Mystery of Salamander Limb Regrowth Solved

Scientists on Wednesday shed light on how the salamander, one of nature's great oddities, is able to regrow an amputated leg. The insight may one day help researchers to replicate the achievement among people, they hope.

All living creatures have the ability to regrow some part or parts of their body, but the salamander tops the list for regenerative agility. Mammals like us can regenerate skin or fuse broken bones back together, but salamanders can replace a lost limb in a few weeks, regrow damaged lungs, mend a severed spinal cord and even replenish lost chunks of brain.

Until now, biologists pondering the little amphibian's trick have generally surmised it uses "pluripotent" cells, which charge into action at the point of amputation, called a blastema.

Pluripotent cells are spectacularly versatile cells that, like human embryonic stem cells, are somehow coaxed by chemical signals into differentiating into the specific tissues that make up skin, bone, nerves, muscle and so on. But in a paper released by the British journal Nature, scientists from the United States and Germany say the regrowth appears to happen through more humdrum, tissue-specific cells -- and this is good news.

The seven researchers first took axolotls (Ambystoma mexicanum), a species native to Mexico that is widely used as a model for vertebrate development, and genetically modified them. They added a gene from a fluorescent jellyfish that is commonly used as a telltale in lab experiments. Cells that carry the gene glow a livid green under ultraviolet, thus giving researchers an immediate indication of the cells' origin and progression.

Using embryonic axolotls, the researchers transplanted transgenic tissues into sites already known to develop into certain body parts, then observed how and where the cells organized themselves as the embryo grew. They then worked on genetically modified axolotls, cutting away limbs or organs from them.

They grafted that tissue onto normal axolotls, then cut away some of it and observed what happened to the signature "green" cells as the blastema area regenerated. What they found was that regeneration comes not through pluripotent cells, as thought, but through cells that keep a "memory" of their tissue origin.

In other words, only "old" muscle cells make new muscle cells, only "old" nerve cells make new nerve cells, only "old" skin cells make new skin cells, and so on. The only cells that appeared to be versatile were those that made skin and cartilage. In some circumstances, these two cell types could swap roles.

The findings are important because the salamander's magic appears to derive from tissue-specific cells, which makes it somewhat closer to mammalian processes than thought. "I think it's more mammal-like than was ever expected," one of the authors, Malcolm Maden, a University of Florida professor of biology, said in a press release. "It gives you more hope for being able to some day regenerate individual tissues in people."

Much more work lies ahead, though, before the vision of salamander-style regeneration can be achieved for humans who have lost a hand or leg can be taken seriously. In a commentary, also published by Nature, University of Utah neurobiologist Alejandro Sanchez Alvarado hailed the work as unveiling "a new dimension to our understanding of regeneration."

"Like all important work, it also leaves us with questions that will probably occupy researchers for the next few years," he said.

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Source: http://dsc.discovery.com/news/2009/07/02/salamander-regeneration.html

Tags: Salamander, limb regeneration, mammals, science, Nature magazine, Malcolm Maden, a University of Florida professor biology, Germany, USA, jellyfish, University of Utah neurobiologist Alejandro Sanchez Alvarado, global development news,

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US Draws Line With China On Climate Technology

WASHINGTON (AFP) – Access to green technology is becoming a growing stumbling block in global efforts to fight climate change, with US lawmakers bristling at what they see as China's attempt to "steal" US know-how.

China and India have led calls for developed nations to share technology to help them battle global warming as the clock ticks to a December meeting in Copenhagen meant to seal a successor to the Kyoto Protocol. The US House of Representatives this month unanimously voted to make it US policy to prevent the Copenhagen treaty from "weakening" US intellectual property rights on a wind, solar and other eco-friendly technologies.

Congressman Rick Larsen, a member of President Barack Obama's Democratic Party who authored the measure, said the United States was caught between concern both over the climate and its soaring trade deficit with China. "The US can be part of China's solution for the problems that they admittedly have with energy efficiency and emissions. And I think legitimately we want to be part of that solution -- we're the two largest emitters of C02 in the world," Larsen said.

"But we need to couple being part of that solution with making it part of the solution on the trade deficit as well," he said ahead of the measure's approval. Representative Mark Kirk, a Republican who joined Larsen on a recent trip to China, said that climate change was the most contentious issue during talks with Chinese leaders.

Kirk said the Chinese essentially were seeking "the stealing of all intellectual property" related to energy efficiency and climate change. Kirk warned that China's position could change the political dynamics in Washington, where promoters of a bill to force emission cuts say the United States stands to create millions of jobs in a new green economy. "Right now a number of green industries like the climate change bill coming out. But if an international treaty sanctions the theft of their intellectual property, then there will be hardly any green jobs built in the United States," Kirk said.

The United States is the only major industrialized nation to reject the Kyoto Protocol, with former president George W. Bush saying it was unfair by making no demands of fast-growing developing nations such as China and India. Despite a recession, President Barack Obama has vowed to work to halt the planet's warming, which UN scientists warn will threaten severe weather and the extinction of plant and animal species later this century if unchecked.

More than 180 countries promised at a December 2007 meeting in Bali, Indonesia to take part in the next global treaty with a "common but differentiated responsibility" for developed and developing economies. But 12 days of talks this month in Bonn came up with no visible progress, with top Chinese negotiator Li Gao accusing rich nations of reneging on sharing technology and watering down commitments to cut emissions.

"There is an attempt to obliterate the principle of 'common but differentiated responsibility' and to split up the developing countries," Li told China's state Xinhua news agency.

Shyam Saran, India's envoy on climate change, also criticized rich nations, which he said bore the historic responsibility for climate change. India has proposed setting up global "innovation centers" to work on green technology.

A report last month by experts for the UN climate body called for a "balanced" approach, stressing the importance of intellectual property rights but saying all nations needed to accept the terms.

Technology transfer "is certainly a big and important question that might be a roadblock" in global negotiations, said Daniel Kessler of Greenpeace.

The environmental group has called for public and private funds on climate change to be pooled into an independent global body, funded to the tune of at least 140 billion dollars a year. But such funding may prove hard to come by. The European Union, champion of the Kyoto Protocol, has come under fire from environmentalists for declining to put a figure on climate aid, saying it is waiting to see other nations' proposals.

Source: http://news.yahoo.com/s/afp/20090623/bs_afp/uschinaclimatewarmingtechnology_20090623022226

Tags: China, USA, Obama, Kyoto Protocol, EU, Greenpeace, Xinhua, Li Gao, Daniel Kessler, Shyam Saran, Global Development News, US House of Representatives, Copenhagen, Bali, Mark Kirk, Rick Larsen, Intellectual Property, Global Best Practice,

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