bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of thermal properties for human femora
Authors: Biyikli Suleyman , Modest Michael F. , Tarr Richard
Published: December 2004

In this study, density, specific heat, thermal conductivity, and thermal diffusivity were measured experimentally along the lengths of human cadaveric femora. Fresh and dry bone samples were selected from both male and female specimens, and for different age groups varying between44 and 73 years old. Measured values for specific heat vary between 1.14 and 2.37 J/gm°C; forthermal conductivities the range is from 0.16 to 0.34 W/m°C; and for thermal diffusivities the range is from 0.10 to 0.23 cm2/sec, depending on whether the bone samples were freshor dry, cancellous or cortical. The experimental results are presented in non‐dimensional coordinates and are compared with the few other data available in the literature.
Macrophage activation with multi‐porous beads prepared from partially deacetylated chitin
Authors: Nishimura Keiko , Nishimura Shin‐Ichiro , Seo Hiroshi , Nishi Norio , Tokura Seiichi , Azuma Ichiro
Published: December 2004

The effect of multi‐porous beads prepared from 80% deacetylated chitin on the activation of mouse peritoneal macrophages was examined. Deacetylated chitin bead (DAC‐bead) preparations were shown to activate macrophages for tumoricidal activity depending on the increasing concentration of acetic acid used for the pretreatment of beads. The large DAC‐bead was more susceptible to treatment with acetic acid than small DAC‐bead, and showed more potent capacity for the activation of macrophages under the same pretreatment conditions with acetic acid. Reacetylated bead preparations, on the other hand, showed less activities. In addition, DAC‐bead pretreated with acetic acid stimulated macrophages to produce interleukin 1. The possibilities of multi‐porous beads as cancer chemotherapeutic‐carrier were examined by the method of column chromatography and of in vitro antitumor experiment. Forty‐four percent of adriamycin adsorbed on the surface of and in bead was released within the first 60 min. of elution, and then adriamycin was released more slowly in proportion to the elution time. Antitumor activity of adriamycin‐adsorbed bead was less effective than that of free adriamycin if they were compared on the basis of total content of adriamycin.
Molecular weight distribution of a bulk ultra‐high molecular weight polyethylene product—impax 5M+ UHMW–NAT
Authors: Kusy R. P. , Whitley J. Q.
Published: December 2004

A bulk ultra‐high molecular weight polyethylene product, IMPAX 5M+ UHMW–NAT, was fractionated using an increasing‐temperature sequential‐extraction technique. In the presence of an inert atmosphere and an antioxidant, 5 g of material were methodically dissolved in decahydronaphthalene over the temperature range, 80–191°C. Initially, intrinsic viscosities were measure in decalin at 135°C by single point capillary viscometry. From this data the viscosity average molecular weights were estimated using a logarithmic expression. Results showed that the intrinsic viscosities (molecular weights) increased linearly with extraction temperature over a range from 10 to 40 dL/g (1 to 8 × 106) and that the molecular weight distribution was log normal. Mass balances both before and after extraction indicated that less than 0.3% of the material had a molecular weight less than 106 and that less than 0.1% of the material was gel. Zero shear viscometry of bulk fractionated polymer and powdered whole polymers confirmed that capillary viscometry increasingly under‐estimates the true intrinsic viscosities as the polymer chain lengths (molecular shear forces) increase. Indeed, the actual molecular weights ranged from about 2–14 × 106. Knowledge of the molecular weight distribution of bulk products and the presence of either volatiles or crosslinked networks is critical for the continued design and development of superior wearing and fatigueresistant implants.
Textile arterial prostheses: Is water permeability equivalent to porosity?
Authors: Guidoin Robert , King Martin , Marceau Daniel , Cardou Alain , De La Faye Dominique , Legendre Jean‐Michel , Blais Pierre
Published: December 2004

Porosity and water permeability are two distinct terms that describe different characteristics of vascular prostheses. The porosity is a measure of the void fraction within the prosthesis wall and is believed to give a rough prediction of the capacity of the graft to anchor newly formed surrounding tissue after implantation, whereas the water permeability indicates the rate at which water can flow through the prosthesis wall and, when measured under physiological pressure conditions, provides the surgeon with information about the need for preclotting prior to implantation. The literature has not always clearly distinguished between these two terms, and some authors in fact have suggested that they both refer to the same property of a prosthesis. In an attempt to clarify the issue, porosity and water permeability measurements were made on 34 commercial vascular prostheses having different textile constructions. Linear regression analysis demonstrated that these two characteristics are only weakly related (r = 0.59). It is therefore recommended that the current draft standards for such devices reference both properties: porosity and water permeability.
A calorimetric study of the interaction of synthetic phospholipid liposomes with lipid‐soluble small molecules used as dental materials and devices
Authors: Fujisawa Seiichiro , Kadoma Yoshinori , Masuhara Eiichi
Published: December 2004

The interaction of 22 lipid‐soluble small molecules, widely used in dental materials and devices, with synthetic phospholipid liposomes, was investigated by the application of differential scanning calorimetry (DSC), in order to clarify the mechanism of small molecules in biological systems. Dimyristoyl phosphatidyl choline (DMPC) and dipalmitoyl phosphatidyl choline (DPPC) were used as lipids. The interaction of various monomers with liposomes has been reported by us in this journal.1 In this experiment, various compounds such as redox‐initiator, photo‐initiator or photo‐sensitizer, inhibitor, root‐canal disinfectant, cement‐base materials (eugenol and 2‐ethoxybenzoic acid) etc., were investigated. From changes in the phase transition temperature (T), enthalpy (ΔHkcal mol−1) and H/HHW values of both DMPC and DPPC liposomes induced by these molecules, it was concluded that aromatic tertiary amine, benzoyl peroxide and hydroquinone monomethyl ether had a relatively large effect on liposomes, and that in phenol derivatives, m‐cresol and p‐chlorophenol had a large effect on liposomes compared to phenol. Eugenol used as dental cement also had a large effect on liposomes due to its high hydrophobicity. Changes in the transition properties of liposomes induced by small molecules (characterized by shift of T to a lower temperature, an increase or decrease in cooperativity (H/HHW), and a decrease in ΔH of a endothermic peak) seemed to be related to biological activities.
A kinetic study on the effects of anticoagulants on the interaction of fibrinogen and thrombin
Authors: Nakanishi Eiji , Sato Hiroko , Nakajima Akio
Published: December 2004

The inhibitory effect of heparin and antithrombin III (AT) on the interaction of fibrinogen and thrombin was investigated in preference to studies on heparinizing devices. The turbidity was measured kinetically as a measure of the concentration of fibrin polymer formed in the system. It was found that AT did not act on fibrinogen but, rather, on thrombin, and the main role of heparin is to accelerate the AT‐thrombin reaction. On the other hand, dextran sulfate (DSc) did not accelerate the AT‐thrombin reaction. When heparin and AT were incubated with thrombin, inhibition did not depend on the mixing order but on the incubation time. Thus, a ternary complex of heparin, AT, and thrombin was supposed to form for the inhibition. The reaction of heparin with fibrinogen and thrombin in the presence of AT was well‐explained by assuming a Freundlich‐type adsorption of heparin analogous with the reaction of heparin with fibrinogen.
Polarimetric assay for the determination of the native collagen content of soluble collagen
Authors: Nagelschmidt Manfred , Viell Burckhard
Published: December 2004

Two standardized assays for determining the amount of native collagen in a collagen solution are described which are based on polarimetric measurements. Native collagen content is calculated from the loss of optical rotation during transition from the original to the denatured conformation using constants which were obtained from standard collagen of highest available native collagen content. While Method I gives information on the content of helical collagen, Method II estimates collagen which is resistant to peptic degradation. Both methods are simple to perform and suitable for routine quality control.
Biodegradation of a polyurethane in vitro
Authors: Phua S. K. , Castillo E. , Anderson J. M. , Hiltner A.
Published: December 2004

This study examines the effect of in vitro exposure to enzymes on the performance properties of Biomer®, a segmented polyetherurethane used in a number of blood‐contacting devices such as catheters, heart assist pumps, and chambers for artificial hearts. The ultrathin samples were treated with two proteolytic enzymes, papain and urease, for periods of 1–6 months at 37°C. The treated Biomer® samples were subjected to chemical and physical analysis. Effects of biodegradation by the enzymes were assessed by fatigue tests, gel permeation chromatography (GPC), and attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) analysis. Papain was found to be more effective in degrading the polymer than urease. Mechanisms for enzymic degradation are proposed.
Quantitative bone remodelling resulting from the use of porous dental implants
Authors: Keller J. C. , Young F. A. , Natiella J. R.
Published: December 2004

Histomorphometric analyses were used to quantitatively determine the patterns of bony ingrowth which resulted from the placement of porous‐surfaced dental implants into the mandibles of Rhesus monkeys for up to 74 months utilizing a two‐stage approach. Quantitative histopathologic evaluations were made using ground section microscopy. Implant stability resulting from bone remodelling and ingrowth occurred to varying degrees with all implants. Bone ingrowth occurred from medullary trabeculae and contact with the adjacent cortical plates. Quantitative histomorphometric analyses revealed that in only one case was the bone ingrowth into the available internal pores less than 45%. Minimal fibrous connective tissue ingrowth was observed in the implant crypts and was not thought to be due to micromotion. The observed bone remodelling indicated a favorable prognosis for long‐term implant performance.
Collagen at interfaces II: Competitive adsorption of collagen against albumin and fibrinogen
Authors: Deyme Michel , Baszkin Adam , Proust Jacques Emile , Perez Eric , Albrecht Geneviève , Boissonnade Marie Martine
Published: December 2004

Adsorption of chemically radiolabeled [14C] collagen from binary mixtures with albumin or fibrinogen was studied on the solution/air and solution/polyethylene interfaces and revealed the preferential adsorption of albumin. This phenomenon is confirmed by the data of surface tension measurements of single protein, collagen‐albumin, and collagen‐fibrinogen solutions. Desorption experiments clearly show that more irreversibly adsorbed collagen was found on polyethylene surfaces when adsorption was performed from collagen‐fibrinogen than from collagen‐albumin solutions. The combined adsorption‐desorption and the surface tension data show that competitive adsorption of collagen at the hydrophobic surfaces is strongly influenced by the surface tension properties of the proteins in solution.
Water sorption of polymethacrylate networks: Bis‐GMA/TEGDM copolymers
Authors: Kalachandra S. , Turner D. T.
Published: December 2004

Polymethacrylate networks were made by copolymerization of a range of compositions of bis‐GMA and triethylene glycoldimethacrylate (TEGDM). Polymerization was initiated both by heating with benzoyl peroxide or by photopolymerization (λ > 400 nm) using camphoroquinone as sensitizer. The uptake of water increased from 3 to 6% as the proportion of TEGDM increased from 0 to 1.0. Intermediate compositions took up less water than would be predicted from the law of mixtures. Volumetric changes were determined and clinical significance discussed. A copolymer prepared by photopolymerization took up more water as the temperature was increased from 24–60°C. In this range, values of the diffusion coefficient (D) conformed to the Arrhenius equation, D = D0 exp (−E/RT), giving E = 42–46 kJ/mol and D0 = 0.13 cm2 s−1.
Ion implantation of surgical Ti‐6Al‐4V for improved resistance to wear‐accelerated corrosion
Authors: Buchanan R. A. , Rigney E. D. , Williams J. M.
Published: December 2004

The influence of nitrogen‐ion implantation on the wear‐accelerated corrosion behavior of surgical Ti‐6Al‐4V was studied. Non‐passivated and prepassivated unimplanted Ti‐6Al‐4V specimens were employed as controls for comparison. Corrosion rates as a function of time at open‐circuit corrosion potentials were electrochemically measured in saline and serum solutions under both static and wear conditions. The wear parameters simulated those of a total artificial hip under average walking conditions. The results indicated that prepassivation of the control material was beneficial under static‐corrosion conditions, but not under wear‐corrosion conditions. The nitrogen‐ion implantation process was found to significantly improve the material's resistance to wear‐acceler‐ated corrosion in both saline and serum solutions.
Vascular graft‐associated complement activation and leukocyte adhesion in an artificial circulation
Authors: Kottke‐Marchant Kandice , Anderson James M. , Miller Kathleen M. , Marchant Roger E. , Lazarus Hillard
Published: December 2004

Complement‐associated leukocyte adhesion appears to be a consistent in vitro and in vivo finding for many types of polymers; however, very little work has been done on the interaction of leukocytes with vascular graft materials. An in vitro perfusion system was used to study complement and leukocyte activation associated with the following vascular graft materials when tested with human blood: expanded polytetrafluoroethylene (ePTFE), crimped Dacron Bionit (DB) and preclotted Dacron Bionit. A decrease in the total leukocyte concentration with perfusion time was seen for all materials tested, and paralleled leukocyte adhesion to the graft surface as observed by scanning electron microscopy. The most dramatic decrease in leukocyte concentration was observed for the interaction of heparinized whole blood with Dacron. This was due to a selective decrease in neutrophils and monocytes, and was correlated with an increase in both leukocyte adhesiveness and complement activation, as measured by C5a elevation. Inhibiting complement activation by use of the anticoagulant, sodium citrate, curtailed Dacron‐induced leukocyte adhesion. Little leukocyte or complement activation was observed for ePTFE or the silicone rubber control regardless of the anticoagulant used.
Aging test and dynamic fatigue test of apatite‐wollastonite‐containing glass ceramics and dense hydroxyapatite
Authors: Kitsugi Toshiaki , Yamamuro Takao , Nakamura Takashi , Kakutani Yoshiaki , Hayashi Tetuya , Ito Setsuro , Kokubo Tadashi , Takagi Masataka , Shibuya Takehiro
Published: December 2004

The purpose of this study is to examine the changes in mechanical strength of two bioactive ceramics in living tissue. An aging test and dynamic fatigue test were performed using apatite‐wollastonite‐containing glass ceramics (A · W – GC) and dense hydroxyapatite (HA). Specimens (5mm × 5mm × 25mm, abraded with No. 2000 Al2O3 powder) were implanted into subcutaneous tissue of rats for varying periods of time. The bending strength of aged samples was measured by the three‐point loading method. The bending strength of A · W – GC was greater than that of HA (P < 0.001). There was no reduction in bending strength for both A · W – GC and HA in living tissue. The n value of both A · W – GC and HA did not decrease significantly after implantation as assessed by the results of the dynamic fatigue test according to analysis of covariance. SEM‐EPMA showed that Si and Mg contents decreased, Ca content did not change, while P content increased in the surface of A · W – GC. The area where x‐ray intensity changed increased moderately after implantation. There were no changes in Ca and P at the interface between HA and soft tissue. In macroscopic and microscopic observations, specimens were found to be encapsulated with a thin layer of connective tissue. Foreign body giant cells, obteoblasts, or osteoclasts were not observed in the soft tissue. There was no bonding between ceramics and soft tissue.
The influence of bioglass on the growth of fibroblasts
Authors: Matsuda T. , Yamauchi K. , Ito G.
Published: December 2004

The influence of Bioglass (BG) on the growth of L cells was studied by means of tissue culture, to get an idea on its bonebonding mechanism. Growth rate of L cells on BG was lower than that on the control silica glass (SG). L cells on BG diminished in size and took up long and slender polygonal shapes with radially spread long pseudopods, which probably meant that the cell cycle was detained at the synthetic period. From these findings, BG is thought to have an inhibitory effect on the growth of L cells, which might arrest the fibrous tissue encapsulation and allow bonding with bone.
The use of coral as a bone graft substitute
Authors: Guillemin G. , Patat J.‐L. , Fournie J. , Chetail M.
Published: December 2004

Experiments have been performed to investigate the use of coral skeletons as bone graft substitutes. Skeletal fragments of different coral genera were implanted into cortical and spongy bone defects and used to bridge transcortical resections in the femur. The implant site was monitored for up to 18 months. Radiographically, both cortical and spongy bone defects were at least partially filled by new bone after 8 weeks while the implants underwent continuous resorption. Coral resorption and replacement by new tissue was also observed in the transcortical resections. The process of resorption was attributed to the enzymatic attack, especially carboanhydrase. This was confirmed by experiments in which dogs were implanted with coral in transcortical resections and treated daily with acetazolamide, a carboanhydrase inhibitor; the absorption appeared delayed and the reseections failed to heal.
An in vitro study of the adhesion of blood platelets onto vascular catheters. Part I
Authors: Engbers G. H. M. , Dost L. , Hennink W. E. , Aarts P. A. M. M. , Sixma J. J. , Feijen J.
Published: December 2004

The adhesion of human blood platelets onto vascular catheters was studied using a specially designed perfusion chamber. Polyurethane catheters were exposed to citrated human blood for different periods (up to 20 min) and at different wall shear rates (190, 260, 330 sec−1). The rate of platelet adhesion was determined using 111In‐labeled platelets, while the morphology of adhering platelets was investigated using scanning electron microscopy. A linear increase in platelet adhesion was found within the first 10 min of perfusion, after which a plateau value was reached. The number of adhering platelets did not vary significantly with the shear rates applied, which may indicate that within the range of shear rates studied, the adhesion of platelets onto the catheter surface is mainly determined by the rate of the reaction between the platelets and the material surface. Catheters coated with a conjugate of heparin and albumin showed a four‐ to five‐fold reduction in platelet adhesion as compared to uncoated catheters. This reduction in platelet adhesion was not only due to the presence of albumin moieties at the surface but also to the presence of heparin residues in the adsorbed albumin‐heparin conjugate.
Adsorption of low density lipoproteins onto selected biomedical polymers
Authors: Dong D. E. , Andrade J. D. , Coleman D. L.
Published: December 2004

This study examines the interaction of human low density lipoprotein (LDL) with a select group of biomedical polymers. The adsorption characteristics of LDL on cured filler‐free poly(dimethyl Siloxane) (C‐PDMS), Biomer, Cardiomat 610, Kraton 1650, poly(hydroxyethyl methacrylate) (PHEMA) and glass are presented. Adsorption of LDL to charged hydrophilic glass control surfaces occurred rapidly, reaching plateau concentrations within one minute (0.19 ± 0.01 ug/cm2). Adsorption of LDL to polymer surfaces appeared to be dependent upon both the polymer hydrophobicity (or apolar nature), and flexibility (or dynamic nature) at the interface. Increased surface concentrations were observed for Biomer (0.32 ± 0.01 ug/cm2) as well as other polymers which exhibited both hydrophobic and elastomeric próperties. Temperature changes between 25°C and 37°C were found to significantly influence the surface concentration of LDL on Biomer (0.16 ± 0.01 ug/cm2 at 25°C versus 0.32 ± 0.01 ug/cm2 at 37°C). A lipid core phase transition at 36°C was believed to be responsible for the temperature influence. Preliminary competitive adsorption studies of LDL with albumin (HSA) and serum on silicone surfaces suggests that LDL adsorption occurred rapidly and preferentially (0.25 ± 0.01 ug/cm2 for LDL alone; 0.33 ± 0.01 ug/cm2 for LDL + HSA; 0.15 ± 0.01 ug/cm2 LDL + serum). Preliminary studies on the role of LDL in calcification were not conclusive. It can be concluded that LDL adsorption is dependent upon polymer hydrophobicity, flexibility and temperature. Competitive adsorption experiments suggests that LDL may have substantial influence on protein adsorption.
Thick‐section histometry of porous hydroxyapatite implants using backscattered electron imaging
Authors: Holmes Ralph E. , Hagler Herbert K. , Coletta Craig A.
Published: December 2004

A histometry system has been developed to measure bone ingrowth into porous hydroxyapatite implants utilizing the backscattered electron image of thick sections. The system consists of a scanning electron microscope (SEM) with backscattered electron detector, digital beam controller, minicomputer based image digitization, and microcomputer based image processing, point counting, and lineal analysis. The SEM backscattered electron imaging mode yields high tissue contrast and sharp tissue boundaries, substantially reducing the lost cap and projection effect errors of thick sections. High‐resolution digitization of the image substantially reduces the standard error of the estimates. By using the digitized image the tedious process of filtering artifacts and recording actual point counts, intersections, and intercept lengths is delegated to computer software. Performance of this system in a recent study demonstrated substantial ease of operator use and speed of measurement. In the absence of a digital beam controller an inexpensive video digitizer circuit board may be used to digitize photographic prints of the SEM images. The combination of increased accuracy, precision, operator ease, and speed suggests that this system can be useful for soft tissue‐bone‐implant histometry.
Chemically modified collagen: A natural biomaterial for tissue replacement
Authors: Nimni M. E. , Cheung D. , Strates B. , Kodama M. , Sheikh K.
Published: December 2004

Glutaraldehyde crosslinking of native or reconstituted collagen fibrils and tissues rich in collagen significantly reduces biodegradation. Other aldehydes are less efficient than glutaraldehyde in generating chemically, biologically, and thermally stable crosslinks. Tissues crosslinked with glutaraldehyde retain many of the viscoelastic properties of the native collagen fibrillar network which render them suitable for bioprostheses. Implants of collagenous materials crosslinked with glutaraldehyde are subject long‐term to calcification, biodegradation, and low‐grade immune reactions. We have attempted to overcome these problems by enhancing crosslinking through (a) bridging of activated carboxyl groups with diamines and (b) using glutaraldehyde to crosslink the ϵ‐NH2 groups in collagen and the unreacted amines introduced by aliphatic diamines. This crosslinking reduces tissue degradation and nearly eliminates humoral antibody induction. Covalent binding of diphosphonates, specifically 3‐amino‐1‐hydroxypropane‐1, 1‐diphosphonic acid (3‐APD), and chondroitin sulfate to collagen or to the crosslink‐enhanced collagen network reduces its potential for calcification. Platelet aggregation is also reduced by glutaraldehyde crosslinking and nearly eliminated by the covalent binding of chondroitin sulfate to collagen. The cytotoxicity of residual glutaraldehyde—leaching through the interstices of the collagen fibrils or the tissue matrix—and of reactive aldehydes associated with the bound polymeric glutaraldehyde can be minimized by neutralization and thorough rinsing after crosslinking and storage in a nontoxic bacteriostatic solution.
The effect of surface preparation on metal/bone cement interfacial strength
Authors: Bundy K. J. , Penn R. W.
Published: December 2004

This study is concerned with finding practical ways for strengthening metal/bone cement (M/BC) interfaces via surface alterations and identifying fundamental mechanisms underlying M/BC adherence. Shear strengths have been inferred from torsion tests using shear lag analysis. The variables examined with regard to their effects on interfacial strength are substrate material, surface roughness, interface porosity, passivation and sterilization, surface cleaning procedures, and use of bone cement precoated metals. M/BC interfaces can be substantially strengthened by applying the bone cement to the metal with high pressure. This would be a practical way to strengthen interfaces for precoated implants. The acrylic polymerized in vivo would employ the usual low pressure method. Otherwise, the main method for improving M/BC interfaces is through changing surface topography. Cleaning or chemical treatments have relatively minor effects. Roughened surfaces, as expected, produce stronger interfaces. Dramatic strength improvements occurred with a porous arc plasma sprayed layer on the substrate. Surprisingly, highly polished surfaces also improve interface strength (compared to less polished surfaces). The hypothesis is advanced that M/BC adherence depends upon superposition of mechanical interlocking and atomic interaction effects, with the latter predominating for finer finishes and vice versa. Differences exist between materials which are independent of roughness.
Effects of alkyl grafting on surface properties and blood compatibility of polyurethane block copolymers
Authors: Grasel Timothy G. , Pierce Jeffrey A. , Cooper Stuart L.
Published: December 2004

In order to probe the factors which affect the interaction between the surface of a multiphase polyurethane material and blood, a series of butanediol‐chain‐extended polyetherurethanes was synthesized. These polyurethanes contained different levels of phase separation, produced by systematically varying the hard segment chemical structure by grafting ethyl and octadecyl groups to the urethane nitrogen atom. Surface characterization using high vacuum, air‐equilibrated, and water‐equilibrated methods was performed. A canine ex vivo arteriovenous series shunt was used to monitor initial platelet and fibrinogen deposition on these polymers. The ex vivo response to these materials, along with contact angle and ESCA surface chemistry, was found to vary with the degree of alkyl derivatization. This study demonstrated that an increase in the degree of phase separation and also the incorporation of long chain (C18) alkyl groups can affect surface properties and improve the short‐term blood compatibility of the underivatized polyurethane.
Adherence of Streptococcus mutans to implant materials
Authors: Fujioka‐Hirai Yumi , Akagawa Yasumasa , Minagi Shogo , Tsuru Hiromichi , Miyake Yoichiro , Suginaka Hidekazu
Published: December 2004

The adherence of Streptococcus mutans OMZ‐176 to six implant materials (polycrystal alumina, single‐crystal alumina, titanium alloy, cobalt‐chromium‐molybdenum alloy, hydroxyapatite, and heat‐curing polymethylmethacrylate resin) was studied in vitro. The change of free energy, which corresponds to the adherence process, was also evaluated for hydrophobic interaction. Adherence of S. mutans to poly‐crystal alumina was lower than adherence to other materials. The adherence of S. mutans to the test materials was highly correlated with the change of free energy, which suggests that hydrophobic interaction plays an important role in the adherence of S. mutans to the implant materials.
Prostacyclin immobilized albuminated surfaces
Authors: Joseph George , Sharma C. P.
Published: December 2004

The adhered platelets on artificial surfaces play a crucial role in inducing thrombosis. Therefore, it is very much desirable to have surfaces which can effectively retard platelet adhesion and aggregation. Prostaglandins like PGI2, PGE1 and PGD2 possesses potent antiplatelet activity, but have very short half life. A chemically stable prostacyclin analog, 10,10‐difluoro‐13‐dehydroprostacyclin (DF2—PGI2) seems to be promising. Polyelectrolyte (PE) synthesized from natural poly cis‐1,4 isoprene has also been found to possess outstanding anticoagulant and antiplatelet activity. Modification of polyethurerethane urea (PEUU) by immobilizing DF2—PGI2 and polyelectrolyte in various combinations using glow discharge technique has been attempted. Surfaces thus modified showed negligible platelet adherence. The inhibition of platelet adherence in presence of inducing agents like fibrinogen, thrombin and ADP was also remarkable. The interactions of albumin and fibrinogen with the modified surfaces were studied using 125I labelled proteins.
Alternative techniques of seeding cultured endothelial cells to ePTFE grafts of different diameters, porosities, and surfaces
Authors: Lindblad Bengt , Wright Seth W. , Sell Ruth L. , Burkel William E. , Graham Linda M. , Stanley James C.
Published: December 2004

Attachment of 111Indium‐oxine labeled cultured canine venous endothelial cells to expanded polytetrafluorethylene (ePTFE) grafts was evaluated in vitro. Three alternative seeding techniques were studied in grafts having different diameters, porosities, and surfaces, including: (I) manual milking of blood contiaining endothelial cells within the graft; (II) a two‐step procedure of incubating grafts initially with blood and then with an endothelial cell suspension; and (III) mechanical spinning of grafts filled with blood containing endothelium. Method II had significantly higher cell attachment to the graft (11.6%) than did Method I (1.5%) or III (4.7%). A somewhat higher seeding efficiency was noted in 10‐mm‐I. D. grafts (11.6%) compared to 6‐mm‐I. D. grafts (6.3%). Different graft porosity, created by altering internodal distances, did not cause significant changes in cell attachment (10 m̈m, 13.4%, 30 m̈m, 6.3%; 90 m̈, 16.0%). Fibronectin‐coated surfaces, which should have enhanced cell adhesion, demonstrated a 6.0% cell attachment, a lower efficiency than the 11.6% observed with a blood coating alone. Acetone‐soaked surfaces, which should have predictably exhibited less hydrophobicity, produced quite variable attachments (range 3.4 to 59.7%, mean 23.4%). In the present investigation the best seeding technique was method II, the two‐step incubation procedure. Consistant differences were not noted with various ePTFE graft configurations or surfaces.
Carbon/graphite fiber reinforced poly(methyl methacrylate): Properties under dry and wet conditions
Authors: Ekstrand Karl , Ruyter I. Eystein , Wellendorf Hanne
Published: December 2004

The flexural properties of poly(methyl methacrylate) (PMMA) reinforced with carbon/graphite (C/G) fibers with three different surface treatments were investigated by transverse bend testing after dry and wet storage. The fibers used were (1) commercially available fibers, (2) cleaned fibers, and (3) cleaned and sized fibers. The coating agents of commercial unidirectional and braided C/G fibers as well as impurities on C/G fibers for medical uses were characterized by means of high‐performance liquid chromatography (HPLC). The agar overlay technique was used to assess the cytotoxicity of leachable elements from different fibers and processed composites. Composites with both unidirectional and braided tubular C/G fibers were investigated after storage in water. Fracture stress and flexural modulus decreased when “commercial” fibers were used as reinforcing material. Composites with cleaned and sized fibers gave only minor differences in flexural properties after dry and wet storage. By means of SEM micrographs the adhesion behavior of unsized C/G fibers, epoxy sized fibers were assessed. After water storage a substantial part of the cleaned fibers adhered to the matrix material. The adhesion capacity of the other fibers was reduced since the water absorption caused separation of fiber and matrix.
Experimental demonstration of the immunogenicity of silicone–protein complexes
Authors: Kossovsky Nir , Heggers John P. , Robson Martin C.
Published: December 2004

Although silicones, as a class, are nontoxic in animal and tissue studies, implanted silicone prostheses and medical devices are associated with various local and systemic host inflammatory reactions. They also have been associated with a form of autoimmune disease. To test the hypothesis that silicones may evoke an immunologically mediated inflammatory reaction, 10 guinea pigs were stimulated for 1 month with intraperitoneal injections of sterile medical‐grade silicone oil admixed with homologous serum and complete Freund's adjuvant. Ten controls were stimulated with salin. Four additional animals were passively sensitized with splenic homogenates from four sensitized animals. Intradermal antigenic challenges consisted of silicone‐homologous serum, pure silicone, saline‐homologous serum, pure silicone, saline‐homologous serum, and purified protein derivative. Cutaneous reaction patterns were graded grossly and microscopically. Silicone‐serum and purified protein derivative antigens evoked three to four times greater palpable lesions in all 10 actively and all 4 passively sensitized animals at approximately 24 h compared to controls. Biopsies showed a moderate to marked lymphocytic infiltrate. Control sites and naive animals showed only edema at the challenge sites. The data suggest that silicone‐protein complexes are potentially immunogenic.
Pluronic F‐127 gel preparation as an artificial skin in the treatment of third‐degree burns in pigs
Authors: Nalbandian Robert M. , Henry Raymond L. , Balko Kenneth W. , Adams Dennis V. , Neuman Norwood R.
Published: December 2004

A blinded study was designed to provide qualitative and quantitative evaluation on the possible therapeutic benefits of the use of Pluronic® Polyol F‐127 as a substitute skin in standardized third‐degree thermal burns. Three separate burns, approximately 1600 mm2, were induced on the shaved backs of young, anesthetized pigs. Each animal served as its own control. One burn site was left untreated while the other two sites were covered with coded preparations of the Pluronic® F‐127 gel with additives. Polaroid photographs with a fixed focal‐length camera were taken of all burn sites for planimetry analysis. Biopsies taken confirmed that third‐degree burns were achieved. The pigs were followed for 30 days. The rate of healing of third‐degree thermal burns was significantly accelerated over control sites when treated with Pluronic® Polyol F‐127 plus propylene glycol. When the bacteriostatic agent Garamycin was also added, the rate of healing remained significantly better than untreated controls. With the addition of Piracetam, burn wound healing was actually retarded within 30 days, when applied topically. Thus, wound healing was both accelerated and retarded as a function of the particular Pluronic® preparation used to treat specific burn sites. This experimental modulation of wound healing suggests that the non‐ionic poloxamer, Pluronic F‐127, can significantly enhance the rate of wound healing by some unknown mechanism, possibly by stimulation of epithelial growth factor (EGF).
The influence of surface area on the in vitro cytotoxicity of a range of dental materials
Authors: Meryon Sylvia Diana
Published: December 2004

In the toxicity testing of dental materials the quantity of material used may have a profound influence on the biological response obtained. This was investigated in vitro by assessing the cytotoxicity of equal volumes of nine materials in artificial cavities of three different diameters, chosen to cover the range found in vivo. With seven materials there was a significant increase in toxicity with increasing surface area. The pattern of response of different materials within specific groups was fairly uniform. The degree of toxicity of the test materials relative to controls was also investigated. From the data obtained it is apparent that the maximum cavity diameter appropriate for the material under test must be considered when evaluating the toxicity of dental materials.
Blood hemolysis by PTFE and polyurethane vascular prostheses in an in vitro circuit
Authors: Martz Hugues , Paynter Royston , Losier Michel , Domurado Dominique , Forest Jean‐Claude , Guidoin Robert
Published: December 2004

In order to improve understanding of the appearance of bright yellow stains in vivo (consecutive to the absorption of bilirubin) on a novel microporous, hydrophilic polyetherurethaneurea vascular prosthesis, the in vitro hemolytic activity of the material was compared with expanded polytetrafluoroethylene and silicone rubber. The results show that the tendency of the polyetherurethaneurea to produce free hemoglobin is low, so that the yellow staining observed is likely to be a result of the contact between the polymer and thrombi: Bilirubin is produced because of hemoglobin degradation in the thrombi rather than an active hemolysis on the surface of the prosthesis itself.
Release of corrosion products by F‐75 cobalt base alloy in the rat. III: Effects of a carbon surface coating
Authors: Black J. , Oppenheimer P. , Morris D. M. , Peduto A. M. , Clark C. C.
Published: December 2004

A pyrolytic carbon coating was applied to F‐75 chromium‐cobalt‐molybdenum alloy in an effort to reduce the release of corrosion products in vivo. After intramuscular implantation in the rat, a complex pattern of serum and urine concentration elevations of chromium, cobalt, and nickel was seen. The carbon‐coated implants released more chromium and cobalt than uncoated controls, as seen by significantly elevated metal concentrations in serum and urine. Animals receiving carbon‐coated implants showed a high rate of recurrent implant site inflammation. Neoplastic infiltration of the implant site occurred in 3 out of 24 animals with coated implants, but not in any of the 16 animals which received either uncoated F‐75 microsphere or poly(ethylene) particulate implants.
Intraocular biocompatibility of hydroxyethyl methacrylate and methacrylic acid copolymer/partially hydrolyzed poly(2‐hydroxyethyl methacrylate)
Authors: Smetana K. , Šulc J. , Krčová Z. , Pitrová Š.
Published: December 2004

A strip of partially hydrolyzed poly (2‐hydroxyethyl methacrylate) containing 65%–75% H2O was implanted into the anterior eye chamber of 11 Chinchilla rabbits. No pathological changes were found in the iris or in the ciliary body. The pathological findings in the cornea accompanying implanation of a hydrogel strip to the anterior chamber were rare and not significant. The low occurrence of the foreign body giant multinucleate cells was observed on the implant surface 6 months after the implantation. Favorable properties of this hydrogel depend probably on its high water and acidic groups content.
SEM‐EPMA observation of three types of apatite‐containing glass‐ceramics implanted in bone: The variance of a Ca‐P‐rich layer
Authors: Kitsugi Toshiaki , Nakamura Takashi , Yamamura Takao , Kokubu Tadashi , Shibuya Takehiro , Takagi Masataka
Published: December 2004

The progressive changes of a Ca‐P‐rich layer between bone and three types of apatite‐containing glass‐ceramics of the same chemical composition: MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF2 0.5 (in weight ratio) were examined. Plates (15 mm × 10 mm × 2 mm, mirror surface) containing apatite (35 wt%) (designated A‐GC), apatite (35 wt%) and wollastonite (40 wt%) (designated A · W‐GC), and apatite (20 wt%), wollastonite (55 wt%), and whitlockite (15 wt%) (designated A · W · CP‐GC) were prepared. They were implanted into the tibia of mature male rabbits for 5 days, 10 days, 20 days, 30 days, 60 days, 6 months, and 12 months. All three types of glass‐ceramics showed direct bonding to the bone 30 days after implantation. It was observed by SEM‐EPMA 30 days after implantation that Si and Mg content decreased, P content increased, and Ca content did not change across the reactive zone from the glass‐ceramics to bone. The level of P and Si in the A · W · CP‐GC changed five days after implantation. In A · W‐GC and A‐GC, a little change in P and Si levels was observed between 10 and 20 days after implantation. The width of reactive zone was narrowest with A‐GC, wider with A · W‐GC, and widest with A · W · CP‐GC. The dissolution of glass‐ceramics stopped 6 months after implantation. This phenomenon shows that the glass‐ceramics may be suitable for clinical use.
Morphological study of biodegradable PEO/PLA block copolymers
Authors: Younes Hani , Cohn Daniel
Published: December 2004

A series of PEO/PLA copolymers, covering a wide range of compositions and segmental lengths, was synthesized, and their morphology was investigated by means of DSC and IR studies. For matrices comprising PEO chains with molecular weights below 3400, no soft‐segment crystallinity was detected. When long hard segments were present, essentially monophasic, semicrystalline polymers were obtained, with PLA blocks melting around 130°C. Polymers containing longer soft segments (PEO 6000) exhibited a two‐phase matrix, with both components being able to crystallize. The relative degree of crystallinity of PEO and PLA blocks was also determined. The thermal history of the sample strongly affected the morphology of the matrix, especially when both blocks were long enough to crystallize. To further explore these polymers, solvent cast films were prepared and their morphology assessed. Casting from acetone, which is an excellent solvent for PLA, resulted in hard blocks exhibiting lower degrees of crystallinity, while methanol had a similar effect on PEO soft segments.
Effect of molecular weight (Mw) ofN‐(2‐hydroxypropyl)methacrylamide copolymers on body distribution and rate of excretion after subcutaneous, intraperitoneal, and intravenous administration to rats
Authors: Seymour L. W. , Duncan R. , Strohalm J. , Kopeček J.
Published: December 2004

A copolymer ofN‐(2‐hydroxypropyl) methacrylamide (HPMA) andN‐methacryloyltyrosinamide was prepared and fractionated using Sepharose 4B/6B (1:1) chromatography to produce eight HPMA copolymer fractions of narrow polydispersity and mean molecular weight (Mw) ranging from 12 to 778 kD. These fractions were radioiodinated and injected intravenously, subcutaneously, and intraperitoneally into rats. Their bloodstream‐concentration profiles were monitored and rates of excretion assessed. Following intravenous administration the circulating blood volume available to the copolymers was not molecular‐weight‐dependent. A molecular‐weight threshold limiting glomerular filtration was identified at approximately 45 kD, and preparations greater than this threshold were lost from the bloodstream only slowly by extravasation. Molecular weight did not influence the movement of copolymers from the peritoneal compartment to the bloodstream after intraperitoneal injection. The transfer rates observed could be accounted for by bulk phase lymphatic drainage alone, no transcapillary routes being implicated. Following subcutaneous administration the largest HPMA copolymer fraction (Mw= 778 kD, diameter approximately 30 nm) showed increased retention at the site of injection, approximately 20% of the dose remaining there after 21 days. This could result from physical restriction of movement or from internalization into local phagocytic cells. The smaller copolymer fractions moved readily into the bloodstream whence they were either lost in the urine or they gradually penetrated into other tissues and organs. Long‐term (21 days) body distribution of copolymers following both intraperitoneal and subcutaneous administration showed size‐dependent accumulation in organs of the reticuloendothelial system.
Magnetically enhanced insulin release in diabetic rats
Authors: Kost Joseph , Wolfrum Jackie , Langer Robert
Published: December 2004

Polymer matrices containing insulin and embedded magnets were implanted subcutaneously in diabetic rats for 51 days. Passive release of insulin from the polymer resulted in a decrease in the blood glucose level. When the diabetic rats were exposed to an oscillating magnetic field, the blood glucose levels were additionally lowered by nearly 30%. No statistically significant effect in blood glucose decrease was observed in four different sets of control animals subjected to the magnetic field. Because of the very small size of the implants, they may, with additional study, provide an alternative to current modes of therapy using programmable implantable infusion pumps.
Interaction between erythrocytes and a perfluorochemical blood substitute
Authors: Tuliani Vinod V. , O'Rear Edgar A. , Fung B. M. , Sierra Barry D.
Published: December 2004

Perfluorochemicals (PFCs) are being widely developed for use as erythrocyte substitutes to carry oxygen to tissue in acute crises. Oxypherol, a commercially available PFC preparation commonly used for animal tests, reduces erythrocyte deformability in the presence of plasma. This undesirable effect further complicates oxygen delivery by erythrocytes. Our experiments indicate that one or more plasma proteins must be present to observe Oxypherol‐induced reduction in erythrocyte deformability, but the latter is not protein specific. Neither platelet activation nor enhanced protein adsorption could account for the mechanism of altered erythrocyte flexibility. Using fluorine‐19 NMR, it was found that a small amount of Oxypherol droplets is adsorbed on the surface of the erythrocytes. The amount of adsorbed droplets increases when Oxypherol is incubated with the erythrocytes in the presence of plasma, in parallel with a decrease in erythrocyte deformability. Therefore, it seems likely that the loss of deformability of the erythrocytes is caused by the adsorption of small Oxypherol droplets on the erythrocytes.
The tensile strength of natural and chemically modified bovine pericardium
Authors: Crofts C. E. , Trowbridge E. A.
Published: December 2004

Nondestructive and destructive uniaxial load tests were performed on natural and chemically modified bovine pericardium. Five specimens were selected from the same sites in different pericardial sacs by using a template. The mean maximum extension of one particular site in both the natural and chemically modified material was significantly greater than that of the other positions at a stress level of 0.6 Nmm.−2 The maximum extensibility of the fixed tissue was significantly greater (p < 0.01) than that of the natural tissue. There was also an anatomical variation in tensile strength of the natural material which was retained after chemical modification. However, the overall tensile strength of the pericardium was not increased by this procedure. In contrast, glutaraldehyde fixation did increase the percentage strain at which fracture of this biomaterial occurred.