Degree Of Bone Mineralization Research Articles

Effects of variations in dietary calcium and phosphorus supply on plasma and bone osteocalcin concentrations and bone mineralization in growing pigs.

Growing pigs were fed diets supplying 45% (low), 70% (intermediate) and 100% (high) recommended dietary allowances of calcium (the Ca:P ratio was kept constant), but otherwise adequate in nutrients. The effects of varying calcium and phosphorus intakes on bone and plasma osteocalcin were monitored. Mineral content of the diet did not affect feed conversion and live weight gain. Plasma phosphorus concentrations decreased significantly in pigs fed a low mineral diet compared with those fed the high mineral diet, but there were no changes in plasma calcium and osteocalcin concentrations. Bones from the low mineral group had marked reductions in dry matter, calcium and phosphorus contents, as well as increased collagen, pyridinoline and deoxypyridinoline concentrations: osteocalcin concentrations in bone were unaffected by treatment. The results showed no direct link between osteocalcin and the degree of bone mineralization.

Effects of low-dose long-term sodium fluoride preventive treatment on rat bone mass and biomechanical properties.

Effects of fluoride on bone strength and cortical bone mass remain controversial. We compared 9-month, low-dose sodium fluoride (NaF) treatment with estrogen replacement therapy. Female Wistar rats 4.5 months old were divided into baseline, sham-operated (sham), sham-treated with NaF at 0.5 mg NaF/kg/day in drinking water, and ovariectomy (OVX), OVX treated with NaF and with estrogen. Bone mass was measured by dual X-ray absorptiometry (DXA) in vitro. Dimensions of the first lumbar vertebral body (L1) were determined by radiogrammetry. The right femur was processed undecalcified to obtain a midshaft cross-section to determine cross-sectional moments of inertia (CSMIs). L1 compressive test and left femoral torsional test were performed. OVX induced significant bone loss in L1 and femoral midshaft. Bone mass was increased to a greater extent in NaF-treated rats than in rats receiving estrogen replacement therapy. Femoral CSMIs in OVX rats, both L1 sizes and femoral CSMIs in NaF-treated rats, were significantly increased. Estrogen treatment had the least dimension expansion. OVX significantly decreased L1 compressive variables. There was no statistical difference in compressive parameters between NaF-treated groups and controls. OVX significantly increased femoral torsional strength but NaF treatment did not. Bone fluoride content was significantly increased after treatment with NaF. No significant difference in bone mineralization degree (ash and calcium) was found between treated and control rats. The discrepancy that an increase in bone mass and geometric properties in both trabecular and cortical bones by low-dose, long-term NaF treatment did not increase vertebral strength nor proportionally improve femoral strength indicated that the bone intrinsic biomechanical properties could be changed by NaF treatment.

Elevated bone phosphorus/hydroxyproline ratio following jejunoileal bypass surgery.

The degree of bone mineralization, estimated as the bone phosphorus/hydroxyproline ratio (P/Hypro), was studied in 33 patients who had undergone jejunoileal bypass surgery for massive obesity. Low values of bone P/Hypro are expected in osteomalacia. We found an elevated mean bone P/Hypro (p < 0.001) with the highest values in patients with the longest postoperative periods (rS = 0.65, p < 0.001). The study indicates that bypass surgery, in spite of vitamin D deficiency, is associated with an increased average degree of bone mineralization or a defect in bone collagen synthesis.

Bone mineralization and bone mineral content in primary hyperparathyroidism.

The degree of bone mineralization and the bone mineral content (BMC) was evaluated in 6 patients with primary hyperparathyroidism. The degree of bone mineralization was estimated as the phosphorus/hydroxyproline ratio (P/Hypro) in bone biopsies; BMC was estimated by photon absorptiometry on both forearms. The mena values of both parameters were significantly lower than normal (P less than 0.001 for P/Hypro; P less than 0.02 for BMC). As no significant correlation was found between P/Hypro and BMC in hyperparathyroidism, the findings of low values of P/Hypro and of BMC in patients with elevated serum calcium point to primary hyperparathyroidism.

The degree of bone mineralization in different parts of human skeleton estimated from bone phosphorus/hydroxyproline

The degree of bone mineralization in different parts of human skeleton estimated from bone phosphorus/hydroxyproline

Bone composition and parathyroid function in chronic renal failure.

