bluuebunny/crossref_metadata_2025_split huggingface dataset:
Müller cells in the retina of the cane toad,Bufo marinus, express neuropeptide Y-like immunoreactivity
Authors: Zhu Bao-Song , Gibbins Ian 
Published: June 2009

AbstractWe have used light- and electron-microscopic immunohistochemistry to identify the presence of immunoreactivity to neuropeptide Y (NPY) within Müller cells in the retina of the cane toad,Bufo marinus.Müller cells containing NPY-like immunoreactivity (NPY-LI) were identified at the light-microscopic level by the coexistence with immunoreactivity to glial fibrillary acidic protein (GFAP) and at the ultrastructural level by their characteristic relationship to neuron cell bodies and processes. At the light-microscopic level, those cells which contained both NPY-LI and GFAP-LI usually had small cell bodies in the inner nuclear layer, while those cells which contained only NPY-LI were identified as large and small amacrine cells. The radially oriented primary processes in the inner plexiform layer and the vitreal end feet of GFAP-LI Müller cells also expressed NPY-LI. At the ultrastructural level, thin lamellar processes of Müller cells with NPY-LI enclosed some amacrine cell bodies in the inner nuclear layer and amacrine cell dendrites in the inner plexiform layer. These observations suggest that NPY-LI is localized in Müller cells in addition to two types of amacrine cells previously identified in theBuforetina. This study provides the first evidence that glial elements in the vertebrate retina express NPY-LI.
Cue-dependent deficits in grating orientation discrimination after V4 lesions in macaques
Authors: De Weerd Peter , Desimone Robert , Ungerleider Leslie G. 
Published: June 2009

AbstractTo examine the role of visual area V4 in pattern vision, we tested two monkeys with lesions of V4 on tasks that required them to discriminate the orientation of contours defined by several different cues. The cues used to separate the contours from their background included luminance, color, motion, and texture, as well as phase-shifted abutting gratings that created an “illusory” contour. The monkeys were trained to maintain fixation on a fixation target while discriminating extrafoveal stimuli, which were located in either a normal control quadrant of the visual field or in a quadrant affected by a lesion of area V4 in one hemisphere. Comparing performance in the two quadrants, we found significant deficits for contours defined by texture and for the illusory contour, but smaller or no deficits for motion-, color-, and luminance-defined contours. The data suggest a specific role of V4 in the perception of illusory contours and contours defined by texture.
Similar effects of carbachol and dopamine on neurons in the distal retina of the tiger salamander
Authors: Hare William A. , Owen W. Geoffrey 
Published: June 2009

AbstractThough there is considerable evidence that dopamine is an important retinal neuromodulator that mediates many of the changes in the properties of retinal neurons that are normally seen during light adaptation, the mechanism by which dopamine release is controlled remains poorly understood. In this paper, we present evidence which indicates that dopamine release in the retina of the tiger salamander, Ambystoma tigrinum, is driven excitatorily by a cholinergic input. We compared the effects of applying carbachol to those of dopamine application on the responses of rods, horizontal cells, and bipolar cells recorded intracellularly from the isolated, perfused retina of the tiger salamander. Micromolar concentrations of dopamine reduced the amplitudes of rod responses throughout the rods' operating range. The ratio of amplitudes of the cone-driven to rod-driven components of the responses of both horizontal and bipolar cells was increased by activation of both D1 and D2 dopamine receptors. Dopamine acted to uncouple horizontal cells and also off-center bipolar cells, the mechanism in the case of horizontal cells depending only upon activation of D1 receptors. Carbachol, a specific cholinomimetic, applied in five- to ten-fold higher concentrations, produced effects that were essentially identical to those of dopamine. These effects of carbachol were blocked by application of specific dopamine blockers, however, indicating that they are mediated secondarily by dopamine. We propose that the dopamine-releasing amacrine cells in the salamander are under the control of cells, probably amacrine cells, which secrete acetylcholine as their transmitter.
Overrepresentation of the central visual field in the superior colliculus of the pigmented and albino ferret
Authors: Quevedo C. , Hoffmann K.-P. , Husemann R. , Distler C. 
Published: June 2009

