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  • Osteopenia  (2)
  • Biomechanics  (1)
  • Bone mass  (1)
  • Cyclic AMP and hormonal preparations  (1)
  • 1
    ISSN: 1432-0827
    Keywords: Membrane potential ; Electrolyte and protein contents ; Cell pH ; Cyclic AMP and hormonal preparations ; Endosteal bone cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The mean transmembrane potential of cultured osteoblastlike cells isolated from the cortical endosteal surface of rabbit long bones was −16.9±0.64 mV (n=335). Elevation of potassium concentration in medium caused a decrease in potential. As the external concentration of potassium reached 15 mmol/liter and above, there was a linear relationship between the potassium concentration in log scale and the membrane potential with a slope of −13 mV per 10-fold change in external potassium concentration. Dibutyryladenosine 3′,5′-cyclic monophosphate, parathyroid extract, hydrocortisone, and sodium fluoride all depolarized the membrane of osteoblast-like cells after both short (1–2 h) and long (24 h) exposures at suitable doses, whereas calcitonin and prostaglandin E2 hyperpolarized the membrane after long exposures. The Na+, K+ and Cl− concentrations of cultured osteoblastlike cells were 0.538, 0.984, and 0.358 mmol/g protein or 52.6, 96.3, and 35.0 mmol/liter cell water, respectively. The protein content of these cells was 8.18±0.6 g/100 g cells and the water content was 83.7 g/100 g cells. The above-mentioned chemical and hormonal preparations in doses that produced significant changes in the membrane potential of these cultured cells did not alter their electrolyte or protein contents 24 h after exposure. Intracellular pH of cultured osteoblastlike cells as determined by [14C]-dimethyloxazolidine-2,4-dione and3H2O averaged 7.03 ± 0.11 when the pH of culture medium was maintained at 7.4. Calculations based on the values for the membrane potential and the electrolyte concentrations observed in this study indicate that Na+, and H+, and Cl− are actively transported out of the cells and K+ into the cells.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 233-238 
    ISSN: 1432-0827
    Keywords: Osteopenia ; Tibia ; Aging ; Beagles ; Bone mineral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In a cross-sectional study, 154 Beagles (79 males, 74 females) ranging in age from 14 to 187 months were measured for bone mineral, bone width, and mineral-to-width ratio on the distal shaft of the right tibia using a photon absorptiometer. The measurements were evaluated with regard to age, sex and body weight. The results indicate that males were heavier than females in body weight, with weight being reduced in the older animals of both sexes. When compared on an age basis, males had more mineral, a wider tibia, and a greater mineral-to-width ratio than females. The males and females reach their peak mineral, and mineral-to-width ratio at about 6 years of age and then decline. On a body weight basis, mineral, width and mineral-to-width ratio all increase with increasing body weight, with bone width being the least affected by changes in body weight. The values for females are less than those for males in all parameters with the greatest differences occurring at the greater weights. The only variance from these observations was the greater mineral-to-width ratio in the lighter females. It is concluded that, when examining cortical bone, the Beagle is a model of age-related osteopenia, and body weight is an important consideration when explaining changes in bone mineral.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 240 (1994), S. 447-455 
    ISSN: 0003-276X
    Keywords: Aseptic necroses ; Biomechanics ; Bone mass ; Endochondral ossification ; Epiphyseolisthesis ; Fracture ; Osteopenia ; Wolff's law ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A biomechanical model of endochondral ossification (Frost and Jee, 1994. Anat. Rec., 240:435-446) can help to explain: (1) some differences in fracture patterns in children and adults, (2) increased fractures during the human adolescent growth spurt, (3) localization of stress fractures and pseudofractures to cortical instead of trabecular bone, (4) increased bone mass in adult-acquired and childhood obesity, (5) subchondral bone densification and osteopenia in some arthroses, (6) why and where mammals lose spongiosa with aging, (7) why, as percents of the original bone stock, metaphyseal trabecular bone losses with aging usually exceed cortical bone losses, (8) why osteochondritis dissecans and aseptic necroses of bone localize in epiphyses instead of metaphyses, (9) some features of growth plate histology in rickets and the chondrodystrophies, (10) why spontaneous fractures in osteoporotic patients affect vertebral more than metaphyseal spongiosa, (11) why osteopenias develop in most chronic, debilitating diseases, and (12) why histomorphometric values can differ in iliac bone biopsies obtained by the “vertical” Jamshidi and “horizontal” Bordier-Meunier techniques. © 1994 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
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