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  • Articles  (636)
  • Polymer and Materials Science  (636)
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  • Chemical Engineering
  • Electronic structure and strongly correlated systems
  • 1985-1989  (636)
  • Technology  (636)
  • 1
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 63-80 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study of the fracture behavior of poly-(methyl methacrylate) (PMMA) bone cement reinforced with short ultra-high-molecular-weight polyethylene (Spectra 900) fibers is presented. Linear elastic and nonlinear elastic fracture mechanics results indicate that a significant reinforcing effect is obtained at fiber contents as low as 1% by weight, but beyond that concentration a plateau value is reached and the fracture toughness becomes insensitive to fiber content. The flexural strength and modulus are apparently not improved by the incorporation of polyethylene fibers in the acrylic cement, probably because of the presence of voids, the poor mixing practice and the weakness of the fiber/ matrix interfacial bond. The present polyethylene/PMMA composite presents several advantages as compared to other composite cements, but overall the mechanical performance of this system resembles that of Kevlar 29/PMMA cement, with a few differences. Scanning electron microscopy reveals characteristic micromechanisms of energy absorption in Spectra 900/PMMA bone cement. A scheme for the strength of random fiber-reinforced composites, which is a simple extension of the Kelly and Tyson model for the strength of unidirectional composites, is presented and discussed. Young's modulus and the fracture toughness results are discussed in the framework of existing theories. More fundamental modeling treatments are needed in terms of fracture micromechanisms to understand and optimize the various mechanical properties with respect to structural parameters and cement preparation technique.
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  • 2
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 137-137 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 3
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 253-266 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We report the biocompatibility in the rat brain of a controlled-release, biodegradable polymer, the polyanhydride poly-[bis(p-carboxyphenoxy)propane-sebacic acid] copolymer (PCPP-SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood - brain barrier and avoiding the consequences of having to administer toxic doses systemically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP-SA was compared to that seen with other standard neurosurgical implants. Fifty-six adult Sprague-Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP-SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP-SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP-SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard neurosurgical implants.
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  • 4
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 339-350 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study was designed to examine the heterogeneity of the adsorption of proteins onto metallic materials. The materials studied included pure Ag, Au, and Ti and sintered Ag 10% Ti and Ag 10% Ta. The distribution of the protein adsorption was studied using I-125 labeled albumin detected by microautoradiography. The surface morphology of the specimens was examined in the scanning electron microscope prior to exposure to the protein solution. A heterogeneous distribution in albumin adsorption was observed over the Ag surface. Similar regions were observed over parts of the mixed metal specimens, but superimposed on this pattern were distinct regions of very low protein adsorption which appeared to correlate closely with the regions of Ti or Ta observed in the scanning electron microscope. A uniform distribution of adsorbed albumin was observed on the Au and Ti, with Au giving a much denser microautoradiograph than Ti. This work demonstrates that variations in the protein adsorption to heterogeneous materials can be observed on a microscopic scale.
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  • 5
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 399-415 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: No difference in in vitro platelet reactivity was found between an immobilized heparin containing hydrogel (heparin-PVA) and the hydrogel without heparin (PVA), in a variety of experimental assays. There was no significant difference between the heparin-PVA and PVA coated polyethylene tubing in the number of 51Cr-labeled platelets, the extent of 14C serotonin release by the adherent platelets or in the degree of platelet count decrease after 1 h exposure to citrated canine whole blood in a Chandler loop system. Furthermore, adhesion and release values were lower than those observed with the uncoated polyethylene tubing (e.g., 9.3 ± 4.3 plt/103 μ2 on PVA; 18.3 ± 4.6 plt/103 μ2 on polyethylene). There was also no significant difference between heparin-PVA and PVA in bead column retention values with canine blood and with the previously reported washed human platelet adhesion/release values. Thus there appears to be no effect of the immobilized heparin by itself on the in vitro interactions of PVA with platelets, with the reactivity towards platelets dominated by that of the underlying substrate (i.e., PVA).
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  • 6
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 453-453 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 7
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 8
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 9
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 45-61 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Yttrium-oxide-partially-stabilized zirconia (YPSZ) belongs to a new class of ceramics exhibiting an improved toughness when compared to alumina. The toughening mechanism is related to a martensitic-like transformation of tetragonal metastable grains into a monoclinic state occurring at the crack tip. Specific tests showed that YPSZ exhibited a high bending strength (900-1200 MPa), a low Young's modulus (200 GPa), and a high toughness (KIC = 9-10 MN/m3/2). Its average grain size of 0.5 m̈m allows a surface roughness as low as 0.008 m̈m. Sterilization or aging in saline solution at room temperature for 100 days did not affect the toughness of this material. Cylindrical YPSZ samples, manufactured by cold isostatic pressing and sintering, were implanted in the paraspinal muscles in the rat up to 12 weeks. The tissue reaction was evaluated with reference to alumina (ISO requirements) by means of quantitative histomorphometry. No significant differences were found between YPSZ and alumina for both the membrane thickness and cell distributions surrounding the implants.
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  • 10
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 91-104 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An implant may release a drug either by diffusion concurrent with dissolution of the polymeric implant material without depolymerization (Type A) or by bioerosion involving depolymerization (Type B). The Type A material may induce immune response, while the erosion of Type B polymer releases fragments which could cause toxicity problems. It is proposed that a combination of the two types of polymers may attenuate the intensity of immune response and toxicity, because the presence of one in an implant of the same weight reduces the amount of the other. However, it is important to determine first, if sustained delivery may be achieved by such an implant. In this study, partially hydrolyzed poly(vinyl acetate) (PVA) and polycaprolactone (PCL) were chosen as the model Type A, and B polymers, respectively, to evaluate this objective in vitro. Pellet discs were prepared to assess the effects of compression, proportion of PVA to PCL, acetyl content of PVA, PCL hydrolysis catalyst and drug loading, using methylene blue (MB) as a model drug. Results showed that sustained delivery could be effected, but PCL erosion did not occur as planned. Therefore, PCL served only as a passive component of the implant, while PVA was eroded with the release of MB. Consequently, it was inferred that a polymer may not be required as a passive component, which suggested the use of other compounds of known biocompatibility. Tests with insulin in a compressed solid admixture with cholesterol showed that reduction of hyperglycemia in diabetic Wistar rat could be effected reproducibly for at least 2 weeks. Thus, the present study, originally planned to test a proposed concept, indicates that many nonpolymeric materials of known biocompatibility may be suitable for drug delivery implants as well.
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  • 11
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 12
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyethylene terephthalate in textile form (Dacron®) has been used extensively as a surgical implant material for applications such as vascular grafts and percutaneous access devices. It is moderately histocompatible eliciting a chronic inflammatory reaction predominnately in tissue which has grown into the pores of the fabric. Titanium implants on the other hand, induce only the slightest inflammatory response and connective tissue adhesion to the titanium oxide surface is excellent. It was, therefore, hypothesized that a titanium coating on Dacron® fabric might improve its histocompatibility while leaving its desirable mechanical properties unaffected. To test this idea, Dacron® velour specimens were coated with titanium by vacuum deposition and were implanted together with uncoated controls in rabbits subcutis. After various implantation times, the specimens were recovered and the associated tissue was examined histologically. Qualitative and semiquantitative analysis revealed that tissue ingrowth quantity and quality was highly variable, not only between test and control specimens, but also between animals and even between specimens within the same animal. This indicated that there may be a number of factors influencing tissue ingrowth that were not adequately controlled in this study. The titanium coating which was undoubtedly highly oxidized had a profound qualitative and quantitative effect on fibroblast activity (ground substance formation) and fibroblast adhesion to the Dacron® fibers. The results obtained after these short-term implantation periods indicate that titanium coating affects the quality of the interfacing tissue and may actually improve long-term histocompatibility. Long-term studies will have to confirm these preliminary data.
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  • 13
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 283-283 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 14
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    Journal of Biomedical Materials Research 23 (1989), S. 863-881 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A poly-ether-urea-urethane was synthesized by copolymerization of 4,4′-diphenylmethanediisocyanate (MDI), propanediamine, and poly-oxytetra-methylene glycol (M.W. 1000). Two other corresponding copolymers were also synthesized by adding amino terminated poly-amidoamine macromonomers, purposely synthesized, so as to insert relatively small amounts (6 and 15 weight %) of two types of poly-amidoamine segments in the final product. Of the three copolymers several physicochemical and mechanical properties have been determined, and their heparin adsorption ability, blood compatibility, and cytotoxicity evaluated.
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  • 15
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 955-956 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 16
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    Journal of Biomedical Materials Research 23 (1989), S. 9-11 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and standards-related activities. Standards are descriptive documents given official status by their producers and, in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to all members of any and all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat - since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in January, 1989.
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  • 17
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    Journal of Biomedical Materials Research 23 (1989), S. 273-283 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The biologic response to surgical implants is of importance in understanding the host interactions relating to long-term patency of implants. The methodology currently available for the assessment of host - biomaterial interactions is subjective and is limited to identification of inflammatory responses and general histopathological staining procedures associated with these processes. A clearer appraisal of the nature and type of extracellular matrix-components related to the host response to the implanted biomaterials would assist in the development of biomaterials and would allow an earlier means of predicting biocompatibility. The extracellular matrix consists of a range of similar collagen types which are difficult to distinguish using polyclonal antibodies. However, with the advent of hybridoma technology, monoclonal antibodies with the desired specificities can be produced to provide very powerful probes for assessing host - implant interactions. There were several problems associated with the production of these antibodies, mainly arising from collagens being extremely poor immunogens. The present study has examined these problems and has demonstrated that monoclonal antibodies against a range of collagen types can be produced. These antibodies were all highly specific for collagen type, but for a given collagen type, antibodies with different species specificities could be obtained. These antibodies were shown to be suitable for immunohistology of various connective tissue samples and were used to examine collagen-based vascular prostheses (Omniflow Vascular Graft) after retrieval from canine models. These data demonstrated that the monoclonal antibodies to collagens were excellent for the analysis of surgical implants and biomaterials after retrieval.
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  • 18
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    Journal of Biomedical Materials Research 23 (1989), S. 337-347 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Undecalcified histology has proved of immense value in the examination of the interface membrane between the prosthesis and bone. However, to provide such histological sections, dehydrating and clearing fluids as well as plastic infiltrating fluids must be used. This study investigates the possibility that some of these commonly used fluids may alter the biomaterial after removal from the body and be misinterpreted as an in vivo product. Ten different routinely used fluids were tested on 11 different biomaterials that are commonly used in prosthetic devices. The nonmetal biomaterials were placed in glass tubes containing the different fluids at room temperature for 5 days. The biomaterials were assessed for changes each day. After 5 days the biomaterial was examined and discarded and the glass tube was centrifuged. The pellet was examined using polarized light microscopy. Polysulfone and bone cement was found to be considerably altered in vitro by most of these fluids. While the components (plasticizer and catalyst) of the plastic fluids caused some changes to the biomaterial. Spurr's and GMA did not cause any alterations to any of the biomaterials that were examined.
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  • 19
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    Journal of Biomedical Materials Research 23 (1989), S. 321-335 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Several analytical pyrolysis methods, namely pyrolysis mass spectrometry (Py-MS), time-resolved pyrolysis mass spectrometry (TRPy-MS), and pyrolysis short column gas chromatography mass spectrometry (Py-GC/MS) were used to analyze polymers of clinical interest both before and after implantation. A sample of Biomer, a poly(ether urethane urea) used in the Utah artificial heart, was analyzed using these methods. Two poly(ether urethanes) (Tecoflex and Pellethane) and a poly(dimethylsilicone) (Silastic) sample were analyzed using Py-GC/MS. The direct Py-MS of Biomer identified the components used in the manufacture of Biomer. Py-GC/MS of Biomer, Tecoflex, Pellethane, and Silastic also identified the components used in their manufacture. The analysis of explanted Biomer detected the presence of adsorbed cholestadiene, the reaction of chloride ions with a stabilizer, and the presence of a siloxane contaminant. The cholestadiene was detected on the outside housing of an artificial heart which had been implanted for 297 days. The cholestadiene was detected at low levels and was identified by library search on the MS data system. The siloxane contaminant was also identified by the MS data system. All of the methods demonstrated required only short instrumental analysis times (10 min or less). Data analysis required much more time, but much of the data analysis can be automated.
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  • 20
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    Journal of Biomedical Materials Research 23 (1989), S. 381-381 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 21
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Morphological, histological, and scanning electron microscopy examinations were performed on 90 surgically excised human umbilical vein grafts. Most of the explanted grafts were removed because of thrombosis or infection and were removed typically from a patient in the mid 60s and after an average duration of implantation of 11 months. Multiple structural defects were found including deep folds, breaks on the luminal surface, and delamination. These areas as well as anastomotic sites represented potential areas for thrombotic accumulation. A higher incidence of infection was observed in grafts composed of 2 or 3 segments. Bacteria were often found in folds and could be seen invading the wall of the prosthesis. In addition, bacteremic colonization was often seen in noninfected grafts. The late aneurysmal formations were also of particular concern. The biodegradation of the wall and the disruption of the polyester mesh were the probable causes. The second generation Dardik Biograft aimed at reducing these formations. The success of this new processing remains to be evaluated.
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  • 22
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    Journal of Biomedical Materials Research 23 (1989), S. 349-361 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The corrosion behavior of commercially available copper, nickel, and gold alloys for dental castings was investigated. The alloys investigated included: three copper alloys (76-87Cu, 6-11Al, 0-12Zn, 1-5Ni, 0-4Fe, 0.5-1.2Mn). two nickel alloys (68-78Ni, 12-16Cr, 4-14Mo, 0-1.7Be), and one gold alloy (77Au, 14Ag, 8Cu, 1Pd). Anodic and cathodic polarization curves, long-term immersion tests in saline and artificial saliva solutions, and dog crown studies were conducted to evaluate both the in vitro and in vivo corrosion characteristics of the alloys. All evaluations conducted demonstrated that the copper alloys were highly susceptible to corrosion attack. High corrosion currents were observed in the in vitro tests, and SEM of the alloys specimens showed significantly altered surfaces. The anodic polarization curves predicted that the beryllium-containing nickel alloy should be susceptible to localized corrosion and SEM revealed an etched surface with corrosion of certain microstructural features. No significant corrosion was predicted or observed for the non-beryllium nickel alloy and the gold alloy. The in vitro corrosion evaluations predicted the in vivo corrosion behavior for the alloys. Since the three copper alloys and the beryllium-containing nickel alloy demonstrated significant corrosion under the tested conditions, the use of these alloys for restorative procedures is questionable due to the release of significant levels of selected ions to the oral cavity.
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  • 23
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    Journal of Biomedical Materials Research 23 (1989), S. 267-279 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Random copolypeptides and block copolypeptides were synthesized, and an interaction between these polypeptide membranes and the cells was studied by a cell culture method (cell line, Ca. 9.22). In random copolypeptides composed of γ-methyl L-glutamate and γ-benzyl L-glutamate, cell attachment and cell growth depended on the monomer composition, and showed a maximum at around 70 mole % of benzyl glutamate. Block copolypeptide composed of L-methionine and oxyethylene exhibited low cell attachment and cell growth even at 10 mole % of oxyethylene content, compared to L-methionine homopolymer. ESCA study of the membrane suggested this result to be due to concentration of the poly(oxyethylene) block chain of the polymer on the surface of the membrane. Block copolypeptide composed of N5-(3-hydroxypropyl) L-glutamine and L-leucine exhibited low cell attachment and cell growth, while the corresponding random copolypeptide exhibited high cell attachment and cell growth. This difference is attributable to the microheterophase structure with the hydrophilic domains embedded in the hydrophobic matrix in the block copolypeptide membrane.
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  • 24
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    Journal of Biomedical Materials Research 23 (1989) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 25
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    Journal of Biomedical Materials Research 23 (1989), S. 417-441 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyvinyl alcohol (PVA) hydrogel, with or without heparin, was reactive towards canine platelets in a chronic artriovenous shunt as demonstrated by an increase in platelet regeneration time, a systemic decrease in platelet count and transient decrease in platelet serotonin content. Immobilized heparin (heparin-PVA) had no effect whereas unmodified polyethylene was found to be unreactive despite similar levels of platelet deposition as measured by SEM and a higher in vitro reactivity (J. Biomed. Mater. Res., this is sue). Tewnty-centimeter lengths of hydrogel coated polyethylene tubing were inserted between the arterial and venous portions of the shunt and left in place for 4-6 days, without the complicating artifacts of anticoagulation, anesthesia, or surgical intervention. Regeneration time was measured as the return to normal platelet cyclooxygenase (co) activity after a single 240-mg dose of aspirin, with co activity measured in vitro as malondialde hyde production. Although measuring new platelet production, regeneration time is an indirect measure of platelet consumption, so that the reduced regeneration time seen here was presumed to reflect enhanced material associated consumption and thromboembolism. Like other hydrogels, PVA does not appear to be “thromboadherent” but it does appear thrombogenic. Immobilized heparin had no additional effect, presumably because the platelet response was dominated by the reactivity of the underlying substrate.
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  • 26
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    Journal of Biomedical Materials Research 23 (1989), S. 477-489 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Our previous article suggested that control of the extensibility of aldehyde-fixed pericardium could be achieved by controlling shrinkage during fixation. Therefore, to prevent shrinkage, we have used sandpaper-lined plexiglass plates to clamp circular samples of bovine pericardium during fixation in glutaraldehyde, tethering them at their original dimensions. As well, we have applied transmural pressures of 50 or 100 mm Hg during fixation using a hydraulic column of glutaraldehyde solution. Strips cut at 0°, 30°, 60° and 90° to the base-to-apex cardiac direction have been examined for cyclic stress-strain response, stress relaxation, plastic deformation, and fracture behavior. Under physiological stresses, tethered and pressure-fixed materials were both nearly isotropic. Tethering during fixation produced a material with extensibility nearly identical to that of fresh tissue. Plastic deformation during cyclic loading was reduced below that seen in simple fixation while stress relaxation was unchanged. Pressure-fixation produced reduced extensibility similar to that produced in porcine aortic valve leaflets. Plastic deformation and stress relaxation were both markedly reduced. Pressure-fixation reduced the strain at fracture, but fracture behavior was otherwise unaffected. Tethering and pressure-fixation offer attractive means to control the mechanical behavior of bovine xenograft materials.
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  • 27
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    Journal of Biomedical Materials Research 23 (1989), S. 523-528 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new acetabular cup prosthesis made of alumina and bioactive glass was studied and evaluated using nondestructive and noninvasive Raman laser spectroscopy. The prosthesis consists of an alumina socket coated with a double layer of alumina beads bonded to the prosthesis with a layer of glass. Raman spectroscopy showed that both the socket and the beads are composed of α-Al2O3 (corundum), while the bioactive glass (alkaline and alkaline earth alumosilicate with a small quantity of zirconium oxide) showed this to have an intermediate structure between that of vitreous silica and that of the alkaline and alkaline earth disilicate glasses. The Raman spectra of the contact surfaces between the bioactive glass and the alumina of the assembled prosthesis and of an alumina disk coated with the same glass showed the presence of new bands which may be correlated with a chemical interaction between the components of the prosthesis.
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    Journal of Biomedical Materials Research 23 (1989), S. 591-610 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Protein adsorption is the first event which occurs when polymer surfaces are exposed to blood. The adsorption of proteins modifies the surface properties of the substrates and therefore influences subsequent cell - surface interactions. In an attempt to elucidate the fundamental mechanisms governing cell - proteinated-surface interactions, the extent of fresh human erythrocyte adhesion and spreading on protein-coated surfaces was examined. Five human serum proteins (albumin, fibrinogen, immunoglobulin G, fibronectin, and transferrin) were used at bulk concentrations ranging from 0.01 mg/mL to 50 mg/mL. Polymer substrates covering a wide range of wettability were employed. Protein adsorption significantly reduces erythrocyte adhesion and spreading on all test surfaces with minimum adhesion observed on fibrinogen: IgG 〉 albumin 〉 fibronectin 〉 transferrin 〉 fibrinogen. The extent of these effects is dependent on the nature of the adsorbed protein, the protein bulk concentration, and the surface properties of the underlying polymer substrates.
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  • 29
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    Journal of Biomedical Materials Research 23 (1989), S. 661-668 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The cytotoxicity of methyl- and isobutyl-2-cyanoacrylate adhesives was determined using a rat polymorphonuclear leukocyte suspension. Cell degranulation increased and migration decreased on addition of the alkyl-2-cyanoacrylates to the suspension in a concentration-dependent manner. When. acetylsalicylic acid or indomethacin, inhibitors of prostaglandin H Synthase, were present, the cytotoxicity observed on addition of the adhesives to the leukocytes decreased up to eightfold in a dose-dependent manner as detected by trypan blue exclusion. Likewise, glutathione peroxidase and superoxide dismutase lowered such cytotoxicity resulting from the cyanoacrylates up to eight- and sevenfold, respectively. The data suggested that the adhesives may have generated prostaglandin and thromboxane biosynthesis, and participated in membranal oxidation and lysis. Such a mechanism may contribute to under standing the thrombotic events associated with the necrosis observed on application of these adhesives to tissues in vivo.
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  • 30
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    Journal of Biomedical Materials Research 23 (1989), S. 685-703 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Creation of life involves establishing an organism that is capable of self-maintenance, self-reproduction, and adjustment to a changing environment. A Bioactive Substrate Theory of the origin of life is proposed, where the function of the bioactive substrates was to achieve the irreversible ordering of macromolecules into replicative structures. The ordering was a result of six precytic ordering factors which provide the mechanisms for simultaneous formation of primitive codonic-bases, anabolic processes and energy-producing, catabolic processes on bioactive inorganic glassy crystalline assemblages. Time dependent changes in the isoelectric point of the inorganic assemblages enabled the anabolic and catabolic processes to be isolated within the same bilipid membrane. The enormous diversity of inorganic glass-crystal assemblages associated with volcanic activity resulted in many alternative evolutionary pathways for the precytic structures, eventually producing the major genetic pathways for life observed today. The evidence for bioactive ordering factors is examined including selective adsorption of optically active amino acids on optically active mineral substrates and specific cellular responses to bioactive implant materials. The implications of this theory on the biochemical design of implants, and prevention of disease states in modern man are discussed.
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    Journal of Biomedical Materials Research 23 (1989), S. 765-779 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals, Porites and Acropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 ± 2%, 12 ± 4%, respectively) and mean size (250 vs. 500 μm) of porosities. The non-decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto-, allo-, or xenografts.
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    Journal of Biomedical Materials Research 23 (1989) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 33
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    Journal of Biomedical Materials Research 23 (1989), S. 833-844 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of gamma irradiation on the physicochemical properties of injectable human amninon collagen was investigated. Pepsin-extracted human amnion collagen was purified, reconstituted, and irradiated with varying doses of gamma irradiation (0.25 Mrads to 2.5 Mrads). Gamma irradiation had a significant impact on the physical characteristics of the collagen. The neutral solubility of collagen in PBS at 45°C was decreased from 100% for the nonirradiated control sample to 16% for the 2.5 Mrads irradiated sample. SDS polyacrylamide gel electrophoresis also demonstrated the dose-dependent effect of gamma irradiation on collagen crosslinks. Electron microscopic observation revealed that even at low irradiation dose (0.25 Mrads), collagen fibril diameter increased. The average diameter was 50 nm for nonirradiated control fibrils, while 4.4% percent of the irradiated collagen fibrils had a diameter greater than 100 nm. Irradiated collagen showed little evidence of damage. Well-preserved cross-strations were found in collagen fibrils at all doses of irradiation. Native amnion collagen irradiated with gamma rays demonstrated a slight increase in resistance to collagenase degradation compared with nonirradiated native collagen samples. Increased resistance to collagenase did not correlate with increasing irradiation dose. After 30 min of incubation at 37°C, both irradiated and non-irradiated collagen was completely digested by collagenase. However, gamma-irradiated collagen did become more sensitive to hydrolysis by trypsin. The higher the irradiation doses used, the greater sensitivity to trypsin was observed. At 0.25 Mrads irrdiation only a slight increase was found. No marked differences in amino acid composition were noted among the high dose irradiated, low dose irradiated and control amnion collagen.
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    Journal of Biomedical Materials Research 23 (1989) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 35
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    Journal of Biomedical Materials Research 23 (1989), S. 491-506 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Our previous two articles have shown that glutaraldehyde-fixed bovine pericardium is nearly isotropic, whether fixed without constraints, with tethering, or with pressure. In this study, we have used uniaxial stress during fixation to produce bovine pericardial material with marked tensile anisotropy. Rectangular and cruciate pericardial samples have been mechanically examined after one of four treatments: (i) fixation under 88-kPa uniaxial stress, (ii) fixation under 176-kPa uniaxial stress, (iii) 3 h of 176-kPa uniaxial stress in saline followed by 24-h fixation under the same stress, (iv) fixation under 176-kPa uniaxial stress followed by a second fixation under 176-kPa stress in a direction normal to the first. Strips of material were cut at 0°, 30°, 60°, and 90° to direction of the initial stress, and tested for response to cyclic loading, stress relaxation, plastic deformation, and fracture properties. Fixation under uniaxial stress produced anistropy similar to that seen in porcine aortic valve leaflets; however, the overall extensibility of the material depended on the applied stress and the aspect ratio of the stressed sample. While loading in saline produced no change, the sequential biaxial stressing produced a reduction in anisotropy, suggesting exposure of additional crosslinking sites. Uniaxial stress during fixation may be a useful method for construction of anisotropic heart valve leaflets.
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    Journal of Biomedical Materials Research 23 (1989), S. 535-548 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: These studies involved the evaluation of human monocyte/macrophage activation by biomedical polymers coated with human blood proteins. The biomedical polymers were polyethylene, polydimethylsiloxane, woven Dacron fabric, expanded polytetrafluoroethylene, Biomer®, and tissue culture treated polystyrene as the control. They were adsorbed with human blood proteins: albumin, fibrinogen, fibronectin, hemoglobin, and gamma globulin. The protein adsorbed polymers were evaluated for their potential to activate the monocyte/macrophage cellular population in vitro as assessed by the induction of the monocyte/macrophage inflammatory mediator, Interleukin 1 (Il1). Suppression of IL1 was observed when protein adsorbed polymers were compared to the appropriate protein adsorbed control. Protein adsorbed polymers, when compared to polymers without protein adsorption, stimulated IL1 production. The data presented in this manuscript show the level of induction and secretion of IL1 was dependent on the biomedical polymer and the protein adsorbed, as well as the requirement of lipopolysaccharide. These results show differential interactions occur between the proteins, monocytes/macrophages, and biomedical polymers which alter activation and induction of IL1.
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    Journal of Biomedical Materials Research 23 (1989), S. 631-648 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this study, it was found that a Ca—P layer and a Si layer were formed on the interface of the mother glass of apatite-wollastonite containing glass-ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgO—CaO—SiO2—P2O5—CaF2) is necessary to form a chemical film (a Si layer and a Ca—P layer). The three kinds of glasses used were (1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated G—AW (mirror)), (2) an abraded surface of G—AW (designated G—AW (#2000)), (3) a mirror surface SiO2 glass (designated G—Si, 100%SiO2). The glass plates (15 mm × 10 mm × 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM-EPMA. Failure loads in G—Si, G—AW (mirror), and G—AW (#2000) 10 weeks after implantation were 0.18 ± 0.24, 3.06 ± 1.29, and 2.94 ± 1.77 kg, respectively. Those in G—Si, G—AW (mirror), and G—AW (#2000) 25 weeks after implantation were 1.30 ± 1.18, 3.88 ± 1.06, and 3.55 ± 1.51, respectively. The failure loads in G—Si vs. G—AW (mirror) and those in G—Si vs. G—AW (#2000) differed significantly (P 〈 0.01). There were no significant differences in the failure load according to the surface roughness of G—AW. As shown by SEM-EPMA observation, a Si layer next to G was adjacent to a Ca—P layer next to the bone. The chemical film showed no increase in thickness as time passed. A Ca—P layer did not form on the interface of Si—G and bone.
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    Journal of Biomedical Materials Research 23 (1989) 
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    Journal of Biomedical Materials Research 23 (1989), S. 809-811 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 40
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    Journal of Biomedical Materials Research 23 (1989), S. 883-894 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Specially prepared biphasic calcium phosphate (BCP) macroporous ceramics consisting of an intimate association of beta tricalcium phosphate (b̃-TCP) and hydroxyapatite (HA) with b̃-TCP/HA weight ratios of 15/85, 35/65, and 85/15 were implanted in surgically created periodontal osseous defects in dogs and recovered after 6 months. A decrease in average size of crystals in BCP ceramics and an increase in the size of microporosities in the surface and at the core of the ceramic after implantation were observed, indicating that in vivo dissolution has taken place. The resorbability (reflecting in vivo dissolution) of BCP ceramics depended on their b̃-TCP/HA ratios, the higher the ratio, the greater the resorbability. The formation of microcrystals with crystallographic properties and Ca/P ratio similar to those of bone apatite crystals were also observed. The abundance of these crystals were directly related to the b̃-TCP/HA ratio of the BCP ceramic before implantation. The formation of the bone apatite-like crystals may be due to the precipitation of calcium and phosphate ions released from the dissolving ceramic crystals (the b̃-TCP component dissolving preferentially to the HA component). Results from this study suggested that one of the means of controlling resorbability (in vivo dissolution) of BCP ceramic is by varying its b̃-TCP/HA ratio.
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    Journal of Biomedical Materials Research 23 (1989), S. 911-930 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomedical polymers used in constructing implantable artificial devices may affect host responses to the material and ultimately contribute to the success or failure of a device via mechanisms of cell-polymer interactions. Human peripheral blood monocytes (MO) cultured in the presence of several such biomedical polymers released factors that stimulated fibroblast proliferation and/or collagen synthesis. The factors that stimulated fibroblast proliferation were differentially released from monocytes cultured in the presence of Dacron, polyethylene, expanded polytetrafluoroethylene (ePTFE), polydimethylsiloxane, and polystyrene (control). Supernatants obtained from monocytes cultured in the presence of Biomer, a segmented polyetherurethane, were unable to stimulate fibroblast proliferation. However, supernatants from all cultures, including MO-Biomer cultures, were able to induce collagen production from the same target fibroblasts. These same supernatants also were shown to contain interleukin 1 (IL1) activity. Neutralization of the fibroblast stimulatory potential (FSP) activity with antibodies directed against human IL1 and human PDGF demonstrated that IL1 and not PDGF was responsible for the FSP activity. Results of this study show that by affecting macrophage activation, different biomedical polymers can affect host biocompatibility responses by altering fibroblast proliferation and function.
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    Journal of Biomedical Materials Research 23 (1989), S. 41-71 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The usefulness of patent literature for research and development is mostly unknown. Therefore a specific patent retrieval has been carried out concerning calcium phosphate-containing biomaterials. This research field includes chemical, medical, and engineering problems and is of importance to the development of bioactive materials for bone replacement. The preliminary work includes information on the characteristics and the availability of patent literature as well as about patent classification systems according to which the documents are filed in patent collections. By reading the non-patent literature searching questions can be formulated. The proper patent retrieval starts with the study of secondary literature especially that in Chemical Abstracts, which report on patents since 1907. The structure of Chemical Abstracts, their indexes and sections help to find relevant patents of chemical or chemical engineering contents fast and inspire to read patents of bordering areas. This retrieval from Chemical Abstracts led to 171 patents disclosed 1975-1985 and to 95 patents disclosed in 1986; the latter are listed in a table. The contents of the abstracts inform on the research activity and help to reduce time and effort for a continuation of the retrieval in a patent collections or database.
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    Journal of Biomedical Materials Research 23 (1989), S. 157-169 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adsorption of fibrinogen from both human whole blood and plasma to a number of “foreign” surfaces is reported. Adsorption was measured as a function of plasma or blood dilution using radioiodine labeling. We showed previously that adsorption of fibrinogen from plasma exhibits a maximum at a plasma dilution of about 100:1, and have attributed this behavior to competition from other plasma proteins. (The same phenomenon is manifest as a time transient in fibrinogen adsorption.) In the present work we show that exactly the same trends are observed in whole blood. For each of the four surfaces, glass, siliconized glass, collagencoated glass and polyethylene, the adsorption of fibrinogen as a function of dilution is the same in whole blood as in plasma. Each of these surfaces shows a unique dependence of fibrinogen adsorption on plasma or blood dilution. On cuprophane and a hydrophilic polyether urethane there is essentially no adsorption of fibrinogen from blood or plasma. For the hydrophilic polyurethane this result may be artifactual, but the absence of fibrinogen binding to cuprophane in blood or plasma is real since fibrinogen is found to be adsorbed in monolayer amounts from buffer.
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    Journal of Biomedical Materials Research 23 (1989), S. 223-239 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Attachment and growth of mouse fibroblast cells on polypeptide derivatives with different wettabilities were studied in the presence or absence of serum proteins. In the presence of serum, a peak level of cell attachment was observed for substrates with a contact angle of around 70°. However, no relationship was found between cell attachment and water contact angle of the substrate in the absence of serum. Ca2+-dependent cell attachment was observed on hydrophobic polypeptides in the absence of serum proteins. This suggests that Ca2+-dependent membrane proteins function as mediators for cell attachment to hydrophobic polypeptides. In the presence of serum proteins, it was found that cell attachment is affected by the metabolism, Ca2+, and the cytoskeleton of the cell. Cell growth rate on hydrophilic polypeptide substrates was higher than that on intermediate or hydrophobic polypeptide substrates. This demonstrates that the strong interaction between cells and substrates will be unfavorable for a dewebbing process during mitosis.
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    Journal of Biomedical Materials Research 23 (1989), S. 143-156 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ethylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i. e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i. e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (C) dependent and the relationship which best describes this dependence was D(c) ∝ In C. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost-effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equipment.
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    Journal of Biomedical Materials Research 23 (1989), S. 207-222 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioprosthetic heart valves are being used more often because of certain advantages they have over artificial valves. The bioprostheses are less thrombogenic, cause a lower incidence of hemolysis, and usually fail in a slow progressive manner. A combination of flow characterization and accelerated testing was used to assess the durability of two types of pericardial valves, the Ionescu-Shiley Low Profile Mitral and the Carpentier-Edwards Low Profile Aortic valve. The flow characterization work was done in an aortic chamber designed for in vivo simulation. The function of the valve was monitored between different stages of the accelerated testing using laser Doppler anemometry. Accelerated testing was performed at 1300 cardiac cycles per minute, and physiologic conditions both in closing pressures and the ambient temperature were maintained. Results indicated a change in flow characteristics owing to cyclic loading of the leaflet tissue. The flow orifice increased over time leading to a decrease in peak velocity. Future developments in Doppler ultrasound may facilitate non-invasive assessment of these peak velocity variations. Calcification of the tissue was not considered, since this was an in vitro study.
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    Journal of Biomedical Materials Research 23 (1989), S. 571-589 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study was performed to test the feasibility of using a biodegradable delivery system for the local controlled release of sodium fluoride as a mechanism for the stimulation of local bone growth. Sodium fluoride grains were mixed with poly-DL-lactic acid (PLA), and the mixture was then dissolved in acetone. After driving off the solvent, sheets of this material were rolled into rods 3.2 mm in diameter and 28.6 mm long. These were inserted into the intramedullary canals of the right femora of adult New Zealand White rabbits. A sham implant, made the same way but containing no fluoride, was inserted into the contralateral left leg. The effects of three different concentrations of sodium fluoride, 0.125 g NaF/g PLA, 0.250 g NaF/g PLA, and 0.500 g NaF/g PLA, were determined after a 4-week implantation period. In a second set of experiments, the concentration was fixed at 0.500 g NaF/g PLA with implantation durations of 4, 8, and 16 weeks. Expressed in terms of property ratios (experimental/control), bending strengths of the femora were significantly raised in most groups with the notable exception of Group 3 (0.500 g NaF/g PLA, 4 weeks). Cross-sectional area ratios in the distal femora were increased in all groups compared to right/left values for a normal unoperated group (p 〈 0.05), with the highest ratio being 1.50 (SD = 0.44) for Group 4 (0.500 g NaF/g PLA, 8 weeks). Only Group 4 animals showed significant (p 〈 0.05) increases in midshaft area ratio and none had responses proximally. Growth rates, measured by sequential fluorochrome labeling of bone followed the area ratio data and were only significant for the distal femora.
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    Journal of Biomedical Materials Research 23 (1989), S. 649-660 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The organization of collagen in custombuilt biosynthetic vascular prostheses (Omniflow Vascular Graft), which are suitable for periphareral revascularization, has been examined. The grafts were a glutaraldehyde-tanned ovine-collagen composite with a polymer mesh reinforcement. Comparisons were made between grafts using different mesh fiber polymers and knit patterns. There was a basic similarity in the arrangement of the tissue structure in all graft types. Scanning electron microscopy and light microscopy showed that the collagen formed a layered structure which fully encased the polymer mesh and held it firmly in position. Rather than polymer mesh, the inner surface of the graft was found to be collagen, and lined with a layer of flattened cells. Collagen formed a continuous layer surrounding the mesh, with no distinct boundary membrane or structurally weak point being apparent. Immunohistology, using a monoclonal antibody specific for type III collagen, and chemical analysis, indicated that there was a high proportion of type III collagen in the grafts, particularly in the region surrounding the mesh fibers.
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    Journal of Biomedical Materials Research 23 (1989), S. 679-684 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Uncemented total hip replacements have resulted in a higher incidence of postoperative complaints than cemented ones. The theoretical explanation of these not well defined discomforts is based on the differences of the stress and strain fields around the distal portions of the femoral components. While the noncemented stems are press-fitted and most of them tapered distally, thus creating hoop stresses and strains in the surrounding cortical bone, the shrinkage of the cement prevents these mechanical irritations. The relatively sudden disappearance of these discomforts within the first 2 postoperative years is attributed to the shift of the main zone of load transmission from the distal to the proximal portion of the stems following bone remodeling.
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    Journal of Biomedical Materials Research 23 (1989), S. 735-752 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si-rich film covered by a CaP-rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber-reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless-steel or wrought Co-Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be measured.
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    Journal of Biomedical Materials Research 23 (1989), S. 781-808 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Three different granule coatings (a granular alumina ceramic coating, a granular hydroxyapatite coating, and a polished granular hydroxyapatite coating) applied to alumina ceramic substrate were evaluated for their strengthening effects of the bone - implant interface in rabbit tibiae. For a comparison, noncoated alumina ceramics, and dense hydroxyapatite were assessed in the same way. The granular alumina ceramic coating, creating a bioinert, porous surface, was effective due to a strong mechanical bond between the bone and implant. The interface strength was even higher than that of the dense hydroxyapatite. The granular hydroxyapatite coating, creating a bioactive, porous surface, was less effective than the granular alumina ceramic coating because of the brittleness of the hydroxyapatite granules, although it formed a direct and mechanical bond with bone tissue. The polished granular hydroxyapatite coating, creating a bioactive, smooth surface, was least effective because of the brittleness of the hydroxyapatite granules, though it presented an improved interface strength compared with that of the noncoated alumina ceramics due to a direct bond between the bone and hydroxyapatite granules.
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  • 52
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    Journal of Biomedical Materials Research 23 (1989), S. 285-294 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The luminal surfaces of polyethylene and polyurethane tubings of 1 mm inner diameter and 1 m in length were coated with heparin by end point attachment and thereafter sterilized in ethylene oxide. The tubings were inserted as arterio-venous shunts from the aorta to the superior caval vein via a carotid artery and a jugular vein. Patency was assessed with an ultrasound doppler flow meter and flow measurements. All nonheparinized shunts occluded within 10 days with a mean elapsed time from the insertion of the tubing is the last positive doppler registration being 3.5 days. The corresponding patency time for heparinized shunts was 25.9 days. The occlusion of the heparinized tubings was due to the incorporation of the ends of the tubings in the walls of aorta and caval vein, whereas the nonheparinized tubings occluded as a result of clot formation. It is concluded that surface immobilization of heparin with sequences capable of activating antithrombin may be beneficial in the development of small-diameter vascular protheses.
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  • 53
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    Journal of Biomedical Materials Research 23 (1989), S. 295-309 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A series of methacrylate oligomers containing pendant isocyanate groups were synthesized by reacting 2-isocyanatoethyl methacrylate (IEM) and/or m-isopropenyl- α, α-dimethylbenzyl isocyanate (TMI) in ethoxyethyl acetate with methacrylates ranging from methyl to stearyl methacrylate or allyl-, cyclohexyl-, glycidyl-, i-bornyl-, or dicyclopentenyloxyethyl methacrylate. The oligomers which are stable at room temperature were characterized by IR for NCO, ester, and C = C groups and by their refractive indices. They have a small number of residual double bonds and a molecular weight low enough so that the compounds are liquids at room temperature and dissolve readily in esters and chlorinated hydrocarbons. HPLC showed no residual monomer. GPC and intrinsic viscosity of selected oligomers indicated a molecular weight range from 1400 to 2600. Isocyanate groups were determined titrimetrically and ranged from 15.9% to 5.1%. Concurrent studies have demonstrated that these oligomers bond strongly to hard and soft tissues. Thus, subject to their biocompatibility they could find many applications as tissue adhesives.
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  • 54
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    Journal of Biomedical Materials Research 23 (1989), S. 351-368 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyethylene oxide(PEO)-containing non-ionic polymeric surfactants were studied as a possible means to produce PEO-rich surfaces by a simple coating treatment of a common hydrophobic medical material - polyethylene. Surface tension and adsorption properties of PEO/polypropylene oxide(PPO) and PEO/polybutylene oxide(PBO) block copolymer surfactants on a hydrophobic surface (low density polyethylene, LDPE) were investigated, using the Wilhelmy plate surface tension technique and x-ray photoelectron spectroscopy(XPS). The protein resistance of the surfactant-treated surfaces was evaluated by XPS and 125I-labeled proteins. The data presented indicate that adsorption of the surfactants on LDPE is dependent on the molecular geometry of the surfactants. Adsorption of human albumin was significantly decreased on the surfactant-treated LDPE surfaces, as compared with the untreated surface. Surfactants suitable for the preparation of PEO-rich surfaces and possible mechanisms for their protein resistance are discussed.
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    Journal of Biomedical Materials Research 23 (1989), S. 443-450 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Information obtained from physical and chemical characterization of vascular grafts can prove valuable in obtaining a preliminary assessment of potential in vivo performance. The data presented illustrate the concept and show that the new biological graft made from bovine ureters has adequate performance characteristics for use as a potentially successful vascular graft.
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  • 56
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    Journal of Biomedical Materials Research 23 (1989), S. 931-945 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Aqueous suspensions of glutaraldehyde cross-linked fibrillar collagen and non-cross-linked fibrillar collagen were examined by rheometry, particle size analysis, and microscopic techniques. Although cross-linked collagen suspensions were similar to non-cross-linked suspensions by microscopic and size analyses, they differed in rheometric properties. Concentric cylinder Couette flow, shear creep, uniaxial creep, and porous bed flow all revealed that cross-linked collagen was more resistant to deformation and flow than non-cross-linked collagen. These results were in agreement with in vivo dermal implantation studies, both in pig and human; i.e., compared to non-cross-linked collagen, the cross-linked formulation was more difficult to inject into tissue and did not spread uniformly, sometimes giving rise to palpable lumps or large masses evident in histological sections. When hyaluronic acid was blended with cross-linked collagen to achieve a final hyaluronate concentration of 5 mg/mL, there was a significant improvement in ease of injection into tissue. Rheometry on blends of hyaluronate and cross-linked collagen demonstrated that the blend required lower forces to achieve deformation and flow, compared to cross-linked collagen alone. Particle size analysis on the blend showed a reduction in fiber aggregate dimensions, compared to crosslinked collagen alone.
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    Journal of Biomedical Materials Research 23 (1989), S. 13-22 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ti4+ and V5+ ions were studied in two biologically relevant in vitro test systems to determine their effect on hydroxyapatite (HA) formation. System 1 involved direct HA precipitation from solution, and system 2 dealt with the growth of HA seed crystals. The experiments were carried out in a pH-stat by continuously recording NaOH uptake, which follows HA formation kinetics, at pH 7.4, 37°C, and 0.15 MNaCl. In systems 1 and 2, Ti decreased HA formation kinetics in a dose-related manner without delaying the onset of HA formation. For V, the rate of HA proliferation decreased in system 1 in a dose-related manner, but the curves displayed a complicated shape. In system 2, V brought about a decrease in the HA seeded growth rate. Previous work has shown that A1 blocks HA proliferation by adsorbing to active growth sites on the surface of HA crystals. By contrast, in this study V was found not to be adsorbed to the surface of HA. The mechanism of action of V probably involves the poorly understood hydrolysis and solution complex formation chemistry of the metal ion. We have shown here that V ions form V-PO4 complexes in solution in the HA formation systems; undoubtedly these are involved in the mechanism of V inhibition of HA formation. On the other hand, Ti was shown to bind to the surface of HA crystals in this study, which means that the ion may poison active crystal growth sites, as does aluminum. Ti-6Al-4V alloy is widely used in cementless total hip implants. Previous studies have shown that Ti concentrations 10 to 100 times higher than used here accumulate in osseous tissues around porous Ti implants in dogs 6 to 12 months after implantation. Ions leaching out over long periods of time into the implant interface could interfere with the normal osteoid mineralization and remodeling processes of bone in that region, which would result in subsequent loosening of the implant. This research suggests that further in vitro and animal studies should be carried out to determine the extent of Ti and V ion leaching from implants and their effect on tissue mineralization.
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    Journal of Biomedical Materials Research 23 (1989), S. 73-86 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Clinical failures of central nervous system fluid shunts remain a vexing problem. Attributed largely to infectious and technical etiologies, it has been hypothesized recently that inflammatory mechanisms may play a role in this clinical phenomenon. In order to obtain morphologic evidence for this hypothesis, a study of failed shunts was performed. Twenty-five of 57 sequentially removed CNS fluid shunt assemblies or components over the course of 18 months contained sufficient intraluminal tissue to allow a histomorphologic assessment. Tissue was removed from either the intraventricular or intraperitoneal portion and examined with routine light microscopical and histochemical techniques to assess the degree of cellularity, composition of the cells, presence of debris, and organisms. Morphologic findings were correlated with the clinical courses and microbiological cultures. Data were analyzed nonparametrically using the χ2 test. There was a substantially significant association between repeated failures and non-infectious obstructions. Eight demonstrated evidence of active inflammatory processes; and although not statistically significant, the presence in 3 cases of giant cells, macrophages, lymphocytes, and eosinophils all suggestive of a hypersensitivity reaction correlated with the occurrence of culture negative clinical failures. These morphologic findings will stimulate further experimental and clinical research into possible inflammatory mediators of shunt failure.
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    Journal of Biomedical Materials Research 23 (1989), S. 87-104 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Surfaces of commercial polyurethanes (PUs) were modified by poly(ethylene oxide) (PEO) grafting and/or heparin immobilization for long-term biomedical applications. PU surfaces were treated with diisocyanate and then reacted with PEO or heparin. The heparin immobilized by various methods on the PU surface was very stable, with concentrations of 1.45-1.84 m̈g/cm2. Surface structure and characteristics of each modified PU were examined by performing the following surface analyses: attenuated total reflection infrared (ATR-IR), electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), and dynamic contact angle measurements. The reaction scheme and surface chemical structure of modified PUs were confirmed by ATR-IR and ESCA, respectively. SEM results showed that the PU-PEO surface was very smooth and that the smoothness of the heparinized PU surfaces varied, depending upon the solvent and coupling agent used in the process. The hydrophilicity of the surface was significantly increased after PEO grafting or heparin immobilization. Increase in the chain length of the grafted PEO resulted in significant increases in hydrophilicity and surface mobility.
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    Journal of Biomedical Materials Research 23 (1989), S. 129-143 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because needle bending resistance is such an important factor in the selection of surgical needles, a standard quantitative test of needle bending has been devised to study the biomechanics of deformation of needles from three different commercial manufactures. The superior resistance to deformation of needles made by one manufacturer has been related to the specific alloy, ASTM 45500 stainless steel, employed in its production. The needles produced from ASTM stainless steel 45500 have stronger tensile and yield strengths than those of the other alloys, accounting for their greater resistance to bending.
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    Journal of Biomedical Materials Research 23 (1989), S. 145-152 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new method using an image processing system developed in our laboratories is used to measure the pore size in Mersilene, Marlex, and Teflon surgical meshes. All three meshes appear to have sufficiently large pores and should facilitate tissue growth/attachment. Results obtained in this study are compared to results of an earlier paper.
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    Journal of Biomedical Materials Research 23 (1989), S. 105-116 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Orthopaedic internal fracture fixation plates are subjected to combined axial, bending, and torsional loads in vivo which can cause screw loosening and implant failure. This paper outlines a relatively simple technique which allows controlled application of combined axial, bending, and torsional loading to examine the loosening rate of cortical screws used to attach these plates. Fiber reinforced polycarbonate rods with a tensile strength similar to that of cortical bone were cut at half their length to simulate fractured tibii. These were compression plated using a standardized technique and placed in a loading fixture. Joint loads at the knee determined from force plate analysis and statics were applied to a plated fixture during testing. The design of the fixture allowed adjustment of the proportion of bending and torsional loads applied to the test samples. It also allowed a reproducible means of applying a predetermined axial, bending, and torsional load. Screw loosening following cyclical loading was evaluated by measuring the amount of angular displacement required to retighten screws to a prescribed torque value. A torque wrench was modified to allow the measurement of these displacements.
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    Journal of Biomedical Materials Research 23 (1989) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 23 (1989), S. 269-271 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 23 (1989), S. 311-319 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A commercially available mammary implant containing a soft polyester polyurethane foam shell has been examined for possible diamine hydrolysis products. Fourier Transform Infrared (FT-IR) analysis has shown ester and aromatic structures present in the intact foam shell Vigorous hydrolysis conditions using NaOH have produced a mixture with large amounts of toluene diamine (TDA) present as determined by Gas Chromatography-Mass Spectrometry (GC/MS), and GC/FT-IR. There are numerous clinical reports of the degradation of this implant shell after implantation with incorporation of fragments into phagocytic cells at the implantation site. Recent reports have discussed late pain and other allergic reactions to this implant. Release of the known toxic material, TDA, is consistent with these observations and strongly suggests that an alternative material be used in this application.
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    Journal of Biomedical Materials Research 23 (1989), S. 1-16 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A biodegradable particulate composite bone cement consisting of a crosslinked gelatin matrix and tricalcium phosphate particles was implanted intraosseously in rabbits for up to 12 weeks. Cured cylindrical implants were inserted in holes drilled in the proximal tibial metaphysis. Sequential fluorochrome labeling and radiographs were done, and specimens were processed for decalcified and nondecalcified histology. At 4 weeks, the cross-sectional diameter of the implant was slightly greater than at implantation. There was considerable dissolution of the matrix and some new bone ingrowth. At 12 weeks, the diameter was reduced to half the original diameter and bone had grown throughout the matrix. In the distal femur, freshly mixed cement was used to stabilize an osteochondral fracture. Mechanical testing of the cement-stabilized fracture revealed a decrease in compressive strength and modulus at 4 weeks followed by an increase to greater than initial values at 12 weeks. Over time, the osteochondral fragment subsided into the underlying cement, but the subsidence did not correlate with mechanical strength. This osteochondral fracture model permits measurement of the overall material properties of a cement simultaneously weakened by resorption and reinforced by ingrowing bone.
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    Journal of Biomedical Materials Research 23 (1989), S. 81-90 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: One aim of this in vitro investigation was to determine the effect of substituting four phenols and two methacrylates with vinyl functions on the dentin bond strengths of several new experimental dentin bonding agents. Another objective was to determine the effect of postextraction age and dentin level within the tooth on tensile bond strengths of these toluene diisocyanate-derived adhesives. Extracted third molars were divided into postextraction age groups and sectioned into three slices ∼400 m̈m thick. The four substituted phenols were: eugenol, o-methoxyphenol, o-chlorophenol, and p-cresol. Substituted methacrylates with vinyl ligands were 2-hydroxyethyl methacrylate (HEMA) and 6-hydroxyhexyl methacrylate (HHMA). Results showed that adhesives made with o-chlorophenol, p-cresol, and methoxyphenol with HEMA were the best, while those made with eugenol and HHMA were the worst. The post extraction age of the tooth and the dentin depth had no consistent effect on most adhesive bond strengths which were generally around 10.3 MPa (1500 psi).
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    Journal of Biomedical Materials Research 23 (1989), S. 125-133 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue biocompatibility of cellulose and its derivatives was examined in two in vivo tests, one for absorbance by living tissue and one for foreign body reaction. The samples examined were regenerated celluloses and cellulose derivatives: methylcellulose, ethyl cellulose, aminoethyl cellulose, hydroxyethyl cellulose, and cellulosic polyion complexes. The in vivo absorbance by living tissue was found to depend on the degree of crystallinity and the chemical structure of the sample. The foreign body reaction was relatively mild for all the samples examined, showing that cellulose can be converted to biocompatible materials by physical and/or chemical transformation.
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    Journal of Biomedical Materials Research 23 (1989), S. 507-521 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The fracture behavior of two types of urinary stones, namely struvite and calcium oxalate, during compression testing was studied. Scanning electron microscopy (SEM) was used to characterize the fracture surfaces. Both types of stone showed pseudo-plastic behavior as indicated by their load-displacement curve. The onset of nonlinear behavior was found to correspond to development of microcracks in the specimens. The compressive strength was defined as the stress calculated at the maximum load. In struvite samples, the maximum load corresponded with the development of large cracks parallel to the compressive axis. For oxalate stones a separation of the outer layer (crust) from the inner layer (core) marked the point of maximum load. The compressive strength of the struvite samples was found to depend on the orientation of lamellae relative to the loading axis. Struvite stones, when loaded parallel to the lamination direction showed a higher compressive strength than oxalate stones did. The fracture behavior and compressive strength of a model material (z-brick) were also characterized and compared to those of the urinary stones.
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    Journal of Biomedical Materials Research 23 (1989), S. 705-718 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The peritoneal cavity is a convenient site for implantation of encapsulated hormonesecreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspresed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.
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    Notes: Biodegradable beta-tricalcium phosphate disks (TCP) of two configurations were inserted into 15-mm-diameter craniotomy wounds and nontreated control sites were evaluated in 60 rabbits. There were no adverse tissue reactions and no apparent difference in the clinical appearance of the 12- and 24-week implanted disks. By 36 weeks and continuing to 48 weeks, the omnidirectional TCP (OTCP) implants were degrading more rapidly than the unidirectional TCP (UTCP) implants, with degradation progressing centripetally and replacement by woven bone and maturing lamellar bone. Host-implant interface of both TCP configurations was a bone bond without interposed soft tissue. TCP disks may be clinically useful for craniotomy repair.
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    Journal of Biomedical Materials Research 23 (1989), S. 31-44 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The brain tissue reaction to permselective polymer capsules implanted in rats was evaluated for 1 to 54 weeks. The polymer capsules were well tolerated in all animals and no recognizable neurological or behavioral deficits were associated with the implants. Necrosis at the brain/polymer interface, as assessed with Nissl stain, was not observed. Foreign body giant cells were consistently absent. Immunocytochemically identified reactive neuroglial cells showed a remarkably low-grade tissue response to the synthetic material be yond the first 2 weeks of observation. Immunolabeled cortical neurons revealed conserved columnar arrays around the implants. Transmission electron microscopy showed a minimal degree of collagen deposition compared to implants in peripheral sites, and normal synapses within a few micrometers from the brain/polymer interface, supporting the prospect of biocompatible, immunoisolated xenografts in the central nervous system.
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    Journal of Biomedical Materials Research 23 (1989), S. 105-123 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Understanding how platelet activation responses are affected by polymers having varied surface physicochemical properties can lead to improved materials for vascular applications. The in vitro responses of human platelets were studied upon adherence to four polyurethaneureas with different soft segments, as well as to Biomer, and to Formvar. Platelets were observed by video-enhanced light microscopy (VLM) as they adhered to polymer films. Platelets were subsequently prepared for high-voltage transmission electron microscopy (HVEM) to view the cytoskeleton and other ultrastructural features. Scanning electron microscopy (SEM) was then used to characterize cell surface morphology and to survey platelet populations. Shape change and cytoskeletal reorganization differed on the various surfaces. The extent of shape change and cytoskeletal reorganization was related to polyurethane surface energetic properties. While the most extensive shape change was observed on the hydrophilic and polar Formvar surface, the least shape change was observed on a polyethylene oxide soft segment polyurethane with similar surface-water energetic properties. Therefore properties other than surface-water energetics must be involved in determining platelet responses to different classes of polymers. HVEM also showed that cytoskeletal reorganization proceeded to completion only on Formvar. Polyurethane adherent platelets, although appearing fully spread by SEM or VLM, never exhibited complete cytoskeletal reorganization.
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 23 (1989), S. 191-206 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Interactions of platelet with novel polyetherurethaneurea and its heparinized derivative were investigated. Platelet adhesion onto the material and release of serotonin or adenosine phosphate from platelet-rich plasma (PRP) were suppressed by an introduction of amino groups to polyetherurethaneurea, by quaternization of the polymer. When the material was precoated with one of major plasma proteins and the protein-coated materials were taken to contact with washed platelet suspension (WP), the dependence of platelet adhesion and activation on the properties of polymers was different from that observed for PRP interaction. Platelet adhesion and activation were promoted according to the nature of coating proteins in the order albumin 〈 γ-globulin 〈 fibrinogen and with increasing degree of denaturation of coating proteins. When the polymer materials were coated with proteins by immersing in aqueous solution containing two kinds of plasma proteins, adhesion behaviors of platelet were similar to those observed for PRP - uncoated material interaction. These experimental facts indicate that the selectivity of platelet for proteincoated material cannot be assessed by the interaction of WP with materials coated with a single kind of protein. It was concluded that material surface to which albumin is selectively adsorbed without denaturation does not stimulate adhering platelets for release reactions.
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  • 76
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    Journal of Biomedical Materials Research 23 (1989), S. 241-252 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: At high frequencies, electrochemical impedance behavior for corroding dental amalgams cannot be interpreted in terms of a simple Randles equivalent circuit. This may often be ascribed to the imperfect cell geometry resulting in a nonuniform current distribution. However, the insertion of a constant phase element (CPE) in the nonfaradaic branch of the equivalent circuit offers a new scope for interpretation as the circuit provides an m-parameter corresponding to the degree of distortion. The decrease of m as a function of time was explained by a mathematical model reflecting an increasing number of pores. Moreover, that same model allows a better understanding of the passivating effect of NaHCO3 and of the differences between conventional and Cu-rich dental amalgams.
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  • 77
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    Journal of Biomedical Materials Research 23 (1989) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 78
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    Journal of Biomedical Materials Research 23 (1989), S. 311-338 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In order to investigate the factors affecting the interaction of polyurethanes and blood, a series of poly (tetramethylene oxide)-based polyurethane block copolymers was synthesized with systematically varying levels of ion incorporation in the hard segment block. A bimolecular nucleophilic substitution reaction was used to replace up to 20% of the urethane hydrogens with propyl sulfonate groups. Bulk and surface characterization was performed, and a canine ex vivo arteriovenous shunt was used to monitor initial platelet and fibrinogen deposition on these surfaces. The microphase separation and bulk physical properties were found to vary with ionic content. Surface analysis using both in vacuo (ESCA) and water-equilibrated (contact angle) methods indicated that these polymers, and especially the highly sulfonated materials, could rearrange to minimize their interfacial tension, depending on the contacting environment. Platelet deposition onto these materials decreased as the level of sulfonation increased, with the highly sulfonated polymer showing substantially less platelet spreading and activation than previously seen in the same experiment with other polymers.
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  • 79
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    Journal of Biomedical Materials Research 23 (1989), S. 369-371 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 80
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    Journal of Biomedical Materials Research 23 (1989), S. 373-373 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 81
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    Notes: The fatigue properties of Simplex P and Palacos R bone cements were compared to their antibiotic impregnated counterparts AKZSupported in part by EM Laboratories, 5 Skyline Drive, Hawthorne, NY 10532; and The William H. Harris Foundation. and Palacos R with gentamycinAKZ bone cement is the trade name used by Howmedica Inc. of Rutherford, NJ to describe Simplex P mixed with 0.5 g of erythromycin and 0.24 g of colistin methane sulphonate Both the Simplex P and AKZ cements were obtained from Howmedica. Palacos R and Palacos R with gentamycin (0.5 g/40 g.) were supplied by E. Merck Laboratories. The effect of porosity reduction by centrifugation of all four cement types was also assessed. Fifteen specimens of each cement type were prepared according to manufacturer's instructions and 15 additional specimens of each cement type were prepared by mixing the powder with chilled monomer (0°C) and then centrifuging the cement immediately after mixing. Fifteen fully reversed tension-compression fatigue tests were performed at 15 MPa in stress control for each cement preparation in vitro while simulating the in vivo state (37°C and 100% humidity). The number of cycles to failure were recorded. There was no significant difference in the fatigue life of Palacos R and Simplex P when both cements were prepared in the standard fashion. The addition of 1/2 g of gentamycin to Palacos R did not significantly alter its fatigue properties. The addition of 0.5 g of erythromycin and 0.24 g of colistin did not decrease the fatigue life of Simplex P. Centrifugation significantly improved the fatigue properties of Simplex P and AKZ. The fatigue lives of Palacos R and Palacos R with gentamycin were not improved by centrifugation. The fatigue life of centrifuged Simplex P was significantly greater than the fatigue life of Palacos R and of Palacos R with gentamycin, whether the Palacos R based cements were centrifuged or not.
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  • 82
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    Journal of Biomedical Materials Research 23 (1989), S. 457-475 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tensile testing of tissue strips has been used to examine the effect of simple fixation in glutaraldehyde and formaldehyde on the viscoelastic properties of bovine pericardium. To assess tissue anisotropy, tissue strips were cut at 0°, 30°, 60°, and 90° relative to the base-to-apex direction. Fresh anterior pericardium was modestly anisotropic, being least extensible in the base-to-apex direction; however, fixation removed this anisotropy. Fixation also produced a marked change in the response of the material to initial cyclic loading during preconditioning. Overall extensibility of the fixed material was significantly greater than that for the fresh tissue, consistent with a 10.7% shrinkage in aldehydes calculated from strain at fracture data. Reductions in stress relaxation and creep after fixation were noted as well, consistent with intrafibrillar crosslinking. Cyclic hysteresis and ultimate tensile strength were unaffected. Since the observed changes in the stress-strain response were largely attributable to shrinkage, control of shrinkage by physical means would allow for engineering modification of bovine pericardial mechanics for controlled anisotropy.
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  • 83
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    Journal of Biomedical Materials Research 23 (1989), S. 529-530 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 84
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    Journal of Biomedical Materials Research 23 (1989), S. 549-569 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The adsorption of bovine serum albumin from flowing solutions onto germanium and three polyetherurethanes varying in soft segment content was studied by a Fourier transform infrared/attenuated total reflectance technique. Spectral differences observed in the amide I, II, and III regions upon adsorption to all four surfaces were consistent with a loss of helix and gain of β-structure. There appeared to be a slight difference between BSA adsorbed to germanium and the PEUs, but no distinction could be made between BSA adsorbed to the different PEUs.
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  • 85
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    Journal of Biomedical Materials Research 23 (1989), S. 611-630 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A covalently bonded conjugate of commercial grade heparin and prostaglandin E1 (PGE1) was synthesized to prevent both fibrin formation and platelet aggregation during thrombus formation. The PGE1-heparin conjugate was immobilized on an imidazole carbamate derivatized sepharose bead surface through hydrophilic spacer groups (diamino-terminated polyethylene oxides). One end of the spacer group was coupled to the derivatized surface through a urethane bond between the amine group of the spacer and the derivatized surface. The free amine group of the immobilized spacers was coupled to a carboxylic group of the PGE1-heparin conjugate through an amide bond. Bioactivity of the immobilized conjugate (heparin activity) was measured in terms of increased clotting times (thrombin time assay) and for the inactivation of Factor Xa. Bioactivity of the immobilized compound (PGE1 activity) was analyzed by platelet adhesion and platelet release reactions using C14-5-hydroxytryptamine (5-HT). The conjugate immobilized via the C2 spacer showed the highest incidence of platelet adhesion, 5-HT released and the lowest activity for coagulation factors. In contrast, the 1000 and 4000 immobilized systems showed a significant reduction in platelet activation, while having the greatest effect on coagulation factors. The results of these experiments imply that the immobilized conjugate is active in preventing both pathways of thrombus formation, and the efficacy is improved thorugh the use of long-chain hydrophilic spacer groups.
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  • 86
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    Journal of Biomedical Materials Research 23 (1989), S. 671-673 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 87
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    Journal of Biomedical Materials Research 23 (1989), S. 719-733 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The influence of type and quantity of five different crosslinking agents on tensile creep properties of multiphase acrylic systems has been studied. The polymeric materials, commonly applied in bioengineering, were processed by polymerization of a mixture of liquid methacrylate monomers and poly(methyl methacrylate) powder. The specimens were made with various ratios of methyl methacrylate and crosslinking agents in the monomer liquid. Two different processing conditions were used, i.e., heat-polymerization at 100°C and autopolymerization at 45°C. Creep behavior was determined at 37 ± 0.2°C and 50 ± 0.5°C. The investigation showed higher creep values for autopolymerized than for heat-polymerized materials. In heat-polymerized materials the creep curves showed little variation with type and quantity of crosslinking agents at low stress levels. However, at high stress levels the creep values decreased with increasing quantity of crosslinking agents. The autopolymerized materials showed a more inhomogeneous structure, and great variation in creep. Both among the heat-polymerized and autopolymerized materials, the systems with diethyleneglycol dimethacrylate clearly deviated from the others by showing higher creep values.
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  • 88
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    Notes: The adhesive properties of a series of oligomers prepared from 2-isocyanatoethyl methacrylates (IEM) and/or m-iso-propenyl-α,α-dimethylbenzyl isocyanate (TMI) and various acrylates or methacrylates were studied. The bond strength of bone, dentin, or soft tissue specimens joined with these oligomers respectively to bone, dental composite restorative, or denture base resin were determined by tensile adhesion or shear tests. These oligomers are more effective in forming stronger bonds to bone than are other tissue adhesives. Fracture occurs cohesively, usually within the bone. Thermocycling in water for 1 week between 5°C and 55°C did not decrease adhesion indicating that exposure to water or thermal shock produced no deterioration of the bond. Tensile adhesion of bovine or human dentin joined to composite restorative resin by means of the oligomers is similar to that of the best dental bonding agents such as Gluma (glutaraldehyde and 2-hydroxyethyl methacrylate) or ferric oxalate + Nphenylglycine + dimethylacryloxyethyl-pyromellitate. These oligomers also strongly bond soft tissues and calfskin and to acrylic resins and composites.
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  • 89
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    Journal of Biomedical Materials Research 23 (1989), S. 819-831 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This study was conducted to investigate some fundamental fatigue testing variables as they apply to the response characteristics of acrylic bone cement. Cyclic loading under load control was conducted at frequencies of 1, 2, 5, 10, and 20 Hz in air at room temperature. At a tensile stress range of 0.3-20.0 MPa the fatigue life increased linearly with logarithmic frequency. The effect of conditioning and testing in saline at both room temperature and 37°C at similar stress levels and a frequency of 10 Hz were also examined. When compared to dry testing at room temperature, testing in saline at 37°C resulted in a reduction in fatigue life while testing in saline at room temperature produced an increase in fatigue life. Of a number of statistical distributions considered, the Weibull was found to be the most appropriate in documenting the findings of this investigation. A companion fractographic investigation of the failure surfaces demonstrated distinct regions of crack growth and fast fracture.
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  • 90
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    Journal of Biomedical Materials Research 23 (1989), S. 845-862 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study was conducted to determine the ability of hamsters to eliminate in the urine, or store in the organs, large quantities of metal salts given over a period of several months. In addition, the effect of prior immunization on metal ion clearance was determined. The results indicated that nickel was rapidly eliminated in the urine and that the level in the organs was similar to that of control animals. Cobalt was eliminated more slowly than was nickel. The organ levels of cobalt were similar to those of control animals with a slight elevation in the liver of the injected animals. Chromium was eliminated in the urine very slowly, was red cell associated, and the levels were elevated in all the organs (liver, lung, spleen, kidney) compared to control. Prior immunization with metal salts increased the storage of chromium.
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  • 91
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    Journal of Biomedical Materials Research 23 (1989), S. 895-909 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Identically prepared, screw-type ceramic and titanium endosteal dental implants were inserted in the jaws of adult mongrel dogs for periods of up to 6 months. Sixteen of the 32 total implants supported fixed bridgework. The interface of bone and soft connective tissues with the dental implants was examined by routine and innovative scanning electron microscopic (SEM) techniques using both secondary and backscattered electron imaging. Results demonstrated excellent bone adaptation to both titanium and ceramic implants. Direct adaptation of bone to the upper third of both type implants was observed with only minimal amounts of any intervening fibrous connective tissue. A composite of trabecular bone and fibrous connective tissue was observed in the lower two-thirds of the implants examined. Areas of bone alteration suggestive of osteoid were observed at the thread apicis of some loaded implants. From this investigation we concluded that similar longitudinal tissue responses were generated to one-piece, cylindrical screw-type titanium and alpha alumina oxide ceramic dental implants. Possible bone remodeling was observed at the thread apicis of the loaded implants, an area where occlusal forces may be distributed. We further suggest that one-stage endosteal implants are capable of maintaining a proportional bone-to-implant interface at the apical support region, similar to that suggested to two-stage implant systems.
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  • 92
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    Journal of Biomedical Materials Research 23 (1989), S. 947-951 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: There are no differences in the multinucleate cell formation in normal and athymic mice after the subcutaneous implantation of a cellophane strip. The number of Ia+ epitheloid cells and multinucleate foreign body giant cells was lower and the number of epitheloid cells sharing the marker of activated macrophages (M 57) was higher in athymic compared to normal mice. The epitheloid cells of athymic and euthymic animals exhibited no difference in the expression of Mac-2 molecule. The difference of the expression of surface markers between athymic and euthymic animals does not influence the foreign body giant cell formation.
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  • 93
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    Journal of Biomedical Materials Research 23 (1989) 
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  • 94
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    Journal of Biomedical Materials Research 23 (1989), S. 1027-1047 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The surface reactivity of the dog heartworm (D. immitis) was evaluated by comprehensive contact angle measurements and a platelet retention test. Contact angle data yielded calculated surface energy terms very similar to those previously reported for intact vascular endothelium. The platelet test revealed the native worm surface to be nonreactive, retaining fewer platelets than glass or worms whose surfaces had been modified by extraction with acid and high salt solutions. The cuticular morphology of the heartworm was studied with both light and electron microscopy, the latter coupled with ferritin-conjugated double-layer immunolabeling to reveal adsorbed host protein on the cuticle surfaces. Multiple attenuated internal reflection (MAIR) IR spectroscopy confirmed the general composition of this surface layer to be glycoproteinaceous. Morphological and histochemical studies confirmed and extended previous descriptions of nematode cuticle, adding ultrastructural detail on cortical, medial, and basal layers. A trilaminar membrane, apparently corresponding to a mammalian cell membrane (plasmalemma), constituted the external cortical layer as observed in high magnifications. The existence of a glycocalyx of varying thickness was demonstrated in ruthenium red-stained sections. MAIR IR spectra showed this glycoproteinaceous film to appear, in fully hydrated samples, as a loose biological gel. Ferritin-antibody conjugate labeling confirmed the presence of adsorbed dog albumin, dog immunoglobulin class G (IgG) and dog complement fraction 3 (C3) in the cuticular surface layer. It is likely, therefore, that D. immitis heartworms demonstrate long-term thromboresistance at least in part due to their passive low-surface-energy overcoating with host proteins.
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  • 95
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The cytotoxicity of hydroxyapatite (HA), tricalcium phosphate (TCP), and two types of phosphate (TCP), and two types of apatite-containing glass-ceramics designated A · W-GC and A · W · CP-GC was evaluated by the direct contact method using V79 cells. Compatibility of the cells was assessed as a function of cellular attachment and subsequent growth using scanning electron microscopy. Although all of the tested materials have surfaces available for cellular attachment, cell growth was markedly inhibited by HA sintered at 600°C and 900°C, and slightly inhibited by HA sintered at 1200°C, TCP and the glass-ceramics. In attempts to clarify the cause of this toxicity, the interactions of the ceramics with culture medium was assessed by measurement of calcium (Ca), inorganic phosphate (P), magnesium (Mg), pH and albumin content in the medium. The grade of toxicity corresponded to the degree of reduction of Ca, P, and albumin in the medium. Furthermore, surface reactions of the ceramics were demonstrated to vary in both mode and degree depending on their chemical structure and level of microporosity. Thus, the surface reactivity of ceramic materials should be always taken into account in discussing their biocompatibility in vivo.
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  • 96
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    Notes: Collagen fibers composed of type I collagen molecules were studied for biocompatibility and mechanical properties. These fibers were crosslinked using two different processes: (1) glutaraldehyde, (2) dehydration followed by exposure to cyanamide (DHT/C); the latter method produces only urea as a by-product of the crosslinking process and is postulated to be more biocompatible. An in vitro model using rat tendon fibroblasts growing on individual fibers was used to evaluate outgrowth rates, cell/fiber interactions, and cell morphology. These studies showed an advantage with DHT/C crosslinking, relative to glutaraldehyde crosslinking, in promoting fibroblast growth. In vivo intramuscular implantation in rats showed excellent biocompatibility for both kinds of collagen implants. In addition, aligned ingrowth into the implant from the medial collateral ligament when applied in that location was demonstrated. Mechanical testing demonstrated the higher strength of dry fibers; however, upon hydration, there was a marked decrease in stress to failure. This reduction in strength was due principally to an increase in cross section due to swelling. These collagen fibers appear to be very biocompatible even in the presence of low concentrations of glutaraldehyde. They promote fibrous aligned ingrowth in a setting of ligament healing. Thus, they represent a strong candidate as a scaffold ligament or tendon prosthesis if crosslink density can be increased.
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  • 97
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    Journal of Biomedical Materials Research 23 (1989), S. 1067-1085 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of a grooved titanium-coated substratum on epithelial (E) cell behavior were studied in vitro and in vivo. V-shaped grooves, 10 m̈m deep, were produced in silicon wafers by micromachining, a process which was developed for the fabrication of microelectornic components. The grooved substrata were replicated in epoxy resin and coated with 50 nm of titanium. More E cells were found attached to the grooved titanium surfaces than to adjacent smooth surfaces. In comparison to the smooth surfaces where clusters of E cells were randomly oriented, on the grooved surfaces, clusters of E cells were markedly oriented along the long axis of grooves. Grooved and smooth titanium-coated epoxy implants were placed percutaneously in the parietal area of rats. Electron and light microscopic obsrvations indicated that E cells were tightly attached to the implant surfaces and this attachment is through basal lamina-like and hemidesmosome-like structures. In the grooved portion of the implant, E cells interdigitated into the grooves and had rounded nuclei. Histomorphometric measurements indicated that there was a shorter length of epithelial attachment, longer length of connective tissue attachment, and less recession in the grooved, compared to the smooth portion of implants after 7 and 10 days. These results indicate that horizontal grooves produced by micro-machining can significantly impede epithelial downgrowth on titanium-coated epoxy implants.
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    Journal of Biomedical Materials Research 23 (1989), S. 1097-1100 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 99
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    Journal of Biomedical Materials Research 23 (1989), S. 979-1005 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hydrophilic-hydrophobic multiblock copolymers synthesized from telechelic oligomers of poly(ethylene oxide) (PEO) and polystyrene (PS) have been used to study the influence of hydrophilic and hydrophobic balance on interfacial interactions of these surfaces with blood components. In vitro coagulation assays show no inherent ability of these amphiphilic surfaces to affect contact activation or coagulation factors. In vitro platelet adhesion and release reactions from rabbit platelet-rich plasma were shown to be greatest on Biomer and PS homopolymer surfaces and least on cross-linked PEO surfaces, with the PEO-PS block copolymers demonstrating intermediate responses. These same substrates were tested in a new low-flow, low-shear arterio-artery shunt system in rabbits. Whole blood occlusion times were not a direct function of hydrophilic content as both PEO and PS homopolymers and Biomer showed short occlusion times, while PEO-PS block copolymers prolonged occlusion times considerably, depending on composition. Overall, results suggest that PEO-PS block copolymers promote unique whole blood responses in contrast to homopolymer and Biomer controls which are more complex than direct correlations to bulk hydrophilic and hydrophobic contents.
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    Journal of Biomedical Materials Research 23 (1989), S. 1007-1026 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Of the many factors determining host biocompatibility responses to implanted biomedical polymers, the cellular interactions at the tissue/material interface have been recognized to be some of the most important. The present study has combined results both from an in vitro cell culture system and from an in vivo animal model to examine this host response. In vitro results suggest that a variety of polymer materials can differentially activate human monocytes to produce a protein(s) having different biological activites. The polymers tested induce the production of the regulatory inflammatory protein interleukin 1 as well as a factor that enhances fibroblast proliferation and collagen synthesis. The observed activities of these factors appear to be related but not identical, and are dependent upon the specific polymer. Evaluation of exudate and tissue responses to these same polymer materials in an in vivo model are also presented. Both in vitro and in vivo results support the hypothesis that monocyte/macrophage activation with subsequent synthesis of regulatory factors such as interleukin 1 plays a significant role in determining the host response to biomedical polymer implants.
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