bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyester prostheses as substitutes in the thoracic aorta of dogs. II. Evaluation of albuminated polyester grafts stored in ethanol
Authors: Guidoin R. , Martin L. , Marois M. , Gosselin C. , King M. , Gunasekera K. , Domurado D. , Sigot‐Luizard M. F. , Sigot M. , Blais P. 
Published: December 2004

AbstractIn an attempt to find an alternative procedure to the preclotting of porous textile vascular prostheses, the feasibility of an albumin coating and ethanol preservation technique has been evaluated by implanting albuminated polyester prostheses as substitutes in the thoracic aorta of dogs. Nine different grafts representing woven, knitted, and velour constructions were implanted for periods ranging from 4 h to 6 months. At the sacrifice, the grafts were excized for measurement of the thrombogenicity of the flow surface, for pathological examination by light microscopy and SEM, and for quantifying the changes in the textile structure during implantation. Also the kidneys were removed and examined for infarcts caused by trapped circulating emboli. The healing characteristics of the nine different grafts proved similar and followed the same sequence of events as preclotted control grafts. The albumin coating and ethanol preservation resulted in a somewhat slower rate of healing. Yet, given sufficient time, a more completely healed graft was achieved as evidenced by the presence of endothelial‐like cells throughout the length of the graft. In addition, the albumin is believed to reinforce the textile structure by reducing the tendency to stretch and dilate in vivo.
Regulation of drug release from polymer matrices by oscillating magnetic fields
Authors: Edelman E. R. , Kost J. , Bobeck H. , Langer R. 
Published: December 2004

AbstractThe reproducible regulation of release of a macromolecule (bovine serum albumin) from biocompatible polymer systems has been demonstrated. Small magnetic spheres or cylindrical magnets were embedded within the polymer matrix which was then subjected to an oscillating magnetic field. In this fashion baseline release rates could be increased 5‐ to 10‐fold with 5–10% standard error. Parameters critical to the regulation of this release included the position, orientation, and magnetic strength of the embedded objects and the amplitude and frequency of the applied magnetic field. Scanning electronmicrographs of the polymer matrix surface reveal that a gap, approximately 100/μm wide, is formed between the embedded object and adjacent polymer material after repeated exposure to an oscillating magnetic field.
Creep of posterior dental composites
Authors: Papadogianis Yannis , Boyer Daniel B. , Lakes Roderic S. 
Published: December 2004

AbstractThe creep of microspecimens of posterior dental composites was studied using a torsional creep apparatus. Shear stresses were maintained for 3 h and recovery was followed for 50 h. Creep curves were obtained at 21, 37, and 50°C and four torque levels. The effect of conditioning the specimens in water up to 8 weeks was studied. The posterior composites exhibited linear viscoelastic behavior at low deformations. They had higher shear moduli and greater resistance to creep than conventional and microfilled composites. In aging experiments, maximum shear moduli occurred when specimens were 48 h to 1 week old. Subsequent softening was attributed to water absorption. Residual strain was highest when the composites were stressed within 24 h of initiating polymerization. Residual strain was very low in specimens 48 h to 8 weeks of age.
Heparinized polyurethanes: In vitro and in vivo studies
Authors: Heyman P. W. , Cho C. S. , McRea J. C. , Olsen D. B. , Kim S. W. 
Published: December 2004

AbstractHeparin immobilization chemistry using alkyl spacer arms was adapted to optimize yield on polyurethane (PU) surfaces. The resultant biological activity of immobilized heparin (HI) was examined in vitro and in vivo, and compared with a heparin releasing (HR) system. Immobilized heparin retained its ability to bind and inactivate thrombin and Factor Xa; nonspecific coagulation factor binding was insignificant. Such activity cannot be attributed to the leakage of improperly bound heparin. Immobilized heparin–polurethane catheters implanted in canine femoral and jugular veins for 1 h periods exhibited significant reduction in thrombus formation compared with untreated PU contralateral controls. Polyurethane catheters coated with a 9% heparin dispersion in PU (HR) system provided even greater improvement in antithrombogenicity.
Biocompatibility of Delrin 150: A creep‐resistant polymer for total joint prostheses
Authors: Fister James S. , Memoli Vincent A. , Galante Jorge O. , Rostoker William , Urban Robert M. 
Published: December 2004

