scholarly journals The Duplex Nature of the Retina of the Nocturnal Gecko as Reflected in the Electroretinogram

1961 ◽  
Vol 44 (6) ◽  
pp. 1143-1158 ◽  
Author(s):  
Eberhard Dodt ◽  
Karl Heinz Jessen
Keyword(s):  
Electrical Activity ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Slow Phase ◽  
Strong Light ◽  
Increment Threshold ◽  
Hemidactylus Turcicus ◽  
Low Levels ◽  
Different Levels ◽  
Effect Of Light

The effect of light and dark adaptation on the electrical activity in two species of nocturnal gecko, Hemidactylus turcicus and Tarentola mauritanica was studied. The electroretinogram of both species changes from the scotopic type in the dark-adapted state to the photopic type after strong light adaptation. For the scotopic response fusion frequencies up to 18 flashes per sec. are obtained in both species. For the photopic response fusion frequencies up to 50 flashes per sec. are seen in Tarentola, and up to 25 flashes per sec. in Hemidactylus. Proceeding from dark to light adaptation the increment threshold (dI) is measured at different levels of adaptive illumination (I). At low levels of illumination the dI/I ratio is found to be small and at high levels of illumination to be large. No difference in the dI/I ratio is obtained for test lights of 462 and 605 mµ. During dark adaptation the change of threshold after exposure to moderate and weak lights (up to 103 times dark threshold) is rather fast. After light adaptation to strong light (106 times dark threshold) duplex dark adaptation curves are seen with a break separating a fast and a slow phase of dark adaptation. The significance of these results from a retina which possesses sense cells of only one type is discussed.

scholarly journals Neural and Photochemical Mechanisms of Visual Adaptation in the Rat

1963 ◽  
Vol 46 (6) ◽  
pp. 1287-1301 ◽  
Author(s):  
John E. Dowling
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
Slow Component ◽  
Neural Adaptation ◽  
Visual Adaptation ◽  
Slow Phase ◽  
Rapid Phase ◽  
Increment Threshold ◽  
Slow Adaptation ◽  
Wide Range

The effects of light adaptation on the increment threshold, rhodopsin content, and dark adaptation have been studied in the rat eye over a wide range of intensities. The electroretinogram threshold was used as a measure of eye sensitivity. With adapting intensities greater than 1.5 log units above the absolute ERG threshold, the increment threshold rises linearly with increasing adapting intensity. With 5 minutes of light adaptation, the rhodopsin content of the eye is not measurably reduced until the adapting intensity is greater than 5 log units above the ERG threshold. Dark adaptation is rapid (i.e., completed in 5 to 10 minutes) until the eye is adapted to lights strong enough to bleach a measurable fraction of the rhodopsin. After brighter light adaptations, dark adaptation consists of two parts, an initial rapid phase followed by a slow component. The extent of slow adaptation depends on the fraction of rhodopsin bleached. If all the rhodopsin in the eye is bleached, the slow fall of threshold extends over 5 log units and takes 2 to 3 hours to complete. The fall of ERG threshold during the slow phase of adaptation occurs in parallel with the regeneration of rhodopsin. The slow component of dark adaptation is related to the bleaching and resynthesis of rhodopsin; the fast component of adaptation is considered to be neural adaptation.

scholarly journals Dark-adapted rod suppression of cone flicker detection: Evaluation of receptoral and postreceptoral interactions

2006 ◽  
Vol 23 (3-4) ◽  
pp. 531-537 ◽  
Author(s):  
DINGCAI CAO ◽  
ANDREW J. ZELE ◽  
JOEL POKORNY
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
Central Field ◽  
Magnocellular Pathway ◽  
Stimulus Field ◽  
Independent Control ◽  
Detection Evaluation ◽  
Different Levels

