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  • 1
    Electronic Resource
    Electronic Resource
    Scanning and light microscope studies of the development of the chick embryo semilunar heart valves (1979)
    Springer
    Anatomy and embryology 157 (1979), S. 69-80 
    Details
    ISSN: 1432-0568
    Keywords: Chick embryo ; Semilunar valves ; Cell death ; Heart morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of the semilunar valves of the great arteries was studied by light and scanning electron microscopy in the chick embryo. The results show that three distinct developmental periods can be distinguished. The formation of the anlage of the valves takes place in the first period (stages 26–29). These early anlage consist of three pyramidal shaped cusps formed by a core of loosely packed mesenchymal cells covered by a flattened endothelium. In the second period (stages 30–35) the cusps undergo excavation on their distal face. Morphological evidence is reported suggesting that this excavation process is produced by an initial solid ingrowth of the endothelium of the arterial face of the cusps which is immediately luminated by detachment of cells towards the bloodstream and by cell death. The histogenesis of the valves takes place in the third period (from stage 36 until hatching). It was observed that during this period some myocardial cells of the outflow tracts of the ventricles invade the valvular tissue and that in the upper part of the cusps a prominent fibrous layer is formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315641
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  • 2
    Electronic Resource
    Electronic Resource
    The surface anatomy of the human aortic valve as revealed by scanning electron microscopy (1985)
    Springer
    Anatomy and embryology 172 (1985), S. 61-67 
    Details
    ISSN: 1432-0568
    Keywords: Heart valves ; Human heart ; Endothelial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The anatomy of the human aortic valve was studied by SEM in 36 subjects without cardiac pathology who had died of various accidental causes. Villous and lamellar tissue excrescences were observed at the node of Arantius and at the limit between the lunules and the load-bearing portion of the leaflets. The morphology of these structures suggests that they represent areas in which valve tissue becomes detached into the bloodstream. Fenestrations were present in the lunules of 14 specimens, with a higher incidence in specimens from subjects who were middle-aged or older. Our observations suggest that fenestrations appear initially as small perforations which then coalesce to form larger apertures. Two main types of endothelial cells, elongated and polygonal were detected on the endothelial surface of the leaflets. Both types of cells display a constant mode of arrangement on the different segments of the leaflets (lunules, node of Arantius and load-bearing portion of the leaflet). The possible relationships between endothelial cell morphology and the pattern of mechanical stress to which the leaflets are subjected is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318944
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  • 3
    Electronic Resource
    Electronic Resource
    Cell shape and cytoskeletal organization of the endothelial cells of the semilunar heart valves in the developing chick (1986)
    Springer
    Anatomy and embryology 174 (1986), S. 83-89 
    Details
    ISSN: 1432-0568
    Keywords: Endothelial cells ; Cytoskeleton ; Semilunar valves ; Heart morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The composition and arrangement of the cytoskeletal elements of the endothelium of the semilunar valves have been studied in the embryonic chick heart during the stages 30 to 38. Microtubules, vimentin intermediate filaments and actin microfilaments were constant components of the valvular endothelial cells in the studied stages. Scanning electron microscopy after Triton-X-100 extraction revealed significant differences in the tridimensional arrangement of the cytoskeleton in the course of valve development. In the ventricular face of the cusps the cytoskeletal elements displayed a progressive longitudinal alignment, while in the arterial face of the cusps the cytoskeleton maintained the appearance of a network. Transmission electron microscopy revealed that these differences were especially prominent for vimentin intermediate filaments, although a similar tendency was also observed for microtubules. Microfilaments were scarce in the endothelial cells of both faces of the cusps, and the stress fibers typical of the endothelial cells of the adult valves were not observed in the embryonic material. The significance of these results in valve morphogenesis and histogensis and a possible linkage with differences in the local characteristics of the blood flow are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318339
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  • 4
    Electronic Resource
    Electronic Resource
    Immunofluorescent localization of tenascin during the morphogenesis of the outflow tract of the chick embryo heart (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 149-155 
    Details
    ISSN: 1432-0568
