SOME OBSERVATIONS ON THE ULTRASTRUCTURE OF THE ADENOHYPOPHYSIS OF THE RABBIT

Abstract
SUMMARY: The ultrastructure of the adenohypophysis of the rabbit is described preliminary to reporting changes after experimental procedures. Fixation by perfusing with gluteraldehyde enabled selected regions of the gland to be removed with accuracy. Separate descriptions of the pars distalis proper, zona tuberalis, pars tuberalis and pars intermedia are therefore included. In the pars distalis proper four types of granular cell were recognized although their function cannot be accurately determined. For convenience, therefore, they have been designated 1, 2, 3 and 4. In addition a fifth type of cell (type 5) is described which is also present in the other areas. This cell, as well as having possible phagocytic functions, appears to be concerned in the formation of a perivascular channel. Two types of cell are recognized in the zona tuberalis, which are similar in appearance to the 3 and 4 cells of the pars distalis, although not necessarily identical in function. The characteristic cells of the pars tuberalis are rich in cytoplasmic RNA and contain large numbers of intracellular fibrils. It is suggested that the ribosomes are concerned in the synthesis of a sedentary protein which may take the form of the microfibrils. The pars intermedia contains a predominant cell type with large granules of varying density. The relationship of these granules to the specific hormone is discussed.

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