AbstractA thermoplastic polymer, Delrin 150 (polyoxymethylene homopolymer), with creep resistance ten times that of ultrahigh‐molecular‐weight polyethylene, is used as a material for total joint protheses. A study was made of the local and systemic host response to this polymer when implanted in three different mammalian species. 316 LC stainless steel was used as a control. The materials were implanted into muscle and bone as solid cylinders. A total of 446 samples were implanted into 74 animals. The duration of implantation ranged from 2 weeks to 2 years. A semiquantitative evaluation of local tissue reaction was performed. For each implant, 16 histological criteria were graded for severity of host tissue reaction. The liver, spleen, kidneys, pancreas, and lungs from each animal were also studied for evidence of systemic toxicity. The polymer implants exhibited a mild tissue reaction with the same characteristics as the control. Local tumor formation, bone osteolysis, and surrounding muscle necrosis were not seen. No pathological changes compatible with systemic toxicity by Delrin 150 were observed in the study of the organs. Delrin 150 in solid form did not exhibit local or systemic toxicity and is therefore biocompatible by this study. Powder implantation studies should be performed to simulate tissue response to wear particles.
The interaction of blood components with PDMS(polydimethylsiloxane) and LDPE (low‐density polyethylene) in a baboon ex vivo arteriovenous shunt model
Authors: Keough E. M. , Mackey W. C. , Connolly R. , Foxall T. , Ramberg‐Laskaris K. , McCullough J. L. , O'Donnell T. F. , Callow A. D. 
Published: December 2004

AbstractThe interaction of 111Indium‐labeled platelets, and other blood components with the luminal surface of polydimethylsiloxane (PDMS) and low‐density polyethylene (LDPE) was determined using an ex vivo arteriovenous shunt in the baboon. Both PDMS and LDPE showed little platelet accumulation at either high (200 cc/min) or low (25 cc/min) flow rates. PDMS accumulated more platelets at low than at high flow. When the surfaces of PDMS and LDPE were examined under scanning electron microscopy after 2.5 h of flow in the shunt circuit, red and white blood cells were attached. Platelets appeared to be confined to patchy areas covered by a fibrinlike network. The low platelet reactivity of LDPE and PDMS suggests their potential use as coatings for conventional, more platelet reactive, vascular graft materials.
Influence of 4‐methacryloxyethyl trimellitic anhydride on composites subjected to hygrothermal cycling
Authors: Nagata K. , Turner D. T. 
Published: December 2004

AbstractPastes were made by spatulating a hydroxyapatite powder into triethylene glycol dimethacrylate (TEGDMA) that contained benzoyl peroxide. For comparison, similar pastes included 5 wt‐% 4‐methacryloxyethyl trimellitic anhydride (4‐META) in the TEGDMA. Composites were made by heating at 120°C under pressure. Inclusion of 4‐META reduced the rate of diffusion of water by about one‐third, at 27°C. Also after thermal cycling in water, inclusion of 4‐META decreased the fractional drop in compressive strength by about one‐half. Examination of fracture surfaces indicated that inclusion of 4‐META improved the wetting of filler particles and gave more coherent composites. All these findings are consistent with the view that 4‐META acts as a coupling agent.
Wire‐induced osteogenesis in marrow
Authors: Schaberg S. J. , Liboff A. R. , Falk M. C. 
Published: December 2004

AbstractAlthough it has been reported, in observations connected to electrically stimulated bone repair, that intramedullary electrodes not attached to any electrical source can also induce osteogenesis, there has been only one systematic attempt to study this effect per se. We have extended these studies, implanting selected metal and plastic wires longitudinally into the medullary diaphyses of rat femora. Atomic absorption analysis was used for the first time in analyzing for medullary calcium. This technique and the histologic evaluation clearly indicate that osteogenesis occurs within 2 weeks after this wire implantation. Osteogenesis was not observed when the wire was immediately removed after the original trauma of wire insertion.
Change in creep rate and microstructure in an aged, low‐copper amalgam
Authors: Okabe Toru , Mitchell Richard J. , Butts Michael B. , Galloway Sidney S. , Twiggs Warren S. 
Published: December 2004

