Serous cells

The serous cell of the rat has a relatively electron-lucent cytoplasm but also abundant rough endoplasmic reticulum. Its secretory granules are discrete and electron dense and do not fuse with one another. Spicer et al. (1990) found numerous mitochondria ranging from sUghtly larger than normal to several micrometers in diameter (giant) in about one-half of the serous secretory cells in the surface 

A protease inhibitor with a low molecular weight of about 15 kDa inhibits the activity of the leucocyte-derived proteases cathepsin G (EC 3.4.21.20) and elastase (EC 3.4.21.37) (Mooren et al. 1982). This protease inhibitor has been called antileucoprotease . Its importance Hes in the fact that during infection the bronchial mucosa becomes purulent and leucocytes degenerate, die, and 

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Lysosyme Serous cells, neutrophils, macrophages Gram positive bacteria Lyse gram positive bacteria via cleavage of peptidoglycan Decreased production after ozone exposure [121]... 

Figure 10.1 Typical tracheo-bronchial and bronchiolar epithelia showing the major cell types. The tracheo-bronchial epithelium showing the pseudostratified nature of the columnar epithelium, principally composed of ciliated cells (C), interspersed with goblet cells (G), brush cells (Br), serous cells (S), Kulchitsky s cells (K) and basal cells (B). The bronchiolar epithelium showing the cuboidal nature of the epithelium, principally composed of ciliated cells (C), Clara cells (Cl) and infrequent basal cells. Muc = mucus Ci = cilia N = nucleus Sec = secretory granules.

Calu-3 (American type culture collection ATCC HTB-55) is a human bronchial epithelial cell line derived from an adenocarcinoma of the lung [59], This cell line has been shown to exhibit serous cell properties and form confluent monolayers of mixed cell phenotypes, including ciliated and secretory cell types [60], but the cilia are formed very irregularly and seem to disappear with increasing passage number (unpublished observations, C.E. and B.F.). Calu-3 cells have shown utility as a model to examine transport [61-63] and metabolism in human bronchial epithelial cells for many therapeutic compounds [64], Furthermore, they have been used in a number of particlecell interaction studies [65-67], The interactions between respiratory epithelial cells and particulates are discussed more in detail in Chap. 19. 

Pepsin This acid-stable endopeptidase is secreted by the serous cells of the stomach as an inactive zymogen (or proenzyme), pepsinogen. In general, zymogens contain extra amino acids in... 

In the stomach, hydrochloric acid denatures dietary proteins, making them more susceptible to proteases. Pepsin, an enzyme secreted in zymogen form by the serous cells of the stomach, releases peptides and a few free amino acids from dietary proteins. 

Alio, J.-C., Midoux, P., Merten, M., Souil, E., Lipecka, J., Figarella, C. et al. (2000) Efficient gene transfer into human normal and cystic fibrosis tracheal gland serous cells with synthetic vectors. Am. J. Res. Cell Mol. Biol., 22, 166-175. 

The trachea and bronchi likewise have a protective function. Mucous and serous cells secrete fluids that together comprise the mucus, which is moved toward the pharynx by the cilia of the ciliated cells. The movement of mucus serves to move entrapped particles toward the pharynx where they are eliminated by swallowing or expectoration. The mucus may also have other protective functions, protecting the epithelial cells by free radical scavenging and antioxidant properties. The Clara cells are known to contain high concentrations of xenobiotic metabolizing enzymes. 

Conducting airways Trachea 0 20-18 Pseudostrati fled cell Ciliated cell Columnar cell Goblet cell Serous cell Mucous cell 20-40... 

Bronchioles, terminal bronchioles 12-16 1.0-0.4 Ciliated cuboidal cell Clara cell Serous cell 10... 

These are lined predominantly with ciliated and goblet cells. Some serous cells, brush cells and Clara cells are also present with few Kulchitsky cells. 

These are primarily lined with ciliated cuboidal cells. The frequency of goblet and serous cells decreases with progression along the airways while the number of Clara cells increases. The epithelium is much thinner and there is less mucus in this region. 

