Action potentials (APs) are the functional units of fast electrical signaling in excitable cells. The upstroke and downstroke of an AP is generated by the competing and asynchronous action of Na+- and K+-selective voltage-gated conductances. Although a mixture of voltage-gated channels has been long recognized to contribute to the generation and temporal characteristics of the AP, understanding how each of these proteins function and are regulated during electrical signaling remains the subject of intense research. AP properties vary among different cellular types because of the expression diversity, subcellular location, and modulation of ion channels. These complexities, in addition to the functional coupling of these proteins by membrane potential, make it challenging to understand the roles of different channels in initiating and “temporally shaping” the AP. Here, to address this problem, we focus our efforts on finding conditions that allow reliable AP recordings from Xenopus laevis oocytes coexpressing Na+ and K+ channels. As a proof of principle, we show how the expression of a variety of K+ channel subtypes can modulate excitability in this minimal model system. This approach raises the prospect of studies on the modulation of APs by pharmacological or biological means with a controlled background of Na+ and K+ channel expression.

An alternating-treatments design was used to investigate the relative effects of illustrations on the oral reading in context and comprehension accuracy of five elementary-school learning disabled students. Social comparison data were used to verify oral reading deficiencies. Results showed no apparent relationship between the presence or absence of illustrations and changes in oral reading rates or response accuracy of comprehension questions. Results are discussed in relation to the purported benefits of illustrations. Finally, implications for instruction and suggestions for future investigations are discussed.

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