Barylypa unieuttata (Grav., 1829)

After scientists remove an inner cell mass (ICM) from a blasto-cyst (usually one left over from an attempt at in vitro fertiliza-tion), the cells are placed on a plate with feeder cells. Scientists have found that cells from mouse skin work particularly well for this. A totipotent stem cell comes from a fertilized egg and can develop into any type of cell in the human body. A pluripotent stem cell is slightly more limited. The ability to divide and pro-duce more cells is key. If all goes well in the process, then in a few days new cells grow and form colonies. These cells are deter-mined to be embryonic stem cells only if they display certain

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molecular markers agreed upon by scientists and go through sev-eral generations of cell divisions.

Stem cells in an adult are present in lesser numbers than they are in embryos, though bone marrow in all people is filled with stem cells. The role of adult stem cells (also called somatic stem cells) is generally believed to be in repair of damaged and injured tissue. As early as the 1960s, Till and McCulloch developed a cell-cloning technique that permitted bone marrow transplants for dis-eases like leukemia and other blood disorders.

Stem cells have a very specific hierarchy that depicts how they can be used. The top level, the totipotent cell, has the potential to become any type of cell. The other cells do not have quite the breadth of possibilities as do the totipotent cells.

Many scientists feel that embryonic stem cells are a better source for further medical research and application, as these cells have not yet become specialized in any way. (Parents today are now encouraged to have stem cells from their newborn’s umbili-cal cord frozen for possible use later for to-be-discovered mediumbili-cal cures.) There is particular hope that stem cells will be helpful in managing degenerative illnesses such as Parkinson’s disease.

Neurological diseases like this are so complex that drugs, or even gene therapy, often prove to be inadequate. Stem cells offer hope.

Only 22 stem cell lines have been available for federally funded research in the United States, and during George W.

Bush’s administration it was mandated that the National Insti-tutes of Health (NIH) should not support work on lines created after August 2001. (Once created a stem cell line can be kept going perpetually through freezing and storage.) One of Presi-dent Barack Obama’s early actions in 2009 has been to loosen these restrictions, though scientists had already begun to create new ways to make stem cell lines.

Because of the Bush administration rulings, scientists had been looking for alternative ways to gain stem cells. In 2005, scientists at Harvard succeeded in turning ordinary skin cells into what appear to be embryonic stem cells—without having to use human eggs or make new human embryos. This was a big step forward in gaining access to stem cells without having to work with embryos, which stir up such controversy. A possible benefit of the technique is that the cells come directly from the patient, so the DNA in the new stem cells is an exact match. This could enhance the chances of a person’s body more readily accepting whatever it is the stem cells need to be used to replace.

Embryonic stem cells must be directed to specialize before they are used. In experiments with mice, scientists saw that direct introduction of embryonic stem cells can cause cancer. If stem cells were to be used to produce insulin for diabetics, for example, it would be vital that the stem cells had been fully converted and that there were absolutely no stem cells remaining before they

were introduced into a patient. Scientists are just learning what variables and nutrients are necessary to accurately guide stem cells so that they become stable nerve or muscle cells.

Scientists are experimenting with how to cultivate stem cells in order to learn more about biology and how the stem cells may eventually be used to improve human health.

In addition to the controversy over stem cells (discussed in the following section), there are still many obstacles to using stem cells. Scientists need to develop better and more reliable ways to obtain embryonic stem cells, and they need to learn to control the way they differentiate. Most countries are struggling similarly to the United States with the ethical issues surrounding stem cells, reproductive cloning, and therapeutic cloning. (See the sidebar

“How a Cloned Sheep Could Help Medicine” on page 78.) In the United States, there has been some activity in various states to permit the research before the federal government did. California was one of the first states to break with the Bush sentiment on stem cell research.

Though no one yet understands exactly how the stem cells can be put to work, the following are some of the ways it is anticipated that stem cells might be used:

to further studies of genetics

to shed light on inherited diseases, particularly degenera-tive ones

to correct genetics in children. For example, if a child has poor immune response to certain stimuli, this may be corrected by working on a specific gene.

to create cell-based therapies to study biological processes drug discovery and development to repair spinal cord injury

Amazingly, stem cells have already been featured in scams.

Patrons of Russian beauty parlors have been told that stem cell injections can be given to them, and promises are made of a long list of ills the process can cure.