The flowering plant purple loosestrife - Lythrum salicaria - has been heading north since it was first introduced to the eastern seaboard from Europe 150 years ago. This exotic invader chokes out native species and has dramatically altered wetland habitats in North America.

But as this invasive plant has spread north it has run into challenges posed by a shorter growing season, according to a study conducted by researchers from the University of Toronto's Department of Ecology and Evolutionary Ecology. Scientists have found that adapting to the Great White North carries a severe reproductive penalty that may limit its spread. The results are highlighted this week in Nature.  

Cigarette smoking may increase the risk of experiencing an aneurysm for people who carry common gene variants, according to research presented at the American Stroke Association's International Stroke Conference 2010.

In one study, researchers found that the chance of an intracranial aneurysm increased between 37 percent and 48 percent for people who carried one copy of an identified risky gene variation. However, when the gene variant was combined with smoking the equivalent of one pack a day for 20 years, the risk increased more than five-fold. People with two copies of the gene variant were at even higher risk.

University of Pennsylvania scientists have found that mixed lineage leukemia (MLL), has an unusual way to keep the molecular motors running. The cancer cells rely on the normal version of an associated protein to stay alive.

MLL happens when a piece of chromosome 11 breaks off at the normal MLL-associated gene. The broken gene attaches itself to another chromosome, resulting in a fusion protein that eventually causes uncontrolled growth of blood cells.

Researchers discovered that this runaway growth triggered by the fusion protein is blocked when the gene for the normal protein is deleted from leukemia cells. This indicates that the normal protein is required for MLL to proliferate.

Comets are thought to be some of the oldest, most primitive bodies in the solar system, but new research on the comet Wild 2 indicates that inner solar system material was transported to the comet-forming region at least 1.7 million years after the formation of the oldest solar system solids.

Published in Science, the research provides the first constraint on the age of cometary material from a known comet. The findings are published in the Feb. 25 edition of Science Express.

The NASA Stardust mission to comet Wild 2, which launched in 1999, was designed around the premise that comets preserve pristine remnants of materials that helped form the solar system. In 2006, Stardust returned with the first samples from a comet.

Video games may help recovering stroke patients improve their motor function, according to research presented at the American Stroke Association's International Stroke Conference 2010.The pilot study focused on movements with survivors' impaired arms to help both fine (small muscle) and gross (large muscle) motor function.

Twenty survivors (average age 61) of mild to moderate ischemic or hemorrhagic strokes were randomized to playing recreational games (cards or Jenga, a block stacking and balancing game) or Two Nintendo Wii games,  tennis or Wii Cooking Mama, which uses movements that simulate cutting a potato, peeling an onion, slicing meat and shredding cheese.

New research using magnetic resonance imaging (MRI) shows that abuse or emotional neglect during childhood combined with genetic factors can result in structural brain changes, rendering some individuals more vulnerable to  depression. The study results appear in Neuropsychopharmacology.