bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accumulation of calcium in degenerating photoreceptors of severalDrosophilamutants
Authors: Sahly Iman , Schröder Walter H. , Zierold Karl , Minke Baruch 
Published: June 2009

AbstractThe hypothesis that a large, possibly toxic, increase in cellular calcium accompanies photoreceptor cell degeneration in several differentDrosophilamutants was tested. The calcium content of wild type and mutant photoreceptors ofDrosophilawas measured using rapid freezing of the eyes and energy-dispersive x-ray analysis (e.d.x.) of cryosections and semithin sections of cryosubstituted material. Light- and dark-raised mutants of the following strains were studied: retinal degeneration B (rdgB);retinal degeneration C (rdgC);neither inactivation nor afterpotential C (ninaC), and no receptor potential A (norpA).These are light-dependent retinal degeneration mutants in which the affected gene products had been previously shown as myosin-kinase (ninaC), calcium-dependent phosphoprotein phosphatase (rdgC), phosphoinositide transfer protein (rdgB), and phospholipase C (norpA).In light-raised mutants, ommatidia of variable degrees of degeneration were observed. Mass-dense globular bodies of 200–500 nm diameter in relatively large quantities were found in the degenerating photoreceptor of all the mutants tested. These subcellular globules were found to have a very high calcium content, which was not found in wild type or in nondegenerating photoreceptors of the mutants. Nondegenerating photoreceptors were found not only in dark-raised mutants, but in smaller quantities also in light-raised mutants. Usually these globular structures contained high levels of phosphorus, indicating that at least part of the calcium in the mutant photoreceptors is precipitated as calcium phosphate. The results indicate that a large increase in cellular calcium accompanies light-induced photoreceptor degeneration in degeneratingDrosophilamutants even when induced by very different mutations, suggesting that the calcium accumulation is a secondary rather than a primary effect in the degeneration process.
A sequence upstream of the mouse blue visual pigment gene directs blue cone-specific transgene expression in mouse retinas
Authors: Chiu M. Isabel , Nathans Jeremy 
Published: June 2009

AbstractA 6.4–kb sequence upstream of the mouse blue visual pigment gene has been assayed in transgenic mice for the ability to direct cell-type-specific expression of a linked β-galactosidase (lacZ) reporter. The construct is expressed specifically in cone photoreceptors in three independent lines. Transgene expression is found in the developing retina on the first postnatal day, increases rapidly in subsequent days, and persists through adulthood. A gradient of transgene expression is observed across the retina, with the transgene-expressing cones found almost exclusively in the lower retina and rarely in the upper retina, a pattern that parallels the distribution of blue cones in the mouse retina. Double-labeling with anti-cone pigment antibodies shows that transgene expression is confined to blue cones. These results imply that all of the sequence elements necessary for the control of blue cone-specific expression are encoded within the 6.4–kb DNA fragment tested.
Brain-stem modulation of the response properties of cells in the cat's perigeniculate nucleus
Authors: Murphy P. C. , Uhlrich D. J. , Tamamaki N. , Sherman S. Murray 
Published: June 2009

