Actin is unevenly distributed in the pituitary gland

Pituicytoma with gelsolin amyloid deposition

Pituicytoma is a rare low-grade (WHO grade I) sellar region glioma. Among sellar tumors, pituitary adenomas, mainly prolactinomas, may show amyloid deposits. Gelsolin is a ubiquitous calcium-dependent protein that regulates actin filament dynamics. Two known gene point mutations result in gelsolin amyloid deposition, a characteristic feature of a rare type of familial amyloid polyneuropathy (FAP), the Finnish-type FAP, or hereditary gelsolin amyloidosis (HGA). HGA is an autosomal-dominant systemic amyloidosis, characterized by slowly progressive neurological deterioration with corneal lattice dystrophy, cranial neuropathy, and cutis laxa. A unique case of pituicytoma with marked gelsolin amyloid deposition in a 67-year-old Chinese woman is described. MRI revealed a 2.6-cm well-circumscribed, uniformly contrast-enhancing solid sellar mass with suprasellar extension. Histologically, the lesion was characterized by solid sheets and fascicles of spindle cells with slightly fibrillary cytoplasm and oval nuclei with pinpoint nucleoli. Surrounding brain parenchyma showed marked reactive piloid gliosis. Remarkably, conspicuous amyloid deposits were identified as pink homogeneous spherules on light microscopy that showed apple-green birefringence on Congo red with polarization. Mass spectrometric-based proteomic analysis identified the amyloid as gelsolin type. Immunohistochemically, diffuse reactivity to S100 protein and TTF1, focal reactivity for GFAP, and no reactivity to EMA, synaptophysin, and chromogranin were observed. HGA-related mutations were not identified in the tumor. No recurrence was noted 14 months after surgery. To the knowledge of the authors, amyloid deposition in pituicytoma or tumor-associated gelsolin amyloidosis has not been previously described. This novel finding expands the spectrum of sellar tumors that may be associated with amyloid deposition.

Cytoskeletal proteins in cultured secretory cells from rat pituitary

Cultured cells from female rat pituitaries were examined by immunofluorescence microscopy for the presence of pituitary hormones and for cytoskeletal proteins. The cells attach well to glass coverslips and, when well-dispersed initially, develop networks of branching processes. Their cytoplasm appears granular and shows granular fluorescence when the cells are permeabilized and treated with antisera to pituitary hormones. The cultures contain fibroblasts which are morphologically distinct and much larger than the secretory cells. Consequently, they provide an internal control for cytoskeletal proteins in nonsecretory cells. Fibroblasts have relatively prominent stress fibres. By contrast, the secretory cells have a diffuse cytoplasmic distribution of all cytoskeletal proteins investigated. One cell type, the gonadotrope, which secretes luteinizing hormone and follicle-stimulating hormone, was examined in particular detail.

Multiple-rate components of axonally transported proteins in the hypothalamo-neurohypophysial system of the rat

The transport of labeled proteins from the hypothalamus to the neurohypophysis following 35S-methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short-axon systems. Multiple-rate components to those found in other neuronal systems were demonstrated. Neurosecretory vesicle-containing proteins (e.g., neurophysins) were transported at fast rates (greater than 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two-dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in this system.