Concentration dependence of inductive activity in the mixture of lens epithelium proteins

As shown elsewhere, the mixture of proteins secreted by lens epithelium cells in the process of microcultivation can selectively induce eye and forebrain tissues in the early gastrula ectoderm (Zemchikhina et al., 2000, 2003). In the present work, the dependence of inductive activity of this protein mixture on its concentration in culture solution has been studied. The test-system was the early gastrula ectoderm of Xenopus laevis frogs. The results of the experiments revealed no direct dependence of the spectrum of induced tissues on the concentration of the protein mixture. At a concentration of 0.5 mg/ml, brain appeared being accompanied by retina, pigmented epithelium, and lentoids, while at 0.031 mg/ml a perfect lens developed along with brain, retina and pigmented epithelium. At 0.125 mg/ml not only brain with accompanying structures but also muscle fibers were equally differentiated. These data suggest a new approach to the problem of dependence of the character of induction on the concentration of inducing factors, and they enable us to suppose that this dependence is not realized as a simple concentration dependence but may de determined by some adaptive, yet not elucidation processes.