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PubMed1994

Mapping and chromosome analysis: the potential of fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) is a method widely used for the delineation of chromosomal DNA. FISH is applied in many areas of basic research as well as in clinical cytogenetics. In this review important technical improvements as well as the various applications of this method are summarized. In the first part different labeling and detection procedures are described and the potential of various kinds of probes are discussed. Recent developments in optical instrumentation and digital imaging procedures are outlined in the second part. The following important applications of FISH are discussed: (a) new strategies for high resolution mapping of DNA sequences; (b) detection of chromosomal aberrations in clinical material; (c) techniques allowing the simultaneous detection of numerous probes by multiple color FISH; and (d) the new approach of comparative genomic hybridization, allowing a rapid and comprehensive analysis of chromosomal imbalances in cell populations, which is particularly useful for the cytogenetic analysis of tumor samples.

Animals↗
PubMed1989

Two distinct visual pathways through the superficial pretectum in a percomorph teleost.

The connections of the superficial pretectum and of nucleus isthmi were examined in a percomorph teleost, Lepomis cyanellus. Horseradish peroxidase was injected either with a pin into the parvicellular nucleus of the superficial pretectum or pressure injected into nucleus isthmi; the isthmal injections retrogradely labelled the neurons of the magnocellular nucleus of the superficial pretectum. Two main visual pathways can be recognized: The first projects from the retina to the parvicellular nucleus, and then to the intermediate nucleus of the superficial pretectum, the inferior raphe nucleus, and the trochlear nucleus. The second projects from the retina via the optic tectum to the magnocellular nucleus of the superficial pretectum, and from there to nucleus isthmi and the lateral thalamic nucleus; nucleus isthmi and the lateral thalamic nucleus project back to the optic tectum, and nucleus isthmi also projects back to the magnocellular nucleus. The two pathways are interconnected to some extent because both nucleus isthmi and the optic tectum project to the parvicellular nucleus; nevertheless, we suggest that they may be functionally and evolutionarily distinct. Compared to percomorphs, the first pathway appears reduced in cyprinid teleosts such as goldfish. Furthermore, the magnocellular nucleus of the second pathway is completely different in cyprinids, both in cellular architecture and in efferent connections. A phylogenetic analysis suggests that cyprinid ancestors went through a period of reduced vision and that the magnocellular nucleus of the superficial pretectum in modern cyprinids has been either extensively modified from the primitive condition or lost entirely and replaced by a superficially similar structure.

Animals↗
PubMed2005

Two-dimensional thickness measurements based on internal reflection ellipsometry.

An imaging ellipsometer technique on internal reflection geometry that can measure the thickness distribution of a thin film possessing an assumed refractive index is described. Because a prism is used for the internal reflection geometry, it was theoretically predicted that angular derivation from the normal incidence on the prism surface affects only the psi value by a factor of 0.97 at maximum. Measurements were carried out for an optical system of silica substrate-TiO2 layer-silica layer-protein film-air, with a thin-film array of dried protein as the sample film. Thickness of the protein films was two-dimensionally estimated only from the measured map of the delta value by use of the simulated relationship between the thickness and the delta value. The thickness map obtained was coincident on the whole with the results according to a mechanical scanning. The detection limit was approximately +/- 0.2 nm. These findings validate the optical effect of a high-index additional layer to improve the sensitivity and precision of thickness measurements of the sample film on transparent substrates.

Coated Materials, Biocompatible↗
PubMed2026

Multi-Ancestry Genome-Wide Association with Fine-Mapping Identifies Novel Loci for Pigment Dispersion Syndrome and Pigmentary Glaucoma.

PURPOSE: Pigment dispersion syndrome and pigmentary glaucoma are important causes of ocular hypertension and glaucomatous optic neuropathy, yet their genetic determinants remain incompletely defined, particularly across diverse ancestries. This study aimed to use a large multi-ancestry cohort from the All of Us Research Program to investigate the genetic basis of pigment dispersion syndrome and pigmentary glaucoma. DESIGN: Case-control study. PARTICIPANTS: In total, 572 cases and 37 808 controls with array genotyping and 537 cases and 35 493 controls with whole-genome sequencing. METHODS: Using electronic health record phenotyping in the All of Us Research Program, we performed multi-ancestry genome-wide association analyses using both array-based data and whole-genome sequencing-based data, comparing patients with pigment dispersion syndrome or pigmentary glaucoma to those without either condition. We also performed Firth penalized regression and Fisher analyses, and we performed principal component analyses to assess effect sizes across genetic ancestries. We applied statistical fine-mapping, examined for cross-trait overlap, and assessed expression quantitative trait locus associations for lead variants. MAIN OUTCOME MEASURES: P values and odds ratios of lead loci from genome-wide association analyses; size of credible sets determined from fine-mapping; allele frequency of lead variants in cases, controls, and the general population; expression quantitative trait loci effect size and P values linking lead variants to gene expression. RESULTS: We identified 4 loci reaching genome-wide significance across analyses, including signals near EPHA7 (which mediates cell-cell signaling), within TYR (involved in melanin synthesis and replicated from prior studies), within LINC01138, and near OTX2. Statistical fine-mapping refined 3 of these loci to single-variant 95% credible sets and narrowed the TYR locus to small credible sets, prioritizing possible causal variants. Effect estimates were broadly consistent across genetic ancestry clusters. Lead variants showed regulatory evidence in expression quantitative trait locus, including reduced EPHA7 expression. CONCLUSIONS: These findings implicate both melanogenesis and cell-cell adhesion and signaling pathways in pigment dispersion syndrome and pigmentary glaucoma. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Genome-wide association study↗
PubMed2005

