bluuebunny/crossref_metadata_2025_split huggingface dataset:
Animal study on surface‐modified defibrillator systems: Indications for enhanced infection resistance
Authors: van Wachem Pauline B. , Brouwer Linda A. , Kors Geert , Dijk Freark , Bel Klaas , Elstrodt Jan , van Wijk Frank , Cahalan Patrick T. , Hendriks Marc , van Luyn Marja J. A. 
Published: October 2004

AbstractOne of the most important problems with ICD systems is infection. The aim of this study was an in vivo evaluation of the efficacy of defibrillator systems in terms of infection resistance. The polyurethane leads were coupled with heparin and loaded with the antibiotic gentamicin, while the PGs were modified to release gentamicin. Group I was comprised of 10 pigs implanted with either a standard or a modified system for 2 weeks; group II was implanted during 4 weeks. The lead was inserted into the heart wall via the jugular vein. The other end was subcutaneously tunneled to the armpit where the PG was positioned. A cocktail of Staphylococcus aureus and epidermidis was injected at the site of the PG. Evaluation was performed macroscopically, by taking bacterial swabs during explantation and by microscopic processing. The results showed that 3 out of 5 modified defibrillator‐systems in group I and 1–2 out of 5 in group II were judged as noninfected, whereas all standard systems were infected. Infection rates of the remaining modified defibrillators showed variances, as found with the standards, from slight to moderate to high, to even high/severe in group II (1× standard and 1× modified). With the modified systems, this may be related to production of humoral factors by an intensified early tissue reaction, as indicated by a swelling at day 6 at the site of the PG. When infected, whether or not modified, usually only Staphylococcus aureus was present. Spreading of infection seemed to occur by inoculation via blood, for example, based on the observation that group II in general showed an increase in infected fibrotic overgrowth in the heart, while infectious problems were low in the jugular vein. It is concluded that the modification at short term shows enhanced infection resistance. An increased infection rate already at 4 weeks, however, indicates that the modification may not hold in the long run. Special attention is needed concerning the more intense early tissue reaction. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 384–392, 2001
New pulsatile bioreactor for fabrication of tissue‐engineered patches
Authors: Sodian Ralf , Lemke Thees , Loebe Matthias , Hoerstrup Simon P. , Potapov Evgenij V. , Hausmann Harald , Meyer Rudolf , Hetzer Roland 
Published: October 2004

AbstractTo date, one approach to tissue engineering has been to develop in vitro conditions to ultimately fabricate functional cardiovascular structures prior to final implantation. In our current experiment, we developed a new pulsatile flow system that provides biochemical and biomechanical signals to regulate autologous patch‐tissue development in vitro. The newly developed patch bioreactor is made of Plexiglas and is completely transparent (Mediport Kardiotechnik, Berlin). The bioreactor is connected to an air‐driven respirator pump, and the cell culture medium continuously circulates through a closed‐loop system. We thus developed a closed‐loop, perfused bioreactor for long‐term patch‐tissue conditioning, which combines continuous, pulsatile perfusion and mechanical stimulation by periodically stretching the tissue‐engineered patch constructs. By adjusting the stroke volume, the stroke rate, and the inspiration/expiration time of the ventilator, it allows various pulsatile flows and different levels of pressure. The whole system is a highly isolated cell culture setting, which provides a high level of sterility, gas supply, and fits into a standard humidified incubator. The bioreactor can be sterilized by ethylene oxide and assembled with a standard screwdriver. Our newly developed bioreactor provides optimal biomechanical and biodynamical stimuli for controlled tissue development and in vitro conditioning of an autologous tissue‐engineered patch.© 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 401–405, 2001
Quantitative characterization of polyethylene debris isolated from periprosthetic tissue in early failure knee implants and early and late failure Charnley hip implants
Authors: Howling Graeme I. , Barnett Petra I. , Tipper Joanne L. , Stone Martin H. , Fisher John , Ingham Eileen 
Published: October 2004

