bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thrombogenicity of some biomedical materials: Platelet‐interface reactions
Authors: Mason Reginald G. , Scarborough D. Emerson , Saba Sabiha R. , Brinkhous Kenneth M. , Ikenberry Lynn D. , Kearney James J. , Clark Howard G. 
Published: December 2004

AbstractFifty‐eight polymers and other materials were evaluated for compatibility with human blood in an in vitro test system. Assays for platelet factor 3 activation, activation of the coagulation sequences, and release of hemoglobin and adenine nucleotides were performed on blood exposed to each of the 58 test materials. Of the materials tested, collagen, heparinized hydrin rubber, poly (methyl methacrylate), graphite‐benzalkonium‐heparin, poly (methyl acrylate), isotactic poly(methyl methacrylate), grafted poly (ethylene oxide) on poly (acrylic acid), balata rubber, L‐1624 from 3M Co., and chlorinated poly (vinyl chloride) appeared most compatible with blood. Chemical affinities appeared to have little to do with blood compatibility of the materials tested. Electron microscopic examination of blood components adherent to selected test materials following exposure to blood was carried out. Each of the three polymers with “good” and the two polymers with “poor” blood compatibility characteristics which were examined by electron microscopy was coated with a thin unilaminar adsorbate from blood. Platelets and fibrin were focally deposited on this adsorbate. Of the test surfaces examined, only glass was covered by a trilaminar adsorbate. Mechanisms of formation of the adsorbates are discussed.
Composite hydrophilic materials suggested by a simple model of cartilage. I
Authors: Flam Eric , Schubert Maxwell , Kapfer William H. , Brenner Walter 
Published: December 2004

AbstractSedimentation of collagen or cellulose fibers freshly precipitated from aqueous solutions containing certain soluble, flexible polyelectrolytes compacts them to pellets which may incorporate considerable amounts of the polyelectrolyte. The amount of polyelectrolyte incorporated increases with its chain weight and with its concentration in the solution from which the fibers were precipitated. The amount of water held by the pellets after compaction under a standard set of conditions generally increases with the amount of polyelectrolyte which has been incorporated into the pellet. Pellets formed by the compaction of cellulose fibers in the presence of polyelectrolyte are coherent although those formed in the absence of polyelectrolyte are not; all collagen pellets are coherent. All coherent pellets can be dried and, subsequently, reconstituted by being soaked in.15 M KCl. Reconstituted collagen pellets hold over two times as much water as the initial wet pellet formed by compaction; reconstituted cellulose pellets hold on the average about ⅓ the amount of water as the initially compacted pellets. The reconstituted pellets can again be dried and reconstituted with generally little further loss of polyelectrolyte or change in capacity to take up water.
The search for the nonthrombogenic property of colloidal graphite
Authors: Milligan Herbert L. , Davis Janover W. , Edmarkm K. William 
Published: December 2004

AbstractThe nonthrombogenic property of the graphite‐Benzalkonium‐heparin surface has not been consistently attained by those using this coating. In addition, there is mounting evidence that this property is not dependent entirely on the presence of heparin. A series of tests were conducted to further define the properties of colloidal graphite materials, methods of control and possible relationships to thrombus formation. These tests included electrokinetic investigations, dielectric measurements and other physical/chemical property evaluations. It was found that the colloidal graphite coating approximates many properties which are characteristic of animal tissue. However, considerable scatter in the duplication of these properties was encountered. The properties which seemed to separate the Acheson Colloids Company DAG‐35 coating from other graphite products were those of porosity and permeability. Control of these parameters may be critical to achieving consistent uniform success.
A testing device for evaluation of gas transfer through synthetic membranes
Authors: Lautier André , Laurent Daniel , Granger Alain , Sausse André 
Published: December 2004

