conditions. No differences in the polypeptide composition were noted between irradiated and control samples using either Coomassie- or silver-staining techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Laser-assisted microvascular anastomosis using CO2 and KTP/532 lasers.

The milliwatt carbon dioxide (CO2) laser has been shown to be an effective device for performing laser-assisted microvascular anastomosis (LAMA) with consistently high patency rates, minimal tissue disruption, and rapid surgical time as well as the potential for reduced inflammation due to fewer foreign bodies (sutures) in the wound. The purpose of this investigation was to determine the feasibility of using the potassium titanyl phosphate (KTP) laser to perform LAMA and to compare it to CO2 LAMA in both arteries and veins. Patency rates, inflammatory response, and course of healing were evaluated through histological analysis. Twenty-eight rats were divided into two groups, which underwent either CO2 or KTP LAMA and then were sacrificed at 3 days, and 1, 2, 4, 8, and 12 weeks postoperatively. Patency rates for arteries and veins were comparable for both wavelengths (CO2: 100% for arteries, 93% for veins; KTP: 93% for arteries, 93% for veins). Histological grading of inflammation and fibrosis showed no significant difference between the two groups. This study demonstrated the efficacy of using the KTP/532 laser in performing LAMA. We found the KTP and CO2 LAMA to have comparable patterns of tissue damage and course of healing. Although this experiment did not investigate the mechanism(s) of tissue welding, our results suggest that successful LAMA may be independent of wavelength.

Anastomosis, Surgical↗

PubMed1992

CO2 laser urethroplasty in the rabbit: a preclinical model.

Our previous work has shown that the CO2 laser can be successfully used in urethral reconstruction in a rat model. This new experiment investigates the use of the CO2 laser to perform a patch graft urethroplasty in the rabbit, as a preclinical model to its use in the repair of hypospadias in humans. Using sterile technique, a patch graft of preputial skin was welded in the repair of a standardized urethral defect in 10 rabbits. In another cohort, the same urethral defect was repaired using standard microsuture technique. In a control group the patch graft was placed with microsuture in a nonwatertight fashion. All animals were followed for 3 weeks. Histologic and radiologic analyses were done in a blinded fashion. Our study showed that CO2 laser repair, when compared to microsuture in urethral reconstruction, required 40% less operative time and produced better graft healing and less intraluminal scarring.

Animals↗

PubMed1994

Determination of efficient parameters for argon laser-assisted anastomoses in rats: macroscopic, thermal, and histological evaluation.

The aim of this study was to determine efficient parameters for an argon laser (spot diameter = 200 microns) to obtain and reproduce vessel anastomoses. It was performed in two groups of Wistar rats. In the first group (89 Laser impacts on 10 carotids), the fluence was continuously adjusted from 30 to 3,000 J/cm2 in order to determine efficient sets of parameters (power from 90-200 mW, pulse duration from 0.1 to 5 seconds, pulsed or continuous mode). In the second group, 30 end-to-end carotid anastomoses were performed. The results were evaluated by macroscopic thermal, and histological studies. The second group proved the efficiency of the selected parameters. Vessel welding was obtained with 100 mW, 3 seconds, continuous mode (fluence = 950 J/cm2, irradiance = 320 W/cm2) for a mean temperature of 77 degrees C corresponding to collagen denaturation. In the second group the patency rate was 93% (28/30) with three pseudo-aneurisms and two thromboses. Histological studies noted slight modifications of the media.

Anastomosis, Surgical↗

PubMed1995

Lasers in urology.

Ever since Mulvany first described use of Ruby laser for lithotripsy, urologists have been exploiting every possible application of this technology. Laser lithotripsy in the 1980s and now laser prostatectomy in the 1990s have dominated laser usage in urology. Applications of lasers for superficial lesions (e.g., condylomata acuminata and carcinoma of penis) have found an established role. Interests in laser welding, photodynamic therapy and fluorescence continues to grow and evolve. The laser industry at the same time is striving to provide more efficient lasers. High power lasers (Holmium:YAG, KTP:YAG) and laser machines combining double wavelengths (Nd:YAG and KTP, Ho: YAG and Nd:YAG) are commercially available. Diode lasers with their portability and reliability qualities can now provide high output powers in various wavelengths. Here, we have reviewed different lasers, laser tissue interaction and clinical laser applications relevent to urology.

