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Biomedical subjects

D Behrend

Publications and source records attributed to D Behrend.

At least 19 recordsLinked to original sources
PubMed2005

[Concept and anatomical feasibility study of an "endosteal electrode" for bimodal stimulation in severely deaf ears].

BACKGROUND: Many patients with severe hearing loss could benefit from a bimodal stimulation unilaterally: acoustically in the apical region of the cochlea with some residual low frequency hearing and electrically via a cochlear implant in the basal turn with lost high hearing in the high frequency range. As a new concept we introduce the idea of an "endosteal electrode" - to be inserted between spiral ligament and endosteum of the bony wall without opening the fluid-filled inner ear. In this paper the feasibility from the anatomical point of view is to be proven. MATERIALS AND METHODS: In 10 human temporal bone specimens the bone covering the membraneous inner ear is carefully removed in the site of a typical cochleostomy. It should by proven whether or not the soft tissue layer covering the inner ear could be left intact and, furthermore, whether a "dummy-electrode array" could be inserted "endosteally". RESULTS: In 10 of the 10 specimen the preparation could be carried out in the desired way, leaving the spiral ligament intact. The regular site of the "electrode" was morphologically proven after embedding the specimens for histological evaluation. CONCLUSIONS: From the anatomical point of view, an "endosteal cochlear implantation" seems feasible. Further experiments including animal studies must show, whether this concept might succeed functionally.

Cochlear Implantation↗
PubMed2002

A polyhydroxybutyrate biodegradable stent: preliminary experience in the rabbit.

PURPOSE: The lifelong persistence of foreign bodies within the arteries may contribute to restenosis. Thus, biodegradable devices might decrease recurrence rates. METHODS: Eleven polyhydroxybutyrate biodegradable stents and 13 tantalum stents were implanted into the iliac arteries of New Zealand white rabbits for up to 30 weeks. After killing the animals, the specimens were harvested, fixed in formalin, processed in paraffin, and stained. RESULTS: Polyhydroxybutyrate instigated intense inflammatory and proliferative reactions with an increase in collagen (2.4- to 8-fold vs native segments), thrombosis and in-stent lumen narrowing (375.5-606.6 mm vs 655.6 +/- 268.8 mm in native segments). The elastic membranes were destroyed in all specimens. The tantalum stents increased the in-stent lumen progressively (769.7 +/- 366.6 mm vs 1309.9 +/- 695.3 mm), penetrated the external elastic membrane, and increased mural collagen content (6- to 8.6-fold vs native segments). Neither restenoses nor thromboses occurred. CONCLUSIONS: In the rabbit iliac artery, polyhydroxybutyrate stents caused intensive inflammatory vascular reactions which ban them from clinical use.

Animals↗
PubMed2002

[Poly-beta-hydroxybutyric acid (PHB) films and plates in defect covering of the osseus skull in a rabbit model].

BACKGROUND: Titan plates have proven a success in the operative assistance of middle face fractures for stabile osteosynthesis. Also bioresorbant materials are being used increasingly. METHOD: Films and plates made from poly-beta-hydroxybutyric acid (PHB) with two holes and bolts are tested subperiostally on the osseus skull of 15 rabbits or respectively on cut trough zygomatic arches. The test bodies and the surrounding tissue are explantated after a defined period and are clinically and histologically prepared. RESULTS: All implants healed well. There were no macroscopic or microscopic signs of inflammation. A very slow, clinically not recordable decomposition followed. A "leap" in the decomposition evidently took place between the 20th and 25th month. Only initial signs of resorbation were to be found microfocally on the surface of the implant until 20 months after implantation but no more test body could be detected after 25 months. CONCLUSION: PHB is suitable for defect covery of the osseus skull or respectively as osteosynthesis material for fractures of the visceral cranium.

Animals↗
PubMed2002

Optimization of the neck region of dental implants with a bioactive, resorbable coating.

With the goal of shortening the postoperative healing phase and the minimization of the risk of peri-implantitis around dental implants, a polymer coating, with improved surface biocompatibility in the region of soft tissue penetration by the implant, was investigated. The polymer used was the relatively slowly resorbable poly-beta-hydroxybuterate (PHB) whose surface was further activated in a NH3--plasma. The influence of surface roughness of the substrate (commercially pure titanium) as well as the influence of the edge radii on the test samples was determined in prior studies. These studies formed the basis for an optimised coating process. In-vitro biocompatibility was determined using a human gingival primary cell culture. Surface morphology was determined with SEM and AFM to complement the cell culture studies.

Cell Division↗
PubMed2002

[Comparative analysis of in vitro test procedures for evaluating hemocompatibility of cardiovascular stents].

Within the scope of this study existing in vitro techniques for testing the hemocompatibility of coronary stents were analysed and optimised. Static and quasi-stationary systems were compared to a pulsed flow model with respect to platelet activity. The streamlines were visualized by dye injection. Blood flow was measured by ultrasonic Doppler velocity meter and electromagnetic flow meter. Uncoated stainless steel (316 L) stents were tested. Surrogate parameters of the hemocompatibility were the change in surface morphology after blood contact and the rise of biomechanical activation markers as C3a and beta-thromboglobulin. The results were correlated to the stent design and to the flow characteristics of the test systems.

