Bone effect

Frolik CA, Black EC, Cain RL, et al. Anabolic and catabolic bone effects of human parathyroid hormone (1-34) are predicted by duration of hormone exposure. Bone. 2003 33 372-379. 

Bone effects were observed in children (Compere 1930a Phemister 1918 Sontag 1938) and young animals (Adams 1938a, 1938b Adams and Samat 1940 Whalen et al. 1973) following acute and intermediate oral exposure to white phosphorus. Because white phosphorus-related effects were observed in growing bones, these effects were considered developmental effects, and are discussed in Section 2.2.2.6. 

Whalen JP, O Donohue N, Krook L, et al. 1973. Pathogenesis of abnormal remodeling of bones Effects of yellow phosphorus in the growing rat. Anat Rec 177 15-22. 

Parathyroid hormone (PTH) is an 84-amino acid peptide secreted by the parathyroid glands, and is the principal regulator of extracellular calcium levels [44, 45]. The effects of PTH on extracellular calcium are mediated directly or indirectly through effects on bone, kidney, and intestine. A decrease in extracellular calcium causes an increase in PTH secretion. As a consequence, the rise in PTH levels causes increased bone resorption and the release of calcium from bone, decreased calcium excretion by the kidney, and increased intestinal calcium absorption. The therapeutic application of PTH has centered on the bone effects as an anabolic treatment for osteoporosis. PTH increases the activity of both osteoblasts (which form bone) and osteoclasts (which mediate bone resorption). The desirable anabolic effects of PTH on osteoblasts appear to be highly dependent on dose schedule and the duration of daily exposure. 

However, other isoenzymes of alkaline phosphatase are found in parts of the body such as bone, kidney, intestine and placenta, hence an isolated raised alkaline phosphatase may not be associated with liver dysfunction. In late pregnancy, alkaline phosphatase can increase to three times ULN, which may persist for several months after delivery, particularly if the mother is breastfeeding, owing to bone effects. In... 

Relationship between cadmium-induced renal and bone effects... 

Itai-itai disease is considered the most advanced stage of chronic Cd intoxication. Cadmium-induced bone effects are also suggested to occur in the more advanced stage. Originally, attention was focused on osteomalacia in the diagnosis of this disease. Recent studies, however, showed that osteopenia, a main characteristic of osteoporosis, can be detected in the early stage of chronic Cd intoxication. 

Out of these results, one may deduce that itai-itai disease only represents the tip of the iceberg. Indeed, in the earlier stage of chronic Cd exposure, the presence of Cd-induced bone effects such as osteopenia may be reflected by both microdensitometry and biochemical indices of bone turn-over. The degree of bone damage closely parallels the degree of renal damage. 

Based on the current knowledge obtained from both experimental and human studies, three different mechanisms might be active in development of Cd-induced bone effects. 

To date, however, no clear-cut data are available that inevitably present evidence for a particular mechanism underlying the development of Cd-induced bone effects in human subjects. 

Jarup L, Alfven T. Low level cadmium exposure, renal and bone effects—the OSCAR study. Biometals 2004 17(5) 505-9. 

Medical researchers are not limiting their studies to dairy products alone. A study published in the American Journal of Clinical Nutrition links high meat consumption to an increased rate of bone density loss and an increased incidence of fractures.32 Another study in the same journal found that cola consumption contributes to low bone-mineral density.33 Similarly, research published in Osteoporosis International links increased cola consumption with adverse bone effects and a possible increase in the risk of osteoporosis, even in the short term.34... 

Although estrogens increase bone mineral density and decrease fractures, they are no longer recommended for osteoporosis prevention because of toxicity concerns. When used to treat menopausal symptoms, they will have a positive bone effect. 

Adequate calcium and vitamin D intake (see Table 88-4) should be assured. For seniors with severe osteoporosis, a 25(OH) vitamin D concentration should be used to guide vitamin D supplementation. Centenarians have a particularly high rate of hypovitaminosis D. Smoking cessation and exercise begun late in life still have positive bone effects. 

Keyak, J. H., and Skinner, H. B. (1992), Three-dimensional finite element modelling of bone effects of element size, J. Biomed. Eng. 14(6) 483-489. 

Although the major effect of parathormone is to mobilize calcium from bone, effects on other organs have also been described. Whereas the effect of parathormone on calcium mobilization is independent of any action of the hormone on the kidney, the phospha-turic action of parathormone is likely to result from a direct effect of the hormone on tubular excretion of phosphate. Parathyroidectomy leads to a decrease in urinary excretion of phosphate, and parathormone administration increases phosphate excretion in rats. An effect on glomerular filtration of phosphate was excluded, but it was established that parathormone acts on the tubular excretion of phosphate. 

While strong evidence exists implicating cadmium as a major causative factor in itai-itai disease, other factors, such dietary deficiencies in minerals and vitamins, may have contributed to the disease (Tsuchiya 1978 Kjellstrom 1986). Serum la,25(OH)2-vitamin D concentrations were depressed in cadmium-exposed cohorts presenting with clinical nephropathy (Nogawa et al. 1987), which suggests that cadmium-induced bone effects may result from disruption of vitamin D and parathyroid hormone metabolism. Because kidney injury results from chronic cadmium exposure, a cadmium-related inhibition of the renal conversion of 25(OH)-vitamin D to la,25(OH)2 Vitamin D may lead to decreased calcium reabsorption, demineralization of bone, and eventually osteomalacia (Friberg et al. 1986). 

Finally, the effect of water cooled galleries close to the working face is shown in Figs. 9,10,12. The temperature in the centre of the pad face is reduced by about 20°C, but In addition, the bulk of the pad is at a nearly uniform temperature, which almost eliminates thermal distortion. The relatively large distance between the support arcs causes the centre of the pad to deflect, which gives a "dog-bone" effect to the pressure field. 

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