AbstractTransmission through the lateral geniculate nucleus is facilitated following activation of the cholinergic input from the brain stem, which is thought to reflect activity patterns seen during arousal. One of the underlying mechanisms is the suppression of inhibitory circuits local to the lateral geniculate nucleus. However, evidence exists that some visually driven inhibitory inputs to geniculate relay cells may be preserved or even enhanced under conditions of arousal, and during electrical activation of the parabrachial region of the brain stem. We have therefore reexamined the effect of brain-stem activation on the visual responses of one group of local inhibitory inputs to geniculate relay cells, those emanating from the adjacent perigeniculate nucleus. We recorded single perigeniculate cells in anesthetized, paralyzed cats. Axons innervating the lateral geniculate and perigeniculate nuclei from the parabrachial region of the brain stem were electrically activated, and the effect of this activation was assessed on both spontaneous and visually evoked responses. Visual stimulation consisted of sinusoidally modulated sine–wave gratings of varying spatial and temporal frequency. For the great majority of perigeniculate cells (32 of 40), brain-stem activation inhibited spontaneous activity, while one cell was excited, three showed a mixed effect and four were unaffected. Nevertheless, the responses of most cells (30 of 40) were facilitated when brain-stem activation was paired with certain spatio-temporal patterns of visual stimulation. Spatial tuning curves were constructed for 17 cells and temporal tuning curves for 14, before and during parabrachial activation. The responses of any one cell could be facilitated, unchanged, or suppressed, depending on the visual stimulus used. In some cases, this substantially modified the cell’s spatial and temporal tuning properties. We conclude that activation of the brain stem disinhibits geniculate relay cells in the absence of visual stimulation, but it has the potential to enhance either the magnitude or specificity of visually driven inhibition arising from the perigeniculate nucleus.
Neurochemical signatures revealed by glutamine labeling in the chicken retina
Authors: Kalloniatis Michael , Tomisich Guido , Marc Robert E. 
Published: June 2009

AbstractPostembedding immunocytochemistry was used to determine the retinal distribution of the amino acid glutamine, and characterize amino acid signatures in the avian retinal ganglion cell layer. Glutamine is a potential precursor of glutamate and some glutamatergic neurons may use this amino acid to sustain production of glutamate for neurotransmission. Ganglion cells, cells in the inner nuclear layer, and some photoreceptors exhibited glutamine immunoreactivity of varying intensity. Ganglion cells demonstrated the highest level of immunoreactivity which indicates either slow glutamine turnover or active maintenance of a large standing glutamine pool relative to other glutamatergic neurons. Müller's cells in the avian retina are involved in glutamate uptake and carbon recycling by the rapid conversion of glutamate to glutamine, thus explaining the low glutamate and high glutamine immunoreactivity found throughout Müller's cells. Most chicken retinal ganglion cells are glutamate (E) and glutamine (Q) immunoreactive but display diverse signatures with presumed functional subsets of cells displaying admixtures of E and Q with GABA (7) and/or glycine (G). The four major ganglion cell signatures are (1) EQ; (2) EQγ; (3) EQG; and (4) EQγG.
Recoverin immunoreactivity in mammalian cone bipolar cells
Authors: Milam Ann H. , Dacey Dennis M. , Dizhoor Alexander M. 
Published: June 2009

AbstractHuman, macaque monkey, and rat retinas were immunostained with a polyclonal antibody preparation against purified recoverin, a 23-kD calcium-binding protein isolated from bovine retina that localizes to rods and cones (Dizhoor et al., 1991). In addition to immunoreactive photoreceptors, we have identified subpopulations of recoverin-positive bipolar cells in all three species. Results from immunostaining with progressive dilutions of anti-recoverin and preadsorption of the antibody with a dilution series of purified recoverin showed that photoreceptors and bipolar cells had similar affinities for the antibody and suggested that the molecule recognized by the antibody in both cell types is recoverin. Immunoreactivity for recoverin and protein kinase C, a selective marker for all rod bipolar cells, was found in separate bipolar cell populations. Recoverin immunoreactivity is therefore a characteristic of certain cone bipolar cell types.In rat retina, anti-recoverin labeled two morphologically distinct subpopulations of cone bipolar cells whose axonal arbors stratified at different depths in the inner plexiform layer (IPL). The bipolar cells labeled with anti-recoverin did not correspond to those that were reactive for calbindin, another cone bipolar cell marker.Human and monkey retinas also had two populations of cone bipolar cells that were recoverin-positive. One population showed a distinct pattern of narrow bistratification at the outer border of the IPL and a regular mosaic arrangement of its axonal arbors, suggesting that the entire population of a single cone bipolar type was labeled. Cell density, dendritic morphology, and axonal-field size and stratification indicate that anti-recoverin selectively stains the flat midget (presumed OFF-center) cone bipolar cell type observed previously in Golgi preparations. By contrast the second bipolar cell population had axonal stratification in the inner half of the IPL and showed an unusual but consistent morphology and spatial distribution. Individual cells were intensely stained but were present at an extremely low density (~2−5 cells/mm2). These cells had multibranched dendritic trees characteristic of the diffuse bipolar cell class, but very small axonal fields in the size range of the midget bipolar class. Neither of the two recoverin-positive bipolar cell types in monkey was labeled with anti-calbindin or anti-cholecystokinin. An antibody preparation against bovine pineal hydroxyindole-O-methyltransferase (HIOMT) labeled photoreceptors and bipolar cells that closely resembled the recoverin-positive bipolar cells in human and rat retinas. Preadsorption of this antibody preparation with purified recoverin abolished immunostaining of the bipolar cells, suggesting that the anti-HIOMT preparation contains antibodies against recoverin, which is known to be present in the bovine pineal gland.
Temporal asynchrony interferes with vernier acuity
Authors: Wehrhahn Christian , Westheimer Gerald 
Published: June 2009