Carcinoma↗

PubMed2004

Intraluminal laser light source and external solder: in vivo evaluation of a new technique for microvascular anastomosis.

BACKGROUND AND OBJECTIVES: Current laser-assisted end-to-end anastomoses are performed by irradiating the vessel wall from outside after additional fixation with three to six sutures. These sutures are needed to provide adequate approximation of the vessel stumps. We present a new laser soldering technique that is based on an intraluminal laser light source centered in a balloon catheter, and external application of a solder. This technique was applied in vivo in order to test its feasibility under clinical conditions. STUDY DESIGN/MATERIALS AND METHODS: Seven white pigs were treated with a total of fourteen end-to-end laser-anastomoses of their saphenous arteries having outer diameters of 2 mm. The vessels were stented over an intraluminal balloon catheter, which was maximally dilated and which allowed for a precise approximation of the vascular stumps. An 808 nm diode laser was coupled into a specially designed optical fiber producing a 360 degrees radiation ring inside the balloon catheter. An indocyanine green (ICG) doped liquid albumin solder was applied on the external surface of the vascular stumps. Laser soldering was achieved by irradiating with a 808 nm laser diode for 75 seconds. Tightness of the anastomoses was evaluated by clamping the artery distal to the anastomosis for 1 hour, and patency was tested over an observation period of 3 hours, during which the animals were heparinized. Thereafter, the anastomoses were harvested for histomorphological examination. RESULTS: All anastomoses remained patent over the entire observation period. Some leakage was observed in three anastomoses, which was explained by a deviation of the illumination fiber from the center of the balloon leading to an inhomogeneous irradiation of the vessel wall. Histology revealed perfect adaptation of the vascular stumps. A segment of denaturated vascular collagen was observed, that corresponded to the irradiated, solder-covered zone. CONCLUSION: Patent, maximally dilated and well adapted microvascular anastomoses could be obtained without the need of stay sutures. A well centered laser light source is indispensable for avoiding inhomogenous welding, thus causing leakage.

Anastomosis, Surgical↗

PubMed2003

Carbon dioxide laser-assisted nerve repair: effect of solder and suture material on nerve regeneration in rat sciatic nerve.

In order to further improve and explore the role of lasers for nerve reconstruction, this study was designed to investigate regeneration of sharply transected peripheral nerves repaired with a CO(2) milliwatt laser in combination with three different suture materials and a bovine albumin protein solder as an adjunct to the welding process. Unilateral sciatic nerve repair was performed in 44 rats. In the laser group, nerves were gently apposed, and two stay sutures (10-0 nylon, 10-0 polyglycolic acid, or 25 microm stainless steel) were placed epi/perineurially. Thereafter, the repair site was fused at 100 mW with pulses of 1.0 s. In the subgroup of laser-assisted nerve repair (LANR), albumen was used as a soldering agent to further reinforce the repair site. The control group consisted of nerves repaired by conventional microsurgical suture repair (CMSR), using 4-6 10-0 nylon sutures. Evaluation was performed at 1 and 6 weeks after surgery, and included qualitative and semiquantitative light microscopy. LANR performed with a protein solder results in a good early peripheral nerve regeneration, with an optimal alignment of nerve fibers and minimal connective tissue proliferation at the repair site. All three suture materials produced a foreign body reaction; the least severe was with polyglycolic acid sutures. CMSR resulted in more pronounced foreign-body granulomas at the repair site, with more connective-tissue proliferation and axonal misalignment. Furthermore, axonal regeneration in the distal nerve segment was better in the laser groups. Based on these results, CO(2) laser-assisted nerve repair with soldering in combination with absorbable sutures has the potential of allowing healing to occur with the least foreign-body reaction at the repair site. Further experiments using this combination are in progress.

Albumins↗

PubMed1988

Induction of experimental aneurysms on the rat common carotid artery using a microsurgical CO2 laser.

Aneurysms were produced on the common carotid artery of rats by milliwatt CO2 laser welding of an adventitia patch over a hole. Sixty-nine animals were operated on. Aneurysms were present in 35 animals (51%), 7 of which ruptured spontaneously. The time to aneurysm formation was 1 week or longer. The adventitia patch aneurysm model has features (reliability, minimal vessel manipulation, histology similar to human berry aneurysm, and spontaneous bleeding tendency) that make it theoretically suitable for the induction of intracranial aneurysms in experimental animals. The microsurgical skills required to create and dissect the aneurysm make our experimental aneurysm useful as a teaching model in the development of microneurovascular surgery skills.

