Ebselen protects glutamate uptake inhibition caused by methyl mercury but does not by Hg2+

Alterations of the neurotransmitter release systems in CNS have been reported in a variety of neuropathological processes associated with heavy metal toxicity. Neurotoxic effects of mercurials were investigated in vitro in cerebral cortex slices from young rats. The present study indicates that: (i) the environmental contaminants methylmercury (MeHg) and mercuric chloride (Hg2+) (50 microM) inhibited the glutamate net uptake from the cerebral cortex of 17-day-old rats; (ii) ebselen (10 microM) reverted the MeHg-induced inhibition of glutamate net uptake but did not protect the inhibition caused by Hg2+. At same time, we investigated another diorganochalcogenide, diphenyl diselenide (PhSe)2 and it was observed that this compound did not revert the action of MeHg or Hg2+; (iii) in addition, we observed that exposure of slices to 50 microM MeHg and Hg2+ for 30 min followed by Trypan blue exclusion assay resulted in 58.5 and 67.5% of staining cells, respectively, indicating a decrease in cell viability. Ebselen protected slices from the deleterious effects of MeHg, but not of Hg2+ on cell viability. Conversely, ebselen did not modify the reduction of MTT caused by MeHg and Hg2+; (iv) the protective effect of ebselen on MeHg-induced inhibition of glutamate net uptake seems to be related to its ability in maintaining cell viability.

Diminished concentration of the NF-H subunit of neurofilaments in cerebral cortex of rats chronically treated with proline, methylmalonate and phenylalanine plus alpha-methylphenylalanine

Wistar rats from the same litter were randomly divided into four groups and received subcutaneously from the 6th to 28th day post partum one of the following drugs: L-proline, methylmalonate, L-phenylalanine plus alpha-methylphenylalanine, or equivalent volumes of 0.9% (w/v) saline (controls). On day 30, the animals were killed, the brain was removed and the cerebral cortex and cerebellum was immediately dissected. Total intermediate filament fraction (IF) was obtained from cerebral cortex and cerebellum by using a high-salt phosphate-buffered solution supplemented by 1% Triton X-100. The pellet contained the bulk of the IF proteins. Following SDS-polyacrylamide gel electrophoresis, these proteins were identified as the 200, 150 and 68 kD subunits of neurofilaments (NF-H, NF-M and NF-L, respectively), the 66 kDa associated protein, the 57 kDa intermediate filament-like protein and the 52 kDa glial fibrillary acidic protein (GFAP). They were further scanned through densitometry from enriched fractions of controls and of animals treated with the various drugs in order to determine the effects of the treatments on their concentration. Our results showed that the concentration of IF protein in cerebellum was not affected by the treatments, whereas chronic administration of all drugs significantly decreased NF-H subunit concentration in rat cerebral cortex.

Malnutrition induces an increase in intermediate filament protein content of rat cerebral cortex

Wistar rats were fed a normal protein (25% casein) or an isoenergetic low protein (8% casein) diet from the day of giving birth until pups were weaned. Some litters were killed at weaning; others (both normal and malnourished animals) received the 25% protein diet until d 90 when they were killed. Intermediate filament (IF) preparations were obtained by extraction of the cerebral cortex with a high salt PBS solution containing 1% Triton X-100. The pellet contained the bulk of the cytoskeleton proteins from tissue, identified as the 150- and 68-kDa subunits of neurofilaments (NF-M and NF-L, respectively), the 66-kDa associated protein, the 57-kDa intermediate filament-like protein, and the 50-kDa glial fibrillary acidic protein. Intermediate filament-enriched fractions from control and malnourished rats at both d 21 and 90 were scanned following two-dimensional gel electrophoresis to determine the effects of postnatal malnutrition on the intermediate filament protein content. The results indicated that postnatal malnutrition imposed during the brain growth spurt period did not alter the expression of IF proteins of the cerebral cortex in 21-d-old rats, but increased the expression of NF-L and NF-M proteins in adult rats.

A network of 2-4 nm filaments found in sea urchin smooth muscle. Protein constituents and in situ localization

In this report the coisolation of two proteins from sea urchin smooth muscle of apparent molecular weights (Mr) 54 and 56 kD respectively, as determined on SDS-PAGE, is described. Like the intermediate filament proteins, these two proteins are insoluble in high ionic strength buffer solution. On two-dimensional gel electrophoresis and by immunological methods it is shown that these proteins are not related (by these criteria) to rat smooth muscle desmin (54 kD) or vimentin (56 kD). Furthermore, in conditions where both desmin and vimentin assemble in vitro into 10 nm filaments, the sea urchin smooth muscle proteins do not assemble into filaments. Ultrastructural studies on the sea urchin smooth muscle cell show that the thin and thick filaments organization resembles that described in the vertebrate smooth muscle. However, instead of 10 nm filaments, a network of filaments, 2-4 nm in diameter, is revealed, upon removal of the thin and thick filaments by 0.6 M KCl treatment. By indirect immunofluorescence microscopy, and in particular by immunocytochemical electron microscopy studies on the sea urchin smooth muscle cell, it is shown that the antibodies raised against both 54 and 56 kD proteins appear to specifically label these 2-4 nm filaments. These findings indicate that both the 54 and 56 kD proteins might be constituents of this category of filaments. The possible significance of this new cytoskeletal element, that we have named echinonematin filaments, is discussed.