The heart's regular rhythm is crucial to the delivery of oxygenated blood and nutrients to all the organs of the body. It is regulated by a bundle of cells called "the pacemaker," which use electrical signals to set the pace of the heart. Dysfunction in this mechanism can lead to an irregular heartbeat, known as arrhythmia, and often necessitates the implantation of an artificial pacemaker.
Previously, scientists found that many cases of inherited arrhythmias originating in the pacemaker could be attributed to functional defects in the channels responsible for the flow of sodium and calcium. Now Prof. Bernard Attali of Tel Aviv University's Sackler Faculty of Medicine and his fellow researchers have discovered a previously unidentified potassium channel in the cardiac pacemaker which helps to regulate the heartbeat. He hypothesizes that some cases of unexplained arrhythmia could be traced back to irregularities in this channel.
Developing therapies to target this potassium channel could be a significant step towards circumventing artificial pacemakers in favor of biological options, says Prof. Attali. This research has been reported in the journal PNAS.
A cellular heart model
To further investigate the workings of the biological pacemaker, Prof. Attali and his fellow researchers turned to embryonic stem cells isolated from human subjects. Once coaxed into differentiating into cardiac tissue, these cells began to beat automatically, like a small human heart.
While observing and recording the cells' electrical activity, researchers discovered the existence of a new channel in the pacemaker. Facilitating the flow of potassium from the pacemaker cells, this channel triggers the repolarization of the cells -- returning the cell membrane from a "beating" to a "resting" state -- and automatically renews or "restarts" the cycling of the heart.
Since discovering this channel in the embryonic heart, the researchers have shown that the channel exists in the adult heart as well. This finding deepens medicine's understanding of the heart's pacemaker function, which has been the subject of scientific research for over a century.
Screening for mutations
The next step is to conduct screening for mutations in the gene encoding the potassium channel, a process already underway at the TAU-affiliated Sheba Medical Center. "We would like to understand if there are genetic diseases linked to this channel," such as a previously unknown cause of arrhythmia, explains Prof. Attali. If a mutation is found, researchers can begin the hunt for drug compounds, which target this channel. The ultimate goal, he adds, is to be able to treat heart arrhythmias biologically by altering the properties of the pacemaker bundle, rather than relying on a human-made electric pacemaker.
Read more at Science Daily
Jun 11, 2013
Dog Disease Threatens Sumatran Tigers
The International Union for the Conservation of Nature estimates the viable breeding population of the Sumatran tiger numbers only 176 to 271 individuals out of a total population of 400 to 500 on the Indonesian island of Sumatra. Troubling signs of an outbreak of canine distemper virus (CDV) may threaten those surviving Sumatran tigers, reported the BBC.
Brain damage from CDV can cause the cats to lose their natural fear of humans. The cats will then wander into villages or fail to flee from illegal hunters. In either case, the tiger usually ends up shot. A few cases of this behavior have been noted in Sumatra, but veterinarians haven’t been able to test for CDV in these wandering tigers.
“The big threats facing tigers are habitat loss and degradation and poaching, but I think the third big threat now is likely to be disease, particularly one like CDV,” John Lewis, director of Wildlife Vets International, told the BBC.
In September, Lewis will work with a team of Indonesian veterinarians to develop a system to monitor for CDV and find a laboratory where samples can be analyzed.
“Once we have got that nailed down then we start work and try to design some sort of mitigation strategy, and that won’t be easy,” said Lewis.
Canine distemper virus kills most animals it infects. A paper in the Journal of Zoo and Wildlife Medicine noted that disease is second only to rabies in mortality rate and has been identified in all families of land carnivores: Canidae, Felidae, Hyaenidae, Mustelidae, Procyonidae, Ursidae, and Viverridae.
A study in the Journal of Veterinary Diagnostic Investigation documented CDV infections that killed 17 lions, tigers and leopards in zoos. Vets believed the cats had contracted the disease after eating infected racoons. A similar study in Clinical and Vaccine Immunology determined that CDV had killed at least 19 lions and tigers in Switzerland over the past few decades.
From Discovery News
New Layer of Human Eye Found
“Having identified this new and distinct layer deep in the tissue of the cornea, we can now exploit its presence to make operations much safer and simpler for patients,” she said in a press release.
