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T Gehrke

Publications and source records attributed to T Gehrke.

17 recordsLinked to original sources
PubMed2006

[Differential diagnosis of rheumatoid granuloma].

Rheumatoid granuloma (RG) is histomorphologically defined as a subcutaneous palisading granuloma with central fibrinoid necrosis. Clinically, it presents as a nodule typically localized at pressure points near the joints. From the rheumatic pathological point of view, the main diagnostic challenge is the differentiation of RG from granuloma anulare, especially if clinical information on the site of removal, known diseases, duration of illness, medication and existing American College of Rheumatology (ACR) criteria are missing. Other granulomatous lesions, such as mycobacterial infections, foreign body granulomas, necrobiosis lipoidica or sarcoidosis, can be differentiated from RG by histopathological criteria or by additional examinations such as pathogen specification or PCR. An immunohistochemical marker for the differential diagnosis of granulomas is not yet available. Diagnosis is based on conventional H-E staining, alcian blue-PAS staining, polarizing analysis or PCR. In the following article, the most important granulomatous entities in the differential diagnosis of RG are introduced and the main diagnostic characteristics are discussed.

Arthritis, Rheumatoid↗
PubMed2006

[Histopathological diagnostics in endoprosthesis loosening].

The implantation of total joint endoprostheses has become a routine procedure, being executed about 1.5 million times per year worldwide. The indications are osteoarthritis, rheumatic diseases, trauma and bone neoplasia. However, about 5-12% of patients develop pain and impaired function of the endoprosthesis within 10 years, necessitating revision surgery. During this operation, the so-called periprosthetic membrane between bone and prosthesis is removed. This connective tissue membrane has a pathogenetic impact on the loosening process and can be evaluated by histopathology. This article aims at elucidating the defined histomorphological criteria for the standardized diagnostics of periprosthetic membranes using a recently established classification system.

Aged↗
PubMed2006

[Wear particles: key to aseptic prosthetic loosening?].

The aseptic prosthetic loosening of hip and knee prosthesis is the most important cause of implant insufficiency. Bone loss as a result of the biological effect of wear particles is the main cause of such loosening. Wear particles develop their biological activity along different cellular pathways, above all via macrophages, foreign body giant cells as well as fibroblasts of the periprosthetic membrane. These cells induce particle-dependent bone resorption by means of proinflammatory cytokines, such as IL-1beta, TNF-alpha, IL-6 and PGE2. These factors induce the activation of osteoclasts as well as the suppression of osteoblasts. Neutrophil granulocytes and lymphocytes do not play an important role in the process of aseptic loosening. The different wear particles, such as ultra-high molecular weight polyethylene, metal particles, ceramic particles and polymethylmethacrylate can be morphologically recognized very easily. From the clinical point of view, the differentiation between acute or chronic implant infection and particle induced prosthetic loosening is very important, with the histomorphological differential diagnosis between septic and aseptic loosening and their combination being the key clinicopathological factor.

Arthroplasty, Replacement, Hip↗
PubMed2006

Proposal for a histopathological consensus classification of the periprosthetic interface membrane.

AIMS: The introduction of clearly defined histopathological criteria for a standardised evaluation of the periprosthetic membrane, which can appear in cases of total joint arthroplasty revision surgery. METHODS: Based on histomorphological criteria, four types of periprosthetic membrane were defined: wear particle induced type (detection of foreign body particles; macrophages and multinucleated giant cells occupy at least 20% of the area; type I); infectious type (granulation tissue with neutrophilic granulocytes, plasma cells and few, if any, wear particles; type II); combined type (aspects of type I and type II occur simultaneously; type III); and indeterminate type (neither criteria for type I nor type II are fulfilled; type IV). The periprosthetic membranes of 370 patients (217 women, 153 men; mean age 67.6 years, mean period until revision surgery 7.4 years) were analysed according to the defined criteria. RESULTS: Frequency of histopathological membrane types was: type I 54.3%, type II 19.7%, type III 5.4%, type IV 15.4%, and not assessable 5.1%. The mean period between primary arthroplasty and revision surgery was 10.1 years for type I, 3.2 years for type II, 4.5 years for type III and 5.4 years for type IV. The correlation between histopathological and microbiological diagnosis was high (89.7%), and the inter-observer reproducibility sufficient (85%). CONCLUSION: The classification proposed enables standardised typing of periprosthetic membranes and may serve as a tool for further research on the pathogenesis of the loosening of total joint replacement. The study highlights the importance of non-infectious, non-particle induced loosening of prosthetic devices in orthopaedic surgery (membrane type IV), which was observed in 15.4% of patients.

