Crosstalk between G-protein and Ca2+ pathways switches intracellular cAMP levels

Cyclic adenosine monophosphate and cyclic guanosine monophosphate are universal intracellular messengers whose concentrations are regulated by molecular networks comprised of different isoforms of the synthases adenylate cyclase or guanylate cyclase and the phosphodiesterases which degrade these compounds. In this paper, we employ a systems biology approach to develop mathematical models of these networks that, for the first time, take into account the different biochemical properties of the isoforms involved. To investigate the mechanisms underlying the joint regulation of cAMP and cGMP, we apply our models to analyse the regulation of cilia beat frequency in Paramecium by Ca(2+). Based on our analysis of these models, we propose that the diversity of isoform combinations that occurs in living cells provides an explanation for the huge variety of intracellular processes that are dependent on these networks. The inclusion of both G-protein receptor and Ca(2+)-dependent regulation of AC in our models allows us to propose a new explanation for the switching properties of G-protein subunits involved in nucleotide regulation. Analysis of the models suggests that, depending on whether the G-protein subunit is bound to AC, Ca(2+) can either activate or inhibit AC in a concentration-dependent manner. The resulting analysis provides an explanation for previous experimental results that showed that alterations in Ca(2+) concentrations can either increase or decrease cilia beat frequency over particular Ca(2+) concentration ranges

New half-life limits on the 2beta+ decay processes of Cd-106

The study of the 2beta+ decay of the 106Cd was performed at Gran Sasso National Laboratory. Two low-background NaI(Tl) crystals and enriched (68%) 106Cd samples (about 154 g) were used. New T_1/2 limits for the 2beta+, beta+EC, 2EC decay of 106Cd have been set in the range (0.3-4)x10^20 yr at 90% C.L. higher by a factor 6 to 60 than those already published

Quest for electron decay e^- -> neutrino_e + gamma with liquid Xenon scintillator

A new lifetime limit on the charge nonconserving (CNC) electron decay through the channel electron into neutino+gamma has been established analyzing a 2257.7 kg day event sample collected by the about 6.5 kg liquid xenon DAMA scintillator at the Gran Sasso National Laboratory of INFN. This limit is tau>2.0(3.4) x 10^{26} yr at 90% (68%) C.L., one order of magnitude higher than the current limit for that channel

Quest for electron decay e^- -> neutrino_e + gamma with liquid Xenon scintillator

A new lifetime limit on the charge nonconserving (CNC) electron decay through the channel electron into neutino+gamma has been established analyzing a 2257.7 kg day event sample collected by the about 6.5 kg liquid xenon DAMA scintillator at the Gran Sasso National Laboratory of INFN. This limit is tau>2.0(3.4) x 10^{26} yr at 90% (68%) C.L., one order of magnitude higher than the current limit for that channel

New limits on spin-dependent coupled WIMPs and on 2 beta processes in Ca-40 and Ca-46 by using low radioactive CaF2(Eu) crystal scintillators

The development of highly radio pure CaF2(Eu) crystal scintillators has been performed aiming at a substantial sensitivity enhancement of the 2 beta decay investigation and of the search for dark matter particles with spin-dependent (SD) interaction. The results of CaF2(Eu) background measurements and simulation are presented. New and highly improved T-1/2 limits on the 2 beta decay of Ca-46 and the double electron capture of Ca-40 are obtained as well as further results on SD coupled WIMPs. (C) 1999 Elsevier Science B.V. All rights reserved