Neurochemical and electrophysiological evidence for the existence of a functional gamma-hydroxybutyrate system in NCB-20 neurons.

Clonal neurohybridoma NCB-20 cells express a valproate-insensitive succinic semialdehyde reductase activity that transforms succinic semialdehyde into gamma-hydroxybutyrate. This activity (1.14+/-0.16 nmol/min/mg protein) was similar to the lowest activity existing in adult rat brain. [3H]gamma-Hydroxybutyrate labels a homogeneous population of sites on NCB-20 cell membranes (Kd=250+/-44.4nM, Bmax=180+/-16.2fmol/mg protein) that apparently represents specific gamma-hydroxybutyrate binding sites characterized previously on brain cell membranes. Finally, an Na+-dependent uptake of [3H]gamma-hydroxybutyrate was expressed in NCB-20 cells with a Km of 35+21.1 microM and a Vmax of 80+/-14.2 pmol/min/mg protein. A three-day treatment with 1 mM dibutyryl-cyclic-AMP induced a three-fold increase in the cellular succinic semialdehyde reductase activity. In parallel, a K+-evoked release of [3H]gamma-hydroxybutyrate occurred. This release was Ca2+ dependent and was not present in undifferentiated cells. Cyclic-AMP treatment induced a decrease of [3H]gamma-hydroxybutyrate binding sites, which could be due to spontaneous gamma-hydroxybutyrate release. Patch-clamp experiments carried out on differentiated NCB-20 cells revealed the presence of Ca2+ conductances which were partially inhibited by 50 microM gamma-hydroxybutyrate. This gamma-hydroxybutyrate-induced effect was blocked by the gamma-hydroxybutyrate receptor antagonist NCS-382, but not by the GABA(B) antagonist CGP-55845. These results demonstrate the presence of an active gamma-hydroxybutyratergic system in NCB-20 cells which possesses the ability to release gamma-hydroxybutyrate. These cells express specific gamma-hydroxybutyrate receptors which modulate Ca2+ currents independently of GABA(B) receptors.

Detection of RAPD markers correlated with chloroquine resistance in Plasmodium falciparum.

We described the use of the random amplified polymorphic DNA (RAPD) technique on Plasmodium falciparum DNA to detect genetic markers for chloroquine-resistant strains. Fourteen RAPD primers were tested, three of which generated banding patterns correlated with chloroquine resistance. To measure this correlation, the RAPD profiles were analyzed using the Nei and Li similarity coefficient. Detection of distinctive RAPD bands allowed us to synthesize specific PCR primers to be used on whole-blood samples. Two primer sets were synthesized and tested on sensitive and resistant strains for their ability to amplify the DNA fragment corresponding to the RAPD marker. These results suggest that RAPD and PCR techniques can be used as powerful tools for the detection of genetic markers associated with drug resistance.

Lipid peroxidation in insulin-dependent diabetic patients with early retina degenerative lesions: effects of an oral zinc supplementation.

DESIGN: Placebo for 3 months, followed by 30 mg/day zinc gluconate in identical capsules. SETTING: Diabetic out patients clinic at the University Hospital, Grenoble. SUBJECTS: Diabetic patients cared for type I diabetes mellitus. 22 patients began the study, 4 dropped out. 10 patients suffered of an early retinopathy, 8 patients had no retinopathy. INTERVENTIONS: In this order: T0 biological measurements, 3 months placebo treatment, T1 biological measurements, 3 months zinc gluconate treatment, T2 biological measurements. Plasma Zn, Cu, Se, thiobarbituric acid reactants and antioxidant enzymes were measured [plasma and red glutathione peroxidase (Se-GPx), red cell superoxide dismutase (Cu-Zn-SOD)]. RESULTS: Lower plasma zinc level in the two groups. An increase in zinc level was observed and was more important in diabetic patients with no retinopathy (P = 0.05). The thiobarbituric acid reactants were above the reference values in all the patients, and were decreased at T2 (P < 0.05). Increase of GPx activity after zinc supplementation in patients with retinopathy. CONCLUSIONS: Zinc deficiency in insulin-dependent diabetic patients is corrected by a zinc supplementation. Moreover this supplementation decreases lipid peroxidation. The effects of zinc are different in diabetic patients with or without retinopathy. The increase in Se-GPx activity observed in patients with retinopathy could be linked to the protective effect of zinc on the protein itself.