Epithelial membrane vesicle

The epithelial membrane of the GI tract consists of a continuous barrier of cells, which allows the transport of low-molecular-weight molecules by simple diffusion or various carrier processes. Macromolecules such as proteins may be absorbed from the intestinal lumen by cellular vesicular processes, through fluid-phase endocytosis (pinocytosis), or by receptor-mediated endocytosis or transcytosis (Fig. 6). In pinocytosis, extracellular fluid is captured within an epithelial membrane vesicle. It begins with the formation of a pocket... 

Biochemical studies of plasma membrane Na /H exchangers have been directed at two major goals (1) identification of amino acids that are involved in the transport mechanism and (2) identification and characterization of the transport pro-tein(s). To date, most studies have been performed on the amiloride-resistant form of Na /H" exchanger that is present in apical or brush border membrane vesicles from mammalian kidney, probably because of the relative abundance of transport activity in this starting material. However, some studies have also been performed on the amiloride-sensitive isoform present in non-epithelial cells. 

Other blockers of epithelial Cl -channels are of the aryl-amino-benzoate type or phenoxy-acetic-acid type [70]. Very few systematic surveys comparing different classes of blockers in one type of Cl -channel are available at this stage. One such study has been performed in membrane vesicles from kidney cortex [80]. In this study IAA-94 and NPPB (cf. Fig. 2) turned out to be the most potent blocker of conductive Cl -flux. In another systematic survey the Cl -conductance of the sweat duct was examined, and it was found that dichloro-DPC (Fig. 2) was the most potent inhibitor of the transepithelial Cl -conductance [90]. 

Inui, K., Saito, H. and Hori, R. (1985). H+ gradient-dependent active transport of tetaethyl-ammonium cation in apical-membrane vesicles isolated from kidney epithelial cell line LLC-PK Biochem. J. 227 199-203. 

INTESTINE Characterization of a membrane potassium ion conductance in intestinal secretory cells using whole cell patch-clamp and calcium-sensitive dye techniques, 192, 309 isolation of intestinal epithelial cells and evaluation of transport functions, 192, 324 isolation of enterocyte membranes, 192, 341 established intestinal cell lines as model systems for electrolyte transport studies, 192, 354 sodium chloride transport pathways in intestinal membrane vesicles, 192, 389 advantages and limitations of vesicles for the characterization and the kinetic analysis of transport systems, 192, 409 isolation and reconstitution of the sodium-de-pendent glucose transporter, 192, 438 calcium transport by intestinal epithelial cell basolateral membrane, 192, 448 electrical measurements in large intestine (including cecum, colon, rectum), 192, 459... 

Murer, H. Kinne, R. (1980). The use of isolated membrane vesicles to study epithelial transport processes. J. Memb. Biol. 55, 81-95. 

Kidney Uptake Blood Epithelial cells Kidney slices, isolated and cultured renal epithelial cells, basolateral membrane vesicles, transporter expressions system... 

Excretion Epithelial cells Urine Brush border membrane vesicles, transporter expression system... 

Small intestine Uptake Digestive tract Epithelial cells Everted sac, Ussing-chamber experiments using intestinal epithelium, brush border membrane vesicles, Caco-2 cells monolayer, transporter expression system... 

Primary cultured choroid epithelial cells, immortalized cell line Cell line, membrane vesicles Cell line, membrane vesicles... 

The lysosomal enzymes The lysosomes are membrane vesicles ubiquitous to mammalian cells and contain a panoply of hydrolytic enzymes, estimated to be over 60 in number, that function to digest practically any biological macromolecule. They are important to the discussion of oral macromolecular drug delivery for two reasons. First, any macromolecules that escape digestion by the pancreatic and brush border enzymes are likely to be taken up into the epithelial cells by the process of endocytosis. In this process, the apical membrane invaginates and the target molecules enter endocytic vesicles that then fuse with the lysosomes and are subjected to intracellular hydrolysis by the lysosomal enzymes. Second, the sloughing-off of the epithelial cells means that the lysosomal enzymes will be released into the lumen of the intestine. They may be... 

Inui K, Saito H,Takano M, OkanoT, Kitazawa S, Hori R. Enzyme activities and sodium-dependent active D-glucose transport in apical membrane vesicles isolated from kidney epithelial cell line (EEC-PK1). Biochim Biophys Acta 1984 769(2) 514-518. 

Caco-2Ceiis Brush Border Membrane Vesicles Epithelial Cell Model Isolated Intestinal Cells Non-Intestinal Cell Systems To determine mechanism an rate of drug passage arxl transport. 

Bianchi, J. Rose, R. C. 1985. Transport of L-ascorbic acid and dehydro-L-ascorbic acid across renal cortical basolateral membrane vesicles. Biochim. Biophys. Acta 820(2) 265-273. Bode, A. M. Yavarow, C. R. 1993. Enzymatic basis for altered ascorbic acid and dehydro-ascorbic acid levels in diabetes. Biochem. Biophys. Res. Commun. 191 1347-1353. Biondi, C. Pavan, B. Dalpiaz, A. Medici, S. Lunghi, L. Vesce, F. 2007. Expression and characterization of vitamin C transporter in the human trophoblast cell line HTR-8/ SVneo Effect of steroids, flavonoids, and NSAIDs. Mol. Hum. Reprod 13(1) 77-83. Boyer, J. C. Campbell, C. E. Sigurdson, W. J. Kuo, S. M. 2005. Polarized localization of vitamin C transporters, SVCTl and SVCT2, in epithelial cells. Biochem. Biophys. Res. Commun. 334 150-156. 

Attempts to study the entry of ES products into cells using markers of fluid phase endocytosis yielded unexpected results. When larvae browse resistant IEC-6 cells in the presence of extracellular fluorescent dextran, dextran enters the cytoplasm of a significant proportion of the cells in the mono-layer (Butcher et al., 2000). The parameters of dextran entry are most compatible with the conclusion that larvae wound the plasma membranes of IEC-6 cells that is, they create transient breaches in the membrane that allow impermeant markers to enter the cell (McNeil and Ito, 1989). Wounding is considered to be a common occurrence in intestinal epithelia (McNeil and Ito, 1989). Injured cells are able to heal their wounds by recruiting vesicles to seal the breach (Steinhardt et al., 1994). In an experimental system, healing allows the injured cell to retain cytoplasmic dextran. In epithelial cell cultures inoculated with T. spiralis larvae, the relationship between glycoprotein delivery and injury of plasma membranes is not clear, i.e. dextran-laden cells do not always stain with Tyv-specific antibodies and... 

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