FEATURED IMAGE: The Tarantula Nebula
What a name for a nebula! Explanation: The Tarantula Nebula is located in our neighboring galaxy, in the Large Magellanic Cloud (LMC). The red and pink gas indicates a massive emission nebula.The images were obtained by the Hubble Space Telescope. Visit our group The Daily Cosmos for many more beautiful nebula pictures posted by Doone in the comments section.
MICROBIOLOGY: 86 million year-old bacteria still alive in deep ocean mud. This is not the first time that living bacteria have been discovered many meters into marine sediments. But a new Science article this week, by Danish and German scientists, describe bacteria breathing oxygen at least 30 meters in deep red clay at the bottom of the Pacific ocean north of Hawaii. These bacteria have not had exposure to sunlight or organic matter for 86 million years! I will say it again: the last time these microbes saw fresh oxygen or sunlight, dinosaurs walked the Earth! So how are they still alive? The bacteria living in these sediments are breathing oxygen at a much, much slower rate than other microbial communities. Scientists calculated that the respiration rate of these bacteria dropped ten thousand fold at 30 meters compared with at or near the surface of the sediment. Thus, aerobic metabolism can persist in deep marine sediments, although at an extremely low rate. It is amazing how little it takes to sustain life! The scientists measured the oxygen in the core with special sensors; because they know how much oxygen should have diffused down to each mud depth, any "missing" oxygen had to mean that microbes had consumed it. What is special about this North Pacific sediment is that the microbial community was too sparse to consume it all, which is why they detected oxygen all the way down to ~30 meters. In most places, bacteria consume all the oxygen within 10 cm of sediment. The very slow oxygen consumption by the microbes allow them to subsist on very small amounts of long-buried organic materials. This type of research may be useful in the search for life on other planets, given the extreme conditions in these deep clay sediments. Of course, to be absolutely sure these extreme microbes are alive, one would need to see them divide. But while E. coli divides every 1/3 hour, the calculated rate for these extremely slow microbes would be 1,000 years. We may need to wait a bit to see these microbes divide.
ANIMAL BEHAVIOR: Insect uses its victims’ carcasses as camouflage. Acanthaspis petax, an assassin bug that lives in East Africa and Malaysia, hunts its prey by piercing it with its proboscis, dissolving the tissue with its potent saliva, and sucking it dry from the inside out. But this is not novel. Other assassin bugs do this, too. What is special about A. petax is that it camouflages itself with the bodies of dead ants that it carries on its back, all bound together with a sticky substance. Although some scientists believed the dead ant exoskeletons were for olfactory camouflage when hunting, it turns out that the ghastly camouflage is for protection against their natural predators, jumping spiders. But New Zealand scientists showed experimentally that “naked” bugs were attacked 10 times more frequently than the ones carrying the dead ants on their backs. Jumping spiders hunt guided by vision, so the protection was not olfactory, but visual. For some reason, jumping spiders do not hunt ants, therefore they rejected the masked assassin bugs as prey.
GENETICS: Gene variant associated with better memory and higher risk for PTSD. Some researchers have hypothesized that the risk for post-traumatic stress disorder (PTSD)depends on the capacity a person has to form strong memories, especially emotional memories. Now a team of Swiss scientists has found that a variant of the gene PRKCA, that encodes an enzyme involved in the formation of emotional memories, correlates with PTSD in Rwandan refugees. The scientists tested 700 healthy volunteers by showing them photos with highly charged emotional content and quizzing them about details of the photos. Volunteers with two copies of the A allele of PRKCA remembered the most detail, those with two copies of the G variant the least amount of detail, and heterozygotes, with one copy of the A variant and one of the G variant, fell somewhere in the middle. The researchers also studied the distribution of the A allele in a group of 347 survivors of the 1994 Rwandan genocide; 134 of them had been diagnosed with PTSD, although all 347 refugees had experienced traumatic events. Carriers of the A allele had a 2-fold increase in risk for PTSD. The A allele is more frequent in Europeans than in African people. Larger studies will be needed to determine which other genes and variants are involved in PTSD; however, this finding is in itself very interesting because it confirms the hypothesis that increased emotional arousal can lead to the formation of stronger memories and to increased PTSD risk.
