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1992

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Articles 1 - 30 of 56

Full-Text Articles in Biomedical Engineering and Bioengineering

High-Level Expression Of A Heterologous Protein In The Milk Of Transgenic Swine Using The Cdna Encoding Human Protein C, William H. Velander, John L. Johnson, Raymond L. Page, Christopher G. Russell, Anuradha Subramanian, Tracy D. Wilkins, Francis C. Gwazdauskas, Christoph Pittius, William N. Drohan Dec 1992

High-Level Expression Of A Heterologous Protein In The Milk Of Transgenic Swine Using The Cdna Encoding Human Protein C, William H. Velander, John L. Johnson, Raymond L. Page, Christopher G. Russell, Anuradha Subramanian, Tracy D. Wilkins, Francis C. Gwazdauskas, Christoph Pittius, William N. Drohan

William H. Velander Publications

Transgenic pigs were generated that produced human protein C in their milk at up to 1 g/liter. The gene construct was a fusion gene consisting of the cDNA for human protein C inserted into the first exon of the mouse whey acidic protein gene. These results demonstrate that the mouse whey acidic protein gene contains regulatory elements that can direct cDNA expression at high levels in the pig mammary gland. Recombinant human protein C that was produced at about 380 pg/ml per hr in transgenic pig milk possessed anticoagulant activity that was equivalent to that of protein C ...


Viscosities Of Vegetable Oils And Fatty Acids, Hossein Noureddini, B C. Teoh, L Davis Clements Dec 1992

Viscosities Of Vegetable Oils And Fatty Acids, Hossein Noureddini, B C. Teoh, L Davis Clements

Papers in Biomaterials

Data for viscosity as a function of temperature from 24 to llO°C (75 to 230°F) have been measured for a number of vegetable oils (crambe, rapeseed, corn, soybean, milk- coconut, lesquerella) and eight fatty acids in the from Cg to CZZ The viscosity measurements were performed according to ASTM test methods D 445 and D 446. Several correlations were fitted to the experimental data. Correlation constants for the best fit are presented. The range of temperature in which the correlations are valid is from 24'C (75'F), or the melting point of the substance, to llO°C ...


Densities Of Vegetable Oils And Fatty Acids, Hossein Noureddini, B C. Teoh, L Davis Clements Dec 1992

Densities Of Vegetable Oils And Fatty Acids, Hossein Noureddini, B C. Teoh, L Davis Clements

Papers in Biomaterials

Complete data for density as a function of temperature have been measured for a number of vegetable oils (cramhe, rapeseed, corn, soybean, milkweed, coconut, lesquerella), as well as eight fatty acids in the range CS to C,, at temperatures from above their melting points to llQ°C (23Q°F). The specific gravity and density measure mente were performed according to American Society for Testing and Materials (ASTM) standard test methods D 368, D 891 and D 1298 for hydrometers and a modified ASTM D 369 and D 891 for pycnometers. Correlation constants, based on the experimental data, are presented for ...


Sediment Delivery On Rill And Interrill Areas, John E. Gilley, D. C. Kincaid, W. J. Elliot, J. M. Laflen Dec 1992

Sediment Delivery On Rill And Interrill Areas, John E. Gilley, D. C. Kincaid, W. J. Elliot, J. M. Laflen

Biological Systems Engineering: Papers and Publications

Equations which relate sediment delivery to a power function of flow rate and slope gradient were calculated in this study. The data used to parameterize the calculations were obtained from sites where crop residues had been removed. and moldboard plowing and disking had occurred. Measurements of sediment delivery resulting from simulated rainfall were obtained from preformed rills and interrill areas. The equations provided reliable sediment delivery estimates for selected soils located throughout the United States. To use the sediment delivery equations, soil-related parameter values must be identified. Multiple regression analyses were performed to relate parameter values used in the equations ...


