scholarly journals Ultraviolet-Induced Sensitivity to Visible Light in Ultraviolet Receptors of Limulus

1972 ◽  
Vol 59 (2) ◽  
pp. 186-200 ◽  
Author(s):  
John Nolte ◽  
Joel E. Brown
Keyword(s):  
Spectral Sensitivity ◽  
Electrical Response ◽  
Receptor Potential ◽  
Ion Concentration ◽  
Sensitivity Curve ◽  
Long Wavelength ◽  
Median Ocellus ◽  
Wavelength Light ◽  
Reversal Potentials ◽  
Spectral Sensitivity Curve

In the UV-sensitive photoreceptors of the median ocellus (UV cells), prolonged depolarizing afterpotentials are seen following a bright UV stimulus. These afterpotentials are abolished by long-wavelength light. During a bright UV stimulus, long-wavelength light elicits a sustained negative-going response. These responses to long-wavelength light are called repolarizing responses. The spectral sensitivity curve for the repolarizing responses peaks at 480 nm; it is the only spectral sensitivity curve for a median ocellus electrical response known to peak at 480 nm. The reversal potentials of the repolarizing response and the depolarizing receptor potential are the same, and change in the same way when the external sodium ion concentration is reduced. We propose that the generation of repolarizing responses involves a thermally stable intermediate of the UV-sensitive photopigment of UV cells.

scholarly journals The Spectral Sensitivities of Single Cells in the Median Ocellus of Limulus

1969 ◽  
Vol 54 (5) ◽  
pp. 636-649 ◽  
Author(s):  
John Nolte ◽  
Joel E. Brown
Keyword(s):  
Visible Light ◽  
Spectral Sensitivity ◽  
Uv Light ◽  
Single Cells ◽  
Chromatic Adaptation ◽  
Sensitivity Curve ◽  
Receptor Cells ◽  
Intracellular Microelectrodes ◽  
Median Ocellus ◽  
Spectral Sensitivity Curve

The spectral sensitivities of single Limulus median ocellus photoreceptors have been determined from records of receptor potentials obtained using intracellular microelectrodes. One class of receptors, called UV cells (ultraviolet cells), depolarizes to near-UV light and is maximally sensitive at 360 nm; a Dartnall template fits the spectral sensitivity curve. A second class of receptors, called visible cells, depolarizes to visible light; the spectral sensitivity curve is fit by a Dartnall template with λmax at 530 nm. Dark-adapted UV cells are about 2 log units more sensitive than dark-adapted visible cells. UV cells respond with a small hyperpolarization to visible light and the spectral sensitivity curve for this hyperpolarization peaks at 525–550 nm. Visible cells respond with a small hyperpolarization to UV light, and the spectral sensitivity curve for this response peaks at 350–375 nm. Rarely, a double-peaked (360 and 530 nm) spectral sensitivity curve is obtained; two photopigments are involved, as revealed by chromatic adaptation experiments. Thus there may be a small third class of receptor cells containing two photopigments.

scholarly journals Timing of Ca2+ Release from Intracellular Stores and the Electrical Response of Limulus Ventral Photoreceptors to Dim Flashes

2000 ◽  
Vol 115 (6) ◽  
pp. 735-748 ◽  
Author(s):  
Richard Payne ◽  
James Demas
Keyword(s):  
Latent Period ◽  
Electrical Response ◽  
Cyclopiazonic Acid ◽  
Receptor Potential ◽  
Ion Concentration ◽  
Free Calcium ◽  
Flash Intensity ◽  
Stochastic Variation ◽  
Highly Correlated ◽  
Indicator Dyes

Light-induced release of Ca2+ from stores in Limulus ventral photoreceptors was studied using confocal fluorescence microscopy and the Ca2+ indicator dyes, Oregon green-5N and fluo-4. Fluorescence was collected from a spot within 4 μm of the microvillar membrane. A dual-flash protocol was used to reconstruct transient elevations of intracellular free calcium ion concentration (Cai) after flashes delivering between 10 and 5 × 105 effective photons. Peak Cai increased with flash intensity to 138 ± 76 μM after flashes delivering ∼104 effective photons, while the latent period of the elevation of Cai fell from ∼140 to 21 ms. The onset of the light-induced elevation of Cai was always highly correlated with that of the receptor potential. The time for Cai to exceed 2 μM was approximately equal to that for the receptor potential to exceed 8 mV (mean difference; 2.2 ± 6.4 ms). Cai was also measured during steps of light delivering ∼105 effective photons/s to photoreceptors that had been bleached with hydroxylamine so as to reduce their quantum efficiency. Elevations of Cai 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 Cai and the receptor potential still rose at approximately the same time, indicating a shared process generating the latent period. Light-induced elevations of Cai resulted from Ca2+ release from intracellular stores, being abolished by cyclopiazonic acid (CPA), an inhibitor of endoplasmic reticulum Ca2+ pumps, but not by removal of extracellular Ca2+ ions. CPA also greatly diminished and slowed the receptor potential elicited by dim flashes. The results demonstrate a rapid release of Ca2+ ions that appears necessary for a highly amplified electrical response to dim flashes.

