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81.
Jornayvaz FR Birkenfeld AL Jurczak MJ Kanda S Guigni BA Jiang DC Zhang D Lee HY Samuel VT Shulman GI 《Proceedings of the National Academy of Sciences of the United States of America》2011,108(14):5748-5752
Mice overexpressing acylCoA:diacylglycerol (DAG) acyltransferase 2 in the liver (Liv-DGAT2) have been shown to have normal hepatic insulin responsiveness despite severe hepatic steatosis and increased hepatic triglyceride, diacylglycerol, and ceramide content, demonstrating a dissociation between hepatic steatosis and hepatic insulin resistance. This led us to reevaluate the role of DAG in causing hepatic insulin resistance in this mouse model of severe hepatic steatosis. Using hyperinsulinemic-euglycemic clamps, we studied insulin action in Liv-DGAT2 mice and their wild-type (WT) littermate controls. Here, we show that Liv-DGAT2 mice manifest severe hepatic insulin resistance as reflected by decreased suppression of endogenous glucose production (0.8 ± 41.8 vs. 87.7 ± 34.3% in WT mice, P < 0.01) during the clamps. Hepatic insulin resistance could be attributed to an almost 12-fold increase in hepatic DAG content (P < 0.01) resulting in a 3.6-fold increase in protein kinase Cε (PKCε) activation (P < 0.01) and a subsequent 52% decrease in insulin-stimulated insulin receptor substrate 2 (IRS-2) tyrosine phosphorylation (P < 0.05), as well as a 64% decrease in fold increase pAkt/Akt ratio from basal conditions (P < 0.01). In contrast, hepatic insulin resistance in these mice was not associated with increased endoplasmic reticulum (ER) stress or inflammation. Importantly, hepatic insulin resistance in Liv-DGAT2 mice was independent of differences in body composition, energy expenditure, or food intake. In conclusion, these findings strengthen the link between hepatic steatosis and hepatic insulin resistance and support the hypothesis that DAG-induced PKCε activation plays a major role in nonalcoholic fatty liver disease (NAFLD)-associated hepatic insulin resistance. 相似文献
82.
Birkenfeld F Steiner M Becker ME Kern M Menzebach M Wiltfang J Lucius R Becker ST 《The Journal of craniofacial surgery》2011,22(5):1641-1646
The objective of this study was first to establish a method to measure forces and displacement of the orbital content in defects of the orbital floor in truncated fresh and unfixed heads and second to characterize reconstruction materials with regard to punctuation strength and compression.Orbital floor defects (10 × 20 mm and 15 × 20 mm; 3 mm behind the orbital rim) were prepared after Le Fort I osteotomy. The values of force and displacement were recorded in 6 freshly frozen human heads. In addition, the punctuation strength of 2 reconstruction materials (polydioxanone [PDS] foil and collagen membrane) was evaluated using a Zwick Z010 TN1 universal testing machine. The forces of the orbital content (28.41 [SD, 1.6] g) applied to the defects of 10 × 20 mm and 15 × 20 mm with an intact periorbita were 0.04 (SD, 0.003) N (0.0002 MPa) and 0.07 (SD, 0.02) N (0.0002 MPa), respectively, and with a split periorbita were 0.06 (SD, 0.03) N (0.0003 MPa) and 0.08 (SD, 0.06) N (0.00026 MPa), respectively. The displacement values without reconstruction materials of the 10 × 20-mm and 15 × 20-mm defects were 0.94 (SD, 0.7) mm and 1.2 (SD, 0.5) mm, respectively. The PDS foil could withstand forces of 118.9 (SD, 14.1) N (0.375 MPa), and the collagen membrane could withstand forces of 44.5 (SD, 5.3) N (0.14 MPa). This is the first study to report forces charging the orbital floor. The presented results support the use of PDS foils and collagen membranes as reconstruction materials for orbital floor defects, at least in smaller and medium-sized fractures. 相似文献
83.
