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PubMed2001

The use of vacuum-assisted closure therapy for the treatment of lower-extremity wounds with exposed bone.

Lower-extremity wounds with exposed tendon, bone, or orthopedic hardware present a difficult treatment challenge. In this series of patients, subatmospheric pressure therapy was applied to such lower-extremity wounds. Seventy-five patients with lower-extremity wounds, most of which were the result of trauma, were selected for this study. Dressings made of sterile open-cell foam with embedded fenestrated tubing were contoured to the wound size and placed into the wound. The site was covered with an adhesive plastic sheet. The sheet was placed beneath any external fixation devices, or the fixation device was enclosed within the sheet. The tubing was connected to the vacuum-assisted closure pump. Continuous subatmospheric suction pressure (125 mmHg) was applied to the wound site. The wounds were inspected and the dressings were changed every 48 hours.Vacuum-assisted closure therapy greatly reduced the amount of tissue edema, diminishing the circumference of the extremity and thus decreasing the surface area of the wound. Profuse granulation tissue formed rapidly, covering bone and hardware. The wounds were closed primarily and covered with split-thickness skin grafts, or a regional flap was rotated into the granulating bed to fill the defect. Successful coverage was obtained without complication in 71 of 75 patients. Wounds have been stable from 6 months up to 6 years.

Bandages↗

PubMed1958

Araldite as an embedding medium for electron microscopy.

Epoxy resins are suitable media for embedding for electron microscopy, as they set uniformly with virtually no shrinkage. A mixture of araldite epoxy resins has been developed which is soluble in ethanol, and which yields a block of the required hardness for thin sectioning. The critical modifications to the conventional mixtures are the choice of a plasticized resin in conjunction with an aliphatic anhydride as the hardener. The hardness of the final block can be varied by incorporating additional plasticizer, and the rate of setting can be controlled by the use of an amine accelerator. The properties of the araldite mixture can be varied quite widely by adjusting the proportions of the various constituents. The procedure for embedding biological specimens is similar to that employed with methacrylates, although longer soaking times are recommended to ensure the complete penetration of the more viscous epoxy resin. An improvement in the preservation of the fine structure of a variety of specimens has already been reported, and a typical electron microgram illustrates the present paper.

Electrons↗

PubMed2000

Three-dimensional graphic reconstruction of the insect exoskeleton through confocal imaging of endogenous fluorescence.

The exoskeleton of the cockroach leg was imaged via confocal microscopy to generate digital graphic reconstructions of its three-dimensional structure. The cuticle is autofluorescent and can be visualized without staining, but is maximally imaged in aldehyde-fixed preparations viewed under krypton-argon laser illumination (yellow green (568 nm) excitation, commonly used in confocal microscopes). Images of the entire trochanteral segment of the leg were constructed as montages from optical sections taken as overlapping series that were coincident in the z-axis. Reconstructions of the exoskeleton from these images showed that strain sensing mechanoreceptors are located in association with buttresses and thickenings that form a consistent internal architecture in both juvenile and adult animals. Accuracy of reconstructions was gauged by embedding specimens in Spurr's resin and histologically sectioning them perpendicular to the optical plane of section (z-axis). Comparison of plastic sections with two-dimensional images generated by "resectioning" the software model showed that reconstructed exoskeleton had a high level of accuracy. Imaging of older and larger animals was limited by the sclerotization and increased thickness of the cuticle. Surface extraction algorithms were used to generate vector graphic files in CAD format for export to software used in engineering and design. Among other potential uses, these models have been studied by Finite Element Analysis to examine the distribution of mechanical strains in the exoskeleton that occur during posture and locomotion. The advantages and limitations of the techniques are discussed. These methods may be used in studying the exoskeleton and the anatomy of cuticular mechanoreceptors of other arthropods to similar advantage.

Animals↗

PubMed2002

Corrosion susceptibility of lingual wire extensions in removable appliances. An in vitro study.

MATERIAL AND METHODS: The corrosion resistance of ten different round orthodontic wires as plastic-encased extensions was evaluated in vitro. Following the production of defined test samples with free as well as with acrylic-embedded wire segments, ten samples of each product were subjected to gap provocation by deflecting the free-running wire ends with an electric drive, while 10 samples remained provocation-free. The tests were run under standardized conditions (7 days, 37 degrees C, pH 2.3, 0.1 mol NaCl/CH3CHOHCOOH), and the findings were analyzed by stereo light microscopy and scanning electron microscopy. RESULTS: The following alterations were observed on the wire surfaces: a) crevice corrosion with substantial linear surface erosion and opaque discolorations, b) localized pitting corrosion, and c) mild surface erosion with translucent discolorations. The reactions of the test samples were similar in both those that were subjected to addition mechanical loading in the electrolyte and those that were not. Cr-Ni steels were susceptible to corrosion, whereas Co-Cr alloys as well as low-nickel manganese steels had only slight visible alterations, if any, in the embedded wire sections. CONCLUSIONS: Clinically occurring discolorations in the acrylic can be attributed to corrosion processes on the embedded wire extensions. These processes can be simulated and observed in vitro. During the processing of acrylic materials now customary in the orthodontic laboratory, crevices are inevitably formed between the wire and the acrylic, furthering the corrosion process. Our results suggest that, being more resistant to crevice corrosion, Co-Cr alloys or low-nickel steels can be considered as alternatives.

