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November 2012 Archives

Why Are Crocodiles so Ugly?

Crocodiles are nasty critters. They're built like armored tanks; they eat almost anything -- including humans, pet dogs, footballs and diapers; and, if you haven't noticed, their skin is cracked and ugly. Now, scientists at the University of Geneva think they know why. 

SaltwaterCrocodile.jpg
Lotion can't help this cracked skin.

Reptile skin is scaly. The spatial layout of the scales is largely controlled by genetics, although other positional factors can be involved. On the head of a snake, for instance, the scales overlap and are symmetrical on both sides of its face. If there are three shiny scales beneath one eye, you will find three shiny scales beneath the other eye.

But that's not true for crocodiles. While the scales on the rest of its body conform to a set of genetic rules in regard to layout, the scales on its head do not. Instead, they are non-overlapping, irregularly shaped, randomly positioned, and asymmetrical on both sides of its face. Why is a snake's face so aesthetically pleasing, while a crocodile's face looks like an old leather purse?

The authors believe that the positions of the head scales on a crocodile are largely determined by physical forces. As the underlying skeleton rapidly grows, the tough, keratinized skin of the crocodile cracks in response. Of course, genetics controls some of this (e.g., skull shape), but it also appears that randomness plays a big role in the placement of head scales.

And that's why crocodiles have a face that only a mother could love.


Source: Michel C. Milinkovitch, Liana Manukyan, Adrien Debry, Nicolas Di-Poï, Samuel Martin, Daljit Singh, Dominique Lambert, Matthias Zwicker. "Crocodile Head Scales Are Not Developmental Units But Emerge from Physical Cracking." Science (Published Online November 29, 2012) DOI: 10.1126/science.1226265
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November 2012 Archives

How Do Antifreeze Agents Work?

Preventing ice crystals from forming in undesirable locations is a constant challenge. We add salt to icy roads, and we put antifreeze (a mixture of ethylene glycol and water) in our cars' radiators to prevent them from freezing. The cells of some organisms produce antifreeze proteins to prevent the lethal formation of ice crystals. All of these processes work because of a chemistry concept known as "freezing-point depression," i.e., the lowering of a freezing point.

The extent of freezing-point depression is based on two factors: (1) The number of dissolved particles present (a feature known as a "colligative property") and (2) The nature of the dissolved particle. Exactly how this process works -- even including how water freezes -- is not well understood.

Researchers at New York University are trying to shed light on freezing-point depression, specifically which properties of antifreeze agents cause the biggest drop in freezing point and the greatest reduction in the growth of ice crystals. They used short organic polymers called peptoids, which are similar in structure to peptides (short proteins). (See diagram.) 
peptoids.jpg

The N is "nitrogen" and O is "oxygen," while the "R" stands for some generic organic side chain. The molecule is shown in brackets to indicate that the structure can repeat over and over again. By changing the R group and/or the number of repeating units, the scientists could systematically analyze how this affected the freezing point of water and the growth rate of ice crystals.

They analyzed three different R groups: methyl (-CH3), ethyl methyl ether (-CH2CH2-O-CH3) and ethyl alcohol (-CH2CH2OH). For controls, they used glycerol and a short peptide made from repeating units of serine, a type of amino acid similar in structure to the peptoid they made using ethyl alcohol.

They found that a peptoid with 3 repeating units bearing the ethyl alcohol side chain was the most effective experimental molecule because it both lowered the freezing point of water and greatly slowed the growth rate of ice. Further, they found that this had less to do with colligative effects (i.e., the number of molecules present), and more to do with the inherent nature of the molecule itself. In other words, its specific structure was key to these abilities.

Bizarrely, if the molecule had 4 or 5 repeating units, the freezing point of water was still lowered, but the growth rate of ice was increased over that of water alone. However, if there were 6 repeating units, once again, the growth rate of ice was decreased.

This research demonstrates just how complex the seemingly simple process of water freezing actually is. Additionally, the authors hope that they have laid the foundation for further investigations into discovering the most effective antifreeze molecules.

