bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonuniform retinal expansion during the formation of the rabbit's visual streak: Implications for the ontogeny of mammalian retinal topography
Authors: Robinson Stephen R. , Dreher Bogdan , McCall Murray J. 
Published: June 2009

AbstractWe have studied the distribution of retinal ganglion cells (RGCs) which have been retrogradely labeled from massive bilateral injections of the enzyme horseradish peroxidase into the retino-recipient nuclei of foetal and postnatal albino rabbits aged from the 24th postconceptional day (24PCD) to adulthood. The number of labeled RGCs increases from about 447,000 on the 24PCD to a peak of about 525,000 on the 27PCD. From the 29PCD to birth (31/32PCD), the number of RGCs rapidly declines to about 375,000. During the next 20 d, the number of RGCs stabilizes at about 335,000. After the 51PCD, the number of RGCs gradually declines to the adult value of about 280,000. Retinal area steadily increases from about 40 mm2 on the 24PCD to about 500 mm2 in the adult, while RGC density decreases. However, the reduction in RGC density is nonuniform: RGC density in the visual streak drops from 18,600 RGCs mm2 on the 24PCD to 4700 RGCs/mm2 in the adult, whereas RGC densities at the superior and inferior edges of the retina decrease proportionally much more (from 9300 to 105 RGCs/mm2 and from 12,000 to 170 RGCs/mm2, respectively). As a result of this differential reduction in RGC density, the streak:superior edge RGC density ratio changes from 2.0:1 on the 24PCD to about 45:1 in the adult, while the streak/inferior edge ratio changes from 1.6:1 to about 28:1. In the periods from the 24PCD to the 29PCD and from the 32PCD to adulthood, the proportional increases in the streak/superior edge and streak/inferior edge RGC density ratios are linearly related to the proportional increases in retinal area. However, between the 29PCD and 32PCD, the RGC density ratios increase at a greater rate than retinal area. We conclude that (1) the centro-peripheral difference in RGC density that is already present on the 24PCD might be attributable to differential RGC generation; (2) the redistribution of RGCs between the 24PCD and adulthood is mainly due to nonuniform expansion of the retina, with minimal expansion of the visual streak and maximal expansion at the superior and inferior retinal edges; and (3) a small component of the increase in the centro-peripheral RGC density ratio, which becomes apparent between the 29PCD and 32PCD, is probably due to differential RGC loss. We discuss the pattern of retinal expansion in the rabbit and the factors which might contribute to it.
The ontogeny of ultraviolet photosensitivity in rainbow trout (Salmo gairdneri)
Authors: Hawryshyn Craig W. , Arnold Margaret G. , Chaisson Duane J. , Martin Patricia C. 
Published: June 2009

AbstractThe present study examines the changes in ultraviolet (UV) photosensitivity that occur during the growth of rainbow trout (Salmo gairdneri). A comparison of the ocular media transmission of small (n = 3) and large (n = 3) trout eyes did not reveal large changes in the transmission of UV radiation through the eye. We used the heart-rate conditioning technique to measure spectral sensitivity in immobilized trout. Four trout, each weighing less than 30 g, exhibited a UV-sensitivity peak at 360 nm while four additional trout weighing more than 60 g each exhibited no evidence of UV sensitivity. Spectral-sensitivity measurements of two trout weighing 44 g and 60 g revealed UV sensitivity, but when measured one month later (after a 25% increase in body weight) both fish exhibited no UV-sensitivity peak. At this time their sensitivity appeared to conform to the known blue-sensitive cone mechanism.
Neurons of the medial terminal accessory optic nucleus of the rat are poorly collateralized
Authors: Clarke R. J. , Giolli R. A. , Blanks R. H. , Torigoe Y. , Fallon J. H. 
Published: June 2009

AbstractThe vast majority of neurons of the rat medial terminal nucleus (MTN) project to the nucleus of the optic tract (NOT), but the MTN also projects to a lesser degree upon a number of other brainstem nuclei controlling optokinetic nystagmus. Because of the diversity of targets of the MTN, it is possible that individual neurons have branched axons that project to two or more brainstem nuclei. The possibility that axons of MTN-NOT neurons collateralize to innervate other MTN targets is examined in the rat with the fluorescent, double-labeling, retrograde tracer technique. Fluoro-Gold was injected into the NOT while Fast Blue was simultaneously injected into each of five other known targets of the MTN: the supraoculomotor-periaqueductal gray; the dorsal cap of the inferior olive; the visual tegmental relay zone; the dorsolateral nucleus of the basal pons; and the superior/lateral vestibular nuclei. Brainstem sections were processed for fluorescence microscopy and the MTN was examined for single- and double-labeled neurons. Results show that virtually all neurons of the MTN (>97.5%), together with neurons in the visual tegmental relay zone immediately surrounding the MTNd, are single-labeled in all paired injections involving the NOT and the other target nuclei. It was found that about 69% of MTN neurons project exclusively to the NOT, 5–10% project to each one of the other nuclei, and 3% of MTN neurons project to more than one target. Based upon cell counts from the fluorescent material, and previous analysis of Nissl-stained serial sections, the findings show that virtually all MTN neurons are projection neurons. It was concluded that the MTN is comprised of independent projection systems, possibly involved in different aspects of generating optokinetic nystagmus.
Cortical interactions in texture processing: Scale and dynamics
Authors: Victor Jonathan D. , Conte Mary M. 
Published: June 2009

AbstractWe investigate the neural computations underlying pattern processing with stimuli based on textures balanced for spatial frequency content (and second-order correlations) but not for higher-order correlations (Julesz et al. 1978). Interchange between two such isodipole textures produces a robust human visual evoked potential (VEP). The difference in population activity driven by two isodipole textures is quantified by the antisymmetric component of the VEP. Statistical properties of the textures eliminate contributions from linear mechanisms to the antisymmetric VEP.The dependence of the antisymmetric VEP on check size and fourth-order correlation statistics is used to test nonlinear models for the underlying neural computations. Linear summation, followed by a simple nonlinearity (such as rectification, saturation, or threshold), is inconsistent with the data. More elaborate models, in which a second nonlinear stage combines the output of local nonlinear mechanisms, are consistent with the data, provided that an appropriate spatial scale is chosen for the second stage of processing. For checks 4 min or smaller, the deduced interaction length is 10–15 min. For checks larger than 4 min, the interaction length is proportional to check size.
Protein Kinase C-like immunoreactivity in rod bipolar cells of the rat retina: A developmental study
Authors: Zhang Danru , Yeh Hermes H. 
Published: June 2009

AbstractIn the retina of a variety of vertebrate species, a monoclonal antibody against protein kinase C (PKC) has been shown to label preferentially bipolar cells. Although the functional consequences of PKC activation in these cells is yet to be revealed, the present study was motivated in part by the possibility that the antibody might be used as a selective marker for examining the development of bipolar cells in the rat retina. Here, the developmental pattern and the dynamic changes of retinal cells expressing PKC-like immunoreactivity (PKC-LI) were studied and analyzed throughout postnatal life until adulthood. Upon its initial detection by immunohistochemistry on postnatal day (PD)-10, faint PKC-LI was limited to the central region of the retina, labeling cell bodies located at the scleral margin of the inner nuclear layer (INL) adjacent to the outer plexiform layer (OPL). On subsequent days, PKC-LI spread progressively to the peripheral retina and axon terminal bulbs at the vitreal margin of theinner plexiform layer (IPL) began showing the first signs of immunoreactive labeling. Not until PD-15, the time of eye opening, did PKC-LI in these cells increase to the extent such that their thin axons were immunoreactive. Each of these axons traversed the entire thickness of the IPL and divided into two or three short branches before ending as enlarged terminal bulbs. The morphology and the location of PKC-LI cells in both the developing and adult retina observed in our study are consistent with them being rod bipolar cells. By the end of the fourth postnatal week, the rod bipolar cells appeared mature, resembling those found in the adult. Overall, more dynamic changes occurred at the axon terminal bulbs than at the cell bodies during the maturational process of rod bipolar cells. Interestingly, PKIC-LI was expressed precociusly in these cells when rat pups were reared in complete darkness starting from the day of birth.
Synchronous neurite branchings in single goldfish retinal ganglion cells
Authors: Ishida A. T. , Cheng M.- H. 
Published: June 2009

AbstractWe have examined the time course of branch formation in neurites of retinal ganglion cells isolated from adult goldfish (Carassius auratus). These neurites elongate at approximately 13 μm/h, and usually branch by bifurcation of growth cones at their tips. The times elapsed between branchings in different neurites of single cells can be described by a Poisson distribution with a mean interval of approximately 2 h. As predicted by this distribution, a relatively large number of branchings occur simultaneously in different neurites of individual cells. Simultaneous branchings of neurites elongating at a common rate generate branch points that lay equidistant from their soma. Since similar branching patterns can be seen in dendrites of retinal ganglion and amacrine cellsin situ, these results are consistent with the possibility that dendrites of individual neurons branch synchronously and grow at common rates during development.
Spectral sensitivity of the electroretinogram b-wave in dark-adapted goldfish
Authors: Nussdorf Jonathan D. , Powers Maureen K. 
Published: June 2009

AbstractThe action spectrum of the ERG b-wave was measured under dark-adapted conditions in intact goldfish (Carassius auratus). It is substantially broader than the absorption spectrum of goldfish rod porphyropsin. Neither prolonged dark adaptation nor removal of possible efferent neural activity affected its shape. Moreover, a 682-nm background did not produce a selective loss of sensitivity to long wavelengths. The results imply that the spectral sensitivity of the b-wave in dark-adapted goldfish reflects the influence of at least two photoreceptor types which act as a single univariant mechanism near absolute threshold.
Laminar organization and ultrastructure of GABA-immunoreactive neurons and processes in the dorsal lateral geniculate nucleus of the tree shrew (Tupaia belangeri)
Authors: Holdefer Robert N. , Norton Thomas T. , R. Ranney Mize 
Published: June 2009

AbstractThe distribution and ultrastructure of neurons and neuropil labeled by an antiserum to gamma-aminobutyric acid (GABA) were examined in the lateral geniculate nucleus (LGN) of the tree shrew (Tupaia belangeri). The LGN of this species segregates center type and cell class into three distinct pairs of laminae: a medial pair (laminae 1 and 2) containing ON-center cells, a more lateral pair (4, 5) containing OFF-center cells, and 2 laminae (3, 6) containing W-like cells. The relationship between this laminar segregation and the distribution of GABA immunoreactivity was investigated in the present study. GABA-immunoreactive neurons and neuropil were present in all six of the laminae. However, both the density of labeled cells (adjusted for neuronal density across laminae) and the density of labeled neuropil showed a medial-to-lateral gradient. The adjusted density of labeled cells was higher laterally than medially, and the density of labeled neuropil was significantly greater in the more lateral OFF-center laminae and W-like laminae than in the medial two ON-center laminae. Thus, inhibitory, GABAergic influences may modulate to different degrees the visual signals in the ON, OFF, and W pathways. Labeled cells had a mean cross-sectional area (107 μm2) approximately one-half that of unlabeled cells (216 μm2). They constitute 16–34% of the neurons in the LGN. At the electron microscope level, three different kinds of labeled profile were observed. Vesicle containing profiles like the F2 profiles of cat were postsynaptic to retinal terminals and presynaptic to conventional dendrites. Fl axon terminals with dense clusters of vesicles were also labeled as were some myelinated axons. Another labeled profile, which we suggest should be called an F3 process, was a large dendrite of irregular caliber with punctate groups of vesicles near the synapse. Our results suggest that GABAergic circuitry is an important part of the functional organization in the LGN of the tree shrew.
Regeneration of the dopamine-cell mosaic in the retina of the goldfish
Authors: Hitchcock Peter F. , Vanderyt Jeff T. 
Published: June 2009

AbstractA fundamental anatomical feature of retinal neurons is that they form planar mosaics. Each mosaic can be described by its density, pattern, and regularity (non-randomness). As part of ongoing studies to quantitatively describe the anatomy of regenerated retina in the goldfish, we determined the planimetric density and regularity of the mosaic of dopaminergic interplexiform cells in patches of regenerated retina and compared this to the mosaic generatedde novo.In addition, we selectively ablated dopaminergic neurons with the neurotoxin 6–hydroxydopamine (6–OHDA) before inducing local regeneration and determined whether or not the absence of the extant dopaminergic neurons modulated the planimetric density or number of regenerated ones. The results showed that dopaminergic neurons are regenerated at higher planimetric densities and in less orderly arrays than normal. Furthermore, there was no statistical difference in the density or number of regenerated cells in normal retinas and retinas treated with 6–OHDA.
Steady discharges of X and Y retinal ganglion cells of cat under photopic illuminance
Authors: Troy J.B. , Robson J.G. 
Published: June 2009

AbstractThe discharges of ON- and OFF-center X and Y retinal ganglion cells in the presence of stationary patterns or of a uniform field of photopic luminance were recorded from urethane-anesthetized adult cats. The interval statistics and power spectra of these discharges were determined from these discharge records. The patterned stimuli were selected and positioned with respect to a cell's receptive field so as to generate steady discharges that were different in mean discharge rate from that cell's discharge for the diffuse field. The interval statistics of discharges recorded for diffuse or patterned illumination for all cell types can be modeled, approximately, as coming from renewal processes with gamma-distributed intervals. The gamma order of the interval distributions was found to be nearly proportional to the mean discharge rate for X cells, but not for Y cells. Typical values for the gamma orders and their dependence on mean rate for different cell types are given. The same model of a renewal process with gamma-distributed intervals is used to model the measured power spectra and performs well. When the gamma order is proportional to mean rate, the power spectral density at low temporal frequencies is independent of discharge rate. Gamma order was proportional to mean rate for X cells but not for Y cells. Nonetheless, the power spectral densities of both cell types at low frequencies were approximately independent of discharge rate. Hence, noise in this band of frequencies can be considered additive. The consequences of departures from the renewal process and of the gamma order not being proportional to mean rate are considered. The significance of different rates of discharge for signaling is discussed.
ATP-independent deactivation of squid rhodopsin
Authors: Kahana Alon , Robinson Phyllis R. , Lewis Laura J. , Szuts Ete Z. , Lisman John E. 
Published: June 2009

AbstractDeactivation of light-activated squid rhodopsin was studiedin vitrousing GTPγS binding by G-protein as a direct measure of rhodopsin activity. Deactivation was inhibited by dilution of the retinal suspension or by removal of soluble components. Deactivation could be restored by addition of soluble material to washed membranes. These results indicate that the deactivation is not due entirely to a conformational transition within rhodopsin itself, but depends on the interaction with other molecules. The possibility that phosphorylation is involved in the deactivation was studied. Deactivation occurred in the presence and absence of added ATP. Deactivation also occurred in the presence of kinase inhibitors and after addition of apyrase, which reduced residual ATP levels to below 1μM. These results indicate that light-induced phosphorylation is not required for deactivation of squid rhodopsin. In this regard deactivation of squid rhodopsin is different from that of vertebrate rhodopsin, which requires phosphorylation.
White-noise analysis in visual neuroscience
Authors: Sakai Hiroko M. , Ken-Ichi Naka , Korenberg Michael J. 
Published: June 2009

AbstractIn 1827, plant biologist Robert Brown discovered what is known as Brownian motion, a class of chaos. Formal derivative of Brownian motion is Gaussian white-noise. In 1938, Norbert Wiener proposed to use the Gaussian white-noise as an input probe to identify a system by a series of orthogonal functionals known as the Wiener G-functionals.White-noise analysis is uniquely suited for studying the response dynamics of retinal neurons because (1) white-noise light stimulus is a modulation around a mean luminance, as are the natural photic inputs, and it is a highly efficient input; and (2) the analysis defines the response dynamics and can be extended to spike trains, the final output of the retina. Demonstrated here are typical examples and results from applications of white-noise analysis to a visual system.
Contributions to the electroretinogram of currents originating in proximal retina
Authors: Frishman Laura J. , Sieving Paul A. , Steinberg Roy H. 
Published: June 2009