AbstractAn experimental set‐up was designed to allow the determination of the gas transfer rates between human blood and pure O2 through a synthetic membrane. This device permitted the obtention of known steady states. It consisted of a thermostated closed blood loop containing a capillary oxygenating cell with a functional area of 400 cm2. The thickness of the blood film in the capillaries was about 150 μ. The type of membrane under study consisted of a supporting cellulosic paper, impregnated with a silicone elastomer. The manufacturing process allowed to get reproduceable hydrophobic microporous membranes without selective permeability in gas to gas phase. The continuous evaluation of the “expired” CO2 flow rate was achieved with an accurate titration method. O2 and CO2 transfer rates were also determined on the blood phase. In parallel mounting of two oxygenators permitted an intercomparison of membranes. The results gained from this study permitted to consider one of these membranes (6.5 g silicone/m2) as suitable for incorporation into a blood oxygenator. Moreover, agitation of the blood capillaries at a suitable frequency resulted in a substantial increase of O2 and CO2 transfer rates.
Corrosion effects of three sterilization methods on experimental implant surfaces
Authors: Sandrik J. L. , Wragg L. E. 
Published: December 2004

AbstractAutoclave sterilization of paper‐wrapped stainless steel implants resulted in slight general surface corrosion and crystalline contamination. Such artifacts may produce microanodes which induce local tissue reactions, thereby lowering the pH and further activating the corrosion process. Implants sterilized in ethylene oxide or benzalkonium chloride did not show artifact corrosion or contamination. Mechanisms are presented to show the effects contaminants have upon both the corrosion behavior and the tissue reaction of implant materials.
Parameters affecting preparation of nylon‐based hemodialysis membranes
Authors: Luttinger Manfred , Cooper C. W. 
Published: December 2004

AbstractNylon‐based membranes of greater dialyzing capacity than Cuprophan have been prepared by solution casting. Good permeability is being achieved by the use of diluents such as dimethylsulfoxide in the casting solution. Modifying resins, primarily epoxies, contribute to higher permeability, good aging stability, and heat‐sealing properties. Drying time between film casting and water immersion as well as the temperature and composition of the immersion bath are important factors in membrane performance. Methods for attaching heparin to the film surface have been developed, thus imparting good blood compatibility to the membranes.
Preliminary evaluation of porous metal surfaced titanium for orthopedic implants
Authors: Hahn H. , Palich W. 
Published: December 2004

AbstractRecent results indicate varying degrees of bone ingrowth into porous metal and ceramic bodies. Such homogeneously porous ceramic and metal implants generally possess inadequate mechanical properties, limiting their application to low stress or nonstructural applications. An experiment was performed wherein titanium porous coatings were applied to a wrought titanium bone implant. These surfaces were achieved by plasma spraying of titanium hydride powder, depositing a mixture of wellbonded titanium‐titanium oxide with pore diameters varying from .002 to .005 in.Implant specimens were placed in sheep femora for periods of 14 and 26 weeks. No adverse affects were noted. Interface shear strengths were determined by torque tests which indicated approximately a twenty‐fold increase over similar tests performed on uncoated control specimens.
Amino acid polymers for biomedical applications. I. Permeability properties of L‐leucine DL‐methionine copolymers
Authors: Martin E. C. , May P. D. , McMahon W. A. 
Published: December 2004

AbstractA series of DL‐methionine/L‐leucine copolymers was prepared from the coresponding N‐carboxy‐anhydrides. The copolymers formed clear flexible films having low water vapor transmission rates. Peroxide oxidation of the pendant methyl‐theioethyl groups to methyl‐sulfinoethyl groups enhanced the hydrophilic properties of the membranes, and the water vapor transmission rates rapidly increased with an increase in the number of pendant methyl‐sulfinoethyl groups. Increasing the leucine content of the membranes produced a 13‐fold increase in the carbon dioxide permeability and a 6‐fold increase in oxygen permeability, whereas, an increase in the methionine content doubled the carbon dioxide‐oxygen separation factor.Synthetic poly (α‐amino acids) are very similar to naturally occurring proteins with respect to composition and conformation. Because of these similarities, they are being considered in aerosol spray bandages, synthetic skin applications and as coatings for plastic prostheses. The unusual permeability characteristics of the DL‐methionine/L‐leucine copolymers make them interesting membranes for possible use in artificial kidney machines and blood oxygenators.
Transport properties of a new dialysis membrane
Authors: Brauman Sharon K. , Fritzinger Bruce K. 
Published: December 2004

