Kök hücre elde etmede yeni teknik

Amerikan Cell Stem Cell dergisinde yayınlanan araştırmaya göre bilim insanları, ceninden aldıkları bir hücreye, cenin kök hücre özelliklerini koruyacak biçimde “laminin” adı verilen bir protein yerleştirdiler.

Bu teknikle alınan hücreler, rahatlıkla organizmanın herhangi bir dokusu durumuna gelme özelliğine kavuşurken, tedavisi olanaksız birçok hastalığın iyileştirilmesi ve kanser veya bir kaza sonucu tahrip olan organların onarılması için de büyük umut yarattı.

Bu yöntemle hücrenin alındığı embriyo da herhangi bir olumsuzluktan etkilenmemiş oldu ve normal gelişimini sürdürebildi.

Bu yeni tekniğin, özellikle ABD’de tıbbi araştırmalar için insan embriyosu kullanımı konusundaki ahlaki tartışmalara son vermesi bekleniyor. Şu anki teknikle kök hücre alınması sırasında cenin yaşamını ve gelişimini sürdüremiyor.

2 different neural pathways regulate loss and regain of consciousness during general anesthesia

University of Pennsylvania School of Medicine researchers have answered long-running questions about the way that anesthetics act on the body, by showing that the cellular pathway for emerging from anesthesia is different from the one that drugs take to put patients to sleep during operations. The findings will be published this week in Proceedings of the National Academy of Sciences.

The research focuses on orexins, the small, specialized fraction of the brain’s 100 billion neurons that play a key role in regulating the body’s wakeful state. Studying mice whose orexin systems had been genetically destroyed – a state similar to humans suffering from narcolepsy, a neurological condition that causes unusual daytime sleepiness – Max B. Kelz, MD, PhD, an assistant professor in Penn’s Department of Anesthesiology and Critical Care and the Mahoney Institute of Neurological Sciences, found that these mice took much longer to emerge from general anesthesia than those with normal orexin signaling systems. However, the mice with faulty orexin systems did not appear to fall asleep faster during anesthesia, which suggests that different processes are at play when transitioning to and from the anesthetized stated.

“The modern expectation is that anesthesiologists can simply flip a consciousness switch as easily as we might turn the room lights on or off,” says lead author Max B. Kelz, MD, PhD, an assistant professor in Penn’s Department of Anesthesiology and Critical Care and the Mahoney Institute of Neurological Sciences. “However, what patients do not realize is that despite 160 years of widespread clinical use, the mechanisms through which the state of anesthesia arises and dissipates remain unknown.”

Kelz became interested in these questions after treating a narcoleptic patient who took more than six hours to regain consciousness after anesthesia, compared to the typical six minutes or so. By probing what’s different about the narcoleptic brain, the Penn study has established for the first time that the process of entry into and exit from the anesthetized state are not mirror images of one another.

Kelz and his colleagues, including Sigrid Veasey, MD, associate professor in the Department of Medicine’s Sleep Medicine division, hope that further research on the brain’s neural signaling systems will lead to novel ways to administer anesthesia and “jump start” a speedy, safe return to consciousness – particularly among patients who struggle to wake up or in patient groups that may be more prone to anesthesia side effects such as the elderly and patients with neurodegenerative disorders. The findings might also be used to create designer anesthetic agents that “hijack” the body’s natural sleep cycles to mimic a state closer to natural sleep than a chemically-induced coma, Kelz says.

Older Arctic sea ice replaced by young, thin ice

A new study by University of Colorado at Boulder researchers indicates older, multi-year sea ice in the Arctic is giving way to younger, thinner ice, making it more susceptible to record summer sea-ice lows like the one that occurred in 2007.

The team used satellite data going back to 1982 to reconstruct past Arctic sea ice conditions, concluding there has been a nearly complete loss of the oldest, thickest ice and that 58 percent of the remaining perennial ice is thin and only 2-to-3 years old, said the lead study author, Research Professor James Maslanik of CU-Boulder's Colorado Center for Astrodynamics Research. In the mid-1980s, only 35 percent of the sea ice was that young and that thin according to the study, the first to quantify the magnitude of the Arctic sea ice retreat using data on the age of the ice and its thickness, he said.