AbstractThis study isolated and characterized UHMWPE particles from 3 explant groups: early Charnley hip failures (ECE; < 10 years), late Charnley hip failures (LCE; > 10 years) and early knee failures (EKE; < 10 years). Debris isolated from the 3 groups had percentage particle number and percentage volumetric concentration distributions that were not significantly different. The greatest number of particles were found in the 0.1–0.5 μm size range and 19–20.6% of the volumetric concentration was below 1 μm in size in all groups. However, there were significant differences in the total volumetric concentration of debris isolated per g of tissue. LCE had significantly higher volumes of debris than ECE and EKE, there was no significant difference in the volume of debris from the EKE and ECE. The mean aspect ratio and mean irregularity ratio of the LCE group were also significantly higher than the ECE and EKE, suggesting that different wear mechanisms were occurring in the late Charnley group compared to the early Charnley and knee groups. These results also suggest that early knees, with normal surface wear, may have similar wear mechanisms to early Charnley hips and indicate that similar volumes of biologically active micrometer and sub‐micrometer UHMWPE particles were produced. This may have important implications in the longer‐term outcome of total knee arthroplasties, because it indicates a similar potential for osteolysis induced by wear debris. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 415–420, 2001
Air‐flow resistances of silicone rubber voice prostheses after formation of bacterial and fungal biofilms
Authors: Elving G. J. , van der Mei H. C. , Busscher H. J. , van Weissenbruch R. , Albers F. W. J. 
Published: October 2004

AbstractLaryngectomized patients use silicone rubber voice prostheses to rehabilitate their voice. However, biofilm formation limits the lifetime of voice prostheses by causing leakage or an increased air‐flow resistance and the prosthesis has to be replaced. To determine which bacterial or yeast strains, isolated from explanted voice prostheses, contribute most to increases in air‐flow resistance of silicone rubber voice prostheses, biofilms consisting of either a bacterial or a yeast strain were grown on voice prostheses in the artificial throat model. The effects of these biofilms on air‐flow resistances were determined by calculating the difference in air‐flow resistance of the individual voice prosthesis as covered with a 7‐day‐old biofilm with the situation prior to biofilm formation. Conspicuously, voice prosthetic biofilms formed by the bacterial strains Staphylococcus aureus GB 2/1 and Rothia dentocariosa GBJ 41/25B and their excreted organic matter showed larger increases in air‐flow resistance (more then 30 cm H2O.s/L) than biofilms formed by Candida species. This is contrary to the literature, where there seems to be agreement that Candida species are mainly responsible for clinical failure of silicone rubber voice prostheses. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 421–426, 2001
Physicochemical, mechanical, and biological properties of commercial membranes for GTR
Authors: Milella E. , Ramires P.A. , Brescia E. , La Sala G. , Di Paola L. , Bruno V. 
Published: October 2004

AbstractBarrier membranes for guided tissue regeneration (GTR) to treat bone defects have to satisfy criteria of biocompatibility, cell‐occlusiveness, spacemaking, tissue integration, and clinical manageability. In this study, the morphological and mechanical properties of two commercial biodegradable membranes (Resolut® LT and Biofix®) as a function of the incubation time have been compared. Moreover, their permeability to both fluids and epithelial cells as well as the bacteria adhesion have been evaluated. The membranes are asymmetric and composed of a dense polymeric layer coupled with nonwoven (Resolut® LT) or woven (Biofix®) fibers. Both of the membranes, when incubated in complete culture medium, completely lose the structural and mechanical properties within 30 days. Moreover the results of solute permeability show that Resolut® LT and Biofix® membranes cannot be considered selective membranes to the solute crossing. On the contrary, they act as a barrier to the passage of the gingivial cells and to S. mutans bacteria. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 427–435, 2001
Biodegradable poly(D,L‐lactide) coating of implants for continuous release of growth factors
Authors: Schmidmaier G. , Wildemann B. , Stemberger A. , Haas N. P. , Raschke M. 
Published: October 2004

