To understand the etiology of bone modulation and hypercalcemia observed in granulocytosis of a tumor-bearing animal model and to gain insight into the implication of sustained hematopoietic stimulation on the bone tissue, in vivo responses of normal mouse hematopoietic and bone tissues to long-term injections of recombinant human and murine granulocyte colony-stimulating factor (G-CSF), murine granulocyte- macrophage CSF (GM-CSF), and human erythropoietin were quantitatively analyzed. Osteoclast activation was estimated by the osteoclast- endosteal ratio, determined by morphometric analyses of femoral sections. Medullary and bone areas were measured on transverse ground bone sections of the tibia. Recombinant murine G-CSF provoked marked granulocytosis associated with significant increases in the number of marrow granulocytes and their progenitors, and caused expansion of granulopoietic marrow into fatty marrow. The bone of G-CSF-treated mice showed a significant increase in endosteal osteoclast numbers with medullary area enlargement and a reduction in the bone thickness; indicative of endosteal bone resorption. Although GM-CSF had little effect on granulopoiesis, it caused peritoneal macrophages to increase and induced similar bone changes as those observed in G-CSF treatment. Enhanced erythropoiesis stimulated by erythropoietin was also associated with evidence of endosteal bone resorption. Bone changes induced by these growth factors were not associated with hypercalcemia. These animal studies document association of bone modulation in sustained stimulation of hematopoiesis, and implicate important physiologic effects of hematopoietic growth factors on skeletal tissue in vivo.

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The glomus body is a neuromyovascular, arteriovenous structure primarily found in the skin and, less commonly, other organs, and is involved with thermoregulation. Neoplasms of the glomus organ are most commonly encountered in the skin and soft tissues of the extremities, particularly the subungual region. Glomus tumors are rare vascular neoplasms originating from the glomus body resulting from proliferation of modified muscle cells within this organ. Glomus tumors are commonly subdivided, based on the prominence of glomocytes, vascular structures, and smooth muscle cells, into solid glomus tumors (the most common variant), glomangioma, and glomangiomyoma. Previous reports of intrathoracic glomus tumors have shown that these tumors are most commonly encountered within the tracheobronchial tree or pulmonary parenchyma; mediastinal lesions are exceptionally rare. On the basis of imaging appearance of the glomangioma reported in this case as well as prior reports of tracheobronchial and pulmonary glomus tumors, mediastinal glomus tumors manifest as intensely enhancing masses with circumscribed or poorly defined margins, closely resembling thymic carcinoid tumor, pheochromocytoma, or hypervascular lymphadenopathy. Secretion of catecholamines and tracer uptake on Indium-111 octreotide scintigraphy, as seen in the present case, is probably exceptional. Because glomus tumors may be difficult to diagnose on routine histopathologic specimens, radiologists should be aware of this rare lesion and consider the diagnosis of glomus tumor when an intensely enhancing mediastinal mass is encountered.

Multidetector computed tomography (MDCT), with its ability to rapidly acquire very thin sections, has become the cornerstone of imaging of pulmonary embolism (PE). Its availability, speed, and high negative predictive value (95-99%) make it an ideal modality for the evaluation of PE. MDCT also allows the concurrent evaluation of a wide variety of other thoracic disorders, including pulmonary parenchymal diseases, aortic dissection, and coronary artery disease. This article discusses attempts to validate computed tomography (CT) as the primary imaging modality for PE using both comparison with angiography as the gold standard and outcomesbased methods. Additionally, the advantages of MDCT over singledetector scanners, CT findings of acute and chronic PE, common CT artifacts, radiation, and CT-PE in pregnancy are discussed.

The increasing number and variety of patients with compromised immune systems poses a diagnostic challenge for the chest physician. Manifestations of pulmonary disease on imaging studies are diverse, with substantial overlap possible between entities. This article reviews radiologic findings in common disease states encountered when treating immune compromised patients and provides a framework for approaching common imaging manifestations, such as air-space consolidation, ground-glass opacities, and nodules.