"This thinner, younger ice makes the Arctic much more susceptible to rapid melt," Maslanik said. "Our concern is that if the Arctic continues to get kicked hard enough toward one physical state, it becomes increasingly difficult to reestablish the sea ice conditions of 20 or 30 years ago."

A September 2007 study by CU-Boulder's National Snow and Ice Data Center indicated last year's average sea ice extent minimum was the lowest on record, shattering the previous September 2005 record by 23 percent. The minimum extent was lower than the previous record by about 1 million square miles -- an area about the size of Alaska and Texas combined.

The new study by Maslanik and his colleagues appears in the Jan. 10 issue of Geophysical Research Letters. Co-authors include CCAR's Charles Fowler, Sheldon Drobot and William Emery, as well as Julienne Stroeve from CU-Boulder's Cooperative Institute for Research in Environmental Sciences and Jay Zwally and Donghui Yi from NASA's Goddard Space Flight Center in Greenbelt, Md.

The portion of ice more than five years old within the multi-year Arctic icepack decreased from 31 percent in 1988 to 10 percent in 2007, according to the study. Ice 7 years or older, which made up 21 percent of the multi-year Arctic ice cover in 1988, made up only 5 percent in 2007, the research team reported.

The researchers used passive microwave, visible infrared radar and laser altimeter satellite data from the National Oceanic and Atmospheric Administration, NASA and the U.S. Department of Defense, as well as ocean buoys to measure and track sections of sea ice.

The team developed "signatures" of individual ice sections roughly 15 miles square using their thickness, roughness, snow depth and ridge characteristics, tracking them over the seasons and years as they moved around the Arctic via winds and currents, Emery said. "We followed the ice in sequential images and track it back to where it had been previously, which allowed us to infer the relative ages of the ice sections."

The replacement of older, thicker Arctic ice by younger, thinner ice, combined with the effects of warming, unusual atmospheric circulation patterns and increased melting from solar radiation absorbed by open waters in 2007 all have contributed to the phenomenon, said Drobot. "These conditions are setting the Arctic up for additional, significant melting because of the positive feedback loop that plays back on itself."

"Taken together, these changes suggest that the Arctic Ocean is approaching a point where a return to pre-1990s ice conditions becomes increasingly difficult and where large, abrupt changes in summer ice cover as in 2007 may become the norm," the research team wrote in Geophysical Research Letters.

New understanding for superconductivity at high temperatures

An international research team has discovered that a magnetic field can interact with the electrons in a superconductor in ways never before observed. Andrea D. Bianchi, the lead researcher from the Université de Montréal, explains in the January 11 edition of Science magazine what he discovered in an exceptional compound of metals – a combination of cobalt, indium and a rare earth – that loses its resistance when cooled to just a couple of degrees above absolute zero.

“This discovery sharpens our understanding of what, literally, holds the world together and brings physicists one step closer to getting a grip on superconductivity at high temperatures. Until now, physicists were going around in circles, so this discovery will help to drive new understanding,” said Prof. Bianchi, who was recruited to UdeM as a Canada Research Chair in Novel Materials for Spintronics last fall and performed his experiments at the Paul Scherrer Institute in Switzerland, in collaboration with scientists from ETH Zurich, the University of Notre Dame, the University of Birmingham, U.K., the Los Alamos National Laboratory and the Brookhaven National Laboratory.

Magnetic tornado that grows stronger

Using the Swiss Spallation Neutron Source (SINQ), Prof. Bianchi and his team cooled a single-crystal sample of CeCoIn5 down to 50mK above absolute zero and applied a magnetic field nearly high enough to entirely suppress superconductivity. They found that the core of the vortices feature electronic spins that are partly aligned with the magnetic field. This is the first experimental evidence that a theory that describes the properties of superconducting vortices and, for which Abrikosov and Ginzburg received the Nobel Prize in 2003, which does not generally apply in magnetically-induced superconductors.

“When subjected to intense magnetic fields, these materials produce a completely new type of magnetic tornado that grows stronger with increasing fields rather than weakening,” said Prof. Bianchi. “The beauty of this compound is how we can experiment without breaking it.”

