The long-standing model of pigment cell origins is implicitly based upon a progressive fate restriction model of neural crest development and postulates the existence of a partially restricted progenitor common to all pigment cell types (i.e., a chromatoblast) [38] .
Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride.
Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Many sodium compounds are useful, such as sodium hydroxide (lye) for soap-making and sodium chloride for use as a de-icing agent and a nutrient (edible salt). Sodium is an essential element for all animals and some plants.Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure, and thus ECF compartment volume.odium /ËsoÊdiÉm/ is a chemical element with symbol Na (from New Latin natrium) and atomic number 11. It is a soft, silver-white, highly reactive metal.