I have an announcement to make: I will be a speaker at the Women In Secularism 2 conference next May in Washington DC, probably in a panel on pseudoscience, alternative medicine, etc.
I always find hard to wrap my head around phenomena of such magnitude as supernovae, and I always end up with the feeling that I haven’t really understood anything or even begin to imagine the events described by astronomers, but the scale of our universe and the extraordinary events occurring in it never cease to amaze me. Even more so when I think about us, sophisticated apes building sophisticated instruments to give us a peek into the incomprehensible beyond.
Rare type of supernova found. Davy posted an interesting discussion on supernovae. I learned a lot from it. There are two types of supernova events: normal, Type Ia supernova events, which occur once or twice every 100 years. But there is an even rarer type, occurring once in every 1000 supernovae. This is the type that was just observed. Peter Nugent of the Lawrence Berkeley National Laboratory discovered the new supernova, PTF 11kx, at Palomar Observatory on January last year. It is believed that the majority of Type Ia supernovae arise from the collision of two white dwarf stars, producing a massive burst of light and energy. In contrast, novae produce far less energy, and are the result of a white dwarf star capturing gas from the red giant it is orbiting, and causing a brilliant explosion called a nova. Even though the white dwarf eventually accumulates more gas and erupt another nova, it was believed that the energy would never be enough to cause a supernova event. But this is what happened in the case of PTF 11kx. When PTF 11kx went supernova, it produced a strong calcium signal, which is a hallmark of supernovae and partially how it was detected. As the team monitored the supernova, the calcium signal slowly subsided, as expected. Then, 58 days after the supernova was detected, the team once again received a strong calcium signal. The researchers think that this second signal originated in the collision of the supernova's gases with expanding shells of gas, thought to be the remnants of previous novae. The findings are important because supernovae are considered to be the "standard candles"used for estimating distances across the cosmos, because they are supposed to have the same intrinsic brightness. If the different origins cause the supernovae to have different brightness, this could lead to errors in distance measurements. (The image is an artist's rendition of a white dwarf star capturing gas from a red giant, from Romano Corradi and the Instituto de Astrofisica de Canarias)
A hat tip to archaeopteryx for pointing me to this exciting finding in the field of astrobiology/chemistry:
Precursor to RNA sugar discovered around sun-like star. Although glycolaldehyde, a simple form of sugar, has been previously found in space, this is the first time it is detected in the gas surrounding a sun-like star. This is exciting because glycolaldehyde is one of the components in the formation of RNA molecules, one of the key nucleic acids in living organisms. Glycolaldehyde can react with propenal and form ribose, which is the sugar in RNA. RNA is considered by many to be a key molecule at the origins of life (RNA World Hypothesis). The sugar was found in the disk of dust and gas surrounding a young star, IRAS 16293-2422, which has a similar mass to the sun and is located in the constellation of Ophiuchus, ~400 light-years away from us. The sugar molecules were detected by the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile. The glycolaldehyde molecules were found to be moving towards the star, raising the exciting possibility that complex molecules that can form part of living organisms can get incorporated on into newly forming stars and planets. Since IRAS 16293-2422 is not too far from our planet, in astronomic terms, astronomers will be able to study the chemical makeup of the gas and dust around the star, and study how the molecules interacts as new planets are formed.
Meanwhile, back on our own planet, inside our own primate heads, we still have a lot to learn about how we learn.
How to learn in your sleep. Mo Costandi, one of my favorite neuroscience writers, reports on this intriguing publication: although it does not mean we can learn algebra or chemistry effortlessly while we sleep, results published in Nature Neuroscience this week demonstrate that humans can learn entirely new information while sleeping. Israeli scientists at the Weizmann Institute of Science used classical conditioning to teach 55 healthy participants to associate smells with sounds as they slept. What they did was to expose the sleeping volunteers to pleasant smells (like perfumes) and unpleasant smells (rotting fish), and accompany the odor with a specific sound. When the volunteers were awake, in the absence of any pleasant or unpleasant odors, they unconsciously sniffed deeper if they heard the sound associated with the nice smells, while they sniffed more weakly if the sound played was the one they heard in conjunction with the bad smells in the sleeping conditioning phase. This controlled sniffing reaction was already known in people who were awake while undergoing conditioning. Although the limits of what we can learn while we sleep are not known, the Israeli researchers are optimistic that it won’t be limited to simple Pavlovian-type reflexes, and they hope that their findings will lead to possible treatments, sleep therapies, to alter behavior in conditions such as phobias. A very interesting question is whether the neural networks involved in sleep-learning are similar to the ones used during wakeful learning.
