Chemicals in brown algae may protect against skin cancer

Chemicals in brown algae may protect against skin cancer

Substances extracted from a marine seaweed may protect against skin cancer caused by too much sun, new research suggests.

The animal study indicates that chemicals called brown algae polyphenols (BAPs), which are found in a type of brown marine seaweed, might protect against skin cancers caused by ultraviolet B (UVB) radiation.

UVB radiation in sunlight is thought responsible for 90 percent of the estimated 1.3 million cases of non-melanoma skin cancer diagnosed in the United States annually.

Researchers applied the BAPs to the skin of hairless mice and fed it to the animals in their diet. In both cases, the substances reduced the number of skin tumors by up to 60 percent and their size by up to 43 percent. They also reduced inflammation.

The study, led by researchers at the Ohio State University Comprehensive Cancer Center, is published in the Dec. 15 issue of the International Journal of Cancer.

"These compounds seemed to be dramatically effective at fairly low doses both orally and topically," says principal investigator Gary D. Stoner, professor emeritus of internal medicine and a cancer chemoprevention researcher.

"These findings suggest that, even when eaten, these compounds get to skin cells and neutralize the cancer-causing oxygen radicals that are produced by UV exposure."

Laboratory research has shown that BAPs are strong antioxidants and may have anticancer properties.

For this study, Stoner and his collaborators used a strain of hairless mice that are particularly susceptible to UVB-induced skin cancer. Nine experimental groups were used, each with 20 mice.

In two groups, BAPs were applied to the skin in concentrations of 3 milligrams or 6 milligrams in a mild solvent. In two other groups, BAPs made up 0.1 percent or 0.5 percent of the diet.

A group of untreated control mice was also exposed to UVB.

The remaining groups were additional controls: Two were fed the standard diet with and without UV exposure, and two had the BAP solvent applied to the skin with and without UV exposure.

The mice received the BAPs for two weeks before UVB exposure began, followed by 24 weeks of increasing UVB exposure according to a standardized schedule.

The researchers then counted the number of tumors in the treatment and control groups and calculated their size.

Animals exposed only to UVB developed an average of 8.5 skin tumors. The animals fed the lower and the higher dose of BAPs developed an average of 4.7 and 3.7 tumors respectively. Of those given the topical treatment, the lower and higher doses developed 3.4 and 4.6 tumors respectively.

In terms of tumor volume, the animals fed BAPs at the lower and higher doses had tumors that were 34 percent and 40 percent smaller than those in animals exposed to UVB alone. Of those given the topical treatment, the lower and higher dose animals had tumors that were 27 percent to 43 percent smaller than animals exposed to UVB alone.

In addition, the researchers compared the groups for skin levels of the enzyme cyclooxygenase-2 (COX-2) and of the hormone-like substance prostaglandin E2, both of which are strong indicators of inflammation, and for cell proliferation rates.

Animals treated with BAPs showed lower levels of both COX-2 and prostaglandin E2.

The researchers found that the dietary BAPs reduced COX-2 activity by 74-82 percent, and that the topical BAPs reduced it by 66-82 percent. They also measured lower rates of cell proliferation in BAP-treated animals.

"Both the oral and topical BAP treatment reduced COX-2 and prostaglandin E2 cell proliferation levels in the skin," Stoner says, "which corresponds with fewer tumors and small tumors in the treated animals."

Fish know their social strata

Fish know their social strata

A male fish can size up potential rivals, and even rank them from strongest to weakest, simply by watching how they perform in territorial fights with other males, according to a new study by Stanford University scientists. The researchers say their discovery provides the first direct evidence that fish, like people, can use logical reasoning to figure out their place in the pecking order.

The study, published in the Jan. 25 edition of the journal Nature, is based on a unique experiment with cichlids (SIK-lids), small territorial fish from Africa.

"In their natural habitat, male cichlids are constantly trying to ascend socially by beating each other up," said study co-author Russell D. Fernald, professor of biological sciences at Stanford. "It would be really valuable for them to know in advance who to pick a fight with."

The Nature experiment was designed by lead author Logan Grosenick, a graduate student in statistics at Stanford, and Tricia S. Clement, a former postdoctoral fellow. Their goal was to determine whether territorial fish use a type of reasoning called "transitive inference," in which known relationships serve as the basis for understanding unfamiliar ones.

"Transitive inference is essential to logical reasoning," Fernald explained. "It's something that kids generally figure out by age 4 or 5—Mary is taller than Fred, Fred is taller than Pete, therefore Mary is taller than Pete. It's been demonstrated in primates, rats and some bird species, but how and why it evolved in animals is a matter of debate."

