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Biomedical subjects

D Schaefer

Publications and source records attributed to D Schaefer.

At least 19 recordsLinked to original sources
PubMed2006

FMIP controls the adipocyte lineage commitment of C2C12 cells by downmodulation of C/EBP alpha.

Fms interacting protein (FMIP) is a substrate for Fms tyrosine kinase, and a nuclear/cytoplasm shuttling protein with a leucine zipper. As the phosphorylation of FMIP is observed in insulin-stimulated preadipocytes, we examined the role of FMIP in adipocyte differentiation, using the mesenchymal multipotent stem cells, C2C12 cells, that can differentiate into adipocytes, muscle cells and osteoblasts. Ectopic expression of FMIP in C2C12 impairs the adipocyte differentiation induced by treatment with insulin, dexamethasone and 3-isobutyl-1-methylxanthine. These cells exhibit muscle phenotype with multinuclear morphology. Furthermore, knockdown of endogenous FMIP expression by small interfering RNA improves adipocytic lineage commitment of C2C12 cells, while impairing muscle differentiation. Upon stimulation with insulin, CCAAT/enhancer binding protein (C/EBP)beta, but not C/EBPalpha, is upregulated in cells expressing ectopic FMIP, whereas in FMIP knockdown cells, C/EBPalpha is constitutively expressed. Ectopic expression of C/EBPalpha counteracts the effects of FMIP, whereas C/EBPalpha knockdown partially mimics the effects of FMIP in this system. Northern blot analysis and reverse transcriptase-polymerase chain reaction study reveal that ectopic FMIP-expressing cells do not contain the polyadenylated C/EBPalpha mRNA, but contain the C/EBPalpha pre-mRNA, suggesting that FMIP plays a role in RNA processing and/or export. Indeed, a member of the THO complex that plays a role in mRNA export, THOC1, is co-precipitated with FMIP. The data we have acquired on FMIP suggest that it is a target for tyrosine kinase receptors that potentiate mRNA export.

Adipocytes↗
PubMed2006

Endothelial and epithelial expression of eotaxin-2 (CCL24) in nasal polyps.

BACKGROUND: Nasal polyposis is mostly associated with eosinophilia of mucosal tissue. This points to the implication of CC chemokines in nasal eosinophilia. Recently the CC chemokine eotaxin-2 (CCL24) was identified. This study was initiated to localize the cellular source, analyze expression of mRNA, and quantify protein synthesis of CCL24. METHODS: Specimens of nasal inferior turbinates from controls and polypous tissue from patients suffering from chronic polypous sinusitis were collected. Furthermore, fibroblasts and epithelial cells were cultured. CCL24 protein was analyzed by immunohistochemistry and ELISA, expression of mRNA by SQ-RT-PCR. RESULTS: CCL24 was observed in endothelial and epithelial cells. Specimens from patients expressed significantly (>2fold) more CCL24 mRNA than controls. Fibroblasts and unstimulated cells did not express CCL24 mRNA. Upon stimulation with TNF-alpha, INF-gamma, IL-4, or costimulation with TNF-alpha and INF-gamma CCL24 mRNA was significantly enhanced (3.2-19.6%). In controls, fibroblast, and unstimulated cells CCL24 protein was below detection limit. Most polyps comprised significant amounts of CCL24 (mean 0.24 ng/mg). TNF-alpha, INF-gamma or IL-4 induced CCL24 protein (0.1-0.3 ng/ml) in epithelial cells. Costimulation with TNF-alpha and IL-4 (0.1-30 and 1-30 ng/ml, respectively) synergistically induced synthesis of CCL24 protein (0.18-0.31 ng/ml). CONCLUSION: In nasal polyps endothelial and epithelial cells are obviously the main source of CCL24, which was shown for transcription (mRNA) and production (protein) levels and was associated with diseases. Results gave evidence of CLL24- directed migration of cells from inside (the bloodstream) to the epithelial side (mucosa) in eosinophilic inflammatory diseases, e.g. nasal polyposis.

