Matrix-free calcium in isolated chromaffin vesicles

Isolated secretory vesicles from bovine adrenal medulla contain 80 nmol of Ca2+ and 25 nmol of Mg2+ per milligram of protein. As determined with a Ca2+-selective electrode, a further accumulation of about 160 nmol of Ca2+/mg of protein can be attained upon addition of the Ca2+ ionophore A23187. During this process protons are released from the vesicles, in exchange for Ca2+ ions, as indicated by the decrease of the pH in the incubation medium or the release of 9-aminoacridine previously taken up by the vesicles. Intravesicular Mg2+ is not released from the vesicles by A23 187, as determined by atomic emission spectroscopy. In the presence of N H Q , which causes the collapse of the secretory vesicle transmembrane proton gradient (ApH), Ca2+ uptake decreases. Under these conditions A23 187-mediated influx of Ca2+ and efflux of H+ cease at Ca2+ concentrations of about 4 pM. Below this concentration Ca2+ is even released from the vesicles. At the Ca2+ concentration at which no net flux of ions occurs the intravesicular matrix free Ca2+ equals the extravesicular free Ca2+. In the absence of NH4C1 we determined an intravesicular pH of 6.2. Under these conditions the Ca2+ influx ceases around 0.15 pM. From this value and the known pH across the vesicular membrane an intravesicular matrix free Ca2+ concentration of about 24 pM was calculated. This is within the same order of magnitude as the concentration of free Ca2+ in the vesicles determined in the presence of NH4C1. Calculation of the total Ca2+ present in the secretory vesicles gives an apparent intravesicular Ca2+ concentration of 40 mM, which is a factor of lo4 higher than the free intravesicular concentration of Ca2+. It can be concluded, therefore, that the concentration gradient of free Ca2+ across the secretory vesicle membrane in the intact chromaffin cells is probably small, which implies that less energy is required to accumulate and maintain Ca2+ within the vesicles than was previously anticipated

Budget Perspectives 2012. RESEARCH SERIES NUMBER 22 October 2011

The annual Budget Perspectives Conference, co‐hosted by the Economic and Social Research Institute (ESRI) and the Foundation for Fiscal Studies (FFS), provides a forum for discussing key public policy issues of both immediate and longer‐term concern. Against the current backdrop of major economic and fiscal challenges, budgetary policy must be seen to support Ireland’s return to a sustainable growth path. At a time when expenditure cuts are needed and more tax revenue must be generated, equity issues are of great importance to social solidarity. Research on the allocation of benefits and tax burdens allows these equity issues to be addressed systematically

An investigation into combined electroconvulsive and chlorpromazine therapy in the treatment of schizophrenia

No Abstrac

Challenges to Developing a Global Satellite Climate Monitoring System

Satellites are critical to the ability to understand and address climate change, due to their unique ability to provide comprehensive global monitoring of the environment. More than 30 nations have been involved in satellite Earth observations, with more than 200 satellite instruments operating in 2014 alone. However, gaps remain in the ability to adequately monitor global climate change, due in part to a lack of international consensus on the definition of an adequate monitoring system. This paper examines ongoing international efforts to identify the requirements of a global satellite climate monitoring system, including high-level efforts by the Global Climate Observing System (GCOS), the World Meteorological Organization (WMO), and the Committee on Earth Observing Satellites (CEOS), as well as efforts to define more detailed technical requirements being undertaken by GCOS, WMO, and the European Space Agency (ESA). Comparing the distinct processes and interim results of these groups highlights the lack of international consensus on the definition of an adequate global climate monitoring system. Developing such a system is a complex, multifaceted challenge, which requires expert technical knowledge of climate science and satellite capabilities as well as attention to political concerns for sovereignty and long-term international cooperation. The paper examines the adequacy of the current satellite monitoring capabilities by developing a comprehensive dataset including all unclassified Earth observation satellites operating or planned between 1990 and 2020. This analysis shows that within each international effort, gaps in the type of data collected are present. Even when some data is collected on a particular variable, it is not necessarily done in a way that meets technical requirements for climate assessment and forecasting. A lack of free and open data sharing compounds this challenge, further decreasing the amount of data contributing to international climate monitoring efforts. The lack of consensus on the requirements of a global climate monitoring system makes it difficult for nations to use international coordination mechanisms to plan and prioritize future satellite systems. The paper concludes by providing a series of recommended steps to improve harmonization among international efforts. This includes coordinating the bottom-up method used within GCOS with the top-down method used at WMO to identify concrete recommendations that will allow nations to prioritize investments that improve climate monitoring and/or improve the efficiency of the existing system. It recommends consolidating international efforts to define technical requirements to avoid duplication and facilitate prioritization among user groups with regard to which variables should be collected and what technical requirements must be met. A more systematic and integrated approach to system definition will make it possible for nations to shift and/or increase investments in satellite technology to better address agreed-upon needs and priorities