Diagram: Peptoids via CEM

Source: Mia L. Huang, David Ehre, Qi Jiang, Chunhua Hu, Kent Kirshenbaum, and Michael D. Ward. "Biomimetic peptoid oligomers as dual-action antifreeze agents." PNAS. November 19, 2012. doi: 10.1073/pnas.1212826109
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November 2012 Archives

Interspecies Airborne Transmission of Ebola

Ebola virus (EBOV) causes a deadly hemorrhagic fever. The symptoms initially resemble a very bad case of influenza, but they progress to include a rash, splotchy purple skin, and internal and external bleeding. Blood loss is not the primary cause of death, however. Instead, death is due to circulatory shock from low blood pressure and other complications. Experimental treatments are being developed, but currently, there is no official regimen.

There are 5 known species of Ebola: Bundibugyo, Ivory Coast, Reston, Sudan, and Zaire. All of them can cause illness and/or death in humans, with the exception of Reston (which was partially the subject of the bestselling book The Hot Zone). As of May 2012, the World Health Organization reported 21 major outbreaks of Ebola since 1976. Zaire Ebola tends to be the most deadly, with case-fatality rates as high as 90%.

For people, the primary route of transmission is via direct contact with infected humans or animals or their fluids. Airborne transmission was considered theoretically possible, but not a major route of transmission.

That might change now.
ebolatransmission.jpg

Reporting in a new study in Scientific Reports, researchers infected pigs with Zaire Ebola. (In pigs, Zaire Ebola causes a respiratory tract infection, but it is not lethal.) They were placed in close proximity to, but not in direct contact with, four cynomolgus macaques (crab-eating monkeys) located in stacked cages. (See photo.) After 9 days, all the pigs cleared the infection. The monkeys did not fare as well. They all became infected with Ebola virus and were euthanized.

Furthermore, the authors also detected Ebola RNA in air samples taken from the laboratory.

While the results could not conclusively demonstrate that the monkeys weren't infected via some other route (e.g., by touching an infected saliva droplet and rubbing their eyes), other evidence -- including post-mortem analyses -- strongly suggest airborne transmission. 

The authors conclude that farms and other settings which house animals together could be sites of interspecies transmission of Ebola. And of course, their finding suggests that animal-to-human and human-to-human transmission of Ebola can happen through the air.

A couple of things to keep in mind: First, it is very likely that Ebola has always had this ability. However, since most cases of Ebola in humans probably occurred via direct contact, airborne transmission played only a minor role. Second, the pigs and monkeys were housed together for several days, and it is very likely that prolonged exposure is required for airborne transmission.

So, it's not time to panic. But, if you are the panicky type, then definitely don't watch this movie.

Source: Hana M. Weingartl, Carissa Embury-Hyatt, Charles Nfon, Anders Leung, Greg Smith & Gary Kobinger. "Transmission of Ebola virus from pigs to non-human primates." Scientific Reports 2, Article number: 811. November 15, 2012. doi:10.1038/srep00811
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November 2012 Archives

How Do Feminists Explain Immunology?

In certain circles, it is politically incorrect to suggest that men and women are different. (Just ask former Harvard president Lawrence Summers.) Ignoring the entire field of biology, feminist icon Simone de Beauvoir famously philosophized that, "One is not born, but rather becomes, a woman," implying that social constructs hoisted upon women by a patriarchal society explain why women become who they are.

That ideology still persists today.

According to Amazon, the book Delusions of Gender, written by Cordelia Fine, "debunks the myth of hardwired differences between men's and women's brains...[and] gives us a glimpse of plastic, mutable minds that are continuously influenced by cultural assumptions about gender." Basically, it's Simone de Beauvoir's feminist philosophy applied to neuroscience. Fine even uses the word "neurosexism" to disparage research which shows differences between male and female brains.
shutterstock_110533712.jpgOur immune systems are different.

However, as I discuss in my new book, Science Left Behind (in a chapter titled "Boys Have Wee-Wees and Girls Have Hoo-Hoos") the scientific consensus simply does not support her ideological viewpoint. Yet, many neuroscientists are afraid to openly discuss gender differences over the fear of being labeled "sexist" by people like Cordelia Fine.

An article in Slate describes how this timidity has outraged female scientists, two of whom "called the aversion to studying innate differences anti-scientific and an impediment to understanding mental illness in women."

In addition to this growing scientific backlash, feminists have another problem to contend with: immunology.

