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At least 307 records · Page 17Linked to original sources
PubMed2006

Manual control of the visual stimulus reduces the flash-lag effect.

We investigated how observers' control of the stimulus change affects temporal aspects of visual perception. We compared the flash-lag effects for motion (Experiment 1) and for luminance (Experiment 2) under several conditions that differed in the degree of the observers' control of change in a stimulus. The flash-lag effect was salient if the observers passively viewed the automatic change in the stimulus. However, if the observers controlled the stimulus change by a computer-mouse, the flash-lag effect was significantly reduced. In Experiment 3, we examined how observers' control of the stimulus movement by a mouse affects the reaction time for the shape change in the moving stimulus and flash. Results showed that the control reduced the reaction time for both moving stimulus and flash. These results suggest that observers' manual control of the stimulus reduces the flash-lag effect in terms of facilitation in visual processing.

Adult↗
PubMed2006

Cyclopean flash-lag illusion.

Possible physiological mechanisms to explain the flash-lag effect, in which subjects perceive a flashed item that is co-localized with a moving item as trailing behind the moving item, have been found within the retina of lower species, and in the motor pathways of humans. Here, we demonstrate flash-lag employing "second-order" moving and flashed stimuli, defined solely by their binocular-disparity, to circumvent any possible "early" contributions to the effect. A significant flash-lag effect was measured with cyclopean stimuli composed entirely of correlated random dot patterns. When the disparity-defined moving stimulus was replaced with a luminance-defined one, potentially engaging retinal mechanisms, the magnitude of the measured effect showed no significant change. Thus, in primates, though retinal mechanisms may contribute, flash-lag must be explained through cortical processes.

Adaptation, Ocular↗
PubMed2001

Change in feature space is not necessary for the flash-lag effect.

To achieve perceptual match between a flashed target and a gradually changing one, the flashed target should have the feature value corresponding to the value to be obtained by the gradually changing target only later. Flashed target should be positioned ahead of the continuously moving one in order to be perceived as aligned (Nijhawan (1994). Nature, 370, 256-257); with continuously changing colour, spatial frequency, pattern entropy or luminance, the flashed target should have feature value which changing target obtains only later (Sheth, Nijhawan, & Shimojo (2000). Nature Neuroscience, 3, 489-495). It was found that flash-lag effect is present even if the continuously accumulating pre- and post-target input consists in spatially and featurally invariant stimulation. The perceptual precedence of the target in stream over its synchronous single-flashed replica may result from perceptual acceleration where newly arriving visual signals are facilitated by the locally preceding stimulation.

Humans↗
PubMed1996

A simplified and rapid procedure for in situ hybridization on human, flash-frozen, post-mortem brain and its combination with immunohistochemistry.

A simplified and rapid method is described for in situ hybridization (ISHH) studies of human post-mortem brain. Brain tissue was dissected into slices and was flash-frozen at -70 degrees C for storage. ISHH was carried out on 12 microns cryostat sections, post-fixed in 4% paraformaldehyde. The histology of human brain tissue prepared by this technique rivalled that of formalin-fixed, wax-embedded tissue. In ISHH studies, flash-frozen tissue gave superior results to those obtained following long-term fixation of tissue in 10% formalin with subsequent wax-embedding, or short-term prefixation in 4% paraformaldehyde. A systematic evaluation of commonly employed preparative procedures for ISHH was carried out on flash-frozen brain and a simplified protocol, consisting only of fixation and dehydration, was developed as a result of these studies. Specific hybridization of probes to a number of mRNA species was demonstrable in neurons in different brain regions. Using 0.5% glutaraldehyde/4% paraformaldehyde post-fixation, immunohistochemical labelling of TH-positive cortical catecholaminergic neurons and striatal dopaminergic terminals was successfully demonstrated in flash-frozen tissue. The same fixation technique also allowed combination of ISHH and immunohistochemistry for the simultaneous demonstration of tyrosine hydroxylase mRNA and peptide in neurons of human brain stem and cortex. mRNA and peptides in flash-frozen tissue were found to be stable for more than 3 years. ISHH could be readily performed on relatively large brain structures. In addition to permitting excellent ISHH and immunohistochemistry, alone or in combination, flash-freezing allows the maximum versatility of tissue use and does not compromise its study by other neuroscience techniques.

