Day: 01/03/2012

‘Lost world’ discovered around Antarctic vents.

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The discoveries, made by teams led by the University of Oxford, University of Southampton and British Antarctic Survey, include new species of yeti crab, starfish, barnacles, sea anemones, and potentially an octopus.

For the first time, researchers have used a Remotely Operated Vehicle (ROV) to explore the East Scotia Ridge deep beneath the Southern Ocean, where hydrothermal vents, (including ‘black smokers’ reaching temperatures of up to 382 degrees Celsius) create a unique environment that lacks sunlight, but is rich in certain chemicals. The team reports its findings in this week’s issue of the online, open-access journal PLoS Biology.

“Hydrothermal vents are home to animals found nowhere else on the planet that get their energy not from the Sun but from breaking down chemicals, such as hydrogen sulphide,” said Professor Alex Rogers of Oxford University’s Department of Zoology, who led the research. “The first survey of these particular vents, in the Southern Ocean near Antarctica, has revealed a hot, dark, ‘lost world’ in which whole communities of previously unknown marine organisms thrive.”

Highlights from the ROV dives include images showing huge colonies of the new species of yeti crab, thought to dominate the Antarctic vent ecosystem, clustered around vent chimneys. Elsewhere the ROV spotted numbers of an undescribed predatory sea-star with seven arms crawling across fields of stalked barnacles. It also found an unidentified pale octopus, nearly 2,400 metres down, on the seafloor.

“What we didn’t find is almost as surprising as what we did,” said Professor Rogers. “Many animals such as tubeworms, vent mussels, vent crabs, and vent shrimps, found in hydrothermal vents in the Pacific, Atlantic, and Indian Oceans, simply weren’t there.”

The team believe that the differences between the groups of animals found around the Antarctic vents and those found around vents elsewhere suggest that the Southern Ocean may act as a barrier to some vent animals. The unique species of the East Scotia Ridge also suggest that, globally, vent ecosystems may be much more diverse, and their interactions more complex, than previously thought.

In April 2011 Professor Rogers was part of an international panel of marine scientists who gathered at Somerville College, Oxford to consider the latest research on the world’s oceans. A preliminary report from the panel in June warned that the world’s oceans are at risk of entering a phase of extinction of marine species unprecedented in human history.

“These findings are yet more evidence of the precious diversity to be found throughout the world’s oceans,” said Professor Rogers. “Everywhere we look, whether it is in the sunlit coral reefs of tropical waters or these Antarctic vents shrouded in eternal darkness, we find unique ecosystems that we need to understand and protect.”

 

ROV dives were conducted with the help of the crews of RRS James Cook and RRS James Clark Ross. The discoveries were made as part of a consortium project with partners from the University of Oxford, University of Southampton, University of Bristol, Newcastle University, British Antarctic Survey, National Oceanography Centre, and Woods Hole Oceanographic Institution supported by the UK’s Natural Environment Research.

Source:Physics.org

 

Physicists propose test for loop quantum gravity.

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As a quantum theory of gravity, loop quantum gravity could potentially solve one of the biggest problems in physics: reconciling general relativity and quantum mechanics. But like all tentative theories of quantum gravity, loop quantum gravity has never been experimentally tested. Now in a new study, scientists have found that, when black holes evaporate, the radiation they emit could potentially reveal “footprints” of loop quantum gravity, distinct from the usual Hawking radiation that black holes are expected to emit.

In this way, evaporating black holes could enable the first ever experimental test for any theory of quantum gravity. However, the proposed test would not be easy, since scientists have not yet been able to detect any kind of radiation from an evaporating black hole.

The scientists, from institutions in France and the US, have published their study called “Probing Loop Quantum Gravity with Evaporating Black Holes” in a recent issue of Physical Review Letters.

“For decades, Planck-scale physics has been thought to be untestable,” coauthor Aurélien Barrau of the French National Institute of Nuclear and Particle Physics (IN2P3) told PhysOrg.com. “Nowadays, it seems that it might enter the realm of experimental physics! This is very exciting, especially in the appealing framework of loop quantum gravity.”

