Nicotinic receptor binding sites in rat primary neuronal cells in culture: characterization and their regulation by chronic nicotine.

We have characterized high affinity neuronal nicotinic acetylcholine receptors labeled by [3H]cytisine in primary neuronal cell cultures from fetal rat brains. After 15 days in culture, the highest density of [3H]cytisine binding sites (Bmax approximately 57 fmol/mg protein) was found in cells from the brainstem, which includes the following subcortical brain areas: the septum, thalamus, hypothalamus, midbrain, pons and medulla. A lower density of sites was found in cells from the cerebral cortex, hippocampus, and caudate nucleus. [3H]Cytisine binds to receptors in primary cells from the brainstem and cerebral cortex with a Kd of approximately 0. 5 nM, and the binding is inhibited by the agonists nicotine, acetylcholine, and epibatidine with IC50 values of 1 to 20 nM, and by carbachol and the antagonist dihydro-beta-erythroidine with IC50 values of 0.5 to 1.5 microM. Chronic treatment of neuronal cultures with nicotine for 7 days differentially affected the number of nicotinic receptors in cells from different brain areas; it significantly increased the number of nicotinic binding sites in cells from the cerebral cortex, hippocampus, and caudate, but not in cells from the brainstem. The nicotine-induced increase of receptors in cerebral cortical cultures was not blocked by either mecamylamine or dihydro-beta-erythroidine. These results indicate that primary cultures of rat neuronal cells provide a good model system in which to study and compare the properties and regulation of native neuronal nicotinic acetylcholine receptors.

Screening for pulmonary tuberculosis in HIV-infected individuals: AIDS Clinical Trials Group Protocol A5253.

BACKGROUND: Improved tuberculosis (TB) screening is urgently needed for human immunodeficiency virus (HIV) infected patients. METHODS: An observational, multi-country, cross-sectional study of HIV-infected patients to compare a standardized diagnostic evaluation (SDE) for TB with standard of care (SOC). SOC evaluations included TB symptom review (current cough, fever, night sweats and/or weight loss), sputum Ziehl-Neelsen staining and chest radiography. SDE screening added extended clinical signs and symptoms and fluorescent microscopy (FM). All participants underwent all evaluations. Mycobacterium tuberculosis on sputum culture was the primary outcome. RESULTS: A total of 801 participants were enrolled from Botswana, Malawi, South Africa, Zimbabwe, India, Peru and Brazil. The median age was 33 years; 37% were male, and median CD4 count was 275 cells/mm(3). Thirty-one participants (4%) had a positive culture on Löwenstein-Jensen media and 54 (8%) on MGIT. All but one positive culture came from sub-Saharan Africa, where the prevalence of TB was 54/445 (12%). SOC screening had 54% sensitivity (95%CI 40-67) and 76% specificity (95%CI 72-80). Positive and negative predictive values were respectively 24% and 92%. No elements of the SDE improved the predictive values of SOC. CONCLUSIONS: Symptom-based screening with smear microscopy was insufficiently sensitive. More sensitive diagnostic testing is required for HIV-infected patients.