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At least 775 records · Page 43Linked to original sources
PubMed2004

Near-field visualization of light confinement in a photonic crystal microresonator.

By using scanning near-field optical microscopy, we directly map the subwavelength confinement of light around a point defect in a two-dimensional photonic crystal microresonator. Comparison of our results with the outcome of three-dimensional finite-difference time domain calculations allows us to identify small imperfections in the structure that result in the spatial modification of the intensity distribution.

Journal Article↗
PubMed1986

Conduction pattern of excitation in the amphibian atrium assessed by multiple-site optical recording of action potentials.

Spontaneous action potentials were monitored from multiple sites in the bullfrog atrium using a voltage-sensitive merocyanine-rhodanine dye together with a 100-element photodiode matrix array, and we have assessed the spread of the excitation from the pacemaker. Isochrone curves of conduction were obtained by timing the initiation of the action potential-related optical signals: we constructed maps of the spread. Excitatory waves appeared to conduct radially from the pacemaking area over the atrium, and the conduction velocity in the left atrium exceeded that in the right atrium.

Animals↗
PubMed1998

The use of time and trajectory forms as visual information about spatial scale in events.

Spatial metrics are lost but temporal metrics are preserved in the mapping from events to optic flow. In inanimate events governed by gravity, temporal scale is linked to spatial scale in ways specific to particular events. We tested whether time can be used as information about spatial scale in visually recognizable events. On average, observers were able to judge object size in event displays that eliminated information other than time and trajectory forms. However, judgment variability was substantial. After feedback on one event, observers judging distance performed better and generalized training to other events. Observers are sensitive to the general form of the scaling relation, but they require feedback to attune event-specific constants.

Adult↗
PubMed1990

[The epidemiology and importance of metaplasia and dysplasia of the urinary bladder mucosa in autopsy material from a middle-size industrial city (study of Görlitz)].

This study had been conducted for the purpose of obtaining information on incidence and biological significance of metaplasia and dysplasia of the urinary bladder. Therefore, postmortem investigations were made of 1,117 urinary bladders, using optical light microscopy and mapping. They were related to a medium-size industrial town with an autopsy frequency of 98%. Metaplasia (58%) and dysplasia (13%) are no rare urinary bladder findings and occur particularly to individuals in somewhat advanced age, with no significant sex-related difference. Urocystitis was recorded from over 50% of all cases reviewed. More strongly pronounced inflammatory processes appeared to be risk factors for higher severity of dysplasia. Inconspicuous as well as metaplastic von Brunn's nests or squamous and glandular metaplasia without atypical cells should not be considered precarcinomas. However, atypical cells in terms of dysplasia were recordable from a small number of these metaplasias. Precancerous importance might be attributed to few of them, particularly in male patients with dysplastic squamous cell metaplasia. No reliable information, however, was available on premature development of dysplasia in lower age groups which would have meant a long-drawn process of carcinogenesis.

Adult↗
PubMed1994

Calcium imaging of rhythmic network activity in the developing spinal cord of the chick embryo.

