Complex Cell Response depends on Interslit Spacing

PSYCHOPHYSICAL studies have established that the human central visual system contains a large number of independent channels each of which responds maximally to a selectively oriented sine wave grating of a given spatial frequency and hardly at all to gratings of spatial frequencies differing by a factor of two^1–4. Electrophysiological studies with moving sinusoidally modulated grating patterns have demonstrated that there exists a class of neurones in the striate cortex of cats⁵ and monkeys⁶ each member of which is maximally selective to a given spatial frequency and orientation.     

The segregation and integration of colour in motion processing revealed by motion after-effects

Analysis of the colour and motion of objects is widely believed to take place within segregated processing pathways in the primate visual system. However, it is apparent that this segregation cannot remain absolute and that there must be some capacity for integration across these sub-modalities. In this study, we have assessed the extent to which colour constitutes a separable entity in human motion processing by measuring the chromatic selectivity of two kinds of after-effect resulting from motion adaptation. First, the traditional motion after-effect, where prolonged inspection of a unidirectional moving stimulus results in illusory motion in the opposite direction, was found to exhibit a high degree of chromatic selectivity. The second type of after-effect, in which motion adaptation induces misperceptions in the spatial position of stationary objects, was completely insensitive to chromatic composition. This dissociation between the chromatic selectivities of these after-effects shows that chromatic inputs remain segregated at early stages of motion analysis, while at higher levels of cortical processing there is integration across chromatic, as well as achromatic inputs, to produce a unified perceptual output.     

Erratum

AN acute angle appears to be less acute than it really is^1,2. The effect has an obvious similarity to the tilt after-effect, the only difference in procedure being that the lines forming the acute angle are presented simultaneously in one case and successively in the other. Nevertheless, Blakemore et al.² consider that the effect they studied is not the tilt after-effect, on the grounds of different temporal properties: their effect builds up and dissipates very rapidly, which, they argue, is inconsistent with known adaptation phenomena, such as Gibson after-effects^3,4, which have long time constants.     

Slow and fast visual motion channels have independent binocular-rivalry stages

We have previously reported a transparent motion after-effect indicating that the human visual system comprises separate slow and fast motion channels. Here, we report that the presentation of a fast motion in one eye and a slow motion in the other eye does not result in binocular rivalry but in a clear percept of transparent motion. We call this new visual phenomenon 'dichoptic motion transparency' (DMT). So far only the DMT phenomenon and the two motion after-effects (the 'classical' motion after-effect, seen after motion adaptation on a static test pattern, and the dynamic motion after-effect, seen on a dynamic-noise test pattern) appear to isolate the channels completely. The speed ranges of the slow and fast channels overlap strongly and are observer dependent. A model is presented that links after-effect durations of an observer to the probability of rivalry or DMT as a function of dichoptic velocity combinations. Model results support the assumption of two highly independent channels showing only within-channel rivalry, and no rivalry or after-effect interactions between the channels. The finding of two independent motion vision channels, each with a separate rivalry stage and a private line to conscious perception, might be helpful in visualizing or analysing pathways to consciousness.     

Modelling fast forms of visual neural plasticity using a modified second-order motion energy model

The Adelson-Bergen motion energy sensor is well established as the leading model of low-level visual motion sensing in human vision. However, the standard model cannot predict adaptation effects in motion perception. A previous paper Pavan et al.(Journal of Vision 10:1–17, 2013) presented an extension to the model which uses a first-order RC gain-control circuit (leaky integrator) to implement adaptation effects which can span many seconds, and showed that the extended model’s output is consistent with psychophysical data on the classic motion after-effect. Recent psychophysical research has reported adaptation over much shorter time periods, spanning just a few hundred milliseconds. The present paper further extends the sensor model to implement rapid adaptation, by adding a second-order RC circuit which causes the sensor to require a finite amount of time to react to a sudden change in stimulation. The output of the new sensor accounts accurately for psychophysical data on rapid forms of facilitation (rapid visual motion priming, rVMP) and suppression (rapid motion after-effect, rMAE). Changes in natural scene content occur over multiple time scales, and multi-stage leaky integrators of the kind proposed here offer a computational scheme for modelling adaptation over multiple time scales.     