Aggressive bouts

In the experiment, the Stanford team used a popular laboratory fish called Astatotilapia burtoni, one of many cichlid species that inhabit Lake Tanganyika in eastern Africa. A. burtoni males are extremely territorial and regularly engage in aggressive fights, the outcome of which determines who gets access to food and mates.

"Males that repeatedly lose fights are unable to hold territories and consequently descend in social status," the authors wrote. "Success in aggressive bouts is therefore crucial to male reproductive fitness, and the ability to infer the relative strength of rivals before engaging them in potentially costly fights should be highly adaptive."

When A. burtoni males fight, it's easy to spot the winner. Mature males have a menacing black stripe, or eyebar, on their face. After a fight, the winner retains his showy appearance, but the loser's eyebar temporarily disappears as he tries to flee his more aggressive opponent.

The Stanford team took advantage of this reversible transformation by staging a series of short fights between male cichlids. All of the combatants used in the experiment were the same size. During one-on-one combat, the fish whose eyebar disappeared was declared the loser.

After each bout, the loser was separated from his opponent and put back in his original tank. Within minutes, his eyebar returned, and he looked like all the other dominant males again.

Bystanders and rivals

The fights were staged in a square tank divided into several compartments. A lone male observer—the "bystander"—was placed in a cubicle in the center of the tank. Surrounding him were five smaller compartments, each with a solitary male rival identified simply as A, B, C, D or E. Researchers made sure that the bystander and his five potential rivals had never met.

Although the bystander remained alone in his cubicle and never swam with the others, he was allowed to observe a series of fights between rival pairs—A vs. B, B vs. C, C vs. D, and D vs. E. Researchers manipulated the fights so that A would dominate B, B would dominate C, and so forth down the line.

"These fights, taken together, imply the dominance hierarchy A>B>C>D>E," the authors wrote. But did the bystander really comprehend this intricate pecking order, and if so, would he use that knowledge to make logical decisions about the same fish paired in new relationships?

To find out, eight different bystanders were tested in the familiar square tank and in a new setting—a rectangular aquarium with three adjacent compartments. In each test, a bystander was placed in the middle compartment between two sets of rivals that he had never seen together—A and E (AE), and B and D (BD). At this point in the experiment, all the rivals had recovered from earlier losses, so their physical appearance was similar, right down to the eyebar. From the point of view of the bystander, therefore, each rival looked like a winner.

Using a video camera, researchers recorded which rival the bystander approached first, and the overall time he spent next to each of them. "Previous experiments in A. burtoni and other fish have shown that time spent in tank quadrants adjacent to a particular male indicates bystander 'preference,' and that bystanders spend more time near the rival they perceive to be weaker," the authors explained.

Losers and winners

The results were dramatic. Virtually all of the bystanders swam to the weaker rival first and stayed near him for a significantly longer period of time. In the AE tests, bystanders preferred E, the wimpiest of all the losers, over A, the top fish in the tank. In the more subtle BD tests, most bystanders chose D over B, even though these two rivals were ranked very close together on the dominance hierarchy.

"These results show that fish do, in fact, use transitive inference to figure out where they rank in the social order," Fernald said. "I was amazed that they could do this through vicarious experience, just by watching other males fight. In Lake Tanganyika, where conditions change all the time, it would be advantageous for a male to know who the new boss is going to be and who his weakest rivals are. Our experiment shows that male cichlids can actually figure out their odds of success by observation alone. From an evolutionary standpoint, transitive inference saves them valuable time and energy."

The results raise the possibility that fish brains might contain the rudimentary neuronal circuitry for transitive inference that appeared later in birds and mammals. "Any animal that has evolved a social system that requires combat among males will have some kind of eavesdropping capability allowing them to surreptitiously draw inferences about their social rank," Fernald said. "Cognitive capacities that evolved in fish may contribute to human transitive inference, or perhaps this capacity evolved independently. The question remains unresolved."

The Nature study was supported with grants from the National Institutes of Health.

Doomsday clock moves forward 2 minutes

Doomsday clock moves forward 2 minutes

The Bulletin of the Atomic Scientists (BAS) is moving the minute hand of the Doomsday Clock today from seven to five minutes to midnight. Reflecting global failures to solve the problems posed by nuclear weapons and the climate crisis, the decision by the BAS Board of Directors was made in consultation with the Bulletin's Board of Sponsors, which includes 18 Nobel Laureates.

BAS announced the Clock change today at an unprecedented joint news conference held at the American Association for the Advancement of Science in Washington, DC, and the Royal Society in London. In a statement supporting the decision to move the hand of the Doomsday Clock, the BAS Board focused on two major sources of catastrophe: the perils of 27,000 nuclear weapons, 2000 of them ready to launch within minutes; and the destruction of human habitats from climate change. In articles by 14 leading scientists and security experts writing in the January-February issue of the Bulletin of the Atomic Scientists ( http://www.thebulletin.org), the potential for catastrophic damage from human-made technologies is explored further.

