Secondary Embryos Research Articles

Competence tests of early amphibian gastrula tissue containing nuclei of one species (Rana palustris) and cytoplasm of another (Rana pipiens)

ABSTRACT Competence tests of tissue from lethal nucleocytoplasmic hybrids consisting of diploid R. palustris nuclei in R. pipiens cytoplasm were carried out by grafting pieces of early gas-trulae to normal R. palustris early gastrula hosts. In the majority of cases, early gastrula ectoderm of the nucleoplasmic hybrids failed to differentiate further than if left in the intact embryo, although the grafts healed nicely and survived for several days. Grafts of the dorsal lip of the blastopore from nucleocytoplasmic hybrids to normal R. palustris hosts induced small secondary embryos with prominent suckers or sucker Anlage, a characteristic of nucleocytoplasmic hybrid development. These results indicate that the abnormal behaviour of the nucleocytoplasmic hybrids is an inherent property of the tissue, in the sense that contact with normal host does not alter its expression. Furthermore, the results with dorsal lip grafts suggest that nucleocytoplasmic hybrid tissue influences the direction in which normal tissue differentiates.

Transformation of rat liver cells with chicken sarcoma virus B77 and murine sarcoma virus.

Rat liver cells in vitro were transformed with chicken sarcoma virus B77, giving RL(B77) cells, and with murine sarcoma virus (Harvey), giving RL(MSV) cells. Rat liver cells transformed spontaneously in vitro were designated RL cells. In addition, the RL(MSV) cell line was adapted for growth in culture fluid containing 25 mug of 5-bromodeoxyuridine per ml. All cell lines were tumorigenic in 1-wk-old rats. The number of cells needed for induction of tumor growth was 1,000-fold higher in the case of RL(B77) cells in comparison with RL(MSV) cells and RL cells. No production of viral particles from any of the cell lines investigated was detected by plating concentrated supernatant fluid of the cultures on different secondary embryo cells with and without fusion by Sendai virus, by labeling with uridine-5-(3)H, or by assay for deoxyribonucleic acid polymerase activity. The viral genome was rescued by fusion of RL(B77) cells with chicken cells. Chicken sarcoma virus rescued from (RL(B77) cells differed in plating efficiency on duck cells from B77 virus rescued from transformed rat embryo cells. No virus was rescued after fusion of RL(MSV) and RL cells with mouse, rat, or chicken embryo cells. Infectious murine sarcoma virus can be induced by 5-bromodeoxyuridine from RL(MSV) cells.

Genetic factors influencing C-type RNA virus induction.

Genetic factors were studied which affect the inducibility of C-type RNA viruses from embyro cultures of mouse strains with high and low incidence of spontaneous leukemia. Virus was inducible by chemical treatment from secondary embryo cultures of several inbred strains. Both virus inducibility and the capacity of the virus to persist in cells from which it was activated were found to be inherited as dominant genetic characteristics. The results show that the factors controlling virus activation and persistence in culture also play an important role in spontaneous virus expression in the animal.

‘Integration’ of polyoma virus dna into mammalian genomes

Summary Cells of mouse (secondary embryo cultures), hamster (BHK-2l) and human (Hep-2) origin were infected with Polyoma virus, and the high molecular weight cellular DNA was isolated, at various times after infection, by sedimentation velocity through alkaline sucrose gradients. Some of the Polyoma DNA became associated (ie. ‘integrated’) with the mouse and hamster DNA, but little if any with the human DNA. Following viral DNA replication in the mouse cells, approximately half of the newly synthesized Polyoma DNA became cell DNA-associated.

9. Lattice thermal conductivity of antiferromagnetic MnF below its Néel temperature: B.N. Mehrotra (Dept. of Physics, Washington University, St. Louis 30, Missouri, U.S.A.)

To examine the spatial distribution of dorsal determinants in the early embryos ofXenopus laevis, individual cells from the 32-cell embryo were transplanted into the same tier of the ventral side of a synchronous recipient. Their abilities to initiate a secondary embryo were measured by the incidence of secondary embryos and by the length of the secondary axis relative to the primary embryo. The ability was found to be localized in all cells (A1, B1, C1, and D1) of the dorsal most column and in the vegetal cells (C2 and D2) of the dorsolateral column. Transplanted C1 (subequatorial) cells caused the highest incidence of a secondary embryo and the average relative length of the secondary embryo was also greatest. Effectiveness decreased in the order: D1, B1, D2, C2, and A1. When these results were compared with Dale and Slack's fate map of the 32-cell embryo, it was concluded that the distribution of dorsal determinants is unique and does not coincide with the prospective regions for any tissues, though it is somewhat similar to the prospective region of dorsal endoderm or notochord. From these results it seems that dorsal determinants do not determine a particular tissue in an embryo but rather the “dorsal” region of an embryo.

The induction of secondary embryos in the early chick blastoderm by grafts of Hensen's node.

