1
|
Hypertensive retinopathy in a transgenic angiotensin-based model. Clin Sci (Lond) 2016; 130:1075-88. [PMID: 27026533 DOI: 10.1042/cs20160092] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 03/29/2016] [Indexed: 12/18/2022]
Abstract
Severe hypertension destroys eyesight. The RAS (renin-angiotensin system) may contribute to this. This study relied on an established angiotensin, AngII (angiotensin II)-elevated dTGR (double-transgenic rat) model and same-background SD (Sprague-Dawley) rat controls. In dTGRs, plasma levels of AngII were increased. We determined the general retinal phenotype and observed degeneration of ganglion cells that we defined as vascular degeneration. We also inspected relevant gene expression and lastly observed alterations in the outer blood-retinal barrier. We found that both scotopic a-wave and b-wave as well as oscillatory potential amplitude were significantly decreased in dTGRs, compared with SD rat controls. However, the b/a-wave ratio remained unchanged. Fluorescence angiography of the peripheral retina indicated that exudates, or fluorescein leakage, from peripheral vessels were increased in dTGRs compared with controls. Immunohistological analysis of blood vessels in retina whole-mount preparations showed structural alterations in the retina of dTGRs. We then determined the general retinal phenotype. We observed the degeneration of ganglion cells, defined vascular degenerations and finally found differential expression of RAS-related genes and angiogenic genes. We found the expression of both human angiotensinogen and human renin in the hypertensive retina. Although the renin gene expression was not altered, the AngII levels in the retina were increased 4-fold in the dTGR retina compared with that in SD rats, a finding with mechanistic implications. We suggest that alterations in the outer blood-retinal barrier could foster an area of visual-related research based on our findings. Finally, we introduce the dTGR model of retinal disease.
Collapse
|
2
|
|
3
|
Pintor J, Sánchez-Nogueiro J, Irazu M, Mediero A, Peláez T, Peral A. Immunolocalisation of P2Y receptors in the rat eye. Purinergic Signal 2011; 1:83-90. [PMID: 18404404 PMCID: PMC2096566 DOI: 10.1007/s11302-004-5072-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Revised: 10/18/2004] [Accepted: 10/18/2004] [Indexed: 11/04/2022] Open
Abstract
Nucleotides present an important role in ocular physiology which has been demonstrated by recent works that indicate their involvement in many ocular processes. P2Y are important among P2 receptors since they can control tear production, corneal wound healing, aqueous humour dynamics and retinal physiology. Commercial antibodies have allowed us to investigate the distribution of P2Y receptors in the cornea, anterior and posterior chamber of the eye and retina. The P2Y1 receptor was present mainly in cornea, ciliary processes, and trabecular meshwork. The P2Y2 receptors were present in cornea, ciliary processes and retinal pigmented epithelium. P2Y4 was present in cornea, ciliary processes, photoreceptors, outer plexiform layer and ganglion cell layer. The P2Y6 presented almost an identical distribution as the P2Y4 receptor. The P2Y11 was also detectable in the retinal pigmented epithelium. The detailed distribution of the receptors clearly supports the recent findings indicating the relevant role of nucleotides in the ocular function.