Created in 1947 by the Bulletin of the Atomic Scientists, the Doomsday Clock has been adjusted only 17 times prior to today, most recently in February 2002 after the events of 9/11.

By moving the hand of the Clock closer to midnight--the figurative end of civilization--the BAS Board of Directors is drawing attention to the increasing dangers from the spread of nuclear weapons in a world of violent conflict, and to the catastrophic harm from climate change that is unfolding.

The BAS statement explains: "We stand at the brink of a Second Nuclear Age. Not since the first atomic bombs were dropped on Hiroshima and Nagasaki has the world faced such perilous choices. North Korea's recent test of a nuclear weapon, Iran's nuclear ambitions, a renewed emphasis on the military utility of nuclear weapons, the failure to adequately secure nuclear materials, and the continued presence of some 26,000 nuclear weapons in the United States and Russia are symptomatic of a failure to solve the problems posed by the most destructive technology on Earth."

The BAS statement continues: "The dangers posed by climate change are nearly as dire as those posed by nuclear weapons. The effects may be less dramatic in the short term than the destruction that could be wrought by nuclear explosions, but over the next three to four decades climate change could cause irremediable harm to the habitats upon which human societies depend for survival."

Stephen Hawking, a BAS sponsor, professor of mathematics at the University of Cambridge, and a fellow of The Royal Society, said: "As scientists, we understand the dangers of nuclear weapons and their devastating effects, and we are learning how human activities and technologies are affecting climate systems in ways that may forever change life on Earth. As citizens of the world, we have a duty to alert the public to the unnecessary risks that we live with every day, and to the perils we foresee if governments and societies do not take action now to render nuclear weapons obsolete and to prevent further climate change."

Kennette Benedict, executive director, Bulletin of the Atomic Scientists, said: "As we stand at the brink of a Second Nuclear Age and at the onset of unprecedented climate change, our way of thinking about the uses and control of technologies must change to prevent unspeakable destruction and future human suffering."

Sir Martin Rees, president of the Royal Society, professor of cosmology and astrophysics, master of Trinity College at the University of Cambridge, and a BAS sponsor, said: "Nuclear weapons still pose the most catastrophic and immediate threat to humanity, but climate change and emerging technologies in the life sciences also have the potential to end civilization as we know it."

Lawrence M. Krauss, professor of physics and astronomy at Case Western Reserve University, and a BAS sponsor, said: "In these dangerous times, scientists have a responsibility to speak truth to power especially if it might provoke actions to reduce threats from the preventable technological dangers currently facing humanity. To do anything else would be negligent."

Ambassador Thomas Pickering, a BAS director and co-chair of the International Crisis Group, said: "Although our current situation is dire, we have the means today to successfully address these global problems. For example, through vigorous diplomacy and international agencies like the International Atomic Energy Agency, we can negotiate and implement agreements that could protect us all from the most destructive technology on Earth--nuclear weapons."

Mom's smoking can cause cleft lip, palate

Mom's smoking can cause cleft lip, palate

Scientists supported by the National Institute of Dental and Craniofacial Research (NIDCR), part of the National Institutes of Health, report that women who smoke during pregnancy and carry a fetus whose DNA lacks both copies of a gene involved in detoxifying cigarette smoke substantially increase their baby's chances of being born with a cleft lip and/or palate.

According to the scientists, about a quarter of babies of European ancestry and possibly up to 60 percent of those of Asian ancestry lack both copies of the gene called GSTT1. Based on their data, published in the January issue of the "American Journal of Human Genetics", the scientists calculated that if a pregnant woman smokes 15 cigarettes or more per day, the chances of her GSTT1-lacking fetus developing a cleft increase nearly 20 fold. Globally, about 12 million women each year smoke through their pregnancies.

Dr. Jeff Murray, a scientist at the University of Iowa and senior author of the study, noted that parents who are considering having a child and need added motivation for the mother to quit smoking might one day be tested to determine their GSTT1 status. Because the fetus inherits its genes from both mother and father, the test would determine the likelihood of the baby developing without the GSTT1 gene to detoxify the cigarette smoke.

"A test that indicates the GSTT1 gene is present certainly would not eliminate a baby's risk of a cleft because many other genetic and environmental factors can be involved." said Murray. "But the opposite result would give the mother one more compelling reason to quit smoking for her own health and for the sake of her child."

In the United States, about one in every 750 babies is born with isolated, also called nonsyndromic, cleft lip and/or palate. The condition is correctable but typically requires several surgeries. Families often undergo tremendous emotional and economic hardship during the process, and children frequently require many other services, including complex dental care and speech therapy.

