bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of protein kinase C in the monocyte‐derived macrophage‐mediated biodegradation of polycarbonate‐based polyurethanes
Authors: McBane Joanne E. , Santerre J. Paul , Labow Rosalind S. 
Published: May 2005

AbstractPolycarbonate‐polyurethanes (PCNUs) elicit a foreign body reaction during the initial tissue contact, partly mediated by the respiratory burst in monocytes, during which protein kinase C (PKC) activates NADPH (nicotinamide adenine dinucleotide phosphate) oxidase. Using an in vitro cell system, monocytes were differentiated into monocyte‐derived macrophages (MDMs) and then reseeded onto three PCNUs (HDI431, HDI321, or MDI321): hexane (HDI) or 4,4′‐methylene bis‐phenyl (MDI) diisocyanates synthesized with poly(1,6‐hexyl 1,2‐ethyl carbonate) diol (PCN) and 14C‐labeled butanediol (BD) in the ratios 4:3:1 or 3:2:1 (diisocyanate/PCN/BD). MDM‐mediated degradation was assessed by radiolabel release in the presence of a PKC activator (phorbol myristate acetate), inhibitor (H7), and a catalase/peroxidase inhibitor (NaN3). Activating PKC decreased biodegradation and esterase activity in MDMs on HDI431 and HDI321 but not MDI321, whereas H7 and NaN3 inhibited the MDM degradation of MDI321 only. Pretreatment of the PCNUs with H2O2 inhibited esterase‐mediated radiolabel release from HDI431 and HDI321 but stimulated radiolabel release from MDI321. The difference in the effect of H2O2 on the HDI versus MDI PCNUs contributes to explaining the effect of PKC activation on material degradation. Understanding the mechanism by which this pathway is linked to PCNU chemistry may assist in designing materials with tailored biodegradation rates. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Direct measurement of interactions between adsorbed vitronectin layers: The influence of ionic strength and pH
Authors: Zhang Hailong , Bremmell Kristen E. , Smart Roger St. C. 
Published: May 2005

AbstractVitronectin (Vn) is an adhesive protein in the plasma serum and plays an important role in cell attachment, spreading, and proliferation. The interactions between protein bovine vitronectin layers adsorbed onto a silica probe and a mica surface have been investigated with the use of atomic force microscopy (AFM). Adsorption of vitronectin was confirmed by XPS surface analysis. The force‐separation curves and pull‐off forces were measured as a function of ionic strength and solution pH. The pull‐off force (adhesion force) decreased as the salt concentration increased, which suggests that some binding domains of this protein may associate with the ionic species and reduce its binding ability. Discrete jumps, or discontinuities, in the separation force curve were observed to extend to a maximum of 300 nm, evidence that the protein molecules bridge between the surfaces. As a function of pH, the adhesion force on separation of the protein‐coated surfaces showed a maximum at pH 5 (i.e.p. of vitronectin), decreasing in magnitude at lower and higher pH values. At pH 5, the approaching curves illustrated a jump‐in force; whereas for pH values away from 5, the approaching force curves were repulsive. Correlation of the interaction forces with Vn conformational changes in different pH environments, directly visualized with the use of AFM imaging, was developed. In its i.e.p. region, the Vn molecular conformation appeared to be dense and compact. Significantly, at wounds/injured sites the pH is low (approximately 5) which this study discovered to facilitate adsorption and formation of vitronectin aggregates, known to trigger their subsequent biological functions. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Fibrinogen and von Willebrand's factor adsorption are both required for platelet adhesion from sheared suspensions to polyethylene preadsorbed with blood plasma
Authors: Kwak Dean , Wu Yuguang , Horbett Thomas A. 
Published: May 2005

