bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein–platelet interaction on heparinized surfaces
Authors: Salzman Edwin W. , Merrill Edward W. , Binder Andrew , Wolf Carl F. W. , Ashford Thomas P. , Austen W. Gerald
Published: December 2004

Heparin‐coated surfaces exhibit prolonged compatibility with blood in vitro and in vivo. Deposition of platelets occurs on heparinized surfaces and results in thrombocytopenia, if the surface area is sufficient. Interaction of platelets with heparin‐coated materials appears to depend on a protein intermediate. Precoating of heparinized surfaces with fibrinogen solutions, platelet‐free plasma, serum, or exhausted or bentonite‐adsorbed plasma does not protect against platelet interaction but incubation in albumin reduces platelet adsorption. The behavior of platelets in respect to protein‐coated heparinized surfaces parallels the selective adsorption of specific proteins by platelets in suspension.
Interaction of blood and tissue cells with foreign surfaces
Authors: Johnsson‐Hegyeli R. I. E. , Hegyeli A. F.
Published: December 2004

The compatibility of candidate implant materials with living cells was evaluated in vitro. The materials and their interaction with living human blood and tissue cells were observed, recorded, and analyzed by means of reflected light interference microscopy. Blood cells–materials interfaces were prepared by incubating the materials in contanct with whole blood or platelet‐rich plasma. The interaction between the materials and the cells was examined either in a static or a dynamic flow system, and recorded by photography or cinemicrography. The tissue cell–materials interfaces were prepared by cultivating animal and human cells as a monolayer directly on the surface of the material to be evaluated. The resulting implant–cell specimens are suitable for histological fixation and subsequent analysis by modern evaluation techniques such as scanning electron microscopy and elemental analysis by electron microprobe. These studies can be performed on the same implant specimen before, and following its exposure to the biological material. Furthermore, separate analyses of the implant and biochemical analyses of the cells and culture medium can be carried out before and after the interaction. These techniques have been used to investigate the interaction of blood and tissue cells with a variety of promising implant candidate materials such as polymers, metals, glass, and carbon surfaces. As a result of these studies, a number of observations have been made which may be of practical significance to the design engineer in developing and evaluating the safety of prosthetic materials for use in the human body.
Adsorption of plasma proteins in solution to uncharged, hydrophobic polymer surfaces
Authors: Brash J. L. , Lyman D. J.
Published: December 2004

Infraref internal reflection spectroscopy has been used to study the adsorption of certain plasma proteins on a variety of hydrophobic polymer surfaces. The behavior of the systems studied was almost identical. Under Static conditions the proteins appear to be rapidly adsorbed as monomolecular layers from solutions varying in concentration between a few mg‐% and normal plasma levels. These monolayers are deduced to be closely packed arrays in which the protein molecules appear to retain their native globular form. The bearing of these results on the mechanism of surface‐induced coagulation is significant.
Evaluation of synthetic fabrics as artificial skin grafts to experimental burn wounds
Authors: Spira Melvin , Fissette Jean , Hall C. William , Hardy S. Baron , Gerow Frank J.
Published: December 2004

After utilizing the nylon velour Silastic and polypeptide laminates in this experimental pilot study, we can conclude the following:

Both nylon velour Silastic and polypeptide laminates are well tolerated in the clean wound and serve as a satisfactory framework into which fibroblastic proliferation can occur resulting in adherence or take.

In contaminated wounds, infection resulted in exudation with an accumulation of fluid at the interface of granulation tissue and velour. The exudate, not resorbed and unable to transcend the laminate barrier completely, serves as a nidus of progressive bacterial growth and causes separation and rejection of this synthetic fabric cover. The fluid accumulation appeared more common utilizing the Silastic laminate, while the polypeptide laminate appeared to permit an escape of this exudate to inhibit or delay the separation.

The Silastic laminated velour became firm and inflexible, predisposing with motion, to a mechanical type of separation at the margin of fabric and normal skin, possibly a contributing factor in exogeneous infection. This was seen also with the polypeptide laminate, but to a much lesser degree.