Aneurysm↗

PubMed1989

Sutureless microvascular anastomosis using the THC:YAG laser: a preliminary report.

Laser anastomosis of the rat carotid artery was performed using a new mid-infrared laser, the pulsed thulium-holmium-chromium: YAG (THC:YAG) laser (2.15 microns). Solid silicone stents made stay sutures unnecessary for coaptation of vessel edges during laser bonding. Grossly, the laser anastomoses displayed minimal thermal distortion of the vessel contour and no tissue carbonization. Of the 30 anastomoses performed, 27 were patent and 3 had separation of the weld shortly after the approximator clamp was released. Mean anastomotic time was 4 min 48 sec. Mean bursting pressure for the 9 vessels tested was 400 mm Hg. Thrombosis did not occur at any time during our examination of these anastomoses. Fusion of collagen fibers in the media was confirmed histologically. Unlike the CO2 laser, the THC:YAG is transmissible through flexible silica fibers, which greatly facilitates delivery of the laser in a microsurgical operative field. The THC:YAG provides shallower absorption depth than Nd:YAG and argon lasers but somewhat deeper tissue penetration than CO2. For microvessels, this intermediate absorption results in full-thickness fusion of the media, with minimal thermal damage to vascular tissue adjacent to the anastomosis.

Anastomosis, Surgical↗

PubMed1995

Work environment and prostate cancer risk.

A case-referent study of 345 prostate cancer cases and 1,346 referents was carried out in the Netherlands to investigate the relationship between work environment and prostate cancer risk. Cases were selected from the Cancer Registry of the Comprehensive Cancer Centre IKO. Referents (men diagnosed with benign prostate hyperplasia) were recruited with assistance of the pathology laboratories in the IKO region. Questionnaires were mailed to all subjects to obtain information on their work history and occupational exposure. Moreover, workers in farming (n = 323), and in metal work and maintenance (n = 340), were requested to complete short supplements to the questionnaire inquiring in more detail into specific types of exposure. Significantly elevated risks were found for work in food manufacturing and for bookkeepers. Significantly elevated odds ratios (OR) were also observed for jobs held between 1960 and 1970 in administration, in storage, or as farm laborer. In addition, a statistically significant excess risk was found for subjects who reported frequent occupational exposure to cadmium. Cases who worked in farming applied pesticides during significant more days per year than the referents did. A nonsignificantly elevated OR was found for maintenance of tractors and agricultural machinery. Among metal workers, mechanics, and repairmen, nonsignificantly increased ORs were observed with regard to the use of acids, solvents, iron, and steel, and for welding and maintenance of machinery.

Aged↗

PubMed2006

In situ electron microscopy electromechanical characterization of a bistable NEMS device.

A previously proposed two-terminal carbon-nanotube-based device with closed-loop feedback is demonstrated through in situ scanning electron microscopy (SEM) experiments. The pull-in/pull-out tests were carried out using a multi-walled carbon nanotube (MWCNT) welded to a conductive probe attached to a nanomanipulator. The MWCNTs were cantilevered over a gold electrode and electrostatically actuated. The measured current-voltage curves exhibited the theoretically predicted hysteretic loop between the pull-in and pull-out processes. Both experiments and theoretical modeling demonstrated the bistability of the device confirming its utility in applications such as memory elements, NEMS switches, and logic devices. Failure mechanisms observed during the pull-in/pull-out event are also reported and discussed.

Electrochemistry↗

PubMed2000

A geographic information assessment of birth weight and crop production patterns around mother's residence.

A landscape approach using remote sensing (RS) and geographic information system (GIS) technologies was developed to identify the proximity of maternal residence to agricultural areas, and the association between crop production patterns around mothers residences and low birth weight was evaluated. Satellite data obtained for Weld County, Colorado, in 1991 and 1993 were digitally processed to generate crop location maps for this study. GIS procedures were then used to determine crop types within 300- and 500-m circular zones around mothers' homes for 125 births that occurred from 1991 to 1993 in the study area. The relationships between different crop patterns around the mothers' residences and the birth weight of babies were investigated while controlling for potential confounding variables. The results indicated that low birth weight was associated with total crop production area within a 300-m buffer zone around mothers' residences (P=0.058). When each of the study crops was considered separately, low birth weight was associated with sugar beet production (P=0.05) and corn production (P=0.1) within both the 300- and the 500-m buffer zones. This RS/GIS approach provides clues to the potential relationships between birth weight and crop production near the residence.

