bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lagged Y cells in the cat lateral geniculate nucleus
Authors: Mastronarde David N. , Humphrey Allen L. , Saul Alan B. 
Published: June 2009

AbstractWe report on the existence of lagged Y (YL) cells in the A laminae of the cat lateral geniculate nucleus (LGN) and on criteria for identifying them using visual and electrical stimulation. Like the lagged X (XL) cells described previously (Mastronarde, 1987a; Humphrey & Weller, 1988a), YL cells responded to a spot stimulus with an initial dip in firing and a delayed latency to discharge after spot onset, and an anomalously prolonged firing after spot offset. However, the cells received excitatory input from retinal Y rather than X afferents, and showed nonlinear spatial summation and other Y-like receptive-field properties. Three YL cells tested for antidromic activation from visual cortex were found to be relay cells, with long conduction latencies similar to those of XL cells.Simultaneous recordings of a YL cell and its retinal Y afferents show striking parallels between lagged X and Y cells in retinogeniculate functional connectivity, and suggest that the YL-cell response profile reflects inhibitory processes occurring within the LGN. The YL cells comprised -5% of Y cells and -1% of all cells in the A laminae. Although infrequently encountered in the LGN, they may be roughly as numerous as Y cells in the retina, and hence could fulfill an important role in vision.
Evidence for local circuits within the receptive fields of retinal ganglion cells in goldfish
Authors: Levine Michael W. , Zimmerman Roger P. 
Published: June 2009

AbstractA new form of receptive field map, the response-component map, was developed to identify points within a receptive field that produce similar response patterns. The fields were probed with discretely flashed small spots of light. The magnitudes of the responses to stimulus onset and to stimulus offset elicited at each point were represented on the map by a vector radiating from the position representing the location of that point. Thus, response-component maps preserve the spatial distributions of responsivity and temporal nonlinearities. Points with similar response patterns were identified from a scatterplot in which the response at each spatial position was located in a plane representing the angles of the response-component vectors. Points with similar response characteristics that were also spatially contiguous were considered as a distinct response subregion within the receptive field.Barely 10% of the receptive fields of goldfish ganglion cells mapped with this technique proved as simple as the traditional concentric field described for retinal cells. In at least 17% of the cases, the field showed three concentric rings, with a very small “inner center” within the center of the field. In at least 50% of the cases, response subregions of different type lay side by side, rather than in a concentric configuration. Some subregions could be differentiated by the relative strengths of the responses to onset and offset of the stimulus spot, supporting the hypothesis that a push-pull system generates ganglion cell responses. Subregions were evident in successive mappings of the same cell, demonstrating they are not due to the vagaries of individual responses. They probably represent the spatial domains (or their intersections) of individual interneurons distal to the retinal ganglion cells. It is possible that position within the receptive field may be coded by the temporal pattern of the responses.
GABA-Immunoreactive Synaptic Plexus in the Nerve Fiber Layer of Primate Retina
Authors: Koontz Margaret A. , Hendrickson Anita E. , Ryan Marianne K. 
Published: June 2009

AbstractSynaptic contacts onto fibers and somata in the nerve fiber layer (NFL) and ganglion cell layer (GCL) of macaque and human retina were demonstrated at the electron microscopical (EM) level. Many presynaptic processes in monkey NFL are gamma aminobutyric acid (GABA) immunoreactive, using anti-GABA antiserum with an EM immunogold procedure. Immunocytochemistry at the light microscopic level revealed that many GABA-reactive cells in the GCL send branching processes into the NFL, forming a sparse synaptic plexus. The presence of long, unbranched GABA-reactive fibers running horizontally in the NFL and entering the optic nerve suggests that some ganglion cells may be GABAergic. GABA-reactive cells contributing to the plexus appear to be a new class of displaced amacrines that arborize in the NFL.
Calcium/calmodulin-stimulated phosphorylation of photoreceptor proteins inLimulus
Authors: Wiebe Eric M. , Wishart Anne C. , Edwards Samuel C. , Battelle Barbara-Anne 
Published: June 2009