AbstractPrevious studies showed that platelet adhesion to biomaterials from static suspensions was greatly increased by the adsorption of even very small amounts (<5 ng/cm2) of fibrinogen (Fg). In this study, the sensitivity of platelet adhesion to Fg was reexamined by measuring platelet adhesion under flow conditions. The role of adsorbed von Willebrand's factor (vWf) was also studied. Polyethylene (PE) tubing was preadsorbed with Fg, vWf, vWf‐deficient plasma, and Fg‐deficient plasma or serum with added Fg, and Fg adsorption measured with 125I Fg. Platelets in a red blood cell suspension were passed through the tubes at either low (50 s−1) or high (500 or 1000 s−1) shear rates and adhesion measured with an improved LDH assay. Adhesion from flowing suspensions measured after preadsorption with afibrinogenemic plasma or serum was very low, but increased greatly with addition of Fg. Less than 10 ng/cm2 of adsorbed Fg was enough to greatly enhance platelet adhesion. Adhesion at high shear was also strongly affected by vWf, as platelet adhesion at 500 s−1 to PE preadsorbed with vWf‐deficient plasma decreased by more than tenfold compared to adhesion at 50 s−1, but platelet adhesion to PE preadsorbed with normal plasma increased about eightfold when shear rate was increased. The results show that very low amounts of adsorbed Fg are able to support platelet adhesion under shear flow. However, adsorbed vWf also appears to play an important cofactor role in platelet adhesion to biomaterials, as its presence greatly augments platelet adhesion under high shear. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Biocompatible oligochitosans as cationic modifiers of alginate/Ca microcapsules
Authors: Orive G. , Bartkowiak A. , Lisiecki S. , De Castro M. , Hernández R. M. , Gascòn A. R. , Pedraz J. L. 
Published: May 2005

AbstractIn the past, it has been proven that by properly adjusting the molecular mass of the oligochitosan samples, it is possible to optimize the formation of rigid, biocompatible capsules with semipermeable membranes under physiological conditions. In this study, the feasibility of four oligochitosan samples, with varying molar masses (Mn in range 3–5 kDa), as biocompatible coatings of alginate/Ca capsules was investigated. By selection of appropriate depolymerization and purification methods we obtained oligochitosan samples that appeared to be noncytotoxic for C2C12 myoblasts and did not influence the mammalian cell metabolism especially in relative short time during the process of capsule formation. Furthermore, oligochitosans can be used as a tool to reduce the membrane cut‐off of the alginate capsules. However, such reduction, as well as mechanical resistance of formed microcapsules, depend on MM of the cationic polysaccharide and the chemical composition of the alginate (mannuronic/guluronic acid ratio). Here, we address that the use of low molar mass chitosan (< 5000 g/mol) permits the formation of mechanical stable capsules at physiological pH, which represents a strong advantage over other chitosan‐based chemistries. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Controlled release of EGF and bFGF from dextran hydrogels in vitro and in vivo
Authors: Doǧan Alper K. , Gümüşderelioǧlu Menemşe , Aksöz Erol 
Published: May 2005

AbstractIn the present study, dextran‐epichlorohydrin hydrogels were employed as carriers for the controlled release of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). The hydrogels were synthesized from 50% (by weight) monomeric cross‐linker, epichlorohydrin, containing dextran mixtures by intermolecular side‐chain reaction of dextran‐hydroxyl groups with epichlorohydrin‐epoxy groups. The hydrogel disks of 3‐mm diameter and 1.5‐mm thickness have a high swelling capacity (EWC = 650%) and enough mechanical stability for the studies in vivo. Impregnation of EGF and bFGF into the dried hydrogels was carried out by use of phosphate buffered saline solution (PBS, pH =7.4) containing 0.5 μg mL−1 EGF and 0.1 μg mL−1 bFGF, respectively. The in vitro release of growth factors was detected by fluorescence spectroscopy. The prolonged release of EGF is continued up to the 14th day, in comparison with a 26‐day release of bFGF. The in vivo studies were realized with subcutaneously implanted hydrogels in Wistar albino rats. The rate of neovascularization was analyzed statistically using one‐way analysis of significance with EGF and bFGF incorporated hydrogels. In conclusion, dextran‐epichlorohydrin hydrogels were shown to be an alternative delivery system for the release of growth factors. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Poly(D,L‐lactide) coating is capable of enhancing osseous integration of Schanz screws in the absence of infection
Authors: Partale K. , Klein P. , Schell H. , Schmidmaier G. , Wildemann B. , Bail H. , Schiller R. , Bragulla H. , Duda G.N. 
Published: May 2005

