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Results for “Optical mapping”

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At least 1,297 records · Page 72Linked to original sources
PubMed1995

Optical scaling in conspecific Cataglyphis ants

This study examines the effects of body size variation on the optical properties of the compound eyes of visually guided desert ants belonging to the genus Cataglyphis. Although linear head size may vary by a factor of 2 within conspecific workers and most optical parameters change accordingly, the extent of the visual field remains constant. Comparative measurements carried out on workers of three species (C. albicans, C. bicolor and C. fortis) and on reproductive females and males of one species (C. bicolor) show that the form (size and shape) of the visual field is highly characteristic for each caste/species. A constant visual field is realised by reciprocal scaling rules for the number of ommatidia and the angular spacing of ommatidia. While larger ants have more ommatidia per compound eye, interommatidial angles are reduced accordingly, thus giving rise to a constant visual field. Among conspecific ant workers, the relationship between spatial visual acuity and eye size is similar to that found in interspecific comparisons and reflects optical constraints imposed on the design of the compound eye. Mapping of spatial visual directions onto the compound eye surface reveals a characteristic, inhomogeneous distribution of interommatidial spacing, particularly a foveal band with increased visual acuity in the vertical direction. This 'visual stretch' viewing the horizon is similar to that found in a variety of flying insects. Although, among conspecific workers, both the number of ommatidia and the interommatidial angles vary with varying head size, the overall pattern of interommatidial spacing is maintained so that corresponding positions on the compound eye of small and large individuals look in equivalent directions in space. These findings are in accordance with the observation that the shape of the compound eye surface, as expressed by the radius of curvature along cross sections, is similar in small and large ants.

Journal Article↗
PubMed2002

Glomerular representation of plant volatiles and sex pheromone components in the antennal lobe of the female Spodoptera littoralis.

We studied the projection patterns of antennal lobe (AL) interneurones sensitive to plant volatiles and female-produced sex pheromone components in the female moth, Spodoptera littoralis. Ten compounds (eight plant-derived compounds and two sex pheromone components) were singly applied to the antenna and, using intracellular recording and staining techniques, the physiological and morphological characteristics of responding neurones were investigated. In addition, ALs stained with a synapsin antibody were optically sectioned using confocal microscopy, and a three-dimensional map of glomeruli in the anterior aspect of the AL was reconstructed. We used the map as a reference for identification of glomeruli innervated by projection neurones (PNs) that respond to plant volatiles and/or pheromone components. Nineteen PNs, responding to one to seven compounds of the ten tested stimuli, were stained with neurobiotin. These neurones each arborised in a single glomerulus in the frontal side of the AL. PNs responding to the same compound arborised in different glomeruli and PNs arborising in the same glomerulus responded to different compounds. Accordingly, glomeruli harbouring the dendritic arborisations of PNs responding to each of the tested compounds constituted a unique array of glomeruli that were not necessarily adjacent. It was thus clear that, at the output level, a single plant volatile or a sex pheromone component was not represented within a single glomerulus in the AL. We expect complex patterns of glomeruli to be involved in the coding of plant-derived compounds, as well as sex pheromone components, in female S. littoralis.

Animals↗
PubMed2006

Optical waveguide biosensors constructed with subwavelength gratings.

The reflection resonance spectrum of a subwavelength diffraction-grating-coupled waveguide is used to analyze biomolecular interactions in real time. By detecting this resonance wavelength shift, the optical waveguide biosensor provides the ability to identify the kinetics of the biomolecular interaction on an on-line basis without the need for extrinsic labeling of the biomolecules. A theoretical analysis of the subwavelength optical waveguide biosensor is performed. A biosensor with a narrow reflection resonance spectrum, and hence an enhanced detection resolution, is then designed and fabricated. Currently, the detection limit of the optical waveguide sensor is approximately 10(-5) refractive-index units. The biosensor is successfully applied to study of the dynamic response of an antibody interaction with protein G adsorbed on the sensing surface.

Biosensing Techniques↗
PubMed2004

Femtosecond direct space-to-time pulse shaping in an integrated-optic configuration.

We demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. The apparatus is used to generate trains of more than 30 pulses as an ultrafast optical data packet over approximately an 80-ps temporal window.

Journal Article↗
PubMed2003

The representation of retinal blood vessels in primate striate cortex.

The blood vessels that nourish the inner retina cast shadows on photoreceptors, creating "angioscotomas" in the visual field. We have found the representations of angioscotomas in striate cortex of the squirrel monkey. They were detected in 9 of 12 normal adult animals by staining flatmounts for cytochrome oxidase activity after enucleation of one eye. They appeared as thin profiles in layer 4C radiating from the blind spot representation. Angioscotomas can be regarded as a local form of amblyopia. After birth, when light strikes the retina, photoreceptors beneath blood vessels are denied normal visual stimulation. This deprivation induces remodeling of geniculocortical afferents in a distribution that corresponds to the retinal vascular tree. Angioscotoma representations were most obvious in monkeys with fine ocular dominance columns and were invisible in monkeys with large, well segregated columns. In monkeys without columns, their width corresponded faithfully to the inducing retinal shadow, making it possible to calculate the minimum shadow required to produce a cortical representation. The "amblyogenic threshold" was calculated as the fraction of the pupil area eclipsed to trigger remodeling of geniculocortical afferents. It was found to be constant over retinal eccentricity, vessel size, and shadow size. Ambliogenic shadows only three to four cones wide were sufficient to generate a cortical representation, testifying to the remarkable precision of the cortical map. The representations of retinal blood vessels separated by only 0.65 degrees were resolvable in the cortex, yielding an upper limit on cortical resolution of 340 microm in layer 4C.

