Electrical activity of rat retinal ganglion cells

The electrical activity of rat retinal ganglion cells is described. It was found that most such cells generate tonic discharges, while cells that demonstrate a phasic type of activity are less numerous. Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 382–384, July–October, 2007.     

Biosynthesis of mouse Thy-1 antigen

The biosynthesis and the maturation of Thy-1 antigen of mouse thymocytes have been studied by using a xenogeneic rabbit anti-mouse Thy-1 antibody. The earliest form of Thy-1 detected after a 5-min pulse with [35S]methionine and [35S]cysteine had an apparent m.w. of 26,500. During chase, this band converted to a molecular ratio (Mr) = 25,000 polypeptide, probably derived from the latter by trimming of glucose or mannose residues from the three high-mannose glycan units of Thy-1. Mature Thy-1 molecules were detected at the cell surface after a 15-min chase. At least one of the three N-linked oligosaccharide units was shown to be in the high mannose form at the cell surface, as indicated by its susceptibility to endo-beta-N-acetylglucosaminidase H digestion. Treatment of the early and late forms of Thy-1 antigen with endo-beta-N-acetylglucosaminidase F generated a single polypeptide of Mr = 13,500. The same precursor was obtained when cells were labeled in the presence of tunicamycin. This indicates the absence of O-linked glycan in the mature cell surface antigen. Finally, the resistance of Thy-1 antigen to trypsin digestion when associated with membranes confirmed that this molecule has no cytoplasmically oriented portion.     

Trophic responsiveness of purified postnatal and adult rat retinal ganglion cells

Central neurons lose the ability for axonal re-growth during development and typically do not regenerate their axons following axotomy once they become mature unless given a growth-permissive environment i.e. peripheral nerve graft. In the present study, the growth responsiveness of purified retinal ganglion cells (RGCs) at different ages to neurotrophic factors and Schwann cell (SC)-secreted factors were examined directly. The purity of adult RGCs was 97% as assessed by retrograde labelling with 4,6-diamidino-2-phenylindole. The stability of cultures were demonstrated by long-term survival (30 days) in medium contained brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF) and forskolin (F) (BCF). RGCs from postnatal (P) (P0, P4, P8, P21) and adult (P90) rats showed decreasing levels of survival and neuritogenesis when grown in BCF. In contrast, the opposite was observed in SC-conditioned medium (CM)-treated P0-P8 RGCs which were increasingly responsive. SCCM induced maximal neurite outgrowth in P8 RGCs via the activation of extracellular regulated kinase 1/2 (Erk1/2). Inhibition of mitogen-activated protein kinase-Erk1/2 signaling using an Erk1/2-specific inhibitor (UO126) abolished SCCM-induced Erk1/2 phosphorylation and neuritogenesis completely. Although both SCCM and BCF failed to sustain the same levels of growth in P21 or P90 cultures as observed in P8 cultures, SCCM promoted higher survival and neuritogenesis than BCF-treated adult RGCs. This study is the first report of adult rat RGC purification and demonstrates that mature RGCs need multiple factors for survival and neurite outgrowth.     

Annexin 1 protects against apoptosis induced by serum deprivation in transformed rat retinal ganglion cells

To investigate whether Annexin 1 can protect a retinal ganglion cells line (RGC-5) from apoptosis as induced by serum deprivation. Annexin 1 location in RGC-5 cells was determined using an indirect immunofluorescent assay. Expression of Annexin 1 in RGC-5 cultures deprived of serum for 0, 2 days was semi-quantified by western blot and RT-PCR. Effects of varying concentrations of the Annexin 1 peptide fragment, Ac2-26, on the survival of the RGC-5 cells was determined, and apoptotic cells were quantified by flow cytometry. Immunoblot and RT-PCR analysis was preformed to identify caspase 3, bax and bcl-2 in RGC extracts. Annexin 1 was localized in the cytoplasm of RGC-5 cells and the expression of Annexin 1, caspase 3 and bax was upregulated in serum-deprived RGC-5 cells. Ac2-26 attenuated the apoptosis resulting from serum deprivation of RGC-5 in a concentration-dependent manner, decreased caspase 3 and bax levels and produced an increase of bcl-2 in cell lysates. Annexin 1, in specific the peptide fragment Ac2-26, may play an important role in decreasing apoptosis in serum-deprived RGC-5 cells.     