Collapse
Affiliation(s)
- Jesús Pintor
- Departamento de Bioquímica y Biología Molecular IV, E.U. Optica, Universidad Complutense de Madrid, Madrid, Spain,
| | | | | | | | | | | |
Collapse
|
4
|
Marchong MN, Yurkowski C, Ma C, Spencer C, Pajovic S, Gallie BL. Cdh11 acts as a tumor suppressor in a murine retinoblastoma model by facilitating tumor cell death. PLoS Genet 2010; 6:e1000923. [PMID: 20421947 PMCID: PMC2858707 DOI: 10.1371/journal.pgen.1000923] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 03/24/2010] [Indexed: 12/05/2022] Open
Abstract
CDH11 gene copy number and expression are frequently lost in human retinoblastomas and in retinoblastomas arising in TAg-RB mice. To determine the effect of Cdh11 loss in tumorigenesis, we crossed Cdh11 null mice with TAg-RB mice. Loss of Cdh11 had no gross morphological effect on the developing retina of Cdh11 knockout mice, but led to larger retinal volumes in mice crossed with TAg-RB mice (p = 0.01). Mice null for Cdh11 presented with fewer TAg-positive cells at postnatal day 8 (PND8) (p = 0.01) and had fewer multifocal tumors at PND28 (p = 0.016), compared to mice with normal Cdh11 alleles. However, tumor growth was faster in Cdh11-null mice between PND8 and PND84 (p = 0.003). In tumors of Cdh11-null mice, cell death was decreased 5- to 10-fold (p<0.03 for all markers), while proliferation in vivo remained unaffected (p = 0.121). Activated caspase-3 was significantly decreased and β-catenin expression increased in Cdh11 knockdown experiments in vitro. These data suggest that Cdh11 displays tumor suppressor properties in vivo and in vitro in murine retinoblastoma through promotion of cell death. Despite over two decades since loss of RB1 was implicated in initiating retinoblastoma, the unique tissue specificity of this process remains puzzling. Indeed, functional loss of both alleles of the RB1 tumor suppressor gene results in >40,000-fold increase in predisposition to retinal cancer during childhood, while one constitutional RB1 mutant allele confers a broader but much lower cancer predisposition later in life. We have proposed a specific signature of progressive genomic changes that leads to full tumor development. One of these changes is genomic loss of the CDH11 gene, suggesting that this gene normally suppresses the development of retinoblastoma. We present novel data indicating that Cdh11 functions as a tumor suppressor gene in retinoblastoma by facilitating cell death. Our insight into the sequence of events that contribute to retinoblastoma development is important for future therapies and fundamental understanding of cancer.
Collapse
Affiliation(s)
- Mellone N. Marchong
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Christine Yurkowski
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Clement Ma
- Department of Biostatistics, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
| | - Clarellen Spencer
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
| | - Sanja Pajovic
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
| | - Brenda L. Gallie
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Department of Biostatistics, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada
- Department of Ophthalmology, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
| |
Collapse
|
5
|
Pérez-Alvarez MJ, Isiegas C, Santano C, Salazar JJ, Ramírez AI, Triviño A, Ramírez JM, Albar JP, de la Rosa EJ, Prada C. Vimentin isoform expression in the human retina characterized with the monoclonal antibody 3CB2. J Neurosci Res 2008; 86:1871-83. [PMID: 18241054 DOI: 10.1002/jnr.21623] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The antigen recognized by the monoclonal antibody 3CB2 (3CB2-Ag and 3CB2 mAb) is expressed by radial glia and astrocytes in the developing and adult vertebrate central nervous system (CNS) of vertebrates as well as in neural stem cells. Here we identified the 3CB2-Ag as vimentin by proteomic analysis of human glial cell line U-87 extracts (derived from a malignant astrocytoma). Indeed, the 3CB2 mAb recognized three vimentin isoforms in glial cell lines. In the human retina, 3CB2-Ag was expressed in Müller cells, astrocytes, some blood vessels, and cells in the horizontal cell layer, as determined by immunoprecipitation and immunofluorescence. Three populations of astrocytes were distinguishable by double-labeling immunohistochemistry: vimentin+/GFAP+, vimentin-/GFAP+, and vimentin+/GFAP-. Hence, we conclude that 1) the 3CB2-Ag is vimentin; 2) vimentin isoforms are differentially expressed in normal and transformed astrocytes; 3) human retinal astrocytes display molecular heterogeneity; and 4) the 3CB2 mAb is a valuable tool to study vimentin expression and its function in the human retina.
