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PubMed1996

Process of Carbonate Precipitation by Deleya halophila

Scanning electron microscopy and X-ray dispersive energy microanalysis were used to investigate the formation of carbonate crystals by Deleya halophila. The formation of calcium carbonate crystals (polymorphous aragonite) by D. halophila is a sequential process that commences with a nucleus formed by the aggregation of a few calcified bacterial cells and the subsequent accumulation of more calcified cells and carbonate, which acts to weld the bacteria together. The process leads to the formation of spherical bioliths measuring approximately 50 &mgr;m in diameter. The mechanism of carbonate precipitation by D. halophila under our working conditions represents a process of induced biomineralization.

Journal Article↗
PubMed1999

Island length distribution in genome sequencing.

We consider the general problem of constructing a physical map of a genome by welding islands of overlapping clones. Both distribution of clone length and non-uniform probability of overlap detection are taken into account, the latter restricted to the Markov case in which only the location of the end of the developing island is required. Exact results for the distribution of island length are obtained in the special cases of fixed clone length or rigid overlap criterion, and mean and variance for the general situation. Determination of ocean length distribution permits island number and contig number distributions to be found as well.

Chromosome Mapping↗
PubMed2003

Individual prefabricated titanium implants and titanium mesh in skull base reconstructive surgery. A report of cases.

Titanium implants can be shaped by traditional hand forming, press shaping, modular construction by welding, construction on full-size models shaped from CT coordinates and, most recently, by computer-assisted design and computer-assisted manufacturing (CAD/CAM) that consist in the direct prefabrication of individual implants by milling them out of a solid block of titanium. The aim of our study was to present a set of preliminary cases of an ongoing program of reconstructive procedures of the skull base using titanium implants. The subjects underwent ablative procedures of the skull base with reconstruction either by titanium mesh or individual prefabricated CAD/CAM implants. Six patients have been operated on successfully since 2000: two received prefabricated CAD/CAM titanium plates and four others underwent reconstruction with titanium mesh. The stability of CAD/CAM plates is superior to that of mesh, thus it is more useful in reconstructing large lesions of the frontal skull base and the temporal and occipital bones. Titanium mesh was successfully used for defects smaller than 100 cm(2) or where selected viscerocranial defects are complicated in design and less reproducible by CAD/CAM. The intraoperative design, shaping and adjustment characteristic of titanium mesh can be dispensed with when CAD/CAM implants are used. The 3-D data set used in the CAD/CAM process also operates in the navigated simulation and planning of the ablation contours, the latter being of great assistance in establishing the optimal future defect. As a disadvantage, CAD/CAM technology is more expensive than titanium mesh, and the process is time-consuming as it is carried out in advance of surgery.

Adult↗
PubMed2003

Experimental study of a porous rat tracheal prosthesis made of T40: long-term survival analysis.

In order to repair large defects in the laryngotracheal area, we developed a biomaterial based on porous titanium (Ti40) formed of spherical particles that are welded together. These Ti40 beads were arranged in several layers to create the rat tracheal prosthesis. After a partial tracheal resection, the prosthesis was fixed to both extremities to replace the missing part. Tissue surrounding the prosthesis was collected from 33 surviving animals after an implantation period of 3 to 12 months. Histological analyses showed that the periphery of the prosthesis was covered with fibroblasts and a few lymphocytes that penetrated the titanium layers. A ciliary cylindrical epithelium of respiratory type was found on the endoluminal side. The inflammatory reaction observed was minimal. These data indicate that the prosthesis, implanted in a laryngotracheal environment, is well tolerated by animals. Our results represent the first step towards the construction of a total laryngeal prosthesis that should allow restoration of the essential functions of the larynx after a laryngectomy in cancer treatment.

Animals↗
PubMed1998

Amyotrophic lateral sclerosis: an introduction.

Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease that results in the degeneration of lower and upper motor neurones in the brain and the spinal cord. Early onset and modern therapies, including assisted ventilation, improve survival in this disease, although its cause remains uncertain. Amongst the possible causes are deficiency of nerve growth factor, deficient glutamate re-uptake, autoimmunity and mutation of superoxide dismutase 1 gene. Additional factors may be industrial pollutants and occupational exposure to chemicals associated with welding and soldering. The criteria for the diagnosis of ALS, proposed by the World Federation of Neurology, are presented together with a review of the clinical features of the disease.

