Science-- there's something for everyone

Tuesday, May 31, 2011

Girls not getting on kidney transplant list

According to a study led by Stephanie Nguyen from the University of California, Davis, girls are much less likely than boys to get on the kidney transplant waiting list. This was true at each stage of diagnosis. The most common reason given for the delay in being registered on the list was that the patient’s ‘work-up was in progress.’

Nguyen and her colleagues reviewed data from almost 4500 pediatric renal patients. Not only were girls less likely to be placed on the transplant list when first undergoing dialysis, but even twelve months after dialysis they were still less likely to be on the list than boys. In addition, boys were more likely to have pre-emptive transplants, receiving new kidneys before undergoing dialysis.

These delays can have critical repercussions for the patient’s survival. The longer a child is on dialysis, the more likely it is that he or she will reject the new organ. In fact, the best outcomes are for patients who never underwent dialysis at all. This is true for adults as well, by the way.

Obviously, renal specialists need to be cognizant of this discrepancy and take steps to eliminate it.

Monday, May 30, 2011

Shield the body to protect the brain

In combat conditions, helmets are of course essential to protect soldiers’ brains. However, body armor can also go a long way toward protecting brains. Vassilis Koliatsos of Johns Hopkins University and his colleagues have found that shock waves directed at the torso can have severe repercussions on the brain.

When a body encounters a shock wave, as from an explosive devise, that impulse can ripple through the chest and up to the brain. The explosion creates an increase in fluid pressure that travels up into the axons, particularly those in the cerebellum/brainstem and the optic tract. Fortunately, wearing body armor can ameliorate these effects, as shown by blast tests on mice.

When the researchers compared mice that were fitted with body armor (which conjures an amusing visual) to those who were unprotected, the differences were stark. After being subjected to a shock wave (at a force designed to induce a mild traumatic brain injury), the unprotected mice took twice as long to socialize with new mice and were clumsier. In contrast, the shielded mice performed just like mice that had not been exposed to the blast. Remember, these mice were not wearing head protection, but only body armor. In fact, adding a helmet offered no additional protection.

The authors caution that helmets are still critical to protect soldiers from direct impact to the head. This study makes it clear that in order to protect the head, you have to protect the torso as well.

Sunday, May 29, 2011

Another Earth-like planet from Gliese 581

Astronomers are on the lookout for exoplanets that could sustain life. Such a planet would have to have a rocky (as opposed to gaseous) surface, and orbit its star at a distance that allowed for the presence of liquid water. In their search, astronomers led by Robin Wordsworth of the Laboratoire de Météorologie Dynamique have turned once again to Gliese 581.

At just over 20 light years from Earth, the red dwarf Gliese 581 is one of our closest neighbors. The star is known to have at least four planets, several of which have been of great interest. In particular, astronomers once believed that the planet Gliese 581g might be about the same size as Earth with an orbit that placed it well within the habitable zone. Unfortunately, Gliese 581g may not exist, which would be drawback for sustaining life. Since then, astronomers have taken a second look at another Gliese 581 planet: Gliese 581d.

Gliese 581d was originally discounted as an Earth-like planet because it’s too far from its star (receiving less than a third of the starlight that Earth receives from the sun) and may be tidally locked (no longer rotating, but keeping one side of the planet in perpetual darkness). However, computer modeling now indicates that the planet might have a stable and life-sustaining climate. If Gliese 581d has a thick carbon dioxide atmosphere (which is not unlikely), the mostly red light from that star could penetrate the atmosphere and keep the underlying planet warm and cozy. Wind simulations show that heat absorbed on the day-side could be redistributed over the whole planet.

Schematic of the global climate model used to study Gliese 581d. Red / blue shading indicate hot / cold surface temperatures, while the arrows show wind velocities at 2 km height in the atmosphere.

Credit: © LMD/CNRS.

At this stage of the game, finding an Earth-like planet requires a lot of speculation and computer modeling. However, because Gliese 581 is so close, the astronomers are hopeful that we’ll one day have telescopes powerful enough to visually examine its planets. That should make things really interesting.

