bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact resistance of highly crosslinked plastic denture teeth
Authors: Suzuki Shiro , Sakoh Mitsuo , Shiba Akihiko 
Published: December 2004

AbstractThe impact resistance of highly crosslinked plastic denture teeth materials such as SR‐Orthosit (R), Crystal‐ND (R), and Mitel‐OM (R) was investigated and compared to that of conventional denture teeth materials. Dentures with upper second molars were placed on a metal model. The thicknesses of the denture teeth were 1.4, 1.0, and 0.4 mm. An impact force was repeatedly applied to the central fossae of the denture teeth with an impact test machine. Impact resistance was defined as the number of impacts sustained by the tooth material prior to fracture. The results showed that the impact resistance of highly crosslinked plastic teeth decreased with decreasing thickness, but was comparable to that of conventional plastic teeth when the teeth were 1.4 mm thick and supported by denture base resin. It is hypothesized that the layer of PMMA denture base resin beneath the denture teeth functions as a shock absorber during impact.
Interactions of proteins in human plasma with modified polystyrene resins
Authors: Boisson‐Vidal C. , Jozefonvicz J. , Brash J. L. 
Published: December 2004

AbstractInvestigations are reported on the composition of protein layers adsorbed from plasma to various modified polystyrene resins. As well as polystyrene itself, polystyrene bearing sulfonate groups in the benzene rings, and polystyrene sulfonate in which the sulfonate groups were converted to amino acid sulfamide, were investigated. Some of these resins were shown in previous work to have anticoagulant properties. To study the adsorption of proteins from plasma, the resins were exposed to citrate anticoagulated human plasma for 3 h. Adsorbed proteins were then eluted sequentially by 1M Tris buffer and 4% SDS solution, and examined by SDS‐PAGE. The gel patterns were similar on all resins except polystyrene. From the MWs of the gel bands, the major protein component appeared to be fibrinogen. Smaller amounts of plasminogen, transferrin, albumin, and IgG were also present. In addition, Ouchterlony immunoassay of the eluates from one resin gave positive identification of complement C3, fibronectin, IgG, and IgM. Many other minor gel bands remain unidentified. A consistent finding for all resins was the presence of plasmin‐type fibrinogen degradation products though the amounts varied with resin type. It is concluded from this (and from experiments showing FDP formation when fibrinogen was adsorbed to the resins, from buffer containing a trace of plasminogen) that the functional groups in these materials promote the adsorption of plasminogen and its activation to a plasmin‐like molecule. It appears from the substantial quantities of fibrinogen adsorbed to these materials after 3 h exposure to plasma that the Vroman effect (giving transient adsorption of fibrinogen) is not operative on these materials. It is hypothesized that specific interactions occur between fibrinogen and sulfonate groups.
Effects of injecting massive amounts of bioactive ceramics in mice
Authors: Kawanabe Keiichi , Yamamuro Takao , Nakamura Takashi , Kotani Seiya 
Published: December 2004

AbstractThe effects of massive administration of bioactive ceramic powder (Bioglass (45S5), Ceravital (KGS), apatite‐wollastnite containing glass ceramics (A‐W GC), and hydroxyapatite (HA)), by intraperitoneal (IP), intramuscular (IM), or subcutaneous (SC) injection in Balb/c mice were examined in this investigation. Alumina, Silica Glass (SG), and A‐W‐A1 (containing the same amount of crystal as A‐W GC and 6.3% Alumina) were used as nonbioactive controls. The particle size of each material injected was smaller than 44 μm. In addition to the above, two more sizes (smaller than 105 μm and smaller than 255 μm) of A‐W GC powder, and a 1 × 1 × 0.2 cm plate of the A‐W GC were also evaluated. When the particle size was smaller than 44 μm, intraperitoneal injections of 5 mg per g of body weight of BG, KGS, A‐W GC, and A‐W‐A1 were lethal to the mice. Ceramics in fine powder form, which are generally believed to have higher bioactivity, are associated with higher mortality except A‐W‐A1. On the other hand, when the particle size of the ceramic was increased, the fatal effects of ceramic powders in mice decreased. Plate form of ceramics implanted I.P. had no systemic effects. Intramuscular or SC injections of bioactive ceramic powder with a particle size smaller than 44 μm had almost no systemic effects. Both the particle size of the ceramic powder and the route of administration influenced the reactivity of the bioactive ceramics in the mice. In conclusion, regardless of particle size, neither SC nor IM injection of large doses of highly bioactive ceramics had an adverse effect on the host (mouse).
Bone‐particle‐impregnated bone cement: An in vivo weight‐bearing study
Authors: Dai K. R. , Liu Y. K. , Park J. B. , Clark C. R. , Nishiyama K. , Zheng Z. K. 
Published: December 2004

