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PubMed1982

Visual orienting deficits in frogs with various unilateral lesions.

We have studied the visual prey acquisition behavior of frogs with unilateral optic nerve section, unilateral tectal lobe ablation, and unilateral transverse hemisection at a level between the tectum and the cerebellum. The first two groups of animals oriented normally to stimuli throughout the region of visual field overlap and failed to respond to more peripheral stimuli on one side. Hemisected animals responded to stimuli at all positions in the visual field. For stimuli located contralateral to the lesion, the frogs oriented normally. For ipsilateral stimuli, the frogs oriented forward.

Animals↗
PubMedDate not supplied

One axon-multiple functions: specificity of lateral inhibitory connections by large basket cells.

The functional specificity of the projections of single large basket cells of the cat primary visual cortex was studied using novel analytical approaches. The distribution of the labelled axons and that of the target cells were three-dimensionally reconstructed and compared quantitatively to orientation, direction and ocular dominance maps obtained with the intrinsic signal optical imaging technique. Quantitative analysis was carried out (i) for the entire basket cell, (ii) separately, for local and distal projections of the axon and (iii) by dissecting the same axon into two projection fields at the first bifurcation. It was found that although the functional distributions (orientation, direction and ocular dominance) for the entire cell were multi-modal and broadly tuned, individual main branches of the same cell displayed highly specific topography. In the further analysis, 2-dimensional probability density estimates of the target cell distributions revealed clear clustering which may be important for local subfield antagonism. These findings provide support to the idea that the same basket cell mediates several specific receptive field operations depending on the location of the target somata in the functional maps.

Animals↗
PubMed2006

The layout of functional maps in area 18 of strabismic cats.

Strabismus (or squint) is both a well-established model for developmental plasticity and a frequent clinical symptom. To analyze experience-dependent plasticity of functional maps in the brain we used optical imaging of intrinsic signals to visualize both orientation and ocular dominance domains in cat area 18. In strabismic animals, iso-orientation domains exhibited a pinwheel-like organization, as previously described for area 18 of normally raised animals and for area 17 of both normally raised and strabismic cats. In area 18, mean pinwheel density was similar in the experimental (2.2 pinwheel centers per mm2 cortical surface) and control animals (2.3/mm2 in normally raised animals), but significantly lower than in area 17 of both normally raised and strabismic cats (2.7-3.4/mm2). A comparison of orientation and ocular dominance domains revealed that iso-orientation domains were continuous across the borders of ocular dominance domains and tended to cross these borders at steep angles. Thus, the orientation map does not seem to be modified by experience-dependent changes in afferent activity. Together with our recent observation that strabismus does not enhance the segregation of ocular dominance domains in cat area 18, the present data indicate that the layout of functional maps in area 18 is less susceptible to experience-dependent manipulations than in area 17.

Animals↗
PubMed1990

Activity-dependent tuning and the NMDA receptor.

The refinement of the topographic map of visual space within the optic tectum of the frog is activity-dependent. The use of the three-eyed frog preparation to assay the operation of this fine-tuning mechanism indicates that this process is mediated by the NMDA receptor: Chronic in vivo treatment with APV, an NMDA antagonist, disrupts the segregation of retinal afferents into eye-specific zones while NMDA treatment sharpens this pattern. This latter effect is accompanied by a decreased sensitivity of the system to applied NMDA. Activation of the NMDA receptor may mediate the fine-tuning mechanism by initiating the stabilization of appropriate synapses. The requirements for NMDA receptor activation necessitate the convergence of terminals carrying correlated activity patterns. Such patterns of activity are provided by ganglion cells whose cell bodies lie near one another in the retina, and who should therefore, in an accurate visual map, terminate near one another in the tectum. Synapses from ganglion cells who do not neighbor one another in the retina have uncorrelated firing patterns and therefore do not activate the NMDA receptor. These synapses then would not be stabilized relative to one another. In addition to organizing the retinal projection, NMDA receptor activation may also modulate retinal ganglion cell arbor morphology, since chronic in vivo APV or NMDA treatments decrease arbor density. These results are discussed in terms of the effect of NMDA receptor activation on branch initiation and the rate of branch retraction.

