Day: 02/27/2011

Vertebroplasty for Symptomatic Monostotic Paget Disease

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Paget disease (PD) is a chronic metabolically active bone disorder. The spine is the second most commonly involved site; the pathologic changes can cause back pain, myeloradiculopathy, and vertebral fracture. Symptomatic patients are treated medically, and surgery is required when certain complications occur. A case is presented of monostotic vertebral PD treated by percutaneous vertebroplasty (PV) with successful outcome characterized by pain relief and improved disability at 6-month follow-up. PV is proposed as a primary treatment for back pain secondary to PD when unresponsive to conservative therapy and when not associated with other complications.

source: sciencedirect

A Fungal ‘Vaccine’ for Malaria-Carrying Mosquitoes

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Researchers have genetically modified a fungus so that it attacks the malaria parasite within a mosquito. They hope the fungus’s spores, applied to the walls of houses or mosquito traps, could help stop the spread of the disease in an environmentally friendly way.

Fungi that attack insects are present in soils worldwide, and they are used in gardens, greenhouses, and open fields to control agricultural pests. In 2005, scientists showed that strains of two different fungi, Beauveria bassiana and Metarhizium anisopliae, could attack the mosquitoes that spread malaria. When the fungal spores come in contact with the mosquito’s exoskeleton, they bore their way into the hemolymph—the insect’s equivalent of blood—where they grow, ultimately killing the mosquito.

But the fungi take about 2 weeks to kill the insects. “They want to kill slowly, extracting as many nutrients as possible so they can produce more spores,” says Raymond St. Leger, an entomologist at the University of Maryland, College Park. Because it takes only 12 to 14 days for the malaria parasite to mature into its infective form inside the mosquito, an insect often has time to spread the parasite before a fungal infection has killed it off, especially if the mosquito is exposed to the fungus several days after it picks up the parasite.

St. Leger and his colleagues originally created a genetically modified version of the fungus M. anisopliae that, thanks to the insertion of an insect-specific neurotoxin, kills mosquitoes more quickly. But a quick kill also has a disadvantage: It can lead to mosquitoes that are resistant to the fungus, because the resistant insects are the only ones who survive long enough to reproduce.

Now St. Leger and his colleagues have engineered strains of M. anisopliae to block the malaria parasite from developing inside the infected mosquito. Online today in Science, they describe inserting different combinations of three different genes into the fungus to block the malaria parasite from entering the mosquito’s salivary glands. (Parasites from the salivary glands infect new hosts when an infected mosquito bites a new victim.) One gene codes for a peptide—a short piece of a protein—called SM1 that resembles the parasite protein the parasite uses to enter the salivary glands. The copies of SM1 produced by the fungus block the parasite’s way in. Another added gene codes for part of a human antibody that binds to the parasites and causes them to clump together. A third is an antimicrobial protein called scorpine—it was found in scorpions—that kills the malaria parasite.

When the researchers sprayed spores of the genetically modified fungus strains onto mosquitoes in the lab, the spores did not kill the insects faster than the normal fungus did. But they did significantly reduce the number of parasites in the mosquitoes’ salivary glands: Six days after receiving spores of the genetically modified strains, the mosquitoes had 98% fewer parasites in their salivary glands than did those treated with normal fungus.

And the genetically modified fungus acts quickly. After giving mosquitoes a malaria-infected blood meal, the researchers waited 11 days before spraying some with normal fungal spores and others with the enhanced spores. Two days later, 86% of fungus-free mosquitoes could transmit malaria, as could 72% of the insects infected with normal fungus, but only 20% of the mosquitoes exposed to the transgenic fungus could do so.

The results are impressive, says Marit Farenhorst, who studies insect-attacking fungi at In2Care, a start-up company in Wageningen, the Netherlands. “In case you are a little bit late in getting the mosquito infected in field, you can still be in time to affect the transmission of malaria,” she says. “It’s kind of like vaccinating the mosquito.” The main drawback of the approach, says Farenhorst, is that fungal spores survive only a few months when applied to walls or other surfaces. It’s currently impractical and expensive to have to keep reapplying spores. But several teams are working on better ways to apply the spores and keep them alive, she says.

Although St. Leger acknowledges that widespread suspicion of genetically modified organisms might make it more difficult to persuade people to apply the fungus in their houses, he says the approach is extremely low risk: The fungus strain that the scientists modified infects only mosquitoes, the genes they inserted only recognize human malaria, and the genes are only turned on once the fungus is inside the mosquito. None of the genes give the fungus a survival advantage over the wild strains that are common in soils, he says. Still, St. Leger says, completing relevant safety tests will take several years.

source: science now

Indonesia’s mud volcano

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Since it roared to life in May 2006, a mud volcano near Indonesia’s coastal city of Sidoarjo has swallowed homes, rice paddies, factories, and roads, killing 15 people, displacing 40,000, and harming the livelihoods of many more. As the ongoing eruption nears its 5th anniversary, observers wonder whether it will ever stop. The answer: Not anytime soon. A new study predicts the volcano will continue spewing significant amounts of mud for another 2 decades. A second study forecasts that it could grind on as long as 87 years.

