Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    An SEM study of cellular morphology, contact, and arrangement, as related to gastrulation inXenopus laevis (1977)
    Springer
    Development genes and evolution 182 (1977), S. 165-186 
    Details
    ISSN: 1432-041X
    Keywords: Gastrulation ; Xenopus ; SEM ; Gastrula ; Blastula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cellular morphology, contact, and arrangement in the late blastula and in various stages of gastrulation ofXenopus were examined by SEM of specimens dissected after fixation or fractured in amyl acetate. The prospective ectoderm of the blastocoel roof consists of several layers of interdigitating cells connected by numerous small protrusions which may function in the decrease in number of cell layers observed during ectodermal epiboly. During gastrulation, prospective mesoderm is regionally differentiated by cellular morphology and arrangement into preinvolution mesoderm, the mesodermal involution zone, and involuted mesoderm. The involuted anterodorsal (head), lateral, and ventral mesoderm consists of a stream of loosely-packed, irregularly shaped cells having large extensions of the cell body attached locally to other cells by small protrusions. Involuted posterodorsal mesoderm (chordamesoderm) consists of elongated cells arranged in palisade fashion and connected by similar protrusions. Involuted mesodermal cells in all regions are attached to the overlying prospective ectodermal cells by numerous small protrusions along the entire interface between the two cell layers. Suprablastoporal endodermal cells involute as an epithelial sheet, changing in shape in the process, to form the roof of the archenteron. Bottle cell morphology, arrangement, and position with respect to the mesodermal cell stream is described. Evidence presented here and elsewhere suggests that involution of mesoderm and of the archenteron roof inXenopus is dependent primarily upon the relative movement of the mesodermal cell stream and of the overlying ectoderm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848055
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Morphogenetic processes involved in the remodeling of the tail region of the chick embryo (1981)
    Springer
    Anatomy and embryology 162 (1981), S. 183-197 
    Details
    ISSN: 1432-0568
    Keywords: Morphogenesis ; Tail ; Chick embryo ; Cell death
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tail regions from chick embryos at three to ten days of incubation were examined by light and electron microscopy to determine what morphogenetic processes occur during transformation of the embryonic tail into the definitive type. The embryonic tail attained its maximum length (0.6 mm) between four and five days of incubation. Thereafter, the tip and base of the tail developed differently. The diameter of the tip of the tail decreased during four to six days of incubation, and many macrophages and presumptive necrotic cells appeared in this area. The tip of the tail then gradually increased in diameter during six to ten days of incubation, and changed in shape from conical to pyramidal. Only a few macrophages and presumptive necrotic cells were present during these latter stages. In most embryos during seven to ten days of incubation, the caudal end of the neural tube was cystic and small hemorrhagic zones were present in the ventral part of the tip of the tail. Near the end of this period, the ectoderm overlying the cystic portion of the neural tube often ruptured. The base of the tail increased gradually in breadth during all stages. Between six and ten days of incubation, as the leg buds elongated rapidly, the cranial part of the base of the tail became incorporated into the caudal part of the trunk. These results suggest that during morphogenesis of the tail region three morphogenetic events occur: differential growth, incorporation of part of the tail into the trunk, and cell death. The definitive tail of late incubation and posthatching stages is derived from mainly the distal portion of the base of the embryonic tail; the tip of the embryonic tail is mostly lost.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306490
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Axis development in avian embryos: the ability of Hensen's node to self-differentiate, as analyzed with heterochronic grafting experiments (1993)
    Springer
    Anatomy and embryology 188 (1993), S. 1-11 
    Details
    ISSN: 1432-0568
    Keywords: Chick and quail embryos ; Chimeras ; Gastrulation ; Neurulation ; Notochord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A series of experiments consisting of transplantation of Hensen's nodes has been conducted to examine axis development in avian embryos. In the first group of experiments, Hensen's nodes from quail embryos were transplanted homotopically and either isochronically or heterochronically to chick embryos, and the structures derived form the grafted nodes were assessed. The grafted Hensen's nodes typically self-differentiated structures appropriate for their stages, and the host embryos developed normally; the structures formed from grafted tissue usually merged caudally with the comparable host structures. Thus, even when the stages of the donor and host tissues were significantly mismatched (e.g., stage 3 donors and stage 9 hosts or vice versa), the graft was unable to repattern the host's neuraxis, and the host was unable to respecify the types of structures derived from the