Stem Cells, Part 2 – How are they obtained?

Adult Stem Cells

The term “adult stem cells” is somewhat misleading. Adult stem cells do not come exclusively from adults. Human adult stem cells are obtained from a developed person, whether he is a senior citizen, an adult, an adolescent, a child, or even a fetus. Perhaps they should be called “somatic stem cells” because they can be obtained from body tissue. Adult stem cells are cells that have not yet developed into specialized tissue, but are capable of doing so, and are also capable of reproducing themselves indefinitely.

Adult stem cells can be obtained from many places in the body. The most familiar source, because it was the first to be used to treat illness in real persons is from the bone marrow.
Adult stem cells are unspecialized cells that are present in small quantities in already specialized tissue. They are needed by the body because both illness and age destroy tissue cells, and the stem cells can regenerate that damage. Adult stem cells also allow for growth.

Adult stem cells can be used for therapy to treat conditions that involve cell degeneration or even abnormalities. Once again, the flagship example is bone marrow stem cells. A treatment for leukemia, a cancer of the blood, involves taking bone marrow from the patient or a blood relative, extracting the stem cells, treating the extracted material by growing it in a nutritive solution, using drugs or radiation to destroy the patient’s abnormal bone marrow, then reintroducing the extracted material into the patient, where it develops into normally functioning bone marrow. This has been done regularly for more than three decades, and is a well established medical practice.

Researchers have reported finding adult stem cells in bone marrow, muscle tissue, liver tissue, fat, nasal mucus tissue, blood and blood vessels, brain tissue, and skin. Adult stem cells are also richly present in umbilical cord and placenta (“afterbirth”). A thorough summary of the state of research on adult stem cells as of 2003 is located here.

Embryonic Stem Cells

As you will recall from part 1 of this series, what are called embryonic stem cells are really the type of stem cells that are termed “pluripotent”; they are capable of developing into any of the more than 200 types of cells in the human body. This stage of development only exists in nature between conception and a few days later, when the fertilized egg has started to divide, but before the specialization process starts.

There are currently only two ways to obtain embryonic stem cells; the first and most common way is to extract them from a pre-embryo (“blastocyst”), and the other by a process called nuclear transfer, commonly referred to as “therapeutic cloning”.

The only practical source of blastocysts that can be used by scientists is the ones created by them in the laboratory. This process is frequently called “artificial conception” or “in-vitro fertilization”, and is aimed primarily towards assisting women who for one reason or another are unable to conceive in the normal way.

The process involves extracting a large number of eggs from the ovary of a volunteer, combining these ova with the sperm of a volunteer in laboratory conditions, testing the results to determine whether a successful fertilization has occurred, and if so, implanting the fertilized ovum in the uterus of a volunteer. Ideally, the sperm and egg donors are the father and mother, but not always. A woman undergoing this procedure may be unable to ovulate and will need another woman’s ova, or she may ovulate normally but be unable to carry the child, and a surrogate mother will provide the uterus.

This is a very “hit-or-miss” process with a low yield of successfully fertilized eggs. Consequently, because of the difficulty and expense involved, a large number of eggs are extracted and processed in this manner. This leads to a situation where sometimes extra fertilized eggs become available briefly. That is the source of the existing embryonic stem cells that are currently available to the researcher.

The other process, called nuclear transfer, starts with a human ovum also. In the laboratory, the researcher cuts into the ovum, removes the nucleus (the part that carries all the genetic material) and replaces it with the nucleus of an adult cell. If this hybrid cell is nurtured properly, it will develop into a new blastocyst that contains only the genetic information of the person who donated the adult tissue cell from which the nucleus was obtained. Such an individual then will be a clone, with DNA that is identical to the nucleus donor.

In common terminology, this is sometimes called “therapeutic cloning”, but this is also a misnomer. Nothing in the way of therapy can be done with this clone currently (although the research for which it was created may some day do so), so it more precisely should be called “cloning for research”.

A good description of how embryonic stem cells are made can be found here. And this article describes what is involved in Somatic Cell Nuclear Transfer (SCNT).

Next: Stem Cells, Part 3 - How are they handled in research?

Stem Cells, Part 1 - What are they?

One of the most promising areas of medical research is the use of human stem cells. Stem cells are specific undeveloped cells in the human body that can be induced to develop into one or more of the specialized cells of mature human tissue. Stem cells can develop into blood cells, brain cells, kidney cells, or any of the other types of cells that make up our bodies.

