Biomedical subjects

F Ruiz-Manresa

Publications and source records attributed to F Ruiz-Manresa.

3 recordsLinked to original sources

PubMed1976

Temperature dependence of the four ionic processes of spike electrogenesis in eel electroplaques.

Spike electrogenesis of eel electroplaques involves four ionic processes which are controlled by the membrane potential. A threshold depolarization causes normally closed Na permselective channels to open (Na-activation) and normally open K channels to close (K-inactivation). The Na channels then close (Na-inactivation), and as the spike is terminated, the K channels reopen (K-reactivation). The temperature dependence of these four processes has been examined in the present work. Opening of the Na channels and closure and reopening of the K-channels are either effectively instantaneous or are relatively independent of temperature in the range of at least 5 degrees to 22 degrees. Closure of the Na-channels has a Q10 (increase in rate of reaction for each 10 degrees increase in temperature) of about 9, and activation energy (Ea) of this reaction is about 31.5 kcal/mole (132 kJ/mole).

Action Potentials↗

PubMed1971

Synaptic electrogenesis in eel electroplaques.

Whether evoked by neural or by chemical stimulation, the synaptic membrane of eel electroplaques contributes a depolarizing electrogenesis that is due to an increased conductance for Na and K. The reversal potential (E(S)) is the same for the two modes of synaptic activation. It is inside-positive by about 30-60 mv, or about midway between the emf's of the ionic batteries for Na (E(Na)) and K(E(K)). The total conductance contributed by synaptic activity (G(S)) varied over a fivefold range, but the individual ionic branches, G(SSNa), and G(SSK), change nearly equally so that the ratio G(SSNa):G(SSK) is near unity. G(SSK) increases independently of the presence or absence of Na in the bathing medium, and independently of the presence or absence of the electrically excitable G(K) channels. When activated, the synaptic membrane appears to be slightly permeable to Ca and Mg. When the membrane is depolarized into inside positivity the conductance of the synaptic components decreases and approaches zero for large inside-positive values. Thus, the synaptic components become electrically excitable when the potential across the membrane becomes inside-positive, responding as do the nonsynaptic components, with depolarizing inactivation.

Animals↗

PubMed1970

Potassium inactivation and impedance changes during spike electrogenesis in eel electroplaques.

Various degrees of pharmacological K inactivation were induced by Cs or Ba in isolated single electroplaques of the electric eel. The resulting changes in K conductance give rise to very different steady-state current-voltage characteristics. They also induce differences in ion dynamics during spike electrogenesis. The dynamic changes were studied by AC bridge methods, registering the changes in impedance in synchrony with the neurally or directly evoked spikes. While spike electrogenesis was virtually unaffected by addition of Cs or Ba, the patterns of impedance changes were very different. The various patterns are accounted for by the changes in the respective current-voltage characteristics. The data constitute new evidence for regarding the electrically excitable component of the reactive membrane as a heterogeneous electrochemical system with separate and independently reactive channels that in the electroplaques are permselective for Na and K, respectively.

Animals↗