bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinked agarose encapsulated sorbents resistant to steam sterilization. Preparation and mechanical properties
Authors: de Koning Henk W. M. , Chamuleau Rob A. F. M. , Bantjes Adriaan 
Published: December 2004

AbstractThe application of agarose in hemoperfusion is hampered by the lack of a suitable sterilization method. A technique has been developed for the crosslinking of agarose encapsulated sorbents by the reaction with 1,3‐dichloro‐2‐propanol (DCP) under strong alkaline conditions. A twofold molar excess of DCP with respect to agarose and an equimolar amount of sodium hydroxide at a concentration of 0.3 mol/L with a reaction time of 1–4 h at 50°C are found to be the optimal conditions. The compressive strength of crosslinked beads is increased by a factor of 4. Agarose capsules are found to degrade by the influence of γ radiation, but are resistant to steam sterilization at 134°C during at least 30 min when crosslinked.
Compressive strength of implanted porous replamineform hydroxyapatite
Authors: Piecuch Joseph F. , Goldberg A. Jon , Shastry Chakrakody V. , Chrzanowski Robert B. 
Published: December 2004

AbstractPorous replamineform hydroxyapatite is a nontoxic, nonallergenic synthetic ceramic currently under investigation as an implant for restoration of atrophic edentulous ridges. Previous studies have demonstrated its capacity to permit the ingrowth of bone into its pores. Evaluation of the material was carried out to determine its eventual compressive strength following implantation. Bony penetration results in a significant increase in strength, judged to be sufficient for support of dentures.
Influence of blood flow and the effect of protamine on the thromboresistant properties of a covalently bonded heparin surface
Authors: Arnander C. , Olsson P. , Larm O. 
Published: December 2004

AbstractPolyethylene tubings, 2‐mm inner diameter and the length of 1 m, untreated or furnished with a covalently bonded heparin surface layer, were inserted as arterio‐venous shunts bilaterally in dogs. By compressing the middle part, the initial blood flow was adjusted to 10 or 40 mL/min. The thrombogenecity of the tubings was assessed by the patency of the shunts and by assaying the generation of fibrinopeptide A (FPA) in arterial blood and in blood after its passage through the shunts. In untreated shunts clotting rapidly occurred preceded by high FPA generation in blood passing through the shunts. The blood flow in heparinized shunts remained unchanged throughout the test period. At the low flow rate a certain degree of FPA generation in the shunts occurred. At the high flow rate no changes in FPA levels occurred. The function of the heparin surface is thus flow rate dependent. Systemtic heparinization and subsequent neutralization with protamine or administration of protamine alone did not interfere with the function of the heparin surface.
The effect of glass–ceramic bone implant materials on the in vitro formation of hydroxyapatite
Authors: Blumenthal N. C. , Posner A. S. , Cosma V. , Gross U. 
Published: December 2004

AbstractThe extracts of four glass‐ceramic bone implant materials were investigated for dissolved material, for effects on in vitro formation of hydroxyapatite, and for surface morphology of glass–ceramic particles in scanning electron microscopy. In vitro leaching released substances that affected in vitro formation of hydroxyapatite, i.e., initiation time and growth of crystals. Leaching also changed the surface morphology of the materials. The ability of the materials to bond to bone did not correlate with the inhibition of hydroxyapatite formation by the released substances. Surface morphology and other factors at present not yet known are probably involved in controlling the bonding to bone of these ceramics.
In situ polymerization of a microencapsulating medium round living cells
Authors: Dupuy B. , Gin H. , Baquey C. , Ducassou D. 
Published: December 2004

AbstractA new process for microencapsulating living cells is described. Pancreatic islet cells in solution in agarose were extruded from a syringe into a paraffin‐oil‐containing medium. A rigid interface around each bead was produced when the agarose gelled. A polymerizable mixture of monomers containing 30% of acrylamide and 1.5% of bisacrylamide was then added to these beads. Polymerization was initiated by a photochemical process using riboflavin as a photosensitizer, which enabled use of oxygenated solutions. As other polymerizations initiated by an oxido‐reduction reaction, this method did not require heating, and could thus be carried out at ambient temperature. The oil phase near the agarose beads effectively prevented any rise in temperature, and also led to formation of an acrylamide concentration gradient in the aqueous phase, which reduced the potential cytotoxicity of the reaction. Radioimmunoassay of insulin liberated from encapsulated islets of Langerhans demonstrated a good viability of the cells.
Enzymatic activity toward poly(L‐lactic acid) implants
Authors: Schakenraad J. M. , Hardonk M. J. , Feijen J. , Molenaar I. , Nieuwenhuis P. 
Published: December 2004