According to Murray, researchers have built a strong statistical case over the past several years that pregnant women who smoke put their unborn babies at greater risk of developing a cleft. The data raised two related questions. "Do genetic variations in the mother influence her own metabolism of the cigarette smoke and its byproducts, thus setting in motion developmental changes that cause the cleft in the fetus? Or do genetic variations in the fetus itself compromise its ability to metabolize the cigarette smoke and cause the cleft?" said Dr. Min Shi, now a scientist at NIH's National Institute of Environmental Health Sciences and a lead author of the paper.

To find the answers, Murray's group teamed with colleagues in Denmark to perform a large, complex, and possibly first-of-its-kind international study. The group first assembled a list of 16 genes of interest, each of which encode proteins that plug into various pathways in the body involved in detoxifying dangerous chemicals. "We picked genes that previous evidence shows either are directly involved in cigarette smoke toxicity or are major players in general toxicity management in people," said Dr. Kaare Christensen, a scientist at the University of Southern Denmark in Odense and an author on the paper.

"These genes tend to be quite variable from person to person in their precise DNA structure, or spelling," Christensen added. "We wanted to see if any of these variations might adversely affect a person's ability to break down the toxic products of cigarette smoke."

Christiansen and his colleagues then turned to their existing database of kids with clefts, their parents, and siblings. In all, the scientists analyzed 5,000 DNA samples from both continents -- including 1,244 from children born with clefts. Importantly, the families in Denmark and Iowa provided the opportunity to independently confirm the findings in two distinct populations.

In addition, they had free public access to the NIDCR-funded COGENE project, a comprehensive online database of genes expressed throughout the various stages of development. Working closely with Dr. Mike Lovett at Washington University in St. Louis, one of COGENE's founders, the database proved especially helpful because cleft lip and/or palate occurs during the first 5-to-12 weeks of development. This meant the scientists had to be sure not only that their genes of interest are expressed during this vital period but are switched on in fetal craniofactial structures. If the genes met both criteria, the investigators said they hoped their subsequent data might point them to a gene-environment interaction.

As reported, the scientists determined from their analyses that the mother provides the toxic environmental exposure, which then can be greatly amplified by the genetics of the fetus to produce the cleft. This marks the first time a gene-environment interaction in clefting has been documented at a molecular level. The data also point the way for future studies to define the specific molecular chain of events that lead to the cleft, vital information to understand and hopefully one day prevent the process.

While sifting through the data, the researchers took particular note of the GSTT gene and its contribution to clefting. The gene encodes one of the body's approximately 20 different glutathione S-transferase enzymes. These enzymes collectively play roles in common detoxification processes, ranging from chemically altering drugs and industrial chemicals to detoxifying polycyclic aromatic hydrocarbons, a key component of cigarette smoke.

The scientists found that pregnant women who smoked and also carried fetuses that lacked the GSTT1 enzyme were much more likely to give birth to a baby with a cleft. This finding was true in Iowa and Denmark, and they noted in the COGENE database that the gene is highly expressed in developing craniofacial structures. "It may be that be that the lip and palate can form normally without GSTT1," said Murray. "But if the chemicals in cigarette smoke challenge the normal development of these structures, fetuses that lack the gene are at a distinct disadvantage."

Murray and his collaborators continue their genetic analyses. "We now have data from about 350 genes on this cohort of families," he said. "It's certainly a more complicated analysis to perform, but we're working our way through it and hope to have some very interesting data in the months ahead."

The article is titled "Orofacial Cleft Risk is Increased with Maternal Smoking and Specific Detoxification-Gene Variants," and is published in the January 2007 issue of the "American Journal of Human Genetics". The authors are Min Shi, Kaare Christensen, Clarice R. Weinberg, Paul Romitti, Lise Bathum, Anthony Lozada, Richard W. Morris, Michael Lovett, and Jeffrey C.Murray.

The National Institute of Dental and Craniofacial Research (NIDCR) is the nation's leading funder of research on oral, dental, and craniofacial health.

A bumpy shift from ice house to greenhouse

A bumpy shift from ice house to greenhouse

The transition from an ice age to an ice-free planet 300 million years ago was highly unstable, marked by dips and rises in carbon dioxide, extreme swings in climate and drastic effects on tropical vegetation, according to a study published in the journal Science Jan. 5.

"This is the best documented record we have of what happens to the climate system during long-term global warming following an ice age," said Isabel Montanez, professor of geology at the University of California, Davis, and lead author on the paper. But she added that these findings cannot be applied directly to current global warming trends.

In the mid-Permian, 300 million years ago, the Earth was in an ice age. Miles-thick ice sheets covered much of the southern continent, and floating pack ice likely covered the northern polar ocean. The tropics were dominated by lush rainforests, now preserved as coal beds.

