Posts Tagged 'science'

Ticklish?

Today for lunch, I decided to figure out what it means to be ticklish. I’ve always been curious about it. I’m not super ticklish, but I can remember more than one time laughing so hard from tickling that it hurt. Over the last few days, I have been thinking about laughing and thought about writing about the biology/anatomy of laughing but it just became too big of a story for the amount of time I had today. So tickling it is.

First of all, there’s two kinds of tickling: knismesis, which is the weird ticklishness you get when someone lightly strokes your skin, or a bug is crawling on your skin, and gargalesis, which is the full-on crazy ticklishness most people have in their armpits and soles of the feet. Gargalesis is also my new favorite word. Although the sensations are similar, the mechanisms behind them seem to be very different.

Knismesis is theorized to be a serve as a protective function of the skin, alerting the organism that something foreign is on the body. The sensation is mediated by neurons that mediate pain and neurons that mediate touch, so in cases where one type of nerve modality is damaged or removed, ticklishness can still remain although in a weaker sense. In general, this type of tickling does not result in laughter. You can induce the knismesis response in yourself if you lightly rub the roof of your mouth with your finger. Careful when you do it though, it’s kind of intense. This type of ticklishness has also been well-documented in animals, and widely studied in cats.

Gargalesis is similar to knismesis in that the same neurons seem to be activated in response to the “heavy tickling” stimulus as were activated by a “light feather” stimulus. However, it is different from knismesis in that it is found only in specific sites of the body. The most common sites are the armpits, soles of the feet, sides of the torso and ribs, neck and knee. Gargalesis is also different from knismesis in that it is generally not possible to induce the response on yourself. I think that’s pretty obvious to most people. When you wash your armpits in the shower you don’t laugh hysterically. At least I don’t. However, the issue is more complicated than that. In studies where subjects used a joystick to operate a tickling robot on themselves, researchers found that the subjects did not laugh in response to tickling. So, even though the tickling stimulus was coming from somewhere else, simply anticipating the stimulus is enough to dampen the response. The cerebellum seems to be the source of this cancellation of self-produced gargalesis. Conversely, if subjects were blindfolded and the tickling robot was operated by someone else, they would respond with laughter as though they were being authentically tickled by a person (so it’s not just that the robot sucks as a tickler). I tried in vain to find an image of the tickling robot used in these studies but I’m not sure it exists on the web, so until I find it, I’m going to assume it looks like this:

So what’s the use of gargalesis? There are several popular theories but no one knows for sure why. One theory suggests that it is a defense mechanism, since most of the commonly ticklish areas are areas of particular vulnerability to injury during hand-to-hand combat. The reflexive pulling-away that most people get during tickling would be a boon to survival. Another theory suggests that maybe the ticklish spots developed in utero and were used as a means to reflexively orient the fetus’ body correctly in the womb. Yet another theory posits that tickling is in fact rooted in the need for social connection and rough play during early development. The laughing and smiling reflex to tickling serves to encourage the tickler to continue.¬† Most people’s first experiences with tickling are with their mothers, maybe ticklishness is a way to enhance the mother-child bond. Of course at the end of the day, these are only theories and no one really knows for sure why it exists.

It is interesting that gargalesis is much less common amongst animals, and has only been well-documented in humans and a few primates. Recent work though has shown that rats can be tickled and even laugh an ultrasonic laugh (~50Hz) that can only be heard with special equipment. Apparently the rats go totally bananas, rolling around and playing, in fact actively begging to be tickled. Bearing that need for an ultrasonic listening device in mind, who knows what other animals are laughing, tickling each other, and developing complex relationships without our awareness. Certainly bonding is no unique thing to humans, so that would tend to fit the bonding theory of tickling’s origins.

After all of this exploration, I hope that this enlightens your view of what it means to be human and I haven’t ruined for you the simple pleasure of getting tickled. ūüôā

Blakemore SJ, Walpert DM, Frith CD (1998). “Central cancellation of selfproduced
tickle sensation”. Nat. Neurosci. 7:635-40.

Panksepp J, Burgdorf J (2003). ““Laughing” rats and the evolutionary antecedents of human joy?“. Physiol. Behav. 79 (3): 533‚Äď47.