AbstractThe dialysis and flow properties of a selected copolymer system, consisting of polyethylene terephthalate and polyoxyethylene glycol, have been studied in some detail. Such transport information should serve as a guideline to future development of improved, synthetic, hemodialysis membrane materials. By varying the size of the polyoxyethylene glycol segment, the transport properties of this copolymer have been examined as a function of the chemical and physical properties of the system. Membrane transport has been described by three flow parameters: the filtration, reflection, and solute permeability coefficients. Data for three copolyether‐ester compositions and several aqueous solutes are discussed and compared with data on cuprophane, the cellulose material currently used in the Kiil hemodialyser.
Hollow fiber membrane oxygenator
Authors: Skiens W. E. , Lipps B. J. , Clark M. E. , McLain E. A. 
Published: December 2004

AbstractHollow fibers have been produced and evaluated for use as membrane oxygenators in an artificial heart device. Gas permeable capillaries now commercially available are unsuitable for this use because of: (1) low percent open cross‐sectional area, (2) large internal diameter, and (3) high cost. A number of polymers were initially selected for evaluation because of their reported high gas permeabilities. Those selected include a number of rubbers of various compositions, certain poly‐α‐olefins and an experimental thermoplastic silicone rubber copolymer. These materials were first evaluated as flat membranes (films) for their gas permeabilities and also for ease of preparation in hollow fiber form. Hollow fibers were prepared from the most promising of those studied, poly‐4‐methylpentene‐1 and the thermoplastic polydimethylsiloxane copolymer. Fibers, ranging in the size from 30 to 300 μ ID, were spun with open cross‐sectional areas of 40‐65%. Oxygen and carbon dioxide permeabilities measured on these fibers were compared to that of SilasticDow Corning medical grade poly (dimethylsiloxane).
rubber membranes. These permeabilities range from 1/20 that of Silastic rubber for unmodified poly‐4‐methylpentene‐1 to 2/3 for the thermoplastic silicone copolymer. Modification of poly‐4‐methylpentene‐1 has made it possible to increase it's permeability by tenfold, while still maintaining physical properties necessary to spin and fabricate this material.
Compatibility of porous ceramics with soft tissue; application to tracheal prostheses
Authors: Hulbert S. F. , Morrison S. J. , Klawitter J. J. 
Published: December 2004

AbstractThe trachea is a rather simple structure, and partly because of this simplicity, many attempts have been made to effect replacement with various types of prosthetic tubes. Unfortunately, the basic design of the trachea is not easily duplicated, and thus far there is no completely satisfactory prosthetic replacement. A series of porous and non‐porous ceramics implanted in muscle tissue of rabbits indicated that rigid, porous materials can be compatible with soft, viable tissue. A prosthesis of porous ceramic rings and alternate bands of Dacron mesh was constructed and employed to bridge 6‐cm defects created in the tracheas of mongrel dogs. After 6 months an asymptomatic animal was sacrificed. Firm fixation was accomplished and the lumen was completely patent, but histological sections demonstrated that ingrowth and scarring did not satisfactorily contain bacterial infection. Encouragement of epithelial regeneration or some artificial barrier is necessary for successful implants. Work in progress includes devices using both methods to provide this barrier.
The use of ceramics in augmentation and replacement of portions of the mandible
Authors: Topazian Richard G. , Hammer Wade B. , Talbert Christian D. , Hulbert Samuel F. 
Published: December 2004

AbstractMandibular form and structrue are critically important in outlining the lower face and providing anchorage for the lower teeth. Mandibular function is also essential for mastication. Destruction and deformity of the mandible may, therefore, be crippling both physically and psychologically. The usual problems affecting the mandible are reduction in the substance of the alveolar ridge through inflammation or atrophy, presence of small bone gaps resulting from non‐union of fractures and avulsive injuries, neoplasia, and existance of contour deficiencies. The procedures necessary to deal with these problems are: (1) augmentation of the deficient mandibular alveolar ridge, (2) replacement of small discontinuity defects of the mandible, (3) replacement of large portions of mandible, and (4) correction of deficiencies in the contour of the mandible. Bone grafts, metals, and medical polymers have been widely used in the treatment of bony defects but these materials have serious shortcomings, particularly with reference to host acceptance and inertness. Additionally, soft tissue and bone seldom attach firmly to these materials. The ceramics appear to offer many advantages over materials used earlier. Calcium aluminate ceramic prostheses with interconnecting pores in the 150 to 200‐μ range were implanted in dogs to correct a variety of mandibular deficiences. They show considerable promise as an implant material.
The role of the porcelain inlay in restorative dentistry
Authors: Myerson Richard L. , Dogon I. L. 
Published: December 2004

