Ursula Heine

The behavior of HeLa-S3 cells under the influence of supranormal temperatures

HeLa cells exposed to environmental temperatures higher than the usual 37°C undergo marked morphological and biochemical changes which are reversible after return to normal temperatures. Exposures to 41°C had little effect, but at 42 to 43°C changes were evident by 30 minutes and pronounced at 1–2 hours. At 44–45°C degenerative changes and cell death were frequent. At 42–43°C cell response was characterized by partial loss of the granular component of the nucleolus with retention of its fibrils. Synthesis of the 45 S ribosome precursor RNA was partially inhibited at 43°C as was the conversion to ribosome RNA of precursor molecules formed at 37° and then metabolized at 43°. The number of perichromatin granules was markedly increased in the nuclei of heated cells and threadlike structures of the approximate diameter and density of the peri-chromatin granules appeared. Mitochondria and Golgi apparatus remained essentially unchanged morphologically but the polysome arrangement of the ribosomes was completely lost and they were distributed as monosomes after heating. Cell recovery from exposure to 2 hours at 43°C was complete within 24 hours, the only alteration remaining being an increase in the number of lysosomes.

Rapid membrane changes in mouse epithelial cells after exposure to epidermal growth factor

Cells of the recently established epithelial mouse embryo cell line, MMC-E, possess abundant surface receptors for the polypeptide hormone, epidermal growth factor (EGF). The influence of EGF on these cells and on the human epidermoid carcinoma line, A431, was compared by scanning electron microscopy (SEM) and light microscopy. Within seconds after the addition of medium containing 100 ng/ml EGF, the MMC-E cells uniformly develop marginal surface ruffles in association with macropinocytosis, and these activities subside within 1 hr. The addition of fresh prewarmed medium lacking EGF elicits no discernible change in MMC-E cell morphology over this period. In contrast, cells of the human epidermoid carcinoma line, A431, respond less uniformly and the addition of fresh prewarmed medium lacking EGF elicits similar changes in these cells. Thus, the stable nontransformed MMC-E mouse epithelial cell line may prove an especially promising model for studies of the action of polypeptide growth factors on epithelial cell biology.

Epidermal growth factor-induced alterations in proliferating mouse epithelial cells

Abstract The effects of epidermal growth factor (EGF) on the growth and morphology of mouse embryo epithelial cells (MMC-E) were studied in culture. Growing cultures of epithelial cells were incubated in the media containing EGF or certain other mitogenic peptides. It was found that nanogram (ng) quantities of EGF stimulated growth in these cells and caused reversible phenotypic changes in these cells. These changes were not observed in cultures treated with the other mitogens. The compact growing islands of MMC-E cells were surrounded by elongated border cells [12]. EGF induced the elongated border cells to flatten and spread. The change of the elongated border cells into polygonal, flattened cells was dependent on the dose of EGF. After treatment with higher concentrations of EGF all cells appeared more flattened and their cytoplasm was more granular than that of the controls. Scanning electron microscopic studies (SEM) showed that the elongated border cells in the control cultures were distinctly higher than the cells inside the islands, while after exposure to EGF they flattened and had fewer surface microvilli than control cells. When EGF was removed and the cells were further cultivated in media without EGF, the border cells became smaller and elongated, eventually resembling those in the control cultures. These results show that EGF may act as a regulatory factor in the control of the proliferation and differentiation of mouse epithelial cells.

Aberrant cytoplasmic structures in avian virus tumor cells

Abstract Cells of avian virus-induced tumors occasionally show cytoplasmic masses containing structures of characteristic morphology. These consist of essentially spherical bodies of a 30–40 mμ diameter consisting of an electron-dense material enclosed in a shell of higher density surrounded by an indefinite outer zone with associated ribosome-like electron-dense bodies. The spherical bodies resemble somewhat the immature avian virus particles budding at the cell surface. Structures of this appearance are unique to avian virus tumors and occur in different neoplastic cell types in growths induced by a wide variety of avian tumor virus strains. The structures were interpreted to be the result of abortive processes of cytoplasmic virus synthesis in the absence of components and conditions for elaboration of the complete virus particle. No evidence indicated that the spheres developed into typical virus particles or were a stage in or contributed to the usual processes of virus assembly by budding at the cell membrane. There was the appearance, however, of possible involvement of cytoplasmic ribosome-like bodies in virus-budding from chondrocytes in which budding was impeded by cartilage components elaborated at the cell surface.