Video-rate imaging of spinal neurons loaded with calcium-sensitive dyes was used to investigate the calcium dynamics and cellular organization of spontaneously active rhythm-generating networks in the spinal cord of E9-E12 chick embryos. Spinal neurons were loaded with bath-applied fura-2am. Motoneurons were also loaded by retrograde labeling with dextran-conjugated, calcium-sensitive dyes. Dye-filled motoneurons exhibited large fluorescent changes during antidromic stimulation of motor nerves, and an increase in the 340/380 fura fluorescence ratio that is indicative of increased intracellular free calcium. Rhythmic fluorescence changes in phase with motoneuron electrical activity were recorded from motoneurons and interneurons during episodes of evoked or spontaneous rhythmic motor activity. Fluorescent responses were present in the cytosol and in the perinuclear region, during antidromic stimulation and network-driven rhythmic activity. Optically active cells were mapped during rhythmic activity, revealing a widespread distribution in the transverse and horizontal planes of the spinal cord with the highest proportion in the ventrolateral part of the cord. Fluorescent signals were synchronized in different regions of the cord and were similar in time course in the lateral motor column and in the intermediate region. In the dorsal region the rhythm was less pronounced and the signal decayed after a large initial transient. Video-rate fluorescent measurements from individual cells confirmed that fluorescent signals were synchronized in interneurons and in motoneurons although the time course of the signal could vary between cells. Some of the interneurons exhibited tonic elevations of fluorescence for the duration of the episode whereas others were rhythmically active in phase with motoneurons. At the onset of each cycle of rhythmic activity the earliest fluorescent change occurred ventrolaterally, in and around the lateral motor column, from which it spread to the rest of the cord. The results suggest that neurons in the ventrolateral part of the spinal cord are important for rhythmogenesis and that axons traveling in the ventrolateral white matter may be involved in the rhythmic excitation of motoneurons and interneurons. The widespread synchrony of the rhythmic calcium transients may reflect the existence of extensive excitatory interconnections between spinal neurons. The network-driven calcium elevations in the cytosol and the perinuclear region may be important in mediating activity-dependent effects on the development of spinal neurons and networks.

Animals↗
PubMed2001

High resolution gel-dosimetry by optical-CT and MR scanning.

The increased intricacy of Intensity-Modulated-Radiation-Therapy (IMRT) delivery has created the need for a high-resolution 3D-dosimetry (three-dimensional) system capable of measuring and verifying the complex delivery. Present clinical methods are inadequate being restricted to single points (e.g., ion-chambers) or to 2D planes (e.g., film), and are labor intensive. In this paper we show that gel-dosimetry in conjunction with optical-CT scanning can yield maps of dose that are of sufficient accuracy, resolution and precision to allow verification of complex radiosurgery deliveries, and by extension IMRT deliveries. The radiosurgery dose-distribution represents the most challenging case encountered in external beam therapy by virtue of the steep dose-gradients and high resolution of delivery. We characterize the stringent radiosurgery requirements by the RTAP (Resolution-Time-Accuracy-Precision) criteria defined as < or = 1 mm3 spatial resolution, < or = 1 hour imaging time, accurate to within 3%, and within -1% precision. The RTAP criteria is applied to an in-house laser-based optical-CT scanning system presented here, and evaluated using gel-flasks containing BANG3 gel. The same gel flasks were subsequently imaged using the MR imaging protocol recommended by the gel manufacturer, but modified to match as closely as possible the RTAP. The resulting dose-maps demonstrate the high precision (< 1.3% noise at high dose) achievable with optical CT scanning while preserving high spatial resolution (<1 mm3). Using the sequence above, the MR gel-dose maps were found to have poorer precision by a factor of 5, under the strict conditions of the RTAP. The optical CT gel-dosimetry system was further evaluated for the verification of a complex 3-isocenter radiosurgery delivery. In conclusion, this work demonstrates that gel-dosimetry and optical-CT scanning approach an important long-term goal of radiation dosimetry, as specified by the RTAP criteria, and have potential to impact the clinic by improving and facilitating clinical dose verification for the most complex external beam radiation treatments.

Calibration↗
PubMed2005

Focusing surface plasmons with a plasmonic lens.

We report the focusing of surface plasmon polaritons by circular and elliptical structures milled into optically thick metallic films or plasmonic lenses. Both theoretical and experimental data for the electromagnetic nearfield is presented. The nearfield is mapped experimentally using nearfield scanning optical microscopy and plasmonic lithography. We find that the intensity at the focal points of the plasmonic lenses increases with size.

Journal Article↗
PubMed1998

SOLH, a human homologue of the Drosophila melanogaster small optic lobes gene is a member of the calpain and zinc-finger gene families and maps to human chromosome 16p13.3 near CATM (cataract with microphthalmia).

