Abstract: The present invention provides a process of producing an immortalized hybrid neuronal cell comprising the steps of transducing a primary embryonic brain cell from a specific brain region with a temperature-sensitive oncogene to produce a transductant cell, and fusing the transductant cell with a mature primary neuron from the same brain region to produce the hybrid cell. Hybrid cells produced by such a process are also provided.

Abstract: A novel 100 kDa protein from Drosophila melanogaster (dp100) that recognizes both mammalian epidermal growth factor (EGF), insulin and insulin-related growth factors, and crossreacts with antisera against the human EGF receptor. The binding spectrum and relative binding affinities of dp100 for growth factors and hormones, related and unrelated to EGF or insulin, demonstrate that dp100 binds to insulin-like and EGF-like factors with dissociation constants ranging from 10.sup.31 6 M to 10.sup.-9 M. Dp100 binds to human synthetic transforming growth factor-alpha (TGF-alpha) and insulin-like growth factor-II with the highest affinity and, unlike the mammalian EGF receptor, has the unique ability to differentiate between EGF and TGF-alpha with a difference in affinity of three orders of magnitude. Further, dp100 is able to differentiate on the basis of binding affinity between native TGF-alpha, TGF-alpha that has been synthesized chemically and TGF-alpha that has been produced in E.