Collapse
Affiliation(s)
- M J Pérez-Alvarez
- Department of Physiology, School of Medicine, Universidad Complutense, Madrid, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Ishii M, Fujita A, Iwai K, Kusaka S, Higashi K, Inanobe A, Hibino H, Kurachi Y. Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K+ channels in retina. Am J Physiol Cell Physiol 2003; 285:C260-7. [PMID: 12686518 DOI: 10.1152/ajpcell.00560.2002] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kir5.1 is an inwardly rectifying K+ channel subunit whose functional role has not been fully elucidated. Expression and distribution of Kir5.1 in retina were examined with a specific polyclonal antibody. Kir5.1 immunoreactivity was detected in glial Müller cells and in some retinal neurons. In the Kir5.1-positive neurons the expression of glutamic acid decarboxylase (GAD65) was detected, suggesting that they may be GABAergic-amacrine cells. In Müller cells, spots of Kir5.1 immunoreactivity distributed diffusely at the cell body and in the distal portions, where Kir4.1 immunoreactivity largely overlapped. In addition, Kir4.1 immunoreactivity without Kir5.1 was strongly concentrated at the endfoot of Müller cells facing the vitreous surface or in the processes surrounding vessels. The immunoprecipitant obtained from retina with anti-Kir4.1 antibody contained Kir5.1. These results suggest that heterotetrameric Kir4.1/Kir5.1 channels may exist in the cell body and distal portion of Müller cells, whereas homomeric Kir4.1 channels are clustered in the endfeet and surrounding vessels. It is possible that homomeric Kir4.1 and heteromeric Kir4.1/Kir5.1 channels play different functional roles in the K+-buffering action of Müller cells.
Collapse
Affiliation(s)
- Masaru Ishii
- Department of Pharmacology II, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Weruaga E, Velasco A, Briñón JG, Arévalo R, Aijón J, Alonso JR. Distribution of the calcium-binding proteins parvalbumin, calbindin D-28k and calretinin in the retina of two teleosts. J Chem Neuroanat 2000; 19:1-15. [PMID: 10882833 DOI: 10.1016/s0891-0618(00)00046-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Using monoclonal antibodies against parvalbumin (PV) and calbindin (CB), and a polyclonal antiserum against calretinin (CR), the expression patterns of these proteins in the retina of the tench and rainbow trout were studied at light microscopic level in in toto preparations and radial sections. Parvalbumin was present in subpopulations of small amacrine cells in both species, but these cells were more abundant and had a clear centre-periphery gradient distribution in the tench. Using the McAB 300 monoclonal antibody against CB, glial cells such as Müller cells, astrocytes in the nerve fibre layer, and sparse large cells close to the entrance of the optic nerve were observed in both species. Moreover, this antibody strongly labelled H1 horizontal cells and their thick axon terminals in the tench retina, whereas only a small population of amacrine cells was stained in the trout. Calretinin was expressed in different types of ganglion cells and numerous neurones located in the inner plexiform layer in both species, but was more abundant and more strongly stained in the trout retina, where some bipolar cells were easily distinguishable. A comparison to current results in other vertebrate species is offered.
Collapse
Affiliation(s)
- E Weruaga
- Departamento de Biología Celular y Patología and Instituto de Neurociencias de Castilla y León, Facultad de Mledicina, Universidad de Salamanca, Spain
| | | | | | | | | | | |
Collapse
|
8
|
OCHS MATTHIAS, MAYHEW TERRYM, KNABE WOLFGANG. To what extent are the retinal capillaries ensheathed by Müller cells? A stereological study in the tree shrew Tupaia belangeri. J Anat 2000; 196 ( Pt 3):453-61. [PMID: 10853967 PMCID: PMC1468081 DOI: 10.1046/j.1469-7580.2000.19630453.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cellular ensheathment of capillaries in the 3 outer capillary layers of the central retina of the adult tree shrew Tupaia belangeri was studied quantitatively by transmission electron microscopy. Using a stereological approach, the relative surface of capillary basal lamina ensheathed by Müller cells and by nonmacroglial cells (collectively termed non-Müller cells) was estimated in 5 animals. The participation of Müller cells was distinctly different in the 3 capillary layers studied. In the outermost capillary layer 1, the mean (standard deviation) percentage surface coverage by non-Müller cell processes was 46.8 (15.3)%. Much less of the capillary basal lamina was ensheathed by non-Müller cells in capillary layers 2 and 3 (3.0 (2.1)% and 0.3 (0.3)% respectively). The observed total variation of the stereological estimates for the surface fraction of Müller cells (expressed as the between-subject coefficient of variation) was significantly higher in capillary layer 1 (28.8%) compared with capillary layers 2 (2.2%) and 3 (0.3%). In capillary layer 1, the high observed total variation was due to a high biological variation among animals for the fractions of both Müller cell and non-Müller cell ensheathment. The rare occurrence of direct contacts between the capillary basal lamina and the perikarya of either microglial cells (capillary layer 3) or amacrine cells (capillary layer 2) corresponded well to the low stereological values obtained for the relative capillary surface ensheathed by non-Müller cells in these capillary layers. Previously, extensive and frequent contacts between the basal lamina of capillaries belonging to capillary layer 1 and horizontal cells had been observed in single sections. The present study quantitatively demonstrates a marked paucity of macroglial investment of capillaries located in capillary layer 1 of Tupaia. It can be concluded that horizontal cells ensheath most of the capillary surface not invested by Müller cells.