Selden ST (2004). “Tickle”. J. Am. Acad. Dermatol. 50 (1): 93‚Äď7.


Fun Facts About Pepper

I like pepper. And I don’t mean Sandy Denton of Salt n Pepa. But I really don’t know anything about where it comes from, what the different kinds are, etc. At least I didn’t until 10 minutes ago when I started a procrastination-induced research project on the topic. Here are my findings.

Pepper is a little round berry from the pepper plant (Piper nigrum), which is a flowering vine with big, deeply veined leaves. It can grow in a pot or in the ground provided winter temperatures stay above freezing. To make those darling little berries into peppercorns, you start by briefly cooking green unripened berries in hot water to break down the cell walls, which will accelerate the drying process. As it dries, the fruit part of the berry shrivels around the seed giving it the peppercorn its dark, wrinkly appearance. To make white pepper, you let the berry soak in water for a week and the flesh of the berry decomposes, leaving only the white seed. Green peppercorns are similar to black peppercorns, except the unripe berries are made to stay green by chemicals or freeze drying.

The different colors of peppercorns have different flavors/aromas due to their different composition. The “heat” of pepper comes from a chemical called piperine which is found in both the seed and outer fruit, so both white and black peppercorns are hot. The heat factor of piperine is about 1% of capsaicin, the chemical that gives chili peppers their heat. The outer part of the berry contains a variety of terpene compounds that mostly contribute to the aroma of pepper. Thus, black pepper, which retains the outer dried berry flesh, has a more aromatic quality than white pepper. Green peppercorns taste more like black peppercorns, but with a supposedly “fresher” or “fruitier” flavor. I’ve never had one, so I’ll have to trust the folks at www.bulkpeppercorns.com.

These flavor and aroma compounds are very sensitive to light and air, so once a peppercorn is ground, it will soon lose much of its heat and aroma. This is why pepper mills are often used at the time of cooking or consumption to get the most flavor out of the peppercorns.

Incidentally, bell peppers and chili peppers are not really related to “pepper” other than that they are all plants. Bell peppers were misleadingly called peppers by Columbus when he found them in the New World, because at that time pepper was a very expensive and highly valued spice.

Props to wikipedia, toptropicals.com, and bulkpeppercorns.com for their fun fact resourcefulness.

Gay Science News

I don’t know if you occupy yourself with the scientific press, but there’s been big news in the last couple weeks in homosexuality research. There was a new “gay brain” study in PNAS (Proceedings of the National Academy of Sciences) that looked at differences in primitive brain structures that are fixed after birth showing that these structures in gay men resembled the same structures in straight women. Similarly, these structures in gay women resembled straight men. For those of you who love neuroanatomy, Hetero Male cerebral hemispheres tend to be lateralized or larger on the right side, mostly due to increased frontal and temporal lobes. Women’s cerebral hemispheres tend to be more similar on both sides. The Homo Male cerebral hemispheres tend to be the same size on each side, more like straight women’s. The opposite is true for gay women. More striking were changes in connectivity between the amygdala (reactions to external stimuli) and subcallosum and anterior cingulate (regulation of mood and anxiety-linked processes). The authors make a supposition that this could explain the increased prevalence in mood disorders amongst women and the increased depression and suicide rate among gay men. I think both statements are questionable because frankly there are a lot of external factors for both women and gay men that profoundly influence mental health. The authors also show that connections between the sensorimotor cortex and striatum are more robust in Hetero men and Homo women. These connections are more involved with attending to the external environment via fight or flight responses. All interesting stuff indeed.

This week, a paper in PLoS One (Public Library of Sciences) did some crazy genetics studies that I can’t even begin to fully understand, but their conclusions were pretty interesting. The authors were puzzled by the notion of a genetic source of homosexuality because in the simplest sense, if homosexuality is genetic and most homosexuals don’t reproduce, homosexuality should become extinct in the population. They show that homosexuality is equally present in cultures throughout the world and stable in incidence through recent history, indicating that a downslide in homosexuality prevalence or homosexual extinction is probably not happening. Then they use the theory of sexually antagonistic selection (the genes of one sex favor the other sex somehow) to come up with the hypothesis that homosexual men would have female relatives who are more fecund, or reproductively active. The theory being that some of the same genes involved in reproductive potential in women are somehow linked to homosexuality in men within the same maternal blood line.¬† They relate this then to their empirical studies which showed asymmetries in the pedigrees of families with gay men showing that the maternal female relatives (maternal aunts and cousins for example) of gay men do in fact have statistically more children. Interesting stuff as well. So now it’s a matter of doing the genetic linkage studies to identify the genes involved.