AbstractLocal application of growth factors like insulin like growth factor‐I (IGF‐I) and transforming growth factor‐beta 1 (TGF‐β1) from a biodegradable thin layer of poly(D,L‐lactide) (PDLLA) coated implants could stimulate fracture healing. A new “cold coating technique” for metallic implants was established to produce a biodegradable coating with a high mechanical stability that provides a continuous release of incorporated growth factors. The properties of this bioactive coating were investigated in vitro and in vivo. Scanning electron microscope analysis revealed a coating thickness of in average 14.8 μm on titanium and 10.7 μm on steel wires. Intramedullary implantation and extraction experiments depicted a loss of PDLLA coating from titanium and steel implants of less than 5%. After explantation of the implants, the coating displayed a complete and regular layer without any defects of PDLLA uncovering the metallic surface. Smear tests demonstrate that the coating can be performed under sterile conditions. The PDLLA depicted a reduction of about 8% within 6 weeks in vitro and in vivo. The growth factors were incorporated in a stable form and demonstrated a loss of stability of less than 3% within 42 days and less than 5% within one year. In an elution experiment, 54% IGF‐I and 48% TGF‐β1 were released within the first 48 h. After 42 days, 76% of IGF‐I and 71% of TGF‐β1 were detected in the elution fluid by ELISA. Comparable results were obtained in the in vivo experiments after 42 days. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 449–455, 2001
Development of PMMA‐precoating metal prostheses via injection molding: Residual stresses
Authors: Zhao Wenping , Barsun Stephan , Ramani Karthik , Johnson Todd , King Richard , Lin Steve 
Published: October 2004

AbstractInjection molding polymethylmethacrylate (PMMA) was developed as a potential metal prosthesis precoating method for surgical implantation. However, residual stresses generated in the injection‐molded PMMA affect the mechanical performance of the coating polymer. This study used plane polariscope testing to demonstrate the residual stress distribution in the injection‐molded polymer. Slitting and strain gages were combined with finite element analysis to give a quantitative measure of the residual stresses. The residual stress testing indicated that the highest circumferential residual stress in the injection‐molded PMMA was ≈5 MPa in tension. Two methods, water soaking and slitting, were developed for reducing residual stresses. A series of four surgical implantation simulation processes were designed. The two methods for reducing residual stress were used in the simulations. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 456–462, 2001
A tissue sealant based on reactive multifunctional polyethylene glycol
Authors: Wallace D. G. , Cruise G. M. , Rhee W. M. , Schroeder J. A. , Prior J. J. , Ju J. , Maroney M. , Duronio J. , Ngo M. H. , Estridge T. , Coker G. C. 
Published: October 2004

AbstractA rapidly gelling synthetic tissue sealant was developed from tetra‐succinimidyl and tetra‐thiol‐derivatized polyethylene glycol (PEG). The two reagents were dissolved in aqueous buffers at 20% (w/v) solids and sprayed on the tissue site, with the use of a sprayer/mixer device. Good adhesion to collagen membranes, PTFE grafts, and carotid artery was observed in vitro. In a burst test on collagen membranes with a 2‐mm orifice defect, the gel sustained fluid pressures of 125 ± 36 mm Hg (n = 18), fivefold greater than capillary blood pressure and one‐half that observed in hypertension. On 0.4‐mm‐diameter puncture defects in PTFE grafts, pressures of 390–490 mm Hg were sustained, and on 0.6–0.9‐mm puncture defects in carotid arteries, pressures of 490 to 840 mm Hg were sustained. In vitro data corresponded to results in vivo, where bleeding in rabbit arteries was stopped immediately in five out of six trials. A significant reduction in time to hemostasis and blood loss, compared to controls, was observed. Carotid artery and subcutaneous implant data in rabbits showed that the formula was compatible with biological tissue. Rapid gelling and effective sealing were dependent on the presence of active succinimidyl ester and thiol groups on PEG. HPLC and chemical substitution methods were useful in predicting whether batches of derivatized PEG would perform satisfactorily. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 545–555, 2001
A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgery
Authors: Ignatius Anita A. , Ohnmacht Michael , Claes Lutz E. , Kreidler Joachim , Palm Frank 
Published: October 2004

