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Sunday, January 30, 2011

Of Migraines and Blind Spots

As an occasional sufferer of migraines, my ears perked up when Chris Smith, host of the podcast "The Naked Scientist," started talking about the pain effect bright lights have on a person with a migraine.  The word is photophobia. It is not a fear of light, but a description of eye discomfort in bright light.

There are blind people who have photophobia when they have a migraine. This intrigued some scientists at Beth Israel Deaconess Medical Center.  They conducted a study and found that the only blind people who could experience photophobia were those who could tell night from day.

At the back of the eyeball is the optic nerve, sometimes called the blind spot, which carries information from the eye to the brain.  This information about light is carried to the brain and causes electrical stimulation there. When there is already pain and disturbance in the brain from a migraine, this extra electrical stimulation increases the pain.

Those whose blindness involves damage to the optic nerve not only cannot distinguish light and dark, but have a hard time regulating their nights and days.  Light sets our circadian rhythm - telling our body it is time to sleep or wake.

Maybe you have taken a "blind spot test" before.  Here is one you can perform at night outside. Look at the moon.  Gently cover your left eye and continue to look at the moon with your right eye.  Slowly move your gaze to the left.  You might have to adjust your gaze up or down slightly. Soon you will not see the moon anymore, but just the halo around it.

Each of our eyes has a blind spot, but in each eye it is off center enough that the loss is compensated for by the other eye.  Our brains do a good job in filling in the details and we don't really notice what we are missing.

If you would like to read more about the study, you can find it here.

Now you've heard something interesting.

Wednesday, January 12, 2011

What do cats, deer, and wolf spiders have in common?

One of the many podcasts that I listen to on a regular basis is called BrainStuff.  It is well written by Marshall Brain and only lasts 4 or 5 minutes.  There is one episode from October 2010 that really interested me. 

Marshall took a head lamp outside one night.  It was around his head and he turned it on and started looking around the yard.  There was a pile of dirt and it seemed to be sparkling.  Many, many points of light.  He could not figure out what it was.  So he got closer and found that it was many, many wolf spiders.  The light from his headlamp was reflected in their eyes.
It turns out that wolf spiders have the same thing that deer, cats, dogs, and raccoons have in their eyes.  It is called tapetum, a shiny layer behind the retina. Light passes into their eye, hits the retina, reflects from the tapetum and hits the retina again.  This makes things look much brighter, making it easier to hunt at night.  It also makes their eyes seem to glow when light hits it.

The light shining from the head lamp reflected off the spider's eyes and returned again to its source.  If Marshall had been holding a flashlight down by his waist, he would not have seen this reflection. 

(Hmmm.  This is a little like the last post, where light bounces off a corner cube reflector on the moon.)

Have you ever wondered whether a spider is poisonous?  The answer is no. So far as I know, there are no poisonous spiders. There are venomous spiders. Venomous means that the creature's bite or sting is toxic. Poisonous means that it is toxic if you eat it. 

Now you have heard something interesting.

Sunday, January 9, 2011

Mirror, Mirror on the Moon

When Neil Armstrong and Buzz Aldrin walked on the moon more than 40 years ago, I was just a youngster and don't remember it at all.  Most assuredly my mom explained to me the historical event that was happening, but it just didn't stick in my memory banks.  I just learned something about that trip that I had never known before.

Just about an hour before the end of that famous Apollo 11 mission on July 21, 1969, these two astronauts put down a 2-foot wide panel of 100 mirrors. 
 It is called the Apollo 11 lunar laser ranging retroreflector array.
 "Here's how it works: A laser pulse shoots out of a telescope on Earth, crosses the Earth-moon divide, and hits the array. Because the mirrors are 'corner-cube reflectors,' they send the pulse straight back where it came from. 'It's like hitting a ball into the corner of a squash court,' explains Carroll Alley, the projects principal investigator during the Apollo years.  Back on Earth, telescopes intercept the returning pulse--'usually just a single photon,' he marvels."
If you arrange 3 mirrors in a shape like the corner of a rectangular box, with the reflectors on the inside, then any light which hits the reflectors, at essentially any angle, will bounce off each mirror and end up heading back exactly the direction from which it came. This makes such a mirror arrangement very useful, because you always get a nice strong reflection.

Here is another image that shows two different paths of light.  Even though the source is from two different places, the beam is returned to the source of the laser.