AbstractTo evaluate an experimental inorganicbone‐particle‐impregnated bone cement, canine hip prostheses were implanted in dogs using a regular bone cement on one side and the experimental bone cement on the other. In a preliminary feasibility study, bone ingrowth into the resorbed bone‐particle spaces was established 3 months after implantation in three dogs. In a more detailed study, twenty‐eight (28) dogs were divided in four groups to delineate the effects of time on the phenomena of bony ingrowth. One month after implantation, active bone ingrowth into the bone cement was obvious. By 3 months postimplantation, the ingrowth appeared to have traversed the thickness of the bone‐particle‐impregnated cement. By the fifth month, most of the interconnected inorganic bone particles were replaced by new bone. At the end of a year, the ingrown bone was mature and negligible new bone activity was present. Biomechanical pushout tests closely corroborated the histologic observations. The maximum shear strength of the cement/bone interface of the experimental side reached 3.6 times that of the control side at 5 months postimplantation. No further improvements were seen at 12 months postimplantation. A viable bone/cement interface may result in a better orthopedic implant fixation system by combining the advantages of both cement for immediate rigidity and biological ingrowth for longterm stability.
The use of polylactic acid matrix and periosteal grafts for the reconstruction of rabbit knee articular defects
Authors: von Schroeder Herbert P. , Kwan Michael , Amiel David , Coutts Richard D. 
Published: December 2004

AbstractIn order to find a material that would improve cartilage repair, we investigated the use of porous polylactic acid matrix (PLA) with and without periosteal grafts in large articular defects in the medial femoral condyles of 18 New Zealand white rabbit knees. The right knee defect was filled with PLA, the left defect was filled with PLA and a periosteal graft. All animals were killed at 12 weeks. PLA allowed for the de novo growth of neocartilage at the articular surface in all specimens and appeared to serve as a scaffolding for cell migration and matrix formation. Histologically, small amounts of PLA remained under the neocartilage with the majority being replaced by bone. PLA was a suitable carrier for periosteal grafts with a high graft survival rate (89%) and proliferation of a neocartilage which was thicker and more closely resembled articular cartilage than PLA alone knees. Biochemically, there was more type II collagen in the grafted knees (83%) than in the PLA alone knees (65%). Biomechanical tests of the neocartilage included equilibrium displacement, aggregate modulus, and apparent permeability. These tests were not statistically different between PLA alone and grafted knees. Comparison to normal cartilage indicated that the neocartilage was less stiff but had similar permeability. A consistent repair of the articular defects was achieved with and without periosteal grafts resulting in a tissue that closely resembled hyaline articular cartilage.
Effect of soft segment chemistry on the biostability of segmented polyurethanes. I. In vitro oxidation
Authors: Takahara Atsushi , Coury Arthur J. , Hergenrother Robert W. , Cooper Stuart L. 
Published: December 2004

AbstractA series of segmented polyurethanes (SPUs) containing various polyol soft segments was prepared and their resistance to oxidative degradation was investigated after aging in AgNO3 solution. The SPU with the polyether soft segment showed a large reduction in mechanical strength after exposure to the oxidative environment. Surface cracking was often observed for these specimens. XPS measurements revealed that scission of the ether linkage occurs upon oxidation. The oxidative resistance of SPUs containing aliphatic hydrocarbon soft segments was significantly improved over the poly(tetramethylene oxide) (PTMO) based polyurethane.
Interaction of plasma proteins with heparinized gel particles studied by high‐resolution two‐dimensional gel electrophoresis
Authors: Ho C‐H. , Hlady V. , Nyquist G. , Andrade J. D. , Caldwell K. D. 
Published: December 2004

