Promoting Intellectual Discovery
Patents are generally viewed as an effective way to promote
intellectual discovery because they provide strong incentives to invest
in effort, the cost of which can be recuperated from the earnings
generated by applications of the discovery. But the patent system has
also been criticized on various grounds including unfairness (only the
winner is compensated for effort) and the potential for the patent's
ownership to become fragmented, which could inhibit
further discovery. In a Report in the 6 Mar 2009 Science, Meloso
et
al.
reported on an alternative approach to spurring innovation. In a series
of experiments involving the "knapsack problem" -- in which
participants have to determine the most valuable subset of objects that
can fit in a knapsack of fixed volume -- the team compared the
performance of a patent-like prize system and a market-based reward
system. In the patent system, a cash prize went to the first
participant with the winning solution. In the market system, however,
participants were allowed to trade shares in the various objects such
that each item in the winning solution awarded dividends. The
researchers found that the correct solution to the problem was found
under both the prize and market systems, but that more participants
discovered the solution in the market system (listen to the podcast
interview with senior author Peter Bossaerts). They
contend that rewarding only a single winner in the prize
system may discourage others from spending effort, whereas in the
market-based system, participants are more motivated because everyone
in principle has the potential to be compensated. An accompanying
Perspective
by D. K. Levine noted that
"the study lays the groundwork for future experimental investigations
of alternative compensation systems for inducing innovation."
Brain Stimulation and
Parkinson's
Deep brain stimulation (DBS) sends pulses of electric current through
electrodes implanted deep inside the brain and has proven to be an
effective treatment for motor dysfunction in people suffering from
Parkinson's disease. Nevertheless, it is a highly invasive procedure,
and despite its successes, remarkably little is known about how DBS
works. Two studies reported in Science
this month investigated the
mechanisms of deep brain stimulation and a promising, less-invasive
procedure with similar beneficial effects (see the related News
Focus
by G. Miller).
-
Gradinaru et al.
(published online in Science
Express on 19 Mar
2009) used a
sophisticated combination of genetic engineering and optics to dissect
the neural circuitry in the subthalamic nucleus (STN), a common target
for DBS therapy. Parkinsonian mice were engineered with genes encoding
light-sensitive ion pumps and channels, enabling researchers to
selectively stimulate or inhibit them using pulses of laser light
delivered by an optical fiber inserted into the brain. The team found
that neither squelching nor stimulating neuronal firing improved mouse
movement, but that direct selective stimulation of axons that carry
signals into the STN from other areas, including the primary motor
cortex, had a therapeutic effect. In addition to providing insight into
DBS mechanisms, the results demonstrate the power of optogenetics for
systematically dissecting the circuits involved in brain disorders.
-- Fuentes
et al. (20 Mar 2009)
tested
electrical stimulation of the spinal cord dorsal column as an
alternative to DBS. They found that the procedure dramatically improved
locomotion in mouse and rat models of Parkinson's, and thus could
become an efficient and less invasive alternative for treatment of the
disease. The team also monitored neural activity in the basal ganglia
and motor cortex during spinal stimulation. These recordings suggested
that spinal stimulation helps restore normal communication between
these two brain regions by disrupting abnormal oscillations in neural
firing caused by dopamine depletion (a main cause of motor impairment).
Self-Repairing Coatings
Polyurethanes are versatile polymeric materials known for their
hardness and elasticity, but they can still suffer from mechanical
damage. Now, in a Report in the 13 Mar 2009 Science, Ghosh
and Urban describe
the development of a new polyurethane material that can repair itself
simply upon exposure to ultraviolet light and could thus be useful for
scratch-resistance coatings for objects from cars to furniture. The new
material is a network consisting of polyurethane and compounds called
oxetane-substituted chitosan precursors. Chitosan is a derivative of
chitin, the structural component of the exoskeletons of insects and
crustaceans; oxetane is a four-membered ring with three carbon atoms
and one oxygen atom with the molecular formula. Upon mechanical damage
of the network, the oxetane rings open to create two reactive ends.
When then exposed to ultraviolet light, the chitosan chains are cut and
form crosslinks with the reactive oxetane ends, thus repairing the
material. The material can repair itself in less than an hour, and
because the crosslinking reactions are not moisture sensitive, dry or
humid climate conditions do not affect the repair process. Senior
author Marek Urban discussed the work in a related podcast
interview.
Out of the Deep
Scientists have long sought to unravel the combination of physical and
biogeochemical processes responsible for the tight coupling between
atmospheric carbon dioxide concentrations and Earth's climate.
