Dark-adapted Eye Research Articles

Luminescent properties of blue long-lasting phosphorescence phosphors Sr6Al18Si2O37:Eu2+,RE3+

A series of novel blue long-lasting phosphorescence phosphors Sr6Al18Si2O37:Eu2+,RE3+ (RE3+=Ho3+, Gd3+, Dy3+ and Pr3+) were prepared by the conventional high-temperature solid-state reaction in a reductive atmosphere. Their properties were systematically investigated utilizing X-ray diffraction (XRD), photoluminescence, phosphorescence and thermoluminescence (TL) spectra. The phosphors emitted blue light that was related to the emission of Eu2+ due to 5d-4f transition. Bright blue long-lasting phosphorescence (LLP) could be observed after the excitation source was switched off. For the optimized sample, the blue long-lasting phosphorescence could last for nearly 4 h in the light perception of the dark-adapted human eye (0.32 mcd/m2). The effects of RE3+ ions on phosphorescence properties of the phosphors were studied, and the results showed that the co-doping of RE3+ ions greatly enhanced the intensity of the peak around 315 K which was related to the long lasting phosphorescence of the phosphors at room temperature and consequently improved the performance of the blue phosphorescence such as intensity and persistent time.

Diacylglycerol activates the light-dependent channel TRP in the photosensitive microvilli of Drosophila melanogaster photoreceptors.

Drosophila light-dependent channels, TRP and TRPL, reside in the light-sensitive microvilli of the photoreceptor's rhabdomere. Phospholipase C mediates TRP/TRPL opening, but the gating process remains unknown. Controversial evidence has suggested diacylglycerol (DAG), polyunsaturated fatty acids (PUFAs, a DAG metabolite), phosphatidylinositol bisphosphate (PIP2), and H(+) as possible channel activators. We tested each of them directly in inside-out TRP-expressing patches excised from the rhabdomere, making use of mutants and pharmacology. When patches were excised in darkness TRP remained closed, while when excised under illumination it stayed constitutively active. TRP was opened by DAG and silenced by ATP, suggesting DAG-kinase (DGK) involvement. The ATP effect was abolished by inhibiting DGK and in the rdgA mutant, lacking functional DGK, implicating DGK. DAG activated TRP even in the presence of a DAG-lipase inhibitor, inconsistent with a requirement of PUFAs in opening TRP. PIP2 had no effect and acidification, pH 6.4, activated TRP irreversibly, unlike the endogenous activator. Complementary liquid-chromatography/mass-spectrometry determinations of DAG and PUFAs in membranes enriched in rhabdomere obtained from light- and dark-adapted eyes showed light-dependent increment in six DAG species and no changes in PUFAs. The results strongly support DAG as the endogenous TRP agonist, as some of its vertebrate TRPC homologs of the same channel family.

Out of the blue: the spectral sensitivity of hummingbird hawkmoths

The European hummingbird hawkmoth Macroglossum stellatarum is a diurnal nectar forager like the honeybee, and we expect similarities in their sensory ecology. Using behavioural tests and electroretinograms (ERGs), we studied the spectral sensitivity of M. stellatarum. By measuring ERGs in the dark-adapted eye and after adaptation to green light, we determined that M. stellatarum has ultraviolet (UV), blue and green receptors maximally sensitive at 349, 440 and 521nm, and confirmed that green receptors are most frequent in the retina. To determine the behavioural spectral sensitivity (action spectrum) of foraging moths, we trained animals to associate a disk illuminated with spectral light, with a food reward, and a dark disk with no reward. While the spectral positions of sensitivity maxima found in behavioural tests agree with model predictions based on the ERG data, the sensitivity to blue light was 30 times higher than expected. This is different from the honeybee but similar to earlier findings in the crepuscular hawkmoth Manduca sexta. It may indicate that the action spectrum of foraging hawkmoths does not represent their general sensory capacity. We suggest that the elevated sensitivity to blue light is related to the innate preference of hawkmoths for blue flowers.

Brightness discrimination in the day- and night-adapted wandering spider Cupiennius salei.

