bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Stability and Shelf-Life of Liposome Encapsulated Hemoglobin: A Potential Blood Substitute
Authors: Rudolph Alans , Stratton Lewis P. , Knoll Wayne K. , Bayne Sandra , Ligler Frances 
Published: March 2011

AbstractFor any viable blood substitute, questions of long-term storage and shelf-life must be addressed. Recently, we have made great progress in improving the stability of the blood substitute, liposome encapsulated hemoglobin (LEH). We have concentrated our efforts on protecting LEH in solution and in the long-term preservation of LEH by lyophilization. In particular, we have been able to retard and in some cases, reverse the oxidative process of metHb formation in solution by the addition of antioxidants such as NADH and glutathione. We have been able to regenerate Hb preparations with 60% metHb by the addition of 10 mM NADH and glutathione. In these preparations addition of these antioxidants results in a decrease of metHb levels from 62% to 15% over the course of 12.5 days at 4°C. We have also explored the use of protective solutes such as the disaccharide trehalose in the preservation of LEH in the freeze-dried state. Addition of increasing amounts of trehalose and other disaccharides results in the inhibition of lyophilization-induced fusion events and in the retention of hemoglobin within the unilamellar liposomal vesicles following rehydration.
Near Total Blood Exchange with Perfluorochemical Preparations
Authors: Geyer Robert P. , Taylor Kenneth , Eccles Robert , Zerbonne Therese , Gallagher Anna , Goodin Thomas , Williams Steven 
Published: March 2011

AbstractNear total blood replacement in rats has been accomplished with perfluorochemical (PFC) preparations containing hydroxyethylstarch and electrolytes. F-dimethyladamantane (F-DMA) was used alone or mixed with F-N,N-dimethylcyclohexylmethylamine (F-CHA). These compounds were emulsified to yield particles approximately 150 to 250 nanometers in diameter. The nonionic surfactant, Pluronic F68, was used as the emulsifying agent. Over ninety percent of the rats survived when their hematocrits were taken to 3 volume percent or lower from a pre-perfusion value of about 44 volume percent. In spite of the reduction in total mixed venous oxygen concentration, the oxygen partial pressure rose. During the perfusion the rats breathed 100 percent oxygen, but during the subsequent period this was decreased 10 percent per day. Six to 7 days later the hematocrits had risen to 30 to 40 volume percent. Thereafter the animals continued to develop and grow.
Biocompatibility, Osteoconduction and Biodegradation of Porous Hydroxyapatite, Tricalcium Phosphate, Sintered Hydroxyapatite and Calcium Carbonate in Rabbit Bone Defects
Authors: Shors Edwin C. , White Eugene W. , Kopchok George 
Published: March 2011

AbstractThe biocompatibility, osteoconduction and biodegradation characteristics of calcium phosphate ceramics is controversial. Few comparative studies have controlled for material properties as well as biological influences. In this study, we compared the in-vivo response of implants made porous (500 μm pores) using the Replamineforu™ process and composed of hydroxyapatite (HA), sintered hydroxyapatite (SHA), tricalcium phosphate (TCP) or calcium carbonate (CC). In ten rabbits, rod-shaped implants (5mm d × 10m 1) of each material were randomly press-fit into two bilateral defects of either the bicortical iliac crest or unicortical proximal tibial metaphysis. Explants were harvested at 1 to 9 months, sectioned midsagitally with half embedded in plastic for qualitative histomorphometry, and the other half decalcified and stained for histology. The acute and chronic inflammatory response was minimal for all implants. The osteoconduction properties were similar for the calcium phosphate materials, resulting in repair of the cortical defects within three months with partial bony fill of the medullary canal. CC completely degraded by three months, causing incomplete defect closure in some cases. TCP partially degraded in the medullary canal, but remained when surrounded by bone in the cortex. HA and SHA did not degrade. In summary:
Surface Properties, Efficacy and Biological Responses to Biomaterials
Authors: Lemons J. E. 
Published: March 2011