Stereoscopic subsystems for position in depth and for motion in depth.

We describe psychophysical evidence that the human visual system contains information-processing channels for motion in depth in addition to those for position in depth. These motion-in-depth channels include some that are selectively sensitive to the relative velocities of the left and right retinal images. We propose that the visual pathway contains stereoscopic (cyclopean) motion filters that respond to only a narrow range of the directions of motion in depth. Turning to the single-neuron level we report that, in addition to neurons turned to position to depth, cat visual cortex contains neurons that emphasize information about the direction of motion at the expense of positional information. We describe psychophysical evidence for the existence of channels that are sensitive to change size, and are separate from the channels both for motion and for flicker. These changing-size channels respond independently of whether the stimulus is a bright square on a dark ground or a dark square on a bright ground. At the physiological level we report single neurons in cat visual cortex that respond selectively to increasing or to decreasing size independently of the sign of stimulus contrast. Adaptation to a changing-size stimulus produces two separable after-effects: an illusion of changing size, and an illusion of motion in depth. These after-effects have different decay time constants. We propose a psychophysical model in which changing-size filters feed a motion-in-depth stage, and suppose that the motion-in-depth after-effect is due to activity at the motion-in-depth stage, while the changing-size after-effect is due to to activity at the changing-size and more peripheral stages. The motion-in-depth after-effect can be cancelled either by a changing-size test stimulus or by relative motion of the left and right retinal images. Opposition of these two cues can also cancel the impression of motion in depth produced by the adapting stimulus. These findings link the stereoscopic (cyclopean) motion filters and the changing-size filters: both feed the same motion-in-depth stage.     

Distortions of Perceived Orientation

SEVERAL visual discriminations are best for vertical and horizontal test objects and worst for objects oriented at 45° to the main axes^1–3. For resolution acuity it is quite clear that the differences are not due to any optical defects¹ and it seems probable that the same is true for tasks involving the discrimination of differences in orientation^2,3. A likely source of these variations is the orientationally sensitive neurones of the type found in the cat and monkey visual cortex^4,5. Psychophysical evidence^1,3,6 suggests that similar neurones exist in the human visual system and so we might expect some aspect of the sensitivity of these units to vary as a function of the orientation to which they are maximally sensitive.     

Using the optokinetic response to study visual function of zebrafish

Optokinetic response (OKR) is a behavior that an animal vibrates its eyes to follow a rotating grating around it. It has been widely used to assess the visual functions of larval zebrafish^1-5. Nevertheless, the standard protocol for larval fish is not yet readily applicable in adult zabrafish. Here, we introduce how to measure the OKR of adult zebrafish with our simple custom-built apparatus using a new protocol which is established in our lab. Both our apparatus and step-by-step procedure of OKR in adult zebrafish are illustrated in this video. In addition, the measurements of the larval OKR, as well as the optomotor response (OMR) test of adult zebrafish, are also demonstrated in this video. This OKR assay of adult zebrafish in our experiment may last for up to 4 hours. Such OKR test applied in adult fish will benefit to visual function investigation more efficiently when the adult fish vision system is manipulated.Su-Qi Zou and Wu Yin contributed equally to this paper.Open in a separate windowClick here to view.^{(35M, flv)}     