“From a clinical perspective, there are many diseases that affect the back of the cornea which clinicians across the world are already beginning to relate to the presence, absence or tear in this layer.”
The new layer, called the Dua’s Layer in honor of the professor, is described in the journal Ophthalmology. It’s too thin to be seen; at 15 microns, it’s smaller than beach sand and mist, and makes up a small fraction of the cornea, which is 550 microns thick. It’s located toward the back of the cornea. The scientists detected it through electron microscopy after injecting tiny bubbles of air into donated corneas to separate the layers.
Already, scientists say they have a better understanding of certain diseases of the cornea. Corneal hydrops, for example, occurs when fluid builds up in patients with a deformity of the cornea and produces a bulge. Now researchers think the bulging is caused by a tear in the Dua’s layer.
It could also help in eye surgeries: A surgeon could inject a bubble next to the Dua’s layer to test how strong it is, for example.
From Discovery News
Black Hole Snoozes, Not Bothered With Eating Stuff
“Our results imply that the black hole went dormant in the past 10 years,” said Bret Lehmer of the Johns Hopkins University, Baltimore, and NASA’s Goddard Space Flight Center, Greenbelt, Md. “Periodic observations with both Chandra and NuSTAR should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching.” Lehmer is lead author of the new study published in the Astrophysical Journal.
Although the black hole is taking a nap, that doesn’t mean the galaxy isn’t picking up the slack. NGC 253 is one of the nearest “starburst” galaxies to the Milky Way, some 13 million light-years away, churning out newborn stars at an accelerated rate. It may seem surprising, then, that the black hole, with a mass of 5 million suns, is able to sleep through the star-forming commotion.
“Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant,” said co-author Ann Hornschemeier of Goddard. “NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it.”
This apparent contradiction provides an opportunity for astronomers trying to understand the nature of starburst galaxies and the part their central black holes have to play in galactic evolution.
It is thought that the supermassive black holes that live in the hearts of the majority of galaxies grow at the same rate as their host galaxies. However, black holes are also known to extinguish star formation should they start feeding, generating a hellish environment near the galactic hub — intense radiation generated by an active black hole can cause incredible disruption.
In the case of NGC 253, astronomers cannot be sure whether the rate of star formation is increasing or decreasing, but they are keeping a close eye on the black hole.
In 2003, NGC 253′s black hole was an entirely different creature. It was highly active, generating X-ray radiation spotted by NASA’s Chandra X-ray Observatory, indicating it was consuming matter. But in followup studies in 2012 using Chandra and NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), the black hole had fallen silent, indicating it had stopped accreting material.
Read more at Discovery News
Jun 10, 2013
Unfrozen Mystery: H2O Reveals a New Secret
Their work is published in the Proceedings of the National Academy of Sciences.
When water freezes into ice, its molecules are bound together in a crystalline lattice held together by hydrogen bonds. Hydrogen bonds are highly versatile and, as a result, crystalline ice reveals a striking diversity of at least 16 different structures.
In all of these forms of ice, the simple H2O molecule is the universal building block. However, in 1964 it was predicted that, under sufficient pressure, the hydrogen bonds could strengthen to the point where they might actually break the water molecule apart. The possibility of directly observing a disassociated water molecule in ice has proven a fascinating lure for scientists and has driven extensive research for the last 50 years. In the mid-1990s several teams, including a Carnegie group, observed the transition using spectroscopic techniques. However, these techniques are indirect and could only reveal part of the picture.
A preferred method is to "see" the hydrogen atoms-or protons-directly. This can be done by bouncing neutrons off the ice and then carefully measuring how they are scattered. However, applying this technique at high enough pressures to see the water molecule dissociate had simply not been possible in the past. Guthrie explained that: "you can only reach these extreme pressures if your samples of ice are really small. But, unfortunately, this makes the hydrogen atoms very hard to see."
The Spallation Neutron Source was opened at Oak Ridge National Laboratory in Tennessee in 2006, providing a new and intensely bright supply of neutrons. By designing a new class of tools that were optimized to exploit this unrivalled flux of neutrons, Guthrie and his team-Carnegie's Russell Hemley, Reinhard Boehler, and Kuo Li, as well as Chris Tulk, Jamie Molaison, and António dos Santos of Oak Ridge National Laboratory-have obtained the first glimpse of the hydrogen atoms themselves in ice at unprecedented pressures of over 500,000 times atmospheric pressure.
