Photic modulation of a highly sensitive, near-infrared light-scattering signal recorded from intact retinal photoreceptors.
AUTOR(ES)
Pepperberg, D R
RESUMO
On stimulation by green flashes, the isolated, aspartate-treated bovine retina exhibits transient changes in the scattering of near-infrared (880 nm) light. A single component, termed the "ATR" (a flash-induced scattering signal, where ATR designates amplified transient-retina), dominates the amplitude and rising-phase kinetics of the initial peak of the light-scattering response. Superfusion with physiological solution containing low Na+ concentration reversibly abolishes the photoreceptor electroretinographic response but preserves the ATR signal, indicating a receptoral origin for the ATR. The increase of ATR amplitude (A/Amax) with flash intensity (R*/R, where R indicates rhodopsin) is described by A/Amax = (1- e-kR*/R), with R*/R = k-1 occurring on generation of approximately two photoactivated rhodopsins (R*s) per disc surface in the rod outer segment. Weak background light and bright flashes reversibly depress the ATR. Kinetic and sensitivity data suggest a basis of the ATR in stochastic, unit activation events, each initiated by a single R*. They further suggest an essential invariance of the unit event under differing conditions of illumination. A delay, apparently governed by the lifetime of a light-activated substance regulating ATR generation, precedes ATR recovery after a bright flash. The flash dependence of the delay period indicates an upper limit of 3 s for the lifetime of R* in the ATR-generating process. The unit event appears to be an R*-catalyzed and disc-localized reaction of phototransduction.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=281792Documentos Relacionados
- A long-range attraction between aggregating 3T3 cells mediated by near-infrared light scattering
- Dielectrophoretic dynamic light-scattering (DDLS) spectroscopy
- Near-infrared emission of Nd-PSS films
- High-pressure near-infrared Raman spectroscopy of bacteriorhodopsin light to dark adaptation.
- Interactions of lysozyme in concentrated electrolyte solutions from dynamic light-scattering measurements.