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  • 1
    Electronic Resource
    Electronic Resource
    Formation of neuroblastic layers in chicken retinospheroids: the fibre layer of Chievitz secludes AChE-positive cells from mitotic cells (1992)
    Springer
    Cell & tissue research 268 (1992), S. 401-408 
    Details
    ISSN: 1432-0878
    Keywords: Reaggregation culture ; Retina, histogenesis ; Pigment epithelium ; F11-antigen ; Acetylcholinesterase ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The significance of the classical subdivision of the retinal primitive neuroepithelium into an outer and an inner neuroblastic layer by the transient fibre layer of Chievitz (LOC) is little understood. We examine here the formation of neuroblastic layers by regenerating fully laminated retinospheroids from dissociated cells of the embryonic chick eye margin in rotary culture. By tracing cellular processes with the fibre-specific F11-antibody in retinospheroids, we occasionally find, in addition to an outer and an inner plexiform layer, a cell-free F11-positive LOC homologue, subdividing the inner nuclear layer. Moreover, we demonstrate that the LOC precisely separates postmitotic AChE-positive cells of the inner retina from an AChE-negative outer part holding all BrdU-labelled mitotic cells. These in vitro data suggest that the inner neuroblastic layer is exclusively composed of AChE-positive cells, thus representing a primary differentiation zone of the retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319146
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chicken retinospheroids as developmental and pharmacological in vitro models: acetylcholinesterase is regulated by its own and by butyrylcholinesterase activity (1992)
    Springer
    Cell & tissue research 268 (1992), S. 409-418 
    Details
    ISSN: 1432-0878
    Keywords: Acetylcholinesterase ; Butyrylcholinesterase ; Cholinergic system ; Retina ; Reaggregation culture ; Optic tectum ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The phylo- and ontogenetically related enzymes butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) are expressed consecutively at the onset of avian neuronal differentiation. In order to investigate their possible co-regulation, we have studied the effect of highly selective inhibitors on each of the cholinesterases with respect to their expression in rotary cultures of the retina (retinospheroids) and stationary cultures of the embryonic chick tectum. Adding the irreversible BChE inhibitor iso-OMPA to reaggregating retinal cells has only slight morphological effects and fully inhibits BChE expression. Unexpectedly, iso-OMPA also suppresses the expression of AChE to 35%–60% of its control activity. Histochemically, this inhibition is most pronounced in fibrous regions. The release of AChE into the media of both types of cultures is inhibited by iso-OMPA by more than 85%. Control experiments show that AChE suppression by the BChE inhibitor is only partially explainable by direct cross-inhibition of iso-OMPA on AChE. In contrast, the treatment of retinospheroids with the reversible AChE inhibitor BW284C51 first accelerates the expression of AChE and then leads to a rapid decay of the spheroids. After injection of BW284C51 into living embryos, we find that AChE is expressed prematurely in cells that normally express BChE. We conclude that the cellular expression of AChE is regulated by the amount of both active BChE and active AChE within neuronal tissues. Thus, direct interaction with classical cholinergic systems is indicated for the seemingly redundant BChE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319147
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cholinesterases regulate neurite growth of chick nerve cells in vitro by means of a non-enzymatic mechanism (1993)
    Springer
    Cell & tissue research 273 (1993), S. 219-226 
    Details
    ISSN: 1432-0878
    Keywords: Acetylcholinesterase ; Axon guidance ; Butyrylcholinesterase ; Cell adhesion molecules ; HNK-1 epitope ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cholinesterases present homologies with some cell adhesion molecules; however, it is unclear whether and how they perform adhesive functions. Here, we provide the first direct evidence showing that neurite growth in vitro from various neuronal tissues of the chick embryo can be modified by some, but not all, anticholinesterase agents. By quantifying the neuritic G4 antigen in tectal cell cultures, the effect of anticholinesterases on neurite growth is directly compared with their cholinesterase inhibitory action. BW 284C51 and ethopropazine, inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively, strongly decrease neurite growth in a dose-dependent manner. However, echothiophate which inhibits both cholinesterases, does not change neuritic growth. These quantitative data are supplemented by morphological observations in retinal explant cultures grown on striped laminin carpets, viz., defasciculation of neurite bundles by BW 284C51 and Bambuterol occurs, indicating that these drugs disturb adhesive mechanisms. These data strongly suggest that a) cholinesterases can participate in regulating axonal growth, b) both AChE and BChE can perform such a nonsynaptic function, and c) this function is not the result of the enzyme activity per se, since at least one drug was found that inhibits all cholinesterase activities but not neurite growth. Thus, a secondary site on cholinesterase molecules must be responsible for adhesive functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312823
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cranial nerve growth in birds is preceded by cholinesterase expression during neural crest cell migration and the formation of an HNK-1 scaffold (1991)
    Springer
    Cell & tissue research 265 (1991), S. 393-407 
    Details
    ISSN: 1432-0878
    Keywords: Acetylcholinesterase ; Axonal pathfinding ; Butyrylcholinesterase ; Cell adhesion molecules ; Ectodermal placodes ; Schwann cells ; Chicken ; Japanese quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The expression of the neural crest cell (NCC) markers acetylcholinesterase (AChE) and the HNK-1-epitope is compared from the emigration of cephalic NCC until the formation of the cranial nerves V-X in chicken and quail hindbrain. We show that NCC transiently express acetylcholinesterase (AChE) activity during their emigration; NCC migrate into butyrylcholinesterase (BChE)-positive areas of the cranial mesenchyme. Along these migratory tracks that foreshadow the course of later projecting cranial nerves, BChE increases strongly in cells that may represent immature Schwann cells. Both AChE and BChE, but not HNK-1, are expressed in the ectodermal placodes. In NCC, HNK-1 is expressed strongly only when they approach their destination sites. Their intense expression of HNK-1 then leads to the establishment of tunnel-shaped HNK-1 matrices, within which G4-positive cranial neurites begin to extend. We conclude that AChE and HNK-1 expression in cephalic NCC serve different functions, since AChE is related to their migration, and HNK-1 to their aggregation and the formation of an extracellular neurite scaffold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340862
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    Paper (German National Licenses)
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