AbstractWe have examined the retinotopy in the superior colliculus of pigmented and albino ferrets using both anatomical and electrophysiological methods. While the distribution of contralaterally projecting retinotectal ganglion cells is characterized by the presence of an area centralis superimposed on a visual streak in both strains, the ipsilateral projection from temporal hemiretina is strongly reduced in albinos. In spite of the significantly altered retinotectal projection pattern, the collicular visual field map in the albino ferret reveals the same characteristics as in the pigmented animal with a strongly enlarged representation of the center of visual space. An areal comparison between retinotectal ganglion cell distribution and collicular areal magnification shows that the increase in areal magnification factor between the periphery and the representation of the central visual hemifield exceeds the corresponding increase in retinal ganglion cell density between peripheral retina and area centralis by a factor of three in pigmented and a factor of four in albino ferrets. The areal magnification factor of the representation of the retinal visual streak does not exceed the increase in retinotectal ganglion cell density. Thus, our results suggest that the representation of visual space in the superior colliculus of albino and pigmented ferrets does not simply follow the retinotectal ganglion cell density, but that there is an enhanced representation of the frontal central visual field. The possibility is discussed that the collicular visual field map may be determined either by both retinotectal and corticotectal projections or by the colliculus' intrinsic structure.
The horizontal cells of artiodactyl retinae: A comparison with Cajal's descriptions
Authors: Sandman Daniele , Boycott Brian B. , Peichl Leo 
Published: June 2009

AbstractThe morphology of horizontal cells in ox, sheep, and pig retinae as observed after Lucifer Yellow injections are described and compared with the descriptions of Golgi-stained cells by Ramón y Cajal (1893). Horizontal cells in the retinae of less domesticated species, wild pig, fallow and sika deer, mouflon, and aurochs were also examined. All these retinae have two types of horizontal cell; their morphologies are in common, although with some familial differences. Their basic appearance is as Cajal described; except in one important respect, a single axon-like process could not be identified on the external horizontal cells. It is concluded that external horizontal cells of artiodactyls correspond to the axonless (A-type) cells of other mammals. Cajal's internal horizontal cells have a single axon which contacts rods. This type corresponds to the B-type cells of other mammalian retinae. Artiodactyl A- and B-type horizontal cells differ from those of many other mammals in that the B-type dendritic tree is robust and the A-type dendritic tree is delicate. Historically, this morphological difference between orders of mammals has led to some confusion. The comparisons presented here suggest that the morphological types of primate horizontal cells can be integrated into a general mammalian classification.
Anin vitrostudy of retinotectal transmission in the chick: Role of glutamate and GABA in evoked field potentials
Authors: Dye J. C. , Karten H. J. 
Published: June 2009

AbstractWe have developed two brain slice preparations for studying tectofugal visual pathways in the chick: conventional, 400-μm slices (“thin slices”), and “thick slices” which encompass the rostral pole of the optic tectum and the contralateral optic nerve. Stimulation was delivered with a bipolar electrode positioned instratum opticumin thin slices and in the contralateral optic nerve in thick slices. While the latter preparation provided a means of exclusively and unambiguously activating retinal afferents, several lines of evidence also indicated that the evoked field potentials in thin slices were chiefly consequent to retinal afferent excitation: (1) the similarity of evoked field potentials in thin slices to those in thick slice preparations; (2) their precise localization in retinorecipient layers as shown by prelabeling from retina with FITC-coupled cholera toxin; (3) transmission delays appropriate for retinal afferents as established with the thick slice preparation; (4) patterns of labeled afferents resulting from applications of Dil crystals to slices fixed after recording; and (5) the similarity in transmitter pharmacology between thin and thick slice preparations. Pharmacological manipulations carried out with bath-applied antagonists indicated that glutamate is the principal retinotectal transmitter. The broadly active glutamate receptor blocker, kynurenic acid, reversibly eliminated the postsynaptic component of the field potential as confirmed with 0 Ca2+saline. A complete block was also effected by the non-NMDA antagonists CNQX and DNQX. The specific NMDA antagonist, APS, caused a smaller and variable reduction in response amplitude. The GABA antagonist, bicuculline, caused a prolongation of the monosynaptic field epsp in retinorecipient layers and an enhancement of the long-latency, negative wave in cellular layers below, supporting a late, excitation-limiting role for this inhibitory transmitter.
Synaptic Organization of an organotypic slice culture of the mammalian retina
Authors: Sassoè-Pognetto Marco , Feigenspan Andreas , Bormann Joachim , Wässle Heinz 
Published: June 2009

