Asymmetrical features associated with anger

Don’t anger the asymmetric

After you read this piece, you will probably break out the measuring tape and try to figure out how prone to anger you are, because recent research indicates that anger can be measured in inches.

Using a clever ruse, researchers at Ohio State University found in 2004 that the more asymmetrical a person is in some physical features, the more likely that person is to become angry at rejection. In addition, the scientists found a role for testosterone and sex in these responses.

They duped 51 men and 49 women into thinking that they were attempting to raise money for a (false) charity. Participants had to make two phone calls in an effort to obtain a donation and expected to receive a reward if they were successful. Instead of the person on the other end of the phone being someone in the middle of his dinner, it was really a researcher, pretending to be a solicitee. At the first phone call, the solicitee pretended to be sympathetic, but politely said that he or she had no money to give. For the second phone call, the responder behaved rudely, saying the donation would be a waste of money. The first response was considered a low-provocation incident, and the second a high-provocation response.

Who hangs up phones any more?

When the unknowing study participants hung up the phone, the force of their hang-up was measured, as were their testosterone levels. Additionally, after the exercise, they had a choice of three letters to send to the people they had called; one letter was polite, one moderately pleasant, and the third accusatory and angry.

After collecting data on the ankles, foot width, ear height and width, palms, wrists, and fingers of the participants, the researchers looked for correlations between asymmetry of these characteristics and an angry response, as measured by the force of the telephone hang-up. They found that asymmetrical people became angrier and slammed the receiver more than symmetrical people. In addition, asymmetrical men hung up with more force under the low-provocation scenario, and asymmetrical women hung up with more force after confronting the rude responder.

Oh, testosterone and anger again?

Testosterone levels also played a role, with higher levels causing a more pronounced anger response, and again, the response showed a sex-bias. High-testosterone men were more likely to hang up forcefully after the low-provocation incident, and high-testosterone women after the high-provocation scenario.

What does it all mean? Are the asymmetric people sensitive to rejection, and thus, easily angered by it? Perhaps. But the researchers hypothesize that stress during embryonic development disrupts the embryo on several levels, from physical symmetry to neuronal connections. Scientists have long thought that shifts from symmetry during embryonic development—for example, the right-hand fingers developing a greater length than the left-hand fingers—occur because stressors send developmental signals awry. If the signals operate and are received correctly, both sides should develop the same way; but cigarette smoke, alcohol, and other stressors can disrupt these signals, and asymmetry—and quick anger—can be the result.

Testosterone and asymmetry

One intriguing finding of the study was that the asymmetry results reflected the testosterone levels of the participants. This outcome brings questions of the relationships among the hormonal parameters of development, their disruption, and later manifestations of these interactions.

If you’re wondering why men got so angry with the polite responder and women more so with the rude responder, here’s the researchers’ explanation: Men are quick to react with anger, but are not as comfortable as women with high-anxiety situations. So, when the tension amps up, men back off, but women may actually become more aggressive.

And those letters? More than a third of the participants wanted to send the rudest letter, regardless of their sex or levels of symmetry or testosterone. Perhaps they were merely foreshadowing the anger that now pervades American politics today.

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Bisphenol A: multisystem effects

These bottles were produced without BPA in response to concerns about the chemical. Photo via Creative Commons, attributed to Alicia Vorhees, thesoftlanding

Are endocrine disruptors stealing our future?

Endocrine-disrupting compounds are chemicals in the environment—usually compounds that we have introduced—that can alter normal hormone signaling processes. Often, exposure to these compounds has little immediate effect in adult animals, but it can have big effects on organisms during sensitive developmental periods, like embryogenesis. During embryonic development in vertebrates, steroid hormones govern many processes, and the fetal hormone environment is usually carefully calibrated to ensure that these processes go forward normally.

Tiny amounts, big changes

But many compounds disrupt these processes, knocking them off track and resulting in development that is unusual or abnormal. For example, male alligators exposed in the egg to these compounds—which often persist in fatty tissues or yolk—emerge with serious penile abnormalities that can affect their ability to reproduce. The banned pesticide DDT is probably one of the best-known of these compounds, and exposure to it or its metabolites has been shown to disrupt hormone signaling to the point of altering sex development completely.

When we think of hormones, we often think of puberty, the time when hormones seem to govern our every move. When we think of estrogen, we probably think “female” because estrogen has historically been considered the “female” hormone. What you might not know is that estrogen, which is made in the ovaries, is also made in our brains during embryonic development. In mammals, appropriate male development appears to require neural estrogen synthesis. When estrogen synthesis in embryonic mammals is blocked, the males that develop do not exhibit typical male behaviors when they reach reproductive maturity.