Adult↗
PubMed2005

[Inflammatory reactions in the wear particle induced and infectious periprosthetic membrane of loosened hip- and knee endoprostheses: pathogenetic relevance of differentially expressed genes cd9, cd11b, cd18, cd52 and pdgfrbeta].

BACKGROUND: A previous cDNA-microarray analysis described constantly differentially expressed genes in wear particle induced and infectious SLIM (synovial-like interface membrane). This study aims to validate the cDNA microarray data in order to approve differences of the gene expression profiles of RNA and proteins. METHODS: Tissue from 16 wear particle induced and 20 infectious periprosthetic membranes were analyzed by RT-PCR and immunohistology with regard to the expression of inflammatoric associated genes. RESULTS: RT-PCR showed the genes cd9, cd11b, cd18, cd52 as well as pdgfrbeta in interface membranes. In the wear particle induced membrane the immunohistochemical analysis showed a significantly weaker gene expression of PDGFRbeta, whereas the differential overexpression of CD9, CD11b and CD52 was confirmed. For CD18, there was no difference in expression between wear induced and infectious periprosthetic tissue. CONCLUSION: Different pathomechanisms, which are reflected by different gene expression profiles, might produce different types of periprosthetic membranes. By RT-PCR and immunohistochemical analysis the micro array data of the genes cd9, cd11b, cd52 and pdgfrbeta could be validated. Identifying the gene products of cd9, cd11b and cd52 in blood or tissue may help to differentiate between wear induced and infectious loosening.

Adult↗
PubMed2003

Bioleaching review part A: progress in bioleaching: fundamentals and mechanisms of bacterial metal sulfide oxidation.

Bioleaching of metal sulfides is caused by astonishingly diverse groups of bacteria. Today, at least 11 putative prokaryotic divisions can be related to this phenomenon. In contrast, the dissolution (bio)chemistry of metal sulfides follows only two pathways, which are determined by the acid-solubility of the sulfides: the thiosulfate and the polysulfide pathway. The bacterial cell can effect this sulfide dissolution by "contact" and "non-contact" mechanisms. The non-contact mechanism assumes that the bacteria oxidize only dissolved iron(II) ions to iron(III) ions. The latter can then attack metal sulfides and be reduced to iron(II) ions. The contact mechanism requires attachment of bacteria to the sulfide surface. The primary mechanism for attachment to pyrite is electrostatic in nature. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions in the contact mechanism is mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in the non-contact mechanism. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a complex redox chain located below the outer membrane, the periplasmic space, and the cytoplasmic membrane of leaching bacteria. The dominance of either At. ferrooxidans or Leptospirillum ferrooxidans in mesophilic leaching habitats is highly likely to result from differences in their biochemical iron(II) oxidation pathways, especially the involvement of rusticyanin.

Biopolymers↗
PubMed2003

Receptor activator of nuclear factor kappaB ligand is expressed in resident and inflammatory cells in aseptic and septic prosthesis loosening.