The mud volcano has inflicted a punishing blow to the region of Java island 700 kilometers east of the capital, Jakarta. Nicknamed Lusi, a contraction of lumpur (Indonesian for mud) and Sidoarjo, the volcano has so far disgorged 144 million cubic meters of mud, some of which now covers an area roughly twice the size of New York City’s Central Park. Much of the mud has been diverted to a nearby river, where it has formed a new 83 hectare island and extended a natural delta. Compensation and mitigation have cost at least $767 million, according to Humanitus, a nongovernmental organization in Melbourne, Australia, that is studying the disaster’s social impact. That is a fraction of the real economic toll, which is still being tallied.

Lusi may be a harbinger of disasters to come. “Like a volcanic eruption, a mud eruption is just the effect of geological activity, and I’m sure in the future another mud volcano must erupt in this region,” says Soffian Hadi Djojopranoto, a geologist with the Sidoarjo Mudflow Mitigation Agency. “We need very serious research to understand this phenomenon.”

Despite being the most intensely studied mud volcano ever, scientists have failed to agree on the cause of the eruption, which began in the early-morning hours of 29 May 2006. Mud suddenly started gushing out of vents 200 meters from a rig drilling an exploratory gas well. Drilling logs indicate problems with the well several hours before the eruption, and many scientists believe there was an underground blowout. Others, however, suggest that a magnitude-6.3 earthquake that occurred 2 days earlier and 280 kilometers away activated a local fault. Despite the uncertainty, the Indonesian government pressured the Bakrie family, majority owners of the drilling company and one of the country’s wealthiest families, to foot most of the bill for compensation and mitigation.

Debate now centers on how Lusi’s plumbing works. “The most important piece of work now is to estimate the longevity,” says Richard Davies, a geologist at Durham University in the United Kingdom. That will determine if mud-handling countermeasures are sufficient. Dueling hypotheses have led to different forecasts. Davies argues that the eruption is driven by pressurized water from a deep aquifer in permeable material beneath an impermeable rock layer. He argues that the wellbore pierced the impermeable rock, allowing water to gush up and sweep overlying mud to the surface. Modeling this scenario using combinations of known quantities, such as total ejected mud volume after 1 year and 3 years and assumed parameters, including aquifer size, Davies and colleagues arrived at an estimated longevity of 26 years, published online on 24 February in the Journal of the Geological Society. They also predict that the ground around Lusi will subside up to 475 meters from its original elevation, with mud filling the crater.

Others augur that Lusi will be kicking around far longer. Michael Manga, a geologist at the University of California, Berkeley, contends that pressure and fluid originate not in the deep aquifer but in a shallower mud layer. In a paper in review, his team predicts that an ever-widening circle of subterranean mud will get sucked into the volcanic system and pushed to the surface. The model “is a new way of thinking about how eruptions work,” Manga says. His team estimates a 50% chance that the eruption will last 40 years and a 33% chance that it will drag on for 87 years.

The predictions are getting a mixed reception. Peter Flemings, a geologist at the University of Texas, Austin, has not seen Manga’s results, but he says his “gut feeling” is that tapping into a large permeable aquifer, as Davies proposes, would produce the volume of material spewing from Lusi. The “absolutely critical assumption,” Flemings says, is the aquifer’s size—and calculating that from limited data, he says, “is fraught with uncertainty.” Davies’s subsidence projections, meanwhile, “look big,” says Heri Andreas, a geophysicist at the Institute of Technology Bandung in Indonesia. GPS surveys of ground deformation show that after an initial period during which the ground was sinking up to 4 centimeters per day, subsidence has tapered off to just several centimeters per year.

For more robust projections, says Manga, “we need more and better data.” And more is at stake than scientific models. Long-term social, ecological, and infrastructure programs can’t be planned “until this geological phenomenon is better understood,” says Humanitus Director Jeffrey Richards. Humanitus is organizing a May symposium in Surabaya at which Richards hopes experts will forge a consensus on what studies are most likely to reveal Lusi’s geological secrets. Davies would like to see a well drilled into the aquifer some distance from Lusi to measure pressures. Other options are 3D seismic surveys of the subsurface.

Numerous efforts to plug the volcano have failed. Fortunately, the mud flow is now manageable, says Djojopranoto. After peaking at 180,000 cubic meters per day in early 2007, the rate has tapered to 10,000 cubic meters per day. A system of 6- to 7-meter-high earthen dikes encloses some 700 hectares of ponds where mud and water is collected and then pumped into the Porong River, where it is adding to a natural delta downstream. The impact on the Porong has been minimal, given that it historically carried heavy sediment loads from magmatic volcanoes upstream, Djojopranoto says.

