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  • Spontaneous regeneration of the corticospinal tract after transection in young rats: a key role of reactive astrocytes in making favorable and unfavorable conditions for ... 15207354

    We demonstrated the occurrence of marked regeneration of the corticospinal tract (CST) after a single transection and failure of regeneration after a repeated transection in young rats. To provide convincing evidence for the complete transection and regeneration we used retrograde neuronal double labeling. Double-labeled neurons that took up the first tracer from the transection site and the second tracer from the injection site caudal to the transection site were observed in the sensorimotor cortex. The anterograde tracing method revealed various patterns of regeneration. In the most successful cases the vast majority of regenerated fibers descended in the normal tract and terminated normally whereas a trace amount of fibers coursed aberrantly. In the less successful cases fibers descended partly normally and partly aberrantly or totally aberrantly. To clarify the role of astrocytes in determining the success or failure of regeneration we compared expression of glial fibrillary acidic protein (GFAP), vimentin and neurofilament (NF) immunoreactivity (IR) in the lesion between single and repeated transections. In either transection, astrocytes disappeared from the CST near the lesion site as early as 3 h after lesioning. However, by 24 h after a single transection, immature astrocytes coexpressing GFAP- and vimentin-IR appeared in the former astrocyte-free area and NF-positive axons crossed the lesion. By contrast, after a repeated transection the astrocyte-free area spread and NF-positive axons never crossed the lesion. It appears likely that the major sign, and possibly cause of failure of regeneration is the prolonged disappearance of astrocytes in the lesioned tract area.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Topoisomerase inhibitor induced dephosphorylation of H1 and H3 histones as a consequence of cell cycle arrest. 15962304

    Posttranslational modifications of histones have an integral function in the structural and functional organization of chromatin. Several changes in the modification state of histones could be observed after induction of apoptosis with topoisomerase inhibitors and other inducers. Most of these studies include the analysis of the state of phosphorylation of histones, and the results are to some extent controversial, depending on cell lines and agents used. In the present study we compared the kinetics of the dephosphorylation of H1 and H3 histones with apoptosis markers after treatment of leukemic cell lines with topoisomerase inhibitors. In parallel, we determined cell cycle parameters in detail. Dephosphorylation of both histone classes started within 1 h of induction, and no direct correlation with timing and intensity of the investigated apoptotic features could be observed. In contrast, we show that the effect of topoisomerase inhibitors on the state of H1 and H3 phosphorylation is not directly related to apoptosis, but reflects the changes in the cell cycle distribution of cells treated with these inducers.
    Document Type:
    Reference
    Product Catalog Number:
    07-145
    Product Catalog Name:
    Anti-phospho-Histone H3 (Ser28) Antibody

  • Long-lasting sprouting and gene expression changes induced by the monoclonal antibody IN-1 in the adult spinal cord. 12177206

    Lesion-induced plasticity of the rat corticospinal tract (CST) decreases postnatally, simultaneously with myelin appearance. In adult rats, compensatory sprouting can be induced by the monoclonal antibody (mAb) IN-1 raised against the growth inhibitory protein Nogo-A. In this study, we examined separately the fate of sensory and motor corticospinal fibers after mAb IN-1 application. Intact adult rats treated with the IN-1 antibody exhibited an increase of aberrant CST projections, i.e., sensory fibers projecting into the ventral horn and motor fibers projecting dorsally. Unilateral lesion of the CST [pyramidotomy (PTX)] in the presence of mAb IN-1 triggered a progressive reorganization of the sprouting of the remaining CST across the midline, with sensory fibers projecting gradually into the denervated dorsal horn and motor fibers projecting into the denervated ventral horn. In unilaterally denervated spinal cords, aberrant sprouts were only transient and disappeared by 6 weeks, whereas midline crossing fibers ending in the appropriate target region were stabilized and persisted over the entire study period. Within the spinal cord, IN-1 antibody treatment was associated with upregulation of growth factors (BDNF, VEGF), growth-related proteins (actin, myosin, GAP-43), and transcription factors (STATs), whereas pyramidotomy induced an enhanced expression of guidance molecules (semaphorins and slits) as well as neurotrophic factors (BDNF, IGFs, BMPs). These gene expression changes may contribute to attraction, guidance, and stabilization of sprouting CST fibers.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Activity-dependent codevelopment of the corticospinal system and target interneurons in the cervical spinal cord. 19587289

    Corticospinal tract (CST) connections to spinal interneurons are conserved across species. We identified spinal interneuronal populations targeted by the CST in the cervical enlargement of the cat during development. We focused on the periods before and after laminar refinement of the CST terminations, between weeks 5 and 7. We used immunohistochemistry of choline acetyltransferase (ChAT), calbindin, calretinin, and parvalbumin to mark interneurons. We first compared interneuron marker distribution before and after CST refinement. ChAT interneurons increased, while calbindin interneurons decreased during this period. No significant changes were noted in parvalbumin and calretinin. We next used anterograde labeling to determine whether the CST targets different interneuron populations before and after the refinement period. Before refinement, the CST terminated sparsely where calbindin interneurons were located and spared ChAT interneurons. After refinement, the CST no longer terminated in calbindin-expressing areas but did so where ChAT interneurons were located. Remarkably, early CST terminations were dense where ChAT interneurons later increased in numbers. Finally, we determined whether corticospinal system activity was necessary for the ChAT and calbindin changes. We unilaterally inactivated M1 between weeks 5 and 7 by muscimol infusion. Inactivation resulted in a distribution of calbindin and ChAT in spinal gray matter regions where the CST terminates that resembled the immature more than mature pattern. Our results show that the CST plays a crucial role in restructuring spinal motor circuits during development, possibly through trophic support, and provide strong evidence for the importance of connections with key spinal interneuron populations in development of motor control functions.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • HOT1 is a mammalian direct telomere repeat-binding protein contributing to telomerase recruitment. 23685356

    Telomeres are repetitive DNA structures that, together with the shelterin and the CST complex, protect the ends of chromosomes. Telomere shortening is mitigated in stem and cancer cells through the de novo addition of telomeric repeats by telomerase. Telomere elongation requires the delivery of the telomerase complex to telomeres through a not yet fully understood mechanism. Factors promoting telomerase-telomere interaction are expected to directly bind telomeres and physically interact with the telomerase complex. In search for such a factor we carried out a SILAC-based DNA-protein interaction screen and identified HMBOX1, hereafter referred to as homeobox telomere-binding protein 1 (HOT1). HOT1 directly and specifically binds double-stranded telomere repeats, with the in vivo association correlating with binding to actively processed telomeres. Depletion and overexpression experiments classify HOT1 as a positive regulator of telomere length. Furthermore, immunoprecipitation and cell fractionation analyses show that HOT1 associates with the active telomerase complex and promotes chromatin association of telomerase. Collectively, these findings suggest that HOT1 supports telomerase-dependent telomere elongation.
    Document Type:
    Reference
    Product Catalog Number:
    07-473
    Product Catalog Name:
    Anti-trimethyl-Histone H3 (Lys4) Antibody