bluuebunny/crossref_metadata_2025_split huggingface dataset:
An in vitro study of bacterial response to inert and reactive metals and to methyl methacrylate
Authors: Gristina Anthony G. , Rovere George D. , Shoji Hirumo , Nicastro Joseph F. 
Published: December 2004

AbstractThe clinical use of inert materials for internal fixation and joint replacement decices is increasing rapidly; studies on the effect of these materials on bacteria and host resistance t infection have not kept apace. Any substance placed within the body may interfere with host–parasite interaction, either by its physical presence or by physiohcemical activity at its interface with the surrounding tissue. Either mechanism, by altering the normal host defense mechanisms, may promote or retard bacterial growth. Bacterial growth may also be altered if a trace element essential to or inhibitory to the bacteria or an element that antagonizes or potentiates humoral antibaacterial systems is leached from the substance. We have tested bacterial growth and inhibition in vitro in the presence of substances used as implant materials: surgical silver, iron, zinc‐coated galvanized iron, aluminum alloy, stainless steel, Vitallium, and methyl methacrylate. Our results showed: (1) metals that have low grades of tissue ractivity and little bacteriotoxic effect provided a framework along which bacterial growth and propagation occurred; (2) metals that have higher levels of cellular reactivity, specifically aluminum and galvanized wire, caused selective bacterial toxicity, The in vitro response of bacteria to methyl methacrylate was similar to that of Vitallium to methyl methacrylate.These studies led us to speculate that, if similar phenomena occur in vivo, bacterial growth and dissemination might be increased when an inert implant material was used and decreased when the implant material was more reactive.
An evaluation of bone growth into porous high density polyethylene
Authors: Klawitter J. J. , Bagwell J. G. , Weinstein A. M. , Sauer B. W. , Pruitt J. R. 
Published: December 2004

AbstractThe purpose of this investigation was to study bone growth into porous polyethylene rods as a function of time and pore structure. Previous studies have indicated the biocompatibility of solid polyethylene materials which are currently being used clinically. Porous polyethylene rods were implanted in the femurs of mongrel dogs which were sacrificed four, eight, and 16 weeks postoperatively. The implants were then sectioned and examined histologically and microradiographically. Quantitative techniques were employed to determine the amount of bone ingrowth as a function of time and pore size. The pore structures of the materials were evaluated using optical microscopy and mercury intrusion porosimetry.The results of this investigation have demonstrated that porous polyethylene is capable of accepting bone growth into pores as small as 40 μm. The optimum rate of bone ingrowth was observed in pore sizes of approximately 100 to 135 μm, with no increase in the rate of bone ingrowth observed in samples possessing larger pore sizes. No adverse tissue response was found at implant times up to 16 weeks in pore sizes of 100 μm or larger.
Materials for selective tissue heating in a radiofrequency electromagnetic field for the combined chemothermal treatment of brain tumors
Authors: Moidel R. A. , Wolfson S. K. , Selker R. G. , Weiner S. B. 
Published: December 2004

AbstractA technique of creating localized heating by implanting metallic materials in the brain and inserting the head into a radiofrequency electromagnetic field is described. The heating properties of various materials for implantation were studied, and the two best materials were carbon steel rods and Hysterloy (1000 and 655 cal/g‐min, respectively). Heating of these materials was done primarily by eddy current since their heating rates were significantly affected by their shapes and orientation in the field, rods oriented parallel to the field producing the most heat. There is evidence that warmer cells have a greater uptake of chemotherapeutic agents. This suggests a combined therapeutic approach employing localized brain heating in conjunction with systemic or intrathecal chemotherapy. In this way, large doses of chemotherapeutic drugs might be concentrated in a warmed brain tumor while toxicity is prevented by keeping the rest of the brain and body hypothermic.
A statistical treatment of fatigue of the cast Co‐Cr‐Mo prosthesis alloy
Authors: Miller H. L. , Rostoker W. , Galante J. O. 
Published: December 2004