AbstractVertical Slices of postnatal day 6 (P6) rat retina were cut and cultured using the roller-tube technique. The organotypic differentiation during a culture period of up to 30 days has been described in a previous study (Feigenspan et al., 1993a). Here we concentrated on the synaptic organization in the retinal slice culture. Electron microscopy revealed the presence of ribbon synapses in the outer plexiform layer and conventional and ribbon syanpses in the inner plexiform layer. Immunofluroscence with antibodies that recognize specific subunits of GABAAor glycine receptors revealed a punctuate distribution of the receptors. They were aggregated in “hot spots” that correspond to a concentration of receptors at postsynaptic sites. Different isoforms of GABAAand glycine receptors occured in the slice cultures. The experiments show that there is a differentiation of synapses and a diversity of transmitter receptors in the slice cultures that is comparable to thein vivoretina.
Possible contributions of magnocellular- and parvocellular-pathway cells to transient VEPs
Authors: Valberg Arne , Rudvin Inger 
Published: June 2009

AbstractWe have measured transient visual evoked potentials (VEPs) to low-contrast luminance stimuli favoring responses of magnocellular pathway cells and to low-contrast red-green stimuli favoring parvocellular cells. Stimuli were square-wave alternating, 3-deg homogeneous disks. Low-contrast stimuli modulated in luminance elicited relatively simple responses. For some observers, a negativity was present that saturated at low contrast. This may be the signature of inputs from magnocellular channels to the visual cortex. The slope of the contrast—response curve for low-contrast stimuli was about the same for all subjects. For medium contrasts, these contrast—response curves displayed an abrupt increase of slope. The shallower slope may reflect the responsivity of magnocellular-pathway inputs to the cortex, whereas the steeper slope may be caused by additional parvocellular activation.Contrast-response curves for the most sensitive waveforms of the isoluminant green—red modulation also showed two branches, although not as clearly as for luminance. This may indicate parvocellular-mediated activity for small chromatic differences, and a combination of parvocellular and magnocellular inputs for larger contrasts. Curves of time-to-peak response as a function of contrast often changed their monotonous behavior near the kink of the corresponding contrast—response curve, thus supporting the notion of a contribution from several mechanisms to the main waveforms.
Photoresponses of human rodsin vivoderived from paired-flash electroretinograms
Authors: Pepperberg David R. , Birch David G. , Hood Donald C. 
Published: June 2009

AbstractIn the human eye, domination of the electroretinogram (ERG) by theb−wave and other postreceptor components ordinarily obscures all but the first few milliseconds of the rod photoreceptor response to a stimulating flash. However, recovery of the rod response after a bright test flash can be analyzed using a paired-flash paradigm in which the test flash, presented at time zero, is followed at timetby a bright probe flash that rapidly saturates the rods (Birch et al., 1995). In ERG experiments on normal subjects, the hypothesis that a similar method can be used to obtain the full time course of the rod response to test flashes of subsaturating intensity was tested. Rod-only responses to probe flashes presented at varying timestafter the test flash were used to derive a family of amplitudesA(t) that represented the putative rod response to the test flash. These rod-only responses to the probe flash were obtained by computational subtraction of the cone-mediated component of each probe flash response. With relatively weak test flashes (11–15 scot-td-s), the time course of the rod response to the test flash derived in this manner was consistent with a four-stage impulse response function of time-to-peak ≃170 ms.A(170), the amplitude of the derived response at 170 ms, increased with test flash intensity (Itest) to a maximum valueAmoand exhibited a dependence onItestgiven approximately by the relation,A(170)/Amo= 1 - exp(-kItest), wherek= 0.092 (scot-td-s)−1. In steady background light, the falling (i.e. recovery) phase of the derived response began earlier, and the sensitivity parameterkwas reduced several-fold from its dark-adapted value. As the sensitivity, kinetics, and light-adaptation properties of the derived response correspond closely with those of photocurrent flash responses previously obtained from isolated rodsin vitro, it was concluded that the response derived here from the human ERG approximates the course of the massedin vivorod response to a test flash.
The morphology and distribution of horizontal cells in the retina of a New World monkey, the marmoset Callithrix jacchus: A comparison with macaque monkey
Authors: Chan Tricia L. , Goodchild Ann K. , Martin Paul R. 
Published: June 2009