Forty million years later, all the ice was gone. The world was a hot, dry place, vegetation was sparse, soils little more than drifts of wind-blown dust.

"You'd have to be a reptile to want to live there," Montanez said.

Montanez and her co-authors derived records of atmospheric carbon dioxide from ancient soils that have been preserved as rocks, from coal and from fossils of plants. They extracted a record of sea surface temperatures from the fossils of brachiopod shellfish and looked at the extensive records of past plant life from fossils of the ancient rainforests. To see how the glaciers advanced and retreated, they looked at the scars and clues left by ice sheets that once covered the great southern continent of Gondwanaland, which included most of the land masses of the modern southern hemisphere.

They placed statistical constraints on their data with computer modeling by Deb Niemeier, professor of civil and environmental engineering and director of the John Muir Institute of the Environment at UC Davis.

The new data show that throughout millions of years, atmospheric carbon dioxide levels swung back and forth between about 250 parts per million, close to present-day levels, to more than 2,000 parts per million. At the same time, the southern ice sheets retreated as carbon dioxide rose and expanded again when levels fell, a pattern compatible with the idea that greenhouse gases caused the end of the late Paleozoic ice age.

"We can see a pattern of increasing carbon dioxide and increasing temperatures, with a series of rises and dips," Montanez said.

Scientists had assumed that as the climate warmed, a tipping point would be reached at which the ice sheets would melt rapidly and for good. Instead, the new data shows that the climate went back and forth between the extremes. But the overall trend was to warming, and by 260 million years ago, the ice sheets were gone.

Records of fossil plants show rapid changes in tropical plant communities as the climate changed. On scales of a few thousand years, lush forests of tree ferns in cool, wet periods alternated with conifers and other plants adapted to a harsher, drier and warmer climate.

"The Permian greenhouse is the only record we have of the transition from an ice age to an ice-free climate on a vegetated planet," Montanez said. But instead of a smooth shift, the transition occurred in a series of sharp swings between cold and hot conditions, occurring during perhaps a half-million to few million years.

But Montanez pointed out that these results cannot be directly applied to current global warming. The current rise in atmospheric carbon dioxide is occurring throughout a much shorter timescale, for one thing. But the current work does show that such a major change in climate will likely not proceed in small, gradual steps, but in a series of unstable, dramatic swings. While these data cover millions of years, similar events might take place during a much shorter time span.

"Perhaps this is the behavior one should expect when we go through a major climate transition," Montanez said.

Further, the record of fossil plants shows the drastic effects of major climate change on living things. In the modern era, tropical forests are already stressed by human use and settlement, and ecological researchers have recorded species moving north or south, likely driven by current global warming.

Polar bears may get endangered species status

Polar bears may get endangered species status

U.S. Secretary of the Interior Dirk Kempthorne today announced the U.S. Fish and Wildlife Service is proposing to list the polar bear as a threatened species under the Endangered Species Act and initiating a comprehensive scientific review to assess the current status and future of the species.

The Service will use the next 12 months to gather more information, undertake additional analyses, and assess the reliability of relevant scientific models before making a final decision whether to list the species.

"Polar bears are one of nature's ultimate survivors, able to live and thrive in one of the world's harshest environments," Kempthorne said. "But we are concerned the polar bears' habitat may literally be melting."
"Based on current analysis, there are concerns about the effect of receding sea ice on polar bear populations," he said. "I am directing the U.S. Fish and Wildlife Service and the U.S. Geological Survey to aggressively work with the public and the scientific community over the next year to broaden our understanding of what is happening with the species. This information will be vital to the ultimate decision on whether the species should be listed."
Polar bears are already protected under the Marine Mammal Protection Act of 1972. Under that law, it is generally prohibited to (1) take or (2) import marine mammals and their parts or products.
The species is also protected by international treaties involving countries in the bear's range. In early December, Congress passed the United States-Russia Polar Bear Conservation and Management Act of 2006, implementing a treaty with Russia designed to conserve polar bears shared between the two countries. President Bush is expected to sign this legislation into law.

Today's proposal cites the threat to polar bear populations caused by receding sea ice, which bears use as a platform to hunt for prey. In recommending a proposed listing, the Fish and Wildlife Service used scientific models that predict the impact of the loss of ice on bear populations over the next few decades.

Scientific observations have revealed a decline in late summer Arctic sea ice to the extent of 7.7 percent per decade and in the perennial sea ice area of 9.8 percent per decade since 1978. Observations have likewise shown a thinning of the Arctic sea ice of 32 percent from the 1960s and 1970s to the 1990s in some local areas.