Saturday, May 28, 2011

Just for fun: Ant movement

New Scientist uploads science videos on various topics. For example, the video below compares the movement of ants to that of liquids.

Friday, May 27, 2011

DNR orders associated with poor surgical outcomes

DNR (Do-Not-Resuscitate) orders are intended to prevent doctors from going to extraordinary efforts to prolong a failing patient’s life. Nevertheless, patients who have given such orders often do have surgical or other procedures to decrease pain or treat non-life threatening issues. If so, they may wish to temporarily rescind that DNR order before going under the knife. According to a study by Hadiza Kazaure, Sanziana Roman and Julie Sosa from Yale University School of Medicine, having a DNR order significantly decreases your survival rate.

The doctors compared outcomes in 4128 adult DNR patients to those of an equal number of age and procedure-matched non-DNR patients. The DNR group had longer hospital stays, more complications, and most important, more deaths than the non-DNR group. In fact, almost three times as many DNR patients died within 30 days of surgery as non-DNR patients. And these were for the same types of treatments.

It’s not clear why having a DNR order can be so hazardous. One possibility is that patients who have such orders don’t expect to live as long as their cohorts, and this becomes a self-fullfilling prophecy. Alternatively, doctors may subconsciously come to the same conclusion and fight harder to maintain a patient without a DNR order. In any case, the correlation between DNR orders and poor outcomes must be further analyzed.

Thursday, May 26, 2011

A cluttered mind can’t remember

As we age, it becomes more difficult to remember things. According to Concordia University researchers, that’s largely due to our increasing inability to forget inconsequential things. Those irrelevant bits of information clutter up our minds and slow down our learning processes.

The scientists, led by graduate student Mervin Blair, put about 60 people through a series of memory tests. Half the volunteers were around 23 years old, the other half were around 67. Among other recall tests, both groups were given a sequential task in which information required for one step became irrelevant at the next step. Not surprisingly, the seniors had reduced working memory when compared to the younger group. However, the older individuals also had a harder time eliminating unnecessary data from their consciousnesses. The accumulated clutter of thoughts made it that much harder for them to process and remember new information.

Apart from storing our memories in Dumbledore’s pensieve in order to free up space, there’s not that much we can do to de-clutter our minds. Relaxation exercises may help to a point, but ultimately a longer more memory-filled life equates with a harder time discriminating between thoughts that are no longer important and those that must be kept.

Wednesday, May 25, 2011

For quick reduction in liver fat, limit carbs

Patients suffering from nonalcoholic fatty liver disease are usually advised to reduce the amount of fat in their livers via diet. Jeffrey Browning and his colleagues from the University of Texas Southwestern Medical Center compared two common dietary practices to see which yielded the quickest results: reducing total calories, or only reducing carbohydrates. After two weeks, patients who had limited carbs showed greater improvement than those who had limited total calories.

The researchers divided 18 people into two groups. The first group was put on a low-carb diet (less than 20 grams of carbohydrate/day), and the second on a low calorie diet (1200 calories/day for women, 1500 calories/day for men). Each group had their meals prepared by the UT Southwestern's Clinical and Translational Research Center kitchen to ensure compliance. Participants in both groups lost an average of ten pounds during the two-week trial. However, the amount of liver fat, as determined by hepatic triglyceride levels, was significantly lower in the low carb group.

Reducing carbohydrates rather than total calories is not necessarily the best diet plan for everyone. Even in this study, both diets yielded equivalent weight loss. However, based on this small study, for quick reduction in liver fat though, limiting carbs does seem to be the way to go.

Tuesday, May 24, 2011

Humans have three enterotypes

Thanks to the efforts of 85 researchers from more than ten countries, we have a better understanding of the ecosystem that is the human gut. It seems that people from the Americas, Europe and Japan all have one of three gut environments, or enterotypes.

Each enterotype, like any ecosystem, is the sum of all the types of flora and fauna within that system. In this case, that flora and fauna are all microscopic. You may be wondering how the researchers determined what kinds of flora were in each person’s intestinal tract. After all, many of these microbes have never been observed, let alone grown in a lab. I’ll let the words ‘sequenced faecal metagenomes’ sink in for a minute. Yes, they sequenced DNA from stool samples.

