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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Gerodontology 2 (1983), S. 0 
    ISSN: 1741-2358
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Some physico-chemical properties of the enamel of deciduous and permanent (young and old) teeth were investigated and compared using x-ray diffraction, infrared absorption spectroscopy, scanning electron microscopy and chemical analyses. Results demonstrated the following: all enamel samples gave x-ray diffraction patterns of only apatite; all enamel samples gave IR absorption spectra of carbonate-containing apatite; the α-axis of deciduous enamel apatite was larger than that of permanent (both young and old) enamel apatite (mean values, deciduous = 9.458 ± 0.003A; permanent =9 443 ± 0.003A); apatite crystallite dimensions increased with age especially along the c-axis; when compared to permanent, deciduous enamel contained slightly more carbonate, magnesium and HPO42-; the prism (enamel rods) dimensions were slightly smaller, and the extent of acid-etching was more extensive in deciduous enamel than in permanent enamel. These observations combined with other factors such as the difference in the orientation of and crystal density in prism rods and the difference in conditions of the oral environment between deciduous and permanent enamel may account for the reported observations of a decrease in caries prevalance with age.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Erythropoietin (Ep) is produced mainly by the liver and spleen during fetal and neonatal periods and by the kidney during adolescent and adult life. The liver is also an important extrarenal producer of Ep in the hypoxic, anephric adult animal. Subtotal hepatectomy results in a substantial elevation in serum Ep levels at 30-72 hours after hepatectomy in rats subsequently nephrectomized and rendered hypoxic. Ep production is related to the mass of regenerating liver with peak Ep production occurring during times of greatest tissue proliferation. Regenerative and erythropoietic responses to hepatectomy decline with advancing age. Rats undergoing repeated hepatectomies do not recover full liver mass but the initial rate of regeneration increases following each successive hepatectomy. Ep levels decline in anephric hypoxic rats undergoing multiple hepatectomies when compared to sham-operated controls.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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