Corrosion↗

PubMed1996

The effect of surface roughness on fibroblast adhesion in vitro.

Adhesion of tissue cells to biomaterial implants is a major factor of their biocompatibility. Quantitative or qualitative adhesion measurements would therefore be useful in the screening of new implant materials. Results from a quantitative method of measuring the total cell adhesion area of cultured cells is presented. It is postulated that the more compatible the surface, the greater the amount of cell adhesion. Fibroblastic cells were cultured on discs of plastic (Thermanox), commercially pure titanium (ISO 5832/2) or steel (ISO 5832/1), as used in AO fixation plates. The cells were fixed, stained, embedded in resin and their discs removed. Backscattered electron (BSE) imaging in a scanning electron microscope displayed the stained cells within the unstained resin. Imaging at high beam energy allowed visualization of the entire cell. Low beam energy displayed the regions of cell contact with the substrate, i.e. the focal adhesion sites. Images were analyzed with an image analysis and measurement system which allowed the percentage of the cell area involved with adhesion to be calculated. Results show that the material roughness, with the materials and cells tested, does not affect the total amount of cell adhesion. Implant surface design to encourage cell adhesion and discourage bacterial adhesion is discussed.

Analysis of Variance↗

PubMed1999

Guided bone regeneration using titanium grids: report of 10 cases.

In order to ensure an adequate space where new bone can be formed in guided bone regeneration (GBR), most surgeons fill bone defects with biomaterials. In this work we evaluated new bone regeneration in 10 patients using only a blood clot protected with titanium grids and non-resorbable membranes, without any filling material. A manual measurement of the size of the bone defect, using a plastic probe, was performed at 2 surgical steps. After 5 months of treatment, a biopsy was taken from each patient, fixed and embedded in PMMA, examined microradiographically and morphologically to evaluate the newly-formed bone. Our results showed a good repair of the defects by bone regeneration (about 85% overall), high mineral density of new bone around the implants after 5 months, and steady state deposition processes. These results in GBR, without filling material, appear very promising for implantology and reconstructive odontostomatology practice.

Adult↗

PubMed1999

A soiling system for evaluation of house dust, allergens, and lead retention on carpets and other surfaces.

Artificial soiling of carpeted or other floor surfaces has several important applications in human exposure assessment and textile research including evaluation of textile properties, sampling devices, and cleaning regimens. A method was developed and validated to deposit uniform and reproducible known quantities of house dust, allergens, and leaded dust on carpets. The soiling apparatus consisted of a 100 cm x 60 cm inclined steel track and a plastic cylinder, with a series of staggered holes, that contains a known volume of reference house dust. After deposition, the dust is embedded by dragging a steel rod over the carpet surface. Deposition tests were performed with bulk house dust, sodium chloride, and house dust with reference quantities of dust mite allergen and lead. The apparatus deposited equivalent (arithmetic mean) amounts of dust, sodium chloride, and dust mite allergen on the front and back halves of test carpets. The introduction of inert fumed silica to the reference sample aided in dispersal of dust over test surfaces. Little to no variation in mean deposition was found within or between 4 days of testing. Using a grid containing weighing boats under the apparatus, spatial deposition was found to vary across a 92 x 46 cm surface by 13 percent. The apparatus deposited reproducible mean quantities of bulk dust on test surfaces from 7 g/m2 to 28 g/m2 with a coefficient of variation ranging from 4-6 percent. The apparatus could be altered to deliver smaller or larger amounts of dust.

Allergens↗

PubMed2002

Self-regulation mechanism of temporally asymmetric Hebbian plasticity.

Recent biological experimental findings have shown that synaptic plasticity depends on the relative timing of the pre- and postsynaptic spikes. This determines whether long-term potentiation (LTP) or long-term depression (LTD) is induced. This synaptic plasticity has been called temporally asymmetric Hebbian plasticity (TAH). Many authors have numerically demonstrated that neural networks are capable of storing spatiotemporal patterns. However, the mathematical mechanism of the storage of spatiotemporal patterns is still unknown, and the effect of LTD is particularly unknown. In this article, we employ a simple neural network model and show that interference between LTP and LTD disappears in a sparse coding scheme. On the other hand, the covariance learning rule is known to be indispensable for the storage of sparse patterns. We also show that TAH has the same qualitative effect as the covariance rule when spatiotemporal patterns are embedded in the network.