AbstractFatigue tests have been conducted on commercially produced cast Co‐Cr‐Mo alloy in tension‐tension while surrounded by a physiological solution at 37°C The data have been analyzed by statistical techniques to yield an allowable stress such that there is 95% confidence of less than one failure in 1,000 after 5 × 107 cycles of stress fluctuation. These results are valid for a substantially sounder material than may be common in commercial use and therefore a more conservative allowable stress probably ought to be used for design purposes.
Adhesion of platelets to artificial surfaces: Effect of red cells
Authors: Brash J. L. , Brophy J. M. , Feuerstein I. A. 
Published: December 2004

AbstractAdhesion of Platelets to several polymer‐ and protein‐coated glass surfaces has been studied in vitro. The apparatus consists of a cylindrical probe rotating in a test tube containing the platelet medium and allows close control of fluid shear and mass transport. Suspensions of washed pig platelets constitute the basic platelet medium, and can be modified by adding back red cells and plasma proteins. Adhesion is measured via 51Cr‐labeling of platelets. In the absence of red cells, identical low levels of adhesion were seen on all surfaces and saturation was reached within 2 min. In the presence of red cells, adhesion was greater. Saturation on all surfaces except fibrinogen and collagen again occurred within 2 min. The adhesion levels on polymer surfaces and glass were indistinguishable, while those on albumin were lower and those on fibrinogen were higher. Collagen was the most reactive surface. It did not equilibrate within 15 min, and kinetic data indicated a platelet diffusivity strongly dependent on hematocrit. These effects were attributed to rotational and translational motion of the red cells causing increased diffusion and surface‐platelet collision energy.
Flame‐sprayed alumina on stainless steel for possible prosthetic application
Authors: Baldwin C. M. , Mackenzie J. D. 
Published: December 2004

AbstractVarious methods of roughening type 316 stainless steel substrate surfaces for flame‐spraying alumina (Al2O3) were investigated and tested for the best alumina‐to‐metal bond strength. Best strength values were obtained by means of roughening via anodic polarization pitting of the stainless steel. Subsequent in vitro testing indicated a severe loss in bond strength following exposure to aerated Ringer's solution. It is suggested that the utilization of flame‐sprayed devices has potential in orthopedic prostheses, but precautions must be observed.
Evaluation of a bioglass‐coated Al2O3 total hip prosthesis in sheep
Authors: Griss P. , Greenspan D. C. , Heimke G. , Krempien B. , Buchinger R. , Hench L. L. , Jentschura G. 
Published: December 2004

AbstractA bioglass‐coated fully dense alumina total hip was evaluated in sheep without using polymer bone “cement.” After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone–implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.
Craniofacial contour defect reconstruction with a Dacron/urethane composite: An alloplastic tray for bone induction fabrication and application
Authors: Leake Donald L. , Habal Mutaz B. 
Published: December 2004

AbstractAn alloplastic tray made of poly(ethylene terephthalate) cloth mesh and poly(ether urethane) used in conjunction with cancellous bone‐chip grafts is the basis for this new method for reconstructing facial osseous contour defects. The tray can be prefabricated in quantity and at low cost for standard defects, such as discontinuity defects of the mandible or for chin augmentation. It can be custom‐fabricated for specific defects in individual patients as, for example, gunshot wounds to the forehead. The materials were chosen because of their known histocompatibility, the ease of fabrication, and because the materials can be molded to form esthetic contours. They can be easily modified at the time of surgery. Sterilization is by autoclaving.Initial studies were undertaken in mongrel dogs where mandibular discontinuity defects in the range of 2–4 cm were reconstructed. In man, the technique has been used to reconstruct discontinuity defects of the mandible ranging in size from 1.5–12 cm in 16 patients. Atrophic mandibular alveolar ridges have been augmented using this technique in 7 patients, thus providing an adequate alveolar ridge for dentures. Two patients with defects of the skull secondary to gunshot wounds have had frontal bone restoration using this method.Reconstructions of the ear, the chin, and the orbital floor are currently being evaluated. This technique overcomes many problems of esthetic contour reconstruction and combines the use of autogenous cancellous pmarticulate bone and a tissue‐compatible synthetic composite material.
Interaction effects among cortical bone, cancellous bone, and periodontal membrane of natural teeth and implants
Authors: Widera G. E. O. , Tesk J. A. , Privitzer E. 
Published: December 2004

