January 18, 2006, 9:54 PM CT

Narrowing gap between Human and Chimpanzee

A team of scientists has proposed new limits on the time when the most recent common ancestor of humans and their closest ape relatives -- the chimpanzees -- lived. Researchers at Arizona State and Penn State Universities have placed the time of this split between 5 and 7 million years ago -- a sharper focus than that given by the prior collection of molecular and fossil studies, which have placed the divergence anywhere from 3 to 13 million years ago.

The researchers analyzed the largest data set yet of genes that code for proteins and also used an improved computational approach that they developed, which takes into account more of the variability -- or statistical error--in the data than any other prior study. Gene studies are needed to address this problem because the interpretation of the earliest fossils of humans at the ape/human boundary are controversial and because almost no fossils of chimpanzees have been discovered. "No study before has taken into account all of the error involved in estimating time with the molecular-clock method," said Sudhir Kumar, lead author on the report, which was published early online in the journal, Proceedings of the National Academy of Sciences. The team describes its new statistical technique as a "multifactor bootstrap-resampling approach".........

Posted by: Jaison      Permalink


January 18, 2006, 9:50 PM CT

Sequence DNA of Woolly Mammoth

A team of genome scientists at Penn State University and experts in ancient DNA at McMaster University in Canada has obtained the first genomic sequences from a woolly mammoth, a mammal that roamed grassy plains of the Northern Hemisphere until it became extinct about 10,000 years ago. The team's research on bones preserved in Siberian permafrost will be published on 22 December 2005 by the journal Science on the Science Express website. The project also involved paleontologists from the American Museum of Natural History (USA) and scientists from Russia, the United Kingdom, France, and Gera number of.

"We demonstrated that 50 percent of the total DNA extracted from the bone was mammoth," says Stephan C. Schuster, associate professor at Penn State's Center for Comparative Genomics and Bioinformatics. "This allowed us to compare hereditary information from the cell's nucelus of today's African elephants with the one from this ancient species".

The project became possible through the discovery of exceptionally well preserved remains of a mammoth skeleton in the permafrost soil of northern Siberia, in combination with a novel high-throughput sequencing technique that could cope with the heavily fragmented DNA retrieved from the organism's mandible, its jaw bone. "The bone material used in this study is approximately 28,000 years old, as was shown by beta carbon dating analysis," said Hendrik N. Poinar, associate professor of anthropology at McMaster University. "This was a surprising finding, as it demonstrated that the analyzed material was frozen for more than 10,000 years before the maximum of the last ice age." The research team used a comparative computational approach to demonstrate that an unprecedented large percentage of the bone DNA was indeed mammoth DNA, while the remaining genetic material was shown to belong to microorganisms and plants living the tundra soil.........

Posted by: Jaison      Permalink


January 15, 2006, 7:24 PM CT

In Search Of Larger Trout

To find a way to make something better, it is best to find out how it works first. For geneticists, that means beginning with an organism's genome.

The genome of every species contains the blueprint that guides life's biological processes. Gaining an understanding of genomes, therefore, can give clues to understanding the mechanisms that drive these processes and provide knowledge to manipulate them for a desired outcome. In aquaculture, the tools and technologies of genomics are being used in selective-breeding programs aimed at production efficiency. Desired outcomes include strains that are disease resistant, stress tolerant, fast and efficient growers, and reproductively manageable.

Molecular biologists Scott Gahr and Caird Rexroad III, of the National Center for Cool and Cold Water Aquaculture in Leetown, West Virginia, are comparing genes known to be responsible for growth and development in mammals with similar genes in rainbow trout.

Initial efforts focused on the Inhibitor of DNA Binding/Differentiation (ID) genes. The ID genes interact with factors present in muscle cells to delay differentiation (the process by which cell function is defined) and increase the number of cells. "Affecting the balance of these processes presents an opportunity to dictate an increase in the number of muscle cells, which would result in more edible flesh on the fish," says Gahr.........

Posted by: Jaison      Permalink


January 13, 2006, 5:58 PM CT

The Earliest Animals Had Human-like Genes

Species evolve at very different rates, and the evolutionary line that produced humans seems to be among the slowest. The result, according to a new study by researchers at the European Molecular Biology Laboratory [EMBL], is that our species has retained characteristics of a very ancient ancestor that have been lost in more quickly-evolving animals. This overturns a commonly-held view of the nature of genes in the first animals. The work appears in the current issue of the journal Science.