Bisphenol A: ubiquitous chemical

Among the compounds that have been identified as endocrine disruptors is bisphenol A (BPA). In the United States, we produce about 2 billion pounds of BPA a year. Previous studies have demonstrated that BPA can disrupt thyroid signaling to the point of affecting the thyroid’s role in appropriate brain development. In addition, BPA has been linked to feminization of reptiles. Some scientists were aware of BPA’s hormone-activity potential as far back as the early twentieth century.

But because no one took that knowledge or its potential seriously—the field of endocrine disruptors is relatively young—BPA has found its way into almost every aspect of our lives. It is in the dental sealants we put on our teeth to keep the cavities at bay. It is in the lining that coats the insides of food cans to keep the metal from rusting. It is in the hard plastic that we use for baby bottles and teething rings. And it can leach from these products into the food that we eat. BPA is found at high levels in some pregnant women, and it appears to accumulate in higher concentrations around the umbilical cord and in the fetal amniotic fluid.

BPA and effects on the developing brain

Work from Yale and from researchers in Japan also points to some potentially serious effects on the brain. Part of the role of estrogen in brain development is facilitating synaptic connections in a crucial brain area called the hippocampus. The hippocampus is the center where neurons organize that will later be activated to produce sex-appropriate activity in vertebrates. It is also the area of the brain involved in the formation and retention of memory.

The researchers found that small doses of BPA—doses that fall within EPA-approved levels for exposure—can inhibit hippocampal synaptic formation in rats, counteracting the effect of estrogen. That BPA is an estrogen inhibitor could be serious for our brains if the results translate into human effects. As we age and our endogenous estrogen levels decrease, for example, the hippocampus suffers and our memory does, too. If BPA sets this process in motion even earlier, hippocampal—and thus, memory—decline may occur even earlier.

Rodents, monkeys, and people–oh, my

A recent report in Environmental Health Perspectives concludes that rodents, rhesus monkeys, and people all exhibit similar pharmacokinetics with BPA and that exposures may be far greater than previously calculated. Other recent studies suggest effects on sugar metabolism related to diabetes, an association with polycystic ovarian syndrome in rats, and a relationship to the development of asthma in a mouse model.

Cockroaches are collective food critics

Collective communication guides cockroach dining decisions

Ever drive by a restaurant with an empty parking lot and avoid it yourself because, well, no one else was eating there? If so, you’re not much different from cockroaches. They also appear more attracted to food resources if other cockroaches dine there, as well.

Yes, cockroaches creep me out, too

They’re the only animal about which I’m phobic, but who could resist a story like this? A new study published in Behavioral Ecology and Social Biology has found that cockroaches communicate with each other about preferable food sources, much as people do.  Rather than doing it through visuals of empty parking lots or restaurants or via a critic’s recommendations, however, they probably use pheromones. So, there may be a cockroach pheromone or suite of the chemicals that says, “Hey, this pile of garbage is the best in town!”

The researchers who determined this used a couple of piles of food. The roaches collectively would spend more time and in greater numbers at one pile of food over another. Even more interesting–at least to cockroach researchers–the bugs would linger longer at the dining source if other roaches were there, too. Peer pressure, it appears, is not only a human phenomenon.

It’s not limited only to cockroaches in the insect world, either. There are many other examples of insect chemical communication guiding collective behavior. The most famous is probably the honeybee waggle dance, which the animals use to indicate which way to go to find the best food resources.

Why should we care?

Why would researchers go to the trouble of monitoring cockroach choices over piles of food? One reason is that if we identified the pheromone that communicates “good food pile” to cockroaches, we could use that to lure them into our little pest-control traps. Ever diabolical that way, we humans are. There are some things not even cockroaches can do.

Pesticide link to ADHD

It’s correlation, not causation

A common pesticide and metabolites have been linked in a large study to ADHD, an attention deficit disorder characterized also by hyperactivity and impulsivity. ADHD has previously been associated with specific genes and even hailed as a one-time advantageous evolutionary adaptation. But many neurological differences likely will trace to an interaction of genes and environment, or, in fancy science talk, a multifactorial causality.

