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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 285-286 
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 287-288 
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 1 (1967), S. 170-172 
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les effets de la pression hydrostatique ont été étudiés surSpirostomum ambiguum cilié, à un stade précoce du culture, lorsqu'il n'est pas calcifié et plus tardivement lorsqu'il est calcifié. Les cellules non calcifiées sont sensibles à la pression. Elles deviennent inertes à 250 atm.; elles changent de forme à 30 0atm. et elles éclatent à 550 atm. Par contre, les organismes calcifiés adultes ne sont pas altérés à 550 atm. et ne présentent qu'une faible augmentation transitoire de diamètre qu'au bout de 2 heures de traitement à 1000 atm.
    Abstract: Zusammenfassung Es wird der Einfluß von hydrostatischem Druck auf die CiliatenSpirostomum ambiguum beschrieben, einerseits auf nicht verkalkte, im frühen Stadium der Kultur stehende Infusionen, anderseits auf verkalkte, längere Zeit gewachsene Mikroorganismen. Nicht verkalkte Zellen sind druckempfindlich; bei 250 Atm. verlieren sie ihre Mobilität, bei 300 Atm. verändern sie ihre Form und bei 550 Atm. platzen sie. Im Gegensatz dazu weisen die ausgewachsenen verkalkten Tiere bei 550 Atm. keine Veränderungen auf; nach Einwirkung von 1000 Atm. während 2 Std zeigen sie nur eine kleine vorübergehende Zunahme ihres Durchmessers.
    Notes: Abstract The effects of hydrostatic pressure on the ciliateSpirostomum ambiguum, when the organism is uncalcified in the early stage of culture and when it is calcified after periods of time are described. Uncalcified cells are sensitive to pressure, becoming quiescent at 250 atm, distorting at 300 atm and disrupting at 550 atm. In contrast, the mature calcified animals show no changes at 550 atm. and small temporary increases in diameter only during 2 hr of treatment at 1000 atm.
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  • 6
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une deficience alimentaire en vitamine A provoque chez le rat sevré une pénétration vasculaire dans le cartilage épiphysaire proximal du tibia. Ce fait peut être lié soit à un trouble de diffusion dans la matrice cartilagineuse altérée soit à des microfractures dans la métaphyse.
    Abstract: Zusammenfassung Ein Vitamin A-Mangel in der Nahrung von entwöhnten Ratten erzeught ein Eindringen von Gefäßen in den Epiphysenknorpel des proximalen Tibiaendes. Diese Wirkung könnte entweder durch eine gestörte Diffusion in der veränderten Knorpelmatrix oder infolge von Mikrofrakturen in der Wachstumsfuge entstehen.
    Notes: Abstract A deficiency of vitamin A in the diet of weanling rats resulted in a vascular penetration of the proximal tibial epiphyseal cartilage. This response might be due to either impaired diffusion in an altered cartilage matrix or as a result of microfractures in the growth disc.
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  • 7
    ISSN: 1432-0827
    Keywords: 1,25-(OH)2-D ; Hypophysectomy ; Calcium ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The mechanism by which dietary phosphate deprivation elevates plasma 1,25-(OH)2-D levels is not known. To evaluate the role of the pituitary in regulating plasma 1,25-(OH)2-D concentrations, the responses of plasma 1,25-(OH)2-D to dietary phosphate deprivation and, separately, to dietary calcium deprivation were evaluated in intact and hypophysectomized male rats. Among intact and hypophysectomized rats eating normal diets, plasma 1,25-(OH)2-D levels averaged 228±76 and 148±62 pmol/1, respectively (P〈0.01). During dietary phosphate deprivation, plasma 1,25-(OH)2-D levels rose to 1160±260 in intact rats and fell to 90±26 pmol/l in hypophysectomized rats (P〈0.001). By contrast, during dietary calcium deprivation, plasma 1,25-(OH)2-D levels rose in both intact and hypophysectomized animals to 856±107 and 742±279 pmol/l, respectively (NS). In response to dietary phosphate deprivation, serum calcium concentrations rose as 1,25-(OH)2-D concentrations rose in intact rats but remained at control levels in hypophysectomized rats. These results support the hypothesis that a pituitary hormone acting either directly or indirectly on the kidney mediates the increase in plasma 1,25-(OH)2-D during dietary phosphate deprivation. The hypercalcemia that occurs in rats during dietary phosphate deprivation appears to depend on the elevation of plasma 1,25-(OH)2-D.
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  • 8
    ISSN: 1432-0827
    Keywords: Bone ; Collagen ; Density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The density of a bovine cortical bone matrix sample was found in water, several ethanol-water solutions, and in the dried state. Previously the density of the same mineralized bone was found fresh and when desiccated. The volume in each state was estimated from the dimensional changes axially, tangentially, and radially. Confirmation was found by determining the density of dried specimens upon immersion in xylene. The amount of imbibed xylene provided an estimate of the free pore volume in the dried matrix. The volume fraction of the solid constituent, S, in the wet matrix was found to be 0.57, from which the density of S in various solutions was calculated. Density of wet matrix in 0.15 M saline: 1.180 g/cc; for dried matrix, 1.246 g/cc. Density of wet S in saline: 1.33 g/cc; for dried S, 1.42 g/cc, which matches published values for collagen molecules. Dimensional changes between wet and dried state of matrix match published values for artificially cross-linked rat tail tendon fibers. Axially: 1.04, by area: 2.27; by volume: 2.62. Estimate of intrafibrillar volume, assuming 80% of mineral is within fibrils: 0.73 cc/g dry collagen.
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  • 9
    ISSN: 1432-0827
    Keywords: Calcium-binding protein ; Lymnaea stagnalis ; Mantle edge, shell formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary By means of gel filtration and ionexchange chromatography on calcium-saturated Chelex-100, a calcium-binding fraction was isolated from the mantle edge of the freshwater snailLymnaea stagnalis. This fraction was not present in other tissues. Treatment with trypsin caused a disappearance of the calcium-binding capacity, proving that the active substance in this fraction is a protein (calcium-binding protein; CaBP). Removal of the growth hormone-producing neuroendocrine light green cells resulted in a strong decrease of the amount of CaBP. It is concluded thatL. stagnalis possesses a hormone-dependent CaBP, probably responsible for the maintenance of a high calcium concentration in that part of the mantle that produces the outer crystalline layer of the shell.
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  • 10
    ISSN: 1432-0827
    Keywords: Vitamin D ; Vitamin D deficiency ; Cartilage ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no role in the modeling and mineralization of bone.
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