Case report: acromegaly and Cushing's disease in a patient with synchronous pituitary adenomas.

A 40-year-old white woman presented with hirsutism, amenorrhea, generalized fatigue, diffuse weight gain, acral changes, and coarsened facial features. Physical examination revealed mild diastolic hypertension, acromegalic features, hirsutism, and seborrhea. The growth hormone concentration was elevated and did not suppress after glucose administration. Urinary free cortisol excretion was increased and was not suppressed during a 2 mg low-dose dexamethasone suppression test. Magnetic resonance imaging of the sella demonstrated a 1.3 x 1.2 x 0.8 cm pituitary adenoma. Trans-sphenoidal resection was performed, and portions of the resected tumor were analyzed by routine pathologic methods. Histopathologic and immunohistochemical findings indicated discrete growth hormone- and adrenocorticotropic hormone-producing pituitary adenomas. Coexisting acromegaly and Cushing's syndrome due to pituitary neoplasia was previously reported in two patients. However, to the authors' knowledge, this represents the first description of a patient with acromegaly and Cushing's disease resulting from discrete synchronous adenomas of the pituitary gland as defined by modern histopathologic techniques.

Insulin and insulin-like growth factor 1 stimulate the phosphorylation on tyrosine of a 160 kDa cytosolic protein in 3T3-L1 adipocytes.

Insulin and IGF-1 (insulin-like growth factor 1) rapidly stimulate the phosphorylation on tyrosine of a 160 kDa cytosolic protein (pp160) in intact 3T3-L1 adipocytes. Half-maximal phosphorylation of pp160 is attained with either 4 nM-insulin or 20 nM-IGF-1. A semi-quantitative immunoblotting procedure using anti-phosphotyrosine antibody revealed that the insulin-stimulated 3T3-L1 adipocyte possesses approx. 3 x 10(5) and 0.6 x 10(5) phosphotyrosyl sites, respectively, in pp160 and insulin receptor beta-subunit. Removal of insulin from stimulated cells results in the rapid (within 15 min) loss of phosphate groups from tyrosyl residues in both pp160 and receptor beta-subunit. Whereas pp160 remains maximally phosphorylated on tyrosine for up to 60 min in the presence of 100 nM-insulin, IGF-1 at the same concentration induces only a transient response that is maximally 50% of that observed with insulin. pp160 is not phosphorylated on tyrosine in response to platelet-derived growth factor or epidermal growth factor. Although pp160 appears to be a soluble cytoplasmic protein, in the presence of 1 mM-ZnCl2 it becomes membrane-associated. In view of its apparent cytoplasmic localization and its inability to bind to either wheat-germ agglutinin or concanavalin A, pp160 does not appear to be a typical glycoprotein growth-factor receptor. Our results suggest that pp160 may be a physiologically important cellular substrate of the insulin-receptor tyrosine kinase in the intact 3T3-L1 adipocyte.

A membrane glycoprotein that accumulates intracellularly: cellular processing of the large glycoprotein of LaCrosse virus.

The intracellular transport and certain posttranslational modifications of the large glycoprotein (G1) of LaCrosse virus (LAC) in BHK cells have been studied. G1 from released LAC virus was characterized by complex oligosaccharides (endo H-resistant) and covalently attached fatty acid. Only a small fraction of total cellular G1 was present on the baby hamster kidney cell surface. Cell-surface G1 contained complex oligosaccharides, while total G1 in infected cells contained largely unprocessed (endo H-sensitive) oligosaccharides. In addition, cell G1 contained significantly less fatty acid than virion-associated G1. Pulse-chase experiments showed that the oligosaccharides of G1 were processed to the complex from much more slowly than the oligosaccharides of the vesicular stomatitis virus (VSV) glycoprotein (G). In addition, transit of LAC G1 to the cell surface and into extracellular virions was two to three fold slower than the transit of VSV G. Thus LAC G1 accumulates intracellularly and is only slowly processed by intracellular processing enzymes. Treatment with monensin caused accumulation in the cell of a form of G1 with partial sensitivity toward endo H, suggesting that monensin may act to inhibit the glycosylation process directly.