The follicular structures in the intermediary lobe of the bull hypophysis

Abstract

As a research material we have used the hypophyses of 14 Holstein bulls aged of 3-8 years. The samples have been fixed in Orth, Carnoy, and Helly, led up to paraffin, and serially sectioned at 5 μm. We have finally obtained 420 serial sections stained through the methods Novelli, PAS, Papanicolau, MH2, Fontana, Steedman-Mowry, Bielschowsky, Bodian and Holmes. The intermediary lobe is well developed in the bull. It is always adjacent to the posterior lobe of the bull hypophysis, and separated from it by a discontinuous layer of conjunctive tissue. The follicular structures (110-360 μm), containing colloid in the lumen, were found in the intermediary lobe of 14 bull hypophysis. A thin conjunctive tissue separated these follicular structures. They formed cysts, which contained colloid. The colloid is a palestaining material, PAS-positive, and is surrounded by simple squamous or cubical epithelium. The colloid consists in a glycoprotein in the Steedman-Mowry stain. The intermediary lobe of the hypophysis makes a hormone MSH (Melanocyte Stimulating Hormone), which is responsible for the expansion of melanocytes from the animals’ skin.