Bone treatment with calcium phosphates

Other target organs for the action of 1,25-dihydroxyvitamin D include the kidneys, bone, muscle,vwand skin. The hormone promotes reabsorption of both Ca2+ and inorganic phosphate by kidney tubules. In bone it binds to a specific receptor where it promotes the mobilization of calcium ions. This effect may result in part from stimulation of calcium-activated ATPase of the outer membrane of bone cells. Dissolution of bone also requires the presence of parathyroid hormone (PTH), the 83-residue hormone secreted by the parathyroid gland. In women past the age of menopause and in elderly men the production of 1,25-dihydroxyvitamin D decreases.w This may be a cause of the serious bone loss (osteoporosis) frequently observed. Treatment with 1,25-dihydroxyvitamin D3 or a synthetic analog seems to be helpful to such individuals. /Xy See also Chapter 30, Section A,5. 

J. J. Berzelius prepared lead phosphate by adding a soln. of lead acetate to a nitric acid soln. of bone-ash, and decomposed the lead phosphate by treatment with dil. sulphuric acid, and removed the last traces of lead by hydrogen sulphide and W. Odling treated a soln. of sodium phosphate in ice-cold water with lead acetate, and decomposed the washed precipitate suspended in water with hydrogen sulphide. The soln., freed from the precipitated lead sulphide, was evaporated to remove the hydrogen sulphide. J. Persoz digested the soln. of bone-ash with ferric or aluminium oxide, decomposed the precipitated phosphate with sulphuric acid, and afterwards extracted with phosphoric acid with alcohol. L. Thompson precipitated the lime by treating the calcium phosphate with oxalic acid. W. H. Ross and co-workers purified phosphoric acid by a process of fractional crystallization. 

When the concentration of phosphate in plasma rises to the level where precipitation of calcium phosphate occurs, ionic calcium is depressed and parathyroid stimulation follows. This stimulation is continuous and progressive because the parathyroids are unable to restore the calcium concentration to normal, and enormous enlargement of the parathyroids follows (N8). Continuing parathyroid overactivity makes the bones more soluble than calcium phosphate at pH 7.4 with the result that there is a continuous transfer of mineral from the skeleton (which develops osteitis fibrosa) to blood vessel walls and soft tissues in gaieral (which become calcified). Parathyroidectomy is the only logical treatment and this has been done by Stanbuiy et al. (S5). 

Paget s disease (Table 35.6) is characterized by excessive bone resorption, followed by replacement of the normally mineralized bone with soft, poorly mineralized tissue (20). It has been determined that the osteoclasts have an abnormal structure, are hyperactive, and are present at elevated levels (20). Patients afflicted with this painful condition often suffer from multiple compression fractures. Administration of calcitonin and oral calcium and phosphate supplements had been the treatment of choice until the bisphosphonate risedronate was approved by the U.S. Food and Drug Administration (FDA). Daily administration of risedronate results in a decreased rate of bone turnover and a decrease in the levels of serum alkaline phosphatase and urinary hydroxyproline, two biochemical markers of bone turnover (4,20). A significant advantage to treatment with the bisphosphonates is long-term suppression of the disease (20). Calcium supplementation, which often is necessary in these patients, must be dosed separately from risedronate, because calcium- and aluminum- or... 

Bone is a natural composite comprised of type I collagen and calcium phosphate minerals, of which nanocrystalline apatite is the main component [39, 40]. Certain osteoconductive bioceramics exert an effect on bone cell attachment and growth factor binding or release, and can accelerate the treatment of bone defects [41-43]. Polymer composite scaffolds can be produced, via electrospinning, which contain a specific amount of electrical charge in order to form non-woven fibrous meshes with fibre dimensions in the nano- to microscale [44-46]. 

Chapman, M.W., Bucholz, R., Cornell, C. 1997. Treatment of acute fractures with a collagen-calcium phosphate graft material. A randomized clinical trial. J Bone Joint Surg Am 79(4), 495-502. 

Lobenhoffer, P., Gerich, T., Witte, F. Tscheme, H. 2002. Use of an injectable calcium phosphate bone cement in the treatment of tibial plateau fracmres a prospective study of twenty-six cases with twenty-month mean follow-up. J Orthop Trauma 16(3), 143-149. 

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