Complete Replication of Human Sperm Genome: DISCUSSION(5)

Although the analysis of sperm penetrating Syrian (golden) hamster zona-free eggs (for reviews, see ) can be used to determine the capability of sperm to enter the eggs and decondense, it cannot be used to analyze the postfertilization events that are also critical for the further development of the zygote. With the use of Xenopus…

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Complete Replication of Human Sperm Genome: DISCUSSION(4)

Complete in vitro sperm (or pollen) genome replication of higher organisms such as humans, livestock, and fruit trees could have profound biomedical and economic impacts. Generally, genetic linkage studies through inbreeding are either difficult or impractical in these species. Haploid gametes are ideal for genetic analysis because they are genetically informative. With haploid cells as…

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Complete Replication of Human Sperm Genome: DISCUSSION(3)

The notion that initiation of sperm DNA replication is determined by the degree of pronucleus maturation is supported by the observation made by Naish et al.. By in vivo and in vitro fertilization of hamster eggs and microinjection of hamster sperm into hamster eggs, the authors found that sperm DNA synthesis was not initiated until…

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Complete Replication of Human Sperm Genome: DISCUSSION(2)

Replacement of sperm protamine with histone is another process that is involved during pronucleus formation. Possible mechanisms have been proposed for this process (reviewed in ). These include proteolysis of protamine by proteinases (reviewed in ) and protamine phosphorylation (reviewed in ). Furthermore, the process of pro-tamine-histone exchange was shown to be modulated by nucleoplasmin….

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Complete Replication of Human Sperm Genome: DISCUSSION(1)

We have studied DNA replication in human sperm by using Xenopus laevis egg extracts. The data indicate that Xenopus egg extracts can support complete DNA replication in human sperm within 4-9 h as judged by flow cytometric analyses. The possibility of using Xenopus egg extracts for human sperm genome replication was suggested by several studies….

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Complete Replication of Human Sperm Genome: RESULTS(5)

Because the protein synthesis inhibitor, cycloheximide, inhibits the synthesis of cyclin, which is a key component of the maturation promoting-factor for mitosis initiation, inclusion of cycloheximide blocks mitosis initiation and nuclear membrane breakdown. Hutchison et al. showed that cycloheximide-arrested Xenopus egg extracts did not alter the time required for initiation and termination of DNA replication….

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Complete Replication of Human Sperm Genome: RESULTS(4)

Factors Affecting Human Sperm DNA Replication in Xenopus Egg Extracts The duration of DNA replication in human sperm varied considerably with egg extracts from different female toads. At a sperm density of 1160/цЛ, 9 h was required to replicate the human sperm genomes completely as described above. This was the situation for the extracts from…

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