scholarly journals Retinal mechanisms of visual adaptation in the skate.

1975 ◽  
Vol 65 (4) ◽  
pp. 483-502 ◽  
Author(s):  
D G Green ◽  
J E Dowling ◽  
I M Siegel ◽  
H Ripps
Keyword(s):  
Ganglion Cell ◽  
Cell Activity ◽  
Receptor Potential ◽  
Visual Adaptation ◽  
Cell Discharge ◽  
Cell Responses ◽  
Electrical Potentials ◽  
Rate Of Recovery ◽  
Network Mechanism ◽  
Different Levels

Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly iluminated background that had no measurable effect on the senitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and gaglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.

scholarly journals S-Potentials in the Skate Retina

1971 ◽  
Vol 58 (2) ◽  
pp. 163-189 ◽  
Author(s):  
John E. Dowling ◽  
Harris Ripps
Keyword(s):  
Membrane Potential ◽  
Ganglion Cell ◽  
Dark Adaptation ◽  
Membrane Potentials ◽  
Horizontal Cells ◽  
Photic Stimulation ◽  
Visual Adaptation ◽  
Cell Discharge ◽  
Background Fields ◽  
Potential Level

The S-potentials recorded intracellularly from the all-rod retina of the skate probably arise from the large horizontal cells situated directly below the layer of receptors. These cells hyperpolarize in response to light, irrespective of stimulus wavelength, and the responses in photopic as well as scotopic conditions were found to be subserved by a single photopigment with λmax = 500 nm. The process of adaptation was studied by recording simultaneously the threshold responses and membrane potentials of S-units during both light and dark adaptation. The findings indicate that the sensitivity of S-units, whether measured upon steady background fields or in the course of dark adaptation, exhibits changes similar to those demonstrated previously for the ERG b-wave and ganglion cell discharge. However, the membrane potential level of the S-unit and its sensitivity to photic stimulation varied independently for all the adapting conditions tested. It appears, therefore, that visual adaptation in the skate retina occurs before the S-unit is reached, i.e., at the receptors themselves.

scholarly journals Visual Adaptation in the Retina of the Skate

1970 ◽  
Vol 56 (4) ◽  
pp. 491-520 ◽  
Author(s):  
John E. Dowling ◽  
Harris Ripps
Keyword(s):  
Ganglion Cell ◽  
Light Adaptation ◽  
Cell Activity ◽  
Absolute Threshold ◽  
Close Correlation ◽  
Slow Recovery ◽  
Raja Erinacea ◽  
Cell Discharge ◽  
Fundus Reflectometry

The electroretinogram (ERG) and single-unit ganglion cell activity were recorded from the eyecup of the skate (Raja erinacea and R. oscellata), and the adaptation properties of both types of response compared with in situ rhodopsin measurements obtained by fundus reflectometry. Under all conditions tested, the b-wave of the ERG and the ganglion cell discharge showed identical adaptation properties. For example, after flash adaptation that bleached 80% of the rhodopsin, neither ganglion cell nor b-wave activity could be elicited for 10–15 min. Following this unresponsive period, thresholds fell rapidly; by 20 min after the flash, sensitivity was within 3 log units of the dark-adapted level. Further recovery of threshold was slow, requiring an additional 70–90 min to reach absolute threshold. Measurements of rhodopsin levels showed a close correlation with the slow recovery of threshold that occurred between 20 and 120 min of dark adaptation; there is a linear relation between rhodopsin concentration and log threshold. Other experiments dealt with the initial unresponsive period induced by light adaptation. The duration of this unresponsive period depended on the brightness of the adapting field; with bright backgrounds, suppression of retinal activity lasted 20–25 min, but sensitivity subsequently returned and thresholds fell to a steady-state value. At all background levels tested, increment thresholds were linearly related to background luminance.

Physiological effects of muscarinic vs nicotinic ACh antagonists upon ganglion cell activity in the frog retina

1987 ◽  
Vol 27 (12) ◽  
pp. 2061-2072 ◽  
Author(s):  
N. Bonaventure ◽  
B. Jardon ◽  
N. Wioland ◽  
G. Rudolf
Keyword(s):  
Ganglion Cell ◽  
Cell Activity ◽  
Physiological Effects ◽  
Frog Retina

Relation between Ganglion Cell Activity and the Local Electroretinogram of Cat Retina

Nature ◽  
1967 ◽  
Vol 216 (5119) ◽  
pp. 1008-1010 ◽  
Author(s):  
ROY H. STEINBERG
Keyword(s):  
Ganglion Cell ◽  
Cell Activity ◽  
Cat Retina

scholarly journals PD-L1 – PD-1 interactions limit effector Treg cell populations at homeostasis and during infection

2020 ◽  
Author(s):  
J.A. Perry ◽  
J.T. Clark ◽  
J. Gullicksrud ◽  
J. DeLong ◽  
L. Shallberg ◽  
...  
Keyword(s):  
T Cell ◽  
Treg Cell ◽  
Cell Activity ◽  
T Cell Responses ◽  
Treg Cells ◽  
Whole Body ◽  
Cell Responses ◽  
Early Production ◽  
Ifn Γ ◽  
Specific Deletion

AbstractWhile much is known about the factors that promote the development of diverse Treg cell responses, less is known about the pathways that constrain Treg cell activities. The studies presented here reveal that at homeostasis there is a population of effector Treg cells that express PD-1, and that blockade of PD-L1 or loss of PD-1 results in increased Treg cell activity. In response to infection with the parasite T. gondii, the early production of IFN-γ results in widespread upregulation of PD-L1. Moreover, blockade of PD-L1, whole body deletion of PD-1, or lineage-specific deletion of PD-1 in Foxp3+ cells prevented the loss of the effector Treg cells but resulted in reduced pathogen specific CD4+ T cell responses during infection. Thus, at homeostasis basal PD-L1 expression constrains and tunes the pool of Treg cells, but during infection the upregulation of PD-L1 provides a mechanism to contract the Treg cell population required to maximize the development of pathogen specific CD4+ T cell responses.

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