Superconductors hold great promise for technological applications that will change how modern civilization can store and transmit energy - arguably some of the most pressing challenges today. Other notable applications include superconducting digital filters for high-speed communications, more efficient and reliable generators and motors, and superconducting device applications in medical magnetic resonance imaging machines. The first superconductor was discovered nearly a hundred years ago, and in most materials this curious state with no resistance was shown to arise from the interaction of the electrons with the crystal; however, in this new material, superconductivity is thought to arise from magnetic interactions between electrons.

Greenhouse ocean may downsize fish

During this century, the sea’s rich food web—stretching from Alaska to Russia—could fray as algae adapt to greenhouse conditions.

“All the fish that ends up in McDonald’s, fish sandwiches—that’s all Bering Sea fish,” said USC marine ecologist Dave Hutchins, whose former student at the University of Delaware, Clinton Hare, led research published Dec. 20 in Marine Ecology Progress Series, a leading journal in the field.

At present, the Bering Sea provides roughly half the fish caught in U.S. waters each year and nearly a third caught worldwide.

“The experiments we did up there definitely suggest that the changing ecosystem may support less of what we’re harvesting—things like pollock and hake” Hutchins said.

While the study must be interpreted cautiously, its implications are harrowing, Hutchins said, especially since the Bering Sea is already warming.

“It's kind of a canary in a coal mine because it appears to be showing climate change effects before the rest of the ocean,” he noted.

“It’s warmer, marine mammals and birds are having massive die-offs, there are invasive species—in general, it’s changing to a more temperate ecosystem that’s not going to be as productive.”

Carbon dioxide’s direct effects on the ocean are often overlooked by the public.

“It’s all a good start that people get worried about melting ice and rising sea levels,” he said. “But we're now driving a comprehensive change in the way Earth's ecosystem works—and some of these changes don't bode well for its future.”

The study examined how climate change affects algal communities of phytoplankton, the heart of marine food webs.

Phytoplankton use sunlight to convert carbon dioxide into carbon-based food. As small fish eat the plankton and bigger fish eat the smaller fish, an entire ecosystem develops.

The Bering Sea is highly productive thanks mainly to diatoms, a large type of phytoplankton.

“Because they're large, diatoms are eaten by large zooplankton, which are then eaten by large fish,” Hutchins explained.

The scientists found that greenhouse conditions favored smaller types of phytoplankton over diatoms. Such a shift would ripple up the food chain: as diatoms become scarce, animals that eat diatoms would become scarce, and so forth.

“The food chain seems to be changing in a way that is not supporting these top predators, of which, of course, we’re the biggest,” Hutchins said.

A shift away from diatoms towards smaller phytoplankton could also undermine a key climate regulator called the “biological pump.”

When diatoms die, their heavier carbon-based remains sink to the seafloor. This creates a “pump” whereby diatoms transport carbon from the atmosphere into deep-sea storage, where it remains for at least 1,000 years.

“While smaller species often fix more carbon, they end up re-releasing CO₂ in the surface ocean rather than storing it for long periods as the diatom-based community can do,” Hutchins explained.

This scenario could make the ocean less able to soak up atmospheric carbon dioxide.

“Right now, the ocean biology is sort of on our side,” Hutchins said. “About 50 percent of fossil fuel emissions since the industrial revolution is in the ocean, so if we didn’t have the ocean, atmospheric CO₂ would be roughly twice what it is now.”

Hutchins and colleagues are doing related experiments in the north Atlantic Ocean and the Ross Sea, near Antarctica. The basic dynamics of a greenhouse ocean are not well understood, he noted.

“We’re trying to make a contribution by doing predictive experimental research that will help us understand where we’re headed,” he said. “It’s unprecedented the rate at which things are shifting around.”

The researchers collected the algae samples from the Bering Sea’s central basin and the southeastern continental shelf. They incubated the phytoplankton onboard, simulating sea surface temperatures and carbon dioxide concentrations predicted for 2100.

Each of these variables was tested together and independently. Ratios of diatom to nanophytoplankton in manipulated samples were then compared with those in plankton grown under present conditions.

The scientists found that photosynthesis in greenhouse samples sped up two to three times current rates. However, community composition shifted from diatoms to the smaller nanophytoplankton.

Temperature was the key driver of the shift with secondary impacts from the increased carbon dioxide concentrations, according to the study.