AbstractPin loosening is a major complication in external fixation. Biological and mechanical conditions play an important role in the maintenance and enhancement of the implant–bone interface in fracture fixation. It is thought that biodegradable coatings may be capable of preventing pin track infection and pin loosening. The goal of this study was therefore to analyze the influence of a biodegradeable coating on the osseous integration of Schanz' screws during fracture treatment. Standardized osteotomies (3‐mm fracture gap) of the right tibiae were performed on 16 sheep and stabilized by an AO mono‐lateral external fixator. Additional, mechanically less loaded Schanz' screws were also mounted. All screws were randomly coated with biodegradable poly(D,L‐lactide). The sheep were sacrificed after 9 weeks. All screws were removed and rolled on blood agar plates for microbiological analysis. Histological sections of the pin tracks were histochemically and morphometrically analyzed. Clinically, no signs of severe infection were visible. Microbiological analysis revealed 14.8% colonization by Staphylococcus aureus in the coated and 29% in the uncoated screws. Histomorphometry of the bone surrounding the Schanz' screws revealed that significantly more osseous integration had occurred on poly(D,L‐lactide)‐coated screws in the absence of bacterial colonization. Significantly more bone remodeling and a higher osteoclastic activity was seen near the screw–bone interface in the uncoated screw group. Up to a threefold increase in new bone formation and more severe remodeling was observed around the screw entry compared to the pin exit in all groups. Loaded screws showed significantly more callus formation around the exit sites than their less loaded counterparts. In the present study, poly(D,L‐lactide) coating of Schanz' screws was found to enhance osseous integration in the absence of bacterial colonization in sheep by causing less cortical remodeling and less osteoclastic activity in the cortices compared to uncoated screws. Additionally, the coating appeared to reduce the instances of pin track infections. Mechanical loading showed an adverse effect on bone formation and remodeling. It has been shown that both biological and mechanical factors play an important role in the maintenance of osseous integrity of the pin–bone interface. Poly(D,L‐lactide) coating of Schanz' screws does not prevent osseous destruction and severe bacterial colonization along the pin tracts, but can improve osseous integration of Schanz' screws in the absence of infection. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Vascular graft infections: In vitro and in vivo investigations of a new vascular graft with long‐term protection
Authors: Ueberrueck Torsten , Zippel Roland , Tautenhahn Joerg , Gastinger Ingo , Lippert Hans , Wahlers Thorsten 
Published: May 2005

AbstractWe investigated a polyester vascular prosthesis (PET) coated with elemental silver (SC). Measurement of silver release over a period of 52 weeks by means of inductively coupled plasma atomic emission spectrometry of PET with (PET‐G) and without (PET‐N) gelatine impregnation revealed a silver release on the first day of 1.2 ± 0.2μg (PET‐N) and 1.2 ± 0.1 μg (PET‐G) (calculated for 1 g of prosthesis); from the 90th day onward, it was between 0.22 ± 0.14μg (PET‐N) and 0.18 ± 0.12 μg (PET‐G) per day. The prostheses were incubated with Staphylococcus aureus (S.a.), Staphylococcus epidermidis (S.e.), or Escherichia coli (E.c.) to investigate in vitro antibacterial efficacy. After 6 h of incubation, no colony‐forming units were to be seen for any of the bacterial suspensions for PET with SC (p < 0.001). To investigate in vivo antibacterial efficacy, PET‐G rings with and without SC contaminated with S.a., S.e., or E.c. were implanted in 18 albino rabbits and examined 7 days after agar culture for 48 h. The silver coating was associated with a significant reduction in bacterial growth (S.a., p = 0.001; S.e., p < 0.005; E.c., p < 0.001). The silver‐coated prosthesis, with and without gelatine impregnation, had a significantly antibacterial effect with continuous release of silver. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Manufacture of porous polymer nerve conduits through a lyophilizing and wire‐heating process
Authors: Huang Yi‐Cheng , Huang Yi‐You , Huang Chun‐Chieh , Liu Hwa‐Chang 
Published: May 2005