Collapse
Affiliation(s)
- MATTHIAS OCHS
- Department of Anatomy, University of Göttingen, Göttingen, Germany
| | - TERRY M.
MAYHEW
- School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - WOLFGANG KNABE
- Department of Anatomy, University of Göttingen, Göttingen, Germany
- Correspondence to Dr Wolfgang Knabe, Department of Anatomy, Division of Morphology, Georg-August-University, Kreuzbergring 36, D-37075 Göttingen, Germany. Tel.: +49 551 392354; fax: +49 551 397043; e-mail:
| |
Collapse
|
9
|
Expression and clustered distribution of an inwardly rectifying potassium channel, KAB-2/Kir4.1, on mammalian retinal Müller cell membrane: their regulation by insulin and laminin signals. J Neurosci 1997. [PMID: 9315894 DOI: 10.1523/jneurosci.17-20-07725.1997] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Inwardly rectifying potassium (K+) channels (Kir) in Müller cells, the dominant glial cells in the retina, are supposed to be responsible for the spatial buffering action of K+ ions. The molecular properties and subcellular localization of Müller cell Kir channels in rat and rabbit retinas were examined by using electrophysiological, molecular biological, and immunostaining techniques. Only a single population of Kir channel activity, the properties of which were identical to those of KAB-2/Kir4.1 expressed in HEK293T cells, could be recorded from endfoot to the distal portion of Müller cells. Consistently, Northern blot, in situ hybridization, and RT-PCR analyses indicated expression of Kir4. 1 in Müller cells per se. The Kir4.1 immunoreactivity was distributed in clusters throughout Müller cell membrane. The Kir4.1 expression in Müller cells disappeared promptly after culturing. When the dissociated Müller cells were cultured on laminin-coated dishes in the presence of insulin, Kir4.1 immunoreactivity was detected in a clustered manner on the cell membrane. Because insulin and laminin exist in the surrounding of Müller cells in the retina, these substances possibly may be physiological regulators of expression and distribution of Kir4.1 in Müller cells in vivo.
Collapse
|
10
|
Robinson SR. Relationships between Müller cells and neurons in a primitive tetrapod, the Australian lungfish. Vis Neurosci 1997; 14:795-800. [PMID: 9279007 DOI: 10.1017/s0952523800012748] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We recently proposed a model of cytogenesis which assumes that primitive ancestral mammals and premammalian vertebrates had a retinal composition that consisted of about seven neurons per Müller cell, comprising 1-2 cone photoreceptors, 1-2 rod photoreceptors, 2-3 bipolar cells, 1-2 amacrine cells, less than 1 ganglion cell, and less than 1 horizontal cell (Reichenbach & Robinson, 1995). The Australian lungfish (Neoceratodus forsteri) closely resembles the lobe-finned ancestors of land vertebrates, and has an extremely plesiomorphic nervous system. The present study, therefore, has examined the relative frequencies of retinal neurons and Müller cells (identified by immunolabelling for glutamine synthetase) in the lungfish retina. It was found that for each Müller cell there is an average of 1.9 cone photoreceptors, 1.7 rod photoreceptors, 3.1 amacrine/bipolar/horizontal cells, and 0.6 ganglion cells; amounting to a ratio of 7.3 neurons per Müller cell. These results support our conjecture that the sequence of cytogenesis in mammals is constrained by a developmental program that predates the evolution of mammals. The study also provides the first detailed morphological descriptions of lungfish Müller cells and their relationship with adjacent neurons. It was found that individual Müller cells in lungfish have a volume (more than 12,000 microns3) that is an order of magnitude higher than in mammals, yet the proportion of total retinal volume occupied by these cells (20%) is very similar.