This post starts a series of articles that will delve into the science of stem cells; what they are, how they are formed and develop, their present and potential future medical uses, and the controversy surrounding them. Since this is a medical subject, it would be easy for confusing jargon and jaw-breaking terminology to creep in. At the risk of oversimplification in some cases, this article will avoid the Latinate words as much as possible and will use commonly understood terms wherever possible.

To understand stem cells and why they can be so important, it will first be necessary to describe the normal development of a human being from conception to birth.

How a Baby is Formed

Conception occurs as a result of sexual intercourse. The man contributes sperm cells and the woman contributes an ovum, a human egg cell. Both types of cells, sperm and ovum, are incomplete, each having only 23 of the 46 chromosomes required, but they combine into a single complete cell known as a zygote (fertilized ovum). This occurrence is referred to as conception.

At this point, the zygote is a complete entity, capable of developing into a baby, as long as the conditions are right, and as long as a few more key milestones occur as nature designed. The zygote starts to divide inside its outer surface, once every 12 to 20 hours as it passes down the fallopian tube towards the uterus. At any time during the first 14 days, the zygote may separate into two separate zygotes; this is how twins are formed.

By day three, when the zygote consists of a cluster of 16 cells, it has entered a new phase of development that goes beyond simple division. This cluster, which we shall call a pre-embryo, starts to resemble a hollow sphere. By about day five, the pre-embryo has entered the uterus.

It is at this point that the identical cells of the pre-embryo start to differentiate into specialized cells. The outward-facing cells attach to the lining of the uterus and form the placenta, and the inward-facing cells start to form the embryo. By day ten the pre-embryo is firmly attached, and blood circulation begins in the placenta. Medically, this is considered the start of pregnancy.

The process of differentiation leads to the cells in the pre-embryo (textbook name: blastocyst) to organize into three distinct layers, referred to as the germ layers. The term “germ layer” is not related to infection; it comes from the same root as “wheat germ” or “germinate”. Each germ layer is a region of the hollow sphere. Each layer starts to develop specialized cells of specific types. The outer layer will develop into skin cells and brain cells. The middle layer develops into blood cells, muscle cells, and kidney cells. The inner layer becomes lung cells and the cells of various organs. And just to make it confusing, a fourth type of primitive cell is the germ cells, which become sperm in a male or ova in a female.

These four types of cells are referred to as stem cells. The analogy of development is with a plant, where the stem leads to branches, the branches to twigs, and the twigs to leaves, flowers, and all the other glorious plant parts. Stem cells branch into the four types described above, and these in turn develop into more specialized types of cells, eventually leading to more than two hundred different types of cells in the human body.

At about two weeks after conception, the pre-embryo starts to develop a linear pattern of cells known as the primitive streak. It is at this point that it is no longer possible to separate into twins, and it is at this point that the organism is referred to as an embryo. The primitive streak will eventually develop into the central nervous system.

For the next eight weeks the embryo enters a period of rapid development, with the undifferentiated cells forming into organs, limbs, and other bodily structures. At ten weeks, all the recognizable features are present; arms, legs, head and eyes. At this point, it becomes a fetus.

The fetus, which at ten weeks is less than two inches long and weighs less than an ounce, spends the next six months growing in size and complexity inside the mother. At birth, the average child is about 20 inches long and weighs about seven and a half pounds.

The human body, besides being equipped with over two hundred different types of specialized cells, also continues to grow stem cells throughout the body. These stem cells proliferate throughout a lifetime, and eventually develop into one of the two hundred types of cells. This allows the body to grow and to repair damage.

Embryonic and Adult Stem Cells

A stem cell is a cell that can continue to divide and proliferate for an entire lifetime, and develop into specialized cells. Stem cells are categorized in two ways; by their origin, and by their potential to develop a certain way.

All the cells in the pre-embryo are called “pluripotent”; that is, they have the power to develop into any of the germ layer cells, and to further differentiate into more specialized types of cells.

As they start to specialize, they organize into groups by capability. For example, outer layer stem cells can become a number of different types of cells, but they will not become others; that job falls to the middle layer or inner layer types of cells. This restriction leads to the category “multipotent”. As development continues, further specialization occurs, to the point where a stem cell can be considered “unipotent”, that is, only capable of developing into a single type of cell.

A fully developed human, baby to senior citizen, will have throughout his body a collection of different kinds of stem cells, which are usually multi- or unipotent. These cells are referred to as “adult stem cells”. We all have them.

