Showing papers on "Totipotent published in 2003"

The first half-century of nuclear transplantation

Abstract: Fifty years after Briggs and King first succeeded in obtaining normal tadpoles from transplanted embryo nuclei in vertebrates, two general principles have emerged from work in amphibia and mammals. One is the conservation of the genome during cell differentiation. A small percentage of adult or differentiated cells have totipotent nuclei, and a much higher percentage of cells committed to one pathway of cell differentiation have multipotent nuclei. The other is the remarkable reprogramming capacity of cell, and especially egg, cytoplasm. The eventual identification of reprogramming molecules and mechanisms could facilitate a route toward cell replacement therapy in humans.

Cultures, products and methods using stem cells

Abstract: Stem cells from human sources can have a variety of useful applications in disease treatment and biotechnology. More particularly the umbilical cord matrix cell cultures of the invention have a variety of totipotent, pluripotent, or multipotent cells for a variety of end uses from a non-controversial, universally available, species-specific source. The technology can have application to any amniotic animal, including agricultural and laboratory animals and humans. The invention relates to isolating the stem cells, culturing the stem cells, maintaining the stem cells, transforming the stem cells into useful cell types using genetic or other transformation technologies, stem cell and tissue banking and using untransformed or transformed cells in disease treatment.

Ungulates produced by sequential nuclear transfer

Abstract: The present invention relates to cloning technologies. The invention relates in part to immortalized and totipotent cells useful for cloning animals, the embryos produced from these cells using nuclear transfer techniques, animals that arise from these cells and embryos, and materials, methods, and processes for establishing such cells, embryos, and animals.

Embryonically modified animal and method of constructing the same

Abstract: The present invention relates to a method for efficiently producing a reproducible animal using totipotent cells wherein mitochondrial DNAs (e.g., wild-type DNAs) adapted to nuclear DNAs have been introduced into or substituted with mitochondrial DNAs, and the present invention also relates to an animal obtained by such production method. When the totipotent cells are ES cells derived from an inbred mouse, the tetraploid rescue method is preferably used. In the production of chimeric animals, mitochondrial DNAs of totipotent cells derived from an animal to be used is substituted with wild-type mitochondrial DNAs by the back-crossing method, the nuclear replacement method, or the like, and the cells are injected into a tetraploid fertilized egg, so that a reproducible inbred chimeric animal is produced while avoiding death of the obtained inbred chimeric animal from respiratory disturbances and the like immediately after birth. The thus obtained reproducible chimeric animal can be used for gene function analyses, animal experiments, and the like without carrying out complicated manipulations for generating inbred animals.

Spare Embryos and Stem Cell Research: Consent Issues

Abstract: Introduction Embryonic stem cells are touted as a source of promising treatment for debilitating diseases such as Parkinsons, Alzheimers, diabetes, cardiovascular disease, and many others. (1) In order to exploit the therapeutic potential of stem cells, extensive research is required on the risks and benefits of their use. (2) Respect for ethical boundaries should be included in this risk-benefit evaluation. Different sources of stem cells have different therapeutic potential. The four sources of stem cells are: embryonic stem cells (hESC), adult stem cells (ASC), stem cells of aborted foetuses, and finally, umbilical cord stem cells. hESC are either totipotent or pluripotent. Totipotent cells are found when the embryo is composed of eight cells or less. Each totipotent cell is capable of developing into a complete organism. (3) Pluripotent cells can differentiate into many cellular types but they cannot create an entire organism (i.e. an embryo), hESC that come from the blastocyst, an embryonic structure found six days post-fertilization, are pluripotent. (4) Spare embryos at the blastocyst stage can provide pluripotent hESC. For their part, ASC are multipotent, that is, they can differentiate into certain specialized cellular types. (5) but most often are committed to a single function. (6) Their principal function is to replace differentiated cells in a particular tissue when it is damaged or old. (7) Cells from aborted foetuses are multipotent. These cells can come, for example, from neural foetal tissue and be derived into neural stem ceils. Cells from the umbilical cord also form part of this multipotent cell type category. Haematopoietic stem cells can be extracted from the umbilical cord and represent an interesting alternative to bone marrow graft. (8) The therapeutic potential of each of these stem cell types remains to be established. Each seems full of promise but only research will tell. The most controversial is that which requires the creation of embryos for the research. Indeed, current restrictions on the deliberate creation of embryos for research (9) have led researchers to go to another existing source of embryos: surplus embryos left over from in vitro fertilization (IVF). Access depends on the donation by the couple of embryos for research purposes. It is spare embryos of pluripotent potential that are the subject of this paper. To date, donor consent to research on surplus embryos has been general in nature. Since March 4, 2002, however, the Human Pluripotent Stem Cell Research: Guidelines for CIHR-Eunded Research (hereinafter referred to as the "CIHR Guidelines") require a specific consent for stem cell research. The major reasons provided are as follows: immortalized cell lines will be created that will continue to divide indefinitely and could be used in different research projects for many years; these cell lines could have an important commercial value (10) (without profiting the embryo donors themselves) and such research necessarily requires the destruction of embryos. In Canada, in the absence of the adoption of An Act Respecting Assisted Human Reproductive Technologies and Related Research (Bill C-13), (11) it is the CIHR Guidelines that govern the ethical review of stem cell research protocols. Since 1998, the Tri-Council Policy Statement: Ethical Conduct for Research Involving Human, (hereinafter referred to as "the Tri-Council Policy Statement") governs the process of ethical review of research. Obviously, the general common law and civil law principles and procedures governing consent also apply. We will begin our study of the issue of consent to stem cell research with a brief analysis of Bill C-13, followed by the Tri-Council, Policy Statement and the CIHR Guidelines. We will then examine the conformity of the consent forms used in eight Canadian fertility centres prior to 2003 against these norms. Finally, we will argue that stem cell research on spare embryos is not really that unique. …

Reprogrammed by a frog.

Abstract: ![Graphic][1] A frog oocyte germinal vesicle (center) can reprogram injected nuclei (white). Gurdon/ElsevierDolly, Polly, and friends proved that somatic cells are potentially totipotent, but the reprogramming that a somatic cell nucleus must undergo during cloning remains an error-