The effect of external cesium ions on the muscle fibre resting potential in mealworm larva (Tenebrio molitor L.)

Abstract

The membrane potential of ventral longitudinal muscles of Tenebrio molitor larvae was studied as a function of time and of cesium substituted for all or part of external potassium. The conventional microelectrode technique was applied. The mean value of resting potential was -47.4 mV in standard physiological saline which did not change significantly with time (90 min). Cesium caused, almost immediately, a significant hyperpolarization of membrane potential the magnitude of which depended on cesium concentration. The presence of external potassium enhanced the effectiveness of cesium action, resulting in more pronounced hyperpolarization. The effect of Cs ions was fully reversible upon washing. These data support the idea that inward potassium current can be activated at resting potential level, at least in some cells, including the muscles studied. It is presumed that this potassium current might have some contribution to the resting membrane potential generation in mealworm larva muscles. Key words Cesium 9 Membrane potential 9 Blocking of potassium inward current 9 Insect muscle Abbreviations [K § extracellular concentration of K ions 9 E,, resting membrane potential of a cell when bathed in normal saline 9 EKK + equilibrium potential -MP membrane potential 9 RP resting potential -SD standard deviation 9 SEM standard error of the mean

Difference of ecological half-life and transfer coefficient in aquatic invertebrates between high and low radiocesium contaminated streams

“…The transfer of radiocesium in aquatic ecosystems is also affected by other factors such as pH, temperature and dissolved organic carbon because the physiological function differs depend on the pH and water temperature 37 – 39 . Speciation of cesium and the concentration of other ions also affect the cesium transfer in the body 40 – 42 . Fishes are major functional components of forest stream ecosystems 43 , 44 .…”