Oxidative Mechanisms In Arterial Distension Injury: Observations Relevant To Restenosis After Angioplasty, Charles F. Babbs, Yuan Zhong Nov 1992

Oxidative Mechanisms In Arterial Distension Injury: Observations Relevant To Restenosis After Angioplasty, Charles F. Babbs, Yuan Zhong

Weldon School of Biomedical Engineering Faculty Working Papers

Background: To explore the hypothesis that tissue iron and reactive oxygen species, including superoxide (O2), mediate acute inflammatory and late hyperplastic responses to vascular injury, we studied experimental overdistension of normal carotid and femoral arteries in dogs. Experimental design: Arterial segments isolated in situ were distended with Ringer solution at 2 atmospheres pressure. In initial experiments the arteries were excised immediately after distension and immersed in diaminobenzidine solutions containing Mn++ ions to initiate histochemical reactions for O2. In other experiments distended arterial segments were reperfused with arterial blood in the presence or absence of the iron chelator, deferoxamine, or the ...


Simulated Crystalline Structures Of Aromatic Polyimides, Tze Wing Poon, B. David Silverman, Ravi F. Saraf, Angelo R. Rossi, Paul S. Ho Nov 1992

Simulated Crystalline Structures Of Aromatic Polyimides, Tze Wing Poon, B. David Silverman, Ravi F. Saraf, Angelo R. Rossi, Paul S. Ho

Ravi Saraf Publications

Semicrystalline structures involving molecular packing and optimized chain conformations of three polyimides have been obtained with the CHARMM moleculardynamics program, and their densities calculated. An eclipsed conformation of face-toface stacking of polymer chains with a relative shift is observed, and the shift is found to depend upon the molecular characteristics of the planar unit and chain linearity. Threedimensional structures obtained by calculating the optimized edge-on confirmation of the stacked units yield the smallest calculated density for PMDA-ODA, namely 1.515 g/cm3, followed by BPDA-PDA with 1.644 g/cm3 and PMDA-PDA with 1.712 g/cm3 ...


Quantitative Assessment Of Myocardial Oxygen Supply And Demand Using A Dynamic Model Of The Cardiovascular System, Badrinath R. Puranic Oct 1992

Quantitative Assessment Of Myocardial Oxygen Supply And Demand Using A Dynamic Model Of The Cardiovascular System, Badrinath R. Puranic

Theses

A quantitative understanding of the changes in coronary, pulmonary and systemic hemodynamic variables and their effect on myocardial supply and demand is important to the better management of anesthetic care of patients with impaired cardiac function. Animal studies have identified those hemodynamic factors that play an important role in determining the balance between oxygen supply and demand for the myocardium. These include myocardial contractility, left ventricular end-diastolic volume, systemic arterial pressure, systemic vascular resistance, and heart rate. The interactions of these factors are complex and their combined effects on myocardial oxygen supply and demand are difficult to predict a priori ...


Mathematical Model And Simulation Of The Progression Of Cutaneous T-Cell Lymphoma, Maria L. Agostinho Oct 1992

Mathematical Model And Simulation Of The Progression Of Cutaneous T-Cell Lymphoma, Maria L. Agostinho

Theses

A simple mathematical model and simulation of the progression of cancer with particular emphasis on Cutaneous T Cell Lymphoma was investigated. The mathematical model consists of a set of differential equations that first satisfies the homeostasis levels of the different components present and second predicts the dynamics during a diseased or unhealthy condition. The simulation was done using a FORTRAN program for integrating the differential equations.

Simulation of the immune system is important in evaluating the usefulness of particular sorts of biologically targeted therapies and in selecting the most promising treatment strategies for clinical trials. In particular, the effects of ...


Beginning Of Motion For Selected Unanchored Residue Materials, John E. Gilley, Eugene R. Kottwitz Aug 1992

Beginning Of Motion For Selected Unanchored Residue Materials, John E. Gilley, Eugene R. Kottwitz

Biological Systems Engineering: Papers and Publications

Conservation tillage systems help to maintain residue materials from the previous crop on the soil surface. The potential for serious erosion may exist if crop residues are removed by overland flow. This study is conducted to identify the hydraulic conditions required to initiate residue movement by overland flow. Corn, cotton, peanut, pine needles, sorghum, sunflower, and wheat residue are placed in a flume on smooth and sand surfaces, and flow is then introduced in progressive increments. The discharge rate and flow velocity required to initiate residue movement are identified. Hydraulic measurements are used to calculate the ratio of critical flow ...


Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock Jul 1992

Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock

Nancy A. Burnham

Unusual effects noticed in previous force microscopy data are explained by a model based on work-function anisotropies and their associated patch charges. Measurable forces between macroscopic bodies can be due to the interaction of patch charges, with important consequences in the fields of surface forces, contact mechanics, adhesion, Schottky barriers, and the surface properties of insulators.


Evidence That Free Fatty Acid-Iron Complexes Directly Initiate Lipid Peroxidation In Vitro And In Vivo: A New Mechanism Of Oxidative Stress, Steven C. Salaris, Charles F. Babbs, Joann Pham, John J. Turek Jun 1992

Evidence That Free Fatty Acid-Iron Complexes Directly Initiate Lipid Peroxidation In Vitro And In Vivo: A New Mechanism Of Oxidative Stress, Steven C. Salaris, Charles F. Babbs, Joann Pham, John J. Turek

Weldon School of Biomedical Engineering Faculty Working Papers

Through a series of biochemical and histochemical experiments we explored the novel hypothesis that iron and free fatty acids, liberated after tissue injury, combine to form liposoluble complexes that directly initiate lipid peroxidation. The addition of 100 M ferric iron to 30 mM linoleate suspensions at pH 7.4 produced time dependent lipid peroxidation, measured as conjugated diene formation. Complexes of 100 M ferric iron and 600 M pentanoate also initiated formation of conjugated dienes in linoleate suspensions and formation of malondialdehyde-like materials in rat liver slices. A histochemical stain for free fatty acids revealed positive reactions within cell membranes ...


Wear And Friction Of Titanium Nitride On Ultra High Molecular Weight Polyethylene Under Oscillating Motion For Evaluation Of Use In Articulating Orthopedic Applications, David Scott Jacobson May 1992

Wear And Friction Of Titanium Nitride On Ultra High Molecular Weight Polyethylene Under Oscillating Motion For Evaluation Of Use In Articulating Orthopedic Applications, David Scott Jacobson

Theses

Materials are a factor in the performance of articulating orthopedic implants. An oscillating tribometer is utilized to investigate mechanisms of wear and friction of TiN (titanium nitride) coated on Ti-6Al-4V (titanium) alloy against UHMWPe (ultra high molecular weight polyethylene). Three thicknesses of TiN coating (1.76 pm, 4.15 µm, and 10.5 µm) are used to evaluate the performance of each in UHMWPe wear reduction and coating integrity. An uncoated Co-Cr (cobalt chromium) coupon is used against UHMWPe pins for control purposes. Oscillations are carried out to 10 million cycles to discover and evaluate short- and long-term wear mechanisms ...


Comparison Of Optimization Methodologies For Sustained-Yield Groundwater Pumping Planning In East Shore Area, Utah, Shu Takahashi May 1992

Comparison Of Optimization Methodologies For Sustained-Yield Groundwater Pumping Planning In East Shore Area, Utah, Shu Takahashi

All Graduate Theses and Dissertations

Combined simulation and optimization models, which are helpful for long-term groundwater planning of complex nonlinear aquifer systems, are developed using alternative modelling approaches. The models incorporate a representation of steady-state, quasi-three-dimensional head response to pumping within an optimization . An embedding model which describes exactly the nonlinear flow of an unconfined aquifer is presented. In contrast with the embedding models presented in the Utah State University Ground Water Model, it directly achieves the optimal solution without a "cycling." To address the nonlinearity of the flow system, response matrix models couple superposition with the cycling procedure. Their linear influence coefficients are generated ...