AbstractCalcium (Ca2+) is thought to play a major role in the photoresponse of both vertebrates and invertebrates, but the mechanisms through which Ca2+exerts its effects are unclear. In many systems, some effects of Ca2+on cellular processes are thought to be mediated via activation of calcium/calmodulin protein kinase (CaCAM-PK) and the phosphorylation of specific proteins. Thus, protein substrates for CaCAM-PK in photoreceptor cells may be important in mediating the effects of Ca2+on the photoresponse.In this study, we identify eight substrates for CaCAM-PK found in both the ventral and lateral eyes ofLimulus. We focus on a characterization of one of these, a 46-kD substrate. We show that its subcellular distribution in ventral photoreceptors and its isoelectric forms are identical to the 46-kD light-stimulated phosphoprotein (46A) described by Edwards et al. (1989). Furthermore, we present evidence that 46A is unique to photoreceptor cells, and that it is present throughout the cell. Based on the results of this study, and the previous study by Edwards et al. (1989), we propose that 46A is involved in mediating the effects of Ca2+onLimulusphotoreceptor cell function, and that it may be involved in dark adaptation.
The pupillary light reflex in normal and innate microstrabismic cats, I: Behavior and receptive-field analysis in the nucleus praetectalis olivaris
Authors: Distler C. , Hoffmann K.-P. 
Published: June 2009

AbstractNeurons in the nucleus praetectalis olivaris (NPO) were antidromically identified by electrical stimulation of the nucleus of Edinger-Westphal (EW), the location of preganglionic pupilloconstrictor motoneurons. Electrical stimulation within the NPO leads to bilateral pupil constriction. Single neurons recorded in the NPO respond tonically to light stimuli, and their discharge frequency increases linearly with logarithmic increase in light intensity. This characteristic identifies NPO neurons as luminance detectors. They have large receptive fields mostly lying in the upper and contralateral quadrant of the visual field.Cats with impaired binocular vision show a significantly reduced binocular summation of the pupillary light reflex (BSP), i.e. the increase of pupil constriction during binocular illumination when compared to monocular illumination is less than in normal animals. The investigation of ocular dominance and subthreshold binocular interactions in the NPO of normal and innate microstrabismic cats revealed two possible mechanisms for BSP and its reduction in strabismic subjects. First, the percentage of neurons increasing their discharge rate by illuminating either eye is significantly reduced in the NPO of innate microstrabismic cats (6.6%) when compared to normal cats (22% of all neurons tested). Second, in most NPO neurons of normal cats the subthreshold influence of the ipsilateral eye leads to an increase in neuronal activity during binocular stimulation when compared to monocular stimulation of the contralateral eye (binocular summation). The subthreshold influence of the ipsilateral eye in most NPO neurons of microstrabismic cats, however, is inhibitory, i.e. the neuronal discharge rate during binocular stimulation is decreased when compared to monocular stimulation of the contralateral eye (binocular inhibition). However, there is no significant correlation between BSP and binocularity in the NPO in individual animals. This suggests that BSP may be additionally influenced by visual structures other than NPO.
Topographic organization of the retinocollicular projection in the neonatal rat
Authors: Peter J. , Yhip A. , Kirby Michael A. 
Published: June 2009

AbstractThe topographic order of the retinocollicular projection in the rat was examined from birth until maturity. Small, localized deposits of rhodamine-filled latex microspheres were placed into the superior colliculus at different locations. To minimize labeling fibers of passage deposit sites were typically, although not exclusively, placed into the caudal-lateral pole of the colliculus. Examination of the area and density of labeled cells in the retinae of these animals led to the following conclusions: (1) At each age examined, the location of the majority of labeled cells was observed to be in appropriate topographic register with the deposit site in the superior colliculus. (2) Confirming the work of previous investigators, errors in topographic projection were observed. These were present in both the contralateral and ipsilateral retinae and decreased with increasing postnatal age. The mature pattern was present by P10. (3) Quantitatively, the number of retinal ganglion cells terminating nontopographically within the colliculus constituted a relatively minor proportion of the total number of labeled cells in both retinae. It is concluded that the majority of the retinal ganglion cells make topographically appropriate terminations within the superior colliculus during development.
Effect of intracellularly applied sodium ions on the dark voltage of isolated retinal rods
Authors: Schmidt Karl-Friedrich , Nöll Gottfried N. , Baumann Christian 
Published: June 2009

