| Citation | Professor Nicole le Douarin is the world's leading experimental embryologist. Her early work was on the development of the liver in the chick embryo. This work was characterised by technically difficult operations in ovo which established that the heptocytes developed as a result of interactions between the endoderm and mesoderm. In 1969 she discovered that the nucleus of the quail can be distinguished from that of the chick by cytochemical methods. She at once recognized its potential and the use of this natural marker has been widely adopted and has revolutionised studies on cellular migrations in development. Her own work has concentrated on two systems: the development of the neural crest and the immune system. The early studies of the neural crest demonstrated the contribution of the neural crest to head structures, and the discovery that calcitonin secreting cells, the type I cells of the carotid body and the fluorogenic amine containing cells of the arterial trunk wall are of a neutral crest origin. She also showed that the cells of the neural ectoderm do not give rise to all the cells of the APUD series, thus ending a longstanding controversy. Special attention was given to the origins of the cells of the sympathetic and the parasympathetic nervous systems. In a series of elegant studies in which grafting techniques were coupled with a variety of cell physiological methods, it was shown that although the two types of cells normally originated from different regions of the neural crest, the potentiality is distributed throughout the crest. The expression of a particular phenotype was shown to depend on the nature of the mesenchyme into which the cells migrated. It was shown that a spinal ganglion, even during the course of differentiation, could, under appropriate conditions, give rise to a wide variety of cell types. More recently, she has shown that the crest cells contain at least two types of precursor cells. As regards the immune system she resolved the controversy as to the origin of the lymphocytes by showing that they originated outside the thymus and Bursa, which they later colonised in waved and provided evidence that a chemotactic mechanism is involved. Similarly, she showed that the precursors of blood cells migrated into haemopoietic tissue from the blood islands. Her work, which is of the highest quality, combines the techniques of experimental embryology with cell biology and has resulted in fundamental contributions to the understanding of the development of the automatic nervous system, the immune system and the neural crest in general. |