Science-- there's something for everyone

Monday, July 30, 2012

Street lighting affects invertebrates

Nowadays, much of the world is lit up twenty-four hours a day. This has consequences for invertebrates. We’ve all seen moths and other insects buzzing around streetlights, but the effects of artificial lighting extends much deeper. According to Thomas Davies, Jonathan Bennie and Kevin Gaston of the University of Exeter, even ground-dwelling invertebrates are affected.

The researchers set pitfall traps in the grass either directly under streetlights or midway between them (the darkest area of the street). Occupants of the traps were collected thirty minutes before sunrise and before sunset so that both diurnal and nocturnal creatures were represented.

More organisms were collected under streetlights than between them. Interestingly, the pitfall traps under streetlights yielded significantly more carnivores and scavengers than pitfall traps between lights. This was true for both daytime and nighttime sampling. In other words, it wasn’t just that some creatures were attracted to the streetlights while they were turned on. Different communities of invertebrates were living near streetlights twenty-four hours a day.

Clearly, the communities of organisms found along the roadside are altered by artificial lighting. What’s not clear is how big an effect this has on the entire ecosystem. The authors suggest that further efforts be made to understand the impact of streetlights on the invertebrate world.

Sunday, July 29, 2012

The Goldilocks effect of human attention

Human infants are amazing learning machines. Not only are they capable of surprising levels of computation, but, as Celeste Kidd, Steven Piantadosi and Richard Aslin of the University of Rochester have found, they can even direct their attention to improve their learning opportunities.

Because of their relative immobility, infants must do much of their learning by passively watching things. However, they don’t gaze indifferently at whatever’s in front of them. Instead, they direct their attention to things that offer them the best learning opportunities. This means that they don’t choose to pay attention to things that are too complex (out of their mental grasp), or too simple (already mastered).

Just how did the researchers come to this conclusion? Once again, we turn to the ‘ol ‘how long does the baby stare’ test. It’s well documented that babies only a few months old will stare longer at things that surprise them. Kidd and her colleagues were able to fine-tune that test by presenting babies with more or less predictable computer images.

They found that if you show babies the same images for too long, they grow bored and look away. If you then show them something new, you regain their interest. However, you can’t retain a baby’s interest with just anything. If the new imagery is too random and unpredictable, the baby also turns away. In other words, the babies prefer to look at things that are novel, but not completely weird.

The researchers dubbed the tendency of babies to be particularly attuned to intermediate levels of stimulation the ‘Goldilocks effect’. Although only tested on infants, they believe it applies to everyone. That is, we all lose interest when things are either too simple or too far above our heads.

You can see an explanation below:

Saturday, July 28, 2012

The trouble with presenteeism

You’ve heard of absenteeism: the problem of employees habitually missing work. Well, presenteeism can be even worse if sick people come to work instead of staying home in bed. This is particularly problematic when health care professionals show up for hospital shifts while suffering from contagious diseases. How often does this happen? According to doctors from Massachusetts General Hospital, Harvard Medical School and the University of Chicago, all the time.

The researchers gave an anonymous questionnaire to 150 resident physicians in Illinois. 77% of the residents reported that they had come to work with flu-like symptoms at least once within the past year. I suspect that the remaining 23% just didn’t happen to have the flu that year. Ominously, 9% thought they might have given the illness to a patient, and 21% thought another sick resident might have done so.

There were a number of reasons the doctors gave for not staying home when ill, most commonly that they felt their patients and their colleagues needed them. The authors suggest that residents be given more guidance about the necessity of not coming to work sick. Most of us don’t like to see our colleagues coughing and sneezing in the workplace, but it can be deadly in a hospital.

Friday, July 27, 2012

Designing tests for better performance

There are a number of factors that can interfere with a person’s ability to recall things. For example, asking too many questions about one specific topic results in ‘output interference’, the gradual decrease in correct responses that occurs as a test progresses. Can this handicap be overcome? According to Kenneth Malmberg of the University of South Florida and his colleagues from Syracuse University and from Indiana University, it can at least be diminished.

To test this, the researchers used a master list of 1200 English words, 150 each from eight distinct categories such as countries, professions, animals, etc. 86 undergraduates were each shown 150 target words (75 from one category and 75 from another) along with 150 decoy words from the same two categories. Thus, there were 150 words in each category, half of which had been on the original list. Participants were asked to identify whether each word had been in the original list.

This experiment was run in three different ways. In one case, all 150 words from one category were presented first, followed by the 150 words in the second category (blocked condition). In another case, the 300 words were randomly mixed (random condition). Finally, the categories alternated between subjects after every five words (short-block condition).

All participants showed a decline in recall as the test progressed.  They chose the correct word at least 90% of the time at the start of the exercise but were scoring below 80% by the last few words. However, for those students encountering the blocked condition of word order, accuracy jumped over 10% between the end of one block and the start of the next. Apparently, shifting categories led to a renewed ability to recall words.