Darcy-Weisbach Roughness Coefficients For Gravel And Cobble Surfaces, John E. Gilley, Eugene R. Kottwitz, Gary A. Wieman Feb 1992

Darcy-Weisbach Roughness Coefficients For Gravel And Cobble Surfaces, John E. Gilley, Eugene R. Kottwitz, Gary A. Wieman

Biological Systems Engineering: Papers and Publications

A laboratory study is conducted to measure Darcy-Weisbach roughness coefficients for selected gravel and cobble materials. Varying rates of flow are introduced into a flume in which a given size class of gravel or cobble material is securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to develop regression equations for relating roughness coefficients to surface cover and Reynolds number. The regression relations, which are developed for values of the Reynolds number from approximately 500 to 16,000, are tested using hydraulic data collected on surfaces containing a distribution of ...


Microstructural Changes In Retrieved Amalgam Restorations, Grayson W. Marshall Jr., D. D. Mccoy, John H. Kinney, Hugo Letzel, Sally J. Marshall Jan 1992

Microstructural Changes In Retrieved Amalgam Restorations, Grayson W. Marshall Jr., D. D. Mccoy, John H. Kinney, Hugo Letzel, Sally J. Marshall

Cells and Materials

Many blended or dispersed phase high Cu amalgams show excellent clinical performance in long term clinical trials. However, little is known concerning the microstructural changes that occur during clinical use of these systems. This investigation sought to characterize some of the changes that occur in the Ag-Cu particles and their surrounding reaction zones based on a study by backscattered scanning electron microscopy (BSEM), energy dispersive spectroscopy and a new rnicroprobe technique called Colorad which assigns various colors to elements and element combinations and indicates changes in elemental concentration by changes in color value (brightness). Restorations were retrieved from clinical trials ...


A Model For A Model: Pressure Jackets On Nude Mice With Implants Of Hypertrophic Scars, C. Ward Kischer, Jana Pindur Jan 1992

A Model For A Model: Pressure Jackets On Nude Mice With Implants Of Hypertrophic Scars, C. Ward Kischer, Jana Pindur

Cells and Materials

The hypertrophic scar, a consequence of deep surface injury, is peculiar to humankind. Subcutaneous implants of these tissues in nude mice provide a quasi - animal model for experimental use. An efficacious treatment to promote acceleration of maturation of the hypertrophic scar is controlled topical pressure produced by flexible dacron fabric wraps. Implants in the nude mouse provide a model for study of the effects of pressure. Preliminary results indicate that those implants in nude mice, responding favorably to pressure jackets, show changes consistent with those previously obtained in human studies. The collagen matrix shows reduced density and parallel layering of ...


The Tissue Responses To Tricalcium Phosphate Ceramics In Bone And Marrow, R. S. Archer, S. Downes, M. V. Kayser, S. Y. Ali Jan 1992

The Tissue Responses To Tricalcium Phosphate Ceramics In Bone And Marrow, R. S. Archer, S. Downes, M. V. Kayser, S. Y. Ali

Cells and Materials

Calcium phosphate ceramics are described as "bioactive". Evidence of biological activity associated with calcium phosphate implanted in bone and marrow can be seen as changes in the morphology of the interfaces. In this in vivo model the sequence of progressive bone growth and bone merger with a dense calcium phosphate ceramics were examined by light and transmission electron microscopy. A spectrum of tissue responses to dense tricalcium phosphate ceramics was observed at intervals over a six week period. It is now well established that calcium phosphate ceramics permit bone ingrowth with little or no immunological response; however, a layer of ...


Microstructure Of Mica Glass-Ceramics And Interface Reactions Between Mica Glass-Ceramics And Bone, W. Holand, W. Gotz, G. Carl, W. Vogel Jan 1992

Microstructure Of Mica Glass-Ceramics And Interface Reactions Between Mica Glass-Ceramics And Bone, W. Holand, W. Gotz, G. Carl, W. Vogel

Cells and Materials

This review paper characterizes glass-ceramics containing mica as main crystal phase. The phase formation reactions in dependence of the chemical composition and the microstructure are shown. Microstructure of mica glass-ceramics has been studied by electron replica and scanning electron microscopic (SEM) techniques.

Mica glass-ceramics have previously been developed in Si02-B20rA120rMgO-F--base glasses. The material is machinable because of the precipitation of micas of fluorophlogopite-type. Also, a machinable glass-ceramic for dental applications was developed based on KMg2_5(Si40 10)F2-micas. We developed mica glass-ceramics in the Si02-Al20rMgO-NaiO-K20-F glass system. Phase formation within these glasses was observed by SEM. A double controlled nucleation ...


The Role Of Implant Surface Geometry On Mineralization In Vivo And In Vitro; A Transmission And Scanning Electron Microscopic Study, B. Chehroudi, J. Ratkay, D. M. Brunette Jan 1992

The Role Of Implant Surface Geometry On Mineralization In Vivo And In Vitro; A Transmission And Scanning Electron Microscopic Study, B. Chehroudi, J. Ratkay, D. M. Brunette

Cells and Materials

The purpose of th.is study was to examine the effect of substratum surface topography on bone formation in vivo and in vitro. Precise control over substratum topography was achieved using micromachining, a technique developed from the fabrication of microelectronic components. In the in vivo studies, titanium-coated epoxy replicas of micromachined surfaces were implanted subcutaneously in the parietal area of rats. After 6 weeks, bone-like tissue was found adjacent to some micromachined surfaces. Detailed observation of this tissue with the transmission electron microscope revealed osteoblast/osteocyte-like cells and a fully or partially mineralized collagenous matrix. Mineralized matrix and collagen bundles ...


Fine Structure Of Remodeling Sites On Iliac Cancellous Bone In Senile Osteoporosis: A Study By Scanning Electron Microscopy Using An Improved Organic Specimen Preparation Method, Toshihiko Takita, Tomonori Naguro, Kichizo Yamamoto Jan 1992

Fine Structure Of Remodeling Sites On Iliac Cancellous Bone In Senile Osteoporosis: A Study By Scanning Electron Microscopy Using An Improved Organic Specimen Preparation Method, Toshihiko Takita, Tomonori Naguro, Kichizo Yamamoto

Cells and Materials

We improved on the organic specimen preparation method in order to investigate the details of the functional state of bone in osteoporosis at high magnification level. The usefulness and possibilities of this method are discussed showing fine structural images of remodeling sites. Iliac bones of senile osteoporotic patients obtained by transilial biopsies were studied by scanning electron microscopy (SEM) using the improved preparation method. Excepting the region near the corticoendosteal surface, most of the iliac cancellous bone was composed of thin rod-shaped trabeculae. Remodeling sites on trabeculae appeared as concavities of various sizes and were easily distinguished from inert surfaces ...


The Effect Of Polymethylmethacrylate Bone Cement Vibration On The Bone-Cement Interface, A. M. C. Thomas, D. J. W. Mcminn, M. Haddaway, I. W. Mccall Jan 1992

The Effect Of Polymethylmethacrylate Bone Cement Vibration On The Bone-Cement Interface, A. M. C. Thomas, D. J. W. Mcminn, M. Haddaway, I. W. Mccall

Cells and Materials

Low frequency vibration of polymethylmethacrylate (PMMA) bone cement reduces the viscosity of the cement by shear thinning. The effect of this low frequency vibration on the bone-cement interface was studied using microfocal radiography (MFR) and scanning electron microscopy (SEM). Effects were studied in-vitro and in-vivo. In-vitro, samples of Palacos low viscosity PMMA were placed on blocks of Kiel bone and vibrated. MFR and SEM demonstrated an improvement in the appearance of the bone-cement interface. In-vivo, PMMA was injected into the upper tibia of the dog. An assessment of the effect of high and low pressure injection, and the effect of ...


Reactogenicity Of Biomaterials As Studied By Biochemical, Morphological And Ultrastructural Techniques, Leonid I. Slutskii, Natalya A. Sevastjanova, Ivetta L. Ozolanta, Irina V. Kuzmina, Laimdota E. Dombrovska Jan 1992

Reactogenicity Of Biomaterials As Studied By Biochemical, Morphological And Ultrastructural Techniques, Leonid I. Slutskii, Natalya A. Sevastjanova, Ivetta L. Ozolanta, Irina V. Kuzmina, Laimdota E. Dombrovska

Cells and Materials

Reactogenicity is a characteristic of biocompatible materials that provokes the reparative and proliferative reaction of connective tissues, a compulsory stage of which is inflammation. Thus, reactogenicity studies should include experiments in vivo. A quantitative assessment of reactogenicity can be obtained by subcutaneous implantation of standard olive-shaped specimens covered by the biomaterial under study followed by biochemical, histological and scanning electron microscopical studies of the capsule developing around the implant. Reactogenicity of surgical threads is evaluated by semiquantitative histological analysis of the wound healing process after suture application. Biomaterial reactogenicity can be modified by changing the structure of the surface and ...