Fractographic analyses of three ceramic whole crown restoration failures.

OBJECTIVES: Develop fractographic techniques to perform failure analyses of three ceramic whole-crown clinical failures. METHODS: Three clinical whole-crown failures of different ceramic material systems were studied. The systems included appropriate veneers applied to core materials of cold isostatically pressed alumina, injection molded alumina/alumina-magnesia spinel, and hot pressed lithium disilicate. The surface topography was examined for classical fractographic features, utilizing both optical and scanning electron microscopes independently as well as group examination by four fractographers. RESULTS: All three restorations displayed many common fractographic features, the most important of which was wake hackle. Wake hackle occurs when an approaching crack front sweeps by a small bubble or discontinuity in a brittle material, leaving a trail. The resulting trails can be used to trace back crack progression to an initial starting area. Wake hackle was found to be common in the veneer portions of the crowns, and the strategy of creating a wake hackle map enabled crack paths to be traced from a core area outward in all three restorations. The fracture origin areas were located where hoop stresses are high. Another helpful fracture feature was compression curl, an indication of flexural stress, most visible under low incident optical lighting. SIGNIFICANCE: This study indicates that fractographic analyses can be productively performed on ceramic whole-crown failures. Optical examination under low incident lighting and wake hackle mapping were developed as promising techniques. Hoop stress was implicated as a concern in the three studied specimens, and should be considered when analyzing other whole-crown failures.

Aluminum Oxide↗
PubMed1999

Sex differences in the vocal motor pathway of the zebra finch revealed by real-time optical imaging technique.

Male zebra finches sing, whereas female zebra finches do not. To elucidate the neural mechanisms underlying sexual dimorphism in song behavior, the spatio-temporal properties of neural activity in the vocal motor pathway of the zebra finch were examined in sliced brain preparations using a real-time optical recording technique. Electrical stimulation to higher vocal center (HVC) fibers induced within 20 ms neural activities in the robust nucleus of the archistriatum (RA) of both male and female finches, although the amplitude was smaller and the latency was greater in females than in males. Bicuculline, a GABA(A) receptor antagonist, induced a robust activity in female RA, but had little effect in males. This suggests that neural connections from HVC to RA in female zebra finches are inhibited by GABAergic inputs. The results provide first evidence that an inhibitory neurotransmitter is involved in the sex difference in the motor vocal pathway of song birds.

Animals↗
PubMed2004

Cross-relaxation imaging reveals detailed anatomy of white matter fiber tracts in the human brain.

Cross-relaxation imaging is a new quantitative MRI modality, which allows mapping of fundamental parameters determining the magnetization transfer (MT) effect in tissues, cross-relaxation rate constant (k) and bound pool fraction (f). This study introduces a new time-efficient technique for cross-relaxation imaging, which obtains three-dimensional (3D) whole-brain k and f maps with scan time of <30 min and isotropic spatial resolution of 1.4 mm. The technical principle of the method is based on four-point fit of a matrix model of pulsed MT to imaging data obtained with variable offset frequency saturation while using a complimentary R1 (=1 / T1) map. Anatomical correlations of in vivo cross-relaxation parametric maps were evaluated in three healthy subjects. The f maps revealed correspondence of areas with highly elevated f = 12-15% to major fiber tracts such as corpus callosum, anterior commissure, optic radiations, and major brain fasciculi. The rest of white matter (WM) demonstrated lower f = 9-11%, resulting in clear visual contrast of fiber tracts. Even lower f = 6.5-8.5% were found in gray matter (GM) with the highest f = 8.5% in the anterior thalamus. Distribution of k was relatively uniform in WM and produced sharp contrast between GM and WM (k = 1.6 and 3.3 s(-1), respectively). The most marked feature of k maps was their ability to visualize the corticospinal tract, which had elevated k = 3.4-3.8 s(-1) but appeared invisible on f maps. The observed patterns on f maps can be explained by variations in the density of myelinated fibers, while the trends of k may reflect regional differences in axonal organization. Cross-relaxation imaging can be used in various clinical studies focused on brain development and white matter diseases.

