bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophysiological sensitivity of carotenoid deficient and replaced Drosophila
Authors: Chen De-Mao , Stark William S. 
Published: June 2009

AbstractR1–6 dominated electroretinographic (ERG) spectral sensitivities were determined as a function of days posteclosion from carotenoid deprived and replaced white-eyed Drosophila. The sensitivity of flies deprived from egg to adult waxed (about 1.5 log units by day 3), and then waned gradually from 3–11 days (over 2 log units by day 11). Carotenoid replacement (feeding nothing but carrot juice) effected recovery to near the replete control' level in about 1 day throughout (tested at 0, 4, and 11 days). The normal yellow cornmeal-agar-molasses-brewers yeast fly food (in our laboratory, supplemented with β-carotene) renders a slower recovery (requiring 7–9 days) since it is a medium designed largely for larval growth. Placing replete adults on deprivational medium did not create a deprivational syndrome in over 11 days. At 3–7 days, deprived flies reared and maintained in constant darkness had substantially enhanced sensitivity, beyond the 1.5 log unit increment already described for cyclic light rearing conditions. All spectral analyses are consistent with the ultraviolet (UV) sensitization of the blue (480 nm) rhodopsin by a replacement-dependent retinoid including two unexpected findings: (1) sensitivity recovery with carrot juice was so fast that the UV peak was already high at 6 h; and (2) the waxing of the deprived fly's sensitivity in dark rearing was so great that the UV peak was present at 4–7 days.
Ocular dominance columns and local projections of layer 6 pyramidal neurons in macaque primary visual cortex
Authors: Wiser Anne K. , Callaway Edward M. 
Published: June 2009

AbstractTo study the relationship between ocular dominance columns (ODCs) and axonal projections of individual layer 6 pyramidal neurons in the primary visual cortex, neurons were intracellularly labeled with biocytin in live slices prepared from macaque monkeys that had received an intravitreal injection of tetrodotoxin (TTX). The TTX injection indirectly causes a decrease in cytochrome oxidase (CO) expression in the cortical ODCs corresponding to the treated eye (Wong-Riley & Carroll, 1984). Sections from slices with labeled layer 6 neurons were double stained for biocytin and CO, to allow visualization of neuronal processes as well as ODCs. Twenty-seven layer 6 pyramidal neurons in ODC-labeled slices were analyzed. These neurons were classified according to the criteria of Wiser and Callaway (1996). Eight of these are class I neurons, which have dense axonal projections to the monocular layer 4C. The remaining 19 are class II neurons which project primarily to the binocular layers outside 4C. Among class I neurons, two have dense axonal arbors in layer 4Cα (type Iα), one in layer 4Cβ (type Iβ), and two throughout the depth of layer 4C (type IC). None of these neurons have ODC-specific axonal arbors. The remaining three class I neurons have focused axonal projections in layers 4Cβ and 4A (type IβA). All three appear to have axonal arbors predominantly within their home ODC in layer 4C. The axonal arbors of class II neurons do not appear to relate to ODCs in any specific fashion.
Large retinal ganglion cells in the pipid frog Xenopus laevis form independent, regular mosaics resembling those of teleost fishes
Authors: Shamim K. M. , Tóth P. , Cook J. E. 
Published: June 2009

AbstractPopulation-based studies of retinal neurons have helped to reveal their natural types in mammals and teleost fishes. In this, the first such study in a frog, labeled ganglion cells of the mesobatrachian Xenopus laevis were examined in flatmounts. Cells with large somata and thick dendrites could be divided into three mosaic-forming types, each with its own characteristic stratification pattern. These are named αa, αab, and αc, following a scheme recently used for teleosts. Cells of the αa mosaic (~0.4% of all ganglion cells) had very large somata and trees, arborizing diffusely within sublamina a (the most sclerad). Their distal dendrites were sparsely branched but achieved consistent coverage by intersecting those of their neighbors. Displaced and orthotopic cells belonged to the same mosaic, as did cells with symmetric and asymmetric trees. Cells of the αab mosaic (~1.2%) had large somata, somewhat smaller trees that appeared bistratified at low magnification, and dendrites that branched extensively. Their distal dendrites arborized throughout sublamina b and the vitread part of a, tessellating with their neighbors. All were orthotopic; most were symmetric. Cells of the αc mosaic (~0.5%) had large somata and very large, sparse, flat, overlapping trees, predominantly in sublamina c. All were orthotopic; some were asymmetric. Nearest-neighbor analyses and spatial correlograms confirmed that each mosaic was regular and independent, and that spacings were reduced in juvenile frogs. Densities, proportions, sizes, and mosaic statistics are tabulated for all three types, which are compared with types defined previously by size and symmetry in Xenopus and potentially homologous mosaic-forming types in teleosts. Our results reveal strong organizational similarities between the large ganglion cells of teleosts and frogs. They also demonstrate the value of introducing mosaic analysis at an early stage to help identify characters that are useful markers for natural types and that distinguish between within-type and between-type variation in neuronal populations.
The origin of slow PIII in frog retina: Current source density analysis in the eyecup and isolated retina
Authors: Xu Xijing , Karwoski Chester J. 
Published: June 2009

AbstractThe objective of this research was to determine the sources and sinks of current underlying the slow PIII component of the electroretinogram. Current source density analysis of the ERG evoked by diffuse light flashes was performed in eyecup and isolated retinas of frog. Blockade of synaptic transmission with aminophosphonobutyric + kynurenic acids simplified the CSD profiles through the retina. In addition to the photoreceptor source/sink pair, there was evidence for a major slow PIII source near the outer limiting membrane, a major sink near the inner limiting membrane, and a small source near the inner plexiform layer. Addition of Ba2+ abolished the slow PIII source/sinks, and it left only the photoreceptor source and sink. The results support the idea that slow PIII originates through K+ spatial buffering by Müller cells. Specifically, the light-evoked decrease in [K+]0 in the subretinal space causes a primary K+ efflux from Müller cells (current source) and a primary K+ influx at the Müller cell endfeet (current sink). A decrease in [K+]0 in the proximal retina, caused by diffusion of K+ to the subretinal space, results in K+ efflux (the current source) at the inner plexiform layer.
GABACreceptors on ferret retinal bipolar cells: A diversity of subtypes in mammals?
Authors: Lukasiewicz Peter D. , Wong Rachel O.L. 
Published: June 2009

AbstractThe GABACreceptor subtypes on bipolar cells of rats and cold-blooded vertebrates differ in their pharmacological properties and probably have different molecular compositions. With the exception of the rat, native GABACreceptors in mammals had not been studied. In ferret, whole-cell, voltage-clamp recordings were made from bipolar cells in the retinal slice preparation to determine which subtype of GABACreceptor predominated. Puff-evoked GABA currents in bipolar cells were partially reduced by the GABAAreceptor antagonist bicuculline, indicating that both GABAAand GABACreceptors mediated the responses. By contrast, GABA currents of ganglion cells were always completely blocked by bicuculline, indicating that GABAAreceptors predominated on these cells. Small-amplitude GABA currents of bipolar cells evoked by short-duration puffs were less sensitive to bicuculline than large-amplitude currents evoked by long-duration puffs. This indicates that GABAc receptors mediated proportionately more of the small-amplitude, puff-evoked responses and GABAAreceptors mediated more of the large-amplitude, puff-evoked responses. In bipolar cells, the bicuculline-resistant component of the GABA current was entirely blocked by 3-APMPA (3-aminopropyl-(methyl)phosphonic acid), a GABACreceptor antagonist. Picrotoxin, which is relatively ineffective at rat GABACreceptors, completely blocked GABA currents in ferret bipolar cells, indicating that GABACreceptors on ferret bipolar cells resemble those in lower vertebrates rather than those in the rat retina. These results suggest that there may be a diversity of GABAc receptor subtypes on mammalian bipolar cells.
Inhibition of phospholipase C by U-73122 blocks one component of the receptor current inLimulusphotoreceptor
Authors: Nagy Károly , Contzen Klaus 
Published: June 2009