All of this research is interesting to me as a gay scientist. I always try to read the introductions and discussions of these papers carefully because the meaning and intent behind this research is perhaps more important than the research data itself. Most of the time, these studies are interpreted to say, “See I told you, being gay is not a lifestyle choice.” However, there are a lot of powerful people out there who would love to see these biological explanations for homosexuality turn into medical solutions to cure homosexuality. Check this quote from Rev. Albert Mohler, Jr., president of the Southern Baptist Theological Seminary, “If a biological basis is found, and if a prenatal test is then developed, and if a successful treatment to reverse the sexual orientation to heterosexual is ever developed, we would support its use.” It’s interesting and scary how the position of an anti-gay individual can shift so smoothly from “homosexuality is a choice” to “if it’s not a choice, then let’s fix it with medicine.” And believe you me, if these movers and shakers find ways to fund this sort of gay cure medicine (however far-off and ridiculous it may seem right now), people will want it and use it. Millions of people in China already selectively abort female fetuses to make sure they have a male baby.

All of this comes full circle for me every semester when I teach the pelvis in anatomy. The main message of the pelvis in my class is “having babies is magic, let’s see how much we can learn about how to make, grow and deliver a baby just by studying the anatomy.” It’s really fun, the students seem to absolutely love it, and we are able to talk through all of the anatomy of the male and female by linking it into one cohesive story . I’ve given a lot of thought to whether my approach is too hetero-centric, but you know, the story just isn’t that different for me or any other gay person. The parts all work the same, you just put them in different places. I could talk about gay sexual health issues, but that just goes so far outside the realm of anatomy. Maybe it would be more appropriate for an undergraduate anatomy/physiology class. I feel that my role in doing service to the gay community through my teaching is just being my big bad gay self in the classroom, so¬†my students can see¬†that gay people can be scientists and teachers (and really good ones at that) because they¬†might not¬†get the chance to meet many¬†out role models¬†in their medical education.

Nifty Auditory Illusions

Jason found this cool website out in the depths of the internet. It has a few audio files that were recorded using holophonic technology (a dummy head with microphones in the ears), so if you listen to these recordings with headphones on, you can really hear your surroundings moving around your head. If you close your eyes the effect is even more intense. Check it out friends!

LINK!

Fruits from a Fruit

Here’s another ridiculous scientific list. This one categorizes the different types of fruits. OMG strawberry dachshund costumeIt may come as a surprise to you that the tomato is a berry, or that those whirlibirds that fall off of maple trees are in fact fruits! In a botanical sense, a fruit is a ripened ovary containing seeds and a variety of surrounding tissues. How these tissues are arranged determines how the fruits are classified. There are two fundamental categories of fruits, fleshy and dry, which most people think of as fruits and nuts, respectively. I’ve laid out the details of how each category gets broken up. This is pretty much useless information, but there’s some pretty cool words in here. I heart Pepos. I also heart dachshunds wearing strawberry costumes. Brody, I hope you’re ready for a new outfit!

FLESHY FRUITS

Simple Fleshy Fruits (derived from only one pistil)

Drupes: Single seed enclosed by a hard endocarp (pit)

e.g. peaches, cherries, olives, almonds, coconuts

Berries: Derived from a compound ovary, often have multiple seeds

True Berries: thin skin and soft pericarp (tissue surrounding the seeds)

e.g. tomatoes, grapes, peppers, blueberries, bananas

Pepos: thick rind

e.g. pumpkins, cucumbers, watermelons

Hesperidium: leathery skin containing oils

e.g. oranges, lemons, limes

Pomes: Flesh derived from ovary’s receptacle

e.g. apples, pears

Aggregate Fruits (derived from single flower with many pistils)

e.g. raspberries, blackberries, strawberries

Multiple Fruits (derived from several flowers in a single inflorescence)