"The neutrons tell us a story that the other techniques could not," said Hemley, director of Carnegie's Geophysical Laboratory. "The results indicate that dissociation of water molecules follows two different mechanisms. Some of the molecules begin to dissociate at much lower pressures and via a different path than was predicted in the classic 1964 paper."
"Our data paint an altogether new picture of ice," Guthrie commented. "Not only do the results have broad consequences for understanding bonding in H2O, the observations may also support a previously proposed theory that the protons in ice in planetary interiors can be mobile even while the ice remains solid."
Read more at Science Daily
The Iceman Suffered Brain Damage Before Death
The protein investigation appears to support a 2007 research into the mummy’s brain. The study pointed to a cerebral trauma as the cause of death.
At that time, the research relied on a CAT scan of the mummy’s brain which showed two dark coloured areas at the back of the cerebrum. The inury added to the already known arrowhead wound on the shoulder and wounds on the hand.
Found in Ötzi’s left shoulder in 2001, the stone arrowhead has long been thought to have caused the prehistoric man’s death, fatally severing his left subclavian artery.
The 2007 study suggested that blood loss from the arrow wound would have first made Ötzi lose consciousness, with death coming later, from a violent blow to the head.
Either the man’s killer gave Ötzi the final whack, possibly by hitting him with a stone, or he could have fallen over backwards and hit his head on a rock, the researchers concluded.
The hypothesis had been left unexplored until 2010, when a research team from the European Academy of Bolzano/Bozen (EURAC), Saarland University, Kiel University and other partners decided to investigate the proteome of two pinhead-sized samples of brain tissue from the world-famous glacier corpse.
“The use of new protein-analysis methods has enabled us to pioneer this type of protein investigation on the soft tissue of a mummified human, extracting from the tiniest sample a vast quantity of data which in the future may well answer many further questions,” the researchers said.
Indeed, the scientists were able to identify a total of 502 different proteins.
“Of these, 41 proteins are known to be highly abundant in brain tissue and 9 are even specifically expressed in the brain,” microbiologists Frank Maixner of EURAC, Andreas Tholey of Kiel University, and colleagues wrote in the journal Cellular and Molecular Life Sciences.
“Furthermore, we found 10 proteins related to blood and coagulation. An enrichment analysis revealed a significant accumulation of proteins related to stress response and wound healing,” they wrote.
Found in a corpse almost devoid of blood, the astonishingly well-preserved clotted blood cells provide further evidence that Ötzi’s brain had possibly suffered bruising shortly before his death.
Whether this was due to a blow to the forehead or a fall after being injured by the arrow remains unclear.
“Our data reopens former discussions about a possible injury of the Iceman’s head near the site where the tissue samples have been extracted,” the researchers said.
Read more at Discovery News
Rare 'Sea Serpent' Caught on Video
In Europe, it has been called the “king of herrings,” perhaps because it would sometimes be sighted near herring shoals, which some fishermen believed it guided. In Japan, the coincident appearances of oarfish that have been washed ashore before earthquakes and tsunamis have led to the fish being regarded as a bad omen.
Almost all human encounters with oarfish have been ones in which the fish are dead or drying – washed onto the beach or swimming in a disoriented manner near to shore. The reason for that, simply, is that giant oarfish tend to inhabit deeper waters where human beings rarely venture.
But scientists with the appropriately-named SERPENT project (Scientific and Environmental ROV Partnership using Existing iNdustrial Technology) – a collaboration between marine researchers and the oil-and-gas industry, in which the latter provides the former with resources such as remote operated vehicles (ROVs) – have now recorded not one, not two, but five videos of the giant oarfish in its natural environment.
DNews posted part of one of the videos, complete with narration by lead researcher Mark Benfield, back in 2010; now Benfield and colleagues have compiled all the videos they took between January 2008 and August 2011 – using an ROV at depths of up to 1,600 feet in the Gulf of Mexico – and described their observations in a paper in the Journal of Fish Biology.