Animals↗
PubMed1991

Correlation between amount of retinal afferents to the pretectal nucleus of the optic tract and dorsal terminal accessory optic nucleus and performance of horizontal optokinetic reflex in rat.

Intraocular kainic acid injection in Long-Evans rats induces loss of retinal afferents to subcortical visual centers as assessed by the axoplasmic transport of [14C]valine. The optical terminal fields of the pretectal nucleus of the optic tract (NOT), superior colliculus and accessory optic system (AOS) nuclei appear particularly affected. Since NOT and the AOS dorsal terminal nucleus (DTN) represent the first relay station of the visuomotor pathway mediating horizontal optokinetic nystagmus (HOKR), we have studied the characteristics of HOKR after various degrees of retinal deafferentation of these nuclei induced by intraocular KA injection. Taking advantage of the arrangement of the primary optic projections to NOT-DTN, that in rats are almost entirely crossed, in each animal, monocular HOKR induced by stimulation of the injected eye was compared to monocular HOKR elicited by stimulation of the intact, ipsilateral eye. Following NOT-DTN optic denervation, HOKR gain always worsened, and in a way, that the greater the deficits of retinal afferents, the greater the HOKR inability to compensate for visual motion. Furthermore, for any given retinal denervation the higher the stimulus velocity, the greater the HOKR deficit. While the correlation between HOKR gain and the amount of retinal afferents to NOT-DTN would seem to indicate a functional homogeneity of the retinal ganglion cells sending axons to these nuclei, the finding that the extent of HOKR impairment also varied with velocity might not support the above view.

Animals↗
PubMed2004

Gene expression profiling of purified rat retinal ganglion cells.

PURPOSE: The phenotype of specialized cells arises, in part, from their characteristic gene expression patterns. Retinal ganglion cells (RGCs) are of wide interest in neuroscience and die in glaucoma and other optic neuropathies. In this study the genes expressed by RGCs were profiled by expressed sequence tag (EST) analysis. METHODS: ESTs were generated from a cDNA library constructed from RGCs isolated by immunopanning. The RGC genes were compared with published microarray expression profiles from 13 different neural regions. Immunohistochemistry was performed by standard methods. RESULTS: Clustering of 4791 RGC ESTs identified 2360 unique gene clusters. Of these, 60% represented known genes, 27% uncharacterized genes/ESTs, and 13% novel sequence. Unexpectedly, one of the largest RGC clusters, RESP18, corresponded to a neuroendocrine-specific gene preferentially expressed in the hypothalamus. RESP18 immunoreactivity within the retina was found mainly in the RGC layer. DDAH1, a gene involved in nitric oxide metabolism, was localized to RGC and amacrine layers. Comparison of gene expression patterns across neuronal regions revealed a prominent subset of RGC genes that were overexpressed in dorsal root and trigeminal ganglia. To narrow the search for candidate disease-related genes, RGC genes were mapped to known disease loci for optic neuropathies. CONCLUSIONS: This work is one of the first efforts to profile gene expression in a purified population of retinal neurons, the RGCs. The profiling, in addition to revealing both known and novel genes underlying the RGC phenotype, also uncovered common patterns of gene expression between RGCs and other sensory ganglia.

Animals↗
PubMed2000

Coexistence of linear zones and pinwheels within orientation maps in cat visual cortex.

Revealing the layout of cortical maps is important both for understanding the processes involved in their development and for uncovering the mechanisms underlying neural computation. The typical organization of orientation maps in the cat visual cortex is radial; complete orientation cycles are mapped around orientation singularities. In contrast, long linear zones of orientation representation have been detected in the primary visual cortex of the tree shrew. In this study, we searched for the existence of long linear sequences and wide linear zones within orientation preference maps of the cat visual cortex. Optical imaging based on intrinsic signals was used. Long linear sequences and wide linear zones of preferred orientation were occasionally detected along the border between areas 17 and 18, as well as within area 18. Adjacent zones of distinct radial and linear organizations were observed across area 18 of a single hemisphere. However, radial and linear organizations were not necessarily segregated; long (7.5 mm) linear sequences of preferred orientation were found embedded within a typical pinwheel-like organization of orientation. We conclude that, although the radial organization is dominant, perfectly linear organization may develop and perform the processing related to orientation in the cat visual cortex.

