Biomedical subjects

Harry Gebhard

Publications and source records attributed to Harry Gebhard.

3 recordsLinked to original sources

PubMed2004

Influence of orthopedic particulate biomaterials on inflammation and synovial microcirculation in the murine knee joint.

The purpose of the present study was to examine changes in the synovial microcirculation as well as synovial tissue responses to exposure to titanium, polymethylmethacrylate (PMMA), ceramic (Al(2)O(3)), cobalt-chromium alloy (Co-Cr), and polyethylene (PE) particles in an in vivo model. The particulate biomaterials were injected into the left knee joint of female Balb/c mice and assessment of the synovial microcirculation using intravital fluorescence microscopy as well as histological evaluation of the synovial tissue response were performed on day 7 after particle administration. Intravital microscopic measurements revealed that all tested biomaterials caused significantly (p < 0.05) enhanced leukocyte-endothelial cell interactions and an increase of functional capillary density compared to controls. In the histological examination PMMA, Al(2)O(3), PE, and Co-Cr particles provoked significantly (p < 0.05) enhanced inflammatory tissue responses in comparison to tissue from control animals. Titanium particles showed significantly (p < 0.05) less leukocyte-endothelial cell interactions than the other particulate biomaterials and caused significantly (p < 0.05) minor membrane thickening compared to PE and PMMA particles. In conclusion, all tested particulate biomaterials were capable of inducing inflammatory responses in the present study. Our data suggest that titanium particles may cause less leukocyte activation and inflammatory tissue responses than other particulate biomaterials used in total joint arthroplasty.

Animals↗

PubMed2003

Subtype-selective antagonists of lysophosphatidic Acid receptors inhibit platelet activation triggered by the lipid core of atherosclerotic plaques.

BACKGROUND: Lysophosphatidic acid (LPA) is a platelet-activating component of mildly oxidized LDL (mox-LDL) and lipids isolated from human atherosclerotic plaques. Specific antagonists of platelet LPA receptors could be useful inhibitors of thrombus formation in patients with cardiovascular disease. METHODS AND RESULTS: Short-chain analogs of phosphatidic acid (PA) were examined for their effect on two initial platelet responses, platelet shape change and Ca2+ mobilization. Dioctylglycerol pyrophosphate [DGPP(8:0)] and dioctylphosphatidic acid [PA(8:0)], recently described selective antagonists of the LPA1 and LPA3 receptors, inhibited platelet activation evoked by LPA but not by other platelet stimuli. DGPP(8:0) was more potent than PA(8:0). DGPP(8:0) also inhibited platelet shape change induced by mox-LDL and lipid extracts from human atherosclerotic plaques. Notably, we demonstrate for the first time that the lipid-rich core isolated from soft plaques was able to directly induce shape change. This effect was completely abrogated by prior incubation of platelets with DGPP(8:0). Moreover, coapplication of the lipid-rich core or LPA together with subthreshold concentrations of ADP or epinephrine synergistically induced platelet aggregation; this effect was inhibited by DGPP(8:0). Analysis by liquid chromatography-mass spectrometry revealed the presence of LPA alkyl- and acyl-molecular species with high platelet-activating potency (16:0-alkyl-LPA, 20:4-acyl-LPA). CONCLUSIONS: LPA molecules present in the core region of atherosclerotic plaques trigger rapid platelet activation through the stimulation of LPA1 and LPA3 receptors. Antagonists of platelet LPA receptors might provide a new strategy to prevent thrombus formation in patients with cardiovascular diseases.

Adenosine Diphosphate↗

PubMed2003

COMPARE radiology: creating an interactive Web-based training program for radiology with multimedia authoring software.

RATIONALE AND OBJECTIVES: Computer-based training has two primary benefits: Content can be presented interactively, and students can choose the time, place, and pace of learning. As a subject of medical education, radiology lends itself particularly well to computer-based training because of its highly visual content. To improve the efficiency of radiology training at their institution, the authors decided to create an interactive Web-based training site. MATERIALS AND METHODS: Working with a group of medical students knowledgeable in multimedia authoring, the authors used authoring software to create "COMPARE Radiology," an interactive training program that follows the modality-based structure of the undergraduate curriculum for radiology at the University of Erlangen-Nuremberg, Erlangen, Germany, and at medical schools worldwide. RESULTS: The Web-based program offers cases and exercises in radiographic anatomy at different selectable levels of difficulty, allowing users to test and build their knowledge of radiology. Pathologic images are initially presented without any further information. Additional information (patient history, laboratory results, reports from other imaging studies, and normal images for comparison) can be retrieved selectively and successively. Further information regarding the diagnosis and pathologic findings can be found by following links to external Web sites. The COMPARE Radiology program content is extended and updated regularly. The program is subject to internal peer review and can be evaluated by the user online. CONCLUSION: The authors' experience shows that a highly interactive Web-based training program for radiology, tailored to the requirements of the target group, can be developed economically by a team of medical students using an advanced storing system, with the guidance of a radiologist and without the help of professionally trained computer experts.

Computer-Assisted Instruction↗