There are 19 polar bear populations in the circumpolar Arctic, containing an estimated total of 20,000-25,000 bears.
The western Hudson Bay population of polar bears in Canada has suffered a 22 percent decline. Alaska populations have not experienced a statistically significant decline, but Fish and Wildlife Service biologists are concerned that they may face such a decline in the future.

Recent scientific studies of adult polar bears in Canada and in Alaska's Southern Beaufort Sea have shown weight loss and reduced cub survival. While data are lacking about many populations, the Service suspects that polar bears elsewhere are being similarly affected by the reduction of sea ice
"We have sufficient scientific evidence of a threat to the species to warrant proposing it for listing, but we still have a lot of work to do to enhance our scientific models and analyses before making a final decision," said U.S. Fish and Wildlife Service Director Dale Hall.

The Service extensively analyzed the impact of both onshore and offshore oil and gas development on polar bears and determined they do not pose a threat to the species.

The Service likewise examined the impact of subsistence harvest of polar bears by Alaska Natives. Such harvest is specifically allowed under the Marine Mammal Protection Act and would also be allowed if the polar bear is listed under the Endangered Species Act, unless the Service finds that the harvest is materially and negatively affecting the polar bear.
Harvesting polar bears is of great social, cultural and economic importance to Native peoples throughout much of the Arctic and maintaining a harvest within sustainable limits is one of the department's priorities, Kempthorne noted.

While the proposal to list the species as threatened cites the threat of receding sea ice, it does not include a scientific analysis of the causes of climate change. That analysis is beyond the scope of the Endangered Species Act review process, which focuses on information about the polar bear and its habitat conditions, including reduced sea ice.

However, climate change science and issues of causation are discussed in other analyses undertaken by the Bush Administration. The administration treats climate change very seriously and recognizes the role of greenhouse gases in climate change.

The Service invites the public to submit data, information, and comments on the proposed rule. Comments will be accepted on the proposed rule for the next 90 days.

A copy of the proposed rule and other information about the proposal is available on the Service's Marine Mammal website located at: http://alaska.fws.gov/fisheries/mmm/polarbear/issues.htm .
"Our goal ultimately is to combine the best science available with the power of working hand-in-hand with states, tribes, foreign countries, industry, and other partners to minimize the threats to polar bears and conserve this great icon of the Arctic for future generations," Kempthorne said.

How does a zebrafish grow a new tail?

How does a zebrafish grow a new tail?

If a zebrafish loses a chunk of its tail fin, it'll grow back within a week. Like lizards, newts, and frogs, a zebrafish can replace surprisingly complex body parts. A tail fin, for example, has many different types of cells and is a very intricate structure. It is the fish version of an arm or leg.

The question of how cold-blooded animals re-grow missing tails and other appendages has fascinated veterinary and medical scientists. They also wonder if people, and other warm-blooded animals that evolved from these simpler creatures, might still have untapped regenerative powers hidden in their genes.

People are constantly renewing blood components, skeletal muscles and skin. We can regenerate liver tissue and repair minor injuries to bone, muscle, the tips of our toes and fingers, and the corneas of our eyes. Finding out more about the remarkable ability of amphibians and fish to re-grow complex parts might provide the information necessary to create treatments for people whose hearts, spinal cords, eyes or arms and legs have been badly hurt.

Scientists have discovered some of the genes and cell-to-cell communication pathways that enable zebrafish to restore their tail fins.

"The ability to regenerate body parts such as those that are damaged by injury or disease," said Dr. Randall Moon, professor of pharmacology at the University of Washington (UW), an investigator of the Howard Hughes Medical Institute, and a researcher in the UW Institute for Stem Cell and Regenerative Medicine, "involves creating cells that can take any number of new roles. This can be done by re-programming cells that already have a given function or by activating resident stem cells."

Developmental biologists know that a particular kind of cell-to-cell communication, called Wnt/Beta-catenin signaling, regulates the fate of these as-yet undeveloped cells as an embryo forms. Through a cascade of signals, cells waiting for their calling learn which spot to take to help form the embryo, what kinds of cells to become there, and how many cells like themselves should be reproduced. These streams of signals also tell stem cells in adult organisms what functions to undertake. Once tissue formation starts, something has to tell it to stop before growth gets out of hand.

In the Dec. 21, 2006 online edition of the scientific journal Development, UW researchers report on laboratory evidence that suggests that Wnt/Beta signaling also promotes the regeneration of tail fins in zebrafish. Another, distinct signaling pathway activated by a different kind of Wnt protein called Wnt5b, turns down the genes that are turned on by Wnt/Beta-catenin, impairs cell proliferation, and inhibits fin regeneration. Fish that have a mutant Wnt5b protein regenerate missing tails very quickly. Too much of another related protein, Wnt8, also increases cell proliferation in the regenerating fin.

"We can actually increase the rate of regeneration by turning on these genes," Moon said.