Looking at the data, I’m not convinced that planning tests in this manner is the best policy. While it is true that no such jump in accuracy occurred for either the random or short-block conditions, students exposed to those two conditions did better during the first 150 trials. In other words, the blocked condition gave students an advantage at the break point between categories, but was detrimental up to that point. To me, it seems like a bit of a wash. 

If you’re a teacher constructing a test for your students, I wouldn’t worry too much about question order. Design your tests anyway you like. 

Thursday, July 26, 2012

A catalog of Martian impact craters

Stuart Robbins and Brian Hynek of the University of Colorado at Boulder have compiled a database of all Martian craters at least a kilometer in diameter. This undertaking took four years of assembling data from the various Mars orbiters and landers and resulted in a giant catalog.

Besides size and location, details about shape and structure are listed for each of the 384,343 craters in the catalog. As Robbins says:
Our crater database contains both rim heights and crater depths, which can help us differentiate between craters that have been filled in versus those that have eroded by different processes over time, giving us a better idea about long-term changes on the planet’s surface.
The authors are making that database available to the public. They also have data on about 250,000 more craters not included in the catalog that they’ll provide to anyone who asks. Yes, that means that there have been well over 600,000 asteroid impacts on Mars, and those are just the ones that haven't eroded away yet. Wonder what that looks like? Your wish is my command:

Wednesday, July 25, 2012

Just for fun: Another Higgs boson explanation

I don't usually post two videos the same month explaining the same concept, but this subject is both important and difficult to grasp, at least for me. So here's another take on the recently confirmed Higgs boson, this time by Ian Sample of the The Guardian. 

Hat tip: Not Exactly Rocket Science.

Tuesday, July 24, 2012

Don’t count people, measure biomass

Many calculations about global resources rely on the current and projected world population. However, we may be off by quite a bit by not taking obesity into account. According to Sarah Walpole and her colleagues from the London School of Hygiene and Tropical Medicine, we should be measuring total human biomass rather than counting individuals.

Biomass is the total mass of whatever biological entity you’re interested in. It could be every living thing on Earth, or all plants, or all red pandas. The human biomass is the combined mass of all humans on Earth.

Clearly, fat people have more mass than skinny people. Heavier people not only take up more space than thin people (which is rarely an issue), but they use up more resources, which can be significant when we’re counting up how much of something there is to go around. It simply takes more energy to sustain a larger body than a smaller one. Thus, if you have a population of obese people, they’re going to use up resources much faster than the same number of thin people would have.

The researchers used information from the United Nations, the World Health Organization and national databases to estimate the population and the mean body mass index (BMI) of adults in 190 countries. From this, they extrapolated to the total adult human biomass of the planet.

The scientists estimated that in 2005, the total adult human biomass of the planet was about 287 million metric tonnes. If none of those people had been overweight, the total would have been about 15 million tonnes less, or about a 5% difference. 

The researchers then compared two different scenarios. In the first, the entire planet had BMIs in the same distribution as that seen in Japan, and in the second, the whole world looked like the U.S. These represented normal weight and fat extremes, as it takes about seventeen Asians to make up the same body mass as twelve Americans. If the whole world looked like Japan, it would be the equivalent of losing almost a quarter of a billion people from the world population. On the other hand, if every place looked like the U.S., it would be like gaining close to a billion new inhabitants.

There were some limitations to this study, not least of which was that they did not include children, who make up quite a large fraction of the human biomass, obese or otherwise. And of course, these are only rough estimates. However, it’s important to note that projections about how many people an area can feed or how long a resource is expected to last may be vastly underestimated if people use population counts without adjusting for biomass. As there’s every indication that the rest of the world is emulating the U.S. and not Japan, the discrepancy between predicted resource usage based on population and actual usage will only get greater.

Monday, July 23, 2012

Better health through warning labels

Each year, millions of Americans suffer from ‘adverse drug events’ caused by the inappropriate use of prescription drugs. This doesn’t necessarily mean they purposefully took drugs when they knew they shouldn’t. Often people simply misread or misunderstand warning labels, leading to incorrect dosing or dangerous drug interactions. What can be done about this?

In an effort to prevent these drug reactions, many pharmacies add colorful warning stickers on medicine vials that say things such as ‘do not consume alcohol while taking this medication’. However, as prescription warning labels (PWLs) are not regulated, each pharmacy is free to choose their own wording and design. There have been studies to see what kind of phrasing is most easily understood, but Laura Bix and her colleagues from the University of Michigan and Kansas State University wondered whether a bigger problem might be that people don’t notice the stickers in the first place.

Because elderly people are at greater risk for adverse drug effects, largely because they take more drugs, the researchers used two groups of volunteers, fifteen people aged 20-29 and seventeen people aged 51-77. Each participant was shown five prescription vials with PWLs in different colors. Eye tracking indicated when and for how long each person looked at the main white label, the colored PWL, and the vial’s cap. Next, the subjects were asked to remember which PWLs they had seen on the vials.