Drop in IQ linked to heavy teenage cannabis use. I'm definitively in the camp that marijuana should be legalized, since I don't think any type of prohibition works, except for making the dealers or corrupt officials richer, and tempting kids even further. But I'm also in favor of education. And this latest study suggests that smoking a lot of pot when you are a teenager will have negative effects on cognition, effects that do not appear when people start smoking pot past the teenage years. The study involves >1,000 New Zealanders that were followed from birth, for 40 years. The heaviest adolescent-onset users (<18 years of age) had an average decline of 8 IQ points from childhood to adulthood (tested at age 38). The loss in IQ seems irreversible, meaning those who quit still had decreased IQ, compared to non-users who had no decrease in IQ from childhood. Non-users had on average increased their IQ by around one point. And even after setting aside the heaviest users, a decline of a few IQ points from their childhood value was still seen in less heavy users who had started in their teens. Moreover, persistent potheads who only started when they were older than 18 years did not seem show the same IQ decline. The hypothesis is that THC may have neurotoxic effects when smoked at an age critical for brain development. The mechanism is unknown. There was no difference in the proportion of heavy cannabis users in the full study sample and in those with only a high-school education or less, so the decline in IQ is not education-related.
Older fathers transmit more mutations to their children. A new study just published in Nature correlates age of the father with number of new mutations passed onto the offspring, and suggests that the increase in the age at which men father children may be linked to the increased rates in autism and schizophrenia. The fact that older men's sperm carry more new mutations was already known, but this new study has a ton of data and can therefore quantify the effect, and it's pretty exponential: a 36-year-old father will pass on twice as many mutations to his child as a 20 year old, and a 70-year-old eight times as many. Contrary to popular belief, fathers transmit ~4X times as many new mutations as mothers: on average, 55 versus 14. This is because sperm cells are constantly being generated by rapid division throughout a man's life while women are born with all the eggs they will ever have. For women, the number of mutations possible for each egg is ~14, and it does not increase with the mother's age (the risk of Down syndrome increases with the mother's age because it is a chromosomal abnormality, not a syndrome caused by mutations). The study was carried out by deCODE, a group in Iceland which has now sequenced the entire genome of many Icelandic families, and this allowed to calculate mutation rate. Most mutations are harmless, but it appears that mental illnesses or disorders are caused mostly by new mutations, which is the reason for the possible link between increased paternal age and the increased incidence of these disorders. The scientists estimated that an Icelandic child born in 2011 harbors on average 70 new mutations, compared with 60 for a child born in 1980; the average age of fatherhood rose from 28 to 33 over that time.
Genome Sequencing Clears Up a Cancer Medical Mystery. I hope you guys don't think this is shameless self-promotion: I'm an author on the paper who just made it into the science news at ScienceNOW. It was a great collaboration with a great group of people. I’m honored to be part of the team. Sometimes in clinical trials of cancer drugs, there is a patient or two that shows an extraordinary response. It’s always a reason to rejoice when someone is helped by a drug, but now we have a methodology that can help us understand the reason behind the extraordinary response and to harness that knowledge to identify patients who will benefit from specific drugs. The case in question was of a woman with metastatic bladder cancer whose tumors disappeared after she was given everolimus, a drug that targets mTORC1, a protein involved in cell growth. She has been cancer-free for 2 and a half years now. In the images you can see how her metastases shrunk and disappeared. Everolimus did not work for most patients in the clinical trial and it was abandoned as a single agent for bladder cancer. We first sequenced the tumor DNA to see if there were mutations in a few genes in the mTORC1 pathway, “usual suspects” that could explain why her tumors vanished. Because we found nothing, we decided to sequence the entire genome of the tumor. We found mutations in two genes, NF2 and TSC1, which previous studies indicate that they participate in the mTORC1 pathway (it’s not always crystal clear how many genes influence a certain pathway for growth). We found TSC1 mutations in other patients in the same failed clinical trial, and found that 4 patients whose tumors shrank also had mutations in TSC1. We will now screen bladder cancer patients for TSC1 mutations to test if everolimus gets rid of their tumors. The same paradigm is going to be used for patients with unusual responses to other drugs in clinical trials, so we can identify other mutations that correlate with treatment success.
From the narrow perspective of the developed world, obesity and cardiovascular disease and diabetes are becoming scourges and we all would like to know what to do about it. But before we can take measures, we must understand exactly how our physiology responds to a superabundance of food. And this week a study was published, 25 years in the making. And the results have disappointed some. To me, it was good news.