Linkage of Retinal to Opsin

RHODOPSIN, the visual pigment of vertebrate rods, has been shown to consist of a chromophore (11-cis retinal) bound to a protein (opsin)^1–2. It has been proposed that the linkage is a Schiff base between phosphatidyl ethanolaniine (PE) and retinal and that when exposed to light, the retinal migrates from PE to the ε-amino-group of a lysine residue in opsin^3–7. Most of the support for this theory comes from the observation that N-retinylidenephosphatidylethanolamine (N-RPE) can be extracted in the dark from rod outer segments (ROS)^3,4. Furthermore, N-retinylphosphatidylethanolamine (N-RH₂PE) has been extracted from ROS preparations after treating the visual pigment with acid and NaBH₄—conditions which are assumed fix retinal to its “native” binding site through a secondary amine linkage⁷. All these studies, however, were carried out on crude extracts of ROS in various detergents. These crude extracts contain large amounts of phospholipid and retinal which is not bound to opsin. Thus, the isolation of N-RPE from crude ROS extracts does not necessarily point to its involvement in the binding of retinal to opsin. In contradiction to these reports are findings that purified visual pigment contains no phospholipid^9,10 and that the molar concentration of N-RPE in bovine ROS is less than that of rhodopsin¹¹. We have taken advantage of the observation that visual pigment in the outer segment disks is continually being renewed¹² to label the rhodopsin with ³H-retinal and to show in yet another way that N-RPE does not exist in purified visual pigment.     

THE RELATION BETWEEN VISUAL ACUITY AND ILLUMINATION

1. An apparatus for measuring the visual acuity of the eye at different illuminations is described. The test object is continuously variable in size and is presented at a fixed distance from the eye in the center of a 30° field. Observation of the field is through an artificial pupil. The maximum intensity obtainable is more than enough to cover the complete physiological range for the eye with white light though only 110 watts are consumed by the source. Means for varying the intensity over a range of 1:10¹⁰ in small steps are provided. 2. The relation of visual acuity and illumination for two trained observers was measured, using two different types of test object, a broken circle and a grating. The measurements with both test objects show a break at a visual acuity of 0.16, all values below that being mediated by the rods and those above by the cones. The grating gives higher visual acuities at intensities less than about 30 photons and lower visual acuities above that. The maximum visual acuity attainable with the grating under the same conditions is about 30 per cent lower than that with the C. It is shown that the limiting factor in the resolution of the eye for the grating is the diameter of the pupil when it is less than 2.3 mm. and the size of the central cones when the pupil is larger than that. The value of the diameter of the cone derived on that basis from the visual acuity data agrees with that derived from direct cone count in a unit of area. 3. The data for the cones made with both test objects are adequately described by one and the same form of the stationary state equation derived by Hecht for the photoreceptor system. This fact, together with certain considerations about the difference in the nature of the two test objects with regard to the resolvable area, leads to the conclusion that detail perception is a function of a distance rather than an area. All the data for the rods can likewise be described by another variety of the same equation, although the data are too fragmentary to make the choice of the form as certain as might be desired.     

Identification of PDZ ligands by docking-based virtual screening for the development of novel analgesic agents

Disrupting the interaction between the PDZ protein, PSD-95, and its target ligands (such as the glutamate NMDA receptor or the serotonin 5-HT_2A receptor) was found to reduce hyperalgesia in various models of neuropathic pain. Here, we set out to identify lead molecules which would interact with PSD-95, and hence, would potentially display analgesic activity. We describe the virtual screening of the Asinex and Cambridge databases which together contain almost one million molecules. Using three successive docking filters and visual inspection, we identified three structural classes of molecules and synthesized a potential lead compound from each class. The binding of the molecules with the PDZ domains of PSD-95 was assessed by ¹H–¹⁵N HSQC NMR experiments. The analgesic activity of the best ligand, quinoline 2, was evaluated in vivo in a model of neuropathic pain and showed promising results.     