Animals↗

PubMed1982

[Scanning electron microscope demonstration of wall colonization of water-bearing plastic tubes].

A polyethylene and a silicone tube from water leading system of a dental unit, in which Pseudomonas aeruginosa could be isolated, were investigated by S.E.M. (Scanning Electron Microscopy). In the tubes thick deposits of extracellular material were found, in which microorganisms were embedded or on which they were free-lying. Pretreatment of the water systems by irrigating and by disinfection was unsuccessful. The possible protection of microorganisms by the demonstrated extracellular material against hydraulic forces and disinfection is discussed.

Adhesiveness↗

PubMed1997

A universal post-embedding protocol for immunogold labelling of osmium-fixed, epoxy resin-embedded tissue.

The authors have found that double etching of epoxy-embedded, ultrathin sections with 3% sodium metaperiodate rendered epitope expression comparable to that obtained with either saturated or half-saturated sodium metaperiodate solutions. In contrast to either of the two more concentrated oxidizing solutions, double etching with 3% sodium metaperiodate neither bleached the specimens nor generated holes in the plastic resin.

Animals↗

PubMed2005

Monoclonal antibodies 1B3 and 5C8 as probes for monitoring the integrity of the C-terminal end of soluble angiotensin-converting enzyme.

Angiotensin-converting enzyme (ACE) is a membrane-anchored ectoprotein that is proteolytically cleaved, yielding an enzymatically active soluble ACE. Two mouse monoclonal antibodies, MAbs 1B3 and 5C8, were generated to the C-terminal part of human soluble ACE. MAb 1B3 recognized the catalytically active ACE, as revealed by ELISA and precipitation assays, whereas Western blotting and immunohistochemisty on paraffin- embedded sections using MAb 5C8 detected denatured ACE. MAb 1B3 showed extensive cross-reactivity, recognizing 15 species out of the 16 tested. The binding of this MAb to ACE was greatly affected by conformational changes induced by adsorption on plastic, formalin fixation, and underglycosylation. Furthermore, MAb 1B3 binding to the mutated ACE (Pro1199Leu substitution in the juxtamembrane region, leading to a fivefold increase in serum ACE level) was markedly decreased. MAb 5C8 detected all the known expression sites of full-size ACE using formalin-fixed and paraffin-embedded human tissues. The sequential epitope for MAb 5C8 is formed by the last 11 amino acid residues of soluble ACE (Pro1193-Arg1203), whereas the conformational epitope for 1B3 is formed by a motif within these 11 amino acid residues and, in addition, by at least one stretch that includes Ala837-His839 located distal to the sequential epitope. Our findings demonstrated that MAbs 1B3 and 5C8 are very useful for the study of ACE shedding, for identification of mutations in stalk regions, and for studying alternatively spliced variants of ACE. In addition, binding of MAb 1B3 is a sensitive determinant of the integrity of soluble ACE.

Amino Acid Sequence↗

PubMed2004

Ideal cooling process for paraffin-embedded tissues.

Back in the seventies everybody was convinced that it was no longer necessary to cool paraffinembedded tissues, because of the new advances in the production of paraffin. The reason for this assumption was the addition of plastic polymers and dimethyl sulfoxide. The quality of tissue sectioning improved because of these additives. The daily routine in the histology laboratories shows that it is impossible to produce good quality cutting without cooling. Cooling the paraffin by means of cooling plates or ice dishes creates drastic improvement; the cutting quality improves and it is much easier. Both improvements speed up the process and save time for the technicians and the physician. Long-term study indicates that not only the temperature but also the methodology of cooling and the cooling rate are playing a decisive role in the cutting quality.

Cold Temperature↗

PubMed2006

Viscoelastic properties of individual glial cells and neurons in the CNS.

One hundred fifty years ago glial cells were discovered as a second, non-neuronal, cell type in the central nervous system. To ascribe a function to these new, enigmatic cells, it was suggested that they either glue the neurons together (the Greek word "gammalambdaiotaalpha" means "glue") or provide a robust scaffold for them ("support cells"). Although both speculations are still widely accepted, they would actually require quite different mechanical cell properties, and neither one has ever been confirmed experimentally. We investigated the biomechanics of CNS tissue and acutely isolated individual neurons and glial cells from mammalian brain (hippocampus) and retina. Scanning force microscopy, bulk rheology, and optically induced deformation were used to determine their viscoelastic characteristics. We found that (i) in all CNS cells the elastic behavior dominates over the viscous behavior, (ii) in distinct cell compartments, such as soma and cell processes, the mechanical properties differ, most likely because of the unequal local distribution of cell organelles, (iii) in comparison to most other eukaryotic cells, both neurons and glial cells are very soft ("rubber elastic"), and (iv) intriguingly, glial cells are even softer than their neighboring neurons. Our results indicate that glial cells can neither serve as structural support cells (as they are too soft) nor as glue (because restoring forces are dominant) for neurons. Nevertheless, from a structural perspective they might act as soft, compliant embedding for neurons, protecting them in case of mechanical trauma, and also as a soft substrate required for neurite growth and facilitating neuronal plasticity.