When they compared results from 22 people living in four different countries, they found that the country of origin did not matter. As with A, B, O blood types, the three enterotypes were found at each location and did not seem to discriminate between sex, weight or age. It’s not clear why this should be. It could be that each individual is randomly colonized by a package of flora soon after birth.

There are a few caveats. For one thing, none of the tested volunteers were from non-industrial cities where the diet and lifestyle, and thus the gut flora, might be completely different. Also, 22 is a very small sample size, even when combined with an additional 17 people form earlier studies.

Nonetheless, if this result is valid, it could have widespread implications for how we eat and how we treat illnesses. For example, enterotype 1 produces more vitamin B7 (biotin) and enterotype 2 more vitamin B1 (thiamine). Knowing your enterotype might one day allow for individualized diets. In addition, rather than prescribing antibiotics that kill all your intestinal microbes, doctors might give you a cocktail containing your own enterotype mix in an effort to outcompete the bad bacteria.

Hat tip: The Skeptics' Guide to the Universe.

Monday, May 23, 2011

The best of places and the worst of places

Paradoxically, the happiest places on Earth seem to have the highest suicide rates. Researchers led by Andrew Oswald of the University of Warwick attempted to analyze this conundrum.

For this study, the authors used the United States as a stand-in for the rest of the world. Although extremely diverse, the U.S. does have a unifying language, making it easier to make comparisons. The researchers sampled one million Americans on their suicidal tendencies, if any, and a different 1.3 million Americans on their life satisfaction, if any. They found the same correlation as with the world data, namely that the happiest states tended to have higher suicide rates than the most miserable states.

For example, after adjusting for factors like education and employment, Hawaii is number two in life satisfaction, but has the fifth highest suicide rate. Nevada has the lowest suicide rate in the nation, but is ranked 28th in life satisfaction. New York, the most miserable state, had the 9th lowest suicide rate. The honor of having the highest suicide rate went to West Virginia, which was 34th in happiness, and the happiest state was Louisiana, which was 40th in suicides. While there’s no one-to-one inverse relationship between happiness and suicide rates, these data do suggest a trend.

Although no clear explanation was presented for the discrepancy between average regional happiness and suicide rates, the authors suggest one possible cause. They propose that the unhappy minority living within a mostly happy region are made all the more miserable by comparison with their blissful neighbors.

Sunday, May 22, 2011

Self-healing material

Researchers from Case Western Reserve University and from the University of Fribourg have developed a new substance that can heal itself of scratches when exposed to UV light.

The material in question is called a ‘metallo-supramolecular polymer’. A polymer is simply a long chain of smaller molecules. For example, a protein is a polymer of amino acids. In this case, the smaller molecules, which can vary depending on needs, are attached to one another via metal ions. Upon exposure to UV light, the metal ions absorb the light energy and heat up, in effect ungluing the polymer chain at that site. The components of the polymer are temporarily free to flow together, eliminating cracks or flaws along the way. As soon as the light is switched off, the material re-solidifies without the defects.

Illustration showing optically healing polymers.

Schematic of optically healing polymers. The specially designed polymer molecules that make up the solid item can be disassembled by the UV light so that they flow and fill in the cracks. When the light is turned off, the molecules reassemble themselves and the filled cracks become rigid again.

Credit: Zina Deretsky, National Science Foundation, after Burnworth et al., Nature, April 21, 2011.

The whole process takes only seconds and can be repeated over and over without compromising the integrity of the substance. Although only in the proof of concept stage, the researchers are confident that these materials will soon find widespread use.

As team leader Stuart Rowan says:

One of our next steps is to use the concepts we have shown here to design a coating that would be more applicable in an industrial setting.

Below: an explanation by Case Western Reserve scientist Stuart Rowan.

Saturday, May 21, 2011

Just for fun: Leafsnap

Want to identify the trees in your neighborhood? There's an app. for that. Researchers from the
Smithsonian Institution, Columbia University and the University of Maryland have collaborated to produce Leafsnap, a free plant identification system for mobile phones. I've already downloaded it to my phone and I can't wait to try it.

