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  • 1
    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.
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  • 2
    ISSN: 1432-0827
    Keywords: Estrogen ; Progestin ; Mechanical properties ; Vertebrae ; Hormone replacement therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The purpose of this study was to examine the effects of estrogen replacement, in concert with three different progestin regimens, on the mechanical properties of rat lumbar vertebrae. Ninety-two Sprague-Dawley rats (11 months old) were divided into six groups for treatment. The first group was an intact control, the second group (OVX) was ovariectomized only, and the third group (estrogen-only) was ovariectomized and received continuous estrogen through a 17β-estradiol implant. The remaining groups were ovariectomized and received estrogen and progestin (norethindrone, NET) therapy; 3 μg of NET was injected daily (estrogen plus continuous NET), or 6 μg of NET was injected for 14 consecutive days of a 28-day cycle (estrogen plus cyclic NET), or for 3 consecutive days of a 6-day cycle estrogen plus interrupted NET). The animals were sacrificed after 6 months, and the vertebrae were dissected out. The vertebral processes of the fourth lumbar vertebrae were removed, and the density of the vertebral bodies was determined. They were then subjected to compression testing. We found that all three estrogen/progestin regimens maintain bone density and all mechanical properties at a level indistinguishable from the control. However, the cyclic and continuous NET treatment results were, with the exception of density, also indistinguishable from those of the ovariectomized group. The estrogen plus interrupted NET group on the other hand, has a significantly greater compressive modulus and density than the ovariectomized group. In conclusion, with respect to the ovariectomized group, the estrogen plus interrupted NET treatment resulted in a superior density and compressive modulus. The remaining mechanical properties were equivalent to those resulting from the continuous or cyclic progestin regimens.
    Type of Medium: Electronic Resource
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