Saturday, October 9, 2010

PINPOINTING WHERE VOLCANIC ERUPTIONS COULD STRIKE

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A better way to pinpoint where volcanic eruptions are likely to occur has been produced by an international team of geophysicists.

Scientists from the universities of Leeds, Purdue, Indiana and Addis Ababa, investigated volcanic activity occurring in the remote Afar desert of Northern Ethiopia between 2005 and 2009.

By studying a rare sequence of 13 magmatic events – where hot molten rock was intruded into a crack between the African and Arabian plates – they found that the location of each intrusion was not random. They showed that they were linked because each event changed the amount of tension in the earth's crust.

The findings, published in Nature Geoscience, will help scientists to more accurately predict where volcanic eruptions could strike and contribute to efforts to limit the damage they can cause.

Lead author Dr Ian Hamling, who completed the analysis as part of his PhD in the School of Earth and Environment at the University of Leeds said: "It's been known for some time that a large earthquake has a role to play in triggering subsequent earthquakes, but until now, our knowledge of volcanic events has been based on isolated cases. We have demonstrated that volcanic eruptions can influence each other. This will help us predict where future volcanic eruptions are likely to happen."

The team studied the region around a large volcanic dyke – a vertical crack which is created when Magma seeps from underground through rifts in the surface of the earth – which erupted in the Afar desert in September 2005.

The Magma - hot molten rock - was injected along the dyke between depths of 2 and 9 km, and altered the tension of the earth. The team was able to watch the 12 smaller dykes that subsequently took place in the same region over a four year period.

By monitoring levels of tension in the ground near where each dyke was intruded they found that subsequent eruptions were more likely in places where the tension increases.

Dr Hamling said: "If you look at this year's eruptions at Ejafjallajokull in Iceland, by estimating the tension in the crust at other volcanoes nearby, you could estimate whether the likelihood of them eruption has increased or decreased. Knowing the state of stress in this way won't tell you when an eruption will happen, but it will give a better idea of where it is most likely to occur."

University of Leeds

RED LIGHT REGULATES NECTAR SECRETION

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Flowering plants produce nectar to attract insect pollinators. Some plant species, such as Lima bean, also secrete nectar from so-called extrafloral nectaries to attract ants which in turn fend off herbivores. Scientists of the Max Planck Institute in Jena, Germany, have discovered that the production of extrafloral nectar is light dependent.

They have shown that the plants are able not only to distinguish between day and night, but also to adapt their nectar secretion to current light conditions by using a special photoreceptor, the phytochrome. Phytochrome probably influences the regulation of a special enzyme that binds the plant hormone jasmonic acid (JA) to the amino acid isoleucine (Ile). The emerging JA-Ile molecule affects the secretion of extrafloral nectar in such a way that the plant's defense against herbivores is most effective whenever herbivory is most likely – or, more precisely, during the day.

Plants have to continuously defend themselves against herbivores to survive and reproduce. They do this directly by producing toxic substances, such as nicotine, or indirectly, by calling their enemies' enemies for help. An example of an indirect defense is the release of volatile substances that attract predatory insects or parasitoids and guide them to their prey; for example, predatory wasps or bugs are led to a caterpillar that is feeding on a plant.

Another indirect defense is the secretion of extrafloral nectar from special leaf organs. In this way Lima beans attract ants that not only enjoy the sweet nectar but also defend the plant against herbivores. Scientists in the Department of Bioorganic Chemistry study this "sweet" defense mechanism. Radhika Venkatesan, a PhD student from India, completed a series of experiments on this topic and tested whether nectar secretion in Lima beans is light dependent. "After all, nectar consists mainly of sugars, and sugars are primary products in the process of photosynthesis – which depends on light," notes the scientist. In the course of her studies, which were published in the Early Edition of the "Proceedings of the National Academy of Sciences USA" last week, she came across an old acquaintance in plant research – the so-called phytochrome. Plants contain phytochromes as photoreceptors in their leaves, which is the reason why phytochromes are sometimes called "the eye of the plant."

