bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brain biocompatibility of a biodegradable, controlled‐release polymer in rats
Authors: Tamargo Rafael J. , Epstein Jonathan I. , Reinhard Carla S. , Chasin Mark , Brem Henry 
Published: December 2004

AbstractWe report the biocompatibility in the rat brain of a controlled‐release, biodegradable polymer, the polyanhydride poly‐[bis(p‐carboxyphenoxy)propane‐sebacic acid] copolymer (PCPP‐SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood—brain barrier and avoiding the consequences of having to administer toxic doses systemically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP‐SA was compared to that seen with other standard neurosurgical implants. Fifty‐six adult Sprague‐Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP‐SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP‐SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP‐SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard neurosurgical implants.
The interaction of cultured cells with membranes composed of random and block copolypeptides
Authors: Minoura Norihiko , Aiba Sei‐ichi , Fujiwara Yukihiko , Koshizaki Naoto , Imai Yohji 
Published: December 2004

AbstractRandom copolypeptides and block copolypeptides were synthesized, and an interaction between these polypeptide membranes and the cells was studied by a cell culture method (cell line, Ca. 9.22). In random copolypeptides composed of γ‐methyl L‐glutamate and γ‐benzyl L‐glutamate, cell attachment and cell growth depended on the monomer composition, and showed a maximum at around 70 mole % of benzyl glutamate. Block copolypeptide composed of L‐methionine and oxyethylene exhibited low cell attachment and cell growth even at 10 mole % of oxyethylene content, compared to L‐methionine homopolymer. ESCA study of the membrane suggested this result to be due to concentration of the poly(oxyethylene) block chain of the polymer on the surface of the membrane. Block copolypeptide composed of N5‐(3‐hydroxypropyl) L‐glutamine and L‐leucine exhibited low cell attachment and cell growth, while the corresponding random copolypeptide exhibited high cell attachment and cell growth. This difference is attributable to the microheterophase structure with the hydrophilic domains embedded in the hydrophobic matrix in the block copolypeptide membrane.
Enhanced patency of small‐diameter tubings after surface immobilization of heparin fragments. A study in the dog
Authors: Arnander Claes 
Published: December 2004

AbstractThe luminal surfaces of polyethylene and polyurethane tubings of 1 mm inner diameter and 1 m in length were coated with heparin by end point attachment and thereafter sterilized in ethylene oxide. The tubings were inserted as arterio‐venous shunts from the aorta to the superior caval vein via a carotid artery and a jugular vein. Patency was assessed with an ultrasound doppler flow meter and flow measurements. All nonheparinized shunts occluded within 10 days with a mean elapsed time from the insertion of the tubing is the last positive doppler registration being 3.5 days. The corresponding patency time for heparinized shunts was 25.9 days. The occlusion of the heparinized tubings was due to the incorporation of the ends of the tubings in the walls of aorta and caval vein, whereas the nonheparinized tubings occluded as a result of clot formation. It is concluded that surface immobilization of heparin with sequences capable of activating antithrombin may be beneficial in the development of small‐diameter vascular protheses.
The spatial resolution of protein adsorption on surfaces of heterogeneous metallic biomaterials
Authors: Williams R. L. , Williams D. F. 
Published: December 2004

AbstractThis study was designed to examine the heterogeneity of the adsorption of proteins onto metallic materials. The materials studied included pure Ag, Au, and Ti and sintered Ag 10% Ti and Ag 10% Ta. The distribution of the protein adsorption was studied using I‐125 labeled albumin detected by microautoradiography. The surface morphology of the specimens was examined in the scanning electron microscope prior to exposure to the protein solution. A heterogeneous distribution in albumin adsorption was observed over the Ag surface. Similar regions were observed over parts of the mixed metal specimens, but superimposed on this pattern were distinct regions of very low protein adsorption which appeared to correlate closely with the regions of Ti or Ta observed in the scanning electron microscope. A uniform distribution of adsorbed albumin was observed on the Au and Ti, with Au giving a much denser microautoradiograph than Ti. This work demonstrates that variations in the protein adsorption to heterogeneous materials can be observed on a microscopic scale.
Influence of antibiotic impregnation on the fatigue life of simplex P and palacos R acrylic bone cements, with and without centrifugation
Authors: Davies Jeffrey P. , O'Connor Daniel O. , Burke Dennis W. , Harris William H. 
Published: December 2004

