bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intraocular biocompatibility of hydroxyethyl methacrylate and methacrylic acid copolymer/partially hydrolyzed poly(2‐hydroxyethyl methacrylate)
Authors: Smetana K. , Šulc J. , Krčová Z. , Pitrová Š. 
Published: December 2004

AbstractA strip of partially hydrolyzed poly (2‐hydroxyethyl methacrylate) containing 65%–75% H2O was implanted into the anterior eye chamber of 11 Chinchilla rabbits. No pathological changes were found in the iris or in the ciliary body. The pathological findings in the cornea accompanying implanation of a hydrogel strip to the anterior chamber were rare and not significant. The low occurrence of the foreign body giant multinucleate cells was observed on the implant surface 6 months after the implantation. Favorable properties of this hydrogel depend probably on its high water and acidic groups content.
SEM‐EPMA observation of three types of apatite‐containing glass‐ceramics implanted in bone: The variance of a Ca‐P‐rich layer
Authors: Kitsugi Toshiaki , Nakamura Takashi , Yamamura Takao , Kokubu Tadashi , Shibuya Takehiro , Takagi Masataka 
Published: December 2004

AbstractThe progressive changes of a Ca‐P‐rich layer between bone and three types of apatite‐containing glass‐ceramics of the same chemical composition: MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF2 0.5 (in weight ratio) were examined. Plates (15 mm × 10 mm × 2 mm, mirror surface) containing apatite (35 wt%) (designated A‐GC), apatite (35 wt%) and wollastonite (40 wt%) (designated A · W‐GC), and apatite (20 wt%), wollastonite (55 wt%), and whitlockite (15 wt%) (designated A · W · CP‐GC) were prepared. They were implanted into the tibia of mature male rabbits for 5 days, 10 days, 20 days, 30 days, 60 days, 6 months, and 12 months. All three types of glass‐ceramics showed direct bonding to the bone 30 days after implantation. It was observed by SEM‐EPMA 30 days after implantation that Si and Mg content decreased, P content increased, and Ca content did not change across the reactive zone from the glass‐ceramics to bone. The level of P and Si in the A · W · CP‐GC changed five days after implantation. In A · W‐GC and A‐GC, a little change in P and Si levels was observed between 10 and 20 days after implantation. The width of reactive zone was narrowest with A‐GC, wider with A · W‐GC, and widest with A · W · CP‐GC. The dissolution of glass‐ceramics stopped 6 months after implantation. This phenomenon shows that the glass‐ceramics may be suitable for clinical use.
Morphological study of biodegradable PEO/PLA block copolymers
Authors: Younes Hani , Cohn Daniel 
Published: December 2004

AbstractA series of PEO/PLA copolymers, covering a wide range of compositions and segmental lengths, was synthesized, and their morphology was investigated by means of DSC and IR studies. For matrices comprising PEO chains with molecular weights below 3400, no soft‐segment crystallinity was detected. When long hard segments were present, essentially monophasic, semicrystalline polymers were obtained, with PLA blocks melting around 130°C. Polymers containing longer soft segments (PEO 6000) exhibited a two‐phase matrix, with both components being able to crystallize. The relative degree of crystallinity of PEO and PLA blocks was also determined. The thermal history of the sample strongly affected the morphology of the matrix, especially when both blocks were long enough to crystallize. To further explore these polymers, solvent cast films were prepared and their morphology assessed. Casting from acetone, which is an excellent solvent for PLA, resulted in hard blocks exhibiting lower degrees of crystallinity, while methanol had a similar effect on PEO soft segments.
Effect of molecular weight (Mw) ofN‐(2‐hydroxypropyl)methacrylamide copolymers on body distribution and rate of excretion after subcutaneous, intraperitoneal, and intravenous administration to rats
Authors: Seymour L. W. , Duncan R. , Strohalm J. , Kopeček J. 
Published: December 2004

