Differentiation, epithelial

The mechanisms by which the taste (and also the olfactory) system senses chemical compounds is assumed to occur by way of a chemoreceptory system that interacts effectively with a broad, structural variety of stimulant molecules, by means of a receptor epithelium consisting of the mosaic of adjacent, peripheral membranes of many receptor cells, exposed to a medium carrying stimulus molecules. A receptor cell is conveniently and, for our present purpose, sufficiently defined as a cell equipped to interact, according to some mechanism, with stimulus molecules, to convert the effect of this interaction into a signal, and to project this signal into the system. The taste receptor is thus a differentiated, epithelial cell synaptically contact-... 

In another approach, Parnigotto and coworkers reconstructed corneal structures in vitro by using corneal stroma containing keratocytes to which corneal epithelial cells from bovine primary cultures were overlaid [73], However, this particular corneal model did not contain an endothelial layer. This model was histochemically characterized and the toxicity of different surfactants was tested using MTT methods. This stroma-epithelium model has been reported to show a cornea-like morphology, where a multilayered epithelial barrier composed of basal cells (of a cuboidal shape) and superficial cells (of a flattened shape) is noted. Furthermore, the formation of a basement membrane equivalent and expression of the 64-kDa keratin were reported, indicating the presence of differentiated epithelial cells. The toxicity data for various surfactants obtained with this model correlate well with those seen by the Draize test [73], However, this corneal equivalent was not further validated or used as a model for permeation studies. 

Caveloae are particularly abundant, accounting for 30-70% of the plasma membrane in differentiated epithelial (e.g., pneumocytes) and endothelial cells, fibroblasts, smooth muscle cells, and adipocytes. Indeed there is a general trend for caveolin induction in differentiated cell types. Adipose tissue is replete with caveolae, and caveolin mRNA and protein are strongly induced during differentiation of 3T3-L1 preadipocytes (fibroblasts) to adipocytes [10], While... 

WiGLEY, C.B. (1979). "Hansformation in vitro of adult mouse salivary gland epithelium a system for studies on mechanisms of initiation and promotion, page 3 in Neoplastic Thinsformation in Differentiated Epithelial Cell Systems In Vitro, Franks, L.M. and Wigley, C.B., Eds. (Academic Press, London). 

The limbus is the anatomic junction between the transparent cornea and the conjunctiva, a tissue in which the vessels circulate. At this level, there would be the limbal stem cells, cells generating the differentiated epithelial cells of the cornea. The essential property of the cornea is transparency. The seriousness of the ocular bum consists in the loss of the comeal transparency. Actually the limbus is a real barrier to the conjunctiva. In the following months, a serious ocular bum will result in the development of a conjunctival cover leading to a loss of vision. 

The intrinsic barrier of the gastrointestinal epithelium is characterized by intercellular junctions at the apical (luminal) side of differentiated epithelial cells, the so-called tight junctions (TJ), and the maintenance of epithelial integrity based on the balance between cellular proliferation and cell death, as described above. Barriers against drug absorption by the intracellular and paracellular routes, their modulation, and maintenance will be discussed in the following, with the focus on the intestinal epithelium. 

Vitamin A is an essential fat-soluble compound acquired from the diet. The parent form of vitamin A is all-iram-retinol. Vitamin A is needed to maintain normal vision, normal reproduction (including spermatogenesis, conception, and placenta formation), and normal cell differentiation (including bone remodeling, maintenance of differentiated epithelial linings and skin, em-... 

Because papillomaviruses are specialized for replication in external ep-ithelia, infection is usually confined to the epithelium exposed to the external environment and does not result in systemic dissemination of the virus. While viral replication occurs in differentiated epithelial cells in the upper epidermal layer, viral particles are also often located in the deep epidermal basal layer. The epidermis becomes thickened and hyperkera-totic, and keratinocytes (keratin-containing cells) in the epidermal granular layer become vacuolated as a result of viral infection. The mechanisms by which virions penetrate the stratum corneum and infect viable keratinocytes is poorly understood, as there is a lack of practical in vitro culture systems available for these viruses to serve as study aids. 