Actual vial used in this study:
a. The three label zones of interest: cap, standard white pharmacy label and prescription warning label (PWL). 
(Inset: Five color contrasts of PWLs used in this study) 
b. Flattened, scaled drawing.

Younger people were more likely to spend time looking at the PWL during the eye tracking exercise. They were also better at recalling exactly which PWLs they had seen. However, even young people spent more time looking at the main label than at the PWLs, and were only able to correctly identify the PWLs they’d seen two thirds of the time.

These data suggest that the kinds of PWLs most often used by pharmacies are simply not attracting enough attention, especially among older people. This is true even when the PWLs are in bright colors with bold lettering. In contrast, all the subjects did spend time looking at the plain white label on the front. The authors suggest that people expect to find relevant information on the front of the vial, and may not bother to look around the sides or back. If so, pharmacies may do better to print PWLs on the main label rather than on separate stickers.

Sunday, July 22, 2012

Exercise and depression?

Does exercise help to alleviate depression? That's a great question that unfortunately was not answered by a recent article in the British Medical Journal. Nineteen researchers from the universities of Bristol, Kent and Exeter compared people who were prodded to exercise with those who weren't, and found no differences. 

Three hundred and sixty one study participants were recruited from adults who had come to their doctors with symptoms of depression. Half were given the standard care (including anti-depressants if necessary) and half were also provided with a facilitator who helped them find a physical activity and exercise routine that suited them. People in the second group met with their facilitators in person up to three times and by phone ten times over an eight month period. 

All patients completed self-evaluations at four, eight and twelve months after the start of the study. As stated, there were no differences in depression levels between the two groups. There were also next to no differences in activity level between the groups too. Does anyone see a problem with this?

Although the article is putatively about depression, the only thing it seems to have measured is whether depressed people will exercise more if they're nagged. Answer: not much. 

Scicurious has more on this.

Saturday, July 21, 2012

To develop binocular vision, look around

In humans, binocular vision, also called stereopsis, develops a few months after birth. Gábor Jandóa from the University of Pécs Medical School and his colleagues wondered whether preterm babies would develop that ability at a later age. In other words, does it take about thirteen months post conception or four months of practice to acquire binocular vision?

Fifteen healthy preterm babies (thirty-one weeks gestation) and fifteen healthy full term babies (thirty-nine weeks) volunteered to advance science. The infants were shown a display that would appear to have dots moving about if it were viewed in stereo. Babies that did not have binocular vision would not be able to see the movement. The researchers monitored the electrical signals from the infants’ brains (via scalp caps) to determine what the children could see.

The preterm babies developed stereopsis at about the same age as their full term cohorts. It didn’t matter that their visual systems had less time to mature, as soon as the infants were born, their eyes were ready to work. This strongly implies that binocular vision depends on looking at the three dimensional world around you.

Friday, July 20, 2012

To prevent Lyme disease, encourage foxes to flourish

Some of the diseases that plague humans are transmitted to us via ticks and insects. In North America, one of the most prevalent of these is Lyme disease, an infection caused by the bacteria (Borrelia burgdorferi) and borne by the deer tick (Ixodes scapularis). You might think that the growing incidence of this illness is due primarily to an increase in the deer population upon which the tick feeds. Not so, according to Taal Levi and his colleagues from the University of California, Santa Cruz and from the University of Bergen. It’s actually the red fox population that’s critical.

First of all, let’s delve into the tick life cycle (shown in the diagram below). Starting from an egg (far left), the tick first goes through a larval stage. At this developmental stage, the preferred blood source is a small mammal, such as a mouse. A year later, that larva has become a nymph, and its favorite host is also a mouse. Finally, the tick is all grown up and has one final meal as an adult. This time, it usually chooses a deer. If a human host replaces either the second mouse or the deer, that person can become infected with Lyme disease.

As you can see, Lyme disease can be transmitted either during the nymph or the adult stages (after the tick has had its first blood meal as a larva). However, notice that the adult stage occurs during the winter when people tend to be covered in multiple clothing layers. In contrast, the nymph stage takes place during optimal shorts and swimsuit weather. This means that people are far more likely to be infected by nymphs than by adults. 

Once you get past a minimal threshold necessary to keep the adults laying eggs, increasing the deer population does not affect the abundance of the nymphs. On the other hand, dramatically increasing the number of small mammals has a huge affect on the nymph population. And here’s where the red foxes come in. As foxes have declined, small mammals have proliferated and with them have come infected tick nymphs.

So why has the fox population dwindled? It’s most likely due to the removal of wolves from most of North America. Thanks to the elimination of wolves, many areas have an overabundance of coyotes. These larger predators kill or compete with foxes but do not prey heavily on the small mammals that foxes prefer.

Time again and we’ve seen the consequences of plucking key species, such as top predators, out of an ecosystem. This time, the change may very well be having a continuing effect on human health.

Thursday, July 19, 2012

Can videogame players multitask? No!

