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Posts Tagged ‘Theme: Medical Science’

Post by Vijayalakshmi Kalyanaraman

Cancer takes almost 7.9 million lives around the world every year, 1500 per day in the US alone. Even when treatment is successful, it is likely to be exhausting and painful. However, cancer is also one of the most studied diseases in medical history. One less well-known treatment is photodynamic therapy.

Photodynamic therapy (PDT) combines a light-sensitive chemical compound (a photosensitizer) with light exposure to kill cancer cells. The treatment works like this: The photosensitizer is either injected into the bloodstream via a vein or is applied to the skin, as needed to reach the cancer cells. The compound is absorbed, but stays in cancer cells longer than normal cells. After a few hours or days, these areas are treated with a light of the wavelength that the compound is sensitive to. With this exposure, the photosensitizer produces singlet oxygen that kills nearby cancer cells. PDT can be less painful and grueling than chemotherapy or surgery.

PDT has a few limitations that need to be overcome. The light used to activate the photosensitizer cannot penetrate more than 1 centimeter of tissue, so only areas just below the skin and the linings of inner organs or cavities can be treated this way. However, recently researchers have identified a way to tackle this difficulty using scintillation nanoparticles with attached photosensitizers. The nanoparticles would emit light when they are exposed to x-rays, and the emitted light would then be used by the photosensitizer to produce the active oxygen that kills cancer cells. This would take advantage of x-rays’ deep penetration to affect cancer cells anywhere in the body.  Dr. Wei Chen at the University of Texas, Arlington, published the first research on this technique in 2006.

Of course, the addition of scintillation nanoparticles has led to new challenges. For practical applications, the nanoparticles must be water soluble and at the same time emit the required level of light (high quantum efficiency) when exposed to x-rays. The higher the quantum efficiency, the higher would be the efficiency of the treatment.  Several research groups around the world are now working to develop this technique for practical use.

Nanoparticle–porphyrin conjugates to be used for X-ray stimulated photodynamic therapy. Annexin V is a molecule that can target specific markers found only on tumor cells. Adapted from Wei Chen’s article published in Nanowerk.

PDT can cure or treat cancers and precancers. It is less expensive and invasive than surgical or chemotherapy procedures. Only a fraction of the radiation exposure is required and it is often done as an outpatient treatment. Patients treated with PDT experience relative few side effects. However, they do need to avoid light just after treatment, or photosensitizer still present in healthy tissue will cause rashes and burns.

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Post by Ruthanna Gordon

I fell in love with the brain my second year in college.  Specifically, with the cerebellum.  There, the delicate, tree-like neuronal networks become visible at the macro level.  You can see the way ideas are born out of connection, can imagine the traceries of electricity leaping from node to node just before someone shouts, “Eureka!”  The brain is a metaphor made flesh.  So really, it was poetry that brought me to science.

The brain might not, at first glance, seem like an ideal inspiration for art.  In person, it’s gray and a bit slimy.  At an event designed to draw more students into the sciences, I helped a crowd of high school girls dissect cow brains.  They had 45 minutes to find the hippocampus.  Cattle are not known for their impressive memories—the whole brain was half the size of your fist, the target area a little smaller than your thumbnail.  The ridges and valleys that mark human intelligence were notably absent.  One girl would not touch the thing even with gloves on, only prod it gingerly with her scalpel.  “You’ve got to hold onto it,” I explained.  “Otherwise, it might go like—” and I gestured to indicate the probable trajectory of the disaster.  Holding a slippery internal organ.  I don’t know whether I’m the only psychologist who’s ever thrown a brain at a prospective student, but I don’t recommend it as a recruitment method.

Though the brain may have some difficulty making first impressions, many people do seem to have noticed its beauty.  Anatomical illustrators often get caught up by the intricacies of its structure.  Neural scans and stains may double as art.  And, often, they inspire art.  Some is simply mimetic: a quilt based on an MRI, or a full crocheted brain—anatomically accurate except for the colors!  Other artists are captured by the same metaphorical possibilities that originally inspired me.  The brain may be like the swirling grain of a maple tree, or an ocean wave.  It may be shaped by its contents.  It may be a force for creation.

And then, some people just really like the cerebellum.

Neuropsychology has begun the long process of finding the self in the brain.  Love and awe and inspiration can be seen in their glory, lighting up those branching networks and sending electrochemical surges through the forest of neurons.  But it’s hard for many people to feel comfortable with the connection.  Art can help bridge the philosophical gap.  When we can see the beauty and complexity of the brain itself, it becomes easier to imagine that it could produce such beautiful, complex experiences.

