The barn owl (Tyto alba) has been said to be one of the most successful nocturnal predatory birds that exist in our world today.  As adults, barn owls rarely miss their target prey.  They owe this to their finely tuned auditory system.  Owls combine excellent hearing with visual tracking to perfectly locate prey and maximize their chances of successful capture (http://www.allaboutbirds.org).  Their auditory tracking system functions based on several key features of barn owl morphology.  The first is that barn owls possess asymmetrically shaped ears.  This means that the owl’s left ear points downward and the right ear points upward.  A sound that appears louder in amplitude on the right side of the owl is interpreted as being higher in elevation than a sound that appears louder in amplitude on the left side of the owl.  This helps the owl discern moving target’s elevations.  The second key feature is the owl’s facial disk.  Barn owls are known for having a heart shaped face.  This facial disk acts like the pinna on humans and helps the owl to amplify sounds. (Koppl et al. 2007)  The last key feature is the owl’s ability to detect timing differences in sounds.  The owl’s midbrain can process the differences in arrival times of a sound between one ear and the other.  The owl can then use this information to help them direct their head towards the prey item. (Spitzer et al. 2006)

Section 1:  The owl as a newborn and its development.

In order to get a complete picture of how barn owls’ amazing auditory mapping works, we will first look at barn owls when they are newborns.  Koppl et al. 2007 were interested in investigating the length of time in which the owls hair cell activity, referred to as cochlear microphonics (CM) and the owl’s neuronal response to sound measured from the auditory nerves via compound action potentials (CAP) first showed up in the barn owl’s inner ear post hatching.  They performed the experiment by immobilizing and measuring auditory activity in 26 owlets aged from 5-96 days. Due to the owlets’ face functioning as a pinna, an audio device was inserted directly into their ear canal so as to remove the variable of the sound stimuli amplitude  being altered by the owl’s facial disk.  Then the owl’s round window was exposed by removing the inner ears round window membrane and using various equipment and software, measurements were taken of the electrical activity found when the bird’s ear was exposed to various sound frequencies.

What they found was that unlike other birds, owlets are essentially deaf to most normal, natural intensity sounds during the first two weeks post hatching.   Subsequent to the first two weeks, CM activity gradually improved until the five week period at which point their CM activity was at normal levels.  This meant that they had the ability to hear in the normal ranges up to 10 kHz.  A surprising thing to note was that the data suggested that CM always matured slightly faster than the CAP activity within normal ranges of frequency.  This was directly confirmed using 12 juvenile barn owls with measurements taken consistently at weekly time intervals.  This faster rate of CM maturation indicated that there was a sequence of maturation from low to high frequencies as the owls got older. This experiment was important to science because it helped to understand how auditory mechanisms work.

Section 2: The owl’s behaviors once it’s older

With some basic knowledge of how owls develop in terms of the arrival of their abilities as auditory locators, we can now look more into how Tyto alba hunts as an adult. Fux et al. 2009 were interested in looking at the nature of the visual tracking that has been observed in barn owls specifically whether or not barn owls were interceptor type predators, which tend to look towards where the collision attack will occur, or if they were tracking type predators following their prey as they moved.  The owls were exposed to live voles in captivity and recordings were taken on the owls head movements relative to the movements of the voles themselves.  What was found was that barn owls track their prey horizontally in azimuth using head movements.  This effectively moves their stationary prey into a new location in their retina thus helping them to create a more accurate representation of the position of the prey relative to themselves.  Once the prey is spotted, the owl tracks its head over a large area in order to continue to assess the spatial location and to help with calculating the interception point should the prey start to suddenly move. (Fux et. al. 2009)

Once the owl has spotted its prey it will take off and fly towards it in order to attack it.  Hausmann et al. 2008 looked at the owl’s ability to adapt its flight/attack pathway in mid flight to compensate for moving prey.  The researchers placed barn owls into a sound attenuation chamber in complete darkness and using speakers, played an initial tone for the owls that would mimic the relative position in both elevation and azimuth of a potential prey item.  Once the owls took off to attack the item, the sound was replayed at particular delay intervals suggesting to the owls a change in location of the prey.  The landing positions of the owls relative to the timing of the delay were then plotted.  What researchers found was that if a stimulus was applied before 50 percent of the flight time was over, the owls could correctly adjust their path towards the new stimulus.  However, if 80 percent or more of the flight path had been completed, owls no longer adjusted and continued on their original path regardless of the adjusted location of the prey.  Also noted was that regardless if the owls had to change direction mid-flight or not they tended to just slightly undershoot their target, allowing them to still be successful at attacking their prey while also placing them in the most suitable position to re-launch an attack should their prey move in an unpredicted manner. (Hausmann et al. 2008)

Barn owls have evolved to become deadly efficient hunters, armed with traits like asymmetric ears, and wings that allow them to swoop down on prey in silence. (http://www.allaboutbirds.org)  Researchers looked at the success of barn owls in catching prey and the steps that were taken immediately prior to prey capture.  They then noted and discussed various prey responses and the various benefits and disadvantages that arose between the types of responses of predator evasion.  Three evasion categories were identified, freezing, fleeing, and fighting (defensive attacking). (Ilany et al. 2008).

To measure the success rates of the owls in prey capture and the success rates of the mice in evading the barn owl, researchers looked at actual interactions between the spiny mice and the barn owl.  It was found that the owls were most successful at capturing stationary prey.  They determined that spiny mice have adapted to flee at a particular timing when the owls are approaching in their final moments.  The direction that is best suitable for fleeing is to run sideways to the direction the owl is traveling when the owl is approximately 2 meters away from its target (Ilany et al. 2008).  This strategy works best for the spiny mice, which are nimble and fast runners; however other prey might have different strategies for avoiding the owls. By understanding how the prey react to the owl attacks, researchers can better understand what makes the owl a successful predator and how its auditory system copes with these counter reactions.

Section 3: How does the barn owl do this amazing hunting?

One question that has always fueled barn owl research is how owls are able to hear their prey so well. Therefore much of Tyto alba research therefore deals with the barn owls ears and how their auditory abilities tie in neurologically with their brains and inner ears.  Koppl et al. 2007 were interested at looking at the relationship between the barn owls hair cell activity measured via cochlear microphonics (CM) and the owls’ auditory neuronal activity as measured by compound action potentials (CAP).  They performed several experiments in which owls were immobilized and their round windows membranes removed in order to expose their inner ears.  They then took measurements using an electrode placed on the round window area of the inner ear and an audio implant in the middle ear canal to generate various tones.  Activity was measured at various frequencies. Based on the waveforms they observed, researchers deduced that the CMs of the owl remained relatively constant in terms of reactivity from the lowest frequency inputs measured up to the 10 kHz range.  However the CAP was typically defined by a sharp negative peak, which occurred rapidly after they stimulated the ear.  They also found that the largest of the measured CAP amplitudes were observed when sound stimuli between 6-7 kHz were played.  This increase in CAP activity corresponded to the distribution of the number of afferent nerve fibers coming from the regions of the owl’s papilla that would correspond to 6-7kHz stimulation. (Koppl et. Al 2007)

Barn owls are known for being able to hear up to the 10 kHz range so this was odd in that the findings implied it required more neuronal activity and/or higher decibels for the owl’s ear to process and respond to 10kHz ranges then was required for the owls ear to respond to other frequencies.  They postulated that this might have been overcome by the use of single neuronal units being recruited. They performed control experiments to support their findings by dabbing the round window with a chemical (S-AMPA) that destroyed the afferent nerve fibers. When measurements were taken, only the CM responded to stimulus. (Koppl et. Al 2007) This helped future researchers to understand how cochlear microphonics plays a role in barn owls’ hearing.

One amazing ability that barn owls have is the ability to discern specific sounds even in sound cluttered environments.  Humans also have this ability.  This has been dubbed the cocktail effect.  Spitzer et al. 2006 looked at the owl’s ability to discern two separate sounds when played close together.  Owls were placed in a sound attenuated chamber and played a fixed frequency sounds via a sound system over particular intervals. The first sound played would be designated the leading event.  While the leading event was playing the researchers would then begin to play a second sound at the same frequency as the leading sound yet placed at a different position in azimuth. This created sounds that acted similar to those in an echoic environment.  When sounds were more than 10 ms apart owls were able to easily double saccade (turn their gaze) first towards the leading source and then towards the lagging source with very good accuracy.  Once sounds became quicker than 10 ms in timing, owls exhibited higher error rates in determining the location of the leading vs. the lagging sound and generally would orient towards only the leading sound source.  (Spitzer et al. 2006)  According to Helmut Haas The precedence effect (or Haas effect) states that “When two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first. To the listener, this creates the impression that the sound comes from that location alone due to a phenomenon that might be described as "involuntary sensory inhibition" in that one’s perception of later arrivals is suppressed.” (http://en.wikipedia.org/wiki/Haas_effect)  This study helped to show that the precedence effect does in fact take place in barn owls.  The higher the response time between the sound sources the higher the processing time needed by the owls to discern the sound sources.