Adolescent↗
PubMed2005

Effect of corticosteroids on short-term and long-term memory.

The effect of acute high-dose glucocorticoid therapy on memory function in patients with acute optic neuritis (n = 9) and multiple sclerosis (n = 21) was studied. All patients had reversible impairment of long-term memory functions, whereas measures of short-term memory, attentional functions, and alertness remained unaffected.

Adolescent↗
PubMed2005

Structural characterization and reliable biomechanical assessment of integrative cartilage repair.

Structural and functional characterization of integrative cartilage repair in controlled model systems can play a key role in the development of innovative strategies to improve the long-term outcome of many cartilage repair procedures. In this work, we first developed a method to reproducibly generate geometrically defined disk/ring cartilage composites and to remove outgrown fibrous layers which can encapsulate cartilaginous tissues during culture. We then used the model system to test the hypothesis that such fibrous layers lead to an overestimation of biomechanical parameters of integration at the disk/ring interface. Transmission electron microscopy images of the composites after 6 weeks of culture indicated that collagen fibrils in the fibrous tissue layer were well integrated into the collagen network of the cartilage disk and ring, whereas molecular bridging between opposing disk/ring cartilage surfaces was less pronounced and restricted to regions with narrow interfacial regions (< 2 microm). Stress-strain profiles generated from mechanical push-out tests for composites with the layers removed displayed a single and distinct peak, whereas profiles for composites with the layers left intact consisted of multiple superimposed peaks. As compared to composites with removed layers, composites with intact layers had significantly higher adhesive strengths (161+/-9 vs. 71+/-11 kPa) and adhesion energies (15.0+/-0.7 vs. 2.7+/-0.4 mJ/mm2). By combining structural and functional analyses, we demonstrated that the outgrowing tissue formed during in vitro culture of cartilaginous specimens should be eliminated in order to reliably quantify biomechanical parameters related to integrative cartilage repair.

Adhesiveness↗
PubMed2002

Characterization of three PDI-like genes in Physcomitrella patens and construction of knock-out mutants.

Plant genomes typically contain several sequences homologous to protein disulfide isomerase (PDI). PDI was first identified as an abundant enzyme in the endoplasmic reticulum, where it catalyzes the formation, reduction, and isomerization of disulfide bonds during protein folding. PDI-like proteins have also been implicated in a variety of other functions, such as the regulation of cell adhesion, and may act as elicitors of the autoimmune response in mammals. A PDI-like protein (RB60) was recently shown to be imported into chloroplasts in the unicellular green alga Chlamydomonas reinhardtii and a higher plant, Pisum sativum, where it associates with thylakoid membranes. This suggests that the different PDI-like proteins in plant and animals may have diverse biological roles. To begin to elucidate the roles of PDI-like proteins, we have cloned, characterized, and generated knock-out mutants for three PDI-like genes that have high, medium, and low levels of expression, respectively, in the moss Physcomitrella patens. Phylogenetic analysis indicates that the three PDI-like proteins cluster with RB60 and four proteins from Arabidopsis thaliana. They are typified by an N-terminal domain rich in negatively charged residues. The knock-out mutants, which are the first knock-outs available for PDI-like proteins in a multicellular organism, were found to be viable, indicating that the function of each single gene is dispensable, and suggesting that they may be functionally complementary.

Amino Acid Sequence↗
PubMed2002

Angiofibroblastoma of the skin: a report of seven cases in support of a distinctive entity.

BACKGROUND: Angiofibroblastoma of the skin is a recently described benign tumor with fibroblastic differentiation. The tumor is composed of stellate and spindle fibroblasts embedded in a fibromyxoid and fibrous matrix that contains numerous capillary-sized blood vessels. METHODS: All cases of fibromyxoid tumors of the skin from the files of two dermatopathologic centers and from consultation cases, together with clinical data and histopathologic specimens, were reviewed. Additionally, immunohistochemical studies were performed in all cases. RESULTS: Seven cases of angiofibroblastoma of the skin were found, including two cases previously reported. All cases showed similar histopathologic findings. The morphologic versatility of fibroblasts, however, explains some of the microscopic variations that were observed in three cases of this series. Immunohistochemical studies support the fibroblastic nature of the neoplasms. CONCLUSIONS: Our series provides data suggesting that angiofibroblastoma of the skin represents a distinctive entity, which should be considered in the differential diagnosis of other fibromyxoid tumors of the skin.

