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At least 433 records · Page 24Linked to original sources
PubMed2005

Optical imaging of large-scale correlated wave activity in the developing rat CNS.

Correlated neuronal activity plays a fundamental role in the development of the nervous system. Using a multiple-site optical recording technique with a fast voltage-sensitive dye, we previously reported a novel form of correlated activity in the chick embryo, which showed wide propagation throughout the CNS. In this study, we report that similar wave activity is generated in the embryonic rat CNS. Electrical stimulation applied to the cervical cord evoked wave activity that traveled over a wide region of the CNS including the medulla, pons, midbrain, diencephalon, and spinal cord. Small signals were also detected from the cerebellum and part of the cerebrum. Stimulation applied to the cranial nerves such as the trigeminal and vagus nerves evoked waves with similar patterns, indicating that the wave is triggered by external sensory inputs. This wave activity was inhibited by glutamate-, acetylcholine-, GABA- and glycine-receptor antagonists in addition to gap junction blockers such as octanol and 18beta-glycyrrhetinic acid. In the immunohistochemical study, significant immunoreactivity of connexin26 and connexin32 was also observed. Wave activity detected with a voltage-sensitive dye was accompanied by a Ca(2+)-wave, indicating that it not only provides electrical synchrony but also biochemical signals associated with [Ca2+](i) elevation. These characteristics of the wave activity are similar to those of the depolarization wave reported in the chick embryo, suggesting that the large-scale depolarization wave is globally generated across different species.

2-Amino-5-phosphonovalerate↗
PubMed2000

Spatio-temporal analyses of stimulus-evoked and spontaneous stochastic neural activity observed by optical imaging in guinea pig auditory cortex.

Stimulus-evoked response in the cortex involves random neural activity besides the deterministic responses reproducible to the stimulus. Recently, we have developed a new bright optical system that enables us to investigate the spatio-temporal patterns of such stochastic activity in the guinea pig auditory cortex without averaging. We show that (1) the stochastic neural activity is evoked by a tone-stimulus in addition to the deterministic response, and spontaneous stochastic activity is also observed in a similar manner; (2) our statistical estimation of optical responses such as variance showed that the evoked stochastic activity was increased by the sound stimulus compared to the spontaneous activity; (3) both types of stochastic activity mainly display oscillatory behavior, in the frequency range of 5-11 Hz; (4) there are no significant differences between the stimulus-induced and spontaneous stochastic neural activity in our statistical analyses using the PSD (power-spectrum density) and the spatial correlation function; (5) the spatial area of the evoked stochastic activity is not strongly correlated with the tonotopical area of the deterministic response that is mainly localized in the caudal area of field A of the guinea pig auditory cortex. Thus, the stochastic neural activity existing in the stimulus response and the spontaneous activity in the auditory cortex are possibly generated by a common neural mechanism. These results were confirmed statistically using 27 animals.

Acoustic Stimulation↗
PubMed2001

Optical imaging of neural activity in multiple auditory cortical fields of guinea pigs.

Neural activity of multiple fields in the auditory cortex of anesthetized guinea pigs in response to pure tones was visualized by optical recording using a voltage-sensitive dye (RH795). Ten auditory fields were identified based on the tonotopic organization and response latency: the core fields consisting of the primary (AI) and secondary (AII) fields and surrounding belt areas consisting of dorso-anterior (DA), dorsal (D), dorso-posterior (DP), posterior (P), ventro-posterior (VP), ventro-medial (VM), ventro-anterior (VA) and ventral (V) fields. Tonotopic organization was observed in all the fields apart from DA, D, DP and V. Spatio-temporal displays suggest that the auditory information spreads from the core fields of AI and AII to belt fields via three distinct (dorsocaudal, caudal and ventrorostral) pathways.

Acoustic Stimulation↗
PubMed1987

Oscillatory movement displacement thresholds: resistance to optical image degradation.

Vernier acuity, under optimal conditions, appears remarkably resistant to image degradation. This characteristic has been used to assess neural function in cataract patients who exhibit poor spatial resolution. Conventional resolution tests fail to differentiate between neural and optical causes of visual loss. The oscillatory movement displacement threshold--the smallest amplitude of oscillation which gives rise to the perception of movement--provides an alternative hyperacuity test. This may offer advantages over vernier acuity. The effect of image defocus upon displacement thresholds for a sinusoidal contrast grating of spatial frequency 2 c deg-1 was investigated for high (15 Hz) and low (2 Hz) oscillation frequencies. With visible stationary references, subjects were more sensitive to oscillation frequencies of 2 Hz than to 15 Hz (F 1,9 = 33.34, p less than 0.005) whilst blur of up to 2 dioptres had no significant effect (F3,27 = 1.73, p greater than 0.1). Simulating media opacities by spatial degradation affected both grating acuity and contrast sensitivity functions, whilst displacement thresholds remained largely unaffected. Results suggest that oscillatory movement displacement thresholds may be of value in assessing ocular neural dysfunction in the presence of media opacities.