AbstractIn the ventral nerve photoreceptor ofLimulusa short, intense flash evokes a receptor current consisting of three components. In contrast to other hypotheses, we suggested previously that only the second component of the current is activated by the phospholipase C pathway, which releases calcium from intracellular stores by inositol trisphosphate. The present paper gives further evidence to our suggestion. It is demonstrated that U-73122, a specific inhibitor for the phospholipase C, selectively blocks the second component. The first and third components are moderately affected and could still be activated after the complete block of the second one. Results support the idea that the first and third components areactivated by pathways operating independently of phospholipase C.
Chromatic properties of neurons in macaque area V2
Authors: Kiper Daniel C. , Fenstemaker Suzanne B. , Gegenfurtner Karl R. 
Published: June 2009

AbstractWe recorded from single cells in area V2 of cynomolgus monkeys using standard acute recording techniques. After measuring each cell's spatial and temporal properties, we performed several tests of its chromatic properties using sine-wave gratings modulated around a mean gray background. Most cells behaved like neurons in area V1 and their responses were adequately described by a model that assumes a linear combination of cone signals. Unlike in V1, we found a subpopulation of cells whose activity was increased or inhibited by stimuli within a narrow range of color combinations. No particular color directions were preferentially represented. V2 cells showing color specificity, including cells showing narrow chromatic tuning, were present in any of the stripe compartments, as defined by cytochrome-oxidase (CO) staining. An addition of chromatic contrast facilitated the responses of most neurons to gratings with various luminance contrasts. Neurons in all three CO compartments gave significant responses to isoluminant gratings. Receptive-field properties of cells were generally similar for luminance and chromatically defined stimuli. We found only a small number of cells with a clearly identifiable double-opponent receptive-field organization.
Developmental changes in the pattern of NADPH-diaphorase staining in the cat's lateral geniculate nucleus
Authors: Guido William , Scheiner Christopher A. , Mize R. Ranney , Kratz Kenneth E. 
Published: June 2009

AbstractWe examined the pattern of NADPH-diaphorase (NADPH-d) staining in the lateral geniculate nucleus (LGN) of dorsal thalamus in fetal and newborn kittens, and adult cats. This staining visualizes the synthesizing enzyme of nitric oxide (NO), a neuromodulator associated with central nervous system (CNS) development and synaptic plasticity. In the adult, very few LGN cells stained for NADPH-d, and these were restricted to interlaminar zones and ventral C layers. NADPH-d labeled a dense network of fibers and axon terminals throughout the LGN and adjacent thalamic nuclei. The source of such labelling has been reported to be cholinergic neurons from the parabrachial region of the brain stem (Bickford et al., 1993). A very different pattern of staining was observed in prenatal and early postnatal kittens. Between embryonic (E) day 46–57, lightly stained cells appeared throughout the LGN. From this age, through about the first month of life, the number of stained cells in the LGN rose rapidly. The density (cells/ mm2) of labeled cells peaked at postnatal day (P) 28 (P28), and was about 150 times greater than the level measured in the adult LGN. After P28, cell staining declined rapidly, and fell to adult levels at P41. The reduction in cell staining that occurred between P35–41 was accompanied by the appearance of fine-caliber fiber staining, similar to that observed in the adult LGN. NADPH-d staining, which reveals the presence of nitric oxide synthase (NOS), and thus NO activity, may reflect two processes. In the adult LGN, the labeling of cholinergic axons arising from the brain-stem parabrachial region coupled with a paucity of the LGN cellular staining suggests that NO operates in an orthograde manner, being co-released with ACh to influence the gain and efficacy of retinogeniculate transmission. By contrast, in developing kitten, NADPH-d staining of LGN cells suggests that NO acts in a retrograde fashion, perhaps playing a role in maintaining associative processes underlying activity-dependent refinement of retinogeniculate connections.
Accessibility of colloidal gold and horseradish peroxidase to cytosolic spaces in Limulus ventral photoreceptors
Authors: Rubin L. J. , Womble M. , Brown J. E. , Finger T. E. 
Published: June 2009