Adult↗
PubMed2001

Individual monitoring of aspirin desensitization.

BACKGROUND: Patients with aspirin-sensitive rhinosinusitis, which is frequently associated with intrinsic bronchial asthma, can be desensitized by long-term treatment with oral aspirin. The exact mechanisms of this desensitization remain obscure, but modulations of the eicosanoid pathway occur and can be monitored with the help of a practicable in vitro assay on mixed leukocyte cultures. OBJECTIVE: To monitor the effect of low-dose aspirin desensitization therapy, 100 mg/d, objectively by an in vitro assay. DESIGN: In a prospective study, 30 patients with aspirin intolerance, who were treated following a desensitization protocol with a dose of oral aspirin of only 100 mg/d were followed up for 1 year and reassessed every 3 months clinically and in vitro. RESULTS: Twenty-five patients showed a normalization of in vitro eicosanoid levels during this period, 4 showed some improvement, and 1 showed no therapeutic effect on eicosanoid release. Clinical follow-up revealed a low recurrence rate of nasal polyposis, with recurrent disease only in 4 individuals who also showed no normalization of eicosanoid release levels. Furthermore, a reduction of the average incidence of purulent episodes of sinusitis was seen after 1 year. Of 12 patients with asthma, 9 experienced marked improvement in pulmonary function. Of 16 individuals with a marked impairment of nasal breathing, 14 felt an increase of nasal patency, and 7 of 11 patients with pretreatment hyposmia had an improved sense of smell after 1 year. CONCLUSIONS: Desensitization therapy in patients with aspirin-sensitive rhinosinusitis can be successfully performed with low oral doses of aspirin, and the individual course throughout the desensitization can be monitored with the help of an in vitro analysis of eicosanoid release from mixed leukocyte cultures.

Adult↗
PubMed2001

Up-regulation of cyclooxygenase-1 in neuroblastoma cell lines by retinoic acid and corticosteroids.

Cyclooxygenases-1 and -2 are both expressed in neuronal cells in vivo. In the neuroblastoma cell lines NG108 and N2a, however, only cyclooxygenase-1 was detectable. Differentiation of the cells with retinoic acid increased cyclooxygenase-1 mRNA and protein expression within 24 and 48 h, respectively. A further increase was observed when the cells were concomitantly treated with the glucocorticoid dexamethasone (a 2-3-fold increase compared with retinoic acid alone). In the absence of retinoic acid, dexamethasone only slightly up-regulated cyclooxygenase-1 expression. The inhibitor of protein synthesis cycloheximide abrogated the effect of dexamethasone, indicating the involvement of newly synthesised proteins. Retinoic acid increased the transcription of cyclooxygenase-1 mRNA, determined with a luciferase-coupled promoter construct. Dexamethasone only slightly augmented cyclooxygenase-1-promoter activity but increased cyclooxygenase-1 mRNA stability. Other corticosteroids, hydrocortisone and aldosterone, also up-regulated cyclooxygenase-1 whereas neurosteroids or oestrogen were ineffective. Up-regulation was mediated primarily by the glucocorticoid receptor, because the receptor antagonist RU486 strongly reduced the effects of all corticosteroids. This indicated that in NG108 cells, the mineralocorticoid aldosterone may bind to the glucocorticoid receptor. Treatment of NG108 or N2a cells with corticosteroids did not alter the morphological phenotype obtained during differentiation. We thus show that corticosteroids, which down-regulate cyclooxygenase expression in most cell types, up-regulate cyclooxygenase-1 during neuronal differentiation.

