Study of EEG and CT scan in neurologically normal cases of focal convulsions.

Twenty-three neurologically normal children with focal convulsions were studied with EEG and CT scan. Thirty-five per cent had an abnormal CT scan. Lesions of potential therapeutic significance were seen in 30 per cent of all scans. Abnormalities detected on CT scans were as follows: tuberculomas, five cases; acute infarct, one case; gliosis, one case; multiple cortical cysts, one case. All the cases with intracranial tuberculomas were aged more than 5 years. A good correlation was found between the EEG and the CT scan findings. Maximum percentage (57 per cent) of CT scan abnormality was seen in cases exhibiting focal abnormality on EEG and minimum percentage in those with a normal EEG (18 per cent).

Analysis of the neuroprotective effects of various nitric oxide donor compounds in murine mixed cortical cell culture.

Nitric oxide (NO) has been implicated in both the pathogenesis of and protection from NMDA receptor-mediated neuronal injury. This apparent paradox has been attributed to alternate redox states of nitrogen monoxide, whereby, depending on the redox milieu, nitrogen monoxide can be neuroprotective via nitrosation chemistry or react with superoxide to form secondary toxic species. In our murine mixed cortical cell culture system, the NONOate-type NO donors diethylamine/NO complex sodium (Dea/NO), (Z)-[N-(3-ammoniopropyl)-N-(n-propyl)amino]diazen-1-ium++ +-1,2-diolate (Papa/NO), and spermine/NO complex sodium (Sper/NO), as well as the S-nitrosothiols S-nitroso-L-glutathione (GSNO) and S-nitroso-N-acetyl-D,L-penicillamine (SNAP) (NO+ equivalents), decreased NMDA-induced neuronal injury in a concentration-dependent manner. 8-Bromo-cyclic GMP did not mimic the inhibitory effects of the donors, suggesting that the neuroprotection was not the result of NO-stimulated neuronal cyclic GMP production. Furthermore, neuronal injury induced by exposure of cultures to H2O2 was not altered by the presence of Dea/NO, indicating the absence of a direct antioxidant effect. NONOates did, however, reduce NMDA-stimulated uptake of 45Ca2+, whereas high potassium-induced 45Ca2+ accumulation, a measurement of entry via voltage-gated calcium channels, was unaffected. The parallel reduction of 45Ca2+ accumulation and NMDA neurotoxicity by NONOates mimicked that seen with an NMDA receptor antagonist. Electrochemical measurements of NO via an NO-sensitive electrode demonstrated that neuroprotective concentrations of all donors produced appreciable amounts of NO over the 5-min time frame. Determination of the formation of NO+ equivalents, as assessed by N-nitrosation of 2,3-diaminonaphthylene, revealed little or no observable N-nitrosation by Sper/NO, GSNO, and SNAP with significant N-nitrosation observed by Papa/NO and Dea/NO. However, addition of ascorbate (400 microM) effectively prevented the nitrosation of 2,3-diaminonaphthylene produced by Dea/NO and Papa/NO without altering their neuroprotective properties or their effects on 45Ca2+ accumulation. Present results indicate that the intrinsic NO/NO+ characteristics of NO donor compounds may not be a good predictor of their ability to inhibit NMDA receptor-mediated neurotoxicity at the cellular level.

Differential modulation of prostaglandin H synthase-2 by nitric oxide-related species in intact cells.

Nitrogen monoxide (NO) has been reported to both activate and inhibit prostaglandin (PG) biosynthesis. This apparent paradox might be explained by the production/action of distinct NO-related species formed as a result of the prevailing redox states of different cellular systems. As such, the effect of NO donors with different redox characteristics on the modulation of prostaglandin H synthase-2 (PGHS-2) in primary mouse cortical astrocytes and COS-7 cells engineered to overexpress PGHS-2 was assessed. In general, compounds that released NO(*) or NO(-) enhanced, while a peroxynitrite (OONO(-)) generator inhibited, PGHS-2-dependent prostaglandin production. While the possibility of altered gene transcription was eliminated in the COS-7 system as PGHS-2 was maximally expressed, in primary astrocytes where PGHS-2 expression was induced by lipopolysaccharide (LPS), effects on protein expression were detected. Compounds that released NO(*) synergistically enhanced LPS-mediated PGHS-2 protein synthesis. None of these effects were mediated by cGMP. All donors lost their ability to modulate PGHS-2 expression and function when decayed. These results indicate that the ultimate effect of NO on PGHS-2 enzyme activity and expression is dictated by the prevalent NO-related species formed, suggesting that important interactions which may exist between NO and prostanoid pathways in vivo will be highly dependent on the inherent redox environment.

Cyclooxygenase-2 contributes to N-methyl-D-aspartate-mediated neuronal cell death in primary cortical cell culture.

Cyclooxygenase isozymes (COX-1 and COX-2) are found to be constitutively expressed in brain, with neuronal expression of COX-2 being rapidly induced after numerous insults, including cerebral ischemia. Because overactivation of N-methyl-D-aspartate (NMDA) receptors has been implicated in the cell loss associated with ischemia, we characterized the expression of the COX isozymes in murine mixed cortical cell cultures and used isozyme-selective inhibitors to determine their relative contribution to NMDA receptor-stimulated prostaglandin (PG) production and excitotoxic neuronal cell death. Immunocytochemical analysis of mixed cortical cell cultures revealed that COX-2 expression was restricted to neurons, whereas COX-1 was expressed in both neurons and astrocytes. Brief exposure to NMDA (5 min; 100 microM) elicited a time-dependent accumulation of PGs in the culture medium that preceded neuronal cell death and correlated with the induction of COX-2 mRNA. COX-1 expression remained unchanged. Flurbiprofen, a nonselective COX-1/COX-2 inhibitor, blocked NMDA-stimulated PG production and attenuated neuronal death in a concentration-dependent manner. Similar results were obtained with the specific COX-2 inhibitor NS-398 (10-30 microM) but not with the selective COX-1 inhibitor valeryl salicylate (10-300 microM). Inhibition of total constitutive COX activity with aspirin (100 microM, 1.5 h) before NMDA exposure did not prevent subsequent NMDA-mediated neuronal cell death. However, neuronal injury in aspirin-pretreated cultures was attenuated by flurbiprofen administration after NMDA exposure. Finally, the protection afforded by COX-2 inhibition was specific for NMDA because neither flurbiprofen nor NS-398 protected neurons against kainate-mediated neurotoxicity. Together, these results support the conclusion that newly synthesized COX-2 protein contributes to NMDA-induced neuronal injury.