AbstractTwo dots may be aligned vertically with a precision much higher than that expected from two-point resolution provided they are separated by a visual angle of 3–5 min of arc. This precision suffers when the two dots are not exposed synchronously. Neither onset nor offset asynchronies can be tolerated; exposure differences of the two components of the vernier task as low as 30 ms can lead to a reduction in performance when the total exposure is below 90 ms. This effect cannot be compensated for by synchronizing the onset of one stimulus component with the offset of the other, even when the two are of opposite contrast. The data suggest that vernier acuity may be subserved by a dynamical linking of cortical excitation generated by the synchronous arrival of signals within a range of locations in the cortex whose spatial separation is critical for optimal hyperacuity performance. The evidence presented in this paper must be taken into account when a physiological substrate for hyperacuity is considered.
Visual processing in pigeon nucleus rotundus: Luminance, color, motion, and looming subdivisions
Authors: Wang Yong-Chang , Jiang Shiying , Frost Barrie J. 
Published: June 2009

AbstractThe responses of single cells to luminance, color and computer-generated spots, bars, kinematograms, and motion-in-depth stimuli were studied in the nucleus rotundus of pigeons. Systematic electrode penetrations revealed that there are several functionally distinct subdivisions within rotundus where six classes of visual-selective cells cluster. Cells in the dorsal-posterior zone of the nucleus respond selectively to motion in depth (i.e. an expanding or contracting figure in the visual field). Most cells recorded from the dorsal-anterior region responded selectively to the color of the stimulus. The firing rate of the cells in the anterior-central zone, however, is dramatically modulated by changing the level of illumination over the whole visual field. Cells in the ventral subdivision strongly respond to moving occlusion edges and very small moving objects, with either excitatory or inhibitory responses. These results indicate that visual information processing of color, ambient illumination, and motion in depth are segregated into different subdivisions at the level of nucleus rotundus in the avian brain.
Cytochrome oxidase in the human visual cortex: Distribution in the developing and the adult brain
Authors: Wong-Riley Margaret T. T. , Hevner Robert F. , Cutlan Robert , Earnest Melissa , Egan Robert , Frost Julie , Nguyen Thuytien 
Published: June 2009

AbstractCytochrome-oxidase (CO) histochemistry has revealed important functional subdivisions, modules, and processing streams in the macaque visual cortex. The present study is aimed at analyzing the development and characteristics of CO patterns in the human visual cortex by means of histochemistry and immunohistochemistry. At 26 weeks of gestation, both the ventricular and subventricular zones had low levels of CO, while the cortical plate had moderate levels of CO. At birth, supragranular CO-rich zones (puffs) were not clearly organized, indicating that the development of puffs in the neonatal striate cortex lags behind that of the macaque monkey, whose puffs appear weeks before birth. Puffs were more clearly discernible in human cortex at postnatal day 24, and became well organized by the fourth postnatal month. Layer IVcα in the neonate exhibited a higher level of activity and amount of CO than the central portion of IVcβ, which contained a dense aggregate of small neurons. The base of IVcβ, however, was often as CO reactive as IVcα. In contrast, the majority of specimens available to us from the fourth postnatal month and from adults with no known neurological diseases had significantly greater CO reactivity in layer IVcβ than in IVcaβ. Layer VI was moderately reactive for CO throughout development. In V2, stripes with globular zones of high CO activity were sporadically present at birth, suggesting that their development may parallel or precede that of puffs in VI. These stripes with CO-rich globular zones became more prominent in the adult and radiated orthogonally from the V1/V2 border. They were not, however, clearly organized into alternating thick and thin stripes as they are in the squirrel monkey. Visual cortical areas beyond V2 exhibited high CO activity mainly in layers III and IV and moderate levels in VI, suggesting that sites associated with cortico-cortical pathways may be metabolically most active.
Comparison of subcortical connections of inferior temporal and posterior parietal cortex in monkeys
Authors: Baizer Joan S. , Desimone Robert , Ungerleider Leslie G. 
Published: June 2009

