Induction and improved embryonic development by the nucleus of pander in associated avian blastoderm parts: Influence of δ or γ ooplasm

Abstract

After placing in vitro, central subgerminal ooplasm (containing a central nucleus of Pander) from a quail germ disc of a prelaid egg (before symmetrization) on the upper layer of an isolated chicken antisickle, we observed the induction of a radially oriented preneural plate (without interference of chordamesoblast). This observation suggests the primary existence during the period of symmetrization in utero of an until now unknown temporospatially linked "vertical" effect, emanating from the nucleus of Pander, on the parallel (pre)neural plate anlage forming part of the area centralis in the overlying blastoderm. For comparison, we "sandwiched" in vitro a quail sickle endoblast fragment between the deep side of the upper layer of an isolated chicken antisickle region and a central subgerminal ooplasmic mass. This resulted in a colonization of the subgerminal ooplasmic mass by quail sickle endoblast cells followed by improved neurulation and/or gastrulation phenomena. The latter never occurs in the absence of central subgerminal ooplasm. In both types of experiments there seems to exist a common link between the observed induction phenomena: the presence of delta ooplasm in the involved deep structures. Indeed, the nucleus of Pander contains delta ooplasm as well as the structures derived from it, i.e., endophyll with primordial germ cells and sickle endoblast-derived cells after colonization of the neighboring central ooplasm (present study). Therefore, we think that the preneural plate-inducing effect observed after placing a nucleus of Pander on the antisickle region is due to the presence of a factor in the delta ooplasm that diffuses in the neighborhood. The appearance of gastrulation phenomena in the second type of experiment seems to be due to colonization of the more peripheral part of the central subgerminal ooplasm containing the more superficial and peripheral gamma ooplasm in which Rauber's sickle material can develop. This suggests that the kind of involved ooplasm (delta or gamma) can predetermine the inductive activity of the deep structures that contain it: the central part of the nucleus of Pander and/or endophyll for preneurulation phenomena and sickle endoblast (in the presence of central subgerminal ooplasm) for gastrulation and/or neurulation phenomena.

Fitness costs of reproductive capacity and ovarian development in a Bt‐resistant strain of the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

“…Our results have shown that ovary development is also reduced in the resistant CK2 and BtR strains compared with 96S or CK1 (Figs and ). It has been reported that individuals with more vitellogenic follicles have larger egg production . We propose that factors affecting early life fitness have deleterious effects on fitness in later stages of development, as Bt ‐resistant individuals exhibit a delayed larval development, delayed calling behaviour and reduced mating behaviour .…”

Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

“…This nucleus of Pander is usually considered as a kind of "lost" yolk mass, having no influence on blastoderm development. However, we have shown that when a prelaid nucleus of Pander (from a quail egg extracted before laying) is placed on the deep side of the uncommitted upper layer of an isolated anti-sickle region of an unincubated chicken blastoderm, it induces an early neural plate (Callebaut et al, 2004b). This finding probably also occurs temporally in situ in the unal- tered germ disc region during early development in combination with the also temporal effect of endophyll (both containing ␦ ooplasm).…”

“…There exists also a parallelism between the sickle shape of the predisposed anlage fields and the also sickleshaped layers in the underlying ooplasm (Callebaut et al, 2000c), which seems to indicate that, just as is the case for Rauber's sickle and the nucleus of Pander (Callebaut et al, 2004b), inductive processes emanate vertically from the underlying subgerminal ooplasm. This sickle shape of the anlage fields also suggest that before the eccentric tilting of the subgerminal ooplasm occurred, there existed a perfect circular configuration probably in relation with the histological demonstrable radial symmetry before.…”

Head-tail patterning of the vertebrate embryo: one, two or many unresolved problems?

“…Unlike Xenopus, however, the egg is highly polyspermic and the embryo breaks its radial symmetry at a relatively late, highly multicellular stage. If maternal determinants exist (and there is evidence that gravity as the egg rotates in the mother's oviduct influences polarity and that "δ-ooplasm" may be a critical maternal component; Kochav and Eyal-Giladi, 1971;Callebaut et al, 2001;Callebaut et al, 2004), they may establish a polarity bias but are not required for breaking symmetry. The clearest demonstration of this is the observation that when a "blastula" stage embryo (about 20,000 cells) is cut into several fragments, each fragment can spontaneously initiate formation of its own, complete, embryonic axis (Spratt and Haas, 1960;Bertocchini et al, 2004).…”