bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retrieval and analysis of a clinical total artificial heart
Authors: Coleman Dennis L. , Meuzelaar Henk L. C. , Kessler Thomas R. , McClennen William H. , Richards Joe M. , Gregonis Donald E. 
Published: December 2004

AbstractExamination by light microscopy, scanning electron microscopy (SEM), and x‐ray microanalysis of a clinical total artificial heart (TAH) implanted for 112 days revealed no evidence of calcification, pannus, or vegetative thrombus. A macroscopic thrombus was seen along the suture line in the right atrium but did not obstruct blood flow or valve function. Microscopic thrombi (<0.1 mm) and evidence of microemboli were observed on the pumping diaphragm using SEM. Characterization of selected polyetherurethane (PEU) samples from the pumping bladders and housing by Curie‐point pyrolysis mass spectrometry (Py‐MS) revealed unexpected differences between postmortem retrieved ventricles. Although the origin of these differences could be traced back to batch‐to‐batch variations in the original PEU material (Biomer), the precise nature of the observed differences in chemical structure and/or composition is still unknown. Numerical comparison between pyrolysis mass spectra from PEU samples exposed to blood or tissue and unexposed samples from the same ventricles did not detect evidence of biodegradation. Continual improvements in fabrication and quality control should minimize surface imperfections and ensure polymer reproducibility; however, existing materials and design parameters appear to be adequate for continued clinical implantation.
Preserved and foreign cartilage interpositional materials for silastic finger joint implant arthroplasty
Authors: Powers Dennis L. , Gaisser David M. , Barton Quentelle 
Published: December 2004

AbstractCartilage grafts were implanted as interpositional materials (IPMs) around the stems of silicone finger joint prostheses to protect their surfaces from abrasion with the local bone tissue. The knee joints of New Zealand White rabbits were implanted with finger joint prostheses and grafted with preserved auto‐ and allografts as well as fresh xenografts. Data were obtained after one month and compared to controls that received only the silicone prostheses. The grafting procedures did not cause any variations in joint function or differences in the amount of lipids absorbed by the prosthesis. A thin fibrous capsule formed about the control implants, whereas the capsules of the grafted legs were greater in thickness and area. Gross examination of the implant surfaces, weight analyses, and light microscopic studies of the number of wear particles found in the surrounding tissue capsules all indicated a reduction in prosthetic wear with grafting. The cartilage grafts were surrounded by inflammatory cells and were losing their proteoglycans. As expected, the xenografts exhibited the most degradation. No differences were noted between the preserved grafts. These results indicate that at one month, cartilage has provided protection for early implant motion. The biodegradable graft was being replaced by fibrous connective tissue. Long‐term protection needs to be studied in additional experiments.
The influence of static stress on the corrosion behavior of 316L stainless steel in Ringer's solution
Authors: Bundy K. J. , Vogelbaum M. A. , Desai V. H. 
Published: December 2004

AbstractThe decrease in corrosion resistance of 316L stainless steel due to static stress was studied in vitro using a 37°C Ringer's solution electrolyte. Both potentiodynamic polarization and coulometric techniques were used. Cyclic anodic polarization tests with highly loaded fracture mechanics samples revealed a lowering of breakdown potential and disruption of passive films compared to unstressed controls. Measurements of the time‐averaged current density due to a 100 mV anodic overpotential showed that a stress level causing plastic deformation increases the current density by more than an order of magnitude compared to samples stressed to the yield stress or nonloaded controls. The significance of these findings for surgical implant devices in service is discussed.
Adhesion of coagulase‐negative staphylococci to methacrylate polymers and copolymers
Authors: Hogt A. H. , Dankert J. , Feijen J. 
Published: December 2004