Cupiennius salei is a nocturnal spider with eight eyes, which undergo a remarkable circadian cycle: the rhabdomeric membrane of the photoreceptor cells is dismantled during the day and rebuilt at the beginning of the night. Such drastic changes might influence the brightness discrimination ability. We tested this hypothesis by presenting square-shaped flickering stimuli with certain luminances on stationary backgrounds with other luminances to spiders with day- or night-adapted eyes. When the spider, through its three pairs of so-called secondary eyes, perceives a visible contrast between the stimulus and the background, its principal eye muscle activity should increase. We therefore recorded this activity in vivo to assess the brightness discrimination ability of Cupiennius salei. Our results show that this spider has good brightness discrimination ability, which is significantly better with dark-adapted eyes. A Michelson contrast of 0.1 to 0.2 at night, and of 0.2 to 0.3 for day-adapted eyes, is sufficient to elicit a significant response, except below a critical value of luminance (~16 cd m(-2)), where the minimal perceivable contrast needs to be higher. In the Discussion we compare these performances with those of other animals, in particular with jumping spiders.

ApoE4 Induces Synaptic and ERG Impairments in the Retina of Young Targeted Replacement ApoE4 Mice

The vertebrate retina, which is part of the central nervous system, is a window into the brain. The present study investigated the extent to which the retina can be used as a model for studying the pathological effects of apolipoprotein E4 (apoE4), the most prevalent genetic risk factor for Alzheimer's disease (AD). Immunohistochemical studies of retinas from young (4 months old) apoE4-targeted replacement mice and from corresponding mice which express the AD benign apoE3 allele, revealed that the density of the perikarya of the different classes of retinal neurons was not affected by apoE4. In contrast, the synaptic density of the retinal synaptic layers, which was assessed immunohistochemically and by immunoblot experiments, was significantly lower in the apoE4 than in the apoE3 mice. This was associated with reduced levels of the presynaptic vesicular glutamatergic transporter, VGluT1, but not of either the GABAergic vesicular transporter, VGaT, or the cholinergic vesicular transporter, VAChT, suggesting that the glutamatergic nerve terminals are preferentially affected by apoE4. In contrast, the post synaptic scaffold proteins PSD-95 and Gephyrin, which reside in excitatory and inhibitory synapses, respectively, were both elevated, and their ratio was not affected by apoE4. Electroretinogram (ERG) recordings revealed significant attenuation of mixed rod-cone responses in dark-adapted eyes of apoE4 mice. These findings suggest that the reduced ERG response in the apoE4 mice may be related to the observed decrease in the retinal nerve terminals and that the retina could be used as a novel model for non-invasive monitoring of the effects of apoE4 on the CNS.

Preparation and Long-Lasting Phosphorescence Properties of BaAlSi5N7O2:Eu2+

The oxynitride phosphor BaAlSi5N7O2:Eu2+ was synthesized by using a modified solid-state reaction method with Ba2SiO4:Eu2+ as the precursor. This synthesized product was found to be well-crystallized by utilizing XRD characterization. Under 300 nm excitation, BaAlSi5N7O2:Eu2+ shows an emission band extending from 400 to 650 nm with a main peak at about 515 nm. After irradiation under the 254 nm UV light, the afterglow emission of Eu2+ (4f65d → 4f7) can be obviously observed for at least 40 min in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2).

Temperature-Dependent Long-Lasting Phosphorescence in SrSi2O2N2:Eu2+

Yellow-light-emitting phosphor SrSi2O2N2:Eu2+ was synthesized by using a simple solid-state reaction method with Sr2SiO4:Eu2+ as the precursor. This phosphor was found to be well-crystallized by utilizing XRD. Luminescence and afterglow properties of it have been systematically investigated. After 15 minutes excitation with an unfiltered xenon arc lamp at 1000 lux, its afterglow can be seen for more than 2.5 h in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Furthermore, its temperature-dependent long-lasting phosphorescence (LLP) characteristic was investigated for the first time, combining information from thermoluminescence (TL) spectrum, a possible mechanism for the LLP of SrSi2O2N2:Eu2+ phosphor was discussed in this paper.

Luminescence Properties of Red Long-Lasting Phosphorescence Phosphor AlN:Mn2+

The luminescence properties of red long-lasting phosphorescence phosphor AlN:Mn2+ were reported. Studies show that AlN:Mn2+ phosphors exhibit red emission band in a wavelength range of 570–700 nm centered at ca. 600 nm and FWHM of 43 nm. The concentration quenching of Mn2+ in AlN phosphor is 2.5 mol%. After irradiation under the 254 nm UV light, the afterglow emission of Mn2+ (4T1g(G)-6A1g(S)) can be obviously observed for at least 1 h in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Possible mechanism for the afterglow of AlN:Mn2+ phosphor is explained. All the results indicate that the Mn2+-doped AlN phosphor has promising potential of practical applications as a new red-light-emitting afterglow material.

Retrospective: Julian Jaynes and The Origin of Consciousness in the Breakdown of the Bicameral Mind

Abstract In the previous installment we looked at the circumstances surrounding the great Catastrophe of 1200 b.c.e. That historic moment set the stage for a dramatic change in human consciousness. On the far side of that event we see people unencumbered by the stresses of reflexive self-awareness. On the near side we witness the advent of the self-conscious individual. This transition gave the world great literature, art, religion, and philosophy. But it also guaranteed a troubled existence, from the invitation to "know thyself" that we see in the Dialogues to the expulsion from the garden in Genesis for knowing too much. It does indeed seem that "Hellenistic existence had been propelled into an individualism without instruction, an aimlessness motivated by a profound sense of alienation; in short, into a crisis of freedom" (Martin, 1987, p. 24). This is, of course, the metaphorical self, described by Julian Jaynes. We ended the previous installment with a metaphorical rendering of that transition that I called flash blindness: When the lights come back on after the great Catastrophe, they come on with the psychological equivalent of dark-adapted eyes stabbed by the flash of a thousand halogen lights. Whole civilizations stumble their way into the uncompromising brilliance of human subjective consciousness. What do we do now? Now We Pray

Light and vision in the deep-sea benthos: II. Vision in deep-sea crustaceans

Using new collecting techniques with the Johnson-Sea-Link submersible, eight species of deep-sea benthic crustaceans were collected with intact visual systems. Their spectral sensitivities and temporal resolutions were determined shipboard using electroretinography. Useable spectral sensitivity data were obtained from seven species, and in the dark-adapted eyes, the spectral sensitivity peaks were in the blue region of the visible spectrum, ranging from 470 to 497 nm. Under blue chromatic adaptation, a secondary sensitivity peak in the UV portion of the spectrum appeared for two species of anomuran crabs: Eumunida picta (λ(max)363 nm) and Gastroptychus spinifer (λ(max)383 nm). Wavelength-specific differences in response waveforms under blue chromatic adaptation in these two species suggest that two populations of photoreceptor cells are present. Temporal resolution was determined in all eight species using the maximum critical flicker frequency (CFF(max)). The CFF(max) for the isopod Booralana tricarinata of 4 Hz proved to be the lowest ever measured using this technique, and suggests that this species is not able to track even slow-moving prey. Both the putative dual visual pigment system in the crabs and the extremely slow eye of the isopod may be adaptations for seeing bioluminescence in the benthic environment.

A reddish La2O2S-based long-afterglow phosphor with effective absorption in the visible light region

Abstract Sm 3+ -activated La 2 O 2 S phosphors with good crystallinity were prepared by solid-state reaction. The formation mechanism of La 2 O 2 S formation was assumed and the phase change with different temperatures was discussed. The luminescence properties of phosphors with different sintering temperatures and different doping concentrations of Sm 3+ were investigated. The emission peak at 605 nm showed a well intensity can be attributed to the 4 G 5/2 → 6 H 7/2 transition of Sm 3+ . The optical absorption of La 2 O 2 S phosphors showed a stronger intensity in UV–vis region comparing with the Y 2 O 2 S phosphors. The long afterglow properties were investigated after the phosphors were excited with a fluorescent lamp. Phosphorescence lasted for about 3 min in the limit of light perception of the dark-adapted human eye (0.32 mcdm −2 ).

Changes in the scotopic vision of juvenile Pacific bluefin tuna (Thunnus orientalis) with growth

In cultured juvenile Pacific bluefin tuna (Thunnus orientalis), reducing the mass deaths caused by collision or contact with tank or net walls at night is a priority for seedling production. Pacific bluefin tuna is a visually dependant species, although its scotopic vision is poor. We recorded electroretinograms to investigate the visual function with growth in the dark-adapted eyes of juvenile Pacific bluefin tuna. Peak wavelengths of spectral sensitivity [38-62 days posthatch (dph), 77-167 mm standard length (SL)] were observed between 474 and 494 nm. Visual light sensitivity has a tendency to increase slightly with growth at 28-64 dph in individuals that measured 29-175 mm SL. However, visual temporal resolution did not significantly increase with growth at 38-62 days dph in individuals that measured 77-167 mm SL. These results suggest that the mass death continues between 28 and 64 dph because of low visual function and increasing swimming speed with growth.

