Use of Hybrids between Xenopus laevis and Xenopus borealis in Chimera Formation: Dorsalization of Ventral Cells. (cell lineage/chimera/hybrid/Xenopus/dorsalization)

Approximately 20–25 primordial germ cells leave the endoderm between stages 38–41 and localize in the dorsal root of the mesentery by stage 43/44. At this time all the cells contain large quantities of yolk which is gradually resorbed. The cells begin dividing between stages 48–52. The number and size of the germ cells were measured in tadpoles between stages 48–54 of development. The results indicate that in females the germ cells divide more often than in males. In both sexes the mitoses are grossly unequal, leading to the formation of a new generation of germ cells which are considerably smaller (one-tenth to one-fifth) than the size of the primordial germ cells at stage 48. The germ cells in male tadpoles at stage 54 are larger than in female tadpoles at the same stage. In tadpoles which developed from eggs irradiated in the vegetal hemisphere with u.v. light at the 2- to 4-cell-stage, primordial germ cells migrate into the genital ridges much later (stage 46–48) than in unirradiated embryos. They also differ morphologically from germ cells in control animals at this stage in that they are approximately one-tenth the size, lacking yolk in the cytoplasm and have a more highly lobed nucleus. Comparison of the results in unirradiated and irradiated animals suggests that the germ cell lineage is composed of a series of ordered, predictable events, and serious disruption of one of the events deranges later events.

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28S Ribosomal RNA in Xenopus borealis: gene sequence and differences from Xenopus laevis sequence

Biochemical Society Transactions ◽

10.1042/bst0180657 ◽

1990 ◽

Vol 18 (4) ◽

pp. 657-658 ◽

Cited By ~ 2

Author(s):

PAUL M. AJUH ◽

B. EDWARD H. MADEN

Keyword(s):

Xenopus Laevis ◽

Ribosomal Rna ◽

Gene Sequence ◽

Xenopus Borealis

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Effects of various ammonium salts, amines, polyamines and α-methylornithine on rRNA synthesis in neurula cells of Xenopus laevis and Xenopus borealis

Cell Differentiation ◽

10.1016/0045-6039(86)90004-7 ◽

1986 ◽

Vol 18 (2) ◽

pp. 101-108 ◽

Cited By ~ 6

Author(s):

Koichiro Shiokawa ◽

Yuichi Kawazoe ◽

Kosuke Tashiro ◽

K. Yamana

Keyword(s):

Xenopus Laevis ◽

Ammonium Salts ◽

Rrna Synthesis ◽

Xenopus Borealis

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eFGF is required for activation of XmyoD expression in the myogenic cell lineage of Xenopus laevis

Development ◽

10.1242/dev.129.6.1307 ◽

2002 ◽

Vol 129 (6) ◽

pp. 1307-1315 ◽

Cited By ~ 4

Author(s):

Malcolm E. Fisher ◽

Harry V. Isaacs ◽

Mary E. Pownall

Keyword(s):

Xenopus Laevis ◽

Transcriptional Activation ◽

Molecular Mechanisms ◽

Cell Lineage ◽

Early Response ◽

Myogenic Regulatory Factor ◽

Signalling Molecule ◽

Initial Activation ◽

Embryonic Fibroblast ◽

Antisense Morpholino

This paper addresses the molecular mechanisms that regulate the transcriptional activation of the myogenic regulatory factor XmyoD in the skeletal muscle lineage of Xenopus laevis. Using antisense morpholino oligonucleotide-mediated inhibition, we show that the signalling molecule embryonic fibroblast growth factor (eFGF), which is the amphibian homologue of FGF4, is necessary for the initial activation of XmyoD transcription in myogenic cells. We demonstrate that eFGF can activate the expression of XmyoD in the absence of protein synthesis, indicating that this regulation is direct. Our data suggest that regulation of XmyoD expression may involve a labile transcriptional repressor. In addition, we show that eFGF is itself an immediate early response to activin, a molecule that mimics the endogenous mesoderm-inducing signal. We propose a model for the regulation of XmyoD within the early mesoderm, and discuss the relevance that these findings have for the understanding of myogenic specification in higher vertebrates.

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