The Endeavour

Bill’s comment on my previous post reminded me of a book I read a few years ago, Aging With Grace by David Snowdon. The author describes what he learned about aging and especially about Alzheimer’s disease by studying a community of nuns. (Nuns make ideal subjects for epidemiological studies. They have very similar lifestyles, and so a number of confounding variables are reduced. Also, nuns keep excellent records.) The book is a pleasant mixture of science and human interest stories.

Snowdon says in his book that it is nearly impossible to accurately diagnose the extent of Alzheimer’s disease in a patient without an autopsy. Some nuns in the study who were believed to have advanced Alzheimer’s disease in fact did not. Others who were mentally sharp until they died were discovered on autopsy to have suffered extensive damage from the disease. (Snowdon tells the story of one nun in particular who was believed to be senile but who was actually quite witty. She was hard of hearing and reluctant to talk. Few people had the patience to carry on a conversation with her, but Snowdon drew her out.)

Nuns who had greater vocabulary and verbal skill earlier in their lives (as measured by essays the nuns wrote upon entering their order) and those who remained mentally active (for example, those who were teachers) fared better as they aged. They may have had more redundant mental pathways so that as Alzheimer’s disease knocked out pathways at random, enough pathways survived to allow these women to communicate well.

Today’s Big Ideas podcast carried a lecture by Norman Doidge on neuroplasticity, the recently-discovered ability of the brain to rewire itself. Doidge relates several amazing stories of people who have recovered from severe strokes or other brain injuries by developing detours around the damaged areas. Hearing of people who have had the persistence to re-learn how to use an arm or leg inspires me to not give up so easily when I face comparatively trivial challenges.

Doidge gives several explanations for why it has taken so long to discover neuroplasticity. Until very recently, scientific orthodoxy has held that neuroplasticity is impossible. Patients were told they’d never be able, for example, to use their left arm again. This became a self-fulfilling prognosis as most patients would not work to do that they were told would be impossible. But what about patients who ignored medical advice and were able to recover lost functionality? Why did that not persuade scientists that neuroplasticity was possible? The patient’s recovery was interpreted as evidence that the brain damage must not have been as extensive as initially believed, since the alternative was known to be impossible.

Chemotherapy harms cancer cells as well as normal cells. Chemotherapy is designed to be more harmful to cancer cells than to normal cells, but the damage to normal cells can be brutal.

New studies suggest that fasting prior to receiving chemotherapy may reduce the number of normal cells harmed by the treatment. Fasting may put normal cells in a defensive mode that increases their resistance to chemical attack.

The American Journal of Physics has an article in the June issue about the physics of dropping Mentos into Diet Coke. The spectacular result depends on physical characteristics of the Mentos, not their chemical composition. Here’s an explanation from the 60-Second Science podcast.

Researchers recently discovered that identical twins are not genetically identical after all. They differ in the copy numbers of their genes. They have the same genes, but each may have different numbers of copies of certain genes.

Source: “Copy That” by Charles Q. Choi, Scientific American, May 2008.

Greg Wilson pointed out an article in The Chronicle of Higher Education about scientists using Photoshop to manipulate the graphs of their results. The article has this to say about The Journal of Cell Biology.

So far the journal’s editors have identified 250 papers with questionable figures. Out of those, 25 were rejected because the editors determined the alterations affected the data’s interpretation.

This immediately raises suspicions of fraud which is, of course. However, I’m more concerned about carelessness than fraud. As Goethe once said,

…misunderstandings and neglect create more confusion in this world than trickery and malice. At any rate, the last two are certainly much less frequent. 

Even if researchers had innocent motivations for manipulating their graphs, they’ve made it impossible for someone else to reproduce their results and have cast doubts on their integrity.

The duck-billed platypus is the most recent species to have its genome sequenced. These odd animals are even more strange at the DNA level. Some features of their DNA are avian, some are reptilian, and of course some are mammalian. See the Science Daily article for more details.

