Showing papers by "Joaquín Jordán published in 1996"

Superoxide production in rat hippocampal neurons: selective imaging with hydroethidine

Abstract: Digital-imaging microfluorimetry of the oxidation of hydroethidine (HEt) to ethidium can be used to monitor superoxide (O2-) production selectively within individual rat hippocampal pyramidal neurons in culture and in brain slices. Under assay conditions, oxidation was not accomplished by hydroxyl radical, singlet O2, H2O2, or nitrogen radicals. Neuronal O2- production varied with metabolic activity and age. O2- generation increased after treatment with AMPA, kainic acid, and NMDA, and the mitochondrial uncoupler carbonylcyanide p-(trifluoromethoxy)phenyl hydrazone, but usually not after depolarization (50 mM K+). O2- concentrations were sensitive to scavengers and nitric oxide. HEt oxidation was higher in Ca(2+)-containing versus Ca(2+)-free saline. However, Ca2+ ionophores did not increase oxidation greatly. H2O2 application produced a secondary increase in O2-. The major source of O2- under basal and stimulated conditions appeared to be the mitochondria. Consistent with this, ethidium staining in dendrites was punctate, colocalized with mitochondria, and blocked by CN-.

Protective effect of transforming growth factor-beta 1 on beta-amyloid neurotoxicity in rat hippocampal neurons.

Abstract: Neurodegeneration associated with Alzheimer's disease is believed to involve toxicity to beta-amyloid (A beta) and related peptides. Treatment of cultured rat hippocampal neurons with A beta 1-40 (1 microM) or the active fragment A beta 25-35 (1 microM) for 5 days led to a approximately 40-50% decrease in neuronal viability. The hydrophilic antioxidant ascorbic acid (300 microM) and the lipophilic antioxidant 2-mercaptoethanol (10 microM) both protected significantly against A beta neurotoxicity. Despite the protective effects of these antioxidants, both acute and chronic treatments with A beta 25-35 did not increase production of superoxide anions, as monitored with the fluorescent probe hydroethidine. Similarly, overexpression of Cu/Zn-superoxide dismutase using adenovirus-mediated gene transfer did not protect against A beta neurotoxicity. A beta neurotoxicity, however, was prevented in cultures infected with a recombinant, replication-defective adenovirus overexpressing the Ca2+ binding protein calbindin D28k. Transforming growth factor-beta 1 (TGF-beta 1) has been shown to protect neurons against both Ca(2+)- and free radical-mediated neuronal degeneration. We found that A beta neurotoxicity was significantly attenuated by single treatments with TGF-beta 1 (0.1-10 ng/ml) and prevented by repetitive treatments (10 ng/ml/day). The protective effects of TGF-beta 1 were associated with a preservation of mitochondrial potential and function, as determined with rhodamine-123-based microfluorimetry. Because both increased oxidative stress and pathophysiological Ca2+ fluxes can impair mitochondrial function, preservation of mitochondrial potential by TGF-beta 1 could be directly associated with its protection against A beta neurotoxicity. The ability of TGF-beta 1 to increase the expression of the anti-apoptotic proteins Bcl-2 and Bcl-XL is discussed in this context.

Influence of cephalosporins on intestinal enzymatic activity.

Abstract: The effect of the broad spectrum antibiotics cefaclor, cefadroxil, cephradine, cefatrizine, cephaloglycine and cefroxadine was examined on rat intestinal brush border enzymes, aminopeptidase N (E.C. 3.4.11-2), dipeptidyl peptidase IV (E.C. 3.4.14.5) and alkaline phosphatase (E.C. 1.3.1.3.). All the cephalosporins assayed -except cefaclor- inhibit the aminopeptidase N activity, in an uncompetitive manner. Cefatrizine showed the most important inhibitory effect (52.5%; p < 0.001). Cefaclor and cefadroxil have no effect on the activity of the dipeptidyl peptidase IV, while cephaloglycine and cephradine showed a non competitive type inhibition. In contrast, cefatrizine and cefroxadine showed a competitive inhibition for this enzyme. None of the cephalosporins assayed had any effect on alkaline phosphatase activity.