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Search Results: 1 - 10 of 15638 matches for " Christian Pfeiffer "
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The vestibular system: a spatial reference for bodily self-consciousness
Christian Pfeiffer,Olaf Blanke
Frontiers in Integrative Neuroscience , 2014, DOI: 10.3389/fnint.2014.00031
Abstract: Self-consciousness is the remarkable human experience of being a subject: the ‘I’. Self-consciousness is typically bound to a body, and particularly to the spatial dimensions of the body, as well as to its location and displacement in the gravitational field. Because the vestibular system codes head position in three-dimensional space, vestibular cortex is likely to contribute to spatial aspects of bodily self-consciousness. We review here recent data showing vestibular effects on first-person perspective (the feeling from where ‘I’ experience the world) and self-location (the feeling where ‘I’ am located in space). We compare these findings to data showing vestibular effects on mental spatial transformation, self-motion perception, and body representation that show that vestibular signals contribute to various spatial representations of the body with respect to the external world. Finally, we discuss four posterior brain regions that process vestibular and other multisensory signals to encode spatial aspects of bodily self-consciousness: temporoparietal junction (TPJ), parietoinsular vestibular cortex (PIVC), medial superior temporal region (MST), and ventral intraparietal region (VIP). We propose that vestibular processing in these cortical regions is important for linking multisensory signals from within personal space with those from extrapersonal space, and for spatial aspects of bodily self-consciousness.
Disc height and anteroposterior translation in fused and adjacent segments after lumbar spine fusion
Pfeiffer, Michael,Haas, Oliver,Huber-Stentrup, Martin,Georg, Christian
GMS German Medical Science , 2003,
Abstract: In a series of 46 patients the effects of spinal fusion upon intervertebral height and sagittal alignment in operated and non-operated segments were retrospectively evaluated on digitized radiographs. Data was compared with age- and gender-normalized standard values. The objective was to evaluate the influence of different types of spine fusions primarily upon adjacent segments, particularly in terms of degeneration and sagittal profile of the lumbar spine. Incidence of adjacent segment degeneration (ASD) is still highly controversial. However, not every degeneration adjacent to spinal fusion must be caused by the fusion and responsibility of the fusion for ASD may vary with its range and type. Distortion Corrected Roentgen Analysis (DCRA) was utilized. DCRA is a proven valid, reliable, observer-independent, and accurate tool for assessment of these parameters over time and in comparison with "normal" cohorts. With this method the exact posture of the patients needs not to be known.There was little evidence for serious fusion-related ASD within an average of 40 months follow-up. No difference could be detected for rigid vs. non-rigid fusion and instrumented vs. non-instrumented techniques. Temporary postoperative distraction effects could be detected in operated and non-operated segments. Absolute preoperative values for intervertebral height and vertebral slip were age-related. Retrospectively, the choice of segments for fusion was clearly based upon radiological criteria. Thus we conclude that radiological parameters have an obvious clinical relevance for decision-making and need to be quantified. Within the limitations of this pilot study, true fusion related ASD seems to be infrequent.
Carbon Sequestration in Coastal Soils under Different Land Use in Schleswig-Holstein, Northern Germany
Normah Awang Besar,Christian Knoblauch,Eva-Maria Pfeiffer
Environment and Natural Resources Research (ENRR) , 2011, DOI: 10.5539/enrr.v1n1p53
Abstract: The study was located in the coastal soils “Katinger Watt”, a former tidal flat of the North Sea coast in Schleswig-Holstein, Northern Germany. Carbon sequestration was determined by the ecological approach and calculated as the difference between total annual net primary production and total annual heterotrophic respiration. The measurement was conducted every month from June 2006 to May 2007. All sites were underlain by very young soils that developed after the former marine tidal flat was diked in 1973 which means that soil formation continues since 35 year. The initial conditions after diking were similar in all sites. All soils were classified as Normkalkmarsch according to the German soil classification, as Calcic Fluvisol according to World Reference Database for Soil Resources and as Typic Fluvaquent according to the Soil Taxonomy. The annual carbon sequestration in the arable land was estimated as -0.82 t C ha-1 yr-1 which indicates that the arable land acted as a net CO2 source during the investigation period. In the grassland, about 0.18 t C ha-1 yr-1 was sequestered in the soil. In other words the grassland acted as a carbon sink during the investigation period.