In their study, the scientists have used algorithms to show that primordial black holes are expected to reveal two distinct loop quantum gravity signatures, while larger black holes are expected to reveal one distinct signature. These signatures refer to features in the black hole’s energy spectrum, such as broad peaks at certain energy levels.

Using Monte Carlo simulations, the scientists estimated the circumstances under which they could discriminate the predicted signatures of loop quantum gravity and those of the Hawking radiation that black holes are expected to emit with or without loop quantum gravity. They found that a discrimination is possible as long as there are enough black holes or a relatively small error on the energy reconstruction.

While the scientists have shown that an analysis of black hole evaporation could possibly serve as a probe for loop quantum gravity, they note that one of the biggest challenges will be simply detecting evaporating black holes.

“We should be honest: this detection will be difficult,” Barrau said. “But it is far from being impossible.”

He added that black holes are not the only possible probe of loop quantum gravity, and he’s currently investigating whether loop quantum gravity might have signatures in the universe’s background radiation.

“I am now working on the cosmological side of loop quantum gravity,” Barrau said. “This is the other way to try to test the theory: some specific footprints in the cosmic microwave background might be detected in the future.”

Source:Physics.org

 

 

Silkworms spinning spider webs.

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A spiders silk is strong and more elastic and has a large range of possible medical applications. However, spiders have a history of being territorial and prone to cannibalism, so the idea of having a large population to produce commercial amounts of silk is not possible. However, silk worms have been producing their silk commercially for some time.

It was this idea that led Professor Don Jarvis from the University of Wyoming to develop a way to genetically modify the silkworm to spin silk with spider protein. The results of this recent research have been published in the Proceedings of the National Academy of Sciences.

These new genetically modified silkworms are able to produce composite fibers that contain silk threads from both the spider and the silk worm.

On average, these fibers have proven stronger than the fibers produced by either the silkworm or the spider. This could possible open the door for large scale production and the use of these fibers in many different medical applications.

Possible applications include artificial ligaments and tendons, tissue scaffolds and new biomaterials for wound dressing. The fibers are also strong enough that they could provide a possible new material to be used in bulletproof jackets and vests.

In order to make this happen, the researchers transferred the key spider genes responsible for the thread making into the silkworm. Given that silkworms are capable of creating mile-long threads in their cocoons, they provide a way to greatly increase the stronger threads.

This is not the first time that researchers have tried to create genetically modified spider alternatives. Synthetic spider genes have been placed into bacteria, animals and plants. However, none of these were able to produce enough pure silk protein needed for commercial production. The successful use of the silkworm may prove to finally be the solution they have been looking for.

Source:Physics.org

 

Bisphosphonate Use Extends Implant Survival After Primary Hip and Knee Arthroplasty.

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In a U.K. study, bisphosphonate users had significantly lower rates of revision.

The most common indication for revision hip or knee arthroplasty is implant loosening caused by resorption of bone that supports the implant. In this population-based retrospective cohort study, investigators assessed whether use of bisphosphonates, which have antiresorptive properties, can lengthen implant survival.

Using the U.K.’s General Practice Research Database, researchers identified 42,000 patients who underwent primary total knee or hip arthroplasty from 1986 through 2006. At 5 years, bisphosphonate users (essentially defined as those who took bisphosphonates for at least 6 months) had a significantly lower revision rate than nonusers (0.93% vs. 1.96%). In analyses adjusted for confounding factors, bisphosphonate use was associated with a significant twofold increase in implant survival. Assuming an arthroplasty failure rate of 2% during 5 years, the authors estimated that 107 patients who underwent primary hip or knee arthroplasty would need to be treated with bisphosphonates to prevent one revision arthroplasty.

