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Electron microscopy of early mouse embryos from the 1-cell stage to the blastocyst revealed 2 types of intracisternal A particles, a C-type particle budding into the extracellular space, and an endoplasmic reticulum-associated “dense-cored vesicle.” The morphology of these particles was described. The occurrence and frequency of the particles showed a marked dependence on the developmental stage of the embryo.
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Chase et al. (1973) studied this question.
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