Amyotrophic Lateral Sclerosis↗
PubMed2001

Incidental retinal phototoxicity associated with ingestion of photosensitizing drugs.

BACKGROUND: to report on the possible correlation between incident retinal phototoxicity and the use of photosensitizing drugs. METHODS: four patients were examined because of scotomas and visual loss after an incidental exposure to a strong light source. One patient (two eyes) was exposed to standard camera flash; one patient (one eye) had a brief exposure to welding light; one patient (two eyes) underwent uncomplicated phacoemulsifications with intraocular lens implantation. The fourth patient had a severe retinal phototoxicity following a secondary intraocular lens implantation. All four patients underwent a thorough assessment including history of systemic drug use. These patients had ophthalmologic evaluation including: best corrected visual acuity (ETDRS charts), fundus examination, fluorescein and indocyanine green angiographies and were followed for 1 year. RESULTS: on presentation, the mean visual acuity was 7.5/20 (range: 20/400-20/20). Fundus examination disclosed yellow-gray sub-retinal lesions in all affected eyes. Early phase fluorescein angiography showed one or multiple hypofluorescent spots surrounded by a halo of hyperfluorescent window defect. In the late phase, some of these spots leaked the fluorescein dye. Indocyanine green angiography demonstrated hypofluorescent spots throughout with ill-defined borders of hyperfluorescence observed during the late stages. The common finding in these four patients was the fact that they were all taking one or more photosensitizing drugs (hydrochlorothiazide, furosemide, allopurinol, and benzodiazepines). Three of the patients had a full visual recovery a few months after the phototoxicity. The fourth patient remained with a visual acuity of 20/60 12 months after the light exposure. Despite the visual recovery, non-homogeneous retinal pigment epithelial disturbances persisted in all affected eyes. CONCLUSION: phototoxicity following incidental light exposure may occur in patients taking drugs of photosensitizing potential. Therefore, the thorough history of systemic drug ingestion should be obtained if patients have exposure to strong light sources.

Aged↗
PubMed2005

Reproductive toxicology in occupational settings: an update.

OBJECTIVE: This article mainly attempts to review the recent human literature on the adverse effects of occupational factors on fertility, developmental effects and genetic changes in the germ line, which lead to genetic malformations or to genetic disease. The secondary study aim is to answer whether occupational exposures are quantitative momentously for 15% involuntarily childless couples, 10-20% spontaneous abortions and 3% birth defects. METHODS: A literature survey was conducted for publications on these subjects focusing on the latest publications. PubMed (Medline. 2005) was used for this literature search. RESULTS: Publication bias and a large amount of confounding factors, which have to be controlled, make the design of human fertility studies difficult. Epidemiologic studies using time to conception techniques have been useful in identifying substances and exposure scenarios with proven toxic effect on fertility. The collected studies suggest that the exposure to the following substances or occupational settings may affect fertility function: lead, organic mercury compounds, manganese, carbon disulfide, 2-bromopropane and dibromochloropropane, welding, professional driving and working with heat. Concerning developmental effects even for methyl mercury, which was in group A of the German MAK list, to date no reliable evidence of the damaging effect on the human fetus under actual work conditions has been obtained. It is also difficult to classify substances according to their mutagenic potential for the germ cell, since no direct evidence of an association between exposure against a physical or chemical pollutant and the occurrence of a hereditary disorder has been found yet. CONCLUSION: In conclusion there are only a few substances which may affect reproductive function in the workplace without a doubt. The decreasing fertility of women in Western countries can be explained by the increasing female reproduction age, rather than by occupational exposures. Also the rates for spontaneous abortions and birth defects cannot be explained by industrial exposures at the workplace.

Abortion, Spontaneous↗
PubMed2004

Acute tensile strength analysis of collagen solder for mesh fixation to the peritoneal surface.

