期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：11
页码：4469-4473
DOI：10.1073/pnas.72.11.4469
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Unfertilized sea urchin eggs exposed to low concentrations of ammonia enter into a number of activities which normally appear after fertilization. It is shown that the effects are attributable to ammonia, rather than to NH4+ ions of elevated pH. The same effects are obtained by exposure to isotonic urea and to glycerol at very low ionic strengths. All treatments which produce these changes (such as the turning on of chromosome replication and condensation in unfertilized eggs) also bring about changes of the outer cell surface which are visible in the scanning electron microscope. The most striking indicator is the elongation of the microvilli which cover the surface of the unfertilized egg. The changes of the surface are interpreted as the dissociation of a component from the outer surface layer. This component is not the "vitelline" sheet as defined morphologically or by the ability of the egg to form a fertilization membrane upon insemination. It is proposed further that this component is a peripheral component of the plasma membrane, whose removal modifies the membrane functionally and leads to the derepression of various processes within the egg.
