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An ‘Amazing Race’ of the Senses April 29, 2011

Posted by abueno526 in Biology, Fun, Physiology.
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The last team to check in may be eliminated…

The Amazing Race is a reality tv show in which pairs of contestants race around the world in a challenge of wits, strengths, and abilities to try to ultimately come in first place and win the coveted million dollar prize and of course, bragging rights.  Throughout its 18 seasons in the United States, contestants have been put through a wide array of challenges, including participating in an acrobatic act, carrying furniture and grains across the city, and identifying a correct tune being played in a sea of pianos.

Tea anyone?

In a specific episode this season, the contestants were required to drink a cup of papaya mango tea in a small shop in China. Later on that day, they had to pick out that same flavor of tea from a table of hundreds and hundreds of different cups of tea by recognizing the smell and taste. Although a daunting task, all of the teams successfully completed the challenge by identifying the tea.  But, with so many scents and flavors on the table, how were they able to identify the correct cup?

Olfaction – Odorants

All things considered, humans have the ability to recognize and distinguish 7,000 to 10,000 different smells.  But how is this possible?  The first thing to consider is the human capability to detect odorants, which are typically small organic molecules with some amount of volatility so they can be carried in a vapor from to the nose.  These small odorant molecules are actually detected by their shape, not from any other physical properties that they exhibit.  This means that the different smells come from the way the molecule interacts with the binding site it is associated with.  A common example to better explain this idea can be seen in the molecule carvone (depicted left), which has distinct R and S configurations.  Although the two are mirror images of one another, the R conformation has a scent of spearmint, while the S configuration of caraway, indicating their difference in binding.

Olfaction – Odorant Receptors

Scents are detected in the main olfactory epithelium  of the nose, and are are identified by one of the million sensory neurons that dwell there, which all contain cilia with receptors.  Although we are able to recognize upward of 7,000 distinct scents, humans only have 350 odorant receptors  As seen in the picture to the right,molecules bind to the receptors that are on the cilia, nerve impulses are generated from the binding and travel through the neurons, and finally move to the olfactory bulb.  Throughout this process (binding to olfactory bulb response), cAMP and GTP levels in the body increase, meaning that the process uses 7TM receptors.  These compounds are released in a cascade process, depicted to the left.  When the odorant binds to the receptor, a G protein is activated and binds to

GTP.  This complex then moves to activate an adenylate cyclase, which increases cAMP levels.  High cAMP levels activate and open ion channels, which creates an action potential and allows the smell of an odor to come through.

Olfaction – Scent Recognition

But with only 350 distinct receptors, how are we able to detect thousands of smells?  The answer lies in the fact that most smells are composed of several odorant receptors, which can be activated at different levels of odorant.  In other words, there is not a one to one relationship for odorant to receptor, but instead odorants can activate multiple receptors and receptors can be activated by multiple odorants.  As an example, the odorant C6COOH activates six different receptors, while C5OH, C6OH, and C7OH all activate the same receptor.

Olfaction gone awry 

Sometimes, we are unable to detect some scents, called a specific anosmia.  although everything seems to be functioning normally, certain compounds are not detected by these individuals, indicating that it it a genetic inheritance of a mutation.  Although over 80 have been identified, some examples of molecules that are unable to be smelled include isobutyric acid, which is responsible for the  smell of sweat, and n-Butyl mercaptan, the smell that skunks give off.

Gustation – An Overview

The tongue has the ability to recognize 5 major tastes in the mouth: bitter, sweet, salty,sour, and umami (savory).  A diagram of where these individual taste buds are located can be found to the right, excluding the umami taste.  “Umami” is a word derived from the Japanese language, and includes the tastes of glutamate and aspartate.  Much less is known about this taste than the others because this “savory” flavor has only been distinguished from the others within

the past five to seven years.  Receptors for tastants are more commonly referred to as taste buds, which are made up of about 150 cells.  Microvilli on the surface of the tongue bind to tastants and send an impulse through the sensory neurons to the brain to identify the specific taste.  The tastes use different methods to detect the taste, all of which are outlined below.