Aged↗
PubMed2003

The prediction of the flash point for binary aqueous-organic solutions.

A mathematical model, which may be used for predicting the flash point of aqueous-organic solutions, has been proposed and subsequently verified by experimentally-derived data. The results reveal that this model is able to precisely predict the flash point over the entire composition range of binary aqueous-organic solutions by way of utilizing the flash point data pertaining to the flammable component. The derivative of flash point with respect to composition (solution composition effect upon flash point) can be applied to process safety design/operation in order to identify as to whether the dilution of a flammable liquid solution with water is effective in reducing the fire and explosion hazard of the solution at a specified composition. Such a derivative equation was thus derived based upon the flash point prediction model referred to above and then verified by the application of experimentally-derived data.

Fires↗
PubMed1997

Differential diagnosis of hot flashes.

OBJECTIVE: The purpose of this study is to present the physiology and differential diagnosis of hot flashes, other than associated with menopause, in order to facilitate the proper evaluation of symptomatic patients with hot flashes. STUDY DESIGN: Literature search using Med-Line computer access. RESULTS: Interest in flushing reaction began in historic times. With the rapidly expanding population of women over the age of 45 and prevalence of hot flashes as menopausal symptoms, physicians need to be aware of other medical conditions which may mimic hot flashes. These include flushing due to systemic diseases, carcinoid syndrome, systemic mast cell disease, pheochromocytoma, medullary carcinoma of the thyroid, pancreatic islet-cell tumors, renal cell carcinoma, neurological flushing, emotional flushing, spinal cord injury, flushing reaction related to alcohol and drugs, flushing associated with food additives and eating. CONCLUSION: There is a wide variety of disease processes that can cause hot flashes. Knowledge of the nature of these disease processes is necessary for quick recognition of patients with hot flashes who do not respond to estrogen replacement treatment, and to facilitate the proper evaluation of atypical patients.

Body Temperature Regulation↗
PubMed2002

FTIR detection of water reactions during the flash-induced S-state cycle of the photosynthetic water-oxidizing complex.

Photosynthetic water oxidation is performed via the light-driven S-state cycle in the water-oxidizing complex (WOC) of photosystem II (PS II). To understand its molecular mechanism, monitoring the reaction of substrate water in each S-state transition is essential. We have for the first time detected the reactions of water molecules in WOC throughout the S-state cycle by observing the OH vibrations of water using flash-induced Fourier transform infrared (FTIR) difference spectroscopy. Moderately hydrated (or deuterated) PS II core films from Synechococcus elongatus were used to obtain the FTIR difference spectra upon the first, second, third, and fourth flash illumination, representing the structural changes in the S(1) --> S(2), S(2) --> S(3), S(3) --> S(0), and S(0) --> S(1) transitions, respectively. In the weakly H-bonded OH region, bands appeared at 3617/3588 cm(-1) as a differential signal in the first-flash spectrum and at 3634, 3621, and 3612 cm(-1) with negative intensities in the second-, third-, and fourth-flash spectra, respectively. These bands shifted down by approximately 940 cm(-1) upon deuteration and by approximately 10 cm(-1) upon H(18)O substitution, indicating that they arise from the OH stretches of water including the substrate and its intermediates. Strongly D-bonded OD bands of water were also identified as broad features in the range of 2600-2200 cm(-1) by taking the double difference between the spectra of D(2)(16)O- and D(2)(18)O-deuterated films. In addition, broad continuum features that probably arise from the large proton polarizability of H-bonds were observed around 3000, 2700, 2550, and 2600 cm(-1) in the first-, second-, third-, and fourth-flash spectra, respectively, of the hydrated PS II film, revealing changes in the H-bond network of the protein. The negative OH intensities upon the second to fourth flashes might be related to proton release from substrate water. The results presented here showed that FTIR detection of water OH(D) bands can be a powerful method for investigating the mechanism of photosynthetic water oxidation.