Birkenfeld G 《Der Internist》2007,48(12):1358-1364
Along with the dizzying rise in the world's population and economic globalization, travel activity has also increased. Travelers' diarrhea, caused by changed sanitary conditions, has a very different pathogenic spectrum and clinical course from those of our native forms of infectious enterocolitis. Awareness of the warning signs of complications in the clinical course and of the differential diagnoses is therefore a prerequisite for rational therapy. This covers oral rehydration, motility inhibitors, adsorbents, antisecretory agents, probiotics, and last but not least the use of antibiotics, which make an essential contribution if correctly used. There are interesting developments in the form of nonabsorbable antibiotics and new antisecretory agents, which inhibit protein synthesis and enzymes and are increasingly used as antidiarrheal agents with few side effects. In the combination of various therapeutic options in travelers' diarrhea there is still much scope for research. The priority is the correct implementation of the options available today, in order to avoid, as far as possible, therapeutic setbacks and the development of resistance. 相似文献
84.
Suneel Reddy‐Alla Bertram Schmitt Jörg Birkenfeld Volker Eulenburg Sebastien Dutertre Christian Böhringer Magdalena Götz Heinrich Betz Theofilos Papadopoulos 《The European journal of neuroscience》2010,31(7):1173-1184
Collybistin (Cb) is a brain‐specific guanine nucleotide exchange factor (GEF) that is essential for the synaptic clustering of gephyrin and GABAA receptors in selected regions of the mammalian central nervous system. It has been previously proposed that Cb regulates gephyrin clustering by activating Cdc42, and thus acts as a signal transducer in a membrane activation process which labels postsynaptic membrane domains for inhibitory synapse formation. Here, we dissected the functional roles of the Dbl‐homology (DH) and pleckstrin homology (PH) domains of the constitutively active splice variant Cb II by substituting conserved amino acid residues that are required for GEF activity towards Cdc42 and phosphoinositide binding, respectively. A Cb II mutant lacking any detectable GEF activity towards Cdc42 was still fully active in inducing gephyrin scaffold formation, both in transfected NIH‐3T3 cells and in cultured hippocampal neurons. Furthermore, mice with a forebrain‐specific inactivation of the Cdc42 gene displayed normal densities of gephyrin and GABAA receptor clusters in the hippocampus. In contrast, substitution of Cb II PH‐domain residues essential for phosphoinositide binding abolished gephyrin recruitment to synaptic sites. Our results provide evidence that the formation of gephyrin scaffolds at inhibitory synapses requires an intact Cb II PH‐domain but is Cdc42‐independent. 相似文献
85.
A 1-trial fear conditioning was used to investigate the temporal development of fear responses expressed as increase of freezing or heart rate and its impairment by the protein synthesis inhibitor cycloheximide (CHX) in male C57BL/6N mice. Heart rate was measured with an implanted transmitter. In the memory tests, mice were exposed to tone and context provided either as foreground or background stimulus during training. The fear responses developed differently from 0 to 24 hr after training under these 3 conditions. A single pretraining CHX injection impaired both memory forms, whereas a single posttraining CHX injection impaired tone- but not context-dependent memory, with the context provided as background stimulus. It was concluded that consolidation of tone-, foreground context-, and background context-dependent fear conditioning may be mediated by partly different neuronal or partly different biochemical pathways, or both. 相似文献
86.
Prof. Dr. B. Salzberger A. Schneidewind F. Hanses G. Birkenfeld M. Müller-Schilling 《Der Internist》2012,53(12):1445-1455
Infectious diseases remain one of the most important causes of fever of unexplained origin (FUO). We review the spectrum of infectious diseases in the different clinical situations of patients with FUO, namely in classical FUO, in patients with HIV infection, in health care-associated or nosocomial FUO, and in immunocompromised patients with FUO. The most important question is which clinical features make a specific disease a candidate to cause FUO. 相似文献
87.
88.
