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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 7 (1971), S. 93-102 
    ISSN: 1432-0827
    Keywords: Strontium ; Vitamin D3 ; Calcium ; Absorption ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des poulets, âgés de 2 semaines, après a voir été soumis pendant 7 jours à un régime pauvre en calcium (0,1%), riche en vitamine D3, à contenu stable en strontium à une concentration équimolaire à 1,2% de calcium, reçoivent à nouveau une alimentation normale. Les graves lésions osseuses, provoquées par le régime au strontium, disparaissent au bout de 3 jours d'alimentation normale. L'inhibition du mécanisme d'absorption intestinal du calcium et l'action inhibitrice initiale du strontium alimentaire sont totalement abolies. Cependant les troubles de la minéralisation ne disparaissent que partiellement.
    Abstract: Zusammenfassung Nachdem normale, 2-wöchige Kücken während 7 Tagen eine calciumarme (0,1%), Vitamin D3-reiche und 2,62% kaltes Strontium (molaraequivalent mit 1,2% Calcium) enthaltende Nahrung erhielten, wurden sie wieder auf normales Futter gesetzt. Die schwere Knochenläsion, die sich durch die Strontiumfütterung entwickelt hatte, bildete sich zu einem großen Teil schon nach 3 Tagen normaler Nahrung wieder zurück. Die Hemmung der Calciumabsorption im Darm, die anfängliche inhibierende Wirkung des Strontiums aus der Nahrung, wurde vollständig aufgehoben; dagegen besserte sich der Mineralisationsdefekt nur teilweise.
    Notes: Abstract Two week old normal chicks, after having been fed a low-calcium (0.1%), vitamin D3-replete diet containing stable strontium at a level equimolar to 1.2% calcium for 7 days, were transferred back to a normal diet. The severe bone lesion that developed with strontium feeding was, to a large extent, reversed after only 3 days on the normal diet. The inhibition of the intestinal calcium absorptive mechanism, the initial inhibitory action of dietary strontium, was fully reversed whereas the recovery from the defect in mineralization was only partially reversed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 7 (1971), S. 81-92 
    ISSN: 1432-0827
    Keywords: Strontium ; Vitamin D3 ; Calcium ; Absorption ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des poulets normaux, âgés de 2 semaines, présentent une condition voisine d'une rachitisme grave, lorsqu'on les soumet pendant 7 jours à un régime pauvre en calcium (0,1%), riche en vitamine D3, et contenant une quantité stable de strontium, équimolaire à 1,2% de calcium. Alors que l'on pensait que le rachitisme induit par le strontium était lié à une inhibition directe de la calcification, il apparait qu'avant toute modification osseuse apparente, le strontium inhibe la production du CaPB induit par la vitamine D3, ainsi que le mécanisme d'absorption intestinale du calcium. Il semble que cet effet du strontium soit lié à sa participation dans le mécanisme normal de la régulation du calcium au cours de la synthèse de CaBP.
    Abstract: Zusammenfassung Normale, 2wöchige Kücken gerieten innerhalb von 7 Tagen in einen schweren, rachitisänhlichen Zustand, wenn sie eine calciumarme (0,1%0 und Vitamin D3-reiche Nahrung erhielten, welcher kaltes Strontium in einer Konzentration von 2,62% (molaraequivalent mit 1,2% Calcium) zugesetzt wurde. Während man früher vermutete, daß die “Strontium-Rachitis” nur durch eine direkte Inhibition der Verkalkung entstehe, konnte nun gezeigt werden, daß — bevor eine sichtbare Knochenveränderung eintritt — die Vitamin D3-gesteuerte Bildung von CaBP (calciumbindendes Protein) und gleichzeitig der Mechanismus der Calciumabsorption im Darm durch Strontium gehemmt wird. Die gefundenen Resultate weisen auf die Möglichkeit hin, daß dieser Strontiumeffekt auf dessen Interferenz mit dem normalen Mechanismus der Calciumregulation durch die CaBP-Syntheses zurückgeführt werden kann.