Cataract↗
PubMed2005

Simultaneous optical imaging of membrane potential and intracellular calcium.

Imaging of membrane potential (Vm) and intracellular calcium (Cai2+) is important for studying mechanisms of cardiac excitation, arrhythmias and defibrillation. We have developed an optical technique for simultaneous mapping of Vm and Cai2+ in cultured cell monolayers using fluorescent Vm- and Ca2+-sensitive dyes. Cultures of neonatal rat myocytes were double-stained with dyes RH-237 (Vm) and an analog of Fluo-3 or Rhod-2 dyes (Ca2+). These dyes have overlapping excitation spectra, allowing simultaneous excitation at the same wavelength range, and separate emission spectra allowing division of the fluorescent light into components sensitive to Vm and Cai2+, which were measured with two 16x16 photodiode arrays. It was found that Cai2+ measurements were strongly dependent on the properties of Ca2+-sensitive dyes. Thus, high-affinity Ca2+ dyes such as Fluo-4 and Rhod-2 reported Cai2+ transients approximately twice as long as those reported by low-affinity dyes Fluo-4FF and Rhod-FF. In addition, dyes with different affinities resulted in different measurements of Cai2+ responses to electrical shocks. When shocks were applied during the early plateau phase of the action potential, low-affinity dyes reported transient Cai2+ decreases at sites of both negative and positive Vm changes. In contrast, high-affinity Ca2+ dyes reported only a negligible change of plateau Cai2+ and a large elevation of diastolic Cai2+. These discrepancies between high- and low-affinity dyes were explained by a model of dye-ion interaction, which indicated that apparently long Cai2+ transients and Cai2+ responses to electrical shocks measured with high-affinity dyes were due to their non-linear response. These results indicate that optical measurements of Cai2+ transient duration and shock-induced Cai2+ changes require the use of low-affinity Cai2+ dyes.

Affinity Labels↗
PubMedDate not supplied

Real-time optical imaging of naturally evoked electrical activity in intact frog brain.

A major obstacle to understanding the function and development of the vertebrate brain is the difficulty in monitoring dynamic patterns of electrical activity in the millesecond time domain; this has limited investigations of such phenomena as modular organization of functional units, seizure activities and spreading depression. The use of voltage-sensitive dyes and the recent development of the use of an array of photodiodes has provided a unique technique for monitoring the dynamic patterns of electrical activity in real time from a variety of invertebrate or vertebrate neuronal preparations including the rat cortex. In the present study, this technique has been used to investigate the intact optic tectum of the frog. We demonstrate that optical measurements can be used for real-time imaging of spatio-temporal patterns of neuronal responses and for identification of functional units evoked by natural visual stimuli. We report also the structure of the new voltage-sensitive probe that facilitates the in vivo applications of this technique.

Animals↗
PubMed2005

Optical imaging and functional characterization of the transverse tubular system of mammalian muscle fibers using the potentiometric indicator di-8-ANEPPS.

Potentiometric dyes are useful tools for studying membrane potential changes from compartments inaccessible to direct electrical recordings. In the past, we have combined electrophysiological and optical techniques to investigate, by using absorbance and fluorescence potentiometric dyes, the electrical properties of the transverse tubular system in amphibian skeletal muscle fibers. In this paper we expand on recent observations using the fluorescent potentiometric indicator di-8-ANEPPS to investigate structural and functional properties of the transverse tubular system in mammalian skeletal muscle fibers. Two-photon laser scanning confocal fluorescence images of live muscle fibers suggest that the distance between consecutive rows of transverse tubules flanking the Z-lines remains relatively constant in muscle fibers stretched to attain sarcomere lengths of up to 3.5 microm. Furthermore, the combined use of two-microelectrode electrophysiological techniques with microscopic fluorescence spectroscopy and imaging allowed us to compare the spectral properties of di-8-ANEPPS fluorescence in fibers at rest, with those of fluorescence transients recorded in stimulated fibers. We found that although the indicator has excitation and emission peaks at 470 and 588 nm, respectively, fluorescence transients display optimal fractional changes (13%/100 mV) when using filters to select excitation wavelengths in the 530-550 nm band and emissions beyond 590 nm. Under these conditions, results from tetanically stimulated fibers and from voltage-clamp experiments suggest strongly that, although the kinetics of di-8-ANEPPS transients in mammalian fibers are very rapid and approximate those of the surface membrane electrical recordings, they arise from the transverse tubular system membranes.

