bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compatibility of various plastics with human plasma proteinsm
Authors: Halbert S. P. , Ushakoff A. E. , Anken M. 
Published: December 2004

AbstractA system has been devised to test the potential denaturing effects of large, surfaces of various plastics on the proteins in human plasma. This system permits a blood sample to be drawn, so that from the time it leaves the vein it contacts only the material under study; the plasma is separable in situ, and no air or gas interface is present during the test.Although silicone rubber proved to be relatively inert to the numerous plasma protein parameters investigated, silicone rubber that had been heparinized by treatment with the quaternary ammonium salt TDMAC caused a severe denaturation of the plasma lipoproteins exposed to it. On the other hand, silicone rubber heparinized via treatment of the filler silica particles did not show these effects. Ethylene‐vinyl acetate and acrylamide gel also were found to be inert to the proteins in plasma, while several other plastics revealed only minor alterations. Control plasma samples maintained at 37°C were surprisingly stable under the experimental conditions used.
Development of a toxicity evaluation program for dental materials and products I. Screening for Irritant Responses
Authors: Powell D. , Lawrence W. H. , Turner J. , Autian J. 
Published: December 2004

AbstractA broad dental toxicology screening program has been initiated to develop suitable testing methods for new dental materials or products which presently are not considered as drugs. In the report presented here, 42 materials or products have been included in an acute toxicity screening program for the evaluation of irritancy properties. Depending upon the state of the material or product, one or more testing procedures were employed. These included: (1) implantation in rabbit muscle, (2) a tissue culture test, (3) an intradermal test in rabbits, (4) an eye test in rabbits, and (5) a dermal test in rabbits. With the limited number of materials or products, the most suitable method of testing solids was the implantation method and tissue culture. Tissue culture appeared to be the only useful method for powders while tissue culture and an intradermal test the most suitable method for liquids. Other materials and products will be included using these test procedures to note if one or two might eventually be selected as a preferred method of “irritancy” testing when a large number of materials or products are to be screened for a dental or medical application. The final evaluation of safety for a dental material or product must of course be based upon its intended use.
Membrane characteristics, permeability parameters, and frictional coefficients for cuprophane
Authors: Fritzinger Bruce K. , Brauman Sharon K. , Lyman Donald J. 
Published: December 2004

AbstractThe transport of aqueous urea, glucose, and sucrose through the cellulose membrane, Curophane, is described in terms of permeation and frictional coefficients. As for other cellulose materials, hydraulic flow for Cuprophane is predominantly of a capillary nature. While Cuprophane is relatively selective, reflecting more of these solutes than most other cellulose membranes, the observed flow rates through this very thin membrane are quite high. These permeation properties for Cuprophane are accommodated by the frictional description of membrane transport. The data are discussed and compared with other available data on related cellulose systems.
The use of hydron in resection of the liver
Authors: Michněviš I. , Kliment K. 
Published: December 2004

AbstractThe factor which plays the most important part in surgery of the liver is the liver suture. The considerable tenderness of the hepatic parenchyma causes the sutures to cut through easily, which leads to further complications. Therefore, in their experimental work carried out in rabbits, the authors used Hydron (USA trade‐mark) foils reinforced with polyester netting to serve as bolsters for anchoring the sutures, and to prevent them from cutting through the parenchyma of the operated gland. In addition, the spongy Hydron was tried out to aid the peritonealization process of the resection‐wound surface of the liver.
Some species differences in fibrinolysis and blood coagulation
Authors: Mason R. G. , Read M. S. 
Published: December 2004

AbstractThe plasminogen levels and the reactivities of plasmas in two commonly used blood coagulation tests have been compared for man and seven mammals. The plasmas of three nonhuman primates in general reacted as did human plasma in tests for plasminogen activation and in reactivity in the partial thromboplastin time test. The dog had the highest level of plasminogen, and the goat the lowest, of the eight species tested. Overall, the pig appeared to have the most reactive blood coagulation mechanism, clotting the fastest and lysing the slowest, while man's was among the least reactive in clotting and intermediate in lytic activity of those tested. Aside from the nonhuman primates, the calf's clotting and lytic mechanisms resembled those of man more nearly than did those of the other mammals tested. The influence of these species differences on selection of animals for in vivo evaluation of blood vascular prosthetic materials and devices is discussed.
Application of trans‐1,4 polyisoprene in orthopedic and rehabilitation medicine
Authors: Jones R. H. , Wei Y. K. 
Published: December 2004

