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.

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.

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.

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.

Running and Breathing

On a recent NOVA podcast (09/03/2010 "Chasing Down Dinner"), David Levin talked about the way animals breath.

A quadruped mammal is four legged.  Cows, zebras, and dogs are examples.  In these animals, their stride is synchronized with their breathing.  A stride is one full cycle of leg movement while walking or running..  For instance, in a human, a stride is two steps.  When running, a quadruped's breathing is aided by the movement of the muscles and skeleton.

Here is a picture of a contraption put together by a physiology professor to teach how this happens.  "A" shows the animal moving the front legs forward during running.  The lungs expand at the same time and the animal inhales.  "B" shows the back legs coming forward and the animal would then exhale.  The ratio of stride to breath in a quadruped is 1:1.  One stride, one breath.  When the stride is lengthened, the volume of air into the lungs is increased.

As humans, our natural inclination is to also breath in synchrony to our stride.  But because we are upright and on two feet (bipedal) the ratio is different and can be more flexible.  The normal ratio is 2:1. Two strides to one breath.  A slow run can change that ratio to 4:1.

Humans, as a whole, are better adapted to endurance rather than speed.  Dennis M. Bramble, a biomechanist and vertebrate biologist at the University of Utah in Salt Lake City, and Daniel E. Lieberman, a biomechanist and anthropologist at Harvard University, have been studying the history of running in human beings.  They have come to the conclusion that our ancestors had an advantage with this ability to run long distances.  The animals they were chasing could not sustain a long distance.  Quadrupeds cannot pant when galloping, so their bodies would overheat and they would have to stop and try to cool off.  Meanwhile, the humans would continue in the chase and catch up.  The animals would then run again and soon were too overheated to run any longer, making it relatively easy to catch dinner.

Now you have heard something interesting.

http://advan.physiology.org/content/33/4/315.full
http://findarticles.com/p/articles/mi_m1134/is_3_114/ai_n13664996/

And Eye(tooth) for an Eye

Sharron "Kay" Thornton is a sixty-one-year-old woman who lives in Mississippi.  Ten years ago she lost her eyesight due to a rare skin disease, called Stevens-Johnson syndrome, that attacked her eyes, damaged her cornea (the clear window at the front of the eye), and left her blind.  She was not eligible for a cornea or an artificial cornea transplant.  Doctors tried a stem cell treatment, but it was unsuccessful.

Last year, she went to see Dr. Victor L. Perez of the Bascom Palmer Eye Institute at the University of Miami's Miller School of Medicine.  He decided to try a procedure that was developed in Italy but had never been done in the United States.  It is called modified osteo-odento-keratoprosthesis.

They took out one of her eye teeth, also called canine teeth, and part of the bone above that tooth.  They shaved it down to the proper shape and size and punched a hole in the middle, where an acrylic lens was inserted.  This was implanted into her shoulder for 3 months while they waited for the bone and the lens to fuse. 

The scars from around her cornea were removed and moist cheek tissue was used to cover the eye to rehabilitate it.  When the time was right, the tooth/bone/lens piece was removed from her shoulder and implanted in her eye.  It was carefully aligned with her retina. The bone keeps it from moving out of place. The cheek tissue is still on the eye, but has a hole where the lens pokes out.  She cannot close her eye fully, and the cheek tissue helps to keep it moist.

Here is a graphic from the Bascom Palmer Eye Institute that shows what was done.  When the bandages were removed, she had 20/70 vision!  They expect it will get better with time.

The procedure has been performed on 600 people around the world.  Very ingenious.  It seems to work best for people who have been blinded by chemical burns, thermal burns, rare reactions to drugs, and other cases where normal corneal transplants would not work.



There is another video of a man in the UK who was blind for 26 years.  You can go to youtube to watch it.

http://www.youtube.com/watch?v=L4vE7QlbVak  (7:28 min long)

Now you have heard something interesting.

The Paths of Legends

This past week I finished the book That's Not in My American History Book by Thomas Ayres. It was very interesting and had many stories -- some that were familiar and some that were new to me.  Here is one I didn't know.

Andrew Jackson, the seventh President of the United States, was the first president to have an assassination attempt on his life. It happened on January 30th, 1835. President Jackson had just attended a congressional funeral held in the House Chamber of the Capitol. As he exited, Richard Lawrence, an unemployed house painter, pointed a pistol at Jackson and fired.  The percussion cap exploded, but the bullet did not discharge.

Jackson moved toward Lawrence and started beating him with his cane. During the ensuing scuffle, Lawrence took another pistol out of his pocket and pulled the trigger. But that gun also misfired. Bystanders joined in, wrestling Lawrence to the ground and disarming him. One of them was Rep. Davy Crockett of Tennessee. (For those of you over a certain age, now is the time to start singing, "Davy, Davy Crockett. King of the wild frontier!")

About a hundred years later the Smithsonian Institute examined both of these guns and couldn't find anything wrong that would have made them misfire.

Richard Lawrence was mentally ill. He believed that he was Richard III, rightful heir to the throne of England and that President Jackson was keeping him from it.

The case went to trial. The prosecuting attorney wanted Lawrence to get the death penalty because, he said, any attack on the president of the United States is an attack on the United States. The defense attorney used the reasoning, for the first time in a court of law, that the prisoner should be found not guilty for the reason of insanity.

The jury deliberated for a very short time.  They bought the argument of the defense attorney.  Richard Lawrence spent the rest of his life in mental institutions.  

The prosecuting attorney was very disappointed.  He was the man whom you know as the author of The Star Spangled Banner, written twenty-one years earlier. It was Francis Scott Key.

Now you have heard something interesting.