Evidence for structuring of water in growing oocytes: an X-ray microanalysis and nuclear magnetic resonance study.

Energy dispersive X-ray microanalysis measured the Na, K, Cl, P, Mg, S and Ca contents (mM/kg dry weight) in the nucleus and yolk-free cytoplasm of growing Xenopus laevis oocytes quick frozen in the ovary. Nuclear magnetic resonance measurements of T2, the transverse relaxation time of water protons, were obtained on small immature oocytes and on large, fully grown oocytes. Changes in the nucleus and cytoplasmic content were observed for all elements except for Ca. Nuclear/cytoplasmic macroscopic gradients of K, Cl, Na, and Mg increase with growth. The T2 times of large oocytes were found to be shorter than those of small oocytes. The data in this report further support the hypothesis that intraoocytic water and elements do not exist in an ideal dilute solution and that changes in the states of water and elements occur during oocytic growth.