AbstractIdeally, materials from which splints, braces, casts, and other orthopedic appliances are to be made should be capable of being shaped directly against the patient. They should be simple and quick to use, and require the minimum of special equipment. Appliances made from them should be dimensionally stable in service and acceptable to the patient in terms of comfort, weight, durability, and appearance.Synthetic trans‐1,4 polyisoprene, prepared with a Ziegler catalyst system, is such a material. It crystallizes at temperatures below 130°F; it is a hard semi‐rigid rubber at room temperature; and its compounds can be molded directly against the skin without discomfort. Laboratory tests show that molded shape and strength can be maintained even under stress at temperatures up to about 120°F, and service performance fully supports the results of laboratory testing.This paper describes the properties of trans‐1,4 polyisoprene that make the polymer suitable for many orthopedic appliances, and includes examples of its uses in hospitals and rehabilitation institutions. Special attention is given to describing a recently developed technique for the making of artificial limb sockets using trans‐1,4 Polyisoprene.
A new absorbable suture
Authors: Frazza E. J. , Schmitt E. E. 
Published: December 2004

AbstractAlthough satisfactory nonabsorbable sutures made from a variety of synthetic and natural materials have been available for a number of years, since ancient times only collagenous absorbable sutures have found general acceptance. While adequate, catgut and the more recently developed regenerated collagens have inherent disadvantages common to many complex natural substances, particularly variability in composition and properties.A new synthetic absorbable suture has been developed from polyglycolic acidequation image.This material was chosen after testing a wide variety of polymers for the appropriate absorbability behavior in animals and for the required physical and mechanical properties. Polyglycolic acid suitable for this use was most conveniently prepared by the ring opening melt polymerization of glycolide. Development of a reliable process for this commercially unavailable monomer led to the discovery of the existence of two glycolide polymorphs one of which exhibits erratic polymerization behavior after exposure to trace amounts of moisture.Polyglycolic acid was converted into fiber by melt extrusion, stretching, and heat setting. Braided sutures prepared from these fibers exhibit high strength, excellent handling properties, minimal tissue reactivity, and a similar but more reproducible absorption rate than catgut. Clinical studies with these sutures are in progress.
Complexes of heparin with elastomeric positive polyelectrolytes
Authors: Yen S. P. S. , Rembaum A. 
Published: December 2004

AbstractA new elastomeric heparin complex containing from 7 to 16% of heparin was synthesized from commercially available polyether diisocyanates. Chemical analysis and solubility measurements of intermediates as well of the final product showed beyond doubt that an ionic bond was formed between heparin and the quaternized polyether polyurethane. The solubility of the heparin complex in specific solvents systems permitted to cast films or form coatings on commercial plastics. The films and the coatings were found to be non‐thrombogenic and whole human blood could be stored in 1/8 or 3/16″ID coated tubing for at least 24 hr without occurence of clotting. The values of tensile strength, elongation at break and of the shear modulus as a function of temperature showed that the heparinized complexes were endowed with desirable mechanical properties under ambient conditions.
Heparinized polyester fibers
Authors: Hersh L. S. , Weetall H. H. , Brown I. W. 
Published: December 2004

AbstractTwo methods have been developed to heparinize polyester fibers. One approach involves a thermofixation process. In this process, a water‐insoluble complex of heparin is “fixed” into the bulk of the polyester fiber by the application of heat. The second method uses an amino silane coupling agent. The heparin molecule is ionically bonded to the protonated primary amine. Both processes yield a heparinized fiber which maintains a high level of heparin in contact with NaCl solutions. The thermofixation method has been used to treat several Dacron vascular prostheses (10 mm OD) which have been implanted into the inferior venae cavae of dogs. These preliminary in vivo studies indicate that heparinized polyester fibers result in a vascular prosthesis with increased resistance to blood clotting. One 10 mm OD prosthesis has open for more than 9 months.
New blood‐compatible polymers for artificial heart applications
Authors: Salyer I. O. , Blardinelli A. J. , Ball G. L. , Weesner W. E. , Gott V. L. , Ramos M. D. , Furuse A. 
Published: December 2004