Most people believe they can multitask to some degree. Most people are wrong. Although we may think we’re able to do several things at once, the truth is we’re just doing all those things badly. In almost every case, people would do better to focus their attention on one activity at a time. But are videogame players (VGP) the exception to this rule? After all, if there’s any group that can rapidly react to multiple stimuli, it’s them. Have they learned the secret to successfully dividing their attention?

To find out, Sarah Donohue from Duke University and her colleagues from Duke, Pennsylvania State University and Colby College gave proficient VGPs and non-players a series of three tasks: driving, multiple object tracking and image-search. For the first, they had to play a driving simulation game. For the second task, subjects viewed eight white dots on a screen. Four of the dots flickered a few times, and then all the dots moved around the screen like a shell game. After twelve seconds of movement, the participants had to identify which dots had been flickering. Finally, for the last challenge, subjects were given a paper ‘find the hidden object’ puzzle form a children’s magazine.

Volunteers ran through each of these three tasks either without interruption (single-task), or while answering trivia questions piped in over a loudspeaker (dual-task). The participants were instructed to do their best at the original task (for example, to complete the driving task as quickly as possible with no crashes) plus answer each question rapidly and accurately.

As I’m sure you’ve guessed, the VGPs were no better at multitasking than the non-players. Both groups also showed similar strategies for dealing with distraction, such as slowing down on the driving course. 

By the way, why did I say that most people can’t multitask? It turns out that about one out of every forty people is a ‘supertasker’ who really can concentrate on more than one thing at a time. I’m definitely not in this group, as my family can attest when they’re trying to speak to me while I’m reading something. If you think you might be, this driving test might convince you otherwise:

Wednesday, July 18, 2012

Just for fun: Aquanauts!

I've posted footage about putative Mars explorers, so how about one about ocean explorers? A team of aquanauts has been making the Aquarius Reef Base (located in the Florida Keys National Marine Sanctuary) their home since July 16th. They'll live on the ocean floor for six days.

You can see live footage from the current and (and possibly final) Aquarius mission below:

Streaming video by Ustream

Tuesday, July 17, 2012

The connection between mothers and babies lasts a lifetime

During pregnancy, some fetal cells migrate into their mother’s bloodstream and from there to all points beyond. These cells remain in the mother’s body for decades, possibly for the rest of the mother’s life. This means that women who have ever been pregnant, even if the pregnancy did not result in a living child, are essentially chimeras. That is, they have human cells with two distinct genomes living in their bodies. Granted the mother’s own cells far outnumber the fetal cells, but fetal cells are definitely present.

This information is intriguing to say the least. Is it a specific type of fetal cells that cross over into the mother? Are these fetal cells doing anything? And if so what? The first step in answering these questions is to find and quantify the fetal cells. Stephanie Pritchard and her colleagues from Tufts Medical Center, Tufts University and Sackler School of Graduate Biomedical Genetics used a combination of screening tools to detect fetal mouse cells in their mothers’ lungs.

The researchers bred normal females to male mice that contained a gene that makes their cells glow green. Any babies that resulted from this cross would inherit the green gene from the father. Thus, any cells within the mother’s body that fluoresced would have to be fetal cells. Once the fetal cells were identified, the scientists used gene expression tests to determine what kinds of cells they were.

In this way, they found a variety of types of fetal cells in their mothers’ lungs, including mesenchymal stem cells (MSCs). These are cells that can differentiate into bone, cartilage, fat cells, and other tissues. In fact, fetal MSCs have been observed to differentiate as a response to injury to the mother. In addition, fetal cells seem to be particularly prevalent at tumor sites within the mother. This presents the tantalizing possibility that the fetal cells may be acting as some sort of repair mechanism on behalf of the mother.

The benefit of spreading fetal cells throughout the mother’s body doesn’t just go one way though. The team also identified fetal immune cells in the mother mice, which may play a role in protecting the fetus from the mother’s immune system.

Obviously, there is much more to be learned about fetal cells. You can hear the excellent Robert Krulwich discussing this fascinating story with Kirby Johnson of Tufts University (who developed the fluorescent fetal cell test) on this episode of RadioLab. The story begins at the 2:45 mark.

Monday, July 16, 2012

Watching a fly embryo develop in real time

We know a great deal about Drosophila melanogaster (aka fruit fly) development. After all, D. melanogaster is one of the most common model organisms in all of biological science. However, despite the thousands of studies involving this little insect, no one has been able to track the developmental path of every cell in its body. This is because cells migrate from top to bottom or front to back at specific stages of embryogenesis. If your camera is focused on the top, some of those cells will disappear out of view as they move through the larva’s body.

The solution is to have multiple cameras filming all sides simultaneously. This seemingly simple answer is a lot more complicated than it first appears. First, the organism must be illuminated so that you can see the individual cells without frying the creature. A technique known as ‘light sheet microscopy’, in which light is shined sideways onto the subject, has proven useful for observing single cells. Second, and perhaps most importantly, matching the different views seamlessly requires massive computing power that simply wasn’t available until recently.