AbstractAdhesion of coagulasef‐negative staphylococci (CNS) was studied onto a homologous series of methacrylate polymers and copolymers. The materials varied in wettability (contact angles) and were either positively or negatively charged (zetapotential). Bacterial adhesion experiments performed in a parallel‐plate perfusion system showed that positively charged TMAEMA‐Cl copolymers significantly promoted the adhesion of CNS as compared with all other methacrylate (co)polymers tested. The bacterial adhesion rates onto the positively charged surfaces are diffusion‐controlled, whereas those onto the surfaces with a negative zeta‐potential are more surface‐reaction‐controlled due to the presence of a potential energy barrier. The bacterial adhesion rates onto various poly (alkyl methacrylates) were similar. The number of adhering bacteria onto the negatively charged MMA/MAA copolymer did not differ from that onto pMMA, indicating that sufficient sites on the copolymer surface with the same potential energy barrier as that on pMMA, were available for adhesion. Decreasing rates of adhesion of CNS were observed onto MMA/HEMA copolymers with increasing HEMA content coinciding with increasing hydrophilicity. Low plateau values for the bacterial adhesion were observed on 50MMA/50HEMA, pHEMA, and 85HEMA/15MAA, indicating that the adhesion onto these materials was reversible. Four CNS strains with different surface characteristics all showed higher numbers of adhering bacteria onto 85MMA/15TMAEMA‐Cl than onto 85MMA/15MAA and pMMA.
Molecular and mechanical property changes during aging of bone cementin vitroandin vivo
Authors: Looney M. A. , Park J. B. 
Published: December 2004

AbstractThe changes in mechanical properties and free radical concentration of curing Simplex P Radiopaque Bone Cementin vivoandin vitroconditions were studied. Samples were prepared so that eachin vivosample that cured and aged in the canine femoral intramedullary cavities had anin vitrocounterpart that was cured and aged in a constant‐temperature saline bath at 37°C. An electron paramagnetic resonance (EPR) spectrometer was used to measure the growth and decay (curing) of polymerization radicals. The results of EPR measurements showed that the curing (disappearance of free radicals) ofin vivosamples takes a much longer time (more than 4 weeks) thanin vitrocuring (less than 2 weeks). The mechanical tests indicate that, whether agedin vivoorin vitro, the strength increased rapidly for the first 1–2 weeks and then slight increases were seen for up to 6 months.
Use of concentrated fibrinogen in experimental tracheal repair
Authors: Kram Harry B. , Hino Stanley T. , Harley Daniel P. , Fleming Arthur W. , Shoemaker William C. 
Published: December 2004

AbstractTracheal stenosis is a devastating complication of tracheal resection that may be related to improper suture selection and technique, as well as extensive surgical devascularization. This study evaluated Fibrin Sealant (FS) (Immuno AG, Vienna, Austria), a two‐component biologic adhesive, as a method for reducing the need for sutures in tracheal surgery. This adhesive has been found to be effective in face‐to‐face sealing of tissues, wound healing, and in establishing hemostasis. Six adult mongrel dogs underwent tracheal repair with FS. Three had tracheal hemitransections (approximately three quarters of the circumference) and were repaired using one absorbable suture and FS, and three had complete transections (with resection of two tracheal rings each) repaired using five absorbable sutures and FS. The animals were killed at varying intervals ranging from 6 h to 6 weeks. No animal had gross evidence of significant tracheal stenosis, and the endotracheal mucosa appeared well healed. We conclude that the use of FS in tracheal reconstruction results in a stable, leakless trachea, and that it significantly reduces the number of sutures needed; this may lead to a decreased potential for anastomotic ischemia and tracheal stenosis.
A model of thrombin inactivation in heparinized and nonheparinized tubes with consequences for thrombus formation
Authors: Basmadjian D. , Sefton M. V. 
Published: December 2004

