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Adrihan H. Janbaz, Mona Lindström, Lena Carlsson, Fatima Pedrosa-Domellöf; Differences in Intermediate Filament Composition Among Human Extraocular Muscle Fibers. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2074.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate differences in the distribution of intermediate filament [IF] proteins in human extraocular muscle [EOM] fibers
Three superior rectus samples obtained from 2 donors were serially cross-sectioned and processed for immunocytochemistry, using double-labeling of 5 µm and 1 µm thick sections with specific antibodies [Ab] against a battery of cytoskeletal proteins, different myosin heavy chain [MyHC] isoforms and a basement membrane marker (laminin). Neuromuscular junctions [NMJs] were detected with alpha-bungarotoxin
Desmin was present in the vast majority of muscle fibers. The staining intensity was generally higher in the orbilat layer [OL]. Muscle fibers that contained MyHC slow tonic and/or MyHC slow in both OL and global layer [GL] lacked staining for desmin, detected with monoclonal Ab D33. At high magnification in 1 µm sections, the fine structure of the cytoskeleton was well preserved and readily apparent with Ab against alpha-actinin, whereas desmin staining was absent or very weak in such muscle fibers. Additional small groups of muscle fibers lacked staining with D33 and another desmin monoclonal Ab in limited portions of their cross-sections, whereas staining with the polyclonal Ab was present. The basement membrane of these fibers was intact, but there was interruption in the staining with dystrophin. No NMJs were present in such fiber portions. Desmin staining was stronger underneath NMJs, data on myotendinous junctions is under evaluation.Vimentin staining was not detected in the muscle fibers
Desmin is a ubiquitous muscle cytoskeletal protein, thus far not reported to occur in different isoforms. Lack of desmin has been associated with higher susceptibility for muscle fiber damage. The present data may indicate that a subset of muscle fibers in the human EOMs has a cytoskeletal organisation that precludes the detection of some desmin epitopes, or may contain a new isoform. Additional experiments are under way
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