AbstractTo investigate the subcortical connections of the object vision and spatial vision cortical processing pathways, we injected the inferior temporal and posterior parietal cortex of six Rhesus monkeys with retrograde or anterograde tracers. The temporal injections included area TE on the lateral surface of the hemisphere and adjacent portions of area TEO. The parietal injections covered the posterior bank of the intraparietal sulcus, including areas VIP and LIP. Our results indicate that several structures project to both the temporal and parietal cortex, including the medial and lateral pulvinar, claustrum, and nucleus basalis. However, the cells in both the pulvinar and claustrum that project to the two systems are mainly located in different parts of those structures, as are the terminals which arise from the temporal and parietal cortex. Likewise, the projections from the temporal and parietal cortex to the caudate nucleus and putamen are largely segregated. Finally, we found projections to the pons and superior colliculus from parietal but not temporal cortex, whereas we found the lateral basal and medial basal nuclei of the amygdala to be reciprocally connected with temporal but not parietal cortex. Thus, the results show that, like the cortical connections of the two visual processing systems, the subcortical connections are remarkably segregated.
The determination of total cGMP levels in rod outer segments from intact toad photoreceptors in response to light superimposed on background and to consecutive flashes: A second light flash accelerates the dark recovery rate of cGMP levels in control media, but not in Na+-free, low Ca2+medium
Authors: Cohen Adolph I. , Blazynski Christine 
Published: June 2009

AbstractIn previous experiments we established that a light flash reduced cGMP levels of toad rod outer segments within the transduction time interval, but that recovery of the dark level of cGMP occurred more slowly than reported electrophysiological recovery of membrane potential. We now report that a second light flash accelerates the recovery rate of total cGMP following an initial flash, but that this acceleration is blocked in a medium which is both sodium and calcium deficient. We also noted that calcium deficiency only elevated cGMP levels when sodium was present. For other experiments, we recorded ERG or aspartate isolated PIII responses from eyecups or retinas mounted on our quick-freeze apparatus, the light stimuli originating from the double light-bench of the latter. Whereas background illumination depressed cGMP, no detectable further cGMP loss accompanied the electrical response to a flash superimposed on the background.
Modulation of cone to horizontal cell transmission by Calcium and pH in the fish retina
Authors: Harsanyi Krisztina , Mangel Stuart c. 
Published: June 2009

