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1.
The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N. 相似文献
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Alysia M. Birkholz Amy R. Howell Mitchell Kronenberg 《The Journal of biological chemistry》2015,290(25):15365-15370
Glycosphingolipids are a subgroup of glycolipids that contain an amino alcohol sphingoid base linked to sugars. They are found in the membranes of cells ranging from bacteria to vertebrates. This group of lipids is known to stimulate the immune system through activation of a type of white blood cell known as natural killer T cell (NKT cell). Here we summarize the extensive research that has been done to identify the structures of natural glycolipids that stimulate NKT cells and to determine how these antigens are recognized. We also review studies designed to understand how glycolipid variants, both natural and synthetic, can alter the responses of NKT cells, leading to dramatic changes in the global immune response. 相似文献
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One antigen, one gold? A quantitative analysis of immunogold labeling of plasma membrane 5'-nucleotidase in frozen thin sections 总被引:3,自引:0,他引:3
K E Howell U Reuter-Carlson E Devaney J P Luzio S D Fuller 《European journal of cell biology》1987,44(2):318-327
We present an evaluation of the efficiency of immunogold labeling for a low abundance plasma membrane protein. Several independent methods were used to determine the density of 5'-nucleotidase on the plasma membrane of the Fao cell. These methods include morphometry in combination with either enzymology or cell surface radiometric assay. Immunocytochemistry of frozen thin sections with either single or double layers of antibody and visualized with protein A complexed with 5 nm colloidal gold was used to estimate the same density. The application of a balance sheet to immunogold labeling demonstrates that the labeling is never quantitative. For example, labeling of the cell surface is always greater than labeling on the section. We show that departures from the "one antigen, one gold" ideal are systematic, so that an efficiency can be calculated and quantitative results can be obtained. The ability to obtain reliable quantitative results from immunogold labeling extends the utility of this already powerful technique. 相似文献
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Effects of repetitive activity, ruthenium red, and elevated extracellular calcium on frog skeletal muscle: implications for t-tubule conduction 总被引:2,自引:0,他引:2
In this report we review evidence that indicates that experimental elevation of t-tubular calcium can lead to failure of action potential propagation within the t system and we present some new evidence suggesting that t-tubular calcium concentration may rise during repetitive activity. The evidence for t-tubular conduction failure consists of comparisons of the effects of high calcium and of ruthenium red on excitation and excitation-contraction coupling as well as morphological observations of wavy myofibrils in the axial core of fibers contracting tetanically in solutions containing elevated calcium concentrations. Evidence for elevation of t-tubular calcium concentration during repetitive activity comes from the following. During twitches, the early, large birefringence signal and force development are delayed in onset if the extracellular calcium and (or) potassium concentrations are above normal or if the fiber has been stimulated tetanically just prior to the test twitch. The delays that occur in twitches following tetanic contractions are attenuated when the extracellular and, therefore, the t-tubular calcium concentration is buffered with citrate. 相似文献
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