AbstractBiological responses to synthetic materials used for the construction of surgical implants often determine device longevities. Over the past two decades, individuals from basic and applied disciplines have attempted to better understand the phenomena associated with biomaterial to tissue interfaces and to better control the surface and bulk properties of the synthetic substances for each area of device applications. Surface properties of metals, polymers, ceramics and composites are reviewed and where possible, correlated with tissue responses. Specific examples of solid and porous titanium and cobalt base alloys are presented to demonstrate the importance of surface and bulk properties with respect to biocompatibility.
Morphological Changes of Isolated Osteoclasts in Cell Culture Due to Different Biomaterials
Authors: Lambrecht J. Thomas , Ewers R. , Kerscher A. , Jentzsch R. 
Published: March 2011

AbstractOsteoclasts have been isolated in primary cell culture using femoral bone of laying hens being fed on an eight day calcium free diet. Placing these cells on the surface of fixed cortico-femoral chicken bone provoked the feature of resorption pits proving that they are able to resorb bone.After placing osteoclasts on different biomaterials (Aluminumoxide ceramics, teflon, carbon fibre reinforced polysulphone, polymethylmethacrylate, polydioxanone) scanning electron microscopy was performed. Different materials provoke different morphological features of these cells, probably due to functional variations as a response to the changing surfaces. Adhesion was feasible on all the surfaces, uptake of small surface particles was possible and cell fusion took place on most materials suggesting acceptance of the tested biomaterials by the cells.The results show that morphological changes of isolated osteoclasts in cell culture can be detected due to different functional challenges of the surfaces of different biomaterials.
An Introduction to Liposome Encapsulation of Bioactive Polyanions
Authors: Ottenbrite Raphael M. , Sunamoto Juno 
Published: March 2011

AbstractPolyanionic polymers with differing molecular weight, lipophilicity, and charge density were synthesized and their ability to non-specifically “activate” macrophages was evaluated. The level of activation of test polymer-elicited macrophages was monitored by their tumoricidal capacity. In addition, the ability of test polymers to inhibit growth of Lewis lung in vivo was evaluated. We have determined that the activation of macrophages by test polymers differs from that of the conventional activating agents pyran and C. parvum.We then found that these polycarboxylic acid copolymers could be encapsulated by liposomes and administered intravenously. Superoxide production by murine peritoneal exudate macrophages activated by the test polyanions encapsulated in liposomes was increased by 300% in the first 2 hours compared to macrophages activated by the free polymers.
Sustained Delivery of Bioactive Polypeptide by Compression in Lipid Admixture
Authors: Wang Paul Y. 
Published: March 2011

AbstractBioactive polypeptides are susceptible to inactivation by proteolytic enzymes in body fluids. Instead of many injections, these polypeptides may be specially formulated to prolong their action in vivo to several months by entrapment in a polymer mixture. In a recent fundamental study on implant for drug delivery, it was found in this laboratory that a polymer support component was not mandatory and pharmacologically active macromolecules could be readily delivered on a sustained basis. Consequently, when 10% insulin (Zn) was admixed with cholesterol and then compressed, the hormone action was extended to about 20 days when tested subcutaneously in Wistar rats with streptozotocin-induced diabetes. Evaluation of other lipids has shown that with palmitic acid as the excipient, the 8-hr action of insulin can be extended to about 40 days. The same type of sustained delivery implant containing insulin or pituitary growth hormone can enhance growth in normal Wistar rats. Since no synthetic materials were used, biocompatibility problem is not expected. Further, the fatty acid excipient is gradually eroded in vivo, and explantation of the implant will not be necessary as well. This approach shall be particularly useful in special formulations of other pharmaceutical proteins such as the rDNA-produced somatotropin analog used in growth enhancement of farm animals raised for consumer food products.
Some Unique Properties of a Bilayer and Liposome Forming System
Authors: Macgregor Roderick D. , Taylor Noel , Hunt C. Anthony 
Published: March 2011