AbstractIsolated retinal rods of the frog consisting of the outer segment and the ellipsoid were patch-clamped and recorded in the whole-cell mode. The recording pipettes were filled with solutions of different composition in order to alter the cytoplasmic content of sodium, phosphate, and calcium ions, and guanine nucleotides. When a simple medium with potassium as the principal cation was used, the dark voltage slowly approached more negative values. This tendency of spontaneous hyperpolarization was reduced significantly when cGMP or GTP were present in the pipette medium. Sodium ions, on the other hand, clearly increased the speed of hyperpolarization. In the presence of sodium (20 mM), the stabilizing effect of GTP did not occur and that of cGMP was clearly diminished. Phosphate (20 mM) neutralized the sodium effect. High calcium levels (100 μM) did not measurably influence the time course of hyperpolarization. We conclude that the normal cytoplasmic sodium level in rods does not exceed 10 mM and that higher internal sodium concentrations interfere with the sodium–calcium exchange mechanism.
Time-dependent differential effects of cobalt ions on rod- and cone-driven responses in the isolated frog retina
Authors: Dong Cun-Jian , McReynolds John S. , Qian Hao-Hua 
Published: June 2009

AbstractThe effects of cobalt ions on 502-nm rod- and 575-nm cone-driven components of the b-wave of the electroretinogram were studied in the isolated frog retina. Addition of 100–150 μM cobalt initially caused a suppression of rod-driven responses and an enhancement of cone-driven responses. In the continued presence of cobalt, however, the rod-driven responses gradually recovered and the cone-driven responses became suppressed. These concentrations of cobalt had no effect on the rod- and cone-driven mass receptor potentials which were isolated in the presence of 4 mM glutamate. At higher concentrations of cobalt (1 mM or greater), both rod- and cone-driven b-wave responses were eliminated and there was no recovery in the continued presence of cobalt. The results suggest that cobalt has markedly different, time-dependent effects on signal transmission from rods and cones to second-order cells.
Appearance of cGMP-phosphodiesterase immunoreactivity parallels the morphological differentiation of photoreceptor outer segments in the rat retina
Authors: Colombaioni Laura , Strettoi Enrica 
Published: June 2009

AbstractWe have investigated by immunofluorescence the appearance of immunoreactive guanosine 3′-5′ cyclic monophosphate phosphodiesterase (cGMP-PDE) during the postnatal development of the retina of the pigmented rat. We show that a sudden increase in immunoreactivity takes place during postnatal day five (P5), when rod outer segments begin to form; immunoreactivity develops rapidly in the following days. Labeling is restricted to the developing photoreceptor outer segments, sparing other retinal cells, as confirmed by electron microscopy immunocytochemistry. In addition, cGMP-PDE immunoreactivity follows a center-to-periphery gradient paralleling photoreceptor differentiation. It appears that cGMP-PDE is expressed when the photoreceptor subcellular compartments are already formed, and represents a specific marker of late photoreceptor differentiation. The appearance of cGMP-PDE during development is temporally correlated with the appearance of other proteins of the phototransduction machinery.
A comparison of the 40-Hz response in man, and the properties of macaque ganglion cells
Authors: Regan D. , Lee B.B. 
Published: June 2009

