Biomedical subjects

R J Do Carmo

Publications and source records attributed to R J Do Carmo.

3 recordsLinked to original sources

PubMed1999

Retinal spreading depression induced by photoactivation: involvement of free radicals and potassium.

The threshold for spreading depression (SD) in chicken retina elicited by rose bengal photoactivation was raised by Trolox (water soluble vitamin E) suggesting the participation of reactive oxygen species in SD. The typical increases in K+ concentration associated with SD were preceded by small K+ oscillations that were more sensitive to photoactivation than was SD. It is hypothesised that all these phenomena could be accounted for by a free-radical mediated transient increase in membrane permeability and that this may be relevant to ischemic brain damage.

Animals↗

PubMed1991

Phenytoin and retinal spreading depression.

Several studies indicate that spreading depression is fundamentally related to seizure marches and to the aura of classical migraine. Moreover, recent investigations call attention to its possible relevance in clinical disturbances associated with brain ischemia, trauma, and hypoglycemia. The anticonvulsant phenytoin has been shown to protect the nervous tissue from the effects of anoxia and ischemia. These properties suggest that phenytoin should be able to counteract spreading depression. Therefore, we investigated its effect on spreading depression elicited by mechanical or chemical (KCl) stimulation, in isolated chick retinas. The results showed that phenytoin: (1) increases the threshold concentration of KCl to initiate the phenomenon; (2) decreases the velocity of propagation of spreading depression; (3) shortens considerably the duration of the slow potential, ionic (K+, Ca2+, Cl-), and volume changes of the extracellular compartment during spreading depression. Possible mechanisms underlying the observed effects are discussed.

Animals↗

PubMed1988

Extracellular Ca2+ and retinal spreading depression.

The present study focuses on the influence of changes in extracellular Ca2+ on retinal spreading depression in vitro. It shows that changes in Ca2+ concentration alter the speed of the reaction. This effect is more pronounced for variations occurring within limits close to the physiological concentration level. The experiments also indicate that if the tissue is initially exposed to a lowered extracellular Ca2+ concentration, then the effects of transient variation in Ca2+ are significantly enhanced. Finally, a synergistic action of Ca2+ and K+ is observed with respect to the spreading of the reaction.

Animals↗