Wednesday, March 29, 2006

Wasabi Receptors Unite!

Woohoo!!!!! A ‘wasabi’ receptor!!!

Harking back to a discussion with a colleague from India, we debated the merits and preferences for tasting ‘heat’. By that I mean hot peppers and wasabi. Our preferences were the converse: he preferred peppers and I, wasabi. We also agreed on a similar tendency in that while exhibiting a high tolerance for our preferred ‘heat’ generator, we had a relative high pain sensitivity and intolerance for the other.

We debated that perhaps tolerance may be a function of conditioning: his typical diet incorporated foods prepared with copious amounts of ‘high octane’ peppers. Whereas I tend to prefer Asian foods that are traditionally accompanied by wasabi, or even smearing wasabi on other foods such as ham or even eggs. However, living in Texas, I also eat a fair amount of the typical Southwestern fare often doused with hot peppers. Regardless, I haven’t been able to overreach food with a rating of one by the Scoville chile heat index (100-1,000 Scovlille Units), except for an occasional exploration of a meal that may rate a two if accompanied by plenty of neutralizing chips and iced tea.

The magic ingredient of chili peppers that endows that heated kick is capsaicin, a oily substance found in the veins of a wide variety of peppers. Capsaicin delivers a burning and painful sensation in the mouth and on the skin due to its interaction with sensory neurons. The chemical binds to receptors, classified as TRPV1, that are also stimulated by heat and physical abrasion. When stimulated, these receptors permit ions to pass through the cell membrane and the neuron ultimately signals the brain. The result is the sensation of burning.

Typical of the negative feedback control by most receptors, chronic exposure to capsaicin depletes the neuron of neurotransmitters, leading to a reduction in pain sensation and neurogenic inflammation (a process called ‘desensitization’). After capsaicin is removed and following a short refractory time the neurons recover. This may explain why people who traditionally eat food containing hot peppers have a higher degree of tolerance.

Nevertheless, this does not explain why the differential tolerance, and intolerance, of chili peppers and wasabi. The pain-associated chemicals in wasabi, a Japanese horseradish, are similar to those found in hot mustards: isothiocyanates. The wonderful sinus clearing vapors of wasabi are the primary contrast to the heat of hot chili peppers. Yet both produce painful sensations in the mouth and on the skin when topically applied, exciting sensory nerve fibers.

Whereas hot chili peppers titillated my colleague, I covet the rush through the sinuses and tearing aftermath of wasabi. Both of us exhibited a greater degree of sensitivity (and dislike) for the other source of painful sensation. Could the sensations and tolerance be more than just dietary conditioning? I ventured to posit that perhaps there is a receptor for wasabi!

A recent study in Cell now reports that different receptors are involved in the pain sensations of capsaicin and mustard thiocyanates. While both receptors affect neurons on the pain pathway, TRPV1 receptors are associated with capsaicin and TRPA1 receptors with other plant chemicals specifically found in garlic and various mustards. This implies that they segregate at the molecular level yet elicit similar physiological overlapping responses (irritation and inflammation).

Belonging to a group of neuron receptors in our skin, and on our mouth and tongue, they are part of our natural defense system. Transient receptor potential (TRP) ion channels are like molecular thermometers that detect temperature, mechanical abrasion and irritating chemicals. They help us sense temperature and irritants through the skin and, as we can attest, in spicy and hot foods. Even volatile odors, as evidenced by eating wasabi and the mucus membranes in the sinus cavity and lungs. Ultimately, a message is sent to the brain: “Danger, Danger!” In fact these irritant chemicals are a component of the plant’s natural defense system.

On the other hand, both capsaicin and mustards are used in alternative medicine as topical ointments to relieve pain. Applications to the skin are left on until the area is numb. This is induced by overwhelming the local neurons and depleting their neurotransmitters that create the painful sensation and blocking neurogenic inflammation. Another medicinal use that I discovered serendipitously is to clear the sinuses of mucus from upper respiratory infections.

Alternatively, I just plain enjoy the rush of that volatile wasabi up through my nose and sinuses. You can keep the capsaicin, though.

So, yes, Dr. Sri; there really is a ‘wasabi’ receptor after all.

Cell, 124: 1269-1282, March 2006. TRPA1 mediates the inflammatory actions of environmental irritants and proalgesic agents. Bautista D, Jordt S, Nikai T, et al.

Dear Dairy (No. 3)

This has to be one of the most brilliantly created advertisements I have ever encountered:


And if there is any question regarding the sleep-inducing power of milk? It is highly efficacious.
(tryptophan + carbohydrates = serotonin -----> zzzzzzzzzzzzzzz......... sleeeeep)
I've also noticed an effect on dreams (or dream recall, perhaps both)


Friday, March 24, 2006


Solid phase water encased my windshield this morning,
What planetary constant allows this absence of heat?
Driving into the sunrise admiring hues of blues, violets, and reds
Resisting the urge to vaporize the car in front hogging the passing lane.
Adhesions ripping apart while stretching
my recovering left foot.
Vision rudely disturbed by a large white splat deposited by a flying bird.
My head is drawn away from fragments of last night’s dreams
By the uplifting taunting whine of an electric guitar on my stereo.
Notes take me higher lifting me out of the morning haze
As I ponder finding a windshield that belongs on my bike.
Looking forward to the next morn, after donning warm gear,
Throwing my leg over humming metal, sitting deep in the saddle,
Feeling that infusion of adrenaline, balance it with zen,
Pull face shield, shift down, roll the throttle, and lift off.