Animals↗
PubMed2006

Macular pigment shows ringlike structures.

PURPOSE: The spatial distribution of macular pigment is generally assumed to monotonously decrease to very low values in the periphery. However, there are indications that this picture may be too simple. The purpose of this study was to examine the spatial distribution of the macular pigment optical density. METHODS: Fundus reflectance and autofluorescence maps at 488 and 514 nm Argon laser wavelengths were acquired in 53 healthy subjects with a custom-built scanning laser ophthalmoscope. Because the lens and the macular pigment are the only absorbers in this wavelength region, digital subtraction of log reflectance and log autofluorescence at the two wavelengths provides density maps of the sum of both absorbers. RESULTS: In approximately half of the subjects, we observed a distinct ring pattern at a mean distance of 0.7 degrees of the fovea. In a few subjects, the ring had an even larger optical density than did the central peak. A simple model with an exponentially decaying density as a function of eccentricity, in combination with a Gaussian-distributed ring pattern, yielded a good description of the data for both methods. The widths of the central peak and the Gaussian ring, and also the eccentricity at which the ring peaks, were similar for both methods. The prominence of the ring did not depend on age and gender. CONCLUSIONS: Both reflectance and autofluorescence maps showed ring patterns in the distribution of the macular pigment, which probably follow the inner plexiform layer.

Adult↗
PubMed1997

Gliogenesis in postnatal rat optic nerve: LC1 + microglia and S100-beta + astrocytes.

Lipocortin 1 (LC1) and S100-beta, two Ca(2+)-binding proteins that serve as specific markers for microglia and astrocytes, respectively, have been used to study postnatal gliogenesis in the rat optic nerve. Computerized image analysis was used to quantify and map the stained and unstained glia in transverse sections (10 microns thick) taken 1-2 mm from the chiasm in optic nerves from rat pups at postnatal day 0 (P0), P7, P14, P21, P28, P38 and adults. The number of astrocytes was remarkably constant (100 per section) at all ages. Because the area of the nerve increases 10-fold from P0 to adult, the population density of astrocytes begins al > 5000 mm-2 and drops to 400 mm-2 in the mature nerve; however, because the nerve length increases two-fold, the number of astrocytes doubles over the same period. In contrast, the number of LC1 + cells per section initially is sparse (4 at P0), increases rapidly up to 36 at P21 and levels off at 49 in adults. The microglia population density is relatively stable throughout development (200-300 mm-2) except during the peak of oligodendroblast apoptosis (P21) when it rises to 450 mm-2. Neonatally, LC1 immunoreactivity predominantly labels spherical-ameboid cells; but by P28 they are replaced by mature ramified microglia. The number of unstained cells (putative oligodendrocytes) per section increases from 11 at P0 to a peak of 308 at P21, and declines slightly to 269 in adults. While generally confirming concepts of astrocyte and oligodendrocyte ontogeny from the literature, the present report adds considerable detail regarding microglia, which often have been ignored. Microglia identified by LC1 immunoreactivity comprise 12% of the glia in adult optic nerve near the chiasm.

Animals↗
PubMed2000

[Diagnosis of swollen optic disks using color Doppler ultrasonography] .

The Goal of this study was prospective evaluation of the blood flow parameters-maximal systolic velocity (MSV), minimal diastolic velocity (MDV) and Pourcelot's resistivity index (RI) in patients with swollen optic dis. 63 patients (79 eyes) were examined with swollen optic disc-10 patients (17 eyes) with intracranial hypertension, 12 patients (14 eyes) with pseudoedema of disk of the optic nerve, 7 patients (7 eyes) with inflammation swollen optic disc, 3 patients (6 eyes) with pseudotumor cerebri, 8 patients (12 eyes) with arteritic anterior ischemic optic neuropathy (A-AION) and 23 patients (23 eyes) with nonarteritic anterior ischemic optic neuropathy (N-AION) and 23 patients (23 eyes) with nonarteritic anterior ischemic optic neuropathy (N-AION). All patients had ophthalmological examinations and Color Doppler ultrasonography in central retinal artery (CRA), posterior ciliary artery (PCA), ophthalmic artery (OA) and in central retinal vein (CRV). The blood flow parameters of the swollen optic disc and normal optic disc were not significant changed at intracranial hypertension, pseudooedema cerebri, inflammation swelling, and at pseudotumour od the optic disc. A-AION and N-AION acallocated significant changes of the blood velocities and resistivity index. A-AION: significant increasing resistivity index at CRA, CPA, significant decrease of MSV and MDV and difficult mapping of the CPA in Color doppler mapping. At the fellow eye (without swollen optic disc) was significant decreasing of the blood velocities of the CRA, CPA, but not so much as at the defective eye with swollen optic nerve disk. N-AION: defective eye with swollen optic disc--there were: nonsignificant decreasing of MSV, MDV, significant decreasing of MSV, MDV and increasing of resistivity index of the CRA, CPA at the fellow eye. AO was without significant changes. Color Doppler information allowed to specify diagnosis of A-AION and N-AION.