Adrenal Cortex Hormones↗
PubMed2001

Thromboxane A2 release in ischemia and reperfusion of free flaps in rats, studied by microdialysis.

Several studies have implicated enhanced eicosanoid production in reperfusion injury. The reported study investigated the use of microdialysis in the in vivo measurement of thromboxane levels during reperfusion in ischemic and reperfused experimental free muscle flaps. Microdialysis probes were inserted, via a guide, into the gracilis and semitendinosus free flap in the rat. The probe was perfused at a flow of 5 microl/min, with samples collected at intervals of 20 min, and analyzed by the ELISA technique. Animals were randomly distributed into three groups. After ischemic periods of 2, 4, and 6 hr, respectively, the free muscle flaps were revascularized on the contralateral femoral vessels. The mean thromboxane level during ischemia was 1785.34 +/- 124.81 pg/ml. The mean levels of thromboxane rose significantly (p < 0.05), compared to base level, with 151.65 percent in the 2-hr ischemia group, 192.33 percent in the 4-hr ischemia group, and 294.69 percent in the 6-hr ischemia group, and correlated well with histologic observations. The results suggest that a microdialysis technique, combined with a sensitive assay for measuring thromboxane, is a useful method for in vivo monitoring of inflammatory processes during ischemia and reperfusion. The evolution of thromboxane release following 6 hr of ischemia indicates that this mediator may be involved in facilitation of cell death, following ischemia and reperfusion, since its tissue level correlates with histologic tissue damage.

Animals↗
PubMed2001

Plasmid gene delivery to human keratinocytes through a fibrin-mediated transfection system.

We have developed a matrix-mediated transfection system to deliver plasmids to human keratinocytes. The matrix is a soluble, self-hardening fibrin matrix (Tissucol), Baxter) that has been used clinically. Recently it has been shown that full thickness burn wounds can be successfully treated with a keratinocyte fibrin glue suspension. Further, it has been demonstrated that hEGF transfected cells accelerate wound healing. In this study, we inoculated the matrix with the hEGF expression plasmid and resuspended the matrix with either cultured or noncultured human keratinocytes. We obtained successful transfection rates of these cells (up to a 100-fold increase compared to controls containing no EGF expression plasmid) in vitro. After transplantation to full thickness wounds on athymic mice we were able to show a 180-fold increase in EGF concentration compared to controls, which persisted over the entire 7-day monitored period, decreasing from 180 to 20 pg/mL at day seven. This unique approach indicates the possible utility to combine a matrix for cell transplantation with a transfection system to release therapeutic proteins in vitro and in vivo.

Animals↗
PubMed2000

Calretinin staining pattern aids in the differentiation of mesothelioma from adenocarcinoma in serous effusions.

BACKGROUND: The differentiation between malignant mesothelioma and adenocarcinoma based on morphology alone can be a diagnostic challenge. The majority of the available antibodies recognize molecules expressed by adenocarcinoma whereas to the authors' knowledge specific markers for mesothelial cells are lacking. Calretinin, a calcium-binding protein, has been reported to be a selective marker for mesothelioma and largely is absent from adenocarcinoma on histologic material. The results with cytologic preparations have been inconsistent. METHODS: To evaluate the specificity of calretinin in differentiating mesothelioma from adenocarcinoma in cytologic preparations, 21 paraffin embedded cells blocks of serous effusions from 15 patients with metastatic adenocarcinoma and 16 cell blocks from 9 patients with malignant mesothelioma were stained with a monoclonal antibody against calretinin. The immunoreactivity was evaluated blindly by two observers. Positive staining was defined as nuclear and cytoplasmic staining with or without intense membranous decoration. The former resulted in a characteristic "fried egg" appearance. RESULTS: Calretinin staining was positive in all but 2 cases of mesothelioma (14 of 16 cases; 87.5%). The latter contained predominantly spindle-shaped neoplastic mesothelial cells in the cell block preparations. All adenocarcinoma specimens were classified as negative for calretinin staining; 9 (42.9%) lacked any immunoreactivity and 12 (57.1%) showed weak, sparse, coarse, granular cytoplasmic staining without nuclear or membranous staining. Benign reactive mesothelial cells, when observed in association with adenocarcinoma, also showed the characteristic "fried egg" appearance. The difference in the staining pattern of calretinin between cells of mesothelial origin and adenocarcinoma cells was statistically significant. CONCLUSIONS: Calretinin is a useful marker in differentiating mesothelioma of the epithelial type from adenocarcinoma in serous effusions. The "fried-egg" appearance or cytoplasmic and nuclear staining pattern is characteristic of cells of mesothelial origin.