The sun is shining and it is Friday.

This is good.

Sunday, March 19, 2006

Time Machine: Journey One

During a visit to the National Museum of Natural History and Science (New York, NY) years ago, I was awestruck by the display of creatures that roamed this planet before we were ever a gleam in evolution’s eye. Always captivated by the giants who preceded us, I commented to my companion during that visit that if we had time travel I would be one of the first to volunteer to go back and be an ‘Observer’. When prodded what I would like to see or do if I had once chance to go back in time, I couldn’t respond (perhaps for the first time). Too many events flooded my mind.

During the three years ensuing that visit, I have pondered that question again and often: What would I do, where and when would I go, and what event in time do I want to see? This is a series of responses to that question. Sorry, Mark; life is not that simple to provide one answer.


Spring is here in Texas; it is the time of flowing pheromones and nature’s drive to reproduce where ever it can. Two and four-footed creatures are on the move to seek a mate, or just mate. As I drive down country roads I see and smell that little black and white furry bugger that isn’t so cute: skunk. Occasionally I wake to the malodour of Pepe Le’ Pew, such as this morning. Having been a victim at close range many years ago, suffering a direct hit, I still have an associated cringe and and clenching of the stomach, along with an almost reflexive attempt to block the smell and taste of skunk perfume.

This morning I was awoken by a strong skunk presence, enough to incite me to jump out of bed and clang the bedroom windows shut. Glancing out one window, I saw my arch enemy returning my gaze below with what could be interpreted as a “Heheee…gotcha” expression.

During my drive to town with a slight scent of skunk lingering on my clothes, I contemplated going back in time to find the ancestor with the culprit scent gland before it mated with the scentless ancestor of our modern skunk and removing it from the evolutionary chain.

The skunk family Mephitidae (derived from Mephitis, Latin for "bad odor") comprises of 11 species in four genera. Nearly all carnivores have scent glands, but they are especially enlarged in skunks and relative families, with skunks taking that enlargement to an extreme. Rather than a duct like it’s close ‘cousins’, the skunk scent glands at the base of the tail has a nipple. The glands contain approximately 15 cc of a yellowish, oily liquid. With highly coordinated muscle control, the skunk can aim and direct the spray as far as 15 feet and spay up to six times in succession. The only relief is that it takes up to 10 days to replenish the supply of liquid after full discharge.

The odoriferous liquid contains various thiols (sulfur compounds) and thioacetates (salts of sulfur compounds). The principle compound in skunk musk is butyl mercaptan, similar to the popular laboratory compound mercaptoethanol used to cleaving disulfide bonds in organic solutions (to this day I cannot go into a lab without cringing at the smell of mercaptoethanol). Being sprayed in a direct hit can cause temporary blindness, nausea, convulsions, loss of consciousness and burns of the skin.

To neutralize skunk odor, the thiols have to be changed into compounds that have little or no odor. This can be done by oxidizing the thiols to sulfonic acids. Common oxidizing agents are hydrogen peroxide and baking soda (sodium bicarbonate) and are mild enough to be used on pets and yourself although it may change hair color. For clothes and inanimate objects sodium hypochlorite solutions (liquid laundry bleach) works well.

Skunk Evolution

Scent glands are ubiquitous throughout the class of mammals and serve as a form of olfactory communication. Distinctive and long-lasting smells are distributed in urine, sweat, or released by rubbing. These scents are deposited on the ground, on territorial boundaries, on offspring or mates, or their habitats. Yet the skunk has evolved to use their scent glands as a defensive weapon. Tail up, point, aim and shoot. Anyone taking a direct hit can attest to burning eyes, gagging, inability to breathe and rubbing any exposed skin to rid thyself of the noxious semi-viscous fluid and its aerosols.

What ancestor provided this adaptive trait? The oldest fossil identified as a skunk was discovered in Germany and dates to 11–12 million years ago. However, genetic data indicate the family originated about 30–40 million years ago. Research traces the evolution of the skunk from some of the earliest ancestors of modern carnivores and as members of the superfamily containing those of otters, badgers, and weasels, raccoons, and red panda. It is suggested that the origin of the skunk lineage occurred in the Oligocene approximately 40 million years ago (about 30 million years before the appearance of the first recognized fossil).

At some point in time, a weasely mammal sauntered up to a close relative and whispered in its ear “Hey baby, I have a secret weapon. Want to see it work?” Thus the lineage of the cute little furry buggers avoided becoming someone’s dinner. And they multiplied, with the semi-viscous stench dictating survival and adaptation.

I wonder if they had scent gland firing ranges for practice.

Tuesday, March 14, 2006

Dear Dairy (No. 2)

A recent quote by Jose' Mourinho, manager of Chelsea Football Club, when explaining why the team's soccer pitch in London is 'not as bad as it looks':

"Sometimes you see beautiful people with no brains. Sometimes you have ugly people who are intelligent, like scientists."

I am a scientist. Ergo, I am ugly. But I am intelligent and have a brain. Oh, woe is me.

However, my contribution to the reproductive success of intelligence genes has been, shall we say, limited by a matter of choice. Mine. Yet when I flip through the television channels and see the plethora of beautiful bodies with empty craniums, I feel guilt over my contribution to the 'reverse evolution' of our species. My selfish lack of interest in 'Bringing Up Baby' won over my patriotic duty to propagation of average appearance coupled with an intelligence factor that probably equals that of several TV starletts combined. That puts me at least with a positive quotient.

Can I still be sexy even if I have a brain? I don't need anyone's approval for that.
My pitch isn't bad either.