OBJECTIVE: The pathogenesis of periprosthetic bone loss in aseptic and septic prosthesis loosening is unclear. There is considerable evidence that macrophages and osteoclasts play a key role in focal bone erosion and osteolysis around the prosthesis. RANKL (receptor activator of nuclear factor kappaB ligand) was shown to be a potent osteoclastogenic factor, and to be involved in bone destruction of myeloma and rheumatoid arthritis patients. Osteoprotegerin (OPG) is the natural RANKL inhibitor and may prevent periprosthetic bone loss. METHODS: The presence and distribution of RANKL, its receptor RANK and OPG in the periprosthetic interface of septically (n = 5) and aseptically (n = 6) loosened prostheses was examined by immunohistochemistry and immunoblotting. Additionally, the immunophenotype of the inflammatory infiltrate was determined [CD3, CD68, Ki-67, tartrate-resistant acid posphatase (TRAP)]. RESULTS: Aseptic and septic cases revealed a different histopathologic pattern. However, in all cases RANKL and RANK could be demonstrated in macrophages and giant cells. In addition, RANKL detected by immunoblot analysis proved to have the same molecular weight as a recombinant RANKL used as a control (31 kD and approximately 48 kD). OPG was detected in aseptic loosening, where macrophages showed a strong staining, but multinucleated giant cells were only weakly stained. A weak OPG staining was also observed in septic loosening. CONCLUSION: The pathogenesis of bone loss in septic loosening remains unclear, because the septic membrane bears few macrophages and giant cells, and half of them express OPG. In aseptic loosening, macrophages might not be stimulated by RANKL as a result of OPG expression. But multinucleated giant cells may be activated, as they hardly express OPG. They might be responsible for periprosthetic bone loss in aseptic loosening as a result of their RANKL and RANK expression.

Aged↗
PubMed2003

[Differential gene expression in the wear particle induced and infectious periprosthetic membrane of loosened knee-endoprostheses].

About 5 to 12 % of hip endoprostheses will loosen after ten years. The periprosthetic membran between bone and prosthesis plays a crucial role in prosthesis loosening. Different pathomechanisms lead to the growth of such a membran, which can be discriminated by different histomorphologies: wear particle induced type, infectious type, combined type, indifferent type. 8 hybridizations were performed on PIQOR cDNA arrays. Objects of the study were periprosthetic interface tissue samples from 3 patients with particle induced and 2 patients with infectious prosthesis loosening. Tissue parts directly adjacent to the site of RNA-isolation were analyzed immuno-/ histopathologically in order to overcome the problem of tissue heterogeneity. 34 genes were found constantly differentially expressed, among which were cd9, cd11b, cd18, cd68, osteopontin, ferritin heavy-chain upregulated in the particle induced membrane and collagen types 1alpha-1, 3alpha-1, integrin alpha-1, thrombospondin 2 and nidogen upregulated in the infectious membrane. The most striking finding was the strong upregulation (from 20 fold to 323 fold) of megakaryocyte stimulating factor (msf) in all wear particle cases and 1 out of 2 infectious cases, which was confirmed by real-time RT-PCR. The upregulation of msf suggests an important pathogenetic role: The msf splice product lubricin is responsible for the lubrification of healthy joints, but its excellent lubrification ability may disturb the tight interaction between bone and prosthesis and thereby contribute to prosthesis loosening.

Antigens, CD↗
PubMed2001

Combination of reduced oxygen tension and intermittent hydrostatic pressure: a useful tool in articular cartilage tissue engineering.

Cartilage cells are normally studied under atmospheric pressure conditions and without loading. However, since cartilage exists in a condition of reduced oxygen and intermittent hydrostatic pressure we hypothesized lower partial oxygen pressures (PO2) and different intermittent hydrostatic pressures (IHP) would increase articular chondrocyte proliferation and matrix production and to stabilize chondrocyte phenotype in vitro. Monolayers of adult bovine articular chondrocytes were cultured under 5% or 21% PO2 in combination with IHP (0.2 MPa amplitude, frequencies 5/5s = 0.1 Hz, 30/2 or 2/30 min on/off loading). We measured proliferation (3H-thymidine incorporation) and collagen secretion (protein-binding assay, collagen type II-ELISA and immunocytochemical staining of pericellular collagen types I, II and IX). Reduced PO2 stimulated proliferation and collagen type II and IX secretion of chondrocytes in comparison to 21% PO2. Additionally, collagen type I expression was delayed by low PO2, indicating a stabilization of the cell phenotype. IHP 5/5s and 30/2 min inhibited proliferation but increased collagen secretion (pericellular collagen type IX was decreased). IHP 30/2 min delayed first expression of collagen type I. In contrast, IHP 2/30 min increased proliferation, but lowered collagen expression. All stimulating or inhibiting effects of PO2 and IHP were additive and vice versa. Reduced PO2 and different settings of IHP increased proliferation, collagen secretion, and phenotype stability of chondrocytes. The oxygen- and IHP-induced effects were additive, suggesting that a combination of these parameters might be a useful tool in cartilage tissue engineering.