AbstractFollowing the initial successes of Goldberg and Gershkoff (Dental Digest, 5, 11, 1947) with the placement of subperiosteal implants, interest in all types of implants emerged. As an aid to the evaluation of various designs and materials without resorting to clinical testing, finite element analyses are being conducted by a number of researchers to determine the stress system induced in bone. The present study investigates the effects of variation in the thicknesses of the periodontal membrane and cortical bone and of the model boundary on the stresses developed around a natural tooth or a tooth‐shaped implant. The results show that strong effects due to the variation in these parameters can be expected. As a consequence, the problem of the analysis of any single implant must consider additional factors. These can influence overall implant design and may eventually help to explain what could appear as anomalies in clinical test results.
Biocompatibility of nitinol alloy as an implant material
Authors: Castleman L. S. , Motzkin S. M. , Alicandri F. P. , Bonawit V. L. , Johnson A. A. 
Published: December 2004

AbstractThe biocompatibility of nitinol alloy as a potential implant material was investigated through in vivo studies on beagles. A high‐purity alloy was fabricated into prototype bone plates and implanted into the femurs of beagles. Commercial cobalt–chromium (CoCr) alloy bone plates served as reference controls, and additional control data were obtained from beagles subjected to “sham” operations.The bone plates were removed from the animals and examined after exposures of 3, 6, 12, and 17 months. There was no evidence of either localized or of general corrosion on the surfaces of the bone plates and screws. Gross clinical, radiological, and morphological observations of the tissue at the implantation sites during the autopsies uncovered no signs of adverse tissue reactions resulting from the implants. Histological analyses were performed on samples of muscle and bone adjacent to the implantation sites, and of tissues removed from such organs as the liver, spleen, brain, and kidneys. No significant differences were noted between samples taken from controls and those taken from dogs exposed to the implants. Neutron activation analyses were carried out on suitable samples. The analysis data suggest that there is no metallic contamination in the organs due to the implants; however, there does appear to be some chromium contamination from the CoCr alloy implants in the adjacent bone.On the basis of the totality of the data, it is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.
In vitro effects of bone cement on S. aureus growth and phagocytosis and glucose metabolism of macrophage: A preliminary study
Authors: Shoji Hiromu , Nicastro Joseph F. , Rovere George D. , Gristina Anthony G. 
Published: December 2004

AbstractA preliminary study of the effects of Surgical Simplex, mixed for various time periods, was performed on S. aureus growth rate, and phagocytosis and glucose metabolism of macrophage in vitro. Quantitatively, no significant effects of the mixture on S. aureus growth rate were observed. The cement mixed for less than 4 min tended to cause adverse effects on phagocytosis rate and hexose monophosphate shunt activity of macrophage. This information may not be directly applicable to in vivo, but in vitro the cement mixture in a certain situation can cause decreased phagocytosis and hexose monophosphate shunt activity of macrophage.
A unified mathematical model for diffusion from drug–polymer composite tablets
Authors: Fu J. C. , Hagemeir C. , Moyer D. L. , Ng E. W. 
Published: December 2004

AbstractThe derivation and experimental verification of a unified mathematical model for the estimation of drug release rate from drug–polymer composite tablets are presented. Cylindrical coordinates are utilized in the solution of the diffusion equation for a three‐dimensional system. The model is applicable to tablets that range from the shape of a flat disk (radius > thickness) to that of a cylindrical rod (radius < thickness). The general solution for the fraction of drug released at a time t is

