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The distribution and requirements of microtubules and microfilaments in bovine oocytes during in vitro maturation

Published online by Cambridge University Press:  01 February 2000

Nam-Hyung Kim
Affiliation:
Department of Animal Science, Chungbuk University, Chungbuk, Korea.
Seong Koo Cho
Affiliation:
Department of Animal Science, Chungbuk University, Chungbuk, Korea.
Seok Hwa Choi
Affiliation:
Department of Veterinary Science, Chungbuk University, Chungbuk, Korea.
Eun Young Kim
Affiliation:
Maria Infertility Medical Institute, Seoul, Korea.
Se Pill Park
Affiliation:
Maria Infertility Medical Institute, Seoul, Korea.
Jin Ho Lim
Affiliation:
Maria Infertility Clinics, Seoul, Korea.

Abstract

Microtubules and microfilaments are major cytoskeletal components and important modulators for chromosomal movement and cellular division in mammalian oocytes. In this study we observed microtubule and microfilament organisation in bovine oocytes by laser scanning confocal microscopy, and determined requirements of their assembly during in vitro maturation. After germinal vesicle breakdown, small microtubular asters were observed near the condensed chromatin. The asters appeared to elongate and encompass condensed chromatin particles. At the metaphase stage, microtubules were observed in the second meiotic spindle at the metaphase stage. The meiotic spindle was a symmetrical, barrel-shaped structure containing anastral broad poles, located peripherally and radially oriented. Treatment with nocodazole did not inhibit germinal vesicle breakdown. However, progression to metaphase failed to occur in oocytes treated with nocodazole. In contrast, microfilaments were observed as a relatively thick uniform area around the cell cortex and overlying chromatin following germinal vesicle breakdown. Treatment with cytochalasin B inhibited microfilament polymerisation but did not prevent either germinal vesicle breakdown or metaphase formation. However, movement of chromatin to the proper position was inhibited in oocytes treated with cytochalasin B. These results suggest that both microtubules and microfilaments are closely associated with reconstruction and proper positioning of chromatin during meiotic maturation in bovine oocytes.

Type
Research Article
Copyright
© 2000 Cambridge University Press

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