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  • 1990-1994  (3)
  • 1
    Publication Date: 2011-08-24
    Description: We have studied the chemistry, hydroxyapatite crystal size, and maturational changes in bone and dentin from rats exposed to microgravity for 12 days in a Soviet biosatellite (Cosmos 1887). Bone ash was reduced in vertebrae (L5) but not in the non-weight-bearing calvaria or mandibles. All tissues had a relatively normal percentage composition of Ca, P, and Mg. Nevertheless, flight rat calvaria and vertebral tissues tended to exhibit lower Ca/P and higher Ca/Mg ratios that any of their weight-matched controls groups, and gradient density analysis (calvaria) indicated a strong shift to the fractions lower specific gravity that was commensurate with impaired rates of matrix-mineral maturation. X-ray diffraction data were confirmatory. Bone hydroxyapatite crystal growth in the mandibles of flight rats was preferentially altered in such a way as to reduce their size (C-axis dimension). But in the mandibular diastemal region devoid of muscle attachments, flight rat bone and dentin were normal with respect to the Ca, P, Mg, and Zn concentrations and Ca/P and Ca/Mg ratios of age-matched controls. These observations affirm the concept that while microgravity most adversely affects the maturation of newly formed matrix and mineral moieties in weight-bearing bone, such effects occur throughout the skeleton.
    Keywords: Life Sciences (General)
    Type: The FASEB journal : official publication of the Federation of American Societies for Experimental Biology (ISSN 0892-6638); Volume 4; 1; 29-33
    Format: text
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  • 2
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract To evaluate the accuracy of bone mineral composition determination by electron microprobe analysis (EDX) the measurements have been compared to instrumental neutron activation analysis (INAA) and chemical analysis (ICPES). Bone specimens from five femoral heads were used. The trabecular content of calcium (Ca) and phosphorus (P) was analyzed by the three different methods. The FDX method allows for a microstructural analysis of intact, methylmetacrylate-embedded, undecalcified bone and the measuring points can thus be distinctly identified centrally in each trabecula. The analysis yielded 25.8±0.7 wt% Ca and 10.5±0.1 wt % P, compared with 22.2±0.5 and 23.0±1.0 wt % Ca, and 9.83±0.21 and 10.02±0.44 wt % P for INAA and ICPES, respectively. The EDX analysis was calibrated by consecutive measurements of a hard, pressed tablet of hydroxyapatit of known content. The mean Ca content deviated with-0.38 wt % from the given content and P with-0.89 wt %. We could not verify any particular interference from the embedding procedure, however, it is possible that the relatively lower P content still may reflect this. The magnesium (Mg) concentration was 0.31±0.02 wt % by EDX and 0.26±0.02 wt % by INAA. The EDX analytical method provides a useful tool for simultaneous elemental quantification in bone. It has the advantage of permitting the use of cation bone biopsy material and thus allowing for a unique microstructural evaluation of the degree of mineralization. By comparison with other established methods, the assessment of accuracy and reliability indicates that the measurements are well in range for the major constituents, Ca and P, whereas INAA is more sensitive in determining trace elements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 55 (1994), S. 288-294 
    ISSN: 1432-0827
    Keywords: Bisphosphonate ; Bone mineralization, structure, mechanical properties ; Dog ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The goal of this study was to find out if bone can recover after long-term administration of bisphosphonate. Disodium pamidronate (APD) was given orally by gavage to mature beagle dogs at doses of 0, 2.5, 12.5, and 25 mg/kg/day for 1 year (0.1% concentration) and the animals were allowed to recover for another year. At sacrifice, the os ilium was used to determine bone mineralization profile and, subsequently, each density fraction was analyzed chemically. The ribs were used to determine the lattice parameters and the size of the apatite crystals of bone. The sternum was used to determine selected morphometric parameters using image analysis of specimen X-ray films and, subsequently, to determine bone mechanical properties using a 3-point bending technique. We found that the 12.5 and 25 mg/kg/day doses exhibit a significant shift towards greater mineralization versus control, whereas the lower dose (2.5 mg/kg/day) was indistinguishable from the controls. The lattice parameters and crystal size of bone apatite remained unchanged. The image analysis shows a dose-related increase in trabecular volume and thickness. The connectivity increased with dose but the anisotropy of bone remained unchanged. Both the elastic modulus and the maximum stress of bone remain unaffected by APD. We conclude that when dogs are treated with APD for 1 year, their bones can reestablish their physical-chemical characteristics (mineralization profile, chemistry, and crystal size/strain) after 1 year of recovery, provided that the treatment doss is 2.5 mg/kg/day. In addition, the mechanical properties of the bone remained unaffected and the gains in trabecular volume and thickness are maintained.
    Type of Medium: Electronic Resource
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