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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative studies of mitotic cells in the chick embryo optic stalk during the early period of invasion by optic fibres (1989)
    Springer
    Anatomy and embryology 180 (1989), S. 343-351 
    Details
    ISSN: 1432-0568
    Keywords: Mitosis ; Optic stalk ; Optic fibres ; Chick embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In addition to mitoses of neuroepithelial cells at the ventricular surface of the chick embryo optic stalk, mitoses in nonventricular stalk zones begin to be observed from stage 19 on. These latter represent the division phase of glioblasts detached from the ventricular surface. Thus, the topographical location of mitotic cells could be considered a morphological marker of neuroepithelial and glioblast populations in the optic stalk. Quantitative analysis of ventricular (VMCs) and extraventricular (EMCs) mitotic cells revealed that the total number of VMCs decreases through the developmental stages studied, while the number of EMCs simultaneously increases exponentially. These results suggest that the glioblast population arises from both division of the early glioblasts and progressive transformation of neuroepithelial cells. The first EMCs in the ventral region of the stalk wall are observed in stage 19, previous to the stages in which the first EMCs appear in the dorsal region. Moreover, EMCs are much more numerous in the ventral than in the dorsal stalk wall in all stages analysed. Keeping in mind that the invasion of the stalk by optic fibre fascicles occurs essentially in the ventral region, these results suggest that EMCs are strongly related to axon fascicle outgrowth in the stalk. Cell division features are different in neuroepithelial cell and glioblast populations, as the proportions of the mitotic phases differ in VMCs and EMCs. In addition, the patterns of mitotic spindle orientation in VMCs and EMCs are also different. In the former, orientations are predominantly longitudinal parallel and transverse parallel, with a smaller proportion of radial mitoses, which are slightly more frequent through stages 23 to 28 than in earlier development. In the EMCs, radial and longitudinal parallel spindle orientations are the most frequent, the proportion of mitoses with transverse parallel orientation being very low through stages 24 to 28. The significance of these results is discussed with reference to stalk developmental mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311166
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  • 2
    Electronic Resource
    Electronic Resource
    Cell death in the ventral region of the neural retina during the early development of the chick embryo eye (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 222 (1988), S. 272-281 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study deals with morphologic and quantitative changes that take place in the area of cell death in the ventral part of the presumptive retinal wall of the chick embryo. These changes were followed from the optic vesicle stage until the first optic fiber fascicles leave the neural retina. Our results show that both the volume occupied by the area of cell death and the density of its pyknotic fragments undergo considerable variation during the period between Hamburger and Hamilton's (1951) stages 12 to 20. In the optic vesicle stages, cell death in the ventral wall of the vesicle was observed in 50 to 75% of the embryos studied. During stages 14 and 15, this zone was seen in more than 90%. By the time invagination of the optic cup was complete, the ventral retinal zone of cell death had disappeared entirely in a large proportion of embryos; in all other, it shrank significantly both in volume and density of pyknotic fragments. In stage 19, when the first optic fiber fascicles begin to emerge from the retina, a dramatic increase occurs in the number of pyknotic fragments in the posterior pole of the retina. The appearance of dying cells, in a region shortly to be traversed by developing ganglion cell axons, supports the hypothesis that cell death processes are apparently somehow related to the creation of a suitable environment for the emergence of fibers toward the optic stalk. Densities of mitotic and interphasic cells as well as the mitotic index were determined in both the retinal zone of cell death and in areas devoid of dead cells. In all developmental stages analyzed, the mitotic index was notably lower in the former than in non-necrotic zones, suggesting that cell proliferation is partially inhibited in retinal areas of cell death.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092220308
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  • 3
    Electronic Resource
    Electronic Resource
    Shaping, invagination, and closure of the chick embryo otic vesicle: Scanning electron microscopic and quantitative study (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 228 (1990), S. 315-326 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Scanning electron microscopy, light microscopy, and morphometric analysis were used to study the morphological changes of the otic placode and vesicle before and during invagination and closure processes. Our results reveal that the otic placode undergoes shaping between stages HH9 and HH12; during this period the rostrocaudal axis is shortened, while the lateromedial axis of the placode lengthens. The presence of long cytokinesis bridges during this period suggests that cellular displacements after mitosis may participate in the shaping of the otic placode. The shaping process appears to facilitate the approach of the otic placode to the neural tube. From stage HH12 on, the otic anlage gradually becomes a U-shaped structure with its medial portion in intimate apposition to the rhombencephalic neural tube. The coincidence in time between the beginning of intimate otic anlage-rhombencephalon contact and active invagination suggests that these two processes are related.Changes occurring at the edges of the otic vesicle until their disappearance in stage HH17 suggest that, in addition to a process of invagination, the edges of the otic anlage become bent. During closure, cells at the edges of the otic vesicle differ in apical morphology according to their topographical location: The cells between the rostral and lateral edges have elongated apices, in contrast with the polygonal shape of the cell apices in other places of the edges. In the opposite side (between the caudal and medial edges) cell death is observed. Closure of the otic vesicle conceptualized as a zipper-like model is discussed.We propose that early development of the otic anlage takes place in four stages: (1) shaping (stages HH9-11); (2) triggering of the invagination (stage HH12); (3) early invagination and lateral bending (stages HH13-15); and (4) late invagination and closure (stages HH16-17).
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092280311
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  • 4
    Electronic Resource
    Electronic Resource
    Monoclonal antibodies identifying subsets of ectodermal, mesodermal, and endodermal cells in gastrulating and neurulating avian embryos (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 235 (1993), S. 591-603 
    Details
    ISSN: 0003-276X
    Keywords: Auditory placode ; Chick and quail embryos ; Chimeras ; Endoderm ; Gastrulation ; Germ layers ; Mesoderm ; Neural plate ; Neurulation ; Notochord ; Primitive streak ; Surface ectoderm ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The goal of our laboratory research is to elucidate the mechanisms underlying gastrulation and neurulation, using the avian embryo as a model system. In previous studies, we used two approaches to map the morphogenetic movements involved in these processes: (1) we constructed quail/chick transplantation chimeras in which grafted quail cells could be identified within chick host embryos by the presence of nucleolarassociated heterochromatin, and (2) we microinjected exogenous cell markers. However, it would be advantageous to be able to detect endogenous markers to demarcate various subsets of cells within the unmanipulated embryo. To elucidate such a series of natural markers, we have used monoclonal antibodies to identify epitopes found on subsets of ectodermal, mesodermal, and endodermal cells. Antibodies were made by immunizing mice against either homogenized ectoderm (i. e., Prospective neural plate and surface ectoderm) or primitive streak, which had been microdissected from stage 3 chick embryos. Additionally, we screened a panel of antibodies made against soluble protein obtained from isolates of cell nuclei from late embryonic chick brain. Here, we describe the labeling patterns of three monoclonal antibodies, called MAb-GL1, GL2, and GL3 (GL, germ layer), during avian gastrulation and neurulation. Our results show that labeling early avian embryos with monoclonal antibodies can reveal previously undetected distributions of cells bearing shared epitopes, providing new labels for subsets of cells in each of the three primary germ layers. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092350412
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