The development of bone abnormalities has been studied in 24 patients with severe chronic renal failure. The glomerular filtration rate (GFR) was between 5 and 25 ml/min. The mean values of plasma calcium, degree of bone mineralization (P/Hypro) and bone mineral content (BMC) were subnormal, whereas the mean values of plasma phosphorus and serum parathyroid hormone (PTH) were elevated. Analysis of the data revealed that the various parameters became increasingly pathological with decreasing renal function. Serum PTH correlated inversely with both GFR and plasma calcium. The decrease in bone P/Hypro with decreasing renal function could be explained by an inverse correlation to serum PTH. Plasma alkaline phosphatase correlated inversely to both bone P/Hypro and BMC. The present study on individual patients with varying degrees of renal insufficiency shows that the development of secondary hyperparathyroidism correlates with a reduction in the degree of bone P/Hypro and suggests that significant bone changes appear when the GFR falls below 15 ml/min.

The degree of bone mineralization in different parts of human skeleton estimated from bone phosphorus/hydroxyproline

To evaluation the uniformity of the degree of mineralization in the skeleton the bone phosphorus/hydroxyproline ratio (bone P/Hypro) was determined in different localizations of ten human skeletons. Marked differences in bone P/Hypro were found between cortical bone and spongy bone. No difference was found between cortical bone from humerus, femur and cranium. But the mean value of these cortical bones was significantly higher than the mean value of the studied spongy bones. No significant correlation was found between the two bone types. Differences in bone P/Hypro were also found between different spongy bones. In pelvis the value did not differ between four spongy bone localizations but the mean value was significantly lower than for the other spongy bones (thoracal column, lumbal column and clavicle). Between these other spongy bones no difference was found in mean bone P/Hypro, and the mean of the pelvic bone localizations correlated significantly to the other spongy bones. The study demonstrates differences in the chemical composition of the human skeleton. A value of bone P/Hypro in the iliac crest can be used to estimation of bone P/Hypro in other spongy bones but not in cortical bones.

The degree of bone mineralization in hyperthyroidism estimated from the phosphorus to hydroxyproline ratio in bone.

The proportion between mineral and collagen in bone tissue, "the degree of mineralization", can be evaluated from the phosphorus to hydroxyproline ratio (P/Hypro ratio), determined in bone biopsies. The ratio was measured in 27 unselected hyperthyroid patients. No significant correlation was found between the P/Hypro ratio and the age of the patient, the duration of the disease or the value of serum thyroxine. The mean value of the P/Hypro ratio for the group studied was not significantly different from the normal mean. The results of the study indicate a normal degree of mineralization in the bone of patients with hyperthyroidism.

The degree of bone mineralization in chronic renal failure estimated from phosphorus/hydroxyproline ratio in bone biopsies.

The degree of bone mineralization is the proportion between the contents of mineral and collagen in bone. As phosphorus (P) and hydroxyproline (Hypro) constitute a constant fraction of bone mineral and collagen, respectively, the P/Hypro ratio in bone tissue provides an estimate of the degree of mineralization. The P/Hydro ratio has been studied in bone biopsies from 42 patients with severe chronic renal failure. A few of them had a subnormal P/Hypro ratio and these patients corresponded to the diagnosis of classical osteomalacia or probably hyperparathyroidism. However, the mean bone P/Hypro ratio was significantly higher than normal, indicating a general tendency towards a higher degree of bone mineralization in patients with chronic renal failure.

Effect of previous dietary history of calcium intake on the skeleton and calcium absorption in the rat.

1. Rats were fed either a high or a low calcium diet for 6 weeks. Thereafter all were given the low calcium diet, and the time during which differences persisted between the two groups in apparent absorption of calcium and urinary excretion of calcium has been studied. The apparent absorption of calcium is the same in the two groups after 15 days but the differences in urinary excretion of calcium persist longer.2. Faecal endogenous calcium and true absorption of calcium have been measured by an isotope dilution technique. The fall in apparent absorption of calcium seen in rats fed a high calcium diet is in part due to a fall in true absorption. Faecal endogenous calcium is also increased in these animals.3. The amount of calcium and phosphate in the bones is increased by feeding a high calcium diet and decreased by feeding a very low phosphate diet. Femur, humerus, caudal vertebrae and calvaria are equally affected by the different diets.4. There are strong inverse correlations between absorption of calcium and the percentage of calcium in the bones. This suggests that absorption of calcium may be regulated by the degree of bone mineralization.5. Rats were fed diets with different calcium phosphate ratios for 6 weeks. Thereafter all were given a low calcium diet with a calcium: phosphorous ratio of 1 and absorption and urinary excretion of calcium were studied. The effects of the different diets may be explained by their effect on calcium status and bone mineralization.