Actin desmin and

The immunohistochemical profile of RMS includes the myogenic transcriptional regulatory proteins myogenin and Myo-Dl, as well as muscle-specific actin, desmin, and myoglobin. 

The leucine zipper DNA-binding proteins, described in Chapter 10, are examples of globular proteins that use coiled coils to form both homo- and heterodimers. A variety of fibrous proteins also have heptad repeats in their sequences and use coiled coils to form oligomers, mainly dimers and trimers. Among these are myosin, fibrinogen, actin cross-linking proteins such as spectrin and dystrophin as well as the intermediate filament proteins keratin, vimentin, desmin, and neurofilament proteins. 

Accurate flow cytometric measurements depend on clear discrimination between intact cells and cellular debris. Both cytoplasmic (bcl-2, CD68, lipocortin-1, a-smooth muscle actin, and desmin) and nuclear antigens (p53, PCNA, Ki-67) have been simultaneously detected with this combined protocol (Lan et al., 1996 Millard et al., 1998). 

Intermediate filaments (10 nm) are intermediate in diameter between microtubules (25 nm) and actin filaments (7 nm). Intermediate filaments are classified into five groups cytokeratin, desmin, vimentin, neural, and glial filaments (for review, see Lazarides, 1980). In skeletal muscle, there are both desmin and vimentin filaments. 

In vitro, o -actinin and filamin bind actin, the major protein of thin filaments. One a-actinin molecule binds to two actin filaments, one from each side of the Z-disk. Four a-actinin molecules bind to each actin filament at 90° angles, so that the actin filaments are bound into the Z-disks in a square array, although in most of the length of the sarcomere their arrangement is hexagonal. Desmin, an intermediate filament protein, forms a network from one Z-disk to the next across the myofibril. Such links, aided by attachment of desmin and dystrophin to the sarcolemma, help hold the sarcomere structure in... 

MYG) is probably the most frequently detected in E-RMS. Nuclear labeling for myogenin is stronger than that seen with anti-Myo-Dl. i In our experience, the sensitivity of MYG is comparable to that of desmin and muscle-associated actins with respect to rhabdomyosarcomas. ES/PNET typically lacks any MYG reactivity" ... 

Rangdaeng S, Truong LD. Comparative immunohistochemical staining for desmin and muscle specific actin A study of 576 cases. Am J Clin Pathol. 1991 96 32-45. 

Sarcomatoid melanomas are consistently SIOOP positive, but only 3% to 10% can be labeled for other, more specific melanocytic determinants (Fig. 7.16). °420,121,123,192 Because a proportion of such lesions becomes transmogrified into spindle-cell proliferations with divergent phenotypes, immunoreactivity for CD56, CD57, nerve growth factor receptor, desmin, and actin isoforms is potentially observed in them (Figs. 

Moran and colleagues have reported the existence of primary mediastinal leiomyosarcomas, which may be observed in either the anterior or posterior compartments. These spindle-cell malignancies are uniformly immunoreactive for desmin (Fig. 11.35), muscle-specific actin, alpha-isoform actin, caldesmon, and calponin vimentin also may be present. Conversely, EMA, keratin, Myo-Dl, myoglobin, myogenin, and... 

All squamous carcinomas of the skin lack S-100 protein, chromogranin, synaptophysin, CD99, CD 15, and CD57. Further, reactivity with HMB-45 or anti-melan-A is consistently absent, as are desmin and muscle-specific isoforms of actin in most spindle-cell forms of these neoplasms. ... 

Leiomyoma of the muscularis mucosae is the most common mucosal-based mesenchymal lesion of the GI tract that may present as a polypoid mass." ° " ° These tumors often arise in the colon leiomyomas are also likely to occur within the wall of the esophagus.Unlike many of the previously mentioned lesions, this tumor displaces the colonic crypts and does not grow between crypts. As with leiomyomas elsewhere, these lesions stain strongly with smooth muscle actin and desmin and are negative for c-kit. 

The ovarian-like stroma cells also label with antibodies to smooth muscle actin, muscle-specific actin, desmin, h-caldesmon, and also variably for alpha-inhibin and calretinin. 

Ogawa K, Suzuki J, Mukai H, Mori M. Sequential changes of exttacellulat mattix and proliferation of Ito cells with enhanced exptession of desmin and actin in focal hepatic injury. Am J Pathol. 1986 125 611-619. 

Embryonal primitive spindled, stellate, round, and polygonal cells in variably myxoid background. Variable rhabdomyoblasts, strap cells, multinucleated cells, and myotube forms. Embryonal myogenin, Myo-DI, muscle-specific actin, desmin. Loss of heterozygosity at 11 pi 5.5 and other nonspecific abnormalities. 

The muscle actins (MSA and SMSA), desmin, and h-caldesmon are useful in identifying smooth muscle cells. Normal endometrial stromal cells express vimen-tin and muscle actins, but they generally lack expression... 

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