This approach to a three‐dimensiona system, utilizing cylindrical coordinates, presents a comprehensive method for the estimation of drug release rates from sustained release tablets with drug distributed homogeneously throughout a polymer matrix. The calculated and experimental drug diffusion rate of pyrimethamine from pyrimethamine‐silicone rubber composite tablets that range in shape from that of a disk to a cylinder, and of hydrocortisone from EVA, poly‐caprolactone, and PVA terpolymer, are compared.
Fracture characteristics of acrylic bone cements. I. Fracture toughness
Authors: Freitag Thomas A. , Cannon Stephen L. 
Published: December 2004

AbstractThe vital first phase of the overall materials study to protract the life of the total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. This study is concerned with the fracture toughness of Zimmer and Simplex‐P cold‐curing bone cements.Following cement fabrication conditions which closely approximate clinical procedures, fracture toughness testing was conducted on cement specimens which were immersed in bovine serum at 37°C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens, tested in air at ambient temperature for purposes of comparison. Results of this procedure, when analyzed by a Student's t‐test at the 95% confidence level with eight degrees of freedom, indicate that both Zimmer and Simplex‐P exhibit a higher fracture toughness in the simulated physiological environment.In order to determine whether the addition of barium sulfate to these cements compromises the fracture toughness, the above described testing rationale was repeated, indicating the existence of a complicated relationship between the different testing environments and barium sulfate. The importance of these results lies in the fact that an increased fracture toughness indicates that a cement will inherently exhibit a greater degree of resistance to the propagation of cracks, which could contribute to the ultimate failure of the total joint replacement.
Carbon fiber‐reinforced bone cement in orthopedic surgery
Authors: Pilliar R. M. , Blackwell R. , Macnab I. , Cameron H. U. 
Published: December 2004

AbstractA tougher, more fatigue‐resistant bone cement consisting of short, highmodulus carbon fibers dispersed randomly in normal poly(methyl methacrylate) bone cement has been developed. Fatigue and impact tests are reported that demonstrate the superior fracture resistance and prolonged load‐carrying ability of this system.The use of this carbon fiber‐reinforced bone cement in the treatment of a pathological fracture of the femur associated with neoplastic disease of the bone is reported. The tougher cement has provided long‐term stability of the fracture.
New types of synthetic infusion solutions. III. Elimination and retention of poly‐[N‐(2‐hydroxypropyl)methacrylamide] in a test organism
Authors: Šprincl L. , Exner J. , Štěrba O. , Kopeček J. 
Published: December 2004

AbstractThe elimination and retention of a new, fully synthetic plasma prosthesis of Czechoslovak origin under the working name of Duxon (poly[N‐(2‐hydroxypropyl)methacrylamide]) was investigated in experiments on rabbits by using a 14C‐labeled polymer. Results published earlier on elimination have been confirmed and extended. Retention was examined after repeated application. The effect of molecular weight prevailed both in elimination and in retention. Polymers of lower molecular weights, which possess a good therapeutical effect, are not permanently deposited in the organism.
Role of protein and fatty acid adsorption on platelet adhesion and aggregation at the blood–polymer interface
Authors: Kim S. W. , Wisniewski S. , Lee E. S. , Winn M. L. 
Published: December 2004

AbstractThrombus formation on a foreign surface is a complicated process, involving many factors. However, there is little doubt that a foreign surface adsorbs plasma proteins upon blood contact and that the nature of this adsorbed layer may determine the mechanism of platelet adhesion and aggregation. The adhesion and aggregation of platelets play an important role in the initial events of thrombus formation on a foreign surface. In this work, adsorption studies using human blood plasma were done on several polymer surfaces. Some drugs which prevent platelet adhesion were utilized to verify the proposed mechanism for platelet adhesion which includes glycosyl transferase reaction. Also, adsorption and release of fatty acid salts, including fatty acid‐bonded albumin, were investigated at different polymer interfaces. It is postulated that adsorbed fatty acid salts are released from the surface upon contact with plasma to form a high local concentration of fatty acid, and that this fatty acid suspension would cause platelet aggregation at the interface.
Reactions of human platelets with microspheres of poly(hydroxymethyl methacrylate) and polyacrylamide
Authors: Kronick Paul L. , Rembaum Alan 
Published: December 2004