    Keywords: Heart morphogenesis ; Truncus Arteriosus ; Extracellular matrix ; Tenascin ; Collagen type I
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cono-truncus constitutes a complex segment of the developing heart that gives rise to the outflow tract of the ventricles and root of the pulmonary and aortic arteries. Numerous studies have revealed that the extracellular matrix plays a relevant role in most morphogenetic processes modulating cell behaviour. By means of immunofluorescence, we studied the distribution and possible involvement of tenascin during morphogenesis of the conus and truncus in chick embryo hearts between days 4.5–10 of incubation. Tenascin is an extracellular matrix glycoprotein with a significant role in morphogenesis and cell and tissue differentiation. Our results reveal a specific distribution of tenascin in the areas of the cono-truncus undergoing significant structural changes during morphogenesis of this cardiac segment, appearing mainly in the mesenchymal layer subjacent to the myocardial layer, the cono-truncal ridges and the aorto-pulmonary septum. The distribution of tenascin was compared and contrasted with that of collagen type I, which constitutes a further component of the extracellular matrix common to most developing connective tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198954
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  • 5
    Electronic Resource
    Electronic Resource
    Interdigital chondrogenesis and extra digit formation in the duck leg bud subjected to local ectoderm removal (1992)
    Springer
    Anatomy and embryology 186 (1992), S. 27-32 
    Details
    ISSN: 1432-0568
    Keywords: Duck embryo ; Limb development ; Chondrogenesis ; Cell death
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the chick embryo the interdigital tissue in the stages previous to cell death exhibits in vitro a high chondrogenic potential, and forms extra digits when subjected in vivo to local ectodermal removal. In the present work we have analyzed the chondrogenic potential both in vivo and in vitro of the interdigital mesenchyme of the duck leg bud. As distinct from the chick, the interdigital mesenchyme of the duck leg bud exhibits a low degree of degeneration, resulting in the formation of webbed digits. Our results show that duck interdigital mesenchyme exhibits also a high chondrogenic potential in vitro until the stages in which cell death starts. Once cell death is finished chondrogenesis becomes negative and the interdigital mesenchyme forms a fibroblastic tissue. In vivo the interdigital mesenchyme of the duck leg bud subjected to ectoderm removal forms ectopic foci of chondrogenesis with a range of incidence similar to that in the chick. Unlike those of the chick the ectopic cartilages of the duck are rounded and smaller, and appear to be located at the distal margin of the interdigital mesenchyme. Formation of extra digits in the duck occurs with a lower incidence than in the chick. It is concluded that ectopic chondrogenesis and formation of extra digits is related to the intensity of interdigital cell death. The non-degenerating interdigital mesenchymal cells destined to form the interdigital webs of the duck appear to contribute very little to the formation of interdigital cartilages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00710399
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  • 6
    Electronic Resource
    Electronic Resource
    Modification of the phalangeal pattern of the digits in the chick embryo leg bud by local microinjection of RA, staurosporin and TGF β's (1993)
    Springer
    Anatomy and embryology 188 (1993), S. 201-208 
    Details
    ISSN: 1432-0568
    Keywords: Chick limb bud ; Digit formation ; Retinoic acid ; Staurosporin ; Growth factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Many experimental studies show that in the avian chick limb the digits are specified at early stages of development by characteristic concentrations within the limb mesoderm of a still unidentified morphogen diffusing from the posterior margin of the bud, linked with a specifie pattern of homeobox gene expression. In ail these studies, digits are distinguished by their size, morpholgy and phalangeal pattern rather than by their position within the autopodium. In this work we report the induction of digits that have otherwise normal morphology but lack an interphalangeal joint. This suggests that the patterning of these joints is not necessarily linked to the control of the outgrowth of the digital rays. Missing interphalangeal joints were induced by microinjection into the third interdigital space of the leg bud of stage 28 to 31 chick embryos of retinoic Acid (RA), staurosporine and TGF β1 and β2, but not by microinjection of FGF or EGF. Our results also suggest that the pattern of insertion of the long tendons and the formation of the flexor cutaneous pad at the plantar surface of the digits are both linked to the establishment of the interphalangeal joints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186253
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  • 7
    Electronic Resource
    Electronic Resource
    Structural arrangement of the extracellular matrix network during myocardial development in the chick embryo heart (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 451-460 
