Electrophoretic Studies of Intact Nuclei Isolated from Mammalian Brain. I: Electrokinetic characteristics and effects of cations

Abstract

1) An apparatus for electrophoresis of nuclei and for observation of nuclear migration is described.

2) Intact nuclei isolated from rat cerebral cortex migrate in an electric field. At the stationary level, the nuclei migrate to the positive electrode at all pH values of the medium above pH 4.0. In 10 mM phosphate buffer, the peak velocity is observed at approximately pH 6.8. The nuclei present the same behaviour independent of the buffer used: Tris, sodium or potassium phosphate, or sodium bicarbonate. Analysis of the population of velocity values obtained indicates that there are at least two distinct groups within the nuclear population. Red blood cells isolated from the same animals were used for reference, as well as for calibration of the electrophoretic chamber.

3) The electrophoretic mobility of the nuclei is found to be a function of the molarity of the buffer used. It decreases as the molarity of the buffer increases.

4) Nuclei were treated with cations at different concentrations. Treatment with divalent cations at a concentration of 4 mM results in a decrease of the electrophoretic mobility.

5) Intact nuclei obtained from cerebral grey and white matter of human origin also migrate in an electric field. Tumor nuclei, also from human cerebral material, migrate faster than those from normal grey matter.

6) The effect of an applied electric field on the nuclear morphology is also discussed.

7) The results are discussed in relation to what is presently known concerning the charge properties of intact cells and cellular organelles.