AbstractThe role of flow and mass transport in determining procoagulant concentration at the wall of synthetic and natural cylindrical blood vessels is analyzed theoretically. The model assumes steady laminar flow and considers, in addition to the fluid dynamic parameters, three rate‐determining steps: production of procoagulant (thrombin) and its inactivation at the wall, as well as inactivation in the fluid bulk. The ratio of thrombin wall concentration to production rate Cw/N emerges as a critical parameter in characterizing the behavior of the tube wall. With a wall‐inactivation rate typical of heparinized materials, Cw/N = 11.1 s/cm, independent of flow (shear rate) and axial position. This is significantly less than the range of Cw/N (50–500 s/cm) for which the thrombin concentration is high enough to result in significant fibrin formation and thrombosis. Hence little fibrin formation and a high degree of thromboresistance is expected for heparinized materials. Nonheparinized materials have Cw/N values above this range, which are only weakly dependent on shear rate and diameter, suggesting that flow‐induced dispersion of thrombin (or other procoagulants) has limited impact on the thrombin wall concentration. These latter results appear to refute the conventional wisdom that attributes the relative patency of large‐diameter vesels and differences between venous and arterial thrombi to such flow effects. It is likely that additional factors such as flow pulsatility and wall geometry must be considered to account for these observations.
The influence of substratum surface free energy on growth and spreading of human fibroblasts in the presence and absence of serum proteins
Authors: Schakenraad J. M. , Busscher H. J. , Wildevuur C. R. H. , Arends J. 
Published: December 2004

AbstractTo determine whether the surface free energy of polymer materials influences the spreading and growth of cells, surface free energies of 13 polymers and glass were related to spreading and growth of human skin fibroblasts. Experiments were performed in both the presence and absence of serum proteins. We calculated the surface free energy from contact angles of phosphate‐buffered saline (PBS), n‐propanol/PBS mixtures, and α‐bromonaphthalene on the polymers, using the concept of polar and dispersion components accounting for spreading pressures. Cell spreading and substratum surface free energy (γs) showed a characteristic sigmoid relationship both in the presence and in the absence of serum proteins; good spreading only occurred when γs was higher than approximately 57 erg · cm−2. In the presence of serum proteins, cell spreading is similar on most materials; only few materials show relatively high cell spreading. Cell growth in the presence of serum proteins did not differ significantly on the various polymers with reference to their γs values. In contrast, two groups of polymers could be distinguished in the absence of serum with respect to cell growth. The first group showed increasing γs, whereas the second group showed consistently low cell growth. The results demonstrate the complex relationship between cell spreading and substratum surface free energy as well as the role of serum proteins in modifying the surface characteristics of polymers in relation to cell spreading and growth.
Displacements of precious and nonprecious dental bridges utilizing endosseous implants as distal abutments
Authors: Bidez M. W. , Lemons J. E. , Isenberg B. P. 
Published: December 2004

AbstractAn investigation was conducted to establish qualitative trends regarding the relative displacements exhibited by the distal and mesial abutments in a five‐unit fixed dental bridge as a function of bridge material and implant design utilized in the distal abutment site. Both Au and Ni‐based bridge systems utilizing double, natural‐tooth mesial abutments and three types of distal abutments (natural second molar, blade dental implant, and hollow‐basket implant) were tested on a dried human mandible and subjected to a controlled force applied distally. Dial gauges were positioned around each abutment site bilaterally to provide displacement data in the x (mesial/distal), y(buccal/lingual), and z(occlusal/gingival) directions. The results indicate some significant differences exist in the displacement profiles exhibited by the bridge systems as a function of both bridge material and abutment type.
The biocompatibility of solution cast and acetone‐extracted cast biomer
Authors: Marchant Roger E. , Anderson James M. , Hiltner Ann , Castillo E. J. , Gleit J. , Ratner B. D. 
Published: December 2004

AbstractThe cellular response to films of cast Biomer and acetone‐extracted Biomer were investigated over a 21‐day implantation period, using an in vivo cage implant system. Film samples were characterized by scanning electron microscopy (SEM), attenuated total reflectance infrared (ATRIR), electron spectroscopy for chemical analysis (ESCA) and by contact angle measurements before implantation, and by SEM and ESCA after implantation and cleaning. Cellular and protein components of the inflammatory response were analyzed at periodic observation points after implantation. In addition, film samples were retrieved at 4, 7, and 21 days after implantation and analyzed for leukocyte adhesion by light microscopy and SEM. The results demonstrated that cast Biomer contains an extractable fraction, which when removed significantly improves the biocompatibility of the material.
Dependence of curing time, peak temperature, and mechanical properties on the composition of bone cement
Authors: Brauer G. M. , Steinberger D. R. , Stansbury J. W. 
Published: December 2004