Analysis of Variance↗
PubMed1998

Expression and tyrosine phosphorylation of Eph receptors suggest multiple mechanisms in patterning of the visual system.

The EphA3 receptor tyrosine kinase has been implicated in guiding the axons of retinal ganglion cells as they extend in the optic tectum. A repulsive mechanism involving opposing gradients of the EphA3 receptor on retinal axons and its ligands, ephrin-A2 and ephrin-A5, in the tectum influences topographic mapping of the retinotectal projection. To investigate the overall role of the Eph family in patterning of the visual system, we have used in situ hybridization to localize nine Eph receptors in the chicken retina and optic tectum at Embryonic Day 8. Three of the receptors examined correspond to the novel chicken homologs of EphA2, EphA6, and EphA7. Unexpectedly, we found that many Eph receptors are expressed not only in retinal ganglion cells, but also in tectal cells, In particular, EphA3 mRNA is prominently expressed in the anterior tectum, with a pattern reciprocal to that of ephrin-A2 and ephrin-A5. Similarly, ephrin-A5 is expressed not only in tectal cells but also in the nasal retina, with a pattern reciprocal to that of its receptor EphA3 and partially overlapping with that of its other receptor EphA4. Consistent with the even distribution of EphA4 and the polarized distribution of EphA4 ligands in the retina, probing EphA4 immunoprecipitates from different sectors of the retina with anti-phosphotyrosine antibodies revealed spatial differences in receptor phosphorylation. These complex patterns of expression and tyrosine phosphorylation suggest that Eph receptors and ephrins contribute to establishing topography of retinal axons through multiple mechanisms, in addition to playing a role in intraretinal and intratectal organization.

Amino Acid Sequence↗
PubMed2004

Involvement of the optic tectum and mesencephalic reticular formation in the generation of saccadic eye movements in goldfish.

The circuitry and physiological properties underlying saccadic eye movement generation have been studied mainly in monkeys and cats. By contrast, current knowledge in nonmammalian species is rather scarce. We review here some of our recent findings about the involvement of the optic tectum and mesencephalic reticular formation in the generation of saccades in goldfish. Electrical microstimulation of the optic tectum evokes contraversive saccadic eye movements. In goldfish, as in mammals, the amplitude and direction of saccades are encoded in a spatial topographical map. In addition, there are some areas that have evolved, such as the extreme anteromedial tectal zone, whose activation yields eye convergence. Injections of the bidirectional tracer biotin dextran amine within functionally identified sites of the tectum provide reciprocal, site-dependent connectivity with different downstream structures. Of these structures, the major tectofugal target is the mesencephalic reticular formation. In goldfish, as in mammals, the mesencephalic reticular formation and optic tectum establish reciprocal connections at regional and neuronal levels which support the presence of feedback circuits. Electrical microstimulation demonstrates that the mesencephalic reticular formation can be functionally parceled-the rostral part is linked to vertical saccades, while the caudal part is related with horizontal ones. Finally, these zones are also differently connected to the optic tectum. From these data, we conclude that the involvement of the optic tectum and mesencephalic reticular formation in eye movement generation in goldfish is similar to that reported in cats and monkeys.

Animals↗
PubMed1989

Complementary global maps for orientation coding in upper and lower layers of the monkey's foveal striate cortex.

A population of 269 cells recorded from the foveal representation of striate cortex in 2 rhesus macaque monkeys was examined for orientation preference as a function of receptive field position relative to the center of gaze. Cells recorded in supragranular and infragranular layers were segregated and compared. Within the foveolar region (0.0-0.5 degrees) supragranular cells showed a vertical bias which was not evident in the infragranular layers. At larger eccentricities (0.5-2.5 degrees) supragranular cells showed a radial bias (preferred orientation points toward the center of gaze), whereas infragranular cells showed a concentric bias (preferred orientation is tangent to a circle around the center of gaze). These results are consistent with our earlier report of an orientation shift between the supragranular and infragranular layers (Bauer et al. 1980, 1983; Dow and Bauer 1984). The diagonal orientation bias which we noted earlier (Bauer et al. 1980; Dow and Bauer 1984) in supragranular cells at eccentricities between 0.5 and 2.5 degrees can be explained by the radial bias, combined with a tendency for recording sites to favor receptive field locations closer to the diagonal meridia than to either the horizontal or vertical meridia. Given other evidence that upper layer cells in macaque striate cortex tend to show either orientation or color selectivity, while lower layer cells tend to show movement sensitivity (Dow 1974; Livingstone and Hubel 1984), the present data suggest a functional dichotomy between a supragranular system involved in fixational eye movements and pattern vision and an infragranular system activated primarily by optical flow fields during ambulation.

