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BackgroundEthanol (EtOH), one of the most widely consumed substances of abuse, can induce brain damage and neurodegeneration. EtOH is centrally metabolized into acetaldehyde, which has been shown to be responsible for some of the neurophysiological and cellular effects of EtOH. Although some of the consequences of chronic EtOH administration on cell oxidative status have been described, the mechanisms by which acute EtOH administration affects the brain's cellular oxidative status and the role of acetaldehyde remain to be elucidated in detail.MethodsSwiss CD‐I mice were pretreated with the acetaldehyde‐sequestering agent d‐penicillamine (DP; 75 mg/kg, i.p.) or the antioxidant lipoic acid (LA; 50 mg/kg, i.p.) 30 minutes before EtOH (2.5 g/kg, i.p.) administration. Animals were sacrificed 30 minutes after EtOH injection. Glutathione peroxidase (GPx) mRNA levels; GPx and glutathione reductase (GR) enzymatic activities; reduced glutathione (GSH), glutathione disulfide (GSSG), glutamate, g‐L‐glutamyl‐L‐cysteine (Glut‐Cys), and malondialdehyde (MDA) concentrations; and protein carbonyl group (CG) content were determined in whole‐brain samples.ResultsAcute EtOH administration enhanced GPx activity and the GSH/GSSG ratio, while it decreased GR activity and GSSG concentration. Pretreatment with DP or LA only prevented GPx activity changes induced by EtOH.ConclusionsAltogether, these results show the capacity of a single dose of EtOH to unbalance cellular oxidative homeostasis.

An assay for vesicle--vesicle fusion involving resonance energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl), the energy donor, and rhodamine, the energy acceptor, has been developed. The two fluorophores are coupled to the free amino group of phosphatidylethanolamine to provide analogues which can be incorporated into a lipid vesicle bilayer. When both fluorescent lipids are in phosphatidylserine vesicles at appropriate surface densities (ratio of fluorescent lipid to total lipid), efficient energy transfer is observed. When such vesicles are fused with a population of pure phosphatidylserine vesicles by the addition of calcium, the two probes mix with the other lipids present to form a new membrane. This mixing reduces the surface density of the energy acceptor resulting in a decreased efficiency of resonance energy transfer which is measured experimentally. These changes in transfer efficiency allow kinetic and quantitative measurements of the fusion process. Using this system, we have studied the ability of phosphatidylcholine, phosphatidylserine, and phosphatidylcholine--phosphatidylserine (1:1) vesicles to fuse with cultured fibroblasts. Under the conditions employed, the majority of the cellular uptake of vesicle lipid could be attributed to the adsorption of intact vesicles to the cell surface regardless of the composition of the vesicle bilayer.

1. We have investigated the effects of ethanethiol, methanethiol and dimethyl sulphide on some metabolic processes of isolated rat hepatocytes, isolated mitochondria from liver and brain and ox-heart submitochondrial particles. 2. Ethanethiol, but not dimethyl sulphide, inhibited both gluconeogenesis and ureogenesis from various substrates in rat hepatocytes, depressed cellular ATP content and caused an increased reduction of the mitochondria. 3. Ethanethiol inhibited respiration in isolated rat-liver mitochondria with several substrates, both in the presence of ADP and phosphate or in the presence of an uncoupling agent. Ethanethiol also inhibited respiration in isolated rat-brain mitochondria. Dimethyl sulphide was much less effective in inhibiting mitochondrial respiration. 4. In ox-heart submitochondrial particles ethanethiol inhibited electron transfer between cytochrome c and oxygen. 5. Purified cytochrome c oxidase was inhibited by ethanethiol in a non-competitive manner. 6. Methanethiol inhibited cytochrome c oxidase and was an effective inhibitor of mitochondrial electron transfer, both in liver and brain. 7. The difference in inhibitory properties between ethanethiol, methanethiol and dimethyl sulphide observed in our experiments coincides with the difference in potency to elicit coma in rats. We suggest that inhibition of mitochondrial electron transfer by mercaptans may be relevant to the mechanism by which energy production in brain is depressed during hepatic coma.