But it’s also not a surprise

This study looked at metabolites in the urine of more than 1000 children, 119 of whom had ADHD. It’s not mechanistically outre to think that pesticides designed to send a pest’s nervous system astray might have a similar effect on vertebrate systems. But this study showed links, not mechanisms, which often is a necessary first step to justify further pursuing a hypothesis. The researchers found that levels of specific metabolites of organophosphate pesticides are associated with an increased risk–by as much as two-fold–of developing ADHD.

Join the ever-expanding club

If further research does identify a mechanistic tie to this identified correlation, then these pesticides will join an ever-growing suite of chemicals we’ve introduced into the environment that influence our endocrine and neural systems. These chemicals are called endocrine disruptors.

The mysterious reproductive life of the giant panda

Photo credit: Mehgan Murphy, Smithsonian’s National Zoo

National Zoo’s giant panda had pseudopregnancy

National Zoo officials announced today that Mei Xiang (link has Panda Cam!), who had been monitored for several months for pregnancy, was not pregnant after all. Instead, she was experiencing a common feature of panda endocrinology, the pseudopregnancy.

Panda pseudopregnancy a common event

How could officials not be sure for months about whether or not the pregnancy was real? Panda pseudopregnancy so perfectly mimics an actual pregnancy that even hormone levels follow those of a real gestation. Staff had been monitoring her by ultrasound and blood testing, and even though ultrasound had yet to show a viable fetus, whether the pregnancy was real or pseudo was not confirmed until the hormones wrote the final chapter.

Pseudopregnancy hormones like pregnancy hormones

Late this month, Mei Xiang showed a drop in progesterone hormone. When hormone levels hit baseline in a possibly pregnant panda, one of two things can happen: a birth, or confirmation of pseudopregnancy. The progesterone decline set the clock on a 24-hour watch to see if Mei Xiang would bear a cub. She didn’t.

Ovulation once a year!

Giant pandas ovulate only once a year. Regardless of whether conception occurs, the female panda will appear pregnant, behave as though she is pregnant, and register the hormone patterns of pregnancy. If conception does not occur in that one annual opportunity, a female panda will almost always enter into a pseudopregnant state. Mei Xiang has done that five times. She’s also experienced a genuine pregnancy, bearing a cub in 2005 that now lives in China as part of a panda breeding program.

Panda soon to be back for public viewing

Mei Xiang has been sequestered during her pseudopregnancy, but her habitat at the zoo will now open again for public viewing. During her pseudopregnancy, her behaviors included reduced activity and appetite. These are now both expected to increase.

For your consideration

Pandas have some unusual life history strategies, including being food specialists and often accidentally suffocating their offspring. And, it appears that many ovulations result in pseudopregnancy. What might be an explanation for why pandas are so prone to entering a pseudopregnant state if conception does not occur? Could the behaviors that accompany the pseudopregnancy have anything to do with it?

In pandas, the hormones of a pseudopregnancy are similar to those of a real pregnancy. What pathways underlie the female’s production of these hormones of pseudopregnancy?

Women can also experience pseudopregnancy, sometimes referred to as “hysterical pregnancy.” It can even involve abdominal distention and in some cases, hormonal changes. What are some of the physiological underpinnings of a pseudopregnancy in women?

Finally, dogs and mice are also known for having pseudopregnancies. Do you think the pressures that result in these pseudopregnancies are similar to those that result in a false pregnancy in the panda? Why or why not?

Leeches model reproductive behavior

No, not that kind of modeling.

Leeches have a bad reputation because they dine on blood. Even forgetting for the moment such human-designed culinary delicacies as blood pudding or blood sausage, let’s just say that sucking blood does not necessarily an incubus make.

Not just blood-sucking boneless terrors

In fact, leeches have recently made a comeback in the shape–the slimy, creepy shape–of their use as medical therapy. Their former role was to suck bad humors from the body. Today, with our improved understanding of molecular biology and relegation of humor to Jon Stewart, leeches serve a different purpose. Pracititioners encountering venous insufficiency and premature clotting during certain surgeries can apply leeches–and their salivary anti-clotting factors–locally to address the problem. By the way, the medicinal use of leeches–which has a history stretching back for milliennia–is called hirudotherapy.

Model leeches

And leeches also make an oxytocin-related hormone called hirudotocin that plays a role in their reproductive behavior. A reproductively aroused leech, it seems, undergoes a maneuver that involves a sloooow, five-minute rotation of its body. The rotation results in alignment of reproductive pores with complementary pores on a presumably adjacent partner.

