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Search Results: 1 - 10 of 5187 matches for " Christine Radtke "
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Peripheral Nerve Injuries and Transplantation of Olfactory Ensheathing Cells for Axonal Regeneration and Remyelination: Fact or Fiction?
Christine Radtke,Jeffery D. Kocsis
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms131012911
Abstract: Successful nerve regeneration after nerve trauma is not only important for the restoration of motor and sensory functions, but also to reduce the potential for abnormal sensory impulse generation that can occur following neuroma formation. Satisfying functional results after severe lesions are difficult to achieve and the development of interventional methods to achieve optimal functional recovery after peripheral nerve injury is of increasing clinical interest. Olfactory ensheathing cells (OECs) have been used to improve axonal regeneration and functional outcome in a number of studies in spinal cord injury models. The rationale is that the OECs may provide trophic support and a permissive environment for axonal regeneration. The experimental transplantation of OECs to support and enhance peripheral nerve regeneration is much more limited. This chapter reviews studies using OECs as an experimental cell therapy to improve peripheral nerve regeneration.
Development of a Middle Cerebral Artery Occlusion Model in the Nonhuman Primate and a Safety Study of I.V. Infusion of Human Mesenchymal Stem Cells
Masanori Sasaki, Osamu Honmou, Christine Radtke, Jeffery D. Kocsis
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026577
Abstract: Background Most experimental stroke research is carried out in rodents, but given differences between rodents and human, nonhuman primate (NHP) models may provide a valuable tool to study therapeutic interventions. The authors developed a surgical method for transient occlusion of the M1 branch of middle cerebral artery (MCA) in the African green monkey to evaluate safety aspects of intravenous infusion of mesenchymal stem cells (hMSCs) derived from human bone marrow. Methods The left Sylvian fissure was exposed by a small fronto-temporal craniotomy. The M1 branch of the MCA was exposed by microsurgical dissection and clipped for 2 to 4 hours. Neurological examinations and magnetic resonance imaging (MRI) were carried out at regular post-operative course. hMSCs were infused 1 hour after reperfusion (clip release) in the 3-hour occlusion model. Results During M1 occlusion, two patterns of changes were observed in the lateral hemisphere surface. One pattern (Pattern 1) was darkening of venous blood, small vessel collapse, and blood pooling with no venous return in cortical veins. Animals with these three features had severe and lasting hemiplegia and MRI demonstrated extensive MCA territory infarction. Animals in the second pattern (Pattern 2) displayed darkening of venous blood, small vessel collapse, and reduced but incompletely occluded venous flow and the functional deficit was much less severe and MRI indicated smaller infarction areas in brain. The severe group (Pattern 1) likely had less extensive collateral circulation than the less severe group (Pattern 2) where venous pooling of blood was not observed. The hMSC infused animals showed a trend for greater functional improvement that was not statistically significant in the acute phase and no additive negative effects. Conclusions These results indicate inter-animal variability of collateral circulation after complete M1 occlusion and that hMSC infusion is safe in the developed NHP stroke model.
Is tamoxifen associated with an increased risk for thromboembolic complications in patients undergoing microvascular breast reconstruction? [Ist die Einnahme von Tamoxifen zum Zeitpunkt der mikrovaskul ren Brustrekonstruktion mit einer erh hten Rate an thrombembolischen Komplikationen assoziiert?]
