Abstract
Rat ascites hepatoma AH109A cells (present as a free form in vivo) can aggregate and then develop well-defined tripartite junctional complexes, including intermediate junctions, desmosomes and focal tight junctions, on incubation with a glycoprotein separated from rat ascites hepatoma AH136B cells (forming cell islnds in vivo). The development of binding structures was strongly inhibited by actinomycin D. AH109A cells or rat ascites hepatoma YS cells (present as a free form in vivo) previously treated with the glycoprotein for 24 h, when inoculated i.p., proliferated as free cells in the ascitic fluid, like the untreated cells. AH109A cells actively proliferating in the skin do not form any junctional complexes. The reason for the failure of island formation by AH109A cells or YS cells in vivo is discussed.
Highlights
Summary.-Rat ascites hepatoma AH109A cells can aggregate and develop well-defined tripartite junctional complexes, including intermediate junctions, desmosomes and focal tight junctions, on incubation with a glycoprotein separated from rat ascites hepatoma AH136B cells
On the basis of preliminary observations indicating that the amount of aggregation-promoting factor (APF) separated from AH109A cells is apparently smaller than that of APF from AH136B cells (Kudo, Hanaoka and Hayashi, 1972), it was of interest to investigate the reason why most of AH109A cells are present in a free form in vivo
The results presented here demonstrate that APF induces a strong cell aggregation and a distinct cell adhesiveness, characterized by development of well-defined binding structures in the adherent cells, when AH109A cells in a aggregating substance in culture (Hausman free form were treated with APF for only and Moscona, 1973)
Summary
Summary.-Rat ascites hepatoma AH109A cells (present as a free form in vivo) can aggregate and develop well-defined tripartite junctional complexes, including intermediate junctions, desmosomes and focal tight junctions, on incubation with a glycoprotein separated from rat ascites hepatoma AH136B cells (forming cell islands in vivo). As PREVIOUSLY DESCRIBED (Kudo et al, 1974), a thermostable glycoprotein, capable of inducing tumour cell aggregation, has been separated from rat ascites hepatoma AH 1 36B cells forming cell islands in vivo, and partially purified by chromatography. This aggregation-promoting factor (APF) was non-cytotoxic and clearly effective for aggregation of dissociated AH136B cells as well as SV40 transformed cells, but not for normal rat liver cells and red blood cells. It has further been shown that the APF can cause both aggregation of rat ascites hepatoma AH109A cells present in a free form in vivo and adhesiveness of the cells, characterized by gradual development of known binding structures, including intermediate junctions, desmosomes and focal tight junctions (Ishimaru, Ishihara and Hayashi, 1975). The purpose of the present communication is to describe the electron microscopic evidence that AH109A cells only develop the binding structures when the APF is applied to the cells in a sufficient amount
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