Syndicate content

Archive - May 15, 2013

Date

Brain Rewires Itself after Damage or Injury

When the brain's primary "learning center" is damaged, complex new neural circuits arise to compensate for the lost function, say life scientists from UCLA and Australia who have pinpointed the regions of the brain involved in creating those alternate pathways — often far from the damaged site. The research, conducted by UCLA's Dr. Michael Fanselow and Moriel Zelikowsky in collaboration with Dr. Bryce Vissel, a group leader of the neuroscience research program at Sydney's Garvan Institute of Medical Research, was published online on May 15, 2013 in PNAS. The researchers found that parts of the prefrontal cortex take over when the hippocampus, the brain's key center of learning and memory formation, is disabled. Their breakthrough discovery, the first demonstration of such neural-circuit plasticity, could potentially help scientists develop new treatments for Alzheimer's disease, stroke, and other conditions involving damage to the brain. For the study, Dr. Fanselow and Ms. Zelikowsky conducted laboratory experiments with rats showing that the rodents were able to learn new tasks even after damage to the hippocampus. While the rats needed more training than they would have normally, they nonetheless learned from their experiences — a surprising finding. "I expect that the brain probably has to be trained through experience," said Dr. Fanselow, a professor of psychology and member of the UCLA Brain Research Institute, who was the study's senior author. "In this case, we gave animals a problem to solve." After discovering the rats could, in fact, learn to solve problems, Zelikowsky, a graduate student in Fanselow's laboratory, traveled to Australia, where she worked with Dr. Vissel to analyze the anatomy of the changes that had taken place in the rats' brains.

Natural Selection Shapes Collective Behavior in Harvester Ants

In ancient Greece, the city-states that waited until their own harvest was in before attacking and destroying a rival community's crops often experienced better long-term success. It turns out that ant colonies that show similar selectivity when gathering food yield a similar result. The latest findings from Stanford biology ProfessorDeborah M. Gordon's long-term study of harvester ants reveal that the colonies that restrain their foraging except in prime conditions also experience improved rates of reproductive success. Importantly, the study provides the first evidence of natural selection shaping collective behavior, said Dr. Gordon, who is also a senior fellow at the Stanford Woods Institute for the Environment. A long-held belief in biology has posited that the amount of food an animal acquires can serve as a proxy for its reproductive success. The hummingbirds that drink the most nectar, for example, stand the best chance of surviving to reproduce. But the math isn't always so straightforward. The harvester ants that Gordon studies in the desert in southeast Arizona, for instance, have to spend water to obtain water: an ant loses water while foraging, and obtains water from the fats in the seeds it eats. The ants use simple positive feedback interactions to regulate foraging activity. Foragers wait near the opening of the nest, and bump antennae with ants returning with food. The faster outgoing foragers meet ants returning with seeds, the more ants go out to forage. (Last year, Dr. Gordon, Katie Dektar, an undergraduate, and Dr. Balaji Prabhakar, a professor of computer science and of electrical engineering at Stanford, showed that the ants' "Anternet" algorithm follows the same rules as the protocols that regulate data traffic congestion in the Internet).

Human Skin Cells Converted to Embryonic Stem Cells

Scientists at Oregon Health & Science University (OHSU) and the Oregon National Primate Research Center (ONPRC) have successfully reprogrammed human skin cells to become embryonic stem cells capable of transforming into any other cell type in the body. It is believed that stem cell therapies hold the promise of replacing cells damaged through injury or illness. Diseases or conditions that might be treated through stem cell therapy include Parkinson's disease, multiple sclerosis, cardiac disease, and spinal cord injuries. The research breakthrough, led by Shoukhrat Mitalipov, Ph.D., a senior scientist at ONPRC, follows previous success in transforming monkey skin cells into embryonic stem cells in 2007. This latest research was published online on May 15, 2013 in Cell. The technique used by Drs. Mitalipov, Paula Amato, M.D., and their colleagues in OHSU's Division of Reproductive Endocrinology and Infertility, Department of Obstetrics & Gynecology, is a variation of a commonly used method called somatic cell nuclear transfer, or SCNT. It involves transplanting the nucleus of one cell, containing an individual's DNA, into an egg cell that has had its genetic material removed. The unfertilized egg cell then develops and eventually produces stem cells. "A thorough examination of the stem cells derived through this technique demonstrated their ability to convert, just like normal embryonic stem cells, into several different cell types, including nerve cells, liver cells, and heart cells. Furthermore, because these reprogrammed cells can be generated with nuclear genetic material from a patient, there is no concern of transplant rejection," explained Dr. Mitalipov.

Malaria Parasites “Talk” to Each Other Via Exosome-Like Vesicles

Melbourne scientists have made the surprise discovery that malaria parasites can 'talk' to each other – a social behaviour to ensure the parasite's survival and improve its chances of being transmitted to other humans. The finding could provide a niche for developing antimalarial drugs and vaccines that prevent or treat the disease by cutting these communication networks. Professor Alan Cowman, Dr. Neta Regev-Rudzki, Dr. Danny Wilson, and colleagues from the Walter and Eliza Hall Institute, in collaboration with Professor Andrew Hill from the University of Melbourne's Bio21 Institute and Department of Biochemistry and Molecular Biology, showed that malaria parasites are able to send out messages in exosome-like vesicles to communicate with other malaria parasites in the body. The study was published on March 15, 2013 in Cell. Professor Cowman said the researchers were shocked to discover that malaria parasites work in unison to enhance 'activation' into sexually mature forms that can be picked up by mosquitoes, which are the carriers of this deadly disease. "When Neta showed me the data, I was absolutely amazed, I couldn't believe it," Professor Cowman said. "We repeated the experiments many times in many different ways before I really started to believe that these parasites were signalling to each other and communicating. But we came to appreciate why the malaria parasite really needs this mechanism – it needs to know how many other parasites are in the human to sense when is the right time to activate into sexual forms that give it the best chance of being transmitted back to the mosquito." Malaria kills about 700,000 people a year, mostly children aged under five and pregnant women. Every year, hundreds of millions of people are infected with the malaria parasite, Plasmodium, which is transmitted through mosquito bites.