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Monday, October 6, 2008
Rise and fall of the dinosaurs
Friday, October 3, 2008
The Queen of Trees Introduction
NATURE reveals the importance of an unlikely partnership between a regal tree and a tiny wasp in The Queen of Trees.
It may be one of nature’s oddest couples: a tiny wasp that can barely be seen, and a giant fig tree, the sycomore, which shelters a remarkable menagerie of wildlife among its limbs. The wasp and the fig depend on each other for survival. Without the wasp, the tree could not pollinate its flowers and produce seeds. Without the fig, the wasp would have nowhere to lay its eggs.
The Queen of Trees shows this delicate dance of survival in exquisite detail, including spectacular close-ups of the wasp’s remarkable life inside a ripening fig. To capture such incredible images, filmmakers Victoria Stone and Mark Deeble spent two years camped out near a giant sycomore fig in Kenya’s outback, documenting the tree’s pivotal role as a source of food and shelter for everything from gray hornbills, Africa’s largest bird, to swarms of invading insects searching for food. In a surprising turn, some insects come to the tree’s aid — sparking a battle you won’t want to miss.
Video: An Exciting New Season of NATURE
NATURE’s 27th season premieres October 26 and promises to be one of the series’ most exciting, featuring such locations as the Arctic wilderness, the Drakensberg mountain range in southern Africa, and the wondrous Victoria Falls on the border of Zambia and Zimbabwe. NATURE will also feature what’s in our own “backyard” with an in-depth look at the American bald eagle, as well as a new chapter in the chronicle of the Rockies’ most famous stallion: Cloud. To tantalize your appetite, here’s a sneak peak at three upcoming shows.
Beautifully photographed, White Falcon, White Wolf takes place on the Canadian Arctic’s otherworldly Ellesmere Island, and features an intimate view of the struggles of two families — a pack of white wolves and a family of rare gyrfalcons.
In The Wolf That Changed America, NATURE takes a decidedly different approach by using historical recreations to tell the story of one of America’s earliest conservationists, Ernest Thompson Seton, and his obsession with Lobo — the wolf that changed his life.
Finally, sizzling up the screen is Kilauea: Playing With Fire. Emmy Award-winning cameraman Paul Atkins boldly goes where few would dare — into waters as toasty as 100 degrees Fahrenheit to film lava flows and explosions from Hawaii’s Kilauea volcano. Caution — this footage is hot!
Dogs That Changed the World
In the same way that inbreeding among human populations can increase the frequency of normally rare genes that cause diseases, the selective breeding that created the hundreds of modern dog breeds has put purebred dogs at risk for a large number of health problems, affecting both body and behavior.
Some conditions are directly related to the features breeders have sought to perpetuate among their dogs. As they deliberately manipulated the appearance of dogs to create or accentuate physical characteristics that were considered aesthetically pleasing, like the flat face of a bulldog or low-slung eyelids of a Bloodhound, breeders also created physical disabilities. The excessively wrinkled skin of the Chinese Shar-Pei causes frequent skin infection; Bulldogs and other flat-faced (or brachycephalic) breeds such as the Pekingese have breathing problems because of their set-back noses and shortened air passages; Bloodhounds suffer chronic eye irritation and infection.
The unnaturally large and small sizes of other breeds encourage different problems. For example, toy and miniature breeds often suffer from dislocating kneecaps and heart problems are more common among small dogs. Giant dogs such as Mastiffs, Saint Bernards, and Great Danes are nearly too big for their own good. Researchers have found a striking correlation between a dog’s large size and a frequency of orthopedic problems like hip dysplasia. Large dogs are often prone to heat prostration because they can’t cool down their bodies (tiny dogs, by contrast, have a hard time staying warm), and because of the massive weight they must support, these breeds are prone to malignant bone tumors in their legs. Meanwhile, the huge head and narrow hips of the Bulldog can necessitate that their pups must be born by Caesarean section.
Other health problems among purebreds are the product of both inbreeding and bad genetic luck. The genes responsible for many genetic diseases are “recessive,” which means that two copies of a damaged gene, one from the mother and one from the father, must be present in an individual for the disease to occur. Individuals that carry only one copy of the disease gene don’t have the condition, and are carriers of the disease. Normally, because disease genes are relatively rare, it is unlikely that both the mother and the father will be carriers, and even less likely that they’ll both give the disease gene to their offspring. But that’s not the case for purebred dog breeds, where genetically similar individuals are intentionally mated, increasing the concentration of disease genes. It’s like stacking a deck of cards with ten extra aces and ten extra face cards; the loaded deck increases your chance of hitting blackjack in a game of 21-but what you “win” might be allergies or a predisposition to cancer.
