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  • 1
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Programmed neuronal cell death is common during development, and is thought to be important in the elimination of errors in axonal projection, cell position and sculpting of neuronal circuits. However, the potential importance of programmed cell death for complex behaviour in the adult animal has never been addressed. We studied motor abilities in a strain of transgenic mice with neuronal overexpression of the human Bcl-2 protein, which have supernumerary neurons due to reduced developmental cell death. Our results show that these mice have a clear deficiency in fine timing of motor coordination without impairment of basic motor functions. This is the first indication that altered developmental cell death and the consequent neuronal surplus can impair complex behaviour in the adult animal.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 10 (1998), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Molecular mechanisms of neuronal cell death are still largely unknown. In the present study, the signal transduction pathway of cell death in cerebellar granule neurons was examined by employing various death-preventative agents. When death was induced by the depletion of serum and a depolarizing level of potassium, transient increase in active c-Jun, mitochondrial membrane potential (Δψ) loss, activation of caspase-3 (-like) proteases, and nuclear condensation and fragmentation were observed. The protein synthesis inhibitor cycloheximide blocked all these phenomena, whereas RNA synthesis inhibitor actinomycin-D, survival factor such as insulin-like growth factor-1, brain-derived neurotrophic factor, high K+ (25 m m) and overproduced antiapoptotic protein Bcl-2, prevented Δψ loss, caspase activation, and nuclear change, but not an increase in active c-Jun. The caspase inhibitor z-Asp-CH2-DCB (carbobenzoxy-l-aspartyl-α-[(2,6-dichlorobenzoyl) oxy]methane) only inhibited activation of caspases and nuclear change. These results suggest that the death signal in cerebellar granule neurons is sequentially transduced in the order of c-Jun activation, de novo RNA synthesis, mitochondrial Δψ loss, activation of caspase-3 (-like) proteases and nuclear change.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Overproduced Bcl-2 oncoprotein has been shown to suppress cell death induced by a variety of stimuli in many cell types, including neuronal cells. Because bcl-2 is expressed in the nervous system where massive cell death is observed during development, endogenous Bcl-2 is likely to be involved in regulating neuronal cell death. Here we examined the possible role of endogenous Bcl-2 in the regulation of neuronal cell survival in the central nervous system using primary cultured cerebellar granule neurons from bcl-2-deficient, wild-type and NSE-bcl-2- transgenic mice. Cerebellar granule neurons from bcl-2-deficient mice were more susceptible than those from normal littermates to death induced by reducing the K+ concentration of the medium from high (25 mM) to low (5 mM), and neurons from bcl-2-transgenic mice were least susceptible. Similar results were obtained when cell death was induced by serum withdrawal under high K+ conditions or by the presence of etoposide, A23187 or nimodipine. Consistently, bcl-2 deficiency reduced the number of cerebellar granule neurons per mouse. These results indicate that Bcl-2 impedes neuronal cell death induced by various stimuli in a dose-dependent manner, and that endogenous levels of Bcl-2 are able to regulate neuronal cell survival in the central nervous system.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The causes of death of transplanted neurons are not known in detail, but apoptotic mechanisms involving caspase activation are likely to play a role. We examined whether overexpression of the anti-apoptotic protein Bcl-2 may enhance the survival of dopaminergic [tyrosine hydroxylase (TH)-immunoreactive] grafted neurons. For this purpose, we prepared cells from embryonic day 13 ventral mesencephalon (VM) of mice overexpressing human Bcl-2, or from their wild-type littermates. The bcl-2 transgene was strongly expressed in these cells, and resulted in protection of neuronal cultures from death triggered by serum deprivation or exposure to staurosporine. To model pretransplantation stress more closely in vitro, we stored dissociated embryonic mesencephalic cells for 8 h in the same type of medium used for intracerebral transplantation. This resulted in massive cell death as quantified by lactate dehydrogenase (LDH) release, and increased DNA fragmentation. Although this cell loss was strongly reduced by a caspase inhibitor, Bcl-2 had no significant protective effect. Finally, mesencephalic cell suspensions were xenografted into the striatum of immunosuppressed hemiparkinsonian rats. Neither the survival of TH-immunopositive transplanted neurons nor the functional recovery of the rats was improved by Bcl-2, although the Bcl-2 protein was strongly expressed in transgenic grafts 5 weeks after implantation, and dopaminergic fibre outgrowth from the grafts was significantly improved. These data suggest that cell death in neuronal transplants involves apoptotic mechanisms that can bypass negative regulation by Bcl-2.
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The bcl-2 gene codes for a protein that acts as a powerful inhibitor of active cell death. Since the transection of the optic nerve in adult mammalians starts a massive process of degeneration in retinal ganglion cells, we investigated whether the overexpression of bcl-2 in adult transgenic mice can protect the axotomited ganglion cells. We performed intracranial optic nerve transection on both wild type and transgenic adult mice, and we tested cell survival 2 or 3.5 months after axotomy. The percentage of surviving ganglion cells after optic nerve section was computed by combining the counts of the optic nerve fibres in intact nerves with the cell density measures of the ganglion cell layer of axotomized retinae. From these data we found that in transgenic mice˜65% of ganglion cells survived 3.5 months after axotomy. In contrast, 2 months after surgery, 〈10% of ganglion cells were left in wild type retinae. We have also examined the morphology and fine structure of the proximal stump of the sectioned optic nerves by light and electron microscopy. In the transgenic mice a very large number of axons survived after surgery and they still exhibited fairly normal morphology and ultrastructure. On the other hand the wild type transected nerves had only a few visible axons that displayed clear signs of degeneration. We conclude that the overexpression of Bcl-2 protein in central neurons is a very effective strategy to ensure long-term survival in axotomized cells.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 434-439 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To examine the growth of CNS axons of mice, we established an organotypic co-culture model of the retinotectal system in which the growth pattern of retinal axons closely mimics that seen in vivo2. Tissues from retinae and midbrain tecta of C57BL/6J mice were abutted in a culture well. Quantitative ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 399 (1999), S. 411-412 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The mitochondrion, which was once thought simply to generate energy for a cell, is, in fact, a pivotal decision centre — it controls life and death by releasing death-promoting factors into the cytosol. One of these factors is cytochrome c, a protein that normally shuttles electrons between ...
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To identify E1B 19K binding proteins, we used the yeast two-hybrid system18'19 to screen an Epstein-Barr virus (EBV)-trans-formed human B-cell library and found several interacting clones. These include two independently isolated complementary DNAs encoding large fragments of the lamin A/C ...
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