Animals↗
PubMedDate not supplied

[Optical biosensor study and molecular modeling of interactions between cytochrome P450cam and cytochrome b5].

The formation of complexes of cytochrome P450cam (P450cam) with full-length cytochrome b5 (d-b5) and its tryptic water-soluble fragment (t-b5) was analyzed using a two-channel IAsys+ optical biosensor. It was found that t-b5 can form complexes with P450cam, while d-b5 does not interact with P450cam. The involvement of amine groups of P450cam in the complex formation was demonstrated. The temperature dependence of t-b5(im)/P450cam complex formation was measured. The association rate constant (k(on)) increased with temperature, while the dissociation rate constant (k(off)) practically remained unchanged. It was concluded that hydrophobic interactions play a key role in the complex formation, while electrostatic interactions are significant for complex stabilization. Based on temperature dependence the activation energy, enthalpy and entropy of complex formation were calculated. It was shown that the entropy component plays a key role in t-b5(im)/P450cam interaction. Computer modeling of P450cam/t-b5 and P450cam/d-b5 interactions was carried out. Using the method of molecular docking some hypotheses of protein-protein complexes were advanced and the best ones were selected based on geometric complementarity, calculated binding energy and probability of electron tunneling between proteins. The computer modeling has shown that only P450cam and t-b5 can form the stable complex. These results are in good agreement with the experimental data obtained with the optical biosensor.

Amino Acid Sequence↗
PubMed1983

[Retinotopic projections of the trout (Salmo gairdneri)].

The retinotopic organization of the thalamic and tectal and visual centres was studied by Fink and Heimer method and radioautography. Quadratic lesions were achieved in the right retina of 21 adult trouts and 23 six month old specimens. Fourteen animals (adults) were kept alive for 20 to 25 days after operation, in running water at 13 degrees C and prepared for the Fink technique. In the remaining 7 adults and in the 23 six month specimens, we injected, 48 hours after the lesion, respectively, 2,5 microCi (in 20 microliters) and 0,5 microCi (in 1 microliter) of 14 C proline into the operated eye. The brains were prepared for radioautography. Results show that the thalamic pathways is not correlated with a peculiar quadrant. Nevertheless the temporo dorsal hemiretina sends the more numerous projections at this level. A topographic parallelism exists between retino-geniculate and retino-tectal projections. At the tectal level our data are somewhat at variance with those of electrophysiological mapping, since quadratic projections show a partial overlapping. In the optic tract, the fibres from every quadrant follow always the same pathway.

Animals↗
PubMed2006

Thermooptical properties of gold nanoparticles embedded in ice: characterization of heat generation and melting.

We investigate the system of optically excited gold NPs in an ice matrix aiming to understand heat generation and melting processes at the nanoscale level. Along with the traditional fluorescence method, we introduce thermooptical spectroscopy based on phase transformation of a matrix. With this, we can not only measure optical response but also thermal response, that is, heat generation. After several recrystallization cycles, the nanoparticles are embedded into the ice film where the optical and thermal properties of the nanoparticles are probed. Spatial fluorescence mapping shows the locations of Au nanoparticles, whereas the time-resolved Raman signal of ice reveals the melting process. From the time-dependent Raman signals, we determine the critical light intensities at which the laser beam is able to melt ice around the nanoparticles. The melting intensity depends strongly on temperature and position. The position-dependence is especially strong and reflects a mesoscopic character of heat generation. We think that it comes from the fact that nanoparticles form small complexes of different geometry and each complex has a unique thermal response. Theoretical calculations and experimental data are combined to make a quantitative measure of the amount of heat generated by optically excited Au nanoparticles and agglomerates. The information obtained in this study can be used to design nanoscale heaters and actuators.

Gold↗
PubMed2003

Distorted odor maps in the olfactory bulb of semaphorin 3A-deficient mice.

