Action of rat submaxillary gland extracts on neural tube growth in organ culture.

FOR a long time embryologists have been interested in mechanisms which control growth of the neural tube. The results of experiments made on amphibian and chick embryos suggested that the differential growth of different portions of the neural tube is dependent both on genetic factors and on the degree of development of peripheral tissues (see Weiss, 1955). The mechanism of this peripheral action has not yet been elucidated. It has been attributed to diffusible substances from peripheral tissues acting on the growing neural tube. However, according to Hamburger (1958), the junction between neurons and peripheral tissue is necessary for this growth effect to occur. Studies on a neural growth factor found in mouse sarcoma 180 tissue, snake venom and mouse and rat submaxillary glands (Levi Montalcini, 1959) has renewed interest in this problem. However, this factor acts only on sympathetic and spinal ganglia and not on neural tube derivatives. Recently organ culture techniques have been used with increasing frequency by embryologists, and their use has broadened our understanding of many aspects of morphogenesis (see Borghese, 1958). However, to the best of our knowledge, these techniques have not so far been used with success in the analysis of neural tube growth. In the present work, organ cultures of portions of chick embryo neural tube together with surrounding tissues, were made to test the action of other tissues in nearby culture, or of organ extracts added to the medium.