What researchers noticed about Tyto alba was that sounds of the prey themselves played a huge role in auditory localization of prey, however visual cues also played a large part in how well the owl was able to localize prey.  Whitchurch et al. 2006 measured the timing of head saccades in response to both visual and auditory stimuli and attempted to correlate the amount of error found with both the directionality and intensity of a sound stimulus.  Barn owls use both visual tracking and auditory stimulation in order to create a spatial map of the location of their potential prey.  In response to a sound stimuli, a precise spatiotopic map (a map of a stimuli in space.)  comes first from the brains external nucleus of the inferior colliculus and then translates to the retinotopic map (a map of a stimuli in visual space) towards its optic tectum.  In this way, the barn owl gets both a visual and auditory interpretation of the location of that sound in space.  Researchers tried to find positive violations of Miller’s traditional race model.  The race model states that when two sensory signals race along separate pathways towards a common response generation site, the winning sensory signal will get to trigger the response.  If both sensory stimuli have an equal chance, the race model predicts that on average a multisensory scheme will be faster than a unisensory reaction time. (Whitchurch et al. 2006)  This suggests that by employing both auditory and visual inputs an animal can increase the probability of identifying the source of a weak stimulus.  The chances of accomplishing this are greater than if only one pathway existed.  According to the race model, although both potential pathways for sensory inputs exist, only one is chosen in the end as the primary sense used to track the prey.  The data found by the research actually disproves this.  When owls were presented with stimulation that evoked a shorter response time from head saccades that would typically yield an accurate visual response, the audio visual saccade occurred just as fast as the purely auditory response. (Whitchurch et al. 2006)  This implies that rather than a “one or the other” type response, neuronal responses to stimuli might instead favor a mixed usage of both auditory and visual stimuli to help locate prey.

Section 4: The neurological explanations of the owl’s abilities.

Although researchers have been able to identify and pinpoint how auditory specialization occurs on the part of the owl’s ears and head saccades themselves, there is more research which looks at the owl’s brain itself and tries to identify how the spatial mapping occurs on a neurological level.  Winkowski et al. 2006 took research like Whitchurch et al. performed and looked further into the process of visual and auditory cues.  Winkowski et al. were interested in the interaction between areas of the brain responsible for vision and how those areas are integrated with other particular areas of the brain.  When micro stimulation was placed onto the gaze control area of the barn owl’s forebrain, there was an activation of the auditory midbrain and they became more spatially selective.  This meant that the owl’s direction of their gaze was more selective for sounds that it might hear.  This was able to be measured by looking at electrical activity of the gaze center of the owls forebrain when microstimulation was placed on the corresponding auditory center of the midbrain. Other areas of the midbrain responsible for auditory processing which were not being stimulated by the forebrain area were not activated during stimulation of the forebrain.  The forebrain area known as the optic tectum is responsible for processing visual information.  The area specific stimulation of the midbrain by the forebrain shows a clear integration between visual information and its conversion into auditory spatial information.  When stimulation occurs, sensitivity to interaural timing differences (a measured difference in the rates of the arrival times of sounds) increases in various areas of the midbrain.  This increase in sensitivity showed that the owl’s midbrain was being regulated by the forebrain of Tyto alba (Winkowski et al 2006).  This helps to confirm that the owl’s vision and hearing not only work together in symposium but enhance one another’s functioning as well.

The mesencephalicus lateralis pars dorsalis (MLd) is a region of the midbrain nucleus found in birds that is responsible for the processing of acoustic behavior.  All birds have acoustic behaviors, including the echolocators, the song birds, the vocal learners and the auditory specialists like the owls.  The researchers decided to look at whether or not the variation in the size and volume of the MLd corresponded to the complexity of the tasks the animals had to accomplish.  This was done by dissecting the brains from 72 different species of birds and taking measurements of the brains overall volume, the volume of the optic tectum, and the mesencephalicus lateralis pars dorsalis.  The ratios of volumes of these structures were then compared to each other and log plots of the correlation of these values across the 72 species were identified.  When this was combined with the already published knowledge about the behavior of these animals in terms of whether they echolocate, or hunt via auditory specialization like the barn owl for example, they found a direct correlation to the size of the birds midbrains relative to the task that was required of them.  Owls, the auditory specialists all had a significantly larger midbrain nucleus than all the other types of birds.  This would logically correspond to the fact that owls hunt using special maps made via hearing.  Researchers also looked more closely at the relationship of asymmetrically eared owls vs. symmetrically eared owls.  They found that asymmetrically eared owls have an even larger volume midbrain than the symmetrically eared owls. (Iwaniuk et. Al. 2006) This logically made sense to the fact that most symmetrically eared owls do not rely mainly on hearing to hunt their prey.  Although Tyto alba uses vision as Winkowski et al pointed out, this still makes the asymmetrically eared owls like Tyto alba true auditory specialists.