Dark-adapted rods in the area surrounding a luminance-modulated field can suppress flicker detection. However, the characteristics of the interaction between rods and each of the cone types are unclear. To address this issue, the effect that dark-adapted rods have on specific classes of receptoral and postreceptoral signals was determined by measuring the critical fusion frequencies (CFF) for receptoral L-, M-, and S-cone and postreceptoral luminance ([L+M+S] and [L+M+S+Rod]) and chromatic ([L/(L+M)]) signals in the presence of different levels of surrounding rod activity. Stimuli were generated with a two-channel photostimulator that has four primaries for a central field and four primaries for the surround, allowing independent control of rod and cone excitation. Measurements were made either with adaptation to the stimulus field after dark adaptation or during a brief period following light adaptation. The results show that dark-adapted rods maximally suppressed the CFF by ∼6 Hz for L-cone, M-cone, and luminance modulation. Dark-adapted rods, however, did not significantly alter the S-cone CFF. The [L/(L+M)] postreceptoral CFF was slightly suppressed at higher surround illuminances, that is, higher than surround luminances resulting in suppression for L-cone, M-cone, or luminance modulation. We conclude that rod-cone interactions in flicker detection occurred strongly in the magnocellular pathway.

scholarly journals Visual pigment and photoreceptor sensitivity in the isolated skate retina.

1978 ◽  
Vol 71 (4) ◽  
pp. 369-396 ◽  
Author(s):  
D R Pepperberg ◽  
P K Brown ◽  
M Lurie ◽  
J E Dowling
Keyword(s):  
Dark Adaptation ◽  
Visual Pigment ◽  
Response Curve ◽  
Time Course ◽  
Light Adaptation ◽  
Receptor Sensitivity ◽  
Strong Light ◽  
Receptor Response ◽  
Intensity Response ◽  
Isolated Retina

Photoreceptor potentials were recorded extracellularly from the aspartate-treated, isolated retina of the skate (Raja oscellata and R. erinacea), and the effects of externally applied retinal were studied both electrophysiologically and spectrophotometrically. In the absence of applied retinal, strong light adaptation leads to an irreversible depletion of rhodopsin and a sustained elevation of receptor threshold. For example, after the bleaching of 60% of the rhodopsin initially present in dark-adapted receptors, the threshold of the receptor response stabilizes at a level about 3 log units above the dark-adapted value. The application of 11-cis retinal to strongly light-adapted photoreceptors induces both a rapid, substantial lowering of receptor threshold and a shift of the entire intensity-response curve toward greater sensitivity. Exogenous 11-cis retinal also promotes the formation of rhodopsin in bleached photoreceptors with a time-course similar to that of the sensitization measured electrophysiologically. All-trans and 13-cis retinal, when applied to strongly light-adapted receptors, fail to promote either an increase in receptor sensitivity or the formation of significant amounts of light-sensitive pigment within the receptors. However, 9-cis retinal isin. These findings provide strong evidence that the regeneration of visual pigment in the photoreceptors directly regulates the process of photochemical dark adaptation.

scholarly journals Some Properties of the Photoreceptors of the Brook Lamprey

1950 ◽  
Vol 27 (3) ◽  
pp. 350-364
Author(s):  
D. M. STEVEN
Keyword(s):  
Spectral Sensitivity ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Intensity Discrimination ◽  
Light Reaction ◽  
Principal Characteristics ◽  
Simple Curves ◽  
Physiological Properties ◽  
Time Relation ◽  
Different Levels

1. A method is described for measuring the principal characteristics of the light reaction of the ammocoete, and data are presented on the relation between the intensity and duration of the stimulus, dark adaptation, intensity discrimination and spectral sensitivity. 2. The intensity/time relation approximates to the Bunsen-Roscoe Law at low intensities of illumination. Use is made of this fact to define a criterion for a constant response to a given stimulus, for measuring the other physiological properties of the system. 3. Dark adaptation and intensity discrimination at different levels of adapting illumination both yield simple curves, which suggest that the system contains a single photosensitive pigment. The range of dark adaptation following a period of light adaptation is from 10 to 30 times. The threshold of excitation of a dark adapted ammocoete is from 0.25 to 0.95 millilambert. 4. The spectral sensitivity possesses a sharply peaked maximum about 530 mµ. Reasons are presented for suggesting porphyropsin (visual violet) as the photosensitive pigment concerned.

scholarly journals DARK ADAPTATION IN AGRIOLIMAX

1928 ◽  
Vol 12 (1) ◽  
pp. 83-109 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf
Keyword(s):  
Dark Adaptation ◽  
Light Adaptation ◽  
The Body ◽  
Differential Sensitivity ◽  
Different Types ◽  
The Difference ◽  
Two Sides ◽  
Kinetics Of ◽  
Different Levels ◽  
Continuous Excitation