Full body illusion is associated with widespread skin temperature reduction
Roy Salomon,Christian Pfeiffer,Roger Gassert,Olaf Blanke
Frontiers in Behavioral Neuroscience , 2013, DOI: 10.3389/fnbeh.2013.00065
Abstract: A central feature of our consciousness is the experience of the self as a unified entity residing in a physical body, termed bodily self-consciousness. This phenomenon includes aspects such as the sense of owning a body (also known as body ownership) and has been suggested to arise from the integration of sensory signals from the body. Several studies have shown that temporally synchronous tactile stimulation of the real body and visual stimulation of a fake or virtual body can induce changes in bodily self-consciousness, typically resulting in a sense of illusory ownership over the fake body. The present study assessed the effect of anatomical congruency of visuo-tactile stimulation on bodily self-consciousness. A virtual body was presented and temporally synchronous visuo-tactile stroking was applied simultaneously to the participants' body and to the virtual body. We manipulated the anatomical locations of the visuo-tactile stroking (i.e., on the back, on the leg), resulting in congruent stroking (stroking was felt and seen on the back or the leg) or incongruent stroking (i.e., stroking was felt on the leg and seen on the back). We measured self-identification with the virtual body and self-location as well as skin temperature. Illusory self-identification with the avatar as well as changes in self-location were experienced in the congruent stroking conditions. Participants showed a decrease in skin temperature across several body locations during congruent stimulation. These data establish that the full-body illusion (FBI) alters bodily self-consciousness and instigates widespread physiological changes in the participant's body.
Low Molecular Weight pDMAEMA-block-pHEMA Block-Copolymers Synthesized via RAFT-Polymerization: Potential Non-Viral Gene Delivery Agents?
Olga Samsonova,Christian Pfeiffer,Markus Hellmund,Olivia M. Merkel,Thomas Kissel
Polymers , 2011, DOI: 10.3390/polym3020693
Abstract: The aim of this study was to investigate non-viral pDNA carriers based on diblock-copolymers consisting of poly(2-(dimethyl amino)ethyl methacrylate) (pDMAEMA) and poly(2-hydroxyethyl methacrylate) (pHEMA). Specifically the block-lengths and molecular weights were varied to determine the minimal requirements for transfection. Such vectors should allow better transfection at acceptable toxicity levels and the entire diblock-copolymer should be suitable for renal clearance. For this purpose, a library of linear poly(2-(dimethyl amino)ethyl methacrylate- block-poly(2-hydroxyl methacrylate) (pDMAEMA -block-pHEMA) copolymers was synthesized via RAFT (reversible addition-fragmentation chain transfer) polymerization in a molecular weight (Mw) range of 17–35.7 kDa and analyzed using 1H and 13C NMR (nuclear magnetic resonance), ATR (attenuated total reflectance), GPC (gel permeation chromatography) and DSC (differential scanning calorimetry). Copolymers possessing short pDMAEMA-polycation chains were 1.4–9.7 times less toxic in vitro than polyethylenimine (PEI) 25 kDa, and complexed DNA into polyplexes of 100–170 nm, favorable for cellular uptake. The DNA-binding affinity and polyplex stability against competing polyanions was comparable with PEI 25 kDa. The zeta-potential of polyplexes of pDMAEMA-grafted copolymers remained positive (+15–30 mV). In comparison with earlier reported low molecular weight homo pDMAEMA vectors, these diblock-copolymers showed enhanced transfection efficacy under in vitro conditions due to their lower cytotoxicity, efficient cellular uptake and DNA packaging. The homo pDMAEMA 115 (18.3 kDa) self-assembled with DNA into small positively charged polyplexes, but was not able to transfect cells. The grafting of 6 and 57 repeating units of pHEMA (0.8 and 7.4 kDa) to pDMAEMA 115 increased the transfection efficacy significantly, implying a crucial impact of pHEMA on vector-cell interactions. The intracellular trafficking, in vivo transfection efficacy and kinetics of low molecular weight pDMAEMA -block-pHEMA are subject of ongoing studies.
