Cytological studies on egg fragments of the salamander triton. IV. The cleavage of egg fragments without the egg nucleus

Fankhauser, Gerhard

doi:10.1002/jez.1400670302

Cited by 61 publications

(5 citation statements)

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“…On the latter problem, Fankhauser (1948) concluded that a cytoplasmic, inhibitory factor emanates from the zygote nucleus and causes the degeneration of the accessory sperm nuclei. This conclusion was based on extensive work on the rescue of accessory sperm nuclei in androgenetic egg fragments (Fankhauser, 1934;Fankhauser and Moore, 1941b). The rescue of accessory sperm nuclei in androgenetic egg fragments was confirmed in Cynops eggs whose egg nuclei were removed by bisection of fertilized eggs, by sucking with a micropipet, or by UV-irradiation (Iwao et al, , 1993.…”

Section: Introductionmentioning

confidence: 92%

Changes in microtubule structures during the first cell cycle of physiologically polyspermic newt eggs

et al. 1997

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The unfertilized egg of the newt, Cynops pyrrhogaster, has a second meiotic spindle at the animal pole and numerous cortical cytasters. After physiologically polyspermic fertilization, all sperm nuclei incorporated into the egg develop sperm asters, and the cortical cytasters change into bundles of cortical microtubules. The size of the sperm asters in the animal hemisphere is ∼5.6‐fold larger than that in the vegetal hemisphere. Only one sperm nucleus moves toward the center of the animal hemisphere to form a zygote nucleus with the egg nucleus. This movement is inhibited by nocodazole, but not by cytochalasin B. The centrosome in the zygote nucleus divides into two parts to form a bipolar spindle for the first cleavage synchronously with the nuclear cycle, but centrosomes of accessory sperm nuclei in the vegetal hemisphere remained to form monopolar interphase asters and subsequently degenerate around the first cleavage stage. The size of sperm asters in monospermically fertilized Xenopus eggs was ∼37‐fold larger than those in Cynops eggs. Since sperm asters that formed in polyspermically fertilized Xenopus eggs exclude each other, the formation of a zygote nucleus is inhibited. Cynops sperm nuclei form larger asters in Xenopus eggs, whereas Xenopus sperm nuclei form smaller asters in Cynops eggs compared with those in homologous eggs. Since there was no significant difference in the concentration of monomeric tubulin between those eggs, the size of sperm asters is probably regulated by a component(s) in egg cytoplasm. Smaller asters in physiologically polyspermic newt eggs might be useful for selecting only one sperm nucleus to move toward the egg nucleus. Mol. Reprod. Dev. 47:210–221, 1997. © 1997 Wiley‐Liss, Inc.

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Section: Introductionmentioning

confidence: 92%

Changes in microtubule structures during the first cell cycle of physiologically polyspermic newt eggs

et al. 1997

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“…The pronuclear fusion has been suggested to be not required for the initiation of DNA synthesis in many organisms (Bucher and Mazia, 1960; Simmel and Karnofski, 1961;Zimmerman and Silberman, 1967; Longo and Plunket, 1973;Katagiri and Moriya, 1976). Cleaving activity of the eggs independent of the nucleus has been reported in the sea urchin (Harvey, 1956) and the amphibia (Fankhauser, 1934;1941;Briggs et al, 1951).Previously, we demonstrated with fertilized echinoderm eggs that pronuclear fusion and cleavage occurred in the presence of aphidicolin (Nagano et, 1981;Hirai et al, 1984). Aphidicolin has been reported to be a specific inhibitor of eukaryotic DNA polymerase-a and to inhibit replicative DNA synthesis but not RNA and protein synthesis (Ikegami et al, 1978;Oguro et al, 1979;Brachet and De Petrocellis, 1981).…”

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confidence: 89%

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confidence: 99%

The fate of DNA originally existing in the zygote nucleus during achromosomal cleavage of fertilized echinoderm eggs in the presence of aphidicolin: Microscopic studies with anti‐DNA antibody

