bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localization of substance P and GABA in retinotectal ganglion cells of the larval tiger salamander
Authors: Watt Carl B. , Glazebrook Patricia A. , Florack Valarie J. 
Published: June 2009

AbstractThe present study was performed as part of a systematic examination of the transmitter specificity of neuronal populations in the larval tiger salamander retina. Backfill-labeling of ganglion cells from the optic tectum was combined with double-label immunofluorescence histochemistry to determine if substance P and GABA are localized to ganglion cell populations in the tiger salamander retina. The triple-label analysis revealed the presence of substance P- and GABA-ganglion cells in both central and peripheral regions of the retina. Substance P-immunoreactive ganglion cells comprised 2% of the total population of backfill-labeled ganglion cells, while less than 1% of backfill-labeled ganglion cells expressed GABA immunoreactivity. Ganglion cells were not found to co-label for both substance P and GABA. Backfill-labeled displaced ganglion cells, which comprised 1.4% of the ganglion cell population, were not observed to be immunoreactive for either substance P or GABA. Forty-six point nine percent of substance P-cells in the ganglion cell layer were backfill-labeled and were identified as ganglion cells. GABA ganglion cells comprised less than 1% of GABA-immunoreactive cells in the ganglion cell layer.
Changes in fiber organization within the chiasmatic region of mammals
Authors: Reese Benjamin E. , Baker Gary E. 
Published: June 2009

AbstractIntroductionClassical views of the optic chiasm maintain four propositions about the retinofugal pathways: (1) each optic nerve contains a retinotopic representation of its respective retinal surface; (2) this retinotopic map in the nerve is the basis for the subsequent segregation of the decussating from the non-decussating fibers; (3) this retinotopy in the nerve is also the basis for the presence of retinotopy found within the half-retinal maps in the optic tracts; and (4) the half-retinal maps from each optic nerve are brought together within the chiasm to yield a unified, binocularly congruent, map in the optic tract (Brodal, 1969; DukeElder, 1961; Polyak, 1957; Wolff, 1940). The appeal of this classical view is in its simplicity, based on the assumption that the retinofugal pathway should replicate the sensory surface along its course. We now know that each of these four propositions is incorrect, and that the error is not one simply of degree or extent (Guillery, 1982, 1991). Rather, the above description of the visual pathway is fundamentally flawed because it has failed to take into account the constraints under which the pathway develops. We shall first consider the evidence for rejecting the classical view, from recent studies on the organization of the retinofugal pathway in adult animals and on the development of that organization. We shall then describe three transformations in the fiber order which all occur in the chiasmatic region, two of which were only recently recognized, and for which we must account.Observations from adult organizationThe difference in the fiber order in the optic nerve and tract
Neuropharmacological analysis of the role of indoleamine-accumulating amacrine cells in the rabbit retina
Authors: Brunken William J. , Daw Nigel W. 
Published: June 2009

AbstractIn order to elucidate the role of putative indoleaminergic amacrine cells in visual processing, we have employed pharmacological agents specific for the two classes of serotonin receptor, 5-HT2and 5-HT1, which have been identified in both the retina and brain. Perfusion of the rabbit retina with 5-HT2selective antagonists decreases the ON-excitation of all classes of ganglion cell as well as the spontaneous activity of these cells. The effect on OFF-responses depends on the cell type: OFF-excitation of center-surround brisk and sluggish cells is increased or not affected by these drugs, but OFF excitation of ON/OFF direction selective cells is reduced. No disruption of the trigger features of direction selective or orientation selective cells was discovered, suggesting that indoleaminergic amacrine cells do not play a role in the generation of the complex properties of these cells.5-HT1receptors are heterogeneous and classified asa, b, orcsubtypes. Since no selective antagonists are available for these sites, we have employed specific agonists. The most specific of these are for the 5-HT1Areceptor. Perfusion with these agonists had physiological effects similar to those with perfusion of 5-HT2antagonists. Thus, we have suggested that these two classes of serotonin receptors mediate opponent processes in the neural pathway. Since indoleaminergic cells make reciprocal synaptic connections with rod bipolar cell terminals, which are depolarizing in the rabbit retina, we hypothesize that 5-HT2receptors facilitate the synaptic transmission from the depolarizing rod bipolar cell thus facilitating ON-excitation in the retinal network while 5-HT1Areceptors mediate an inhibitory process. Similar self-opponent processing appears to take place in the hypothalamic and hippocampal serotonergic systems as well as in the dopaminergic retinal system. Thus, it is likely that this organization is a general feature of monoamine signal transmission in the central nervous system.
Photic responses of geniculo-hypothalamic tract neurons in the Syrian hamster
Authors: Harrington Mary E. , Rusak Benjamin 
Published: June 2009

AbstractThe putative neural pacemaker controlling circadian rhythms in mammals is contained in the suprachiasmatic nuclei of the hypothalamus. These nuclei receive a projection, the geniculo-hypothalamic tract (GHT), from neurons in the intergeniculate leaflet (IGL) and portions of the ventral lateral geniculate nucleus (vLGN) of the thalamus. We examined the responses of putative GHT neurons to diffuse illumination using extracellular electrophysiological recordings. The great majority of IGL neurons showed sustained ON responses to diffuse retinal illumination; vLGN neurons showed more variation in their responses. Discharge rates of sustained ON neurons increased monotonically as light intensity was increased and saturated over 2–3 log units of intensity changes. Many IGL neurons had binocular input, and input from the ipsilateral eye was often inhibitory. These results indicate that GHT neurons may provide information about ambient light intensity to the suprachiasmatic nuclei.
Developing eyes that lack accommodation grow to compensate for imposed defocus
Authors: Schaeffel Frank , Troilo David , Wallman Josh , Howland Howard C. 
Published: June 2009

AbstractThe eyes of growing chicks adjust to correct for myopia (eye relatively long for the focal length of its optics) or hyperopia (eye relatively short for the focal length of its optics). Eyes made functionally hyperopic with negative spectacle lenses become myopic and long, whereas eyes made functionally myopic with positive spectacle lenses become hyperopic and short. We report here that these compensatory growth adjustments occur not only in normal eyes but also in eyes unable to accommodate (focus) because of lesions to the Edinger-Westphal nuclei. Thus, at least in chicks, accommodation is not necessary for growth that reduces refractive errors during development, and may not be necessary for the normal control of eye growth.
Retinal ganglion cell axon diameter spectrum of the cat: Mean axon diameter varies according to retinal position
Authors: Fitzgibbon Thomas , Funke K. 
Published: June 2009

AbstractAxon diameters of retinal ganglion cells were measured from electron micrographs of the nerve fiber layer of the cat. Three adult retinae were examined which had mean axonal diameters of 1.18 ± 0.86 (n= 5553), 1.12 ± 0.79 (n= 7265), and 1.47 ±1.11 μm (n= 10,867). Cumulative histograms from several locations adjacent to the optic disc were unimodal (modal peaks: 0.6–0.8 μm). This unimodal distribution, however, did not reflect the regional differences in axonal diameters found throughout the retina. In many locations, especially those related to axons of the temporal retina, axon diameter distributions were clearly bimodal or even trimodal (modal peaks: 0.6–0.8, 1.4–2.1, and 3.3 μm). Measurements from one retina indicated that the mean diameters of axons arising from thearea centralisand visual streak (0.94 ± 0.63 and 0.98 ± 0.68, respectively) were not significantly different from each other; however, when compared to other areas around the optic disc, the percentage of fibers with diameters between 1.5–2.0 μm was highest in the sample adjacent to thearea centralis.Axons temporal to the optic disc were found to be on average larger than those nasal to the optic disc; similarly superior axons were larger than inferior axons. Axonal distributions at the retinal periphery were found to be significantly different from those at the optic disc (p≤ 0.05) and contained a higher percentage of medium-sized axons and fewer small axons. In each of the three retinae the proportions small, medium, and large axons were respectively γ: 46; 47; 48, β: 50; 49; 48, and α: 4; 4; 4; regional differences in the proportions of each axonal class are compared to previously published ganglion cell density maps. Differences between axonal bundles within each sample location were not significantly different; however, in one retina axons in the scleral half of the fiber layer were significantly larger (P≤ 0.01) than axons in the vitreal half of the nerve fiber layer adjacent to the optic disc. When compared to the axonal diameter distributions found within the optic nerve (Cottee et al., 1991) and optic tract (Reese et al., 1991), our data indicates that the diameter of retinal axons may increase by up to 30% along the length of the visual pathway.
The network properties of bipolar–bipolar cell coupling in the retina of teleost fishes
Authors: Umino Osamu , Maehara Michiyo , Hidaka Soh , Kita Shigeo , Hashimoto Yoko 
Published: June 2009