Blood Flow Velocity↗
PubMed1979

Anomalous ipsilateral optic fibre projection in Xenopus induced by larval tectal ablation.

Unilateral left tectal ablation was carried out in Xenopus between stage 48 and 1 month after metamorphosis. Six to 12 weeks after metamorphosis the retinal projection from the right eye was examined with the use of [3H]proline autoradiography. The autoradiographs indicated that optic fibres whose tectal target was destroyed recrossed to the ipsilateral tectum and basal optic nucleus via the posterior and pretectal commissures. No anomalous recrossing occurred if the tectal ablation was carried out at stage 58 or later. The aberrant optic fibres were restricted to the rostrolateral and central parts of the ipsilateral tectum and they terminated in a discontinuous manner. It is concluded that available surfaces serving as contact guidance cues are needed to direct aberrant optic fibres to the ipsilateral tectum.

Action Potentials↗
PubMed1992

Dynamic surrounds of receptive fields in primate striate cortex: a physiological basis for perceptual completion?

Visual receptive fields (RFs) were mapped inside and outside the cortical representation of the optic disk in the striate cortex (area V1) of anesthetized and paralyzed Cebus monkeys. Unexpectedly, most cells were found to be binocularly driven, and the RFs mapped with contralateral-eye stimulation progressed in a topographically appropriate fashion as the optic disk sector was crossed. Activation of these neurons by the contralateral eye was shown to depend on stimulation of the parts of the retina around the optic disk. Outside the optic disk representation, a similar effect was demonstrated by obstructing the "classical" RF with masks 5-10 times larger in size. In all cases, visual stimuli presented around the mask could be used to accurately interpolate the position of the hidden RF. These properties reflect, at a cellular level, the process of "filling in" that allows for completion of the visual image across natural and artificially induced scotomas.

Animals↗
PubMed2026

A STORM-based protocol for nanoscale imaging and quantitative analysis of protein-associated and phospholipid-associated structures in natural rubber.

Stochastic Optical Reconstruction Microscopy (STORM) enables nanoscale mapping of molecular components beyond the diffraction limit; however, its reproducible implementation in hydrophobic polymer matrices remains challenging because fluorescence-labeling specificity, fluorophore photoswitching, three-dimensional localization, chromatic registration, and quantitative image analysis must be carefully controlled. This protocol presents a standardized experimental workflow for dual-color labeling, astigmatism-based three-dimensional STORM acquisition, and quantitative analysis of protein-associated and phospholipid-associated structures in natural rubber (NR). The workflow covers sample pretreatment, Cy5 NHS ester labeling of protein-associated primary amines, DiI labeling of phospholipid-rich domains, STORM imaging-buffer preparation, three-dimensional single-molecule localization, dual-channel registration, generation of standardized xy projections, aggregate-size analysis, and projected lateral spatial correlation assessment. Reproducibility is supported by defined acquisition and localization criteria, three independent sample preparations with at least five fields of view analyzed per condition, and unlabeled, single-color, dye-only matrix, and processing-associated Cy5 controls. Mean lateral localization precisions of 11.8 ± 2.3 nm for Cy5 and 13.5 ± 2.9 nm for DiI were obtained, while two-dimensional Fourier ring correlation analysis of the xy projections yielded effective lateral image resolutions of approximately 25 and 28 nm, respectively. Image-based particle segmentation and localization-coordinate-based density-based spatial clustering of applications with noise (DBSCAN) were applied to standardized xy projections as complementary quantitative approaches. Application of the protocol to untreated, centrifuged, and protease-treated NR samples demonstrated treatment-associated changes in the detected abundance and projected size distributions of protein- and phospholipid-associated aggregates, together with a non-monotonic change in their projected lateral spatial correlation. These observations describe alterations in nanoscale organization but do not, by themselves, establish stable protein-phospholipid complex formation. Unlike previous studies that primarily demonstrated the feasibility of STORM imaging in rubber materials, the principal contribution of this work is an end-to-end, step-by-step protocol incorporating defined controls, three-dimensional localization, image-quality metrics, chromatic-registration procedures, and complementary quantitative-analysis pipelines for non-expert users. The workflow may be adaptable to other hydrophobic polymers and soft-material systems after appropriate optimization and validation.

