The glenohumeral joint is the most frequently dislocated major joint in the body, and instability due to permanent deformation of the glenohumeral capsule is a common pathology. The corresponding change in mechanical properties may have implications for the ideal location and extent of plication, which is a common clinical procedure used to repair the capsule. Therefore, the objective of this study was to quantify the mechanical properties of four regions of the glenohumeral capsule after anterior dislocation and compare the properties to the normal glenohumeral capsule. Six fresh-frozen cadaveric shoulders were dislocated in the anterior direction with the joint in the apprehension position using a robotic testing system. After dislocation, mechanical testing was performed on the injured glenohumeral capsule by loading the tissue samples in tension and shear. An inverse finite element optimization routine was used to simulate the experiments and obtain material coefficients for each tissue sample. Cauchy stress–stretch curves were then generated to represent the mechanical response of each tissue sample to theoretical loading conditions. Based on several comparisons (average of the material coefficients, average stress–stretch curve for each region, and coefficients representing the average curves) between the normal and injured tissue samples, the mechanical properties of the injured tissue samples from multiple regions were found to be lower than those of the normal tissue in tension but not in shear. This finding indicates that anterior dislocation primarily affects the tensile behavior of the glenohumeral capsule rather than the shear behavior, and this phenomenon could be caused by plastic deformation of the matrix, permanent collagen fiber rotation, and/or collagen fiber failure. These results suggest that plication and suturing may not be sufficient to return stability to the shoulder after dislocation in all individuals. Thus, surgeons may need to perform a procedure that reinforces or stiffens the tissue itself, such as reconstruction or augmentation, to improve repair procedures. 相似文献
Cultures were cloned from a sample containing Microcystis aeruginosa, M. flos-aquae and a few morphological intermediates. The M. aeruginosa cultures remained distinct from the M. flos-aquae cultures in (a) cell size, (b) cell aggregation pattern, (c) width of the mucilage surrounding the multicellular colonies, (d) sharpness of the mucilage boundary, (e) efect of 0.1–1.0 μM calcium chloride on the disaggregation of multicellular colonies, (f) frequency of mucilage mutants and (g) colony morphology on agar media. No M. flos-aquae culture produced morphs resembling M. aeruginosa, inconsistent with proposals that M. flos-aquae is a developmental stage or environmentally-induced variant of M. aeruginosa. After longterm cultivation, but not soon after origanal isolation, several M. aeruginosa cultures contained mutants with diminished mucilage production and an altered colony shape. 相似文献
The feeding apparatus of the marine nematode Rhabdodemania minima Chitwood, 1936 has been examined with light and transmission electron microscopy. The buccal capsule consists of a posterior region with smooth walls bearing three sets of three minute denticles at its posterior end and three large onchia in its mid region; a middle region with grooved walls; and an anterior region with costae and six odontia. The anterior and middle portions of the buccal capsule are enveloped by the cephalic cuticle, whereas the posterior region, which is set off from the middle region by a buccal seam, is partially enveloped by the anterior end of the esophagus. Two subventral esophageal glands open into the lumen of the esophagus. Secretions of each of three paraesophageal glands are conveyed through a duct in each of the three corresponding corners of the buccal wall to an opening between labia. A pair of wing-like thickenings, termed pterons, embraces the duct of each paraesophageal gland in the posterior and middle regions of the buccal capsule. A model of how the buccal capsule operates is proposed and tested. Morphological and functional aspects of the buccal apparatus and cephalic cuticle are compared with those of other taxa of the Enoplida, and their phylogenetic implications are discussed. 相似文献
The extracellular polysaccharides elaborated by most or all bacterial species function in cell-to-cell and cell-substratum adhesion, cell signaling, and avoidance or inhibition of noxious agents in animal hosts or free-living environments. Recent advances in our understanding of exopolysaccharide synthesis have been facilitated by comparative approaches in both plant and animal pathogens, as well as in microorganisms of industrial importance. One of the best understood of these systems is thekps locus for polysialic acid synthesis inEscherichia coli K1. The genes for sialic acid synthesis, activation, polymerization and translocation have been identified and assigned at least tentative functions in the synthetic and export pathways. Initial studies ofkps thermoregulation suggest that genetic control mechanisms will be involved which are distinct from those already described for several other exopolysaccharides. Information about the common as well as unique features of polysialic acid biosynthesis will increase our knowledge of microbial cell surfaces which in turn may suggest novel targets for therapeutic or industrial interventions. 相似文献
The relationship between Corynebacterium rathayi and the infective second stage ‘dauer” larva (DL2) of Anguina agrostis has been studied with particular regard to the nature and extent of bacterial adhesion to the nematode. Viability of the 1-year-old DL2 was high, the number of dead specimens per gall only ranging from 5.1% to 8.3%. The DL2 were exposed to C. rathayi either from cultures or galls and the numbers with and without adhering bacteria were counted. A total of 22,917 DL2 from 15 galls were examined, the mean number of DL2 per gall being 1,528. The mean percentage per gall of DL2 with bacteria adhering was 42%. However there was much variability (from 0 to 98%). The significance of galls with DL2 that did not succumb to bacterial adhesion is discussed. The sequence of events associated with the process of bacterial adhesion to the nematode cuticle was examined with the aid of the electron microscope. The process involves fusion of the glycocalyx with the bacterial capsule followed by thickening and, at times, displacement of the epicuticle together with changes in the main body of the cuticle. The possible nature of the process of adhesion is discussed. 相似文献
Liver surface is covered by a collagenous layer called the Glisson's capsule. The structure of the Glisson's capsule is barely seen in the biopsy samples for histology assessment, thus the changes of the collagen network from the Glisson's capsule during the liver disease progression are not well studied. In this report, we investigated whether non‐linear optical imaging of the Glisson's capsule at liver surface would yield sufficient information to allow quantitative staging of liver fibrosis. In contrast to conventional tissue sections whereby tissues are cut perpendicular to the liver surface and interior information from the liver biopsy samples were used, we have established a capsule index based on significant parameters extracted from the second harmonic generation (SHG) microscopy images of capsule collagen from anterior surface of rat livers. Thioacetamide (TAA) induced liver fibrosis animal models was used in this study. The capsule index is capable of differentiating different fibrosis stages, with area under receiver operating characteristics curve (AUC) up to 0.91, making it possible to quantitatively stage liver fibrosis via liver surface imaging potentially with endomicroscopy.