"We select out the unwanted cell types to achieve pure stem cells, " explains Kraus.
They need other cell types nearby to feel comfortable enough to go on living.
But getting stem cells to divide without them turning into other cell types is an even bigger problem.
The researchers were able to extract cells from some of their blastocysts, and grow tissues containing all three cell types.
The blastocyst was "missing a few cell types that it would need to implant" and was suffering other deficiencies, said Dr. Mitalipov.
She'd like to isolate the signals the liver cells get from neighboring cells and perhaps eliminate the need for other cell types.
These proteins transmit chemical signals into a wide variety of cell types.
They would also like to push other stem-cell types, such as those found in the intestine, to the limit in their embryo experiments.
Researchers made all 9, 000 and tested them for biological activity, using automated robots to mix them with various cell types to see their effects.
The mouse work also showed that the retrotransposons were jumping mainly into genes that are active while precursor cells are changing into their destined cell types.
ECONOMIST: Brain development may be influenced by genetic parasites
Embryonic stem cells have great potential for treating human disease because of their ability to generate almost all the cell types found in the adult body.
At the time, the hot research area was in testing G-protein-coupled receptors, or GPCRS. These proteins transmit chemical signals into a wide variety of cell types.
The adult cells are thought to revert to a state similar to that of embryonic stem cells, which are even less specialised, before becoming the new cell types.
The university's Schaap laboratory studied a simple multicellular organism, Dictyostelium, in which motile cells (those which can move spontaneously) differentiate into two immobile cell types: stalk cells and spores.
He injected stem cells he had cultured from his patients into mouse brains and found that they successfully differentiated into the various cell types found in the nervous system.
Linda Griffith, a tissue engineer at MIT, said one of the main problems of the idea would be getting all the right cell types to grow in the right places.
At this stage the structure, though still just a featureless ball of cells, has started to differentiate into the body's three basic cell types (known as endoderm, mesoderm and ectoderm).
Professor Azim Surani, of the University of Cambridge, said the research should allow scientists to create a large range of human stem cell types, which could prove invaluable in studying disease.
To achieve that, the engineers will have to include multiple cell types and devise a system that allows the lab-built creature to sense its environment and use an internal "decision-making circuit" to pick different behaviors.
Embryonic stem cells are advantageous in research because they can be grown more easily than adult stem cells in a culture, and are pluripotent, meaning they can develop into any of the various cell types of the body, according to the National Institutes of Health.
Dr Lorenz Studer, head of the Stem Cell and Tumor Biology Laboratory at the centre, and the lead researcher on the study, told BBC News Online that the study was "proof of principle" that cloned embryonic stem cells could be reliably transformed into a variety of useful cell types.
In the absence of information about the mechanism by which these tumors form (and as I have mentioned before there is no possibility of determining this in rats or humans because of the inaccuracy of the definition of the histology of the cell types) we clarify the safety margin in rats relative to humans.
Nerve-cell precursors can turn into two types of brain cell besides nerve cells.
ECONOMIST: Brain development may be influenced by genetic parasites
Changing the quantities of proteins such as the one made by PSD-93 would probably change the nature of the affected cell quite radically, and might even be responsible for generating the different types of nerve cell that are known to exist.
ECONOMIST: Brain development may be influenced by genetic parasites
Certainly, the brain has many more different types of cell in it than any other organ.
ECONOMIST: Brain development may be influenced by genetic parasites
Some C4 plants, for example, absorb CO2 and photosynthesise it at either end of special elongated cells, instead of separating the functions out into two different types of cell.
Professor Robin Franklin, a regeneration biologist at the Wellcome Trust-MRC Stem Cell Institute and report co-author, said: 'Our findings are extremely exciting because they show for the first time that transplanting these types of cell into a severely damaged spinal cord can bring about significant improvement.
Leading types of distraction include using cell phones, eating and texting -- the last being the most dangerous of all types according to the Centers for Disease Control and Prevention.
ENGADGET: Editorial: Self-driving cars FTW, but not for everybody
The researchers are now trying to develop probes which will only stick to specific types of cancer cell.
But the parts list says those regions contain, or are close to, a particular kind of genetic switch turned on and off in various types of immune cell.
应用推荐