AbstractCommercial bone cements usually contain hydroquinone as the polymerization inhibitor and N,N‐dimethyl‐p‐toluidine as the accelerator in the benzoyl peroxide‐initiated redox polymerization. The former compounds have certain shortcomings in their biocompatibility profile. Measurements of the setting times, polymerization exotherms, and postpolymerization strengths of the cured monomer‐polymer compositions show that the hydroquinone can be replaced by food grade di‐tert‐butyl‐p‐cresol (BHT). The more reactive 4‐N,N‐(dimethylamino)phenethanol can replace 4‐N,N‐dimethyl‐p‐toluidine, yielding cements with shorter setting times and increased strengths. Excessive heat liberated on polymerization can be reduced by partial substitution of higher‐molecular‐weight methacrylates, e.g., dicyclopentenyloxyethyl methacrylate for methyl methacrylate, but there is a decrease in strength of the resulting polymer. More successful has been the addition to the monomer of 1% or 2% of the chain transfer agent pentaerythritol tetra(3‐mercapto‐propionate), which lowers the peak temperature without changing the physical properties of the cement. Compositions with short curing times, lower exotherms, and mechanical properties that exceed those of a commercial material have been formulated.
Adhesion behavior of rat lymphocytes to poly(ether)–poly(amino acid) block and graft copolymers
Authors: Yokoyama Masayuki , Nakahashi Takeshi , Nishimura Takao , Maeda Mizuo , Inoue Shohei , Kataoka Kazunori , Sakurai Yasuhisa 
Published: December 2004

AbstractBlock and graft copolymers consisting of poly(ether) and poly(amino acid) were synthesized, and adhesion behavior of rat lymphocytes to the surface of the film made from these copolymers was analyzed by the microsphere column method. Poly(ethylene glycol) (PEG) and poly(benzyl L‐glutamate) (PBLG) were used as poly(ether) and poly(amino acid), respectively. Adhesion behavior of lymphocytes was found to depend on the content and chain length of the components in these copolymers.
Hydrophilic‐hydrophobic microdomain surfaces having an ability to suppress platelet aggregation and their in vitro antithrombogenicity
Authors: Okano Teruo , Aoyagi Takao , Kataoka Kazunori , Abe Kazuhiko , Sakurai Yasuhisa , Shimada Masashi , Shinohara Isao 
Published: December 2004

AbstractBlock copolymers were synthesized by a coupling reaction of hydrophilic chains of poly(2‐hydroxyethyl methacrylate) (PHEMA) with hydrophobic chains of polystyrene (PSt), or poly(dimethyl siloxane) (PDMS). Microstructures of films of the block copolymers exhibited a hydrophilic‐hydrophobic microphase separated structure. For evaluation of in vivo antithrombogenicity, small diameter tubes (1.5 mm I. D. and 20 cm length) coated by the copolymers on their internal surfaces were implanted in rabbits as arteriovenous shunts. Occlusion times of the tubes, measured by formation of thrombus, were three days for PHEMA, two days for PSt, and three days for PDMS. The block copolymers showed excellent antithrombogenic properties: occlusion times were 20 days for HEMA‐St block copolymer and 12 days for HEMA‐DMS block copolymers. In vitro examination of polymer‐platelet interaction in terms of platelet adhesion and aggregation, which are important initial processes of blood coagulation, demonstrated suppressed adhesion and aggregation on microdomain surfaces constructed of hydrophilic and hydrophobic block copolymers. From both in vivo and in vitro examination, it was concluded that HEMA‐St and HEMA‐DMS block copolymers showed promising antithrombogenic activities by suppressing activation and aggregation of platelets.
Effect of microstructure of poly(propylene‐oxide)‐segmented polyamides on platelet adhesion
Authors: Yui Nobuhiko , Sanui Kohei , Ogata Naoya , Kataoka Kazunori , Okano Teruo , Sakurai Yasuhisa 
Published: December 2004

