Inhibition of DNA synthesis and oncogene expression in tumor cells by the biological factor DIF.

A regulatory factor isolated from the maternal part of bovine placentas (decidua inhibitory factor, DIF) inhibits the incorporation of thymidine into the DNA of a variety of animal and human tumors. The degree of inhibition is dependent on the concentration of the factor. Results indicate that signal transduction occurs via a Ca2+ mobilizing pathway after specific binding of the inhibitor to tumor cell surface receptors.

Inhibition of tumor cell proliferation by a novel growth regulator from placenta: modulation of membrane phosphorylation and oncogene expression.

The tumor specific inhibition of thymidine uptake by a negative growth regulator isolated from the maternal part of the bovine placenta is in concert with an inhibited expression of ras oncogenes. The results indicate that primary processing is blocked in case of Ha-ras, while a lower transcription rate or a stimulated degradation of mRNA is more likely for N-ras. These reactions are preceded by a specific binding of the inhibitor to tumor cell surface membranes.

Tumor-specific inhibition of DNA synthesis and cell proliferation by a factor from bovine placenta--possible mechanism.

A polypeptide isolated from the maternal part of bovine placentas inhibits significantly the incorporation of thymidine into the DNA of tumor cells. When normal cells are used, this effect is found only to a very limited degree. Surface membrane components have been identified which are enriched on tumor cells and which are responsible for a better binding of the inhibitor to tumor cells than to normal cells.

The evaluation of an average nucleotide composition from melting curves.

A new formula has been derived for the calculation of the average G + C content - X of DNAs from different origins using thermal melting data. As compared to existing formulas the new method gives highly accurate results, although being much easier to use than similar equations.