BACKGROUND: In this study, we assessed the feasibility of laser-assisted tissue welding as a means of fixing mesh prostheses to the peritoneum. We then tested the initial tensile strength of the bonds. METHODS: Fresh porcine peritoneal coupons were lap-joint bonded with laser-activated solder. Anesthetized New Zealand white rabbits and Yorkshire pigs also underwent laparotomy. Vicryl mesh (2.0 x 1.0 cm) was attached to the peritoneum using a laser system (1.43 mu, 2.5 W, 60 degrees C), solder formulations and configurations, and a 1 cm2 bond area. Control segments were affixed with 4.8-mm staples. After the animals were killed, the segments were excised en bloc. Tensile strength assessment was conducted by measuring peak force breaking strength. RESULTS: The strength of the solder bonds were similar in all groups (range, 261.5 +/- 170.3-465.3 +/- 288.2 g/cm2) and were not statistically different from the controls (215.8 +/- 117.8 g/cm2). CONCLUSIONS: These values are similar to the 200-500 g/cm2 acute strengths reported for sutured or stapled peritoneal closure. Mesh fixation by solder is feasible, and further development of this technology is warranted.

Animals↗
PubMed2000

Hepatic parenchymal transection using ultrasonic coagulating shears: a preliminary report.

Ultrasonically activated coagulating shears (CS) can coagulate and divide blood vessels of up to medium size by a tissue-welding technique. We present an application of CS in hepatic parenchymal transection during liver surgery. Intrahepatic vessels are uncovered by the so-called forceps fracture method, and they are coagulated and divided by CS. Larger vessels are tied only on the preserving side before the application of CS. Although further refinement of the CS tip is needed, this method has the potential to significantly simplify and improve surgical procedures for hepatic parenchymal transection.

Adult↗
PubMed2000

Bioabsorbable thread for tight tying of bones.

The purpose of this research was to develop a bioabsorbable thread for tight fixation of fractured bones and to examine its mechanical performance in an in-vitro simulation study. The thread is a blend of bioabsorbable poly(L-lactic acid); (PLLA) and poly(epsilon-caprolactone); (PCL) fibers and can be tightly connected by fusion welding of the PCL fibers. The tying strength of the PLLA-PCL blend thread was 39.7 N, which was comparable to that of stainless steel wire. A testing machine was fabricated to measure the fatigue strength of the tying by simulating bone fixation. The results showed that metal wires always failed because of breakage within 25,000 loading cycles, whereas the blend threads did not fail until 50,000 loading cycles. The looseness of tying for simulated bone fixation by the blend thread was within 1mm even after 50 000 loading cycles. In-vivo testing using rats revealed that the blend thread did not cause any severe inflammatory reaction.

Animals↗
PubMed2002

Thermally induced irreversible conformational changes in collagen probed by optical second harmonic generation and laser-induced fluorescence.

Irreversible thermal conformational changes induced to collagen have been studied by optical methods. More specifically, second harmonic generation (SHG) from incident nanosecond Ng:YAG 1064 nm radiation and laser-induced fluorescence by 337 nm, pulsed nanosecond nitrogen laser excitation, at 405, 410 and 415 nm emission wavelengths were registered at eight temperatures (40 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C) and normalised with respect to the corresponding values at the ambient temperature of 30 degrees C. The heating protocol used in this work, was selected to monitor only permanent changes reflecting in the optical properties of the samples under investigation. In this context, the SHG, directly related to the collagen fibril population in triple helix conformation, indicated on irreversible phase transition around 64 degrees C. On the other hand fluorescence related to the destruction of cross-linked chromophores in collagen, some of which are related to the triple helix tertiary structure, also indicated a permanent phase transition around 63 degrees C. These results are in agreement with previous results from studies with differential scanning calorimetry. However SHG and fluorescence, being non-invasive optical methods are expected to have a significant impact in the fields of laser ablative surgery and laser tissue welding.

Animals↗
PubMed2006

Effect of laser soldering irradiation on covalent bonds of pure collagen.