    Details
    ISSN: 1432-0568
    Keywords: Extracellular matrix ; Ventricular myocardium ; Chick embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We analyzed the extracellular matrix and the connective tissue of the developing chick myocardium (“myocardial interstitium”). The importance of this myocardial element for heart function has been well documented both for the normal and pathologic adult hearts. However, little information is available on the organization of the embryonic myocardial interstitium and its modifications during development and increasing intracardiac pressure. In the present study we used light and scanning electron microscopic techniques, and lectin probes to study the interstitium of the ventricular myocardium of chick embryos from stage 29 (day 6 of development) until hatching. Our observations trace the progressive appearance and organization of the elements of the extracellular matrix, comprising the epimysium, perimysium and endomysium, which form a well-defined architectural network. Finally, we discuss the role of these elements of the extracellular matrix and their possible relation with the biomechanical properties of developing heart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01236051
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  • 8
    Electronic Resource
    Electronic Resource
    Development of mouse semilunar valves (1980)
    Springer
    Anatomy and embryology 160 (1980), S. 83-91 
    Details
    ISSN: 1432-0568
    Keywords: Mouse embryo ; Semilunar valves ; Heart morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of the semilunar valves of the great arteries of the mouse is studied by light and scanning electron microscopy. The earliest anlage of the valves is observed at day 11.5 of gestation, as three pairs of tubercles protruding towards the lumen of the truncus arteriosus. These early cusps consist of a core of mesenchymal tissue covered by the endocardium. From day 12.5 to 14 a process of excavation takes place in the arterial face of the cusps resulting in the achievement of their final shape. Our observations suggest that the excavation process is produced by a selective growth of the free edges of the cusps. Numerous pieces of evidence are reported suggesting that the selective growth of the cusps is due to an inductive interaction between the endocardium of the arterial face of the cusps and the underlying mesenchyme. The histogenesis of the cusps takes place very late in development and possibly continues into the postnatal period. The results are compared with studies made in other vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315651
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in the endothelial morphology of the developing semilunar heart valves (1983)
    Springer
    Anatomy and embryology 167 (1983), S. 67-83 
    Details
    ISSN: 1432-0568
    Keywords: Endothelium ; Semilunar valves ; Hemodynamics ; Embryonic heart ; Heart morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In view of recent evidence showing that shape and orientation of endothelial cells is determined by blood flow, the endothelium of the semilunar valves was studied in the developing chick heart using transmission and scanning electron microscopy. The results reveal significant developmental modifications of endothelial morphology and structure. These modifications can be linked to modifications of local blood flow and can also explain several aspects of valvular morphogenesis. The results substantially support the hypothesis of an involvement of hemodynamics in the development of the semilunar valves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304601
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  • 10
    Electronic Resource
    Electronic Resource
    Maturation of the extracellular material of the semilunar heart valves in the mouse (1981)
    Springer
    Anatomy and embryology 162 (1981), S. 343-352 
    Details
    ISSN: 1432-0568
    Keywords: Heart embryology ; Heart valves ; Semilunar valves ; Histogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The developmental changes of collagen and mucopolysaccharides in the semilunar valves of the mouse were studied during the embryonic, fetal and postnatal period. The valvular collagen was investigated using Van Gieson and Sirius red-polarization microscopy methods. These procedures showed that the establishment of the fibrosa layer of the cusps does not occur until the second week of the postnatal period. The nature and distribution of the valvular mucopolysaccharides were investigated by staining with Alcian blue at specific pH values and at various critical electrolyte concentrations, with the appropiate enzymatic controls using Streptomyces and testicular hyaluronidase. The results show that hyaluronate and chondroitin 4- and 6-sulphate are the major components during the embryonic and fetal period. In the older fetal stages and during the postnatal period the relative amount of hyaluronate decreases, while chondroitin sulphate increases. It is concluded from this study that the maturation of the valves occurs over a long period of the postnatal life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299977
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