Intrinsically photosensitive retinal ganglion cells

A new mammalian photoreceptor was recently discovered to reside in the ganglion cell layer of the inner retina.These intrinsically photosensitive retinal ganglion cells(ipRGCs) express a photopigment,melanopsin,that confers upon them the ability to respond to light in the absence of all rod and cone photoreceptor input.Although relatively few in number,ipRGCs extend their dendrites across large expanses of the retina making them ideally suited to function as irradiance detectors to assess changes in ambient...     

Gap-43 immunoreactivity and axon regeneration in retinal ganglion cells of the rat

Retinal ganglion cells (RGCs) in rats were retrogradely labeled with the fluorescent tracer Fluorogold (FG) and subjected to GAP-43 and c-JUN immunocytochemistry to identify those RGSs that are capable of regenerating an axon. After optic nerve section (ONS) and simultaneous application of FG to the nerve stump (group 1 experiments), GAP-43 immunoreactive RGCs (between 2 and 21 days after ONS) always represented a subfraction of both FG-labeled (i.e., surviving) RGCs and RGCs exhibiting c-JUN. GAP-43 immunoreactive RGCs represented 22% of RGCs normally present in rat retinae and 25% of surviving RGCs at 5 days after ONS but were reduced to 2% and 1%, which is 6% and 5% of survivors at 14 and 21 days, respectively. In animals that received a peripheral nerve (PN) graft after ONS (group 2 experiments), RGCs with regenerating axons were identified by FG application to the graft at 14 and 21 days. When examined at 21 and 28 days, all FG-labeled RGCs exhibited GAP-43 immunoreactivity, and FG/GAP-43-labeled RGCs were 3% and 2% of those resent in normal rat retinae. In relation to surviving. RGCs GAP-43 immunoreactive RGCs represented 10% at both time points. FG-/GAP-43 labeled RGCs also exhibited c-JUN, but c-JUN immunoreactive RGCs were at both time points at least twice as numerous a FG-/GAP-43-labeled RGCs. These data suggest that regenerating axons in PN grafts derive specifically from GAP-43 reexpressing RGCs. Appearance of GAP-43 immunoreactivity may therefore identify those RGCs that are capable of axonal regeneration or sprouting. 1994 John Wiley & Sons, Inc.     

Function of the hydrophobic transmembrane portion of Thy-1 antigen

Thy-1 antigen is anchored in the cell membrane by glycophosphatidyl inositol linkages instead of hydrophobic protein domains. The hydrophobic portion of Thy-1 antigen is cleaved by putative "transamidase." Mutated genes were constructed by using site-directed mutagenesis. One mutant gene codes Thy-1 antigen lacking carboxy terminal amino acids from 112Cys to 143Leu including cell membrane binding amino acid 112Cys. The other mutant gene codes Thy-1 antigen lacking from 124Trp to 143Leu that includes leucine core portion. DNA transfection analysis and Northern blot analysis revealed that hydrophobic portion of Thy-1 antigen is essential to express Thy-1 molecule onto the cell surface.     

Localization of axonally transported 125I-wheat germ agglutinin beneath the plasma membrane of chick retinal ganglion cells

The distribution of 125I-wheat germ agglutinin (WGA) transported by axons of chick retinal ganglion cells to layer d of the optic tectum was studied by electron microscopic autoradiography. We found that 52% of the radioactivity was located in axons and axon terminals in the contralateral optic tectum 22 h after intravitreal injection of affinity-purified 125I-WGA. Axons comprised 43% of the volume of layer d. Dendrites, glial cells, and neuron cell bodies contained 20%, 17%, and 3% of the label, whereas these structures comprised 24%, 21%, and 2% of the tissue volume, respectively. We also measured the distances between the autoradiographic silver grains and the plasma membranes of these profiles, and compared observed distributions of grains to theoretical distributions computed for band-shaped sources at various distances from the plasma membranes. This analysis revealed that the radioactive source within axons was distributed in a band of cytoplasm extending in from the plasma membrane a distance of 63 nm. Because WGA is known to bind to specific membrane glycoconjugates, we infer that at least some glycoconjugates may be concentrated within an annular region of cytoplasm just beneath the axonal plasma membrane after axoplasmic transport from the neuron cell body.     

