J Elliott Brown

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The signalling pathway and the behavioural strategy underlying chemotaxis of sperm are poorly understood. We have studied the cellular events and motor responses that mediate chemotaxis of sperm from the sea urchin Arbacia punctulata. Here we show that resact, a chemoattractant peptide, initiates a rapid and transient rise in the concentration of cyclic(More)
Aequorin, which luminesces in the presence of calcium, was injected into photoreceptor cells of Limulus ventral eye. A bright light stimulus elicited a large increase in aequorin luminescence, the aequorin response, indicating a rise of intracellular calcium ion concentration, Ca/. The aequorin response reached a maximum after the peak of the electrical(More)
During intracellular iontophoretic injection of Ca(++) into Limulus ventral photoreceptor cells, there is a progressive diminution of the light response. Following Ca(++) injection, the size of the light response slowly recovers. Similarly, there is a progressive diminution of the light response during intracellular injection of Na(+) and recovery after the(More)
Ventral tegmental area (VTA) GABA neurons are critical substrates modulating the mesocorticolimbic dopamine system implicated in natural and drug reward. The aim of this study was to evaluate the effects of ethanol on glutamatergic and GABAergic modulation of VTA GABA neuron electrical synaptic transmission. We evaluated the effects of systemic ethanol(More)
The responses of Limulus ventral photoreceptors to brief test flashes and to longer adapting lights were measured under voltage clamp conditions. When the cell was dark adapted, there was a range of energy of the test flashes over which the peak amplitude of the responses (light-induced currents) was directly proportional to the flash energy. This was also(More)
Aequorin, which luminesces in the presence of calcium, was injected into photoreceptor cells of Limulus ventral eye. A bright light stimulus elicited a large increase in aequorin luminescence, the aequorin response, indicating a rise of intracellular calcium ion concentration, Ca(i). The aequorin response reached a maximum after the peak of the electrical(More)
Photoreceptor cells of Limulus ventral eyes were bathed in artificial sea water (ASW) that contained 10 mM-EGTA and no added Ca2+ (EGTA-ASW). Test flashes elicited responses that increased to a maximum size within 10 min in EGTA-ASW but did not change further when dark-adapted cells were bathed for an additional 35 min in this solution. Light responses(More)
1. The metallochromic indicator dye, arsenazo III, was injected intracellularly into Limulus ventral photoreceptor cells to concentrations greater than 1 mM.2. The absorption spectrum (450-750 nm) of the dye in single dark-adapted cells was measured by a scanning microspectrophotometer. When a cell was light-adapted, the absorption of the dye changed; the(More)
Eggs attract sperm by chemical factors, a process called chemotaxis. Sperm from marine invertebrates use cGMP signalling to transduce incident chemoattractants into changes in the Ca2+ concentration in the flagellum, which control the swimming behaviour during chemotaxis. The signalling pathway downstream of the synthesis of cGMP by a guanylyl cyclase is(More)
1. Membrane potentials were recorded from single rods in the isolated retina of Bufo marinus while the ionic composition of the extracellular medium was rapidly changed. Substitution of 2 mM aspartate(-) for Cl(-) produced a prompt depolarization of horizontal cells, but no modification of either resting potential or response to light in receptor cells.(More)