    Notes: Abstract Normal 2-week-old chicks, when fed a low-calcium (0.1%), vitamin D3-replete diet containig stable strontium at a level equimolar to 1.2% calcium, developed a severe rachiticlike condition within 7 days. Whereas formerly it was suspected that “strontium rickets” resulted from direct inhibition of calcification only, it was shown that, preceding any detectable bone change, strontium inhibited vitamin D3-induced CaBP production and, simultaneously, the intestinal calcium absorptive mechanism. The results suggest the possibility that this effect of strontium may be due to its interference with the normal mechanism of calcium regulation of CaBP synthesis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 92 (1953), S. 513-529 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 105 (1959), S. 389-399 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 154 (1977), S. 459-477 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A process of nucleolar reorganization apparently identical to that encountered in intestinal epithelial cells (Adamstone and Taylor, '72) develops in kidney cells of aging rats. The polymorphic nucleoli of young tubule cells soon change to amphinucleoli and, while terminal nucleolar reorganization is delayed in cells of collecting tubules, in the nephrons nucleoli soon begin to undergo terminal reorganization becoming bipartite structures with separate plasmosomes and karyosomes. This suggests disruption of the DNA-dependent RNA protein transcription system and failure to maintain the flow of messenger RNA into the cytoplasm. Old cells are not discarded immediately from the kidney tubules and they retain much rough endoplasmic reticulum, numerous ribosomes and polysomes and large plasmosomes. Thus a high RNA concentration is known to develop in old kidney tissue while protein synthesis is also known to be low (Kanungo et al., '70; Buetow and Ghandi, '73). Nucleolar counts show gradual increase in bipartite nucleoli at the expense of amphinucleoli and in the senescent kidney bipartite nucleoli predominate. It is suggested that nucleolar reorganization, with final separation of plasmosomes and karyosomes, includes the process of nucleolar segregation and is triggered by some innate nucleolar mechanism in response to encoded genetic information stored in the nucleolus during nucleogenesis. At this time both DNA and RNA are incorporated into the developing nucleolus. It is also to be noted that two shifts in nucleolar dominance occur with advancing age. These may be fundamental to the process of aging and to the onset of senescence. Furthermore, the changes in dominant nucleolar types are the direct result of the process of nucleolar reorganization.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 161 (1979), S. 211-219 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The nucleoli of rat liver cells duplicate in great detail the lifelong series of reorganizational changes encountered in kidney and intestinal epithelial cells. The ultrastructural components of the large, loosely organized polymorphous nucleoli, which are dominant in the rapidly multiplying stem cells of embryos, are readily accessible for chemical activities. Smaller, more compact amphinucleoli are dominant in more mature cells, which were characterized by Smetana ('70) as “idling” cells, showing slowly continuing ribosome formation and RNP synthesis. In older cells bipartite nucleoli become dominant and are reorganized in increasing numbers from the younger amphinucleoli. These, however, are not replaced in equal numbers from the shrinking pool of polymorphs of young cells which have greatly reduced mitotic potential. Paralleling the shifts in dominant nucleolar types, the high level of protein synthesis declines in older cells not only in the quantity of proteins synthesized but also in kinds of enzymes produced. These fail to meet the structural and functional requirements of aging cells leading ultimately to the onset of age-related degenerative changes. Again it is noted that separation of the karyosomal DNA from the plasmosomal RNA-protein complex of the nucleolus may lead to possible breakdown of the DNA-dependent RNA-protein transcription system ultimately bringing protein synthesis to a very low level in the senescent animal.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning and transmission electron microscopy were used to investigate the surface area and number per unit area of microvilli from jejunal villus epithelial cells in the rat, hamster and dog.The calculated mean microvillus surface area was 0.419 μ2, 0.573 μ2, 0.751 μ2 for the rat, hamster and dog respectively.The largest number of microvilli per square micron freeze dried villus surface was measured in the rat with a mean value of 65. Hamster and dog freeze dried specimens had lower mean values of 54 and 34 microvilli respectively.The total microvilli surface area in square micron per square micron villus surface was more closely related for the three species with values of 27.23 for the rat, 30.94 for the hamster and 25.53 for the dog.These data indicate an inverse relationship between the mean microvillus surface area and population density in the species studied. However, the total microvilli surface area per unit villus surface is relatively similar for the three species.The observed number of microvilli per unit villus surface was shown to vary depending upon the dehydration technique employed for preparation of scanning electron microscopic specimens. This variation probably reflects shrinkage artifact and should be considered in soft tissue studies involving the scanning electron microscope.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 90 (1952), S. 217-241 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light microscope studies were made on nucleoli of jejunal epithelial cells of normal rats fixed in OsO4, glutaraldehyde, F.A.A. and HgCl2 and stained with basic fuchsin-alkaline methylene blue. Nucleolar reorganization is extensive and clearly resembles the phenomenon of nucleolar segregation. Polymorphous nucleoli of undifferentiated crypt cells show intermingled constituents and stain purple whereas similar nucleoli of definitive absorptive cells show two homogeneous components-A, stained red and B, stained blue. Cytochemical studies indicate that component A is largely protein and acidophilic and component B is largely nucleic acids and basophilic. These nucleoli become compacted, each forming an amphinucleolus with the two components at opposite poles. Further changes occur along the villi and the components generally separate to form a condensed plasmosome and a diffuse karysome. Extruded cells show nucleolar fragmentation.Electron micrographs of OsO4 material were used in preparation of wax models. These, along with electron micrographs of glutaraldehyde material stained with uranyl acetate and lead citrate, clearly illustrate and duplicate light microscope findings and strongly resemble nucleolar segregation produced by antimetabolites.Cells of the villi with reorganized nucleoli do not undergo mitosis whereas undifferentiated crypt cells do so. Furthermore, nucleolar reorganization is correlated with aging since it begins in crypt cells and culminates in senescent cells at the tips of the villi.A review is given of the extensive evidence showing that, in the intestine certain functional changes occur similar to those demonstrated in experimental nucleolar segregation. These include gradually changing patterns of DNA, RNA and protein synthesis as well as enzyme activity. The accompany and probably result from nucleolar reorganization.
    Additional Material: 2 Ill.
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  • 10
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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