Comment: As the authors note, revision hip or knee arthroplasty has “a poorer clinical outcome than primary joint surgery and is more costly.” Needless to say, patients (and their physicians) would like to avoid this outcome. These results suggest that bisphosphonate use is associated with a lower rate of hip and knee revision arthroplasty and longer implant survival.


Source: Journal Watch General Medicine

Update on AAN Guidelines for Treatment of Essential Tremor.

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No new positive recommendations emerge.

To revise and update the 2005 American Academy of Neurology practice parameters for treating essential tremor (ET), the Quality Standards Subcommittee examined the ET literature from 2004 to April 2010. A computer-based search identified 589 articles, of which 252 were scrutinized fully by two or more committee members.

The committee concluded that the following recommendations from 2005 should remain unchanged:

  • Propranolol and primidone should be offered for limb tremor (Level A).
  • Drugs that are probably effective and should be considered (Level B) are alprazolam, atenolol, gabapentin, sotalol, and topiramate for limb tremor and propranolol for head tremor.
  • Treatments that remain categorized as possibly effective for limb tremor (Level C) are nadolol, nimodipine, clonazepam, botulinum toxin A injection, thalamic deep brain stimulation, unilateral thalamotomy, and clozapine.
  • Drugs still judged possibly not effective for limb tremor are methazolamide, mirtazapine, nifedipine, and verapamil.
  • Drugs that are probably not effective are acetazolamide, isoniazid, pindolol, and trazodone.

New or altered recommendations since 2005 are as follows:

  • Levetiracetam and 3,4-diaminopyridine are probably not effective (Level B), based on two Class II randomized, crossover studies of levetiracetam and one Class I study of 3,4-diaminopyridine.
  • Clozapine has now been transferred from possibly effective for limb tremor to unknown (Level U), as a new study showed no benefit.
  • The present review adds flunarizine to the list of drugs judged possibly not effective for limb tremor, based on two negative Class III studies.
  • Treatments already categorized as Level U (for which evidence is contradictory or insufficient, so recommendations cannot be made) were gamma knife thalamotomy, direct subthalamic stimulation and/or zona incerta/prelemniscal stimulation, amantadine, clonidine, glutethimide, L-tryptophan/pyridoxine, metoprolol, nicardipine, oxcarbazepine, phenobarbital, quetiapine, sodium oxybate, tiagabine, and theophylline. To this list, the present review adds pregabalin, zonisamide, clozapine, and olanzapine.

Comment: Essential tremor is the most common movement disorder, causing significant disability in the population. New therapies are needed, yet this evidence-based review of a 6-year period did not add a single new positive recommendation. The failure to find new therapies reflects serious underfunding of ET research.

 

Source: Journal Watch Neurology

Vitamin D Prevents Fractures, But Role in Cancer Remains Unclear.

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The analysis was requested by the U.S. Preventive Services Task Force, and was the only study requested in advance of its draft statement on recommendations for vitamin D intake.

Taking vitamin D, along with calcium supplements, may reduce your risk of breaking a bone, but there’s not yet enough evidence to say whether it may lower your risk of cancer, a new analysis concludes.

People who were taking vitamin D and calcium supplements were 11 percent less likely to fracture a bone than people not taking the supplements, according to the study.

There was an even larger reduction in fractures — about 30 percent — among elderly people living in institutions who were taking vitamin D, said study researcher Mei Chung, a nutritional epidemiologist and assistant director of the evidence-based-practice center at Tufts Medical Center.

Chung’s analysis was requested by the U.S. Preventive Services Task Force, and was the only study the group requested be done in advance of their draft statement on recommendations for vitamin D intake, set to be issued in January, she said.

As to the studies examining the vitamin’s role in cancer prevention, “We just don’t have good enough information,” Chung said, and factors such as how much vitamin D people were getting in their diets, and how much sun exposure they got were not well-controlled in the previous studies she reviewed for her analysis.

The results of the new study are published online today (Dec. 19) in the journal Annals of Internal Medicine.

