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At least 1,567 records · Page 87Linked to original sources
PubMed2001

No evidence for early decrease in blood oxygenation in rat whisker cortex in response to functional activation.

Using optical methods through a closed cranial window over the rat primary sensory cortex in chloralose/urethane-anesthetized rats we evaluated the time course of oxygen delivery and consumption in response to a physiological stimulus (whisker deflection). Independent methodological approaches (optical imaging spectroscopy, single fiber spectroscopy, oxygen-dependent phosphorescence quenching) were applied to different modes of whisker deflection (single whisker, full whisker pad). Spectroscopic data were evaluated using different algorithms (constant pathlength, differential pathlength correction). We found that whisker deflection is accompanied by a significant increase of oxygenated hemoglobin (oxy-Hb), followed by an undershoot. An early increase in deoxygenated hemoglobin (deoxy-Hb) proceeded hyperoxygenation when spectroscopic data were analyzed by constant pathlength analysis. However, correcting for the wavelength dependence of photon pathlength in brain tissue (differential pathlength correction) completely eliminated the increase in deoxy-Hb. Oxygen-dependent phosphorescence quenching did not reproducibly detect early deoxygenation. Together with recent fMRI data, our results argue against significant early deoxygenation as a universal phenomenon in functionally activated mammalian brain. Interpreted with a diffusion-limited model of oxygen delivery to brain tissue our results are compatible with coupling between neuronal activity and cerebral blood flow throughout stimulation, as postulated 110 years ago by C. Roy and C. Sherrington (1890, J. Physiol. 11:85--108).

Animals↗
PubMed2002

Changes in blood flow, oxygenation, and volume following extended stimulation of rodent barrel cortex.

Simultaneous optical imaging spectroscopy and laser-Doppler flowmetry were used in rodent barrel cortex to examine the hemodynamic response to extended electrical stimulation (20 s, 5 Hz) of the whisker pad. Stimulation results in a fast early increase in deoxyhemoglobin concentration (Hbr) followed by a later decrease to a "plateau" phase approximately 4 s after stimulation onset. There was no corresponding decrease in oxyhemoglobin (HbO(2)), which simply increased after stimulation, reaching a plateau at approximately 5 s. The time series of flow and volume had similar onset times and did not differ significantly throughout the presentation of the stimuli. Following stimulation cessation all aspects of the hemodynamic response returned to baseline with a long decay constant (>20 s), CBV doing so at a slower rate than CBF. The time courses of CBF, CBV, Hbr, and HbO(2) were very similar to that produced by a brief stimulus up to peak. The relationship between the flow and the volume changes is well approximated by the expression CBV = CBF(phi). We find phi to be slightly lower under stimulation (0.26 +/- 0.0152) than during hypercapnia (0.32 +/- 0.0172). Saturation and flow data were used to estimate changes in CMRO(2) for a range of baseline oxygen extraction fractions (OEF). In the case of hypercapnia CMRO(2) was biphasic, increasing after onset and sharply decreasing below baseline following cessation. If it is assumed that there is no "net" increase in CMRO(2) (i.e., SigmaDeltaCMRO(2) = 0) following the onset and offset of hypercapnia, then the corresponding estimate of baseline OEF is 0.45. Evidence for increased oxygen consumption was obtained for all stimulation intensities assuming a baseline OEF of 0.45.

Animals↗
PubMed1997

Population behavior and self-organization in the genesis of spontaneous rhythmic activity by developing spinal networks.

During development spinal networks generate recurring episodes of rhythmic bursting that can be recorded from motoneurons and interneurons. Optical imaging has identified a set of propriospinal interneurons that may be important in the production of this activity. These neurons are rhythmically active, are recurrently interconnected and have powerful projections to motoneurons. The excitability of this propriospinal network is depressed by activity and recovers in the interval between episodes. These and other observations have been formulated into a qualitative model in which population behavior and self-organization are responsible for the spontaneous activity generated by developing spinal networks.

Journal Article↗
PubMed1997

Evaluation of DNA "fingerprinting" for predicting the potential of E. coli O157:H7 isolates to cause hemolytic uremic syndrome (HUS).

