Bone calcium

Four of the main-group cations are essential in human nutrition (Table A). Of these, the most important is Ca2+. About 90% of the calcium in the body is found in bones and teeth, largely in the form of hydroxyapatite, CatOH)2 - SCa PO. Calcium ions in bones and teeth exchange readily with those in the blood about 0.6 g of Ca2+ enters and leaves your bones every day. In a normal adult this exchange is in balance, but in elderly people, particularly women, there is sometimes a net loss of bone calcium, leading to the disease known as osteoporosis. 

Vitamin K Is Also Important in the Synthesis of Bone Calcium-Binding Proteins... 

The cations Mg and Ca are major components of bones. Calcium occurs as hydroxyapatite, a complicated substance whose chemical formula is Cas (P04)3 (OH). The structural form of magnesium in bones is not fully understood. In addition to being essential ingredients of bone, these two cations also play key roles in various biochemical reactions, including photosynthesis, the transmission of nerve impulses, and the formation of blood clots. 

Yamaguchi and Gao, 1998 Rat femoral-metaphyseal tissues cultured for 48 h with bone resorbing factors PTH, PGE2 or EPS) +/- genistein measured bone calcium content, acid and alkaline phosphatases Genistein (10 Yi O M) inhibited bone resorption. Effect reversed by anti-estrogen, tamoxifen. 

The rat has been used rather widely to study the relation between dietary protein, or acid salt feeding, and calcium loss. Barzel and Jowsey (19) showed that the rat fed a control diet supplemented with ammonium chloride excreted excessive urinary calcium, and experienced a concomitant loss of fat-free bone tissue. Draper, et al. (20) extending this work, reported an inverse relation between dietary phosphate and loss of bone calcium and dry, fat-free tissue. In subsequent studies (21), they reported that this process was accompanied by reduced serum calcium levels the high phosphorus, low calcium diet increased urinary calcium loss. Whereas, increasing the phosphorus content of the diet stopped the excessive urinary calcium loss. To test possible zinc loss that might result from this sort of acid salt feeding, Jacob and her coworkers (22) fed rats a supplement of ammonium chloride and then measured urinary zinc and calcium. The hypercalciuria occurred exclusive of an effect upon urinary zinc loss. 

These data about the effect of dietary protein and calcium loss are consistent with epidemiological evidence linking diet and bone calcium loss. Walker, et al. (6) reported fracture rates ten times greater among white South Africans eating a meat-rich European type diet than among the local Bantu who consumed a vegetarian diet. 

Figure 4. The effect of different ration levels of calcium (Cai = 0.3% and Ca2 = 1.27o) and phosphorus (Pi = 0.37> and P = 1 27>) on mice femur bone calcium. P-Ca-protein interaction P < 0.0001...

High levels of dietary zinc were associated with marked decreases in bone calcium deposition and in the apparent retention of calcium in male weanling albino rats. Marked increases in fecal calcium levels were also observed in the zinc-fed rats. Excessive dietary zinc was associated with a shifting of phosphorus excretion from the urine to the feces. This resulted in an increase in fecal phosphorus and provided an environmental condition which would increase the possibility of the formation of insoluble calcium phosphate salts and a subsequent decrease in calcium bioavailability. The adverse effect of high dietary zinc on calcium status in young rats could be alleviated and/or reversed with calcium supplements. 

Table II shows the effects of varying dietary levels of zinc on weight gains and on bone calcium and phosphorus levels of young rats at the end of a 4-week experiment. Increases in dietary zinc were associated with significant linear decreases in bone calcium and phosphorus deposition. The bones taken from animals at the time of sacrifice and used for the mineral analyses were very soft in nature and could be easily squeezed with the fingers.

Table IV shows data from another experiment in which the levels of calcium and phosphorus supplements were 0.4%, 0.8%, and 1.2%. Supplements of calcium resulted in significant Improvements in bone calcium levels of zinc-fed rats, whereas phosphorus supplements had little effect on bone calcium levels in zinc-fed rats. Increasing the calcium supplement from 0.4% to 0.8% resulted in additional increases in bone calcium deposition, and a level of 1.2% added calcium resulted in the same increase in bone calcium levels of rats fed 0.75% zinc as did the 0.8% calcium supplement. Mean bone calcium values of zinc-fed rats supplemented with either 0.4% calcium and phosphorus or 0.8% calcium and phosphorus were essentially the same as mean bone calcium values of zinc-fed rats supplemented with either 0.8% or 1.2% calcium. A combination supplement of 1.2% calcium and phosphorus was found to completely alleviate the decrease in bone calcium deposition associated with the feeding of a 0.75% level of zinc. Calcium supplements partially alleviated the decrease in bone phosphorus level associated with the feeding of the...

