Ischemia of rat liver is followed by recovery or cell death. Since heat shock proteins may be essential to cell survival under stress, we determined levels of heat shock proteins in liver after different periods of blood deprivation and correlated the results with cellular recovery. Cell-free synthesis by poly (A+)-mRNA and polysomes revealed 70 and 89 kd proteins which appear similar to proteins produced by the liver of rats with amphetamine-induced hyperthermia. The 70 and 89 kd proteins increased in the liver of rats which recovered from ischemia.
The permeation properties of KAT1, an inward rectifying potassium channel from plant cells, were investigated with different ions in the external medium. With either K+, NH4+ or methylammonium (MA) in the external solution, the channel, expressed in Xenopus oocytes, appeared permeable to K+ and, to a lesser extent, to NH4+ but not to the slightly bigger, methylated analogue of NH4+, MA. Substituting NH4+ for K+ shifted the voltage dependency of channel activation further negative and hastened activation kinetics. This suggests that channel operation depends on the transported substrate. In mixed solution (50 mM K+, 50 mM MA) MA inhibited K+ current in a voltage-independent manner. The maximum block did not exceed 50% of the K+ current. In contrast, when NH4+ was the permeant ion (50 mM NH4+, 50 mM MA) MA caused a voltage-dependent, slowly developing open channel block, achieving complete inhibition at very negative voltages. The latter block could be partially overcome by the addition of K+ in the external solution. The data support a model in which ions, after entering the channel pore, compete with different affinities for binding sites on their permeation pathway.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.