Vitamin D in the body

Vitamin D is present in very few foods, though some foods are fortified with it, according to the National institutes of Health. Fish such as salmon and tuna, and egg yolks are good sources of it. It’s also synthesized by the skin when we’re exposed to ultraviolet rays in sunlight.

Research has shown that vitamin D is involved with the depositing of mineral in bone, Chung said, but its potential role in cancer is less clear. Some research has suggested it may promote cell division and other processes that may lead to cancer, but other work has shown it may have the opposite effect, she said. The vitamin’s effect of the vitamin may vary across different parts of the body — it could promote some cancers, but inhibit the development of others.

Chung’s analysis included 19 studies examining the effects of vitamin D on bone fractures, and 28 studies of its effects on cancer.

In terms of reducing fractures, vitamin D only reduced the risk when taken in conjunction with calcium, the study showed. The benefit was seen among people taking from 300 International Units (IU) to 1,100 IU daily, according to the study.

The studies she examined conflicted in their findings about whether vitamin D might prevent cancer, Chung said. Three of the studies were prospective randomized controlled trials — considered the strongest type of scientific evidence, in which participants are divided into two groups at the study’s start and asked to either take vitamin D or a placebo — and these studies suggested that high doses of vitamin D (1,000 IU a day) may reduce cancer.

However, the levels of vitamin D in the blood of participants in those studies were not measured, Chung said, and without such measurements, conclusions cannot be drawn. Some people in the placebo group may have in fact been taking vitamin D supplements, perhaps as part of a multivitamin, and study participants could vary greatly in terms of the levels of vitamin D in their diets, and their sun exposure.

Some of the prospective, observational studies Chung analyzed — in which researchers did measure blood levels of vitamin D, and tracked those levels with cancer cases — suggested that people with higher levels may have a lower risk of colorectal cancer, but also showed that higher vitamin D levels brought an increased risk of having any type of cancer in general. Therefore, a general conclusion about vitamin D and cancer risk could not be made, she said.

To better determine whether vitamin D lowers cancer risk, controlled trials are needed in which participants’ blood levels are measured, and other data on diet and supplements is collected, Chung said.

Taking vitamin D along with calcium has been associated with an increased risk of kidney stones, she noted.

In the body, almost every organ has receptors for the active form of Vitamin D found in our blood, Chung said, which is known to affect many cellular processes. Better understanding of the vitamin’s role in all such processes would be helpful in assessing the vitamin’s potential in preventing diseases, she said.

Source:Scinetific American.

 

 

 

Leishmania major parasite stage-dependent host cell invasion and immune evasion.

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Leishmania pathogenesis is primarily studied using the disease-inducing promastigote stage of Leishmania major. Despite many efforts, all attempts so far have failed to culture the disease-relevant multiplying amastigote stage of L. major. Here, we established a stably growing axenic L. major amastigote culture system that was characterized genetically, morphologically, and by stage-specific DsRed protein expression. We found parasite stage-specific disease development in resistant C57BL/6 mice. Human neutrophils, as first host cells for promastigotes, do not take up amastigotes. In human macrophages, we observed an amastigote-specific complement receptor 3-mediated, endocytotic entry mechanism, whereas promastigotes are taken up by complement receptor 1-mediated phagocytosis. Promastigote infection of macrophages induced the inflammatory mediators TNF, CCL3, and CCL4, whereas amastigote infection was silent and resulted in significantly increased parasite numbers: from 7.1 ± 1.4 (after 3 h) to 20.1 ± 7.9 parasites/cell (after 96 h). Our study identifies Leishmania stage-specific disease development, host cell preference, entry mechanism, and immune evasion. Since the amastigote stage is the disease-propagating form found in the infected mammalian host, the newly developed L. major axenic cultures will serve as an important tool in better understanding the amastigote-driven immune response in leishmaniasis.—Wenzel, U. A., Bank, E., Florian, C., Förster, S., Zimara, N., Steinacker, J., Klinger, M., Reiling, N., Ritter, U., van Zandbergen, G. Leishmania major parasite stage-dependent host cell invasion and immune evasion.