Normal testes expressed only small amounts of /nyc-encoded p62 (S4). Seminomas showed increased nuclear and cytoplasmic staining. Undifferentiated teratomas showed little activity, whereas c-wyc-encoded p62 was abundant in the nuclei of differentiated epithelial structures, yolk sacs, and embryoid bodies. 

Ordonez NG. Role of immunohistochemistry in differentiating epithelial mesothelioma from adenocarcinoma. Am J Clin Pathol. 1999 112 75-89. 

Ordonez NG. Value of the MOC-31 monoclonal antibody in differentiating epithelial pleural mesothelioma from lung adenocarcinoma. Hum Pathol. 1998 29 166-169. 

Ordonez NG. Value of calretinin immunostaining in differentiating epithelial mesothelioma from lung adenocarcinoma. Mod Pathol. 1998 11 929-933. 

FIGURE 12.48 Most well and moderately well differentiated epithelial mesotheliomas and a few sarcomatoid mesotheliomas show cytoplasmic and nuclear immunostaining for calretinin. X 400. 

Additional studies have shown a high degree of specificity and sensitivity for calretinin in differentiating epithelial mesotheliomas from pulmonary adenocarcinomas and other epithelioid neoplasms. 733... 

FIGURE 12.49 Most well to moderately well differentiated epithelial mesotheliomas show thick cell membrane immunostaining for HBME-1.X400. 

These authors use a battery of antibodies to evaluate mesothelial proliferative lesions, including reactive and neoplastic processes. Keratin antibodies, with the exception of CK5/6, are generally not used to differentiate an epithelial mesothelioma from another neoplasm or from a reactive process, but are used to identify the extent of a neoplastic or reactive mesothelial cell process. The antibodies we use to differentiate a well or moderately well differentiated epithelial mesothelioma from a pulmonary adenocarcinoma or nonpulmonary adenocarcinoma include AE1/AE3 cytokeratin, CK5/6, CK7, CK20, vimentin, EMA, EIBME-1, calretinin, mesothe-lin, WTl, D2-40, caldesmon, CEA, LeuMl, B72.3, BerEP4, and TTE-1. 

The immunohistogram of a well to moderately well differentiated epithelial mesothelioma is shown in Fig. 12.51. A comparison of the immunohistochemical profile of well to moderately well differentiated epithelial mesothelioma and pulmonary adenocarcinoma is shown in Table 12.29. 

TABLE 12.29 Comparison of Immunohistochemical Profiles of Well to Moderately Well Differentiated Epithelial Mesotheliomas and Well to Moderately Well Differentiated Pulmonary Adenocarcinomas ... 

Well to moderately well differentiated epithelial mesothelioma + + + S + S S S S +... 

Unusual/uncommon types of mesothelioma should be mentioned because they can cause diagnostic confusion. Mucin-positive epithelial mesotheliomas are not uncommon." Between 1% and 5% of all moderately well to well differentiated epithelial mesotheliomas show mucicarmine and/or PAS-diastase staining (Fig. 12.59). Patterns of mucin staining have been extensively described by this author." Mucin-positive epithelial mesotheliomas most frequently express immunohistochemical markers that are negative in most epithelial mesotheliomas and usually positive in pulmonary adenocarcinomas (CEA, LeuMl, B72.3, BerEP4). Mucinpositive epithelial mesotheliomas express calretinin and... 

Tateyama H, Eimoto T, Tada T, et al. Immunoreactivity of a new CD5 antibody with normal epithelium and malignant tumors including thymic carcinoma. Am J Clin Pathol. 1999 111 235-240. Ordonez NG. Value of calretinin immunostaining in differentiating epithelial mesothelioma from lung adenocarcinoma. Mod Pathol. 1998 11 929-933. 

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