Collapse
Affiliation(s)
- S R Robinson
- Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Australia
| |
Collapse
|
11
|
Vecino E, Velasco A, Caminos E, Aijón J. Distribution of S100 immunoreactivity in the retina and optic nerve head of the teleost Tinca tinca L. Microsc Res Tech 1997; 36:17-25. [PMID: 9031258 DOI: 10.1002/(sici)1097-0029(19970101)36:1<17::aid-jemt2>3.0.co;2-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The distribution of S100 immunoreactivity within the normal and regenerating retina and optic nerve head of the teleost Tinca tinca L. has been investigated using the avidin-biotin complex (ABC) method and a polyclonal antibody against S100. Astrocytes and Müller cells were labeled with this antibody. This represents the first description of astrocytes localized in the optic nerve head and in the nerve fiber layer of the fish retina displaying a typical bipolar morphology. Horizontal cells in the inner nuclear layer were immunolabeled; we also observed species-specific S100 labeling of horizontal cells of the H1 subtype. No significant changes were seen in the S100 immunoreactive Müller cells, astrocytes, or horizontal cells in the tench retina after optic nerve crushing and during regeneration. These results might help to understand the function of glial cells in the normal and experimentally induced regenerating fish visual system.
Collapse
Affiliation(s)
- E Vecino
- Dpto. Biología Celular y Ciencias Morfológicas, Facultad de Medicina, Universidad del País Vasco, Vizcaya, Spain
| | | | | | | |
Collapse
|
12
|
Akopian G, Kressin K, Derouiche A, Steinhäuser C. Identified glial cells in the early postnatal mouse hippocampus display different types of Ca2+ currents. Glia 1996; 17:181-94. [PMID: 8840160 DOI: 10.1002/(sici)1098-1136(199607)17:3<181::aid-glia1>3.0.co;2-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Based on their typical pattern of membrane currents, four populations of glial cells could be identified in thin brain slices of the postnatal hippocampus. In the present study, we applied the patch-clamp technique to glial cells in the hippocampal CA1 region, which are characterized by a complex pattern of different Na+ and K+ currents ("complex" cells). These cells were identified as non-neuronal cells, most likely astrocytes, by their glutamine synthetase immunoreactivity. Two types of glial Ca2+ currents could be identified that differed in their kinetics and pharmacological properties. A low-voltage activated (LVA), fast inactivating component was activated at membrane potentials positive to -60 mV and reached maximum current amplitudes at about -20 mV. This current was sensitive to amiloride and thus displayed properties of neuronal LVA currents. The threshold potential of the second Ca2+ current component was at about -40 mV, and peak currents were observed at 0 mV. In contrast to the LVA component, the inactivation of these high-voltage activated (HVA) currents slowed down with increasing depolarizations. This current was sensitive to low concentrations of Cd2+ but was not affected by amiloride. A small fraction of the HVA currents was sensitive to nifedipine, and omega-conotoxin GVIA (omega-CgTx) was also found to reduce the glial HVA component. The study provides electrophysiological and pharmacological characterization of different types of Ca2+ currents in gray matter glial cells in situ.
