The Eyes Have It: A Step Toward Creating Peepers in a Petri Dish

The Eyes Have It: A Step Toward Creating Peepers in a Petri Dish

Study fingers a enzyme that jump starts the pathway leading to the generation of eye tissues

	COMING TO A LAB NEAR YOU:  Researchers identify an enzyme that starts a cascade of cellular events involved in the development of eyes.

An accidental discovery could pave the way to one day coaxing stem cells to develop into human eyes in the lab.

A team of scientists at the University of Warwick in England studying the development of motility in frogs found that a certain ectoenzyme (a cell-surface protein) injected into a tadpole embryo triggered the development of tissues that eventually form eyes.

Further experimentation led the researchers to conclude that the surface protein is, in fact, an early player in the cellular cascade that leads to eye formation. Researchers say the finding could be harnessed in the future to make an "eye in a dish," a tool that would be invaluable in coaxing stem cells to develop into ocular tissues.

"Our study provides clear discovery of upstream signals controlling a previously known pathway controlling eye development and therefore provides a step closer to being able to manipulate eye development," explains Elizabeth A. Jones, a professor in the university's biological sciences department and a co-author of the study published in Nature.

Ectonucleoside triphosphate diphosphohydrolase 2 (E-NTPDase2) is an ectoenzyme that, along with family members E-NTPDase1 and E-NTPDase3, is known to degrade the chemical compound ATP (adenosine triphosphate) into ADP (adenosine diphosphate) for the purpose of sending messages to cells to change the fleet of proteins they are producing. Primarily, ATP functions as the energy currency of cells but, in some varieties, a tiny amount is secreted into the space between cells, where it latches onto a neighbor to induce particular responses and modulations. Both ATP and ADP, known as purines, can transmit signals to cells that change their developmental activity. The research team found that when it increased levels of E-NTPDase2 in tadpole embryos that consisted of only eight cells, they could cause parts of the eye to form not only on the heads of the amphibians, but also in tissues in other parts of their bodies, including their tails. Minute pulses of ATP are released into extracellular areas mostly by cells in the head where the eyes are supposed to develop. Jones notes that at temporally distinct moments, other cells in the body may expel small packets of ATP, which in the presence of E-NTPDase2 can cause eye tissue to form.

Through many rounds of analysis, both by amplifying and decreasing the levels of certain chemicals as well as knocking out the function of certain genes that code for proteins that regulate eye development (called eye field transcription factors), the scientists determined that E-NTPDase2 (although not E-NTPDase 1 or 3) was the only ectoenzyme that could drive eye development. Further, they determined that it must act early in the pathway that leads to the formation of the eye. After it converts ATP to ADP, the level of the latter accumulates outside the cell and the purine can bind to a purine receptor called P2Y1.

"It is the activation of this receptor that either directly or indirectly turns on the expression of the eye-field transcription factors," Jones says. "We don?t quite know the mechanisms involved between going from the receptor and turning on the genes, and this is an area for future investigation."

Jones and her colleagues believe that most of the eye development pathway is conserved between frogs and humans. Damage to human chromosome 9 (of the cell's 24 pairs) where the gene that codes for E-NTPDase2 resides is known to cause eye and brain defects, such as microphthalmia—literally, small eyes. This means that down the road, researchers might be able to create an "eye in a dish."

"This work may have interesting implications for the stem cell field," says Richard Lang, a professor of developmental biology at the Cincinnati Children's Hospital Research Foundation. "The activity of purine signaling in inducing eye field precursors," he says, "might be a very useful tool for the culture dish–generation of progenitor cells for a variety of eye cell types."

 

The Elderly Always Sleep Worse, and Other Myths of Aging

The Elderly Always Sleep Worse, and Other Myths of Aging 

 

As every sleep researcher knows, the surest way to hear complaints about sleep is to ask the elderly.

“Older people complain more about their sleep; they just do,” said Dr. Michael Vitiello, a sleep researcher who is a professor of psychiatry and behavioral sciences at the University of Washington.