Laser tissue welding and soldering is being increasingly used in the clinical setting for defined surgical procedures. The exact induced changes responsible for tensile strength are not yet fully investigated. To further improve the strength of the bonding, a better understanding of the laser impact at the subcellular level is necessary. The goal of this study was to analyze whether the effect of laser irradiation on covalent bonding in pure collagen using irradiances typically applied for tissue soldering. Pure rabbit and equine type I collagen were subjected to laser irradiation. In the first part of the study, rabbit and equine collagen were compared using identical laser and irradiation settings. In the second part of the study, equine collagen was irradiated at increasing laser powers. Changes in covalent bonding were studied indirectly using the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) technique. Tensile strengths of soldered membranes were measured with a calibrated tensile force gauge. In the first experiment, no differences between the species-specific collagen bands were noted, and no changes in banding were found on SDS-PAGE after laser irradiation. In the second experiment, increasing laser irradiation power showed no effect on collagen banding in SDS-PAGE. Finally, the laser tissue soldering of pure collagen membranes showed virtually no determinable tensile strength. Laser irradiation of pure collagen at typical power settings and exposure times generally used in laser tissue soldering does not induce covalent bonding between collagen molecules. This is true for both rabbit and equine collagen proveniences. Furthermore, soldering of pure collagen membranes without additional cellular components does not achieve the typical tensile strength reported in native, cell-rich tissues. This study is a first step in a better understanding of laser impact at the molecular level and might prove useful in engineering of combined collagen-soldering matrix membranes for special laser soldering applications.

Animals↗
PubMed2007

Polymer particle-based micromolding to fabricate novel microstructures.

Conventional micromolding provides rapid and low-cost methods to fabricate polymer microstructures, but has limitations when producing sophisticated designs. To provide more versatile micromolding techniques, we developed methods based on filling micromolds with polymer microparticles, as opposed to polymer melts, to produce microstructures composed of multiple materials, having complex geometries, and made using mild processing conditions. Polymer microparticles of 1 to 30 microm in size were made from PLA, PGA and PLGA using established spray drying and emulsion techniques either with or without encapsulating model drug compounds. These polymer microparticles were filled into PDMS micromolds at room temperature and melted or bonded together to form microstructures according to different protocols. Porous microstructures were fabricated by ultrasonically welding microparticles together in the mold while maintaining the voids inherent in their packing structure. Multi-layered microstructures were fabricated to have different compositions of polymers and encapsulated compounds located in different regions of the microstructures. More complex arrowhead microstructures were fabricated in a two-step process using a single mold. To assess possible applications, microstructures were designed as microneedles for minimally invasive drug delivery. Multi-layer microneedles were shown to insert into cadaver tissue and, according to design, detach from their base substrate and remain embedded in the tissue for controlled release drug delivery over time. We conclude that polymer particle-based micromolding can encapsulate compounds within microstructures composed of multiple materials, having complex geometries, and made using mild processing conditions.

Biocompatible Materials↗
PubMed2003

Laser tissue soldering: applications in the genitourinary system.

Within the past 25 years, lasers have transitioned from merely destructive or ablative tools to those with reconstructive uses. It has been shown that the application of laser thermal energy to tissue will result in welding of the approximated areas. Furthermore, the addition of protein solder and chromophores (tissue soldering) has increased wound tensile strength while decreasing peripheral tissue damage. Laboratory studies have demonstrated application of laser tissue soldering to virtually all components of the genitourinary system. Increasing human experience in recent years has reinforced the success of this technique.

Animals↗
PubMed1991

Coronary artery stenting after angioplasty with self-expanding parallel wire metallic stents.

Parallel wire stents were implanted over exchange guide wires at percutaneous transluminal coronary angioplasty sites in 27 canine coronary arteries that were predilated with slightly oversized balloons. Stents were stainless steel, self-expandable, 3.5 to 4.5 mm in diameter, 9 to 12 mm in length, and were made of 10 wires that were longitudinally laser-welded in a zig-zag design. The compressible stent was delivered by the withdrawal of a Teflon outer catheter (4.2 to 4.9F) and the push of a polyethylene inner catheter. Aspirin, 80 mg per day, was given from the day before the study began, and heparin (150 U/kg) was administered during implantation. Quantitative angiography and pathologic examinations were performed at day 0 and at weeks 2, 4, 12, 26 and 52. The coronary angiographic diameter at the stent site immediately after stenting marginally increased from diameter before stenting: 3.22 +/- 0.40 mm versus 3.14 +/- 0.37 mm (p = 0.03), and during a mean of 14 weeks of follow-up, remained unaltered from immediate post-stenting: 3.29 +/- 0.43 mm versus 3.22 +/- 0.40 mm (p = NS) with no stent displacement. Comparisons of patency and thrombosis between heparin-coated and uncoated stents, between left anterior descending and circumflex arteries, and among the three different diameters of stents showed uniformly good results. At microscopy, the wires were oriented perfectly and embedded in the arterial wall, and by 2 weeks they were covered by mucopolysaccharide ground substance, smooth muscle cells, and an almost complete monolayer of neoendothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1985