AbstractIn order to further the understanding of protein‐surface interactions in the coagulation system, we have chosen to study plasma protein adsorption onto heparin immobilized surfaces. Heparin‐binding proteins are abundant in plasma: a search of amino acid sequences revealed that many plasma proteins have possible heparin binding sites. Plasma protein adsorption to the heparinized surfaces is monitored by a novel technique in which the solution depletion of proteins is analytically determined using quantitative two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE). This method enables simultaneous, quantitative detection of the majority of plasma proteins before, during, and after their adsorption onto high surface area adsorbents. Using computerized densitometry of silverstained 2‐D PAGE gels, the amount of each protein can be determined from the integrated optical density of each protein “spot.” Kinetics of adsorption and adsorption isotherms of four important heparin binding proteins, antithrombin III (ATIII), complement factor C3 (C3), apolipoprotein AI (Apo‐AI) and apolipoprotein AIV (Apo‐AIV) are reported in this paper. From the adsorption isotherms, the apparent binding constants of each protein‐immobilized heparin complex, Ka, were calculated. The surface binding constants were of the same order of magnitude as the respective solution binding constants in the literature. The surface binding constants followed the same order as the respective solution binding constants: Ka (ATIII) > Ka (Apo‐AIV) > Ka (C3) > Ka (Apo‐AI), indicating that protein binding to the immobilized heparin used is not essentially different from solution binding.
Dental implant design–effect on bone remodeling
Authors: Pilliar R. M. , Deporter D. A. , Watson P. A. , Valiquette N. 
Published: December 2004

AbstractBone remodeling around three different endossesous dental implant designs placed in dog mandibles was studied using radiography during lengthy periods of function and by histology after animal sacrifice. The three designs investigated were (a) threaded (c.p. titanium), (b) fully porous‐coated (titanium alloy), and (c) partially porous‐coated (titanium alloy). The implants were kept in function for either 32 weeks (fully porous‐coated) or 73 to 77 weeks (partially porous‐coated and threaded). The studies indicated that some crestal bone loss occurred for both the threaded and partially porous‐coated implants while no significant bone loss was seen with fully porous‐coated implants in the absence of plaque‐associated infection. It is suggested that these observed differences are a result of the different stress states that develop in bone surrounding the three designs underlying the importance of implant design on bone remodeling.
Human vascular graft failure and frequency of infection
Authors: Vinard E. , Eloy R. , Descotes J. , Brudon J. R. , Guidicelli H. , Patra P. , Streichenberger R. , David M. 
Published: December 2004

AbstractAmong 212 vascular prostheses collected in a cascular explant retrival programe, 50 exhibited one or more criteria of graft infection i.e., (a) clinical evidence of graft infection, (b) positive bacteriological analyses of the graft, and (c) presence at the blood‐prosthetic interface of characterized microorganisms. Whereas each of these criteria was noted respectively in 25, 26, and 20 cases, there was no complete overlapping among the three criteria, but their combination led us to consider 50 cases of infected vascular grafts among the 212 collected. These results, and the occurrence in two cases among six investigations for viral infection, suggest that extensive bacteriological investigations of cascular explanted should be inculded in an implant retrieval program, and that infection may represent a high risk in graft failure.
Immunomodulating effects of serum‐material interactions
Authors: Omokawa Susumu , Malchesky Paul S. , Goldcamp James B. , Savon Susan R. , Nosé Yukihiko 
Published: December 2004

AbstractThe objective of this study is to evaluate an in vitro model to assess the effects of serum‐material interactions on complement activation, macromolecular adsorption, and lymphocyte response. Minifilters of clinically available materials (PVA, EVAL‐4A, and EVAL‐D) used in extracorporeal therapies were evaluated. The test circuit consisted of a pump, sterile tubing, collection vessels, and the minifilter. A sham circuit similar to the test circuit was constructed, but without the filter. Serum flow rates and volumes processed were scaled down to those of clinical use. Post PVA serum showed the highest degree of complement activation, macromolecular solute adsorption, and lymphocyte suppressive response when incubated with Con‐A, PHA, PWM, and Candida. Post EVAL‐4A sera enhanced the response of lymphocytes to Con‐A and PHA, while Post EVAL‐D sera showed a slight suppression to these mitogens. Blood‐material interactions have been shown to cause blood cellular changes. The in vitro model employed is simple to apply and does not require an animal or patient. The membrane modules used are a mini‐type of clinically available extracorporeal filters, and there is a greater direct relevancy to clinical applications than there would be using specially formulated materials. This system would provide useful preclinical information in evaluating the effects of serum‐material interactions.
In vitro tendon cell growth rates on a synthetic fiber scaffold material and on standard culture plates
Authors: Ricci J. L. , Gona A. G. , Alexander H. 
Published: December 2004

