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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 197 (1988), S. 110-114 
    ISSN: 1432-041X
    Keywords: Mouse embryos ; Cytokinesis ; Midbodies ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have examined the persistence of midbody channels during the second, third, and fourth cleavage cycles of the mouse using immunofluorescence to map the distribution of midbody microtubule bundles in intact embryos. Electron microscopy showed these bundles to be a characteristic feature of midbodies throughout the interphase period. In recently-divided embryos at each cleavage stage the number of midbodies was half the number of blastomeres, and declined towards zero as the next cleavage approached. This indicated to us that the only midbodies present in each stage were those which had arisen in the immediately-preceding division. Of those blastomeres which were in mitosis at the time of fixation, less than 4% were connected via a midbody to another blastomere, demonstrating that persistence of midbodies beyond a single cleavage cycle is a rare event. We conclude that midbody channels in our embryos are likely to connect only pairs of sister blastomeres because midbodies do not persist through multiple cleavage cycles. Midbody channels cannot, therefore, be regarded as providing extensive cell coupling in advance of the onset of gap junctional communication.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 376-381 
    ISSN: 1040-452X
    Keywords: Embryogenesis ; Fetal development ; IGFBP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Recent observations suggest that the diverse actions of the insulin-like growth factors (IGFs) are the result of interactions of the various components that make up the IGF system. The components of this system include IGF-I and -II and their variants, the type 1 and 2 IGF receptors and the insulin-like growth factor binding proteins (IGFBPs). Various components of the IGF system are expressed in the developing mouse embryo and the adjacent tissues of the reproductive tract in which the embryo develops. Thus there is the potential for paracrine interactions between the maternal and fetal tissues. Transcripts for the IGF receptors, IGF-I and IGF-II, have been demonstrated in the periimplantation mouse embryo. While there are now data from gene ablation experiments indicating that IGF-II is important in embryogenesis, the role of other components of the IGF system such as the IGFBPs remains unclear. The data accumulated so far are largely empirical, and there is as yet little compelling evidence that maternal IGFs derived from oviduct or uterine fluid and maternal tissues are necessary for normal fetal development. We have started to develop transgenic mice lines overexpressing IGFBPs to attempt to address the role of these binding proteins in fetal development. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0192-253X
    Keywords: Mouse embryos ; Gap junctions ; Connexin43 ; mRNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Gap junctions appear de novo during compaction in the eight-cell stage of mouse development. This is a critical event in the life of the embryo, because gap junctional intercellular communication is an essential requirement for maintaining compaction and, hence, for development of the blastocyst. Recently, a family of genes encoding gap junction proteins (connexins) has been identified and cloned, and we have taken advantage of the availability of antibodies and cDNA probes to investigate the expression of these genes in early development. We found that a protein with antigenic and size similarity to the “liver” gap junction protein, connexin32, is present throughout preimplantation development from the zygote through the late morula. Connexin32 mRNA, however, could not be detected in any preimplantation stage. This, and the presence of connexin32 in zygotes before activation of embryonic transcription, leads us to conclude that this protein is inherited as an oogenetic product that persists well beyond the transition from the oogenetic to embryonic program of gene expression. Furthermore, we found that mRNA for another gap junction protein, connexin43, is fairly abundant in preimplantation embryos. We conclude that it is more likely connexin43, and not connexin32, that is used to assemble new connexons as the level of intercellular coupling increases after compaction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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