Collapse
Affiliation(s)
- G Akopian
- Institute of Physiology, Friedrich-Schiller University Jena, Germany
| | | | | | | |
Collapse
|
13
|
Abstract
Carbonic anhydrase activity was characterized in freshly dissociated Müller cells of the salamander retina. Intracellular pH was monitored using ratio imaging of the indicator dye BCECF as extracellular PCO2 was varied. The extracellular solution was switched rapidly (141 ms rise time) from a HEPES buffered to a CO2-HCO3- buffered solution (both pH 7.4). Introduction of CO2-HCO3- produced a rapid cell acidification. Cell pH dropped from a steady-state pH of 7.02 in HEPES solution to pH 6.81 in CO2-HCO3-. Methazolamide, a carbonic anhydrase inhibitor, dramatically reduced the initial rate of acidification, demonstrating that the acidification was produced by the carbonic anhydrase-catalyzed hydration of CO2. The initial rate of acidification, 52.6 pH units per min (0.88 pH units per s), was reduced approximately 150-fold to 0.36 pH units per min by 10(-3) M methazolamide. Half-maximal inhibition occurred at a methazolamide concentration of 5.6.10(-7) M. The carbonic anhydrase inhibitor acetazolamide (10(-3) M) also greatly reduced the rate of cell acidification. The latency to the onset of carbonic anhydrase inhibition was 660 ms for methazolamide and 7.5 s for acetazolamide. The carbonic anhydrase inhibitor benzolamide (10(-4) M, 4 min exposure), which is poorly membrane permeant, had little effect on the rate of cell acidification, indicating that the site of carbonic anhydrase action was intracellular. The activity of Müller cell carbonic anhydrase may help to buffer extracellular CO2 variations in the retina.
Collapse
Affiliation(s)
- E A Newman
- Department of Physiology, University of Minnesota, Minneapolis 55455
| |
Collapse
|
14
|
Schütte M, Schlemermeyer E. Depolarization elicits, while hyperpolarization blocks uptake of endogenous glutamate by retinal horizontal cells of the turtle. Cell Tissue Res 1993; 274:553-8. [PMID: 7904899 DOI: 10.1007/bf00314553] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have employed an immunoreaction against glutamate to qualitatively demonstrate varying levels of glutamate in retinal horizontal cells of the turtle. Glutamate-like immunoreactivity (GLI) in horizontal cells could be demonstrated after glutamate decarboxylase was inhibited by aminooxyacetic acid (AOAA) and its degradation to GABA was blocked. Depolarization of horizontal cells by kainic acid (KA) induces strong glutamate immunoreactivity in these cells, whereas hyperpolarization by 2,3-cis piperidine dicarboxylate (PDA) abolishes glutamate-like immunoreactivity in horizontal cells. When glutamate release from cones and bipolar cells is blocked in the absence of calcium, or when glutamate uptake is blocked by DL-threo beta-hydroxy aspartate, KA/AOAA treatment of the retina does not induce GLI in horizontal cells. Our data show that horizontal cells are capable of taking up glutamate from the endogenous retinal pool in an activity dependent way. Our interpretation of these findings is that retinal horizontal cells are capable of regulating glutamate levels in the extracellular space of the cone pedicle complex by an activity-dependent uptake system. We suggest that inhibition of glutamate uptake upon hyperpolarization rather than inhibition of GABA release may evoke the antagonistic surround response of retinal bipolar cells.
