摘要:

AbstractIn order to investigate the interaction between various sulfonated polyurethanes (PUs) and blood, a commercial PU surface was chemically modified by poly(ethylene oxide) (PEO), dodecanediol(DDO), and propane sultone to give hydrophilic, hydrophobic, and negative sulfonated surfaces, respectively. The blood compatibility of modified PUs was evaluated by anin vitroplatelet adhesion test, activated partial thromboplastin time (APTT), and prothrombin time (PT) measurements as well as anex vivorabbit A‐A shunt method. In the platelet adhesion test, the hydrophilic PEO grafted PUs showed less platelet adhesion than untreated PU and hydrophobic DDO grafted PU. Sulfonated PU‐PEO exhibited a lower degree of adhesion and shape change of platelet. The APTT and PT, especially APTT, of the sulfonated PUs were extended, whereas those of PU‐PEO and PU‐DDO did not show any significant change compared with untreated PU. Meanwhile, in theex vivoexperiment, hydrophilic PEO grafted PUs showed longer occlusion times than untreated PU or hydrophobic DDO grafted PU. In addition, the incorporation of SO3groups at the end of PU‐DDO and PU‐PEO, particularly PU‐PEO‐SO3, exhibited an enormous prolongation in occlusion time, indicating a synergistic effect of the hydrophilic PEO and the negative SO3groups on thromboresistance. These occlusion times corresponded well to invitroevaluation results: the less adhesion and shape change of platelet and the longer APTT and PT, the more extended theex viv

ISSN:0021-9304    

DOI:10.1002/jbm.820250502

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo types of liquid crystal (LC)‐immobilized membranes were prepared by a soaking method and sandwich method to control the permeation of indomethacin, as a model drug, in response to local and systemic fever. Monooxyethylene trimethylolpropane tristearate (MTTS) was used as a model LC because it has a gel‐liquid crystal phase transition temperature near the body temperature, 39–40°C in phosphate buffered saline (pH 7.4). Two porous polypropylene (PP) membranes were soaked into 20% MTTS chloroform solution in the soaking method, and two PP membranes were poured with the melted MTTS and pressed in the sandwich method. Thermo‐response efficacy of the soaked membrane was dependent upon the content of MTTS in MTTS membrane, and the MTTS content above the void volume of PP membrane (38%) was needed for high efficacy. On the other hand, the sandwich membrane exhibited higher thermo‐response efficacy than the soaked membrane, because more LC was embedded in the pores of sandwich membrane than that of the soaked membrane. The sandwich membrane permeation of indomethacin was sharply controlled by temperature changes between 3

ISSN:0021-9304    

DOI:10.1002/jbm.820250503

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractSingle and multi‐strand stainless steel and cobalt‐nickel alloy wires, with strand diameters from 26 to 46 μm, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi‐stranded wires have the same average fatigue life as their individual constituent strands but the variance of that life is smaller (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure, (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodesin vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize servic

ISSN:0021-9304    

DOI:10.1002/jbm.820250504

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe present study was designed to ascertain if dynamic ionic matrices that mimic the mineralization front could be used as active scaffolds for bone repair. Dentinal phosphophoryn calcium salts were extracted from unerupted bovine dentin using chatopic buffers and EDTA. The phosphophoryns were subsequently isolated following precipitation with CaCl2. The phosphophoryn‐Ca+2salts were then mixed with pepsin solubilized bovine skin collagen and lyophilized into hardened sponges. Three groups of 4 beagle dogs were employed such that one leg served as an experimental test site for a mechanical wound, while the contralateral leg served as a control. Animals were sacrificed at 1, 3, and 6 month intervals. The test specimens were harvested, fixed, and processed for routine histology, examined with image histomorphometric analysis, and scored. Tabulation of these data indicated that phosphophoryn‐Ca+2‐collagen enhances the repair of mechanically formed osseous defects in the distal femur of beagle dogs. This enhanced rate of bone repair was manifest by earlier filling of bony voids with osteoid and trabecular bone. Eventually, this process was followed by recortification of the surface defects. These data suggest that components derived from a mineralization front may influence bone formation in unicortical defects within long

ISSN:0021-9304    

DOI:10.1002/jbm.820250505

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe objective of this study is to evaluate anin vitromodel to assess the effects of serum‐material interactions on complement activation, macromolecular adsorption, and lymphocyte response. Minifilters of clinically available materials (PVA, EVAL‐4A, and EVAL‐D) used in extracorporeal therapies were evaluated. The test circuit consisted of a pump, sterile tubing, collection vessels, and the minifilter. A sham circuit similar to the test circuit was constructed, but without the filter. Serum flow rates and volumes processed were scaled down to those of clinical use. Post PVA serum showed the highest degree of complement activation, macromolecular solute adsorption, and lymphocyte suppressive response when incubated with Con‐A, PHA, PWM, and Candida. Post EVAL‐4A sera enhanced the response of lymphocytes to Con‐A and PHA, while Post EVAL‐D sera showed a slight suppression to these mitogens. Blood‐material interactions have been shown to cause blood cellular changes. Thein vitromodel employed is simple to apply and does not require an animal or patient. The membrane modules used are a mini‐type of clinically available extracorporeal filters, and there is a greater direct relevancy to clinical applications than there would be using specially formulated materials. This system would provide useful preclinical information in evaluating the effects of serum‐ma

ISSN:0021-9304    

DOI:10.1002/jbm.820250506

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe activation of cells by interaction with solid surfaces is important in many settings, including the response of tissue to implanted materials. However, few comprehensive studies of both cell migration and activation have been performed so that the connection between these events and immunological activation against foreign material is not well understood. In the present study, synthesis and expression of Ia antigens by peritoneal exudate macrophages after implantation of different carbon fiber composites in the rat peritoneal cavity have been investigated in order to determine whether the type of material implanted affected the composition of Ia‐bearing cells of the exudate. The results have confirmed the low level of expression of Ia on resident peritoneal macrophages; while we have found that macrophages, harvested after implantation, express a different amount of Ia related to the different cure cycles of the composite materials use

ISSN:0021-9304    

DOI:10.1002/jbm.820250507

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractGrowth rates of rat tendon fibroblasts cultured in a three‐dimensional carbon fiber matrix were compared with those of cells cultured on standard flat culture plates. The carbon fiber has been used as a tissue scaffold for tendon and ligament repair in animal and clinical studies. While cell growth on the culture plates appears to follow a growth curve containing a lag phase, a log phase, and plateau phase of growth, cell growth in the fiber matrix was characterized by a suppressed log phase of growth. SEM and cytotoxicity studies indicated that this effect was not caused by growth‐inhibiting or cytotoxic substances from the carbon fiber. While we cannot rule out the possibility that cell growth was influenced by the surface chemistry of the carbon substrate, evidence from this and other studies suggests that the observed effect was caused by a lack of readily available surface area for cell attachment and growth on the small fibers. Because cell colonies growing on individual fibers are limited (at least in theory) to growing in two directions only, they enjoy limited opportunities for cell migration and growth– in contrast with cell colonies on flat culture plates. These results suggest fundamental differences in the mechanisms controlling cell growth on planar vs. three‐dimensional fiber sub

ISSN:0021-9304    

DOI:10.1002/jbm.820250508

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractProgesterone‐loaded microspheres are fabricated by a solvent evaporation process from a poly(D,L‐lactide‐co‐glycolide) (85/15 PLG) and from α‐progesterone. Methylene chloride is used as solvent and polyvinyl alcohol and methylcellulose are used as surfactants. The microspheres are characterized by scanning electron microscopy, differential scanning calorimetry, and x‐ray powder diagrams. Our study shows that the morphology and the thermal behavior of PLG microspheres can vary significantly with progesterone loading and sample thermal history. Below and at 16.5% loading the microspheres exhibit a smooth outer surface. Above 23% loading, the surface becomes rough, embedded by copolymer particles or well‐defined crystals. Pores and cracks can also be observed. Below 35% the progesterone is molecularly dispersed. At 35% and above crystal doMayns of the steroid appear and two crystalline forms are found: α‐ and β‐progesterone. The physical state of progesterone and the nature of its crystal doMayns dispersed in the PLG matrix can change during storage. Also a progressive development of an endothermic peak at theTgevent of the copolymer is observed during storage. No well defined relationship of peak size to progesterone

ISSN:0021-9304    

DOI:10.1002/jbm.820250509

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractHealing of large open dermal wounds is associated with decreased values of the tensile strength even up to 6 months postwounding. Results of previous studies have shown that healing is facilitated in the presence of a type I collagen sponge by promoting deposition of newly synthesized large‐diameter collagen fibers parallel to the fibers of the sponge. In this study healing is evaluated in dermal wounds treated with a collagen sponge seeded with fibroblasts or coated with basic fibroblast growth factor (bFGF).Experimental results indicate that the presence of a collagen sponge results in increased wound tensile strength and increased collagen fiber diameters in the upper dermis 15 days post‐wounding in an excisional guinea pig dermal wound model. In comparison, dermal wounds treated with collagen sponges seeded with fibroblasts or coated with bFGF showed increased tensile strengths 15 days postimplantation and increased degree of reepithelialization. These results indicate that fibroblast seeding and bFGF coating in conjunction with a type I collagen sponge matrix facilitate early dermal and epidermal wound heal

ISSN:0021-9304    

DOI:10.1002/jbm.820250510

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820250511

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY