bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of opsin mRNA in normal and vitamin A deficient retinas of the sphingid mothManduca sexta
Authors: Chase Michael R. , Bennett Ruth R. , White Richard H. 
Published: June 2009

AbstractTwo distinct opsin-encoding cDNAs, designated MANOP1 and MANOP2, were isolated as 3′ fragments from the sphingid mothManduca sexta. They were obtained by reverse transcription of retinal RNA and amplification with the polymerase chain reaction (PCR) using a degenerate primer designed to an amino-acid sequence conserved in arthropod opsins. The cDNA fragments labelled bands at approximately 1.8 kb on Northern blots of retinal RNA extracts. Levels of opsin message were compared in retinas from normal moths, whose diets were fortified with carotenoid precursors of theManducarhodopsin chromophore, 3-hydroxyretinal, and those reared on carotenoid/retinoid (vitamin A) deficient diets. The chromophore-depleted retinas contained more opsin mRNA; this was particularly true for MANOP2. Thus, the chromophore is not required for opsin gene transcription inManduca.
The optic tract in embryonic hamsters: Fasciculation, defasciculation, and other rearrangements of retinal axons
Authors: Jhaveri Sonal , Erzurumlu Reha S. , Schneider Gerald E. 
Published: June 2009

AbstractThe early development of the optic tract in hamsters was studied by labeling retinal axons with Dil applied to the eye, and then examining the labeled axons in flatmount preparations of the rostral brain stem. This technique permits a panoramic view of the entire retinal projection, from the chiasm to the caudal end of the superior colliculus. In the Ell embryo, retinal axons have reached the chiasm. They defasciculate as they emerge from the nerve, prior to reaching the ventral midline of the diencephalon, then converge again as they pass over to the opposite side. At the midline, many axonal trajectories crisscross, implying some shuffling of relative positions. Retinal axons are tightly bundled within the optic tract. Upon reaching the ventral border of the lateral geniculate body (LGB), they splay out over the nucleus, revealing a wavefront of pioneer axons individually distributed across the rostro-caudal extent of the LGB. Later-emerging retinal axons course over the surface of the thalamus inwaves; subsequent waves of axons interdigitate between the lead fibers without fasciculating along them. Past the LGB, the axons undergo a second change in relative positions as the ribbon of fibers swerves caudally, prior to entering the superior colliculus. Retinal axons are tipped with growth cones of varying morphologies. No strong correlation is evident between the Structural complexity of the growth cone and its position within the tract. In the majority of cases, ipsilaterally and contralaterally directed axons follow a similar developmental course along the optic tract, without any indication of a temporal lag in the ipsilateral projection as claimed in earlier reports. Understanding the changes in spatial distribution of embryonic retinal axons as they navigate along the optic tract provides a further step towards elucidating how point-to-point projections form in developing sensory systems.
Calcium-binding proteins immunoreactivity in the human subcortical and cortical visual structures
Authors: Leuba G. , Saini K. 
Published: June 2009

AbstractThe distribution of neurons and fibers immunoreactive (ir) to the three calcium-binding proteins parvalbumin (PV), calbindin D-28k (CB), and calretinin (CR) was studied in the human lateral geniculate nucleus (LGN), lateral inferior pulvinar, and optic radiation, and related to that in the visual cortex. In the LGN, PV, CR, and CB immunoreactivity was present in all laminae, slightly stronger in the magnocellular than in the parvocellular laminae for CB and CR. PV-ir puncta, representing transversally cut axons, and CR-ir fibers were revealed within the laminae and interlaminar zones, and just beyond the outer border of lamina 6 in the geniculate capsule. In the optic radiation both PV- and CR-immunoreactive neurons, puncta, and fibers were present. CB immunoreactivity was revealed in neurons of all laminae of the lateral geniculate nucleus, including S lamina and interlaminar zones. There were hardly any CB-ir puncta or fibers in the laminae, interlaminar zones, geniculate capsule, or optic radiation. In the lateral inferior pulvinar, immunoreactive neurons for the three calcium-binding proteins were present in smaller number than in the LGN, as well as PV-ir puncta and CR-ir fibers within the nucleus and in the pulvinar capsule. In the white matter underlying area 17, fibers intermingled with a few scattered neurons were stained for both PV and CR, but very rarely for CB. These fibers stopped at the limit between areas 17 and 18. Area 17 showed a dense plexus of PV-ir puncta and neurons in the thalamo-receptive layer IV and CR-ir puncta and neurons both in the superficial layers I-II, IIIC, and in layer VA. Cajal-Retzius CR-ir neurons were present in layer I. CB-ir puncta were almost confined to layer I-III and CB-ir neurons to layer II. Finally the superior colliculus exhibited mostly populations of PV and CR pyramidal-like immunoreactive neurons, mainly in the intermediate tier. These data suggest that in the visual thalamus most calcium-binding protein immunoreactive neurons project to the visual cortex, while in the superior colliculus a smaller immunoreactive population represent projection neurons.
Intrinsic circuitry in the deep layers of the cat superior colliculus
Authors: Behan M. , Kime N.M. 
Published: June 2009

AbstractThe mammalian superior colliculus is involved in the transformation of sensory signals into orienting behaviors. Sensory and motor signals are integrated in the colliculus to produce movements of the eyes, head, and neck. While there is a considerable amount of information available on the afferent and efferent connections of the colliculus, almost nothing is known about its intrinsic circuitry, particularly that of its deepest layers. It is likely that intrinsic connections in these deeper layers of the colliculus participate in the sensory-motor transformations leading to orienting movements. In this study, we used the neuroanatomical tracer biocytin to label small groups of neurons in the deeper layers of the cat superior colliculus and examine the distribution of their axons and terminals. We found a broadly distributed network of intrinsic projections throughout the deep layers of the superior colliculus. While the majority of terminals were found in a 1–2 mm radius around the injection site, labeled terminals were found throughout the deep layers of the colliculus up to 5 mm from the injection site. In addition, these injections sometimes labeled terminals in the superficial tectum. Extensive projections were demonstrated by the more superficial injections, but few terminals were found when injections were confined to the deepest layers of the colliculus. There was no evidence of anisotropy in the distribution of terminals from injections made at different rostrocaudal or mediolateral locations; neurons located in any one region in the colliculus could potentially influence any other region. This network of intrinsic connections in the cat superior colliculus could provide a means for deeper-layer efferent neurons to associate, and to modulate or coordinate their output. Interneurons could also provide a substrate for mutual inhibition between neurons at the rostral pole of the colliculus that are active during fixation, and more caudally located neurons whose activity is associated with saccadic eye movements.
Effects of eliminating retinal Y cell input on center-surround interactions in the dorsal lateral geniculate nucleus of the cat
Authors: Wang Chun , Dreher B. , Burke W. 
Published: June 2009

AbstractThe aim of this project was to investigate the interaction between Y retinal ganglion cells and the cells of the dorsal lateral geniculate nucleus (LGNd) of the cat, with particular reference to center-surround antagonism and intrageniculate inhibition. Responses of cells in the LGNd were studied by stimulating the retina with spots of light of constant contrast but varying size. The peak discharges of nonlagged X (XN) cells were strongly suppressed with increase in spot size but the responses of lagged X (XL) cells and nonlagged Y (YN) cells were inhibited much less strongly. The effect of the Y system on these responses was examined by producing a selective block of conduction in Y fibers in one optic nerve by means of a pressure cuff (Y-blocking). These effects were assessed by measuring the peak discharge rates and by calculation of a “peak suppression index.” Y-blocking had no significant effect on the peak suppression index of XL, cells in either lamina or on YN cells in the normal (not Y-blocked) lamina but had significant effects on the responses of XN cells, causing a decrease in peak suppression index, both for cells in laminae receiving their principal excitatory input from the Y-blocked eye (both lamina A and lamina A1 ) as well as those in lamina A (but not lamina A1 ) receiving their excitatory input from the normal eye. These effects were obtained with relatively large spots of light. Thus Y optic fibers have both intralaminar (monocular) and interlaminar (binocular) inhibitory effects on XN cells. In addition to these suppressive effects, the experiments also show that ipsilaterally projecting Y fibers have facilitatory effects on XN cells in lamina A when small spots of light, about optimal size for the XN cell, are used. These results suggest that the Y system plays a powerful role in shaping the responses of XN cells, possibly enhancing visual acuity.
Tectal neurons that participate in centrifugal control of the quail retina: A morphological study by means of retrograde labeling with biocytin
Authors: Uchiyama Hiroyuki , Yamamoto Naoyuki , Ito Hironobu 
Published: June 2009

AbstractAn avian retinopetal nucleus, the isthmo-optic nucleus (ION), is known to receive predominant inputs from the ipsilateral optic tectum. We injected biocytin into the ION in the Japanese quail, and retrogradely labeled tectal neurons projecting to the isthmo-optic (IO) neurons, or the tecto-IO neurons, with an extraordinary Golgi-like quality. Somata of the tecto-IO neurons were located in layer 9 of the tectum. The tecto-IO neurons did not have apical dendrites extending into superficial retino-recipient layers (layers 2–7), but had descending dendrites ramified in layers 9–12. They also possessed short ascending dendrites ramifying in the upper half of layer 9. This dendritic morphology suggests that main input to the tecto-IO neurons may not be of retinal origin. The tecto-IO neurons were spatially arranged in a regular pattern. Distances between neighboring tecto-IO neurons were 50–100 μm. The dendrites of each tecto-IO neuron were not widely dispersed in the horizontal plane, and were confined in a vertically oriented column of 100–200 μm diameter. They possessed axon collaterals extending horizontally in layers 12 and 13. The estimated total number of the tecto-IO neurons was approximately 7000–10,000, which is almost identical to the total cell number of the IO neurons. To label a small number of the tecto-IO terminals, biocytin was injected into a confined area of the optic tectum. The tecto-IO fibers densely arborized in a restricted space of the ION, which is comparable to the dimension of dendritic arborization of individual IO neurons. It is suggested that single tecto-IO neurons may make contact with single IO neurons. IO neurons are known to make synaptic contact with single target cells (association cells of Cajal) in the retina (Uchiyama & Ito, 1993; Uchiyama et al., 1995). The arborization pattern of the tecto-IO neurons' dendrites indicates that the tecto-IO neurons receive very local information in sensory and sensorimotor coordinate space. The morphology of the tecto-IO terminals suggests that the spatially confined information that drives the tecto-IO neurons is sent in parallel to single IO neurons, and then further to single retinal association cells of Cajal. Cellular-level restricted projection patterns of the tecto-isthmo-retinal system may reflect its function for centrifugal control of retinal function.
Quantitative analyses of synaptic contacts of interneurons in the dorsal lateral geniculate nucleus of the squirrel monkey
Authors: Wilson James R. , Forestner Donna M. , Cramer Ryan P. 
Published: June 2009

AbstractThree interneurons were recorded from and then injected with horseradish peroxidase in the parvocellular laminae of the squirrel monkey's (Saimiri sciureus) dorsal lateral geniculate nucleus. They were then examined using the electron microscope for their synaptic contacts, both the afferent contacts onto their dendrites and their presynaptic dendritic contacts onto presumptive projection (relay) neuron dendrites. The somata of these interneurons were small (mean = 178 μm2), but the dendritic trees were large compared with those of projection neurons. All three interneurons had similar synaptic patterns onto their dendrites with about equal numbers of retinal, cortical, and GABAergic contacts. The distribution of these contacts was more uniform compared with the same types of contacts made onto projection neurons. The presynaptic dendrites were observed to contact only the dendrites of presumptive projection neurons, and these contacts were nearly all in the form of geniculate triads. None of the three interneurons displayed an axon. The receptive fields of these interneurons were similar to those of projection cells, but were larger and had center-response signs that were the opposite of the projection neurons around them (e.g. OFF center for the dorsal part of the parvocellular mass where ON-center projection neurons reside). The squirrel monkey data provides additional evidence that one aspect of the laminar pattern observed in the parvocellular pathway of the primate's dLGN might be related to a segregation of projection neurons of one center-response sign with interneurons of the opposite center-response sign.
Removal of two halves restores the whole: Reversal of visual hemineglect during bilateral cortical or collicular inactivation in the cat
Authors: Lomber Stephen G. , Payne Bertram R. 
Published: June 2009

AbstractThe purpose of the present study was to compare visual orienting behavior in the adult cat during (1) unilateral and bilateral cooling deactivation of posterior-middle suprasylvian (pMS) sulcai cortex, and (2) unilateral and bilateral deactivation of the superior colliculus. As expected, unilateral cooling deactivation of either pMS cortex or the superior colliculus resulted in a profound visual neglect of the contracooled hemifield. The addition of cooling the homotopic region in the opposite hemisphere largely reversed this deficit and restored visual orienting into the previously neglected hemifield. These results show that (1) pMS cortex and the superior colliculus are essential for normal detection and orienting to visual targets, and (2) unilateral visual neglect results from an imbalance of activities in the two hemispheres induced at either cortical or subcortical levels. These conclusions have implications for understanding neural bases of visual hemineglect following unilateral lesions in humans.
Ultrastructural study of the optic nerve in blind mole-rats (Spalacidae,Spalax)
Authors: Herbin M. , Rio J.-P. , RepéRant J. , Cooper H.M. , Nevo E. , Lemire M. 
Published: June 2009

AbstractThe optic nerve in two species of subterranean mole-rats (Spalacidae) has been examined at the ultrastructural level. The axial length of the eye and the diameter of the optic nerve are 1.9 mm and 52.5μm inSpalax leucodon, and 0.7 mm and 80.8μm inSpalax ehrenbergi, respectively. An anti-glial fibrillary acidic protein postembedding procedure was used to distinguish glial cell processes from axons. In both species, the optic nerve is composed exclusively of unmyelinated axons and a spatial distribution gradient according to the size or the density of fibers is lacking. The optic nerve ofS. leucodoncontains 1790 fibers ranging in diameter from 0.07–2.30μm (mean = 0.57μm), whereas inS. ehrenbergi, only 928 fibers, with diameters of 0.04–1.77μm (mean = 0.53μm) are observed. InS. ehrenbergi, a higher proportion of glial tissue is present and the fascicular organization of optic fibers is less obvious. Distribution gradients according to size frequency or density of fibers in the optic nerve are absent in both species. Comparison with other mammals suggests that although ocular regression in microphthalmic species is correlated with a significant decrease in the total number of optic fibers and the relative proportion of myelinated fibers, no difference in the absolute size range of unmyelinated axons is observed. The total absence of myelinated fibers inSpalaxmay be related to the subcutaneous location of the eyes. The unique presence of unmyelinated fibers in the optic nerve is discussed in relation to the possible conservation of a single class of W-like ganglion cells in the retina, in relation to photoperiodic perception.
Characterization and localization of an aldehyde dehydrogenase to amacrine cells of bovine retina
Authors: Saari John C. , Champer Robert J. , Asson-Batres Mary Ann , Garwin Gregory G. , Huang Jing , Crabb John W. , Milam Ann H. 
Published: June 2009

AbstractAn enzyme of bovine retina that catalyzes oxidation of retinaldehyde to retinoic acid was purified to homogeneity and a monoclonal antibody (mAb H-4) was generated. MAb H-4 recognized a single component (Mr= 55,000) in extracts of bovine retina and other bovine tissues. The antibody showed no cross-reactivity with extracts of rat, monkey, or human retinas. A 2067 bp cDNA was selected from a retina cDNA expression library using mAb H-4. The cDNA hybridized with a similarly sized, moderately abundant mRNA prepared from bovine retina. Nucleotide sequence analysis indicated that the cDNA contained a single open reading frame encoding 501 amino acids that have 88% sequence identity with the amino-acid sequence of human hepatic Class 1 aldehyde dehydrogenase. Amino-acid sequence analysis of purified enzyme demonstrated that the cDNA encodes the isolated enzyme. MAb H-4 specifically labeled the somata and processes of a subset of amacrine cells in bovine retinal sections. Labeled amacrine somata were located on both sides of the inner plexiform layer, and their processes ramified into two laminae within the inner plexiform layer. The inner radial processes of Müller (glial) cells were weakly reactive with mAb H-4. Weak immunostaining of amacrine cells was found in monkey retina with mAb H-4, but no signal was detected in rat or human retina. The results provide further evidence for metabolism and function of retinoids within cells of the inner retina and define a novel class of retinal amacrine cells.
The influence of input from the lower cortical layers on the orientation tuning of upper layer V1 cells in a primate
Authors: Allison John D. , Casagrande Vivien A. , Bonds A.B. 
Published: June 2009

AbstractThe receptive fields of cells in the primary visual cortex (area 17 or V1) show clear orientation selectivity, unlike those of the lateral geniculate nucleus (LGN) cells which provide their visual input. The intrinsic circuitry of V1 cells is believed to be partly responsible for this selectivity. We investigated the influence of ascending projections from neurons in the lower layers (5 and 6) of V1 on the orientation selectivity of single neurons in the upper layers (2, 3, and 4) by reversibly inactivating (“blocking”) lower layer neural activity with iontophoretic application of γ-aminobutyric acid (GABA) while recording from upper layer cells in the prosimian primate, Galago crassicaudatus. During lower layer blocking, the majority (20/28 = 71.4%) of upper layer neurons exhibited a change in the orientation of their preferred stimulus, a reduction in their orientation tuning, and/or an increase in their response amplitude. Twelve (42.9%) neurons exhibited shifts in their preferred orientation averaging 11 (±4) deg. These neurons were located, on average, 272 (±120) μm tangential from the vertical axis of the pipette center. Eleven neurons (39.2%) exhibited an average reduced orientation tuning of 52.5%. Their average location was 230 ± (115) ftm away from the vertical axis of the pipette. Five (17.9%) neurons with average location 145 (±75) firn from the vertical axis exhibited both effects. Two (7.1%) neurons that exhibited significant increases in response amplitude to stimulus angles within 10 deg of the peak excitatory stimulus without changes in orientation selectivity or tuning were located less than 100 μm from the vertical axis. The effects on the orientation tuning of cells were restricted in all cases to within ±30 deg of the preferred stimulus orientation. This suggests that layer blocking affects cells with preferred stimulus orientations similar to those of the recorded neurons. Only cells located within 500 μm tangential to the vertical axis of the injection site exhibited these effects. These results suggest that cells within layers 5 and 6 provide organized, orientation-tuned inhibition that sharpens the orientation tuning of cells in the upper cortical layers within the same, or closely neighboring, cell columns.
Seeing beyond the midline: The role of the contralateral isthmotectal projection in the leopard frog
Authors: Weber Brett C. , Waldeck Robert F. , Gruberg Edward R. 
Published: June 2009

AbstractThe ground level visual field of each eye of the leopard frog includes the entire ipsilateral 180-deg field and approximately 60 deg into the frontal contralateral field. When one eye is covered with an opaque patch, a frog responds to prey stimuli over the entire field of the other eye. Nevertheless, when one optic nerve is cut, the animal responds to prey in the ipsilateral hemifield of the connected eye, but only responds as far as about 30 deg past the frontal midline. If one optic tract is cut, the animal does not respond to prey past the frontal midline. We hypothesized that the responses past the frontal midline might be mediated by input from contralaterally projecting isthmotectal fibers. These fibers originate in the nucleus isthmi, a posterior midbrain structure. We found that when we placed an opaque patch over one eye and either ablated the ipsilateral nucleus isthmi, or cut crossing isthmotectal fibers in the optic chiasm, or blocked input to nucleus isthmi by ablating the ipsilateral tectal lobe, animals did not respond to prey stimuli past the frontal midline. We found that when we placed an opaque patch over one eye and cut crossing optic fibers in the anterior part of the optic chiasm (sparing crossing isthmotectal fibers), animals responded to prey stimuli in the nasal half of the seeing eye's contralateral frontal field. Our results suggest that contralaterally projecting isthmotectal fibers enable the frog to respond to stimuli past the frontal midline. We suggest a one-dimensional model of how nucleus isthmi influences tectal function.