AbstractGrowth rates of rat tendon fibroblasts cultured in a three‐dimensional carbon fiber matrix were compared with those of cells cultured on standard flat culture plates. The carbon fiber has been used as a tissue scaffold for tendon and ligament repair in animal and clinical studies. While cell growth on the culture plates appears to follow a growth curve containing a lag phase, a log phase, and plateau phase of growth, cell growth in the fiber matrix was characterized by a suppressed log phase of growth. SEM and cytotoxicity studies indicated that this effect was not caused by growth‐inhibiting or cytotoxic substances from the carbon fiber. While we cannot rule out the possibility that cell growth was influenced by the surface chemistry of the carbon substrate, evidence from this and other studies suggests that the observed effect was caused by a lack of readily available surface area for cell attachment and growth on the small fibers. Because cell colonies growing on individual fibers are limited (at least in theory) to growing in two directions only, they enjoy limited opportunities for cell migration and growth– in contrast with cell colonies on flat culture plates. These results suggest fundamental differences in the mechanisms controlling cell growth on planar vs. three‐dimensional fiber substrates.
A physicochemical study of the morphology of progesterone‐loaded microspheres fabricated from poly(D,L‐lactide‐co‐glycolide)
Authors: Rosilio V. , Benoit J. P. , Deyme M. , Thies C. , Madelmont G. 
Published: December 2004

AbstractProgesterone‐loaded microspheres are fabricated by a solvent evaporation process from a poly(D,L‐lactide‐co‐glycolide) (85/15 PLG) and from α‐progesterone. Methylene chloride is used as solvent and polyvinyl alcohol and methylcellulose are used as surfactants. The microspheres are characterized by scanning electron microscopy, differential scanning calorimetry, and x‐ray powder diagrams. Our study shows that the morphology and the thermal behavior of PLG microspheres can vary significantly with progesterone loading and sample thermal history. Below and at 16.5% loading the microspheres exhibit a smooth outer surface. Above 23% loading, the surface becomes rough, embedded by copolymer particles or well‐defined crystals. Pores and cracks can also be observed. Below 35% the progesterone is molecularly dispersed. At 35% and above crystal doMayns of the steroid appear and two crystalline forms are found: α‐ and β‐progesterone. The physical state of progesterone and the nature of its crystal doMayns dispersed in the PLG matrix can change during storage. Also a progressive development of an endothermic peak at the Tg event of the copolymer is observed during storage. No well defined relationship of peak size to progesterone loading can be shown.
Hylan gel composition for percutaneous embolization
Authors: Larsen Nancy E. , Leshchiner Edward A. , Parent Edward G. , Hendrikson‐Aho Julie , Balazs Endre A. , Hilal Sadek K. 
Published: December 2004

AbstractViscoelastic, pseudoplastic, radiopaque injectable hylan gel for percutaneous embolization was developed and evaluated by in vitro and in vivo tests. The embolization gel is composed of cross‐linked hylan (hyaluronan, hyaluronate), tantalum, microcrystalline cellulose, hexamethonium chloride, and thrombin. Upon delivery through small‐lumen catheters to the appropriate vascular site, the gel induces formation of a solid blood/gel coagulum. Results from animal studies (rat aorta, rabbit auricular artery) demonstrate that formation of complete and long‐lasting arterial blockage is readily achievable without complications due to blood flow, partial vessel obstruction, uncontrolled polymerization, or movement of the gel or its components (specifically thrombin and hexamethonium chloride) into the circulation. Microscopic evaluation indicates that arterial occlusion initially occurs as a result of the injected gel and formed fibrin; at 7 weeks and beyond, arteries are occluded by injected gel, inflammatory cells and fibrosis (scar tissue).
Osteoblast responses to orthopedic implant materials in vitro
Authors: Puleo David A. , Holleran Lisa A. , Doremus Robert H. , Bizios Rena 
Published: December 2004