AbstractThe unique procedure developed for forming artificial red cells (Science 230, 1165, 1985) allows encapsulation of proteins to concentrations in excess of 20g%. The procedure requires a hypotonic starting solution, whereas the final suspension is equilibrated at 300 mOsm. Hemoglobin (Hb) was one of several proteins encapsulated. The procedure is based on emulsion formation and subsequent evaporation of the nonaqueous phase, a common liposome-formation procedure, but has unique features. The densities of the phases are matched by adding a Freon. The emulsion is formed using conditions that eliminate protein denaturation. This research was designed to evaluate the fine structure at each critical stage using thin section electron microscopy. The results revealed remarkable, previously unseen detail that raises questions about the variety of properties that can be engineered into lipid bilayer structures. The initial emulsion was nonclassical. Submicron particles in large relative numbers suggested a minimal surface tension difference between the two phases. After nearly complete evaporation of the nonaqueous phase, “microcapsule” particles were present but their architecture showed little in common with classical liposomes; there was no evidence of bilayer membranes. Following extrusion, a slow increase in the osmolality to 300 mOsm dramatically altered the architecture of the microcapsules: The encapsulated protein concentration increased, and lipid bilayer membranes were formed. The resulting “liposomes” were often chambered rather than having concentric bilayer structures. Two closely opposed bilayers surrounding a volume of protein solution was a common structure.
Alcap Delivery Devices and the Sustained Release of Difluoronethylornithine (DFNO) in Vitro and in Vivo Using Male Rats
Authors: Benghuzzi Haned A. , Bajpai Praphulla K. 
Published: March 2011

AbstractSprague-Dawley albino male rats (25) were divided into five groups consisting of five rats each. Polymer (polylactic acid) impregnated ALCAP capsules filled with 40 mg DFMO were implanted subcutaneously (SC) or intraperitoneally (IP) in Group I and II rats respectively. Rats in Group III were implanted with empty polymer impregnated ALCAP capsules (ALCAP control). Group IV rats were administered orally 3% DFMO in drinking water. Rats in Group V served as controls. Blood samples were collected every week for nine weeks via the tail artery. The concentration of DFNO in the plasma was determined. Data obtained showed that the levels of DFMO in the serum of rats in groups I, I, and IV were 64.71 ±4.08. 219.18 ± 14.48, 16.71 ± 5.21 ug ml−1, respectively at the end of nine weeks. Body weights of the controls and DFMO treated rats were not significantly different (p<0.05). The diarrhea often noted in rats treated orally with DFHO was not observed in rats implanted with ALCAP or ALCAP capsules filled with DFMO. The results of this study suggest that: (1) polymer impregnated ALCAP ceramic implants can be used to deliver DFMO in vivo in a sustained manner for long durations of time, and (2) a ceramic system can be designed to deliver DFNO and drugs such as DFMO in a sustained manner over long durations of time in humans.
Effect of an Electromagtnetic Field Used for Bone Gwoth Stimulation on Corrosion of 316L Stainless Steel
Authors: Edwards Brian , Posey-Dowty Jessica , Highm Paul 
Published: March 2011

AbstractA recent development in fracture treatment is that of electrical stimulation to enhance healing. Since the fractured limb receiving treatment may have been inmmbilized or fixed with 316L stainless steel (SS) internal fixation devices, there is an interest in docu.menting how the electromagnetic field affects corrosion of this alloy. The stimulator under investigation produces an electrcnagnetic field having a 3.5 ± IMV pulse height delivered at 75 Hz within the treatment coils. Corrosion, as quantified by analyzing test solutions for Ni and Cr levels, was measured for specimens in and out of the stimulator field.Three-week in vitro corrosion tests were conducted at 37°C in 0.9% NaCl adjusted to pH levels of 7.4 and 4.0. Specimen were 316L SS rods with surfaces finished to 600 grit. 0-rings were added to form crevices in order to accelerate corrosion. Stimulation was continuous for test specimens. An equal number (ten for each pH) of control specimens received no stimulation.
A statistical comparison of the data reveals that at a 95% confidence level the stimulator field did not affect corrosion of the 316L SS.
Cast Co-Cr-Mo Alloy as a Substrate for Porous Coated Prosthetic Devices
Authors: Gustavson L. , Crippen T. , Dumbleton J. H. , Bushelow M. 
Published: March 2011

AbstractThe application of metallic porous coatings on hip prostheses stems has increased the need for evaluating the interrelationship of implant design, material properties, and manufacturing process relative to component fatigue resistance.In testing the PCA®(porous-coated anatomical) hip a three phase approach was followed comparing Vitallium® and Ti-6AI-4V alloys. Material and component fatigue tests were conducted, followed by in vitro stress analysis. The results of these studies are discussed.
Indentation Fracture Toughness Testing of and Crack Propagation Mode in Dental Composites
Authors: Ferracane Jack L. 
Published: March 2011