Adenocarcinoma↗
PubMed2000

In vitro generation of osteochondral composites.

Osteochondral repair involves the regeneration of articular cartilage and underlying bone, and the development of a well-defined tissue-to-tissue interface. We investigated tissue engineering of three-dimensional cartilage/bone composites based on biodegradable polymer scaffolds, chondrogenic and osteogenic cells. Cartilage constructs were created by cultivating primary bovine calf articular chondrocytes on polyglycolic acid meshes; bone-like constructs were created by cultivating expanded bovine calf periosteal cells on foams made of a blend of poly-lactic-co-glycolic acid and polyethylene glycol. Pairs of constructs were sutured together after 1 or 4 weeks of isolated culture, and the resulting composites were cultured for an additional 4 weeks. All composites were structurally stable and consisted of well-defined cartilaginous and bone-like tissues. The fraction of glycosaminoglycan in the cartilaginous regions increased with time, both in isolated and composite cultures. In contrast, the mineralization in bone-like regions increased during isolated culture, but remained approximately constant during the subsequent composite culture. The integration at the cartilage/bone interface was generally better for composites consisting of immature (1-week) than mature (4-week) constructs. This study demonstrates that osteochondral tissue composites for potential use in osteochondral repair can be engineered in vitro by culturing mammalian chondrocytes and periosteal cells on appropriate polymer scaffolds.

Animals↗
PubMed2000

Combined cuboid/cuneiform osteotomy for correction of residual adductus deformity in idiopathic and secondary club feet.

We used a combined cuboid/cuneiform osteotomy to treat residual adductus deformity in idiopathic and secondary club feet. The mean follow-up for 27 feet (22 idiopathic, four arthrogrypotic and one related to amniotic band syndrome) was 5.0 years (2.0 to 9.8). All healed uneventfully except for one early wound infection. No further surgery was required in the 22 idiopathic club feet but four of five with secondary deformity needed further surgery. At follow-up all patients with idiopathic and two with secondary club feet were free from pain and satisfied with the result. In the idiopathic feet, adductus of the forefoot, as measured by the calcaneal second metatarsal angle, improved on average from 20.7 +/- 2.0 degrees to 8.9 +/- 1.8 degrees (p < 0.05). In four feet, with a follow-up of more than six years, there was complete recurrence of the deformity. In the secondary club feet, there was no improvement of the adductus. We conclude that in most, but not all, idiopathic club feet a cuboid/cuneiform osteotomy can provide satisfactory correction of adductus deformity. Those with secondary deformity require other procedures.

Adolescent↗
PubMed1999

[The diabetic foot--state of the art from the orthopedic point of view].

A 15-30% rate of amputation of diabetic feet suggests that efforts have to be directed towards improvement of preventive measure including instruction of patients and relatives concerning foot wear. So called foot rules have been established. If surgery is indicated, an angiological and neurological assessment should be performed preoperatively. An ulcer should undergo debridement, plantar pressure release with a full contact cast and antibiotic therapy, if infected. The goal of treatment of Charcot's disease is prevention of deformity. Usually orthoses are sufficient, in irreducible deformities an arthrodesis should be considered. There is no doubt that the interdisciplinary approach improves the treatment of the diabetic foot.

Diabetic Foot↗
PubMed1999

Experimentally induced nasal irritation.