As many of the investigations on Tyto alba have shown, the midbrain is part of the brain that allows Tyto alba to have its amazing auditory abilities.  Because of this midbrain specialization, McBride et. al used the owl’s middle brain as testing ground for the neurological model of learning.   Young juvenile owls were raised with a prism over their eyes that shifted the visual field 19 degrees.  After one year the dendritic numbers and spatial layouts of owls with prisms vs. owls without, were measured to see if there were any differences.  By  using a fluorescently labeled tracer, the tissue samples taken from juvenile barn owls raised with prismatic lenses over their eyes, showed that the owls exhibited a different and more complex set of dendritic neurons. It was observed that dendritic clusters that were spaced closer than 20 µm where shown to have higher rates of contact where as dendritic clusters that were spaced greater than 20 µm apart had less contact and there for implied a lack of neurological learning.  (McBride et al 2008)  This is the first time that a study has demonstrated that there is a change in the patterns of dendrites in the brain that correlates directly to an animal’s ability to adjust and learn.  However, generalizations and an unequal sample pool might cause this data to come under some scrutiny.  If this research is accurate it would paints a picture of the owl’s midbrains as being plastic and flexible.  It would also show on a neurological level a direct correlation between learning and neurological spacing.

Conclusions

Barn owls are amazing creatures with an amazing ability to locate prey based on sounds. The barn owls midbrain processes the timing differences between sounds heard on either side of the owl’s asymmetrical ears.  The owl’s forebrain stimulates the midbrain and helps to cue it’s visual system to gaze in a particular area.  Once gazing the owl can track its prey’s motion using head saccades and predict where the prey will be in order to intercept it.  It then takes off and attacks its prey with great speed being able to generally adjust its flight path accordingly.  All of this is done in pitch darkness in a matter of seconds.  Tyto alba research is important to understanding how we as humans process complex sounds and how our own brains are tuned to focus and pay attention to our surroundings.  Audio spatial mapping might have huge potential in military applications in activites such as tracking and espionage or even in planes, shipping or mining applications.  Spitzer and Takahashi’s research in particular helps us to understand how we are able to identify and pinpoint specific sounds in a loud and echoic environment.  Future research should look more into claims of Tyto alba being able to fly silently, as well as the owl’s midbrain nucleus and potential abilities for this area of the brain to learn and adapt to different sensory stimuli. For example, some research by Terry Takahashi, a major contributor of auditory research in Tyto alba, might look into the owls complete sensory fields and attempt to map the effects on the gaze center over a broad range of stimuli rather than a set few.  Other future research might test the pathways of control from the forebrain to the midbrain itself, paying special attention to a neurological ability to create new pathways, how different stimuli inputs map across the regions of the brains and how the owls respond to having modified sounds as stimuli inputs.  Regardless of the future research, current research shows us that Tyto alba is indeed one of the best audio locators in the animal kingdom.

Bibliography

1. http://www.allaboutbirds.org (Cornell Universities Bird Website)

2. http://en.wikipedia.org/wiki/Haas_effect (Wikipedia entry on Helmut Haas and his discovery of the Precedence Effect)

3. Fux M, Eilam, D (2009) How barn owls (Tyto alba) visually follow moving voles (Microtus socialis) before attacking them, Physiology & Behavior 98:359-366

4. Hausmann, L., Plachta, D. T.T., Singheiser, M., Brill, S., Wagner, H., (2008) In-flight corrections in free-flying barn owls (Tyto alba) during sound localization tasks, The Journal of Experimental Biology 211:2976-2988

5. Ilany, A., Eilam D., (2008) Wait before running for your life: defensive tactics of spiny mice (Acomys cahirinus) in evading barn owl (Tyto alba) attack, Behavioral Ecology and Sociobiology 62:923-933

6. Iwaniuk, A. N., Clayton, D. H., Wylie, D. R. W., (2006) Echolocation, vocal learning, auditory localization and the relative size of the avian auditory midbrain nucleus (MLd), Behavioural Brain Research, 167:305-317.

7. Koppl, C., Gleich, O., (2007) Evoked cochlear potentials in the barn owl,  Journal of Comparative Physiology 193:601-612.

8. Koppl, C., Nickel, R., (2007) Prolonged maturation of cochlear function in the barn owl after hatching, Journal of Comparative Physiology 193:613-624.

9. McBride, T. J., Rodriguez-Contreras, A., Trinh, A., Bailey, R., Debello, W. M., (2008) Learning Drives Differential Clustering of Axodendritic Contacts in the Barn Owl Auditory System, Journal of Neuroscience 28:6960-6973

10. Spitzer, M. W., Takahashi, T. T., (2006) Sound Localization by Barn Owls in a Simulated Echoic Environment, Journal of Neurophysiology 95:3571-3584

11. Whitchurch, E. A., Takahashi T. T.,(2006) Combined Auditory and Visual Stimuli Facilitate Head Saccades in the Barn Owl (Tyto alba) Journal of Neurophysiology 96:730-745

12. Winkowski, D. E., Knudsen, E. I., (2006) Top-down gain control of the auditory space map by gaze control circuitry in the barn owl Nature 439:336-339

In the spirit of Thanksgiving, todays post will deal with tryptophan and if it makes you sleepy.  We all know thanksgiving as a holiday of food.  A veritable cornicopia of various dishes.  What most people complain about is the feeling of sleepyness after eating lots of turkey.  Most of us like to blame the copious amounts of food we consume on causing what we colloquially call “food coma.”   However there is known evidence over the last 20 years that shows that in fact its turkey’s higher levels of L tryptophan (an essential amino acid) that creates that sleepy feeling. Tryptophan is converted into Seratonin via a biochemical pathway. Since seratonin is a neurotransmitter often responsible for sleep/ tiredness one can infer that more turkey = more tryptophan = more seratonin= more sleepy.

