D W Corson

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Single pressure injections of 1-2 mM calcium aspartate into the light-sensitive region of Limulus ventral photoreceptors resulted in a rapid, 20-40-mV depolarization lasting approximately 2 s. The depolarization closely followed the rise in intracellular free calcium caused by the injection, as indicated by aequorin luminescence. The depolarization was(More)
Single pressure injections of 1-10 pl of inositol 1,4,5 triphosphate (IP3) or inositol 4,5 bisphosphate [I(4,5)P2] excite Limulus ventral photoreceptors by inducing rapid bursts of inward current. After excitation by IP3, responses to subsequent injections of IP3 or light flashes are often reversibly diminished (adapted). Single injections of IP3 and(More)
Many pharmacological probes must be applied to the interior of cells to produce their effects. Ideally, a method for injecting such materials should be simple, rapid, and independent of the chemical properties of the material to be injected. In addition, one might desire to confirm immediately that an injection occurred and to estimate the volume injected(More)
A central question concerning vision is the identity of the biochemical pathway that underlies phototransduction. The large size of the ventral photoreceptors of Limulus polyphemus renders them a favourite preparation for investigating this problem. The fact that a single photon opens approximately 1,000 ionic channels in these photoreceptors suggests the(More)
Bright light bleaches visual pigment and leads to a persistent desensitization of isolated rod and cone photoreceptors called bleaching adaptation. Bleaching adaptation results from the combined effects of pigment depletion and adaptational modulation of certain cellular reactions in the visual transduction cascade. Here, we present evidence that in(More)
The 9-methyl group of 11-cis-retinal plays a crucial role in photoexcitation of the visual pigment rhodopsin. A hydrogen-substituted analogue, 11-cis-9-desmethylretinal, combines with opsin to form a pigment that produces abnormal photoproducts and diminished activation of the GTP-binding protein transducin in vitro. We have measured the formation of this(More)
Molybdate, tungstate, fluoride, vanadate, and GTP-gamma-S [guanosine-5'-0-(3-thiotriphosphate)] were injected into Limulus ventral photoreceptors by ionophoresis from microelectrodes. All of these drugs induce discrete waves of depolarization similar in waveform to, but smaller in amplitude than, those normally elicited by dim light. As for light-evoked(More)
Following bright flashes, rod photoreceptors exhibit a period of photocurrent saturation that increases linearly with the logarithm of flash intensity. In a recent report, Pepperberg et al. (1992) presented evidence that the slope of the function relating the saturation period (T) to the natural logarithm of flash intensity (ln If) represents the(More)
Discrete voltage fluctuations that occur spontaneously or in response to dim lights can be recorded from the ventral photoreceptors of Limulus. The injection of vanadate or the hydrolysis-resistant analog of guanosine triphosphate, GTP-gamma-S, into ventral photoreceptors induces the production of discrete waves in the dark. The chemically induced discrete(More)