AbstractLow‐copper amalgams aged at 37°C, 50°C, 60°C, 70°C, and 80°C for periods of 7 and 30 days were examined using a scanning electron microscope and an x‐ray diffractometer. Gamma‐one Ag‐Hg grain size and γ2 Sn‐Hg volume fraction, and surface area were determined by quantitative metallography. At 60°C and below, γ1 was the predominant matrix phase. Little β1 Ag‐Hg was found. In this temperature range, both γ1 grain size and ADA creep were found to obey an Arrhenius law. A linear relationship was found between the log of the mean ADA creep and the mean γ1 grain size. Above 60°C, the γ1 phases and the majority of the γ Ag‐Sn particles disappeared. In their place, β1 appeared. Gamma‐two volume fraction increased during aging at temperatures over 60°C, but a coarsening of γ2, reflected in a decrease in γ2 surface area per unit volume, also took place. Aging for 30 days or less resulted in decreases in ADA creep. At 60°C and below, the decrease was caused by increases in γ1 grain size. Above 60°C, the decrease in ADA creep was caused by several factors, one of which was the appearance of large β1 grains.
Human platelet spreading on substrata of known surface chemistry
Authors: Baier R. E. , Depalma V. A. , Goupil D. W. , Cohen E. 
Published: December 2004

AbstractUsing platelet‐rich plasma freshly obtained by plasmapheresis, the spread areas of human platelets settled onto substrata of different surface energies were measured to evaluate the hypothesis that initial platelet spreading response is surface dependent. At 37°C, minimal platelet spread areas were found on substrata with critical surface tension between 20 and 30 mN/m (dynes/cm), and increased spreading and morphologic changes occurred on substrata of both higher and lower critical surface tension. This differential response was absent at 25°C. Therefore, measurement of spread platelet area at physiologic temperature rather than number of attached cells is proposed as a superior method of estimating apparent blood compatibility of new biomaterials.
An examination of the biologic response to injectable, glutaraldehyde cross‐linked collagen implants
Authors: McPherson J. M. , Sawamura S. , Armstrong R. 
Published: December 2004

AbstractThe biologic response to injectable, glutaraldehyde cross‐linked, fibrillar collagen implants in the rat subcutaneous model was shown to be a function of the concentration of glutaraldehyde used for cross‐linking. The collagen was prepared from bovine hide by pepsin solubilization and reconstituted as a fibrillar suspension of 35 mg collagen/mL. Fibrillar collagen implants cross‐linked with glutaraldehyde concentrations equal to or less than 0.01% exhibited a response characterized by fibroblast invasion, neovascularization and little, if any, evidence of inflammation. Implants cross‐linked with 0.1 and 1.0% glutaraldehyde elicited a foreign body/giant cell reaction and varying degrees of implant erosion. The interaction of human skin fibroblasts with 0.01% glutaraldehyde cross‐linked collagen in vitro was found to be dependent on the culture conditions utilized to evaluate the interaction. When the ratio of cell culture media to collagen was 20:1, cell invasion of the cross‐linked preparations was observed, whereas, when this ratio was reduced to 1:1, such interactions could not be detected. Noncross‐linked preparations were colonized by cells regardless of the experimental conditions used. Studies of implants in both the rat and guinea pig subcutaneous models indicated that glutaraldehyde cross‐linking concentrations as low as 0.0075% provided enhanced wet weight recovery (wet weight persistence) and resistence to biologic degradation (collagen persistence) as compared to noncross‐linked fibrillar collagen preparations. These cross‐linked implants also exhibited a greater degree of fibroblast infiltration and vascularization. Between 30 and 60 days, some degree of calcification developed in both collagen formulations implanted in rats and guinea pigs; however, the reaction occurred with greater frequency and intensity in cross‐linked preparations in guinea pigs. Calcification in the guinea pig was followed by the appearance of focal areas of ossification.
SEM analysis of surface‐treated dialdehydestarch
Authors: Shimizu Toshimi , Tanaka Yoshio , Yamazaki Yoshihiko , Ueda Masayoshi , Isa Isao 
Published: December 2004

