The differentiation of the sucker in amphibian ectoderm
Başlık:
The differentiation of the sucker in amphibian ectoderm
Yazar:
Boonyasidh, Prayong, author.
ISBN:
9780438052574
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (60 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: D. R. Newth.
Özet:
1. Ectoderm of the blastula (stage 8) of Xenopus has been isolated by explantation and by exogastrulation.Explants gave rise to suckers associated with atypical ectoderm in 33% of cases, sometimes nervous tissue was also formed. Exogastrulae showed suckers in 90% of the collapsed sac of 'ectoderm', while notochord and muscle are found in the 'endomesoderm'. The size and the degree of development of the suckers formed in both explants and exogastrulae are less than in the intact embryo. 2. When actinomycin D was administered to the blastocoel of a blastula (stage 7), it is found that the treated embryos have relatively retarded development when compared with the controls which were injected with saline. Sucker formation was little affected by the injection of lower concentration (2 mug/ml). Higher concentrations (10 mug/ml) seem to be almost completely inhibitory although rather poor differentiation of all tissues was occasionally found. The results do not suggest that sucker development is less susceptible to the action of actinomycin D than that of other tissues. In other words, sucker differentiation is not independent of RNA synthesis in post-blastula life. 3. Presumptive sucker ectoderm from blastulae (stage 8) was grafted to many sites on neurula hosts (stages 14-16) and cultured for 48 hours after the operation. Every graft along the dorsal side of the embryo from the head to the tail showed sucker formation either alone or with other structures. The ventral grafts on the belly show nothing except atypical ectoderm and spaces filled with necrotic cells. The second highest frequency of sucker development is found over the sense organs (around the eye and the ear). The frequency of the suckers formed and the size of the individual suckers seem to correlate with the cranio-caudal and the dorso-ventral positions of the grafts. Histological study showed that every graft in which a sucker is differentiated also had nervous tissue either developed within the graft or of host origin. Most of the grafts that show sucker alone are found along the head and the anterior part of the spinal cord. These suckers are found in close contact with the host central nervous system and the sense organs. Notochord differentiation that was seen in some grafts never occur near the sucker. Melanophores and mesenchymal tissue found in the graft might be of host or of graft origin.4. The results of inversion of uncleaved eggs showthat Siamese twins may be induced by a process of redistribution of the yolk with respect to the cortex. Only a rather well developed additional head shows sucker differentiation. On the other hand, those twin pairs of which one twin had only a rudimentary induced head show suckers on the main head alone. Similarly, in the animals deprived of presumptive sucker ectoderm at blastulae suckers are formed only when head formation is good. 5. We may, therefore, conclude that: (a) suckers can be formed by Xenopus ectoderm isolated from inductive influences and cultured in saline; (b) nevertheless sucker formation does not appear to be independent of de nevo synthesis of RNA in post-blastula life; (c) presumptive sucker ectoderm is not determined to differentiate into suckers in the sense that it fails to do so when grafted to the ventral surface of neurulae; (d) there is evidence that sucker differentiation is promoted by the presence of central nervous tissue and can be induced by head structures.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684403.1) | 684403-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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