Alcohol consumption and binge drinking in adolescents: comparison of different migration backgrounds and rural vs. urban residence - a representative study
Carolin Donath, Elmar Gr??el, Dirk Baier, Christian Pfeiffer, Deniz Karagülle, Stefan Bleich, Thomas Hillemacher
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-84
Abstract: In the years 2007/2008, a representative written survey of N = 44,610 students in the 9th. grade of different school types in Germany was carried out (net sample). The return rate of questionnaires was 88% regarding all students whose teachers respectively school directors had agreed to participate in the study. Weighting factors were specified and used to make up for regional and school-type specific differences in return rates. 27.4% of the adolescents surveyed have a migration background, whereby the Turkish culture is the largest group followed by adolescents who emigrated from former Soviet Union states. The sample includes seven large cities (over 500,000 inhabitants) (12.2%), independent smaller cities ("urban districts") (19.0%) and rural areas ("rural districts") (68.8%).Life-time prevalence for alcohol consumption differs significantly between rural (93.7%) and urban areas (86.6% large cities; 89.1% smaller cities) with a higher prevalence in rural areas. The same accounts for 12-month prevalence for alcohol consumption. 57.3% of the rural, re-spectively 45.9% of the urban adolescents engaged in binge drinking in the 4 weeks prior to the survey. Students with migration background of the former Soviet Union showed mainly drinking behavior similar to that of German adolescents. Adolescents with Turkish roots had engaged in binge drinking in the last four weeks less frequently than adolescents of German descent (23.6% vs. 57.4%). However, in those adolescents who consumed alcohol in the last 4 weeks, binge drinking is very prominent across the cultural backgrounds.Binge drinking is a common problem behavior in German adolescents. Obviously adolescents with rural residence have fewer alternatives for engaging in interesting leisure activities than adolescents living in cities. This might be one reason for the more problematic consumption patterns there. Common expectations concerning drinking behavior of adolescents of certain cultural backgrounds ('migrants w
Multisensory Origin of the Subjective First-Person Perspective: Visual, Tactile, and Vestibular Mechanisms
Christian Pfeiffer, Christophe Lopez, Valentin Schmutz, Julio Angel Duenas, Roberto Martuzzi, Olaf Blanke
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061751
Abstract: In three experiments we investigated the effects of visuo-tactile and visuo-vestibular conflict about the direction of gravity on three aspects of bodily self-consciousness: self-identification, self-location, and the experienced direction of the first-person perspective. Robotic visuo-tactile stimulation was administered to 78 participants in three experiments. Additionally, we presented participants with a virtual body as seen from an elevated and downward-directed perspective while they were lying supine and were therefore receiving vestibular and postural cues about an upward-directed perspective. Under these conditions, we studied the effects of different degrees of visuo-vestibular conflict, repeated measurements during illusion induction, and the relationship to a classical measure of visuo-vestibular integration. Extending earlier findings on experimentally induced changes in bodily self-consciousness, we show that self-identification does not depend on the experienced direction of the first-person perspective, whereas self-location does. Changes in bodily self-consciousness depend on visual gravitational signals. Individual differences in the experienced direction of first-person perspective correlated with individual differences in visuo-vestibular integration. Our data reveal important contributions of visuo-vestibular gravitational cues to bodily self-consciousness. In particular we show that the experienced direction of the first-person perspective depends on the integration of visual, vestibular, and tactile signals, as well as on individual differences in idiosyncratic visuo-vestibular strategies.
Prevalence, clinical relevance and characterization of circulating cytotoxic CD4+CD28- T cells in ankylosing spondylitis
Christina Duftner, Christian Goldberger, Albrecht Falkenbach, Reinhard Würzner, Barbara Falkensammer, Karl P Pfeiffer, Elisabeth Maerker-Hermann, Michael Schirmer
Arthritis Research & Therapy , 2003, DOI: 10.1186/ar793
Abstract: The immunogenetic link between HLA-B27 and ankylosing spondylitis (AS) is the strongest reported association of an HLA class I molecule with a disease to date. HLA-B27 presents specific peptides to CD8+ T lymphocytes in the presence of β2-microglobulin [1,2], and much work has concentrated on characterizing B27 restricted cytotoxic T lymphocytes in spondyloarthropathy patients [3,4]. CD8+ cytotoxic T lymphocytes identified by the CD28- phenotype account for up to 78% of peripheral CD8+ T cells [5].Several more recent studies have raised the possibility that HLA-B27 may be more than a restriction element of CD8+ T cells in AS, and that HLA-B27 may be recognized even by CD4+ T cells [6,7]. In HLA-B27 transgenic rats CD4+ T cells were used to transfer AS disease [8,9], and in autoimmune MRL/lpr mice CD4+ T cell depletion prevented the development of arthritis [10]. MHC class II molecules, which usually present antigenic structures to CD4+ T cells, are not necessarily required for development of AS, and MHC class II negative, B27+ transgenic mice may still develop spontaneous