Magnesium cation transporters

This transporter is selectively blocked by diuretic agents known as "loop" diuretics (see later in chapter). Although the Na+/K+/2Cr transporter is itself electrically neutral (two cations and two anions are cotransported), the action of the transporter contributes to excess K+ accumulation within the cell. Back diffusion of this K+ into the tubular lumen causes a lumen-positive electrical potential that provides the driving force for reabsorption of cations—including magnesium and calcium—via the paracellular pathway. Thus, inhibition of salt transport in the TAL by loop diuretics, which reduces the lumen-positive potential, causes an increase in urinary excretion of divalent cations in addition to NaCI. 

From a pharmaceutical perspective, phospholipids-stabilized emulsions are remarkable. For example, they are relatively stable, with shelf lives of 18 months to 2 years being obtained after the initial heat sterilization. They resist the increased shear rates as the bottles are transported from producer to user and they can tolerate the addition of a wide variety of monovalent electrolytes for at least short periods prior to administration. However, they cannot resist freezing and changes in droplet size following exposure to freeze-thaw cycles can be used as a measure of the stability of the emulsion system. Most injectable emulsions are sensitive to multivalent cations such as calcium or magnesium salts, which rapidly flocculate the phospholipids-stabilized systems. 

Magnesium is an activator of more enzymes than any other element. It is an essential constituent of chlorophyll where about 2.7% of the weight of the chlorophyll molecule is magnesium. It is also involved in ion transport and cation balance in... 

This is the case for magnesium and calcium electrodes whose cations are bivalent. The surface films formed on such metals in a wide variety of polar aprotic systems cannot transport the bivalent cations. Such electrodes are blocked for the metal deposition [28-30], However, anodic processes may occur via the breakdown and repair mechanism. Due to the positive electric field, which is the driving force for the anodic processes, the film may be broken and cracked, allowing metal dissolution. Continuous metal dissolution creates an unstable situation in the metal-film and metal-solution interfaces and prevents the formation of stable passivating films. Thus, once the surface films are broken and a continuous electrical field is applied, continuous metal dissolution may take place at a relatively low overpotential (compared with the high overpotential required for the initial breakdown of the surface films). Typical examples are calcium dissolution processes in several polar aprotic systems [31]. 

Alterations in magnesium-controlled, monovalent cation permeability pathway Inhibition of calcium transport Formation of hydrogen peroxide... 

Quantifying the sources and rates of input of base cation nutrients (calcium, magnesium, potassium, and sodium) to forest ecosystems is an important goal in forest biogeochemistry, particularly when seeking to understand the recovery from environmental disturbances such as acid rain and forest clear-cutting. The earliest study to use isotopes as an indicator of atmospheric inputs to soils was by Dymond et al. (1974), who used strontium isotope measurements of micas in Hawaiian soils to determine that a significant proportion of the potassium input to Hawaiian soils was from deposition of dust transported... 

Studies on the uptake of Ni by M. bryantii have demonstrated the presence of a highly specific uptake system with = 3.1 ji-mol dm. This pathway was not afiected by high levels of other metal cations, including Mg but with the exception of 00 . Transport of Ni is coupled to movement of protons. Usually uptake of Ni into bacteria occurs by the transport process for magnesium, not surprisingly in view of their similar ionic radii. It is appropriate, therefore, that an organism such as M. bryantii which has a specific requirement for Ni should have a specific transport system for its uptake. 

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