EFFECTS OF MERCAPTOETHANOL ON THE FURROWING CAPACITY OF ARBACIA EGGS

¹ Department of Zoology, University of Toronto, Toronto, Canada, and Marine Biological Laboratory, Woods Hole, Massachusetts

1. The fertilized eggs of Arbacia punctulata were immersed into various concentrations of mercaptocthanol, and the structural state of the cortical cytoplasm, as well as the "cleavage potential" of the cells, were measured.

2. Pressure-centrifuge measurements of the structural state of the cortical cytoplasm were made at various pressures (6000-12,000 lbs./in.²) at 20° C., employing a centrifugal force of 33,000 g. A blocking concentration of mercaptoethanol, 0.075 M, yielded a value for the strength of the cortical gel which was 22-24% lower than that found in the non-treated controls. At a lower mercaptoethanol concentration, 0.01 M, division was not blocked and the gel strength curve was parallel to the curve for the blocking concentration and the control curve, but lying intermediate between the two.

3. The decrease in the gel strength was shown to be related to a decrease in the "cleavage potential." A pressure of 4500 lbs./in.² applied at the time of furrowing will, in general, block about 50% of the cells from cleaving. When the eggs were pretreatcd with 0.01 M mercaptoethanol 20 minutes prior to division, there was a 24% lowering in the number of cells which completed division under pressure treatment, as compared to time non-treated pressurized controls.

4. In general, the data support the hypothesis that interference with the [See equation in the PDF file] interaction in protoplasmic gel system is similar in both the mitotic gel systermm and thec cortical gel system, and any interference with the delicate balance may markedly disrupt mitosis and cytokinesis.