AbstractPorcelain inlays coupled by a silane treatment to composite resins which were used as cementing media and in turn retained by an undercut were evaluated as to their marginal integrity and retention against conventionally restored teeth. These included restorations in teeth with undercuts of resins, composites, and porcelain inlays cemented with zinc oxyphosphate cements.The evaluations were determined by isotope penetration during thermal cycling (180 cycles from 12 to 50°C), scanning electron microscopy of sectioned restorations, and mechanical pull tests.The results showed improved retentive qualities and markedly improved resistance to marginal penetration. Improved adaptation of the composite to the tooth surface was produced by the mechanical action of seating the porcelain inlay.
Factors influencing longevity of low‐profile prosthetic heart valves
Authors: Boretos John W. , Detmer Don E. , Braunwald Nina S. 
Published: December 2004

AbstractAbrasion and performance of artificial heart valves are related to geometrical configuration, blood flow dynamics, manufacturing techniques, and interaction of materials. Incidence of thromboembolism, valve insufficiency, and shortened longevity are critically dependent upon these factors. The effect of construction parameters on valve performance is discussed in general terms and illustrated from in vivo experience with a specific low‐profile design.
Tissue reaction to three ceramics of porous and non‐porous structures
Authors: Hulbert S. F. , Morrison S. J. , Klawitter J. J. 
Published: December 2004

AbstractIn this investigation, ceramics were studied to determine their role as rigid, abrasive implants in soft, living tissue. Discs and tubes of three ceramics, CaO·Al2O3, CaO·TiO2, and CaO·ZrO2, were introduced as porous and non‐porous structures into muscle and connective tissue sites in rabbits. The animals were observed grossly to determine the duration of redness and swelling following surgery, and samples were retrieved at 1 week, 3 months, 6 months, and 9 months after implantation. A mild, acute inflammatory response immediately followed the implantation of all three materials in both the porous and non‐porous forms. Histological sections of the ceramics and surrounding tissue, cut and stained for light microscopy, demonstrated the absence of inflammatory cells and revealed the normal morphology and organization of the cells present around all types of implants tested. Tissue around discs of porous ceramics healed faster and exhibited thinner fibrous encapsulations than with impervious discs of the same material. Healthy fibrous connective tissue with an ample blood supply occupied those implants with pores of 45–100 mμ, and even more rapidly filled the samples with a 100‐ to 150‐μ pore size. The tissue ingrowth and tight adherence to the porous samples was believed responsible for the more moderate response to porous implants. No adverse responses of any kind were observed, except in a very few, atypical specimens.
Attachment of bone to threaded implants by ingrowth and mechanical interlocking
Authors: Predcki Paul , Auslaender B. A. , Stephan J. E. , Mooney Vert L. , Stanitski Carl 
Published: December 2004

AbstractThreaded cylindrical samples of titanium, aluminum oxide, and titanium flame‐sprayed with Al2O3 were implanted trasnversely in dog femurs. Half the samples were pushed into slightly oversize holes in the femurs, and half were screwed into slightly undersize holes. After implantation for 4 weeks, the former samples were pushed out and the latter torqued out.Metallographic and electron microprobe examination showed that essentially complete ingrowth of new trabecular bone had occurred into the threads of all samples. The highest push‐out shear strengths, (of the order of 2000–2500 psi), were obtained with sharp V‐threads on surface oxidized titanium at 56 thread/inch. In these samples, the fracture path was mostly through the new bone rather than along the bone/implant interface. Torque‐out shear strengths were substantially lower (300–1000 psi) with the fracture path following the macroscopic bone‐implant boundary.
Reduction of tissue and bone adhesion to cobalt alloy fixation appliances
Authors: Homsy Charles A. , Stanley Rufus F. , Anderson M. Sidney , King Joe W. 
Published: December 2004