Semaphorin 3A (Sema3A) repels growing olfactory axons that express neuropilin-1 (NP-1), a receptor for Sema3A. The Sema3A-mediated axon guidance seems to be essential for the formation of the glomerular sensory map in the olfactory bulb (OB). To understand whether and how Sema3A is involved in sensory map formation, we examined the glomerular map in the OB of adult Sema3A-deficient mice. In wild-type mice, NP-1-positive glomeruli form the lateral and medial bands and avoid the anteromedial and ventral regions of the OB. In the Sema3A-deficient OB, NP-1-positive glomeruli spread over the entire OB, and we consistently found the ectopic arrangement of NP-1-positive glomeruli in the anteromedial and ventral regions. In addition, a specific subset of NP-1-negative and olfactory cell adhesion molecule-positive glomeruli, especially those in the anteromedial region, disappeared from the mutant OB. These results show a critical role for Sema3A in the spatial arrangement of glomeruli in the OB. Optical imaging from the dorsal OB showed that the distorted glomerular map conserved molecular-feature domains. However, the positions of the domains were shifted, which suggests a secondary rearrangement of the glomerular map in the Sema3A-deficient OB.

Animals↗
PubMed1975

Oculomotor areas in the rabbits midbrain and pretectum.

The role of some meso- and diencephalic structures in eye movements was investigated by ablation and stimulation experiments. Optokinetic nystagmus was abolished by small lesions in the lateral pretectum, but not by complete removal of the superior colliculi. Stimulation of the superior colliculus and other visual centers was effective in eliciting nystagmus (slow phase ipsilateral), but the most efficient trigger zones are found in the lateral pretectum and the midbrain tegmentum. Only from these areas could nystagmus still be elicited after degeneration of the primary optic fibers. The lateral pretectal trigger zone is probably identical with the nucleus of the optic tract. It is postulated that this nucleus is an essential station for horizontal optokinetic reactions. Saccades were obtained by stimulation of the mesencephalic central grey, but not for any visual centers such as the superior colliculus.

Animals↗
PubMedDate not supplied

Heat shock protein 90 in retinal ganglion cells: association with axonally transported proteins.

The mRNAs for heat shock protein 90 (HSP90) are found at highest levels (differentially expressed) in the primate retinal fovea, the region of highest visual acuity, compared to the peripheral retina. HSP90 expression and retinal associations were analyzed by immuno-localization, in situ hybridization, and western analysis. Retinal ganglion cells (RGCs) express much of the HSP90 mRNA present in the primate retinal fovea. A large fraction of RGC synthesized HSP90 is apparently present in the axonal compartment. To identify the role of HSP90 protein in the optic nerve and retina, co-immunoprecipitation experiments were performed, using antibodies specific for HSP90 isoforms. The immunoprecipitates were analyzed for neurotrophin receptor and ligand activities, and MAP kinase activity. MAP kinase assay was used to determine the activation state of MAP kinase associated with HSP90. HSP90 proteins selectively associate with the inactive form of full-length tyrosine kinase growth factor receptor trkB, suggesting utilization during anterograde axonal transport. Activated MAP kinase, associated with the trk downstream signaling cascade, was found to co-immunoprecipitate with optic nerve HSP90, suggesting that HSP90 may be utilized in retrograde transport of the secondary messengers associated with neurotrophin signaling. HSP90 can thus be hypothesized to play a role in bidirectional RGC axonal protein transport.

Animals↗
PubMed2003

Imaging of non-parabolic velocity profiles in converging flow with optical coherence tomography.

The optical coherence tomography method was explored for two-dimensional flow mapping of a highly scattering fluid in flow with complex geometry. Converging flow (capillary entry) with 4:1 constriction was used for demonstration of non-invasive and remote methods of mapping varying velocity profiles. Downstream of the geometry was scanned with approximately 10 x 10 x 10 microm3 spatial resolution and structural imaging of the lumen and images of one particular velocity were acquired. Stable concave, blunted and parabolic profiles are obtained at different distances of the inlet length. Application of the technique for the blood circulation is also discussed.

Algorithms↗
PubMed2006

Clinical application of rapid serial fourier-domain optical coherence tomography for macular imaging.

PURPOSE: To introduce and examine the utility of a retinal imaging technique using high-speed optical coherence tomography (OCT) for creating a more complete retinal structural map to aid in the evaluation of patients with macular pathology. DESIGN: Prospective observational case series. PARTICIPANTS: Five patients with a variety of macular pathologies. METHODS: Patients were imaged with a Fourier-domain high-speed high-resolution OCT system built at our institution. A sweeping serial OCT B-scan of the macula was acquired to create a detailed retinal structural map. The data were then used to make individual clinical observations. RESULTS: Rapid serial OCT B-scans produced detailed macular maps for all 5 patients. Diagnoses of imaged patients included macular hole, lamellar macular hole, regressed macular hole or macular microhole, choroidal neovascular membrane (CNV) from age-related macular degeneration, and CNV from presumed ocular histoplasmosis syndrome. Reconstructed B-scans and C-scans are shown for selected patients to illustrate the additional perspectives gained by obtaining a detailed retinal map. CONCLUSIONS: Rapid serial Fourier-domain OCT B-scanning can be used to create a detailed retinal structural map. This technique provides additional information that can be missed on single OCT images and provides an accurate way to image large or complex lesions, and allows B-scan and C-scan reconstructions to be made that provide additional perspectives into retinal structures that may be missed using traditional imaging methods.

Adult↗