So now, knowing what we know, lets take a look at these two molecules.  When you look at the molecular structure of Tryptophan and the structure of Seratonin, its not suprising that one turns into the other.

A molecule of Tryptophan

A molecule of seratonin

Seratonin can be found in neurons of the central nervous system (CNS) where it functions in several ways.  Its been found to process in  regulation of mood, appetite, sleep, muscle contraction, and some cognitive functions including memory and learning.   When excess tryptophan is eaten more seratonin is produced by the body.  This means that more seratonin is present in the neuronal synapses and thus with a constant level of neurotransmitter reuptake more neurotransmitter is creating action potentials (or firing of neurons) at the post synaptic gap.  In other words you can state that more seratonin means an increase in mood,a decrease in appetite, an increase in sleep and relaxed muscles in the sympathetic nervous system and an increase in the para-sympathetic nervous system leading to digestion.

So this thanksgiving lets all go eat some turkey, and while we sit an begin to doze off we can think about how tryptophan and seratonin are playing a role in our drowzyness. 

HAPPY THANKSGIVING!!!!!!

When you hurt your arm, leg, or back, the first thing you’d often notice is that ones’ range of motion tends to decrease.   It hurts to move, or your muscles feel achy. Despite this pain previous  medical research has no solid explanation for the fact that despite pain and obvious torn/ damaged muscles, individuals are still able to perform tasks with the same amounts of force as an individual who is not in pain.  Researchers recently have hypothesised that individuals who are experiencing deep tissue pain, in fact recruit more muscles to help out the torn/ damaged muscle do its task.   This might seem painfully obvious but it is not.  Up until this point the current theory/ model of muscle recruitment during pain stated that muscle groups take from other limbs or major muscles to help get a task completed.  Lets dive a bit further into this issue and I”ll attempt to lay it out nice and simple.

First off we need to understand what a functional motor unit is, in order to understand how this works.  For the purpose of simplicity we will use the bicep as our model muscle in the following explanations.  As you may know muscles have the ability to flex and relax.  Simply put a muscle is in fact a bundle of fibers which each act independently to add to a larger whole.  The reason you can flex your arm and wave vs. flex your arm to lift a weight is that the more labor, force your body needs , the more motor units are recruited to get the job done.  The neat thing is these muscle fibers actually recruit in an orderly fashion from smaller to larger.

So what happens when you’ve torn a muscle or injured a limb?  Say you need to get a task done but your injured.  How do your muscles deal with this situation?  Researchers set out to answer this exact question.  They did this by getting a patient pool of volunteers who let them inject 5% saline solution into the subcutaneous fat of their forearms and their triceps.  These researchers then looked at the electrical levels of the neurons that innervate each functional motor unit and took recordings from these while their patients were asked to perform tasks with a given force.  These neurons that innervate each motor unit, control the muscles flexion and relaxation abilities.  When a task is performed a certain electrical charge can be measured of each one and with some sophisticated software researchers can tell how many individual units exist and which ones in particular are being recruited.

Diagram of the quadricep muscle

When all was said and done they were astonished.  What they found was that the current model of motor unit recruitment during pain was in fact wrong! As they predicted,  muscle groups that were undergoing deep tissue pain in did in fact show the same electrical activity as normal muscles.  They also were able to generate force just like a non injured muscle could.  However, what they didn’t expect was that the muscles were actually recruiting in a different order than the normal recruitment order from smallest to largest.  This basically means that when your injured your brain knows to switch which muscle unit it chooses to help you get a task done, rather than always recruiting them in the same pattern and order.  This has huge implications for studies on pain and how the human body is able to cope with injury.

The motor unit as seen coming from the spine out to the muscle groups

When most people think of venomous animals, their first reaction is to think of snakes.  This is an accurate thought process as snakes are indeed venomous animals, infamous for killing individuals in a terrible way.  However, snakes are not the only creatures that have evolved a chemical defense like venom.  There are venomous birds, frogs, fish, even mollusks!  The duck billed platypus contains a venomous barb on its hind paws that it can use for defense.    Todays post will deal with one of these venomus animals that should be coming into fame soon.  The Geographic Cone Snail. 

