Hypophysial and Meningeal Melanocytes in the Zucker Rat

Abstract

Melanocytes have not been described in the pituitary of mammals or in the meninges of the rat. In this paper, we report the presence of the cluster of melanocytes in the intermediate lobe of the pituitary and around the median eminence of the hypothalamus forming an 'infundibulo-hypophysial circle', and also describe the characteristics of meningeal melanocytes in Zucker rats. In the leptomeninges, numerous melanocytes were found on the ventrolateral surface of cerebral hemisphere in the area of the middle cerebral artery. Pigment granules were also observed in the surrounding tissue outside the melanocytes as well as incorporated in the cytoplasm of neural and epithelial cells. Electron microscopy revealed that melanosomes in hypophysial and meningeal melanocytes were in different (II-IV) stages of maturity. In the leptomeninges of Zucker rats, HMB-45 immunoreactivity was found in round non-melanosome-containing cells, while no HMB-45 reaction was found in the leptomeninges of the albino rat. We conclude that both obese and lean Zucker rats possess functionally active melanocytes in the meninges and the pituitary and transfer pigment granules to neighboring cells. The distributions of melanocytes in proximity to blood vessels in the leptomeninges and in the 'infundibulo-hypophysial circle' suggest an endocrine secretory function.

Spatiotemporal gene control by the Cre‐ERT2 system in melanocytes

“…1a) was amplified from the expressed plasmid. Classical melanocytes are effectively found in the skin and eye and nonclassical melanocytes are present in the heart (Mjaatvedt et al, 2005) and brain, at various levels in the meninges, including the leptomeninges and in the pituitary gland (Goldgeier et al, 1984;Fetissov et al, 1999). No Cre-ERT2 expression was detected in the spleen, liver, or kidney of the Tyr::Cre-ERT2 transgenic mice or in any of the wildtype tissues analyzed.…”

Primary sellar melanocytic tumor: report of new case and literature review

“…In humans, melanocytes originate from the neural crest during early embryonic development and are normally found in the leptomeninges at the base of the brain, in the brainstem and in the spinal cord [21]. Although this has not been confirmed in humans, melanocytes are physiologically present in the pituitary of Zucker rats [22]. Therefore primary sellar melanocytic lesions may arise from the melanocytes harbored in the leptomeningeal tissue lining of the sellar floor or from the diaphragma sellae.…”

Melanoma of the sellar region mimicking pituitary adenoma

“…A study by Fetissov et al . (1999) demonstrated that in Zucker rats melanocytes are aggregated about leptomeningeal and hypophysial vessels 11 …”

“…Melanocytes are known to occur normally within the leptomeninges and are more concentrated at the base of the brain, particularly the ventrolateral surface of the medulla 10,11 . Primary sellar melanomas are believed to be leptomeningeal in origin, as are other intracranial melanomas 12 .…”