AbstractThe effects of small changes in the calcium and sodium concentrations and in the pH of superfusion medium on the membrane potential and light-evoked responses of cone horizontal cells in the goldfish retina were examined. Conventional intracellular recording, a bicarbonate-based superfusion medium, and a specially designed superfusion apparatus that reduced pressure wave disturbances were used. An increase in the extracellular calcium concentration, [Ca2+]∘ from control levels (0.1 mM) to 1.0 mM hyperpolarized cone horizontal cells and reduced the magnitude of their light responses at all stimulus intensities. Addition of 20 mM NaCl to the 1.0 mM Ca2+Ringer’s solution reversed the hyperpolarizing effect of the 1.0 mM Ca2+but addition of 20 mM choline, a monovalent cation that does not pass through cyclic GMP-activated channels, did not. Reduction of the superfusate pH from 7.6 to 7.2 by switching from a Ringer’s solution gassed with 3% CO2to one gassed with 10% CO2hyperpolarized horizontal cells and reduced the magnitude of their light responses at all stimulus intensities for both 0.1 and 1.0 mM Ca,2+Ringer’s solutions. An increase in pH to 8.2 by gassing the superfusate with 1% CO2slightly depolarized the cells in 0.1 mM Ca2+Ringer’s solution but slightly hyperpolarized the cells in the 1.0 mM Ca2+Ringer’s solution. Following pharmacological isolation of the horizontal cells from synaptic input with high doses of glutamate (4–5 mM) and/or Co2+(4 mM) treatment, no effect on horizontal cell membrane potential due to changes in pH or [Ca2+]∘ was observed. These findings are discussed with respect to the cellular mechanisms and sites of action in the outer retina that are affected by changes in pH∘ and [Ca2+]∘.
Pontine projection from striate and prestriate visual cortex in the macaque monkey: An anterograde study
Authors: Fries W. 
Published: June 2009

AbstractThe projection from striate and prestriate visual cortex to the pontine nuclei has been studied in the macaque monkey by means of anterograde tracer techniques in order to assess the contribution of anatomically and functionally distinct visual cortical areas to the cortico-ponto-cerebellar loop. No projection to the pons was found from central or paracentral visual-field representations of V1 (striate cortex) or prestriate visual areas V2, and V4. Small patches of terminal labeling occurred after injections of tracer into more peripheral parts of V1, V2 and V3, and into V3A. The terminal fields were located most dorsolaterally in the anterior to middle third of the pons and were quite restricted in their rostro-caudal extent. Injections of V5, however, yielded substantial terminal labeling, stretching longitudinally throughout almost the entire pons. This projection could be demonstrated to arise from parts of V5 receiving input from central visual-field representations of striate cortex, whereas parts of V4 receiving similarly central visual-field input had no detectable projection to the pons. Its distribution may overlap to a large extent with the termination of tecto-pontine fibers and with the termination of fibers from visual areas in the medial bank (area V6 or P0) and lateral bank (area LIP) of the intraparietal sulcus, as well as from frontal eye fields (FEF). It appears that the main information relayed to the cerebellum by the visual corticopontine projection is related to movement in the field of view.
Dual controls for screening pigment movement in photoreceptors of theLimuluslateral eye: Circadian efferent input and light
Authors: Kier Christian K. , Chamberlain Steven C. 
Published: June 2009

AbstractThe radial and longitudinal distribution of retinular screening pigment in the lateral eye of the horseshoe crabLimulus polyphemuswas quantified under a variety of experimental conditions. Pigment position was characterized by the center and width of the radial distribution at four levels in the ommatidium.Under diurnal lighting, intact animals show movement of pigment granules from the periphery of the retinular cell at night towards the junction of the arhabdomeral and rhabdomeral segments of the retinular cell in the day. In constant darkness, intact animals exhibit the same circadian rhythm in pigment migration. Animals with bilaterally cut optic nerves do not receive circadian efferent input from the brain and show little pigment movement in diurnal lighting. In all of these cases, pigment was either aggregated in a band just peripheral to the rays of the rhabdom or dispersed to the periphery of the retinular cell.When dark-adapted animals are exposed to a sudden large light increment, pigment moves inward between the rays of the rhabdom. During the day, this inward response begins immediately and reverses as the ommatidial aperture begins to close. At night, the onset of the inward movement is delayed, but then occurs more rapidly than during the day. No significant longitudinal movement of photoreceptor screening pigment was detected under any of these experimental conditions.Two opposing mechanisms control the movement of screening pigment in these cells. Release of neurotransmitters from the circadian efferents causes outward movement; large increments of light cause inward movement. In the absence of sudden changes in light intensity, circadian efferent input, not cyclic lighting, appears to be the major determinant of screening pigment position. A sudden and large increment of light triggers the rapid inward movement which appears to be a protective mechanism optimized for daytime performance.