Cyanobacteria↗
PubMed2001

Perceptual organization of moving stimuli modulates the flash-lag effect.

When a visual stimulus is flashed at a given location the moment a second moving stimulus arrives at the same location, observers report the flashed stimulus as spatially lagging behind the moving stimulus (the flash-lag effect). The authors investigated whether the global configuration (perceptual organization) of the moving stimulus influences the magnitude of the flash-lag effect. The results indicate that a flash presented near the leading portion of a moving stimulus lags significantly more than a flash presented near the trailing portion. This result also holds for objects consisting of several elements that group to form a unitary percept of an object in motion. The present study demonstrates a novel interaction between the global configuration of moving objects and the representation of their spatial position and may provide a new and useful tool for the study of perceptual organization.

Fixation, Ocular↗
PubMed2004

Visual grouping by motion precedes the relative localization between moving and flashed stimuli.

A flashed stimulus is perceived as spatially lagging behind a moving stimulus when they are spatially aligned. When several elements are perceptually grouped into a unitary moving object, a flash presented at the leading edge of the moving stimulus suffers a larger spatial lag than a flash presented at the trailing edge (K. Watanabe. R. Nijhawan. B. Khurana, & S. Shimojo. 2001). By manipulation of the flash onset relative to the motion onset, the present study investigated the order of perceptual operations of visual motion grouping and relative visual localization. It was found that the asymmetric mislocalization was observed irrespective of physical and/or perceptual temporal order between the motion and flash onsets. Thus, grouping by motion must be completed to define the leading-trailing relation in a moving object before the visual system explicitly represents the relative positions of moving and flashed stimuli.

Cues↗
PubMed1993

[Dynamic inversion recovery snapshot FLASH MRT of focal nodular hyperplasia of the liver].

11 lesions of focal nodular hyperplasia (FNH) in 6 patients were studied by means of dynamic snapshot-FLASH MRI before and after bolus injection of Gd-DTPA. In addition, plain snapshot-FLASH images were compared with T1- and T2-weighted spin-echo (SE) images and with T1-weighted breathhold-FLASH images. Highest FNH-liver signal-difference-to-noise ratios were obtained with snapshot-FLASH followed by T2-SE. In all patients contrast-enhanced serial snapshot-FLASH demonstrated reliably the typical haemodynamic appearance of FNH known from dynamic computed tomography. Because of its high intrinsic lesion-liver contrast and high time-resolution dynamic snapshot-FLASH MRI may facilitate differential diagnosis of hepatic tumours.

Adult↗
PubMed1998

[Multi-flash ERG in cone dystrophies and cone-rod dystrophies].

BACKGROUND: Scotopic electroretinograms elicited with a multiple flash procedure were reported to be helpful in diagnosis of macular diseases. To evaluate the contribution of rods and cones to the recovery of light responses as recorded with this technique we performed a triple flash ERG procedure in patients with cone dystrophies and cone-rod dystrophies. MATERIALS AND METHODS: In 8 patients with cone dystrophy and 8 patients with cone-rod dystrophy and also in 18 healthy controls we recorded a standard ERG and the scotopic triple flash ERG with intensities between 0.01 and 0.2 cds/m2. Interflash intervals were adjusted at 140, 280, and 560 ms. Responses of the standard ERG were analysed as well as b-wave amplitudes at the short dark interval (140 ms) and the longer dark interval (280 ms). These responses were compared to responses after a long interflash interval (560 ms). Using a theoretical model parameters of b-wave recovery were determined and compared between the groups. RESULTS: In cone dystrophies responses of the scotopic triple flash ERG and the b-wave recovery parameters were normal whereas in combined dystrophies the triple flash responses were abnormal and the recovery data were pathologic. CONCLUSIONS: Cones did neither contribute to responses obtained with the multiple flash technique nor did they affect b-wave recovery as tested with this technique. Pathologic responses as described earlier with this technique in macular diseases could only be attributed to pathomechanisms globally affecting the rod system, e.g. dysfunction of retinal energy metabolism.