AbstractWe have investigated responses in proximal retina of the cat that contribute to two kinds of electroretinogram (ERG) recordings: (1) the pattern ERG, a light-adapted response and (2) the threshold and near threshold ERG, a dark-adapted response (Sieving et al., 1986a, 1986b; Sieving & Steinberg, 1985). In intraretinal, extracellular recordings, two negative-going responses were identified that are maximal around the inner plexiform layer, and distinct from PII, which is maximal in distal retina: under light-adapted conditions, a spatially tuned response at light onset and light offset, the “M-wave” (previously described in cold-blooded animals by Karwoski & Proenza (1977, 1980)), and under dark-adapted conditions, the scotopic threshold response, or “STR,” a response at light onset. The results under dark-adapted conditions are examined in more detail here.The STR is a very sensitive response whose threshold is 1.5–2.0 log units below that of the dc-component of PII and therefore well below the threshold of the a-, b-, and c-waves. It saturates about 2.4 log units below rod saturation. The STR contributes a negative-going potential to the dark-adapted ERG that is dominant near threshold; while PII (dc-component and b-wave) contributes a positive-going potential that is dominant at higher intensities (Sieving et al., 1986b). Investigation of the mechanism of the proximal retinal responses that contribute to the ERG supports a K+-Müller cell hypothesis of their origin.
Immunocytochemical localization of glycine in the retina of the turtle (Pseudemys scripta)
Authors: Eldred William D. , Cheung Kristin 
Published: June 2009

AbstractWe have localized glycine-like immunoreactivity to provide new anatomical detail about glycinergic neurons in the turtle retina. A rabbit antiserum directed against a glycine/albumin conjugate was used with standard fluorescent and avidin-biotin labeling techniques. Some processes in the outer plexiform layer and many processes in the inner plexiform layer, numerous somata in the inner nuclear layer, and isolated somata in the ganglion cell layer were immunoreactive.The vast majority of labeled neurons were amacrine cells. One class of amacrine cells had well-labeled somata near the inner nuclear/inner plexiform layer border, which gave rise to thick primary processes that entered the inner plexiform layer and arborized near the border of strata 1 and 2 and in stratum 3. A second class of glycinergic neurons, consisting of putative interplexiform cells, was unique in that it gave rise to dendritic arborizations in both the outer plexiform layer and the inner plexiform layer. Some of the immunoreactive neurons in the ganglion cell layer were apparently displaced amacrine cells, while others were probably true ganglion cells because they gave rise to labeled axons, and many labeled axons were visible in the ganglion cell axon layer. These results suggested that glycine played an extensive role in the turtle retina, and that it was involved in many diverse synaptic interactions in both the outer plexiform layer and the inner plexiform layer.
Involvement of ON and OFF retinal channels in the eye and head horizontal optokinetic nystagmus of the frog
Authors: Yücel Y. H. , Jardon B. , Bonaventure N. 
Published: June 2009

AbstractThe specific role of ON and OFF retinal information channels in the generation of the horizontal optokinetic nystagmus (OKN) of the frog was studied. Coil recordings of monocular eye and head OKN were obtained before and after intravitreal injection of two drugs that block either ON or OFF channels. The intravitreal injection of 2-amino-4-phosphonobutyrate (APB), a glutamate analog that selectively blocks the ON retinal channel, strongly reduced or even cancelled the monocular OKN of the head and of the eye. The intravitreal injection of another glutamate analog, the cis-2, 3-piperidine dicarboxylic acid (PDA) that especially blocks the OFF retinal channel, did not affect the gain velocity of the slow phase of both the horizontal monocular head and eye OKN, for low stimulus velocities. Our results suggest that the retinal ON information channel, but not the OFF channel, is involved in the generation of the slow phase of the OKN of the frog, at least at low drum velocities.
Spatial- and temporal-frequency selectivity as a basis for velocity preference in cat striate cortex neurons
Authors: Baker Curtis L. 
Published: June 2009

AbstractMeasurements were made of the optimal velocity for drifting bar-shaped stimuli to excite striate cortex neurons of the cat. These data were compared to the optimal spatial and temporal frequencies of the same neurons, as determined with drifting sine-wave grating stimuli. A systematic relationship was revealed, whereby those neurons preferring higher velocities of bar motion also preferred lower spatial and higher temporal frequencies of gratings. The optimal bar velocity for a given neuron could be quantitatively predicted from the ratio of that neuron's optimal temporal frequency to its optimal spatial frequency.