e.g. osage oranges, pineapples, figs

DRY FRUITS

Dry Fruits That Split at Maturity

Follicles: Split along one seam

e.g. larkspur, milkweed, peony

Legumes: Split along two seams

e.g. peas, beans, lentils, peanuts

Siliques: Split along two seams, but seeds are held along a central partition

e.g. broccoli, cabbage, radishes

Capsules: Split any other way

e.g. irises, orchids, poppies

Dry Fruits That Do Not Split at Maturity

Achenes: Single seed is attached to the pericarp at the base

e.g. sunflower seeds

Nuts: Same as achenes except thicker pericarp, cluster of bracts at base

e.g. acorns, hazelnuts, chestnuts

Grains: Pericarp and seed are inseparable

e.g. corn, wheat, rice, oats

Samaras: Specialized pericarp extends out as a wing to aid in dispersal

e.g. maple, ash, elm

Schizocarp: Twin fruits

e.g. parsley, carrot, anise, dill

Anatomy in the news: Obstetric Fistula

Okay, let me just start this one off with a disclaimer. This is probably a subject many people would find unpleasant, so if you’re eating lunch, maybe come back after you’ve finished. Nonetheless, it’s a significant health issue worth talking about and it’s all about anatomy, so I feel like I have something to say about it.

You may have recently seen or heard something in the news about a condition called Obstetric Fistula. It’s a complication usually seen in cases of prolonged or obstructed labor. What happens is the walls of the vagina (or birth canal if the “v word” is too much for you to handle) tear during delivery. The rectum and bladder, situated behind and in front of the vagina, respectively, can then also tear. Then when they heal, they heal together creating an artificial opening from the bladder to the vagina or from the rectum to the vagina. Check out the illustration of a midline cut pelvis for clarification, courtesy ADAM.

This is not a significant medical problem in the developed world where perinatal and obstetric medicine is sophisticated and freely available. However, in undeveloped countries, such as many in Africa, obstetric medical aid is often not available and when it is, there is usually a lack of basic tools that would allow the physician to do their job to the best of their ability. A recently released documentary called A Walk to Beautiful does a great job of telling the story of four women from Ethiopia who deal with this debilitating condition. I caught it on PBS, but it comes out on DVD soon. After their traumatic deliveries, which almost always result in stillborn infants, the women do not have the option to get surgical repair, so they are forced back into their communities with no bladder or fecal control at all. I’m not just talking leaking during coughing, like stress incontinence (which affects millions of women after childbirth, here and everywhere else in the world), I’m talking constant flow of urine with no regulation whatsoever, or even worse, the same scenario with feces. It’s not hard to imagine that these women are completely cast out of their societies. They are perceived as filthy and broken, often useless to even their husbands.

As I mentioned before, this is not a significant problem here in America and in other similar countries, because when this happens here, the physician immediately repairs the tears and the mother can heal in the hospital before returning to her normal life. In Africa, the supplies and staff it would take to perform the fistula repair are cost-prohibitive for many of the obstetric clinics, so the surgery is not even an option. And when I say cost-prohibitive, let me be totally clear, the total cost of the surgery is $300.00. Crazy world! Thankfully there are a growing number of “doctors without borders” who are bringing this surgery to the women of Ethiopia and other countries in Africa for no cost. Hopefully their compassion can relegate fistula to the fringes of medical concern in these places.

I could probably go on for days about the anatomy of the pelvis and how delivering a baby is a unique anatomical challenge for humans. Did you know that we are one of only two species of mammals that has difficulty delivering babies? This is because of two things. First, we walk on two legs. Walking on two legs requires a narrow pelvis, so the center of gravity can easily shift as we step from one leg to the other. If we had larger pelvises to make deliveries easier, we would tip over when we walked. Second, we have larger brains for our body size than any other mammal, which is probably not a surprise when you think about all of our abilities to process complicated thoughts and emotions into decision-making. Interestingly, we’ve already evolved to reduce brain development as much as possible until after birth to accommodate for our mothers’ smaller pelvic dimensions. Consider the relative brain development of a newborn baby and a newborn horse. The newborn horse is running around in a matter of hours, walking alongside its mother. The newborn baby can’t see colors or discriminate complicated sounds, has little motor control and most certainly can’t walk alongside mommy for many months. It’s funny that even that adaptation isn’t enough to counteract the narrow pelvis-large brain dilemma.

