The kinetics of the membrane current during the anomalous or inward-going rectification of the K current in the egg cell membrane of the starfish Mediaster aequalis were analyzed by voltage clamp. The rectification has instantaneous and time-dependent components. The time-dependent increase in the K conductance for the negative voltage pulse as well as the decrease in the conductance for the positive pulse follows first-order kinetics. The steady-state conductance increases as the membrane potential becomes more negative and reaches the saturation value at about -40 mV more negative than the K equilibrium potential, Va. The entire K conductance can be expressed by ¢K'n; gK represents the component for the time-independent conductance which depends on V-VK and[K+]o, and n is a dimensionless number (1 -> n -> 0) and determined by two rate constants which depend only on V-VK. Cs + does not carry any significant current through the K channel but blocks the channel at low concentration in the external medium. The blocking effect increases as the membrane potential is made more negative and the potential-dependent blocking by the external Cs + also has instantaneous and time-dependent components. Katz (1949) studied the membrane property of the frog skeletal muscle fiber in isotonic potassium sulfate solution, and found that the membrane resistance was low for the inward current but was high for outward current. This property has been referred to as the inward-going or anomalous rectification and others have studied this extensively (Hodgkin and Horowicz, 1959; Adrian and Freygang, 1962 a, b;Nakajima et al., 1962;Adrian, 1964Adrian, , 1969 Horowicz et al., 1968; Nakamura et al., 1965;Adrian et al., 1970;Almers, 1971Almers, , 1972. Recently, a similar rectification has been found in the membrane of an egg cell of a tunicate (Takahashi et al., 1971;Miyazaki et al., 1974) and of a starfish (Hagiwara and Takahashi, 1974; Miyazaki et al., 1975 b). In both cases the membrane current for the rectification is carried by K ions under normal conditions. The present study deals with the inward-going or anomalous rectification in the membrane of a giant egg cell (about 1 mm in diameter) of the starfish Mediaster aequalis. The

Permeability constant ratios among monovalent cations were studied in the resting membrane of a giant axon of a Pacific squid,Loligo opalescens, by observing the relationship between the membrane potential and the ion concentration.The average permeability ratios are: Tl, 1.8; K, 1.0; Rb, 0.72; Cs, 0.16; Na, <0.08; Li, <0.08. These permeability ratios suggest that neither valinomycin nor nonactin are adequate models for the sites producing the resting permeability in the axonal membrane.Cyclic polyetherbis(t-butyl cyclohexyl) 18-crown-6 does not increase the permeability ratioP Cs/P K except when applied at concentrations (5×10(-5) M) at which the surfactant properties of this molecule may become significant.

Excessive warming from climate change has increased the total wildfire burned area over the past several decades in California. This has increased population exposure to both hazardous concentrations of air pollutants from fires such as fine particulate matter (smoke PM2.5) and extreme heat events. Exposure to PM2.5 and extreme heat are individually associated with negative health impacts and recent epidemiological evidence points to synergistic effects from concurrent exposures. This study characterizes the frequency and spatial distribution of co-occurring extreme heat and smoke PM2.5 events in California during the record-setting wildfire season of 2020. We measure exceedances over extreme thresholds of modeled surface-level smoke PM2.5 concentrations and heat index based on observed temperature and humidity. We estimate that, during the studied period, extreme smoke and heat co-occurred at least once within 68% of the State’s area (~288,000 km2) and an average 2.5 times across all affected areas. Additionally, 16.5 million people, mostly in lower population density areas, were impacted at least once in 2020 by such synergistic events. Our findings suggest that public health guidance and adaptation policies should account for co-exposures, not only distinct exposures, when confronting heat and smoke PM2.5.

Extreme heat and wildfire smoke events are increasingly co-occurring in the context of climate change, especially in California. Extreme heat and wildfire smoke may have synergistic effects on population health that vary over space. We leveraged high-resolution satellite and monitoring data to quantify spatially varying compound exposures to extreme heat and wildfire smoke in California (2006–2019) at ZIP code level. We found synergistic effects between extreme heat and wildfire smoke on cardiorespiratory hospitalizations at the state level. We also found spatial heterogeneity in such synergistic effects across ZIP codes. Communities with lower education attainment, lower health insurance coverage, lower income, lower proportion of automobile ownership, lower tree canopy coverage, higher population density, and higher proportions of racial/ethnic minorities are more vulnerable to the synergistic effects. This study highlights the need to incorporate compound hazards and environmental justice considerations into evidence-based policy development to protect populations from increasingly prevalent compound hazards.

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