Jokuszies, Andreas,Radtke, Christine,Betzler, Christopher,Branski, Ludwik
GMS German Medical Science , 2013, DOI: 10.3205/000173
Abstract: [english] Introduction: Tamoxifen is associated with a twofold increased risk of thromboembolic events. Third generation aromatase inhibitors (AIs), such as letrozole, anastrozole, and exemestane have therefore replaced tamoxifen in the adjuvant therapy of hormone receptor-positive breast cancer. A retrospective review was performed in patients who underwent delayed microvascular breast reconstruction and received tamoxifen at the time of surgery in order to assess the risk of both minor and major flap complications including thromboembolic events.Patients and methods: Twenty-nine patients who underwent delayed microsurgical breast reconstruction with autologous tissue between 2006 and 2012 were included in the study. The overall complication rates were compared between patients who did versus those who did not receive tamoxifen at the time of microsurgical breast reconstruction. Results: Breast reconstruction was performed with a DIEP flap in and with a TRAM flap in 4 patients. Overall, the complication rate was 37.9% (n=11) consisting of 5 major (including one total flap loss) and 6 minor complications. In patients receiving tamoxifen (n=5), we observed one minor complication and one major complication with a total flap loss due to thrombus formation at the anastomosis site. In one patient pulmonary embolism occurred without association to tamoxifen. The number of thromboembolic events was equivalent in both groups (p=0.642). No increase of major (p=0.858) or minor (p=0.967) complications in the tamoxifen group could be observed. Taking the overall complication rate into account there was no statistically difference between the two groups (p=0.917).Conclusion: In our study we could not observe an increased risk for thromobembolic events in patients receiving tamoxifen while undergoing autologous microvascular breast reconstruction. [german] Aromatasehemmer der dritten Generation haben mittlerweile Tamoxifen in der neoadjuvanten und adjuvanten Therapie des hormonrezeptorpen Brustkrebses postmenopausaler Frauen abgel st. Tamoxifen ist mit einem ca. zweifach erh hten Risiko für thrombembolische Komplikationen (tiefe Beinvenenthrombose, Lungenembolie) assoziiert. Vor dem Hintergrund einer aktuellen und im Februar 2012 im Journal of Plastic and Reconstructive Surgery erschienenen retrospektiven Studie mit Nachweis einer erh hten Komplikationsrate freier Lappentransplantate zur Brustrekonstruktion unter Tamoxifen-Einnahme haben wir unser Patientenkollektiv nach mikrochirurgischer Brustrekonstruktion retrospektiv auf Minor- und Major-Komplikationen einschlie
Schwann Cell Metabolic Activity in Various Short-Term Holding Conditions: Implications for Improved Nerve Graft Viability
Insa Janssen,Kerstin Reimers,Christina Allmeling,Stella Matthes,Peter M. Vogt,Christine Radtke
International Journal of Otolaryngology , 2012, DOI: 10.1155/2012/742183
Abstract: Strategies for improvement of nerve regeneration and optimal conditions to prevent Schwann cell (SC) loss within a nerve transplant procedure are critical. The purpose of this study was to examine SC viability, which plays an important role in peripheral nerve regeneration, under various incubation conditions up to three hours. To address this issue, Schwann cell metabolic activity was determined using different independent test methods. The following experimental conditions were compared: SCs prepared from nerves were incubated in (1) isotonic saline solution (2) Dulbecco's modified Eagles medium as used for cell culturing, (3) Hannover bioreactor medium, and (4) Leibovitz's medium. SC metabolic activity of excised rat sciatic nerve was determined at 4°C, 18°C, and 37°C over 3 hrs. The results indicate that SC activity was optimized by the usage of Leibovitz's medium or HBRM at 37°C. Greater SC viability at the time of surgical nerve grafting could contribute to improved axonal regeneration and remyelination after nerve transplantation, and thus more successful functional recovery.
CNPase Expression in Olfactory Ensheathing Cells
Christine Radtke,Masanori Sasaki,Karen L. Lankford,Vittorio Gallo,Jeffery D. Kocsis
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/608496
Abstract: A large body of work supports the proposal that transplantation of olfactory ensheathing cells (OECs) into nerve or spinal cord injuries can promote axonal regeneration and remyelination. Yet, some investigators have questioned whether the transplanted OECs associate with axons and form peripheral myelin, or if they recruit endogenous Schwann cells that form myelin. Olfactory bulbs from transgenic mice expressing the enhanced green fluorescent protein (eGFP) under the control of the 2-3-cyclic nucleotide 3-phosphodiesterase (CNPase) promoter were studied. CNPase is expressed in myelin-forming cells throughout their lineage. We examined CNPase expression in both in situ in the olfactory bulb and in vitro to determine if OECs express CNPase commensurate with their myelination potential. eGFP was observed in the outer nerve layer of the olfactory bulb. Dissociated OECs maintained in culture had both intense eGFP expression and CNPase immunostaining. Transplantation of OECs into transected peripheral nerve longitudinally associated with the regenerated axons. These data indicate that OECs in the outer nerve layer of the olfactory bulb of CNPase transgenic mice express CNPase. Thus, while OECs do not normally form myelin on olfactory nerve axons, their expression of CNPase is commensurate with their potential to form myelin when transplanted into injured peripheral nerve.
