Showing papers on "Totipotent published in 1980"

Somatic embryogenesis from Sorghum bicolor leaves

Abstract: Plant regeneration from totipotent cultured cells or protoplasts is a prerequisite for the often proposed genetic modification of plants through somatic cell genetics, and has been achieved in many species. The cereals (and the rest of the Gramineae) have, however, proved to be extremely unresponsive to in vitro culture techniques1. The most convenient source of plant protoplasts is the leaf tissue because it allows the isolation of a large, relatively uniform cell population without the necessity of killing the plant. However, despite considerable efforts, sustained cell division has never been obtained from cereal leaf blade protoplasts2. Thus, a crucial question arises of whether leaf cells from cereals are actually totipotent and consequently, whether they can be useful for somatic cell genetics. We now report that young leaf tissue of a cereal can express totipotency even to the extent of forming somatic embryos. However, the ability to respond is rapidly lost during leaf maturation. We think that this phenomenon can explain many difficulties faced in cereal tissue culture. Moreover, the leaf culture we describe may help to ascertain whether mature cereal cells are merely no longer competent (in the sense of Halperin3) to respond to tested in vitro conditions or whether they actually lose their totipotency.

Role of the blastocoele microenvironment in early mouse embryo differentiation

Abstract: During preimplantation development, the mouse embryo differentiates into an outer layer of cells, the trophectoderm, and an inner group, the inner cell mass. Tarkowski and Wroblewska1 proposed that this differentiation depends on the position of blastomeres in the morula, with outside cells giving rise to trophectoderm and inside cells producing the inner cell mass. This epigenetic hypothesis has been confirmed by other studies in which blastomere position was altered at the 4-cell or 8-cell stage, thus demonstrating the totipotency of the blastomeres at these stages2–4. It was recently found that the inner cell mass of the early blastocyst is also totipotent and can form trophectoderm when isolated by immunosurgery5–8. Because inner cells apparently become committed during the time that they are exposed to the distinct microenvironment of the blastocyst9–11, we postulated that diffusible components or other factors in the blastocoele may have a role in the commitment of cells in the inner cell mass. We report here results, obtained by injecting donor cells into host blastocysts, showing that totipotent cells exposed only to blastocoele fluid differentiate into morphologically normal blastocysts, whereas those in contact with the blastocyst's inner surface do not.

Expression of the teratocarcinoma phenotype in hybrids between totipotent mouse teratocarcinoma and myeloma cells.

Abstract: We have produced somatic cell hybrids between totipotent mouse teratocarcinoma and myeloma cells. These hybrids behave like the teratocar-cinoma cell parent and express teratocarcinoma embryonal antigens. However, they also express the myeloma H-2 antigens. The availability of these hybrids should make it possible to study the expression of already rearranged immunoglobulin genes during mouse development.