Foregut Cysts

Foregut cysts frequently cause symptoms in the first three decades of life. The symptoms consist of dyspnea, wheezing, cough and sputum, dysphagia, stridor, and those associated with right heart strain. Symptoms and the radiological appearance of the uncomplicated cyst mimic mediastinal tumour and mediastinal obstruction. The symptoms and radiological appearance of the ruptured infected cyst simulate those of lung abscess, diaphragmatic hernia, ruptured hydatid cyst, cavitated peripheral carcinoma and pulmonary tuberculosis. In this series the differentiation from other cysts was made thus: with intralobar sequestration, a systemic arterial blood supply was demonstrated; with hydatid cyst, there was a positive intradermal skin test and (radiologically) following rupture, the appearance of a pericystic pneumatocele followed by the water-lily sign was diagnostic; with emphysematous cysts, the signs of associated bronchitis were present; in the presence of pseudocysts, there was a previous history of lung abscess, staphylococcal infection or tuberculosis. Cysts should be removed when first diagnosed.     

A Highlights from MBoC Selection: Unregulated ARF6 Activation in Epithelial Cysts Generates Hyperactive Signaling Endosomes and Disrupts Morphogenesis

Tumor development in glandular tissues is associated with structural alterations in the hollow ducts and spherical structures that comprise such tissues. We describe a signaling axis involving sustained activation of the GTP-binding protein, ARF6, that provokes dramatic changes in the organization of epithelial cysts, reminiscent of tumorigenic glandular phenotypes. In reconstituted basement membrane cultures of renal epithelial cysts, enhanced ARF6 activation induces the formation of cell-filled glandular structures with multiple lumens and disassembled cadherin-based cell–cell contacts. All of these alterations are accompanied by growth factor receptor internalization into signaling endosomes and reversed by blocking ARF6 activation or receptor endocytosis. Receptor localization in signaling endosomes results in hyperactive extracellular signal-regulated kinase signaling leading to Bcl-2 stabilization and aberrant cysts. Similarly, formation of hyperproliferative and disorganized mammary acini induced by chronic stimulation of colony-stimulating factor 1 receptor is coupled to endogenous ARF6 activation and constitutive receptor internalization and is reversed by ARF6 inhibition. These findings identify a previously unrecognized link between ARF6-regulated receptor internalization and events that drive dramatic alterations in cyst morphogenesis providing new mechanistic insight into the molecular processes that can promote epithelial glandular disruption.     

Giant Cysts and Cysts with Multiple Central Bodies in Azotobacter vinelandii

Cyst germination in Azotobacter vinelandii ATCC 12837 was studied by using phase contrast and electron microscopy. Germination in this organism was accompanied by the formation of large cyst forms of two different types: giant cysts and cysts containing multiple central bodies. Previously, these two types have been reported only when yeast extract was added to the encystment medium. In this study, we observed giant cysts and cysts with multiple central bodies in nitrogen-free liquid medium. The germination of "normal" cysts is often preceded by enlargement to the giant form and division of the central body to produce cysts with multiple central bodies. Structures similar in appearance to ribosomal aggregates were observed only in cysts undergoing pregermination transformations.