A handfull of various types of Conidae shells

Conus geographus belongs to a family of snails known as the Conidae.  Snails belonging to this family are distinguished by having a cone shaped shell.  We often see these for sale on hawaiian necklaces or at shell stores.  The geographic cone snail  is an amazing beautiful creature but has a deadly venom.  This small snail is packed with a potent venom known as Conotoxin.  This venom is a classic nicotenic acetylcholinesterase inhibitor.  It blocks the reuptake of acetylcholine into the nervous system.  Acetylcholine is a neurotransmitter often responsible for muscle movement.  When the inhibitor for acetylcholine is blocked, tons of it builds up in the neuro synapses.  This causes the body to convluse and go rigid due to over signaling.  Eventually you cannot exhale and you suffocate and die. 

A Cone Snail with its harpoon excised

Conotoxin, therefore, is a wonderful weapon for Conus geographus to use to capture prey.  This tiny snail can actually eat a fish whole!  It has a proboscis which it uses like a nose.  It searchers around for food and when it smells it, it injects a harpoon like structure into the skin of the prey.  This harpoon pumps the deadly conotoxin into the prey causing it to become paralized.  It then devours the food alive. 

A molecule of Conotoxin

What is amazing about this compound is that it has pharmaceutical applications.  A novel drug has been developed from it.  The drug, known as conotropin, is a powerful analgesic, pain killer.   Said to be 1,000 times more powerful than morphine with no known side effects, Conotropin, has the potential to help thousands of sufferers of pain wordwide.  People with debilitating ailments such as sciatica can now rely on this drug to finally give them relief without destroying their bodies.  This drug is still in clinical trials however so look for it in the near future.

The word pharmacognosy is derived from the greek words “pharmakon” which means drug and “gnosis” or knowledge.  This is the study of drugs from natural products.  These natural products are typically derived from plant sources, like aspirin, or methanphedamines or caffeine.  However some compounds come from animal sources, such as the novel drug Conotropin, which is derived from conotoxin ( a potent neurotoxin found in geographic cone snails).  Think of the pharmacognosist as the modern day alchemist.

TLC of a plant extract

As their assays typically require identifying the base constituents of a larger compound, these scientists rely on an array of separation techniques to help them sort out compounds into their base components.  One such technique is thin layer chromatography.  Thin layer chromatography or TLC as its more commonly known, is based on the general concept that objects will move through a medium of evenly spaced particles based on their molecular weight.  Think of this analogy.  You have two small children running from two fat men.  If the children run to a play ground and move through the playground equipment they will get out of the climbing structure much faster than the two fat men will.  These children have passed through quickly because of their smaller size.  This is true also of molecules in an aqueous solution.  The larger particles will move slower through a matrix than smaller particles will.  In this case it become possible with a consistent media usually of powered glass (silica) to separate things by molecular weight.  This is the basic idea for chromatography.  Now thin layer chromatography relies on several key factors.  First it relies on the fact that a solute system has been designed that due to its polarity helps to separate out the compounds of interest ( think of this as a liquid to help move the particles through the matrix).  In high school chem lab, many of us performed the simple experiment where we took a sharpie or black inked pen and drew a dot on it.  We then placed one end in water and let the water wick upward.  This separated the ink out by color.  The reason this worked is because the water is an extremely polar compound.  It thus pulls the ink apart into its basic components which happen to be multiple colors of ink.  These components then travel along the plate until the solvent front stops at the top.    This can be seen in the example below.  The ink has separated out based on its components molecular weights.  To help more with this explanation, the yellow ink is the lightest in weight and thus has traveled farthest on the plate.

Black ink on a TLC Plate

So how is this useful you might ask?  Does this assay tell us anything about the constituents themselves?  Can I identify what they are?  Do I know the molecular make up of that yellow banding?  The answer is of course no.  However, TLC can be used as a basic step to help us later answer these questions.  Variations to our TLC assay can help us to actually identify what the banding patterns are.  Special sprays that interact with the separated compounds can produce a color change for example that help to identify the compounds within.  For example, potassium dichromate spray can help to identify the presence of any organic compounds within the original sample.   Also by varying the solvent system, (mixing in water with an alcohol or organic solvent) we can change not only the rate at which the solvent travels but also the clarity and resolution of separation.  We can also use a fluorescent plate that will cause particular samples within the matrix to change color under a UV light.

So how do we setup a basic TLC assay.  First your compound of interest must be obtained in a liquid delivery system.    This allows the liquid to transport through the media. You would first place blot your sample onto the TLC plate making sure to measure the starting position.  Then place your plate upright into a container with a seal able top .  Then place a piece of filter paper to help wick the solvent upward.  Then pour in just enough solvent to cover the base of your plate.  Cover and wait.  Remove your plate before the solvent front runs off the glass slide.  Take a look at the below figure for perhaps a better explanation as to how TLC assays can be setup.  The  final interesting point about TLC assays is that the particular bandings, once separated can be literally cut out and reconstituted in alcohol or an organic solvent for further analysis with other equipment.