AbstractTissue reactions toward biodegradable poly(L‐lactic acid) implants were monitored by studying the activity pattern of seven enzymes as a function of time: alkaline phosphatase, acid phosphatase, α‐naphthyl acetyl esterase, β‐glucuronidase, ATP‐ase, NADH‐reductase, and lactate dehydrogenase. Cell types were identified by their specific enzyme patterns, their morphology and location. Special attention was paid to the enzyme patterns of macrophages, fibroblasts and polymorphonuclear granulocytes (PMNs), being involved in foreign body reactions or inflammatory responses. One day after implantation, an influx of neutrophilic and eosinophilic granulocytes was observed, coinciding with activity of alkaline phosphatase (PMN's) and β‐glucuronidase (eosinophils). From day 3 on, macrophages containing ATP‐ase, acid phosphatase and esterase could be observed. From day 7 on, lactate dehydrogenase, the enzyme normally involved in the conversion of lactic acid, and its coenzyme NADH‐reductase were observed in macrophages and fibroblasts. These two enzymes demonstrated more activity than expected on basis of wound‐healing reactions upon implantation of a nonbiodegradable, inert biomaterial (as, e.g., Teflon). It is concluded that the biodegradable poly (L‐lactic acid) used in these implantation studies is tissue compatible, and evokes a foreign body reaction with minor macrophage and giant cell activity, as observed during this 3‐week implantation period. Most enzyme patterns were simply due to a wound‐healing reaction. The slightly increased levels of LDH and NADH suggest the release of lactic acid from the implant, and thus confirms the biodegradable nature of this polymer.
Effect of vacuum mixing on the mechanical properties of antibiotic‐impregnated polymethylmethacrylate bone cement2
Authors: Askew Michael J. , Kufel Mark F. , Fleissner Paul R. , Gradisar Ivan A. , Salstrom Sara‐Jane , Tan James S. 
Published: December 2004

AbstractPolymethylmethacrylate bone cement, containing either no added antibiotic, 0.5 g of Vancomycin, 1.0 g of Vancomycin, or 1.0 g of Tobramycin, was mixed either in air or a vacuum chamber. Following storage in a water bath at 37°C for 48 h, the specimens were tested in four‐point bending. The porosity of the specimens was assessed radiographically, and their antibacterial activity was monitored for 21 days. The bending strength of the vacuum mixed specimens containing no antibiotic was 40% greater than that of similar air‐mixed specimens. However, there were no significant differences in the bending strength of either the air‐or vacuum‐mixed specimens when any of the antibiotic dosages were added. The bending modulus of the vacuum‐mixed specimens, containing no antibiotic, was significantly greater than the moduli of all the other specimen groups which did not differ from each other. Vacuum mixing reduced the apparent porosity of the specimens fivefold, and while the addition of antibiotic did not effect porosity of the air‐mixed specimens, that of the vacuum‐mixed specimens was doubled. Although initial rapid decreases were seen, leaching of antibiotic from the cement and antibacterial activity continued through the 21‐day monitoring period.
Biological response to chopped‐carbon‐fiber‐reinforced peek
Authors: Jockisch K. A. , Brown S. A. , Bauer T. W. , Merritt K. 
Published: December 2004

AbstractPolymer composites are being recognized as important implant materials for fracture fixation plates. The use of a composite material is dependent upon the mechanical properties of the material and its biocompatibility. The primary objective of this project was to evaluate 30% chopped‐carbon‐fiber‐reinforced poly(etherether‐ ketone) (CFRPEEK) as a potential material for use as a fracture fixation plate. A two‐ phase study was conducted. The first phase analyzed the short‐term biocom‐patibility of CFRPEEK through rabbit muscle implant testing. CFRPEEK exhibited a nonspecific foreign body tissue reaction similar to the response observed with ultra‐high‐molecular‐weight polyethylene (UHMWPE). In the second phase, four‐hole CFRPEEK plates were implanted as internal fixation devices for transverse midshaft femoral osteotomies in beagles. The plates were effective in promoting fracture healing. A nonspecific foreign body reaction was observed to the plates and to particulate debris.
Acute nephrotoxicity as an adverse effect after intraperitoneal injection of massive amounts of bioactive ceramic powders in mice and rats
Authors: Kawanabe Keiichi , Yamamuro Takao , Kotani Seiya , Nakamura Takashi 
Published: December 2004

