Calcium removal

In smooth muscle, myosin crossbridges have less myosin ATPase activity than those of skeletal muscle. As a result, the splitting of ATP that provides energy to "prime" the crossbridges, preparing them to interact with actin, is markedly reduced. Consequently, the rates of crossbridge cycling and tension development are slower. Furthermore, a slower rate of calcium removal causes the muscle to relax more slowly. 

Changes in heart rate also affect the contractility of the heart. As heart rate increases, so does ventricular contractility. The mechanism of this effect involves the gradual increase of intracellular calcium. When the electrical impulse stimulates the myocardial cell, permeability to calcium is increased and calcium enters the cell, allowing it to contract. Between beats, the calcium is removed from the intracellular fluid and the muscle relaxes. When heart rate is increased, periods of calcium influx occur more frequently and time for calcium removal is reduced. The net effect is an increase in intracellular calcium, an increased number of crossbridges cycling, and an increase in tension development. 

Removal of calcium from HRP C has a significant effect not only on enzyme activity and thermal stability, but also on the environment of the heme group. The calcium-depleted enzyme has optical, EPR, and H NMR spectra that are different from those of the native enzyme (211). Temperature dependence studies indicate that the heme iron exists as a thermal admixture of high- and low-spin states. Kinetic measurements at pH 7 show that ki, the rate constant for compound I formation, is only reduced marginally from 1.6 0.1 x 10 to 1.4 x lO M s , whereas k, the rate constant for compound II reduction, is reduced from 8.1 1.6 x 10 to 3.6 x lO M s (reducing substrate p-aminobenzoic acid), 44% of its initial value (211). There can be little doubt that this is the main reason for the loss of enzyme activity on calcium removal. 

Calcium removal, in contrast, involves destruction of the calcified structure in roro. There is no evidence that only particular structures arc resorhed, e g., those with tt given degree of mineralization. 

The concentration of lime used in the nixtamalization process is ten times in excess of the saturation point. After cooking and steeping, about 40% of the original calcium ion remains in the lime water suspension. Of the 60% of calcium removed, about one-third is associated with the... 

Apart from the phosphorylation theory, other regulatory mechanisms have also been suggested for smooth muscle contraction. A thin-filament protein that has been proposed as a regulatory component is caldesmon [102], Purified caldesmon is a potent inhibitor of actin-tropomyosin interaction with myosin. The mechanisms by which calcium removes this inhibition are controversial. Furthermore, phosphorylation of caldesmon by a caldesmon kinase in vitro has also been implicated in this... 

The new process includes an upstream nanofiltration twofold pre-concentration step. Thereafter, the regular process including an UF concentration step to achieve the final dry matter value follows. In this case, however, the calcium losses into the serum are much lower as compared to the conventional process, because the final concentration step only has to remove a small amount of serum including the ionic calcium. The final UF step, that is, a partial calcium removal is still necessary to prevent the product to assume a bitter taste during shelf-life. 

The other method of calcium removal involves the case when the hardness is in the form of the noncarbonate, such as in the form of CaCl2. In this case, a carbonate ion must be provided, whereupon Equation (10.9) will apply, precipitating calcium as calcium carbonate. The usual source of the carbonate ion is soda ash. 

Fraction of noncarbonate hardness of calcium removed Overall removal of the calcium hardness Overall removal of the magnesium hardness Fraction of Ca(HC03)2 removed... 

Mass of noncarbonate hardness of calcium removed Mass of calcium carbonate solids produced from the precipitation of the noncarbonate hardness of calcium Mass of calcium carbonate solid produced from the calcium bicarbonate removed... 

In the method described in [35], the seawater, after calcium removal by adsorption on zeolites, is passed at a high flow rate through one of the sections of the countercurrent column filled with KB-4 resin. At the same time, the exhausted part of the resin bed, containing Mg ion, is eluted with HCl solution and finally with NaOH solution. The regenerated resin is directed back into the sorption seaion and the cycle continues. 

Specimen tubes should be centrifuged with stoppers in place. Closure reduces evaporation, which occurs rapidly in a warm centrifuge with the air currents set up by centrifugation. Stoppers also prevent aerosolization of infectious particles. Specimen tubes containing volatiles, such as ethanol, must be stoppered while they are spun. Centrifuging specimens with the stopper in place maintains anaerobic conditions, which are important in the measurement of carbon dioxide and ionized calcium. Removal of the stopper before centrifugation allows loss of carbon dioxide and an increase in blood pH. Control of pH is especially important for the enzymatic measurement of acid phosphatase, which is labile under alkaline conditions engendered by CO2 loss. Indeed, once the serum is separated for acid phosphatase tests, a tablet of disodium citrate should be added to stabilize the pH at about 6.2. 

Cows milk is more salty than milk from human mothers, and this limits its use in the preparation of infant formula. Desalting of cows milk by ED allows larger quantities of cows milk solids to be used for these purposes. Research has shown that desalting by ED to remove calcium improved the protein stability of frozen skim milk and its concentrates.7 The lumpy texture of thawed frozen milk has been attributed to clumping of micellar casein, and calcium removal led to the dissociation of micellar to serum casein. 

The resin, which is initially light in color, became dark brown in service as iron was picked up from the mild steel equipment and incoming sea water and retained. However, calcium removal capacity did not appreciably decline during the testing period. The iron is readily stripped by HC1 and the resin returned to its original color. 

This chosen calcium removal level was sufficient to keep the calcium concentration below that needed to prevent hemihydrate precipitation at the evaporator temperature. The evaporator was operated to maintain a constant vapor head pressure at zero-pound gage, which kept the brine at the atmospheric boiling point. 

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