Animals↗

PubMed1990

Contraction phenomenon of type I collagen gel by melanoma cells.

In order to study the interaction between melanoma cells and collagen, B16 murine melanoma cells were embedded and cultured in type I collagen gel. Melanoma cells cultured in the collagen gel became elongated, as compared with those cultured on plastic, and some of them assumed a dendritic form. The gel contracted very slowly but steadily during culturing of melanoma cells, as in the experiment using fibroblasts. On the 20th day of culture the area of the gel accounted for only 32% of that when culture started. This contraction was enhanced by retinoic acid, which is known to induce cell differentiation. The contractility of the gel differed between various lines of melanoma cells. The present observations raise the possibility of interaction between melanoma cells and type I collagen.

Animals↗

PubMed2004

Subgingival foreign body embedment in a preschool child: management with three and a half years follow-up.

CASE REPORT: This is a case report of diagnosis and management of a foreign body embedded in the gingivae of a preschool child. A 3 year-old girl presented with pain, mobility and intraoral oedema of the upper left primary canine (#63). An angular, diffuse radiolucency on the mesial aspect of the primary canine was observed in the periapical radiograph and within this radiolucency, a linear radiopacity was noted in contact with the mesial surface of the root. A clinical diagnosis of severe localized periodontal involvement due to foreign body embedment was made. It was initially attempted unsuccessfully to remove the foreign body by subgingival root scaling and planning. The area was then surgically exposed. Upon flap elevation, a tubular plastic material similar to those used for the insulation of electric wires was found to encircle tightly the cervical area of the root of the primary canine, which was removed. Three months after the surgery, the gingiva of the affected tooth had attained its normal color but had started to recede for about 1 mm. One year post surgery, the gingival recession had progressed to 3 mm and a carious lesion had already developed at the denuded root surface. Three and a half years post surgery a mild inflammation of the buccal gingivae was apparent, but periodontal healing had occurred. CONCLUSION: The dentist must always consider the possibility of a foreign body embedment in the periodontal tissues of children and be familiar to the clinical signs and symptoms as well as the proper treatment procedures.

Child, Preschool↗

PubMed1992

Techniques to optimize post-embedding single and double staining for amino acid neurotransmitters.

We report a number of technical refinements for single and double staining with post-embedding electron microscopy for glutamate, aspartate, and gamma-aminobutyric acid. Best results were obtained with 2.5% glutaraldehyde in the fixative and by minimizing the duration of plastic polymerization and the interval between cutting and reacting. Quantitative documentation of the ability of exogenous glutamate, aspartate, and gamma-aminobutyric acid to block their immune staining is provided. Increased intensity of staining with the glutamate and aspartate antisera resulted from preincubation of glutamate antiserum with aspartate and aspartate antiserum with glutamate. To perform double staining with antisera raised in the same species, it was necessary to block antigenicity of the first antiserum; best results were obtained with hot paraformaldehyde fumes. By using a detergent instead of etching, these methods permitted the simultaneous visualization of tracers to identify neuroanatomic pathways.

Afferent Pathways↗

PubMed1990

Immunocytochemical study of the endocrine pancreas in the grey kangaroo (Macropus fuliginosus).

The endocrine pancreas of the grey kangaroo, Macropus fuliginosus, was investigated by means of immunocytochemistry using the PAP method on the same section at the light- and electron-microscopic levels. Semithin plastic sections were stained individually with primary antibodies for insulin, glucagon, somatostatin and pancreatic polypeptide (PP), and then photographed. Sections were osmicated, re-embedded in BEEM capsules, and ultrathin sections made and examined. The same labelled cells as in the semithin sections were localised in the thin sections, photographs taken and the morphology of secretory granules studied. The insulin cells were pleomorphic; their secretory granules displayed an electron-dense core surrounded by an empty halo. The glucagon cells possessed granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells had larger, less dense secretory granules. The PP cells showed small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by correlated immunocytochemical data at the light- and electron-microscopic levels.

Animals↗

PubMed1993

Simplified fabrication of orbital prostheses using posterior attachment for the artificial eye.

The ocular component of an orbital prosthesis can be held firmly during fabrication by attaching a plastic needle cover with autopolymerizing acrylic resin to the posterior surface of the eye in the wax-sculpted prosthesis. This index is subsequently embedded in the master cast. Compared with other techniques described in the literature, this technique spares the corneal surface of the artificial eye and allows duplicate fabrication of silicone orbital prostheses in nonmetal durable molds.

Acrylic Resins↗