Friday, May 20, 2011

Hidden dangers of dietary supplements

Although the case for using dietary supplements has become more controversial, many people still subscribe to the practice. Putting aside the issue of how effective supplements are, they may also have unexpected drawbacks. In particular, Wen-Bin Chiou of National Sun Yat-Sen University, Chao-Chin Yang of National Kaohsiung University of Hospitality and Tourism, and Chin-Sheng Wan of Southern Taiwan University have found one additional problem with supplements. They may encourage people to make riskier lifestyle choices.

The researchers divided volunteers into two groups. Group A was instructed to take what they thought was a daily multivitamin, but was in fact a placebo. Group B was told they would be taking a placebo. In other words, everyone was taking the same exact thing, which was nothing. The people in group A exercised less and ate more poorly than the people in group B. It appears that the people who thought they were getting dietary supplements took less care with their health, perhaps because they assumed that any deficiencies would be compensated for by the supplements.

Thursday, May 19, 2011

Coexisting with our bacteria

Our guts contain ten times more microbial cells than human cells. Why don’t our immune systems attack all these invaders? The answer may be that the bacteria don’t let us.

To be clear, it’s a very good thing that our immune systems don’t attack most of our gut flora. Many of these hitchhiking guests are extremely beneficial, helping us digest our food, providing nutrients and preventing more lethal invaders from finding living space. Still, even good bacteria are not human cells, and should be recognized as such and cleared by our immune systems. According to Sarkis Mazmanian and his colleagues from Caltech, the University of Chicago and UCLA, the reason this doesn’t happen is that bacteria can convince our immune systems that they are us.

The researchers found that rather than hiding from our immune systems in the lumen or center of our guts, as was previously thought, bacteria burrow deep into the mucosal surface of the colon. There, they activate a group of regulatory T (Treg) cells whose job it is to shut down our immune response. Ordinarily, Treg cells prevent our immune systems from attacking our own bodies. Without them, we suffer from such autoimmune diseases as arthritis, type 1 diabetes and lupus. In this case, the bacteria are tricking our immune system, by way of the Treg cells, into thinking that they are us. And for all practical purposes, perhaps they are us. Mazmanian suggests that we revise our concept of ‘self’ to include the trillions of microbes that have been part of us for our entire lives.

Caption: The image depicts symbiotic microbes in the process of colonizing the mucosal surface of the mouse colon. Yellow cells are Escherichia coli; red cells are Bacteroides fragilis. Intestinal tissues are labeled in green with blue nuclei.

Credit: S. Melanie Lee/Caltech.

Wednesday, May 18, 2011

Pain evaluation for Spanish speakers

Very young surgical patients cannot tell their caregivers how much pain they are enduring. For this reason, hospital staff must carefully evaluate the behavior of their young charges in order to determine whether the children require more or less pain medication. The current pain evaluation tools are expressed in English, which can make it hard for Spanish-speaking medical professionals to distinguish nuanced changes. In order to remedy this situation, doctors at Hospital Universitario La Paz have created a new scale especially for Spanish-speakers.

The most common pain evaluation scale for young children is called the CHEOPS scale, which stands for Children’s Hospital Eastern Ontario Pain Scale. It is recommended for children aged 1 to 7 years old, and assesses things like rigidity, in addition to more obvious cues like crying. The new pediatric acute pain scale is dubbed LLANTO, which is a Spanish acronym of crying, attitude, breathing, muscle tone and facial expression. Besides being in Spanish, the new scale does not rely on any electronic monitoring devices.

The LLANTO scale was compared to the CHEOPS scale in 54 children, aged one month to six years. Each child was evaluated on both pain scales before and after receiving a post-operative analgesic treatment. There was a high correlation between the two scales, meaning that an attending health care professional could confidently use either scale to assess her patients. Having a quick way to determine the pain levels in young children without having to translate anything would be a big help in many parts of the world.

Tuesday, May 17, 2011

Calculate your carbon footprint

Although climate change is an accepted fact, most people have little idea of what to do about it. What can an individual do to help make a difference? In order to answer that question, a person must first know their particular carbon footprint. Christopher Jones and Daniel Kammen of the University of California, Berkeley have created a series of carbon footprint calculators to allow people to assess their lifestyle and purchasing choices.

