Muscle Cell Markers Research Articles

Ultraviolet irradiation during ooplasmic segregation prevents gastrulation, sensory cell induction, and axis formation in the ascidian embryo

The effect of ultraviolet (uv) light on embryonic development was examined in the ascidian Styela clava. uv irradiation (3.0 × 10 −3 J mm −2) of the entire surface of fertilized eggs during ooplasmic segregation prevented gastrulation, sensory cell induction, and embryonic axis formation. The uv-irradiated embryos completed ooplasmic segregation and cleaved normally, but vegetal blastomeres did not invaginate at the beginning of gastrulation, sensory cells in the larval brain did not develop tyrosinase or melanin pigment, and the larval tail did not develop. Endoderm, epidermis, and muscle cells differentiated in the uv-irradiated embryos, however, as evidenced by expression of endodermal alkaline phosphatase (AP), an epidermal-specific antigen, and α-actin, myosin heavy chain, and acetylcholinesterase (AChE) in muscle cells. Higher doses of uv light (6.0–9.0 × 10 −3 J mm −2) suppressed expression of the epidermal antigen and muscle cell markers, whereas the development of endodermal AP was insensitive. Irradiation at various times between fertilization and the 16-cell stage revealed that gastrulation, sensory cell differentiation, and axis formation are sensitive to uv light only during ooplasmic segregation. Irradiation of restricted regions of the zygote during ooplasmic segregation showed that the uv-sensitive components are localized in the vegetal hemisphere. The absorption characteristics of the uv-sensitive components suggest that they are nucleic acids. The results show that uv-sensitive components that specify gastrulation, sensory cell induction, and embryonic axis formation are localized in the vegetal hemisphere of Styela eggs.

Immunohistochemical Spectrum of Rhabdomyosarcoma and Rhabdomyosarcoma-like Tumors

Twenty-five rhabdomyosarcomas (RMSs), including 12 alveolar and 13 embryonal types, were immunohistochemically studied for the presence of different classes of intermediate filament proteins and muscle actins (MAs). For the most part, formaldehyde-fixed and paraffin-embedded tissue was used in immunostaining. All RMSs showed desmin and MAs, usually in a major portion of tumor cells. The number of MA-positive cells was sometimes higher than that of desmin-positive cells. Vimentin was present in all tumors studied in frozen sections. Eight of 12 alveolar RMSs showed small number of cytokeratin-positive neoplastic cells. Cytokeratin-positive cells were present less commonly in embryonal RMS (3/13 cases). The 68-kD neurofilament protein was found in frozen sections of two embryonal RMSs. The cytokeratin and neurofilament immunostaining could be reproduced by immunofluorescence technique. In addition, we studied three childhood sarcomas, which showed abundant desmin and MA immunostaining but did not conform to the ultrastructural criteria of RMS. Scattered cytokeratin-positive cells were found in two of these tumors, and neurofilaments were found in the two cases for which frozen sections were available. The results show that typical RMS may demonstrate immunohistological pleomorphism with cytokeratin and neurofilament immunoreactivity suggesting the presence of multidirectional differentiation. In addition, there are tumors that by morphology look like RMS and have muscle cell markers but cannot be verified as RMS by electron microscopy; also, these tumors seem to show immunohistological pleomorphism. The presence of nonmyoid markers in RMS should be considered when making immunohistological diagnosis of soft tissue sarcomas.