Small intestine mucosa

Mechanistic studies have shown that TBT and certain other forms of trialkyltin have two distinct modes of toxic action in vertebrates. On the one hand they act as inhibitors of oxidative phosphorylation in mitochondria (Aldridge and Street 1964). Inhibition is associated with repression of ATP synthesis, disturbance of ion transport across the mitochondrial membrane, and swelling of the membrane. Oxidative phosphorylation is a vital process in animals and plants, and so trialkyltin compounds act as wide-ranging biocides. Another mode of action involves the inhibition of forms of cytochrome P450, which was referred to earlier in connection with metabolism. This has been demonstrated in mammals, aquatic invertebrates and fish (Morcillo et al. 2004, Oberdorster 2002). TBTO has been shown to inhibit P450 activity in cells from various tissues of mammals, including liver, kidney, and small intestine mucosa, both in vivo and in vitro (Rosenberg and Drummond 1983, Environmental Health Criteria 116). 

Svensson M, Marsal J, Ericsson A, et al. CCL25 mediates the localization of recently activated CD8alphabeta(+) lymphocytes to the small-intestinal mucosa. J Clin Invest 2002 110 1113-1121. 

EE Sterchi, JF Woodley. Peptide hydrolases of the human small intestinal mucosa Distribution of activities between brush border membranes and cytosol. Clin Chim... 

Soergel, K. H., Whalen, G. E., Harris, f. A., Passive movement of water and sodium across the human small intestinal mucosa, J. Appl. 

Biopsy Small intestinal mucosa Normal Normal ladder" appearance Abnormal... 

In tropical sprue, gluten does not appear to play much part in relatively early cases, such as those studied in Hong Kong. There is evidence, however, that patients with chronic sprue of many years duration may show some improvement on a gluten-free diet (C2). This may be a secondary phenomenon, due to general reduction of the enzymes in the small intestinal mucosa other mucosal enzymes have been shown to be reduced or ineffective in these patients. The important question is whether such patients will still react to gluten when the mucous membrane is brought back to normal by appropriate therapy, if this can be achieved. The rehabilitation of a malnutritional state induced over a period of many years is an extremely complex problem. 

Shiner, M., Coeliac disease histopathological findings in the small intestinal mucosa studied by a peroral biopsy technique. Gut 1, 48-54 (1960). 

At the beginning of the 1990s, the general acceptance of Caco-2 cell monolayers as a model of the small intestinal mucosa caused a significant push toward the field of permeability testing [2, 43], For detailed information about the Caco-2 cell line, the reader is referred to Chap. 8. As a consequence, the pharmaceutical community became more aware that permeation through intestinal epithelia is oftentimes more sophisticated than mere diffusion through a lipophilic membrane. 

The intracellular localization of carboxylesterases is predominantly microsomal, the esterases being localized in the endoplasmic reticulum [73] [79] [93], They are either free in the lumen or loosely bound to the inner aspect of the membrane. The carboxylesterases in liver mitochondria are essentially identical to those of the microsomal fraction. In contrast, carboxylesterases of liver lysosomes are different, their isoelectric point being in the acidic range. Carboxylesterase activity is also found in the cytosolic fraction of liver and kidney. It has been suggested that cytosolic carboxylesterases are mere contaminants of the microsomal enzymes, but there is evidence that soluble esterases do not necessarily originate from the endoplasmic reticulum [94], In guinea pig liver, a specific cytosolic esterase has been identified that is capable of hydrolyzing acetylsalicylate and that differs from the microsomal enzyme. Also, microsomal and cytosolic enzymes have different electrophoretic properties [77]. Cytosolic and microsomal esterases in rat small intestinal mucosa are clearly different enzymes, since they hydrolyze rac-oxazepam acetate with opposite enantioselectivity [95], Consequently, studies of hydrolysis in hepatocytes reflect more closely the in vivo hepatic hydrolysis than subcellular fractions, since cytosolic and microsomal esterases can act in parallel. 

Lussier, C., Basora, N., Bouatrouss, Y., and Beaulieu, J.-F. (2000). Integrins as mediators of epithelial cell-matrix interactions in the human small intestinal mucosa. Microsc. Res. Tech. 51, 169-178. 

The colonic mucosa resembles the small intestinal mucosa with respect to the spectrum of metabolizing enzymes [26], However, the total metabolic capacity of the colonic wall is inferior, since the mucosal mass in the lower part of the intestine is several times smaller than in the upper part. But this may be more than offset by the high metabolic capacity foimd in the gut flora in the large intestine. 

One of the physiological mechanisms which can help poorly lipid-soluble molecules to cross the small intestinal mucosa is the process of active transport-molecules actively shuttled across the membrane, commonly riding on transporter molecules and moving through the expenditure of cellular energy. 

FA089 Platel, K., and K. Srinivasan. Influence of dietary spices or their active principles on digestive enzymes of small intestinal mucosa in rats. Int J Food Sci Nutrl996 47(1) 55-59. 

FU (12.5 mg/kg twice daily) plus chitosan (150, 375 and 750 mg/kg twice daily) inhibited the tumor growth as well as 5-FU alone. Chitosan (150 and 750 mg/kg twice daily) blocked the reduction of blood leukocyte number caused by 5-FU administration, and it prevented the injury of the small intestinal mucosa membrane and delayed the onset of diarrhea induced by 5-FU Fig. (1), Fig. (2) and Fig. (3) . Furthermore, chitosan (750 mg/kg twice daily) prevented the reduction of spleen weight induced by 5-FU in sarcoma 180-bearing mice Fig. (4) , and the reduction of lymphocyte, CD8+ and NK1.1.+ T cell numbers induced by 5-FU Fig. (5) . 

Fig. 8. The preventive effects of chitosan on doxorubicin-induced gastrointestinal toxicity in sarcoma 180-beanng mice, a) small intestine weight b) sucrase activity in small intestinal mucosa.

Enzymes required for fructose to enter intermediary metabolism, Fructose is first phosphorylated to fructose 1-phosphate by fructokinase, and then cleaved by aldolase B to dihydroxyacetone phosphate and glyceraldehyde. These enzymes are found in the liver, kidney, and small intestinal mucosa. 

Rat, small-intestinal mucosa Porcine, submaxillary mucin o-Fue-(l— 2) none 51... 

Hohn, P., Gabbert, H., and Wagner, R., Differentiation and aging of the rat intestinal mucosa. II. Morphological, enzyme histochemical and disc electrophoretic aspects of the aging of the small intestinal mucosa, Mech, Ageing Dev., 7, 217, 1978. 

Small intestine Mucosa, submucosa, muscularis Adsorbs food... 

In genetically susceptible individuals, ingestion of cereal prolamins from wheat, barley, rye, and possibly oats initiates an inflammatory disorder during which the small intestinal mucosa is damaged. This process is accompanied by malabsorption, activation of the intestinal immune system, and... 

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