Reddish orange long lasting phosphorescence of Sm 3+ in Sr 2ZnSi 2O 7:Sm 3+ phosphors

Long lasting phosphorescence phosphors with composition of (Sr 1- x Sm x) 2ZnSi 2O 7 were prepared by conventional high-temperature solid-state method. Their properties were systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence spectra. The results showed that these phosphors emitted reddish orange light that corresponds to the characteristic emission due to the 4G 5/2→ 6H 5/2, 6H 7/2 and 6H 9/2 transitions of Sm 3+. After the UV light excitation source was switched off, the bright reddish orange long lasting phosphorescence could be observed and it could last for about 30 min in the limit of light perception of dark-adapted human eyes (0.32 mcd/m 2). A wide TL band raging from room temperature to 700 K with two dominating peaks at 340 and 602 K appeared in the TL spectrum. The TL curve could be fitted to five TL peaks and the low temperature TL peak at 340 K was found to be responsible for the long lasting phosphorescence. Also, the mechanism was discussed.

P92 Catechol-O-methyl transferase (COMT) expression in severe, early onset pre-eclampsia: is there a role in the pathophysiology of pre-eclampsia?

Biochemical and immunological techniques were used to determine the emergence of interstitial retinol binding protein (IRBP), rhodopsin, and stored retinyl esters (all-trans and 11-cis) during retinal development in normal and rd mice. IRBP could be demonstrated at embryonic Day 17 (E17), corresponding to an early stage of inner segment development. Although all-trans retinyl esters were present earlier, 11-cis retinyl esters did not appear until postnatal Days 6–7 (P6–P7), corresponding to rod outer segment (ROS) disc formation. Rhodopsin was detected at the same developmental stage. The proportion of 11-cis retinyl esters reached a maximum of 40–50% at P15–P20. Thereafter, the proportion dropped, due to more rapid accumulation of the all-trans isomer. Rhodopsin and IRBP increased in parallel with ROS elongation up to P25, when the ROS had reached their mature lengths. The increases then continued up to P40–P50. In rd (retinal degeneration) mice, IRBP and rhodopsin were identical with the controls until P12, but then dropped as the photoreceptors degenerated. Synthesis and secretion of IRBP in vitro was less than 10% of the controls in rd retinas at P26, when only 4–5% of the photoreceptors survived. The quantities of retinyl esters (mainly stearate and palmitate in the ratio of 6:1, respectively) stored in dark-adapted mouse eyes progressively increased as the animals aged, representing 0.5 mole eq. of the rhodopsin at 8 months. Although retinyl esters (11-cis and all-trans) also accumulated in rd mouse eyes up to P12, little further increase occurred. At P93, the retinyl esters (0.01 nmole · eye−1) were only 4% of the controls at P91. A peak in the proportion of 11-cis isomer occurred at P10–P20, but it averaged only 15% of the total ester and declined to 5% at P93. These findings support the hypothesis that IRBP is synthesized by the rods and cones, and suggest that its synthesis and secretion are initiated when the photoreceptor inner segments start to differentiate. 11-cis Retinoids and rhodopsin do not appear until the outer segments start to form. It is suggested that in the rd mouse the absence of photoreceptors, perhaps coupled with lack of normal interphotoreceptor matrix, leads to a loss in the ability of the pigment epithelium to store retinyl esters.

Photoresponses of the Compound Eye of the Sandhopper Talitrus saltator (Crustacea, Amphipoda) in the Ultraviolet-Blue Range

The semi-terrestrial sandhopper Talitrus saltator uses celestial visual cues to orient along the sea-land axis of the beach. Previous spectral-filtering experiments suggested that it perceives directional information from wavelengths in the ultraviolet (UV)-blue range. Binary choice experiments between dark and UV (380-nm) light carried out on dark-adapted individuals of T. saltator showed photopositive movement to UV. Morphologically, each ommatidium in the eye consists of five retinula cells, four large and one small. In electroretinogram experiments, sensitivity of the dark-adapted eye is dominated by a receptor maximally sensitive at about 390-450 nm and secondarily sensitive at about 500-550 nm. Selective light-adaptation experiments at 580 nm showed the apparent sensitivity decreasing at around the secondary sensitive range, thus disclosing the existence of UV-blue photoreceptor cells. Here the existence of UV-blue detection is confirmed, and evidence is provided that green and UV-blue visual pigments are located in the large and small retinula cells, respectively.

Reddish-Orange Long-Lasting Phosphorescence of Ca2Si5N8 : Eu2 + , Tm3 + Phosphor

Reddish-orange long-lasting phosphorescence materials, various amounts of - and -co-doped phosphors , were prepared by the conventional high temperature solid-state reaction method, and their luminescence properties were systematically investigated by photoluminescence spectra, afterglow spectra, afterglow decay curves, and thermoluminescence spectra. The materials exhibited strong reddish-orange emission bands in a wavelength range of 500–750 nm with peak positions at about 600 nm due to the transition of the ion. Furthermore, these phosphors emitted strong reddish-orange long-lasting phosphorescence with an afterglow time of more than 1 h after turning off the activating lamp in the light perception of the dark-adapted human eye . Such afterglow of phosphors was attributed to the recombination of holes and electrons that were trapped within the lattice defect centers. The results of the thermoluminescence spectra indicated that the increase in the predominating band at 350 K, which was associated with the charge-trapping centers, was responsible for the enhancement of the afterglow properties of .