Source:FASEB

 

Lymphadenoma of the salivary gland: clinicopathological and immunohistochemical analysis of 33 tumors.

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Lymphadenomas (LADs) are rare salivary gland tumors. Their clinicopathologic characteristics and etiopathogenesis are poorly understood. We examined 33 LADs in 31 patients (17 women and 14 men) aged 11–79 years (median 65 years). There were 22 sebaceous LADs in 21 patients (9 women and 12 men) and 11 non-sebaceous LADs in 10 patients (8 women and 2 men). Two patients had synchronous double tumors. Twenty-six tumors (79%) arose in parotid, three in the neck, and two each in submandibular gland and oral cavity. Extraparotid tumors were seen in 2 of 21 (10%) patients with sebaceous and 4 of 10 (40%) patients with non-sebaceous LADs. Seven of twenty-three (30%) patients had immunosuppressive therapy for unrelated diseases. The tumors were well circumscribed, encapsulated (n=28, 84%) painless masses, varying in size from 0.6 to 6 cm (median 2.2). The cut surfaces were gray-tan to yellow, homogeneous and multicystic (n=24, 72%). The epithelial cells were basaloid, squamous and glandular, forming solid nests, cords, tubules, and cysts. Sebaceous differentiation was restricted to sebaceous lymphadenoma. The epithelial cells expressed basal cell markers (p63, 34BE12, and/or CK5/6, 18/18, 100%) and the luminal glandular cells expressed CK7 (12/12, 100%). Myoepithelial cells were absent (n=10/16, 63%) or focal. The lymphoid stroma was reactive, with germinal centers in 28 (84%). There was no evidence of HPV (0/11), EBV (0/7), and HHV-8 (0/8). Malignant transformation to sebaceous and basal cell adenocarcinoma was seen in one patient each. None of the 11 patients with follow-up (1–8 years) recurred. In summary, sebaceous and non-sebaceous LADs are benign, encapsulated, solid and cystic tumors affecting older adults. Non-sebaceous LADs affect women and extraparotid sites more frequently than sebaceous LADs. Altered immune status may have a role in their etiopathogenesis. Multiple synchronous tumors, origin in buccal mucosa, and malignant transformation may rarely occur.

Source:Modern Pathology.

 

Histopathological and immunohistochemical findings of 20 autopsy cases with 2009 H1N1 virus infection.

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Twenty autopsy cases with 2009 pandemic influenza A (2009 H1N1) virus infection, performed between August 2009 and February 2010, were histopathologically analyzed. Hematoxylin–eosin staining, immunohistochemistry for type A influenza nucleoprotein antigen, and real-time reverse transcription-PCR assay for viral RNA were performed on formalin-fixed and paraffin-embedded specimens. In addition, the D222G amino acid substitution in influenza virus hemagglutinin, which binds to specific cell receptors, was analyzed in formalin-fixed and paraffin-embedded trachea and lung sections by direct sequencing of PCR-amplified products. There were several histopathological patterns in the lung according to the most remarkable findings in each case: acute diffuse alveolar damage (DAD) with a hyaline membrane (four cases), organized DAD (one case), acute massive intra-alveolar edema with variable degrees of hemorrhage (three cases), neutrophilic bronchopneumonia (five cases) and tracheobronchitis with limited histopathological changes in alveoli (four cases). In two cases, the main findings were due to preexisting disease. Influenza virus antigen was only detected in the respiratory tract in 10 cases by immunohistochemistry. The antigen was detected in type II pneumocytes (three cases) in the epithelial cells of the trachea, bronchi and glands (six cases), and in the epithelial cells in both of the above (one case). The four cases with acute DAD presented with antigen-positive type II pneumocytes. In one case, the D222G substitution was detected in the lung as a major sequence, although 222D was prominent in the trachea, suggesting that selection of the viral clones occurred in the respiratory tract. In five cases, the pathogenesis of 2009 H1N1 was confirmed to be viral infection in pneumocytes, which caused severe alveolar damage and fatal viral pneumonia. Further studies on both host and viral factors in autopsy or biopsy materials will be essential to elucidate the other pathogenic factors involved in influenza virus infection.