Schwann Cell Metabolic Activity in Various Short-Term Holding Conditions: Implications for Improved Nerve Graft Viability
Insa Janssen,Kerstin Reimers,Christina Allmeling,Stella Matthes,Peter M. Vogt,Christine Radtke
International Journal of Otolaryngology , 2012, DOI: 10.1155/2012/742183
Abstract: Strategies for improvement of nerve regeneration and optimal conditions to prevent Schwann cell (SC) loss within a nerve transplant procedure are critical. The purpose of this study was to examine SC viability, which plays an important role in peripheral nerve regeneration, under various incubation conditions up to three hours. To address this issue, Schwann cell metabolic activity was determined using different independent test methods. The following experimental conditions were compared: SCs prepared from nerves were incubated in (1) isotonic saline solution (2) Dulbecco's modified Eagles medium as used for cell culturing, (3) Hannover bioreactor medium, and (4) Leibovitz's medium. SC metabolic activity of excised rat sciatic nerve was determined at 4°C, 18°C, and 37°C over 3?hrs. The results indicate that SC activity was optimized by the usage of Leibovitz's medium or HBRM at 37°C. Greater SC viability at the time of surgical nerve grafting could contribute to improved axonal regeneration and remyelination after nerve transplantation, and thus more successful functional recovery. 1. Introduction Axonal regeneration and remyelination after peripheral nerve injury can be robust with significant functional recovery in contrast to the central nervous system where long white matter tract regeneration is absent or minimal [1]. After peripheral nerve transection, for example, after tumor resection, Wallerian degeneration characterized by macrophage infiltration, axonal membrane digestion, and retraction and proliferation of SCs occurs in the distal nerve segment [2]. The detached SCs from the degenerating axons upregulate the expression of nerve growth factor (NGF) and its low-affinity receptor p75NGFR [3]. For a period of time these SCs are activated [4] and provide trophic support for regeneration. Regeneration occurs from the proximal stump by axonal sprouting and elongation and continues into the distal stump or nerve transplant [5]. The status of a nerve transplant is critical for successful nerve regeneration. While nerve regeneration through Schwann-cell-enriched basal lamina tubes can reestablish connections with peripheral targets such as skin and muscle, a number of issues, such as navigation of axons across a complex nerve injury site where scarring can occur and appropriate targeting to peripheral end structures are major clinical concerns [6]. Although local endogenous SCs play an important role in regeneration of peripheral nerve, transplantation of additional Schwann cells into a lesion site was shown to assist this regenerative process [7,
Cultivation of Keratinocytes and Fibroblasts in a Three-Dimensional Bovine Collagen-Elastin Matrix (Matriderm?) and Application for Full Thickness Wound Coverage in Vivo
Jasper Killat,Kerstin Reimers,Claudia Y. Choi,Sabrina Jahn,Peter M. Vogt,Christine Radtke
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms140714460
Abstract: New skin substitutes for burn medicine or reconstructive surgery pose an important issue in plastic surgery. Matriderm ? is a clinically approved three-dimensional bovine collagen-elastin matrix which is already used as a dermal substitute of full thickness burn wounds. The drawback of an avital matrix is the limited integration in full thickness skin defects, depending on the defect size. To further optimize this process, Matriderm ? has also been studied as a matrix for tissue engineering of skin albeit long-term cultivation of the matrix with cells has been difficult. Cells have generally been seeded onto the matrix with high cell loss and minimal time-consuming migration. Here we developed a cell seeded skin equivalent after microtransfer of cells directly into the matrix. First, cells were cultured, and microinjected into Matriderm ?. Then, cell viability in the matrix was determined by histology in vitro. As a next step, the skin substitute was applied in vivo into a full thickness rodent wound model. The wound coverage and healing was observed over a period of two weeks followed by histological examination assessing cell viability, proliferation and integration into the host. Viable and proliferating cells could be found throughout the entire matrix. The presented skin substitute resembles healthy skin in morphology and integrity. Based on this study, future investigations are planned to examine behaviour of epidermal stem cells injected into a collagen-elastin matrix under the aspects of establishment of stem cell niches and differentiation.