graft. In the second group of experiments, Hensen's nodes from quail embryos were transplanted to sites located just lateral to Hensen's nodes of host chick embryos, thereby providing the potential for development of additional axes. A single axis always resulted in each case in which further development occurred, with the graft self-differentiating its typical stage-specific structures, all of which merged caudally with comparable host structures. A final group of experiments served principally as a control and tested the ability of a part of Hensen's node, when it was transplanted to the extraembryonic germ cell crescent, to organize an ectopic embryo. In these experiments, the entire thickness and length of each Hensen's node, but only the central one-third to one-half of its width, was transplanted to host blastoderms, yet ectopic embryos, complete with induced neuraxes, were formed. Therefore, a part of Hensen's node has the ability to function fully as an organizer when placed in a conducive environment. Collectively, these results provide further documentation of the strong ability of Hensen's node to self-differentiate, and they suggest that once morphogenetic movements are under way, neuraxial structures can form, and characteristic rostrocaudal patterning of the neuraxis can occur, without sustained influence from Hensen's node.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191446
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Neural plate- and neural tube-forming potential of isolated epiblast areas in avian embryos (1989)
    Springer
    Anatomy and embryology 179 (1989), S. 541-549 
    Details
    ISSN: 1432-0568
    Keywords: Chick embryo ; Epiblast ; Neural plate ; Neural tube ; Neuroepithelium ; Neurulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Formation, shaping, and bending of the neural plate and closure of the neural groove are complex processes resulting in formation of the neural tube. Two experiments were performed using avian embryos as model systems to examine these events. First, we transected blastoderms near the level of Hensen's node to determine the potential of prenodal neural plate to form neural tube in isolation from primitive streak regression. Our results demonstrate that shaping and bending of the prenodal neural plate occur under these conditions, but neural groove closure is inhibited. Second, we isolated various areas of postnodal epiblasts to determine their potential to form neural plate. Our results suggest that the area of the postnodal epiblast that can form neural plate consists of paired tracts lying adjacent to the definitive primitive streak and extending caudally at least 1 mm from its cranial end.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315697
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Programmed cell death and the morphogenesis of the hindbrain roof plate in the chick embryo (1999)
    Springer
    Anatomy and embryology 200 (1999), S. 509-519 
    Details
    ISSN: 1432-0568
    Keywords: Key words Apoptosis ; Neural crest cells ; Neurulation ; Neuroepithelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The spatial and temporal distribution of apoptosis in the dorsal midline of the developing chick hindbrain was examined in relation to the development of the neuroepithelium and neural crest using scanning and transmission electron microscopy, immunocytochemistry and in situ hybridization. The pattern of TUNEL labeling and Slug expression in the dorsal midline at stages 10 and 11 differed from that at stages 12–15. At stages 10 and 11, TUNEL labeling and Slug expression were observed in the dorsal part of location II of rhombomere 1/2 (i.e., between the surface ectoderm and the neuroepithelium), but from stage 12 onward, they were observed in both the dorsal and ventral parts of location II. The implication is that whereas apoptosis may be restricted to a subpopulation of the early migrating neural crest at stages 10 and 11, it presumably occurs in subpopulations of both neural crest and neuroepithelial cells from stage 12 onward. Furthermore, as judged by the pattern of TUNEL labeling and Slug expression in r3 and r5, apoptosis in these two rhombomeres likely occurs in subpopulations of both neural crest and neuroepithelial cells. The eminence present in location I of r1/r2 between stages 10 and 12 consisted of both neural crest and neuroepithelial cells. These cells gradually underwent apoptosis until stage 12, when the eminence disappeared in most embryos. The formation of the inner (neuroepithelial) aspect of the hindbrain roof plate involved both cell migration from adjacent neuroepithelium and an alteration in the shapes of the cells, such that cells with flattened surfaces eventually lined the roof plate. During these processes, some of the neuroepithelial cells underwent apoptosis (i.e., in location IV). The results of this study thus demonstrate that subpopulations of both neuroepithelial and neural crest cells may be involved in programmed cell death in the hindbrain. Additionally, apoptosis in the hindbrain contributes significantly to morphogenetic thinning during roof plate formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050299
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Experimental analyses of the rearrangement of ectodermal cells during gastrulation and neurulation in avian embryos (1995)
    Springer
