1. Portions of jejunal biopsy specimens from patients with coeliac disease were homogenized in isotonic sucrose solution and subjected to analytical subcellular fractionation by sucrose-densitygradient centrifugation.2. The activities and distribution of marker enzymes for the principal subcellular organelles were determined by highly sensitive enzymic microassays employing fluorigenic and radiolabelled substrates.3. In untreated coeliac disease the brush border showed decreased activities of five marker enzymes, which were reduced to up to one-eighth of control values. On sucrose density gradients the distinct brush-border peak at density 1.21 was replaced by a broad peak at density 1-16.4. Two out of three lysosomal enzymes showed increased activities and there was evidence of enhanced fragility of both lysosomes and peroxisomes.5. There were reduced activities of both mitochondria1 and cytosol malate dehydrogenase, with increased activities of cytosol lactate dehydrogenase.6. The endoplasmic reticulum and basal-lateral membranes were relatively unaffected except that the equilibrium densities were slightly increased and decreased respectively.

1. Homogenates of guinea-pig left ventricle were fractionated by differential pelleting and by centrifugation on continuous sucrose density gradients. 2. The principal subcellular organelles of myocardium, characterized by their marker enzyme content, were resolved by density gradient centrifugation in a small-volume zonal rotor. The equilibrium densities (p) of the principal organelles are (with marker enzymes in parentheses): sarcolemma, 1-12 (5'-nucleotidase); lysosomes, 1-16 (N-acetyl-beta-glucosaminidase); mitochondria, 1-17 (cytochrome oxidase); peroxisomes, 1-18 (catalase); cytosol (lactate dehydrogenase). 3. The subcellular distribution of various adenosine triphosphatase activities and previously unassigned enzymes was determined. Leucyl-beta-naphthylamidase and gamma-glutamyl transpeptidase showed both cytosol and sarcolemma components. Ca2+-dependent adenosine triphosphatase showed dual localization to the mitochondria and to the sarcolemma.

1. Jejunal biopsies from five patients with non-responsive coeliac disease have been subjected to analytical subcellular fractionation and enzymic microassay in order to compare the organelle pathology of this group with untreated but glutensensitive patients. 2. Compared with the gluten-sensitive group these non-responsive patients showed marked reduction of the endoplasmic reticulum enzymes, normal activities of lysosomal enzymes and slightly less severely reduced brush border activities. 3. It is suggested that the present biochemical studies in combination with previous clinical reports and measurements of DNA and protein synthesis by cultured mucosal biopsies delineate non-responsive coeliac disease as a distinct entity. 4. The patients were treated with oral prednisolone (20 mg daily) for between 5 and 9 weeks and the properties of the jejunal biopsies restudied. 5. Although morphologically there was only a partial restoration of the villus architecture the enzymic alterations and organelle abnormalities returned essentially to normal values.

1. Enterocytes, isolated from the proximal jejunum and distal ileum of normal and prednisolone-treated rats, were homogenized and fractionated by isopycnic centrifugation on sucrose density gradients. The distributions of marker enzymes for the principal subcellular organelles, RNA and protein were determined and related to the activities per enterocyte. 2. In enterocytes fromthe jejunum and ileum of prednisolone-treated animals the activities of particulate brush-border enzymes and of both soluble and mitochondrial malate dehydrogenase were increased compared with those of the control system. The equilibrium density of the brush borders was enhanced in the prednisolone-treated jejunum. The modal densities of the other organelles were unaltered by prednisolone administration. 3. There was a large increase in the total RNA content of enterocytes from the jejunum and ileum of prednisolone-treated animals. This was predominantly associated with a distinct particulate component, indicative of a proliferation of the rough endoplasmic reticulum and consistent with an enhanced rate of protein synthesis. 4. Studies of latent brush-border enzyme activities, the mechanical fragility of isolated brush borders and electron microscopy suggest that steroid administration results in no marked alterations in the gross conformation of the brush-border membrane or in the orientation of the enzymes within the membrane.

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