AbstractThe morphology and distribution of horizontal cells was studied in the retina of a New World monkey, the marmoset, Callithrix jacchus, and compared with that of the Old World macaque monkey. Horizontal cells in macaque and marmoset were either labelled with the carbocyanine dye, Dil, and then photoconverted, or were labelled by intracellular injection with Neurobiotin. The marmoset has two types of horizontal cell, H1 and H2, which have dendritic and axonal morphology similar to their counterparts in Old World monkeys and human. The dendritic-field size of both cell types increases with distance from the fovea. Both types make contact with the vast majority of the cones within their dendritic field. The dendrites of H1 cells in marmoset contact almost twice as many cones as H1 cells in macaque at an equivalent eccentricity. With increasing distance from the fovea, H1 cells make contact with more cones but have, on average, fewer terminal knobs inserted in each cone. The increase in dendritic-field area of H1 cells is balanced by a decrease in spatial density (from 4500 cells/mm2 at 25 deg eccentricity to 1000 cells/mm2 in far peripheral retina), so coverage of the retina remains fairly constant, between 5 and 8. Overall, the results show that the qualitative morphological properties, as well as quantitative population properties of horizontal cells, are common to both New World and Old World primates.
GABA-induced inactivation of functionally characterized sites in cat striate cortex: Effects on orientation tuning and direction selectivity
Authors: Crook John M. , Kisvárday Zoltan F. , Eysel Ulf T. 
Published: June 2009

AbstractMicroiontophoresis of γ-aminobutyric acid (GABA) was used to reversibly inactivate small sites of defined orientation/direction specificity in layers II-IV of cat area 17 while single cells were recorded in the same area at a horizontal distance of ~350–700 jam. We compared the effect of inactivating iso-orientation sites (where orientation preference was within 22.5 deg) and cross-orientation sites (where it differed by 45–90 deg) on orientation tuning and directionality. The influence of iso-orientation inactivation was tested in 33 cells, seven of which were subjected to alternate inactivation of two iso-orientation sites with opposite direction preference. Of the resulting 40 inactivations, only two (5%) caused significant changes in orientation tuning, whereas 26 (65%) elicited effects on directionality: namely, an increase or a decrease in response to a cell's preferred direction when its direction preference was the same as that at an inactivation site, and an increase in response to a cell's nonpreferred direction when its direction preference was opposite that at an inactivation site. It is argued that the decreases in response to the preferred direction reflected a reduction in the strength of intracortical iso-orientation excitatory connections, while the increases in response were due to the loss of iso-orientation inhibition. Of 35 cells subjected to cross-orientation inactivation, only six (17%) showed an effect on directionality, whereas 21 (60%) showed significant broadening of orientation tuning, with an increase in mean tuning width at half-height of 126%. The effects on orientation tuning were due to increases in response to nonoptimal orientations. Changes in directionality also resulted from increased responses (to preferred or nonpreferred directions) and were always accompanied by broadening of tuning. Thus, the effects of cross-orientation inactivation were presumably due to the loss of a cross-orientation inhibitory input that contributes mainly to orientation tuning by suppressing responses to nonoptimal orientations. Differential effects of iso-orientation and cross-orientation inactivation could be elicited in the same cell or in different cells from the same inactivation site. The results suggest the involvement of three different intracortical processes in the generation of orientation tuning and direction selectivity in area 17: (1) suppression of responses to nonoptimal orientations and directions as a result of cross-orientation inhibition and iso-orientation inhibition between cells with opposite direction preferences; (2) amplification of responses to optimal stimuli via iso-orientation excitatory connections; and (3) regulation of cortical amplification via iso-orientation inhibition.
Severity of ganglion cell death during early postnatal development is modulated by both neuronal activity and binocular competition
Authors: Scheetz A.J. , Williams Robert W. , Dubin Mark W. 
Published: June 2009