AbstractSilicon elution from bioactive ceramic powders was measured using an in uitro solubility test, in which the powders were soaked in phosphate buffer solution. Silicon elution was highest in Bioglass (BG), followed by Ceravital (KGS), apatite‐ wollastonite‐containing glass ceramics (A‐W·GC), and hydroxyapatite (HA), respectively. Silicon elutions on this in uitro solubility test were correlated with the rates of rapid death in mice following intraperitoneal injection of each of these bioactive ceramic powders. Histopathological examination of the mice revealed nephropathy, which was considered to be the cause of death. The nephropathy was characterized by epithelial degeneration in the renal tubules and increased silicon content throughout the entire kidney, findings suggesting silicon nephropathy. It is considered that, because a large quantity of silicon eluted from the powder was absorbed from the peritoneum, concentration in the glomerular filtrate and urine increased until silicon polymerization occurred, after which the silicon polymer became deposited in the renal tubules. A single injection of furosemide prevented the acute nephrotoxicity of bioactive ceramic powder.
Platelet adherence and detachment with adsorbed fibrinogen: A flow study with a series of hydroxyethyl methacrylate‐ethyl methacrylate copolymers using video microscopy
Authors: Feuerstein Irwin A. , Glenn McClung W. , Horbett Thomas A. 
Published: December 2004

AbstractThe adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) with preadsorbed fibrinogen. Observations of the interactions of acridine‐orange‐labeled washed platelets with these surfaces from a flowing (500 s−1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). In some cases preadsorbed materials were incubated for 24 h, during which little or no loss of protein occurred. Protein surface concentration, by itself, was a poor indicator of expected cell adhesion and morphology. Surface chemistry was a second important factor which must be considered. A third observation is that for the 100% EMA copolymer, 24 h of incubation led to a large reduction in platelet adhesion when compared to the 100% EMA material without incubation. For the 0% and 100% EMA polymers, the percentage of contacting platelets which adhere and detach is greater for the 24‐h incubation cases than for those not incubated. These results led to the conclusion that our most hydrophilic surface favors adhesion with detachment, transient cell contact, over long‐term adhesion, as does incubation of adsorbed protein. A brief discussion is presented of a possible connection between this behavior and platelet consumption in viuo for hydrogels.
Investigation of an organic delivery system for demineralized bone matrix in a delayed‐healing cranial defect model
Authors: Damien Christopher J. , Parsons J. Russell , Prewett Annamarie B. , Rietveld Derk C. , Zimmerman Mark C. 
Published: December 2004

AbstractThe osteogenic potential of demineralized bone matrix (DBM) has been demonstrated in multiple animal models and clinical applications. A particulate form of DBM is generally used to fill defects because it is easily packed into a defect site without operative planning or shaping. One potential disadvantage in the use of a particulate is the migration of particles from the defect site. To stem this, glycerol was added to DBM to improve handling properties. A study was undertaken to compare two forms of DBM with glycerol, with DBM particulate and autograft in a bony defect site. The model chosen consisted of bilateral 8‐mm trephine defects created in the parietal skull of 40 rabbits. Animals were sacrificed at 2 and 8 weeks. Results demonstrated both cartilage and bone induction with the three forms of DBM, with 75–90% of the linear width of the defect filled with new bone by 2 weeks. This was similar to the autograft (86%) and significantly greater than the unfilled defects (26%) at 2 weeks. The addition of glycerol to the DBM did not affect the inductive capacity, and produced a response similar to that of DBM particulate alone or autogenous bone. © 1994 John Wiley & Sons, Inc.
Diffusive and convective solute transport through hemodialysis membranes: A hydrodynamic analysis
Authors: Langsdorf Leah J. , Zydney Andrew L. 
Published: December 2004

