title: Behavior and DNA synthesis of the nuclei produced after meiosis in Paramecium caudatum.
abstract: Haploid micronuclei produced by meiosis in Paramecium caudatum are destined either to survive or to degenerate depending upon their position in the cytoplasm. The behavior of the four meiotic division products in living cells and their DNA synthesis patterns were examined to determine whether there were differences between nuclei destined to survive and those destined for degeneration. Some prospective degenerating nuclei divided, as did the surviving nuclei, but then became pycnotic immediately after division. This indicates that division and pycnosis are not alternative nuclear fates, but are independent processes. Microspectrophotometric measurements of DNA content showed that each meiotic product had 1 C amount of DNA at the second meiotic telophase and then increased the amount to 2 C linearly with time after the telophase. The time course of the DNA synthesis in the prospective degenerating nuclei was not different from that in the surviving ones. These results suggest that the determination of survival or degeneration of meiotic products is a process independent of division and DNA replication. But spindles and daughter nuclei of prospective degenerating nuclei showed some morphological differences from those of surviving ones. Furthermore, the degenerating nuclei became indistinct and small at the beginning of the degeneration, whereas this change was not observed in the surviving ones. Most of the surviving nuclei were surrounded by a clear region of the cytoplasm before their division. These morphological differences between the prospective surviving and degenerating nuclei may be related to their eventual outcomes.
authors.affiliation: Department of Biotechnology, Senshu University of Ishinomaki, Ishinomaki, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Yanagi