AbstractThe aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL‐lactide) and α‐tricalcium phosphate in comparison to a membrane made of pure poly(L, DL‐lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 °C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 ± 2.4 MPa and 27.7 ± 2.3 MPa and the elastic modulus 3106 ± 108 MPa and 3101 ± 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 564–569, 2001
Time‐dependent mechanical properties of HA/TCP particles in relation to morsellized bone grafts for use in impaction grafting
Authors: Verdonschot N. , van Hal C. T. H. , Schreurs B. W. , Buma P. , Huiskes R. , Slooff T. J. J. H. 
Published: October 2004

AbstractIn reconstructive surgery human bone defects are sometimes filled with the use of the impaction bone grafting technique. Currently different types of biomaterial particles are being developed as bone‐substitute materials. Before these biomaterials can be applied their mechanical and biological behavior should be characterized. In this study the time‐dependent mechanical behavior of biomaterial particles with different tri‐calcium‐phosphate/hydroxy‐apatite (TCP:HA) ratios, particle sizes, and porosities is determined and compared to the behavior of human bone grafts, the latter being the standard material currently used to augment bone defects. The mechanical properties were assessed with the use of dynamic confined compression creep tests with a loading and unloading phase. Different graft material groups were tested, consisting of 100% human bone grafts, 100% biomaterial particles, and 50:50 weight mixtures of human grafts and biomaterial particles. No damage to the particles was observed by the impaction in the test chamber or by the dynamic load. Relative to the human graft material, the biomaterial particles hardly deformed under loading, were much stiffer, and showed almost no viscoelastic behavior. The mixtures showed intermediate results. Particle size and porosity influenced the behavior of the biomaterial particles. TCP:HA ratio did not have a great effect. The conclusion is that the application of these particles should be done with great care, as their mechanical behavior is drastically different than that of the human graft material. Mixing it with human bone grafts gave the material some biphasic, viscoelastic behavior that may be important for its biological response. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 599–604, 2001
Heat shock proteins of adult and embryonic human ocular lenses
Authors: Bagchi M. , Katar M. , Maisel H. 
Published: October 2004

AbstractWe investigated the presence and distribution of heat shock proteins, HSP‐70 [Horwitz, J. 1992. Proc Natl Acad Sci 89:10449–10453], HSP‐40, HSc‐70, HSP‐27, and αβ‐crystallin in different regions of adult and fetal human lenses and in aging human lens epithelial cells. This study was undertaken because heat shock proteins may play an important role in the maintenance of the supramolecular organization of the lens proteins. Human adult and fetal lenses were dissected to separate the epithelium, superficial cortex, intermediate cortex, and nucleus. The water soluble and insoluble protein fractions were separated by SDS–PAGE, and transferred to nitrocellulose paper. Specific antibodies were used to identify the presence of heat shock proteins in distinct regions of the lens. HSP‐70 [Horwitz, 1992], HSP‐40, and HSc‐70 immunoreactivity was mainly detected in the epithelium and superficial cortical fiber cells of the adult human lens. The small heat shock proteins, HSP‐27 and αβ‐crystallin were found in all regions of the lens. Fetal human lenses showed immunoreactivity to all heat shock proteins. An aging study revealed a decrease in heat shock protein levels, except for HSP‐27. The presence of HSP‐70 [Horwitz, 1992], HSP‐40, and HSc‐70 in the epithelium and superficial cortical fiber cells imply a regional cell specific function, whereas the decrease of heat shock protein with age could be responsible for the loss of optimal protein organization, and the eventual appearance of age‐related cataract. J. Cell. Biochem. 84: 278–284, 2002. © 2001 Wiley‐Liss, Inc.
Calcium‐ and FK506‐independent interaction between the immunophilin FKBP51 and calcineurin*
Authors: Li Ta‐Kai , Baksh Shairaz , Cristillo Anthony D. , Bierer Barbara E. 
Published: October 2004