And for years, sleep scientists thought they knew what was going on: sleep starts to deteriorate in late middle age and steadily erodes from then on. It seemed so obvious that few thought to question the prevailing wisdom.

Now, though, new research is leading many to change their minds. To researchers’ great surprise, it turns out that sleep does not change much from age 60 on. And poor sleep, it turns out, is not because of aging itself, but mostly because of illnesses or the medications used to treat them.

“The more disorders older adults have, the worse they sleep,” said Sonia Ancoli-Israel, a professor of psychiatry and a sleep researcher at the University of California, San Diego. “If you look at older adults who are very healthy, they rarely have sleep problems.”

And new studies are indicating that poor sleep may circle back to cause poor health. At least when it comes to pain, a common cause of disrupted sleep, a restless night can make pain worse the next day. Then with worse pain, sleep may become even more difficult — a vicious cycle common in people with conditions that tend to afflict the elderly, like back pain and arthritis.

The new view of sleep emerged from two parallel lines of research. The first asked what happened to sleep patterns when healthy people grew old. The second sought to uncover the relationship between sleep and pain.

To find out what happens with aging, some investigators, including Dr. Vitiello, studied older people who reported no sleep problems. They actually make up a large group — nearly half of people over 65. Were these people somehow spared age-related changes in sleep?

They were not. Their sleep turned out to be different from sleep in young people: it was lighter, more often disrupted by brief awakenings, and shorter by a half hour to an hour. Dr. Vitiello reasoned that the age-related changes in sleep patterns might not be an issue in themselves. Something else was making people complain about their sleep.

Dr. Vitiello and his colleagues also asked what normally happened to sleep over the life span. It had long been known that sleep changes, but no one had systematically studied when those changes occurred or how pronounced they were in healthy people.

With analysis of 65 sleep studies, which included 3,577 healthy subjects ages 5 to 102, the investigators had their next surprise. Most of the changes in sleep patterns occurred when people were between the ages of 20 and 60. Compared with teenagers and young adults, healthy middle-aged and older people slept a half hour to an hour less each night, they woke up a bit more often during the night, and their sleep was lighter. But after age 60, there was little change in sleep, at least in people who were healthy.

And even though sleep changed during adulthood, many of the changes were subtle. Middle-aged and older people, for example, did not have more difficulty falling asleep. The only change in sleep latency, as it is called, emerged when the investigators compared latency at the two extremes, in 20- and 80-year-olds. The 80-year-olds took an average of 10 more minutes to fall asleep.

Contrary to their expectations, the investigators found no increase in daytime drowsiness in healthy older people. Nor did aging affect the time it took for people to start dreaming after they fell asleep.

Instead, the biggest change was the number of times people woke after having fallen asleep.

Healthy young adults sleep 95 percent of the night, said Dr. Donald Bliwise, a sleep researcher at Emory University. “They fall asleep,” he said, “and don’t wake up until the alarm goes off.”

By age 60, healthy people are asleep 85 percent of the night. Their sleep is disrupted by brief wakeful moments typically lasting about 3 to 10 seconds. “There is some aspect of sleep that isn’t going to be as good as when you were 20,” Dr. Bliwise said. But he added, “When that crosses the threshold and becomes a significant complaint is difficult to say.”

The real sleep problems, he and others say, arise when people have any of a number of conditions that make them wake up in the night, like sleep apnea, chronic pain, restless leg syndrome or urinary problems. That, of course, describes many older people.

“The sheer number of challenges to maintaining solid sleep in old age is just huge,” Dr. Bliwise said. “You come out with the question, Well, what is normal? What should I expect?”

The new frontier of what to expect, and what to do about it, involves studies of the relationship of sleep to pain. It’s no surprise that pain can disrupt sleep. But what is new is that a lack of sleep can apparently increase the sensation of pain.

Michael T. Smith, the research and training director of the behavioral sleep medicine program at Johns Hopkins School of Medicine, reached that conclusion with a study of healthy young people. One group slept normally for eight hours in the hospital. Another was awakened every hour by a nurse and kept up for 20 minutes. Their sleep pattern was meant to mimic the fragmented sleep of elderly people. A third group was allowed four hours of solid sleep.

Comparing the second and third groups allowed Dr. Smith to tease apart the causes of the problems that arise from fragmented sleep: were they because of the short total sleep time, or because of the disrupted nature of the sleep?

Fragmented sleep, he found, led to severe impairments the next day in pain pathways. The subjects felt pain more easily, were less able to inhibit pain, and even developed spontaneous pain, like mild backaches and headaches.

Timothy Roehrs, director of the sleep disorders research center at Henry Ford Hospital in Detroit, also found that healthy young people became exquisitely sensitive to pain after a night of fragmented sleep.

And getting more sleep, Dr. Roehrs found, had the opposite effect. His subjects were young healthy people who said they were chronically sleepy, just not getting enough time to sleep at night. Dr. Roehrs had them stay in bed 10 hours a night. The extra sleep, he said, reduced their sensitivity to pain to the same degree as a tablet of codeine.

Now, Dr. Smith says, he and others have markedly changed their attitude about sleep problems and aging.

Of course, he said, sleep is different in 20-year-olds and 70-year-olds. But he added, “It’s not normal to get a clinical sleep disorder when you get old.” 

The Enduring Mysteries of the Sun

	The Enduring Mysteries of the Sun

The sun lies at the heart of our solar system, but it still holds back many secrets from science. Unlocking these mysteries could shed light on puzzling activity seen in other stars and even safeguard lives.

An explosive star

The sun is literally bursting with energy, violently exploding with solar flares, coronal mass ejections and other kinds of eruptions up to hundreds of times per year. The number of explosions and sunspots the sun experiences tends to rise and fall in a roughly 11-year-long "solar cycle," the roots of which remain uncertain.

Astrophysicists generally agree the solar cycle is driven by the solar dynamo—the flowing, electrically charged gas within the sun that generates its magnetic field—and that magnetic fluctuations trigger solar explosions. "But which of the many dynamo models is right is uncertain," said solar physicist Paul Charbonneau of the University of Montreal.

Shedding light on the solar dynamo could help predict when solar explosions happen, "which can endanger astronauts and satellites in space and damage power lines on Earth," Charbonneau said. But whether or not scientists can ever predict the solar cycle remains unknown—some claim it is physically impossible to predict.

The super-hot corona

Just as a fire feels warmer the closer one gets to it, so is the core of the sun hotter than its surface. Mysteriously, however, the corona—the sun's atmosphere—is also far hotter than its surface.

The sun's surface is roughly 5,500 degrees Celsius. The corona, on the other hand, is one to three million degrees C or more.

Why the corona is super-hot is hotly debated. Some researchers suggest the sun's magnetic fields heat the corona, while others propose that waves from the sun do. "I wouldn't be surprised if these mechanisms are at work together. They're not mutually exclusive," said Bernhard Fleck, project scientist for the Solar and Heliospheric Observatory (SOHO) spacecraft.

The Maunder Minimum

Oddly, the solar cycle once seemed to go on vacation for roughly 70 years. Only 50 sunspots were seen during this Maunder Minimum between 1645 to 1715, as opposed to the expected 40,000 to 50,000.

Research does suggest that similar phases of suppressed activity have occurred in the past 10,000 years, with the sun in such "quiet" modes about 15 percent of the time, Charbonneau said. Why these occur remains unclear, although there are models of the sun that suggest the solar dynamo can rev solar cycles up or down.

Also, the Maunder Minimum coincided in part with the Little Ice Age, leading to debates over whether or not the sun was the cause of that past climatic shift or the current one the world is undergoing. "The agreement of the majority of the scientists is that while the sun has had an influence on Earth's climate in the past, the recent dramatic change in climate is not caused by the sun but due to man-made greenhouse gases," Fleck said.

