University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Lithium inhibits caspase 3 activation and dephosphorylation of PKB and GSK3 induced by K+ deprivation in cerebellar granule cells

Abstract: Lithium protects cerebellar granule cells from apoptosis induced by low potassium, and also from other apoptotic stimuli. However, the precise mechanism by which this occurs is not understood. When cerebellar granule cells were switched to low potassium medium, the activation of caspase 3 was detected within 6 h, suggesting a role of caspase 3 in mediating apoptosis under conditions of low potassium. In the same conditions, lithium (5 mm) inhibited the activation of caspase 3 induced by low potassium. As lithium did not inhibit caspase 3 activity in vitro, these results suggest that this ion inhibits an upstream component that is required for caspase 3 activation. Lithium is known to inhibit a kinase termed glycogen sythase kinase 3 (GSK3), which is implicated in the survival pathway of phosphatidylinositol 3-kinase/protein kinase B (PI3K/PKB). Here we demonstrate that low potassium in the absence of lithium induces the dephosphorylation, and therefore the activation, of GSK3. However, when lithium was present, GSK3 remained phosphorylated at the same level as observed under conditions of high potassium. Low potassium induced the dephosphorylation and inactivation of PKB, whereas when lithium was present PKB was not dephosphorylated. Our results allow us to propose a new hypothesis about the action mechanism of lithium, this ion could inhibit a serine-threonine phosphatase induced by potassium deprivation.

Control of the common-mode component in CMOS continuous-time fully differential signal processing

Abstract: A general description of fully differential (FD) amplifiers with common-mode feedback (CMFB) network is carried out in this article. The general requirements that any CMFB loop must satisfy allow us to deduce three suitable figures of merit (linear interaction or conversion gain, relative performances and nonlinear interaction between the common-mode and differential-mode loops) in order to compare the different approaches. The gain or transconductance, sensitivity to mismatching in the devices, and nonlinearity for every common-mode (CM) signal detector block have been derived. By identifying all the input-output signal paths in a generic FD amplifier with CMFB, the conversion signals are quantified. From the gain of the detector and the technique used for injecting back the CM correction signal, the performances provided by the CMFB loops in regard to the differential-mode counterpart are evaluated. From the CM signal detector nonlinearity, it is shown how the CM loop impacts on the distortion (nonlinear interaction) on the amplifier. Finally, all the considerations are verified by means of simulations, and the CMFB networks classified according to these figures of merit. A low-distortion CMBF loop based on the current steering principle of injection is proposed as well.