Interestingly, despite its long, lean form, the oarfish does not swim like a snake or an eel, but hangs almost vertically in the water. Renfield and colleagues report that the fact the fish did not immediately flee from the ROV’s bright lights suggest that they have few natural predators.
Read more and see the video at Discovery News
The Metallic Snow-Capped Mountains of Venus
As you might expect from a planet with such an alien atmosphere, the snow which caps the Venusian mountains is seemingly no less exotic. With the high temperatures on the planet’s surface, water ice is impossible (not that there is much water on Venus). It’s made from lead sulfide and bismuth sulfide, more commonly known as the minerals galena and bismuthinite.
We got our first glimpses under the corrosive clouds of Venus down into its dense, scorching interior late last century. Swathed in thick layers of cloud, roughly 50 kilometers (30 miles) deep, we have only two ways to see the surface of Venus — either descend to the harsh surface as the Soviet Venera landers did, or use radar to see through the clouds from orbit.
When orbiting space probes such as Pioneer Venus and Magellan used their radar instruments to look under the clouds though, they were met with something unusual. The highlands of Venus seemed unusually reflective, appearing much brighter than the lava plains of the Venusian lowlands.
This was quite a puzzle at first, which planetary scientists took some time to disentangle. There were a few possible explanations to choose from. A different surface texture on the mountaintops, perhaps looser soil, might cause them to appear differently, or a different kind of weathering at high altitude might cause the terrain to be different. Alternatively the surface at high altitude may be chemically different.
After Magellan arrived in the orbit of Earth’s twisted sister in the 1990s, it took some more detailed measurements. Everything pointed towards some form of chemical deposition occurring on the higher ground.
As we now understand it, the snow on Venus’ surface is probably more similar to frost. On the lower Venusian plains, temperatures reach a searing 480°C (894°F). This is hot enough that reflective pyrite minerals on the planet’s surface are vaporized, entering the atmosphere as a kind of metallic mist, leaving only the dark volcanic rocks like basalt in the Venusian lowlands.
At higher altitudes, this mist condenses, forming shiny, metallic frost on the tops of the mountains. And Earth’s simmering sibling has plenty of high altitude terrain. Maxwell Montes, the tallest peak on Venus, stands at an altitude of 11 kilometers (6.8 miles) — 3 kilometers (1.8 miles) higher than Mount Everest.
Whether snow genuinely falls on Venus is still unknown, but it’s certainly possible. Sulfuric acid rains have been observed plentifully on Venus as virga — rain which evaporates before it hits the ground, just like over the rainforests on Earth.
The heavy metal snows can be observed anywhere on the surface of Venus over about 2.6 kilometers (1.6 miles). It may not be any coincidence that below this altitude Venus’s atmosphere is technically no longer a gas.
Over 96 percent of the Venusian atmosphere is carbon dioxide, and our sister planet has nearly 100 times as much atmospheric gas as Earth does. This is what causes the huge crushing pressure at Venus’s surface, but that pressure also has a rather strange effect on the gas.
At the pressures and temperatures found near the surface of Venus, carbon dioxide becomes a “supercritical fluid” — an unusual state of matter, partway between a liquid and a gas. Often used on Earth as an industrial solvent, this supercritical carbon dioxide is expected to be found on Venus, coincidentally, at altitudes below around 2 – 3 kilometers (1.2 – 1.8 miles).
Read more at Discovery News
Jun 9, 2013
Opportunity Finds More Hints of Mars Habitability
The detection of aluminum-rich clays in a rock called “Esperance,” raises expectations for what may be Opportunity’s grand finale. The golf cart-sized rover, which is closing in on its 10th anniversary on Mars, is heading toward a 180-foot tall stack of rock that may answer questions about when the planet transitioned from a warm, wet world to the acidic dry desert that appears today.
Opportunity spent three years driving across Mars to reach a large impact basin known as Endeavour Crater. Mineral maps complied from Mars orbiters showed it contained slight amounts of clay minerals.
Clays form when water interacts with rock. Different types of water -- acidic or neutral pH, saltiness, etc. -- and different types of rock form different clays.
Opportunity does not have the onboard chemistry lab that NASA’s follow-on rover Curiosity is using to explore a different region of Mars for life-friendly habitats. But it can scratch into rocks and derive basic mineralogy.