A method is described which measures the excitation of Agriolimax by light, during the progress of light adaptation, by assuming that the orientating effect of continuous excitation is expressed as a directly proportionate tension difference in the orienting muscles of the two sides of the body. The tendency toward establishment of such a tension difference is caused to work against a similar geotropic effect at right angles to the phototropic one. This enables one to study the kinetics of light adaptation, and of dark adaptation as well. The situation in the receptors is adequately described by the paradigm See PDF for Equation similar to that derived by Hecht for the differential sensitivity of various forms, but with the difference that the "dark" reaction is not only "bimolecular" but also autocatalysed by the reaction product S. The progress of dark adaptation is reflected (1) in the recovery of the amplitude of the orientation and (2) in the rates of light adaptation at different levels of the recovery; each independently supports these assumptions, for which the necessary equations have been provided. These equations also account for the relative variabilities of the angles of orientation, and, more significantly, for the two quite different kinds of curves of dark adaptation which are obtained in slightly different types of tests.

scholarly journals The Activity of Slugs

1954 ◽  
Vol 31 (2) ◽  
pp. 188-197
Author(s):  
BARBARA H. DAINTON
Keyword(s):  
Temperature Gradient ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Red Light ◽  
The Body ◽  
Nocturnal Activity ◽  
Low Level ◽  
Daytime Activity ◽  
Induce Activity ◽  
Effect Of Light

1. Slugs are normally active at night, but this is not a response to darkness. The onset of nocturnal activity does not necessarily coincide, either in the field or in the laboratory, with the onset of darkness. On the contrary, dark-adapted, inactive animals become active on illumination. 2. The activity which follows illumination is short-lived, adaptation being complete within an hour. 3. Dark-adaptation is slower than light-adaptation and takes between 1 and 2 hr. 4. The response occurs whether illumination is constant or intermittent and in white or red light. Once adapted to red light the slugs do not respond to illumination by white light. 5. This effect of light, in initially activating the slugs, clearly cannot account for the occasional daytime activity observed in the field, when the slugs emerge from dark resting places. 6. Once the slugs are light-adapted, the activity during the daytime remains at a very low level even under continued illumination. This low level is probably the same as occurs in the dark under similar conditions. 7. Air currents played on the body or tail of the slug increase the speed of locomotion or induce activity if the animal is at rest. 8. Air currents played on the head or tentacles results in a klinotactic response whereby the animal turns from the region of draught or moves down stream. 9. These reactions must supplement the reactions in a temperature gradient which lead the slugs at the close of activity to sheltered resting places.

Effect of light intensity on assimilation characteristics of detached tea leaves

1964 ◽  
Vol 63 (2) ◽  
pp. 265-271 ◽  
Author(s):  
D. N. Barua
Keyword(s):  
Light Intensity ◽  
Chlorophyll Concentration ◽  
Leaf Lamina ◽  
Tea Leaves ◽  
Tungsten Filament ◽  
Strong Light ◽  
Filament Lamp ◽  
Sun Leaves ◽  
Different Sources ◽  
Effect Of Light

Photosynthetic rates of detached, mature tea leaves from four different sources were determined in excess CO2 and light of 4, 10, 16 and 32 klux intensities from a tungsten-filament lamp. Temperature was maintained at 25°C. The assimilation rates were significantly different for the four sources both in weak and in strong light. Neither thickness of the leaf lamina nor chlorophyll concentration could explain the cause of this difference.The effect of shade adaptation on the subsequent rate of assimilation was examined in one of the four sources of leaf. Shade-adapted leaves had significantly higher rates of photosynthesis at the weakest light intensity of 4 klux and lower rates in 16 and 32 klux intensities than the corresponding sun leaves.

