A vegetalizing inducing factor. Isolation and chemical properties.

A vegetalizing factor which induces the formation of endodermal and mesodermal organs in amphibian gastrula ectoderm was purified from chicken embryos. Preparative sodium dodecyl sulfate polyacrylamide electrophoresis and gel permeation chromatography on sephadex with different eluants were employed. In buffer containing 6 M urea the molecular weight of the factor was estimated to about 28 000-30 000.

Formation of mesodermal pattern by secondary inducing interactions.

A highly purified vegetalizing factor induces endoderm preferentially in amphibian gastrula ectoderm. After combination of this factor with less pure fractions, a high percentage of trunks and tails with notochord and somites are induced. The induction of these mesodermal tissues depends on secondary factors which may act on plasma membrane receptors of the target cells.

Template active chromatin structures: degradation by deoxyribonuclease I.

Chicken embryos were pulse-labelled in vivo with [3H]uridine (10 min), the chromatin isolated and treated with DNAse I. The residual chromatin was separated from the degradation products by centrifugation. The nascent pulse-labelled RNA is completely recovered in the residual chromatin even after prolonged incubation with DNAase I, whereas the DNA is completely degraded to 80 base polynucleotide fragments and smaller fragments.