The aim of this study was to develop a method that is suited for the induction of nasal irritation. For this purpose inflammatory responses were analysed after challenging the nasal mucosa with experimentally induced cold, dry air (8 l/min, 22 degrees C, 20 %RH). To assess inflammatory effects we determined inflammatory mediators (prostaglandin E2 [PGE2], thromboxane B2 TXB2[, peptide leukotrienes pLT: LTC4, LTD4, LTE4[) in nasal lavage fluid which was sampled before, immediately after suprathreshold stimulation, and one hour after termination of the stimulation. In addition, subjects estimated the intensity of pain during the stimulation. Cold, dry air produced strong painful sensations which increased throughout the stimulation period. A significant increase of the inflammatory mediator pLT was observed after stimulation; mean concentrations of PGE2 and TXB2 also showed a tendency to increase. One hour after termination of the stimulation the concentration of these inflammatory mediators returned to baseline which indicates the reversibility of the effects of nasal irritation. These data suggest, that this model may be a useful tool in investigations of mucosal irritation as, for example, induced by environmental agents.

Adult↗
PubMed1997

Differential regulation of cyclo-oxygenase-2 and 5-lipoxygenase-activating protein (FLAP) expression by glucocorticoids in monocytic cells.

1. The objective of the present study was to determine the effects of dexamethasone on key constituents of prostaglandin and leukotriene biosynthesis, cyclo-oxygenase-2 (COX-2) and 5-lipoxygenase activating protein (FLAP). The human monocytic cell line THP-1 was used as a model system. mRNA and protein levels of COX-2 and FLAP were determined by Northern and Western blot analyses, respectively. 2. Low levels of COX-2 and FLAP mRNA were expressed in undifferentiated THP-1 cells, but were induced upon differentiation of the cells along the monocytic pathway by treatment with phorbol ester (TPA, 5 nM). Maximal expression was observed after two days. 3. Coincubation of the undifferentiated cells with dexamethasone (10(-9) - 10(-6) M) and phorbol ester prevented induction of COX-2 mRNA, but did not affect the induction of FLAP mRNA. 4. Dexamethasone downregulated COX-2 mRNA and protein in differentiated, monocyte-like THP-1 cells. In contrast, FLAP mRNA and protein were upregulated by dexamethasone in differentiated THP-1 cells. After 24 h, FLAP mRNA levels were increased more than 2 fold. Dexamethasone did not change 5-lipoxygenase mRNA expression. 5. Release of prostaglandin E2 (PGE2) and peptidoleukotrienes was determined in cell culture supernatants of differentiated THP-1 cells by ELISA. Calcium ionophore-dependent PGE2 synthesis was associated with COX-2 expression, whereas COX-1 and COX-2 seemed to participate in arachidonic acid-dependent PGE2 synthesis. Very low levels of peptidoleukotrienes were released from differentiated THP-1 cells upon incubation with ionophore. Treatment with dexamethasone did not significantly affect leukotriene release. 6. These data provide evidence that prostaglandin synthesis is consistently downregulated by glucocorticoids. However, the glucocorticoid-mediated induction of FLAP may provide a mechanism to maintain leukotriene biosynthesis through more efficient transfer of arachidonic acid to the 5-lipoxygenase reaction, in spite of inhibitory effects on other enzymes of the biosynthetic pathway.

5-Lipoxygenase-Activating Proteins↗
PubMed1996

Acute and chronic effects of morphine in pigeons responding under a progressive-ratio schedule of food delivery.

Although progressive-ratio schedules have often been used by behavioral pharmacologists to index the relative reinforcing effects of drugs of abuse, they have been ignored in the study of tolerance to opioids. The present study examined tolerance to morphine in pigeons responding under a progressive-ratio 5 schedule of food delivery. Acute administrations of morphine produced general dose-dependent reductions in response rates and breaking points. Dose-response curves for both measures shifted rightward substantially (roughly fivefold) following chronic (daily) exposure to morphine, indicating that tolerance developed to the drug's effects.

Animals↗