Properties of the primary organization field in the embryo of Xenopus laevis

Development ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 47-56
Author(s):  
J. Cooke
Keyword(s):  
Xenopus Laevis ◽  
Host Tissue ◽  
Animal Pole ◽  
Axial Structure ◽  
Dorsal Mesoderm ◽  
Primary Organization ◽  
Set Up

An experiment is described whose results strengthen the classical conclusion, due to Spemann and co-workers, that amphibian gastrulation movements are co-ordinated and controlled by properties intrinsic to the invaginating mesodermal zone, rather than by interaction between this and any field of cell-guiding information, symmetrically disposed about the presumptive head ectodermal region in the animal hemisphere of the blastula/gastrula. The possibility remains, however, that the field of information coming to reside in the marginal mesodermal zone, is itself originally set up utilizing the animal pole as an origin, as well as the presumptive organizer site. Experiments are then described where whole organizer apices, and also subapical squares of dorsal mesoderm from stage-10 donors, are implanted with presumptive polarity reversed 180° relative to that of the host. It is found that reasonably extensive migration, on the part of the graft and the influenced host tissue, is required for the individuation of recognizable axial structure, and that such migration is often prevented in reversed implants due to a retention of autonomous polarity in host and graft. Reasons are suggested for the apparently greater autonomy, in this respect, of apical organizer plugs, but evidence is given that autonomy is nevertheless expressed even by squares of dorsal presumptive mesoderm of side ca. 0·1 mm. The significance of this observation, for theory concerning the nature of the cellular properties involved in the maintenance of embryonic fields, is discussed.

An ultrastructural study of the effects of wheat germ agglutinin (WGA) on cell cortex organization during the first cleavage of Xenopus laevis eggs. II. Cortical wound healing

1979 ◽  
Vol 37 (1) ◽  
pp. 59-67
Author(s):  
M. Geuskens ◽  
R. Tencer
Keyword(s):  
Wound Healing ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Ultrastructural Study ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Cell Cortex ◽  
Animal Pole ◽  
Annular Zone

Uncleaved fertilized eggs of Xenopus laevis treated with wheat germ agglutinin (WGA) have been pricked at the animal pole both inside and outside the regressed furrow region. The wounded cortex of both regions has been studied with the electron microscope and compared with the same region of wounded, untreated eggs. In all 3 cases, filaments are organized in an annular zone in the damaged cortex. When the surface is pricked outside the regressed furrow of WGA-treated embryos, bundles of microfilaments radiate from the ring and extend in deep folds which form a ‘star’ around the wound at the surface of the embryo. However, when the surface is pricked in the new membrane of the regressed furrow, filaments are intermingled with internalized portions of the plasma membrane. It is suggested that, when the surface is pricked outside the furrow region, more filaments are mobilized to counteract the tangential retraction of the membrane which has acquired more rigidity after WGA binding.

The origins of primitive blood in Xenopus: implications for axial patterning

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 423-434 ◽  
Author(s):  
M.C. Lane ◽  
W.C. Smith
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Cell Stage ◽  
Axial Patterning ◽  
Xenopus Embryos ◽  
Spemann's Organizer ◽  
Dorsal Mesoderm

The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90(degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.

scholarly journals The mRNA encoding a β subunit of heterotrimeric GTP-binding proteins is localized to the animal pole of Xenopus laevis oocyte and embryos

1996 ◽  
Vol 59 (2) ◽  
pp. 141-151 ◽  
Author(s):  
Eric Devic ◽  
Laurent Paquereau ◽  
Karine Rizzoti ◽  
Armelle Monier ◽  
Bernard Knibiehler ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Binding Proteins ◽  
Xenopus Laevis Oocyte ◽  
Β Subunit ◽  
Animal Pole ◽  
Gtp Binding Proteins ◽  
Gtp Binding