Opportunity and a now-defunct rover twin, Spirit, were launched in 2003 to look for signs of past water on Mars. What they primarily discovered were chemical fingerprints of highly acidic water, more like sulfuric acid.
Esperance tells a different story.
“What we have here is a very different chemistry,” planetary scientist Steve Squyres, with Cornell University, told reporters on a conference call Friday.
“This is water you can drink. This is water that was probably much more favorably in its chemistry, in its level of acidity, for things like pre-biotic chemistry, the kind of chemistry that could lead to the origin of life,” Squyres said.
“This is the most powerful evidence for neutral chemistry water that has been found by Opportunity,” he added.
Curiosity, which landed on Mars in August, also found evidence of pH-neutral water changing the chemistry of a piece of bedrock in its Gale Crater landing site. Analysis of powder drilled out from the inside of the rock also showed all the elements needed to support microbial life.
Results of a second rock sample are pending.
Curiosity is on the move as well, making its way toward Mount Sharp, a 3-mile-high mound of rock rising from the crater’s floor that also shows signs of clay minerals.
Read more at Discovery News
By Trying It All, Predatory Sea Slug Learns What Not to Eat
The research appears in the Journal of Experimental Biology.
Pleurobranchaea californica is a deep-water species of sea slug found off the west coast of the United States. It has a relatively simple neural circuitry and set of behaviors. It is a generalist feeder, meaning, as University of Illinois professor of molecular and integrative physiology and leader of the study Rhanor Gillette put it, that members of this species "seem to try anything once."
Another sea slug species, Flabellina iodinea, commonly known as the Spanish shawl because of the orange outgrowths called cerata that cover its purple back, also lives off the west coast. Unlike Pleurobranchaea, however, the Spanish shawl eats only one type of food, an animal called Eudendrium ramosum. According to Gillette, the Spanish shawl digests the Eudendrium's entire body except for its embryonic, developing stinging cells. The Spanish shawl instead transports these stinging cells to its own cerata where they mature, thereby co-opting its victim's body parts for its own defense.
The story of Gillette's Pleurobranchaea-Flabellina research began with a happy accident that involved showing a lab visitor Pleurobranchaea's penchant for predation.
"I had a Pleurobranchaea in a small aquarium that we were about to do a physiological experiment with, and my supplier from Monterey had just sent me these beautiful Spanish shawls," Gillette said. "So I said to the visitor, 'Would you like to see Pleurobranchaea eat another animal?'"
Gillette placed the Spanish shawl into the aquarium. The Pleurobranchaea approached, smelled, and bit the purple and orange newcomer. However, the Flabellina's cerata stung the Pleurobranchaea, the Spanish shawl was rejected and left to do its typical "flamenco dance of escape," and Pleurobranchaea also managed to escape with an avoidance turn.
Some minutes later, his curiosity piqued, Gillette placed the Spanish shawl back into the aquarium with the Pleurobranchaea. Rather than try to eat the Spanish shawl a second time, the Pleurobranchaea immediately started its avoidance turn.
"I had never seen that before! We began testing them and found that they were learning the odor of the Spanish shawl very specifically and selectively," Gillette said.
Gillette and his team later replicated that day's events by placing a Pleurobranchaea in a training arena 12-15 centimeters from a Spanish shawl, then recorded the Pleurobranchaea's behavior. They returned the Pleurobranchaea to the arena for four more trials in 20-minute intervals, then repeated the procedure 24 and 72 hours later.
In the experiments, those Pleurobranchaea whose feeding thresholds were too high (meaning they were already full) or too low (they were extremely hungry) would either not participate or completely consume the Spanish shawl, respectively. Those that were hungry, but not ravenously so, continued to exhibit the avoidance-turn behavior when placed with the Spanish shawl even 72 hours later.
This showed that Pleurobranchaea was selective in its food choices, but only on a case-by-case basis; the sea slugs already trained to avoid the Spanish shawl would readily eat a species closely related to Flabellina called Hermissenda crassicornis.
Such behaviors come in handy in Pleurobranchaea's natural environment, Gillette said.
"If you're a generalist like Pleurobranchaea, it's highly strategic and advantageous to learn what's good and what's not good so you can decide whether or not to take the risk or of attacking certain types of prey," he said.
Read more at Science Daily
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