Mutations in the Drosophila melanogaster small optic lobes (sol) gene cause a sever reduction in the neuropiles of the medulla and lobula complexes of the adult optic lobes. The predicted protein product of sol contains zinc-finger-like repeats, a calpain-like protease domain, and a C-terminal region of unknown function. We have isolated human brain cDNA for SOLH, a human homologue of sol. The human SOLH gene consists of 14 exons distributed over more than 45 kb of genomic DNA. The encoded SOLH protein of 1086 amino acids has strong similarity to the D. melanogaster protein. The calpain-like domain and C-terminal region are highly conserved (58% identity), and similar Cys2-Cys2 zinc fingers are present in the N-terminal region. A reported Caenorhabditis elegans homologue contains the calpain domain and C-terminal region, but appears to lack the zinc finger region. A single copy of the zinc finger sequence is present in adjacent C. elegans genomic cosmid DNA sequence, and we show that it is part of the C. elegans sol-like transcript. Northern analysis of human tissues revealed a SOLH transcript of approximately 5 kb that was strongest in human brain. We have mapped the SOLH gene to chromosome 16p13.3 by in situ hybridization. SOLH is a candidate gene for CATM (hereditary cataracts with microphthalmia), which maps in this region.

Amino Acid Sequence↗
PubMed1987

The position of the crossed and uncrossed optic axons, and the non-optic axons, in the optic tract of the rat.

The position of the crossed and uncrossed optic axons, and of the non-optic axons, within the optic tract was determined in the adult hooded rat. Horseradish peroxidase histochemistry and lesion-induced degeneration of axonal profiles were independently used to study the position of the three relevant populations of axons within the optic tract. The boundaries of the optic tract are distinct at all but its caudomedial border, where it abuts the supra-optic commissures running parallel to the fibres of the optic tract. Labelling the crossed population of optic axons, or inducing their degeneration, both demonstrate a clear caudomedial border of the optic tract, although a number of optic axons stray out of the optic tract and course within the supra-optic commissures immediately caudomedial to the tract. The uncrossed optic axons are, as a population, positioned relatively deep in the optic tract, towards its dorsal border. A few occur at further ventral positions, but their density is greatly reduced there. There is also a very thin region along the dorsalmost edge of the optic tract free of uncrossed optic axons. The relative position of the uncrossed to the crossed optic axons is discussed in the context of the mammalian optic tract as a chronological map: spatial position in the tract may reflect temporal order of axonal arrival during early development. A large population of non-optic axons belonging to Gudden's commissure courses within the boundaries of the optic tract at a relatively ventral position. They are most frequent caudomedially, and are absent rostrolaterally. Hence, axons of the optic tract and Gudden's commissure are substantially intermingled in the caudomedial half of the optic tract. These non-optic axons greatly outnumber the uncrossed optic axons, and will consequently distort counts of uncrossed optic axons based on intact profiles that remain after removal of the opposite eye. However, they are still a minority in comparison to the crossed optic axons in this region.

Animals↗
PubMed1990

Observations on the arrangement of axons according to diameter in the optic tract of the opossum Didelphis marsupialis.

The spectra of fiber sizes at different depths of the optic tract of the opossum Didelphis marsupialis were examined by electron microscopy in order to test for correlations between the eventual location of axons and relevant developmental events. Frequency histograms showed 1) a predominant representation of medium-sized axons and the virtual exclusion of coarse fibers from the deepest portion of that pathway, and 2) a progressive increase in the proportion of thin axons from deep to superficial sites of the tract. These findings are discussed in terms of the view of the optic tract as a chronological map of axon arrival.

Animals↗
PubMed1989

Reproducibility of pallor measurements with the optic nerve head analyzer.

