Epithelial Organization

The thymus is a lympho-epithelial organ, located within the upper thorax. One of its fimctions is the conversion of certain lymphoid hematopoietic precursor cells originating from the bone marrow into thymus-derived lymphocytes (T-cells). 

Horvath G, Schmid N, Fragoso MA, Schmid A, Conner GE, Salathe M, Wanner A (2007) Epithelial organic cation transporters ensure pH dependent drug absorption in the airway. Am J Respir Cell Mol Biol 36 53-60. 

Lang MA, Muller J, Preston AS, and HandlerJS. Complete response to vasopressin requires epithelial organization in A6 cells in culture. Am J Physiol 250 Cl 38-145,1986. 

Lymphoid Elements. The thymus plays a central role in the differentiation of T lymphocytes (Cantor and Weissman, 1976), and although much recent emphasis has focused on the thymic epithelial cells, it must be emphasized that the thymus is a lymphoid structure composed predominantly of thymic lymphocytes or thyntocytes. The thymus can be viewed as a solid epithelial organ, penetrated by blood vessels and infiltrated with thymocytes in four discrete areas the subcapsular cortex, the inner cortex, the medulla, and the perivascular connective tissue. 

Signaling by ErbB-3 and ErbB-4 inflicts an additional level of complexity by applying a wide but shared variety of direct ligands to both receptors. Genetic evidence implies that signaling by neuregulins is essential for epithelial organs, for effectors of the nervous system such as Schwann cells and neu-... 

Two groups of hormones regulate development and reproduction in insects, namely the ecdysteroids and the JHs. In crustaceans too, ecdysteroids are involved in the hormonal control of growth, and a chemical compound, which is similar to the JHs of insects, is present and thought to play a role in crustacean reproduction and development. The insect JH is a species-specific acyclic sesquiterpenoid epoxide, which is synthesized in a pair of retrocerebral epithelial organs called the corpora allata (CA see Fig. 1). In decapod crustaceans, MF is the unepoxidated form of the insect JH III and it is synthesized and secreted from the MOs (see Section 3.2.4). 

Immunolocalization reveals LN as being concentrated in basal laminae around embryonic epithelial organs, but immunoreactivity can also be found interstitially in the mesenchymal compartments (Rogers et al., 1986 Simon-Assman et al.,... 

Urinary bladder. Kreft and coworkers (Kreft, Romih et al. 2002) established an in vitro culture model that closely resembles whole mouse urothelial tissue. When examined at the ultrastructural level, the cultured urothelium was polarized and organized as a multilayered epithelium, and epithelial organization was stabilized by well developed cell junctions. Desquamation of urinary bladder epithelial cells can be induced by constant illumination for 96 hours or by application of endotoxin lipopolysaccharide. Cell detachment involves interruption of TJ between neighbouring cells (Jezemik 1996). Urothelium permeability was studied in an experimental ischemic model of mouse urinary bladder by means of lanthanum nitrate tracer (Korosec and Jezemik 2000). Ischemia induces breakdown of the blood-urine permeability barrier by dismption of the TJ. 

Recent studies indicate that hyaluronan is important in branching morphogenesis of epithelial organs [52] and in formation and remodeling of blood vessels [53-55]. In these cases it appears again that hyaluronan provides a hydrated milieu that favors proliferation and movement of epithelial, endothelial and smooth muscle cells. The influence of hyaluronan on vascular smooth muscle cell movement and proliferation may be an important factor in progression of atherosclerotic lesions [54, 55]. 

Sorokin, L., Klein, G., Mugrauer, G., Fecker, L., Ekblom, W.M., Ekblom, P. Development of kidney epithelial cells. In Epithelial organization and development. (T.P. Fleming, ed.— Chapman Hall, London) 1992, 163 190. 

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