AbstractSurface characteristics of protein‐treated dialdehydestarch (DAS), which is utilizable as a gastrointestinal sorbent for the treatment of uremia, are examined by scanning electron microscopy (SEM). Unique wrinkles or continuous depressions were observed on the surface of some albumin‐treated DAS particles. An increase in concentration and composition of albumin to DAS produces more particles with this kind of rugged surface. On the other hand, gelatin treatment provided a DAS with somewhat rough surface. As the stoichiometric ratio of gelatin to DAS increases, some fibrous or thin‐leaves‐like projections became outstanding on the surface. Urea‐binding properties of protein‐treated DAS are just about the same regardless of the protein concentration or composition. In addition, wrinkles or depressions partly observed on the surface of albumin‐treated DAS are of little benefit in terms of effective urea binding. These results mean that inherent physical properties of DAS such as dialdehyde content would be a critical factor in urea‐sorption ability, rather than surface characteristic or the presence of protein.
Immobilization of factor XIII on collagen membranes
Authors: Blanchy B. G. , Coulet P. R. , Gautheron D. C. 
Published: December 2004

AbstractFactor XIII from placenta was successfully grafted onto collagen membranes by the acyl‐azide procedure. The transamidase activity retained on collagen membranes was determined by measuring the increase of fluorescence resulting from dansylcadaverine incorporation into casein. We studied the effect of different factors on the grafting: concentration and composition of the factor XIII preparation in the coupling solution and influence of the preactivation of factor XIII by thrombin. Stability studies have shown that the activity of factor XIII grafted on collagen membranes was almost constant over a period of 8 months. Sterilization by γ‐irradiation of factor XIII revealed a drastic loss of activity while the use of high‐energized electron bombardment caused a reduced loss of activity. The potential of such a material for biomedical use is presently under investigation.
Acute surface‐induced thrombosis in the canine ex vivo model: Importance of protein composition of the initial monolayer and platelet activation
Authors: Park Kinam , Mosher Deane F. , Cooper Stuart L. 
Published: December 2004

AbstractThe initial events occuring at the blood‐polymer interface were examined using a canine ex vivo arteriovenous shunt model. Thrombogenic (fibrinogen) and nonthrombogenic (albumin) proteins were preadsorbed on poly(vinyl chloride), polyethylene, and silicone rubber shunt surfaces, and the blood responses were analyzed using the platelet deposition profile as an indicator of surface thrombogenicity. The distributions of preadsorbed protein molecules on the various polymer surfaces were studied using an immunogold bead (colloidal gold particles coated with antibodies) staining technique and shown to be homogeneous. A sequential protein adsorption technique was developed to probe the nature of competitive protein adsorption and to observe the effect of surface protein concentration on thrombogenicity. The thrombogenicity of a surface was determined by the composition of the initial protein layer rather than the total concentration of protein on the polymer surfaces. The composition of this layer determines the extent of platelet activation and the adhesive strength between platelets and the polymer surface.
Collagen‐based wound dressings: Control of the pore structure and morphology
Authors: Doillon C. J. , Whyne C. F. , Brandwein S. , Silver F. H. 
Published: December 2004

AbstractCollagen‐based sponges have been used as both temporary and permanent coverings for dermal defects in animals and humans. Cellular ingrowth within such a sponge has been shown to depend on the porosity and the presence of fibrous structure. Collagen sponges were made by freezing and freezedrying dispersions under acidic conditions. These studies involved the effects of dispersion pH and viscosity as well as freezing temperature on the surface and bulk morphology of collagen‐based sponges. Using scanning electron and light microscopy, the results of these studies indicated that large surface pores that form connections (channels) with the interior of the sponge were formed using low‐viscosity collagen dispersions. At high dispersion pH (3.2) and at a moderate freezing temperature (−30°C), fibrous structure and a large number of channels were present. When a lower dispersion pH (2.0) and freezing temperature (−80°C) were used, pores sizes were smaller with channels and fibrous structure, whereas a higher freezing temperature (−20°C) resulted in a sheet‐like structure and increased pore sizes. Differences in pore size and surface morphology were explained on the basis of ice crystal growth. In the case of abundant free water (high pH) and high freezing temperature, the pore size was greatest because of enhanced ice crystal growth.
Optical methods for the nondestructive evaluation of collagen morphology in bioprosthetic heart valves
Authors: Hilbert Stephen L. , Ferrans Victor J. , Swanson W. Milton 
Published: December 2004