AbstractWe have developed a method for nerve tissue regeneration using longitudinally oriented channels within biodegradable polymers created by a combined lyophilizing and wire‐heating process. This type of cell‐adhesive scaffold provides increased area to support and guide extending axons subsequent to nerve injury. Utilizing NiCr wires as mandrels to create channels in scaffold increased safety, effectiveness, and reproducibility. The scaffolds tested were made from different biodegradable polymers, chitosan and poly(D,L‐lactide‐co‐glycolide) (PLGA), because of their availability, ease of processing, low inflammatory response, and approval by the FDA. According to our experimental results, the high permeability and the characteristic porous structure of chitosan proved to be a better material for nerve guidance than PLGA. The scanning electron micrographs revealed that the scaffolds were consistent along the longitudinal axis with channels being distributed evenly throughout the scaffolds. There was no evidence to suggest merging or splitting of individual channels. The diameter of the channels was about 100 μm, similar to the 115 μm diameter of the NiCr wire. Regulating the size and quantity of the NiCr wires allow us to control the number and the diameter of the channels. Furthermore, the neutralizing processes significantly influenced the porous structure of chitosan scaffolds. Using weak base (NaHCO3 1M) to neutralize chitosan scaffolds made the porous structure more uniform. The innovative method of using NiCr wires as mandrels could be easily tailored to other polymer and solvent systems. The high permeability and the characteristic porous structure of chitosan made it a superior material for nerve tissue engineering. These scaffolds could be useful for guiding regeneration of the peripheral nerve or spinal cord after a transection injury. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Novel intramedullary plug with sliding mechanism used in revision total knee arthroplasty
Authors: Fujita H. , Kitaori T. , Iida H. , Shimizu K. , Hiroshima Y. , Kawanabe K. , Nakamura T. 
Published: May 2005

AbstractA novel intramedullary plug with sliding mechanism has been developed and evaluated clinically in the settings of revision total knee arthroplasty (TKA). The new plug consists of a pair of specially designed components. Each component is shaped like an obliquely cut cylinder. Postoperative plain radiographs of 8 arthroplasties that include 7 stemmed femoral components and 6 stemmed tibial components (total 13 regions) were examined. No radiolucent line between the cement and the cortical bone was observed. Plugging was complete in 11 regions. No migration of the plug was observed. Slight leak of the cement was observed in 2 of 7 femoral components, but not found in tibial components. Our study demonstrated the efficacy of the plug in occluding the femoral and tibial canal completely in 11 out of 13 regions in revision TKAs. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
The large‐scale separation of fluids from fibrous pulps
Authors: Pirie N. W. 
Published: May 2005

AbstractMost of the free fluid can generally be expressed from fibrous pulps in a few seconds at 50 lb/in2 if the layer of pulp is kept thinner than 1 in. after it has been pressed, and if the fluid is allowed to run away freely. The need for this time and the frictional properties of many pulps are serious obstacles to the design of any strictly continuous press. Roller presses do not allow enough time, screw expellers create too much friction, continuous centrifuges and some other arrangements are intricate and vulnerable.An intermittent but automatic press which avoids these defects is described. In this the material on a perforated conveyor is pressed by a ram and then moved forward as the ram lifts. One such machine has already been made. An outline is given of the principles on which an improved design will depend.
Development of Streptomyces aureofaciens in submerged culture
Authors: Doskočil J. , Hošťálek Z. , Kašparová J. , Zajíček J. , Herold M. 
Published: May 2005

AbstractDuring the biosynthetic production of chlortetracycline on a medium with sucrose, soy meal, corn steep extract, sodium chloride, ammonium sulphate, calcium carbonate and beet molasses, the amount of nucleic acids synthesized by the culture and the maximum respiration of the culture is determined by the amount of inorganic phosphate in the original medium. Chlortetracycline production does not start until all the inorganic phosphate has been consumed. The adverse influence of increased amounts of inorganic phosphate upon production of chlortetracycline is more apparent in flasks on a shaking machine than in agitated and aerated fermentation tanks with higher oxygen transfer numbers.
Surface culture in the mass growth of bacteria
Authors: Porter F. E. , Nack H. 
Published: May 2005

AbstractThe present study was conducted to determine the feasibility of growing bacteria in quantity on solid media in closed vessels. Five techniques were investigated in the laboratory, including growth on agar, growth on packing in beds, growth on solids in a fluidized bed, growth in foamed medium, and growth on semipermeable membranes. Data obtained from the laboratory experiments were used to scale up these techniques on paper and compare the projected plants with a conventional submerged fermentation production. All the techniques compared unfavourably with submerged culture on the basis of plant and operating costs, operating complexity, equipment complexity, and safety. One technique of surface culture, growth on semipermeable membranes, appears to offer a decided advantage over submerged culture, in that the cell product can be recovered directly as a paste. Further work on this technique is recommended.
Cation exchangers on a sugar‐beet pulp base. Application for decontaminating radioactive waste water
Authors: Langenhorst W. Th. J. P. , Tels M. , Vlugter J. C. , Waterman H. I. 
Published: May 2005