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Post by Minna Krejci

Let’s take a short journey through our senses.  Take a look at the image below:

Some of the green cell nuclei in this taste bud contain the KATP sugar sensor, indicated in red. One of several sugar sensors recently shown to be present in sweet-sensing taste cells, KATP may help regulate sensitivity to sweet taste under different nutritional conditions. (Photo by Karen Yee, courtesy of the Monell Chemical Senses Center)

Within this mad swirl of color lie important clues as to how we taste “sweetness.”

It’s long been known that a taste receptor called T1r2+T1r3 is largely responsible for the detection of sweet compounds by our taste buds.  This receptor is sensitive to sugars like glucose and sucrose, as well as artificial sweeteners such as saccharin and aspartame.  However, evidence has also shown that mice that are missing the T1r3 part of the receptor still respond to certain sugars, particularly glucose.

To find the missing piece of the puzzle, a research team at the Monell Chemical Senses Center in Philadelphia cleverly thought to look to other organs in the body that sense glucose, such as the intestine and the pancreas.  (For more information, see their paper published in the Proceedings of the National Academy of Sciences last week).

As it turns out, sugar sensors in these other organs are also present in our sweet-sensing taste buds, in the same cells that contain the T1r2+T1r3 receptor.  These taste sensors seem to have various roles in detecting sugars.  Have you ever noticed that sweets taste sweeter in the presence of salt?  (I did have the pleasure of trying some salted caramels from Fran’s Chocolates in Seattle a few months ago and they were quite delicious…)  This effect may be at least partially a result of a glucose sensor called SGLT1 (originally found in the intestine), which transports glucose into the cell when sodium is present.

Another sugar sensor, called KATP, monitors glucose levels in the pancreas and triggers insulin responses.  Also found in sweet-sensing taste cells, this protein may have a role in modulating the sweet-sensitivity of the cells depending on the local environment (i.e., if you just ate something sweet) or overall blood glucose levels.

“The taste system continues to amaze me at how smart it is and how it serves to integrate taste sensation with digestive processes,” says senior author on the paper Robert F. Margolskee.

So what does all this mean?  One thing we can take away is that it’s not as easy to trick our body with artificial sweeteners as we may have thought.  The authors suggest that combining artificial sweeteners with a small amount of sugar may lead to enhanced sweet perception compared with artificial sweeteners or sugar alone.  Also, the relationship between taste and digestive processes may provide clues as to why we crave sweets under certain conditions – hopefully, that knowledge could be used to help prevent overconsumption of these kinds of foods.

It seems like scientists are working hard to solve the mysteries of why we often crave unhealthy foods, and how to combat the health problems that often result, such as obesity and type 2 diabetes.  In reading about the sweet sensors, I also happened to come across an article from about a year ago that reported that in addition to the five previously known tastes that we can detect (sweet, salt, sour, bitter, and umami), we also have a sixth “fat” taste.  Apparently, some people are more sensitive to this taste than others, and long-term consumption of fatty foods may lead to decreased sensitivity.  It’s a vicious cycle where those with a history of high fat intake may be more at risk for overeating these kinds of foods.

There’s obviously much more to our sense of taste than that “tongue map” we learned in school (which apparently isn’t correct anyway).

Can someone just find a way to make broccoli taste like jellybeans?  I’d be the healthiest and happiest girl in the world.  Until then, as White House pastry chef William Yosses puts it, “we are hard-wired to like things that are bad for us.”  Oh well, I guess I’d better work on my self-control…

Here are a few other interesting stories out there regarding some of our other senses – I know there’s more, so please share!

How the brain “sees” words: http://www.nytimes.com/2011/02/22/science/22obbrain.html

Eye pigments that also sense temperature: http://www.sciencenews.org/view/generic/id/70998/title/Light-sensor_pulls_perplexing_double_duty

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Post by Justin Breaux

In the future, medical technologies will be seamlessly integrated with our bodies.  Not unlike the recent movie Repo Men, we will be able to have these implanted and increase our mobility and ability.   Though, hopefully no one will be coming to re-collect your new cybernetic heart.

But what types of technologies are available now, that can help us lead richer lives if we’re missing a limb or encountering a body part that’s not working the way it’s supposed to?

Here are just a few examples of our cybernetic future.  Watch, and imagine.

Prosthetic Arms:

Robot-Assisted Walkers:

Minimally Invasive Surgery Robots (you’ll never think about grapes the same way):

Power Knees:

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