Escherichia coli O157:H7 has been recognized since 1982 as a serious human pathogen spread by contaminated food and water. Pulsed-field gel electrophoresis has proven useful for identification of specific isolates/strains of this organism. Hemolytic uremic syndrome (HUS), generally occurring in children or the aged, is the most severe sequela associated with E. coli O157:H7 infection. The presently described work was designed to compare the genomic profile of isolates known to have caused HUS with those having had no such involvement. We asked the question: "Can we develop the means to recognize an 'HUS-prone' E. coli isolate and thereby alert medical personnel to the increased risk?" Twenty-two HUS-related and 10 HUS-unrelated E. coli O157:H7 samples were chosen for genomic analysis. Isolates were cultured overnight prior to being embedded in agarose gel plugs. Plugs were digested, using Xbal restriction endonuclease, and subjected to pulsed-field gel electrophoresis (PFGE) for 20 hours. Gels were stained with ethidium bromide, photographed under ultraviolet light, and Southern blotted. Radiolabeled toxin gene probes were used for hybridization assays. The two classes of isolates were compared by optical imaging software. A computer-generated dendrogram, based on restriction profiles, offered strong initial evidence that the HUS sequela may be produced by a particularly virulent and identifiable clone. The predictive value of this finding appears to be substantial.

DNA Fingerprinting↗
PubMed2006

Multiphoton laser scanning microscopy as a tool for Xenopus oocyte research.

Multiphoton laser scanning microscopy (MPLSM) has become an increasingly invaluable tool in fluorescent optical imaging. There are several distinct advantages to implementing MPLSM as a Xenopus oocyte research tool. MPLSM increases signal-to-noise ratio and therefore increases image quality because there is no out-of-focus fluorescence as would be created in conventional or confocal microscopy. All the light that is generated can be collected and used to generate an image because point detection of descanned fluorescence is not required. This is particularly useful when imaging deep into tissue sections, as is necessary for Xenopus oocytes, which are notoriously large (approximately 1-mm diameter). Because multiphoton lasers use pulsed energy in the infrared wavelengths, the energy can also travel further into tissues with much less light scattering. Because there is no out-of-focus excitation, phototoxicity, photodamage, and photobleaching are significantly reduced, which is particularly important for long-term experiments that require the same region to be scanned repeatedly. Finally, multiple fluorophores can be simultaneously excited because of the broader absorption spectra of multiphoton dyes. In this chapter, we describe the advantages and disadvantages of using MPLSM to image Xenopus oocytes as compared to conventional and confocal microscopy. The practical application of imaging oocytes is demonstrated with specific examples.

Animals↗
PubMed1982

Reading and the ophthalmologist. An introduction into the complex phenomenon of ordinary reading as a guideline for analysis and treatment of disabled readers.

Reading problems are a frequent source of complaint in ophthalmological practice. In many cases suitable optical correction is all that is needed. However, difficulties may remain despite adequate optical correction. This paper describes visual reading processes with the aim of making such difficulties understood and, if possible, providing remedies. Four different types of visual reading processes are distinguished: (a) optical imaging, (b)eye movement control, (c) visual word recognition and (d) integration of information across eye fixations. Next the attempt is made to use our insight to obtain a better understanding of actual reading problems, such as those of elderly readers, low-vision patients, and dyslexics as well as those of the blind. Therapeutic options, including visual aids are given due attention.

Accommodation, Ocular↗
PubMed1987

A method of measuring pupil-blocking force in the human eye.

A new method of measuring pupil-blocking force in the human eye is reported. The anterior segment of the eye was photographed using a slit-lamp apparatus and the color photographs then analyzed with a digitizer for converting the optical image of the anterior eye segment into the true image using a computer. This technique permits precise estimation of the relative positions of the anterior chamber, such as pupil margins, iris root insertions, and central anteroposterior pupillary axis. Pupil-blocking force was calculated from these data according to Hook's law. There was a statistically significant difference in pupil-blocking force between normal subjects (mean +/- SD, -0.027 +/- 0.029 lambda; lambda = Young's module) and patients with primary angle-closure glaucoma (mean +/- SD, +0.134 +/- 0.068 lambda) (P less than 0.001). In patients with primary angle-closure glaucoma, during an acute attack the pupil-blocking force was markedly high. This technique for measuring pupil-blocking force will provide valuable data for the analysis of the mechanism of primary angle-closure glaucoma.

Aged↗
PubMed1986

Retinoic acid enhances and depresses in vitro development of cartilaginous bone anlagen in embryonic mouse limbs.

