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Such consideration is so significant that the concept of developmental restriction of differentiation does not have any support in the origin of experimental embryology, and Spemann wrote, in 1924, regarding the "differentiation center" in the dorsal lip of the blastopore that the designation "organizer" (rather than, perhaps," determiner") issupposed to express the idea that the effect emanating from these preferential regions is not determinative in a definite restricted direction, but that it possesses all those enigmatic peculiarities which are known to us only from living organism .
 documented the formation of blastopores with separate invagination in P.
(2001) for eggs of the Pimelodus maculatus that showed blastopore closure after 5h 5 min.
First cell division was not apparent until day 4, after which divisions occurred daily until the blastopore appeared at day 28.
At 20-30 [micro]M (Figures 4 and 6), the larvae remained motile, retained the blastopore and the lower part of archenteron and generally survived through the next 1-2 days; they did not lose their extralarval caps (category III).
erythrogramma, the movement and destination of cells as they travel over the blastopore lip and into the archenteron differ from typical feeding larval development (Wray and Raff 1991a).
Eleven hours post-fertilization (hpf), after blastopore closure, fertilized eggs (translucent with apparent normal embryonic development) and non-fertilized eggs (white and opaque) were counted.
During the late gastrula stage, however, most embryos consistently accumulated cells in one of the poles, where a small blastopore will form (St.
The evaluation of the fertilization rate was performed approximately seven hours after insemination (blastopore stage closure) by counting the eggs with normal development of a sample of 260 eggs from each incubator.
The early stage comprised eggs from fertilization to blastopore closure, with the embryo not visible in preserved eggs (Ahlstrom and Moser, 1980).
* Stage 2: gastrulation, cellular organization, and differentiation are evident; first embryonic membrane is ruptured as the embryo becomes asymmetrical; blastopore can be discerned
After a period of 120 degree-hours from fertilization (blastopore closure, Weber et al., 2012) 100 eggs of each female were separated to estimate the fertilization rates (RF = number of eggs x 100 / total number of eggs, Romagosa et al., 1990).
Six hours later (20 h after fertilization), an oval blastula with an invaginated pore at the vegetal pole (blastopore) appears (Fig.
Eggs were then binned into three broader categories that comprised 1) early-stage eggs (E: stages 1-12), which includes all stages before the closing of the blastopore; 2) middle-stage eggs (M: stages 13-15), when the blastopore is closed, the margin of the tail is defined, and the tail bud is thick, but the margin remains attached to the yolk; and 3) late-stage eggs (L: 16-23), when the tail lifts away from yolk and lengthens and encircles the top half of the yolk to extend just beyond the head of the embryo.
After the closing of the blastopore (eight hours after the fertilization) (Amorim et al., 2009), the percentage of the artificial fertilization were gauged.
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- blasting cap
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