The Effects of Selenium on Physiological Traits, Grain Selenium Content and Yield of Winter Wheat at Different Development Stages

The paper evaluated the effects of Se application time and rate on physiological traits, grain Se content, and yield of winter wheat by field experiment. Se application significantly increased grain Se content and yield, and the increased amount treated with 20 and 30 mg Se?L^?1 was the highest. At blooming–filling stage, Se application significantly increased grain Se content, but did not affect yield. Chlorophyll content was increased by Se application, and the increased amount at heading–blooming stage was higher than that in wheat leaves at the other stages. At four development stages, Se treatments (except for 10 mg Se?L^?1 at jointing–heading stage) significantly decreased the rate of superoxide (O₂ ^?) radical production. At heading–blooming (except for 50 mg Se?L^?1) and blooming–filling stages, hydrogen peroxide (H₂O₂) content was significantly decreased by Se treatments. The rate of O₂ ^? production and H₂O₂ content at 20 and 30 mg Se?L^?1 was the lowest. Se treatments (except for 10 mg Se?L^?1 at regreening–jointing and blooming–filling stages) also induced an evident decrease in malondialdehyde content. Proline content induced by Se treatments at jointing–heading and heading–blooming stages was higher than that in wheat leaves at regreening–jointing and blooming–filling stages. At four development stages, Se treatments all significantly increased glutathione peroxidase activity, and the treatments with 20 and 30 mg Se?L^?1 also evidently increased reduced glutathione content. These results suggested that Se application at different development stages increased antioxidant capacity of wheat, reduced oxidant stress to some extent, and the effects of Se treatments was the best if Se concentration ranged between 20 and 30 mg Se?L^?1. In addition, Se application time was more beneficial for Se accumulation and yield in wheat grain at heading–blooming stage.     

Surface-Enhanced Raman Scattering (SERS) on 1D Nano-gratings

Surface-enhanced Raman scattering (SERS) enhancement factor (EF) is among the major applications of surface plasmon polaritons (SPP’s). In this work, the SERS EF of 1D rectangular and sinusoidal-shaped gold (Au) grating structures has been designed and optimized on Au film using COMSOL multiphysics (5.3a) RF module taking glass as substrate. The 1D grating models are simulated by variation in slit width ranging 200–600 nm while other parameters including periodicity of 700 nm and Au film thickness of 50 nm remained fixed. In order to study the several phenomena including enhanced optical transmission and SERS EF, the transmission and electric field spectra have been obtained from both types of grating structures. In agreement with fundamental plasmonic mode, the slit width of two-thirds of the periodicity found to be optimum for SERS EF. Remarkable value of SERS EF is obtained in the case of a sinusoidal Au grating device (6.4 × 10⁹) which is calculated to be five times that of the rectangular grating (1.2 × 10⁹). These devices are also the fingerprints of molecules, hence find applications in biosensing, pollution control, and chemical and food industry.

     

Ano6 disruption impairs acinar cell regulatory volume decrease and protein secretion in murine submandibular salivary glands

The widely expressed Anoctamin 6 (Ano6) supports different Ca²⁺-dependent functions, but little is known about its role in salivary glands. Mouse submandibular gland (SMG) acinar cells exhibited a robust regulatory volume decrease (RVD) following cell swelling that was reduced approximately 70% in Ano6^–/– mice. Ca²⁺-free conditions nearly eliminated the RVD response suggesting that Ano6 is an obligatory component of the cell volume-activated, Ca²⁺-dependent RVD pathway in salivary gland acinar cells. Ex vivo agonist-stimulated secretion of water and ions was unaffected by Ano6 disruption under both isotonic and hypotonic conditions suggesting that Ano6 does not play a major role in fluid and electrolyte secretion. In contrast, the total amount of β-adrenergic-dependent protein secretion by the SMG was significantly reduced in Ano6^–/– mice. Closer inspection of these latter results revealed that protein secretion was affected only in the female SMG by Ano6 disruption. These results indicate that Ano6 modulates the RVD response and protein secretion by salivary gland acinar cells.     