AbstractThe fatigue properties of Simplex P and Palacos R bone cements were compared to their antibiotic impregnated counterparts AKZSupported in part by EM Laboratories, 5 Skyline Drive, Hawthorne, NY 10532; and The William H. Harris Foundation.
and Palacos R with gentamycinAKZ bone cement is the trade name used by Howmedica Inc. of Rutherford, NJ to describe Simplex P mixed with 0.5 g of erythromycin and 0.24 g of colistin methane sulphonate Both the Simplex P and AKZ cements were obtained from Howmedica. Palacos R and Palacos R with gentamycin (0.5 g/40 g.) were supplied by E. Merck Laboratories.
The effect of porosity reduction by centrifugation of all four cement types was also assessed. Fifteen specimens of each cement type were prepared according to manufacturer's instructions and 15 additional specimens of each cement type were prepared by mixing the powder with chilled monomer (0°C) and then centrifuging the cement immediately after mixing. Fifteen fully reversed tension‐compression fatigue tests were performed at 15 MPa in stress control for each cement preparation in vitro while simulating the in vivo state (37°C and 100% humidity). The number of cycles to failure were recorded. There was no significant difference in the fatigue life of Palacos R and Simplex P when both cements were prepared in the standard fashion. The addition of 1/2 g of gentamycin to Palacos R did not significantly alter its fatigue properties. The addition of 0.5 g of erythromycin and 0.24 g of colistin did not decrease the fatigue life of Simplex P. Centrifugation significantly improved the fatigue properties of Simplex P and AKZ. The fatigue lives of Palacos R and Palacos R with gentamycin were not improved by centrifugation. The fatigue life of centrifuged Simplex P was significantly greater than the fatigue life of Palacos R and of Palacos R with gentamycin, whether the Palacos R based cements were centrifuged or not.
In vitro platelet interactions with a heparin–polyvinyl alcohol hydrogel
Authors: Cholakis Cynthia H. , Sefton Michael V. 
Published: December 2004

AbstractNo difference in in vitro platelet reactivity was found between an immobilized heparin containing hydrogel (heparin–PVA) and the hydrogel without heparin (PVA), in a variety of experimental assays. There was no significant difference between the heparin–PVA and PVA coated polyethylene tubing in the number of 51Cr‐labeled platelets, the extent of 14C serotonin release by the adherent platelets or in the degree of platelet count decrease after 1 h exposure to citrated canine whole blood in a Chandler loop system. Furthermore, adhesion and release values were lower than those observed with the uncoated polyethylene tubing (e.g., 9.3 ± 4.3 plt/103 μ2 on PVA; 18.3 ± 4.6 plt/103 μ2 on polyethylene). There was also no significant difference between heparin–PVA and PVA in bead column retention values with canine blood and with the previously reported washed human platelet adhesion/release values. Thus there appears to be no effect of the immobilized heparin by itself on the in vitro interactions of PVA with platelets, with the reactivity towards platelets dominated by that of the underlying substrate (i.e., PVA).
The bovine pericardial xenograft: III. Effect of uniaxial and sequential biaxial stress during fixation on the tensile viscoelastic properties of bovine pericardium
Authors: Lee J. Michael , Ku Michael , Haberer Sean A. 
Published: December 2004

