Glomus tympanicum chemodectomas: radiographic and clinical characteristics

Glomus tympanicum chemodectomas are benign neoplasms that develop from normal glomus bodies located along the Jacobson (tympanic) nerve in the middle ear. The medical charts and radiographic studies of 55 patients with these tumors were reviewed. Women outnumbered men in a ratio of 3.5:1, and the patients' average age when they initially reported symptoms was 52 years. Tinnitus, ear pulsations, and diminished hearing were the most frequent symptoms. No patient had a second chemodectoma, and none of seven patients who were tested had elevated neuroendocrine compounds. Review of the radiographic examinations showed that direct coronal, thin-section computed tomography (CT) was the most sensitive means of demonstrating glomus tympanicum chemodectomas. Magnification angiography was also a sensitive diagnostic study, typically depicting a trapezoidal, hypervascular, middle-ear mass that appeared initially in the middle-to-late arterial phase and quickly disappeared in the venous phase. Differentiation from an aberrant internal carotid artery is critical to prevent arterial biopsy.     

Association of the p85 regulatory subunit of phosphatidylinositol 3- kinase with an essential erythropoietin receptor subdomain

Using an active, HAI epitope-tagged form of the murine erythropoietin (EPO) receptor and via direct coimmunoprecipitation, the p85 regulatory subunit of phosphatidyl inositol-3 kinase (p85/PI3-K) is shown to associate with the EPO receptor in transfected FDC-P1 cell lines. Coimmunoprecipitation of p85 with epitope-tagged EPO receptors was observed initially in FDC-HER cells labeled metabolically with [32P]orthophosphate, and association of these factors was confirmed by Western analyses of receptor immunoprecipitates using p85 antiserum. Interestingly, this association occurred in the absence of ligand, and exposure of FDC-HER cells to EPO did not detectably affect levels of receptor-associated p85 or overall levels of p85 phosphorylation. However, EPO was observed to stimulated the rapid formation of phosphatidylinositol 32P-phosphate in FDC-HER and FDC-ER cells. Through baculovirus-mediated expression of epitope-tagged EPO receptor forms in SF9 cells, domains for p85 association were mapped. Analyses of receptor forms with cytosolic truncations and deletions delineated a candidate subdomain for p85 binding to an essential extended box-2 region (P329-E374; including a putative motif for SH2 binding, Y343LVL). These findings extend a mechanistic alignment between the EPO receptor and protein tyrosine kinase-encoding receptors that likewise activate PI3-K, and expand the importance of further defining pathways to PI3-K activation.