Gustation – Salty and Sour

Salty and sour tastes opperate in a similar manner in the fact that they both utilize ion channel interactions.  In the case of salty flavors, this is done through sodium ion and their corresponding amiloride sensitive Na+ channels.  Sodium ions pass through the channels on the front of the tongue creating a current, amiloride attempts to block this current, and a salty flavor can be tasted.  Similarly, the sour taste acts through a hydrogen ion channel .  Hydrogen ions flow through the pores on the sides of the tongue, and a sour taste is observed.

Gustation – Sweet and Bitter 

Unlike the salty and sour tastes, both the sweet and bitter receptors utilize a 7TM receptor complex, as mentioned above in the olfaction discussion.  Because of this, they respond to a larger range of stimulants.  Sweet receptors typically respond to glucose, sucrose, aspartame, saccharine, and even some proteins.  While being researched, scientists discovered that these compounds interact with the T1R1, T1R2, and T1R3 receptors in different combinations with one another.  They all pick of variations of sweetness, with the T1R2 and T1R3 receptor being the most sensitive to the sugary taste and the T1R1 receptor by itself being the least sensitive to the taste.  The bitter receptor acts in a similar manner, however, its receptors respond to toxic alkaloids.  TR2 receptors are responsible for this taste, which is typically recognized at the back of the tongue.  In this regard, it should be noted that taste receptors are much less selective than the scent receptors due to sheer number (350 vs. 5).  For example, in the case of the bitter taste, we usually recognize just bitter in general and are unable to distinguish one bitter compound from another.

Gustation – Umami 

The final taste is umami, which is recognized as the savory flavoring and utilizes 7TM receptors as well.  These receptors respond to glutamete, aspartate, and even MSG.  It is similar to the sweet receptor in the fact that it utilizes the T1R3 receptor, but it is also paired with the T1R1 receptor.  Unlike the sweet receptor that may utilize different combinations of the receptor, the savory flavor can only be obtained with activation of both the T1R3 and T1R1 receptors simultaneously.

A Complimentary Combination 

So, through a combination of the senses, contestants were able to identify the correct cup of tea.  Using the odorant receptors to bind to the scent molecules and the specific taste buds on the tongue to identify the tastes, it is possible to identify a particular item in a sea of many.  As a tip for the contestants for next time, they may want to rely on their nose more than taste due to the high specificity of the olfaction system!

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Crazy for “Catnip” March 14, 2011

Posted by mhostetler099 in Behavior, Biology, Chemistry, Fun, Health, Uncategorized.
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“Catnip,” a feline favorite, is a perennial herb in the mint family

Nepeta cataria, more commonly known as “Catnip” is a perennial herb that belongs to the mint family.  This herb packs a powerful punch to cats by provoking a state of euphoria usually lasting several minutes (video).   Many times herbs are utilized for medicinal purposes , but “catnip” obviously doesn’t affect human beings in the same way that it does cats.  What is it about “catnip” that provokes a euphoric response in cats but not in human beings?

The chemical component responsible for the effects of catnip

Studies suggests that the chemical nepetalactone found in “catnip” is primarily responsible for triggering the response in cats.  Nepetalactone evokes a psychosexual response in both male and female cats by mimicking a sex pheromone found in cat urine.

Bugs aren’t so crazy for “catnip”

The chemical nepetalactone may attract felines, but does quite the opposite to some insects.  Researchers at Iowa State University found that the chemical nepetalactone is a successful repellent of mosquitoes, flies, and cockroaches.  Particularly, the research team at Iowa State found that a solution of catnip extract is comparable in effectiveness to a ten times more concentrated solution of DEET.  Research in finding alternatives to repellents or pesticides, such as DEET, is very important because chemicals contained in most pesticides pose a serious threat to human health and the environment.  Unfortunately, the essential oils in “catnip” are extremely volatile and have a potent, but short lived repelling effect.  Further research in reducing its volatility is essential before such repellents can be used by the general public.

