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Oct 2008  
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    SNRP Community Publications

    Highlights publications, news items, interviews, etc from SNRP Directors, Collaborators and Participants

     

    Franze K, Grosche J, Skatchkov SN, Schinkinger S, Fojo C, Schild D, Uckermann O, Travis K, Reichenbach A, Guck J

    Muller cells are living optical fibers in the vertebrate retina
    Proc Natl Acad Sci USA. 2007 May 15; 104(20): 8287-92.
    Although biological cells are mostly transparent, they are phase objects that differ in shape and refractive index. Any image that is projected through layers of randomly oriented cells will normally be distorted by refraction, reflecting and scattering. Counterintuitively, the retina of the vertebrate eye is inverted with respect to its optical function and light must pass through several tissue layers before reaching the light-detecting photoreceptor cells. Here we report on the specific optical properties of glial cells present in the retina, which may contribute to optimize this apparently unfavorable situation. We investigated intact retinal tissue and individual Muller cells, which are radial glial cells spanning the entire retinal thickness. Muller cells have an extended funnel shape, a higher refractive index than their surrounding tissue, and are oriented along the direction of light propagation. Transmission and reflection confocal microscopy of retinal tissue in vitro and in vivo showed that these cells provide a low-scattering passage for light from the retinal surface to the photoreceptor cells. Using modified dual-beam laser trap we could also demonstrate that individual Muller cells act as optical fibers. Furthermore, their parallel array in the retina is reminiscent of fiber optic plates used for low-distortion image transfer. Thus, Muller cells seem to mediate the image transfer through the vertebrate retina with minimal distortion and low loss. This finding elucidates a fundamental feature of the inverted retina as an optical system and ascribes a new function to glial cells.

    Zhao HW, Ross AP, Christian SL, Buchholz JN, Drew KL

    Decreased NR1 phosphorylation and decreased NMDAR function in hibernating Arctic ground squirrels.
    J Neurosci Res. 2006 Aug 1; 84(2): 291-8.
    Heterothermic mammals such as ground squirrels tolerate ischemia and N-methyl-D-aspartate (NMDA) better than homeothermic mammals such as rats both in vivo and in vitro, and this tolerance is enhanced in the hibernating state. However, the cellular mechanisms underlying this tolerance remain unclear. NMDA receptors (NMDAR) play a key role in excitotoxicity. The purpose of the current study was therefore to test the hypothesis that NMDAR are down-regulated in hibernating Arctic ground squirrels (hAGS; Spermophilus parryii). To address this hypothesis, we used Western blot analysis to investigate NMDAR phosphorylation, an activator of NMDAR function, and internalization in naive hippocampal tissue from hAGS, interbout euthermic AGS (ibeAGS), and rats. Furthermore, we used fura-2 calcium imaging to examine NMDAR function in cultured hippocampal slices from hAGS, ibeAGS, and rats. We report that phosphorylation of the NMDAR1 (NR1) subunit is decreased in hippocampal tissue from hAGS and that the NMDAR component of Glu-induced increase in [Ca(2+)](i) is decreased in hippocampal slices from hAGS. Moreover, the fraction of NR1 in the functional membrane pool in AGS is less than that in rats.

    Filbin MT

    How inflammation promotes regeneration
    Nat Neurosci. 2006 Jun; 9(6): 715-7.
    No abstract available.

    Ford G, Xu Z, Gates A, Jiang J, Ford BD

    Expression Analysis Systematic Explorer (EASE) analysis reveals differential gene expression in permanent and transient focal stroke rat models
    Brain Res. 2006 Feb 3; 1071(1): 226-36.
    To gain greater insight on the molecular mechanisms that underlie ischemic stroke, we compared gene expression profiles in transient (tMCAO) and permanent middle cerebral artery occlusion (pMCAO) stroke models using Expression Analysis Systematic Explorer (EASE) pathway analysis software. Many transcripts were induced in both stroke models, including genes associated with transcriptional pathways, cell death, stress responses and metabolism. However, EASE analysis of the regulated genes indicated molecular functions and biological processes unique to each model. Pathways associated with tMCAO included inflammation, apoptosis and cell cycle, while pMCAO was associated with the induction of genes encoding neurotransmitter receptors, ion channels, growth factors and signaling molecules. An intriguing finding was the involvement of tyrosine kinases and phosphatases following pMCAO. These results provide evidence that neuronal death following tMCAO and pMCAO involves distinct mechanisms. These findings may give new insight to the molecular mechanisms involved in stroke and may lead to novel neuroprotective strategies.

     

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