Adolescent↗
PubMed2000

Flash pulmonary edema: association with hypertension and reoccurrence despite coronary revascularization.

BACKGROUND: The sudden development of acute (flash) pulmonary edema may be an indication for coronary angiography and revascularization. However, the prevalence of coronary artery disease in these patients and the outcome after revascularization are not known. METHODS AND RESULTS: We evaluated 46 patients with an initial presentation of flash pulmonary edema requiring hospitalization and obtained up to 3 years of follow-up in 45 patients. There were 22 men and 24 women, 44 to 84 years of age (67 +/- 10 years, mean +/- SD). Systolic blood pressure on admission was 194 +/- 38 mm Hg. Twenty-four patients required intubation and mechanical ventilation. Left ventricular ejection fraction was >40% in 27 of 46 patients. Thirty-eight patients underwent coronary angiography; 33 had obstructive coronary artery disease. One other patient had regional wall motion abnormalities. Nineteen patients underwent coronary revascularization surgically and 8 percutaneously. Overall, flash pulmonary edema reoccurred in one half of the patients. Of the 19 patients who underwent coronary revascularization, by 6 months there was 1 death and 9 patients had been hospitalized with recurrent pulmonary edema. CONCLUSIONS: Many patients with flash pulmonary edema have preserved systolic left ventricular function and coronary artery disease. Flash pulmonary edema frequently reoccurs in association with marked systolic hypertension, even after coronary revascularization. This suggests that control of hypertension is important and that coronary revascularization may not be adequate to prevent reoccurrence of flash pulmonary edema.

Adult↗
PubMed2006

FLASH is required for histone transcription and S-phase progression.

Cajal bodies are nuclear subdomains that are involved in maturation of small ribonucleoproteins and frequently associate with small nuclear RNA and histone gene clusters in interphase cells. We have recently identified FADD-like IL-1beta-converting enzyme (FLICE) associated huge protein (FLASH) as an essential component of Cajal bodies. Here we show that FLASH associates with nuclear protein, ataxia-telangiectasia, a component of the cell-cycle-dependent histone gene transcription machinery. Reduction of FLASH expression by RNA interference results in disruption of the normal Cajal body architecture and relocalization of nuclear protein, ataxia-telangiectasia. Furthermore, FLASH down-regulation results in a clear reduction of histone transcription and a dramatic S-phase arrest of the cell cycle. Chromatin immunoprecipitation reveals that FLASH interacts with histone gene promoter sequences. These results identify FLASH as an important component of the machinery required for histone precursor mRNA expression and cell-cycle progression.

Animals↗
PubMed2002

Tumor necrosis factor alpha receptor- and Fas-associated FLASH inhibit transcriptional activity of the glucocorticoid receptor by binding to and interfering with its interaction with p160 type nuclear receptor coactivators.

Tumor necrosis factor alpha (TNF alpha) and its downstream transcription factor nuclear factor kappa B (NF-kappa B) suppress glucocorticoid action, contributing to tissue resistance to glucocorticoids in several pathologic inflammatory states. p160 nuclear receptor coactivators on the other hand, contribute to the transcriptional signal of the glucocorticoid receptor (GR) through interaction with it via LXXLL motifs in their nuclear receptor-binding (NRB) domain. To discover TNF alpha-induced factors that regulate GR activity at the coactivator level, we performed yeast two-hybrid screening using the NRB domain of the glucocorticoid receptor-interacting protein 1 (GRIP1) as bait. We found that FLICE-associated huge protein (FLASH), which transduces TNF alpha and Fas ligand signals, bound the NRB domain of GRIP1 at a region between the second and third LXXLL motifs. FLASH suppressed both GR transactivation and GRIP1 enhancement of the glucocorticoid signal and inhibited the physical interaction between GR and the GRIP1 NRB domain. Transfected green fluorescent protein-fused FLASH was located in both the cytoplasm and nucleus, while endogenous FLASH shifted its subcellular localization from the cytoplasm into the nucleus in response to TNF alpha. FLASH antisense and super-repressor I kappa B alpha inhibited the action of TNF alpha independently of each other and additively. These findings indicate that FLASH participates in TNF alpha-induced blockade of GR transactivation at the nuclear receptor coactivator level, upstream and independently of NF-kappa B.