Researchers suspect that the Southern Ocean may have provided a
reservoir for atmospheric carbon dioxide during cold glacial periods,
and that release of some of this carbon dioxide could help explain why
atmospheric concentrations rose by roughly 50% during each of the last
five deglaciations. In a Research Article in the 13 Mar 2009 Science,
Anderson
et al. reported
that vigorous wind-driven upwelling in the Southern Ocean may have
coaxed carbon dioxide out of deep waters and into the atmosphere during
the last deglaciation, about 17,000 years ago. The team used the burial
rate of biogenic opal, the silica cell walls of marine diatoms, as a
proxy for ocean upwelling. Diatoms grow and thrive in sunlit surface
waters but depend on the silica and other nutrients that are abundant
in deeper waters. Because the total amount of biogenic opal produced
each year is ultimately limited by the supply of dissolved silica,
changes in the production and burial of opal can be tied to changes in
ocean upwelling. The team found that opal burial rates, and thus
upwelling, increased during the transition out of the last ice age in
each sector of the Southern Ocean. They also found evidence for two
intervals of enhanced upwelling concurrent with the two intervals of
rising atmospheric carbon dioxide concentrations during deglaciation. A
related Perspective
by J. R. Toggweiler explained
how a poleward shift of the westerly winds, drawing more carbon
dioxide- and silica-rich water up to the surface, can account for these
results.
Herding Herring
Many species of oceanic fish band together in large groups called
shoals that can span tens of kilometers and involve hundreds of
millions of individuals. These groups offer survival advantages
including enhanced mating and predator avoidance, but little has been
known about how they form -- until now. In a Report in the 27 March
2009 Science, Makris
et al. documented
the formation and dynamics of shoals of Atlantic herring, which come
together every evening in early autumn to spawn (see the related ScienceNOW story by J. Kaiser).
The
team used an imaging technology called Ocean Acoustic Waveguide Remote
Sensing, which enables real-time, continuous monitoring of fish
populations over tens of thousands of square kilometers over periods of
days. They found that shoaling begins in deep water when clusters of a
few individual herring reach a critical density of 0.2 fish per square
meter near sunset. These leading clusters then aggregate more closely
together and attract other fish in horizontal waves, leading to the
formation of dense shoals (>5 fish per square meter) over tens of
kilometers within tens of minutes -- an order of magnitude faster than
the speed at which herring swim. The shoals then migrate to shallower
spawning grounds, remaining stable through the evening, and then
dissipate with sunrise. The new observations are consistent with
general theoretical predictions, as well as simulations and laboratory
experiments on animal swarming behavior, and could provide information
useful to the conservation of marine ecosystems that vast oceanic fish
shoals inhabit.
Antarctic Meltdown
Over the past several decades, the climate of the western shelf of the
Antarctic Peninsula (WAP) has been transitioning from a cold and dry
polar-type climate to a warmer, more humid climate marked by retreating
glaciers. As a result, populations of species that depend on sea ice --
such as krill and Adelie penguins -- are being displaced poleward and
replaced by other species that are typically averse to ice. According
to a Report by Montes-Hugo
et al. in the 13
Mar 2009 Science,
climate-related shifts at the base of the marine
food web may be contributing to these displacements. Using three
decades of satellite and field data, the team documented that ocean
biological productivity, inferred from concentrations of chlorophyll,
has significantly changed along the WAP. The team
attributes this to shifting patterns of ice cover, cloud formation, and
windiness affecting water-column mixing. In the northern region of the
WAP, the skies have become cloudier, reducing the amount of light
reaching phytoplankton. Less light, together with less freshwater from
melting sea ice and stronger winds, both of which inhibit water column
stratifications, results in lower plankton productivity. By contrast,
in the southern region, the skies are staying cloudless for longer and
the Antarctic current has increased its flow rate, pulling up more
micronutrients and thus contributing to greater primary productivity.
These regional changes in phytoplankton coincide with observed shifts
in krill, fish, and penguin populations in the western Antarctic.
Clues to Hardy Wheat
Given the growing human population and increased food demand worldwide,
improved strategies to reduce crop losses due to pathogens are vital.
Understanding the molecular basis of specific plant resistances has
enabled the development of crop varieties that resist common diseases.
Now, two Reports in the 6 Mar 2009 Science
(published online 19 Feb
2009) offer insight into the molecular mechanisms that control durable,
broad-spectrum fungal disease resistance in wheat, the
second-most-produced cereal crop in the world. Fu et al. cloned the Yr36 gene, which confers resistance
to a devastating fungal disease
called stripe rust. This gene encodes a kinase domain as well as a
lipid-binding domain, suggesting a role for plant lipids in cell
signaling mechanisms that confer disease resistance. Moreover, Yr36
is present in wild wheat but absent in almost all modern commercial
varieties of pasta and bread wheat, and could therefore be used to
improve resistance to stripe rust in a broad set of varieties through
backcrossing. Krattinger
et al. cloned the
gene Lr34, which is
associated with resistance to leaf rust, stripe
rust, and powdery mildew. The team found that the LR34 protein
resembles so-called ABC transporters, or pleiotropic drug resistance
transporters, which move diverse chemical compounds, including plant
natural products, across membranes. Lr34
also appears to be involved
in leaf senescence (the shedding of old leaves), which could aid
disease resistance. Alternatively, LR34 may play a direct role in
resistance by exporting metabolites that affect fungal growth. An
accompanying Perspective
by D. J. Kliebenstein and H. C. