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Record 4181 to 4200

The sinus lift with phycogenic bone substitute. A histomorphometric study
Simunek, A., M. Cierny, et al. (2005), Clin Oral Implants Res 16(3): 342-8.
Abstract: OBJECTIVES: The aim of this histomorphometric prospective study was to ascertain the efficacy of phycogenic bone substitute in an augmented sinus. The process of graft healing, bone remodeling, and biomaterial replacement was examined. MATERIAL AND METHODS: The phycogenic material (fluorohydroxyapatite) made from calcium-encrusted sea algae was used for the sinus lifts. Twenty-four procedures were carried out (one-stage and two-stage equally) and 45 titanium stepped-screw implants were placed. The patients were followed for 12-23 months. In intervals of 6, 9, 12, or 15 months after the sinus lift, 24 graft specimens were taken with a trephine bur. These specimens were examined histomorphometrically. RESULTS: The grafting material was gradually resorbed and replaced by newly formed bone. Between the sixth and 15th month after the sinus lift, the percentage of newly formed bone grew linearly (from 15.5+/-9.6% to 40.8+/-15.3%) and the percentage of bone substitute decreased linearly (from 34.5+/-8.6% to 13+/-9.6%). After 15 months, the density of trabeculae in grafted bone corresponded to cancellous bone of good quality; however, the bone substitute was not completely resorbed during this period. No significant difference between the quality of the newly formed bone in the cases of the one- and two-stage sinus lifts was found. CONCLUSION: Sinus lift carried out with phycogenic bone substitute was shown to be an effective method with limited invasiveness and a high survival rate of implants (97.8%).

The spatial resolution of protein adsorption on surfaces of heterogeneous metallic biomaterials
Williams, R. L. and D. F. Williams (1989), J Biomed Mater Res 23(3): 339-50.
Abstract: 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.

The S-ROM stem and its use with alternative bearings
Politi, J. (2005), Orthopedics 28(9 Suppl): s1053-5.
Abstract: Many long-term studies of total hip arthroplasty (THA) show excellent results. This long-term success depends on many factors, including implant fixation and bearing surface wear. As THA is commonly performed on patients with a steadily increasing life span and activity level, the issue of wear has become critical. Advances in the wear properties of polyethylene have been significant, but, in the search for low long-term wear rates, hard bearing surfaces are frequently used.

The S-ROM stem: versatility of stem/sleeve combinations and head options
Buly, R. (2005), Orthopedics 28(9 Suppl): s1025-32.
Abstract: The S-ROM stem (DePuy Orthopaedics Inc., Warsaw, Ind) is a modular cementless hip implant that has a modular proximal sleeve that mates with a fluted stem. Various sleeves, stem lengths, diameters, proximal body types, and heads can be configured into 10,398 combinations. Independence of the sleeve and stem version permits correction of excessive anteversion found in types of dysplasia and the retroversion deformities found in revision total hip arthroplasty (THA). The fluted distal segment provides stability if a corrective osteotomy is required. The stem is a versatile tool in primary or onversion hip arthroplasty with unusual deformity and in revision THA.

The stability of methacrylate biomaterials when enzyme challenged: kinetic and systematic evaluations
Yourtee, D. M., R. E. Smith, et al. (2001), J Biomed Mater Res 57(4): 522-31.
Abstract: This study addressed whether methacrylate monomers and polymers used in dentistry might degrade from enzymolysis by acetylcholinesterase (ACHE), cholesterol esterase (CHE), porcine liver esterase (PRLE), and a pancreatic lipase (PNL). Short (hour) and long-term (day) exposures were performed. Product ratios were used to determine surface hydrolysis of the polymeric materials. Enzyme kinetics were studied for the monomers when challenged by ACHE, CHE, and PRLE. In the case of PRLE, the V(max) for the dimethacrylate substrates varied slightly, but amounted to as much as 10% of that of p-nitrophenylacetate. The K(m) for triethylene glycol dimethacrylate (TEGDMA) was 197 microM for ACHE and 1107 microM for CHE. The V(max) was 2.7 nmol/min for ACHE and 3.5 nmol/min for CHE. TEGDMA was converted by CHE at 2% the rate of cholesteryl oleate. Long-term incubations of monomers with CHE and ACHE produced degrees of hydrolysis that evidenced structure dependency in the ability of the enzymes to effect hydrolysis. Particularly resistant were aromativ derivatives and those with branching in methacrylate linkages. Overall, the study confirms the ability of physiologically important esterases to catalyze the hydrolysis of biomaterial methacrylates.

The structure of a biomaterial rather than its chemical composition modulates the repair process at the peritoneal level
Bellon, J. M., F. Jurado, et al. (2002), Am J Surg 184(2): 154-9.
Abstract: BACKGROUND: This study was designed to establish whether the spatial structure of a prosthesis conditions its behavior at the peritoneal level. METHODS: Abdominal defects comprising all the wall (except skin) were created in rabbits and repaired with a laminar (DM) or reticular (CV-4) ePTFE-prosthesis. Fourteen days postimplant, specimens were obtained for scanning electron and light microscopy. Peritoneal adhesions, resistance to traction, and neoperitoneum thickness were quantified. RESULTS: Adhesions to CV-4 were firm and integrated within surrounding tissue; only scarce adhesion formation was observed for DM. Adhesion area was significantly greater (P <0.01) in the CV-4 than in DM (7.00 +/- 2.6; 0.15 +/- 0.08 cm(2)). The neoperitoneum was organized for DM and disorganized for CV-4. This layer was significantly thicker (P <0.05) in DM than CV-4 (455 +/- 3.4; 70 +/- 3.1 microm). The CV-4 showed a greater resistance to traction than the DM (26.75 +/- 3.71; 14.11 +/- 3.71 N; P <0.05). CONCLUSIONS: The structure of a biomaterial, rather than its chemical composition, modulates behavior at the peritoneal interface.

The susceptibility of prosthetic biomaterials to infection
Carbonell, A. M., B. D. Matthews, et al. (2005), Surg Endosc 19(3): 430-5.
Abstract: BACKGROUND: Despite the use of a sterile technique and the administration of prophylactic antibiotics during surgical procedures, mesh infection continues to complicate the use of biomaterials. The purpose of this study was to compare the susceptibility to infection of prosthetic biomaterials in a live-animal model. METHODS: The following seven prosthetic mesh biomaterials were used in this study. Expanded polytetrafluoroethylene (ePTFE) with silver/chlorhexidine (DM+), ePTFE (DM), porcine intestinal submucosa (S), polypropylene (M), ePTFE/polypropylene (X), hyaluronate/carboxymethylcellulose/polypropylene (SM), and human acellular dermal matrix (A). Lewis rats (n = 108) underwent creation of a single ventral hernia; 105 of them were repaired with a different mesh (2-cm2 piece). Twelve pieces of each mesh were inoculated at the time of hernia repair with 10(8) Staphylococcus aureus (n = 84). Three pieces of each mesh were placed without bacterial inoculation (n = 21). In three animals, no mesh was placed; instead, the peritoneum of the hernia defect was inoculated (n = 3). After 5 days, the animals were killed and the mesh was explanted (peritoneum for the nonmesh control). The mesh was vortex-washed and incubated in tryptic soy broth. Bacterial counts were determined using serial dilutions and spot plates and quantified in colony-forming units (CFU) per square centimeter of mesh present in the vortex wash fluid (wash count) and the soy broth (broth count). Data are presented as the mean log(10), with analysis of variance (ANOVA) and Tukey's test used to determine significance (p < 0.05). RESULTS: The DM+ material had no detectable live bacteria in the wash or broth counts in 10 of 12 tested samples (p = 0.05). Of the samples that showed bacterial growth, the peritoneum control group had a lower wash count than A (p = 0.05) and the lowest broth count of all the materials except for DM+ (p = 0.05). In addition, SM had a significantly lower wash count than A (p = 0.05), with no broth count difference. In regard to wash and broth counts, DM, M, X, SM, S, and A were no different (p = NS). CONCLUSIONS: The DM+ material was the least susceptible to infection. Impregnation with silver/chlorhexidine killed the inoculated bacteria, preventing their proliferation on the mesh surface. Other than DM+, native peritoneal tissue appears to be the least susceptible to infection. Silver/chlorhexidine appears to be an effective bactericidal agent for use with mesh biomaterials.

The SV stent study: a prospective, multicentre, angiographic evaluation of the BiodivYsio phosphorylcholine coated small vessel stent in small coronary vessels
Bakhai, A., J. Booth, et al. (2005), Int J Cardiol 102(1): 95-102.
Abstract: OBJECTIVE: To evaluate the use of the phosphorylcholine (PC) coated BiodivYsio small vessel (SV) stent in native coronary vessels of small calibre. DESIGN AND SETTING: Prospective, multi-centre, multi-national registry with 6-month clinical and core-lab angiographic follow-up. Adverse events were adjudicated by a Clinical Events Committee (CEC) and included peri-procedural analysis of cardiac enzymes. PATIENTS: Patients with signs or symptoms of ischaemia with an identified target lesion in an epicardial vessel with reference diameter 2.0-2.75 mm were enrolled. Intervention in other epicardial territories in the same patient was permitted. RESULTS: Recruitment of 150 consecutive lesions (in 143 patients) was completed in 19 centres in Europe and Israel. The stent was deployed successfully in all but one lesion. At 6 months, 1 patient (1%) had experienced sudden cardiac death, 4 further patients (3%) had a non-Q wave MI, and a further 24 patients (17%) had repeat revascularisation of a study target vessel. The mean reference vessel diameter prior to stenting was 2.2 mm (S.D. 0.4). Mean minimal luminal diameters at pre-procedure, post procedure and follow-up were 0.6 mm (S.D. 0.3), 2.0 mm (S.D. 0.4) and 1.2 mm (S.D. 0.6), respectively. The late lumen loss index was 0.55 (S.D. 0.53) with a binary restenosis rate of 32%. CONCLUSIONS: In stenting of selected lesions in small vessels, the BiodivYsio SV stent demonstrated high rates of implant success. The rates of major adverse cardiac events (MACE), angiographic restenosis and repeat revascularisation are similar to those reported in other small vessel bare metal stent studies.

The synthesis and antioxidant activity of the Schiff bases of chitosan and carboxymethyl chitosan
Guo, Z., R. Xing, et al. (2005), Bioorg Med Chem Lett 15(20): 4600-3.
Abstract: Five kinds of Schiff bases of chitosan and carboxymethyl chitosan (CMCTS) have been prepared according to a previous method and the antioxidant activity was studied using an established system, such as superoxide and hydroxyl radical scavenging. Obvious differences between the Schiff bases of chitosan and CMCTS were observed, which might be related to contents of the active hydroxyl and amino groups in the molecular chains.

The synthesis of GoldMag nano-particles and their application for antibody immobilization
Cui, Y., Y. Wang, et al. (2005), Biomed Microdevices 7(2): 153-6.
Abstract: Fe3O4/Au (GoldMag) particles with core/shell structure were synthesized by reduction of Au3+ with hydroxylamine in the presence of Fe3O4. The synthesized particles have an average size smaller than 100 nm in diameter with of superparemagnetic properties due to their Fe oxide cores. The particles show optical features with a plasmon resonance peak from 550, 570 to 590 nm correlating with increasing diameters from 50 nm, 70 nm to 100 nm.The GoldMag particles need only a single step for antibody immobilization and have high binding capacity for antibodies. These advantages permit improved methods of isolating and detecting biomolecules.

The telescoping suture--Part 1: Does this technique improve the mechanical behavior of a biomaterial? Calf pericardium
Garcia Paez, J. M., E. Jorge Herrero, et al. (2002), J Biomater Appl 17(2): 85-103.
Abstract: The authors study the mechanical behavior of calf pericardium employed in the construction of cardiac valve leaflets when subjected to telescoping suture, followed by tensile stress until rupture. One hundred twenty pericardial tissue samples were employed, 60 cut from root-to-apex and another 60 cut in transverse direction. Each of these two groups consisted of 12 control samples that were left unsutured and four sets of 12 samples each that were rejoined by telescoping suture using silk, Prolene, nylon or Gore-Tex., and subjected to tensile stress. At the rupture of the sutured tissues, the tensile stress of the suture materials ranged between 57.54 MPa for the series sewn lengthwise with Gore-tex and 114.08 MPa for the series sewn crosswise with silk. At these levels of stress, the deformation of the suture thread was much less marked than that of the calf pericardium, and internal stresses were produced that were difficult for the biomaterial to absorb. There was a loss of real load in all the sutured series when the observed resistance to rupture, expressed in kilograms, was compared with the estimated value. This loss of resistance did not invalidate the telescoping suture technique since the resistance to rupture was still much greater than that associated with suturing the two edges of the cut pericardium together. This report confirms the deleterious role of the shear force generated in the pericardium by the suture.

The telescoping suture--Part II: A novel method to improve the mechanical behavior of a new biomaterial: ostrich pericardium
Garcia Paez, J. M., E. Jorge Herrero, et al. (2002), J Biomater Appl 17(2): 105-23.
Abstract: Ostrich pericardium, sutured using a telescoping or overlapping technique, was studied to determine its mechanical behavior. From each of 12 pericardial sacs, four contiguous strips were cut longitudinally, from root to apex, and another four contiguous strips were cut in transverse direction. One of the strips in each set of four was used as an unsutured control and the remaining three were sutured by overlapping 0.5 cm of the tissue and sewing with Gore-tex, Prolene or Pronova. These 96 samples were then subjected to tensile testing along their major axes until rupture. The tensile stresses recorded in the suture materials at the moment tears appeared in the pericardium ranged between 55.99 MPa and 70.23 MPa for Gore-tex in samples cut in the two directions. Shear stress became ostensible at 56 MPa, with clearly evident tears. However, microfracture of the collagen fibers must be produced at much lower stress levels. The comparison of the resistance in kilograms (machine-imposed), without taking into account the sections in which the load was applied, demonstrated only a slight loss of load when the telescoping suture was employed in ostrich pericardium samples. Ostrich pericardium may continue to be an alternative biological material for the construction of heart valve leaflets.

The theory of viscoelasticity in biomaterials
Dorrington, K. L. (1980), Symp Soc Exp Biol 34: 289-314.

The transforming growth factor-beta family members bone morphogenetic protein-2 and macrophage inhibitory cytokine-1 as mediators of the antiangiogenic activity of N-(4-hydroxyphenyl)retinamide
Ferrari, N., U. Pfeffer, et al. (2005), Clin Cancer Res 11(12): 4610-9.
Abstract: PURPOSE: Tumor growth appears to be an angiogenesis-dependent process. N-(4-hydroxyphenyl)retinamide (fenretinide; 4HPR) has been found to inhibit and/or prevent tumor growth under diverse conditions. Although 4HPR is antiangiogenic, the molecular mechanisms of this effect remain largely unknown. EXPERIMENTAL DESIGN: Endothelial cells were treated with 4HPR in vitro to study the effects on migration, invasion, and organization, as well as gene expression by microarray and quantitative PCR studies. In vivo angiogenesis was evaluated in the Matrigel model. RESULTS: 4HPR treatment substantially modified the biological activities of endothelial cells, repressing their capacity to migrate, invade, and organize into capillary-like structures. The inhibition of invasion induced by 4HPR was also associated with decreased activities of the metalloproteases matrix metalloproteinase-2 and CD13/APN. Using oligonucleotide microarrays, we observed that bone morphogenetic protein-2 and macrophage inhibitory cytokine-1, two multifunctional cytokines of the transforming growth factor-beta family that regulate the growth, differentiation, apoptosis, and matrix accumulation of a variety of cells, are up-regulated in vitro by 4HPR. Both these molecules specifically inhibited endothelial cell growth, migration, and invasion in vitro and suppressed angiogenesis in the Matrigel plug assay in vivo. Blocking antibodies to bone morphogenetic protein-2 were able to reverse the suppressive effects of 4HPR in vitro and in vivo. CONCLUSIONS: These data support the conclusion that 4HPR inhibits tumor growth by repression of new vessel growth and identify novel points of regulation of angiogenesis in transforming growth factor-beta family proteins.

The urokinase-type plasminogen activator, its receptor and u-PA inhibitor type-1 affect in vitro growth and invasion of Kaposi's sarcoma and capillary endothelial cells: role of HIV-Tat protein
Margheri, F., S. D'Alessio, et al. (2005), Int J Oncol 27(1): 223-35.
Abstract: The aggressive and malignant nature of AIDS-associated Kaposi's sarcoma (KS) lesions have largely been ascribed to Tat, the HIV-1 transactivator protein. Among other activities, HIV-Tat induces the migration and invasion of KS and endothelial cells. Since cell invasion is strictly correlated to the activity of lytic enzymes, we elucidated the role of the cell-associated plasminogen activation system in Tat-dependent and in constitutive invasion and proliferation of KS and of microvascular endothelial cells (MVEC). We demonstrate that KS cells and MVEC express the u-PA receptor (u-PAR) and release plasminogen activators and plasminogen activator inhibitor type-1 (PAI-1). The urokinase-type plasminogen activator (u-PA) is chemotactic, chemoinvasive and mitogenic for KS cells and for MVEC. Conditioned medium from KS cells induced invasion and proliferation of MVEC through the u-PA/u-PAR system. Tat is motogenic and mitogenic on KS cells and MVEC, and stimulates morphogenesis of MVEC. These activities were inhibited following antagonization of u-PA and u-PAR, which also reduced constitutive proliferation and invasion of KS cells and MVEC. These data indicate that the u-PA/u-PAR/PAI-1 system is involved in KS-induced endothelial cell invasion, proliferation, and differentiation. Further, exogenous Tat protein could up-regulate the fibrinolytic system, increasing its influence on KS and endothelial cell proliferation and migration, potentially promoting KS progression. These observations suggest the potential for application of u-PA/u-PAR system inhibitors for control of AIDS-associated KS, that has a high risk of recurrence with highly active antiretroviral therapy failure, and of other KS forms.

The use of a coin shaped implant for direct in situ measurement of attachment strength for osseointegrating biomaterial surfaces
Ronold, H. J. and J. E. Ellingsen (2002), Biomaterials 23(10): 2201-9.
Abstract: Most animal models currently used to study the retention of implants in bone are influenced by shear forces introduced during the retention test. This is mainly due to the implant design, which most often are cylindrical, conical or threaded. In these models interlocking between bone and implant surface will increase the effect of genuine bone bonding and thus give a false positive outcome. The purpose of the present study was to establish a model for testing functional attachment of implants in situ, with minimal influence of interlocking and shear forces. The model involves the use of flat coin shaped implant placed onto the cortical bone of rabbit tibia without mechanical fixation to the bone. The implant is passively retained on the cortical bone by a titanium band retainer. During the healing period, the contact between the coin shaped implants and the bone is restricted to the flat test surfaces. To prevent interlocking effects from lateral bone attachments a polytetrafluoroethylene (PTFE) cap covering the vertical and the upper faces of the implants were used. The tensile test was performed with a gradual, calibrated pull, perpendicular to the bone-implant interface. This pullout model makes it possible to study the kinetics and strength of bone bonding with negligible influence of shear forces or mechanical interlocking.

The use of alloplastic biomaterials in bladder substitution
Gleeson, M. J. and D. P. Griffith (1992), J Urol 148(5): 1377-82.

The use of biomaterials in the repair of abdominal wall defects: a comparative study between polypropylene meshes (Marlex) and a new polytetrafluoroethylene prosthesis (Dual Mesh)
Bellon, J. M., L. A. Contreras, et al. (1997), J Biomater Appl 12(2): 121-35.
Abstract: In this study we compared the behaviour of the non-porous on one side ePTFE Dual Mesh prosthesis and the macroporous polypropylene mesh Marlex in the repair of abdominal wall defects in rabbits. We evaluated the degree of integration with recipient tissue, biological tolerance, adhesion formation with viscera and the biomechanical resistance of the repair zone. Our results showed good biological tolerance of both prostheses and a high degree of adhesion formation in Marlex implants. In animals with Dual Mesh implants, only loose adhesions were seen. Marlex implants induced the presence of disorganized scar tissue, while the Dual Mesh prostheses were encapsulated by organized tissue. The macrophage response was similar in both decreasing with time. The resistance to traction was higher when the reparation was done with polypropylene. We concluded that the structure of the prosthesis determines its degree of integration and the resistance to traction of the repaired zone.

The use of biosynthetic skin substitute (Biobrane) for axillary reconstruction after surgical excision for hidradenitis suppurativa
Melkun, E. T. and J. W. Few (2005), Plast Reconstr Surg 115(5): 1385-8.

The use of drug-eluting stents in everyday clinical practice: can the results of randomised trials be achieved in the "real world"?
Sionis, D. G. (2005), Hellenic J Cardiol 46(2): 124-7.

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