Bone Regeneration Materials For The Mandibular And Craniofacial Complex, Jeffrey Hollinger, Anshumali Chaudhari Jan 1992

Bone Regeneration Materials For The Mandibular And Craniofacial Complex, Jeffrey Hollinger, Anshumali Chaudhari

Cells and Materials

Due to different functional demands and vascularity, the mandibular and craniofacial complex require bone regenerating materials with physical and chemical properties that are different from long bone. However, certain common requirements to both locales must be addressed. Furthermore, reasons why the autograft and allogeneic bank bones are successful in regenerating bone need to be understood if the researcher is to develop satisfactory alternatives. The purpose of this paper is to review some of the requirements needed for bone regenerating materials for mandibular and craniofacial bone repair. In that effort, we have briefly described the autograft and allogeneic bank bones, animal ...


Comparative Assessment Of The Cytotoxicity Of Various Substrates In Organ Culture And Cell Culture: A Scanning Electron Microscopy Study, J. L. Duval, R. Warocquier-Clerout, M. F. Sigot-Luizard Jan 1992

Comparative Assessment Of The Cytotoxicity Of Various Substrates In Organ Culture And Cell Culture: A Scanning Electron Microscopy Study, J. L. Duval, R. Warocquier-Clerout, M. F. Sigot-Luizard

Cells and Materials

A comparative study of the behavior of chick embryo endothelial cells grown on various substrates was performed in order to establish the reliability and the limitation of both cell and organ culture methods. Following substrates were analyzed to compare these two different culture techniques: bovine serum albumin, pigskin gelatin and albumin + gelatin cross-linked by glutaraldehyde or carbodiimide, fibrin glue and negative control (Thermanox*). Parameters of cell growth and adhesion were calculated and compared with electron microscopic observations of cell morphology and of the extracellular matrix. Both culture methods provided complementary results and led to a similar classification of the biomaterials ...


Effect Of Surface Treatments On Dentin Bonding Shear Strength, James L. Drummond, D. Racean, J. Van Scoyoc, A. Steinberg Jan 1992

Effect Of Surface Treatments On Dentin Bonding Shear Strength, James L. Drummond, D. Racean, J. Van Scoyoc, A. Steinberg

Cells and Materials

The purpose of this study was to determine whether four different treatments on wet or dry teeth, on the buccal and occlusal surfaces, affected the shear bond strength. The surface treatments consisted of a dentin conditioner (pH = 4.0), 10% phosphoric acid (pH = 1.6), 2.5 % nitric acid (pH = 1.0), and 2.5 % citric acid (pH = 1.0). One dentin bonding system and one dental composite was used for all of the specimens. The teeth were mounted in acrylic, ground and etched with the appropriate agent for 15 seconds. The dentin adhesive and composite were applied and the ...


Scanning Electron Microscopy Of The Bone Interface With Titanium, Titanium Alloy And Hydroxyapatite, R. D. Orr, J. D. De Bruijn, J. E. Davies Jan 1992

Scanning Electron Microscopy Of The Bone Interface With Titanium, Titanium Alloy And Hydroxyapatite, R. D. Orr, J. D. De Bruijn, J. E. Davies

Cells and Materials

Screw implants of commercially pure titanium and titanium alloy together with rods of slip-cast dense hydroxyapatite were implanted transfemorally in young adult rats. The femora were harvested after fixation and freeze-fractured in liquid nitrogen to create two tissue fragments of each specimen. The first contained the implant while the second enabled examination of the tissue immediately adjacent to the implant. In all cases, the tissue abutting the implant was a cement line-like layer which separated the implant from the surrounding bone proper. Greater adherence of this interfacial tissue was demonstrated to hydroxyapatite samples compared with the titanium screws, while no ...