Using a brand new microscope system they called SimView (simultaneous multi-view), Raju Tomer and his colleagues from Howard Hughes Medical Institute were able to simultaneously capture images of a fly larva from four different views. It took about 11 terabytes to merge them into the film you see below. As a reminder, this is a single fly embryo filmed from above and below at the same time. Each dot of light is a cell nucleus.

A similar study was led by Lars Hufnagel of the European Molecular Biology Laboratory. These researchers used their own new microscope, dubbed MuVi-SPIM for multi-view selective-plane illumination microscopy, to produce the following 3D film of a fruit fly embryo.

Needless to say, being able to track the developmental progress of each cell in a fly embryo is not just of interest to entomologists. D. melanogaster is a model for studying processes that occur in other organisms, including humans. Therefore, the more we understand about them, the more we understand about us.

Sunday, July 15, 2012

Dyslexia helped by wider letter spacing

Update 7/16: Craig Wright at Understanding Minds disagrees with the following interpretation. You can read his criticism here.

Dyslexia is a broad term describing a number of learning disabilities. In general, it’s a reading deficiency. Children who are dyslexic tend to have more difficulty learning to read and spend much less time reading than their peers. This, of course, only increases the differences in reading ability between them and their agemates. Though there is no agreed upon cause, let alone cure, Marco Zorzi of the University of Padova and his colleagues have hit upon one possible treatment: wider letter spacing.

If letters are too close together, we all have difficulty making them out. However, many dyslexics see letters as crowded together even when other people think the letters are properly spaced. Zorzi and his colleagues wondered whether this perceived crowding could be one of culprits behind the poor reading performance of dyslexics.

The researchers recruited 34 Italian and 40 French children between the ages of 8 and 14 who had been diagnosed with dyslexia. The kids were each asked to read 24 short unrelated sentences in their own language. Half the kids got the sentences printed up with normal spacing, the other half got the same sentences, but with roughly double the space between letters. There were compensatory increases in the spacing between words and between lines. Two weeks later, the groups of kids were switched so that by the end of the test period each child had had the opportunity to read the samples with both spacings.

The children were twice as accurate in reading the widely spaced sentences. They also read more quickly by the equivalent of jumping up one school year. Kids were also better at identifying letters when those letters were more widely spaced.

Taken together, this suggests that upon diagnosis with dyslexia, children should be provided with widely spaced reading material. Ideally, this would also encourage children to practice reading more frequently so that they would eventually become proficient enough to read normally-spaced material.

By the way, in most reading material, the letter spacing is optimized for skilled readers, not beginners or dyslexics. If that spacing is increased or decreased, reading pace is slowed down. Compare these paragraphs for yourself to see how spacing alters your reading fluency.

By the way, in most reading material, the letter spacing is optimized for skilled readers, not beginners or dyslexics. If that spacing is increased or decreased, reading pace is slowed down. Compare these paragraphs for yourself to see how spacing alters your reading fluency.

Saturday, July 14, 2012

Using the mother’s blood to sequence her fetus’s genome

The decision as to whether to have a fetus tested for genetic disorders can be a difficult one. Some conditions can be treated more effectively immediately after or even before birth. On the other hand, current sequencing methods (amniocentesis and chorionic villi sampling) are not without their drawbacks. Ideally, doctors could determine a baby’s genome by taking a simple blood sample from the mother with no risk to the child. Well, that’s just what Jacob Kitzman from the University of Washington and his colleagues did.

The idea of using maternal blood to access information about her child is not new. About 10% of the cell-free DNA floating around a pregnant woman’s bloodstream is actually from her child. This information has been used to detect gross genetic abnormalities such as trisomies (having three copies of a chromosome rather than two). Trying to resolve an entire fetal genome is much trickier because you have to separate the mother’s DNA from the baby’s.

The researchers sequenced the genomes of a mother and father in a mother/father/fetus trio. They then got a mix of maternal and infant DNA from the mother’s plasma. By using the known sequences of the parents, they were able to deduce the baby’s genome. This was confirmed at birth when a sequence was obtained from the cord blood. Similar results were obtained for a second family trio.

The authors are the first to admit that this technique is only in its earliest stages. However, it’s not hard to imagine that any parents facing an at risk pregnancy, either due to family history or environmental factors, will one day wish to consider this noninvasive option.

Friday, July 13, 2012

Calcium supplements—too much of a good thing?

Calcium supplements are often taken to stave off osteoporosis. Unfortunately, there is some evidence that they can increase the risk of heart attacks. This has been difficult to assess because in most studies, some of the participants were already taking their own calcium supplements as well as the ones assigned by the test protocol. For example, one of the largest calcium studies was the Women’s Health Initiative Calcium/Vitamin D Supplementation (WHI CaD) study. This seven-year long study included over 36,000 postmenopausal women who were allocated to either the calcium and vitamin D (1g calcium and 400 IU vitamin D daily) group, or the placebo group. Both placebo and CaD groups included women who were already taking calcium supplements. Needless to say, this makes the conclusions somewhat problematic.

