Development of division asynchrony and bilateral symmetry in the first quartet of micromeres in eggs of Lymnaea.
نویسنده
چکیده
Experiments were undertaken to investigate the cleavage pattern of eggs of Lymnaea developing into exogastrulae after a treatment for 2 h with 5x 10~ M-LiCl at 6 °C at the beginning of second cleavage. It appeared that the 16-cell stage is reached normally, but that in the vegetative cells the following division is considerably retarded. It is assumed that this delay is associated with the suppression of division asynchrony in the first quartet of micromeres, which normally adumbrates bilateral symmetry in the animal hemisphere, and with suppression of gastrulation.
منابع مشابه
The echinoid mitotic gradient: effect of cell size on the micromere cleavage cycle.
Like other euechinoids, the fertilized eggs of the sand dollar Dendraster excentricus proceed through cleavages that produce a pattern of macromeres, mesomeres, and micromeres at the 4th division. The 8 cells of the macro-mesomere lineage proceed through 6 additional cleavages before hatching. At the fifth overall division, the 4 micromeres produce a lineage of large micromeres that will divide...
متن کاملTiming of the phases of the cell cycle during the period of asynchronous division up to the 49-cell stage in Lymnaea.
The duration of the phases of the cell cycle (M-G!-S-G2) has been determined from the 8up to the 49-cell stage in eggs of Lymnaea, using autoradiography and cytophotometry of Feulgen-stained nuclei. Division asynchrony of corresponding cells in different quadrants is primarily caused by unequal lengthening of the G2 phases. In general it appeared that in the vegetative cells lengthening of the ...
متن کاملSpecification of first quartet micromeres in Ilyanassa involves inherited factors and position with respect to the inducing D macromere.
In the embryos of the gastropod Ilyanassa obsoleta, the development of several ectodermal structures requires an inductive interaction between the micromeres and the D macromere. The first quartet micromeres (1a, 1b, 1c and 1d) contribute to the head of the larva and descendants of 1a and 1c normally develop the eyes. The eyes do not develop if 1a and 1c are removed at the eight-cell stage. How...
متن کاملEvaluation of the role of unilateral and bilateral tooth extraction treatment on maxillary arch symmetry in Class II subdivision cases
Background and Aim: Unilateral extractions have been proposed as potential treatment options to correct Class II subdivision malocclusion, suggesting that most side effects associated with asymmetrical mechanics can be avoided, however the post-treatment arch form may not be symmetrical. Therefore, the aim of this study was to determine the post-treatment effects of unilateral premolar extrac...
متن کاملCell contact-dependent positioning of the D cleavage plane restricts eye development in the Ilyanassa embryo.
In embryos of the gastropod Ilyanassa obsoleta, the first-quartet micromeres of the A, B and C lineages (1a, 1b, and 1c) are each competent to form an eye in response to signaling from the 3D cell. The first-quartet micromere of the dorsal D lineage (1d) is smaller than the others, divides at a slower rate, and lacks the ability to form an eye. These properties of 1d all depend on inheritance o...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of embryology and experimental morphology
دوره 26 3 شماره
صفحات -
تاریخ انتشار 1971