Erratic siblings

Most stars like the sun actually behave more erratically than our sun. "More than half of sun-like stars either have cycles that are slowly increasing or decreasing in how active they are over time instead of remaining steady, or they're completely irregular," said solar physicist Karel Schrijver at Lockheed Martin Advanced Technology Center in Palo Alto, Calif. "We don't really know why."

NASA's upcoming Solar Dynamic Observatory spacecraft could shed light on the inner workings of the sun and therefore its siblings, Schrijver said, "and therefore shed light on these mysteries."

Ruins of royal complex of Thang Long are excavated in Hanoi

 

Excavation work being carried out at Thang Long in Hanoi. Only one percent of the site has been excavated so far. (Chau Doan for The New York Times)

Ruins of royal complex of Thang Long are excavated in Hanoi

Nine hundred years before Ho Chi Minh declared Hanoi the capital of a newly independent Vietnam in 1945, the first king of the Ly Dynasty issued a similar decree.

In 1010 King Ly Thai To picked Thang Long ("Ascending Dragon"), situated within present-day Hanoi, as the capital for a country that had defeated the Tang Dynasty less than a century before, ending a millennium of Chinese rule.

"It is situated at the very heart of our country," the king declared in Edict on the Transfer of the Capital. "It is equally an excellent capital for a royal dynasty for ten thousand generations."

The enormous royal complex that Ly Thai To built did last, not 10,000 generations, but 900 years, through three major dynasties and repeated foreign invasions. For the last five years, archaeologists from the Vietnam Institute of Archaeology have been slowly unearthing the remains of Thang Long, uncovering millions of artifacts and building features spanning 1,300 years. Hanoi is gearing up to celebrate its 1,000th anniversary in 2010, and Thang Long, a potential Unesco World Heritage Site, is its centerpiece.

"The history of Thang Long citadel is the history of the Great Viet," Bui Minh Tri, an archaeologist, said as he looked over the 7.3-square-mile site, thought to be the largest archaeological excavation in the history of Southeast Asia. The Great Viet are considered the founders of northern Vietnam. They probably descended from the Bronze Age Dong Son culture, which is famous for its enormous bronze drums. In 2002, the site, across the street from where Ho lies in state, was scheduled to be the new home of the National Assembly, the highest government body. Modern residences were razed. Archaeologists were called in to see whether anything remained of the citadel.

They had a good sense of where to look. The flag tower and Confucian university, the Temple of Literature, survive as tourist attractions. The area had also been mapped twice, by Vietnamese cartographers in the 15th century and by the French 400 years later. Earlier archaeological work had turned up a 13th- to 14th-century brick road.

One to four meters beneath the surface, the archaeologists found the foundations of at least 11 palaces, pillar bases, brick roads, drainage systems and deep wells. A dried riverbed held what immediately became the largest collection of ceramics in Vietnam, virtually all imprinted with imperial marks.

Terra cotta sculptures of five-toed dragons and coil-tongued phoenixes, symbols of the king and queen, eyed the excavators from the dirt. Similar artifacts had been found in the past at Buddhist temples built by Great Viet rulers. Now archaeologists had a confirmation of their royal origin.

After 1010, the Great Viet ruled the northern half of present-day Vietnam, continually expanding southward in wars against the Indian-influenced Champa state. The north-south divide witnessed in "the American War" had a precedent going back a millennium.

By the 18th century, the south was ascendant. The Nguyen Dynasty moved the capital to Hue in central Vietnam in 1802, and the Thang Long citadel fell into disuse. Shortly after Hanoi became the capital of French Indochina in 1887, the French destroyed it.

The royal complex once covered an area now home to Ba Dinh Square, the modern military citadel, the military history museum, the presidential palace and Ho's mausoleum. It had dozens of palaces for the king, queen and royal family; pagodas and communal houses for the court and staff; and audience halls for government business.

As the military command center, it was enclosed by brick walls and guarded by armies who were also laborers.

From architecture to diet, Thang Long was an imperial capital in the tradition of Beijing's Forbidden City and Japan's Heijo Palace. The court feasted on deer, pig, chicken, fish and shellfish. They drank clean water from nearly 12 wells, the earliest dating from the seventh century. The rulers commissioned artisans to create ceramics and sculptures with classic Chinese designs.