Hui-Young Lee Arijeet K. Gattu João-Paulo G. Camporez Shoichi Kanda Blas Guigni Mario Kahn Dongyan Zhang Thomas Galbo Andreas L. Birkenfeld Francois R. Jornayvaz Michael J. Jurczak Cheol Soo Choi Zhen Yan R. Sanders Williams Gerald I. Shulman Varman T. Samuel 《Diabetologia》2014,57(6):1232-1241
Aims/hypothesis
Aerobic exercise increases muscle glucose and improves insulin action through numerous pathways, including activation of Ca2+/calmodulin-dependent protein kinases (CAMKs) and peroxisome proliferator γ coactivator 1α (PGC-1α). While overexpression of PGC-1α increases muscle mitochondrial content and oxidative type I fibres, it does not improve insulin action. Activation of CAMK4 also increases the content of type I muscle fibres, PGC-1α level and mitochondrial content. However, it remains unknown whether CAMK4 activation improves insulin action on glucose metabolism in vivo.Methods
The effects of CAMK4 activation on skeletal muscle insulin action were quantified using transgenic mice with a truncated and constitutively active form of CAMK4 (CAMK4●) in skeletal muscle. Tissue-specific insulin sensitivity was assessed in vivo using a hyperinsulinaemic–euglycaemic clamp and isotopic measurements of glucose metabolism.Results
The rate of insulin-stimulated whole-body glucose uptake was increased by ~25% in CAMK4● mice. This was largely attributed to an increase of ~60% in insulin-stimulated glucose uptake in the quadriceps, the largest hindlimb muscle. These changes were associated with improvements in insulin signalling, as reflected by increased phosphorylation of Akt and its substrates and an increase in the level of GLUT4 protein. In addition, there were extramuscular effects: CAMK4● mice had improved hepatic and adipose insulin action. These pleiotropic effects were associated with increased levels of PGC-1α-related myokines in CAMK4● skeletal muscle.Conclusions/interpretation
Activation of CAMK4 enhances mitochondrial biogenesis in skeletal muscle while also coordinating improvements in whole-body insulin-mediated glucose. 相似文献89.
Performance characteristics and evaluation of an automated-developed and quantitative, immunochemical, fecal occult blood screening test 总被引:2,自引:0,他引:2
Vilkin A Rozen P Levi Z Waked A Maoz E Birkenfeld S Niv Y 《The American journal of gastroenterology》2005,100(11):2519-2525
OBJECTIVES: Guaiac fecal occult blood colorectal cancer (CRC) screening tests (FOBT) are faulted for low sensitivity and nonspecificity for human hemoglobin (Hb). Automated-developed, immunochemical, human Hb FOBT (I-FOBT) is specific, eliminates diet restrictions, and Hb quantification allows selection of a threshold for colonoscopy. Aims were to determine 1) test reproducibility; 2) test stability; 3) intrapatient daily I-FOBT variation; 4) test sensitivity and specificity for neoplasia in 500 symptomatic/high-risk patients undergoing colonoscopy; and 5) to correlate fecal Hb measurements with findings. METHODS: The desktop instrument OC-Sensor (Eiken, Japan) automatically develops and quantitates 50 tests/h for Hb. Patients prepared three tests, which were quantified and then 1) repeatedly re-examined; 2) stored at 4 degrees C or 20 degrees C or 28 degrees C and repeatedly examined; and 3) fecal Hb levels were correlated with colonoscopic findings. RESULTS: Five I-FOBTs re-examined five times in 1 day had no significant measurement changes. Thirty tests stored for 21 or more days had a decay/day of 0.3%+/- 0.4 at 4 degrees C (NS), 2.2%+/- 1.7 at 20 degrees C (NS), and 3.7%+/- 1.8 at 28 degrees C (p < 0.05). There were intrapatient variations between the three daily I-FOBTs (NS). At the recommended 100 ng Hb/mL threshold, all six cases of CRCs and 20 out of 28 cases of advanced adenomas were detected; evaluated together their sensitivity and specificity were 76.5% and 95.3%. CONCLUSIONS: Desktop, automated-developed, quantitative I-FOBT is now available. Refrigerated OC-Sensor samples are stable for 21 days, easy to prepare and develop and, at the 100 ng Hb/mL threshold, have high sensitivity, specificity, and negative predictive values for significant neoplasia. Suitability for population CRC screening awaits further evaluation. 相似文献