Animals↗
PubMed2001

Functional connections between the HVC and the shelf of the zebra finch revealed by real-time optical imaging technique.

Auditory-motor interaction is essential for the understanding of avian song learning and maintenance. The HVC is thought to be the most important station for auditory-motor integration in the avian song system. However, little is known about where and how auditory inputs are conveyed into the HVC. The shelf, a multi-auditory recipient region located along the ventral border of the HVC, is thought to be a possible source of auditory inputs to the HVC. Here, we investigated the functional neural connections between the HVC and surrounding area of the HVC including the shelf in zebra finch brain slices, using the real-time optical recording technique. Unexpectedly electrical stimulation of the shelf region did not induce signal propagation into the HVC, but stimulation within the HVC propagated strong signals into the shelf. These results suggest that the shelf is the region that receives output signals from the HVC, rather than a major source of auditory inputs to the HVC.

2-Amino-5-phosphonovalerate↗
PubMed2001

Using optical imaging summary data to detect glaucoma.

PURPOSE: To evaluate the sensitivity and specificity for discriminating between early to moderate glaucomatous and normal eyes using summary data reports from the Heidelberg Retina Tomograph (HRT), the GDx Nerve Fiber Analyzer (GDx), and the Optical Coherence Tomograph (OCT). DESIGN: Comparative cross-sectional study PARTICIPANTS: One eye each of 50 normal subjects and 39 glaucoma patients with early to moderate visual field damage (mean deviation, -5.04 +/- 3.32 dB; range, -0.85 to -13.2 dB). METHODS: Three experienced graders masked to patient identity and diagnosis evaluated each summary data report from the HRT, GDx, and OCT independently. MAIN OUTCOME MEASURES: Each summary report was classified as either normal or glaucomatous. Sensitivity and specificity are reported for each grader, and agreement between graders is reported. RESULTS: For the HRT, sensitivity and specificity ranged from 64% to 75% and 68% to 80%, respectively. Agreement (kappa +/- standard error [SE]) between observers one and two, two and three, and one and three was 0.73 +/- 0.07, 0.77 +/- 0.07, and 0.67 +/- 0.08, respectively. For the GDx, sensitivity and specificity ranged from 72% to 82% and 56% to 82%, respectively. Agreement (kappa +/- SE) between observers one and two, two and three, and one and three was 0.66 +/- 0.08, 0.66 +/- 0.08, and 0.50 +/- 0.09, respectively. For the OCT, sensitivity and specificity ranged from 76% to 79% and 68% to 81%, respectively. Agreement (kappa +/- SE) between observers one and two, two and three, and one and three was 0.73 +/- 0.07, 0.58 +/- 0.08, and 0.51 +/- 0.09, respectively. CONCLUSIONS: When used alone, HRT, GDx, and OCT summary data reports can differentiate between normal and glaucomatous eyes with mild to moderate visual field loss. However, none of the instruments provided sensitivity and specificity that justify summary data reports being used as a screening tool for early to moderate glaucoma.

Adult↗
PubMed1993

Optical imaging of cytosolic calcium, electrophysiology, and ultrastructure in pyramidal neurons of organotypic slice cultures from rat hippocampus.

Organotypic slice cultures from rat hippocampal cortex grown in an interface between culture medium and a CO2-enriched atmosphere maintained much of the morphological connectivity characteristic of the hippocampus in situ and thinned out considerably, facilitating optical measurements of fluorescent dyes sensitive to Ca2+ in individual neurons. Pyramidal neurons of the CA3 region presented morphological features of differentiated cells, including complex dendritic arborization and large numbers of dendritic spines. The fine cytoskeletal substructure at the postsynaptic density, below the plasma membrane, and within the core of the head and neck of dendritic spines in rapidly frozen slice cultures presents the characteristic morphology previously described for Purkinje cell dendritic spines in acutely dissected cerebellar cortex slices after rapid freezing. CA3 neurons responded to intracellular current injection with a train of action potentials, spike frequency adaptation, and a slow afterhyperpolarization. These spike trains caused rapid increases in dendritic [Ca2+]i that decayed to resting levels after termination of the current pulse. Dendritic spines were clearly observed in proximal dendrites of CA3 neurons in live preparations. [Ca2+]i transients in these dendritic spines closely followed the changes observed in the main dendritic shaft. Orthodromic synaptic stimulation from the dentate hilus generated long-lasting synaptic potentials accompanied by large [Ca2+]i transient in CA3 pyramidal neurons. The [Ca2+]i response was first observed in the proximal dendrites, after which the soma exhibited a [Ca2+]i increase, returning to resting levels within 10 s after the synaptic stimulus. Slice cultures thus provide a favorable opportunity to investigate [Ca2+]i responses in individual neurons maintained in an organotypic synaptic environment, taking advantage of high-resolution optical techniques.