Angioplasty, Balloon, Coronary↗
PubMed2001

Laser cutting: influence on morphological and physicochemical properties of polyhydroxybutyrate.

Polyhydroxybutyrate (PHB) is a biocompatible and resorbable implant material. For these reasons, it has been used for the fabrication of temporary stents, bone plates, nails and screws (Peng et al. Biomaterials 1996;17:685). In some cases, the brittle mechanical properties of PHB homopolymer limit its application. A typical plasticizer, triethylcitrate (TEC), was used to overcome such limitations by making the material more pliable. In the past few years, CO2-laser cutting of PHB was used in the manufacturing of small medical devices such as stents. Embrittlement of plasticized PHB tubes has been observed, after laser machining. Consequently, the physicochemical and morphological properties of laser-processed surfaces and cut edges of plasticized polymer samples were examined to determine the extent of changes in polymer properties as a result of laser machining. These studies included determination of the depth of the laser-induced heat affected zone by polariscopy of thin polymer sections. Molecular weight changes and changes in the TEC content as a function of distance from the laser-cut edge were determined. In a preliminary test, the cellular response to the processed material was investigated by cell culture study of L929 mouse fibroblasts on laser-machined surfaces. The heat-affected zone was readily classified into four different regions with a total depth of about 60 to 100 microm (Klamp, Master Thesis, University of Rostock, 1998). These results correspond well with the chemical analysis and molecular weight measurements. Furthermore, it was found that cells grew preferentially on the laser-machined area. These findings have significant implications for the manufacture of medical implants from PHB by laser machining.

Absorbable Implants↗
PubMed2001

Structural alterations of adhesion mediating components in cells cultured on poly-beta-hydroxy butyric acid.

Polymers may serve as a biodegradable material in tissue engineering. To assess the biocompatibility of poly-beta-hydroxy butyric acid (PHB), we studied the structural organization of cellular molecules involved in adhesion using osteoblastic and epithelial cell lines. On PHB, both cell lines revealed a rounded cell shape due to reduced spreading. The filamentous organization of the actin cytoskeleton was impaired. In double immunofluorescence analyses we demostrated that the colocalization of the fibronectin fibrils with the actin filaments was lost in cultures on PHB. Similarly, collagen II distribution was altered, whereas the organization of collagen I was not obviously affected. Further evidence for impaired structural organization was obtained for the beta1-integrin receptor and vinculin which mediate the interaction of the cytoskeleton with the extracellular matrix. In confluent epithelial cells, the tight junction protein ZO-1 showed a larger lateral extension in the cell-cell contacts when cells were grown on PHB. Because structural organization of components which mediate cell-matrix and cell-cell adhesion controls cell physiology these parameters could be a sensitive indicator for the biocompatibility of implant materials.

Actins↗
PubMed2000

[Biomaterials in urology].

Biomaterials are defined as non-living materials which are used in interaction with biological systems. Especially in the field of urology, biomaterials are applied in urinary diversion, urinary incontinence, erectile dysfunction, and as cosmetic prostheses. Biomaterial-tissue interaction is caused by the physical and chemical characteristics of the biomaterial, its degradation, and the resulting protein denaturation. General requirements include biocompatibility and functionality and the avoidance of carcinogenic, mutagenic, toxic, and allergic reactions. This is most important when there is permanent contact between urine and epithelial tissue, which may lead to biofilminfection and incrustation. Continuous modification of known materials, inauguration of new materials, as well as the possibilities of tissue engineering will determine their development in the years to come.

Biocompatible Materials↗
PubMed2000

Assessment of explanted PTCA balloons.

The data presented here are part of a on-going study to define the surface characteristics and properties of explanted PTCA catheters in a further effort to address some of the ramifications of the re-use issue. PTCA balloon catheter were examined after angioplasty in one hundred and sixty-eight patients (n = 168). This series included six balloon types from three manufacturers. The fresh fixed and dehydrated balloons were examined at first with light microscopy and then in a scanning electron microscope. X-ray semiquantitative microanalysis and FT-IR-ATR analysis were also performed on the balloons. Because most blood proteins are water soluble, we examined unfixed balloons with a protein silver staining kit for detection of adhered proteins described by Heukeshoven. A further method for protein detection is the Lowry-analysis. With this method water insoluble proteins can be observed. Our study has shown convincingly that all deployed angioplasty catheters were coated with adherent protein layers. Plaque particles were found embedded in the surfaces of most of the balloons examined. Fissuring and micro tearing of balloon surfaces was noted. FT-IR-ATR analyses of the blood contacted balloon surfaces did not show any peaks indicative of proteins on the balloon surface. The silver staining method also did not show any evidence of protein adsorption on the balloons. On the other hand, the Lowry-analysis yielded clear evidence that water insoluble proteins were adherent to the balloon surfaces. The average measured protein concentration was 17 microg/ml.

Angioplasty, Balloon, Coronary↗