One eye each of ten healthy volunteers was tested with the Rodenstock Optic Nerve Head Analyzer on ten separate occasions. A color-coded pallor map was developed for each examination. A color transparency of each pallor map was then obtained from the television monitor of the Optic Nerve Head Analyzer, using a camera mounted on a tripod at a fixed distance from the screen. A color-coded zone within the center of the disc was chosen for each set of ten studies, and the area of this zone was measured by boundary analysis with another computerized image analyzer, the Oasys Image Processor. There was wide intrasubject variation in all ten volunteers, suggesting that the pallor map generated by the Optic Nerve Head Analyzer, when used in the manner described in this paper, is not adequate for following subtle changes in optic nerve head pallor.

Humans↗
PubMed2000

A candidate pathway for a visual instructional signal to the barn owl's auditory system.

Many organisms use multimodal maps to generate coherent neuronal representations that allow adequate responses to stimuli that excite several sensory modalities. During ontogeny of these maps, one modality typically acts as the dominant system the other modalities are aligned to. A well studied model for the alignment of sensory maps is the calibration of the auditory space map by the visual system in the optic tectum of the barn owl. However, a projection from the optic tectum to the site of plasticity in the auditory pathway that could deliver an instructive signal has not been found so far. We have analyzed the development of the connectivity between the bimodal (visual and auditory) map of space in the barn owl's optic tectum and the auditory space map in the inferior colliculus with tracing methods and intracellular fills. Neurons in the tectal stratum griseum centrale were found to be suited to deliver an alignment signal from the visual midbrain to the auditory pathway. These neurons are presumably part of the efferent tectal projection pathway that mediates head saccades. The implications of a sensory alignment signal possibly being delivered by a (pre)motor command pathway are discussed.

Animals↗
PubMed2000

In vivo mapping of the vascular changes in skin burns of anaesthetised mice by fibre optic confocal imaging (FOCI).

Burns (3 mm in diameter, 50 degrees C, 20 s duration) were induced on the skin of anaesthetised hairless mice. Anaesthesia was maintained throughout all experiments. Subsurface changes in the microvasculature at the burn site were imaged confocally following i. v. injection of fluorescently labelled (FITC) dextran. Blood cells moving through dermal blood vessels were seen and recorded on video tape. Multiple adjacent 2-D confocal images of the burn site and surrounding areas were assembled and enabled microscopic vascular imaging of the whole burn area (including zones of coagulation, stasis and hyperaemia) and the surrounding normal vessels. This mapping of the burn area by fibre optic confocal imaging (FOCI) in vivo demonstrated good congruence with vascular casts (Microfil MV-120, Flow tech, USA) made at 4 h post burn. This study demonstrates the usefulness of FOCI for in vivo vascular imaging in burns.

Animals↗
PubMed2006

Optical coherence tomography in group 2A idiopathic juxtafoveolar retinal telangiectasis.

OBJECTIVE: To describe the changes observed with optical coherence tomography in group 2A idiopathic juxtafoveolar retinal telangiectasis. METHODS: We retrospectively reviewed the medical records of 13 patients (25 eyes). All eyes underwent optical coherence tomography examination consisting of 6 radial scans, fundus color photography, and fluorescein angiography. We calculated retinal foveal and central foveal thicknesses from software mapping results. We compared the optical coherence tomography data with fundus photography and fluorescein angiography findings. RESULTS: Foveal cystoid spaces, very small or more prominent, were present in 20 of 25 eyes. Some degree of disruption of the inner segment/outer segment photoreceptor junction line was observed in 18 eyes as from stage 2 of idiopathic juxtafoveolar retinal telangiectasis, and intraretinal pigmentary proliferation was observed in 9. A foveal detachment without subretinal new vessels was also present in 2 eyes. Despite these abnormalities, central foveal thickness was below or within the range of reference values in all eyes; foveal thickness, in 23 of 25. In the more advanced cases, severe disruption of the inner segment/outer segment photoreceptor junction line and outer retinal atrophy were seen. CONCLUSIONS: Early in the evolution of group 2A idiopathic juxtafoveolar retinal telangiectasis, the optical coherence tomography examination disclosed intraretinal cystoid spaces without foveal thickening and disruption of the inner segment/outer segment photoreceptor junction line. Foveal thinning was present in later stages.

