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Cellular magnesium acquisition : an anomaly in embryonic cation homeostasis

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Experimental and Molecular Pathology 83 (2007): 224-240, doi:10.1016/j.yexmp.2007.03.007.The intracellular dominance of magnesium ion makes clinical assessment difficult despite the critical role of Mg++ in many key functions of cells and enzymes. There is general consensus that serum Mg++ levels are not representative of the growing number of conditions for which magnesium is known to be important. There is no consensus method or sample source for testing for clinical purposes. High intracellular Mg++ in vertebrate embryos results in part from interactions of cations which influence cell membrane transport systems. These are functionally competent from the earliest stages, at least transiently held over from the unfertilized ovum. Kinetic studies with radiotracer cations, osmolar variations, media lacking one or more of the four biological cations, Na+, Mg++, K+, and Ca++, and metabolic poison 0.05 mEq/L NaF, demonstrated: (1) all four cations influence the behavior of the others, and (2) energy is required for uptake and efflux on different time scales, some against gradient. Na+ uptake is energy dependent against an efflux gradient. The rate of K+ loss is equal with or without fluoride, suggesting a lack of an energy requirement at these stages. Ca++ efflux took twice as long in the presence of fluoride, likely due in part to intracellular binding. Mg++ is anomalous in that early teleost vertebrate embryos have an intracellular content exceeding the surrounding sea water, an isolated unaffected yolk compartment, and a clear requirement for energy for both uptake and efflux. The physiological, pathological, and therapeutic roles of magnesium are poorly understood. This will change: (1) when 28Mg is once again generally available at a reasonable cost for both basic research and clinical assessment, and (2) when serum or plasma levels are determined simultaneously with intracellular values, preferably as part of complete four cation profiles. Atomic absorption spectrophotometry, energy-dispersive x-ray analysis, and inductively coupled plasma emission spectroscopy on sublingual mucosal and peripheral blood samples are potential methods of value for coordinated assessments.AEC Grant No. 134

Ueber die Zusammensetzung der Körperflüssigkeiten von Myxine glutinosa L.

Über die Zusammensetzung des Blutes und die Art der Osmoregulation bei Fischen liegen nur sehr vereinzelte Daten vor, und besonders ist über die Chemie der Körperflüssigkeiten bei Cyclostomaten bis jetzt nichts näheres bekannt. Man weiss nicht, ob diese Fische eine Isotonie der Körperflüssigkeiten gegen das Aussenmedium, wie die marinen Evertebraten, durch hohe Elektrolytenkonzentration aufrechterhalten, oder ob sie eine gewisse Hypotonie in Bezug auf Elektrolyte, wie die Elasmobranchier, durch eine erhöhte Harnstoffkonzentration bis an schwache Hypertonie kompensieren. Schliesslich besteht die Möglichkeit, dass sie sich an die marinen Teleostier anschliessen, deren Körperflüssigkeiten im Verhältnis zum Medium hypotonisch sind. Es wurden deshalb bei dieser Untersuchung die Körpersäfte von Myxine glutinosa L. auf Chlor und Harnstoff untersucht

INDEPENDENCE OF POST-FERTILIZATION RESPIRATION IN THE SEA-URCHIN EGG FROM THE LEVEL OF RESPIRATION BEFORE FERTILIZATION

Volume: 96Start Page: 117End Page: 12

DECLINE AND REFORM: A STUDY OF THE STATECRAFT ESSAYS OF KUNG TZU-CHEN.

Abstract not availabl