AbstractA copolymer ofN‐(2‐hydroxypropyl) methacrylamide (HPMA) andN‐methacryloyltyrosinamide was prepared and fractionated using Sepharose 4B/6B (1:1) chromatography to produce eight HPMA copolymer fractions of narrow polydispersity and mean molecular weight (Mw) ranging from 12 to 778 kD. These fractions were radioiodinated and injected intravenously, subcutaneously, and intraperitoneally into rats. Their bloodstream‐concentration profiles were monitored and rates of excretion assessed. Following intravenous administration the circulating blood volume available to the copolymers was not molecular‐weight‐dependent. A molecular‐weight threshold limiting glomerular filtration was identified at approximately 45 kD, and preparations greater than this threshold were lost from the bloodstream only slowly by extravasation. Molecular weight did not influence the movement of copolymers from the peritoneal compartment to the bloodstream after intraperitoneal injection. The transfer rates observed could be accounted for by bulk phase lymphatic drainage alone, no transcapillary routes being implicated. Following subcutaneous administration the largest HPMA copolymer fraction (Mw= 778 kD, diameter approximately 30 nm) showed increased retention at the site of injection, approximately 20% of the dose remaining there after 21 days. This could result from physical restriction of movement or from internalization into local phagocytic cells. The smaller copolymer fractions moved readily into the bloodstream whence they were either lost in the urine or they gradually penetrated into other tissues and organs. Long‐term (21 days) body distribution of copolymers following both intraperitoneal and subcutaneous administration showed size‐dependent accumulation in organs of the reticuloendothelial system.
Magnetically enhanced insulin release in diabetic rats
Authors: Kost Joseph , Wolfrum Jackie , Langer Robert 
Published: December 2004

AbstractPolymer matrices containing insulin and embedded magnets were implanted subcutaneously in diabetic rats for 51 days. Passive release of insulin from the polymer resulted in a decrease in the blood glucose level. When the diabetic rats were exposed to an oscillating magnetic field, the blood glucose levels were additionally lowered by nearly 30%. No statistically significant effect in blood glucose decrease was observed in four different sets of control animals subjected to the magnetic field. Because of the very small size of the implants, they may, with additional study, provide an alternative to current modes of therapy using programmable implantable infusion pumps.
Interaction between erythrocytes and a perfluorochemical blood substitute
Authors: Tuliani Vinod V. , O'Rear Edgar A. , Fung B. M. , Sierra Barry D. 
Published: December 2004

AbstractPerfluorochemicals (PFCs) are being widely developed for use as erythrocyte substitutes to carry oxygen to tissue in acute crises. Oxypherol, a commercially available PFC preparation commonly used for animal tests, reduces erythrocyte deformability in the presence of plasma. This undesirable effect further complicates oxygen delivery by erythrocytes. Our experiments indicate that one or more plasma proteins must be present to observe Oxypherol‐induced reduction in erythrocyte deformability, but the latter is not protein specific. Neither platelet activation nor enhanced protein adsorption could account for the mechanism of altered erythrocyte flexibility. Using fluorine‐19 NMR, it was found that a small amount of Oxypherol droplets is adsorbed on the surface of the erythrocytes. The amount of adsorbed droplets increases when Oxypherol is incubated with the erythrocytes in the presence of plasma, in parallel with a decrease in erythrocyte deformability. Therefore, it seems likely that the loss of deformability of the erythrocytes is caused by the adsorption of small Oxypherol droplets on the erythrocytes.
The tensile strength of natural and chemically modified bovine pericardium
Authors: Crofts C. E. , Trowbridge E. A. 
Published: December 2004

AbstractNondestructive and destructive uniaxial load tests were performed on natural and chemically modified bovine pericardium. Five specimens were selected from the same sites in different pericardial sacs by using a template. The mean maximum extension of one particular site in both the natural and chemically modified material was significantly greater than that of the other positions at a stress level of 0.6 Nmm.−2 The maximum extensibility of the fixed tissue was significantly greater (p < 0.01) than that of the natural tissue. There was also an anatomical variation in tensile strength of the natural material which was retained after chemical modification. However, the overall tensile strength of the pericardium was not increased by this procedure. In contrast, glutaraldehyde fixation did increase the percentage strain at which fracture of this biomaterial occurred.
Quantitative analysis of early in vivo tissue response to synthetic apatite implants
Authors: Ellies L. G. , Carter J. M. , Natiella J. R. , Featherstone J. D. B. , Nelson D. G. A. 
Published: December 2004

AbstractStudies have shown synthetic calcium phosphates such as hydroxyapatite and beta tricalcium phosphate to be biocompatible in vivo. However, few studies have quantitated histological responses to the implants.The aim of this study was to develop a method for the quantitative assessment of tissue biocompatibility to ceramic materials in vivo and to use this method to compare noncarbonated and carbonated apatite implants. Synthetic sintered apatites of 0, 3, and 6% carbonate by weight were prepared and cut into implants 4 × 4 × 1 mm. These were placed 2 mm into the medial aspect of rat fermurs. Following sacrifice at 4 weeks, the femurs were fixed in formalin, demineralized in formic acid, and embedded in glycol methacrylate. Sections were cut on an ultramicrotome set at 1.5 μm and stained with toluidine blue. A point counting technique using standard stereological grids and a low‐power microscope was used to measure areas of new bone formation. The width of the connective tissue zone adjacent to muscle was measured using an image analyzer. All implants were well accepted by the host tissues judging from criteria of minimal inflammation and degree of fixation. Results showed an increase in new bone formed in the marrow cavity with increasing carbonate content. This may improve stability of the implant in the host bone, particularly during the initial healing period. A technique which should enable quantitative histological evaluation of different ceramic materials has been developed. The use of this method indicates that further studies are warranted to investigate carbonated apatite as an implant material.
Locking mechanism strength of absorbable ligating devices
Authors: Hay D. L. , von Fraunhofer J. A. , Chegini N. , Masterson B. J. 
Published: December 2004

AbstractThe locking mechanism strenghts of the absorbable Absolok and Lactomer ligating clips and the absorbable Lactomer staple have been determined following implantation in an animal model. Three sizes of each type of clip and the single size of staple were enclosed in open mesh nylon pouches and implanted subcutaneously in rabbits for periods of 4, 7, 14, 21, and 28 days before tensile testing of the lock mechanisms. No change in the lock mechanism strength was detected for the Absolok clips before 21 days. The Lactomer clips and staples, however, showed significant decrease in lock mechanism strength within 7 days of implantation, this loss increasing with longer implantation times. A proportion of all the devices were found to have dissolved to an extent that precluded testing at 21 and 28 days. The findings indicate that the lock mechanisms of absorbable ligating clips differ significantly in their short‐term (30 days) durability.
Albumin adsorption on alkyl chain derivatized polyurethanes: I. The effect of C‐18 alkylation
Authors: Pitt W. G. , Cooper S. L. 
Published: December 2004

AbstractThe initial adsorption rate of delipidized Human Serum Albumin (HSA) is increased by addition of C‐18 alkyl chains to a poly‐urethane. The presence of alkyl chains does not appear to influence the total amount of HSA adsorbed after one hour exposure to a 5.0 mg/mL HSA solution. Neither does the desorption following one hour of adsorption appear to be influenced by the presence of alkyl chains. A study of the effects of solution concentration and temperature showed that the initial adsorption rates on both polymers are proportional to the protein concentration raised to the 0.36 power, and that alkylation of the polymer increases the activation energy of the initial adsorption rate above the 14 kJ/mol observed for the underivatized polyurethane. A new technique is presented to quantify the mass of adsorbed protein using Fourier transform infrared spectroscopy and attenuated total reflection optics. This technique uses the absorbance of bulk protein as an internal calibration reference, and appears to be as accurate and perhaps more precise than radiolabeling techniques.
Immobilization of enzymes on polypropylene bead surfaces by anhydrous ammonia gaseous plasma technique
Authors: Sipehia R. , Chawla A. S. , Daka J. , Chang T. M. S. 
Published: December 2004

AbstractAnhydrous ammonia gaseous plasma technique was used for the surface modification of polypropylene beads. Amino groups were added onto the surfaces of beads by exposing them to ammonia plasma. Through these amino groups covalent immobilization of glucose oxidase and peroxidase were carried out. The total amounts of immobilized glucose oxidase and immobilized peroxdase were found to be 52 and 43 μg/cm2, respectively. To assess the stability of enzyme–polypropylene linkage, beads with covalently immobilized glucose oxidase and peroxidase were washed with phosphate buffer. It was found that after the removal of the adsorbed enzymes, the concentration of covalently immobilized enzymes tended to reach a steady state. After additional washing with buffer for 5 to 6 h, 40–55% of the immobilized enzymes were found to be in the active form.
Mineralization and calcium fixation within a porous apatitic ceramic material after implantation in the femur of rabbits
Authors: Krajewski A. , Ravaglioli A. , Mongiorgi R. , Moroni A. 
Published: December 2004