Forget severe calorie restriction, it does not extend lifespan. A 25 year long, very famous experiment, involving semi-starving a bunch of rhesus macaques, has ended. The hypothesis that calorie restriction extends life span has faltered: the skinny monkeys died at roughly the same age as their normal weight counterparts. And by calorie restriction we mean 30% fewer calories than those required to maintain a normal weight. Those poor macaques were the equivalent of a 6 foot tall man weighing 130 lbs. To keep this low weight, the animals must have been constantly hungry. Maybe they believed they indeed lived longer, but it just seemed that way to them because they must have been kind of miserable. It makes me question the ethics of the experiment. Even if it had proven to result in a bit of life extension, how many people would ever realistically adopt such a drastic way of life? In the meantime, a few people, including some scientists, put themselves on severe calorie restriction, hopeful to extend their lives, because in 2009, a study reported that macaques on calorie restriction diets died of age related causes at a lower rate than the control group. The problem with that study is that the monkeys were fed a fatty, unhealthy diet, so the ones that ate less junk food, lived longer. In this new study, all the monkeys were fed a healthy diet, what changed was the number of calories consumed. The field of calorie restriction studies has been giving contradictory results for a while, especially in mice. This is attributed to the different genetic backgrounds of the mouse strains used. Provisional conclusion: eat healthy, not too much, and don't starve yourself. Healthy diets and genetics matter more to your longevity than 30% calorie restriction.
And while we are thinking about food, what about exercise?
Debunking the Hunter-Gatherer Workout. What is the biggest culprit in the current developed countries epidemics of obesity, cardiovascular disease and diabetes, inactivity or the super-abundance and easy availability of very caloric foods? It’s probably both, but which is causing the most harm? Much attention has been paid to our sedentary habits, citing that when we evolved as hunter-gathers we spent a lot more calories than we currently do. But do hunter-gatherers spend more calories that couch potatoes do? The Hadza come to our rescue once again. The African hunter-gatherer people from Tanzania have graciously agreed to be part of a study to measure their energy expenditure, and the results were just published in PLoS One. The Hadza sure spend a lot of time doing physical work: the walk for miles in hilly terrain, every single day, to collect tubers and berries, often while carrying the weight of their babies, firewood, or water. The men often cover 15 to 20 miles daily to hunt or find honey. But astonishingly, the number of calories they burn per day is comparable to those of sedentary Western people! (even after adjusting for parameters such as body mass, lean body mass, age, sex and fat mass). One hypothesis is that Hadzas spending less energy in the unseen physiological tasks that maintain our cells working and our systems functioning. There are some studies reporting differences in metabolic-hormone profiles between hunter-gatherers and Western populations, which would support this hypothesis, but more data is needed. The scientists believe that this Hadza study shows that we need to reduce the number of calories that we eat, because if we temporarily increase our energy expenditure, the body ultimately adapts by keeping the expenditure in check; after all, we evolved to survive in environments in which resources were limited. Now that resources are no longer limited, and our primate brains crave sugar, we end up getting fat no matter how much we exercise, if we don’t also keep the calorie intake in check.
If you think of our physiology and food, our first relationship with food as the mammals that we are is with mother’s milk, a marvelous secretion shaped by millions of years of evolution. Milk is so ubiquitous, and many of us consume it as adults, too, but we rarely think about milk. And sometimes really unexpected stuff crops up.
Mothers make different milk for sons and daughters. This is totally new to me, and very interesting. Recent research has shown that a few mammal species, such as deer, seals, monkeys, and humans produce milk of different composition for their male and female offspring. Different species make of course, milk of different composition according to the developmental needs of the babies, for example, rapidly growing species needs milk rich in proteins, species for which the young have to get fat very quickly (think seals) is very rich in fat, etc. So it makes sense that, if male and female young have different developmental rates, they may benefit from different types of milk. Evolutionarily speaking, at times mothers may favor one or other sex in their offspring, according to the environmental pressure. The first evidence for sex-biased milk, according to this lengthy but fascinating article, comes from a study of captive Iberian red deer from a few years ago. Mothers produced higher milk yields for sons, and also the milk was higher in protein content. Male calves are bigger than females, but they also have more lean muscle mass, hence the increased protein content in mother’s milk. In captive rhesus monkeys, the milk for sons was significantly higher in fat but there was an interaction with maternal parity. First-time mothers produced milk higher in fat than mulitparous mothers (10% richer milk). What could be an explanation for this? First-time rhesus monkey mothers are usually very young and smaller than older mothers and their offspring tends to be smaller; since for males, body size is important in competition, it makes more evolutionary sense to stuff their baby boys full of fat milk so that in the future they can compete with the sons of bigger mothers. A 2010 small study of human mothers in Boston showed that mothers of sons produced ~25% higher energy density in milk than mothers of daughters. And a very recent study of 72 women in rural Kenya revealed sex-biases in the milk fat concentration, with mothers of sons producing significantly fatter milk. But this effect was only seen in women whose household owned more land and dairy animals. Relatively poorer women produced higher fat concentration in their milk for daughters. These results provide support for the Trivers-Willard hypothesis that mothers in the best condition would favor sons because they will likely have high reproductive success, but that women in poor condition should favor the “safer” investment in daughters. It’s “safer” because all daughters are likely to have progeny but not all sons are, at least in certain evolutionary scenarios: weaker males may be outcompeted in certain species and leave no offspring at all. Interesting observations, and intriguing hypothesis; too premature in my opinion to jump to any conclusions.
