Epithelial cells columnar

P-glycoprotein is not only expressed in tumor cells, but also in cells of several healthy tissues. In liver it was detected in the biliary canalicular surface of hepato-cytes and the apical surface of small biliary ductules. In the small intestine and colon, it is localized in the apical surface of columnar epithelial cells, and in kidneys it is found in the brush border membrane of proximal tubules. Moreover, it is detectable on the apical surface of small ductules in the pancreas and on the surface of cells in the medulla and cortex of adrenals [2]. 

The epidermis consists of several types of cells. The epidermal cell type apposed to the dermis is the stratum germinativum (basal cell layer), over which are the stramm spinosum, stratum granulosum, stratum ludicum, and the outermost layer or stratum corneum. The basal cell layer consists of one layer of columnar epithelial cells. On division, the basal cells are pushed up and become the stratum spinosum, which consists of several layers of cells. As these cells approach the surface of the skin they become larger and form the stratum granulosum. 

The mucin to which bioadhesive polymers adhere is secreted by columnar epithelial cells and is a network comprising 0.5-2% of highly-hydrated flexible glycoprotein chains [400], which contain negatively charged moieties, and are... 

P-gp is constitutively expressed in nearly all barrier tissues. Techniques involving Northern blots (37) or Western blots with monoclonal antibodies such as C219 (38) and MRK 16 (39) have been used extensively to determine the tissue distribution of P-gp. It is expressed in adrenal cortex, kidney, liver, intestine, and pancreas endothelial cells at blood-tissue barriers, namely, the CNS, the testis, and in the papillary dermis (3,4,38,40,41). P-gp displays specific subcellular localization in cells with a polarized excretion or absorption function. More specifically, P-gp is found at the apical (AP) canalicular surface of hepatocytes, in the AP membrane of the columnar epithelial cells of colon and jejunum, and the AP brush border of the renal proximal tubule epithelium (3,4,40 1-2). In endothelial cells, P-gp is located in the luminal membrane (4,43). 

The columnar epithelial cells of the intestinal mucosa actively absorb and secrete extracellular ions, nutrients, and water. The active secretion of ions by these cells with an accompanying fluid flux acts to dilute and purge microorganisms or toxins in the bowel promotes the transfer of secretory immunoglobulin A, antimicrobial defensin peptides, and mucin into intestinal mucus and the gut lumen and, by affecting intraluminal pH, may alter the growth characteristics of enteric microflora [121]. Mucosal secretion is modulated by several enteric neurotransmitters, as well as inflammatory mediators released by mucosal mast cells that may affect transport indirectly through their ability to stimulate enteric neurons [122],... 

Figure 6.15 Schematic diagram of a portion of the epithelium covering above a lymphatic nodule in a Peyer s patch (mouse). Attenuated M cells (M) extend as membranelike cytoplasmic bridges between the absorptive columnar epithelial cells present on either side (C). Beneath the M cell lies a small nest of intraepithelial lymphocytes (L) together with a central macrophage (Mac). The M cell provides a thin membrane-like barrier between the lumen above and the lymphocytes in the intercellular space below. This M cell has taken up the macromolecules and particulate matter that reach it and macrophages (Mac) may ingest them. Modified from D.H. Cormack. Lymphatic tissue and the immune system. D.H.Cormack (ed.) (1987) Ham s Histology, J.B. Lippincott Company, Philadelphia, pp. 234-263...

Q2 Unlike the small intestinal mucosa, the colonic mucosa does not contain any villi. There are columnar epithelial cells and mucus-secreting goblet cells in the mucosa the columnar epithelium reabsorbs fluid and electrolytes. 

Q1 The mucosa is a mucous membrane which forms the innermost layer of the intestine. In the small intestine the mucosal surface area is increased greatly by folds and by villi, finger-like projections containing a core with a lymph capillary (lacteal) and blood vessels. Villi are covered by absorptive columnar epithelial cells whose luminal surface is further increased by microvilli (brush border) on which digestive enzymes and transport mechanisms for inorganic ions are located. 

The mucosa of the small intestine has an enormous surface area because of the presence of villi. Villi are covered by absorptive columnar epithelial cells whose surface is further increased by microvilli (brush border), on which carbohydrate and peptide digestive enzymes and transport processes involved in absorption are situated. Pits between the villi contain undifferentiated cells which move up the villi, mature, function for a few days and are shed into the lumen of the gut. 

Induction of Calbindin-D In response to crdcitriol administration, there is an increase in mRNA synthesis and then in the synthesis of calbindin-D in intestinal mucosal cells, which is correlated with the later and more sus-teilned increase in calcium absorption. In -vitamin D-deficient animals, there is no detectable calbindin in the intestinal mucosa, whereas in animals adequately provided with vitamin D, it may account for 1 % to 3% of soluble protein in the cytosol of the columnar epithelial cells. Although the rapid response to calcitriol is an increase in the permeability of the brush border membrane to calcium, the induction of calbindin permits intracellulcu accumulation and transport of calcium. The rapid increase in net calcium transport in tissue from -vitamin D-replete animals is presumably dependent on the calbindin that is already present in deficient animals, there cem be no increase in calcium transport until sufficient calbindin has accumulated to permit intracellular accumulation, despite the increased permeability of the brush border. 

Figure 10.2 Electron photomicrographs of the bronchial epithelium. Panel (a) Illustrates columnar epithelial cells showing the presence of cilia. Panel (b) Illustrates details of intercellular junctions between adjacent columnar...

Plate III Eosinophils produce an increase in permeabiiity of the bovine bronchial mucosa and detachment of columnar epithelial cells. Panel (a) shows bronchial mucosa exposed to unstimulated eosinophils. Panels (b) and (c) show bronchial epithelium that had been exposed to ionophore-stimulated eosinophiis. ionophore alone does... 

Metaplasia is the reversible substitution of one type of fully differentiated cell for another within a given tissue. A classic example is the replacement of the normal ciliated columnar epithelial cells in the respiratory tract airways by squamous epithelium (Figure 4) in situations in which there is chronic irritation from certain components of inhaled tobacco smoke. While the squamous epithelium is believed to provide functional protection against the irritant properties of the smoke, the loss of the ciliated columnar epithelium results in reduction of the functional capacity of the lungs to clear particulates from the respiratory tract. When the irritation is removed, the squamous epithelium is replaced by normal ciliated columnar epithelium. 

The mammalian epididymis is a highly coiled duct where sperm undergo maturation and are stored prior to ejaculation. The epididymis is comprised of a head (caput), a body (corpus), and a tail (cauda), which can be defined by their relative location, tissue characteristics, and cell types. Within a connective tissue sheath, the epididymis is a complex of tubules lined with columnar epithelial cells attached to a basement membrane. Epithelial cell height decreases and luminal diameter increases from the initial segment to the cauda of the epididymis. There are several distinct epithelial cell types found in the mammalian epididymis, including the principal, narrow, basal, clear, and halo cells. The principal cells... 

Mayra-Makinen, A., Manninen, M., and Gyllenberg, H. 1983. The adherence of lactic acid bacteria to the columnar epithelial cells of pigs and calves. J. Appl. Bacteriol. 55, 241-245. 

In primary culture of human nasal cells, the cells most relevant for transport studies are pseudostratified ciliated columnar epithelial cells from the medium and inferior turbinates 48 These cells show a high degree of differentiation, grow to a confluent monolayer in 6 to 8 days, and form tight junctions however, they are expensive, their availability and life span are limited, and the model does not reflect the heterogeneity of cells in vivo.47 49... 

---