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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for intussusceptive capillary growth in the chicken chorio-allantoic membrane (CAM) (1993)
    Springer
    Anatomy and embryology 187 (1993), S. 121-130 
    Details
    ISSN: 1432-0568
    Keywords: Chorio-allantoic membrane ; Capillary growth ; Development ; Endothelial cell ; Microcirculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of our investigations was to test whether the chicken chorio-allantoic membrane (CAM) could be an adequate in vivo model for a new mode of capillary growth, originally described in the rat lung and termed intussusceptive microvascular growth. According to that concept the capillary system does not grow by sprouting of vessels, but expands by insertion of transcapillary tissue pillars or posts which form new intercapillary meshes. In the present study, we observed slender transcapillary tissue pillars with diameters around 1 μm in the CAM by in vivo microscopy, and analyzed their ultrastructure by transmission electron microscopic investigation of serial sections. The pillars corresponded in size to those previously described in rat lung microvasculature. On day 7, the pillar core contained endothelial-, endothelial-like cells and collagen fibers, and on day 12 additionally chorionic epithelial cells. As a hypothesis we propose that slender cytoplasmic extensions of endothelial cells, heavily interdigitated in the post area and often projecting into the vascular lumen, could initiate the first step of pillar formation, i.e., interconnect opposite capillary walls. During both stages of development endothelial-like cells were observed in close relationship with the pillars. These cells seem to be relevant for tissue post completion and growth, as they were found to invade the core of the pillars. From the localization of the interendothelial junctions in the post region, a certain similarity to the concept proposed for the lung can be found. The observations confirm that the CAM is a very suitable material for the in vivo investigation of intussusceptive capillary growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171743
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  • 2
    Electronic Resource
    Electronic Resource
    Morphometric analysis of fetal rat lung development (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 237 (1993), S. 38-48 
    Details
    ISSN: 0003-276X
    Keywords: Lung development ; Fetal rats ; Lung compartments ; Lung parenchyma ; Airways ; Pulmonary vasculature ; Cellular differentiation ; Morphometry ; Reference space ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Applying the zone concept described previously, we quantitatively analyzed fetal rat lung development. The zone concept allowed us to coherently define reference spaces in the developing lung, a prerequisite for morphometric analysis.The peripheral zone I corresponds to a zone of growth of yet undifferentiated tissues; zone II arises from zone I and represents a region of structural and cellular differentiation; zones III and IV comprise the conducting airways and vessels.Lungs of fetal rats aged 17-23 days and 20 hours postnatal were fixed with OsO4 and glutaraldehyde and processed for light and electron microscopic morphometry implemented by point and intersection counting.Fetal lung volume grew in proportion to body weight. Zone II being the largest compartment, its volume changes largely determined lung growth rates. Zone II increased in mass owing to differentiation processes at the interface to zone I where the proximal portions of zone I were continuously shifted into zone II by differentiation. New tissue was generated within zone I. Due to these combined processes zone I changed little in volume until it disappeared at the end of the canalicular stage. The presence in the pseudoglandular stage of half of the parenchymal epithelial mass available around birth indicated that parenchymal development started earlier than assumed so far.While the endothelial surface increased most at birth, the epithelial surface grew by more than 600% at day 21, reflecting the onset of canalisation.The study confirmed the usefulness of the zone concept for morphometry and provided some new insights into lung development. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092370105
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  • 3
    Electronic Resource
    Electronic Resource
    Structural analysis of fetal rat lung development (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 234 (1992), S. 399-418 
    Details
    ISSN: 0003-276X
    Keywords: Lung development ; Lung compartments ; Lung parenchyma ; Airways ; Pulmonary vasculature ; Cellular differentiation ; Morphometry ; Reference space ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The primary aim of this morphological investigation was to elaborate a concept allowing us to coherently define reference spaces for morphometric analysis of fetal lung development. Beyond this quantitative goal, morphological analysis of cell types, definition of compartments, and reflection about the prospective fate of their constitutents provided per se new insights into the developmental processes.Lungs of rat fetuses aged 17-23 days and newborns aged 20 hours were fixed with an osmium tetroxide and glutaraldehyde mixture and their volume determined. Left lungs were embedded in Epon and investigated by light and electron microscopy. The right lung of one animal per group was embedded in methacrylate and step sections obtained to precisely locate the airways within the mesenchyme.The various cell types, their topographical relationships, and their morphological alterations with ongoing development were analyzed with regard to their prospective potentials of differentiation.The developing lung could be partitioned into four zones further subdivided into defined compartments. Zone I forms a superficial mantle around the lobes and the future acini. Consisting of primitive mesenchymal cells, it represents a zone of growth which disappears with the onset of the saccular stage. Zone II is mainly a zone of differentiation. Its interstitium stains intensely due to a dense population of dark cells. Up to gestational day 19, zone II contains future conductive airways with their vessels. After day 21, it comprises the whole prospective gas exchange region. Zones III and IV contain the elements of the airway tree and vascular system, zone IV corresponding to the most proximal generations with an adventitial layer. For all differentiation processes, a centrifugal directionality is manifested.© Willey-Liss, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092340310
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