Scanning Electron Microscopy Study Of Biofilms On Silicone Voice Prosthesis, T. R. Neu, F. Dijk, G. J. Verkerke, H. C. Van Der Mei, H. J. Busscher Jan 1992

Scanning Electron Microscopy Study Of Biofilms On Silicone Voice Prosthesis, T. R. Neu, F. Dijk, G. J. Verkerke, H. C. Van Der Mei, H. J. Busscher

Cells and Materials

Patients after laryngectomy often receive silicone made voice prostheses fot speech rehabilitation. The prosthesis is inserted in a shunt between the trachea and the digestive tract. As the prosthesis is placed in a nonsterile environment it becomes rapidly colonized by microorganisms eventually leading to failure and frequent exchange of the implant. In this study, explanted "Groningen Button" silicone voice prostheses were used to investigate by scanning electron microscopy the biofilm developing on the implant. Two main types of microbial colonization forms could be distinguished. Firstly, macroscopically visible, single colonies dominating on the esophagus side of the prosthesis were found, which ...


Projection Effect Errors In Biomaterials And Bone Research, K. N. Bachus, R. D. Bloebaum Jan 1992

Projection Effect Errors In Biomaterials And Bone Research, K. N. Bachus, R. D. Bloebaum

Cells and Materials

Micoradiography and backscattered electron (BSE) imaging are techniques used to investigate the morphologic, histometric, and mineral content changes at the bone/biomaterials interface. Investigators have shown that the superimposition of multiple tissue layers can cause errors with both the morphologic observations and the histometric measurements of bone. The objective of this study was to document errors in the bone mineral content measurements associated with overlapping tissues.

Using a digital image analysis system, microradiographic and BSE images from canine cortical and cancellous bone were captured and analyzed. The results of this study showed that microradiography had more projection effect errors associated ...


The Incorporation Of Glass-Ceramic Implants In Bone After Surface Conditioning Glow-Discharge Treatment, C. M. Muller-Mai, C. Voigt, R. E. Baier, U. M. Gross Jan 1992

The Incorporation Of Glass-Ceramic Implants In Bone After Surface Conditioning Glow-Discharge Treatment, C. M. Muller-Mai, C. Voigt, R. E. Baier, U. M. Gross

Cells and Materials

Glow discharge (GD)-treated and autoclaved glass-ceramics of bone-bonding and non-bonding type were implanted into the femoral diaphysis of rats for 3, 7, 14 and 28 days and were investigated by applying light microscopy and histomorphometry , and scanning and transmission electron microscopy. More bone and chondroid, and faster osteoid development were observed at glow-discharge treated implants even in nonbonding implants when compared to autoclaved controls. Ultrastructural investigations showed a higher leach ing- rate of GD-treated bone-bonding implants during the early days after implantation leading to a higher rugosity, whereas no morphological changes were observed on non-bonding implant surfaces. More extracellular ...


Evidence Of Changes In Regional Blood Perfusion In Human Intracranial Tumours During Conductive Interstitial Hyperthermia, U H. Patel, Charles F. Babbs, J A. Deford, W M. Bleyer, J A. Marchosky, C J. Moran Jan 1992

Evidence Of Changes In Regional Blood Perfusion In Human Intracranial Tumours During Conductive Interstitial Hyperthermia, U H. Patel, Charles F. Babbs, J A. Deford, W M. Bleyer, J A. Marchosky, C J. Moran

Weldon School of Biomedical Engineering Faculty Publications

Human intracranial tumours were treated using local heat therapy produced by surgically implanted catheters containing local resistive heating elements. Changes in local tumor blood flow were assessed indirectly from an algorithm based on the bioheat transfer equation. The algorithm used the ratio of catheter power to catheter temperature rise to estimate regional blood perfusion. Local heat therapy produced consistent reductions in local apparent perfusion. Changes in apparent regional perfusion occurred in intriguing patterns that gave clues to possible vascular events of therapeutic significance.