AbstractFlexible and rigid epoxy and urethane polymers containing heparin chemically and uniformly incorporated throughout and/or ionically complexed to quaternized amine grops were prepared and shown to have excellent thromboresistance in vitro and in vivo. These heparin‐modified polymers were implanted into the vena cava of dogs and successfully passed multiple acute (2 hr) and chronic (2 week) exposure periods. It was also demonstrated that the chemically coupled heparinized epoxies had no measurable adverse effects on blood cells, platelets, or plasma proteins, and that the heparin was not extractable. Significantly, epoxies containing polyoxypropylene/polyoxyethylene glycol (an additive which had no thrombus‐inhibiting properties of its own) also exhibited excellent thromboresistance when characterized in vivo in dogs. The applicability of these various materials for the fabrication of circulatory assist device components was demonstrated. The effect of polymer polarity, surface charge, and conductivity were investigated with indeterminate results and unmodified commercial polymers uniformly exhibited poor clotting characteristics. In vitro clot‐inhibiting characteristics were shown to be a sufficient, but not necessary, condition for indicating in vivo thromboresistant activity in polymer systems.
Implantable impermeable flexible encapsulants for artificial organs
Authors: Enger Carl C. , Rhinelander Frederic W. 
Published: December 2004

AbstractThese studies have furthered the development of a flexible impermeable encapsulant for implantable electronic devices. Medical grade silicone rubber, a widely used implantable material, is well known to be permeable to water vapor. We have demonstrated that silicone rubber is apparently permeated by electrolytes. This permeability to electrolytes can be blocked by impregnation of the silicone rubber with certain naturally occurring waxes during vulcanization. Implantation into living tissue has shown this material to be well tolerated. Of the natural waxes studied thus far, spermaceti has revealed the best overall properties as an impregnant for silicone rubber.
Composite resins as a dental restorative material
Authors: Johnson Leonard N. 
Published: December 2004

AbstractThe objective of this study was to assess the finished surfaces of various dental composite resin restorative materials using common rotating abrasive devices and diamond and iron‐carbide dental burs. The “finished” surfaces were compared with surfaces created by a polyester matrix band. The “finished” composite resin materials were also compared with filled resins as well as the unfilled polymethyl methacrylate resin. Evaluation of the various finishing procedures was made from scanning electron micrographs. Results indicated that “finished” resins, both filled and composite, departed greatly from an acceptable polished surface and that the use of any resin filled with glass rods would be contraindicated.
A hydrophilic polymer‐coated antimicrobial urethral catheter
Authors: Lazarus Stephen M. , LaGuerre Joseph N. , Kay Harold , Weinberg Sidney , Levowitz Bernard S. 
Published: December 2004

AbstractAn antibiotic eluting catheter has been designed to suppress bacteriuria associated with indwelling catheter drainage of the bladder. A coating of hydrophilicgel plastic, Hydron, is used as the vehicle from which the antimicrobial agent is locally released. In 15 dogs, indwelling Hydron‐cephalothin catheters provided a high degree of protection against bacteriuria up to 96 hr. After 48 hr, all 12 control animals became infected.In preliminary clinical trials involving 60 definitive cases Hydron‐cephalothin (Group II) and plain Hydron (Group III)‐coated indwelling catheters prevented the development of bacteriuria to a significant degree compared with uncoated latex controls (Group I). At the end of 5 days, the cumulative per cent infected for Groups I, II, and III was 75, 33, and 4.7%, respectively. Increased lubricity and reduced urethral mocosal reaction at the catheter interface promote drainage and prevent accumulation of detritus at the meatus. An indwelling antibiotic eluting catheter appears to interdict bacterial invasion of the bladder by, through, and around the catheter.
Sterilization problems of synthetic biocompatible materials
Authors: Bruck Stephen D. 
Published: December 2004