    Cell & tissue research 280 (1995), S. 243-251 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Convergent-extension ; Ectoderm ; Neural plate ; Domestic fowl ; Quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The rearrangement of ectodermal cells was studied in chimeras in which grafts were transplanted during late gastrula and early neurula stages to heterotopic locations in avian embryos. Three types of experiments were done. In all experiments, Hensen’s node was extirpated completely and replaced with an epithelial plug derived from 1 of 3 regions of the prospective ectoderm. In type-1 experiments, Hensen’s node was replaced with a plug consisting of precursor cells of the floor plate of the neural tube. In type-2 experiments, Hensen’s node was replaced with a plug consisting of precursor cells of the lateral wall of the neural tube. In type-3 experiments, Hensen’s node was replaced with a plug consisting of precursor cells of the epidermal ectoderm. In all experiments, the amount and direction of cell rearrangement that occurred in the transplanted ectodermal plug was essentially typical for prospective ectodermal cells normally residing within Hensen’s node. That is, transplanted ectodermal cells underwent lateral-to-medial cell-cell intercalation and contributed to the ventral midline of the neural tube along its entire rostrocaudal extent. In most embryos, a notochord was reconstituted from host cells, despite the fact that Hensen’s node – the prime source of prospective notochordal cells in intact embryos – was extirpated completely; however, a few embryos had long notochordal gaps. In such essentially notochordless embryos, the ventral midline of the neural tube still derived from grafted cells, but it failed to form a floor plate, providing further confirmation of the results of several previous studies that the notochord is required to induce the floor plate. Collectively, our results provide evidence that the rearrangement of ectodermal cells does not require the presence of a ”trail” of prospective floor plate cells (laid down by the regressing Hensen’s node), or of a notochordal substrate, and that the continued presence of an organizer per se, ostensibly Hensen’s node, is not required. In addition, our results demonstrate that the rearrangement of cells still occurs in the absence of ”boundaries” between ectodermal cells of different phenotypes (e.g., between cells of the floor plate and lateral walls of the neural tube). Finally, our results reveal further that the amount and direction of cellular rearrangement is not regulated in a cell-autonomous fashion, but rather it is determined by the overall magnitude and vector of the displacement of the community of rearranging cells within a developmental field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307795
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Experimental analyses of the rearrangement of ectodermal cells during gastrulation and neurulation in avian embryos (1995)
    Springer
    Cell & tissue research 280 (1995), S. 243-251 
    Details
    ISSN: 1432-0878
    Keywords: Convergent-extension ; Ectoderm ; Neural plate ; Domestic fowl ; Quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The rearrangement of ectodermal cells was studied in chimeras in which grafts were transplanted during late gastrula and early neurula stages to heterotopic locations in avian embryos. Three types of experiments were done. In all experiments, Hensen's node was extirpated completely and replaced with an epithelial plug derived from 1 of 3 regions of the prospective ectoderm. In type-1 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the floor plate of the neural tube. In type-2 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the lateral wall of the neural tube. In type-3 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the epidermal ectoderm. In all experiments, the amount and direction of cell rearrangement that occurred in the transplanted ectodermal plug was essentially typical for prospective ectodermal cells normally residing within Hensen's node. That is, transplanted ectodermal cells underwent lateralto-medial cell-cell intercalation and contributed to the ventral midline of the neural tube along its entire rostrocaudal extent. In most embryos, a notochord was reconstituted from host cells, despite the fact that Hensen's node — the prime source of prospective notochordal cells in intact embryos — was extirpated completely; however, a few embryos had long notochordal gaps. In such essentially notochordless embryos, the ventral midline of the neural tube still derived from grafted cells, but it failed to form a floor plate, providing further confirmation of the results of several previous studies that the notochord is required to induce the floor plate. Collectively, our results provide evidence that the rearrangement of ectodermal cells does not require the presence of a “trail” of prospective floor plate cells (laid down by the regressing Hensen's node), or of a notochordal substrate, and that the continued presence of an organizer per se, ostensibly Hensen's node, is not required. In addition, our results demonstrate that the rearrangement of cells still occurs in the absence of “boundaries” between ectodermal cells of different phenotypes (e.g., between cells of the floor plate and lateral walls of the neural tube). Finally, our results reveal further that the amount and direction of cellular rearrangement is not regulated in a cell-autonomous fashion, but rather it is determined by the overall magnitude and vector of the displacement of the community of rearranging cells within a developmental field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307795