An anomaly in the response of the eye to light of short wavelengths

1977 ◽  
Vol 278 (960) ◽  
pp. 207-240 ◽  
Keyword(s):  
Field Experiment ◽  
Spectral Sensitivity ◽  
Large Range ◽  
Fusion Frequency ◽  
Long Wavelength ◽  
Human Eye ◽  
Vision Experiment ◽  
Wavelength Light

Adaptation of the human eye to long-wavelength light leaves it insensitive to short-wavelengths: a blue flash that is visible in the presence of a yellow adapting field may remain invisible for several seconds after the field has been turned off (see experiment 1 and Appendix). This ‘transient tritanopia’ occurs for a large range of adapting intensities, but is abolished if the adapting field is very bright (experiment 2). The loss of sensitivity is primarily confined to the blue-sensitive cone mechanism (experiments 2 a , 3 and 4 ; and Appendix) and can be produced by small attenuations of the adapting field (experiment 5). It occurs in both foveal and parafoveal vision (experiment 6) but is absent when adapting and test stimuli are presented to opposite eyes (experiment 7). It was found in a protanope (experiment 9 a ) and, in a modified form, in a deuteranope (experiment 9 b ). No differences in sensitivity were found for blue flashes presented in the light and dark phases of a field flickering at a rate above the fusion frequency (Appendix). The sensitivity of the blue-sensitive mechanism of the eye appears to be controlled not only by quanta absorbed by the blue receptors but also by a mechanism with a different spectral sensitivity

Phototaktische Reaktion von Asplanchna priodonta bei monochromatischem Reizlicht/Phototactic Reactions of Asplanchna priodonta to Monochromatic Light

1979 ◽  
Vol 34 (1-2) ◽  
pp. 148-152 ◽  
Author(s):  
Horst Hertel
Keyword(s):  
Spectral Sensitivity ◽  
Monochromatic Light ◽  
Rapid Decrease ◽  
Sensitivity Curve ◽  
Test Light ◽  
Asplanchna Priodonta ◽  
Light Stimuli ◽  
Spectral Sensitivity Curve ◽  
The Way

Abstract 1. The spectral sensitivity curve of the positive phototactic reaction of the rotifer Asplanchna priodon ta has a triple peak. The maxima lie at 363 nm, 453 nm and 552 nm.2. In the shortest wavelength tested and in the area of 453 to 594 nm was the precision of the phototactic orientation found to be high. In between lies a minimum at 395 nm, above 594 nm occurs a rapid decrease in phototactic orientation.3. No wavelength specific differences in the way of orientation were found when using dif­ ferent monochromatic test light stimuli. This leads the same mixture of photopigments.

scholarly journals THE RESPONSES OF THE PUPIL OF GEKKO GEKKO TO EXTERNAL LIGHT STIMULUS

1956 ◽  
Vol 40 (2) ◽  
pp. 201-216 ◽  
Author(s):  
E. J. Denton
Keyword(s):  
Light Intensity ◽  
Spectral Sensitivity ◽  
Light Stimulus ◽  
Spatial Summation ◽  
Large Degree ◽  
Absorption Curve ◽  
Sensitivity Curve ◽  
Pupil Response ◽  
Retinal Rod ◽  
Spectral Sensitivity Curve

1. The responses of the pupil of a nocturnal gecko (Gekko gekko) to external light stimulus were studied. 2. The responses of the pupil are determined by light entering the pupil and not by light acting directly on the iris. 3. The responses of the pupil are very uniform in sensitivity including spectral sensitivity for light coming in different directions to the eye. 4. The possible change in area of the pupil is more than 300-fold and probably represents an effort to shield the pure rod retina from saturating light intensities. 5. The pupil continues to contract sharply for changes in external light intensity which give retinal illuminations corresponding to 106 quanta/sec. striking a retinal rod. 6. There is a large degree of spatial summation of the response; circular external light fields subtending 5 and 140° giving the same illumination at the pupil give approximately the same pupil response. 7. The spectral sensitivity curve agrees with the absorption curve of an extracted pigment from a closely related gecko described by Crescitelli in the followig paper. It is similar to the human scotopic curve but its maximum is displaced about 20 to 30 mµ towards the red end of the spectrum. The fall in sensitivity towards the red end of the spectrum is described by the equation See PDF for Equation

scholarly journals Comparisons of Scotopic/Photopic Ratios Using 2- and 10-Degree Spectral Sensitivity Curves

2019 ◽  
Vol 9 (20) ◽  
pp. 4471
Author(s):  
Jianhua Ding ◽  
Qi Yao ◽  
Lei Jiang
Keyword(s):  
Spectral Sensitivity ◽  
Light Sources ◽  
Sensitivity Curve ◽  
P Values ◽  
Practical Applications ◽  
Luminance Difference ◽  
Maximum Value ◽  
Sensitivity Curves ◽  
Conversion Coefficients ◽  
Spectral Sensitivity Curve

Despite the fact that a 2-degree spectral sensitivity curve (SSC) is extensively used in scientific research and relevant applications, the choice between the 10-degree or the 2-degree photopic SSCs in practical applications for the calculation of scotopic/photopic ratios (S/P ratios) depends on actual needs. We examined S/P ratios for more than 300 light sources for correlated colour temperatures (CCTs) from 2000 K to 8000 K and blackbody radiant spectra from 10000 K to 45000 K using 2- and 10-degree SSCs. Results showed that the ratio of the S/P values calculated using the 10-degree and 2-degree SSCs was approximately equal to 0.916. The average mesopic luminance difference increased from 0% to 5.7% at a photopic adaptation luminance from 0.005 to 5 cd/m2. For most practical applications, the mesopic luminance values calculated using these two SSCs were different by several percentage units, yet these differences could be neglected. At extremely high CCTs over 10000 K, the mesopic luminance difference may approximate the maximum value of 16%. This work proposes the conversion coefficients for S/P ratios and the transforming mesopic luminance values calculated for 2- and 10-degree SSC systems. These results may help researchers clarify differences between the S/P ratios calculated using different SSCs.

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