Water calcium concentration modifies whole-body calcium uptake in sea bream larvae during short-term adaptation to altered salinities

Whole-body calcium uptake was studied in gilthead sea bream larvae (9–83·mg) in response to changing environmental salinity and [Ca2+]. Calcium uptake increased with increased fish size and salinity. Fish exposed to calcium-enriched, diluted seawater showed increased calcium uptake compared with fish in diluted seawater alone. Calcium uptake was unchanged in Na+- enriched, diluted seawater. Overall, [Ca2+], and not salinity/osmolarity per se, appears to be the main factor contributing to calcium uptake. By contrast, drinking was reduced by a decrease in salinity/osmolarity but was little affected by external [Ca2+]. Calculations of the maximum contribution from drinking-associated calcium uptake showed that it became almost insignificant (less than 10%) through a strong decrease in drinking rate at low salinities (0–8‰). Diluted seawater enriched in calcium to the concentration present in full-strength seawater (i.e. constant calcium, decreasing salinity) restored intestinal calcium uptake to normal. Extra-intestinal calcium uptake also benefited from calcium addition but to a lesser extent

Surface charge, fluidity, and calcium uptake by rat intestinal brush-border vesicles

AbstractBiological membrane outer surfaces are negatively charged and interact with positively charged calcium ion during calcium uptake. Positively charged polycations such as polyarginine bind to membranes with high affinity, displacing bound calcium from the membrane. We tested the effect of polyarginine on uptake of calcium by brush-border membrane vecicles and examined the responses in terms of membrane fluidity by electron paramagnetic resonance (EPR). Polyarginine inhibited the saturable component of calcium uptake by a mechanism combining inhibition characteristics of strontium (competitive) and magnesium (non-competitive). Unlike the inhibition of non-saturable calcium uptake by strontium and magnesium, polyarginine increased kD, the rate constant for non-saturable calcium uptake, by a concentration dependent mechanism. These effects of polyarginine on calcium uptake were associated with decreased membrane fluidity at the uptake temperature. These findings are consistent with a role for surface negative charge in determining both saturable and non-saturable calcium uptake. Increased membrane fluidity is associated with decreased saturable and increased non-saturable calcium uptake. Although increased fluidity might be involved in the increased kD for non-saturable uptake, the concentration-specific stimulating effect of polyarginine suggests a gating mechanism

ER-mitochondria contacts: Actin dynamics at the ER control mitochondrial fission via calcium release.

The formin-like protein INF2 is an important player in the polymerization of actin filaments. In this issue, Chakrabarti et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201709111) demonstrate that INF2 mediates actin polymerization at the endoplasmic reticulum (ER), resulting in increased ER-mitochondria contacts, calcium uptake by mitochondria, and mitochondrial division

EFFECTS of FOUR RATES of THREE NITROGEN SOURCES on YIELD and CHEMICAL COMPOSITION of MANCHAR BROMEGRASS FORAGE in the MATANUSKA VALLEY

Paper copies available in Archives, Acc# 2013-0059List of Tables -- List of Figures -- Summary --Introduction -- Experimental Procedure -- Results and Discussion: Yield, Nitrogen Percentage, Nitrogen Uptake, Nitrogen Recovery, Phosphorus Percentages, Phosphorus Uptake, Phosphorus Recover, Potassium Percentages, Potassium Uptake, Potassium Recovery, Calcium Percentages, Calcium Uptake, Magnesium Percentages, Magnesium Uptake, Sodium Percentages and Uptake, Aluminum, Barium, Boron, Chromium, Copper, Iron, Manganese, Molybdenum, Strontium, Zinc -- Acknowledgment -- Literature Cite

Calcium uptake and Fruit Quality Improving calcium uptake in an 'organic' way

Die positive Korrelation zwischen einem hohen Kalziumgehalt in den Früchten und guter Qualität wird von der Literatur zusammengefasst. Die traditionellen Kalziumspritzungen sind nicht ideal (Synthetische Ursprung, Schalenberostung, Sonnebrand). Wir forschen nach Möglichkeiten für Obstbauern weniger abhängig zu sein von Kalziumchlorid und doch qualitatives Obst zu bekommen. Bei unserer Beurteilung der Kulturmaßnahmen in Bio Obstbau ist der Kalziumgehalt der Früchte eines der Kriterien. Positiv in diesem Rahmen haben sich gezeigt: ein lebendiger Boden, Begrünung, besonders Klee, Begrenzung des Wuchsniveaus, gute Qualität Rosettenblätter, Früchte an der Basis des Triebes und Früchte mit viele Samen

Cryo-EM structure of a fungal mitochondrial calcium uniporter.

The mitochondrial calcium uniporter (MCU) is a highly selective calcium channel localized to the inner mitochondrial membrane. Here, we describe the structure of an MCU orthologue from the fungus Neosartorya fischeri (NfMCU) determined to 3.8 Å resolution by phase-plate cryo-electron microscopy. The channel is a homotetramer with two-fold symmetry in its amino-terminal domain (NTD) that adopts a similar structure to that of human MCU. The NTD assembles as a dimer of dimers to form a tetrameric ring that connects to the transmembrane domain through an elongated coiled-coil domain. The ion-conducting pore domain maintains four-fold symmetry, with the selectivity filter positioned at the start of the pore-forming TM2 helix. The aspartate and glutamate sidechains of the conserved DIME motif are oriented towards the central axis and separated by one helical turn. The structure of NfMCU offers insights into channel assembly, selective calcium permeation, and inhibitor binding