Rapid sex identification of papaya (Carica papaya) using multiplex loop-mediated isothermal amplification (mLAMP)

Papaya (Carica papaya L.) is established as a cash crop throughout the tropical and subtropical regions due to its easy adaptation to diverse agricultural conditions, high yields, and prompt returns. The sex types of papaya plants are hermaphrodite, male, and female. Among them, hermaphroditic plants are the major type in papaya production, because the fruit has commercial advantages over that of the other sexes. Sex inheritance in papaya is determined by the M and M ^h dominant alleles in males and hermaphrodites, respectively, and a recessive m allele in females. Currently, all hermaphrodite seeds are not available due to the lethality of dominant homozygosity. Therefore, in this study, six male–hermaphrodite-specific markers were developed for a rapid sex identification using multiplex loop-mediated isothermal amplification (mLAMP) to efficiently and precisely select hermaphroditic individuals in the seedling or early growth stage. The LM1-LAMP assay consisted of two sex-LAMP reactions for amplifying two male-specific markers (T12 and Cpsm90) in one reaction, and showed several advantages in terms of a rapid reaction time (<1 h), isothermal conditions (less equipment required), a high efficiency (0.5 ng of DNA required in the reaction mixture), and an economical reaction system (5 μl in volume). The established method can be easily performed in the field by visual inspection and facilitates the selection of all hermaphroditic individuals in papaya production.     

Caffeine and artificial insemination

We studied the reactivation of cells and the repair of photomutagenic damage induced by xanthotoxin and visnagin plus NUV in arg-1 cells of Chlamydomonas reinhardii. Maintenance of liquid cultures in the dark resulted only in a slight reactivation of cells, even after 24 h. Repair of photomutagenic damage was more efficient: within 24 h the number of Arg⁺ revertants was reduced by 50% in cells cultured in the dark at 20°C. The repair was more efficient at 30°C. At the beginning of dark cultivation an after-effect could be observed. Cultivation in standard white light instead of dark after treatment resulted in a very strong after-effect. Therefore it was not possible to detect any photoreactivation.After treatment with xanthotoxin plus standard white light (24 h) neither reactivation of cells nor repair of photomutagenic damage was found. The after-effect was higher than after xanthotoxin plus NUV. It is possible that a small amount of repair could be masked by the after-effect.Treatment with visnagin yielded similar results. The photomutagenic effect of visnagin is described for the first time in this paper. The drug is a much less effective photomutagen than xanthotoxin. The photomutagenesis of visnagin may be attributable to photoproducts similar to those formed after treatment with furocoumarins.No definite conclusion can be drawn from the present results regarding the basis for the observed lack of repair (or reduced repair) after standard white light treatment; a possible cause might be a preferential formation of bi-adducts under these conditions.     

Purification and membrane interactions of human KCNQ1100–370 potassium ion channel

KCNQ1 (Kv7.1 or KvLQT1) is a voltage-gated potassium ion channel that is involved in the ventricular repolarization following an action potential in the heart. It forms a complex with KCNE1 in the heart and is the pore forming subunit of slow delayed rectifier potassium current (I_ks). Mutations in KCNQ1, leading to a dysfunctional channel or loss of activity have been implicated in a cardiac disorder, long QT syndrome. In this study, we report the overexpression, purification, biochemical characterization of human KCNQ1_100–370, and lipid bilayer dynamics upon interaction with KCNQ1_100–370. The recombinant human KCNQ1 was expressed in Escherichia coli and purified into n-dodecylphosphocholine (DPC) micelles. The purified KCNQ1_100–370 was biochemically characterized by SDS-PAGE electrophoresis, western blot and nano-LC-MS/MS to confirm the identity of the protein. Circular dichroism (CD) spectroscopy was utilized to confirm the secondary structure of purified protein in vesicles. Furthermore, ³¹P and ²H solid-state NMR spectroscopy in DPPC/POPC/POPG vesicles (MLVs) indicated a direct interaction between KCNQ_100–370 and the phospholipid head groups. Finally, a visual inspection of KCNQ1_100–370 incorporated into MLVs was confirmed by transmission electron microscopy (TEM). The findings of this study provide avenues for future structural studies of the human KCNQ1 ion channel to have an in depth understanding of its structure-function relationship.     