Animals↗
PubMed1995

Temporal coding in the guinea-pig auditory cortex as revealed by optical imaging and its pattern-time-series analysis.

The neural network structure of a guinea-pig's primary auditory cortex is estimated by applying pattern-time-series analysis to the auditory evoked responses. Spatiotemporal patterns in click-evoked responses, observed by optical recording with voltage-sensitive dye, are analyzed by time series analysis using a multivariable autoregressive (MAR) model. Oscillatory neural activities with a distribution of about 10 approximately 40 Hz in the click-induced evoked responses are found in the cortical response field. The cortical regions where the distributed neural oscillations are generated are identified by pattern-time-series analysis. In addition, two types of cortico-cortical connections, unilateral and bilateral connections between the cortical points, are speculated to be the causes of oscillatory neural activity transfer. It can be said that the so-called synchronized neural oscillation, in the sense of coherency or correlation between the two evoked responses at the oscillatory frequency, does not necessarily represent real cortico-cortical neural connections at the evoked response points.

Animals↗
PubMed2005

Synthesis, in vitro, and in vivo characterization of an integrin alpha(v)beta(3)-targeted molecular probe for optical imaging of tumor.

Integrin alpha(v)beta(3) is a widely-recognized target for the development of targeted molecular probes for imaging pathological conditions. alpha(v)beta(3) is a cell-surface receptor protein that is upregulated in various pathological conditions including osteoporosis, rheumatoid arthritis, macular degeneration, and cancer. The synthesis of an alpha(v)beta(3)-targeted optical probe 7 from compound 1, and its in vitro and in vivo characterization is described. A series of aliphatic carbamate derivatives of the potent non-peptide integrin antagonist 1 was synthesized and the binding affinity to alpha(v)beta(3) was determined in both enzyme linked immunosorbent assay (ELISA) and cell adhesion inhibition assays. The hydrophobic carbamate-linked appendages improved the binding affinity of the parent compound for alpha(v)beta(3) by 2-20 times. A Boc-protected neopentyl derivative in the series is shown to have the best binding affinity to alpha(v)beta(3) (IC(50)=0.72 nM) when compared to compound 1 as well as to c-RGDfV. Optical probe 7 utilizes the neopentyl linker and demonstrates increased binding affinity and significant tumor cell uptake in vitro as well as specific tumor accumulation and retention in vivo. These results illustrate the potential of employing integrin-targeted molecular probes based on 1 to image a multitude of diseases associated with alpha(v)beta(3) overexpression.

Animals↗
PubMed1996

Optical imaging of spatiotemporal patterns of glutamatergic excitation and GABAergic inhibition in the guinea-pig auditory cortex in vivo.

1. Glutamatergic excitation and gamma-aminobutyric acid (GABA)-ergic inhibition in layers II and III of the auditory cortex of anaesthetized guinea-pigs were recorded optically using a voltage-sensitive dye RH795 and a 12 x 12 photodiode array. 2. After contralateral ear stimulation with pure tones, transient excitatory responses followed by inhibitory responses were observed in fields A (primary) and DC of the auditory cortex. The area of the excitatory responses was sandwiched or surrounded by the areas of the inhibitory responses. 3. Optically recorded excitatory responses to pure tones had two components: a component sensitive to 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-N-methyl-D-aspartate (non-NMDA) receptor antagonist, and a component sensitive to 2-amino-5-phosphono-valerate (APV), an NMDA receptor antagonist. Application of CNQX (5 microM) to the auditory cortex suppressed an early, but not a late, phase of the excitation; application of APV (100 microM) had the opposite effect. Concomitant application of CNQX and bicuculline methiodide (BMI, 4 microM), a GABAA receptor antagonist, increased the amplitude of the late phase 4-fold. This enhanced response was suppressed by APV. 4. These results indicate that (i) auditory cortical excitatory responses are mediated by both non-NMDA and NMDA receptors, (ii) inhibition is mediated by GABAA receptors, (ii) the excitatory bands are sandwiched or surrounded by GABAA receptor-mediated inhibitory areas and (iv) GABAA receptors effectively inhibit the NMDA, but not the non-NMDA, receptor-mediated excitation.

2-Amino-5-phosphonovalerate↗