Chloride channel blockers suppress formation of engulfment pseudopodia in microglial cells.

BACKGROUND/AIMS: Phagocytosis depends on the formation of engulfment pseudopodia surrounding the target. We tested in microglia, monocyte-derived cells in the brain, whether a swelling-activated Cl(-)-current (I(Cl,swell)), required for global cell volume (CV) regulation, also contributes to local expansion and retraction of engulfment pseudopodia. METHODS: We used scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) to visualize and quantify the uptake of polystyrene microbeads (MBs) by microglial cells. Flow cytometry was used for cell volume measurments and I(Cl,swell) was measured by whole-cell patch clamp. RESULTS: We found that exposure of microglial BV-2 cells to MBs in Cl(-)-free extracellular solution attenuated MB uptake and that the Cl(-)-channel blockers DIOA, flufenamic acid, NPPB and DCPIB suppressed the uptake of MBs in BV-2 cells and in primary microglial cells. Microglial cells exposed to MBs in the presence of Cl(-) channel blockers failed to extend engulfment pseudopodia. We observed that cells containing at least three MBs revealed an about twofold increase in current density of I(Cl, swell) compared to cells without MB. Osmotic challenges to stimulate global CV regulation before exposure to MBs modulated phagocytosis. Pre-conditioning of cells in hypo- or hypertonic medium for 12-16 hours caused a decrease in MB uptake. CONCLUSION: These findings indicate that I(Cl,swell) contributes to formation of engulfment pseudopodia and participates in engulfment and particle uptake in microglial cells.

Cortisol titre increases with novelty of academic oral examinations.

OBJECTIVE: In the present study we evaluated whether intensity and novelty of oral academic examinations are reflected in saliva cortisol titre. DESIGN AND SETTING: 91 pupils completed questionnaires on sensation seeking according to Zuckerman as well as on stress coping strategies and rated their individual stress intensity upon minor oral examinations. 26 of these students donated saliva samples before as well as ten and 30 minutes after the examination to quantify cortisol using an immuno assay. Oral examinations during the school year, where students may re-adjust their grade on subsequent examinations, were regarded as minor oral examinations, whereas school exit examinations, where students do not have the chance to correct their grade anymore and may even risk a delay of several months in their academic career when they fail, were regarded as major examinations. RESULTS: Minor oral examinations revealed either a moderate, but significant, increase in saliva cortisol titre by 1.1 fold or did not have a significant impact on cortisol titre. In contrast, school exit exams elevated cortisol titre 5.2 fold. In minor oral examinations, moderate correlations between cortisol titre and subsets in sensation seeking and coping strategies, respectively, were identified. CONCLUSION: Intensity and novelty of an academic examination is significantly correlated to cortisol titre. Minor oral examinations, with little consequences on academic career, only have a minor impact on cortisol titre, whereas school exit examinations, which are novel to students and may have major consequences on the academic career, elicit a major increase in cortisol titre.