"Not the light intensity, but light quality or composition plays a decisive role in regulating nectar production in Lima bean," says Wilhelm Boland, director of the Max Planck Institute. As he explains, the phytochrome in the plant absorbs red light that enables the plant to distinguish the diurnal and seasonal variation of sunlight quality. Radhika Venkatesan's experiments are the first to demonstrate that plants also use the phytochrome system to set up their lines of defense effectively and economically.

The hormone jasmonic acid is known as an important signal that plants produce after wounding by herbivores. It also plays a central role in regulating nectar secretion. The scientists have discovered that phytochrome-mediated light regulation has a significant impact on the signaling effect of jasmonic acid: Free jasmonic acid inhibits nectar secretion in the dark but stimulates its production in the light. Radhika Venkatesan found the key to this light-regulated behavior in a reaction that binds jasmonic acid to the amino acid isoleucine. The emerging conjugate JA-Ile is a signal molecule already known from other studies. For the first time, it has been identified as the actual elicitor of nectar secretion. Additional experiments have confirmed that nectar production doesn't increase if binding of JA and isoleucine is prohibited by an inhibitor. If plants are wounded in the dark to stimulate JA production, JA-Ile is produced only in those leaves that were previously exposed to red light.

Max Planck Institute

UNIQUE HENRY FORD CASE OFFERS CAUTIONARY COTTON SWAB TALE

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The old saying, "never put anything smaller than your elbow in your ear," couldn't be truer for a patient who experienced vertigo and severe hearing loss after a cotton swab perforated her eardrum and damaged her inner ear.

But what makes this patient's case unique is that otolaryngologists at Henry Ford Hospital in Detroit were not only able to alleviate her vertigo with surgery, but restore her hearing – an extremely rare occurrence.

"This case is rare because the goal of surgery is not to recover hearing, but to improve vertigo," says case report lead author Ilaaf Darrat, M.D., an otolaryngologist in the Department of Otolaryngology–Head and Neck Surgery at Henry Ford Hospital.

"Once your hearing is gone, it's usually gone. This case report shows that even in a dead ear, there is hope for hearing recovery."

The report was presented Sept. 28 as part of the poster session at the American Academy of Otolaryngology–Head & Neck Surgery Foundation Annual Meeting in Boston.

Beyond showcasing an unusual case, the Henry Ford report also offers a cautionary tale to those who use cotton swabs to clean their ears: Never put anything in your ears without your doctor's recommendation.

"Using cotton swabs in your ears can cause serious hearing issues," says co-author Michael D. Seidman, M.D., F.A.C.S., director of the Division of Otologic/Neurotolgic Surgery in the Department of Otolaryngology–Head and Neck Surgery at Henry Ford.

"Several times a year, I see patients who have put a hole in their eardrum or damaged the inner ear because they've pushed a cotton swab too far into the ear canal. This type of an injury can deafen a patient, cause vertigo, shatter the eardrum, or even paralyze the face."

Since the ear canal is curved – and a cotton swab is not – Dr. Seidman also sees a lot of patients who cut or scratch their external ear canal using cotton swabs.

The 59-year-old female patient who is the focus of the Henry Ford case report was using a cotton swab to clean her left ear when a sudden movement caused the swab to be pushed deep into the inner ear.

About five hours later, the patient began experiencing symptoms of vertigo, a disturbance of balance and equilibrium, and went to the emergency department at Henry Ford Hospital.

The patient had perforated the ear drum, creating an abnormal opening between the air-filled middle ear and the fluid-filled inner ear called a perilymphatic fistula. A hearing test also revealed deafness in the affected ear, which typically cannot be restored.

The patient was initially treated with bed rest, commonly prescribed for vertigo caused by a perilymphatic fistula. But when this method did not alleviate the patient's vertigo after several days, Dr. Seidman and Dr. Darrat decided to perform surgery to repair the crack in her inner ear organ and the hole in the eardrum.

Nearly six weeks later, the patient's vertigo was gone. But what surprised the physicians was that the hearing test revealed that the patient had recovered most of her hearing.

"It's nearly miraculous that her hearing returned from a non-functioning ear," notes Dr. Seidman. "We were able to perform surgery early and stop the leak of inner ear fluid. We believe that helped to restore the patient's hearing."

Henry Ford Health System

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