AbstractWe have studied the contact interaction of platelets with hydrogels. In the form of microspheres, 0.6–1.0 μ, poly (glycol methacrylate) (poly HEMA) and poly (methyl methacrylate) beads cause platelets to aggregate at concentrations of about 108 beads/ml. Polyacrylamide and (20/80) poly (acrylamide–HEMA) copolymer were ineffective in aggregating platelets. The admixture of 20% methacrylate to polyHEMA rendered the beads inactive. Blood plasma components other than fibrinogen were found essential to the interaction of the beads with platelets. Near‐infrared spectra of the hydrogels polyacrylamide and polyHEMA showed the water hydrogen bonds to be the same for both and different from those in pure water. The monomer HEMA is an inhibitor of platelet aggregation and the release reaction at levels of 0.1%. It is concluded that the two hydrogels have different blood compatibilities, which depend more on the network structures than the water structures in the respective gels.
Mechanochemical studies of enzymatic degradation of insoluble collagen fibers
Authors: Huang C. , Yannas I. V. 
Published: December 2004

AbstractA mechanochemical method was developed for studying the enzymatic degradation of insoluble collagen fibers. The method involves stretching the collagen fiber to a fixed extension in the presence of a solution of collagenase and measuring the rate of relaxation of the force induced on the fiber. In this work, bacterial collagenase was used for reasons of availability. We observed invariably an exponential decrease in force with respect to time. The slope of the linear plot of logarithm of the force versus time was taken as a measure of the rate of enzymatic degradation. This rate was found (a) to vary linearly with collagenase concentration; (b) to be maximized at pH 7–8; (c) to vary with temperature according to the Arrhenius relationship in the range 10–56°C; (d) to be reduced to varying extent by addition of EDTA, o‐phenanthroline, 2,3‐dimercaptopropanol, and D, L‐cysteine; (e) to be minimal when the strain on the fiber was ca. 4%; (f) to be increased dramatically by denaturation of the collagen fiber; and (g) to be reduced by an increase in the crosslink density of the collagen fiber. Except for the effect of strain, which can not be conveniently sudied by existing methods, these results are consistent with those observed by other methods for the study of the enzymatic degradation of collagen. The mechanochemical method is, however, uniquely suited to monitor continuously the enzymatically induced decay in the stress‐bearing ability of collagen fibers. It has also been found useful in the design of collagenous implants with specified resistance to enzymatic degradation in vivo.
Reactions of the articular capsule to wear products of artificial joint prostheses
Authors: Willert H.‐G. , Semlitsch M. 
Published: December 2004

AbstractExamination of a great number of tissue samples taken from the newly formed capsules surrounding artificial joints reveals small particles of prosthetic material. Abraded from the joint by wear and tear, these particles of plastic, metal, and acrylic cement initiate a foreign‐body reaction and result in the formation of granulation tissue, including macrophages and foreign‐body giant cells. Typical features of tissue reactions exist for each of the materials from which prostheses are made. The consequent formation of scar tissue produces a thickening of the capsule, which, in turn, may cause a reduction in the mobility of the joint.In small amounts, the foreign‐body particles are eliminated via the perivascular lymph spaces. Where this transport system is insufficient to handle the volume, however, the foreign‐body response may extend to the whole environment surrounding the joint. In such cases, there may be loosening of the cemented prosthetic parts because of deterioration of contiguous bone anchors by the tissue membrane lining the bone cement.
Immobilization of enzymes on slowly soluble carriers
Authors: Torchilin V. P. , Tischenko E. G. , Smirnov V. N. , Chazov E. I. 
Published: December 2004

AbstractThe preparation and some properties of microspheres composed of oxidized polysaccharides and some vinyl polymers are described. The microspheres contain immobilized enzyme and can be slowly solubilized in water solutions, thereby releasing active a enzyme into the surrounding medium. The kinetic characteristics of the immobilized enzyme bound with a fragment of matrix after complete solubilization are unchanged, but the enzyme exhibits high thermostability. These preparations could have a wide range of medical applications, e.g., to form a drug “depot” directly in an affected organ.