The stem cells in the pre-embryo and embryo are the newest and most potent, capable of differentiating into all types of specialized cells. They can, however, only be obtained by removing them from embryos. Consequently, these are referred to as “embryonic stem cells”.

Next: Stem Cells, Part 2 - How are they obtained?

Names That Fit

I have always been amused by the game of inventing names for people that define the person's occupation. At the end of each program of "Car Talk" on PBS radio, Tom and Ray Magliozzi read a long list of credits for made-up staff members. I have prepared my own list. Feel free to comment with your own creations.

Masseuse	Ophelia Thye
Yoga instructor	Ben Dover
Proctologist	Seymour Butz
Counterfeiter	Bill Passer
Carnival operator	Ferris Wheale
Human resources manager	Bennie Fitz
Pilot	Alana R. Plaine
Urologist	I. P. Daly
Mountain climber	Craig Mounter
Soft drink manufacturer	Aaron D. Waters
Explorer	Ben Dare
Gynecologist	Pat McGroyne
Burlesque dancer	Fannie Mae Jiggle
High-stakes gambler	Betsy Normis
Holdup artist	Robin Banks
Politician	Jerry Mander
Optometrist	I. Kinsey Clearly
Accountant	Carrie D. Balance
Diner waitress	Anita Koffey-Black
Traffic cop	Terry Knott
Tailor	Ken Eumenides
Macrame artist	Matt Weaver
Football cheerleader	Victor E. Dantz
Sporting goods salesman	Dennis Racket
Justice of the peace	Mary N. Haste
Retired senior citizen	Randy O'Gote
Fast food worker	U. Wanda Burger
Project manager	Roy L. Payne-Diaz

Support the Troops is Not a Ribbon

I am amused and somewhat offended by all the people who drive around with these colored ribbon stickers on the back of their vehicles. Pink ribbons are for breast cancer awareness. I am aware of breast cancer and how pervasive and devastating it can be, and It wasn't any ribbon that made me aware. It was the fact that my niece got it before she was thirty, and one of my co-workers lost his wife to it at age 35. But the ribbon that annoys me most is the "support our troops" yellow ribbon.

Putting a ribbon on your car does nothing to support our troops. It may give you a feeling of pride, but what the troops need is real support. Letters from home, gift packages from home, sending them magazines and books to read, helping their families get along without them; that is supporting the troops.

Here is how you can help the troops:

1. Support the USO and send a Care package to a soldier.

2. Adopt a soldier pen pal.

3. Correspond with a soldier and send what he needs.

4. Donate to the American Legion Family Support Network.

5. Donate to Fisher House and provide a place for family members of wounded soldiers to stay near where they are being treated.

6. Help build and modify homes for severely handicapped veterans.

7. Donate blood for the wounded.

8, Provide phone cards to serving and wounded military so they can keep in touch with their families.

9. Ship books, DVDs and supplies to deployed and hospitalized soldiers.

10. Provide a satellite phone for a platoon in Iraq.

11. Donate your frequent flyer miles for use by soldiers on leave and their family members.

12. Help dependents of deployed military buy groceries at the commissary


And while you are at it, how about providing some additional support for the children of Iraq:

1. Operation GIVE. Toys and other items for Iraqi children.

2. School supplies for Iraqi children.

3. More help for Iraqi children.

Instead of wasting five bucks on a bumper sticker or car magnet, enriching an entrepreneur, send that same five bucks or more to one of the truly helpful organizations.

What's in a Name?

Communication in general and political discourse in particular are deteriorating rapidly because of terminology. The use of words that conceal rather than reveal is growing geometrically in this politically correct age.

A leading example is in the area of discussions about government policy concerning abortion. The anti-abortion faction that believes that abortion is simply murder of an unborn child does not want to appear to be negative, so they are not "anti-abortion"; they are "pro-life". Who could be opposed to life? The implication is that any who oppose them have no regard for life.

In perfect symmetry, the pro-abortion crowd, who want no restrictions on a woman's option to kill her fetus before it is born, do not refer to themselves as "pro-abortion"; they are "pro-choice". They avoid the implication that death is involved, and characterize the decision to abort a child as just another female choice, similar to hair color or breast augmentation. Anyone who opposes their viewpoint opposes "a woman's right to choose".

The damage this causes is subtle, but fatal to any reasonable discourse. It starkly polarizes an issue that is affected by myriad subtle factors, and about which a reasonable discussion would be appropriate. "I am right and you are a murderer". "No, I am right and you hate and want to subjugate women".