Carbon footprints (measures of the amount of greenhouse gases released to the atmosphere) must include all aspects of product usage. For example, the carbon footprint of our food choices would include the energy required to grow that food, harvest it, transport it and prepare it. The carbon footprint of our homes includes not only the energy we use heating or lighting it, but the harvesting, manufacturing and constructing of all the materials within the house.

The typical U.S. household dumps 48 tons of carbon dioxide into the atmosphere each year. In this breakdown, blue indicates direct emissions, such as from driving a family car or heating a home. Green indicates indirect emissions, such as carbon emitted by the trucks delivering groceries to a retail store or in the process of growing crops.

Credit: Image courtesy of University of California - Berkeley.

Interestingly, the researchers found that different households in different regions of the country could achieve the same reduction in carbon release by very different means. For example, a childless couple might lower their emissions the most by choosing a more fuel efficient car, whereas a large family might get the same benefit by reducing the amount of red meat they eat. For this reason, it’s important for each household to determine their own carbon footprint.

If you’d like to see how you compare to the average and what changes would make the most sense for you, you can use the calculators yourself.

Monday, May 16, 2011

Celiac vaccine passes Phase I trials

Celiac disease is an autoimmune disorder in which the body destroys its own intestinal lining in response to the ingestion of gluten, a protein found in wheat, rye and barley. I previously discussed how Bob Anderson and his colleagues from the Walter and Eliza Hall Institute’s Celiac Center discovered the three specific peptides responsible for most celiac symptoms. Those same peptides have been used to develop an anti-celiac vaccine called Nexvax2®, which Anderson has been testing in a Phase I trial.

Phase I trials are designed to determine the safety and tolerability of a drug, as well as it’s bioactivity. Thus far, a group of celiac patients have been given weekly injections of Nexvax2® for three weeks. Although the patients were on a strict gluten-free diet, some of them experienced typical celiac symptoms at the highest doses of the drug. Patients also exhibited the desired T-cell response to the vaccine. In all, this indicates that the right peptides were chosen for the vaccine, and that it’s reasonably well tolerated.

The next step (possibly beginning later this year) will be the Phase II trials, in which a larger group of patients receive the vaccine. Dosing and efficacy testing will continue during this phase. If those tests are promising, large scale Phase III testing will begin.

Sunday, May 15, 2011

Hem and haw to a better vocabulary

Or at least, to help your toddlers learn new vocabulary words. According to a study by Celeste Kidd and Richard Aslin of the University of Rochester and by Katherine White from the University of Waterloo, parents shouldn’t worry about the occasional um or er when talking to their toddlers. If anything, the practice actually helps the kids learn new words.

The researchers displayed a set of images to toddlers aged 18 to 30 months. Each pair of pictures contained one that was familiar to the child, such as a book or a ball. The other image was of a made-up object with an unfamiliar name like ‘dax’ or ‘gorp’. The children sat in a parent’s lap and listened to a recorded voice talk about the objects. Occasionally, the voice would stumble, saying things like, “Look at the, uh…”, whereas other times the voice was smooth and articulate.

Children over age two were almost 70% more likely to look at the unknown object when the voice stumbled. In other words, the brief verbal hesitation was priming the kids to learn something new. This was not the case for younger children, who had not yet learned to associate verbal stumbles with novel words.

Kidd warns against making too much of this result:

We’re not advocating that parents add disfluencies to their speech, but I think it’s nice for them to know that using these verbal pauses is okay—the ‘uhs’ and ‘ums’ are informative.

Saturday, May 14, 2011

Just for fun? Mississippi flooding

The Mississippi river is experiencing its second highest rise since 1937. On May 10th, it crested at almost 50 feet above normal, affecting communities in Tennessee, Kentucky, Missouri, and Arkansas, with Mississippi and Louisiana soon to follow. Here are the before and after pictures as taken by the Landsat 5 satellite.

This is a Landsat 5 image of the Mississippi River in the Memphis, Tenn., area on May 12, 2006.


