A Relevant Method for Estimating Cell Cycle of Developing Cell: The Conspicuous Lengthening of Ts during the Early Neural Development of Cynops Embryo: cell cycle analysis/Ts lengthening/early neural development/amphibian embryo).

A new method for estimating cell cycle was proposed and the cell cycles of the presumptive neural cells of Cynops embryo from the gastrula to neurula stages were estimated. Up to the onset of gastrulation, Tg and Tg became recognizable and Ts lengthened more than 10 times of that in the morula stage. The respective phases of cell cycle, espetially Ts became prominently longer as gastrulation and neurulation proceeded.

Changes of Chromosome Length and Constitutive Heterochromatin in Association with Cell Division during Early Development of Cynops pyrrhogaster embryo: (chromatin condensation/constitutive heterochromatin/cell division/ neural differentiation/amphibian embryo).

The length of chromosomes in the presumptive ectoderms of Cynops embryos was measured at nine successive cell divisions from the 6th (cleavage stage) to the 14th (gastrula stage). Up to the 10th cell division (cleavage stage) the chromosome length remained constant. At the 11th cell division the chromosomes began to shorten and continued to shorten at every cell division up to the 14th cell division.

Cell surface changes of the presumptive ectoderm following neural-inducing treatment by concanavalin A.

Scanning electron microscopic studies revealed that Concanavalin A (ConA) induces characteristic changes of the cell surface and the cell architecture of the presumptive ectoderm associated with differentiation into neural tissues. In Con A-treated cells, the filopodia with which cells were connected to each other disappeared from the interior (blastocoelic) surface and the cellular adhesivity decreased significantly. Thereafter, the cells underwent from those of the control explants.

Use of lectins as probes for analyzing embryonic induction.

Lectins were used as probes to investigate the mechanism of embryonic induction. Concanavalin (Con A) and gorse agglutinin out of 7 species of lectins tested were found to have strong neural-inducing effect on the presumptive ectoderm of newt gastrulae. Their effects were abolished by the addition of α-methyl-D-mannoside and α-L-fucose, respectively.

CHANGES OF CHROMOSOMES DURING THE EARLY NEURAL DEVELOPMENT OF A JAPANESE NEWT, CYNOPS PYRRHOGASTER.

The karyotype of Cynops pyrrhogaster was determined on the mitotic chromosomes in the presumptive neural area of an early gastrula. 24 chromosomes of a diploid set consisted of 8 metacentric and 4 submetacentric pairs. Individual chromosomes were identified on the basis of their morphology and characteristic C-binding patterns.