Rubber↗
PubMed2001

Near-field optics on silicon-electrolyte junctions.

A technique allowing near-field photocurrent (PC) mapping of silicon surfaces in contact with an electrolyte is presented. The illumination source is an optical fibre tip with a 100-nm aperture. A shear force detection system controls the tip-sample distance while scanning the tip across the silicon-electrolyte interface. Topographic and PC images on SiO2/Si mesas both show 300 nm resolution. It is shown that this PC contrast is induced by the tip-topography interaction and hence the PC resolution is limited by the resolution of the topography. Indeed, PC mapping on topography-less patterned porous-silicon/silicon samples shows that the lateral resolution is only limited by the aperture size which is of the order of 100 nm.

Journal Article↗
PubMed1999

Mapping and genomic characterization of the gene encoding diacylglycerol kinase gamma (DAGK3): assessment of its role in dominant optic atrophy (OPA1).

The family of diacylglycerol kinases (DAGKs) is known to play an important role in signal transduction linked to phospholipid turnover. In the fruitfly Drosophila melanogaster, a human DAGK ortholog, DGK2, was shown to underlie the phenotype of the visual mutant retinal degeneration A (rdgA). Previously, the gene encoding a novel member of the human DAGK family, termed DAGK3, was cloned and demonstrated to be abundantly expressed in the human retina. Based on these findings we reasoned that DAGK3 might be an excellent candidate gene for a human eye disease. In the present study, we report the genomic organization of the human DAGK3 gene, which spans over 30 kb of genomic DNA interrupted by 23 introns. In addition, we have mapped the gene locus by fluorescence in situ hybridization to 3q27-28, overlapping the chromosomal region known to contain the gene underlying dominant optic atrophy (OPA1), the most common form of hereditary atrophy of the optic nerve. Mutational analysis of the entire coding region of DAGK3 in 19 unrelated German OPA1 patients has not revealed any disease-causing mutations, therefore excluding DAGK3 as a major cause underlying OPA1.

Adolescent↗
PubMed1978

Development of the compound eyes of dragonflies (Odonata). III. Adult compound eyes.

The distribution of ommatidial diameters and interommatidial angles, as determined by measuring the angles between the optic axes of adjacent ommatidia, are mapped across the surface of the compound eyes of a variety of species selected for different adult behaviors, developmental histories, and taxonomic positions. The size of the visual fields, prey capture foveas, foveas composed of large dorsal ommatidia, and other specializations in the numbers of ommatidia that view various directions in the visual field are discussed in relation to adult behavior. Advanced species have less resemblance between their larval and adult eyes than primitive species. In contrast to their larvae, adults increase the monocular resolution of each eye at the expense of binocular vision. Most species have foveas which view in approximately the anterior direction, instead of in a region of binocular overlap, and many species have foveal bands which view along the horizon. Some advanced perching species, which approach their prey and other odonates from below, have an additional vertical foveal band that views along a vertical plane from the anterior direction to a more dorsal direction. The most unusual foveal band is seen in active flying species. The large dorsal ommatidia of the migratory Anax junius, which cover approximately one third of the eye surface, view a narrow region of the visual field that extends along a plane from the most lateral direction of one eye to a dorsal direction, and continues without interruption to the most lateral direction of the other eye.

Animals↗