Identified bandings

Steps for a TCL assay

Today’s post is about the artificial hand the i-limb.  This product has become so lifelike its amazing. People are now able to control the limb almost as though it were the real deal, with far less wires and far less problems.  Also the hands articulation is top notch allowing for all sorts of normal movements that previous claw type artificial limbs could only dream of achieving.  This product is incredibly expensive however, and as far as I’ve found is basically limited to military uses.  I did read that the limb had to be toned down due to it being far to strong.  Pretty cool eh?  The company that makes it is Touch Bionics which looks like its based out of Spain,  I have added their website to the links on the side mostly just cause its so awesome.  Check out some www.youtube.com videos of this thing in action!!! Also their living skin products are amazing as well.  The stuff of sci-fi movies come to life, this company is far ahead in cutting edge technology.

Check out the youtube video here :

Some other advances have come in the shape of artificial skin.  This skin which fits over the prosthetic looks an feels and acts like real skin.  Its pretty incredible to see.  Take a look below at this picture

Look at the Darpa Artifical arm with skin!

All in all I’d say the future of bionic limbs is coming along swimmingly.  I’m curious to see  if advanced technology plus a competitive market will lower the prices on these guys.  Hopefully they can work on some of the articulation of the thumbs and some of the neurological processing.  This company has developed a wheel chair that can be controlled by thoughts:

Also seems pretty cool.

Here’s an interesting schematic on how bionic limbs work.  They don’t look to pretty just yet huh?

A company in germany known as Fiesto-AG have developed this arm which works using 33 artificial muscles and actual metalic articulated bones.  The muscles are pneumatically controlled.  Looks pretty awesome right?  Still needs some kinks worked out to get the arm to have the same type of motion as a real arm.  I think were looking at a few years but then bionic arms here we come!!

Since today I am feeling adventerous, I have decided to post 2 lessions.  The first was a very breif discussion on the history of the San Francisco Bay Bridge and future designs to prevent it from being damaged during an earthquake.  This post will be more true to the nature of the blog however.  We will be discussing a topic in Neuroethology that has been studied intensivly.  That is the ability for animals to see the plane of polarized light and UV light and use it for navigation and identification of food/ communication.

First off we have to discuss what exactly constitutes polarized light.   Light waves are as some of you may know actual particles.  Think of them as molecular size pieces of dust that travel through space in a sinusodal wave like fashion.  They have both an electrical aspect to them as well as a magnetic component to them.  These two aspects are at times perpendicular to one another traveling forward.  When they hit an object they reflect off molecules and then travel at a direction 90 degrees to the original orientation.  They become horizontal rather than vertical for example when they travel through our atmosphere. 

regluar light becoming polarized

polarized light waves

Humans detect polarized light as glare.  Polarized sunglasses have microscopic grooves cut into them to block the light particles that are traveling parallell to the cuts and allow the ones that are traveling opposite to pass through.  This is why when you wear sunglasses that are polarized things seem darker than normal sunglasses.  There are animals however that can view the plane of polarized light with MUCH higher resolution than we can.  This is due to significantly different neruological structures and evolutionary designs in their eyes. 

For the purpose of this post I will use insect eyes as the standard.  Please keep in mind there are very few absoultes in biology.  There most likely are exceptions and alternatives to this.

Insect eyes are multifaceted.  That is that they are made up of hundreds of lenses rather than one single lense as typically found in the human eye.  These lenses have deep pockets each with a single neuron attached at the bottom that absorbe wavelenghts of light and report a single image towards the brain.  Think of these as pixles on a screen.  The more lenses the higher the resolution of the image. 

Insect eye (The dark spot is looking INTO the omatidiums)

 These lenses have cells inside them that are designed to trap the particles of light and best process them into neruonal signals.     The structure collectivly is known as an omatidium.  Think of these omatidium as cylinders stacked very closely together to form the entire eye.  the corneas of each omatidium are what make up the many facets of the insects eye.

cross section of an insect eye showing its many omatidums

A particular protein known as opsin helps to translate the light absorption into a particular neruonal signal and color.  In order to see polarized light, there are small structures that protrude off the Rhabdomere known as microvilli that contain the rhodopsin / opsin proteins.  These structures are aligned at 90 degree angles to eachother in order to best capture those polarized light waves.  Remember the ones that suddnely were horizontal rather than verticle?  Think the same thing.  This is very different than the design of vertebrate rods and cones in which discs containing opsin / rhodopsin proteins in a scattered arrangement are stacked one on top of the other.  I will discuss this at a later post.