AbstractThe influence of postnatal neuronal activity on the magnitude of retinal ganglion cell death has been studied in cats. A constant blockade of activity in one eye starting just after birth does not change the severity of naturally occurring ganglion cell death, and as in normal animals, the ganglion cell population declines from 250,000 to 160,000 over a 4- to 6-week period. However, the population of retinal ganglion cells in the active untreated eye of monocularly deprived cats is increased 12% above normal (180,000 vs. 160,000 in each of four cases). This increase of 20,000 cells is permanent, and presumably reflects the competitive advantage in their target nuclei that the still active axons have over their silenced companions from the treated eye. Surprisingly, in one animal treated successfully for long duration with TTX in both eyes, the population of ganglion cells was elevated in both eyes (200,000 and 208,000 ganglion cells). This increase matches that achieved by early unilateral enucleation (Williams et al., 1983). Our results demonstrate that the complete blockade of activity reduces the severity of naturally occurring cell death in a population of CNS sensory neurons. The effects of unilateral blockade emphasize that the activity-dependent modulation of neuron death only occurs under conditions that do not place the inactive population of neurons at a competitive disadvantage.
Dark-suppression and light-sensitization of horizontal cell responses in the hybrid bass retina
Authors: Baldridge William H. , Weiler Reto , Dowling John E. 
Published: June 2009

AbstractThe responsiveness of luminosity-type horizontal cells, recorded intracellularly from isolated hybrid bass retinas, decreased after superfusion for 2 h in constant darkness. Responsiveness was subsequently increased (light-sensitized) up to 10-fold after exposure to several short (~0.5 min) periods of continuous illumination. The increase in horizontal cell responsiveness following light-sensitization was due to an increase of peak response amplitude rather than a reduction of peak response time. The increased responsiveness after light-sensitization was intensity-dependent with brighter sensitizing stimuli causing a greater increase than dimmer stimuli. The extent of LHC dark-suppression was affected by the time of day, being greater when induced during the night than during the day. However, there was no significant difference in horizontal cell responsiveness after light-sensitization in retinas studied during the night compared to those studied during the day The responsiveness of light-sensitized horizontal cells from isolated hybrid bass retinas was found to be suppressed by relatively brief periods of darkness. The responsiveness of horizontal cells, that were first light-sensitized, decreased by more than 50% following only 5 min of darkness. Suppression of light-sensitized horizontal cell responsiveness after such a short time in the dark has not been described in other teleost retinas. The suppression of light-sensitized horizontal cell responsiveness in hybrid bass retinas may be rapid in comparison to other teleosts.
Catecholamine-, Indoleamine-, and GABA-containing cells in the chameleon retina
Authors: Bennis Mohamed , Versaux-Botteri Claudine 
Published: June 2009

AbstractNeurons containing catecholamine, indoleamine, and gamma-aminobutyric acid (GABA) were identified by immunohistochemistry in the chameleon retina. Tyrosine hydroxylase (TH) and serotonin (5HT) were observed mostly in two subtypes of orthotopic amacrine cells differing in their soma size and process distribution within the IPL. Some labelled cells were displaced either to the IPL (5HT) or to the GCL (TH and 5HT). A multiplicity of retinal cell types contained GABA including cones, horizontal, amacrine, and ganglion cells. Our results confirmed those obtained in the retinas of other lizards except for the presence of interstitial and displaced amacrine cells containing TH or 5HT of which this is the first report.