Adult↗
PubMed2002

Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering in optical coatings.

The control and the characterization of optical losses are crucial elements in the design of high-quality thin films. Nonuniformity of losses and the existence of local defects have led us to perform simultaneous absorption and scattering mapping in exactly the same experimental conditions. An improved setup and new procedures are capable of providing such paired mappings of absorption and partial scattering at various spatial scales. The diameter of the pump beam, which governs lateral spatial resolution, can be chosen to be 3-100 microm. The detectivity threshold can be as low as 0.1 part in 10(6) for absorption and 0.01 part in 10(6) for mapping partial scattering. Spatial windows can range from micrometer-sized areas for the study of micro defects to centimeter-sized areas on which the uniformity of losses can be checked. We study the spatial distribution of absorption and scattering losses under scale transformation by changing the spatial window while keeping the spatial resolution constant. We present one-dimensional and bidimensional multiscale studies. For example, we show that one can use multiscale mapping of defects to evaluate the qualities of substrate cleaning, which are not identical on micrometric and centimetric scales.

Journal Article↗
PubMedDate not supplied

Consistent mapping of orientation preference across irregular functional domains in ferret visual cortex.

The mammalian visual cortex harbors a number of functional maps that represent distinct attributes of stimuli in the visual environment. How different functional maps are accommodated within the same cortical space, especially in species that show marked irregularities in one or more functional maps, remains poorly understood. We used optical imaging of intrinsic signals and electrophysiological techniques to investigate the organization of the maps of orientation preference, ocular dominance, and visual space in ferret. This species shows striking nonuniformity in the arrangement of ocular dominance domains and disruption of the mapping of visual space along the V1/V2 border. We asked whether these irregularities would be reflected in the organization of the map of orientation preference. The results show that orientation preference is mapped consistently within both V1 and V2, and across the interareal boundary, with no reflection of the irregularities in the other maps. These observations demonstrate the accommodation of multiple functional maps within the same cortical space without systematic geometrical relationships that necessarily constrain the organization of each representation. Furthermore, they imply that the structure of the map of orientation preference reflects the architecture and activity patterns of cortical circuits that are independent of other columnar systems established in layer 4.

Animals↗
PubMed1999

Mapping of histologically identified long fiber tracts in human cerebral hemispheres to the MRI volume of a reference brain: position and spatial variability of the optic radiation.

The interpretation of the anatomical basis of functional deficits after subcortical infarcts could be considerably improved, if the precise topography and interindividual variability in size and course of long fiber tracts in adult human cerebral hemispheres were available in a spatial reference system. We therefore developed a method enabling the mapping of long fiber tracts to the volume of a standard reference brain. The examined fiber tracts were identified in myelin-stained histological serial sections of 10 human brains. The reference brain is a 3-D reconstruction of in vivo obtained magnetic resonance images (MRIs). The warping of histological volumes with the labeled fiber tracts to the reference brain by means of linear and nonlinear transformation procedures results in population maps that demonstrate the interindividual variability in position, size, and course of fiber tracts. In this paper, we present population maps of the optic radiation and the lateral geniculate body as a first example of this mapping strategy. Both structures present a considerable interindividual variability. Furthermore, voxel-based morphometry shows significant side differences with larger volumes of both structures in the left hemisphere than in the right hemisphere. A more than twofold variability of size in the interhemispheric extension of the optic radiation and the lateral geniculate body is found even after normalization of absolute brain size. Our observations demonstrate that the present approach based on population maps of fiber tracts and nuclei can improve the anatomical localization and interpretation of brain lesions visible in MRIs at the level of microstructurally identified architectonical units.

Adult↗