Incidentally, the other mammalian species that has difficult deliveries is the squirrel monkey. They are a dwarf species that gradually evolved smaller bodies but neonatal head sizes did not diminish similarly over time. Squirrel monkeys lose something like 30% of their babies in delivery, so obviously it’s a big problem for them. How significant is this problem for women? According the World Health Organization, over 500,000 women die each year in childbirth. And in Africa alone, as many as 3 million women a year are permanently handicapped by obstetric complications.

Some people have said that women have been having babies without obstetric help for thousands of years before doctors came along and ruined it with drugs and hectic deliveries. First of all, people have been helping women have babies for all of those years, only they weren’t called doctors, they were called midwives. And unfortunately due to rampant sexism in the middle ages, we have¬†a rather spotty¬†historical record of the science behind their amazing work until the physicians in the 17th century “medicalized” it. Second, those drugs and hectic deliveries have no doubt saved countless lives of mothers and their babies.

The home birth issue has been hotly debated in recent years. Do I think having a baby at home is irresponsible? Not if the attending midwife is aware of the facts and able to deal with a dangerous situation. If I had a uterus and it was my choice? I’d probably be at the hospital, although I tend to favor medical solutions over natural, homeopathic or faith-based ones in general, and I’m not a woman anyway, so I’m not sure what my opinion really means.

It’s an interesting thing, having babies. Me Mom and Santa ClausIt’s one of my favorite things to teach about in class. We’ve all been born and many of us will have babies of our own, so it’s immediately relevant and captivating to an audience. Everyone can imagine what their own mothers went through, and we should all thank them for taking on the challenge. There’s mine at right trying to make me not fear Santa Claus. I think we also owe a debt of thanks to the medical professionals who helped out our moms, and to the many others who continue to take on this uniquely human issue.

The Entire Animal Kingdom

Have you ever wondered how all of the animals in the animal kingdom are organized? Well, I did once, so I wrote it all down. I just found this in my “personal” folder at work. After reading this, it is clear I might have OCD. The details at each organizational level are limited to principal characteristics of that level (in layman’s terms for the most part), then further subclassification is provided in mostly just the lineages that lead to humans. Sorry all you fish lovers out there, I know this is kind of anthro-centric, but this would be a million miles long if every lineage was included out to the families. This is already ridiculous. So enjoy! You should be able to find your favorite animal somewhere in here. Although perhaps not the popular cat-frog hybrid shown above right. (Note the heading styles have to reset themselves a couple times for the multiple levels of organization.)

**Note: when I assembled this information long long ago, this was pre-genomics revolution. Genetic studies have significantly impacted the taxonomy of animals, so there are several “newer” phyla not represented here. One day I will attempt to update and correct this post accordingly. Don’t hold your breath though.

Kingdom Animalia:

  • Multicellular eukaryotes that characteristically ingest their food.
  • Cells are usually flexible
  • Except in sponges, cells are organized in tissues
  • Cells move during embryonic development forming a blastula (hollow sphere of cells)
  • Most animals reproduce sexually
  • Gametes (sperm and egg) fuse to form a zygote, and do not divide by mitosis (as happens in plants)

Subkingdom Parazoa:

  • Animals that lack definite symmetry, no tissues or organs

Phylum Porifera:

  • Sponges

Subkingdom Eumatozoa:

  • Animals with definite symmetry (radial or bilateral), definite tissues and organs

Phylum Cnidaria: 10,000+ species

  • Coral, Jellyfish, Hydra
  • Radial symmetry
  • Two body forms (polyps and medusae)
  • Digestive cavity with only one opening (things go in and out the same hole)
  • Stinging cells are unique to this phylum

Phylum Ctenophora: 90 species

  • Comb jellies and sea walnuts
  • Radial symmetry
  • Digestive cavity with an anal pore

Phylum Platyhelminthes: 13,000 species

  • Flatworms
  • Bilateral symmetry
  • No circulatory system
  • One-opening guts
  • Hermaphroditic

Phylum Nematoda: 500,000 species

  • Nematodes, Eelworms, Roundworms
  • Bilaterally symmetrical and unsegmented worms

