Blastodisc


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Blastodisc

 

embryonic disc, an aggregate of cytoplasm in the holozoic part of the ovum in animals with discoid cleavage. The blastodisc contains a nucleus and is free from the yolk. In the process of cleavage the blastodisc is transformed into a layer of cells (blastoderm) located on the surface of the nondividing yolk.

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Dieterlen-Lievre, "Early germ cell segregation and distribution in the quail blastodisc," Cell Differentiation, vol.
Embryos were observed for at least 4 h after fertilization during blastodisc formation and after incubation overnight at 17 [degrees]C.
These results suggest that a microtubule-associated mechanism is responsible for ooplasm segregation and blastodisc formation in the squid.
All of the eggs laid by the five virgin females, the four second-clutch females, and the three females allowed to mate with vasectomised males, were "collapsed" at oviposition, and none showed any sign of a blastodisc or its associated vascular rosette.
Thus, we conclude that unfertilised eggs of sand lizards are easily recognizable at laying: they lack turgot and lack blastodiscs and the associated vascularity.
Exposure to cold inhibited blastodisc cap formation in all embryos treated prior to cytoplasmic streaming; it also arrested streaming in embryos treated after second polar body formation.
These results suggest that the ordered movement of cytoplasm, which forms the blastodisc in the squid, is disturbed by cold treatment.
Near the animal pole, microtubules were oriented more or less along meridian lines and appeared to radiate from a microtubule-organizing center near the male and female pronuclei, which were 38.6 [+ or -] 6.7 [[micro]meter] ([Mathematical Expression Omitted], n = 5) below the surface of the blastodisc at [T.sub.n] [approximately equal to] 0.76 [ILLUSTRATION FOR FIGURE 2D-I OMITTED].
In these eggs, the blastodisc has begun to divide into two blastomeres, and essentially all oil droplets have aggregated in a crude ring near the vegetal pole.
Formation of the blastodisc at the animal pole of zebrafish (Danio rerio) and loach (Misgurnus fossilis) eggs is inhibited by cytochalasin - cytochalasin B (CCB) in zebrafish (Katow, 1983) and cytochalasin D (CCD) in loach (Ivanenkov et al., 1987).
In crucian carp (Carassius auratus Linnaeus 1758), HHP shock administered to inseminated eggs disrupted the proper formation of blastodiscs, impaired the development of cytoplasm, and triggered the delay of epiboly and suppression of the dorsoventral differentiation [9].