The researchers also noted, "We show that Wnt/Beta-catenin signaling is activated in the regenerating zebrafish tail and is required for the formation and subsequent proliferation of the progenitor cells of the blastema." A blastema is a little nub of cells that directs regeneration, much like the conductor of an orchestra. By directing cell communication, these few cells grow into an organ or body part, in this case, a tail fin.

"It is most likely the inability of humans to form a blastema in the first place that renders us unable to re-grow arms and legs," said Cristi Stoick-Cooper, a graduate student in the multidisciplinary Neurobiology and Behavior program at the UW, who, with Gilbert Weidinger, now of the Technical University of Dresden (TUD), Germany, was first co-author of the study. The research was done in Moon's lab.

"Our study is the first to identify a gene (Wnt5b) that inhibits regeneration," said Weidinger, a former UW postdoctoral fellow who leads the Wnt Signaling in Development and Regeneration research group at the TUD's Biotechnology Center. "This is very exciting, because this gene might also inhibit regeneration in mammals and man. So, if we find ways of interfering with the function of Wnt5b, we might be able to promote regeneration."

Moon added that, because the same genes for turning on and turning off growth and development are found in humans, and drugs exist that can regulate this pathway, the findings are directly relevant to future testing of whether scientists can increase the capacity of humans to re-build damaged organs.

Male fish turn to cannibalism when uncertain of paternity

Male fish turn to cannibalism when uncertain of paternity | Science Blog

Male fish turn to cannibalism when uncertain of paternity

A study from the February issue of the American Naturalist is the first to demonstrate that male fish are more likely to eat their offspring when they have been cuckolded during the act of spawning. Moreover, the more males that are present during spawning, the more likely it is that a male will try to eat the eggs when they are laid, as it is less likely that he fertilized them.

"The most drastic decision a father can make is to cannibalize his own offspring," writes Suzanne Gray (Ph.D. candidate at Simon Fraser University), Lawrence Dill (Simon Fraser University), and Jeffrey McKinnon (University of Wisconsin – Whitewater). "These results support and extend previous findings suggesting that confidence of paternity is a key factor in determining a male's behavior toward his offspring, including whether or not to eat them."

Predicted by theory, this pattern had never previously before been demonstrated. Studying Telmatherina sarasinorum, a small, colorful fish found in Lake Matano in Indonesia, the researchers found that females, who can be sure of their relationship to their eggs, never cannibalized. However, an increased level of cuckoldry led to an increased rate of cannibalism among males.

"We want to understand how behaviors evolve," says Gray, "and how behaviors, such as cannibalism, contribute to the diversity we see within and between different species."

Melting Arctic draws killer whales, threatening Inuit fishing

ANTARA News :: Melting Arctic draws killer whales, threatening Inuit fishing

Melting Arctic draws killer whales, threatening Inuit fishing

Montreal (ANTARA News) - Killer whales are migrating farther north as the Arctic Ocean's ice cover melts, threatening the livelihood of the native Inuit who traditionally depend on fishing for their food, Canadian researchers said Saturday.

"We found a really direct correlation with decreasing ice in the Arctic and more observations of killer whales so we think they are moving further into the Arctic because of less ice," Steven Ferguson, a scientist at the arctic division of the Canadian fishing ministry, told AFP.

Ferguson's team last year was notified of spottings of the black and white orca, (Orcinus orca, popularly called killer whales) by scientists, tour operators and Inuit fishermen who criss-cross Hudson Bay, a North Canadian inland sea bigger than France.

In the 1980s, experts counted between five and 10 summer spottings of orca each year in the same area. That number jumped to about 30 last year, the Canadian researchers said.

During the same period, the ice cover in the Arctic has sharply declined.