 Bloodhounds suffer chronic eye irritation and infection. |
Skin problems
A skin allergy, atopic dermatitis, inflicts itchy, inflamed skin on as many as 15 percent of all dogs, but certain breeds are particularly susceptible. Dog breeds prone to atopic dermatitis include Dalmatians, Vizslas, and several terriers, such as the Boston Terrier, Bull Terrier, and the West Highland White Terrier. The numerous skin folds of a Chinese Shar-Pei, so valued by some breeders, can become breeding grounds for staphylococcus and other bacteria, which cause frequent skin infections. Also, excess wrinkles of skin on the face can rub on the eye, causing lesions and, potentially, blindness.
Immune system disease
In autoimmune disorders, an individual’s immune system, which normally works to fight off foreign invaders, launches a misguided attack against its own tissues and cells. A number of inherited diseases compromising the immune system have been noted in dogs, including primary severe combined immunodeficiency (a dog version of the “bubble boy” disease) among Basset hounds, Cardigan Welsh Corgis, and Dachshunds. Addison’s disease, an autoimmune disease that affects the hormone-producing adrenal glands, occurs more frequently among several particular breeds, including the Bearded Collie, Portuguese Water Dog, and Standard Poodles. Diabetes mellitus, an autoimmune disorder affecting the body’s response to sugars, shows up more frequently among Samoyeds and Australian Terrier dogs.
Blood disorders
Bassett Hounds are prone to an inherited abnormality the effects the ability of the platelets in the blood to clump together after an injury. The blood doesn’t clot properly, leading to hemorrhage and bruising. Clotting problems also plague dogs with von Willebrand’s disease, a genetic condition frequent in Doberman Pinschers.
Neurological, behavioral, and sensory
Neurological and behavioral problems afflict many pure breeds. Bull Terriers, for example, often compulsively chase their tails. Pugs are be predisposed to Pug Dog encephalitis, a fatal brain disease. Scottish Terriers are affected by Scottie Cramp, a disorder that causes the dogs to lose muscle control when they get excited. German Shepherds may inherit degenerative myelopathy, a crippling spinal cord disease that causes weakness and eventually paralysis.
Hearing and vision
Hereditary hearing loss is common in Dalmatians, Australian Cattle Dogs, and English Setters. Alaskan Malamutes, Siberian Huskies, Samoyeds, Bichon Frise, and more than 60 other purebred dogs suffer from inherited forms of cataracts, while progressive retinal atrophy, a common cause of blindness in purebreds, is particularly a problem in Old English Sheepdogs and Papillons.
Heart disease
Sudden death from cardiac disease is recurrent in several dog breeds, including Doberman Pinschers, Great Danes, Irish Wolfhounds, and German Shepherds. Boxers can be genetically predisposed to an irregular heartbeat. High blood pressure afflicts many small breeds including Poodles, Cocker Spaniels, Staffordshire terriers, among others.
Other organs and systems
Low thyroid function crops up most frequently in Alaskan Malamutes, English Setters, Golden Retrievers, Keeshonds, Samoyeds, and Siberian Huskies. Gastric torsion, or bloat, a potentially life-threatening inability to expel gas from the digestive system, is common among deep-chested breeds such as the Great Dane, Doberman, and German Shepherd. An inherited form of kidney disease affects English Cocker Spaniels, while Dalmatians are prone to kidney stones and Basenjis suffer from Fanconi Syndrome, a potentially fatal inherited disease in which the kidneys fail to reabsorb nutrients. Liver damage and cirrhosis are common in Bedlington Terriers because of an inherited condition called copper toxicosis, in which high levels of copper accumulate in the liver.
Cancer
Cancers are strongly influenced by genetics, and so it is not surprising to find various types of cancer among different dog breeds. For example, bone cancer, or osteosarcoma, is considerably more frequent among large and giant breeds of dogs, such as the Irish Wolfhound, Great Dane, Rottweiler, Labrador and Golden Retriever, Greyhound, and Saint Bernard, because their bones are stressed by carrying so much weight. High rates of malignant blood vessel tumors are seen among Golden Retrievers, which are also prone to leukemia and brain tumors. German Shepherd Dogs and Chow Chows are predisposed to gastric cancer, while Scottish Terriers are 18 times more likely to develop bladder cancer than are other breeds.