Stimulation of antigen Thy-1 expression in mouse bone marrow cells by thymus extracts

The expression of antigen Thy-1 was studied in bone marrow cells of CBA line mice under the effect of thymus extracts. Extracts of the calf thymus--thymosine (fraction 5) and the preparation free of the Comsa factor were obtained by a combination of the Goldstein and Comsa extraction methods. The both extracts stimulate the expression of antigen Thy-1 in bone marrow cells. Incorporation of [14 C]sodium acetate into fragments containing antigen Thy-1 and absorbed by the column with anti-Thy-1-antibodies remains unchanged after stimulation. It is supposed that antigen Thy-1 ability to stimulate expression in bone marrow precursors of T-cells is not due to the synthesis of the antigen and is a property of one of the thymus factors with molecular mass of about 5000.     

Regional,cellular, and subcellular distribution of Thy-1 antigen in rat nervous tissues

The regional, cellular, and subcellular distribution of Thy-1 antigen in rat nervous tissues was investigated with rabbit and anti-rat thymus antiserum. Thy-1 antigen was found most abundantly in the cerebrum, including the cerebral cortical layer, caudate nucleus, thalamus, and hypothalamus, and in the midbrain. It was found in lower amounts in the pons, medulla oblongata, cerebellum, and spinal cord. The content of Thy-1 antigen, however, was low in the retina, cervical sympathetic ganglion, and sciatic nerve, and there was little in the pineal body and adrenal medulla. Thy-1 antigen was present in the neuronal cell-enriched fraction, whereas the glial cell-enriched fraction lacked Thy-1 antigen. In a subcellular fractionation study, Thy-1 antigen was found to occur mainly in the synaptosomal membrane and microsomes and was low in the highly purified myelin fraction. The amount of Thy-1 antigen in the cerebral synaptosomal fraction was much higher than those in the cerebellar synaptosomal fraction. The distribution of Thy-1 antigen among the respective areas within the cerebrum was not significantly different, and it is suggested that Thy-1 antigen may be present evenly in the neuronal membranes of the cerebrum. Based on these results, Thy-1 antigen is considered to represent a useful marker of cerebral neuronal membranes, especially in the synaptic region, regardless of the kind of neurotransmitters.     

Models for the cross-correlation between retinal ganglion cells

Neighboring ganglion cells in the vertebrate retina not only respond to the same stimuli but also display cross-correlated activity on a millisecond time scale. Recent studies of this cross-correlation have indicated that simple linear addition of common variability to each ganglion cell signal does not account for the observations (Levine 1997). In this report, Monte Carlo simulations of various linear and nonlinear models are presented that confirm the earlier speculations. Models in which common variability alters the leakages of a pair of leaky integrate-and-fire neurons account for the data and predict the cross-correlogram lag without invoking temporal delay lines. Received: 23 August 1996 / Received after review process: 18 June 1998 / Accepted in revised form: 13 July 1998     

Asymmetrical dendritic fields of retinal ganglion cells

By use of Golgi chrome—silver impregnation, studies were made of the dendritic branchings of feline and frog ganglion cells. It was shown that besides the known varieties of ganglion cells there were asymmetrical neurones whose dendrites lay all to one side. Essential differences distinguished these ganglion cells in the cat from those in the frog, differences depending upon the architectonics of the inner plexiform layer, which is broad and subdivided into layers in the frog, and narrow in the cat. We discuss the possible role of neurones with a unilateral arrangement of dendrites in relation to know electrophysiological data on retinal detectors and the receptive fields of ganglion cells.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 301–307, May–June, 1971.