The nylon velour Silastic laminate as it is presently constructed is not acceptable as a synthetic skin cover for an infected burn wound, while the polypeptide laminated velour appears to possess physical properties which make it suitable for further investigation as an artificial skin substitute.
Corrosion and fracture of type 316 SMO orthopedic implants
Authors: Colangelo V. J. , Greene N. D.
Published: December 2004

Orthopedic appliances of type 316 (SMO) stainless steel were examined in detail after being removed from human subjects. Techniques included conventional microscopy with various lighting methods, together with electron microscope fractography. Corrosion, fatigue failure, and manufacturing defects were identified and statistically tabulated. Corrosion damage occurred on 91% of all multicomponent devices and the overall incidence of fracture failure was 9%. These results indicate an urgent ueed for stronger, more corrosion‐resistant implant alloys.
The effect of α‐cyanoacrylates on wound healing
Authors: Houston Stuart , Hodge John W. , Ousterhout Douglas K. , Leonard Fred
Published: December 2004

The use of cyanoacrylate tissue adhesives provides a quick method of closing wounds by nonsuture techniques. This study was undertaken to determine the relative effects on healing of a number of alkyl α‐cyanoacrylate tissue adhesives compared to sutured incisions. Tissue bonds were prepared with the alkyl α‐cyanoacrylate adhesives and sutures and tested for bond strength in vivo in rats over periods of 1, 3, 7, 10, and 14 days. A trend of increasing bond strength with the higher homologs was immediately apparent. However, this trend was reversed at the time of the 14 day measurements with the higher homologs of the cyanoacrylate adhesives having the lower bond strength. Microscopic examination of pulled wounds closed with methyl α‐cyanoacrylate showed the cause to be substrate failure with the exception of the one hour postoperative samples which demonstrated adhesive failure. Wound failure in the remaining three monomers was cohesive, gradually decreasing to substrate failure at 10 days postoperative. The tensile strength of all wounds closed with tissue adhesive dropped considerably on the third day postoperative.
Some chemical and biological characteristics of a new collagen–polymer compound material
Authors: Chvapil M. , Holuša R. , Kliment K. , Štoll M.
Published: December 2004

A new compound material is described, consisting of collagen sponge and glycol methacrylate, with a density varying from a compact to a highly porous spongelike material. Mechanical properties, swelling capacity, trypsin digestion rate, structural stability, and dynamics of tissue reactivity after subcutaneous and subperiostal implantation of this material were compared with collagen sponge, and the glycol methacrylate polymer alone. It has been shown that combined polymer collagen sponge with high porosity is quickly penetrated by connective tissue which maintains the character of highly vascularized loose connective tissue. The porosity of the material is a decisive factor for tissue permeation and the size of the pores should exceed 100 μ. The combination of the glycol methacrylate polymer gel with a collagen sponge increases the mechanical strength of this hydrophilic material. Optimal conditions for construction of the gel–collagen sponge were found.
Growth twinning in γ‐crystals of the silver–mercury system
Authors: Baird H. Wallace , Muller Fredrik A.
Published: December 2004

A study by single crystal, x‐ray diffraction methods of a silver amalgam known as “arbor dianae” has shown it to be twinned on the [111] cubic crystal planes. Otherwise, they are identical to the material known mineralogically as moschellandsbergite or the γ‐phase in dental amalgam and the γ1‐phase in the silver–mercury system.
Surgical suture–porcine subcuticular tissue interaction
Authors: Homsy C. A. , Fissette J. , Watkins W. S. , Williams H. O. , Freeman B. S.
Published: December 2004

In this study tissue–suture interaction was evaluated in terms of instantaneous stress and total work at withdrawal, histological response, and photomicrographic suture appearance. Porcine subjects and subcuticular incision closures identical to those of clinical plastic surgery were used; implant periods were 1, 2, and 3 weeks. Monofilamentary sutures (4‐0) of nylon, linear polyethylene, polypropylene, and Teflon FEP were used; stainless steel and braided siliconized silk were included for comparison. Perisutural sleeves, formed by ingrowth of epithelium up to 1 cm from the loci of emergence of the suture through epidermis, were found to account for 70–85% of withdrawal work. The subcutaneous closure is superior to interrupted or running stitches in minimizing these “end effects” and attendant exacerbation of tissue–suture interaction. The degree of the latter combined with consideration of suture strength, suppleness, and knot durability indicate that nylon and Teflon FEP monofilaments are sutures of choice for cutaneous closure.
Surface deactivation of porous glass membranes
Authors: Messing R. A. , Weisz P. F. , Baum G.
Published: December 2004

Protein solutions exposed to porous glass membranes are rapidly depleted of protein. The proteins do not migrate through the membrane, but become trapped at the channel walls. Surface deactivation of porous glass can be accomplished by treatment with methyl trimethoxysilane or γ‐aminopropyl triethoxysilane. Bacitracin slowly transferred through a surface deactivated porous glass membrane.
Nucleation and oriented crystallization apatite in ionotropic gels
Authors: Thiele Heinrich , Awad Aida
Published: December 2004