Amino Acid Sequence↗
PubMed2000

Timing of Ca(2+) release from intracellular stores and the electrical response of Limulus ventral photoreceptors to dim flashes.

Light-induced release of Ca(2+) from stores in Limulus ventral photoreceptors was studied using confocal fluorescence microscopy and the Ca(2+) indicator dyes, Oregon green-5N and fluo-4. Fluorescence was collected from a spot within 4 microm of the microvillar membrane. A dual-flash protocol was used to reconstruct transient elevations of intracellular free calcium ion concentration (Ca(i)) after flashes delivering between 10 and 5 x 10(5) effective photons. Peak Ca(i) increased with flash intensity to 138 +/- 76 microM after flashes delivering approximately 10(4) effective photons, while the latent period of the elevation of Ca(i) fell from approximately 140 to 21 ms. The onset of the light-induced elevation of Ca(i) was always highly correlated with that of the receptor potential. The time for Ca(i) to exceed 2 microM was approximately equal to that for the receptor potential to exceed 8 mV (mean difference; 2.2 +/- 6.4 ms). Ca(i) was also measured during steps of light delivering approximately 10(5) effective photons/s to photoreceptors that had been bleached with hydroxylamine so as to reduce their quantum efficiency. Elevations of Ca(i) were detected at the earliest times of the electrical response to the steps of light, when a significant receptor potential had yet to develop. Successive responses exhibited stochastic variation in their latency of up to 20 ms, but the elevation of Ca(i) and the receptor potential still rose at approximately the same time, indicating a shared process generating the latent period. Light-induced elevations of Ca(i) resulted from Ca(2+) release from intracellular stores, being abolished by cyclopiazonic acid (CPA), an inhibitor of endoplasmic reticulum Ca(2+) pumps, but not by removal of extracellular Ca(2+) ions. CPA also greatly diminished and slowed the receptor potential elicited by dim flashes. The results demonstrate a rapid release of Ca(2+) ions that appears necessary for a highly amplified electrical response to dim flashes.

Animals↗
PubMed1993

Evaluation of a rapid readout biological indicator for flash sterilization with three biological indicators and three chemical indicators.

OBJECTIVE: Flash sterilization is most commonly used for emergency sterilization of unwrapped items in a gravity displacement sterilizer for three minutes. Sterilization quality assurance is monitored by biological indicators that require a 24-hour incubation prior to reading. In this study, we compared a new biological indicator that provides results within 60 minutes with three conventional, 24-hour biological indicators for monitoring flash sterilization and three chemical indicators. DESIGN: Conventional biological indicators tested included the conventional Attest 1261, Proof Flash and Assert, while the rapid readout indicator tested was Attest 1291. Attest Rapid Readout detects the presence of a Bacillus stearothermophilus enzyme by reading a fluorescent product that is produced by the enzymatic break-down of a nonfluorescent substrate. Chemical indicators tested included Comply, Incheque, and Thermalog S. Survival at 132 degrees C in a gravity displacement sterilizer was measured by media color change after incubation for 24 hours at 56 degrees C for the three conventional biological indicators, fluorescence at 60 minutes for the Attest Rapid Readout biological indicator, and color change for the chemical indicators. Each exposure time was replicated four times with 10 of each biological and chemical indicator per run. RESULTS: The conventional biological indicators (Attest, Proof Flash, and Assert) had 90%, 48%, and 40% spore survival at two minutes exposure; 23%, 3%, and 0% at three minutes exposure; and 3%, 0%, and 0% at four minutes exposure respectively. The Attest Rapid Readout biological indicator had 88%, 33%, and 0% enzyme activity detectable at 2, 3, and 4 minutes exposure. The chemical indicators Comply, Incheque, and Thermalog S revealed sterilization failure rates of 100%, 100%, and 100% at 0 minutes exposure; 100%, 100%, and 45% at one minute; 0%, 0%, and 28% at two minutes exposure; 0%, 0%, and 18% at three minutes exposure; and 0%, 0%, and 0% at four minutes exposure, respectively. CONCLUSION: The sensitivity of the Attest Rapid Readout parallels the conventional biological indicators. These data suggest that a 60-minute rapid readout biological indicator is equivalent to the 24-hour biological indicators. If further studies demonstrate that a four-minute flash sterilization cycle provides a needed safety margin to ensure sterilization, then consideration should be given to requiring a four-minute flash sterilization cycle. Chemical indicators were too sensitive to the processing conditions (eg, steam) and are inadequate to ensure adequate sterilization.