Catnip’s properties are multifunctional

Interestingly, researchers at the Max-Planck Society found that birds that used different types herbal plants in their nests produced offspring that were less prone to infestation of mites.  This study indicates that other herbs may have the same insect-repelling power as “catnip” and that organisms other than humans are using this characteristic to their benefit.


In the future, the active ingredient, nepetalactone, may be found in the bottle of repellent you spray on yourself or the pesticide you sprinkle on your plants.  You can be sure that the product you are using is much safer than the products of old, but if you have cats you must beware!  Such products will still provoke the same euphoric response caused by “catnip” sold in pet stores.


Penguins, endangered? May 3, 2010

Posted by Kyle in Behavior, Biology, Climate Change, Ecology, Environment/Conservation, Evolution, Fun.
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"I believe I can fly!"

Cape penguins (Spheniscus demersusare) are an endangered species of penguins off the coast of South Africa. Between 2001 and 2009 there was a 60% decline in population numbers of Cape penguins. Researchers believe that the decline in Cape penguins is partly due to the lack of food as a result of overfishing.  Without food, the penguins obviously can’t survive.  A study done by researchers in South Africa has shown that by managing commercial fishing, they may be able to restore population numbers in penguins.

After doing a little more research, I discovered an easier solution to the problem. The penguins could just fly away (similar to polar bears rapidly evolving), and using a strategy similar to what was done in the movie Fly Away Home, the penguins could be saved. While it may seem slightly unrealistic, just watch the video below and all doubt will be removed. It seems that penguins learning to fly isn’t that crazy of an idea. (The video is obviously not real, and I am not serious.)

Avatar offers more than just a great story line and cool special effects May 3, 2010

Posted by Jill in Fun, Science & Culture.
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Cameron now working with NASA

Although Avatar provided a great turnout for the Marian University Science Club showing of the Earth Day outdoor movie, it appears that the film might have scientific benefits as well. Because of the 3-D camcorders used in the

blockbuster, James Cameron’s Avatar, NASA is partnering with James Cameron to help build 3-D cameras for the next Mars rover, appropriately named Curiosity. Attempts to build such a type of camera were abandoned in 2007 due to the mere cost of production of such a camera. Cameron petitioned to NASA to help build the 3-D cameras for the new rover even though all four cameras, called Mastcams, for the rover have been built.

The last two cameras built will be replaced by the new 3-D camera if construction and testing can be finished in time for final rover testing happening in the early portion of next year. The 3-D zoom Mastcams that NASA plans on building with Cameron’s state-of-the-art equipment will be used to capture better, more detailed images than previously able to capture with the original Mastcams. Another benefit of these cameras is that the rover will be able to shoot 3-D cinematic video while on Mars.

Avatar

The rover was originally set to launch in 2009, but due to funding restraints, the launch was postponed until further funding could be gathered. The mission of Curiosity is to determine if life had existed on Mars and also to prep for an eventual manned mission to land on Mars. Critics, like Steven Hawking, warn about the potential dangers associated with contacting or attempting to find life outside of Earth for many reasons including the problems encountered in the film, Avatar, including the fact that invading or even potentially contacting another life form could “be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.” As Uncle Ben says to Peter Parker in Spiderman, “with great power comes great responsibility.” Hawking, as well as others, admonishes researchers to be weary when contacting or exploring life outside of our planet because it is impossible to know what encounters we will find and how other life forms could potentially react to non-natives.

The full news article can be found at NASA: James Cameron to develop 3-D camera for Mars rover.

The PCR song April 29, 2010

Posted by Dr. O in Biology, Fun, Genetics, Science & Culture, Science Education.
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To build on the post containing the rap song on photosynthesis, I thought I’d add this little music video montage put out by Bio-Rad. It’s hilarious.  See…scientists DO have a sense of humor.

Here is the original Bio-Rad link.

