Amount Of Bone Matrix Research Articles

Measurement of Estrogen Effect on Bone Turnover by 2H2O Labeling

Estrogen loss has been known to increase bone turnover through accelerated bone resorption coupled by increased bone formation. In the present study, we measured estrogen effect on bone turnover by incorporation of 2H from 2H2O into amino acids. At 6 weeks of age, rats were either sham-operated (sham) or ovariectomized (ovx). Two weeks after surgery, 17beta-estradiol (est) was implanted subcutaneously to ovx rats. At 9 weeks of age, 2H2O labeling started by administration of 4% 2H2O to rats for 4 or 7 weeks in drinking water after a single intraperitonial bolus injection with 99.9% 2H2O. Body 2H2O enrichments were stable at approximately 3.0% over labeling period. Fractional replacements (f) of the midshaft femur were higher in the sham group (40.36 +/- 4.89% vs 42.47 +/- 11.22%) than the ovx (28.57 +/- 9.67% vs 37.47 +/- 8.34%) and est (26.57 +/- 4.00% vs 30.35 +/- 5.34%) groups 4 and 7 weeks after labeling, respectively. Ovariectomy-induced bone loss was observed in the trabecular bone along with a significantly increased number of osteoclasts, all of which were normalized after estradiol treatment. Taken together, our results indicate that estrogen deficiency significantly reduces the proportion of newly synthesized bone matrix as well as the total amount of bone matrix. The reduced portion of new matrix in ovx rats, presumably caused by activated osteoclastic degradation, was compensated rapidly with time. In addition, estradiol treatment protected the bone matrix by decreasing bone turnover rate.

Theinnfluenceoof 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) on dental root resorption in the mouse

It has been hypothesized that phagocytosis of a layer of mineralized material which is sometimes deposited along the root surface following trauma is an important factor in the initiation of the resorption of teeth. To test this hypothesis, freezing of the mouse incisor periodontium was used as a model where deposition of mineral was prevented by the systemic administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP, 10 mg P/kg b.w.) for time periods varying from 2 to 31 days. The animals were killed either 24 hours or 1 month after the last injection and their mandibles were processed for light microscopy. In the HEBP-treated animals, killed 24 hours after the last injection, no mineralized material had been deposited along the root surface, and very little resorption was seen. Large amounts of bone matrix were deposited in the intraperiodontal space (often causing localized ankylosis). In HEBP-treated animals killed 1 month after the last injection, again no layer of mineralized material along the root surface was seen, but now root resorption had become manifest, occupying up to 40% of the cement surface. This occurred irrespective of the duration of HEBP administration. In the saline-treated animals, extensive resorption of the incisor was noted (up to 90% of its surface). It is concluded that the layer of mineralized material deposited after the periodontium is frozen does not play a decisive part in the onset of root resorption. HEBP treatment slows down root resorption but does not prevent it.

Biochemical Anatomy of Human Bone: Comparative Study of Compact and Spongy Bone in Femur, Rib and Iliac Crest

Using EDTA extraction procedure, compact and spongy bone from human femur, rib and iliac crest were compared in terms of their content in collagen, sialoprotein, proteoglycan and carbohydrate. The bone matrix sizes displayed significant variations, the femur having the smallest size and iliac crest the largest one. No significant difference in the matrix size has been found between the spongy and compact bone. The EDTA extractability of the spongy bone was higher than that of the compact bone, with femur showing the lowest extractability. The collagen content of the 3 bones studied was similar although the femur had slightly lower values. The sialic and uronic acids and hexose contents were higher in the femur than in the rib and iliac crest. The collagen/hexose, collagen/sialic acid and collagen/uronic acid ratios in the bone matrix were highest in the iliac crest and lowest in the femur, suggesting that alterations in the amounts of bone matrix can affect the mechanical properties of different parts of the bony skeleton and vice versa.

Effect of diets low in calcium and phosphorus on the development of growing lambs

SUMMARYFive groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.Urolithiasis was common in lambs given diets adequate in P.

Effects of lipopolysaccharides on bone resorption in tissue culture.

1. Highly purified lipopolysaccharides stimulate the resorption of bone in tissue culture as assayed morphologically and by the release of45Ca from prelabelled bones. Associated with this effect are increases in: a) lactate released into the cultured medium, b) the total number of cells in the bones, c) the occurrence of osteoclasts and, d) a decrease in the amount of bone matrix. 2. Lipopolysaccharides prepared either by phenol extraction or by ether extraction stimulate bone resorption. 3. Lipopolysaccharide with most of the lipid removed loses its ability to stimulate bone resorption. 4. There is no relationship between the ability of lipopolysaccharides to stimulate the resorption of bone and pyrogenicity or their ability to neutralize antibody. 5. When using a submaximal dose of parathyroid hormone, its effect on bone resorption is additive to that of lipopolysaccharides. 6. Heparin which by itself has no effect on bone resorption potentiates the effect of lipopolysaccharide. 7. Thyrocalcitonin inhibits to a similar degree the resorption stimulated by lipopolysaccharide and parathyroid hormone.