A new review published in the journal BioEssays describes how men and women respond differently to viral infections. From the abstract:

The intensity and prevalence of viral infections are typically higher in males, whereas disease outcome can be worse for females. Females mount higher innate and adaptive immune responses than males, which can result in faster clearance of viruses, but also contributes to increased development of immunopathology. In response to viral vaccines, females mount higher antibody responses and experience more adverse reactions than males. The efficacy of antiviral drugs at reducing viral load differs between the sexes, and the adverse reactions to antiviral drugs are typically greater in females than males. Several variables should be considered when evaluating male/female differences in responses to viral infection and treatment: these include hormones, genes, and gender-specific factors related to access to, and compliance with, treatment. Knowledge that the sexes differ in their responses to viruses and to treatments for viral diseases should influence the recommended course of action differently for males and females. [Emphasis added.]
It is simply not possible to blame immune differences on socially contrived gender roles. Indeed, from genetics to psychology, research shows that men and women are simply different. Rejecting this is denying biological reality.

However, none of this is to imply that social factors and cultural norms don't play a role in shaping male and female behavior. Of course they do. But to throw out accusations of sexism against biologists for simply reporting their data hinders medical progress. As a society, we should embrace scientific reality, not comfortable ideologies.

But I could be wrong. Maybe I'm just an immunosexist.

(Photo: Boys and Girls via Shutterstock)
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November 2012 Archives

A Voter's Guide for the Scientifically Savvy

In case you haven't noticed, there is an election coming up on November 6. A couple of states have issues on the ballot which -- either directly or indirectly -- are related to science. What are they, and how should a scientifically savvy person vote?

California's Proposition 37: GMO Food Labels. Voters in California will have to decide whether or not to label food containing genetically modified ingredients. This is a topic we have covered extensively on RealClearScience. (See our archive on Food Labels and GMOs.) The scientific consensus is that this referendum is a very bad idea. Pro-label activists demand "the right to know" what is in their food, but putting labels on food that mislead consumers about the nature of biotechnology would not advance that goal. That is why the American Medical Association and the American Association for the Advancement of Science -- the world's largest general scientific organization -- are opposed to GMO food labels.

It should also be noted that among Proposition 37's biggest supporters are merchants of organic food. If this law were passed, any food that contains GMOs would be legally banned from using the word "natural," essentially trademarking the word for the organic industry. (And since 75-80% of food already contains one genetically modified ingredient, this law would affect almost every item in the grocery store.) 121101_i_voted_ap_605.jpg

At its heart, Proposition 37 is nothing more than a pseudoscientific marketing ploy by the organic industry. The scientifically savvy voter would vote NO on Proposition 37.

Marijuana Legalization in Washington, Oregon, and Colorado. Blazing up a doobie isn't directly related to science. While they may not be as bad for your lungs as cigarettes, scientists know that smoking marijuana still isn't good for you. It can lead to mental impairment which resembles schizophrenia, and teenagers who use it may see a drop in their IQ. So, what scientific issue is at stake?

Economics. Sure, that's the dismal science, but let's welcome the field into the scientific community for the sake of argument. Keeping marijuana illegal reduces the supply of marijuana, which, according to the economic laws of supply and demand, increases the price. A high price for marijuana incentivizes drug dealers to sell it, and it also incentivizes people to commit crimes in order to scrounge up enough money to buy it. Legalizing the drug would bring it out of the underground economy into the daylight, and that would increase supply. A greater supply would lead to a drop in price, making it less attractive to drug dealers. Very possibly, there would be a concomitant drop in drug-related crime.

By most measures, the War on Drugs has been a complete failure. Maybe it's time to try a market-based economic solution. So, the scientifically savvy person would vote YES on marijuana legalization.

Barack Obama vs. Mitt Romney. Barack Obama promised to "restore science to its rightful place," and in a flourish which took presidential rhetoric to new heights, noted that his election would mark "the moment when the rise of the oceans began to slow and our planet began to heal." But, as I detail in my new book, Science Left Behind, the President has placed politics before science on a whole host of issues -- from vaccines and environmental policy to nuclear waste storage and clean energy. (You can read an excerpt of the book here.) And, unfortunately, the Obama campaign didn't seem to take the online Science Debate quite as seriously as did the Romney campaign.

Having said that, there isn't much reason to believe that one candidate would be better for science than the other. Romney doesn't have an extensive record on science to examine, but we do know he flip-flopped on climate change. After all, he is a politician.

When science and politics collide, more often than not, science loses. The scientifically savvy voter would understand that neither political party has a monopoly on being "pro-science."

(Image: AP photo)
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