Temporal modulation of luminance adapts time constant of fly movement detectors

The time constant of movement detectors in the fly visual system has been proposed to adapt in response to moving stimuli (de Ruyter van Steveninck et al. 1986). The objective of the present study is to analyse, whether this adaptation can be induced as well, if the luminance of a stationary uniform field is modulated in time. The experiments were done on motion-sensitive wide-field neurones of the lobula plate, the posterior part of the third visual ganglion of the blowfly, calliphora erythrocephala. These cells are assumed to receive input from large retinotopic arrays of movement detectors. In order to demonstrate that our results concern the properties of the movement detectors rather than those of a particular wide-field cell we recorded from two different types of them, the H1- and the HSE-cell. Both cell types respond to a brief movement stimulus in their preferred direction with a transient excitation. This response decays about exponentially. The time constant of this decay reflects, in a first approximation, the time constant of the presynaptic movement detectors. It was determined after prestimulation of the cell by the following stimuli: (a) periodic stationary grating; (b) uniform field, the intensity of which was modulated sinusoidally in time (flicker stimulation); (c) periodic grating moving front-to-back; (d) periodic grating moving back-to-front. The decay of the response is significantly faster not only after movement but also after flicker stimulation as compared with pre-stimulation with a stationary stimulus. This is interpreted as an adaptation of the movement detector's time constant. The finding that flicker stimulation also leads to an adaptation shows that movement is not necessary for this process. Instead the adaptation of the time constant appears to be governed mainly by the temporal modulation (i.e., contrast frequency) of the signal in each visual channel.     

Determination of the lactate threshold and maximal blood lactate steady state intensity in aged rats

The reliability of the lactate threshold (LT) determined in aged rats and its validity to identify an exercise intensity corresponding to the maximal blood lactate steady state (MLSS) were analyzed. Eighteen male aged Wistar rats (～365 days) were submitted to two incremental swimming tests until exhaustion, consisting of an initial load corresponding to 1% of body mass (BM) and increments of 1% BM at each 3‐min with blood lactate ([lac]) measurements. The LT was determined by visual inspection (LT_V) as well by applying a polynomial function on the [lac]/workload ratio (LT_P) by considering the vertices of the curve. For the MLSS, twelve animals were submitted, on different days, to 3–4 exercise sessions of 30‐min with workload corresponding to 4, 5 or 6% BM. The MLSS was considered the highest exercise intensity at which the [lac] variation was not higher than 0.07 mM.min^?1 during the last 20‐min. No differences were observed for the test‐retest results (4.9 ± 0.7 and 5.0 ± 0.8 %BM for LTv; and 6.0 ± 0.6 and 5.8 ± 0.6 %BM for LTp) that did not differ from the MLSS (5.4 ± 0.5 %BM). The LT identified for aged rats in swimming, both by visual inspection and polynomial function, was reliable and did not differ from the MLSS. Copyright © 2009 John Wiley & Sons, Ltd.     

Transmission Surface Plasmon Resonance Signal Enhancement via Growth of Gold Nanoparticles on a Gold Grating Surface

We developed a novel technique for increasing the sensitivity of transmission surface plasmon resonance (T-SPR) signals. T-SPR spectroscopy was performed by irradiating, with white light, a gold grating substrate whose surface was nanostructured by growing gold nanoparticles (AuNPs). AuNPs were grown directly on the substrate surface by alcohol reduction and their growth was observed at various stages by UV–visible spectroscopy and standard Kretschmann-type SPR spectroscopy. For comparison, normal gold film with smooth surface was examined under similar condition. The T-SPR results show a possibility of hybrid excitation of both localized and propagating surface plasmon. Significantly, T-SPR spectra of the gold grating substrate obtained during AuNP growth show stronger and narrower peaks in the range 650–800 nm. The maximum T-SPR excitation was at an incident angle of 35°. A layer-by-layer system of 5,10,15,20-tetrakis (1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) molecules and sodium copper chlorophyllin molecules was used to verify the enhancement of the developed system. We believe that the AuNPs/Au grating for T-SPR devices will provide enhanced signals for detecting nanometer order materials and for high-sensitive sensor applications.