Immunohistochemical evidence for the expression and induction of paraoxonase in rat liver, kidney, lung and brain tissue. Implications for its physiological role.

Studies on the localization of paraoxonases (PON's) are of interest because of its involvement in both the detoxication of activated organophosphorus pesticides and in the prevention of peroxidative damage to phospholipids and cholesteryl-esters in LDL and HDL particles and cell membranes during the atherogenic process. In the present study, we have investigated the cellular localization of PON1 by immunohistochemistry in different rat tissues. The protein was mainly detected in the endothelial lining of every tissue studied (liver, kidney, lung and brain). Besides, it was found in hepatocytes from the centrolobular region of the liver, in the glomeruli and basal pole of the proximal convoluted tubule of the kidney, in cells from bronchiolar epithelium and type I pneumocytes of the lung, and in leptomeningeal cells, ependymal cells and ventricular side of choroid plexus cells of the brain. However, neurons and glia lacked immunostaining. After 3-methylcholanthrene induction an increase in the intensity of immunostaining was observed in the same areas, as well as an additional staining in midzonal hepatocytes. On the basis of the tissue distribution observed for PON1, it is proposed that this enzyme might have a function related to the inactivation of oxidative stress by-products (either at a cellular level or blood-vessel wall) and other environmental chemicals. At present it has not yet been established whether the paraoxonase detected in the various tissues is truly a product of the PON1 gene or could represent products of the PON2 or PON3 genes.

Characterization of glycoconjugates in the human cameral mucous gel by lectins.

A cameral mucous gel (CMG) has been described in human eyes lining the anterior and posterior ocular chambers. We assay a battery of 11 lectins to characterize the accessible sugars of the presumed glycoproteins and glycosaminoglycans present in the gel. Results show a predominance of alpha-linked sugars over beta-linked ones. There is evidence for the prominence in the gel of alpha-N-acetyl-D-galactosamine and/or alpha-D-galactose, together with alpha-N-acetyl-glucosamine. The second most important sugars are beta-N-acetyl-D-glucosamine and the dissacharide beta-D-galactose-N-acetyl-D-galactosamine. beta-N-acetyl-galactosamine could possibly be identified in third place. Neither fucose nor mannose are detected. These results point towards heparan and perlecan as possible components of the glycidic fraction of the gel, although a specific proteoglycan adapted to the osmotic role of the CMG is not at all unlikely.

A gel of glycosaminoglycans lining the anterior and posterior chambers in man: histochemical evidence at light and electron microscopy levels.

A thin mucous layer covers the ciliary body and iris epithelium and becomes thicker in the anterior chamber where it covers the anterior surface of the iris, the chamber angle and corneal endothelial surface. It is especially thick at the chamber angle, where it adopts a meniscus shape with the concavity towards the anterior chamber. Cetylpiridinium chloride along with glutaraldehyde was used to precipitate this layer of mucous substance lining the anterior and posterior chambers of the human eye. The staining of the precipitate by cationic dyes suggests that glycosaminoglycans are main components. The specific characterisation with anti-hyaluronic acid monoclonal antibody labelled with colloidal gold reveals the presence of hyaluronic acid in the precipitate. Long unbranched hyaluronic acid molecules may form the skeleton of a gel able to trap and hold virtually any other macromolecule suspended in the aqueous humour. A possible role of such a gel in the regulation of aqueous humour outflow is discussed.

Endocervical polyp with pseudosarcomatous pattern and cytoplasmic inclusions: an electron microscopic study.

A case of endocervical polyp with atypical stromal cells in a 32-year-old woman is reported. Light microscopy showed atypical stromal cells with eosinophilic cytoplasmic inclusions which, by electron microscopy, were nonmembrane-bound, compact fibrillary structures in close relationship with the cytoplasmic microfibrils. The ultrastructural features demonstrated a fibroblastic nature of bizarre cells. These inclusions are similar to those of infantile digital fibromatosis. These findings have not been reported previously.