Anoxia reversibly suppresses neuronal calcium currents in rat hippocampal slices

Intracellular recording from CA1 neurons confirmed that short periods of anoxia (95% N2 + 5% CO2 for 2-4 min) have a hyperpolarizing action, caused by a rise in K conductance. After blockage of K channels with extracellular Cs+ and tetraethylammonium (or intracellular Cs+), large inward currents of Ca were evoked by depolarizing pulses: transient currents at a holding potential near -70 mV, and more sustained ones near -50 mV. Both types of Ca current were much reduced or fully suppressed after 1-3 min of anoxia, but they largely (or fully) recovered within 1-10 min of starting reoxygenation.     

Sterols of the Green‐Pigmented,Freshwater Raphidophyte,Gonyostomum semen,from Scandinavian Lakes

Sterols are a class of membrane‐reinforcing, ringed lipids which have a long history of examination in algae as a means of deriving chemotaxonomic relationships and as potential lipidic biomarkers. The Raphidophyceae represent a class of harmful, bloom‐forming, marine and freshwater algae. To date, there have been four published examinations of their sterol composition, focusing primarily on brown‐pigmented, marine species within the genera, Chattonella, Fibrocapsa, and Heterosigma. Lacking in these examinations has been the species Gonyostomum semen Ehrenb., which is a green‐pigmented, freshwater raphidophyte with a worldwide distribution. The goal of this study was to examine the sterol composition of this nuisance alga, determine the potential of using its sterol profile as a biomarker, and finally to determine if there is any intraspecific variability between isolates. We have examined 21 isolates of G. semen from a number of Scandinavian lakes, and all were found to produce two major sterols, 24‐ethylcholesta‐5,22E‐dien‐3β‐ol and 24‐ethylcholest‐5‐en‐3β‐ol, and 24‐methylcholest‐5‐en‐3β‐ol as a minor sterol; the presence of 24‐ethylcholesta‐5,22E‐dien‐3β‐ol differentiates G. semen from brown‐pigmented, marine raphidophytes which generally lack it. The results of this study indicate that isolates of G. semen from geographically separate lakes across Finland and Scandinavia have the same sterol biosynthetic pathway, and that there is no evolutionary divergence between the isolates with regard to sterol composition. The sterols of G. semen are not considered to be useful biomarkers for this particular organism because they are commonly found in other algae and plants.