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The influence of monomeric methylmethacrylate (MMA) on resting and compound action potential of the isolated desheathed sciatic nerve of the frog (sucrose gap method) was determined. Above 10 mM there was a dose-dependent decrease of the compound action potential and a hyperpolarization of the membrane which was augmented with increasing MMA concentrations (4.1 mV±0.2 S.E.M. after 50 mM MMA). The depolarization in low [Ca2+]0 solutions or with veratrine was reversed by MMA. The homologous ethyl, allyl and n-butyl esters were more effective than MMA, and the isobutyl ester less effective, whereas Na-methacrylate and methacrylamide showed no influence.

Voltage clamp experiments were performed on myelinated nerve fibres of Rana esculenta. The combined effects of increasing extracellular H+ concentration and lowering the Na+ concentration on sodium currents were studied. The presence of negative charges of two types at the external membrane surface could explain the observed shifts in theINa-V curves and the reduction ofINa induced by H+. Accordingly, from the data of shifts of the conductance voltage curves we calculate a density of -1eo/(20 Å)2 for unsepecific charges with an intrinsic pKa=4.3. From the reduction ofINa induced by H+ we estimate a density of -1eo/Na channel for specific charges with an intrinsic pKa=4.5. Na+ ions would bind to these specific charges when passing through the sodium channels and Na+ transport would be blocked if these groups are protonated.

We quantified the relationships between seasonal air temperatures and ice phenology for a 0.54 km2boreal lake in Northwestern Ontario, Canada using a 50‐year time series (1970–2019). Significant temporal trends in the duration of ice cover (−4.0 days decade−1) occurred over the study period and both ice‐on and ice‐off dates were highly predictable from seasonal air temperatures. While temporal trends in ice‐off dates were not significant, ice‐on dates trended later by 2.2 days decade−1, and both ice‐off dates and the duration of ice‐cover became increasingly variable over the study period. For three consecutive winter seasons, we also evaluated regional variations of ice‐phenology and snow and ice‐thickness from 9 to 30 boreal lakes across a lake size gradient (0.02–26 km2) using ground based and satellite observations. Regional variation of ice‐on dates (30–45 days), ice‐off dates (10–21 days), and total duration of ice‐cover (22–38 days) between lakes displayed significant nonlinear relationships to lake size across all years. Regional variation of ice‐off dates was structured according to lake size, and appeared driven by relationships between lake size, snow thickness, and ice thickness. Multiple linear regression and generalized additive modeling approaches to predict ice‐on and ice‐off dates at the regional scale by integrating the effects of air temperature and lake size had similar performance, explaining >90% of the variance of observed. In this study, we used a continuous 50‐year data set of air temperature and ice phenology for a single boreal lake, and a combination of ground‐based and satellite observations to examine regional variation and drivers of ice phenology across 9–30 lakes near the IISD Experimental Lakes Area, Canada. Results indicated that ice‐cover duration declined by approximately 4 days per decade, and ice‐on and ice‐off dates were highly predictable based on seasonal air temperatures. Our regional analysis indicated that the duration of ice‐cover varied by approximately 1 month even for lakes in close proximity to one another and experienced similar weather conditions. This spatial variation of ice phenology was structured along a gradient of lake size. These results provide strong evidence of regional changes in climate since the 1970s and quantify the importance of air temperature and lake size in driving the duration of ice cover at a regional scale and can be incorporated with climate projections to estimate future ice‐conditions across lakes of varying sizes. Long‐term declines in ice‐cover duration (4 days/decade) were highly predictable from seasonal air temperaturesRegional variation of ice‐cover duration was approximately 1 month and structured by factors associated with lake sizeLake‐size effects on ice‐off dates appeared driven by variations in snow and ice thickness Long‐term declines in ice‐cover duration (4 days/decade) were highly predictable from seasonal air temperatures Regional variation of ice‐cover duration was approximately 1 month and structured by factors associated with lake size Lake‐size effects on ice‐off dates appeared driven by variations in snow and ice thickness

A reevaluation of the secondary structure of Na, Ca and K channel proteins led to the following results. Only three segments (S1, S5 and S6) of each repeat are sufficiently hydrophobic to be predicted as transmembrane helices, if a window of 19 amino acids is used. Some of the S2 and S3 segments show higher hydrophobic values when calculated with the window of 9 amino acids and can be predicted as short helices. S4 segments are strongly hydrophilic and cannot be predicted as transmembrane helices. Some of the S2, S3 and S4 segments have an amphipathic character; however, these helices do not span a membrane. A model is proposed where 12 hydrophobic transmembrane helices surround 12 shorter helices, forming a hydrophilic pore. In addition, a unique pattern for S4 segments of voltage-gated channel proteins is defined.