Evaluation Studies as Topic↗
PubMed2006

Bacterial safety of flash-heated and unheated expressed breastmilk during storage.

Heat-treated breastmilk is one infant-feeding option recommended by the WHO to reduce mother-to-child transmission of HIV in developing countries. Flash-heat, a simple pasteurization method that a mother could perform in her home, has been shown to inactivate cell-free HIV-1. Since heating may affect the naturally occurring antimicrobial properties found in breastmilk, storing heated breastmilk may present a safety issue in resource-poor settings due to lack of refrigeration and potential contamination. To address this, we investigated the ability of flash-heat to eliminate bacteria and to prevent growth over time compared with unheated breastmilk. We collected breastmilk samples from 38 HIV positive mothers in South Africa and aliquoted them to flash-heated and unheated controls. Samples were stored at room temperature for 0, 2, 6 and 8 h and then plated and incubated for 24 h at 37 degrees C in CO(2). We performed total colony counts and identified Escherichia coli, Staphylocuccus aureus and Group A and Group B streptococci. Unheated samples had a significantly higher number of samples positive for bacterial growth at each time point (p < 0.0001), as well as mean colony-forming units (CFU)/ml in those samples that were positive at each time point (p < 0.0001). In addition, unheated samples had a significantly higher rate of bacterial propagation over time than flash-heated samples when comparing log values of CFU/ml across 0-8 h (p < 0.005). No pathogenic growth was observed in the flash-heated samples, while the unheated samples showed growth of E. coli (n = 1) and S. aureus (n = 6). Our data suggest that storage of flash-heated breastmilk is safe at room temperature for up to 8 h.

Colony Count, Microbial↗
PubMed2005

Volatile anesthetics enhance flash-induced gamma oscillations in rat visual cortex.

BACKGROUND: The authors sought to understand neural correlates of anesthetic-induced unconsciousness. Cortical gamma oscillations have been associated with neural processes supporting conscious perception, but the effect of general anesthesia on these oscillations is controversial. In this study, the authors examined three volatile anesthetics, halothane, isoflurane, and desflurane, and compared their effects on flash-induced gamma oscillations in terms of equivalent concentrations producing the loss of righting reflex (1 minimum alveolar concentration for the loss of righting [MAC(LR)]). METHODS: Light flashes were presented every 5 s for 5 min, and event-related potentials were recorded from primary visual cortex of 15 rats with a chronically implanted bipolar electrode at increasing anesthetic concentrations (0-2.4 MAC(LR)). Early cortical response was obtained by averaging poststimulus (0-100 ms) potentials filtered at 20-60 Hz across 60 trials. Late (100-1,000 ms) gamma power was calculated using multitaper power spectral technique. Wavelet decomposition was used to determine spectral and temporal distributions of gamma power. RESULTS: The authors found that (1) halothane, isoflurane, and desflurane enhanced the flash-evoked early cortical response in a concentration-dependent manner; (2) the effective concentration for this enhancement was the lowest for isoflurane, intermediate for halothane, and the highest for desflurane when compared at equal fractions of the concentration that led to a loss of righting; (3) the power of flash-induced late (> 100 ms) gamma oscillations was augmented at intermediate concentrations of all three anesthetic agents; and (4) flash-induced gamma power was not reduced below waking baseline even in deep anesthesia. CONCLUSIONS: These findings suggest that a reduction in flash-induced gamma oscillations in rat visual cortex is not a unitary correlate of anesthetic-induced unconsciousness.

Anesthetics, Inhalation↗