Animals↗
PubMed2001

The EPS of Acidithiobacillus ferrooxidans--a model for structure-function relationships of attached bacteria and their physiology.

To dissolve pyrite or sulphur, leaching bacteria like Acidithiobacillus ferrooxidans attach to these substrata by extracellular polymeric substances (specifically, lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrostatic interaction with the negatively charged pyrite surface. Cells grown on sulphur exhibit a different composition of the extracellular lipopolysaccharides, namely with increased hydrophobic properties, and do not attach to pyrite. Thus, the cells adapt the chemical composition of their exopolymers to the substrate/substratum. It is concluded that the mechanism of bacterial pyrite oxidation is basically indirect. The actual corrosive agents are iron(III) ions. Preliminary data indicate that active strains complex more iron(III) ions in their EPS than less active ones. Obviously, the exopolymeric layer comprises a reaction space for the regeneration of these ions by the activity of the iron oxidising bacteria.

Bacterial Adhesion↗
PubMed2000

Evaluation of water content by spatially resolved transverse relaxation times of human articular cartilage.

Non-invasive assessment of cartilage properties, specifically water content, could prove helpful in the diagnosis of early degenerative joint diseases. Transverse relaxation times T(2) of human articular cartilage (34 cartilage slices of three donors) were measured on a pixel-by-pixel basis in a clinical whole body MR system in vitro. In vivo feasibility to measure quantitative T(2) maps was shown for human patellar cartilage. The relaxation times of cartilage with collagen in the radial zone oriented perpendicular to the magnetic field increased from approximately 10 ms near the bone to approximately 60 ms near the articular surface. Cartilage water content of the tibial plateau and femoral condyles could be determined from the correlation with T(2) (R(2) = 0.71) with an error of approximately 2 wt.%. In vivo, directional variation would need to be considered. If confirmed in vivo, T(2) measurements could potentially serve as a non-invasive tool for the evaluation of the status and distribution of water content in articular cartilage.

Adult↗
PubMed1998

Importance of Extracellular Polymeric Substances from Thiobacillus ferrooxidans for Bioleaching.

Leaching bacteria such as Thiobacillus ferrooxidans attach to pyrite or sulfur by means of extracellular polymeric substances (EPS) (lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrochemical interaction with the negatively charged pyrite surface. EPS from sulfur cells possess increased hydrophobic properties and do not attach to pyrite, indicating adaptability to the substrate or substratum.

Journal Article↗
PubMed1997

[Not Available].

Explore the source record for details and available documents.

Journal Article↗
PubMed1993

Biliary atresia--bile acids and prostaglandin E2 in cell cultures of bile duct epithelia.

In a cell culture model of bile duct epithelial cells, the effect of prostaglandin E2, lithocholic acid and deoxycholic acid was studied. Bile acids and prostaglandin are administered postoperatively in biliary atresia empirically as choleretics. Prostaglandin E2 and the bile acids all had inhibitory effects on bile duct epithelial cells in culture. There is no clinical study proving the efficacy of either bile acids or prostaglandin E2 in biliary atresia. The negative results with these substances in cell cultures warrants reserve in their routine clinical use in biliary atresia.

Adult↗
PubMed1990

[Prevention of thrombosis in surgery: low molecular weight heparin/standard heparin].

In a randomized study the efficiency of the low molecular weight heparin (LMWH) Fragmin and unfractionated heparin Calciparin in preventing thromboembolic disease was examined. Ninety patients undergoing a herniotomy participated in the study. The LMWH also showed good efficiency in a laboratory test of anti-factor Xa-activity. There were no complications.

Dose-Response Relationship, Drug↗