AbstractCylinders (0.8 cm long, 1.0 cm of diameter and with an axial hole), constituted, after firing, of a ceramic mixture of hydroxylapatite (HA) and β‐ricalciumphosphate (β‐TCP) in a 10:1 ratio, were implanted into mid‐diaphiseal defects of one femur of 20 rabbits and stabilized with intramedullary rods. The implantation sites were checked radiographically every month, and after 3 months (3 animals) and 6 months (17 animals) the rabbits were sacrificed and the implants with the surrounding tissue were embedded in methylmetacrylate, cut to thick sections and analyzed by scanning electron microscopy (SEM). Porosimetric and x‐rays diffraction analyses were carried out before and after implantation of the cylinders, and the state of mineralization at the bone–implant interface was determined by EDAX microprobe analysis. Bony callus formation started at 1 month at the osteotomy sites, as judged by radiography, but after 3 months a not‐mineralized zone had still been demonstrated between bone and the implants. At 6 months, 13 implants showed themselves firmly fixed in their implantations beds, while 4 implants were only incorporated at their proximal ends. In bone contact zones, an enrichment of Ca2+ was displayed by microanalytical techniques in the outer zone of the implanted samples which may be explained by an apparent additional phase transformation of HA into TCP, thanks to the change of the Ca/P ratio, that takes place in vivo.
Silicone rubber temporomandibular joint (TMJ) meniscal replacements: Postimplant histopathologic and material evaluation
Authors: Hartman Laurie C. , Bessette Russell W. , Baier Robert E. , Meyer Anne E. , Wirth John 
Published: December 2004

AbstractMedical grade silicone rubber has long been considered a suitable meniscal replacement, but there has been increasing concern about migration of this material into adjacent tissues. The objectives of this study were to determine the definitive composition of tissue‐incorporated material which is presumed by light microscopy to be silicone and to identify long term histopathologic sequelae of meniscal replacements. Adult female patients underwent meniscectomy and replacement with silicone rubber (Silastic) implants. After 12 to 18 months, recurrence of symptoms in 8% of these cases led to implant removal with excision of peri‐implant fibrous pseudo‐capsules. Excised tissues, including one preauricular lymph node and implants were submitted for light microscopy, SEM, and energy dispersive x‐ray microanalysis (EDX) for the identification of elemental composition, critical surface tension measurement, and internal reflection infrared spectroscopy. EDX revealed prominent peaks for silicon in both pseudocapsular and nodal tissues. Morphologic findings surrounding the long‐term implants included foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, hyalinization, and scarring. Particulate silicone debris induced a pathologic response in the tissues and migrated to nodes. These findings suggest that periodic evaluation be performed over the life of such implants to rule out breakdown under function. These findings should intensify the search for improvements or replacements for silicone rubber as an interpositional material in the temporomandibular joint.
Analysis of in vitro enzymatic and oxidative degradation of polyurethanes
Authors: Ratner B. D. , Gladhill K. W. , Horbett T. A. 
Published: December 2004

AbstractIn vitro biodegradation studies were performed to assess the long‐term stability of poly(ether urethane) (PEU) implants. Three PEU's and one poly(ester urethane) were treated with enzymes characteristic of those released from inflammatory cells during the foreign body reaction. In addition, the effect of hydrogen peroxide was observed to examine oxidative degradation. Polymers were prepared as thin films on glass, gold, silver, and copper substrates to test the possibility of metal‐catalyzed degradation. Molecular weights and polydispersities of the polymers were measured by gel permeation chromatography (GPC) before and after treatment. Changes in peak shape and location were also monitored. The results demonstrate that varying degrees of both enzymatic and oxidative degradation occurred.
Crystallographic structure and surface morphology of sintered carbonated apatites
Authors: Ellies L. G. , Nelson D. G. A. , Featherstone J. D. B. 
Published: December 2004