Adult↗

PubMed1999

Microstructure of a Biocatalytic Latex Coating Containing Viable Escherichia coli Cells.

Cryogenic scanning electron microscopy (cryo-SEM) was employed to visualize the microstructure of latex coatings in which viable Escherichia coli cells were entrapped for use as biocatalysts. Cryo-SEM examination of surfaces and fracture cross sections of dry and hydrated coatings cast with or without glycerol revealed two different porosities in the films: a macroporosity in which the bacterial cells reside and a microporosity made up of the interstitial voids between partially coalesced latex polymer particles. Polymer particle consolidation and coalescence in the cell-laden coatings were at an earlier stage than in cell-free latex coatings detailed in a companion paper. Coatings cast with glycerol showed a lesser degree of latex particle consolidation and coalescence than those cast without glycerol. However, the effect of glycerol was not as pronounced as in cell-free coatings. We conclude that part of the added glycerol is sequestered inside the bacterial cells and the portion remaining outside the cells retards the latex film formation process and enhances microporosity. Two commercial acrylic acid/vinyl acetate copolymer latexes were examined. Coatings made with the polydisperse latex showed less microporosity and a greater degree of particle welding than those made with the nearly monodisperse latex. Copyright 1999 Academic Press.

Journal Article↗

PubMed2000

Design of a high-power NMR probe for low-temperature studies.

A low-temperature, high-power NMR probe head design is described which eliminates the problem of electric arc discharge commonly experienced during radiofrequency pulse cycling in a helium environment. A polychlorotrifluoroethylene (Kel-F) coil former, fitted with a solenoid coil, is heat-shrunk onto stainless-steel flanges and spot-welded inside a stainless-steel probe head assembly connected to a hollow coaxial transmission-line probe shaft. By this means, the sample coil and all high-voltage elements can effectively be isolated in a vacuum, while at the same time permitting good thermal contact between the sample and cryogenic gas. This design was used in NMR studies in the 4.6 K < or = T < or = 77 K temperature range for RF pulse durations < or = 50 ms (and longer for low RF amplitudes) and amplitudes up to approximately 60 G.

Cold Temperature↗

PubMed1999

Immunohistochemical and ultrastructural characterization of cortical plate microvasculature in the human fetus telencephalon.

The blood-brain barrier (BBB) differentiation was investigated by immunohistochemistry and electron microscopy in the radial microvasculature of the telencephalon cortical plate (CP) of 12- and 18-week human fetuses. The BBB-specific glucose transporter isoform 1 (GLUT1) is expressed in both stages, with a main localization on the ablumenal and lateral plasma membranes of the endothelial cells. The endothelial cells are welded by short junctions with fusion points of the plasma membranes at 12 weeks and by extensive tight junctions at 18 weeks. The basal lamina is discontinuous beneath the endothelium-pericyte layer at 12 weeks and splits into two continuous layers circumscribing the pericytes in the later stage. The expression of laminin, a basal lamina glycoprotein, is continuous already at 12 weeks. The CP microvessels are tightly surrounded by processes of glial cells. Immunodetection of the cytoskeletal filament proteins, vimentin (VIM), and glial fibrillary acidic protein (GFAP), demonstrates that at 12 weeks the perivascular glial processes are mostly represented by VIM-stained fibers of the radial glia. At 18 weeks, GFAP-stained radial glia fibers, processes of VIM-stained astroblasts, and GFAP-positive astrocytes also build the perivascular envelopes. The results indicate that the vessel differentiation is already under way in the human CP at the midgestational age and entails the establishment of some barrier devices. The early relationship between perivascular glia coverage formation and endothelial barrier maturation suggests that also immature astroglial cells are involved in the setting up of the BBB.

Adult↗

PubMed1998

Immunotoxicologic effects of inhaled chromium: role of particle solubility and co-exposure to ozone.