Genes hold the recipes for proteins. The genes of animals commonly contain extra bits of DNA sequence, called introns - information which has to be removed as cells create new molecules. The number of introns in genes, however, varies greatly among animals. While humans have a number of introns in their genes, common animal models such as flies have fewer. From an evolutionary perspective, it was long assumed that the simpler fly genes would be more ancient. The current study reveals the opposite: early animals already had a lot of introns, and quickly-evolving species like insects have lost most of them.

To discover what early animals were like, researchers commonly compare their descendents. This is difficult when comparing distantly-related animals such as humans and flies. In these cases, it helps to look at living organisms that have preserved a number of features of their ancestors. Detlev Arendt's group is doing this with a small marine worm called Platynereis dumerlii. "Similar animals are already found in the earliest fossils from the Cambrium, about 600 million years ago," Arendt explains, "arguing that Platynereis could be something like a 'living fossil'." This makes it an ideal model for evolutionary comparisons to find out what the common ancestors of humans, flies and worms were like".........

Posted by: Jaison      Permalink


January 10, 2006, 11:29 PM CT

Jawless Vertebrates Used Novel Immune Responses

Scientists recently discovered that the sea lamprey, a modern representative of ancient jawless vertebrates, fights invading pathogens by generating up to 100 trillion unique receptors. These receptors, referred to as VLRs, are proteins and function like antibodies and T-cell receptors, sentinels of the immune system in all jawed vertebrates, including humans.

The results, reported in the Dec. 23 Science by Zeev Pancer at the University of Maryland Biotechnology Institute's Center of Marine Biotechnology in Baltimore, and colleagues, proved ancient vertebrates--both jawed and jawless--used more than one strategy to develop an immune system that would recognize and defend against their myriad bodily invaders.

They studied a type of immune defense mechanism called "adaptive," because as the name implies, it adapts to the incredible number of pathogens in the environment by producing 100 trillion potentially different receptor proteins in order to recognize at least one of the invader's molecules. Recognition of the pathogen is a first step in mounting a defensive response against it.

Some 450 million years ago, both jawed and jawless vertebrates began relying on cells called lymphocytes to support the burgeoning adaptive immune system. But within the lymphocytes from the two types of animals, very different mechanisms evolved to reach very similar ends. Comparing the two immune systems is the basis of Pancer's research.........

Posted by: Jaison      Permalink


January 10, 2006, 11:16 PM CT

Too Many Owners Remain Unaware Of Toxic Dog Food

Even though Diamond, Country Value and Professional brand dog foods have been recalled for containing highly toxic aflatoxins, they have caused at least 100 dog deaths in recent weeks, say Cornell University veterinarians, who are growing increasingly alarmed. Some kennels and consumers around the nation and possibly in more than two dozen other countries remain unaware of the tainted food, and as a result, they continue to give dogs food containing a lethal toxin.

To better screen affected dogs so they can be treated as soon as possible, Cornell veterinarians report that they now have a new test, adapted from one used in humans, to accurately assess aflatoxin poisoning in dogs (see companion story). Currently, about two-thirds of dogs that show symptoms after eating the tainted food die.

"Entire kennels have been wiped out, and because of the holiday these past few weeks, the dispersal of recall information was disrupted," says Sharon Center, a professor of veterinary medicine who specializes in liver function and disease at the College of Veterinary Medicine at Cornell, which is emerging as a central clearinghouse for information about the dog food poisoning.

The Cornell Vet College is continually updating its Web site to keep the public and veterinarians informed as new information on the poisonings emerge. Cornell's Animal Health Diagnostic Center (AHDC) is analyzing blood and liver samples from sick dogs around the country, testing suspected dog food, conducting autopsies and collecting as a number of livers as possible from dead dogs to confirm cause of death, tracking dogs that have died and following up on the health of dogs that survive the food poisoning. The AHDC has information for veterinarians on its Web site http://diaglab.vet.cornell.edu/news.asp.........

Posted by: Jaison      Permalink


January 7, 2006, 4:39 PM CT

Snails in Southeastern Salt Marshes

Periwinkles, the spiral-shelled snails usually found along rocky U.S. shorelines, play a primary role in the unprecedented disappearance of salt marsh in the southeastern states, according to new research published in Science.

Based on extensive field studies, the work challenges six decades of salt marsh science. Ecologists have long thought that stressed soil - too much salt, not enough oxygen - was the main killer of this critical marine habitat.

But Brian Silliman, a Brown University research fellow and a University of Florida assistant professor, said drought-stressed soils pave the way for predatory periwinkles that spread fungal disease as they graze on cordgrass.