AbstractFKBP51 is a member of the immunophilin family having intrinsic peptidyl‐prolyl cis‐trans‐isomerase (PPIase) activity. Its enzymatic activity is inhibited by binding either immunosuppressive agent FK506 or rapamycin. Similar to FKBP12, but at higher concentrations of FK506, FKBP51 has been shown to inhibit the serine/threonine phosphatase activity of calcineurin in the presence of calcium and calmodulin. Here we show that a glutathione S‐transferase (GST) fusion protein of FKBP51 on glutathione‐Sepharose beads precipitated both purified calcineurin from bovine brain and calcineurin from murine T cell lysates. Surprisingly, the binding of GST‐FKBP51 to calcineurin was FK506‐independent and independent of a requirement for calcium or exogenous calmodulin. Unlike FKBP12, FKBP51 transiently expressed in COS‐7 cells was precipitated by calcineurin bound to calmodulin‐Sepharose beads in the absence of either FK506 or rapamycin. Unlike FKBP12, however, overexpression of FKBP51 in Jurkat T cells did not significantly affect the transcriptional activation of nuclear factor of activated T cells (NFAT) upon physiological stimulation, nor did it affect the ability of FK506 to inhibit NFAT‐driven transcription. We generated a series of FKBP51 mutations to map the interaction of FKBP51 with calcineurin. Deletion of the aminoterminal, FKBP12‐like domain of FKBP51 did not affect the ability of FKBP51 to bind to purified calcineurin, while deletion of the FKBP51 carboxyterminal domain abrogated the ability of FKBP51 to bind to calcineurin. Taken together, these results demonstrate a novel interaction between calcineurin and the immunophilin FKBP51 that is independent of calcium, calmodulin, and drug. The binding site on calcineurin for FKBP51 is separable from the immunophilin PPIase‐active and drug‐binding site. J. Cell. Biochem. 84: 460–471, 2002. Published 2001 Wiley‐Liss, Inc.
BMP‐6 accelerates both chondrogenesis and mineral maturation in differentiating chick limb‐bud mesenchymal cell cultures
Authors: Boskey A.L. , Paschalis E.P. , Binderman I. , Doty S.B. 
Published: October 2004

AbstractChick limb‐bud mesenchymal cells, plated in micromass culture, differentiate in vitro to form a cartilaginous structure analogous to the epiphyseal growth plate. When inorganic phosphate, Pi, is included in the medium such that the total Pi concentration is 4 mM, apatite mineral precipitates around the “hypertrophic” chondrocytes. These hypertrophic chondrocytes are characterized by their increased expression of type X collagen, alkaline phosphatase activity, and apoptosis, as well as by the ability of their extracellular matrices to support mineral deposition. Under standard mineralizing conditions (0.8 × 106cells/micromass; 4 mM Pi, 1.3 mM Ca2+, 10% FCS, and antibiotics) mineralization does not commence until day 14–16. Based on the ability of bone morphogenic protein 6 (BMP‐6) to stimulate chondrocyte maturation in other systems, 100 ng/ml BMP‐6 was added to chick limb‐bud mesenchymal cell cultures 2 and 5 days after plating, and the effects of this addition on mineral accretion and the characteristics of the mineral and matrix determined. Addition of BMP‐6 accelerated the differentiation of the mesenchymal cells to hypertrophic chondrocytes. In the presence of BMP‐6 added on both days 2 and 5, mineralization (assessed on basis of 45Ca uptake) commenced by day 12. Fourier transform infrared imaging (FTIRI) was used to monitor the mineral content and mineral crystallinity as a function of time from day 9 to 21 in cultures with and without exogenous BMP‐6. While BMP‐6 accelerated the rate of mineral accretion, and the crystals that were formed in the BMP‐6 cultures were initially more mature, by day 21 the crystal size distribution in experimental and control cultures were not significantly different. This study, the first to report the detailed application of FTIRI to cell cultures, indicates the importance of the extracellular matrix in the control of crystal maturation. J. Cell. Biochem. 84: 509–519, 2002. © 2001 Wiley‐Liss, Inc.