Animal behavior results, at its core, from an interaction of hormones and the nervous system. But linking the two directly and assessing the influence of hormones on nerves has proved elusive in more complex animals. Leeches, though, have a nervous system more basic than a mosquito’s. And an injection of hirudotocin yields leech reproductive rotation within minutes, accompanied by a leechy mouthing of the potential reproductive partner. In the world of animal behavior research, this is exciting stuff.

Sliced leech anyone?

To track the effects of this hormone through the animal’s nervous system, researchers at Caltech and UCSD examined nervous response to hirudotocin in slices of leech. Then, they did the ultimate direct assessment, removing all of the leech except the nervous system. This approach allowed them to trace directly the activation of the nervous sytem that led to the corkscrewing muscle movements of leech reproductive behavior.

Their next step will be to use voltage-sensitive dyes to detect electrical nerve signals along these paths to see which ones are involved in maintaining the behavior. They may not be drawing out bad humors any more, but leeches are certainly doing their part in helping us tease out the links between hormones and behavior.

For your consideration

Why is it so difficult to link a hormone and a behavior, especially in vertebrates?

This article says that animal behavior is a manifestation of the interaction of hormones and the nervous system. Can you think of some other examples of this interaction?

Animals are not the only organisms that use hormones. Plants do, too, but they lack a nervous system. Identify some plant hormones and determine what plant systems they influence.

Autism and oxytocin: facilitating social interaction?

Oxytocin: Hormonal bliss

Oxytocin is a peptide hormone the brain produces in the posterior pituitary. It appears to play many roles in our lives, starting with birth, when it manifests one of the few examples of positive feedback during labor: The more you make, the more you make, until the uterus, the most powerful muscle in the body, contracts sufficiently and frequently enough to push a baby out of an area through which you’d think no baby could fit. In fact, in many childbirths, a synthetic form of oxytocin is used to facilitate labor. Following the birth experience, oxytocin works further magic by facilitating the mother-child bond.

Oxytocin doesn’t stop there, however. It also appears to function in facilitating trust among adults. One study found that a whiff of the hormone caused study participants to be more likely to continue in their trusting behavior, even if the target of their trust had betrayed them.

Social deficits characterize autism

Autism is a term that describes a broad spectrum of developmental manifestations that can include problems with verbal communication, social interaction, and motor skills. Some research has indicated that people with autism may have comparatively low levels of oxytocin, which has led to the hypothesis that boosting these levels might facilitate a greater social understanding for them.

Oxytocin boosts social skills?

A recent study from France published in the Proceedings of the National Academy of Sciences appears to bear out this idea. Caveats include the fact that while it was a controlled clinical trial, the study involved only 13 autistic people who had been diagnosed either with high-functioning autism (HFA) or Asperger’s (and 13 age-matched non-autistic participants). The low number of participants and the mix of diagnoses (there is controversy about the overlap or equivalency of HFA vs. Asperger’s) mean that these findings qualify as suggestive only. In addition, the authors in their paper offer some assumptions about autism that do not necessarily apply or apply in equal measure among all autistic people.

With those caveats in mind, the study findings remain intriguing. The autistic participants exhibited a greater awareness of social dynamics after exposure to oxytocin, in addition to also having higher measured levels of the hormone in their blood. Oxytocin, like most hormones, does not persist for long, and these effects would be expected to be only transient.

Is it direct improvement of social function or diminished social anxiety?

Among the assumptions the paper authors make about autism, one is that autistic people do not engage in eye contact and that this indicates a lack of social engagement. Another assumption is that the autistic participants were unable to understand the social dynamics without oxytocin because of a social incapacity.

Other studies, however, suggest a relationship between increased oxytocin and reduced social anxiety. Social anxiety can be a paramount manifestation in autism, and social phobias in general translate into an apparent inability to socialize. So the question that remains is, Did the oxytocin in this study somehow directly affect social capacity in these participants, or did it lower their social anxiety sufficiently enough that they could more comfortably engage in social interpretation?

Ideas for questions

The brain releases oxytocin from the posterior pituitary. Can you identify the feedback pathway that causes this release? What other hormone or hormones does the posterior pituitary release? What about the anterior pituitary?

Oxytocin is involved in parent-child bonding. Were you aware that this “natural” bond has a hormone underlying it? Do you think that this applies only in human parent-child bonding? Research this question and explain why or why not.

One problem autistic people sometimes encounter is being too trusting because they do not recognize when someone is cheating them. Given findings in other studies that oxytocin facilitates trust in people even when they have experienced betrayal, how do you think these results might affect any effort to apply oxytocin therapeutically in autism?

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