Bacteriophages have been found to have new uses–making car fuel! April 29, 2010

Posted by Jill in Biology, Chemistry, Environment/Conservation, Fun, Genetics, Science & Culture.
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hydrogen-fueled car

For those molecular geneticists out there, you will appreciate the new discovery of using a genetically modified M13 phage as a source for making hydrogen fuel out of water!

The M13 bacteriophage is often used in molecular genetics work as a cloning vector. The phage contains a single strand circular DNA genome of 6407 nucleotides that is released into a host cell as a result of the phage absorption. When used in a host cell, the, the host cell proteins will form the double-strand replicative form (RF). This new circular RF DNA is required for M13 packaging because the viral proteins are synthesized from mRNA transcribed off the strand of the RF molecule. From here, M13 DNA is packaged at the host cell membrane, and then releases the infectious particles.

Researchers have found a way to harness the M13 virus in such a way to break apart water molecules, producing hydrogen fuel. Researchers have been able to genetically modify the M13 virus, normally infecting bacteria, so that it would instead bind to a catalyst called iridium oxide and a biological pigment, zinc porphyrins. The viruses then will naturally arrange themselves into a wirelike structure while the catalyst and pigments will harvest sunlight to divide the oxygen from the water molecule. The virus works in this mechanism in that the pigment acts as an “antenna” to collect the sunlight and transfer the energy down to the virus, emulating photosynthesis.

Researchers have successfully been able to separate the oxygen from the water molecule, which is the hardest part of the water-splitting process. The hydrogen will then split into its parts (electrons and protons), but researchers are still attempting to harvest the hydrogen parts in order to collect the gas separately and then convert the gas eventually into hydrogen fuel.

The benefits to this are numerous, including finding a green way of obtaining hydrogen fuel without creating carbon emissions as well as making the process self-sustaining. The ability to harness the mechanisms of photosynthesis in order to control the electron transport in a system is one of the biggest problems in creating a system for artificial synthesis, but this approach allows the transfer of electrons to be controlled.

The full article can be found here: GM viruses offer hope of future where energy is unlimited

I have also included an entertaining rap dealing with photosynthesis: Photosynthesis Rap

And before you’re a skeptic and are thinking that no one would make up a rap about photosynthesis, I found another rap about ATP synthesis: ATP Synthesis Rap

Potential assignment for the new Ecological Physiology class April 27, 2010

Posted by Dr. O in Behavior, Biology, Fun, Neuroscience, Physiology, Science Education.
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MU Science Students as possible Guest Bloggers?

What do you think?  Perhaps my students should star as “guest writers” to this blog , the Animal Review, who’s blog owners “grade” animals based on their wacky adaptations.  Seems a perfect way to celebrate the diversity of physiology in the animal world.  I might just use this as an assignment for Physiological Ecology-BIO 305 in the Spring of 2012

Who needs a brain? (this coming from a neuroscientist…)

After checking out the Animal Review, I for one would have given the jellyfish a “B” and the comb jellies (Ctenophora) an “A+” for living in a “society” and incorporating “tool use” with out a true brain.

The beautiful comb jelly

I would also give the angler fish a solid B+ or A-.  The ladies are okay in their own skin and definitely wear the pants in the relationship.  After all… males are basically no better than parasites.

Let science explain how close the Butler:Duke game was April 8, 2010

Posted by Dr. O in Exercise, Fun, Physics, Science & Culture, Science Education, Uncategorized.
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In case you haven’t heard…America’s current darling (and Marian’s neighboring campus), Butler University, made a major run in this year’s NCAA Basketball Tournament.  This small Midwest liberal arts school spends $370,000 on their basketball team.   Butler’s competitor in the final, Duke, spends $370,000 PER PLAYER!

Butler lost by two points.  Gordon Hayward, who also happens to be a science major at Butler, almost won the game with a long shot at half court.  How close was it? Let science explain…

Butler University student Gordon Hayward is a science major

Poetry and Science. Science and Poetry March 31, 2010

Posted by Dr. O in Fun, Science & Culture.
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Check out these remixes: The Symphony of Science.