Mg/Ca and Sr/Ca ratios of ostracod valves from living species of Lake Geneva

The Mg/Ca and Sr/Ca ratios of living ostracods belonging to 15 different species and sampled monthly over a one year-cycle at five sites (2, 5, 13, 33, and 70 m water depths) in western Lake Geneva (Switzerland) are compared to the oxygen and carbon isotope compositions measured on the same samples as well as to the temperature and chemical composition of the water (δ18OH2O, δ13CDIC, Mg/CaH2O, and Sr/CaH2O) at the time of ostracod calcification. The results indicate that trace element incorporation varied at the species level, mainly because of the ecological and biological differences between the different species (life-cycle, (micro-)habitat preference, biomineralisation processes) and the control thereof on trace element incorporation of the ostracods. In littoral zones, the Mg/Ca and Sr/Ca of ostracod valves increase as temperature and Mg/Ca and Sr/Ca of water increase during spring and summer, hence reflecting mainly seasonal variations. However, given that for Lake Geneva the Mg/Ca and Sr/Ca of water also vary with temperature, it is not possible to distinguish the effects of temperature from those of changes in chemical composition of water on the trace element content in ostracod valves. Results support that both water temperature and water Mg/Ca and Sr/Ca ratios control the final trace element content of Cyprididae valves. In contrast, the trace element content of species living in deeper zones of the basin is influenced by variations in the chemical composition of the pore water for the infaunal species. Trace element content measured for these specimens cannot, therefore, be used to reconstruct the compositions of the water lake bottom. In addition, incorporation of Mg and Sr into the shell differs from one family, sub-family, or even species to the other. This suggests that the distinctive Mg and Sr partition coefcients for the analysed taxa result from different valve calcification strategies that may be phylogenetic.

Localization of the cannabinoid CB1 receptor and the 2-AG synthesizing (DAGLα) and degrading (MAGL, FAAH) enzymes in cells expressing the Ca(2+)-binding proteins calbindin, calretinin, and parvalbumin in the adult rat hippocampus.

The retrograde suppression of the synaptic transmission by the endocannabinoid sn-2-arachidonoylglycerol (2-AG) is mediated by the cannabinoid CB1 receptors and requires the elevation of intracellular Ca(2+) and the activation of specific 2-AG synthesizing (i.e., DAGLα) enzymes. However, the anatomical organization of the neuronal substrates that express 2-AG/CB1 signaling system-related molecules associated with selective Ca(2+)-binding proteins (CaBPs) is still unknown. For this purpose, we used double-label immunofluorescence and confocal laser scanning microscopy for the characterization of the expression of the 2-AG/CB1 signaling system (CB1 receptor, DAGLα, MAGL, and FAAH) and the CaBPs calbindin D28k, calretinin, and parvalbumin in the rat hippocampus. CB1, DAGLα, and MAGL labeling was mainly localized in fibers and neuropil, which were differentially organized depending on the hippocampal CaBPs-expressing cells. CB(+) 1 fiber terminals localized in all hippocampal principal cell layers were tightly attached to calbindin(+) cells (granular and pyramidal neurons), and calretinin(+) and parvalbumin(+) interneurons. DAGLα neuropil labeling was selectively found surrounding calbindin(+) principal cells in the dentate gyrus and CA1, and in the calretinin(+) and parvalbumin(+) interneurons in the pyramidal cell layers of the CA1/3 fields. MAGL(+) terminals were only observed around CA1 calbindin(+) pyramidal cells, CA1/3 calretinin(+) interneurons and CA3 parvalbumin(+) interneurons localized in the pyramidal cell layers. Interestingly, calbindin(+) pyramidal cells expressed FAAH specifically in the CA1 field. The identification of anatomically related-neuronal substrates that expressed 2-AG/CB1 signaling system and selective CaBPs should be considered when analyzing the cannabinoid signaling associated with hippocampal functions.