AbstractRecent clinical studies have shown that the overall effectiveness of hemodialysis is determined by both the convective and diffusive transport of a wide range of different molecular weight solutes. In this study, transport data were obtained for vitamin B12 and for polydisperse dextrans with a wide range of molecular weights using flat sheet Cuprophan and AN69 polyacrylonitrile membranes. The flux dependence of the actual sieving coefficient was described using classical membrane transport theory, allowing accurate measurements of both the diffusive and convective contributions to the overall solute transport through the porous structure of these dialysis membranes. Asymptotic membrane sieving coefficients and hindered diffusivities were in good agreement with a hydrodynamic model that accounts for the membrane pore size distribution through an expression for the solute partition coefficient in a random porous medium. This model provides an accurate quantitative description of both solute diffusion and convection through hemodialysis membranes, which is critical for the effective design and operation of hemodialyzers. © 1994 John Wiley & Sons, Inc.
Stabilization of pericardial tissue by dye‐mediated photooxidation
Authors: Moore Mark A. , Bohachevsky Irina K. , Cheung David T. , Boyan Barbara D. , Chen Wen‐Min , Bickers Rhonda R. , McIlroy Brian K. 
Published: December 2004

AbstractBovine pericardial tissue was stabilized through a dyemediated photooxidation reaction. Shrink temperature analysis of the stabilized tissue indicated a material with similar properties to untreated pericardial tissue and unlike identical tissue treated with glutaraldehyde. Photooxidized tissue was resistant to extraction when compared with untreated tissue or control tissue treated in the absence of light or dye. Photooxidized tissue was also resistant to enzymatic digestion by pepsin and to chemical digestion by cyanogen bromide (CNBr). In contrast, untreated or control treated tissues were readily digested by these reagents. Reduction of photooxidized tissue with β‐mercaptoethanol prior to CNBr digestion partially restored susceptibility of the tissue to CNBr digestion, indicating the photooxidation of methionine residues. Soluble collagen derived from bovine pericardium was used as a model compound for the photooxidation reaction. Polyacrylamide gel electrophoresis analysis indicated the photooxidative conversion of collagen into higher molecular weight aggregates consistent with intermolecular crosslink formation. Photooxidized tissue was stable to in vivo degradation when compared with control tissue. Results presented here indicate a crosslinked pericardial tissue produced by dye‐mediated photooxidation possessing properties of chemical stability, enzymatic stability, in vivo stability, and biomechanical integrity suitable for use as a biomaterial. © 1994 John Wiley & Sons, Inc.
Fibroblast response to microtextured silicone surfaces: Texture orientation into or out of the surface
Authors: Green Andrew M. , Jansen John A. , van der Waerden J. P. C. M. , Von Recum Andreas F. 
Published: December 2004

AbstractPrevious studies suggested that surface topographic configurations of 1–3 μm influence cellular behavior and tissue response. They did not address which specific aspect of the configurations elicits the cellular response. We therefore investigated the effect of the orientation of several surface configurations. Seven different textures on polydimethyl siloxane (silicone; Dow Corning Silastic®) specimens were used to test the question of whether orientation into (down) or out of the surface (up) affected cellular response to a material. The textures were smooth and photoetched configurations of 2 μm up, 2 μm down, 5 μm up, 5 μm down, 10 μm up, and 10 μm down. The response of cultured fibroblasts on these surfaces was compared with that of a standard tissue culture material, polyethylene terephalate (ThermanoxTM). The cell density was measured over a 12‐day period with the use of a colorimetric assay. The uptake of methylene blue was measured daily and compared as an absorbance in a destaining agent. Cells on the 2 and 5 μm up arrays showed increased rates of proliferation and cell density as compared with their down counterparts. This would indicate that textures of 2 and 5 μm have a significant influence on cell growth, and that the surface with hills has a greater effect than the surface with wells. In contrast, the 10 μm up and 10 μm down arrays did not prove to be statistically different from smooth ones. This indicates that the orientation effect is related to the configuration size and that this configuration size is not viewed differently from smooth silicone by the cells. The presented data are in agreement with results of this laboratory and others that fibroblasts recognize the dimensions of surface configurations and react accordingly. Specifically, they appear to react to the uppermost surface area presented to them, but conclusive data can only be obtained from a study of the focal adhesions. © 1994 John Wiley & Sons, Inc.
Studies in hydrogen bonding: Association in methanol using an empirical potential
Authors: Brink George , Glasser Leslie 
Published: December 2004