Forelimbs of Day 11 and Day 12 embryonic mice were excised and cultured for 3 d in the presence of either 0.25 microgram (8 X 10(-7) M), 0.5 microgram (1.7 X 10(-6) M), or 1.0 microgram (3.3 X 10(-6) M) of all-trans retinoic acid (RA) per milliliter of culture medium. Cultured limbs were fixed, stained, and mounted whole on glass slides and evaluated with computerized optical image analysis for RA-induced effects on the area and shape of the total limb and individual bone anlagen. Relative effects of RA on total bone, soft tissue, long bone, and paw regions were also examined. With Day 11 forelimbs total bone area was increased by 10.5% by the low dose of RA. The increase was mostly in long bones and at the expense of soft tissue. Total bone area was increased 9.3% with Day 12 forelimbs. This increase was primarily in the paw. The high dose of RA decreased Day 11 forelimb area, primarily affecting long bones. Day 12 forelimbs were not significantly affected by the high dose of RA. Effects of the intermediate dose were primarily limited to reduction in soft tissue area. Long bone:paw and soft tissue:bone ratios reflected these effects. The high dose produced a consistent rounding or shortening of Day 11 forelimb bones. On Day 12 0.5 microgram/ml RA produced an inconsistent pattern of rounding of bone anlagen. Treatment with the high dose on Day 12 produced angular rather than rounded contours in many cases, as indicated by shape factor values closer to zero than obtained with controls. These data show that direct exposure to RA can affect both the size and shape of bone anlagen of the developing limb; the low dose enhances and the high dose depresses development. The results support previous studies which suggest that RA may play a critical role in the control of cell activities such as cell migration, proliferation, and cytodifferentiation in the development of the cartilaginous bone anlagen.

Animals↗
PubMed2003

Blockade of astrocyte metabolism causes delayed excitation as revealed by voltage-sensitive dyes in mouse brainstem slices.

Fluoroacetate is known to block cell metabolism and to change potassium conductances selectively in astrocytes. In a functional neuronal network with ongoing activity, we investigated the effects of such a blockade of the astrocytic metabolism by fluoroacetate on neuronal signal propagation. Transverse 400- microm slices were prepared from the caudal medulla of mice of postnatal day 3-8, which contained the hypoglossal nucleus receiving excitatory synaptic input from the ventral respiratory group. Propagation of excitation within this network was measured by optical imaging using the voltage-sensitive dye RH 795. A 464-element photodiode array allowed fast recordings of voltage changes within a small population of cells. The spatial and temporal resolution was advanced to 32 microm and 1.27 ms, respectively. Changes of cellular membrane potential levels were expressed as relative changes of fluorescence (DeltaI/I). Stimulus-evoked excitation of neurons propagating from the ventral respiratory group to the hypoglossal nucleus peaked after 7.2+/-0.6 ms ( n=6). The latency of this early excitatory response is consistent with the time course of stimulus-evoked EPSPs in whole-cell recordings. Mean changes of fluorescence in the hypoglossal nucleus were -2.1+/-0.5 x 10(-3) (DeltaI/I). After incubation in 1 mM fluoroacetate, the early depolarization was reduced to 69.1+/-9.8% of control ( n=6, p=0.034). Additionally, fluoroacetate induced a delayed excitatory response, such that fluorescence intensity did not return to baseline within 1s. Propagation velocity and spatial distribution of the voltage signal were not affected by fluoroacetate. Our results suggest that blockade of astrocyte metabolism impairs fast synaptic transmission and induces a delayed excitation, probably resulting from the combination of reduced repolarization of neurons and persistent depolarization of astrocytes.

Animals↗
PubMed2005

Effect of body weight support on cortical activation during gait in patients with stroke.

Treadmill training with body weight support (BWS) was shown to improve locomotion after stroke. We investigated whether BWS affected cortical activation during gait using an optical imaging system. In six patients with subcortical stroke, BWS lowered activation in the sensorimotor cortex (SMC) as assessed by task-related changes of oxygenated hemoglobin levels (P<0.01). The changes of SMC activation correlated with those of cadence (P<0.05). Improvement of asymmetry in SMC activation also correlated with improvement of asymmetric gait (P<0.05). In five age-matched controls, BWS increased overall activation (P<0.05) but did not modify gait parameters and there was no correlation between gait parameters and SMC activation. It is suggested that BWS might improve efficacy of SMC function in patients with stroke.

Adult↗
PubMed2005

Initiation of sodium spikelets in basal dendrites of neocortical pyramidal neurons.