Greenpeace highlights WTO dangers to marine life

Zee News - Greenpeace highlights WTO dangers to marine life

Greenpeace highlights WTO dangers to marine life

Nairobi, Jan 21: Pirates and licenced trawlers are ravaging the world's oceans, while proposals for trade ministers meeting in Switzerland next week could prove the final blow to sea life, Greenpeace said. Three-quarters of global fish stocks are now classed by the United Nations as fully or over-exploited, and the conservation group said World Trade Organisation plans to slash or cancel fish and fish product tariffs would be a disaster. ''Under trade liberalisation, only a few countries will benefit, and then only in the short term,'' Daniel Mittler, a political adviser on trade for Greenpeace, told reporters. ''The reality is, all other countries will lose. There must be regulated trade and proper management...The last thing the world needs is a relaunch of the Doha global trade round.'' The world's seas are already ravaged, with waters off developing nations most at risk from pirate trawlers flying cheaply purchased flags of convenience, Greenpeace said. At any one time, some 600 foreign vessels are fishing off the Kenyan coast, said Athman Seif of the Kenya Marine Forum, particularly targeting lucrative hauls of yellow fin tuna. Some of the boats are licenced, many are not, he said. ''They are sophisticated and unscrupulous, and something must be done,'' he said at the launch of the report in Nairobi. Greenpeace says illegal fishing will boom if tariffs are cut or dropped, as trawler crews hunt valuable export stocks while dumping tons of unwanted ''bycatch'' caught in their huge nets. The tariff plans are included in the suspended Doha round of trade talks begun in 2001. But discussions have continued behind closed doors, Mittler said, and next week in Davos, Switzerland, ministers will try to rescue the round. Greenpeace said studies in Mauritania, Senegal and Argentina showed that trade liberalisation in fisheries was a disaster for the marine environment as well as for local food security. ''Not even the economic case for liberalisation is convincing,'' it said in its report. ''Argentina, for example, is estimated to have lost at least 3.5 million dollars in future earnings by over-exploiting its fish resources after liberalisation.''

Marine life responds to early winter warmth

GloucesterTimes.com, Gloucester, MA - Marine life responds to early winter warmth

Marine life responds to early winter warmth Gloucester Daily Times

Although the calendar, the amount of daylight, the low sun in the midday sky, and the locations of the rising and setting sun clearly tell winter's here, the air and seawater temperatures have pretty much said otherwise.

Three types of Cape Ann marine life - the lobster, common periwinkle and knotted wrack - have been affected by the unseasonably winter warmth in different ways.

The seawater temperature during the first two weeks of January ranged from 43 to 45 degrees Fahrenheit, while the air temperature frequently hit or surpassed the 50-degree mark. The ocean water even felt warm to the bare hand then. Most winters at this time see ocean temperatures below 40 degrees.

Knotted Wrack

Knotted wrack, the common, attached brown algae that resides in the midtide zone, usually goes "spawny" in the early spring. The receptacles at the tips of the plants' long fronds then swell, turn yellowish/brown and gooey and eventually release their gametes during this approximately six-week annual reproductive event.

This winter's warmth already triggered many of the knotted wracks to begin going "spawny" the first week in January. Knotted wrack's commercial value ebbs during the "spawny" period. Not only does the plant look unattractive, but it also gives off a cucumber-like odor and spoils quickly in storage.

Common Periwinkle

Common periwinkles are cold-blooded invertebrates that make their homes along the inter-tidal zone in dime- to quarter-size round shells. They move about there using muscular feet and earn a living grazing on algae and diatoms. Air and water temperatures dictate the periwinkles' levels of activity.

Mother Nature has also told the periwinkles along the rocky coast they can best survive winter's traditional cold and turbulence by bunching up in rocky crevices and on the sides of sheltered rocks at the low-tide mark. The cold usually lulls most of these animals into dormancy. Rising temperatures in the spring get them crawling to the mid- and upper-tidal zones, where they summer in tidal pools and on bare and seaweed-covered rocks.

But so far, the warm winter has not only deprived them of their regular winter break, but also kept them moving about and feeding in the midtidal zone they usually occupy in the spring and fall.

The Lobster

Early winter's exceptionally warm seawater temperatures have kept another cold-blooded creature, the lobster, coming up in the traps both inshore and midshore, flipping and flapping and grabbing at reaching hands at a time when the normally colder water would make them sluggish. These trapped lobsters have also felt warm to the bare hand. They have been so full of life lately that harvesters have even had to apply extra pressure and caution while crisscrossing their extended claws to band them or risk breaking one off.

Most lobsters summer in the shallows, winter in the depths - often in self-made holes in the mud - and spend much of the spring and fall crawling to and from these areas. Like the periwinkles, lobsters used to at least enjoy a period of dormancy during the winter and early spring. Despite this winter's warm water, the lobsters seemed to have still made those traditional movements. Some lobstermen believe they have not moved as far off as they usually do, however.

Many lobstermen believe most lobster activity, including feeding, crawling and trapping, will slow to a near standstill once the bottom water temperature drops below 38 degrees. A few lobsters always seem to trap in the cold water, and longer sets between hauls and dropping the traps practically on top of the lobsters continue to help increase the catches then. Storms also help to occasionally increase winter catches by briefly warming up the water. Sunlight can do the same in the shallow water, especially if it hits directly on the lobsters.

The bottom water temperature typically bottoms out in February and March. The water temperature was so cold last February that it chilled lobsters to the point that one could feel the cold come out of them while handling them bare-handed.

A Side Note

Regarding last week's column on the excavator and the biker, this side note should answer the last sentence in the article on why cyclist Ralph Gorvett also bikes for another challenge: "The biggest challenge is to just continue doing it," he said.