Animals↗
PubMed2004

Computational modeling of retinotopic map development to define contributions of EphA-ephrinA gradients, axon-axon interactions, and patterned activity.

The topographic projection of retinal ganglion cell (RGC) axons to mouse superior colliculus (SC) or chick optic tectum (OT) is formed in three phases: RGC axons overshoot their termination zone (TZ); they exhibit interstitial branching along the axon that is topographically biased for the correct location of their future TZ; and branches arborize preferentially at the TZ and the initial exuberant projection refines through axon and branch elimination to generate a precise retinotopic map. We present a computational model of map development that demonstrates that the countergradients of EphAs and ephrinAs in retina and the OT/SC and bidirectional repellent signaling between RGC axons and OT/SC cells are sufficient to direct an initial topographic bias in RGC axon branching. Our model also suggests that a proposed repellent action of EphAs/ephrinAs present on RGC branches and arbors added to that of EphAs/ephrinAs expressed by OT/SC cells is required to progressively restrict branching and arborization to topographically correct locations and eliminate axon overshoot. Simulations show that this molecular framework alone can develop considerable topographic order and refinement, including axon elimination, a feature not programmed into the model. Generating a refined map with a condensed TZ as in vivo requires an additional parameter that enhances branch formation along an RGC axon near sites that it has a higher branch density, and resembles an assumed role for patterned neural activity. The same computational model generates the phenotypes reported in ephrinA deficient mice and Isl2-EphA3 knockin mice. This modeling suggests that gradients of counter-repellents can establish a substantial degree of topographic order in the OT/SC, and that repellents present on RGC axon branches and arbors make a substantial contribution to map refinement. However, competitive interactions between RGC axons that enhance the probability of continued local branching are required to generate precise retinotopy.

Animals↗
PubMed2002

The structure-function relationship in eyes with glaucomatous visual field loss that crosses the horizontal meridian.

OBJECTIVE: To evaluate the relationship between visual field loss and glaucomatous optic discs in eyes in which field loss spreads across the horizontal meridian. SUBJECTS AND METHODS: Ninety-six patients with glaucoma (9 advanced, 60 moderate, and 27 early) with 2 successive abnormal fields were included. Standard achromatic automated perimetry defects were identified with a nerve fiber bundle map to identify abnormal sectors. Crossover was present if the superior and inferior sectors at the horizontal meridian (nasal, central, or temporal) were both abnormal. Optic disc damage was assessed by masked grading of simultaneous stereophotographs. RESULTS: Only 30% (29) of glaucomatous eyes showed crossover, and only 2 of those eyes had early loss. The most frequent pattern of visual field loss (41% of eyes) was single hemifield damage with defects in contiguous sectors. Regardless of the pattern or severity of visual loss, most eyes (66 [69%] of 96) had both superior and inferior optic disc damage. CONCLUSIONS: Early glaucomatous visual field loss rarely crosses the horizontal meridian, but defects in both hemifields at the horizontal meridian are more common in more advanced field loss. In 26 (90%) of 29 eyes with crossover, it could be explained by changes at the optic nerve head.

Adult↗
PubMed2001

Zebrafish genes rx1 and rx2 help define the region of forebrain that gives rise to retina.

Zebrafish retinal homeobox genes rx1 and rx2 are expressed exclusively in the optic primordia and then in cone photoreceptors of the differentiated neural retina. In this study, we show that the rx expression domain is coextensive with the region identified as the retinal field in published fate maps of the neural plate in zebrafish embryos. Analysis of the spatiotemporal relationships between retinal and forebrain precursors suggests that lateral movement of retinal precursors is responsible for evagination of the optic primordia. Overexpression of either rx1 or rx2 results in the loss of forebrain tissue and the ectopic formation of retinal tissue. We asked whether the deletion of forebrain and expansion of retinal tissue could be explained by the death of telencephalic precursors and enhanced proliferation of retinal precursors, and we found that it could not. Instead, our data are consistent with a change in cell fate of forebrain precursors associated with reduced expression of telencephalic markers (emx1 and BF-1) and ectopic expression of retinal markers (rx1/2/3, pax6, six6, and vsx2) at the neural keel stage. The rx homeodomain alone is sufficient to induce ectopic retinal tissue, although weakly so, and this observation, together with results from deletion constructs, suggests that interactions with unidentified transcriptional regulators are important for rx1 and rx2 function during early eye development. We conclude that regulated expression of zebrafish rx1 and rx2 helps to define the region of the forebrain fated to give rise to retinal tissue and may be involved in the cellular migrations that lead to splitting of the retinal field and formation of the optic primordia.