AML1 is expressed in skeletal muscle and is regulated by innervation

1994 ◽  
Vol 14 (12) ◽  
pp. 8051-8057
Author(s):  
X Zhu ◽  
J E Yeadon ◽  
S J Burden
Keyword(s):  
Skeletal Muscle ◽  
Acute Myeloid Leukemia ◽  
Electrical Activity ◽  
Myeloid Leukemia ◽  
Structure And Function ◽  
Denervated Muscle ◽  
Aml1 Gene ◽  
Low Levels ◽  
And Function ◽  
Acute Myeloid

Although most skeletal muscle genes are expressed at similar levels in electrically active, innervated muscle and in electrically inactive, denervated muscle, a small number of genes, including those encoding the acetylcholine receptor, N-CAM, and myogenin, are expressed at significantly higher levels in denervated than in innervated muscle. The mechanisms that mediate electrical activity-dependent gene regulation are not understood, but these mechanisms are likely to be responsible, at least in part, for the changes in muscle structure and function that accompany a decrease in myofiber electrical activity. To understand how muscle activity regulates muscle structure and function, we used a subtractive-hybridization and cloning strategy to identify and isolate genes that are expressed preferentially in innervated or denervated muscle. One of the genes which we found to be regulated by electrical activity is the recently discovered acute myeloid leukemia 1 (AML1) gene. Disruption and translocation of the human AML1 gene are responsible for a form of acute myeloid leukemia. AML1 is a DNA-binding protein, but its normal function is not known and its expression and regulation in skeletal muscle were not previously appreciated. Because of its potential role as a transcriptional mediator of electrical activity, we characterized expression of the AML1 gene in innervated, denervated, and developing skeletal muscle. We show that AML1 is expressed at low levels in innervated skeletal muscle and at 50- to 100-fold-higher levels in denervated muscle. Four AML1 transcripts are expressed in denervated muscle, and the abundance of each transcript increases after denervation. We transfected C2 muscle cells with an expression vector encoding AML1, tagged with an epitope from hemagglutinin, and we show that AML1 is a nuclear protein in muscle. AML1 dimerizes with core-binding factor beta (CBF beta), and we show that CGF beta is expressed at high levels in both innervated and denervated skeletal muscle. PEBP2 alpha, which is structurally related to AML1 and which also dimerizes with CBF beta, is expressed at low levels in skeletal muscle and is up-regulated only weakly by denervation. These results are consistent with the idea that AML1 may have a role in regulating gene expression in skeletal muscle.

The Cockroach DCMD Neurone: I. Lateral Inhibition and the Effects of Light- and Dark-adaptation

1982 ◽  
Vol 99 (1) ◽  
pp. 61-90 ◽  
Author(s):  
DONALD H. EDWARDS
Keyword(s):  
Lateral Inhibition ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Absolute Intensity ◽  
Recurrent Network ◽  
Light Spot ◽  
Movement Detector ◽  
Threshold Response ◽  
Inhibitory Network ◽  
Local Background

1. The responses of the cockroach descending contralateral movement detector (DCMD) neurone to moving light stimuli were studied under both light- and dark-adapted conditions. 2. With light-adaptation the response of the DCMD to two moving 2° (diam.) spots of white light is less than the response to a single spot when the two spots are separated by less than 10° (Fig. 2). 3. With light-adaptation the response of the DCMD to a single moving light spot is a sigmoidally shaped function of the logarithm of the light intensity (Fig. 3a). With dark-adaptation the response of a DCMD to a single moving light spot is a bell-shaped function of the logarithm of the stimulus intensity (Fig. 3b). The absolute intensity that evokes a threshold response is about one-and-a-half log units less in the dark-adapted eye than in the light-adapted eye. 4. The decrease in the DCMD's response that occurs when two stimuli are closer than 10°, and when a single bright stimulus is made brighter, indicates that lateral inhibition operates among the afferents to the DCMD. 5. It is shown that this inhibition cannot be produced by a recurrent lateral inhibitory network. A model of the afferent path that contains a non-recurrent lateral inhibitory network can account for the response/intensity plots of the DCMD recorded under both light-adapted and dark-adapted conditions. 6. The threshold intensity of the DCMD is increased if a stationary pattern of light is present near the path of the moving spot stimulus. This is shown to be due to a peripheral tonic lateral inhibition that is distinct from the non-recurrent lateral inhibition described earlier. 7. It is suggested that the peripheral lateral inhibition acts to adjust the threshold of afferents to local background light levels, while the proximal non-recurrent network acts to enhance the acuity of the eye to small objects in the visual field, and to filter out whole-field stimuli.

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