AbstractThe aim of the present study was to assess the suitability of nondestructive optical methods as a means of evaluating collagen morphology in bioprosthetic heart valve leaflets. The results of this study demonstrate that transmitted polarized light and incident polarized light optics facilitate the imaging of the inherent birefringence of valvular collagen fibers. Polarized light optics readily document the different patterns of collagen orientation and configuration in porcine aortic valvular (PAV) and bovine pericardial valvular (BPV) bioprostheses. Incident polarized light optics also provide information on leaflet surface morphology. Verification that the birefringence observed by polarized light optics represents leaflet collagen was provided by conventional histologic and transmission electron microscopic methods. Quantitative determinations of the spacing of collagen bundle waves gave similar values in intact and in sectioned BPV leaflets. Potential applications of polarized light optics in the assessment of bioprosthetic valve collagen are as follows: (1) the selection of the desired orientation of collagen bundles within pericardium intended to be configured into bioprosthetic leaflets; (2) evaluation of the effects of mechanical stresses and leaflet motion on collagen morphology in bioprosthetic valve leaflets; and (3) initial screening of leaflet specimens and selection of the desired collagen orientation for embedding and sectioning of samples for conventional morphologic studies.
Long‐term evaluation of five biomaterials for angioplastic enlargement of the pulmonary artery in a young dog model
Authors: Planche C. L. , Fichelle J. M. , Paul J. , Lethias C. L. , Elroy R. , Weiss M. 
Published: December 2004

AbstractIn 45 young dogs an enlargement angioplasty of the left pulmonary artery was performed using patches made from one of three autologous materials (jugular vein, unmodified pericardium, and glycerolized pericardium) or from two heterologous materials (lyophilized human dura mater and modified bovine carotid artery). Catheterization and angiographic studies performed 5 to 6 months after the operation showed that all patched vessels had remained patent, except in three dogs which had received heterologous implants. The animals were killed 5‐24 months after operation (mean weight increase: 84%), and the implants were studied by optical microscopy and morphometry, scanning and transmission electron microscopy, and indirect immunofluorescence with antidog Factor VIII rabbit antiserum. The two heterologous tissues exhibited limited biocompatibility, as estimated from 10 criteria obtained at histologic studies. Conversely, all three autologous biomaterials were characterized by infiltration of noninflammatory cells, near‐complete endothelialization, and neosynthesis of structural proteins; infectious foci were very rare or absent. These results suggest that autologous tissues, although deendothelialized at the time of implantation, constitute the most suitable material for patch angioplasty, as far as endothelial triggering, cellularity and resistance to infection are concerned.
Soft‐tissue response to total hip surface replacement
Authors: Skinner Harry B. , Mebey Monique F. 
Published: December 2004

AbstractTissue reaction to prosthesis wear debris and its relationship to prosthetic loosening was investigated. Eighteen dogs underwent hip surface replacement; 6 animals accounted for 6 control and 6 carbon hips, and 13 experimental animals accounted for 13 implanted carbon and 13 cobaltchromium‐molybdenum (CoCrMo) prostheses. Both kinds of prostheses articulated against a high‐density polyethylene acetabular component. One year after implantation, tissue response to the prostheses was evaluated according to a semiquantitative method, and a total tissue score indicating the degree of tissue response was obtained. The total tissue score was then compared with the normalized final vertical ground reaction force (GRF) for each hip in the animals with bilateral hip replacements. Compared with the controls, significantly greater tissue response was seen in both kinds of prosthetic hips (p = .001). No statistically significant difference in the tissue response of the two types of hip prostheses was noted, although the tissue response score of the CoCrMo demonstrated a trend toward more severe reaction than the carbon. No statistical difference in tissue reaction was noted for loosened components as compared with tightly fixed components. Amount of wear debris was the best predictor of component loosening. Gait analysis demonstrated a statistically significant negative correlation between GRF and total tissue score (p = .036), and between GRF and wear debris score (p = .034). The results of this study suggest that GRF may predict the amount of wear debris in the tissues surrounding a total hip surface arthroplasty, and that severity of pain is related to the degree of tissue response.