Animals↗
PubMed2005

Evidence that cerebral blood volume can provide brain activation maps with better spatial resolution than deoxygenated hemoglobin.

With the aim of evaluating the relative performance of hemodynamic contrasts for mapping brain activity, the spatio-temporal response of oxy-, deoxy-, and total-hemoglobin concentrations were imaged with diffuse optical tomography during electrical stimulation of the rat somatosensory cortex. For both 6-s and 30-s stimulus durations, total hemoglobin images provided smaller activation areas than oxy- or deoxy-hemoglobin images. In addition, analysis of regions of interest near the sagittal sinus vein show significantly greater contrast in both oxy- and deoxy-relative to total hemoglobin, suggesting that oximetric contrasts have larger draining vein contributions compared to total hemoglobin contrasts under the given stimulus conditions. These results indicate that total hemoglobin and cerebral blood volume may have advantages as hemodynamic mapping contrasts, particularly for large amplitude, longer duration stimulus paradigms.

Algorithms↗
PubMed1997

Optic nerve regenerates but does not restore topographic projections in the lizard Ctenophorus ornatus.

In adult fish and amphibians, the severed optic nerve regenerates and visual behaviour is restored. By contrast, optic axons do not regenerate in the more recently evolved birds and mammals. Here we have investigated optic nerve regeneration in a member of the class Reptilia, phylogenetically intermediate between the fish and amphibians and the birds and mammals. We assessed visual recovery anatomically and behaviourally one year after unilateral optic nerve crush in the adult ornate dragon lizard. Ctenophorus ornatus. Ganglion cell densities and numbers of axons in the optic nerve on either side of the crush site indicated that two-thirds of ganglion cells survived axotomy and regrew their axons. However, myelination fell from a mean of 21% in normals to 5.5% and 3%, proximal and distal to the crush, respectively. Anterograde labelling of the entire optic nerve showed that axons regenerated along essentially normal pathways and that the major projection, as in normals, was to the superficial one-third of the contralateral optic tectum. However, localised retinal injections indicated that regenerated projections lacked retinotopic order. Any one retinal region projected to the entire tectum. This feature presumably explains why the experimental lizards consistently appeared blind to stimuli via the regenerated nerve. Our findings indicate that although axons regenerate along essentially normal pathways in adult lizards, conditions within the visual centres do not allow regenerating optic axons to select appropriate central connections. In a wider context, the result suggests that the ability for regenerating central axons to form topographic maps may also have been lost in the more recently evolved vertebrate classes.

Animals↗
PubMed2000

Quantitative analysis of visual field and optic disk in glaucoma: retinal nerve fiber bundle-associated analysis.

BACKGROUND: A study was performed to evaluate whether visual field analysis using a perimetric nerve fiber bundle map gives information additional to global visual field indices and cumulative defect curves for early glaucoma diagnosis. METHODS: One hundred and four control subjects, 124 patients with ocular hypertension (OHT), 97 patients with high-tension glaucoma without visual field defects (preHTG) and 91 patients with open-angle glaucoma with visual field defects [30 low-tension glaucoma (LTG), 61 high-tension glaucoma (HTG)] were included in this study. Correlation analyses were performed between (a) global visual field indices and total neuroretinal rim (NRR) area; (b) local mean values of four visual field areas and the NRR area of the corresponding four optic disk sectors; and (c) local mean values of 10 perimetric nerve fiber bundles (PNFB 1-10) according to Weber and Ulrich (1991) and the four optic disk sectors. The correlations were adjusted for global mean defect and total NRR. RESULTS: There were no significant correlations between NRR area and visual field in control subjects or in patients with OHT or preHTG for all three analyses. Significant correlations were found between the global visual field indices and the total NRR area for LTG and HTG. Significant correlations between local mean defects and NRR area of corresponding optic disk sectors were found only in LTG for the superior and inferior visual field area and the PNFB covering these areas. CONCLUSION: The method used for visual field analysis and sectorization of the optic disk does not give additional information on visual field defects in patients with normal global visual field indices and a normal cumulative defect curve. The nerve fiber bundle-related visual field analysis allows the topographical determination and quantification of glaucomatous damage.

Adult↗