Cortical information processing relies critically on the processing of electrical signals in pyramidal neurons. Electrical transients mainly arise when excitatory synaptic inputs impinge upon distal dendritic regions. To study the dendritic aspect of synaptic integration one must record electrical signals in distal dendrites. Since thin dendritic branches, such as oblique and basal dendrites, do not support routine glass electrode measurements, we turned our effort towards voltage-sensitive dye recordings. Using the optical imaging approach we found and reported previously that basal dendrites of neocortical pyramidal neurons show an elaborate repertoire of electrical signals, including backpropagating action potentials and glutamate-evoked plateau potentials. Here we report a novel form of electrical signal, qualitatively and quantitatively different from backpropagating action potentials and dendritic plateau potentials. Strong glutamatergic stimulation of an individual basal dendrite is capable of triggering a fast spike, which precedes the dendritic plateau potential. The amplitude of the fast initial spikelet was actually smaller that the amplitude of the backpropagating action potential in the same dendritic segment. Therefore, the fast initial spike was dubbed "spikelet". Both the basal spikelet and plateau potential propagate decrementally towards the cell body, where they are reflected in the somatic whole-cell recordings. The low incidence of basal spikelets in the somatic intracellular recordings and the impact of basal spikelets on soma-axon action potential initiation are discussed.

Action Potentials↗
PubMed2003

Olfactory activation patterns in the antennal lobe of the sphinx moth, Manduca sexta.

The sphinx moth Manduca sexta is a well-studied insect with regard to central olfactory functions. Until now, the innervation patterns of olfactory receptor neurons into the array of olfactory glomeruli in the antennal lobe have, however, been unclear. Using optical imaging to visualize calcium dynamics within the antennal lobe we demonstrate specific patterns elicited by sex pheromone components and plant-derived odours. These patterns mainly reflect receptor neuron activity. Within the male-specific macroglomerular complex the two major pheromone components evoke stereotyped activity in either of two macroglomerular complex glomeruli. Based on previous knowledge of output neuron specificity, our results suggest a matching of information between input and output in the macroglomerular complex. Plant odours evoked activity in the sexually isomorphic glomeruli. Two major results were obtained: (1). terpenes and aromatic compounds activate different clusters of glomeruli with only minor overlapping, and (2). the position of certain key glomeruli is fixed in both males and females, which suggests that host-plant related odorants are processed in a similar way in both sexes.

Animals↗
PubMed2003

Co-ordination of Ca(2+) signalling in mammalian cells by the new Ca(2+)-releasing messenger NAADP.

Ca(2+) signalling is one of the most important means in mammalian cells of relaying the action of hormones and neurotransmitters. The great diversity of agonist-induced Ca(2+) signatures, visualized by optical imaging techniques, can be explained by the production of intracellular messengers triggering Ca(2+) release from internal stores and/or by different coupling of Ca(2+) release to Ca(2+) entry. Several messengers, such as inositol trisphosphate and cyclic ADP-ribose, have been identified to date. More recent studies have reported the important role of a newly discovered Ca(2+) releasing messenger, nicotinic acid adenine dinucleotide phosphate (NAADP). These studies have shown important interactions of these messengers in the generation of specific Ca(2+) signals. NAADP acts at a very low concentration and seems to have a key role in sensitising cyclic ADP-ribose and inositol trisphosphate receptors. These points will be discussed in the present review.

Animals↗
PubMed2004

Quantitative analysis of granule cell axons and climbing fiber afferents in the turtle cerebellar cortex.

The turtle cerebellar cortex is a single flat sheet of gray matter that greatly facilitates quantitative analysis of biotylinated dextran amine labeled granule cell and olivocerebellar axons and Nissl-stained granule and Purkinje neurons. On average, ascending granule cell axons are relatively thicker than their parallel fiber branches (mean +/- SD: 0.84 +/- 0.17 vs 0.64 +/- 0.12 microm, respectively). Numerous en passant swellings, the site of presynaptic contact, were present on both ascending and parallel fiber granule cell axons. The swellings on ascending axons (1.82 +/- 0.34 microm, n = 52) were slightly larger than on parallel fibers (1.43 +/- 0.24 microm, n = 430). In addition, per unit length (100 microm) there were more swellings on ascending axons (11.2 +/- 4.2) than on parallel fibers (9.7 +/- 4.2). Each parallel fiber branch from an ascending axon is approximately 1.5 mm long. Olivocerebellar climbing fiber axons followed the highly tortuous dendrites of Purkinje cells in the inner most 15-20% of the molecular layer. Climbing fibers displayed relatively fewer en passant swellings. The spatial perimeter of climbing fiber arbors (area) increased 72% from anteriorly (1797 microm2) to posteriorly (3090 microm2) and 104% from medially (1690 microm2) to laterally (3450 microm2). Differences in the size and spacing of en passant swellings on granule cell axons suggest that ascending axons may have a functionally more significant impact on the excitability of a limited number of radially overlying Purkinje cells than the single contacts by parallel fiber with multiple orthogonally aligned Purkinje cell dendrites. The spatially restricted distribution of climbing fibers to the inner most molecular layer, the paucity of en passant swellings, and different terminal arbor areas are enigmatic. Nevertheless, these finding provide important anatomical information for future optical imaging and electrophysiological experiments.