We regard and handle intercellular tissue like gels with ordered fiber molecules. By this preparative histolysis and histogenesis the formation of bone and tooth can be looked upon as a chemical reaction of a cell‐secretion with the interstitial liquid seen as colloidal. The symplex alginate–collagen was directed by diffusion of Ca and H ions and then mineralized like bone and tooth. Collagen in the symplex with alginate gives big pores similar to the spongiosa of bone. Implantation in animals shows healing without rejection and inflammation. The ionotropic gel for a leading structure was remineralized and calcified with hydroxyapatite. Higher temperature gives better crystals by the increasing rate of diffusion and recrystallization. By alternately changing waves of phosphate and calcium, the content of calcium phosphate of the ionotropic gels could be increased to 50%. The mechanical stability was then increased. Waves of ions cause a shrinking of the gel at the same time. This is the reason for the high stability of bone and tooth, shell and pearl. Citrate favors the transformation of the secondary phosphate Brushit into apatite even at room temperature. X‐Ray diffractions of these crystals show the formation of 90% apatite in ionotropic gels by directed intermicellar crystallization, and only 10% Brushit.
Employment of hydron polymer antibiotic vehicle in otolaryngology
Authors: Majkus V. , Horáková Z. , Výmola F. , Štol M.
Published: December 2004

Hydrophilic poly (glycolmethacrylate) Hydron

U. S. Trade Mark, National Patent Development Corporation, 375 Park Avenue, New York, N. Y.

gels were used as vehicles for selected antibiotics. Polymer vehicles with various antibiotics were prepared and their biological activity tested by sensitivity tests on solid and liquid media by means of reference microbe strains. Polymer vehicles with chosen antibiotics were implanted in rats and the rate of diffusion tested in vivo by removing the vehicles at fixed time intervals and ascertaining the content of the remaining antibiotic in the vehicle. In the clinical part, the favorable results of application of antibiotics saturated gel vehicles in tympanoplastic operations and healing of inflammatory states after middle‐ear operations are described.
Corrosion under stress of materials composing dental amalgam
Authors: Johnson L. B. , Lawless K. R.
Published: December 2004

Corrosion potentials of materials composing dental amalgam have been measured in artificial saliva as the specimens were subjected to an increasing tensile load. Further, tensile tests have been carried out on specimens which had been previously subjected to controlled corrosion.

The corrosion potentials of Cu, Ag, Zn, Ag2Hg3, Ag3Sn and finished dental amalgam showed only a slight increase in the anodic direction as the load increased. The potentials of Sn and Sn amalgams, on the other hand, showed a considerable increase.

Most of the above results were explained as being a consequence of the rupture and repair of protective films as stress was applied or released. For Sn, however, it was necessary to postulate a complex attack by the corrodant to explain the large potential change.

Of the phases of dental amalgam whose tensile strengths were measured after subjection to controlled corrosion, only the γ2 or Sn‐Hg phase was affected. Its strength was lowered by corrosion, whether or not stress was applied.

It was concluded that stress, as such, probably is not a direct factor in the corrosion of dental amalgam under oral conditions.
Collagen membrane for hemodialysis
Authors: Kon Tadamasa , Mrava Gene L. , Weber David C. , Nosé Y.
Published: December 2004

Commercially available collagen membrance was evaluated as a hemodialysis membrane in the Kolff quad‐coil artificial kidney. The inherent physical weakness of the membrane was strengthened by a double‐screen support substracture in a coil. Greater metabolite clearance and ultrafiltration (over four times) were demonstrated with the double‐screen‐supported collagen coil than with either cellophane or cuprophane membrane supported by the same double‐screen support substructure.
Hemolysis associated with plastics—A histopathologic study with polyurethane
Authors: Rigdon R. H.
Published: December 2004

Polyurethane implanted subcutaneously in mice and rats is accompanied by a chronic granulomatous reaction in which there is an excessive amount of hemosiderin. Preceding the occurrence of hemosiderin, many erythrocytes are present, some of which are partially creatinated. Hemosiderin apparently results from the lysis of these red cells. It is suggested that this infiltration of erythrocytes and subsequent hemolysis may result from a positive charge associated with this plastic, attracting the negative charged blood cells. A similar reaction occurs with fragments of nylon and Teflon. There is no significant number of erythrocytes or hemosiderin, however, associated with the inflammatory reaction accompanying carbon black, glass beads, resin or Fuller's earth.
The design of cannulas for maintenance hemodialysis
Authors: Leith W. C. , Cole J. J. , Blagg C. R.
Published: December 2004