Induction of dorsal mesoderm by soluble, mature Vg1 protein

Development ◽  
1995 ◽  
Vol 121 (7) ◽  
pp. 2155-2164 ◽  
Author(s):  
D.S. Kessler ◽  
D.A. Melton
Keyword(s):  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Specific Inhibitor ◽  
Mesoderm Induction ◽  
Binding Assays ◽  
Animal Pole ◽  
Xenopus Development ◽  
Mechanism Of Inhibition ◽  
Dorsal Mesoderm ◽  
High Doses

Mesoderm induction during Xenopus development has been extensively studied, and two members of the transforming growth factor-beta family, activin beta B and Vg1, have emerged as candidates for a natural inducer of dorsal mesoderm. Heretofore, analysis of Vg1 activity has relied on injection of hybrid Vg1 mRNAs, which have not been shown to direct efficient secretion of ligand and, therefore, the mechanism of mesoderm induction by processed Vg1 protein is unclear. This report describes injection of Xenopus oocytes with a chimeric activin-Vg1 mRNA, encoding the pro-region of activin beta B fused to the mature region of Vg1, resulting in the processing and secretion of mature Vg1. Treatment of animal pole explants with mature Vg1 protein resulted in differentiation of dorsal, but not ventral, mesodermal tissues and dose-dependent activation of both dorsal and ventrolateral mesodermal markers. At high doses, mature Vg1 induced formation of ‘embryoids’ with a rudimentary axial pattern, head structures including eyes and a functional neuromuscular system. Furthermore, truncated forms of the activin and FGF receptors, which block mesoderm induction in the intact embryo, fully inhibited mature Vg1 activity. To examine the mechanism of inhibition, we have performed receptor-binding assays with radiolabeled Vg1. Finally, follistatin, a specific inhibitor of activin beta B which is shown not to block endogenous dorsal mesoderm induction, failed to inhibit Vg1. The results support a role for endogenous Vg1 in dorsal mesoderm induction during Xenopus development.

An Experimental Analysis of the Development of the Haploid Syndrome in Embryos of Xenopus laevis

Development ◽  
1963 ◽  
Vol 11 (1) ◽  
pp. 267-278
Author(s):  
Louie Hamilton
Keyword(s):  
Xenopus Laevis ◽  
Experimental Analysis ◽  
Rana Pipiens ◽  
Animal Pole ◽  
Pole Cells

Haploid vertebrates may occur spontaneously but are very rare (Fankhauser, 1941; Humphrey & Fankhauser, 1957); however, haploids may be experimentally produced in fish (Swarup, 1959) and in mammals (Beatty, 1953), while amphibian eggs may be so treated that all developing embryos are haploid (Porter, 1939; Gurdon, 1960). The full descriptions of the development of haploid Rana pipiens (Porter, 1939) and R. nigromaculata (Miyada, 1960) apply so well to Xenopus laevis that only the most important points will be touched on here. Haploid amphibians may be identified at the beginning of gastrulation since their animal pole cells are smaller at a given stage than are those of diploids. In all haploid Anura the onset of gastrulation is delayed, and thereafter haploids become progressively more retarded in their development. Their neural plates are shorter, and when the neural folds have closed it can be seen that the embryos are microcephalic and suffer from lordosis and a bulging abdomen.

Mesoderm-inducing properties of INT-2 and kFGF: two oncogene-encoded growth factors related to FGF

Development ◽  
1989 ◽  
Vol 106 (1) ◽  
pp. 79-83 ◽  
Author(s):  
G.D. Paterno ◽  
L.L. Gillespie ◽  
M.S. Dixon ◽  
J.M. Slack ◽  
J.K. Heath
Keyword(s):  
Growth Factors ◽  
Embryonic Development ◽  
Xenopus Laevis ◽  
Dna Synthesis ◽  
Signalling Pathways ◽  
Control Mechanisms ◽  
Animal Pole ◽  
Receptor Signalling ◽  
Mammalian Embryogenesis ◽  
Mesoderm Formation

Many theories of neoplasia suggest that oncogenic transformations result from aberrations in the control mechanisms which normally regulate growth and differentiation during embryonic development. It has recently become clear that many proto-oncogenes are differentially expressed during embryonic development and may thus be important embryonic regulatory molecules. We report here that the products of two transforming oncogenes int-2 and hst/ks (now called kfgf) can, with different potencies, induce mesoderm formation in isolated Xenopus laevis animal pole explants and stimulate DNA synthesis in mammalian fibroblasts. The results suggest that these proteins may function as mesoderm inducers in mammalian embryogenesis and that similar receptor/signalling pathways may be utilized for developmental and oncogenic processes. Finally, we have shown that the Xenopus assay system used in this study provides a powerful screen for protein factors that are active in development.