AbstractPhysiological studies of intracellular messengers frequently employ intracellular injections of large molecules that either monitor or modulate the metabolism of the messenger cascade. Injected molecules have unknown mobility in the cytosol and unknown accessibility to various cytosolic compartments, including those postulated to be traversed by intracellular messenger molecules. In order to determine whether injected molecules have access to the confined spaces through which messenger molecules must diffuse, we injected 5-nm colloidal gold or horseradish peroxidase, or both, into Limulus ventral photoreceptors. Injections were made by applying pressure pulses to the back of an intracellular micropipette that also monitored membrane voltage. The tissue was fixed at varying times after injection and processed for electron microscopy by conventional techniques. Cells fixed 1–3 min after injection contained HRP reaction product only in the cell body. HRP reaction product was found at varying distances down axons in direct relation to the interval between injection and fixation. Colloidal gold particles were found throughout the cell body but not in axons of tissue fixed 1–3 min after injection. Both HRP reaction product and 5-nm colloidal gold particles were observed within the microvillar projections of internal and external rhabdomere, as well as within the extracisternal spaces of endoplasmic reticulum. We conclude that large molecules injected from an intracellular micropipette into an arbitrary locus of ventral photoreceptor cells have access to all of the presumed sites of the phototransduction cascade.
Vernier acuities of neurons in area 17 of cat visual cortex: Their relation to stimulus length and velocity, orientation selectivity, and receptive-field structure
Authors: Swindale N. V. , Cynader M. S. 
Published: June 2009

AbstractThe sensitivity of neurons in area 17 of the cat's visual cortex to vernier offset was expressed as the percentage reduction in response caused by the introduction of a given offset into a bar stimulus moving across the receptive field. There was a wide variation in sensitivity: in some cells response could be halved by an offset equal to a fifth of receptive-field width (defined as twice the standard deviation of a Gaussian curve fitted to the response profile), while other cells showed no sensitivity. The highest absolute sensitivities of complex and simple cells were similar, although most cells with poor sensitivity were complex.Sensitivity was largely unaffected by changes in stimulus velocity and stimulus length, although there was a tendency for sensitivity to increase with decreasing bar length.Comparisons of orientation tuning curves with vernier tuning curves showed that the response to a vernier stimulus approximated the response to a single bar of the same overall length and an orientation equal to that of a line joining the midpoints of each bar. This was true for a wide range of sensitivity values.Vernier sensitivity was correlated with a measure of length summation H, which is positive when there is net facilitation between the bars, and negative when there is net inhibition. Vernier sensitivity was highest in cells with large values of H, and least in cells where H was negative.We examined a linear model of the simple cell receptive field which, together with a variable response threshold, was able to explain the correlation between vernier acuity and length summation. Although this model accounted qualitatively for many of our findings, the majority of simple cells had tuning curves that were sharper than the predicted ones. This suggests that there are nonlinearities in the behavior of many simple cells whose effect is to increase the sharpness of orientation tuning and consequently vernier sensitivity.
Changing topography of the RPE resulting from experimentally induced rapid eye growth
Authors: Fleming Patricia A. , Harman Alison M. , Beazley Lyn D. 
Published: June 2009

AbstractThe retinal pigment epithelium (RPE) of the quokka wallaby, Setonix brachyurus, grows and changes throughout life. To investigate factors that determine changes in the quokka RPE, we have examined topography of this tissue in experimentally enlarged eyes. Unilateral eyelid suture was conducted at the time of normal eye opening, postnatal day (P) 110, and animals were examined at 1 or 1½ years of age. The numbers and densities of RPE cells and the extent of multinucleation were compared with those in normal animals. Eyelid suture resulted in a 9.8% and 17.4% increase in retinal area at 1 and 1½ years, respectively; a significant degree of myopia was associated with this enlargement. Cell density topography in experimental eyes was not the same as in controls. Cells from central retina were disproportionately larger in the experimental than control eyes. However, the RPE cell topography in sutured eyes was not the same as that of aged retinae of a similar size. Notably, in sutured eyes there was no development of the high or highest cell densities seen in equatorial and temporal central RPE in aged retinae, respectively. Furthermore, the degree of cell enlargement in peripheral regions was slight compared with that observed in similar-sized, aged retinae. There was no increase in RPE cell number; rather, average cell area increased accompanied by no change or a slight decrease in RPE thickness. Consequently, overall volume of cells did not change significantly. The large number of multinucleate cells normally seen in aged animals was not observed in experimentally enlarged eyes, implying that an increase in cell volume may be the trigger for multinucleation.
Tracer coupling among regenerated amacrine cells in the retina of the goldfish
Authors: Hitchcock Peter F. 
Published: June 2009