Because the Silastic‐Teflon cannulas used for maintenance dialysis are far from ideal, usually failing in less than 1 yr, the factors affecting pressure drop in the cannula system have been evaluated theoretically and confirmed by actual measurements in vitro. Total pressure drop results from fluid friction, boundary layer separation and wall damping, and these effects are related directly to cannula size, shape, and material. By appropriate attention to these factors in cannula design, pressure drop in the system can be minimized. Soft Silastic tips for cannulas have been developed but show disappointingly slow flows and early clotting. These results are readily explained in terms of increased wall damping with soft materials. Commercially available hard Silastic cannula tips may be more satisfactory. Optimal cannula design requires large diameter cannula bodies, suitably shaped cannula tips, and the use of stiff tip materials. Such cannulas should allow the achievement of high blood flows with a minimum of boundary layer separation at the tip‐vessel junction and will be helpful in the prolongation of cannula life.
Ag‐Sn‐Hg alloys as electron compounds
Authors: Johnson L. B.
Published: December 2004

The extraordinary stability of the γ1 phase of dental amalgam was believed to indicate that part of the Sn in dental amalgam was contained in this phase. By extending the Hume‐Rothery “electron compound” ideas to the three component Ag‐Sn‐Hg system, an estimate was made of the amount of Sn which could be held in the γ1 structure.

A Ag‐Sn alloy containing 9.1 weight per cent Sn was prepared, spheroidized, and sized. Portions were amalgamated and molded into tensile specimens, parts of which were subjected to X‐ray diffraction, corrosion tests, and tests to determine amalgamation rate and dimensional changes during setting.

X‐ray diffraction patterns showed a complete absence of the γ2 phase, (thus indicating that all Sn was in the γ1 phase) and a stability intermediate between γ Ag‐Hg and the γ1 phase of dental amalgam. Physical tests showed a low amalgamation rate, low 1‐hr strength, high 7‐day strength, and high corrosion resistance.
The absorption of carbon dioxide by thin films containing an ion exchange polymer
Authors: Wolfe Ralph G. , Miller Irving F. , Gregor Harry P.
Published: December 2004

A thin polymeric film, containing a basic polyelectrolyte, was developed with properties that potentially make it highly suitable for use in a membrane blood oxygenator. Its CO2 absorption capacity was correlated as a function of the CO2 partial pressure, temperature and relative humidity of the processed gas. The correlation showed a linear dependence with CO2 partial pressure and relative humidity and an Arrhenius dependence with temperature. A four‐step mechanism for the absorption process was postulated and its parameters were evalutaed. The apparent diffusion constant for CO2 was five times that measured for an ion‐exchange resin made from the polyelectrolyte. The capacity and mechanism correlations obtained are suitable for the design of a CO2 removal unit for a recirculated air atmosphere as well as for a blood oxygenator. The permeability of the film to CO2 and O2 was measured and the ratio was found to be far greater than that of most commercial materials. This suggests that a blood oxygenator utilizing such a film would have the controlling resistance to transfer on the oxygen side, rather than on the blood side, thus perhaps avoiding bubbling on the blood side altogether.
Potential of ceramic materials as permanently implantable skeletal prostheses
Authors: Hulbert S. F. , Young F. A. , Mathews R. S. , Klawitter J. J. , Talbert C. D. , Stelling F. H.
Published: December 2004

The feasibility of the use of porous ceramic materials in the permanent repair of skeletal defects was studied from the standpoint of physiological compatibility and in growth of natural bone. High‐fired calcium aluminate samples in the form of quarter‐inch diameter cylindrical pellets containing interconnecting porous networks were implanted in vivo into canine femurs for 4‐, 11‐, and 22‐week periods. The implants had 65% porosity with pore size falling within one of five distinct ranges from less than 45 μ to about 200 μ in diameter.

Thin sections were prepared by grinding (poly) methyl methacrylate‐mounted cross sections of the femurs containing the implanted ceramic samples and adjacent soft tissues. Tissue‐prosthetic compatibility was determined using standard histological thin section procedures, electron microbeam probe examinations, autoradiographic techniques, microfadiographic techniques, microchemistry techniques, and ultra‐violet fluorescent techniques. Optical microscopic evaluations of each section showed the ceramic samples to be bound lightly by natural bone and gave no detectable signs of tissue incompatibility. Minimum pore size for significant ingrowth of natural bone was indicated to be between 75 and 100 μ.
The role of organics in metallic passivation
Authors: Svare C. W. , Belton G. , Korostoff E.
Published: December 2004

Organic substances are known to affect electrochemical reactions. The passivation characteristics of iron have been shown to be drastically altered in the presence of certain ions. Since passivation must occur to preserve the physical integrity of some materials in vivo, a study was initiated to determine the effect of alanine, bovine plasma albumin, and cystine on this phenomenon for nickel and copper.

