Betty Altenburg

Modification of the phenotype of murine sarcoma virus-transformed cells by sodium butyrate: Effects on morphology and cytoskeletal elements☆

Abstract The effects of sodium butyrate on cellular morphology and the distribution of cytoskeletal elements were examined using a line of normal rat kidney cells transformed by and producing murine sarcoma and leukemia viruses [NRK (MSV-MLV)]. Untreated cells were predominantly round or fusiform in shape and contained few microfilaments and microtubules. Culturing these cells in medium containing 2 mM sodium butyrate induced the formation of long cytoplasmic processes within 12–24 h followed by a progressive flattening of the cells which was apparent in most cells by 72 h. Reversal of these changes in NRK (MSV-MLV) cells grown for several passages in butyrate medium required at least ten cell divisions. The morphological alterations induced by butyrate were accompanied by a striking elaboration of cytoplasmic microfilaments and microtubules as shown by indirect immunofluorescence and by electron microscopy. Butyrate also enhanced the formation of substrate adhesion plaques and intercellular gap junctions, but not adherens junctions. These results suggest that growth of NRK (MSV-MLV) cells in the presence of butyrate induced specific cellular alterations which counteract some of the effects of transformation of NRK cells by MSV.

Ultrastructural Study of Rotavirus Replication in Cultured Cells

A systematic ultrastructural analysis of the replication cycle of the simian rotavirus SA11 in permissive MA104 cells was performed under reproducible conditions. At 8 h p.i., small areas of viroplasm were seen adjacent to swollen vesicles of the rough endoplasmic reticulum (rer) containing a few 80 to 90 nm virus particles. At later times, the size and number of these inclusions increased and the rer contained large numbers of the 80 to 90 nm particles as well as 52 to 65 nm particles. Infected cells eventually lysed, releasing progeny virus. Other cytological alterations included virus particles sequestered in lysosome-like bodies, 15 to 20 nm tubular structures in the nucleus and/or cytoplasm, convoluted membranes within the rer, filament bundles associated with virus particles, and mitochondria containing 1 to 5 virus particles. In addition, SA11 replication was studied in several less permissive cell lines. The results were similar to those with MA104 cells except that a smaller percentage of the cells were productively infected.

Cytochalasin B-induced multinucleation of murine sarcoma virus-transformed cells. Inhibition by sodium butyrate.

Abstract Normal rat kidney (NRK) cells underwent only one nuclear division in the presence of 1–3 μg/ml cytochalasin B (CB), an inhibitor of cytoplasmic cleavage. In contrast, NRK cells transformed by murine sarcoma virus (MSV-NRK cells) became multinucleated when treated with CB. Sodium butyrate (2 mM), which induces striking morphological changes in MSV-NRK cells, prevents CB-induced multinucleation in these cells. Dibutyryl cyclic adenosine monophosphate (db-cAMP) also restores limited nuclear division to CB-treated MSV-NRK cells, but 8-bromo-cAMP does not. CB was found to selectively inhibit DNA synthesis in MSV-NRK cells grown in medium supplemented with 2 mM butyrate, but not in control MSV-NRK cells. This inhibition of DNA synthesis could account for the limitation of nuclear division by sodium butyrate.

Transformation of Baboon Cells with Feline Sarcoma Virus

Testes cells from two baboons have been transformed by the Snyder-Theilen (ST) and Gardner-Arnstein (GA) strains of feline sarcoma virus (FeSV). The resulting cell cultures formed tumors in immunosuppressed mice, but not in the autologous baboons. The cells transformed by GA FeSV contained more feline gs antigen than those transformed by ST FeSV. Conversely, the cells transformed by ST FeSV produced more type-C virus. Unlike FeSV, which has a predilection for feline cells, the virus from baboon cells transformed by ST FeSV replicated in baboon and beagle embryo cells, but not in feline embryo cells, suggesting that this virus is different from FeSV.