They surrounded the complex with walls and roads built from bricks made all over the state. Today, these bricks are stacked in the thousands at the site, imprinted with Chinese characters describing where and when they were made, and for whom.

The Vietnamese clearly inherited their royal tradition from the Chinese. Yet Thang Long shows evidence of singularly Vietnamese traits. Examples are on display in the small on-site museum. Among them are terra cotta tile caps on the roof tiles in the shape of Bodhi leaves decorated with dragons and chrysanthemums, and terra cotta phoenixes that once reared, gargoyle style, from palace roof corners. Neither have been seen before.

"We knew very well the architecture from the 15th to the 19th centuries, but until we found Thang Long, we didn't know about architecture from the 10th to 15th centuries," Dr. Bui said.

Some collections may need to be reassessed in light of Thang Long. At the Smithsonian's Freer Gallery of Art in Washington, a 15th-century bowl long thought to be Chinese was recognized as Vietnamese only after nearly identical examples were found at the site.

These and other finds are discussed in the Vietnamese Institute of Archaeology's bilingual volume "Thang Long Imperial Citadel."

One percent of the site has been excavated. Archaeologists expect to learn more about individual dynasties as the dig continues over the next five years.

Today, the long pits excavated from 2002 to 2004 lie under corrugated metal roofs that channel heavy summer rain to be pumped out. Workers scrape the pottery-laden riverbed clear of moss that grows easily in the humid climate. In an adjacent closed area, some 200 more are excavating a section as large as the initial dig.

Only military officials, a handful of journalists and Vietnamese diplomats can visit Thang Long. Many people expect it to open to the public for Hanoi's celebration in 2010. Although some of the festivities take the form of public works like industrial parks, high-rise housing and road improvements, Thang Long is central to the commemoration.

A museum planned for 2010 will trace the development of the city from its beginnings as Thang Long, and an effort to designate it a Unesco World Heritage Site is in the works.

"It's very important to us that Unesco recognize Thang Long as a World Heritage Site," Dr. Bui said. "Thang Long is a symbol of the country."

Thang Long resonates today. (The city became known as Ha Noi, or between rivers, in the 1830s.)

It can be seen on shop signs for washing machines and on banners draped between sycamores greening the jammed streets. An oilfield discovered a few years ago off the southern coast of Vietnam was renamed Thang Long.

The city will have a second opera house, perhaps meant as an answer to the French-built Hanoi Opera House, by 2012. One guess what its name will be.

Thang Long may also develop as a case study in how archaeology can serve nationalistic goals, said Dr. Robert Murowchick, director of the International Center for East Asian Archaeology and Cultural History at Boston University.

"This is not necessarily a bad thing," Murowchick said. "It can promote tourism and economic development, and inspire national pride and unity."

There can, however, be cause to worry if the information is distorted "to provide 'concrete evidence' of the glory of a particular culture, as we often see in Chinese archaeology," he said.

So far, this doesn't seem to be the case at Thang Long. Considering that the construction of the Parliament building was delayed by the discovery of the site, the finds could have been "disappeared," as occurs in many countries, Murowchick said.

Instead, the project was moved to southwest of the municipal center, and Vietnam enacted its first heritage preservation laws. Unesco and foreign universities have been permitted to run field schools and conferences at the site.

The Ignobility of Wrinkles

The Ignobility of Wrinkles

Researchers win Ig Nobel Prize for study of rumpled sheets

Grab one end of a bedsheet, hand the other end to a partner, and spread it out as if you're going to fold it. But instead of folding it, engage in a tug-of-war, with one of you pulling on the head end of the sheet and the other pulling on the foot end. The sheet will stretch a bit lengthwise and at the same time compress a bit widthwise. That combination will create a funny-looking set of wrinkles with furrows along the length of the sheet.

