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A. New Observation Offers Insight into the Solar System
Narrator: This is Science Today. Astrophysicists at the Lawrence Livermore National Laboratory have gained new insight into the solar system after observing anomalies in the makeup of interplanetary dust particles.
Bradley: Interplanetary dust particles are very small grains of cosmic dust that are pervasive throughout the galaxy and are most abundant in the star forming regions and they're also abundant in the solar system.
Narrator: John Bradley, director of the lab's Institute for Geophysics and Planetary Physics, used electron and ion microscopes to find isotopic fingerprints within these particles of a pre-solar environment.
Bradley: So that means that the Earth was picking up pre-solar molecular material that's much more complicated than we had originally thought. And of course life is composed of relatively complicated molecules and this raises a very provocative suggestion that material that came from outside of the solar system may actually be relevant and a participant in the kinds of molecules that we got together ultimately to form life on Earth.
Narrator: For Science Today, I'm Larissa Branin.
B.
How Prions Jump the Species Barrier
Narrator: This is Science Today. Prions are a type of infectious agent and unlike viruses or bacteria, which have DNA or RNA as a genome, prions are made solely of proteins. For the first time, Jonathan Weissman of the University of California, San Francisco, demonstrated that a change in the folded shape of a prion protein can change its infectious properties, including the prion's ability to jump the “species barrier”.
Weissman: There's this phenomena called the species barrier, which is supposed to protect different animals from infecting each other. So, sheep don't infect people even though people have been living with and eating scrapie-infected sheep for 200 years.
Narrator: It was thought that cows could not infect people, but it turns out that mad cow disease – which is a prion strain – can jump the species barrier.
Weissman: We now believe that the reason mad cow jumped the species barrier to people had less to do with cows being more like people than sheep are like people and more to do with the fact that the shape or the strain of the mad cow was one that was able to be more compatible with the human protein.
Narrator: For Science Today, I'm Larissa Branin.
C.
Another Use for Technology Built for Satellite Re-entry Programs
Narrator: This is Science Today. To measure the melting point of iron at the Earth's core, physicists at the Lawrence Livermore National Laboratory used what's called a two-stage gas gun. Neil Holmes says these guns were originally built for Earth re-entry programs for satellites.
Holmes: They would actually use this to accelerate things that would look like a satellite and simulate re-entry by making a really long tank that had 500 thousand foot elevation air in it.
Narrator: The gun itself is about eighty feet long and housed in its own building. It launches an ice cube-sized projectile at a target, which consists of samples inside a chamber that can be looked at optically or on the computer.
Holmes: If you go through the Earth, you find you have a crust and then a mantle, which are silicates, not iron. It's the center of the Earth that's mostly iron. So what we can do is actually design the projectile to make a shock – to bring us right up to a point inside the core, then squeeze gently as if we were moving right to the center. And then we can, in the same experiment, move out again.
Narrator: For Science Today, I'm Larissa Branin.
D. The Two Major Subtypes of Leukemia
Narrator: This is Science Today. Leukemia is a heterogeneous disease – meaning, there are several different subtypes. The two major subtypes are acute myeloblastic leukemia and acute lymphoblastic leukemia, or ALL. Marilyn Kwan, a postdoctoral researcher in epidemiology at the University of California, Berkeley, says ALL is the most common childhood leukemia subtype.
Kwan: It accounts for probably seventy-five percent of all leukemia cases and it actually has the best prognosis nowadays. I think there's a survival rate of eighty percent in young kids. So it's very encouraging – we've come a long way since 1960 for treatment of childhood leukemia.
Narrator: Kwan led a recent review of studies that found that children who are breastfed have a lower risk of developing childhood leukemia.
Kwan: This study is different because it's a comprehensive, systematic literature review of all the studies that have been conducted on childhood leukemia and breastfeeding to date.
Narrator: For Science Today, I'm Larissa Branin.
E.
Brain Imaging May Improve Prediction of Alzheimer's Disease
Narrator: This is Science Today. Magnetic resonance imaging scans, or MRI, are a valuable tool in neuroscience. Because the brain shrinks in specific areas in people with Alzheimer's disease, William Jagust, a professor of public health and neuroscience at the University of California, Berkeley, says it's an important tool to possibly predict who will get Alzheimer's disease and it can be used to help treat those with this debilitating, neurological disease.
Jagust: If we had a drug that fundamentally affects Alzheimer's disease, the fundamental disease process, we might expect it would slow the range of brain shrinkage.
Narrator: Jagust is part of a national initiative that will test whether imaging, such as MRI and PET scans, can predict the onset of Alzheimer's. Jagust will lead the PET scan research.
Jagust: The PET scan, in this case, is measuring glucose metabolism and it's known that in Alzheimer's disease, there's reductions of glucose metabolism in the brain and also they tend to occur in specific parts of the brain. What we'll be doing with these PET scans is looking at how glucose metabolism declines over time, both in aging and Alzheimer's disease.
Narrator: For Science Today, I'm Larissa Branin.
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