Phylum Mollusca: 110,000 species

  • Snails, Slugs, Clams, Octopuses, Squids, Nautilus
  • Bilateral symmetry
  • Coelomate animals (containing body cavities)
  • Visceral mass and muscular foot

Phylum Annelida: 12,000 species

  • Earthworms, Leeches
  • Segmented, bilaterally symmetrical, protostome coelomates
  • Segments are divided internally by septa
  • Brain is developed
  • Closed circulatory system
  • One-way digestive system

Phylum Arthropoda: ~1,000,000 species

  • Bilaterally symmetrical protostome coelomates
  • Segmental body, chitinous exoskeleton
  • Digestive tract, Brain and paired nerve cord, Jointed appendages
Class Arachnida:
  • Spiders, ticks, mites, scorpions
Class Crustacea
  • Lobsters, crayfish, crabs, shrimps
Class Chilopoda
  • Centipedes
Class Diplopoda
  • Millipedes
Class Insecta
  • Complex mouth parts, three part body, six legs, trachea

Phylum Echinodermata: 6,000 species

  • Sea stars, brittle stars, sand dollars, sea cucumbers, sea urchins
  • Deuterostome coelomates
  • Radially symmetrical

Phylum Chordata: 45,000 species

  • Bilaterally symmetrical
  • Deuterostome coelomates
  • Notochord is present at some point of development
  • Pharyngeal slits, hollow nerve cord on dorsal side, and a tail

Subphylum Urochordata: 1,250 species

  • Tunicates, marine chordates that have notochord only in larval stage
  • Get food by ciliary action

Subphylum Cephalocordata: 23 species

  • Lancelets, permanent notochord, nerve cord, no internal skeleton, food by ciliary action

Subphylum Vertebrata: 43,700 species

  • Notochord is replaced by cartilage or bone (backbone)
  • Distinct head with skull and brain
Class Agnatha: 63 species
  • Lampreys and Hagfishes
  • Cartilaginous fishes, no jaw
  • Parasitic
Class Chondrichthyes: 850 species
  • Sharks, skates and rays
  • Cartilaginous fishes, sex organs present
  • Small pointy scales (denticles), no air bladders
Class Ostheichtyes: 18,000 species
  • Bony fishes
  • Bony skeletons, efficient fins and scales
  • Most have air bladders (regulate density to regulate depth)
Class Amphibia: 2,800 species
  • Salamanders, frogs and toads
  • Tetrapod, egg-laying, ectothermic
  • Gills as larvae, lungs as adults
  • Incomplete double circulation (non-closed ventricular system)
Class Reptilia: 6,000 species
  • Lizards, snakes, turtles, crocodiles
  • Tetrapod, ectotherm vertebrates with an amniotic egg
  • Lungs, covered with scales
  • Incomplete double circulation
  • Four legs are absent in snakes and some lizards
Class Aves: 9,000 species
  • Birds
  • Tetrapod, endothermic vertebrates
  • Forelimbs modified into wings
  • Amniotic eggs
  • Lungs, complete double circulation

Class Mammalia: 4,500 species

  • Tetrapod, endothermic vertebrates
  • Complete double circulation, often hairy skins
  • Monotremes: Lay eggs (Platypus)
  • Marsupials: Retain young in a marsupium
  • Placental mammals: Nourish young in the womb by way of a placenta (modification of amniotic egg)

Order Insectivora

  • Shrews, Moles, Hedgehogs

Order Chiroptera

  • Bats

Order Rodentia

  • Squirrels, Rats, Mice

Order Carnivora

  • Dogs, Cats, Bears, Weasels, Raccoons

Order Proboscidea

  • Elephants

Order Cetacea

  • Whales

Order Primata:

Suborder Prosimii

  • Lemurs

Suborder Anthropoidea:

Infraorder Platyrrhini
  • New world monkeys (South and Central America)
Infraorder Catarrhini
  • All other monkeys and humans
Superfamily Cercopithecoidia
  • Old world monkeys (Africa and Asia)

Superfamily Hominoidia:
  • Family Hylobatidae (Gibbons)
  • Family Pongidae (Orangs, Gorillas, Chimps, Bonobos)
  • Family Hominidae (Humans)