AbstractA cation exchanger suitable for decontaminating low and medium radioactive waste water was sought. Regeneration being considered undesirable, the exchange material had to be cheap and readily obtainable. Sugar‐beet pulp, a weakly acidic cation exchanger, satisfies these conditions. Its capacity is about 0·62 mg eq. per gram of dry matter. In order to study the selectivity of the sugar‐beet pulp exchanger, the equilibrium curve of the reaction

equation image

was determined.This curve was found to have the shape of the hyperbola proposed by Waterman and Weber for the characterization of the course of simultaneous reactions. Sugar‐beet pulp adsorbs the salts of the alkaline earth metals selectively in the presence of both Na+ and La+++. Sugar‐beet pulp was used to decontaminate a solution containing 140BaCl2 and 140LaCl3 and having an activity of about 10−2 μc/ml. The results were satisfactory.By treating sugar‐beet pulp with formaldehyde and hydrochloric acid, the amount of water bound to the pulp is very much decreased. By this treatment a cation exchanger is produced having a capacity per unit volume about six times greater than that of sugar‐beet pulp. The capacity of this exchanger is about 0·5 mg eq. per gram of dry matter. The selective behaviour of sugar‐beet pulp treated with formaldehyde is similar to that of unmodified sugar‐beet pulp.By treating sugar‐beet pulp with formaldehyde, hydrochloric acid and dilute sulphuric acid, a cation exchanger with very good mechanical and filtration properties is obtained. This exchanger has a capacity of about 1·3 mg eq. per gram of dry matter.It seems possible to employ the cation exchangers obtained by treatment of sugar‐beet pulp with either formaldehyde and HCl or formaldehyde, HCl and H2SO4 also for purposes other than the removal of radioactive cations from water.
The recovery of staphylococcal enterotoxin from bacterial culture supernatants by ion exchange
Authors: Bergdoll M. S. , Sugiyama H. , Dack G. M. 
Published: May 2005

AbstractA method has been developed for the recovery of enterotoxin from bacterial culture supernatants of staphylococcus strain S‐6 by use of the ion‐exchange resin Amberlite XE‐64 (IRC‐50). The enterotoxin from 200 ml of bacterial culture supernatant diluted with one volume of water and adjusted to pH 6 can be removed with 1 g of resin pretreated with 0·02 M sodium phosphate, pH 6·2. The enterotoxin is recovered from the resin with 0·2 M sodium phosphate, pH 6·2, with subsequent precipitation with EtOH at −10°C, dialysis, and freeze drying. Partially purified preparations containing 1 emetic dose per 50μg were obtained.
A microcompartmentation analysis of intermediate leakage response to substrate excess in a membrane‐bound bifunctional enzyme: Local control of hydroxyprogesterone channeling efficiency during cytochrome P450XVII‐catalysed androgen biosynthesis
Authors: Kühn‐Velten W. Nikolaus 
Published: May 2005

AbstractEvidence is presented for the first time that the cytochrome P450XVII°Catalysed androgen formation from progesterone (P) in rat testicular microsomal membranes represents a metabolic sequence that exhibits the ability of intrinsic regulation of intermediate transfer and product formation efficiency. Exposure of this system, which catalyses a hydroxylation and oxidative cleavage reaction sequence, to increasing P concentration results in a decreased specific retention of the putative intermediate, 17α‐hydroxyprogesterone (HP) in the membrane compartment, and in a decreased HP conversion to androgens in favour of increasing HP transfer into the extramembrane space. This behaviour results in a decreased ratio of product vs. intermediate formation rates, which is interpreted as a partial “uncoupling” of the normal hydroxylation and cleavage reaction sequence catalysed by P450XVII. A similar pattern can likewise be observed in isolated testicular Leydig cells after exposure to increasing P concentrations under more physiological continuous‐flow conditions. Further calculations indirectly indicate that the specific retention of HP in the membrane compartment can partially be attributed to its specific association with the P450XVII during catalysis. The results strongly suggest the existence of a local “channel” that becomes more leaky and therefore less effective if loaded with high influx rates. This pattern may be related to significant but incomplete competition of exogenously entering P and endogenously formed and transiently bound HP for oxygen attack at the P450XVII active site.