Source:Nature Pathology.

 

 

Enigmatic fossils are neither animals nor bacteria.

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Scanning techniques reveal detailed cell structure of debated relics.

The unusually complex appearance of a group of 570-million-year-old fossils from Doushantuo, China, has sparked debate among palaeontologists. Researchers haven’t been able to decide whether the remains come from animals, bacteria or close relatives of animals that thrived at the dawn of animal evolution. But a team has now used three-dimensional scanning techniques to take a closer look at the fossils — and has decided that in fact, they are none of these.

X-ray microtomography reveals the shape of the ‘cell nuclei’ (yellow) in a computer model of a fossil from Doushantuo in China, shown against the backdrop of the rock in which it is found.

The Doushantuo fossils look like partitioned sand grains. The partitions resemble animal-cell cleavage and this, as well as structures in the fossils that look like cell nuclei, has led palaeontologists to interpret the fossils as dividing embryos of very early animals. But others argued that they were instead the fossils of Thiomargarita — giant sulphur-oxidising bacteria that still exist, can grow to nearly one millimetre in diameter and sometimes look like the cells of other organisms in the fossil record.

Keen to settle the matter, a group led by Philip Donoghue, a palaeontologist at the University of Bristol, UK, and Stefan Bengtson, a palaeontologist at the Swedish Museum of Natural History in Stockholm, used X-ray microscopic tomography to produce three-dimensional images of the interiors of the fossils. The team describes its work in two papers, published in Science1 today and the Proceedings of the Royal Society B2 last week.

Of the 450 fossils scanned, 14 were found to contain structures that look like nuclei. In one of these specimens, three of the eight structures even have the elongated or dumb-bell shape of modern nuclei about to replicate. This hints that the organism died during cellular division.

“We were enthralled to find nuclear division preserved by fossilization. It confirmed that the fossil organisms were not bacteria, but we soon realized that they were not like animals either, as animal nuclei tend to lose their contours during cell division, and these nuclei did not,” says Bengtson.

Animal, vegetable or mineral?

When the researchers took a closer look, they noticed that specimens which seemed to be in later stages of development contained hundreds of thousands of tiny cells, and that the outer envelopes of these specimens had partly burst open. On the basis of this observation, Donoghue and Bengtson suggest that the creatures are similar to modern mesomycetozoeans, single-celled microorganisms that are neither animals nor bacteria.

Mesomycetozoeans reproduce by creating thousands of spore cells inside a protective envelope that bursts when it is time for them to spread into the environment. Once these cells settle, they create a new envelope and begin replicating again. The idea that the Doushantuo fossils might be similar is causing a commotion in the scientific community.

“A lot of mesomycetozoeans start with a single large cell and then divide like this inside a thick cell wall, so the idea being suggested here is not a bad one. With that said, there are other organisms, like some fungi, that behave in a very similar way. For all we know these could be fungal fossils,” says Iñaki Ruiz-Trillo, a biologist at the Institute of Evolutionary Biology in Barcelona, Spain.

Nicholas Butterfield, a palaeobiologist at the University of Cambridge, UK, agrees with that there are other options. “It is premature to dismiss the possibility that these are developing multicellular organisms. There are intriguing similarities between features of these fossils and the green algae Volvox, which are multicellular, albeit of a much simpler type of multicellularity than that found in animals,” he says.

But there are some who think that the palaeontological community is still a long way from a final verdict. “What isn’t widely appreciated is that the Doushantuo rock formation contains billions of microfossils, many of which have no traits that are diagnostic of any living group and contain features that are not of biological origin,” says Jake Bailey, a geobiologist at the University of Minnesota in Minneapolis. “We are still far from understanding the origins of these enigmatic microfossils.

Source:Nature