Liquid MD penetrates skin on contact. Prolonged skin exposure to its arsenic component will lead to systemic damage through bone calcium displacement and subsequent bone marrow destruction. In its traditional form, MD quickly disperses in open terrain but presents a more prolonged hazard in tightly closed buildings, where it concentrates in basements and substructures due to its vapor density.1... 

When the element calcium is mentioned, its function as a constituent of bone (and teeth) is likely to come to mind because most of the calcium of the body is in the bones. Calcium is, however, required for blood coagulation and is needed by muscle and other... 

In an effort to further elucidate the nature of Ca isotope fractionation in animals, Skulan and DePaolo (1999) studied tissues from living and recently deceased (naturally) organisms. For the four animals studied, it was found that bone calcium typically has 5 Ca that is 1.3%o lower than the value in the dietary calcium (Fig. 8). The soft tissue calcium, however, is quite variable, and has values closer to that of the dietary calcium. Skulan and DePaolo (1999) concluded that the primary source of Ca isotope fractionation was in the formation of bone, and that the 5 Ca values of soft tissue were variable in time and dependent on the immediate status of the Ca balance in the organisms. 

Figure 8. Calcium values in vertebrate bone and soft tissue samples versus 6 Ca in dietary source (Skulan and DePaolo 1999). Bone values are systematically about 1.3%o lower than source values. Soft tissue values are more variable. All of the values are hypothesized to reflect the balance between Ca dietary intake and exchange with bone calcium (Fig. 9). The soft tissue values are variable largely because the residence time of Ca in the tissues is short. The high value of the egg white reflects Rayleigh-type distillation the egg white loses light Ca to the shell as the shell forms. The small amount of Ca left in the egg white is highly fractionated. The low 6 Ca value of the seal muscle is interpreted as a sign of distress the seal may have had a dietary Ca deficiency for several days or longer before it died, and hence was deriving most of its Ca from bone dissolution.

Phosphorus homeostasis (see Section 5.2.1) is intimately involved with that of calcium. The most important reservoir of calcium and phosphorus within the mammalian body is in bone—85% of the body s calcium and 85-90% of phosphorus is found there. Ninety-nine percent of bone calcium remains in the mineral phase as Ca3(P04)2, and so on, but the other 1% can rapidly exchange with extracellular calcium. 

It is the divalent metal cation Ca + that is absolutely critical in human physiology. It is important both structurally and functionally. I noted above that hydroxyapatite, a phosphate salt of calcium, is an integral component of bone. As a component of bone, calcium is quantitatively one of the most abundant elements in higher organisms, such as humans. 

Hypercalcemia can be treated by (1) administering 0.9% NaCl solution plus furosemide (if necessary) renal excretion (2) the osteoclast inhibitors calcitonin, plicamycin, or clodro-nate (a bisphosphonate) bone calcium mobilization i (3) the Ca +chelators EDTA sodium or sodium citrate as well as (4) glucocorticoids. 

Abrams, S. A. (2006). Building bones in babies Can and should we exceed the human miUc-fed infant s rate of bone calcium accretion Nutr. Rev. 64,487-M94. 

Bone Calcium and phosphate resorption increased by high doses. Low doses may increase bone formation. Increased calcium and phosphate resorption by l,25(OH)2D bone formation may be increased by l,25(OH)2D and 24,25(OH)2D Decreased mineralization due to hypophosphatemia... 

Alaska pollack back bone Calcium bioavailability Jung et al. (2006)... 

Bones -calcium phosphates m PHOSPHORIC ACID AND PHOSPHATES] (Vol 18) -as mineral nutrient reservoir [MINERALNUTRIENTS] (Vol 16) -prosthetic and biomedical devices for PROSTHETIC AND BIOMEDICAL DEVICES] (Vol 20) -tetracycline m [ANTIBIOTICS - SURVEY] (Vol 2)... 

Selby PL, Peacock M. The effect of transdermal oestrogen on bone, calcium-regulating hormones and liver in postmenopausal women. Clin Endocrinol (Oxf) 1986 25(5) 543-7. 

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