AbstractVisually evoked field potentials in human subjects and single-cell responses from retinal ganglion cells in the macaque monkey were compared in closely similar stimulus situations. The classical heterochromatic flicker photometry (HFP) technique was used to measure spectral sensitivity in man, both psychophysically and by recording the 40-Hz response, and to measure the spectral sensitivity of magnocellular (MC-) pathway cells of the macaque. The three measures gave closely similar spectral-sensitivity curves. Close agreement between the three measures was also found when the variable-modulation HFP technique was used to measure spectral sensitivity. When the relative phase between red and green lights was varied, the point of minimum subjective flicker for human observers was close to a sharp minimum found in the amplitude of the 40-Hz response in human and was also close to a minimum in the response of MC-pathway neurons in the monkey. The human 40-Hz response saturated at between 10 and 30% modulation depth, and so did the response of MC-pathway cells in the monkey.The 16-Hz response in human showed none of the above correlations with MC-pathway properties. On the other hand, parvocellular (PC-) pathway cells responded vigorously to constant-luminance, chromatic modulation, at frequencies higher than can be detected by human observers. The human 16-Hz response also was strong in that stimulus situation. In addition, the response of PC-pathway cells on increasing modulation depth showed little saturation, and this behaviour was paralleled by the human 16-Hz response.We conclude that the properties of MC-pathway neurons in macaque are closely similar to the properties of the human 40-Hz response in the respects just described. We suggest that the 40-Hz response may offer a means of objectively isolating and investigating the contribution of the magnocellular stream to cortical activity in human. In contrast, the properties of PC-pathway neurons in macaque are quite different from the properties of the human 40-Hz response, and in several respects resemble the properties of the human 16-Hz response.
Apomorphine blocks form-deprivation myopia in chickens by a dopamine D2-receptor mechanism acting in retina or pigmented epithelium
Authors: Rohrer Baerbel , Spira Arthur W. , Stell William K. 
Published: June 2009

AbstractStudies of form-deprivation myopia (FDM) in animal models have shown that postnatal ocular growth is regulated by the quality of patterned images on the retina. One of the major challenges in myopia research is to identify the biochemical mechanisms which translate retinal visual responses into signals that regulate scleral growth. Dopamine (DA) has been implicated in this process, since retinal DA levels decline in FDM and subconjunctival injections of apomorphine (Apo, a nonspecific DA agonist) prevent FDM in a dose-dependent way (Stoneet al., 1989).To gain insight into where and how DA ligands act to regulate ocular elongation, we compared the action and distribution of DA receptor ligands injected intravitreallyvs.subconjunctivally in young chicks. Ocular length was measured by A-scan ultrasound. We found that daily intravitreal injections of Apo block FDM at a 50% effective dose (ED50) of 5 pg per day, or a peak concentration in the vitreous humor of 108 pM, compared to an ED50of 2.5 ng for subconjunctival injections as reported by Stoneet al.(1989, 1990). [3H]-spiperone, a D2-receptor antagonist, reached average maximum retinal concentrations of 160 pM and 260 pM, during the first hour after intravitreal and subconjunctival administration, respectively, at theED50dose. In contrast, the maximum spiperone concentrations in the retinal pigment epithelium (RPE) were 30 pM and 410 pM, respectively, after intravitreal or subconjunctivalED50doses. Spiperone concentrations in sclera afterED50doses to the two sites differed by 4 x 104(0.4 pMvs.1.7 nM, respectively). The FDM-preventing action of Apo was blocked completely by simultaneous administration of spiperone but not by SCH 23390 (a D1-receptor antagonist) in 100-fold molar excess.These results show that apomorphine acts to prevent FDM at an intraocular site, presumably in retina and/or pigment epithelium, but not sclera, whether administered intravitreally or subconjunctivally. A dose yielding a concentration of 100–260 pM, delivered ≤1 h per day, produces half-maximal inhibition. This action is mediated by D2-receptors, for which the dissociation constant for apomorphine is ≤1 nM. The retinal pigment epithelium may act as a trophic relay station, responding to a retinal messenger which may be DA and secreting scleral growth-regulator(s) from its basal surface.
Neurophysiology of central retinal degeneration in cat
Authors: Levick W.R. , Thibos L.N. 
Published: June 2009