AbstractThis study sought to characterize the tracer coupling of regenerated amacrine cells in the retina of the goldfish and assess the integration of regenerated neurons into existing retinal circuits. Regeneration of new neurons from injury-induced progenitors was stimulated by surgically excising a small rectangular piece of retina. Several months after regeneration was complete, intracellular injections of Neurobiotin, a gap junction-permeant tracer, were made into single regenerated amacrine cells or nonregenerated (extant) amacrine cells lying outside the regenerated patch. Two groups of amacrine cells were injected: those that in normal retina are tracer coupled and a single type (the radiate amacrine cell) that is not. The data show that regenerated amacrine cells are tracer coupled to each other and to their homologous counterparts outside the patch of regenerated retina. Regenerated radiate cells possess morphologically abnormal dendrites, but these processes can extend out of regenerated retina into surrounding normal retina. Similarly, the dendrites of extant radiate cells, severed by the original lesion, can regenerate into the patch of regenerated retina. These results indicate that in the goldfish retina the cell-specific junctional circuitry present in normal retina is re-created in the regenerated retina, and suggest that regenerated neurons are functionally integrated into the existing retina.
Effect of retinal impulse blockage on cytochrome oxidase-rich zones in the macaque striate cortex: II. Quantitative electron-microscopic (EM) analysis of neuropil
Authors: Wong-Riley Margaret T. T. , Trusk Thomas C. , Tripathi Satish C. , Hoppe Daniel A. 
Published: June 2009

AbstractUnilateral retinal impulse blockage with tetrodotoxin (TTX) induces reversible shrinkage and decreased cytochrome oxidase (CO) activity in alternate rows of supragranular, CO-rich puffs in the adult macaque striate cortex (Wong-Riley & Carroll, 1984b: Carroll & Wong-Riley, 1987). The present study extended the findings to the electron-microscopic (EM) level to determine if various neuropil profiles in control puffs exhibit heterogeneous levels of CO activity, and whether specific processes were more susceptible to intravitreal TTX than others.Within the neuropil of control puffs, 60% of the total mitochondrial population resided in dendrites, and the majority of dendritic mitochondria were highly reactive for CO. Axon terminals forming symmetrical synapses also contained darkly reactive mitochondria, whereas those forming asymmetrical synapses possessed very few and mainly lightly reactive mitochondria. Unmyelinated axon trunks, myelinated axons, and glia all exhibited low levels of CO activity. Synaptic count revealed a 3:1 ratio of asymmetrical to symmetrical synapses.Intravitreal TTX for 2–4 weeks adversely affects dendrites and symmetrical terminals much more so than other neuropil processes. There was a general decrease in darkly and moderately reactive mitochondria and an increase in lightly reactive mitochondria throughout the puffs, especially in dendrites. This indicates that afferent blockade is more detrimental to processes of higher metabolic activity. Changes also differed between central and peripheral regions of puffs, and indications of axonal and synaptic reorganization were more evident in the latter. Thus, stabilization of neuronal structure and synapses appears to be activity-dependent even in the adult. A working model of these metabolic and morphological responses to chronic TTX is proposed.
Characterization of guanylate cyclase in squid photoreceptors
Authors: Robinson Phyllis R. , Cote Richard H. 
Published: June 2009

AbstractLight causes a rapid, 1.7-fold increase in cyclic GMP concentration in intact squid retinas (Johnson et al. (1986)). To determine whether light-induced changes in cyclic GMP concentration result from activation of guanylate cyclase, we have studied the regulation of guanylate cyclase activity in squid (Loligo pealei) photoreceptors. The enzyme is membrane-associated and activity is enhanced by the detergents Triton X-100 or digitonin. The enzyme requires divalent cations, Mn2+being preferred over Mg2+. The dependence of enzyme activity on the MnGTP concentration deviates from simple Michaelis-Menten kinetics. Under conditions where a light-induced binding of GTP to the guanine nucleotide regulatory protein can be observed, no light-induced change in guanylate cyclase could be detected.