AbstractOur previous two articles have shown that glutaraldehyde‐fixed bovine pericardium is nearly isotropic, whether fixed without constraints, with tethering, or with pressure. In this study, we have used uniaxial stress during fixation to produce bovine pericardial material with marked tensile anisotropy. Rectangular and cruciate pericardial samples have been mechanically examined after one of four treatments: (i) fixation under 88‐kPa uniaxial stress, (ii) fixation under 176‐kPa uniaxial stress, (iii) 3 h of 176‐kPa uniaxial stress in saline followed by 24‐h fixation under the same stress, (iv) fixation under 176‐kPa uniaxial stress followed by a second fixation under 176‐kPa stress in a direction normal to the first. Strips of material were cut at 0°, 30°, 60°, and 90° to direction of the initial stress, and tested for response to cyclic loading, stress relaxation, plastic deformation, and fracture properties. Fixation under uniaxial stress produced anistropy similar to that seen in porcine aortic valve leaflets; however, the overall extensibility of the material depended on the applied stress and the aspect ratio of the stressed sample. While loading in saline produced no change, the sequential biaxial stressing produced a reduction in anisotropy, suggesting exposure of additional crosslinking sites. Uniaxial stress during fixation may be a useful method for construction of anisotropic heart valve leaflets.
Plasma protein adsorbed biomedical polymers: Activation of human monocytes and induction of interleukin 1
Authors: Bonfield Tracey L. , Colton Erica , Anderson James M. 
Published: December 2004

AbstractThese studies involved the evaluation of human monocyte/macrophage activation by biomedical polymers coated with human blood proteins. The biomedical polymers were polyethylene, polydimethylsiloxane, woven Dacron fabric, expanded polytetrafluoroethylene, Biomer®, and tissue culture treated polystyrene as the control. They were adsorbed with human blood proteins: albumin, fibrinogen, fibronectin, hemoglobin, and gamma globulin. The protein adsorbed polymers were evaluated for their potential to activate the monocyte/macrophage cellular population in vitro as assessed by the induction of the monocyte/macrophage inflammatory mediator, Interleukin 1 (Il1). Suppression of IL1 was observed when protein adsorbed polymers were compared to the appropriate protein adsorbed control. Protein adsorbed polymers, when compared to polymers without protein adsorption, stimulated IL1 production. The data presented in this manuscript show the level of induction and secretion of IL1 was dependent on the biomedical polymer and the protein adsorbed, as well as the requirement of lipopolysaccharide. These results show differential interactions occur between the proteins, monocytes/macrophages, and biomedical polymers which alter activation and induction of IL1.
IR spectral changes of bovine serum albumin upon surface adsorption
Authors: Lenk Thomas J. , Ratner Buddy D. , Gendreau R. Michael , Chittur Krishnan K. 
Published: December 2004

AbstractThe adsorption of bovine serum albumin from flowing solutions onto germanium and three polyetherurethanes varying in soft segment content was studied by a Fourier transform infrared/attenuated total reflectance technique. Spectral differences observed in the amide I, II, and III regions upon adsorption to all four surfaces were consistent with a loss of helix and gain of β‐structure. There appeared to be a slight difference between BSA adsorbed to germanium and the PEUs, but no distinction could be made between BSA adsorbed to the different PEUs.
The effect of local controlled release of sodium fluoride on the stimulation of bone growth
Authors: Tencer A. F. , Allen B. L. , Woodard P. L. , Self J. , L'Heureux A. , Calhoun J. H. , Brown K. L. 
Published: December 2004