Expression of TNF-related apoptosis-inducing ligand (TRAIL) in keratinocytes mediates apoptotic cell death in allogenic T cells
Kerstin Reimers, Christine Radtke, Claudia Y Choi, Christina Allmeling, Susanne Kall, Paul Kiefer, Thomas Muehlberger, Peter M Vogt
Annals of Surgical Innovation and Research , 2009, DOI: 10.1186/1750-1164-3-13
Abstract: Members of the TNF ligand family control and conduct numerous immunological and inflammation-related reactions. The Fas-FasL system and its associated mechanism of activation-induced cell death play an important role for the maintenance of hemostasis of the lymphoid system and the induction of immune tolerance [1]. The TNF-related apoptosis-inducing ligand (TRAIL) was identified as a homologue of the Fas-ligand (FasL) [2]. Yet, in contrast to FasL, TRAIL expression has been demonstrated in various tissues and organs [2-4], as the expression pattern of TRAIL receptors allows a subtle observation of apoptotic reactions. Until now, five different receptors for TRAIL have been described and all belong to the TNF receptor family. The receptors TRAIL-R1/DR4, TRAIL-R2/DR5, TRAIL-R3/DcR1 and TRAIL-R4/DcR2 exhibit a considerably homologous sequence of their extracellular domain and bind TRAIL as the only known ligand. The soluble receptor osteoprotegerin (OPG) belongs to a different sub-family and binds the ligand RANKL/OPGL as well. Following ligand binding and activation of cytoplasmatic death domains, TRAIL-R1 and TRAIL-R2 start series of signals for apoptosis [4,5], whereas the decoy receptors do not transmit death signals. The ratio of expression of DR4/DR5 and decoy receptors by a tumor cell will determine its sensibility for TRAIL-induced apoptosis [2,4]. An important function of TRAIL is the regulation of the immune response being involved in controlling the extent of the activated lymhocyte reaction [6]. Interactions between TRAIL and lymphocytes can create so-called immune-privileged sites, e.g. the placenta [7].The use of TRAIL for the induction of tolerance against allogenic transplants should be considered in burn medicine. The therapy of massive burn injuries is highly complex and can result in grave personal and socio-economic consequences. The therapeutic gold standard is the early resection of necrotic tissue and subsequent wound coverage with autologous ski
Adhesion, Vitality and Osteogenic Differentiation Capacity of Adipose Derived Stem Cells Seeded on Nitinol Nanoparticle Coatings
Sarah Strau?, Anne Neumeister, Stephan Barcikowski, Dietmar Kracht, J?rn W. Kuhbier, Christine Radtke, Kerstin Reimers, Peter M. Vogt
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053309
Abstract: Autologous cells can be used for a bioactivation of osteoimplants to enhance osseointegration. In this regard, adipose derived stem cells (ASCs) offer interesting perspectives in implantology because they are fast and easy to isolate. However, not all materials licensed for bone implants are equally suited for cell adhesion. Surface modifications are under investigation to promote cytocompatibility and cell growth. The presented study focused on influences of a Nitinol-nanoparticle coating on ASCs. Possible toxic effects as well as influences on the osteogenic differentiation potential of ASCs were evaluated by viability assays, scanning electron microscopy, immunofluorescence and alizarin red staining. It was previously shown that Nitinol-nanoparticles exert no cell toxic effects to ASCs either in soluble form or as surface coating. Here we could demonstrate that a Nitinol-nanoparticle surface coating enhances cell adherence and growth on Nitinol-surfaces. No negative influence on the osteogenic differentiation was observed. Nitinol-nanoparticle coatings offer new possibilities in implantology research regarding bioactivation by autologous ASCs, respectively enhancement of surface attraction to cells.
A Simple Trap for the Capture New-Emergent Salmonid Fry in Streams
Grzegorz Radtke
Archives of Polish Fisheries , 2008, DOI: 10.2478/s10086-008-0007-3
Abstract: A simple trap was built for capturing salmonid fry emerging from natural spawning redds in streams. The trap is shaped like a cap with a vertical PVC tube. Since the trap is not attached permanently to the substrate, settled debris can be cleaned out regularly, and the trap can be deployed in streams with large amounts of drifting organic material. Its simple construction means that it is easy to use. Based on the comparison of the effectiveness of two types of traps on artificial redds, the catch efficiency of the newly constructed trap was determined to be 37%.
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