AS-like disease [11]. In humans, CD4+ T cells are more frequently present than CD8+ T cells in both the peripheral blood and in biopsies of sacroiliac joints [12,13], and T cell clones with specificity for arthritogenic bacteria exhibited the CD4+ phenotype when derived from the synovial fluids of patients with Yersinia, Salmonella, and Chlamydia-induced reactive arthritis [14-16]. However, bacteria and/or autoantigen specific CD8+ and HLA-B27 restricted T cells are also thought to contribute to the pathogenesis and regulation of the spondyloarthropathies [3].In other autoimmune diseases, including rheumatoid arthritis, Wegener's granulomatosis, and multiple sclerosis, an unusual subset of proinflammatory, cytotoxic CD4+ T cells was described that is rare in healthy individuals [17-20]. These T cells are clonally expanded and lack the important CD28 co-stimulatory molecule on their surface. This ch
Circulating cytotoxic CD8+ CD28- T cells in ankylosing spondylitis
Michael Schirmer, Christian Goldberger, Reinhard Würzner, Christina Duftner, Karl-P Pfeiffer, Johannes Clausen, Günther Neumayr, Albrecht Falkenbach
Arthritis Research & Therapy , 2001, DOI: 10.1186/ar386
Abstract: Ankylosing spondylitis (AS) is a seronegative spondyloarthropathy that is frequently associated with human leucocyte antigen (HLA)-B27; 90% of AS patients test HLA-B27 positive. HLA-B27 physiologically binds antigenic peptides and thus presents them to CD8+ T lymphocytes. Single HLA-B27 restricted cytotoxic T lymphocytes (CTLs) have been described in AS patients with specificity for arthritogenic bacteria, viral peptides or autoantigens such as peptides derived from the HLA-B27 molecule itself [1,2,3]. CTLs have been reported to maintain the inflammatory process even after the eradication of the microbial pathogen by antimicrobial immune responses [4].In vivo, MHC-class I restricted CD8+ T cells are clonally expanded and use various αβ T cell-receptors [5,6]. Some of these CD8+ T cell clones represent even more than 50% of all CD8+T cells in single AS patients [7,8,9]. This oligoclonal population which recognizes specific MHC-class I / antigen complexes is characterized by a distinct CD28-CD57+ CD11ahigh phenotype [10]. The presence of this oligoclonal CD28- population in a larger cohort of AS patients has not been examined before. It has been suggested, therefore, that the amount of CD8+ CTLs in a peripheral blood sample can be estimated by determining the percentage of CD8+ CD28- T cells. Furthermore, identification of CD8+ CTLs by the lack of CD28 has provided a helpful tool to investigate this lymphocyte subset in healthy subjects and patients with various diseases [11]. In the healthy population, CD8+ CD28-T cells are not present at birth, and the percentage of CD8+ CD28-T cells increases with age [12,13,14]. This increase of CD8+ CD28-cells, together with reduced circulating naive CD8+ T cells correlates with immunodeficiency during aging [15,16]. As CD8+ CD28-T cells have shortened telomeres, they may have reached a state of replicative senescence [17]. The question as to whether such accelerated senescence is a consequence of viral infections remains open. T
Evaluation of effectiveness of instruction and study habits in two consecutive clinical semesters of the medical curriculum munich (MeCuM) reveals the need for more time for self study and higher frequency of assessment
Sophia Mueller, Nina Weichert, Veit Stoecklein, Ariane Hammitzsch, Giulia Pascuito, Christian Krug, Matthias Holzer, Mona Pfeiffer, Matthias Siebeck, Ralf Schmidmaier
BMC Medical Education , 2011, DOI: 10.1186/1472-6920-11-62
Abstract: Purposes: To analyze students' study habits in relation to exam frequency and to evaluate effectiveness of instruction.Time spent on self study (TSS) and the quantity of instruction (QI) was assessed during the internal medicine and the surgical semester. Students and faculty members were asked about study habits and their evaluation of the current curriculum.The TSS/QI ratio as a measure of effectiveness of instruction ranges mainly below 1.0 and rises only prior to exams. Students and teachers prefer to have multiple smaller exams over the course of the semester. Furthermore, students wish to have more time for self-guided study.The TSS/QI ratio is predominantly below the aspired value of 1.0. Furthermore, the TSS/QI ratio is positively related to test frequency. We therefore propose a reduction of compulsory lessons and an increase in test frequency.Following the new German "Regulation of the Licensing of Doctors" (Approbationsordnung für ?rzte) conducted by the German Federal Ministry of Health in 2002 [1], most German medical schools had to initiate profound modifications of their curricula. In order to fulfill the new requirements, Ludwig-Maximilians University (LMU) Munich implemented a new Medical Curriculum in Munich (MeCuM) in 2003 [2]. In general, medical studies continue to be divided into a preclinical coursework focusing on basic science, and a clinical portion of four years. The clinical portion of MeCuM has been split into 6 modules that are primarily subject-based. Module 2 covers internal medicine and Module 3 is dedicated to operative medicine. The presented analysis focuses on these two basic clinical specialties. Internal surveys repeatedly showed that students and teachers are generally satisfied with the internal medicine and the surgical semester. Nevertheless, we hypothesize that the current curricular structure and mode of assessment, which entail many mandatory courses and a low frequency of testing, do not motivate students to study conti
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