To overcome this confounding detail, Ian Reid and his colleagues from the Universities of Auckland and Aberdeen specifically separated out women who were taking calcium supplements from those who weren’t. To be clear, all the calcium in this study was administered as a supplement. In other words, the four groups of women in the study included those taking no calcium, those who were given a calcium supplement, those who had already been taking their own calcium supplements but were given a placebo, and those who were taking their own personal calcium supplements and were given an additional calcium supplement.

Women with no personal use of calcium who received calcium in the study had a modest increase (6 events/ 1000 women) in cardiovascular events compared to those on placebo. Women who were already taking calcium supplements before the study began showed no such increase.

I find this result a bit puzzling. One possible explanation is that any amount of calcium supplementation will increase the risk of cardiac arrest regardless of dosage. Thus, the women who were already taking calcium supplements did not increase their risk of heart attack when they added more calcium rather than a placebo.

Calcium supplements of any dosage will abruptly increase serum calcium levels, which in turn can lead to more vascular calcification, a common cause of heart problems. However, it's not clear whether that's what's going on here. Like with the vitamin D study I discussed earlier, we need a lot more evidence before we draw any solid conclusions.

That said, I think it's excellent that Reid and his colleagues thought  of personal calcium usage as a possible confounder. I imagine that it's exceedingly difficult to get people to remember, let alone disclose every food or supplement they take during studies, which must affect results. Good for these researchers for attempting to isolate any and all calcium usage for their study.

Thursday, July 12, 2012

Ditch the energy drinks and eat a banana

For those who read my post on energy drinks and are wondering how to replenish metabolites during exercise without damaging their teeth, you can eat a banana instead. David Neiman of Appalachian State University and his colleagues compared eating bananas with drinking sports drinks during heavy exertion. They found no differences in performance outcomes between the two energy sources.

Fourteen male volunteers who were experienced bicycle road racers were asked to compete in a 75 km time trial on stationary bikes. Half the men were given a carbohydrate drink and the other half were given bananas. The drink contained 26.2 g carbohydrate (11.0 g glucose, 9.1 g fructose, and 4.6 g sucrose), whereas the banana contained 27.0 g carbohydrate (6.4 g starch, 5.9 g glucose, 5.7 g fructose, 2.8 g sucrose, and 3.1 g dietary fiber). People who got the bananas also got water to equal the amount of fluids received by the drink group. Three weeks later, the men biked a second 75 km race, but this time the drink and banana receivers were reversed.

The subjects began ingesting their product ten minutes before beginning to cycle and consumed a portion every fifteen minutes once they’d started. Participants provided blood samples just before starting, an hour into the cycling, as soon as they finished and one hour after finishing.

Of the 103 metabolites that were tested for, only one differed between the banana group and the energy drink group: banana eaters had much higher levels of dopamine. Those levels continued to rise even an hour after exercising. It seems that not only was the banana just as good at replenishing athletes during intense exercise, but it made them feel better too.

The authors did not comment on the feasibility of peeling a banana while riding a bicycle. I imagine that once you learn how to do it, you never forget.

Wednesday, July 11, 2012

Just for fun: Higgs boson explained

By now, you undoubtedly know that the much sought after Higgs boson has been confirmed by the physicists using the Large Hadron Collider at CERN. However, you may not know what a Higgs boson is or why it's important.  Here's one explanation:

The PhD Comics explain the Higgs boson:

Here's Phil Plait at Bad Astronomy's take on the discovery.

Tuesday, July 10, 2012

Good news for opening medical marijuana dispensaries—crime doesn’t go up

Seventeen states plus the District of Columbia have legalized marijuana for medicinal purposes. In those areas, people can get a prescription from their doctors to use marijuana, which can be filled at medical marijuana dispensaries (MMD). The fact that this action puts these states into conflict with federal law is not something I wish to get into at the moment.  Instead, I’ll let Nancy Kepple and Bridget Freisthler from the University of California, Los Angeles answer the question of how these marijuana outlets affect the local crime rate.

You might think that dispensing a commodity that is both in high demand and generally illegal would guarantee a high localized crime rate, all the more so because such businesses are mostly cash-based. The dispensaries, the employees and even the customers (on their way in with cash or out with marijuana) are likely targets for attack.

To see if this was so, the authors divided Sacramento into 95 tracts and marked the locations of all known MMDs as of June 16, 2009. They then compared the crime rate in those various tracts. Neighborhoods with a high density of marijuana outlets did not have more crime than regions with few or no outlets.

To be clear, this study only looked at crime rates at one point in time. It may be the case that crime does increase over time in neighborhoods with dispensaries. However, it does appear that the arrival of MMDs in a community does not necessarily result in an increase in crime. 

Monday, July 9, 2012

For longer telomeres, make sure your father was conceived late in life

Dan Eisenberg, Geoffrey Hayes and Christopher Kuzawa of Northwestern University have found that the older men are when they conceive their children, the longer those children’s telomeres are. Why does this matter? Telomere length is thought to have strong implications for longevity.

