Off-components in response to brief light flashes in the oscillatory potential of the human electroretinogram

1978 ◽  
Vol 206 (2) ◽  
pp. 107-120 ◽  
Author(s):  
M. Kojima ◽  
E. Zrenner
Keyword(s):  
Oscillatory Potential ◽  
Light Flashes

scholarly journals An engineered membrane-bound guanylyl cyclase with light-switchable activity

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Yuehui Tian ◽  
Georg Nagel ◽  
Shiqiang Gao
Keyword(s):  
Guanylyl Cyclase ◽  
Green Light ◽  
Chemical Properties ◽  
Light Sensitivity ◽  
Cgmp Level ◽  
Volvox Carteri ◽  
Non Invasive ◽  
Cgmp Signaling ◽  
Membrane Bound ◽  
Light Flashes

Abstract Background Microbial rhodopsins vary in their chemical properties, from light sensitive ion transport to different enzymatic activities. Recently, a novel family of two-component Cyclase (rhod)opsins (2c-Cyclop) from the green algae Chlamydomonas reinhardtii and Volvox carteri was characterized, revealing a light-inhibited guanylyl cyclase (GC) activity. More genes similar to 2c-Cyclop exist in algal genomes, but their molecular and physiological functions remained uncharacterized. Results Chlamyopsin-5 (Cop5) from C. reinhardtii is related to Cr2c-Cyclop1 (Cop6) and can be expressed in Xenopus laevis oocytes, but shows no GC activity. Here, we exchanged parts of Cop5 with the corresponding ones of Cr2c-Cyclop1. When exchanging the opsin part of Cr2c-Cyclop1 with that of Cop5, we obtained a bi-stable guanylyl cyclase (switch-Cyclop1) whose activity can be switched by short light flashes. The GC activity of switch-Cyclop1 is increased for hours by a short 380 nm illumination and switched off (20-fold decreased) by blue or green light. switch-Cyclop1 is very light-sensitive and can half-maximally be activated by ~ 150 photons/nm2 of 380 nm (~ 73 J/m2) or inhibited by ~ 40 photons/nm2 of 473 nm (~ 18 J/m2). Conclusions This engineered guanylyl cyclase is the first light-switchable enzyme for cGMP level regulation. Light-regulated cGMP production with high light-sensitivity is a promising technique for the non-invasive investigation of the effects of cGMP signaling in many different tissues.

Light flashes and shocks from a cavitating flow

1965 ◽  
Vol 16 (5) ◽  
pp. 675-682 ◽  
Author(s):  
P D Jarman ◽  
K J Taylor
Keyword(s):  
Cavitating Flow ◽  
Light Flashes

Study of Cosmic Rays and Light Flashes on board Space Station MIR: The SilEye experiment

2000 ◽  
Vol 25 (10) ◽  
pp. 2075-2079 ◽  
Author(s):  
V. Bidoli ◽  
M. Casolino ◽  
M.P. De Pascale ◽  
G. Furano ◽  
A. Morselli ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Space Station ◽  
Light Flashes

Force relaxes before the fall of cytosolic calcium in the photomechanical response of rat sphincter pupillae

2000 ◽  
Vol 279 (1) ◽  
pp. C274-C280 ◽  
Author(s):  
Andrew P. Krivoshik ◽  
Lloyd Barr
Keyword(s):  
Myosin Light Chain ◽  
Smooth Muscles ◽  
Cytosolic Calcium ◽  
Myosin Phosphorylation ◽  
Primary Signal ◽  
Intracellular Ca ◽  
Phosphorylation Cascade ◽  
Muscle Myosin ◽  
Light Flashes ◽  
Stimulation Of

In the rat sphincter pupillae, as in other smooth muscles, the primary signal transduction cascade for agonist activation is receptor → G protein → phospholipase C → inositol trisphosphate → intracellular Ca2+concentration ([Ca2+]i) → calmodulin → myosin light chain kinase → phosphorylated myosin → force development. Light stimulation of isolated sphincters pupillae can be very precisely controlled, and precise reproducible photomechanical responses (PMRs) result. This precision makes the PMR ideal for testing models of regulation of smooth muscle myosin phosphorylation. We measured force and [Ca2+]iconcurrently in sphincter pupillae following stimulation by light flashes of varying duration and intensity. We sampled at unusually short (0.01–0.02 s) intervals to adequately test a PMR model based on the myosin phosphorylation cascade. We found, surprisingly, contrary to the behavior of intestinal muscle and predictions of the phosphorylation model, that during PMRs force begins to decay while [Ca2+]iis still rising. We conclude that control of contraction in the sphincter pupillae probably involves an inhibitory process as well as activation by [Ca2+]i.

Change in Oscillatory Potential by Thioridazine

1979 ◽  
Vol 178 (4) ◽  
pp. 220-225 ◽  
Author(s):  
Supachui Chotibutr ◽  
Mikio Miyata ◽  
Hiroko Hirosawa ◽  
Satoshi Ishikawa
Keyword(s):  
Oscillatory Potential
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