Some Light- And Electron-Microscopical Observations on the Pars Intermedia of the Pituitary Gland of the Rabbit

Abstract

The cytological appearance of the pars intermedia of the rabbit both at the light and the electron microscopical (E.M.) levels, is described. Two types of cell,one stainable byperiodic acid\p=m-\Schiff's reagent and aldehyde\p=m-\fuchsin and the other chromophilic, non-granular and intercalated between the former, were observed. In E.M. sections the first type had two kinds of granule in its cytoplasm, a few electron-dense about 250 nm in diameter, mostly confined to the Golgi area, and numerous large 'vesicles' or granules of varying density about 500\p=n-\600nm in diameter generally distributed throughout the cytoplasm. The second type of cell when viewed in the electron microscope is characterized by microvilli projecting into intercellular spaces, and long, linked processes ramifying in between the principal cells. Varicose nerve fibres and abundant neurosecretory material were demonstrated in the pars intermedia with chrome alum\p=m-\haematoxylin and Alcian blue. In E.M. sections these neurosecretory granules were similar to those in the infundibular process. At the point where nerve fibres appeared to be making contact with glandular cells, synaptic vesicles of about 50 nm in diameter were also observed.

Some Light- And Electron-Microscopical Observations on the Pars Tuberalis of the Pituitary Gland of the Rabbit

“…The latter are similar to those described for the pars intermedia (Cameron & Foster, 1971 ;Foster, 1971) but they are more highly developed in the p. tuberalis than in any other region of the pituitary. In addition to these two main types there are also numerous fibroblasts (with associated collagen) situated more particularly at the junction between the p. tuberalis and the infundibular stalle, a few heavily ciliated cells, some plasma cells, squamous epithelial cells and a sprinkling of invasive granular cells of the kind found in the zona tuberalis.…”

“…These cells correspond to a similar type which has been described in other regions of the adenohypophysis, particularly in the p. intermedia (Cameron & Foster, 1971;Foster, 1971) but in the p. tuberalis they are far more abundant and more highly developed. They have a very characteristic appearance and are easily picked out from other cells in this region.…”

“…in addition to revealing neurosecretory fibres in the infundibular stem, infundibular process and p. intermedia (Cameron & Foster, 1971) showed the presence of delicate beaded fibres in the p. tuberalis. These often com¬ prised meshes around and between groups of pars tuberalis cells and in several instances the neurosecretory fibres appeared to come into intimate contact with the surfaces of clear-looking cells (PI.…”

The Mammalian Pars Intermedia: A Review of Its Structure and Function

“…(ii) Electron microscopy The various cell types described above can also be distinguished at the electron microscopic level (Kurosumi et al 1961;Ziegler, 1963;Kobayashi, 1964Kobayashi, , 1965Howe & Maxwell, 1966, 1968Vincent & Kumar, 1968Vincent, 1969;Cameron & Foster, 1971). The interpretation of their appearance as revealed by the electron microscope has been dealt with at length by Howe & Maxwell (1968) and by Vincent & Kumar (1969).…”

“…The mammalian pars intermedia, like its counterpart in lower vertebrates, is innervated (Trautman, 1909;Rasmussen, 1938;Green & Harris, 1947;Harris, 1948;Smith, 1956;Bargmann & Knoop, 1960;Kurosumi et al 1961;Ziegler, 1963;Green, 1964;Howe & Maxwell, 1966, 1968Cameron & Foster, 1971). …”