Orthopedic
Hip dysplasia, in which looseness in the hip joint causes excessive wear that eventually leads to arthritis, is most common among large dogs, especially those like the German Shepherd Dog and the Saint Bernard which have heavy, broad hips. The long neck and large head of breeds such as the Great Dane and the Doberman can cause the compression of the spinal cord in neck vertebrae, leading to wobbling and falling (”wobbler syndrome”). Selective breeding of the disproportionately short legs of breeds such as the Basset Hound and the Dachshund has led to bowed legs and chronic problems with elbow dislocation; the short legs and long back of Dachshunds causes them to suffer more often from ruptured vertebral disks. Because of their small bones, toy and miniature breeds are more likely to experience patellar luxation, the slipping or dislocation of the kneecaps.
Wednesday, October 1, 2008
Silicon highlights remaining questions over anthrax investigation
Did Bruce Ivins weaponize deadly spores?
The deadly anthrax bacterium.MedicalRF.com / AlamyNearly two months after the suicide of scientist Bruce Ivins — whom the US Federal Bureau of Investigation (FBI) claims was solely responsible for mailing a series of letters laced with anthrax in 2001 — questions still remain over whether he was actually able to produce those anthrax spores.
Scientists initially believed that the spores had been weaponized – modified to make them disperse more easily and penetrate tissue more deeply.
But one of the scientists who first drew that conclusion has now changed his mind. Nature finds out why he thinks he got it wrong; why it matters for those trying to tie up the Ivins case; and what it means for the chances of a similar attack happening in the future.
What was the initial evidence that the 2001 spores were weaponized?
The powder was described as being 'weightless' and 'smoke-like'. One of the first scientists to work on it was Peter Jahrling, then a virologist at the US Army Medical Research Institute of Infectious Diseases in Frederick, Maryland. He recalls that he couldn't even weigh out a fraction of it: "It literally jumped off the spatula and was repelled by the weighing paper; it was like nothing I had ever seen before." Under an electron microscope, Jahrling and a colleague observed black dots that they speculated might be particles of silicon dioxide, or silica. Materials analysis by the Armed Forces Institute of Pathology in Washington DC confirmed that the sample contained both silicon and oxygen, and many assumed that the elements were combined as silica.
Why would a silicon compound increase the spores' virulence?
Spores are sticky, and tend to clump together. One method of weaponizing the spores is to coat them with something that interrupts the weak van der Waals interactions between each particle. Tiny particles of silica would do the trick, allowing the spores to float individually through the air. Silicon and oxygen can also form polymers called siloxanes, and such compounds are used to make inhaled medicines more dispersible.
Why have Jahrling and others changed their minds?
In 2002, as part of the FBI investigation, scientists at Sandia National Laboratories in Albuquerque, New Mexico, used electron microscopy to analyse the composition of the spores. The results were finally made public last month. They found silicon and oxygen in the spore coat, but not on the most external layer, the exosporium. The location of the silicon, the FBI says, suggests that it was incorporated naturally into the structures during growth, not added as a final coating to weaponize them.
But other experts disagree with the conclusion. "I don't think the guys at Sandia understand that the exosporium is not some kind of brick wall," says Stuart Jacobsen, a research chemist based in Dallas, Texas, who is an expert on the preparation and properties of fine-grained powders and has followed the case closely. "It's more like a chain-link fence." Decades ago, a study found that the exosporium is porous to various small molecules1.
How might silicon get into the spores naturally?
The FBI points to experiments from 1990, in which scientists found some silicon in naturally grown spores2. Another hypothesis, suggested by Serguei Popov, an anthrax researcher at George Mason University, Manassas, Virginia, is that the bacteria picked up a bit of silicon from anti-foaming agents while they were being grown. To produce the large number of spores in the contaminated envelope analysed - one trillion spores per gram — Popov infers that the perpetrator must have had to grow a large-scale bacterial culture in a fermenter, where silicon-containing anti-foaming agents are commonly used.
But this would add a relatively low concentration of silicon to the spores. Deliberate weaponization would probably leave much higher amounts. At a House of Representatives Judiciary Committee hearing on 16 September, Representative Jerrold Nadler (Dem.) quizzed FBI director Robert Mueller about the quantity of silicon present in the spores. Mueller did not answer the question.
