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Biomedical subjects

R D O'Brien

Publications and source records attributed to R D O'Brien.

At least 55 records · Page 3Linked to original sources
PubMed1970

Antagonism by DDT of the effect of valinomycin on a synthetic membrane.

The potassium conductance which is induced by 10(-6) molar valinomycin in a lecithin-decane membrane is reversed by 3 x 10(-6) molar DDT. Membranes not treated with valinomycin are not affected by DDT. This blockade of potassium conductance parallels the effect of DDT on axonic conduction. Dieldrin and lindane, whose physiological actions are in some ways like those of DDT, do not affect valinomycin-induced conductance of lecithin-decane membranes.

Alkanes↗
PubMed1970

A muscarone-binding material in electroplax and its relation to the acetylcholine receptor. II. Dialysis assay.

An equilibrium dialysis technique, applied to lyophilized particulate fractions of Torpedo electroplax, gave data consistent with a single kind of macromolecular binding of muscarone, with binding constant, 7 x 10(-7)M and an amount of 1 nmole per gram original electroplax. The effects on muscarone binding of 38 drugs suggested that muscarone binding reflected acetylcholine receptor activity. Of 18 enzyme preparations, only trypsin, chymotrypsin, and phospholipase C reduced binding activity, suggesting that a phospholipoprotein was binding. Partial "solubilization" of the binding protein was achieved, but the "solubilized" activity did not migrate on electrophoresis. Additional evidence was provided that acetylcholinesterase was not responsible for this muscarone binding.

Acetylcholine↗
PubMed1969

Binding sites of cholinesterases. Alkylation by an aziridinium derivative.

1. Alkylation of acetylcholinesterase and butyrylcholinesterase by 2-chloro-N-(chloroethyl)-N-methyl-2-phenylethylamine was observed. This alkylating agent was more potent than related compounds previously described, and less stable (half-life 8.5min. at 23 degrees ). 2. Alkylation had effects on hydrolysis of substrates varying from activation for indophenyl acetate to inhibition for acetylcholine, and intermediate effects with five other substrates. The effects were on V(max.) and not K(m). 3. Alkylation caused a variety of changes in sensitivity to inhibition by five carbamates, five organophosphates and four other inhibitors, varying from total protection against tetraethylammonium to mildly enhanced sensitivity to urea. 4. The findings suggested the existence of three binding sites, one of which was anionic and another hydrophobic, in addition to the esteratic site.

Acetylcholinesterase↗
PubMed1969

A muscarone-binding material in electroplax and its relation to the acetylcholine receptor. I. Centrifugal assay.

A muscarone-binding material has been found in Torpedo electroplax. The material behaves in several ways as one would expect of the binding component of the acetylcholine receptor, especially in its high affinity for muscarone (approximate K = 7 x 10(-6)M), acetylcholine (approximate K = 1.1 x 10(-6)M), curare, and nicotine, and its insensitivity to noncholinergic agents; the reversibility of its muscarone binding; and its suitably small amount (about 1.8 nmole/gm). The material appears not to be acetylcholinesterase.

Acetylcholine↗