No abstract

Abbreviations used: GPx, glutathione peroxidase; IjB, inhibitory kappa B; NFjB, nuclear factor kappa B; nNOS, neuronal nitric oxide synthase; PB, phosphate buffer; TUNEL, transferase biotin-dUTP nick end labeling. AbstractDifferent mechanisms have been suggested for cocaine toxicity including an increase in oxidative stress but the association between oxidative status in the brain and cocaine induced-behaviour is poorly understood. Nuclear factor kappa B (NFjB) is a sensor of oxidative stress and participates in memory formation that could be involved in drug toxicity and addiction mechanisms. Therefore NFjB activity, oxidative stress, neuronal nitric oxide synthase (nNOS) activity, spatial learning and memory as well as the effect of topiramate, a previously proposed therapy for cocaine addiction, were evaluated in an experimental model of cocaine administration in rats. NFjB activity was decreased in the frontal cortex of cocaine treated rats, as well as GSH concentration and glutathione peroxidase activity in the hippocampus, whereas nNOS activity in the hippocampus was increased. Memory retrieval of experiences acquired prior to cocaine administration was impaired and negatively correlated with NFjB activity in the frontal cortex. In contrast, learning of new tasks was enhanced and correlated with the increase of nNOS activity and the decrease of glutathione peroxidase. These results provide evidence for a possible mechanistic role of oxidative and nitrosative stress and NFjB in the alterations induced by cocaine. Topiramate prevented all the alterations observed, showing novel neuroprotective properties.

Thermal processing of human milk implies a decrease in its antioxidant properties but, when necessary, high pasteurization should be the election method in terms of milk oxidative status.

Breastfeeding and human milk are widely accepted as optimal for human infants' nutrition. Nowadays lifestyle often makes it difficult to maintain or even initiate human lactation. This situation is mostly related to the workload of women away from home. New approaches are needed to enable maternal lactation under these circumstances. Human breastmilk storage for differed use is one possibility. The aim of this study was to assess changes in glutathione peroxidase (GPx) activity and in the concentration of the lipid peroxidation marker, malondialdehyde (MDA), when human milk was kept refrigerated or frozen. Thirty-two human milk samples were assayed for GPx activity and MDA concentration. Samples were divided in three aliquot portions, the first to be immediately analysed, the second to be refrigerated at 4 degrees C and analysed 24 h thereafter, and the third to be frozen at -20 degrees C and assayed after 10 days. GPx activity was significantly decreased in refrigerated and in frozen milk, when compared to their control samples. MDA was increased only in refrigerated milk but not in frozen samples. Thus, freezing seems better than refrigeration in order to prevent lipid peroxidation in stored human milk samples.

When breast milk extraction and storage is required before ingestion, it is important to establish the conditions that ensure the least losses in milk quality, like the antioxidant capacity. The present study evaluates glutathione peroxidase activity and malondialdehyde concentration of breast milk when stored frozen, comparing the effects of 2 temperatures (-20 degrees C and -80 degrees C) and different storage times (15, 30, and 60 days). The results indicate that freezing induces losses in the antioxidant properties of breast milk and that such losses increase with the duration of storage and differ in intensity according to the temperature. It is concluded that to maximally preserve the antioxidant properties of breast milk, it is advisable to store the latter at -80 degrees C for a period of less than 30 days, rather than for shorter time periods at the usual temperature of -20 degrees C.