AbstractThe cobalt‐based alloy containing approximately 30% chromium and 5% molybdenum is widely used for the fabrication of internal fixation appliances. This alloy exhibits superior corrosion resistance in the presence of body fluid because of a durable and rapidly formed surface layer of chromium oxide. Although biocompatible, clinical use of this alloy appears to have been complicated by relatively great adhesion of tissue and bone to the metal. The adhesion engenders considerable difficulty when removal of an applicance should become necessary.It was hypothezied that this adhesion derives from the ceullular growth proceeding within the microporosity of the metal surface; the growth proceeds efficiently because of relatively low levels of cytotoxic metal ions released at the metal surface. In order to limit adhesion, polytetrafluoroethylene polymer (PTFE) was used to virtually eliminate surface microporosity and to substantially reduce metal surface free energy.1 One of the efficient techniques was to lap the metal surface with a solid piece of PTFE.A series of eighteen 12– to 22–kg dogs were used to evaluate the above thesis. Control and treated cobalt alloy plates and screws were used to fix induced longbone fractures in the same animal. Also, five animals received implants on decorticated iliac crests. The histological data for control (untreated) plates showed that in nine of the eleven experiments bone was demonstrated closely adjacent to the surface of the appliance. However, in seven of these cases fibrous tissue was also present to a substantial degree. The presence of bone correlated with generally increased difficulty in removal of the plate. On the other hand, the results with treated implants showed that in ten of eleven cases the appliances were grossly encapsulated with fibrous tissue and were relatively easy to remove.
Intravascular radiopaque catheters in the dog: Tissue reaction and possible lead loss
Authors: Winders Robert L. , Rostorfer Howard H. , Blackschaffer Bernard C. 
Published: December 2004

AbstractMale mongrel dogs were divided into two groups and placed in urine collection cages for 24‐hr urine samples. One group was implanted with sterile radiopaque polyethylene catheter and stainless steel guide wire fragments in the venous vasculature via an incision in the left femoral vein and the remaining group in the arterial vasculature via the left femoral artery. The catheter fragments, made radiopaque by an admixture of 25% lead oxide and 75% polyethylene, were located by roentgenograms and along with the guide wire fragments removed at necropsy 18–46 weeks following implantation. Gross and microscopic tissue lesions consisted of fibrous tissue tubes and slings which completely enclosed and anchored the fragments and intimal hyperplasia with fibrous tissue organization of thrombi, respectively. Tissue staining techniques for lead, catheter fragment weights, blood lead levels, and urine lead content all revealed no evidence of lead loss from the catheter fragment implants.
Poly(ethyleneglycol methacrylate) as a material for hemodialysis
Authors: Špaček P. , Kubín M. 
Published: December 2004

AbstractDiffusion and permeation coefficients of urea, creatinine, and sodium chloride in poly(ethyleneglycol methacrylate) swollen to equilibrium in water were determined; on their basis, geometrical dimensions of a simple artificial kidney are estimated and discussed.
Precipitation hardening in gold‐platinum alloys containing small quantities of iron
Authors: Fuys R. A. , Fairhurst C. W. , O'Brien W. J. 
Published: December 2004

AbstractGold‐10% platinum alloys with additions of minor amounts of iron exhibits age hardening characteristics. Maximum hardness and maximum hardening rate occurred in gold‐10% platinum alloys containing 0.16 wt% iron. Electron microscopy techniques employing replicas of Au‐Pt‐Fe alloys revealed intragranular and intergranular precipitation phenomena occured in the overaged condition. Electron diffraction and x‐ray diffraction methods showed the intergranular phase to be an ordered face‐centered cubic structure.
Splat‐cooled alloys in the Ag‐Sn‐Cu system
Authors: Johnson L. B. , Otani H. , Neary M. J. , Hauck J. W. , Heaven T. M. , Regenitter R. J. 
Published: December 2004

AbstractStrength, dimensional change during setting, and corrosion resistance have been measured for amalgams prepared from splat‐cooled alloys of different compositions in the Ag‐Sn‐Cu system. The amalgam with optimum values of these properties was made from the alloy containing 60 at. % Ag, 25 at. % Sn, and 15 at. % Cu. Tensile strengths for amalgams from this alloy were about 8000 psi, dimensional change during setting near zero, and corrosion resistance was good.X‐Ray diffraction showed that the γ1 and γ2 phases formed during the early stages of setting but that the γ2 phase had essentially disappeared after about 24 hr. At the latter time Cu6Sn5 was present.