AbstractThe use of a Vicker's indenter to measure the fracture resistance of dental composite resins was correlated to fracture toughness results obtained by bending of notched bars. There is a fair correlation between the methods, but many dental composites do not form cracks by the indentation technique, thereby limiting its usefulness. SEM micrographs reveal a crack propagation mode which is mostly through the matrix and along the filler/matrix interface, with evidence of particle fracture
Preparation and Analysis of Ti and Alloyed Ti Surfaces Used in the Evaluation of Biological Response
Authors: Lausmaa J. , Ask M. , Rolander U. , Kasemo B. 
Published: March 2011

AbstractThe biocompatibility of Ti and Ti alloys is closely associated with the passivating surface oxide which covers these materials. In this paper results are presented from a broad surface characterization of pure Ti and Ti6A14V alloy surface oxides prepared by thermal oxidation by machining, or by electrochemical procedures (electropolishing and anodic oxidation). The chemical composition of the surface oxide on both materials is mainly TiO2, as shown by XPS, AES, and SIMS analyses. Significant differences exist for both the thermal and anodic oxides, in that the alloying elements are present in the surface oxide of the alloy. TEM and STEM studies show that the microstructure of the anodic oxide films is rather heterogeneous with areas of different porosity which can be correlated with the grain structure of the bulk metals. Oxides on the alloy are even more heterogeneous than on Ti, due to the more complex (two-phase) microstructure of the bulk metal, and also differ in crystallinity. The differences in the surface oxide properties can be expected to lead to differences in the biological response to these two materials. With the alloy, one must consider the risk of Al and/or V dissolution into the biological system.
Ionic Polyurethanes: Surface and Blood-Contacting Properties
Authors: Okkema Ann Z. , Giroux Thomas A. , Grasel Timothy G. , Cooper Stuart L. 
Published: March 2011

AbstractSulfonated polyetherurethanes, synthesized by the substitution of 0, 5, 10, 15, and 20% of the urethane nitrogens with propane sultone, were evaluated in this study. The water absorption properties are dramatically affected by the sulfonate content. The surface properties are also found to be influenced by the percentage of sulfonate incorporation. The blood-contacting properties, as determined by both an acute and chronic canine ex vivo experiment, show increased thromboresistance with increased propyl sulfonate incorporation. A unique characteristic of the highly sulfonated polymers is the negligible platelet activation and spreading observed using scanning electron microscopy.
The Effect of Alkali Metal Cations on The Structure of Dissolved Silicate Oligomers
Authors: McCormick Alon V. , Bell A. T. , Radke C. J. 
Published: March 2011

AbstractBy means of 29Si spectroscopy, it is established that the distribution of silicate anions in alkaline silicate solutions is a moderate function of base composition. At a fixed SiO2. concentration and silicate ratio, the proportion of Si present in oligomeric and cage-like structures increases in progressing from Li to Cs hydroxide. Interactions between alkali metal cations and silicate anions are investigated using NMR spectroscopy of the cations; in this way the concentration of ion pairs is measured as a function of cation size. As a result the silicate redistribution is ascribed to cation-silicate anion pairing and to a higher selectivity for ion pairing by large silicate anions as cation size increases.
High Resolution Electron Microscopic Study of the Growth of Denser Phases on Zeolite Y and Zeolite L.
Authors: Zandbergen H. W. 
Published: March 2011

AbstractHigh resolution electron microscopy (HREM) is a powerful tool in materials research. This is especially true in the study of zeolites because most of the questions concerning the properties of zeolites require a detailed characterization of the local structure [1]. The potential of HREM is illustrated with studies on the growth of denser phases on Zeolite Y and Zeolite L.
Structure and Epitaxy of Silver/Gold Microclusters on MgO
Authors: Marks L. D. , Hong M. C. , Zhang H. , Teo B. K. 
Published: March 2011

AbstractWe report observations by high resolution electron microscopy of model catalysts produced by impregnating MgO smoke particles with inorganic clusters. With the use of very low beam currents the substrates are of sufficiently low noise that we have been able to image cleanly both single atoms and very small clusters of size l-2nm in sufficient detail to determine their atomic structure. Two types of metal structures are observed: single atoms decorating atomic steps and in a few cases two-dimensional surface rafts, and a population of mainly single crystal with a few multiply twinned particles. The single crystal particles are pseudomorphically epitaxed on the MgO substrates.
Raman Spectra of Ion Intercalated Vermiculites
Authors: Jiang H. X. , Solin S. A. , Kim H. , Pinnavaia T. J. 
Published: March 2011

AbstractThe Raman spectra of ion intercalated Vermiculites have been studied. The torsional mode frequencies exhibit a shift to higher energy with increasing basal spacing d. Using a van der Waals type force model, and the nearest neighbor approximation, we have successfully derived the formula for the torsional mode frequency as functions of basal spacing d and other physical parameters. The calculation results are quite consistent with the experimental observations.
Characterization of Zeolites by Gas Adsorption at Low Pressures
Authors: Venero Agustin F. , Chiou J. N. 
Published: March 2011

AbstractThe nitrogen and argon adsorption isotherms of three different zeolites, calcium A, ZSM-5, and sodium Y were obtained at 77.3 and 87.5 K. Using a continuous volumetric technique high resolution data was obtained in the Henry's Law region of the isotherm at relative pressures below 10−1 P/Po. The data for the two adsorbates indicates that nitrogen, due to its quadrupole moment, shows a high degree of localized adsorption, which makes it difficult to differentiate among zeolites of different pore sizes. Argon, on the other hand, can be used to identify zeolites of different pore sizes. The argon data was used in conjunction with the Horvath-Kawazoe model to obtain a pore size distribution of the zeolite.
Structural Studies of Pillared Clays and Modified Pillared Clays
Authors: Carrado Kathleen A. , Thompson Arthur R. , Winans Randall E. , Botto Robert E. 
Published: March 2011

AbstractThe long-range order of pillared interlayered clays (PILCs) after acid activation with 0.05N HCl has been investigated by X-ray diffraction (XRD) methods. The data show that long-range order in PILCs decreases as AlCH-PB = ZrCH-PB » Zr/AlCH-PB - Cr/AlCH-PB (PB - pillared bentonite; MCH = metal chlorohydroxy pillaring agent, where M - Al, Zr or Cr). Apparently, pure oxide clusters are more stable than mixed oxide clusters. Treatment of PILCs with dilute HCI at 25°C is less damaging than at reflux temperature, and calcined PILCs are more stable than air-dried materials. More structural damage occurs with 3M sulfuric acid treatment than with dilute HCI. Treatment with a weak base also causes some degradation of the pillars. 27AI-MAS NMR has been used to study pillared hectorite (PH), as well as other clay systems. The large increase of the observable octahedral aluminum (AI(VI)) resonance seen after pillaring is explained by loss of water from the [Al13O4 (OH) 24 (H2O)12] 7 +(Al13 ) cation. 27A1 spectra of PILCs derived from different pillaring agents and exposed to various heat and acid treatments are remarkably similar.
A New Family of Photoactive Catalysts Based Upon Bismuth Oxide
Authors: Harriman Anthony , Thomas John M. , Zhou Wuzong , Jefferson David A. 
Published: March 2011

AbstractBismuth(III) oxide, which is pale yellow, functions as an amphoteric semiconductor, although it is relatively unstable upon illumination with UV light. The energy level positioning, corrosion limits and photoactivity of samples of n-type bismuth oxide have been determined by electrochemical techniques. It was found that this material is able to oxidise water to molecular oxygen upon illumination with UV light.Bismuth oxide forms a wide range of well-defined solid solutions with many other oxides and, in particular, niobium oxide can be used to form several distinct structures, each based upon defective fluorite. Each of these structures will function as an n-type semiconductor, retaining the basic properties of undoped bismuth oxide. However, the exact composition of the solid solution determines the band-gap energy of the semiconductor. Low concentrations of niobium in the lattice induce a substantial lowering in the band-gap energy and give rise to orange coloured materials that can collect a higher fraction of the solar spectrum. Photoelectrochemical studies showed that the presence of niobium caused the valence band to move to lower potentials but had little effect upon the energy of the conduction band. The photochemical properties of these solid solutions were studied using the photooxidation of alcohols as a test system. The results are discussed in terms of the structure of the oxide.