Soluble and insoluble hexavalent chromium (Cr6+) agents are concomitantly released with ozone (O3) during welding. Although pulmonary/immunologic implications from exposure to each agent individually have been investigated, the effects from simultaneous exposure, as occurs under actual working conditions, are unclear. To investigate immunomodulatory effects of inhaled Cr6+, F-344 rats were exposed for 5 h/day, 5 days/week for 2 or 4 weeks to atmospheres containing soluble potassium chromate (K2CrO4) or insoluble barium chromate (BaCrO4), each alone at 360 micrograms Cr/m3 or in combination with 0.3 ppm O3. One day after the final exposure, rats were euthanized, their lungs were lavaged, and pulmonary macrophages (PAM) were recovered for assessment of basal and inducible functions. Rats inhaling K2CrO4-containing atmospheres had greater levels of total recoverable cells, neutrophils, and monocytes in bronchopulmonary lavage compared to rats exposed to insoluble Cr6+ atmospheres, O3 alone, or air; these rats also had a reduced percentage of PAM, although total PAM levels remained unaffected. Although Cr exposure-related changes in PAM functionality were evident, any dependence upon Cr solubility was variable. K2CrO4-containing atmospheres modulated PAM-inducible interleukins-1 and -6, and tumor necrosis factor-alpha production to a greater degree than those containing BaCrO4. Conversely, BaCrO4-containing atmospheres affected PAM basal nitric oxide production and interferon-gamma-primed/zymosan-stimulated reactive oxygen intermediate production to a greater extent than did those containing K2CrO4. In none of the PAM assays did co-inhalation of O3 result in a modulation of the effects obtained with either Cr6+ compound itself. The results indicate that, while immunomodulatory effects of inhaled Cr6+ upon PAM are related to particle solubility, the co-inhalation of O3 apparently does not cause further modifications of the metal-induced effects.

Administration, Inhalation↗

PubMed1990

Human cranial bone structure and the healing of cranial bone grafts: a study using backscattered electron imaging and confocal microscopy.

This study explored the microstructure of human cranial bone at different ages, and the survival, remodelling and modelling of cranial bone grafts. A combination of reflection and fluorescence confocal optical microscopy and scanning electron microscopy in the backscattered electron imaging mode was employed to examine highly polished block faces of plastic-embedded bone fragments as harvested for grafting, or recovered after a period in situ as a graft. The methods enabled remarkably detailed information on bone content, maturation and turnover to be gleaned from tiny scraps of bone. Microfractures in the harvested bone were repaired at the graft site, with welding of old and new bone indicating revascularization. Human cranial bone grafts successfully stimulated bone cell differentiation, supported new bone formation on resorbed and unresorbed surfaces, and underwent bone turnover. The type and organization of new bone reflected the growth rate and maturation of the graft rather than the age of the patient.

Adult↗

PubMed1992

Nacre initiates biomineralization by human osteoblasts maintained in vitro.

When nacreous shell produced by the marine oyster Pinctada maxima, used as a biomaterial in oral surgery, is implanted in human bone, new bone formation occurs, resulting in a tight welding of the bone to the nacre [16]. These findings are consistent with the possibility that nacre adjacent to bone can locally stimulate osteogenic activity. To test this hypothesis, we have evaluated the effect of the simultaneous presence of bone and nacre on human osteoblasts in vitro. Nacre chips (1 mm3) were placed at approximately 1 mm distance from a similarly sized bone chip on a layer of first passage human osteoblasts. None of the chemical inducers generally required to obtain bone mineralization in vitro (in particular, beta-glycerophosphate) was added to the cultures. Mineralized sections of the cultures were evaluated by light and electron microscopy, contact microradiography, and Laser Raman Spectroscopy. The results demonstrated that nacre has strong osteogenic effects on human osteoblasts when placed in proximity to bone in vitro. New bone formation occurred by both appositional growth on the existing bone and by the formation of mineralized nodules within the matrix adjacent to the bone explant. Electron microscopic evaluation of these sites demonstrated findings typical of those described in the course of bone formation in vivo, and no evidence of toxicity was observed. In addition, under the conditions of culture used, nacre can also promote the formation by osteoblasts of a structure with characteristics similar to nacre (e.g., lamellar organic matrix mineralized with aragonite, as demonstrated by Laser Raman Spectroscopy).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