A mathematician and physicist working together have found an explanation for this wrinkling pattern. For their study of sheet wrinkles, they have won this year's Ig Nobel Prize in physics. The prize, sponsored by the magazine The Annals of Improbable Research, celebrates research that "first makes people laugh, and then makes them think." Ten prizes are awarded each year in various fields of science.

The researchers' theory helps to explain the wrinkles that form on the skin of an apple as its flesh shrinks. Cerda and Mahadevan/Physical Review Letters

Sheet wrinkle experts Lakshminarayanan Mahadevan, a mathematician at Harvard University, and Enrique Cerda Villablanca, a physicist at the Universidad de Santiago de Chile, are sharing the prize in physics. It does not include a monetary award.

Winners of the much-coveted Ig Nobel Prize receive a statuette of a chicken climbing out of an egg. The chicken is beginning to eat the egg from which it emerged. Eric Workman/Annals of Improbable Research

Mahadevan says he is "neither proud nor sheepish, just amused" to receive the honor. "There is no reason that good science cannot be good fun," he comments, "and I think our research is just one more example of that."

Marc Abrahams, editor of the magazine and administrator of the prizes, says that when he contacted Mahadevan to tell him about the award, "He wasn't too surprised about it. He knew at least roughly what the prize was about, and he's done a lot of colorful research. But he seemed to be surprised that it was for this. I could hear the silence on the other end, and I thought I could hear the words he was thinking, which were, 'What's funny about that?'"

The humor was not lost on everyone, though. "It was fun at the ceremony to see the difference in the audience's first reaction to the scientists' first reaction," says Abraham. "The audience laughed as soon as the prize was announced."

But Abrahams won't reveal why the research amuses him. "Explaining why something is funny is something I don't get into," he says.

Despite the light-heartedness of the prize, the team's work has been in earnest. The pair has deduced "a general theory of wrinkling" which explains why wrinkles form and predicts their number and size based on the characteristics of the fabric.

The researchers clamped this sheet and then stretched it horizontally, forming a set of parallel wrinkles. Cerda, et al./Nature

The theory also offers some insight into the wrinkles that form on people's skin, although it can't predict how many wrinkles any one person will get. Skin forms a flexible surface attached to a more rigid subsurface made of muscles.

The researchers' theory explains why our most obvious wrinkles tend to appear on relatively bony areas like the cheeks and forehead. The skin and fat are both thinner there. Fat provides a stretchy, cushioned connection to the firm muscle beneath, so where there's less fat beneath the skin, the skin connects to a more rigid subsurface. Also, thin skin is more pliable than thicker skin. The rigid subsurface and flexible surface combine to create larger, more visible wrinkles.

The researchers can predict the size of wrinkles created when skin is compressed. Cerda and Mahadevan/Physical Review Letters

The team also examined the patterns that appear when fabric drapes over a solid object such as the body. The equations they developed to describe those possible patterns have many different solutions, and that fact corresponds to our experience that cloth can fall into many different shapes. The researchers say their results could improve our ability to depict moving clothing in computer-generated animation.

Many Renaissance artists were fascinated by how fabric drapes. This 700-year-old piece is a chiaroscuro by Albrecht Durer. Cerda, et al./PNAS

Past Ig Nobel prizes in mathematics and physics have been awarded for research contributions such as the following:

• Calculating the number of photographs you must take to (almost) ensure that each person's eyes will be open in a group photo;
• Calculating the odds that Mikhail Gorbachev was the Antichrist (answer: 710,609,175,188,282,000 to 1); and
• Figuring out why a stick of dry spaghetti often breaks into more than two pieces when you bend it.

Cerda Villablanca was unable to attend the ceremony, but his sister Mariella accepted the prize on his behalf. "My brother dedicates his Ig Nobel prize to all the wrinkled people in the world," she said.

Mahadevan accepted his prize with a bit of doggerel:

Wrinkle, wrinkle, on my skin
How, I wonder, did you begin?
By sagging and swelling and shrinking too,
While stretching and bending were mixed into a brew,
'Til, aha! A formula that fits on a pin.