Nd-YAG laser fusion of human atheromatous plaque-arterial wall separations in vitro.

The hypothesis that thermal fusion of disrupted layers of atheromatous arterial wall can be achieved with a neodymium-yttrium aluminum garnet (Nd-YAG) laser was tested. Fresh postmortem human atheromatous plaque was separated from the underlying arterial wall to simulate a dissection in 1-cm2 arterial wall sections. With the plaque and underlying arterial wall subsequently compressed between glass slides, 17 W of continuous-wave Nd-YAG laser radiation were delivered through an optical fiber to the luminal surface of the plaque over a 4-mm2 area. Fusion of the plaque to the underlying arterial wall invariably occurred when tissue compression was applied during lasing and a thin blood film was present between the tissues. The load supported by tissue welds depended on plaque thickness, plaque composition, and exposure duration and was as great as 25 g. In postmortem, blood-filled, whole-artery segments, in which plaque had been completely separated from the media, this technique was applied intraluminally during angioplasty with a prototype balloon catheter. Lateral dispersion of Nd-YAG radiation from the termination of an optical fiber within the balloon allowed fusion of plaque to the underlying arterial wall during balloon inflation to 2 atm. Histologic examination of laser-treated tissues showed coagulation of tissues at the junction between the intimal plaque and media. It is concluded that thermal fusion of separated layers of atheromatous arterial wall can be achieved with Nd-YAG laser irradiation. This concept may be useful in the treatment of arterial dissections.

Arteries↗
PubMed1987

Percutaneous transluminal coronary angioplasty restenosis: potential prevention with laser balloon angioplasty.

Restenosis after percutaneous transluminal coronary angioplasty may result primarily from the combination of a thrombogenic surface and local flow separation produced by disruption of the arterial wall and lumen. Elastic recoil and, perhaps, cellular proliferation further contribute to luminal compromise after percutaneous transluminal coronary angioplasty. Laser balloon angioplasty, performed during the final inflation of an otherwise conventional balloon angioplasty procedure, uses the coagulative properties of Nd:YAG laser radiation to weld together disrupted tissue elements thermally, to reduce elastic recoil and to destroy viable arterial tissue. Studies in human postmortem atheromatous arteries and in animal models in vivo indicate that laser balloon angioplasty, by creating a lumen that approximates the size and smooth cylindrical shape of the balloon, should be effective in the treatment of important causes of restenosis.

Angioplasty, Balloon↗
PubMed1983

Tubal microsurgery with the carbon dioxide laser.

Thirty New Zealand White female rabbits underwent tubal resection and reanastomosis for comparison of conventional microsurgery and laser microsurgical techniques. The rabbits were divided into three groups. The first group of 10 rabbits had 3 cm of tissue resected by knife from each uterine horn; the cut ends were then reanastomosed in one layer with 8-0 Vicryl sutures with the use of the operating microscope. The second group of 10 rabbits had 3 cm of tissue resected by laser from each uterine horn; the cut ends were then reanastomosed in one layer with 8-0 Vicryl. The third group of 10 rabbits had 3 cm of tissue resected by laser from each uterine horn; the cut ends were then reanastomosed by "welding" the tissues with the laser. All rabbits in the first group became pregnant. Only four in the second group became pregnant, but none in the third group became pregnant. It is concluded that the carbon dioxide laser beam as used in this study has no place in tubal resection and reconstruction.

Animals↗