Telomeres are bits of noncoding DNA that cap the ends of our chromosomes like tassels. Because of the way DNA is replicated, each time a chromosome is copied a bit of the end is lost. That doesn’t matter as long as it’s only the telomeres that get shortened. Eventually, though, you run out of tassel and then the cell can no longer divide properly. Thus, having longer telomeres to start with allows a cell that many more productive divisions. In fact, telomeres in blood decrease by a predictable amount each year.

Diagram of a telomere at the end of a chromosome.

Telomere shortening is not irreversible. There are enzymes that lengthen telomeres. One such enzyme is particularly active in the testes, meaning that as a man ages, the telomeres in his sperm get longer. The researchers found that not only does a man’s age at the conception of his child determine the length of that child’s telomeres, but that the age of the paternal grandfather at the conception of the father also affects the eventual grandchildren’s telomere length. For each year the grandfathers had delayed reproducing, the grandchildren ended up with telomeres that were the equivalent of one year younger. That is, the telomeres were longer by the same amount that they would have ordinarily shortened in one year.

Obviously, there’s nothing you can do about your own birth circumstances, let alone those of your father’s. But should you take this information into account going forward? Should you delay or encourage your male offspring to delay having children as long as possible? I’ll just point out that longevity and child-rearing are both more complicated than simply measuring telomeres. In fact, there is some evidence that children born to older fathers have shorter rather than longer life spans. In short, don't rearrange your life plans to suit your telomeres.

Sunday, July 8, 2012

Good news and bad news for emergency contraception

It turns out that there is an extremely safe and effective way to prevent pregnancy after unprotected intercourse: using an intrauterine device (IUD). According to Kelly Cleland of Princeton and her colleagues, IUDs are at least ten times more effective than hormonal emergency contraception. Unfortunately, IUDs aren’t without their drawbacks.
IUDs are small T-shaped copper devices that are inserted into the uterus. The copper is toxic to sperm. Some IUD devices also release hormones that thicken the cervical fluid so sperm cannot enter the cervix. When inserted within five days of unprotected sex, the IUD failure rate is only 0.1%.

Hormonal emergency contraceptives, known as ‘morning-after pills’ (brand names Plan B and Next Choice) should be used within three days of unprotected sex. They contain levonorgestrel, which prevents ovulation, fertilization and implantation. The failure rate of this method is between 1-3% according to Cleland, but up to 11% according to Planned Parenthood. This may be because hormonal contraception becomes less effective as body mass index increases. IUDs are not affected by body mass index.

Despite their clear superiority in effectiveness, IUDs are rarely offered to women seeking emergency contraception.  There are probably two main reasons for this. One, the devices must be inserted by medical personnel. Not only is this not the case for morning-after pills, but because women can stock up on the pills ahead of time, they can avoid the need to even see a doctor postcoital. Given the political climate in the U.S. today, it may be all but impossible for a woman to find a clinic that can administer an emergency IUD within the necessary time frame.

Second, there’s the cost. A typical IUD can cost well over $500. In contrast, morning-after-pills cost as little as $10. Though to be fair, once inserted, IUDs will prevent pregnancies for up to ten years.

Given the high cost and the additional bother, it’s not hard to see why IUDs are rarely used for emergency contraception. Nevertheless, the authors suggest that health care providers make a greater effort to at least inform their patients about the option of using IUDs.

Image of IUD by Nevit Dilmen, 2011.

Saturday, July 7, 2012

Flowers provide bees with a grippy surface

Yesterday, we learned that flowers are specifically colored to attract bees, but that's not the only service flowers provide for their favorite pollinators. Most flower petals contain conical cells that make it easier for bees to grip them. That conical shape is determined by a single gene, called MIXTA. Without this gene, the cells in a flower’s petals will be flat and smooth. 

Katrina Alcom and Beverly Glover from the University of Cambridge and Heather Whitney from the University of Bristol were interested in determining under what conditions bees prefer flowers with conical cells. Could they be induced to favor flat-celled flowers? Yes, they could.

The researchers presented bees with a variety of petunias: normal flowers with conical cells, mutant flowers with flat cells, and dark flowers with conical cells. The last group of flowers is harder for the bees to see. Under normal conditions, the bees preferred the normal flowers. If given the choice between flat-celled flowers and dark flowers, the bees usually prefer the flat-celled flowers, presumably because they're easier to fine. There was one exception however. Under windy conditions (simulated with a shaking platform), bees preferred the hard to see flowers with conical cells.

This means that a variety of cues can influence a bee's choice of flower. If there’s no wind, color plays a more important role in flower selection. If it is windy, they prefer the grippy surface provided by flowers with conical cells. 

Friday, July 6, 2012

Flower color is shaped by bees

Australia has been geographically isolated from the other continents for over 34 million years. And yet, the flowering plants of Australia display similar colors and reflectance as their North American counterparts. According to Adrian Dyer and his colleagues from RMIT University, Monash University and the Swedish Museum of Natural History, it may be the discriminating eyes of bees that have driven that example of parallel evolution.