"Snails can transform healthy marsh to mudflats in a matter of months," said Silliman, lead author of the Science paper. "This finding represents a huge shift in the way we see salt marsh ecology. For years, researchers thought marsh die-off was simply a 'bottom-up' problem related solely to soil conditions. We found that the trouble also comes from the top down. Drought makes the marsh vulnerable, then the snails move in".

Thousands of acres of salt marsh have disappeared from South Carolina to Texas since 2000, according to several scientific studies. In Louisiana alone, more than 100,000 acres of marsh were severely damaged between June 2000 and September 2001. This drastic decline poses a serious threat to the ecology and economy of the southeastern seaboard and the Gulf Coast. Salt marshes serve as nursery grounds that support commercial fisheries, protect coastline from storm-induced floods, and filter fresh water before it flows out to sea.........

Posted by: Ashley      Permalink


January 4, 2006, 11:11 PM CT

As Amazon's Tree Line Recedes

Scientists have long known that chronic deforestation can spawn a jungle of environmental woes. But now, a study confirms that vanishing forests inflict more than environmental damage: they may cause human diseases, too.

Working in the Peruvian Amazon, a team of researchers from UW-Madison and Johns Hopkins University found that malaria-inducing mosquitoes are likely to bite humans more than 200 times more often in cleared areas versus forested ones. Their results appear this week in the American Journal of Tropical Medicine and Hygiene (Jan. 6, 2005).

"By dramatically changing the landscape, we are tipping the balance in a way that is increasing the risk of malaria transmission," says senior author Jonathan Patz, a former Johns Hopkins scientist and now a professor both in UW-Madison's Nelson Institute for Environmental Studies and the department of population health. "This is one of the most detailed quantitative field studies in the Amazon that directly addresses the potential link between deforestation and malaria".

Over one year, the research team collected mosquitoes at 56 sites in varying stages of deforestation. The sites were located around 14 villages situated along a new road that cuts through the Amazonian rainforest, and connects the towns of Iquitos and Nauta in northeastern Peru. Working in the evenings when mosquitoes are at their thirstiest, the scientists counted how often the insects landed on humans at every site, each of which had been assigned to one of four vegetation categories, including rainforest, shrubby regrowth, cultivated areas and populated villages.........

Posted by: Ashley      Permalink


January 2, 2006, 11:14 PM CT

Human And Insects Share Same Stem Cells

The six-legged fruitfly appears to have little in common with humans, but a new finding shows that they are really just tiny, distant cousins. Researchers at the Carnegie Institution's Department of Embryology have found that adult fruitflies have the same stem cells controlling cell regulation in their gut as humans do. The research is important for understanding digestive disorders, including some cancers, and for developing cures. "The fact that fruitflies have the same genetic programming in their intestines as humans, strongly suggests that we were both cut from the same evolutionary cloth more than 500 million years ago," stated lead author of the December 7, on-line Nature paper, Benjamin Ohlstein.

It may come as a surprise, but insects have the same basic structure to their gastrointestinal tract as vertebrates. They have a mouth, an esophagus, the equivalent to a stomach, and large and small intestines. The Carnegie scientists looked at their small intestines, where food is broken down into its constituent nutrients for the body to absorb. They focused on two cell types-- cells that line the small and large intestines in a single layer to help break up and transport food molecules, called enterocytes; and cells that produce peptide hormones, some of whose functions include regulation of gastric motility as well as growth and differentiation of the gut (enteroendocrine cells).........

Posted by: Jaison      Permalink


January 1, 2006, 11:56 PM CT

A Longer Lifespan By Evolving A Longer Reproductive Period

A UC Riverside-led research team has found that as some populations of an organism evolve a longer lifespan, they do so by increasing only that segment of the lifespan that contributes to "fitness" – the relative ability of an individual to contribute offspring to the next generation.

Focusing on guppies, small fresh-water fish biologists have studied for long, the researchers found that guppies living in environments with a large number of predators have adapted to reproduce earlier in life than guppies from low-predation localities. Moreover, when reproduction ceases, guppies from high-predation localities are far older, on average, than guppies from low-predation localities, indicating that high-predation guppies enjoy a long "reproductive period" – the time between first and last reproduction.

"In earlier work, we showed that guppies from high predation environments have longer lifespans," said David Reznick, professor of biology. "Our new study explores how and why this happens. We found that fish from populations enjoying longer lifespans live longer because there is a selective increase in their reproductive lifespan. Indeed, theory predicts this result because only reproductive lifespan determines fitness."

Study results appear Dec. 27 in the online edition of the Public Library of Science – Biology.........

Posted by: Ashley      Permalink