Margaret E. Greig

The synthesis of acetylcholine by human erythrocytes.

Abstract Human erythrocytes synthesize acetylcholine. Implications of these findings are discussed.

Studies on permeability. IX. Replacement of potassium in erythrocytes during cholinesterase activity.

Abstract It has been shown that potassium can be replaced in both dog and human erythrocytes against a concentration gradient when cells are incubated with acetylcholine and cholinesterase activity is maintained, provided the cell has previously lost a part of its normal complement of potassium. This process is inhibited by physostigmine. Replacement of potassium in human cells during metabolism of glucose is similarly blocked by physostigmine, which is considered to be a specific inhibitor of cholinesterase activity. These results point to a single mechanism for potassium replacement regardless of whether the substrate added is glucose or acetylcholine, and that mechanism depends on an active cholinesterase.

Studies on permeability. VI. Increased permeability of dog erythrocytes caused by cholinesterase inhibitors

Abstract 1. 1. The effects of several inhibitors of cholinesterase activity on the permeability of dog erythrocytes have been studied. The following drugs were investigated: physostigmine, prostigmine, caffeine, and choline. 2. 2. Permeability effects were noted only with drugs in concentrations that produced 50% or more inhibition of cholinesterase activity. 3. 3. Acetyl choline in concentrations of 10 −2 -10 −5 M produced significant increases in resistance of dog erythrocytes to hemolysis, the magnitude of the effects varying with the concentration of drug.

Comparison of Effects of D- and L-Isomers of Amidone and Isoamidone on Cholinesterase.

Summary 1. The D- and L-isomers of amidone and isoamidone inhibit the cholin-esterases of rat brain and dog serum. 2. These drugs exert a greater inhibitory action on serum cholinesterase than on brain cholin-esterase. 3. The L-isomers are more effective than the D-isomers in inhibiting these enzymes. 4. The greatest difference in effect between the D- and L-isomers was observed in experiments on the effect of D- and L-iso-amidone on brain cholinesterase.

Studies on permeability. XI. The effect of physostigmine on the rate of barbital entrance into guinea pig brain slices

Abstract Physostigmine caused an increased rate of entrance of barbital into guinea pig brain slices. In the concentration used, physostigmine inhibited the activity of the brain cholinesterase by about 90% but had little or no inhibitory effect on glycolysis or oxygen consumption by the brain tissue. The increased permeability of the guinea pig brain slices to barbital caused by physostigmine is attributed to its action on cholinesterase.

Effect of the D- and L-isomers of Isoamidone on the Permeability of Dog Erythrocytes.

Summary The theory that the acetyl-choline-cholinesterase system is concerned with membrane permeability is further substantiated by the finding that the L-isomer of isoamidone which has a greater inhibitory action on cholinesterase than has the D-isomer also changes permeability of dog erythrocytes to a different degree than does the D-isomer. The conditions under which the L has a greater effect than the D-isomer on permeability are a medium containing a high proportion of K ions relative to Na ions.