Protection by prostaglandins from glutamate toxicity in cortical neurons.

The growing evidence that glutamate may be an important agent mediating ischemic damage to neurons, led us to investigate the possible protective effects of pharmacological agents against glutamate in a model system of cortical neurons. In this study we examined, in particular, the cytoprotective effect of prostaglandins. Experiments were carried out in vitro by using rat cortical neurons in culture for 10 days. They were incubated for 3h with glutamate (10 microM) in the presence or absence of various pharmacological agents including prostaglandins (PGD2, PGE1, PGE2, PGF2 alpha, PGI2, 6-Keto-PGF1 alpha, carba-TXA2, carba-PGI2 and PGF2 alpha-methylester). Increase in lacticodehydrogenase (LDH) release into the culture medium has been measured as an index of cell injury. When neurons were incubated with glutamate they released LDH due to NMDA-receptor activation since D-L-2-amino-5-phosphonovaleric acid, a specific receptor antagonist, protected the cells. The protective activity of oxypurinol, amflutizole, superoxide dismutase, NG nitro-L-arginine and quinacrine, also suggests that xanthine oxidase activation, the generation of superoxide radical, and nitrix oxide, as well as phospholipase A2 stimulation are responsible for neuron injury (i.e. LDH release). All the tested prostaglandins, except PGF2 alpha-methylester, afforded significant protection at concentrations between 0.1 and 10 microM. The order of potency of the prostanoids was: PGF2 alpha = PGE2 > Carba-TXA2 > PGE1 > PGD2 > PGI2 = Carba-PGI2 > 6-Keto-PGF1 alpha. Additional experiments showed that prostaglandins did not compete for the NMDA binding site and that they did not inhibit free radical-related membrane damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-dependent free radical generation in cultured retinal neurons injured by kainate.

Cultured rat retinal neurons exposed to kainate produced free radicals, as demonstrated by electron spin resonance (ESR) spin trapping using the nitrone 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and the generation of DMPO hydroxyl adduct (DMPO-OH). This DMPO-OH production was abolished by EGTA, nitro-arginine and oxypurinol, suggesting that it was dependent on Ca2+ influx and subsequent activation of nitric oxide synthase and xanthine oxidase. Moreover, kainate induced a receptor-mediated Ca2+ influx and neuronal injury assessed by lactate dehydrogenase release. Neuroprotection afforded by nitro-arginine and oxypurinol shows that calcium-dependent free radical production plays a major role in kainate retinal toxicity.

Trypanosoma cruzi: evaluation of a RAPD synapomorphic fragment as a species-specific DNA probe.

A methodological approach is proposed to select rapidly DNA sequences characterized by a well defined specificity and potentially interesting to be used as diagnostic probes or as taxonomic and phylogenetic markers. A fragment amplified from a diversified sample of Trypanosoma cruzi stocks by the RAPD (random amplified polymorphic DNA) method with the A8 primer, previously found to be monomorphic in all stocks, was separated in 2 fragments using polyacrylamide electrophoresis. RFLP (restriction fragment length polymorphism) analysis of the 750-bp fragment common to all stocks revealed some sequence heterogeneity within the T. cruzi species, whereas hybridization experiments showed a high homology between fragments amplified from different T. cruzi stocks. These results suggest that sequence analysis will allow the design of internal primers to be used as probes to target specific taxonomic levels (clone, family of related clones, or species) and for diagnosis.