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Effects of complete tail bud extirpation on early development of the posterior region of the chick embryo (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 192 (1978), S. 289-295 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The tail bud was completely extirpated down to the yolk from 65 embryos at stages 13-17 to determine whether the posterior part of the noto-chord originates from the tail bud or from a more anterior region (i.e., prospective notochordal region). About 40% of the 44 surviving embryos developed near-normal tails, con̈taining a localized defective region beginning near the base of the tail and extending a short distance posteriorly, about 15% developed truncated, cone-shaped tails, containing a defective region beginning near the base of the tail and extending towards the tip, and about 45% developed short, ventral tail remnants, containing a localized defective region beginning near the base of the tail and extending a short distance posteriorly. The tail was absent in only one embryo. These differences were probably due primarily to variation in the amount of healing and regeneration that occurred, and were independent of the stage at which the operation took place. The tail region has a tremendous capacity for regeneration since a near-normal tail frequently developed. The location of the beginning of the defective region near the base of the tail suggests that the tail bud primarily gives rise to tail structures. All embryos had neural tube defects, about 30% developed large, midline somites within the defective region, and about 25% developed an ourenteric outgrowth. The notochord was always normal within the defective region. These results are consistent with the view that the tail bud contributes cells to the posterior part of the neural tube, but not to the notochord.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091920209
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Descriptive studies of occlusion and reopening of the spinal canal of the early chick embryo (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 209 (1984), S. 251-263 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Occlusion and reopening of the lumen of the spinal cord, two processes believed to be involved in early brain enlargement, were examined in chick embryos to determine what morphological features characterize these events. Occlusion begins at a particular craniocaudal level near the time that the neural folds become apposed in the dorsal midline and blocklike somites form from the segmental plates. During occlusion, the apical sides of the lateral walls of the neural tube are in close apposition. Interdigitating apical surface protrusions, cross-luminal intercellular junctions, and abundant cell-surface materials are lacking. Reopening has occurred by about stage 20 throughout most of the craniocaudal extent of the spinal cord. A lumen suddenly appears during this process, but correlated structural changes that might account for such a dramatic change in morphology were undetectable. Reopening involves the release of the forces that previously maintained occlusion, or the generation of new forces that overcome those causing occlusion, but what these forces are remains to be determined. Observations suggest that forces generated outside of the neural tube might be largely responsible for occlusion, and experiments are in progress to test this possibility.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092090211
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Cell cycle and neuroepithelial cell shape during bending of the chick neural plate (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 218 (1987), S. 196-206 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Neuroepithelial cells change shape from spindle-like to wedge-like within three restricted areas (hinge points) of the bending neural plate. The mechanisms underlying these localized cell shape changes and the specific role that these changes play in bending are nuclear. This study was designed to determine whether changes in neuroepithelial cell shape involve basal cellular expansion owing to alteration of the cell cycle. Neurulating chick embryos were treated with colchicine to arrest and accumulate cells in metaphase, and colchicine indices and cell generation times were calculated for the neural plate. During bending of the neural plate, cell generation time in the median hinge point, which contains predominantly wedge-shaped cells, was significantly longer than that in adjacent lateral areas of the neural plate, which contain predominantly spindle-shaped cells. In addition, cell generation time in the flat neural plate, which contains predominantly spindle-shaped cells and has not yet differentiated into the median hinge point and lateral subdivisions, was identical to that in lateral areas of the bending neural plate but was significantly shorter than that in the median hinge point. These results support the hypothesis that changes in neuroepithelial cell shape from spindle-like to wedge-like involve basal cellular expansion owing to alteration of the cell cycle. Additional tests of this hypothesis and studies on the role of localized cell shape changes in neurulation are in progress.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092180215
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...