AbstractResponses of neonatal rat calvarial osteoblasts to a variety of orthopedic implant materials were examined in vitro. Attachment, proliferation, and collagen synthesis of a well‐characterized line of osteoblasts with 316L stainless steel, Ti‐6Al‐4V, CoCR‐Mo, PMMA, hydroxyapatite, borosilicate glass, and tissue culture polystyrene were studied. Cell adhesion and growth were similar on nonapatitic materials. In contrast, attachment and growth of osteoblasts were significantly lower and slower, respectively, on hydroxyapatite. Collagen synthesis per cell and relative collagen synthesis, however, were comparable on all the materials tested.
Fibroblast and hepatocyte behavior on synthetic polymer surfaces
Authors: Saltzman W. Mark , Parsons‐Wingerter Patricia , Leong Kam W. , Lin Shin 
Published: December 2004

AbstractBiodegradable poly(phosphoesters) with varying side group chemistry and copolymers of styrene and methyl vinyl ketone (MVK) with varying degrees of hydrophobicity were used to study the growth and behavior of surface‐attached fibroblasts and hepatocytes. Mouse 3T3 fibroblasts and chicken embryo fibroblasts attached and proliferated on all of the polymers tested. Fewer cells attached to copolymers of styrene and MVK than to glass or tissue culture polystyrene controls; cell attachment to several poly(phosphoester) surfaces was indistinguishable from controls. The mean speed of fibroblast migration was faster on surfaces where fewer cells attached (59 to 84 μm/h on low attachment surfaces compared with 40 to 46 μm/h on high attachment surfaces). When surface‐attached cells were stained with fluorescently labeled phalloidin, only a fraction of the cells on low attachment surfaces were shown to have prominent arrays of actin filament bundles. Chicken hepatocytes also attached to the polymer surfaces. When a suspension containing a large number of cells was placed over the polymer surfaces, approximately 50% of the hepatocytes attached during the first 9 h. Surprisingly, hepatocyte attachment and viability in culture were relatively insensitive to the chemistry of the synthetic polymer substrates. Cell number increased by about a factor of 2 over the first 48 h of culture, then decreased back to ∼50% of initial cell number over the next several days. Cell morphology did depend on the chemical structure of the substrates.
Biological responses to polyethylene oxide modified polyethylene terephthalate surfaces
Authors: Desai Neil P. , Hubbell Jeffrey A. 
Published: December 2004

AbstractPolyethylene oxide (PEO) of molecular weights 5,000, 10,000, 18,500, and 100,000 g/mol was covalently grafted to surfaces of otherwise cell adhesive polyethylene terephthalate (PET) films. Analysis of these surfaces by measurement of contact angles and ESCA verified the presence of the grafted PEO. Protein adsorption assays of radiolabeled albumin and fibrinogen showed a marked reduction in adsorbed protein for the 18,500 and 100,000 molecular weight PEO coupled surfaces. Cell growth assays using human foreskin fibroblasts in culture showed that the higher‐molecular‐weight PEO surfaces supported cell growth to a much lower extent than the two lower‐molecular‐weight PEOs. Flow of whole blood over these surfaces and visualization of platelet adherence using epifluorescence videomicroscopy showed very low platelet adherence only on the two higher‐molecular‐weight PEO coupled surfaces. Scanning electron microscopy corroborated these results. It was concluded that PEO of molecular weights neighboring 18,500 and higher was effective in reducing protein adsorption and cellular interactions on these surfaces.
TEM immunogold staining of C3 from plasma onto titanium oxides
Authors: McAlarney M. E. , Skalak R. , Kim S. , Neugroschl D. , Machlin E. S. 
Published: December 2004

AbstractImmunogold staining in conjunction with TEM was used to observe C3 adsorption from plasma in relation to the underlying titanium structure of thermal, anodic, and electropolished oxides. Heat treatments and oxide thickness were found to have no significant effect on the adsorption behavior of C3, while surface oxide type possibly has. Surface concentration of C3 was found to be time‐ and plasma concentration‐dependent. Evidence is given for the possible involvement of C3 in protein exchange, i.e., the Vroman effect. Diluted plasma resulted in a random distribution of gold colloids, whereas clustering occurred with undiluted plasma. Although C3 concentrations present on grain boundaries followed the same trend as that found on the surface, C3 was found to have a higher grain boundary than bulk concentration for 0.1% plasma.