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Title: Studies on the brush border of the kidney proximal tubule
Author: Kramers, Mary Teresa Caroline
ISNI:       0000 0001 3602 3966
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1974
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The apical surface of the epithelial cells of the proximal tubule of the kidney is like many other absorptive or secretory cells, elaborated into a brush border composed of microvilli. The distinctive morphology of this region of plasma membrane is a feature which facilitates the isolation of these membranes in a pure form. The preparation of the brush borders is described and some of the biochemical characteristics have been established. Attempts to study the organisation of proteins within the brush borders were made using a variety of solubilising agents. Concentrated salt solutions released up to 40% of the membrane protein without concomitant release of brush border enzymes, antigens, phospholipid, cholesterol or carbohydrate. After such treatment the membrane appeared intact, but the core filaments were removed. Neutral detergents appeared to disrupt the membrane continuum, releasing maltase, trehalase, and leucine aminopeptidase, but lesser amounts of alkaline phosphatase. Some membrane phospholipid (principally the anionic classes), cholesterol, carbohydrate and antigens were also solubilised. Brush border core filaments and desmosomes were resistant to this treatment. Anionic detergents did not achieve selective extraction of brush border components but at high concentrations resulted in wholesale dissolution of the organelles. A proteolipid fraction which comprised 2% of the brush borders was isolated. Distinct subfractions of the brush border organelle were obtained by sequential extraction with 1% Triton X-100 followed by 2M NaCl. No difference in relative turnover of these subfractions was observed, although enzymic and immunologic investigations of the macro- molecular constituents from urine indicated that the selective loss of brush border components may occur via the urine. A protein, (molecular weight 44,500) derived from the core of the brush borders was purified by selective repolymerization and shown to possess structural but not functional properties similar to those of striated muscle actin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available