Why does this matter to the investigation?
Many scientists involved in the investigation still wonder: could Bruce Ivins, in a few late-night lab sessions and in secret, have engineered the powder in the letters? An answer to this would help to determine whether Ivins was guilty, and if so, whether he needed assistance from other parties. It would also help defence experts to assess how easy it would be for others to mount a similar attack in the future.
"I don't think it would be horrendously difficult to make stuff that was moderate quality," Peter Setlow, a microbiologist at the University of Connecticut Health Center in Farmington, told Nature in August. But Jacobsen and others say the fact that the FBI has apparently failed to produce a powder to match the attack material suggests it must be very difficult to make. That might put it beyond Ivins's reach.
If the spores could not be made by a single scientist in a few evenings, that would suggest the spores came from elsewhere – possibly from a state-organized programme.
What happens next?
"The truth will come out when all the data are revealed," Jahrling says. But there is no indication from the FBI that more data are forthcoming anytime soon. Until they are provided, there will continue to be suspicions and speculations about the silicon in the spores.
Successful launch for fledgling rocket company
SpaceX could pioneer a cheaper future for space flight.
Blast off! Falcon 1 launches into space.SpaceXThe fourth time was the charm for SpaceX and its Falcon 1 rocket, which soared into low Earth orbit after a successful launch yesterday.
After a trio of failed flights since March 2006, Space Exploration Technologies (SpaceX), based in Hawthorne, California, hopes that this marks the dawn of a new, substantially cheaper, era of space flight.
The rocket launched on Sunday 28 September at 23:15 GMT from the US Army Kwajalein Atoll on Omelek Island in the Pacific Ocean. "This is a great day for SpaceX and the culmination of an enormous amount of work by a great team," said Elon Musk, CEO and CTO of SpaceX, in a press statement. The company estimates that each launch will cost less than $10 million; existing systems can cost up to four times as much.
Falcon 1 is significant because it was developed from scratch by a private company, says Jonathan McDowell at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Massachusetts. The launch shows that the commercial sector can develop cheaper and, perhaps, better rockets that might one day rival those created by government agencies, adds Wolfgang Demisch, an aerospace consultant based in New York who has served on the US National Science Foundation's Next Generation Launch Technology panel. It's a "transformative step in space exploration," he says.
Right now, however, Falcon 1 can only carry up to one tonne of mass. To compete with existing launch systems, the Falcons must be able to carry more than ten times as much. For example, a space shuttle can carry a payload of about 25 tonnes into low Earth orbit, while the Apollo 11 mission to put man on the Moon carried an eye-watering 47 tonne combined payload.
But SpaceX is ambitious, and the launch bodes well for the company's development of larger heavy-lift rockets. Dubbed Falcon 9 and Falcon 9 Heavy, these rockets could potentially carry much bigger payloads further from Earth. Falcon 9 is designed to take around 12.5 tonnes into low Earth orbit and more than 4 tonnes into a highly elliptical geostationary transfer orbit — a key staging point for a geostationary satellite and for any astronauts or cargo heading to the Moon or Mars.
It could also act as an additional supply vehicle for the International Space Station once NASA winds down its space shuttle program in 2010. Falcon 9's estimated cost of around $37 million is less than a third of competing launchers.
McDowell says, however, that although Falcon 1's launch certainly "keeps SpaceX in the game" the company is "not out of the woods yet" because its commercial future really depends on their heavy-lift vehicles.
Just two days before its smaller sibling's jaunt into space, the company successfully test-fired all nine of the Falcon 9's engines simultaneously; its first launch is slated for next year.
Frontiers in HIV/AIDS
In this focus
- Current Research
Development of an effective HIV/AIDS vaccine and new drugs to treat established disease remain an urgent and pressing need. To conquer the enormous challenge demands a far better understanding of the biology of the virus, its interaction with infected cells, and the response of the immune system, than is currently at our disposal.
This web focus presents a selection of recent research papers in Nature that advance our knowledge in this regard. It also includes a Feature highlighting the expanding HIV epidemic in China, a Review article covering the challenges in vaccine development, and a Commentary calling for better communication and cooperation between vaccinologists, virologists and experts in innate anti-viral immune responses. We hope you will find it helpful.
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