Yesterday’s Science at NASA podcast had an entertaining story about duct tape and Apollo 17. (Transcript, audio)

The lunar rover lost a fender and they taped it back on with duct tape. That worked for a while, then they had to make a new fender with laminated maps and duct tape.

Why is a fender such a big deal? Without a fender, the astronauts would get dirty. So why is that a big deal?

1. Dirt is dark, and dark absorbs sun light. A dirty astronaut may become a fried astronaut.
2. Dirt scratches visors, making it hard to see.
3. Dirt gets in parts like hinges and breaks them.

According to a Science Magazine story, it looks like humans have been in North America one thousand years longer than previously believed. New DNA evidence suggests people were in North America by 12,000 B.C. The study also suggests that the first Native Americans may have arrived via the Pacific Coast rather than migrating across the land bridge that once connected Asia and North America.

Read the article or listed to the podcast.

According to the latest Scientific American podcast, there is no scientific evidence to back up the common belief that everyone should drink eight glasses of water per day. Nor is there scientific evidence to back up many of the claimed benefits of increased water consumption: improved skin, better regulated appetite, etc.

However, the podcast equates “no scientific evidence” with “not true.” The title of the podcast is The Mythical Daily Water Requirement. “Mythical” means “false.” (There are more nuanced uses of the word “myth,” but I don’t think they are relevant here.)

It has been known for some time that the eight-glass-a-day recommendation is not well substantiated by experiments. That’s not to say increased water consumption isn’t beneficial. After all, there have not been any randomized trials to prove that parachutes improve your chances of survival when jumping from an airplane either.

Randomized trials are not the only way to learn about the world, and are not as effective as commonly believed. Most published research findings are false. Randomized trials are a tool for exploring reality, sometimes the best tool for a particular task, but not the only tool.

It’s plausible that drinking eight glasses of water per day is beneficial, or at least harmless, based on anecdotal evidence. Certainly drinking too little water is fatal (though there have been no randomized trials to confirm this!) and so it is reasonable to presume there is some curve showing increased benefit with increased water intake, up to a point. The curve would go back down at some point, as it is possible to drink too much water. It would be interesting to see randomized studies to explore where the curve flattens out, exploring consumption levels safely between the harmful extremes.

It is widely assumed that parachute use improves your chances of surviving a leap from an airplane. However, a meta analysis suggests this practice is not adequately supported by controlled experiments. See the article Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomized controlled trials by Gordon C S Smith and Jill P Pell. The authors summarize their conclusions in the abstract.

As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.

In 1601, an English sea captain did a controlled experiment to test whether lemon juice could prevent scurvy.  He had four ships, three control and one experimental.  The experimental group got three teaspoons of lemon juice a day while the control group received none. No one in the experimental group developed scurvy while 110 out of 278 in the control group died of scurvy. Nevertheless, citrus juice was not fully adopted to prevent scurvy until 1865.

Overwhelming evidence of superiority is not sufficient to drive innovation.

Source: Diffusion of Innovations

The March 6 Nature podcast has a story about the Large Hadron Collider. The LHC is expected to gather 15 petabytes (15,000,000 gigabytes) of data. One of the people interviewed said that 15 petabytes of data would require a stack of DVDs the height of Mount Blanc.

You probabily have someone else’s cells growing inside you.

In a phenomena known as microchimerism, mothers pass some of their cells onto their children, and vice versa, during pregnancy. That’s not too surprising in itself. What is more surprising is that these cells can reproduce for decades. It’s not uncommon to find female cells in a grown man, or male cells in a woman who gave birth to a son. 

See “Your Cells Are My Cells” in Scientific American, February 2008.

The 60-Second Science podcast from February 27, 2008 tells of plans for NASA and MIT to build a giant radio telescope on the dark side of the moon. (The “dark” side is really the “far” side, the side that always faces away from Earth. It gets just as much sunlight as the side we’re familiar with.) This side of the moon is shielded from radio noise from Earth, and so a radio telescope there could detect radio signals further back in time than is possible here. The plan is to use robots to assemble radio antennas over two square kilometers.