AbstractThis study was performed to test the feasibility of using a biodegradable delivery system for the local controlled release of sodium fluoride as a mechanism for the stimulation of local bone growth. Sodium fluoride grains were mixed with poly‐DL‐lactic acid (PLA), and the mixture was then dissolved in acetone. After driving off the solvent, sheets of this material were rolled into rods 3.2 mm in diameter and 28.6 mm long. These were inserted into the intramedullary canals of the right femora of adult New Zealand White rabbits. A sham implant, made the same way but containing no fluoride, was inserted into the contralateral left leg. The effects of three different concentrations of sodium fluoride, 0.125 g NaF/g PLA, 0.250 g NaF/g PLA, and 0.500 g NaF/g PLA, were determined after a 4‐week implantation period. In a second set of experiments, the concentration was fixed at 0.500 g NaF/g PLA with implantation durations of 4, 8, and 16 weeks. Expressed in terms of property ratios (experimental/control), bending strengths of the femora were significantly raised in most groups with the notable exception of Group 3 (0.500 g NaF/g PLA, 4 weeks). Cross‐sectional area ratios in the distal femora were increased in all groups compared to right/left values for a normal unoperated group (p < 0.05), with the highest ratio being 1.50 (SD = 0.44) for Group 4 (0.500 g NaF/g PLA, 8 weeks). Only Group 4 animals showed significant (p < 0.05) increases in midshaft area ratio and none had responses proximally. Growth rates, measured by sequential fluorochrome labeling of bone followed the area ratio data and were only significant for the distal femora.
Human erythrocyte adhesion and spreading on protein‐coated polymer surfaces
Authors: Steinberg J. , Neumann A. W. , Absolom D. R. , Zingg W. 
Published: December 2004

AbstractProtein adsorption is the first event which occurs when polymer surfaces are exposed to blood. The adsorption of proteins modifies the surface properties of the substrates and therefore influences subsequent cell—surface interactions. In an attempt to elucidate the fundamental mechanisms governing cell—proteinated‐surface interactions, the extent of fresh human erythrocyte adhesion and spreading on protein‐coated surfaces was examined. Five human serum proteins (albumin, fibrinogen, immunoglobulin G, fibronectin, and transferrin) were used at bulk concentrations ranging from 0.01 mg/mL to 50 mg/mL. Polymer substrates covering a wide range of wettability were employed. Protein adsorption significantly reduces erythrocyte adhesion and spreading on all test surfaces with minimum adhesion observed on fibrinogen: IgG > albumin > fibronectin > transferrin > fibrinogen. The extent of these effects is dependent on the nature of the adsorbed protein, the protein bulk concentration, and the surface properties of the underlying polymer substrates.
Cytotoxicity of alkyl‐2‐cyanoacrylate adhesives
Authors: Papatheofanis Frank J. 
Published: December 2004

AbstractThe cytotoxicity of methyl‐ and isobutyl‐2‐cyanoacrylate adhesives was determined using a rat polymorphonuclear leukocyte suspension. Cell degranulation increased and migration decreased on addition of the alkyl‐2‐cyanoacrylates to the suspension in a concentration‐dependent manner. When. acetylsalicylic acid or indomethacin, inhibitors of prostaglandin H Synthase, were present, the cytotoxicity observed on addition of the adhesives to the leukocytes decreased up to eightfold in a dose‐dependent manner as detected by trypan blue exclusion. Likewise, glutathione peroxidase and superoxide dismutase lowered such cytotoxicity resulting from the cyanoacrylates up to eight‐ and sevenfold, respectively. The data suggested that the adhesives may have generated prostaglandin and thromboxane biosynthesis, and participated in membranal oxidation and lysis. Such a mechanism may contribute to under standing the thrombotic events associated with the necrosis observed on application of these adhesives to tissues in vivo.
Bioceramics and the origin of life
Authors: Hench Larry L. 
Published: December 2004

AbstractCreation of life involves establishing an organism that is capable of self‐maintenance, self‐reproduction, and adjustment to a changing environment. A Bioactive Substrate Theory of the origin of life is proposed, where the function of the bioactive substrates was to achieve the irreversible ordering of macromolecules into replicative structures. The ordering was a result of six precytic ordering factors which provide the mechanisms for simultaneous formation of primitive codonic‐bases, anabolic processes and energy‐producing, catabolic processes on bioactive inorganic glassy crystalline assemblages. Time dependent changes in the isoelectric point of the inorganic assemblages enabled the anabolic and catabolic processes to be isolated within the same bilipid membrane. The enormous diversity of inorganic glass‐crystal assemblages associated with volcanic activity resulted in many alternative evolutionary pathways for the precytic structures, eventually producing the major genetic pathways for life observed today. The evidence for bioactive ordering factors is examined including selective adsorption of optically active amino acids on optically active mineral substrates and specific cellular responses to bioactive implant materials. The implications of this theory on the biochemical design of implants, and prevention of disease states in modern man are discussed.
Tissue reaction to intraperitoneal polymer implants: Species difference and effects of corticoid and doxorubicin
Authors: Christenson L. , Aebischer P. , McMillan P. , Galletti P. M. 
Published: December 2004