Environmentalists claim that authorities are understating some of Lusi’s ill effects. Studies by nongovernmental organizations in 2007 indicated that high sedimentation was smothering marine life, particularly bottom-dwelling creatures like snails, says Pius Ginting of the Indonesian Forum for Environment. An ongoing concern, he says, is the mud’s toxicity, which he claims is laden with carcinogenic polyaromatic hydrocarbons—a contention that Djojopranoto says has never been independently verified.

In Lusi’s vicinity, the mitigation bureau has rerouted roads and resettled most families. Mud volcano tourism is providing income, says Djojopranoto, but “not enough to revive the economy.” Even after the eruption ends, Lusi may erupt periodically or ooze mud for centuries. “On east Java, we have mud volcanoes that have been active for hundreds of years,” Djojopranoto says. None, however, compare in size, in societal harm, or in the puzzles that Lusi continues to present to scientists.

source: science now

More Evidence Against Dark Matter

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Thousands of physicists, astrophysicists, and astronomers are searching for dark matter, mysterious stuff whose gravity seems to hold the galaxies together. However, an old and highly controversial theory that simply changes the law of gravity can explain a key property of galaxies better than the standard dark-matter theory, one astronomer reports. That claim isn’t likely to win over many skeptics, but even some theorists who favor the standard theory say the analysis hands them a homework problem they should solve.

“The standard theory should explain this, and it doesn’t yet. That’s fair to say,” says Simon White, a cosmologist at the Max Planck Institute for Astrophysics in Garching, Germany, who was not involved in the current analysis.

In 1933, Swiss astronomer Fritz Zwicky suggested the existence of dark matter when he found that the galaxies in a particular cluster swirl about each other too fast to be bound by their gravity alone. In the 1970s, American astronomer Vera Rubin and others discovered that the stars at the edges of individual galaxies also appear to move too fast to be held by the gravity of the stars in the center. Those outer stars ought to move more slowly than the ones circling closer in—just as Jupiter orbits the sun more slowly than Earth. Instead, the speed of the stars generally increases with the distance from the galactic center, eventually flattening out at a maximum value. That observation seemed to clinch the case for some sort of dark matter.

Or did it? In 1983, Mordehai Milgrom a physicist at the Weizmann Institute of Science in Rehovot, Israel, found that he could explain the so-called galaxy rotation curves without dark matter if he simply assumed that on the galactic scale, dynamics and gravity worked a bit differently from what Isaac Newton postulated. Specifically, Milgrom assumed that for very small accelerations, the square of the acceleration, not just the acceleration, is proportional to the gravitational force.

For the past 28 years, Milgrom’s idea, known as Modified Newtonian Dynamics (MOND) has generated a long-simmering debate. Many researchers argue that ever more evidence from clusters of galaxies, the largest scale structure of the universe, and the afterglow of the big bang points to the existence of dark matter. Still, a few researchers counter that when they look at the details, MOND does a better job—at least on the galactic scale.

Now, in the latest shot from the MOND side, Stacy McGaugh, an astronomer at the University of Maryland, College Park, reports that MOND can explain an observed correlation between the mass and the rotation speed of galaxies—that is, the speed of those outer stars—called the baryonic Tully-Fisher relation. MOND researchers had tried to do this before, but for their models to work, they had to make an untested assumption about the relationship between a star’s mass and the amount of light it puts out. That assumption introduces a large uncertainty, weakening the argument.

To avoid that problem, McGaugh gathered data from various sources on 47 galaxies that contain more hydrogen gas than stars. The mass of the gas can then be estimated directly. McGaugh made a plot of visible mass versus rotation speed for the galaxies. He then plotted the prediction that comes straight out of MOND in a few lines of algebra. The MOND line went right through the data. “You draw the line and the data fall right on it,” McGaugh says. “No muss, no fuss.” He reports the result in a paper in press at Physical Review Letters.

Crucially, McGaugh finds very little scatter in the data—just what would be expected if the mass of gas and stars was directly determining the rotation speed. It’s not clear exactly what dark-matter models would predict, McGaugh says. However, such models make no strong connection between the amount of visible matter and the rotation speed. Indeed, galaxies with the same mass of dark matter can have different numbers of stars. So it would be surprising if dark-matter models yielded such a tight correlation.

“I think the data are good, and the fact that MOND fits is striking,” says White, who has worked extensively on simulating the evolution of the universe. “I think Stacy is right in holding this up and saying [to dark-matter modelers], ‘Look at this [correlation]. Go see if you can explain it.’ ” Still, White says, dark matter can explain the variations in the afterglow of the big bang and other cosmological data with which MOND struggles.

But whether MOND is right may be beside the point, says Jerry Sellwood, a theoretical astrophysicist at Rutgers University in New Brunswick, New Jersey. “The real strength of Stacy’s paper is that it points to something that can’t be explained in cold dark matter, irrespective of whether MOND is right.” At the least, Sellwood says, McGaugh deserves credit for keeping others honest about what their models can do.

source: science now