Stem cells in the gut of Drosophila divide in response to food. Photo courtesy of John Tann

Researchers investigated how stem cells in the gut of the fruit fly respond when different amounts of food are present. They found that when food is abundant, stem cells in the gut divide more rapidly, increasing the size of the gut as long as food continues to be available. When food is removed, the cells stop dividing and the gut shrinks down again.

“The real surprise was that the fruit fly intestine is capable of secreting its own insulin,” said principle investigator David Bilder in a press release. “This intestinal insulin spikes immediately after feeding and talks directly to stem cells, so the intestine controls its own adaptation.”

Insulin is also the primary signaling molecule for converting blood sugar into usable energy in muscles, and storing it as fat.

What the current findings mean for human physiology or chronic overeating is still unknown, but it raises many new questions regarding the role of intestinal stem cells and metabolism.

Identical twins are more similar to one another than a clone
will be to the person cloned.

Of course, these cells aren't any less controversial than they were eight years ago. Researchers will still need to destroy embryos to get these cells (at least until they perfect iPS cells which would make this part of the debate moot). Anyone who considers an embryo made up of a few hundred cells to be alive will protest that embryo's destruction.

This is a legitimate argument based on when someone believes life begins. But some protests I heard were from people worried about embryonic stem cells being used to clone humans. What I can't figure out is why anyone would want to clone someone.

Cloning won't be like it is in the movies. Scientists won't take a cell from someone and make an exact copy of a person who is the same age and has the same memory.

Instead, a human will be cloned like any other mammal. First they'll remove the DNA-containing nucleus from an egg. Then they'll fuse that egg with a cell from the person they want to clone.

This "fertilized egg" will then have to grow and develop in a surrogate mother, be born, and then have to grow up. The clone won't have any of the original's memories.

In essence, a clone would be more like an identical twin who has been reared apart from his or her twin. Even though identical twins reared apart have a lot of similarities, they have a lot of differences, too. One article I saw put the amount of behavior/personality similarity due to genes at something around 50%.

And a clone will probably be more different than that. When the cell's nucleus is put into the egg, scientists erase a lot of the markings on the DNA that originally turned it into an adult cell. This "fertilized egg" is now a blank cell which can be shaped by both its genes AND its environment.

Identical twins develop in the same womb at the same time and so are exposed to the same sorts of environmental effects. A clone would not be. And these environmental factors can affect how we develop. They can even alter DNA and as a result, alter who we become.

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