Search Results - (Author, Cooperation:D. A. Weisblat)

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  1. 1
    Staff View
    Publication Date:
    2012-12-21
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Body Patterning/*genetics ; Conserved Sequence/genetics ; *Evolution, Molecular ; Genes, Homeobox/genetics ; Genetic Linkage ; Genetic Speciation ; Genome/*genetics ; Humans ; INDEL Mutation/genetics ; Introns/genetics ; Leeches/anatomy & histology/*genetics ; Mollusca/anatomy & histology/*genetics ; Multigene Family/genetics ; *Phylogeny ; Polychaeta/anatomy & histology/*genetics ; Synteny/genetics
    Published by:
    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    ISSN:
    1432-041X
    Keywords:
    Key words Annelida ; Leech ; Cell fusion ; Endoderm ; Macromeres
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Biology
    Notes:
    Abstract  At the four-cell stage, embryos of glossiphoniid leeches comprise identified blastomeres A, B, C and D. Subsequent cleavages of the A, B and C quadrants yield three large, yolk-rich endodermal precursor cells, macromeres A′′′, B′′′ and C′′′. Eventually, these cells generate the epithelial lining of the gut via cellularization of a multinucleate syncytium. Meanwhile, cleavage in the D quadrant generates ten teloblasts that give rise to segmental mesoderm and ectoderm via stem cell divisions. Here we show that, during cleavage, macromeres A′′′, B′′′ and C′′′ shift clockwise relative to the D quadrant, while C′′′ comes to envelop the nascent teloblasts. During gastrulation, derivatives of the teloblasts undergo epibolic movements over the surface of the A′′′, B′′′ and C′′′ macromeres to form the germinal plate, from which segmental tissues arise. We find that the three macromeres fuse in a stepwise manner to initiate formation of the multinucleate syncytium; cell C′′′ fuses about 25 h after the fusion of A′′′ and B′′′, and the teloblasts fuse with the macromere-derived syncytium later still. When macromeres are biochemically arrested by microinjecting them with the A chain of ricin, a further difference among the macromeres is revealed. Biochemical arrest of A′′′ or B′′′ slightly retards the rate of germinal plate formation, but arrest of C′′′ frequently accelerates this process.
    Type of Medium:
    Electronic Resource
    URL:
    Articles: DFG German National Licenses
  3. 3
    Staff View
    ISSN:
    1432-041X
    Keywords:
    Key words Gangliogenesis ; Leech ; Annelid ; Engrailed ; Nerve formation
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Biology
    Notes:
    Abstract  Using intracellular lineage tracers to study the main neurogenic lineage (N lineage) of the glossiphoniid leech embryo, we have characterized events leading from continuous columns of segmental founder cells (nf and ns primary blast cells) to discrete, segmentally iterated ganglia. The separation between prospective ganglia was first evident as a fissure between the posterior boundary of nf- and the anterior boundary of ns-derived progeny. We also identified the sublineages of nf-derived cells that contribute parallel stripes of cells to each segment. These stripes of cells project ventrolaterally from the dorsolateral margin of each nascent ganglion to the ventral body wall. The position and orientation of the stripes suggests that they play a role in forming the posterior segmental nerve; they are not coincident with the ganglionic boundary, and they form well after the separation of ganglionic primordia. Previous work has shown that cells in the anterior stripe express the leech engrailed-class gene. Thus, in contrast to the role of cells expressing engrailed in Drosophila, the stripes of N-derived cells expressing an engrailed-class gene in leech do not seem to play a direct role in segmentation or segment polarity.
    Type of Medium:
    Electronic Resource
    URL:
    Articles: DFG German National Licenses