Date of Award
Doctor of Philosophy
Richard M. Robson
The major purposes of this study were to: (1) clearly identify intermediate filaments (IFs) and elucidate their structural arrangement at the myofibrillar Z-lines in non-diseased, mature mammalian striated muscle cells, and (2) determine the localization of constituent proteins of the IFs by immunogold localization. IFs running transversely to the long axis of the cell and connecting Z-lines of adjacent myofibrils were identified by high resolution transmission electron microscopy (TEM) of plastic-embedded porcine semitendinosus muscle, especially in areas of cells where myofibrils were less tightly packed. When the plane of section included the periphery of myofibrils at their Z-lines, examination indicated that IFs surround, rather than significantly penetrate, myofibrils. IFs also were identified that connect myofibrils (especially at their Z-lines) to nuclei, mitochondria, and the sarcolemma;In order to examine the three-dimensional structural relationship of IFs and myofibrils, micrographs were taken after tilting the specimen to obtain stereo pairs. The results suggest that IFs primarily surround myofibrils at their Z-lines and that a few IFs are arranged in a longitudinal fashion along the periphery of the myofibrils;Results from TEM-immunogold labeling studies indicate that desmin is located primarily at the periphery of Z-lines and nearby I-band regions in both cardiac and skeletal muscle. A lower level of desmin labeling was observed along the periphery of the long axis of the myofibrils, which suggested the presence of some longitudinal IFs. The immunogold labeling pattern observed with anti-synemin was very similar to that obtained with anti-desmin. However, the intensity of the synemin labeling was generally lower than that observed with anti-desmin. Intense labeling with anti-desmin was observed in some areas near the sarcolemma and nuclei in samples examined after pre-embedding labeling. The linear pattern of the labeling suggests that IFs attach myofibrils to those membranous structures;These results support a cytoskeletal concept that IFs link adjacent myofibrils together at their Z-lines, and myofibrils to membranous structures. The IFs are attached to myofibrils primarily in a lateral rather than end-on fashion. The IFs identified by TEM contain desmin. Synemin is either part of, or attached to, desmin IFs.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Masako Maria Bilak
Bilak, Masako Maria, "Identification of intermediate filaments and their proteins in mature mammalian striated muscle " (1991). Retrospective Theses and Dissertations. 9604.