Bees (order hymenoptera) have trichromatic vision, meaning that their eyes contain three types of photoreceptors (cone cells) just as ours do. Unlike humans, who have blue, green and red cones, bees have blue, green and ultraviolet photoreceptors. This means that the vision of bees is shifted toward the ultraviolet compared to ours. Bees can best discriminate colors with wavelengths of about 400 and 500 nm.


Silverweed (Potentilla anserine)
Left: human vision; Right: bee vision.
Credit: Norwegian scientist-cameraman Bjorn Roslett

As you may have surmised, the majority of both North American and Australia flowers have colors that peak at either 400 or 500 nm. This makes perfect sense if you consider that it’s in the plants best interest to be as attractive as possible to its chief pollinators. Although flowers evolved around 125-130 million years ago, well before Australia went its lonely way, for much of that time flowers were not brightly colored as they are today. By the time flowers began to evolve colors, the Australian flora was no longer in contact with plants from other regions. They were in constant contact with insects, however.

You can compare human vision to bee vision in the video below.

Thursday, July 5, 2012

Good news for kids—you’re more creative than ever

Kids today have far less time for play than some of us remember having in our youths. Between the curtailing of school recess periods, participation in after school and weekend activities and the reluctance of parents to leave their children unsupervised, kids seem to have next to no time for unstructured play. What little time is available is often spent on video and computer games, rather than on playing with toys. What effect has this had on children’s creativity?

To find out, Sandra Russ and Jessica Dillon of Case Western Reserve University compiled data on children at play. Fortuitously, Russ has been conducting studies on children’s play for decades and has videos of children’s play sessions going back to the ‘80’s. The sessions were all administered and scored the same way using the Affect in Play Scale (APS). The APS correlates well to creativity, divergent thinking, coping ability and emotional understanding, though not to intelligence.

Each study followed the exact same protocol so that results could be compared over the years. A 6 to 10 year-old child is presented with two neutral-looking human hand puppets and three wooden blocks to use as she likes. The child is told that the researcher is hoping to learn about play, so please play with the toys and have the puppets speak out loud for the video camera. I’m sure those instructions weren’t at all off-putting for the kids.

In any case, comparing fourteen studies done from 1985 to 2008, the children’s APS scores slowly but steadily increased. In particular, imagination and enjoyment scores have been going up.

Clearly, the lack of free time has not been detrimental to children’s imaginations. Nor has the increased usage of electronic games. That said, I wouldn’t like to see unstructured playtime diminish any further. I’m sure the kids are with me on that one.

Watch Russ describe her research below:

Wednesday, July 4, 2012

Just for fun: Origami masks

Joel Cooper is an origami artist extraordinaire.  His creations, folded from a single sheet of paper without cuts or glue, can be seen on flickr and Etsy.

Here's a work in progress:

Origami Masks and Tessellations by Joel Cooper paper origami

And a finished art piece:

gnome king 2

Hat tip:  Jennifer Ouellette.

Tuesday, July 3, 2012

Too much Vitamin D is bad--maybe

Update 7/8/12: Yet another study shows that high amounts of vitamin D reduce the risk of fractures in elderly women. This makes me even less inclined to accept the results discussed below.

Vitamin D deficiency has been in the news lately as a culprit in a variety of illnesses, including diabetes, immune system diseases, cardiovascular disease and even some cancers. What about having an excess of vitamin D? That may not be good either. Researchers from the University of Copenhagen found that vitamin D, like everything else, is best in moderation. Maybe.

The scientists measured vitamin D levels in almost 250,000 participants between 2004 and 2010. Subjects were then followed to see who lived and who died over the next few years. The lowest mortality rate was observed for patients with intermediate serum vitamin D levels (between 50-60 nmol/liter). People with both lower and higher levels had an increased risk of dying.

I’m not surprised that there’s a sweet spot for vitamin D levels. That said, I’m dubious about this study. The researchers only took one blood sample per subject, and then looked at who had died over the next few years. I’m no clinician, but this seems like a tenuous connection at best. After all, a person’s vitamin D levels are bound to fluctuate depending on diet and sun exposure. To top it off, the researchers admit that their study did not include data on either cause of death, or on attributes well known to affect mortality risk (smoking, body mass index, etc.).

Meanwhile, another large study has shown that vitamin D, in combination with calcium, significantly reduces mortality in elderly people.  Lars Rejnmark of Aarhus University Hospital and an international team of doctors and scientists compiled data from thirteen randomized controlled studies with over 70,000 participants, most of whom were women in their 60’s and 70’s. Their analysis showed a clear (though small) benefit of taking ten times the amount of vitamin D used in the Danish study.

Taken together, this makes me wonder whether the Copenhagen scientists were measuring what they thought they were measuring. If it's true that too much vitamin D is as bad or worse than too little, we'd definitely need more and better studies to prove it.