MYELIN-LIKE STRUCTURES AS A POSSIBLE SOURCE OF THE SMOOTH ENDOPLASMIC RETICULUM IN
EARLY AMPHIBIAN OOCYTES
K. N. Semakova,1 E. V. Kiseleva
Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk, Russia;
1 e-mail: sksu@ngs.ru
A comparative study of amphibian oocyte ultrastructural organization has shown a significant accumulation of elements of the smooth endoplasmic reticulum
in the oocyte cytoplasm at the third stage of development. The analysis of oocytes of two frog species, Xenopus laevis and Rana temporaria, at the first and second
stages of their development enablend us to recognize in the cytoplasm of the oocyte some myelin-like structures (MLs) made of 30-40 densely packaged membranous layers
and shaped as dense bodies. MLs are also present in the adjacent follicular cells and in the intercellular space. In the oocyte cytoplasm these structures are located near the
nuclear envelope and other intracellular organelles. At the third stage of oogenesis, which is characterized by a high functional activity of the cells, MLs are seen to unwrap
sequentially into double-layer membranes similar to the smooth endoplasmic reticulum cisternae. Intermediate steps of this process being also observed. It is supposed that
MLs may play the role of membrane stocks to be used eventually for the formation of nascent endoplasmic membranes in the oocytes.
Key words: myelin-like structures, smooth endoplasmic reticulum, amphibian oocytes, ultrastructure, oogenesis
