Phosphate in bone

Parathyroid hormone is a single-chain polypeptide of 84 amino acids which is produced in the parathyroid glands. It increases serum calcium and decreases serum phosphate. In bone it promotes resorption of calcium. It indirectly increases osteoclastic activity by promoting the action of osteoblasts. It has been shown that in low doses PTH may even increase bone formation without stimulating bone resorption. In the kidney PTH increases resorption of calcium and it increases excretion of phosphate. An other important activity in the kidney is the enhanced synthesis of 1,25-dihydroxyvitamin D. An increased serum calcium level inhibits PTH secretion and increased serum phosphate decreases free serum calcium and thus stimulates PTH secretion. 

Meldrum, 2002), the elaborately shaped spicules in ascidians, and finely the sculpted coccolith shells in coccolithophores (Mann, 2001). For silica structure, the diatoms produce the most exquisite siliceous cell wall (Sumper and Brunner, 2006). Also the calcium phosphate in bone shows a highly regulated organization and arrangement. Interestingly, avians have two main biomineralization systems, one produces calcium carbonate for egg shell and the other produces calcium phosphate for bone (Bauerlein, 2000 Mann, 2001). 

Phosphate i.v. is quickly effective but lowers calcium by precipitating calcium phosphate in bone and soft tissues and inhibiting osteoclastic activity it should be used only when other methods have failed. 

Rey G, Shimizu M, GoUins B, Glimcher MJ (1990) Resolution-enhanced Fourier transform infrared spectroscopy study of the environment of phosphate ion in the early deposits of a solid phase of calcium phosphate in bone and enamel and their evolution with age. 1. Investigations in the V4-PO domain. Galcif Tissue Int 46 384-394... 

Calcium is an electrolyte in extracellular fluid and intracellular fluid and assists in nerve impulse transmission, blood clotting, muscle contraction, and formation of teeth and bone. Calcium combines with phosphate in bone and albumin in serum. 

The answer is b. (Murray, pp 505-626. Scriver, pp 4029-4240. Sack, pp 121—138. Wilson, pp 287-320.) Calcium ions and calcium deposits are virtually universal in the structure and function of living things. In humans, calcium ions are required lor the activity of many enzymes. Calcium is taken up Irom the gut in the presence ol lorms of vitamin D, such as cholecalciferol. Calcium is also primarily excreted through the intestine. When soluble, it is present as a divalent cation. When insoluble, it is found as hydroxyapatite (calcium phosphate) in bone. It is required by muscle cells for contraction and is sequestered into the sarcoplasmic reticulum during relaxation. It is actively transported by a calcium-ATPase across the sarcoplasmic reticulum. 

The phosphate buffer system consists of serum inorganic phosphate (3.5 to 5 mg/dL), intracellular organic phosphate, and calcium phosphate in bone. Extracellular phosphate is present only in low concentrations, so its usefulness as a buffer is limited however, as an intracellular buffer, phosphate is more useful. Calcium phosphate in bone is relatively inaccessible as a buffer, but prolonged metabolic acidosis will result in the release of phosphate from bone. 

In addition to an increase in serum urea and creatinine levels, uric acid and inorganic phosphate levels also increase in chronic renal failure. The increase in serum inorganic phosphate leads to deposition of calcium phosphate in bones, causing hypocalcemia. In the early stages of chronic renal failure, calcium levels are restored by the stimulation of parathyroid hormone. However, as the renal disease progresses, the ability of the kidney to hydroxylate vitamin D and thus convert it to the active form decreases, thereby affecting the uptake of calcium by the gut and thus perpetuating hypocalcemia. Serum alkaline phosphatase levels increase due to disordered bone metabolism. Loss of bicarbonate is seen in some patients with increased parathyroid hormone activity. 

The knowledge of the presence of calcium phosphates in bone (De Fourcroy et al., 1788 Parr, 1809 von Bibra, 1844), teeth (Davy, 1814), blood and milk (De Fourcroy, 1804), urine (De Fourcroy et al., 1788) as well as urinary and renal calculi (Colon, 1770 Pemberton, 1814) was solidly established by the early nineteenth century. Additional historic evidence for this has been painstakingly recorded by the prolific chronicler of calcium phosphates, Dorozhkin (2012), quoting no less than 279 references on the history of calcium phosphate research. Among these treasures there appears faint indication that several calcium phosphate phases, important for biomineralisation, were already known, suspected or suggested early on such as amorphous calcium phosphate, ACP (Brande and Taylor, 1863) and octacalcium phosphate, OCP as well as dicalcium phosphate dihydrate, DCPD (brushite) (Warington, 1866). 

Scheele was, of course, well aware of the source of urinous phosphorus, as it had been originally been reported by Henning Brand a century earlier (see the earlier essay in this book, p. 225). His friend Gahn had discovered calcium phosphate in bone and horn around 1769 or 1770. Scheele treated burned hartshorn with nitric acid, precipitated gypsum with sulfuric acid, concentrated the filtrate and distilled the resulting phosphoric acid over charcoal, and collected the resulting phosphorus. ... 

In addition to drug delivery, collagen has been used in applications in the medical-pharmaceutical interface, including tissue engineering (i.e., composites of collagen with hydroxyapatite and tricalcium phosphate in bone grafts or as artificial valve and vessel substitutes) [417] and surgical sutures [418]. 

The toxicity of arsenic is very different in various compounds. The sulfides have, hke metallic arsenic, low toxicity. Scheele described the very toxic compounds arsenic oxide As Oj and arsenic(iii) hydride AsHj before 1775, thus at about the time he discovered hydrofluoric acid and phosphates in bones. These achievements made Scheele s name known in the whole chemical world. 

Topics under the practical importance of the alkaline-earth metals include their significance in living systems, the incidence of beryllium disease, radiochemical applications as components and residues of nuclear power, metallurgical uses in preparing pure metals and alloys, use in fireworks and X-ray technology, the definition and properties of hard water, and the role of calcium phosphate in bone and teeth structure. 

Dikanov SA, Liboiron BD, Thompson KH, Vera E, Yuen VG, McNeill JH, Orvig C. 1999. In vivo electron spin-echo envelope modulation (ESEEM) spectroscopy first observation of vanadyl coordination to phosphate in bone. J Am Chem Soc 121 11004-11005. 

Scheele Carl Wilhelm (1742-1786) Swed. chem., favored phlogiston theory, demonstrated presence of calcium phosphate in bones, discovered many new substances (oxygen, acids, toxic gases)... 

In the present authors laboratory, the studies focus on the preparation, assembly and appHcation of nano-calcium phosphate in biominerahzation and biomaterials, including the discovery of nano-calcium phosphate in bone and dental enamel, its stability within a biological miheu, biomimetic construction by using nano-calcium phosphates, and their application in biomaterials. 

Phosphorus is present in all the cells of the body. An adult body contains about 1 kg of phosphorus in the form of phosphates. About 75% of phosphorus is present in the form of calcium phosphate in bones and teeth while 10-20% of phosphorus is associated with carbohydrates, proteins and lipids in blood and muscles. Phosphorus is an essential constituent of ADP, ATP, phosphoproteins, phospho lipids, DNA, RNA, coenzyme NAD and NADP etc. present throughout the body. 

Ray, R.D. and Ward, A.A. (1951). A preliminary report on studies of basic calcium phosphate in bone replacement Surg. Forum 2 429-34. 

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