And this is a Landsat 5 image of the Mississippi River in the Memphis, Tenn., area on May 10, 2011.


Friday, May 13, 2011

Starting school later means fewer car crashes

Okay, let’s be perfectly clear about this. The study put out by Robert Vorona of Eastern Virginia Medical School and his colleagues did not prove that letting teenagers start school later would prevent them from getting into car accidents. However, those two effects were strongly correlated with each other.

It’s no surprise that teens are tired in the morning. Their circadian rhythms are shifted compared to younger children or adults such that teenagers tend to stay up later and want to sleep in later. Experiments on starting high schools later in the day have shown that such practices increase student attention span and academic success.

For this study, the researchers compared teen car crash rates in two neighboring Virginia cities, Virginia Beach, where high schools classes begin at 7:20 am, and Chesapeake, where the high schools begin at 8:40 am. In 2008, the teen crash rate was 41% higher in Virginia Beach. Traffic conditions did not suggest any other reasons for the difference in accident rates. In fact, the teen crash rates in both regions were highest at the time the kids would be going to school in the morning, and again for a few hours after school let out.

Again, these results are correlations and do not prove any causation between school start times and car crashes. The authors are planning more studies to further understand the ramifications of school start times. In the meantime, if your community is debating when to set school start times, you may want to bring this study to the attention of the school board.

Wednesday, May 11, 2011

Dinosaurs hunted at night

The conventional wisdom that dinosaurs were entirely diurnal, yielding the night to tiny contemporaneous mammals, appears to be incorrect. A new study by Lars Schmitz and Ryosuke Motani from the University of California, Davis suggests that many dinosaurs were active at night.

First, let’s define a few terms. Diurnal animals are active during the day, nocturnal animals during the night, and cathemeral animals all the time. By the way, although this study didn't address whether any animals were active at twilight (dawn or dusk), such a creature would be 'crepuscular'. Also, dinosaurs, birds and lizards all have a bony ‘scleral ring’ around their eye sockets that can be measured in both living creatures and fossils. The scleral rings of diurnal animals are small, cathemeral animals moderate, and nocturnal animals large.

The researchers measured the scleral rings of 164 living animals with known habits to see whether their predictions about those animals’ lifestyles matched up to reality. Upon finding that they could successfully use the scleral ring data to predict when those animals were active, they applied the technique to 33 fossils.

According to this new data, small carnivorous dinosaurs were active at night, whereas large herbivorous dinosaurs were active all the time. No doubt feeding those huge bodies required a cathemeral lifestyle. Flying reptiles like pterosaurs were mostly diurnal. These results mesh well with the habits of extant animals filling similar ecological niches today.

Photo showing a close-up of the eye socket and ring of the dinosaur Protoceratops.

Close-up of the eye socket and ring of the dinosaur Protoceratops, active by day and night.

Credit: Ryosuke Motani and Lars Schmitz

You can see a gallery of some of the specimens under study here.

Tuesday, May 10, 2011

New hypothesis of Himalaya formation

Alex Copley and his colleagues from Caltech and the University of Cambridge have developed a new hypothesis about the formation of the Himalayan Mountain range.

Currently, the ‘channel flow’ model is the most widely accepted explanation for the formation of Tibetan mountains. In this model, the underthrusting Indian crust is separated from the Tibetan Plateau by a channel of magma. The molten layer of crust between the two tectonic plates finds its way through the weakest sections of the Tibetan crust, forcing the Himalayas higher. The trouble is that this theory cannot account for the different types of stress lines seen along the Tibetan Plateau.

In contrast, Copley’s suggestion that a strong hard Indian crust is locked under the Tibetan crust with no magma buffer between them is born out by simulations. If confirmed, this hypothesis may alter views about other mountain ranges as well.

Earthquake mechanisms and the style of faulting in the Himalaya-Tibet region show that the Himalayan range is under north-south compression, southern Tibet is in east-west extension, and northern Tibet is in both east-west extension and north-south compression. The study shows that this pattern can be explained if the strong Indian crust thrust under southern Tibet is transmitting the north-south push of India to northern Tibet.

(Credit: Caltech).