AbstractThe peritoneal cavity is a convenient site for implantation of encapsulated hormonesecreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspresed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.
Oligomers with pendant isocyanate groups as tissue adhesives: II. Adhesion to bone and other tissues
Authors: Brauer G. M. , Lee C. H. 
Published: December 2004

AbstractThe adhesive properties of a series of oligomers prepared from 2‐isocyanatoethyl methacrylates (IEM) and/or m‐iso‐propenyl‐α,α‐dimethylbenzyl isocyanate (TMI) and various acrylates or methacrylates were studied. The bond strength of bone, dentin, or soft tissue specimens joined with these oligomers respectively to bone, dental composite restorative, or denture base resin were determined by tensile adhesion or shear tests. These oligomers are more effective in forming stronger bonds to bone than are other tissue adhesives. Fracture occurs cohesively, usually within the bone. Thermocycling in water for 1 week between 5°C and 55°C did not decrease adhesion indicating that exposure to water or thermal shock produced no deterioration of the bond. Tensile adhesion of bovine or human dentin joined to composite restorative resin by means of the oligomers is similar to that of the best dental bonding agents such as Gluma (glutaraldehyde and 2‐hydroxyethyl methacrylate) or ferric oxalate + Nphenylglycine + dimethylacryloxyethyl‐pyromellitate. These oligomers also strongly bond soft tissues and calfskin and to acrylic resins and composites.
Strengthening of bone—implant interface by the use of granule coatings on alumina ceramics
Authors: Kakutani Yoshiaki , Yamamuro Takao , Nakamura Takashi , Kotoura Yoshihiko 
Published: December 2004

AbstractThree different granule coatings (a granular alumina ceramic coating, a granular hydroxyapatite coating, and a polished granular hydroxyapatite coating) applied to alumina ceramic substrate were evaluated for their strengthening effects of the bone—implant interface in rabbit tibiae. For a comparison, noncoated alumina ceramics, and dense hydroxyapatite were assessed in the same way. The granular alumina ceramic coating, creating a bioinert, porous surface, was effective due to a strong mechanical bond between the bone and implant. The interface strength was even higher than that of the dense hydroxyapatite. The granular hydroxyapatite coating, creating a bioactive, porous surface, was less effective than the granular alumina ceramic coating because of the brittleness of the hydroxyapatite granules, although it formed a direct and mechanical bond with bone tissue. The polished granular hydroxyapatite coating, creating a bioactive, smooth surface, was least effective because of the brittleness of the hydroxyapatite granules, though it presented an improved interface strength compared with that of the noncoated alumina ceramics due to a direct bond between the bone and hydroxyapatite granules.
Elimination of nickel, cobalt, and chromium following repeated injections of high dose metal salts
Authors: Merritt Katharine , Crowe Timothy D. , Brown Stanley A. 
Published: December 2004

AbstractA study was conducted to determine the ability of hamsters to eliminate in the urine, or store in the organs, large quantities of metal salts given over a period of several months. In addition, the effect of prior immunization on metal ion clearance was determined. The results indicated that nickel was rapidly eliminated in the urine and that the level in the organs was similar to that of control animals. Cobalt was eliminated more slowly than was nickel. The organ levels of cobalt were similar to those of control animals with a slight elevation in the liver of the injected animals. Chromium was eliminated in the urine very slowly, was red cell associated, and the levels were elevated in all the organs (liver, lung, spleen, kidney) compared to control. Prior immunization with metal salts increased the storage of chromium.