Calcium specific needs

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

Clearly, the dosage of a calcium supplement must be determined by the specific needs of each individual. Excessive doses must also be avoided because they may produce symptoms of hypercalcemia, including constipation, drowsiness, fatigue, and headache. As hypercalcemia becomes more pronounced, confusion, irritability, cardiac arrhythmias, hypertension, nausea and vomiting, skin rashes, and pain in bones and muscle may occur. Hypercalcemia is a cause for concern because severe cardiac irregularities may prove fatal. 

Chapter 8 provides a review of the phosphate mineralogy that facilitates discussion on the applications discussed in the latter part of the book. The next five chapters discuss individual phosphate (magnesium, zinc, aluminum, iron, and calcium) ceramics that have potential for use in current and future applications. The approach provided in this book should guide researchers to many more formulations for specific needs in the future. 

The other form of calcium carbonate available to the alkaline papermaker is synthetically produced precipitated calcium carbonate (PCC). PCC is made from limestone that has reduced to lime in a rotary kiln, slaked to calcimn hydroxide then converted to calcium carbonate by reaction with CO2. PCC can be precipitated in many different crystal structures. The particle size and shape can be tailored to the customer s specific needs. 

Special purpose and blended Portland cements are manufactured essentially by the same processes as ordinary Portland cements but have specific compositional and process differences. White cements are made from raw materials of very low iron content. This type is often difficult to bum because almost the entire Hquid phase must be furnished by calcium aluminates. As a consequence of the generally lower total Hquid-phase content, high burning-zone temperatures may be necessary. Past cooling and occasionally oil sprays are needed to maintain both quaHty and color. 

While our data using this technique are still preliminary, we have observed that 25 yU/ml insulin inhibits the rate of calcium efflux from renal slices (28). This effect of insulin was gradually reduced at the higher concentrations of insulin. The effects of insulin on calcium exchange appear to be localized in the mitochondrial compartment. Further work is needed to determine whether insulin affects specific enzyme systems which are known to play a role in renal calcium transport, and which cellular or subcellular compartments are involved. This would substantially increase our understanding of the regulation of urinary calcium excretion, and of ways in which excessive loss of calcium by this route might be avoided. 

An interaction potential between the surface and ions may also be needed in simulating counterion diffusion for the smectite and mica surface models. The form of such an interaction potential remains to be determined. This may not pose a significant problem, since recent evidence (40) suggests that over 98% of the cations near smectite surfaces lie within the shear plane. For specifically adsorbed cations such as potassium or calcium, the surface-ion interactions can also be neglected if it is assumed that cation diffusion contributes little to the water structure. In simulating the interaction potential between counterions and interfacial water, a water-ion interaction potential similar to those already developed for MD simulations (41-43) could be specified. 

As is often the case, tissue-specific control mechanisms operate to optimise adaptation to particular conditions. For example, muscle contraction requires an increase in cytosolic calcium ion concentration (see Section 7.2.1, Figure 7.4). During exercise when energy generation needs to be increased, or from a more accurate metabolic point of view, when the ATP-to-ADP ratio falls rapidly, and the accompanying rise in [Ca2 + ] activate (i) glycogen phosphorylase which initates catabolism of... 

It is well recognized that interrelations exist. How much sodium one needs depends upon his potassium intake his calcium needs are determined in part by his phosphate intake his need for a specific amino acid may be determined in part by the amount of the other amino acids that he gets (they can interfere with each other s utilization). Only by further experimentation can we determine how important antagonisms and other interrelations are in human nutrition. If highly important, they will seriously complicate the picture but will not change its basic outlines. 

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