The cardiac isoform of α-actin in regenerating and atrophic skeletal muscle, myopathies and rhabdomyomatous tumors: an immunohistochemical study using monoclonal antibodies

Abstract

The cardiac isoform of α-actin in regenerating and atrophic skeletal muscle, myopathies and rhabdomyomatous tumors: an immunohistochemical study using monoclonal antibodies Abstract The two sarcomeric isoforms of actins, cardiac and skeletal muscle α-actin, are highly homologous so that their immunohistochemical distinction is extremely difficult. Taking advantage of monoclonal antibodies distinguishing the two conservative amino acid exchanges near the aminoterminus, we have performed an extended immunohistochemical analysis of the cardiac α-actin (CAA) isoform in normal, regenerating, diseased and neoplastic human muscle tissues. Intense and uniform CAA staining is seen in fetal and adult myocardium and in fetal skeletal muscle while adult skeletal muscle is essentially negative, except for muscle spindle myocytes and a few scattered muscle fibres with overall reduced diameter. By contrast, CAA synthesis is markedly induced in regenerating skeletal muscle cells, in Duchenne muscular dystrophy and upon degenerative atrophy. CAA has also been detected in certain vascular and visceral smooth muscle cells. Among tumors, CAA has consistently been seen in rhabdomyosarcomas and rhabdomyomatous cells of nephroblastomas, whereas, smooth muscle tumors have shown only occasional staining. While the synthesis of this actin isoform is less restricted than previously thought, monoclonal antibodies against CAA provide a welldefined, reliable and sensitive diagnostic tool for the definition and detection of aberrant differentiation in diseased skeletal muscle and of striated muscle differentiation in rhabdomyosarcomas.

Aging alters gene expression of growth and remodeling factors in human skeletal muscle both at rest and in response to acute resistance exercise

“…However, the increase in ACTC1 after exercise in the elderly did not reach significance. These results are consistent with work showing induction of ACTC1 expression during muscle regeneration after trauma or during pathology and appears characteristic of activated satellite cells and regenerating myofibers (42). In fact, muscle regeneration has been hypothesized to recapitulate aspects of fetal skeletal muscle development where ACTC1 is highly expressed but is soon largely replaced by ACTA1 (33).…”

Processus and recessus adhaerentes: giant adherens cell junction systems connect and attract human mesenchymal stem cells

“…In general, at this time of culturing, the MSCs Moll et al 2006); these are not only dominant in the central cytoplasm (a) but also extend into the long thin cell processes (b); the processes shown here exceed 100 μm in length. Cell nuclei are stained with 4,6-diamidino-2-phenylindole (DAPI; arrowheads).…”

Endothelial and virgultar cell formations in the mammalian lymph node sinus: endothelial differentiation morphotypes characterized by a special kind of junction (complexus adhaerens)

“…Primary antibodies used, their sources, and methodological details, including antigen retrieval procedures for paraffin sections, are listed in Supplementary Table 1 (see also Schmelz and Franke 1993;Schmelz et al 1994;Borrmann et al 2006;Hämmerling et al 2006;Moll et al 2006;Wuchter et al 2007). Micrographs of serial sections were analyzed by using tomo-and topographical protocols (Schmelz and Franke 1993).…”