AbstractThe empirical potential, EPEN, has been used to establish the structures of isolated hydrogen‐bonded clusters in methanol. The most stable configuration of the dimer is found to have a trans near‐linear form, whereas the most stable forms of the trimer and tetramer are cyclic. Charge interactions in the tetramer make it the most stable, in terms of energy per hydrogen bond, of these three species. These results are in conformity with various types of experiment. Other species of dimer, trimer, and tetramer, corresponding to local energy minima, have also been identified.
Calculation of partition coefficients by the charge density method
Authors: Klopman Gilles , Iroff Linda D. 
Published: December 2004

AbstractA new method is presented for the calculation of partition coefficients of solutes in water lipid systems. Log P values are calculated based on the charge densities of the atoms as determined by quantum mechanical methods. In this article, the results have been obtained from charge densities calculated by two methods: MINDO/3 and Hückel‐type calculation based primarily on topology. Results are favorably compared with those obtained by fragment analysis.
Studies in hydrogen bonding: Association in ammonia using an empirical potential
Authors: Brink George , Glasser Leslie 
Published: December 2004

AbstractThe empirical potential EPEN/2 has been used to establish the structures of isolated hydrogen‐bonding ammonia clusters. The most stable forms of the dimer have a linear or near‐linear structure. The trimer has a closed structure with zero dipole moment. Two stable tetramer forms were found: one with a closed structure and zero dipole moment in agreement with experimental findings, and one with a pyramidal structure with nonzero dipole moment which may be an artifact of the EPEN/2 potential. The relation of the dimer structures to the limited available experimental information is discussed.
Bicyclo[1.1.0]butadiene (trialene): An experimentally viable molecule?
Authors: Andrade Juan G. , Chandrasekhar Jayaraman , Schleyer Paul Von Ragué 
Published: December 2004

AbstractMolecular orbital calculations on the C4H2 potential energy surface indicate singlet trialene (1) not only to be thermodynamically unstable, but also to have negligible barriers to interconversion to diacetylene.
Minimal basis study of inner‐shell ionization potentials for molecules containing sulfur: S,S‐Diphenyl‐N‐p‐Tolylsulfonyl‐Sulfilimine
Authors: Theodorakopoulos G. , Kucsman Á. , Kapovits I. , Náray‐Szabó G. , Csizmadia I. G. 
Published: December 2004

AbstractAb initio calculations with a minimal (STO‐3G) basis set on a number of sulfur‐containing molecules are used to show that Koopmans' theorem and minimal basis calculations may be a simple but adequate way of obtaining inner‐shell ionization potentials and chemical shifts of large molecules. The x‐ray photoelectron spectrum of (C6H5)2SNSO2C6H4CH3 is discussed with reference to an ab initio SCF minimal basis calculation on the model molecule H2SNSO2H.
Determination of electrical double‐layer parameters for the adsorption of neutral molecules at the electrode–solution interface
Authors: Batana A. , Filho R. C. Rocha , Avaca L. A. , González E. R. 
Published: December 2004

AbstractThe study of the structure of the electrode–solution interface usually involves the measurement of the differential capacity–potential characteristics of the system. In order to obtain the double‐layer parameters from these data, integration and differentiation procedures are required and, for this purpose, the use of computational methods is of great value. Two computer programs have been written for the treatment of data for the adsorption of neutral molecules on electrodes. The programs use the charge density and the electrode potential as the electrical variable, respectively, and, in both cases, the differentiation procedures have been optimized by the use of an adequate numerical function. The advantages of doing a simultaneous analysis on both electrical variables are pointed out.
Three electron bonds. I. The H2SSH radical cation
Authors: Clark Timothy 
Published: December 2004

AbstractAb initio molecular orbital calculations are reported for H2S, its radical cation, and the H2SSH radical cation. At the MP2/4‐31G level the SS three‐electron bond is 2.85 Å long, and has a dissociation energy of 31.2 kcal mole−1. The performance of MNDO semiempirical molecular orbital theory is compared with the ab initio results.