Afferent Pathways↗
PubMed2005

Increased DNA breaks and up-regulation of both G(1) and G(2) checkpoint genes p21(WAF1/CIP1) and 14-3-3 sigma in circulating leukocytes of glaucoma patients and vasospastic individuals.

OBJECTIVE: Vascular disorder leading to local ischemia/reperfusion has been shown to play an important role in the glaucomatous damage. A decreased expression level of XPGC-gene has been found in circulating leukocytes of normal-tension glaucoma patients. Although decreased activity of XPGC-gene leads to insufficient DNA-repair, no leukopenia has been observed in glaucoma. Molecular mechanisms ensuring cell survival have not been elucidated yet for glaucoma with vascular disorder. MATERIAL AND METHODS: Using the ex vivo optical imaging method of alkaline "comet assay" comparative quantification of DNA breaks was performed in circulating leukocytes of non-glaucomatous non-vasospastic and vasospastic individuals as well as both normal-tension and high-tension glaucoma patients. Relative expression levels of the anti-apoptotic factors P21(WAF1/CIP1) and 14-3-3 sigma were investigated in all groups tested. RESULTS AND CONCLUSIONS: The quantification of P21(WAF1/CIP1) showed the highest expression rates in high-tension glaucoma patients which were significantly higher than those in all other groups tested. The highest expression rates of 14-3-3 sigma were found in both groups of glaucoma patients. These expression levels correlated well with DNA breaks measured. Since the expression of P21(WAF1/CIP1) in leukocytes was shown to be crucial for their survival under stress conditions, we suppose further that the up-regulation of this gene is the key event in the survival mechanisms of leukocytes in glaucoma accompanied with vascular disorder. The p21(WAF1/CIP1) gene should be further taken into consideration as a potential marker, the up-regulation of which in circulating leukocytes of vasospastic individuals may indicate an increased risk for the developing glaucoma.

14-3-3 Proteins↗
PubMed2006

Neural network model of the primary visual cortex: from functional architecture to lateral connectivity and back.

The role of intrinsic cortical dynamics is a debatable issue. A recent optical imaging study (Kenet et al., 2003) found that activity patterns similar to orientation maps (OMs), emerge in the primary visual cortex (V1) even in the absence of sensory input, suggesting an intrinsic mechanism of OM activation. To better understand these results and shed light on the intrinsic V1 processing, we suggest a neural network model in which OMs are encoded by the intrinsic lateral connections. The proposed connectivity pattern depends on the preferred orientation and, unlike previous models, on the degree of orientation selectivity of the interconnected neurons. We prove that the network has a ring attractor composed of an approximated version of the OMs. Consequently, OMs emerge spontaneously when the network is presented with an unstructured noisy input. Simulations show that the model can be applied to experimental data and generate realistic OMs. We study a variation of the model with spatially restricted connections, and show that it gives rise to states composed of several OMs. We hypothesize that these states can represent local properties of the visual scene.

Action Potentials↗
PubMed2006

Probing the microenvironment of mammary tumors using multiphoton microscopy.

Advances in optical imaging technologies that allow the subcellular resolution of undissected tissue have begun to offer new clues into the biology of development and disease. For cancer, such advances mean that the primary tumor is no longer a black box and that the disease can be studied throughout the metastatic cascade and not just as an endpoint. In this review we examine the advances in multiphoton imaging technology that have been used to define the microenvironment and its role in delineating the invasion and intravasation steps of metastasis inside living mammary tumors. Results show that the tumor microenvironment is a dynamic place where interactions between tumor cells, macrophages, blood vessels, and extracellular matrix fibers define the metastatic phenotype.

Animals↗
PubMed2002

New approaches to lung cancer prevention.

Lung cancer is the most common cause of cancer death worldwide. The overall 5-year survival rate remains disappointing at 14% or less. Several clinician- and community-based interventions show promise for reducing lung cancer incidence through prevention and smoking cessation. However, long-term heavy smokers retain a significant lung cancer risk despite smoking cessation. Half of newly diagnosed lung cancers are now found in former smokers. An additional strategy of lung cancer control through chemoprevention needs to be developed. Advances in optical imaging technologies and genome science will continue to improve our ability to identify individuals with the highest risk of lung cancer for chemoprevention. More accurate surrogate endpoint biomarkers are becoming available for phase II trials of new agents. A number of promising agents are currently being tested in phase II and III trials for prevention of lung cancer.

Animals↗