Properties of the primary organization field in the embryo of Xenopus laevis

Development ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 13-26
Author(s):  
J. Cooke
Keyword(s):  
Marginal Zone ◽  
Organizer Region ◽  
Angular Distance ◽  
Cell Polarization ◽  
Subsequent Paper ◽  
Basic Operation ◽  
Primary Organization ◽  
Organizer Activity ◽  
Set Up ◽  
Cell Immigration

The work presented, in this and the subsequent papers of a series, was begun in order to re-examine the properties of the amphibian primary embryonic field, in the light of current theories concerning the nature of individuation fields in developing animal systems. A detailed description is given of the basic operation whose results are described in this and the subsequent paper. This involves the transplantation, into a late blastula or stage-10 gastrula host, of a supernumerary stage-10 organizer region. The consequences of such operations during the following 4–6 h, up to the late gastrula stage, are also described. Evidence is presented that, from a time some 2·5 h before the organizer site first becomes externally visible, its presumptive region is immune from interference by the proximity of another, implanted organizer, even one which is itself 2·5 h older. That is to say, the final site of development of host organizer activity is not altered by the presence of such an implant. Pairs of early organizers at comparable stages of activity appear to set up competing fields of cellular orientation and immigration, which show a fairly sharp boundary at their interface. This is most obvious for pairs of organizers fairly close together, since the cell polarization and stretching is most pronounced in the region near to the apex of the field, i.e. the initial site of cell immigration. Independent initial fields of immigration due to two organizers can reliably be distinguished in cases where they are as little as 30° of angular distance apart in the marginal zone of the host. These results are to be considered in relation to those of Paper II, for the same series of operations, where the final patterns of cell differentiation are studied, and to those of Paper III, where evidence is given for the development of autonomous polarity in the region of the organizer.

scholarly journals Xenopus laevis oocytes infected with multi-drug–resistant bacteria: implications for electrical recordings

2011 ◽  
Vol 138 (2) ◽  
pp. 271-277 ◽  
Author(s):  
Denice O'Connell ◽  
Karen Mruk ◽  
Jessica M. Rocheleau ◽  
William R. Kobertz
Keyword(s):  
Xenopus Laevis ◽  
Mammalian Cells ◽  
Resistant Bacteria ◽  
Xenopus Laevis Oocytes ◽  
Xenopus Laevis Oocyte ◽  
Drug Resistant ◽  
Animal Pole ◽  
Antibiotic Cocktail ◽  
Storage Media ◽  
Drug Resistant Bacteria

The Xenopus laevis oocyte has been the workhorse for the investigation of ion transport proteins. These large cells have spawned a multitude of novel techniques that are unfathomable in mammalian cells, yet the fickleness of the oocyte has driven many researchers to use other membrane protein expression systems. Here, we show that some colonies of Xenopus laevis are infected with three multi-drug–resistant bacteria: Pseudomonas fluorescens, Pseudomonas putida, and Stenotrophomonas maltophilia. Oocytes extracted from infected frogs quickly (3–4 d) develop multiple black foci on the animal pole, similar to microinjection scars, which render the extracted eggs useless for electrical recordings. Although multi-drug resistant, the bacteria were susceptible to amikacin and ciprofloxacin in growth assays. Supplementing the oocyte storage media with these two antibiotics prevented the appearance of the black foci and afforded oocytes suitable for whole-cell recordings. Given that P. fluorescens associated with X. laevis has become rapidly drug resistant, it is imperative that researchers store the extracted oocytes in the antibiotic cocktail and not treat the animals harboring the multi-drug–resistant bacteria.

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