Scientists still use these mirrors on the moon.  They have learned some interesting things.  First, that the moon is spiraling away from the Earth at a rate of 3.8 cm per year.  The NASA web site says the ocean tides are responsible.  As the moon orbits Earth, it creates a bulge of water that travels round the planet behind it. This bulge - which we experience as tides - exerts a gravitational pull on the moon, slowing it down as it circles Earth at a distance of 240,000 miles. As a consequence of being held back by this pull, the orbit of the moon becomes altered and it moves slowly away from Earth

Second, it is now believed that the moon has a liquid core.  They have also learned that the universal force of gravity is very stable.

There are a total of five of these mirror arrays.  Apollo 11, 14, and 15 missions each placed one, as well as two Soviet Lunokhod landers.  They don't work as well as they used to work.  Dust has accumulated on them and sometimes light doesn't come back, and when it does it is much fainter.  The mirrors are losing their ability to reflect back laser light precisely, which hinders accurate measurements.

Now you have heard something interesting.

Sunday, January 2, 2011

What rhymes with beige? Why, bacteriophage of course!

Bacteriophages are small viruses that infect bacteria and kill them by multiplying and essentially filling the bacterial cell to bursting.  Here is a small animation of the life cycle of one bacteriophage.  The word lytic means that the cell is destroyed by the process.  After the phages reproduce inside the bacteria cell, they burst out and the cell is demolished.  Adsorption is the gathering together of the phage on the surface of the cell.

The bacteriophage has attachment sites on it that correspond with receptor sites on the bacteria.  In other words, they don't attack just any cell, only specific cells.  So a bacteriophage that is meant to destroy e. coli (these are called T4 bacteriophage) will only attach to an e. coli cell and then multiply, destroying the e. coli cell.

These viruses are much smaller than the bacteria that they destroy. Each time a phage invades a bacteria cell, it produces between 50 and 200 new phage viruses within the bacteria cell.  Once the host bacteria are destroyed and are no longer present, the phages die off, too.

Phages are found all over the planet.  Anywhere that bacteria live and thrive phages will be found.  They are especially abundant in water.

Phages have been known since ancient times.  There have been documented reports of river waters having the ability to cure infectious diseases, such as leprosy. In 1896, Ernest Hanbury Hankin reported that something in the waters of the Ganges and Yamuna rivers in India had marked antibacterial action against cholera and could pass through a very fine porcelain filter.

They have been used for over 60 years as an alternative to antibiotics in the former Soviet Union and Eastern Europe.  They are seen as a possible therapy against multi-drug resistant strains of many bacteria. 

Phages were discovered to be anti-bacterial agents but the medical trials performed in western countries in the early 1900's were poorly conducted and the scientists really didn't understand what a phage was.  Many of the trials were conducted on totally unrelated diseases such as allergies or viral infections.  So phage therapy was ruled as untrustworthy.  Soon antibiotics were discovered and widely used.  They are popular because they can treat a wide range of diseases and are easy to manufacture and then store. 

Development of phage therapy was largely abandoned in the West, but continued throughout the 1940s in the former Soviet Union. It was used for treating bacterial infections throughout the country, including the soldiers in the Red Army.  The literature was published in Russian or Georgian and so it was not available for many years in the United States.  It is still used in the country of Georgia and other Eastern European countries.

In August, 2006 the United States FDA approved using bacteriophages on cheese to kill the Listeria monocytogenes bacteria.  In July 2007, the same bacteriophages were approved for use on all food products.

Government agencies in the West have for several years been looking to Georgia and the Former Soviet Union for help with exploiting phages for counteracting bioweapons and toxins, such as anthrax and botulism.  There are many developments with this among research groups in the US.

There seem to be many advantages of developing bacteriophages for use in many fields, including clinically.  But there are a few downsides, also.  One is getting the phage to the bacteria.  If used orally, some might not pass the stomach acid without being destroyed.  If used as a cream or as an injection, it still needs to get to where it is going without the body's immune system seeing it as a foreign threat.

A more non-scientific downside to the use of phage therapy is that due to intellectual property laws and the fact that currently its use is public, so the technique of phage therapy would not be patentable. The development of drugs is very expensive and larger pharmaceutical companies have no motivation to go through the complicated and costly process if there is no patent protection on the products they may create.

Now you have heard something interesting.