The procedure was as follows: (1) potential pH diagrams which show stable metal‐containing forms with respect to pH and electrical potential were constructed to interpret anodic dissolution data; (2) measurements were made to determine potential ranges in which organic adsorption occurs; and (3) data on electrical potential of the metal and associated current were taken for construction of anodic dissolution curves.

The results showed that the presence of cystine inhibited the passivation of nickel and improved the passivation tendency of copper. The other organic substances had little or no effect on passivation. A possible mechanism for these effects is proposed. Further, the results showed a relationship between the onset of passivation and the potentials where metal‐containing solid substances become thermodynamically stable, as determined from the potential pH diagrams.
In vitro performance of the disposable kiil envelope
Authors: Lips Paul , Kon Tadamasa , Weber David , Mrava Gene L. , Nosé Yukihiko
Published: December 2004

For patients performing hemodialysis at home the assembly of the artificial kidney must be simple. To achieve this, a disposable envelope, consisting of two membranes bonded to a supporting substructure, was developed for the Kiil artificial kidney. This envelope was testedin vitrofor metabolite clearance, pressure‐flow relationship, ultrafiltration, and priming volume. The clearance of this envelope for different metabolites proved to be higher than that achieved with conventional assembly of the Kiil with wet Cuprophan membranes. Analysis of the resistance to mass transfer indicated that the disposable envelope has decreased the blood‐ and dialyzate‐side resistances and provides an increase in effective membrane area, thereby enhancing overall mass transfer. The envelope also showed higher resistance to blood flow and a lower priming volume.In vitrotesting of this envelope has shown the feasibility of practical clinical application.
Test systems for evaluation of cyanoacrylate tissue adhesives
Authors: Katz Abraham R. , Woodward Stephen C.
Published: December 2004

A series of tests permitting evaluations of cyanoacrylates as tissues adhesives is presented. Closed coaption of skin is an effective, rapid screening test capable of identifying weak and strong adhesives under use conditions, and is more sensitive for this purpose than bond strength determinations employing aortic lap joints. Tensile strength testing employing skin incisions closed with cyanoacrylates permits evaluation of the continuing effects of cyanoacrylate upon healing skin. In this test system, a number of alkyl cyanoacrylates provides results equivalent to those obtained with sutures. The incorporation of cyanoacrylates into subcutaneous implants permits evaluation of the effects of these materials upon fibroplasia and collagen elaboration, the most critical aspects of wound repair. Implant testing also permits estimation of rates of resportion of cyanoacrylates from subcutaneous deposits.
A stress‐deformation model of the human aorta
Authors: Krokosky E. M. , Krouskop T. A.
Published: December 2004

A finite element stress‐deformation model of the human aorta was developed based on previously determined constitutive relationships. The model was used to predict the deformations experienced by an arota when subjected to localized pressure distributions. The model was further refined so as to analyze a twolayered vascular system. The stress distribution through the wall, particularly at the layer interface, was studied for composite vascular systems subjected to localized internal pressures.
Compatibility of various plastics with human plasma proteinsm
Authors: Halbert S. P. , Ushakoff A. E. , Anken M.
Published: December 2004

A 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

A 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.
Insolubilized L‐asparaginase implant: A preliminary report
Authors: Weetall Howard H.
Published: December 2004

L‐asparaginase, an enzyme used in the treatment of leukemia, has been covalently coupled to a Dacron vascular prothesis. The enzyme activity was determined in vitro and after remaining 7 days in vivo.
Membrane characteristics, permeability parameters, and frictional coefficients for cuprophane
Authors: Fritzinger Bruce K. , Brauman Sharon K. , Lyman Donald J.
Published: December 2004

The 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

The 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

The 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

Ideally, 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

Although 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

A 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

Two 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

Flexible 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

These 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

The 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

An 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

The 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

Copolymers 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

Radiopaque 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

The 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

One‐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.
The acoustic properties of human skull bone
Authors: Martin Bruce , McElhaney James H.
Published: December 2004

The propagation velocity and absorption coefficient of a pulse of megahertz sound was measured in 25 specimens of embalmed human skull bone. The mass densities of the specimens were also measured and their specific acoustic imped‐ ances calculated. The data is discussed and presented in tabular as well as graphic form.
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

This 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

New 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

Test 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

The 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.