American Journal of AnatomyVolume 101, Issue 1 p. 101-133 Article The induction of secondary embryos in the early chick blastoderm by grafts of Hensen's node Casimer T. Grabowski, Casimer T. Grabowski Department of Anatomy, School of Medicine, The University of Pittsburgh, Pittsburgh 13, Pennsylvania This investigation was aided by a grant from the Allegheny County Unit, American Cancer Society.Search for more papers by this author Casimer T. Grabowski, Casimer T. Grabowski Department of Anatomy, School of Medicine, The University of Pittsburgh, Pittsburgh 13, Pennsylvania This investigation was aided by a grant from the Allegheny County Unit, American Cancer Society.Search for more papers by this author First published: July 1957 https://doi.org/10.1002/aja.1001010106Citations: 18 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume101, Issue1July 1957Pages 101-133 RelatedInformation

The Regional Properties of Amphibian Organizer Tissue After Disaggregation of Its Cells in Alkali

ABSTRACT A series of explantation and implantation experiments has been carried out in order to discover if the amphibian organizer is able to induce normally differentiated nervous tissue after disaggregation and reaggregation of its cells. Explants In twenty-one control explants of ectoderm alone, no neural tissue was formed. This made it certain that the inductions in all the experiments were due entirely to the organizer tissue. From a small number of explants of early gastrula dorsal lip into early gastrula ectoderm it was confirmed that, as Holtfreter has claimed (1944b), the regional inducing power of this tissue is in no way inferior after disaggregation of its cells. The numbers of brain, eye and neural tube inductions (Table 1) did not differ significantly as between experiments and controls, and these tissues were often asymmetrical in both series. The archenteron roof from the late gastrula also showed no deterioration in regional inducing powers after disaggregation of its cells. When the percentages of brain, eye and neural tube inductions were compared as between experiments and controls, no significant difference was evident. Combinations of three anterior, three middle or three posterior thirds of the archenteron roof in a control series gave different frequencies of brain, eye and neural tube inductions (Table 4). However, these regional differences were no longer apparent when the separate thirds had been disaggregated before explantation (Table 5). This was apparently due to a reduction of the number of brain inductions by the two anterior thirds. Since no regional differences were detectable in control explants of single thirds of the archenteron roof (Table 3), there seems to be some size factor limiting the range of inductions in small explants. The influence of the quantity of inducing tissue is discussed in the light of Marx’s (1925), Dalcq & Lallier’s (1948) and Lopaschov’s (1935) results. Owing to the frequent asymmetry and the incomplete differentiation of the nervous tissue in explants, some implantation experiments were also carried out. Disaggregated dorsal lip tissue from an early gastrula was implanted into a ventral position in an early gastrula host It appeared to induce just as successfully as the normal dorsal lip. The secondary embryos of both experiments and controls were usually incomplete. In the experiments they were more complete if they lay near the host’s axis, and if the implanted tissue had invaginated for the maximum distance. The possible reasons for this relationship are discussed. In the secondary embryos, the formation of symmetrical, paired somites was always associated with the presence of an archenteron and a notochord. Explants containing no endoderm never form an archenteron, and in the present experiments they also only rarely formed somites. It is concluded that these results confirm Holtfreter’s findings by showing that the complete organizer, even at the late gastrula stage, can differentiate normally itself, and can induce regionally differentiated nervous tissue, after its cell arrangement has been upset by disaggregation. But the results of series 4 show that specific regional properties are no longer demonstrable in separate thirds of the archenteron roof after this treatment. Comparison of explants and implants leads to the conclusion that the completeness and symmetry of all inductions depends on the final layout of the organizer tissue when it begins to induce. The possible influence of the host endoderm on this layout is discussed. It has been shown that all the quantitative data can be explained by postulating the existence of an anterior-posterior gradient in the concentration of a single evocator. Although results of other workers show that qualitatively different inducing substances must exist, there is no reason for rejecting the idea that regional differentiation depends partly on quantitative differences.

Studies on Pregastrular Development, Early Embryonic Development, and Hatchability of Prematurely Laid Eggs of the Hen

A NUMBER of workers, including Dareste (1877), Mitrophanov (1900), Tannreuther (1919), Newman (1940), and others have reported and described various types of monsters and duplicities in the chick embryo. Nalbandov (1942) reported one case of viable twin chicks, presumably of monozygotic origin. Stockard (1921), stated, “in spite of many experimental studies on the developing hen’s eggs by Dareste, Fere, the writer, and others, no double monster, or twin conditions have been produced.” Twieselmann (1935) and others have produced doubling in the chick embryo by injury to the blastoderm, and Waddington and Schmidt (1933) have induced secondary embryos by transplantation of organiser material. Stockard’s theory, that an arrest of development in pregastrula stage embryos caused twinning and double monsters, was tested by Riddle (1923) on pigeons and doves. He obtained eggs from these species at various stages of development before gastrulation and, after cooling them, subsequently incubated them. These eggs were .

Experimental Studies on the Developing Perch (Perca flavescens Mitchill)

The records of experimental analyses of the embryogenic processes in the Teleost are comparatively meagre. The results of defect-experiments performed on Fundulus eggs by Morgan, Lewis,,3 and Hoadley indicate that the ultimate limitation of cellular potencies occurs during gastrulation, but they supply no conclusive evidence concerning the nature of the mechanisms whereby the limitation is accomplished. The time is now ripe for experimental investigation and analysis of Teleost development in the light of the modern concepts of experimental embryology. The eggs of the yellow perch were used for experimental material in the present research. Transplantation of the tissue corresponding to the dorsal lip of the amphibian blastopore induces the formation of a secondary embryo; the experiment and results are comparable to those of Spemann on the egg of Triton. The cytoplasm of the perch egg is large in amount in comparison with the yolk. The germ-ring forms and gastrulation commences when almost one-half the yolk is covered by the blastoderm. Early in gastrulation the lip of the blastoderm at which invagination is principally localized induces the formation of a secondary embryo when transplanted to an extra-embryonic region near the germ-ring of an egg the same age as the donor. The induced embryos are only slightly smaller than the normal, and have been obtained complete as far anterior as mesencephalon and myelencephalon. The parts formed are perfect. Active motility and vigorous heart-beat developed in the oldest induced embryo. The primary embryos are normal.