Laboratory and Field Response of the Emerald Ash Borer (Coleoptera: Buprestidae), to Selected Regions of the Electromagnetic Spectrum

Retinal sensitivity of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) was examined with an aim to improve trap efficacy for the beetle. Electroretinogram (ERG) recordings from dark-adapted compound eyes of male and female were measured at different wavelengths across the spectrum ranging from 300 to 700 nm. The spectral sensitivity curves revealed peaks in the UV (340 nm), the violet/purple (420-430 nm), blue (460 nm), and green (540-560 nm) regions of the spectrum. Females were sensitive to red regions of the spectrum (640-670 nm), whereas males were not. A spectrophotometer was used to measure the wavelength and reflectance for ash foliage, purple corrugated plastic traps, as well as the elytra and abdomen of adult A. planipennis. Traps were painted using colors based on ERG and spectrophotometer measurements and compared with purple corrugated plastic traps currently used by the USDA-APHIS-PPQ-EAB National Survey. In a field assay conducted along the edges of several A. planipennis-infested ash stands, there were no significant differences in trap catch among green, red, or purple treatments. Dark blue traps caught significantly fewer A. planipennis than red, light green, or dark purple traps. In a second assay where purple and green treatments were placed in the mid canopy of ash trees (approximately 13 m in height), trap catch was significantly higher on green treatments. We hypothesize that when placed in the mid-canopy, green traps constitute a foliage-type stimulus that elicits food-seeking and/or host seeking behavior by A. planipennis.

Electroretinographic Analysis of Night Vision in Juvenile Pacific Bluefin Tuna (Thunnus orientalis)

We used electroretinogram recordings to investigate visual function in the dark-adapted eyes of the juvenile scombrid fishes Pacific bluefin tuna (Thunnus orientalis) and chub mackerel (Scomber japonicus) and the carangid fish striped jack (Pseudocaranx dentex). Despite the fast swimming speed of the Pacific bluefin tuna, analysis of flicker electroretinograms showed that visual temporal resolution in this species was inferior to that in chub mackerel. Peak wavelengths of spectral sensitivity in Pacific bluefin tuna and striped jack were 479 and 512 nm, respectively. The light sensitivity of Pacific bluefin tuna was comparable to that of chub mackerel but lower than that of striped jack. The Pacific bluefin tuna may not need high-level visual function under dim light conditions in natural habitat because it is a diurnal fish. However, this low temporal resolution and light sensitivity probably explain the mass deaths from contact or collisions with net walls in cultured Pacific bluefin tuna.

Blue long lasting phosphorescence of Tm3+ in zinc pyrophosphate phosphor

Abstract Phosphate long lasting phosphorescence (LLP) phosphors with composition of (Zn 1− x Tm x ) 2 P 2 O 7 were prepared by the high-temperature solid-state method. Their properties were systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence (TL) spectra. These phosphors emit blue light that is related to the characteristic emission due to the 1 D 2 – 3 H 6 , 1 D 2 – 3 H 4 and 1 G 4 – 3 H 6 transitions of Tm 3+ . After the UV light excitation source was switched off, the bright blue long lasting phosphorescence can be observed which could last for more than 1 h in the limit of light perception of dark-adapted human eyes (0.32 mcd/m 2 ). Two TL peaks at 336 K and 415 K appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.67 eV and 0.97 eV, respectively. Also, the mechanism was discussed in this report.

Synthesis and luminescent properties of a novel bluish‐white afterglow phosphor, b‐Zn3(PO4)2:Hf4+

A new bluish-white long-lasting phosphorescent material, Hf4+-doped b-Zn3(PO4)2, was prepared by the conventional high-temperature solid-state method. The photoluminescence (PL) spectrum reveals that it exhibits a strong blue emission band centred at 470 nm, with asymmetry on the long wavelength side; this material emits bluish-white light and shows strong afterglow phosphorescence after it is excited with a 254 nm UV lamp. The phosphorescence lasts nearly 40 min in the light perception of the dark-adapted human eye (0.32 mcd/m(2)). The possible phosphorescence mechanism is also analysed.