In the early 1970s, it was felt by many researchers in different countries that new terms and concepts were necessary for the group of cells having common properties with neurons. The APUD series of Pearse (1968, 1969) at that time covered only those cells which showed a positive formaldehyde-induced fluorescence (FIF) reaction after administration of amine precursors such as L-dopa. Thus, the ACTH and MSH cells in the pituitary belonged to the APUD series but other cell types did not (Pearse 1968, 1969); the B cells in the pancreatic islets belonged to the APUD series but A and D cells did not (Pearse 1968). It was in 1974 (Pearse and Polak 1974; Pearse 1975a, b) that some FIF-negative cells were included in the APUD series. The concept of the APUD series, although worthwhile for stressing the correlation between the nervous and endocrine cells as mentioned above, appeared incomplete because the APUD ability, which should be the very base of this concept, was lacking or undetectable in many endocrine cells which, in other respects, would be considered to be related to nerve cells, and some of which occurred intermingled with the FIF-positive APUD cells.
KeywordsHair Cell Endocrine Cell Primary Cilium Gustatory Cell Visual Cell
Unable to display preview. Download preview PDF.