AbstractReceptive fields of ganglion cells have been studied in cats possessing a chronic, arrested lesion of central retinal degeneration. Lesions were characterized by an ophthalmoscopically sharp border separating apparently normal retina from the region of the lesion. Under direct ophthalmoscopic guidance, a succession of recordings was obtained from ganglion cells having cell bodies at various positions relative to the lesion. Cells located more than 1 deg outside the ophthalmoscopic border had normal visual sensitivity as assessed by area-threshold experiments. Inside the lesion cells within 1 deg of the border had reduced sensitivity which often precluded functional classification by the usual visual tests. Ganglion cells located more than 1 deg inside the border of large lesions were blind and some had abnormal patterns of maintained discharge of action potentials. Nevertheless, the antidromic latencies of these blind cells fell into the familiar conduction groups (T1/T2/T3). Receptive-field maps of cells near the border of the lesion often appeared truncated, with the missing portion of the field covered by the lesion. These observations were consistent with the abnormal form of area-thresholdcurves. Altlhough the responsiveness of cells near the lesion was abnormally low for grating stimuli, cutoff spatial frequency and orientation bias of these cells were within normal limits.
Development of visual inhibitory interactions in kittens
Authors: Morrone M. Concetta , Speed Harriet D. , Burr David C. 
Published: June 2009

AbstractThis study was designed to monitor the development of inhibitory interactions elicited in the cat visual system by oriented visual stimuli. Steady-state visual-evoked potentials (VEPs) were recorded from the scalp of 11 behaving and alert kittens while they viewed contrast-reversed sinusoidal gratings. In adult cats, the form of VEP contrast-response curves (the amplitude of second harmonic modulation as a function of stimulus contrast) was modified by superimposing a mask grating on the test. Parallel masks displaced the curves to a higher contrast region (probably via contrast gain-control mechanisms), increasing contrast threshold without affecting the slope of the curve. Orthogonal gratings, on the other hand, decrease the slope of the curve without affecting threshold (so called cross-orientation inhibition: Morrone et al., 1981). These effects are similar to those previously reported in human VEPs (Morrone & Burr, 1986; Burr & Morrone, 1987) and single cortical cat cells (Morrone et al., 1982). For young kittens of 20 days, the orthogonal mask had no effect whatsoever on the response curves, and the effect of the parallel mask was much less than for adult cats. At about 40 days, the orthogonal mask began to attenuate responses multiplicatively, and by 50 days the amount of multiplicative attenuation had reached adult levels. The effect of the parallel mask (as indicated by the increase in threshold elevation) increased gradually from 20–50 days. The results are consistent with the existence of at least two types of inhibition in cat visual neurones that develop at different rates.
Coexistence and function of glutamate receptor subtypes in the horizontal cells of the tiger salamander retina
Authors: Yang Xiong-Li , Wu Samuel M. 
Published: June 2009

AbstractEffects of the major glutamate receptor agonists, kainate (KA), α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), quisqualate (QA), N-methyl-D-aspartate (NMDA), L-α-amino-4-phosphonobutyrate (L-AP4), and trans-l-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on horizontal cells (HCs) were studied in superfused larval tiger salamander retina. 20 μM of KA, AMPA, and QA mimicked the action of 3 mM glutamate in the absence and presence of 1 mM Co2+-20 μM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked the actions of KA and AMPA, but not those of QA and glutamate, indicative of the existence of CNQX-resistant QA receptors in the tiger salamander HCs. Prolonged application of ACPD hyperpolarized the HCs and enhanced the light responses, probably by shifting the resting HC voltage (Er) to a more hyperpolarized position. It is possible that the KA, AMPA, and CNQX-resistant QA receptors are involved in mediating the postsynaptic light responses in HCs, and ACPD receptors are involved in sensitivity adjustment of the HC responses.
Visual input to commissural neurons of the cat's superior colliculus
Authors: McIlwain James T. 
Published: June 2009

AbstractCells projecting into the commissure of the cat's superior colliculus were identified during extracellular recording by antidromic activation. Electrical stimulation of the ipsilateral optic tract evoked action potentials in the majority of commissural neurons. Response latencies of 1.4 ± 0.5 ms (mean ± S.D.) in a few cells indicated that some commissural neurons receive direct input from the axons of retinal Y–cells. Most commissural cells responded 5.9 ± 1.9 ms (mean ± S.D.) following optic tract shock, implying that the responsible pathway was composed of more slowly conducting axons or did not proceed directly to the colliculus. Results of previous studies of retinal inputs to cells in the deep tectal layers suggest that the later responses were mediated by an indirect Y pathway through the visual cortex.