Magnesium uptake

Godbold DL, Jentschke G. Aluminium accumulation in root cell walls coincides with inhibition of root growth hut not with inhibition of magnesium uptake in Norway spruce. Physiol Plant 1998 102 553-560. 

Chittendon, E.T., Watson, J. and Hodgson, L. 1967. Magnesium uptake by pastures and apple leaves from top-dressings of ground serpentine and dunite. New Zealand Journal of Agricultural Research 7 28-31. 

Investigation of the effect of seawater pH indicates that pH has a significant effect on magnesium uptake, with an observed decrease of —6 3% per 0.1 pH unit increase for G. bulloides and O. universa. Again assuming an Mg/Ca temperature response of 10% per °C (Section... 

Generally, the uptake of Mg2+ by root cells is much lower that the uptake rate of K+. In the presence of an excess of other cationic species, especially K+ and NH4, the uptake rate of magnesium can be greatly depressed. This competition can lead to Mg2+ deficiency in plants. In acid soils, magnesium uptake by plants is frequently low due to the increased levels of cationic A1 species, which also depresses the uptake of Mg2+. It has also been found that the appearance of Mn toxicity can be prevented by increasing the Mg2+ supply. 

The precautions stated are to avoid uptake of oxygen, nitrogen and other impurities which render the metal brittle the excess magnesium and magnesium chloride can be removed by volatilisation above 1300 K. 

Minerals and Ash. The water-soluble extract solids which iafuse from tea leaves contain 10—15% ash. The tea plant has been found to be rich in potassium (24) and contains significant quantities of calcium, magnesium (25), and aluminum (26). Tea beverages are also a significant source of fluoride (27), owing in part to the uptake of aluminum fluoride from soils (28,29). 

Agricultural Use. Citric acid and its ammonium salts are used to form soluble chelates of iron, copper, magnesium, manganese, and zinc micronutrients in Hquid fertilizers (97—103). Citric acid and citrate salts are used in animal feeds to form soluble, easily digestible chelates of essential metal nutrients, enhance feed flavor to increase food uptake, control gastric pH and improve feed efficiency. 

K+ has a role in substrate uptake and during effident exopolysaccharide synthesis, adequate supplies of this ion is essential for ensuring suffident intracellular carbon substrate is maintained. Other ions, such as phosphate and magnesium, have roles in the acylation of exopolysaccharides and influence their physical properties. 

Direct entry of alumina adjuvants through the skin may occur by the use of therapeutic vaccines, with a resultant transient uptake of aluminium in the brain (Redhead et al., 1992). The injection of talc (magnesium silicate)-containing drugs intended for oral consumption has been shown to induce progressive pulmonary fibrosis in drug abusers (Pare etal., 1989). 

Parathyroidectomy is a treatment of last resort for sHPT, but should be considered in patients with persistently elevated iPTH levels above 800 pg/mL (800 ng/L) that is refractory to medical therapy to lower serum calcium and/or phosphorus levels.39 A portion or all of the parathyroid tissue may be removed, and in some cases a portion of the parathyroid tissue may be transplanted into another site, usually the forearm. Bone turnover can be disrupted in patients undergoing parathyroidectomy whereby bone production outweighs bone resorption. The syndrome, known as hungry bone syndrome, is characterized by excessive uptake of calcium, phosphorus, and magnesium for bone production, leading to hypocalcemia, hypophosphatemia, and hypomagnesemia. Serum ionized calcium levels should be monitored frequently (every 4 to 6 hours for the first 48 to 72 hours) in patients receiving a parathyroidectomy. Calcium supplementation is usually necessary, administered IV initially, then orally (with vitamin D supplementation) once normal calcium levels are attained for several weeks to months after the procedure. 

The clay minerals carried by rivers into the ocean represent a net annual addition of 5.2 X 10 mEq of cation exchange capacity. Most of these exchange sites are occupied by calcivun. Within a few weeks to months following introduction into seawater, sodium, potassium, and magnesium displace most of the calcium. As shown in Table 21.7, this uptake removes a significant fraction of the river input of sodium, magnesium, and potassium. 

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