FEATURED CREATURE PHOTO. OMG! The creationists were right! This is better than crocoduck, it’s a poodle moth! To be precise, a Venezuelan poodle moth. Apparently this photo went viral, and people were frantically trying to determine whether it was photoshopped. But it is a bona fide photograph, taken by Dr. Arthur Anker. Dr. Karl Shuker, zoologist and cryptozoologist set out to find out by asking around. This week, he got an answer from Dr John E. Rawlins, Curator and Chair, Section of Invertebrate Zoology, Assistant Director of Research and Collections, Carnegie Museum of Natural History in Pittsburgh, USA: "Here’s my vote/guess to ID the poodle moth. The antenna is distinctive. Lasiocampidae: Artace or a related genus, probably not Artace cribraria (presumably North America to Argentina, but nobody has revised this group from Mexico south). There are more than a dozen described South American species of Artace, but their delimitation, validity, and even their generic placement is uncertain. It will take two things to solve this problem: a comprehensive revision of Artace and kin, plus an actual specimen of a genuine “Venezuelan poodle moth.”Definitely NOT Lymantriidae or Arctiidae, but easily confused with some Megalopygidae, Limacodidae, even Dalceridae, and Cossidae.” Now you know.
Wasps follow strict order of royal succession. It turns out that humans are not the only ones to have a defined order of succession when a leader dies: for example, if the US President dies or is incapacitated or removed from office, the VP takes his position, if he/she dies, it's the Speaker of the house, etc. Wasps of the species Ropalidia marginata (from South Asia) have an established order of succession, too. This is clearly advantageous because when a queen dies, if the wasps in the nest engaged in conflict to decide who would be queen, they could potentially be taken over by another colony. The line of succession (in scientific terms, "reproductive queue" in the case of wasps) solves the issue of conflict. When a queen dies (or is removed by pesky scientists, in this case), immediately one specific worker wasp becomes hyper-aggressive and starts attacking her neighbors. The interesting thing is, they don't fight back. Then the queen wannabe develops ovaries and becomes peaceful and transforms into the queen. If the scientists remove her, the same thing happens again, down to a 5th line of succession! That's pretty astonishing. Scientists still don't know exactly what determines if a worker is queen potential; age is a good predictor but not a perfect one, since sometimes, potential queens bypass older wasps. Interestingly, dominance hierarchy within workers has nothing to do with it.
Genes evolve new functions and animals evolve new abilities. I absolutely love this story because it is a perfect illustration of how animals acquire new abilities when genes are tweaked by evolution just a tad, and voilà, a new function! As you all know, pit vipers have the ability to sense infrared radiation, and thus, "see" warm-blooded animals even in the dark. The sensors in the pits rely on a protein encoded by the gene TRPA1. The protein is an ion channel: when it binds specific chemicals, the channel opens, the ions to flow into nerve cells and a nerve impulse is produced. In humans, this protein is responsible for the effects of wasabi, for example. In the pit vipers, the protein evolved to be exquisitely heat-sensitive: in the Western diamondback rattlesnake, it starts getting activated at ~80 degrees Fahrenheit (~27 degrees Celsius), for example. In pythons, the ion channel opens when the temperature of target is around 37 degrees Celsius which is normal body temperature for most mammals. Rattlesnakes and pythons are so evolutionarily distant, that TRPA1 could have evolved the infrared sensing abilities separately. What is even more amazing is that in vampire bats, there is a similar protein, called TRPV1, that became an infrared sensor. Vampire bats can thus sense the warmth of their prey in the cool night air. The TRPV1 protein is normally the receptor for capsaicin (the "heat" in hot peppers). Proteins that sense spicy or "hot" compounds evolved to sense actual heat, as in temperature. How cool is that? And snakes are not the ancestors of bats, therefore heat sensing ability evolved totally separately, but still used a similar tool from the genetic tool box: an ion channel that could sense a spicy compound!