AbstractRetinal bipolar cells exhibit a center-surround antagonistic receptive field to a light stimulus (Werblin & Dowling, 1969; Kaneko, 1970), and thus constitute an early stage of spatial information processing. We injected Lucifer Yellow and a small biotinylated tracer, biocytin, into bipolar cells of the teleost retina to examine electrical coupling in these cells. Lucifer-Yellow coupling was observed in one of 55 stained bipolar cells; the coupling pattern was one injected bipolar cell and three surrounding cells. Biocytin coupling was observed in 16 of 55 stained bipolar cells, six of which were ON center and ten OFF center. Although biocytin usually coupled to three to six bipolar cells, some OFF-center bipolar cells showed strong coupling to more than 20 cells. The biocytin-coupled bipolar cells were morphologically homologous. Membrane appositions resembling gap junctions were found between dendrites and between axon terminals of neighboring bipolar cells.In the strongest biocytin-coupled bipolar cells, the contacts between bipolar cells and cone photoreceptor cells were examined after reconstruction of the dendritic trees of five well-stained, serially sectioned OFF-center bipolar cells. Each of these bipolar cells was in contact with different numbers of cones: 11 to 20 for twin cones and two to four for single cones. This implies that, although these bipolar cells belong to the same category, the signal inputs differ among bipolar cells. Numerical simulation conducted on a hexagonal array network model demonstrated that the electrical coupling of bipolar cells can decrease the difference in input (≈80%) without causing significant loss of spatial resolution. Our results suggest that electrical coupling of bipolar cells has the advantage of decreasing the dispersion of input signals from cones, and permits bipolar cells of the same class to respond to light with similar properties.
Effect of hydroxylamine on the subcellular distribution of arrestin (S-antigen) in rod photoreceptors
Authors: Mangini Nancy J. , Garner Grady L. , Okajima Tinging L. , Donoso Larry A. , Pepperberg David R. 
Published: June 2009

AbstractThe immunocytochemical labeling of arrestin (S-antigen) in photoreceptors of the ovine retina was examined following incubation of the retina with hydroxylamine (NH2OH), an agent known to inhibit the phosphorylation of photoactivated rhodopsin. Intact, isolated retinas bathed in medium containing 20 mM NH2OH, or in control medium lacking NH2OH, were maintained in darkness or exposed to bright light for 3 min (dark-adapted and light-adapted conditions, respectively); further incubated in darkness for 10 min; and then fixed and prepared for cryosectioning. Cryosections were incubated with anti-S-antigen monoclonal antibody MAb A2G5; with secondary antibodies that were conjugated with horseradish peroxidase; and with either 3–amino-9–ethyl carbazole or diaminobenzidine as chromogen. Anti-arrestin labeling in cryosections was then analyzed densitometrically using a light-microscopic image processing system. In dark-adapted control retinas, labeling density of the photoreceptor outer segment (OS) layer (0.061 ± 0.004; average ±S.e.m.) was less than that of the inner segment (IS) layer (0.138 ± 0.011). In light-adapted control retinas, OS labeling density (0.139 ± 0.007) exceeded IS labeling density (0.095 ± 0.005). Incubation with NH2OH eliminated this light-dependent increase in labeling of the OS relative to that of the IS, i.e. eliminated the increase in relative OS/IS labeling. Densities of labeling were 0.110 ± 0.006 (OS) and 0.183 ± 0.006 (IS) in NH2OH-treated dark-adapted retinasvs.0.078 ± 0.004 (OS) and 0.182 ± 0.008 (IS) in NH2OH-treated light-adapted retinas. Anti-arrestin labeling was also examined in retinas that were exposed to 3 min or 13 min of bright light and then immediately fixed. Among retinas incubated in the absence of NH2OH, an increase in OS/IS labeling density was evident after 3 min of illumination, and retinas illuminated for 13 min exhibited an even larger increase in OS/IS labeling. An increase in OS/IS labeling was also exhibited by NH2OH-treated retinas that had been illuminated for 3 min; by comparison with dark-adapted NH2OH-treated controls (average value of OS/IS labeling: 0.60), OS/IS labeling in these illuminated retinas was 0.97. However, OS/IS labeling in NH2OH-treated retinas that had been illuminated for 13 min (average value: 0.35) was lower than that of the dark-adapted controls. The results indicate that, within intact rods, NH2OH inhibits the light-dependent increase in OS/IS anti-arrestin labeling that is ordinarily expressed at long times (~10 min) after major bleaching of the visual pigment. Among the possible bases for the effect of NH2OH are a reduction in the driving force for the movement of arrestin from the inner to the outer segment and/or a facilitation of the degradation of arrestin in the outer segment.
Nicotinic acetylcholine receptors in the ground squirrel retina: Localization of the β4 subunit by immunohistochemistry andin situhybridization
Authors: Britto Luiz R. G. , Rogers Scott W. , Hamassaki-Britto Dânia E. , Duvoisin Robert M. 
Published: June 2009

AbstractImmunohistochemical andin situhybridization techniques were used to localize the β4 subunit of the neuronal nicotinic acetylcholine receptors (nAChRs) in the ground squirrel retina. The β4 nAChR subunit was detected in both transverse and horizontal sections of the retina using a subunit-specific antiserum and the avidin-biotin complex technique. Two bands of labeled processes were seen in the inner plexiform layer, corresponding approximately to the laminae where the cholinergic cells arborize. Labeled cells were found in the ganglion cell layer and the inner third of the inner nuclear layer. The cells in the ganglion cell layer were medium- to large-sized and were frequently observed to give rise to axon-like processes. Most of the labeled neurons in the inner nuclear layer were small presumptive amacrine cells, but a few medium-to-large cells were also labeled. These could constitute a different class of amacrine cells or displaced ganglion cells. The latter possibility is supported by the existence of nAChR-containing displaced ganglion cells in the avian retina.In situhybridization with a35S-labeled cRNA probe revealed the expression of mRNA coding for the nAChR β4 subunit in the ganglion cell layer and the inner third of the inner nuclear layer. This finding confirmed the immunohistochemical data of the cellular localization of β4 nAChR subunit.These results indicate that the β4 nAChR subunit is expressed by specific subtypes of neurons on the ground squirrel retina. As the expression of that particular nAChR subunit appears to be very limited in the brain, the present data suggest that the retina might represent a useful model to study the function of nAChRs containing the β4 subunit.
Divergent feedback connections from areas V4 and TEO in the macaque
Authors: Rockland Kathleen S. , Saleem Kadharbatcha S. , Tanaka Keiji 
Published: June 2009

AbstractExtrastriate areas TEO and V4 have been associated with form and color vision. Area V4 has also been suggested to participate in processes concerned with attention, stimulus salience, and perceptual learning. In a continuing effort to elucidate the connectional interactions and microcircuitry of these areas, we describe in this report the pattern of feedback connections from TEO and V4. Connections were demonstrated by injections of the high-resolution anterograde tracers PHA-L or biocytin and further analyzed by reconstruction of 25 individual axons through serial sections. This analysis yielded several new results: (1) Both areas TEO and V4 have widespread feedback connections (defined by their preferential termination in layer 1 and avoidance of layer 4). From TEO, there are dense projections to area V4 and moderate ones to V2 and V1. From V4, there are dense projections to V2 and moderate ones to V3 and V1. (2) Terminal fields span large territories in area V1, up to 6.0 mm in the case of axons originating from TEO; up to 5.0 mm in the case of axons originating from V4. In V2, fields tend to be smaller, between 3.0–5.0 mm. (3) Many axons from TEO and some from V4 have terminations in both areas V1 and V2. (4) Because individual terminal clusters and segments are often larger than cytochrome oxidase compartments, especially in V1, we suggest they may not be correlated with this compartmental organization. These results are consistent with the hypothesis that feedback connections may contribute to processes other than perceptual discrimination.
Receptor demise from alteration of glycosylation site inDrosophilaopsin: Electrophysiology, microspectrophotometry, and electron microscopy
Authors: Brown Gary , Chen De-Mao , Christianson J. Scott , Lee Ron , Stark William S. 
Published: June 2009