There are plenty of other examples:

Insurgent - Calling a fanatic who entices children to strap on explosives and go to a public place to murder as many people as possible an insurgent minimizes the horror and insanity involved. Insurgent, because of its etymological roots, connotes a popular uprising, a replacement of the existing order by new leadership surging in and replacing the old guard. Fidel Castro and Benigno Aquino were insurgents. Calling murderous fanatics insurgents leads to the illogical position that menacing prisoners with dogs and making them wear women's underwear are somehow more reprehensible than the murder of civilians and beheading of prisoners that got the fanatics detained.

Liberal, Progressive, Conservative, Neocon - It used to be that liberal and conservative were fairly concise labels that summarized the general political outlook of a person. A conservative had a working assumption that government exists as a referee to arbitrate when citizens come into conflict, there was nothing wrong with the status quo, and that any changes proposed by government should be examined skeptically and adopted reluctantly, to conserve what is good. A liberal saw problems in society, assumed any change would be an improvement, and looked at government as the solver of problems. Over time, "liberal" became connected in the mind of the public with being liberal with other people's money. Liberal became a negative descriptor, so liberals took to calling themselves "progressives", implying their opponents are against progress. Since "liberal" had become a pejorative and "conservative" had not, liberals soon took to using the term "neoconservative" or "neocon" to label their opponents. Neocon carries overtones of knee-jerk reactionism, probably because of its similarity to neolithic.

When we stop using these code words, perhaps we will be able to regard our opponents as merely persons with a differing opinion, instead of evil incarnate. If we avoid the euphemisms, maybe we can discuss our differences while respecting our opponents, and the nasty and abusive tone in politics can be toned down to a discussion of differences and a compromise that both sides can live with.

Well written doesn't mean right

An email from my sister called my attention to a personal attack on President Bush by one of the best authors currently writing today, E. L. Doctorow.


As always, his piece is well written, because he is one of the best writers at work in the US today. But I see no description in his biography of any training as a psychologist or psychiatrist, much less as a medium. How can this man produce such an intimate psychological portrait of a man he has never met? I believe what you see in this article is more revealing of Mr. Doctorow's psychology than of George Bush's.

Just a few points. Mr. Doctorow says that World War II was a war of national survival, but the war against terrorists is not. I find that logic hard to follow. Eisenhower was the Supreme Allied Commander in Europe. The attack on the US came from Japan, which I am led to believe is not in Europe. We included Germany as an enemy, not because they attacked us, but because a) they allied themselves with our enemies; b) they had a policy of extermination towards anyone within their control that they found to be racially or morally deficient by their standards; c) they were ruled by an amoral dictator who intended to control all neighboring territory; and d) they were actively engaged in scientific development of weapons of mass destruction (it is no coincidence that a large fraction of the Project Manhattan scientists were refugees from the Third Reich). These are almost exactly the same reasons for making Saddam Hussein our enemy. No one can ask Eisenhower whether he would have led the war to liberate Iraq like he did in the war to liberate Europe, but I firmly believe he would. After all, he was a professional soldier and senior military officer who swore an oath to "preserve, protect, and defend the Constitution of the United States against all enemies". That Constitution specifies that the President is the Commander-in-Chief of the military forces, and that Congress declares war against our enemies. Whether you like it or not, that is the way the war in Iraq was decided.

The idea that we should use war as an instrument of policy only when there is no other option may sound reasonable, but it is not; it is no different than saying we should never wage war. There are always other options, but in many circumstances the other options pose more of a risk. We could have continued to pay ransom and tribute to the Barbary Pirates in the nineteenth century, but President Jefferson decided it was in the best interest of the United States to destroy them. We could have tolerated British ships stopping American ships at sea and impressing Americans into the Royal Navy, but once again, President Jefferson found that to be more of a risk to our nation than to declare war on the most powerful nation on earth at that time. The criteria that Mr. Bush elucidated are the same as all 43 of his predecessors; that war should be the last choice when all other options have failed.

There are other illogicalities in this essay, too. Mr. Doctorow at one point claims that "millions of people here and around the world marched against the war". He has sanctified and exaggerated a staged political event into a groundswell of anti-war sentiment that never existed and still does not. Pacifist activists getting their act together for a few days is not any kind of indication of public opinion. Foreign policy and national security are not decided by polls or inflammatory writing or political demonstrations or foreign opinion. They are determined by the elected officials who are answerable to the voters at the next election. The Democrats who voted to authorize the war changed their position as a political strategy. That strategy failed when Mr. Bush was re-elected by a larger margin than before.