NEUROSCIENCE: Phineas Gage's connectome. Mo Costandi, from The Guardian (UK), one of my favorite science writers, who writes the blog Neurophilosophy, has a fantastic, informative, entertaining piece on the connectome of Phineas Gage's brain, after the famous accident he suffered in 1848 while working on the railroad. A 3-foot long metal rod, a "tamping iron", used to compact the powder, was shot through his skull after an accidental explosion (see video for the trajectory). He survived the horrific injuries, but his friends said his personality changed radically after the accident. So what is "connectome"? The Human Connectome Project, started in 2009, has the goal of mapping out all the connections in the human brain, down to the individual cells and their functions. Up to now, the brains mapped as those of healthy adult volunteers who undergo brain scans. But now, a paper has been published with the connectome of Phineas Gage brain. His brain is not preserved, so how was this done? Jack Van Horn and colleagues at UCLA used high-resolution CT scans of his skull, that digitally reconstructed the trajectory of the iron rod as it passed through his brain. Then they compared it with data from 110 healthy volunteers, all male, and approximately 25 years old (Gage's age at the time of the accident). The UCLA researchers estimate that the rod destroyed about 4% of his cerebral cortex, and ~ 11% of the white matter in the frontal lobe. Tracing the damage by building his connectome, it seems obvious that the damage was far more extensive than previously thought. Check out the two connectograms (the colorful circles below): that of 110 healthy adults, compared to his. It does not need a figure legend, I think. Gage's connectogram is consistent with damage to the frontal lobe and "limbic system", and with the behavioral changes that he apparently suffered. Gage died at age 36, after a series of severe convulsions. Here's the connectogram showing the major pathways in the healthy human brain, averaged from the 110 data sets.
MATHEMATICS/HUMAN PHYSIOLOGY: A mathematical model of obesity. The New York Times published today a fascinating interview with mathematician Carson Chow from the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK), who has developed an equation that describes the problem of obesity and how American became so overweight in such a short period of time. He explains that a mathematical model may give an answer to the question much faster than experimental work or fieldwork. He openly admits that the food industry lobby will not like his conclusions. According to Chow, it's the overproduction of food and the fact that it became so inexpensive that is causing this epidemics. Among the many surprising things his model predicts, is that if you're already obese, even an increase of 10 calories per day over long periods will cause you to gain more weight than if you are of normal weight and consume an extra 10 calories, every day. His model also predicts that humans are slow to respond to calorie intake changes, and that what counts is the # of calories consumed over the course of a year, not really daily variations in the food intake. I recommend reading the whole interview, is very interesting.
Science bits and news from other sites:
Translating neuronal activity directly into control signals for devices to assist paralyzed people has been attempted for several decades now, with the latest successes being paralyzed people controlling the cursor on a computer screen, as well as able-bodied monkeys that were trained to control robotic arms. However, up until now, nobody knew if tetraplegic people could control robotic arms to perform fine tasks, such as moving in 3 dimensions, grasping objects, etc. But in a new study published this week in Nature, two people with almost-complete body paralysis were able to reach and grasp small balls and a thermos of coffee with a robotic arm, using only their minds to direct the motion of the robotic arm. The way this works is as follows: the patients had a very small array of electrodes, called BrainGate, implanted in their motor cortex, which is the part of the brain that controls voluntary movements. BrainGate reads brain signals and sends them to an external computer that translates it into a command. Different brain patterns tell robotic arm to move right or left, go up or down, front and back, etc. The device was calibrated to the patients' thoughts. That took only about 30 minutes, and the patiens were not previously trained to use BrainGate. After ~ 200 trials, both patients were able to use their thoughts to maneuver a robotic arm to grasp small foam balls, successfully, 95% of the time. One of the patients (in the video) who suffered a stroke 15 years ago, was able to control the robot arm to grab a thermos with coffee, direct it to her lips, so that she could actually get a sip of coffee by herself! Watch the video, her smile at the end is priceless. This technology could help patients with brain or spinal injuries recover some of the freedom to perform everyday activities. This patient has had her implant for 5 years now, so it is safe to assume that BrainGate does not deteriorate easily with time.
Nanotechnology: Viral electronics! Who would have thought such a thing could be possible? UC Berkeley scientists have built a proof-of-principle generator that used viruses to create electricity! The generator consists of a postage stamp-sized electrode on a small film of viruses. The virus used in the research was an M13 bacteriophage. Bacteriophages attack bacteria but are harmless to humans. The scientists added four negatively charged molecules to one end of the corkscrew-shaped proteins that form the virus coat, using standard genetic engineering techniques; these molecules boost the voltage of the virus because they increase the charge difference between the positive and negative ends of the coat proteins. The viruses naturally self assemble into an orderly film, and this structure is much sought after in nanotechnology. The researchers found that a stack about 20 layers of viruses exhibited the strongest piezoelectric effect (conversion of mechanical energy into electricity). The generator works as follows: a finger was used to apply pressure on the viral layers, which then converted this mechanical energy into ¼ of the voltage of a AAA battery. Of course this is not much, but it is an encouraging first step toward the development of personal power generators or actuators for use in nanodevices. This generator is a precursor to tiny devices that could harvest electrical energy from the vibrations of everyday tasks, such as shutting a door or climbing stairs.