The opsin protein

Omatidia with key

These omatidiums with their specalized rhabdomere cells which absorb those particles have also become specalized to see UV wavelenght type light.  Some insects see these wavelengths as various color differences.  They use these to detect patternings on flowers or even to communicate across species.  The stomatopod, a marine crustacean, has an amazing ocular specality.  It can see the entire color spetrum, UV, polarized light and each eye can see 360 degree’s around!! Its completely difficult to even consider what that would appear like to you and I.  Some stomatopods even have the ablity to flash colored fins on either sides of their head to communicate with eachother.  These flaps have a particular coloration on them and the reflection of these means different thigns to the animal in terms of communcation.    Maybe someday scientist will devolp a way for human beings to view  the plane of polarized light, UV light fields in our own eyes.  Maybe we’ll even adapt and use this for higher communication…you never know.

The stomatopod and its colored fins. Notice the crazy eyes?

            The James Rolph Bridge, (locally known as the San Francisco Bay Bridge)  As many of you know, has been structurally unsound for years.  Infact, some people stipulate that the bridge could collaps at any given moment.  There’s something to think about next time you take a trip down it!  The California Department of Transportation (CALTRANs) has recently posted a video on the design of the new James Rolph Bridge.  This video discusses the steps they have taken to prevent the bridge from collapsing during an earthquake.

            The Bay Bridge actually has one of the longest spans in the world and carries roughly 300,000 cars back and forth between San Francisco and Oakland every day.  It first opened in 1936, six months before the Golden Gate Bridge!!!  Originally cars traveled on the top layer and ONLY trains and trucks were allowed on the bottom level.  Also people had to pay toll going in BOTH directions!

Here are some pictures of the bridge back when it was under construction and how it looks today:

An Arial Shot of The Newly Completed Bridge

Workers Attaching Cables Workers hang Suspension Cables

  

Workers hang Suspension Cables

Watch the below video for a great explanation of how the new bridge will attempt to be much more structurally sound than its current predecesor: (IF THE VIDEO DOESN”T WORK GO TO http://baybridgeinfo.org/earthquake-simulation)

So lets dive right into it.  (That pun will become inherently clear in the next few lines).  Nudibranchs.  My favorite topic and one you can expect to see a variety of and many posts on when I have nothing else to discuss.   Nudibranchs are a shelless gastropod that belongs to the phylum Molluska (Mollusca if your from the USA.  Personally I prefer the European version of Molluska). Little is known about why these creatures lack a shell when their cousins all have one.  There are some who hypothesis that the nudibranchs have always lacked a shell.  There are others who feel they have evolved to discard their shell and take on their current “slug” like appearance.  Current research shows that small pieces of spicule/chitin, can be found in the body tissues of the nudibranch.  Chitin is a chemical that is often found in most mollusk shells. Interesting right?

So how do these little fellas protect themselves with no shell to hide in?!  Well it turns out most nudibranchs are chemically defended.  This chemical ecology is the subject of much research as  secondary metabolites in marine animals (in this case the toxins the nudibranchs have in their bodies) often are the source of new drugs!  These nudibranchs have evolved to in general be very picky eaters.  They on average eat only 1 type of animal.  They tend to steal their toxins and defenses from their food source and incorporate them into their own tissues.  Neat trick.  Some can even steal the stinging cells from jelly fish!

Tritonia diomedea (the pink nudibranch shown above)  Is a deep sea nudibranch that lives off the coast of Baja California and ranges out towards the sea of Japan.  It lives deep in the ocean and typically feeds on a variety of octocorals (soft corals with 8 tentacles around their polyps) Specifically (Renilla sp.) and Ptilosarcus guernyi (the orange sea pen).  Ptilosarcus guernyi (shown to the right)  is chemically defended with a toxin known as ptilosarcenone.  Found by a Dr. Jack Wekell in 1973,  ptilosarcenone is a terpenoid brirane (think molecule kinda like turpentine and subsequently its chemical formula is the title of this blog).  These nudibranchs feast upon this sea pen like locusts to a field of crops.  They only have one predator too!  A sunflower sea star.  They also have this really cool escape mechanism of this sort of back and forth swimming motion that is 90% effective at helping them to evade predation.  Neurologists call this the “swim escape response”.

Tritonia diomedia is actually used quite extensively in all sorts of research!  Neurologists love it because of its simple neurons and its huge brain and therefore use it as a model to study memory, (the Nobel prize was given to a man who researched this sea slug and determined the biochemistry behind memory formation).  They also look at things like learning, locomotion, and in my particular case chemical ecology, chemo taxis and pharmacology. Unpublished data on these actually shows they even have pieces of iron in their cells that help them to potentially orient to the earths magnetic fields!!! Pretty cool stuff.  BTW those bunny ear looking things are their nose and are known as rhinophores.  These little guys are effectively blind.  Future research will hopefully teach us a lot not only about our own neurological design but also about this wonderful creature as well.