Collapse
Affiliation(s)
- M Schütte
- Department of Ophthalmology, New York University Medical Center, NY 10016
| | | |
Collapse
|
15
|
Gábriel R, Wilhelm M, Straznicky C. Morphology and distribution of Müller cells in the retina of the toad Bufo marinus. Cell Tissue Res 1993; 272:183-92. [PMID: 8481951 DOI: 10.1007/bf00323585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have previously shown that an antibody against neuron-specific enolase (NSE) selectively labels Müller cells (MCs) in the anuran retina (Wilhelm et al. 1992). In the present study the light- and electron-microscopic morphology of MCs and their distribution were described in the retina of the toad, Bufo marinus, using the above antibody. The somata of MCs were located in the proximal part of the inner nuclear layer and were interconnected with each other by their processes. The MCs were uniformly distributed across the retina with an average density of 1500 cells/mm2. Processes of MCs encircled the somata of photoreceptor cells isolating them from each other by glial sheath, except for those of the double cones. Some of the photoreceptor pedicles remained free of glial sheath. Electron-microscopic observations confirmed that MC processes provide an extensive scaffolding across the neural retina. At the outer border of the ganglion cell layer these processes formed a non-continuous sheath. The MC processes traversed through the ganglion cell layer and spread beneath it between the neuronal somata and the underlying optic axons. These processes formed a continuous inner limiting membrane separating the optic fibre layer from the vitreous tissue. Neither astrocytic nor oligodendrocytic elements were found in the optic fibre layer. The significance of the uniform MC distribution and the functional implications of the observed pattern of MC scaffolding are discussed.
Collapse
Affiliation(s)
- R Gábriel
- Department of Anatomy and Histology, School of Medicine, Flinders University of South Australia, Adelaide
| | | | | |
Collapse
|
16
|
Wilhelm M, Straznicky C, Gábriel R. Neuron-specific enolase-like immunoreactivity in the vertebrate retina: selective labelling of Müller cells in Anura. HISTOCHEMISTRY 1992; 98:243-52. [PMID: 1459864 DOI: 10.1007/bf00271038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neuron-specific enolase (NSE) immunocytochemistry was carried out in retinae of goldfish, axolotl, clawed frog, cane toad, lizard, chick, guinea-pig, rabbit, rat, cat and human. With the exception of Anura, strong immunoreactivity was seen in the large ganglion, amacrine cells and horizontal cells of the retina in all of the other species. Photoreceptors were found to be labelled in the rat and human retina and only one cone type in rabbit. Photoreceptor pedicles and ellipsoids were stained in the goldfish and the somata and inner segments of some photoreceptors in axolotl. In the axolotl retina, besides neurons, Müller cells (MCs) were also immunolabelled. In the retina of the cane toad and the clawed frog MCs were the only stained elements. Similarly in other parts of the central nervous system of the cane toad, glial elements of the optic tectum and spinal cord were immunoreactive. In contrast, in the peripheral nervous system, neurons of the 1st sympathetic ganglion and the 2nd dorsal root ganglion were labelled. In double-labelling experiments, glial fibrillary acidic protein and NSE showed colocalisation both in the glial elements of the optic tectum and spinal cord and in MCs of the retina of the cane toad.
Collapse
Affiliation(s)
- M Wilhelm
- Department of Anatomy and Histology, School of Medicine, Flinders University of South Australia, Adelaide
| | | | | |
Collapse
|
17
|
Abstract
Gap junction (GJ) endocytosis appears to be part of a cycle of GJ renewal in horizontal cells of the teleost fish retina. At least three stages of GJ endocytosis in these neurons have been identified using conventional electron microscopy (EM): invagination of GJ membranes (GJ blebs); free GJ vesicles; and GJ vesicle fusion with mature lysosomes (Vaughan & Lasater, 1990a). In the present study, EM-level acid phosphatase (AP) histochemistry of white bass retina was used to determine at what stage enzymatic degradation of endocytosed GJs begins. Electron-dense AP reaction product was observed within the trans face of the Golgi apparatus, mature lysosomes, and occasional, internal GJ vesicles. In contrast, GJ blebs, peripheral GJ vesicles, and most internal GJ vesicles lacked AP reaction product. These results support the idea that at least some of the GJ vesicles observed within these retinal neurons arise from endocytosis, are on a degradative pathway, and can be termed GJ "endosomes." Furthermore, GJ vesicles appear to be initially free of AP, but some later acquire it (presumably from transport vesicles bearing degradative enzymes). It is still unclear whether our previous report of GJ vesicle fusion with mature lysosomes is a subsequent step in GJ degradation or part of a different degradative pathway altogether.
Collapse
Affiliation(s)
- D K Vaughan
- Department of Physiology, University of Utah School of Medicine, Salt Lake City
| | | |
Collapse
|