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  • 1970-1974  (4)
  • Cell & Developmental Biology  (4)
Materialart
Erscheinungszeitraum
Jahr
Schlagwörter
  • 1
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Fertile hens eggs were incubated 48 hours. Embryos were removed from the shell and the cervical region from each excised and placed in a balanced salt solution containing 1% trypsin for 40 minutes. Notochords were isolated by microdissection and further incubated in vitro 48 or 72 hours. Following trypsinization, unincubated notochords were rod-shaped and were shown by electron microscopy to be devoid of extracellular materials or contaminating mesenchymal cells. Extracellular materials, ultrastructurally indistinguishable from those in the perinotochordal connective tissue space in vivo, are present on the surfaces of cell clusters at 48 hours of in vitro incubation. Areas of fibrillogenesis, in which microfibrils are separated from the surface of cells by intermittent basement lamina, are common. At 72 hours of in vitro incubation fibrogenic activity is less evident, but occasionally intense concentrations of small and large microfibrils, basement lamina and other extracellular substances are seen adjacent to notochordal cell surfaces. These observations are of special interest in light of the known role of the notochord in embryonic induction and recent demonstrations that surface-associated substances (specifically collagen) are necessary for normal cytodifferentiation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0002-9106
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Two series of chick embryos were treated with hydrocortisone in an attempt to demonstrate the influence of this hormone upon microfibrils found free in the tissue space surrounding the notochord. Embryos in series I were explanted on agar-albumen medium and permitted to survive 1-24 hours after Ringer's solution or hydrocortisone had been pipetted onto the area vasculosa. Doses of hydrocortisone ranged from 5 μg to 1 mg. Series II embryos were similarly treated in ovo through a small shell “window” and then incubated 12 or 24 hours. All embryos were sacrificed at 72 hours incubation age. Ringer-treated embryos in both series exhibited a rich tangle of early extracellular connective tissue fibrils (microfibrils) surrounding the notochord. One hour after treatment with hydrocortisone, embryos in series I showed a reduction in perinotochordal microfibrils. At four hours the effect was maximal and by 12 hours, recovery had been initiated, the morphology of which suggested a re-organization of amorphous material and extracellular debris to form fibrillar structures. Twenty-four hours after treatment, recovery was complete and hydrocortisone-treated embryos exhibited perinotochordal fibril populations that were indistinguishable from Ringer-treated specimens. The results of the series II experiments roughly parallelled those seen in series I but were somewhat less predictable.Possible modes of action of hydrocortisone on connective tissues and their relationship to the present study are discussed. It is suggested that the steroid may induce the release of a substance with an enzymatic activity capable of digesting microfibrils. This catabolic activity may be reflected as an inhibition of connective tissue production if it is assumed that microfibrils are precursors of larger, more mature fibrils. It is further suggested that since microfibrils are thought to contain connective tissue proteins, the initiation of microfibrillar reduction by hydrocortisone could indicate that this hormone may act in a similar manner on more mature connective tissue fibrils.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 141 (1974), S. 441-446 
    ISSN: 0002-9106
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We report here the observation of striated collagen produced by notochordal cells in vitro. Fibrils with collagen-like striations were seen in large intercellular spaces following three days of incubation in vitro. Surprisingly, similar fibrils and large sheets (1,500 Å wide) of collagen showing a 510 Å periodicity were seen in notochordal tissues cultured in the presence of β-aminopropionitrile (BAPN), a known inhibitor of cross-linking in tropocollagen. These observations support the view that the notochord should be considered one of several embryonic epithelial tissues known to secrete collagen.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 136 (1973), S. 77-89 
    ISSN: 0002-9106
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Chick embryos of the White Leghorn strain were incubated from one-half to four days and sacrificed by immersion in toto. in Karnovsky's fixative. The cervical region of each embryo was excised and prepared for electron microscopy. Intercellular materials, which appear indistinguishable from the early connective tissue components of the embryonic tissue space, appear within dilated interstices of the notochordal epithelium beginning at approximately Hamburger-Hamilton stage 14. At progressively older stages this intercellular material appears to organize and aggregate to form fibrils. By stage 22 widely expanded intercellular spaces contain boundary (basement) membrane material, amorphous substance and microfibrils of various sizes. Moreover, larger, more mature fibrils that exhibit collagen-like periodic striations are present. The existence of connective tissue materials in cellular interstices deep within the central portion of the notochord strongly suggests that these substances are derived from notochordal epithelial cells. Furthermore, the similarity of the intercellular connective tissue components to those deposited on the notochordal surface suggests that these latter materials are likewise a secretory product of the notochord. The significance of the perinotochordal connective tissue (notochord sheath) with respect to the recent emphasis on the role of surface-associated substances to cytodifferentiation is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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