Regulation of the appearance of division asynchrony and microtubule-dependent chromosome cycles in Xenopus laevis embryos

Article Abstract:

Initiation of asynchronous division in the animal pole blastomeres depends on the nucleocytoplasmic ratio (N/C) of the cell. Developement of microtubule-dependent cell cycles is age-dependent. In the frog Xenopus laevis at the 12th or 13th cycle, the N/C ratio becomes 128 to 256 times that of the normal cell and asynchronous division starts. The number of nocodozole-treated blastomers exceeded control regularly three to five hours after the first cleavage regardless of the N/C ratio. Alpha-amanitin and heximide treatment does not affect the initiation of asynchronous division.

Cellular control mechanisms, Cell regulation, Xenopus, Cell division

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Maintenance of metaphase in colcemid-treated mouse eggs by distinct calcium- and 6-dimethylaminopurine (6-DMAP)-sensitive mechanisms

Article Abstract:

Examination of the release of both colcemid-treated eggs and colcemid-treated mitotic cells from meiotic metaphase reveals that both exposure to 6-dimethylaminopurine (6-DMAP) and an increase in intracellular calcium are essential for the release of eggs from metaphase. Exposure to 6-DMAP is sufficient for embryonic cells to exit from metaphase. These observations reveal that maintenance of metaphase involves two distinct mechanisms.

Analysis, Cell cycle, Eggs (Food), Calcium, Calcium (Chemical element), Fertilization (Biology)

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Calcium-independent, meiotic spindle-dependent metaphase-to-interphase transition in phorbol ester-treated mouse eggs

Article Abstract:

A study of calcium-independent transition from metaphase to interphase in mouse eggs treated with phorbol esters revealed that in the absence of an increase in Ca(super 2 plus)i, activation of protein kinase C can induce the transition from metaphase to interphase in mouse eggs. An elevation of calcium ion concentration is not essential for the phorbol myristate acetate (PMA)-initiated release from metaphase.

Mice as laboratory animals, House mouse, Eggs (Biology), Incubation, Phorbol esters

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