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J H Calhoun F Li B R Ledbetter C A Gill 《Clinical orthopaedics and related research》1992,(280):15-22
Compression, distraction, and torsion stiffness of the Ilizarov external fixator was measured in two fracture models in autopsy specimens of tibia and fibula. A transverse model was tested in six frame constructions with the osteotomy site preloaded in four different positions. An oblique model was tested in four frame constructions also with four preloaded positions. Stiffness was more dependent on bone preload than wire number, wire type, or frame design. High stiffness was achieved by bone preloading, by compressing the rings together, by increasing the number of wires, and by using olive wires. The stiffness can be decreased (dynamization) by separating the rings and by removing wires. This data is helpful for frame design of the Ilizarov fixator. 相似文献
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K H Calhoun B R Peters C M Stiernberg F B Quinn 《Otolaryngology--head and neck surgery》1988,99(1):76-78
We report a metallic foreign body that entered through the anterior table of the frontal sinus, and rolled down to lodge in the nasofrontal duct. An electromagnet was used to remove the foreign body through a trephination. 相似文献
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The synthesis and localization of alternatively spliced fibronectin EIIIB in resting and thrombin-treated megakaryocytes 总被引:1,自引:1,他引:0
There are several species of alternatively spliced fibronectin (FN). One of these, FN EIIIB, is primarily present in embryonic and in proliferating and migrating cells and is believed to be important for cell maturation. We have studied the synthesis, localization, and secretion of this FN isoform in isolated guinea pig megakaryocytes, nonmegakaryocytic bone marrow cells, and platelets. There was 7.5 times more general FN in megakaryocytes than in nonmegakaryocytic cells based on the analysis of equivalent amounts of protein. FN EIIIB was detected by Western blotting in megakaryocytes but not in nonmegakaryocytic cells present in bone marrow. Neither megakaryocytes nor platelets secreted FN EIIIB, while megakaryocytes secreted 25.3% +/- 4.6% general FN and platelets secreted about 61% general FN in response to thrombin. Analysis of immunostained cells by confocal microscopy revealed that FN EIIIB had been redistributed to the surface of megakaryocytes in response to thrombin. Synthesis was studied by metabolic labeling, and megakaryocytes were shown to synthesize FN and FN EIIIB. Thus, megakaryocytes and platelets are among a small number of adult cells and tissues that synthesize and contain FN EIIIB. The expression of FN EIIIB on the megakaryocyte surface may influence migration and maturation. 相似文献
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Calhoun ME Kurth D Phinney AL Long JM Hengemihle J Mouton PR Ingram DK Jucker M 《Neurobiology of aging》1998,19(6):1881-606
A loss of hippocampal neurons and synapses had been considered a hallmark of normal aging and, furthermore, to be a substrate of age-related learning and memory deficits. Recent stereological studies in humans have shown that only a relatively minor neuron loss occurs with aging and that this loss is restricted to specific brain regions, including hippocampal subregions. Here, we investigate these age-related changes in C57BL/6J mice, one of the most commonly used laboratory mouse strains. Twenty-five mice (groups at 2, 14, and 28–31 months of age) were assessed for Morris water-maze performance, and modern stereological techniques were used to estimate total neuron and synaptophysin-positive bouton number in hippocampal subregions at the light microscopic level. Results revealed that performance in the water maze was largely maintained with aging. No age-related decline was observed in number of dentate gyrus granule cells or CA1 pyramidal cells. In addition, no age-related change in number of synaptophysin-positive boutons was observed in the molecular layer of the dentate gyrus or CA1 region of hippocampus. We observed a significant correlation between dentate gyrus synaptophysin-positive bouton number and water-maze performance. These results demonstrate that C57BL/6J mice do not exhibit major age-related deficits in spatial learning or hippocampal structure, providing a baseline for further study of mouse brain aging. 相似文献