Search PubMed⌕ Search

Biomedical subjects

C C Aickin

Publications and source records attributed to C C Aickin.

7 recordsLinked to original sources
PubMed1979

Decrease of inhibitory driving force in crayfish stretch reception: a mechanism of the convulsant action of penicillin.

The effect of penicillin on the evoked IPSP was investigated in the isolated crayfish stretch receptor. The IPSP driving force (IPSP reversal potential minus membrane potential) was reduced in a dose-dependent fashion but, when necessary correction was made for the decrease in resting membrane conductance, the synaptic conductance was only slightly reduced. The possibility that a penicillin-induced intracellular acidification was responsible for the decrease in IPSP driving force is considered.

Animals↗
PubMed1977

An investigation of the ionic mechanism of intracellular pH regulation in mouse soleus muscle fibres.

1. Intracellular pH (pH(i)) of surface fibres of the mouse soleus muscle was measured in vitro by recessed-tip pH-sensitive micro-electrodes. pH(i) was displaced in an acid direction by removal of external (NH(4))(2)SO(4) after a short exposure, and the mechanism of recovery from this acidification was investigated.2. Removal of external K caused a very slow acidification (probably due to the decreasing Na gradient) but had no effect on the rate of pH(i) recovery following acidification. This indicates that K(+)-H(+) exchange is not involved in the pH(i) regulating system.3. Short applications of 10(-4)M ouabain had no obvious effect on pH(i) and did not alter the rate of pH(i) recovery following acidification. This suggests that there is no direct connexion between the regulation of pH(i) and the Na pump.4. Reduction of external Ca from 10 to 1 mM caused a transient fall in pH(i), but the rate of pH(i) recovery following acidification was unaffected. This suggests that Ca(2+)-H(+) exchange is not involved in the pH(i) regulating system.5. An 11% reduction in external Na caused a significant slowing of pH(i) recovery following acidification. 90% or complete removal of external Na almost stopped pH(i) recovery. This suggests that Na(+)-H(+) exchange is involved in pH(i) regulation.6. Amiloride (10(-4)M) reversibly reduced the rate of pH(i) recovery to much the same extent as removal of external Na. Its effect was not additive to that of removal of external Na.7. Internal Na ion concentration ([Na(+)](i)), measured using Na(+)-sensitive micro-electrodes, fell on application of (NH(4))(2)SO(4) and increased on its removal. The increase transiently raised [Na(+)](i) above the level recorded before (NH(4))(2)SO(4) application. This overshoot of [Na(+)](i) was almost completely inhibited by amiloride. This is consistent with the involvement of Na(+)-H(+) exchange in the pH(i) regulating system.8. Removal of external CO(2) or application of SITS (10(-4)M) caused some slowing of the rate of pH(i) recovery following acidification by removal of (NH(4))(2)SO(4). The effect of SITS was additive to that of Na-free Ringer or amiloride. These results suggest that Cl(-)-HCO(3) (-) exchange is also involved in the pH(i) regulating system and that it is a separate mechanism. Under the conditions used, Cl(-)-HCO(3) (-) exchange formed about 20% of the pH(i) regulating system.9. Decreasing the temperature from 37 to 28 degrees C not only caused an increase in pH(i), but also considerably slowed the rate of pH(i) recovery following acidification. We have calculated a Q(10) for Na(+)-H(+) exchange of 1.4 and for Cl(-)-HCO(3) (-) exchange, 6.9.10. We conclude that the pH(i) regulating system is comprised of two separate ionic exchange mechanisms. The major mechanism is Na(+)-H(+) exchange, which is probably driven by the transmembrane Na gradient. The other mechanism is Cl(-)-HCO(3) (-) exchange, which probably requires metabolic energy.

Amiloride↗
PubMed1975

Micro-electrode measurement of the internal pH of crab muscle fibres.

The internal pH of crab muscle fibres was measured using recessed-tip pH-sensitive micro-electrodes. Immediately following electrode penetration the mean internal pH was 7-21 +/- 0-02 (S.E. of mean) and the mean membrane potential was -64-9 +/- 0-6 mV (S.E. of mean). If H+ ions were passively distributed across the fibre membrane the internal pH would have been 6-39. 2. The internal pH tended to rise before stabilizing at a mean value of 7-27 +/- 0-02 (S.E. of mean). The difference between immediate and stabilized values is highly significant and suggests acid injury on electrode penetration. 3. Changing the membrane potential or external pH had only small, slow effects on internal pH. 4. External CO2 caused a large and rapid decrease in internal pH. With low concentrations of CO2, the effect was dependent on the initial pH as predicted by the Law of Mass Action. During a long exposure to 2-65% CO2 at pH 7-5, the internal pH returned slowly to its previous value, suggesting active transport of H+ (or OH- or HCO3-) ions across the fibre membrane. 5. The internal buffering power calculated from the response to 2-65% CO2 was 47-3 +/- 2-8 slykes (m-equiv H+/pH unit per l.) (S.E. of mean).

Animals↗