Yamada

Hirai

Ikegami

et al. 1985

Journal Cellular Physiology

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In fertilized echinoderm eggs, the male and female pronuclei fuse to form the diploid nucleus even in the presence of aphidicolin, a specific inhibitor of eukaryotic DNA polymerase-alpha. The subsequent first cleavage is independent of chromosomes but dependent on spindle and amphiaster. The fate of DNA originally existing in the fused nucleus during achromosomal cleavage of fertilized sea urchin and starfish eggs induced by aphidicolin was determined using antidenatured DNA antibody. The nucleus is not formed in the divided daughter cells at the two-cell stage but the nuclear-envelope-free chromatin mass which is unassociated with mitotic apparatus remains in the center region of embryos, especially near the first cleavage furrow. These results indicate that the condensed and nonreplicated chromatin can not be associated with spindle and asters in the presence of aphidicolin.

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“…The key enzyme for DNA replication is DNA polymerase a; the amount of the enzyme présent in unfertilized sea urchin eggs is sufficient for the production of 1000 nuclei. During cleavage, it moves from the cytoplasm into the nuclei when the chromosomes swell at anaphase (Fansler and Loeb, 1969). The absolute requirement of DNA polymerase a for DNA synthesis during sea urchin egg cleavage has been demonstrated by Ikegami et al (1978): a spécifie inhibitorof the enzyme, aphidicolin, arrests development soon after amphimixy.…”

Section: Cleavage Of Fertilized Eggsmentioning

confidence: 99%

Nucleocytoplasmic Interactions in Morphogenesis

Brachet

1987

International Review of Cytology

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I. O l d Réminiscences The rôle played by the cell nucleus as a whole in morphogenesis is a very old problem; the most direct approach to its solution is merotomy, that is cutting an egg or a unicellular organisai into two halves, nucleate and anucleate. Merotomy experiments were done almost a century ago by V erworn (1892), Balbiani (1888), Klebs (1889), Townsend (1897), Yatsu (1905), and others on eggs of various species, protozoa, and plant cells. As pointed out by Mazia (1952), the gênerai conclusion is that "there is not a single case where an activity has not continued in an enucleated cell." However, the life span of anucleate cytoplasm, after merotomy, varies considerably from cell to cell: 1 or 2 days for cytoplasts of mammalian cells, about 10 days for amebae, 3 months or more for the giant unicellular alga Acetabularici. The survival of anucleate fragments of protozoa and eggs for a certain length of time came as a complète surprise to me when I attended, in 1927, the first lecture of a cytology course given by Pol Gérard. Naïvely, 1 belleved that removing the nucleus should be the same as cutting off the head of a man. I was so fascinated by the problem that 1 decided to study it in the laboratory headed by my father, Albert Brachet, under the guidance of Albert Dalcq, who was then doing experiments on the effects of X-rays on eggs and sperm of the frog Rana temporaria. He showed, among other things, that injury to the egg or sperm nucleus impeded gastrulation; injury to both the maie and female gamète nuclei allowed at best irregular cleavage (Dalcq and Simon, 1932). This suggested an essential rôle of the nucleus in early morphogenesis. But Albert Brachet was convinced of the major importance of the cytoplasm during thèse first stages of embryonic development: he was one of the pioneers of expérimental embryology, studying at that time the effects of the destruction of a purely cytoplasmic area, the gray crescent (see Section IV) of fertilized frog eggs, on the formation of the nervous System. Earlier experiments on polyspermy in sea urchin eggs had shown him that the nuclei of the supemumerary spermatozoa assumed the same morphology (condensed or swollen) as that of the egg nucleus (see Section IV). He called this phenomenon "la mise à l'unisson" 249

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Cytological studies on egg fragments of the salamander triton. IV. The cleavage of egg fragments without the egg nucleus

Cited by 61 publications

References 8 publications

Changes in microtubule structures during the first cell cycle of physiologically polyspermic newt eggs

Changes in microtubule structures during the first cell cycle of physiologically polyspermic newt eggs

The fate of DNA originally existing in the zygote nucleus during achromosomal cleavage of fertilized echinoderm eggs in the presence of aphidicolin: Microscopic studies with anti‐DNA antibody

Nucleocytoplasmic Interactions in Morphogenesis

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