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  • 1
    ISSN: 1432-0827
    Keywords: 1,25(OH)2D ; Hypophysectomy ; GH ; T3 ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Hypophysectomy abolishes the four- to fivefold increase in plasma 1,25(OH)2D levels that normally accompanies dietary phosphate deprivation in rats despite a smaller but significant decrease in plasma phosphate in these animals. This effect appears within 1 week of hypophysectomy and may be the result of a lack of GH, T3, or some other pituitary hormone. In hypothyroid rats (2 weeks after TPTX) not given replacement T3, plasma 1,25(OH)2D levels rose threefold from 148±57 pmol/l to 402±96 pmol/l (mean±SD) after 4 days of dietary phosphate deprivation. However, in hypophysectomized animals given replacement T3 alone, plasma 1,25(OH)2D levels rose fourfold from 82±13 to 333±230 pmol/l after 4 days of phosphate deprivation. In addition, in hypophysectomized animals replaced with GH alone, plasma 1,25(OH)2D levels rose from 243±86 to 525±85 pmol/l during phosphate deprivation. These results would suggest that both GH and T3 must be absent to prevent enhanced renal 1,25(OH)2D synthesis during phosphate deprivation. GH and T3 appear to play a permissive role since plasma levels of these hormones do not increase when intact rats are deprived of phosphate. Furthermore, bioassayable somatomedin levels are also not increased in intact rats during phosphate deprivation as well as plasma levels of prolactin. As observed previously, plasma 1,25(OH)2D levels were inversely correlated to plasma phosphate concentrations (r=0.46,P〈0.025), despite the inclusion of data points for unreplaced hypophysectomized animals who were hypophosphatemic but showed no increase in plasma 1,25(OH)2D. Thus the possibility remains that GH and T3 may exert their effect by permitting the renal 25OHD-1α-hydroxylase to respond to a change in phosphate concentrations during dietary phosphate deprivation, that, in turn, may ultimately increase renal 1,25(OH)2D synthesis and plasma levels of this hormone.
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 133 (1934), S. 797-798 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WHALES, when breathing, usually keep on the move ; the purpose of this letter is to explain why. All aquatic air-breathing creatures have to contend with the risk of water entering their lungs. Although the blow-holes of whales are valvular and situated on the highest part of the head, these ...
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  • 3
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 119 (1927), S. 923-923 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ALTHOUGH the walrus is usually found near the land subsisting on the shell-fish it finds at the bottom, it is also on rare occasions found amongst the drift ice in deep water, far from land, subsisting on seals and other mammals. A few examples of the latter kind are recorded in the ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 121 (1928), S. 984-984 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] I AGREE with Sir Sidney Harmer (NATURE, May 12, p. 748) that as the whale descends its chest is compressed and the density of its body is consequently increased. It is owing to this very fact (that is, its increased density) that the whale has difficulty in regaining the surface after ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 135 (1935), S. 656-657 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] DR. F. D. OMMANNEY, in his letter in NATURE of March 16 (p. 429), is of opinion that whales cannot descend with impunity below very moderate depths. In his “Discovery” Report on “The Vascular Networks of the Fin-Whale” he limits their normal dives to about 130 ft. and now, in his letter, to 35 ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 135 (1935), S. 473-473 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE recent illegal slaughter of grey seals in the supposed interests of the Cornish fishermen directs attention to the diet of seals. On what do they usually feed ? On fish, as the fishermen and their friends assert, or on some of the other creatures which abound in the waters of the ocean ...
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  • 8
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 10
    ISSN: 1432-0827
    Keywords: 1,25-(OH)2-D3 ; Hypophysectomy ; Growth hormone ; Phosphorus ; 31P NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In order to evaluate a possible role for tissue phosphate or phosphorylated compounds in mediating the increase in plasma 1,25-(OH)2-D3 levels during dietary phosphate deprivation, measurements of total and acid-soluble renal cortical phosphate content have been made in both intact and hypophysectomized (hypox) rats eating a normal diet and also after four days of dietary phosphate deprivation. Similar measurements were also made in phosphate-deprived hypophysectomized rats replaced with growth hormone (GH). Total and acid-soluble renal cortical phosphate content averaged 81±8 µmol/g and 4.1±0.6 µmol/g, respectively, in intact rats eating the normal diet and were not significantly altered after phosphate deprivation despite a fall in plasma phosphate of about 40% and a fourfold increase in plasma 1,25-(OH)2-D3 levels. Total and acid-soluble renal cortical phosphate content levels were higher in hypox rats, averaging 92±8 µmol/g and 4.9±0.7 µmol/g, respectively, but also did not change after phosphate deprivation. Replacement of phosphate-deprived hypox rats with GH resulted in a further fall in plasma phosphate and a significant increase in plasma 1,25-(OH)2-D3 levels, but there was no change in either total or acid-soluble renal cortical phosphate content. The distribution of organophosphorus compounds in the acid-soluble phosphate fraction in these experiments was also evaluated using31P NMR spectroscopy. Although there appeared to be an increase in the total concentration of organophosphorus compounds after phosphate deprivation, this effect was not altered by hypophysectomy or by replacement of phosphate-deprived hypox rats with GH. These data suggest that unless phosphate deprivation affects only a small or specific cellular phosphate pool, some factor other than renal cell inorganic phosphate content must initiate the increase in renal 1,25-(OH)2-D3 synthesis that occurs during phosphate deprivation.
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