AbstractDensely sintered synthetic hydroxyapatite (HA) is used as an implant material because of its excellent tissue biocompatibility. In order to maximize the biological potential of this calcium phosphate, we have investigated the incorporation of carbonate into HA to make a material which more closely resembles the mineral found in bones and teeth. The aim of the present study was to determine the conditions under which sintered carbonated apatites of specific carbonate content could be produced. The apatites were prepared by heating compressed pellets of precipitated carbonated apatite under a carbon dioxide/steam or nitrogen/steam atmosphere between 825 and 1050°C. The products were analyzed chemically and the surfaces examined by x‐ray diffraction, infrared spectroscopy, reflected light microscopy, and scanning electron microscopy. The results showed that carbonate loss during sintering could be reliably predicted, making it possible to produce materials with specific carbonate content, and with specific physical and chemical composition.
Stability of performances of vascular prostheses retrospective study of 22 cases of human implanted prostheses
Authors: Vinard Elisabeth , Eloy Rosy , Descotes Jacques , Brudon Jean Robert , Guidicelli Henri , Magne Jean Luc , Patra Philippe , Berruet Régis , Huc Alain , Chauchard Jacques 
Published: December 2004

AbstractTwenty‐two cases of vascular graft failures (thrombosis, pseudoaneurysm, dilation, infection) were investigated by means of physicochemical, histological, and ultrastructural studies. A general decrease of mechanical resistance to stress of the prostheses was observed. Its magnitude ranged from 2 to 75% of the values of identical virgin prostheses and there was no relation with the duration of implantation. In addition to the breakage of yarn filaments (SEM), migration of fiber debris (histology) was observed in 7 cases. The structure of the polyester molecule had evolved after implantation. A decrease of crystallinity (x‐ray diffraction and differential scanning calorimetry) was noted. These observations raise the question of the established stability of vascular prostheses and emphasize the need for further investigations in human graft retrieval programs.
Corrosion behavior of nickel‐containing alloys in artificial sweat
Authors: Randin Jean‐Paul 
Published: December 2004

AbstractThe corrosion resistance of various nickel‐containing alloys was measured in artificial sweat (perspiration) using the Tafel extrapolation method. It was found that Ni, CuNi 25 (coin alloy), NiAl (colored intermetallic compounds), WC + Ni (hard metal), white gold (jewelry alloy), FN42 and Nilo Alby K (controlled expansion alloys), and NiP (electroless nickel coating) are in an active state and dissolve readily in oxygenated artificial sweat. By contrast, austenitic stainless steels, TiC + Mo2C + Ni (hard metal), NiTi (shape‐memory alloy), Hastelloy χ (superalloy), Phydur (precipitation hardening alloy), PdNi and SnNi (nickel‐containing coatings) are in a passive state but may pit under certain conditions. Cobalt, Cr, Ti, and some of their alloys were also investigated for the purpose of comparison. Cobalt and its alloys have poor corrosion resistance except for Stellite 20. Chromium and high‐chromium ferritic stainless steels have a high pitting potential but the latter are susceptible to crevice corrosion. Ti has a pitting potential >3 V. Comparison between the in vitro measurements of the corrosion rate of nickel‐based alloys and the clincial observation of the occurrence of contact dermatitis is discussed.
Permeability of a heparin–polyvinyl alcohol hydrogel to thrombin and antithrombin III
Authors: Smith Barbara A. H. , Sefton Michael V. 
Published: December 2004

AbstractThe diffusivities of thrombin and antithrombin III in a heparin–polyvinyl alcohol hydrogel were estimated and used to demonstrate that diffusion limits the effectiveness of the immobilized heparin in the interior of such hydrogels. Diffusivities were calculated from permeabilities and partition coefficients measured with films in a diffusion chamber apparatus. The diffusion coefficients were estimated to be 6 ± 4 × 10−8 cm2/s for thrombin and 4 ± 2 × 10−8 cm2/s for antithormbin III in 10% gel membranes with or without immobilized heparin. Using the diffusivity of thrombin and a Thiele‐type modulus, the effectiveness factor of a spherical heparin–PVA bead used to accelerate the inactivation of thrombin by antithrombin III was found to be 4–9% (diameter range 250–105 μm). While indicating that diffusion of thrombin limited the full utilization of the immobilized heparin, these values for the effectiveness factor could not completely account for the low apparent heparin activity (0.2%) in a thrombin time test of heparin–PVA “beads” (J. Biomed. Mater. Res., 17, 359 (1983)). Other factors such as the immobilization chemistry or the diffusion of thrombin–antithrombin III complex must be considered for a full explanation of the thrombin time results.