AbstractThe past, present, and future of biocompatible materials are reviewed as they relate to cardiovascular prostheses. Many of these materials are no longer simple systems and do not lend themselves to conventional steam or heat sterilization procedures by virtue of their lability. The object of this paper is to briefly discuss sterilization problems encountered with these labile materials using ionization radiation and gases, in terms of their physico‐chemical structures.
Hard methacrylic polymers. II. Copolymers of methyl methacrylate and 2,2‐di (4‐methacryloxyphenyl) propane
Authors: Atsuta Mitsuru , Nakabayashi Nobuo , Masuhara Eiichi 
Published: December 2004

AbstractCopolymers of methyl methacrylate and 2,2‐di(4‐methacryloxyphenyl) propane, which are suitable for crown and bridge works and artificial bones, were studied. The physical properties of the copolymer, hardness, abrasion resistance, compressive strength, and resistance against water sorption, etc. were improved by copolymerization of methyl methacrylate (MMA) with the titled co‐monomer.
Development of a radiopaque denture base material
Authors: Chandler H. H. , Bowen R. L. , Paffenbarger G. C. 
Published: December 2004

AbstractRadiopaque glass‐resin composites were made for evaluation as denture base materials. The addition of silane‐treated, radiopaque, powdered glass to clear poly(methyl methacrylate) resulted in composites that had greater optical translucency than commercially available pink denture base resins. These formulations could be pigmented and opacified to produce materials that simulated oral soft tissues in color and translucency.Other composites were made using various monomer, polymer and glass combinations. Those made from mixes of BIS–GMA, methyl methacrylate, poly(methyl methacrylate), and radiopaque glass had excellent translucency but handling characteristics were less than ideal.Removal of very small glass particles (less than a few μm) appeared to improve optical translucency.A radiographic survey of 12 specimens that contained from 29 to 57% of the radiopaque glass, indicated that all had sufficient radiopacity to aid in localization of swallowed or aspirated dentures made from such materials.Finishing procedures on composite specimens were more difficult and timeconsuming and did not produce surfaces as smooth as those obtained on poly(methyl methacrylate). The finished surfaces felt smooth to the tongue but might stain more easily in the mouth.
Fatigue behavior of type 316 stainless steel under simulated body conditions
Authors: Wheeler K. R. , James L. A. 
Published: December 2004

AbstractThe fatigue‐crack propagation behavior of Type 316 stainless steel was studied under simulated body conditions. The fatigue specimens were immersed in circulating Ringers Solution at a temperature of 98°F. Cyclic loading was accomplished at a frequency and load waveform that corresponded to normal level walking. The concepts of linear elastic fracture mechanics were used to evaluate the fatigue behavior, and it was found that the crack‐growth rate was higher under simulated body conditions than for a corresponding test conducted under ambient air conditions.
Quantitative and qualitative changes of spherical gamma particles resulting from amalgamation
Authors: Hegdahl Trond , Silness John 
Published: December 2004

AbstractOne‐thousand gamma particles in spherical amalgam and 1000 spherical gamma particles embedded in resin were sectioned, and the diameters for the sections were measured. Microhardness determinations were done on 50 particle sections in amaglam containing 46% mercury, 50 sections in amalgam of 52% mercury, and 50 sections of nonamalgameted particles embedded in resin.The gamma particles in amalgam seemed to have expanded as a result of their uptake of mercury. The gamma particles in amalgam had a lower hardness than the nonamalgamated particles embeded in resin. The hardness values ofthe particles were not statistically different in amalgam comtaining 46 and 52% mercury.
In vitro performance of installed internal fixation plates in compression
Authors: Bynum D. , Allen G. F. , Ray D. R. , Ledbetter W. B. 
Published: December 2004

AbstractThis paper deals with the performance of current designs of bone fixation plates, mountedon the anterior surface of fractued equine third metacarpale and tested in uniaxial compression. A full factorial experimental design on three variables, plate length, plate width, and fasterner size provided 27 different variations of the basic design. No replicate ests were conducted. All loads were normalized on mid‐shaft done gemetry and compared to he ultimate compressive strength that could be expected of a similar bone of the same age. No capacities above 33% of the strength of an unfractured bone were observed.
Perm‐selective dialysis membranes. I. Films based on dimethylaminoethyl methacrylate copolymers
Authors: Muir W. M. , Courtney J. M. , Gray R. A. , Ritchie P. D. 
Published: December 2004