A high fructose diet is bad for memory and learning. If you are a rat, six weeks of drinking water with a high fructose solution as drinking water, will make your brain slow. UCLA scientists gave two groups of lab rats the fructose-containing solution instead of drinking water, but they gave a supplement of omega-3 fatty acids to one of the groups (flaxseed oil and DHA, or docosahexaenoic acid). Omega-3 fatty acids are known to protect neuronal synapses from damage. Needless to say, healthy synapses are key to memory and learning. Prior to the 6-week diet, the rats were trained on a maze for 5 days; the maze contained visual landmarks to help rats remember the way out. After the 6-week diet, the rats were tested to see how well they remembered the way out of the maze. The animals that were given the omega-3 fatty acids navigated the maze much faster than the rats that did not receive the supplements. The DHA-deprived animals were slower, and they did not recall the escape route that they had learned 6 weeks earlier as well as the other group. Their brains showed a decline in synaptic activity. The DHA-deprived rats developed signs of insulin resistance, meaning that insulin had lost much of its power to influence the brain cells. The researchers are not too concerned with the normal consumption of fruit, since fructose is not concentrated in the fruit, and fruits have other nutrients and fiber as well. The principal investigator, Dr. Fernando Gómez-Pinilla, advises people to keep the intake of sugary treats to a minimum and also eat foods rich in omega-3 fatty acids. For vegetarians, good sources are walnuts and flaxseed; for fish eaters, salmon is an excellent source of DHA.
Why manta rays need trees to survive. Carl Zimmer wrote a very fine piece on new research from the Palymra Pacific atoll that reveals how intimately interconnected sea and land ecosystems are. Scientists tracking manta rays that live around the atoll noticed that the manta rays seems to swim off the coast where there were native forests, and not off the coast were coconut trees were planted as a crop. The data showed that for every 4 manta rays they found off the coast of the native forest areas, they found none by the coconut groves. To find out why native forests help manta rays thrive, the researchers studied both the terrestrial and the marine ecosystems. They found that the native forests had five times more birds, such as red-footed boobies, than the coconut forests. While nesting in the trees, the birds’ droppings (guano) fall to the ground. Guano is very rich in nitrogen; it fertilizes the trees, more leaves are produced and the leaf litter creates a very rich soil. When it rains, the guano-rich soil; is washed into the ocean. The nitrogen and other nutrients flowing out from the native forests fertilize the phytoplankton; thus zooplankton, which feeds off the phytoplankton, was found to be three times more abundant off the coast of native Palmyra forests than off the coasts of palm forests. More zooplankton, more food for manta rays, that are filter eaters. When people in the Pacific cut down native trees to plant coconut palms, they of course had no idea that they are affecting manta ray populations. The link between terrestrial and marine ecosystems is very string, and very important, but also very vulnerable to human intervention. The “dead zones” in places like the mouth of the Mississippi River, for example, are created by pumping too much nitrogen from fertilizers used for crops in a very short time into a marine ecosystem.
Decompression sickness in Jurassic reptiles. Rising too quickly to the surface when diving causes decompression sickness or “the bends”. The changing pressure causes dissolved gases in the blood to form tiny bubbles (the same phenomenon happens when we open a bottle of fizzy water). The bubbles can be fatal, depending on which tissues they end up. Experienced divers know to avoid the bends by rising slowly to the surface. Incredibly, air-breathing diving vertebrates such as dolphins, and extinct marine reptiles can suffer from the bends also. The evidence is in their bones: when the bubbles form in bone, they cut the circulation of blood in that bone area causing the tissue to die and weakening the bone, eventually causing fractures or collapse. Bruce Rothschild has studied bone diseases in prehistoric animals for many decades. He found evidence of decompression sickness in ~15% of fossils of prehistoric turtles, ichthyosaurs, mosasaurs, and sauropterygians. But why would animals adapted to live in the sea make such a mistake? The explanation seems to be that they were swimming to the surface as fast as they could to avoid being eaten by gigantic prehistoric shark. Rothschild figured this out because he found traces of the bend in Jurassic and Cretaceous marine reptiles, but not in ichthyosaurs from Triassic. But wait a minute. The Triassic is BEFORE the Jurassic and Cretaceous. One would expect more decompression sickness in earlier times. But there were no big, fast-swimming predators in Triassic waters that could have preyed on ichthyosaurs! When new predators such as gigantic sharks appeared in the Jurassic, marine reptiles sometimes could not avoid surfacing very quickly to escape the predator! It was either the sharks’ jaws, or the bends.