AbstractIn the δAsn20Drosophilastock, the N-linked glycosylation site of opsin in Rl-6 receptors (Rhl) is absent. We used electroretinography (ERG), microspectrophotometry (MSP), and electron microscopy (EM) to quantify visual cell defects. Positive controls,w9, had wild type Rhl. MSP revealed minimal photopigment in δAsn20for 6 days posteclosion;w9had near normal visual pigment. ERG sensitivity and prolonged depolarizing afterpotential (PDA) were compared for δAsn20andw9.δAsn20's Rl-6 function is decreased 100–fold at eclosion and diminishes until only R7/8 functions at 11 days. What little rhodopsin is routed to the rhabdomere functions. Morphometry showed smaller Rl-6 rhabdomeres in δAsn20for 8 days posteclosion. Rhabdomeres inw9were normal. A negative control,ninaE0117, a deletion of the Rhl gene, also has small rhabdomeres. δAsn20andninaE0117lack the extreme rhabdomere elimination ofora(outerrhabdomeresabsent), a nonsense mutant interrupting Rhl's coding sequence. δAsn20andorahave surplus membrane whileninaE0117does not. Freeze fracture reveals that δAsn20's rhabdomeric P-face particle count is as low as for vitamin A deprivation, consistent with an opsin defect. High particle density, organized into rows, is present in adjacent plasmalemma where surplus membrane accumulates. In summary, δAsn20interferes with either synthesis, deployment, or maintenance of opsin.
Impaired visual thresholds in hypopigmented animals
Authors: Balkema Grant W. , Dräger Ursula C. 
Published: June 2009

AbstractOcular hypopigmentation is associated with neurological defects in structure and function. This paper investigates the ab/Fute visual thresholds in dark-adapted hypopigmented animals compared to their normally pigmented controls. Here we asked (1) whether the threshold elevation found in hypopigmented animals is a general consequence of the reduction in melanin content; (2) if so, which melanin components in the eye are likely to influence visual thresholds; and (3) whether similar threshold defects can be detected in orders other than rodents. By single-unit recordings from the superior colliculus, we compared incremental thresholds of normal black mice of the C57BL/6J strain to hypopigmented mutants: beige (bg/bg), pale ear (ep/ep), and albino (c2J/c2J) mice, three mutants in which melanin pigment throughout the body is affected; and Steel (Sl/Sld) and dorninant-spotting/W-mice (W/Wν), two mutants with normal pigmentation in the retinal pigment epithelium (RPE) but without any melanin in the choroid or the rest of the body. We found that all mutants had elevated thresholds that varied with the reduction in melanin. The albinos were 25 times less sensitive than black mice, pale ear mice 20 times, beige mice 11 times, and Steel and W-mice 5 times. The mean thresholds of dark-adapted black mice were 0.008 cd/m2. Recordings from rabbits showed a similar impairment of visual sensitivity: incremental thresholds were elevated 40 times in New Zealand-White albino rabbits (0.0008 cd/m2) compared to Dutch-Belted pigmented controls (0.00002 cd/m2). Previously, it has been shown that hypopigmented rats have elevated dark-adapted thresholds compared to pigmented controls (Balkema, 1988); here we show that the difference between hypopigmented rats and pigmented controls is not caused by insufficient dark adaptation or excessive variability in the results from albino mutant compared to its control.Mutations that cause a reduction of ocular melanin pigmentation, regardless of the gene mutated or the mechanism underlying the hypopigmentation, are accompanied by an elevation in visual thresholds which is roughly proportional to the reduction in melanin. Melanin both in the RPE and choroid exert an effect on visual thresholds. Like the defects in optic nerve crossing and eye movements, the effect of melanin on visual thresholds is not restricted to rodents, but is seen in other orders. The threshold impairment in hypopigmented animals cannot be explained by impaired photoprotection, but it points to another physiological action of melanin.