AbstractNew synthetic polymer membranes prepared from copolymers of dimethylaminoethyl methacrylate are reported. Membrane transport characteristics are compared with those of standard cellulose films currently used in hemodialysis. The membranes are obtained as films by casting solutions of vinyl copolymers prepared by emulsion polymerization techniques. The new membranes show selectivity towards certain blood components under the test conditions used. The clinical procedure for ethylene oxide sterilization has been adapted to give chemical modification of dimethylaminoethyl methacrylate tertiary amine groups. With acrylonitrile as comonomer, polymer membranes which are both watersensitive and insoluble are obtained. The permeability of such films is controlled by varying processing time. Infrared spectra of processed and unprocessed films are discussed and reasons put forward for the change in membrane properties brought about by processing. Membrane behavior when acrylonitrile is replaced by methacrylonitrile or methyl methacrylate indicates the probable necessity of having a strongly electron‐attracting comonomer for successful modification.
Effect of porosity of heterogeneous poly(glycol monomethacrylate) gels on the healing‐in of test implants
Authors: Šprincl L. , Kopeček J. , Lím D. 
Published: December 2004

AbstractTest implantations were carried out on rats in order to investigate the effects of porosity of heterogeneous poly(glycol monomethacrylate) gels on their healingin. The porosity was varied by changing the water content in initial monomeric mixture. The histological analysis has shown that spongy polymers containing 50 and 60% of water in the initial mixture are healed‐in similarly to the homogeneous gel by encapsulation with collagen fibrous tissue. In polymers having higher content of water in the initial mixture, i.e. higher porosity, the vessels from the new formed fibrous capsula penetrate into the implant. The higher the porosity, the narrower the capsula and the broader the zone of cellulization and new‐formed capillaries, penetrating into the implant. In the case of polymers of higher porosity, giant multinuclear cells are observed in the margin of the implant. The positive Kóssa's calcium reaction was found only sporadically on the margin of the implant.
Permeability studies with cellulosic membranes
Authors: Colton C. K. , Smith K. A. , Merrill E. W. , Farrell P. C. 
Published: December 2004

AbstractThe true diffusive permeabilities of commercial, modified commercial, and laboratory cast regenerated cellulose membranes were measured with a batch dialyzer using 15 solutes (sodium chloride, nine radioactively labelled organic solutes, and five low molecular weight proteins) ranging in molecular weight from 58 to 68,000. Additional measurements included membrane thickness, water content, and strength properties, as well as equilibrium solute partition coefficients and solute diffusion coefficients in free solution. All commercial cellophanes were similar in sodium chloride permeability on a unit thickness basis and were significantly less permeable than hydrophilic wet gel membranes. This difference was attributed to the irreversible collapse of membrane structure upon drying. As the solute characteristic size increased, permeability decreased more sharply with commercial cellophane than with wet gel cellulose, the ratio between the two becoming an order of magnitude for large solutes. The ratio between the solute diffusion coefficient in the membrane and in free solution decreased exponentially with increasing solute size. The results suggest further work for higher permeability cellulosic hemodialysis membranes.
The pressure dependence of the elastic constants of dental amalgam
Authors: Grenoble Dale E. , Katz J. Lawrence 
Published: December 2004

AbstractThe pressure dependence of the elastic constants of dental amalgam has been examined in the 0–50 kilobar range using a solid media, pressure apparatus coupled with an ultrasonic interferometer. Computer analysis of the measured longitudinal and shear ultrasonic wave velocities yields the pressure dependence of the bulk, shear and Young's moduli and Poisson's ratio. Samples were prepared with varying compositions from micro‐cut and spherical dental alloys. The elastic behavior of these samples can be directly related to the sample structure and composition as well as to the manipulation during preparation. In addition, an estimate can be made of the volume concentration of porosity.