AbstractThe relationship between microstructure and platelet adhesivity of six types of poly(propylene oxide) (PPO)‐segmented polyamides based on the polyamide segments nylon 210, 310, 410, 510, 610, and 710 were investigated. These multiblock PPO‐segmented copolymers were prepared by interfacial polycondensation. Physical characterization of these copolymers was by means of thermal analysis, transmission electron microscope, wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS). The WAXD and SAXS measurements showed that the copolymers had microstructures containing crystalline and amorphous phases and that these microstructures, represented by means of crystallite thickness and long period, varied with incorporation of PPO segments. Blood compatibility of these copolymers was evaluated by estimating the amount of adhering platelets on the copolymer surfaces. The amount of adhering platelets was minimum for the surfaces of the copolymers having a crystallite thickness of 6.0–6.5 nm and a long period of 12–13 nm. This result suggests that the particular size and distribution of the crystalline and amorphous phases in the copolymer could be determining factors for suppressing platelet adhesion on the copolymer surface, and that the control of these factors could lead to ideal antithrombogenic polymers.
Effect of pH on the microhardness of renal calculi
Authors: Johrde L. G. , Cocks F. H. 
Published: December 2004

AbstractThe effects of synthetic urine environments of pH 4, 6, and 9.5 on the microhardness of renal calculi have been investigated. Tests were made, using both Vickers and Knoop indenters, on three compositions of calculi: 100% calcium oxalate monohydrate (whewellite), 100% uric acid, and 98% magnesium ammonium phosphate hexahydrate (struvite) mixed with 2% carbonate apatite. Whewellite calculi hardness was lowered, relative to (dry) values by 45–55% when saturated with a solution of pH 9.5. Exposure to lower pH conditions was not as effective in lowering hardness in this case. Struvite calculi hardness was lowered by 41–52% compared to the dry hardness and uric acid calculi hardness decreased by 25–36%, compared to dry hardnesses. For uric acid stones the reduction in hardness did not depend on pH within the range of pH values investigated. For struvite stones, acid pH conditions appear to give an increased softening, compared to other pH values.
Synthesis of novel polyaminoetherurethaneureas and development of antithrombogenic material by their chemical modifications
Authors: Shibuta Ryuichi , Tanaka Masakazu , Sisido Masahiko , Imanishi Yukio 
Published: December 2004

AbstractNovel polyaminoetherurethaneureas containing tertiary amino groups in the main chain were synthesized (PAEUU), quaternized (Q‐PAEUU), and heparinized (H‐PAEUU). Films of PAEUU showed a microphase separation, which was influenced by the quaternization and the heparinization. With increasing content of amino group, the water content of Q‐PAEUU and the heparin content of H‐PAEUU increased. The heparin‐releasing rate from H‐PAEUU into physiological saline solution was slow, but increased with increasing content of quaternary ammonium groups in the polymer. The water content, the heparin adsorption, and the heparin‐releasing rate were controlled by the kind of quaternizing agent. The antithrombogenicity of the polyurethaneureas was improved by quaternization and very much by heparinization, and affected by the kind of quaternizing agent. Heparinization was indispensable for achieving antithrombogenicity of the polymer, although the antithrombogenicity of H‐PAEUU was affected more strongly by the water content than by the heparin content. The surface free energy of these polymer films was also investigated.
The biological performance of calcium phosphate ceramics in an infected implantation site: I. Biological performance of hydroxyapatite during Staphylococcus aureus infection
Authors: Van Blitterswijk C. A. , Grote J. J. , De Groot K. , Daems W. Th. , Kuijpers W. 
Published: December 2004

AbstractIn the present study the biological performance of macroporous and dense hydroxyapatite after implantation in the rat middle ear was evaluated during an induced Staphylococcus aureus middle ear infection. The course of the infection was similar to that in the absence of an implant. Hydroxyapatite was frequently integrated with fibrous ingrowths in the middle ear lumen, originating solely from the infection. Good epithelial covering of the implant with all types of epithelial cells of importance for middle ear defence, was found. Increase of the exudate in the pores due to the infection was relatively small, and most of the exudate was restricted to pores on the implant surface. The bony tissue in the pores was not influenced significantly by the induced infection. Degradation of hydroxyapatite was consistent with earlier results obtained in the noninfected middle ear. The results obtained so far suggest that hydroxyapatite is highly suitable for middle ear implantation.