Sommerhoff, C.P., Caughey, G.H., Finkbeiner, W.E., Lazarus, S.C., Basbaum, C.B. and Nadel, J.A. (1989). Mast cell chymase. A potent secretagogue for airway gland serous cells. J. Immunol. 142, 2450-2456. 

Gashi, A.A., Borson, D.B., Finkbeiner, W.E. et al. (1986). Neuropeptides degranulate serous cells of ferret tracheal glands. Am. J. Physiol. 251, C223-229. 

Mesothelin is a 40-kD glycoprotein of unknown function that is strongly expressed in mesothelial cells, ovarian serous cells, and pancreatic-bile duct cells. Using monoclonal antibody 5B2, Ordonez found it to immu-nostain normal mesothelial cells, mesotheliomas, non-mucinous ovarian carcinomas, and occasionally other neoplasms. Ordonez concluded that mesothelin staining could be used to diagnose mesotheliomas, although it was expressed in 14 of 14 ovarian carcinomas, 12 of 14 pancreatic ductal adenocarcinomas, 7 of 12 desmoplastic small round cell tumors, and 9 of 9 synovial sarcomas. Therefore, this antibody should be interpreted carefully. 

Three of the cell types in the epithelium have secretory functions. These cells are the mucous (goblet) cells, serous cells, and Clara cells. These cells contribute to the secretion of airway mucus, a complex mixture of water, glycoproteins, immunoglobulins, lipids, and salts. The secretion of mucus is a defense function that contributes to the removal of foreign objects from lung airways via the mucociliary transport process, as described in later sections of this chapter. Excess mucus secretion can be detrimental, however, since it can obstruct the movement of air through the airways and is a component of certain pulmonary diseases such as asthma, emphysema, chronic bronchitis, and cystic fibrosis. A hypertrophy of secretory cells in the epithelial layer of the airways is often characteristic of these diseases. 

The Clara cells, unlike the mucous and serous cells, are located predominantly in the smaller airways (e.g., the bronchioles). They are columnar in shape and appear to contain more abundant smooth endoplasmic than other... 

In the sheep, Mariassy and Plopper (1983) observed 6 distinct, granule-containing secretory cells 4 mucous cell categories (M1-M4), serous cells, and nonciliated bronchiolar (Clara) cells. 

Fig. 59. Five serous cells and a brush cell (B) from the tracheal epithelium (block 675) of an unmedicated 200 g male rat. On June 1, 1976 under pentobarbital anaesthesia (30 mg/ kg), the animal was perfused from the abdominal aorta with 2.5 % glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4). Postfixation with 1 % osmium tetroxide in sodium cacodylate buffer. Embedded in Epon 812 and sectioned at 50 nm. Lead citrate and uranyl acetate. Plate 3301...

By electron microscopy the appearance of goblet cells in all species is sirriilar. The cell is distended by electron-lucent secretory granules. The granules are larger than those of the serous cell and sometimes have an electron-dense core. Each granule usually has an incomplete membrane and there is fusion between them. The cytoplasm is electron dense, and like the serous cell, the nucleus irregular in outline. 

Fig. 75. A ciliated and a serous cell from the bronchiolar epithelium of a female white rat (breeder Winkelmann, Borchen-Kirchborchen) which inhaled micronized deptro-pine citrate and isoprenaline hydrochloride aa from a suspension type self-propelled aerosol (Medihaler). 12 Puffs/min were dispersed into a 164.5 1 box where the animals stayed for 15 min. 1 h later under methitural anaesthesia, the lung was fixed by intratracheal instillation of 2.5 % glutaraldehyde in phosphate buffer (pH 7.4) before opening the thorax. Postfix-ation with 1 % osmium tetroxide in phosphate buffer (pH 7.4). Contrasted en bloc for 12 h with 0.5 % uranyl acetate in 70% ethanol. Embedded in a 2 8 mixture of methyl and butyl methacrylate. Sectioned at 50 nm. Lead citrate after Reynolds (1963). Plate 52/03...

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