In this paper, researchers described methods for deriving and maintaining human embryonic stem (ES) cells from the inner cell mass of human blastocysts that were produced through in vitro fertilization (IVF) and donated for research purposes. They also reported the derivation of cells that they identified as embryonic germ (EG) cells. The cells were cultured from primordial germ cells obtained from the gonadal ridge and mesenchyme of 5- to 9-week fetal tissue that resulted from elective abortions. During the experiment, scientists took undifferentiated human stem cells and injected them into severe combined immunodeficient (SCID) beige mice. This means that they used mice that had an X-linked inherited disorder that causes a block in lymphocyte differentiation. The block is caused by mutations in gene encoding and receptors that affect survival and differentiation signals (Sciencemag. org). After being injected, the mice formed teratomas after a few weeks. About 8 weeks after the initial injection, their teratomas were examined histologically. Human embryonic stem cells generated enormous controversy because their derivation involved the destruction of a human embryo.
Figure (4: BDF)
Neural epithelium (B) The neural rosette is the developmental signature of neuro progenitors in cultures of differentiating embryonic stem cells; rosettes are radial arrangements of columnar cells that express many of the proteins expressed in neuroepithelial cells in the neural tube.
Is ectoderm receives bone morphogenetic protein-inhibiting signals from proteins such as noggin, which leads to the development of the nervous system from this tissue?
The epithelium is made up of cells specialized to serve as sensory cells for the reception of external stimuli. Called also sense or sensory epithelium.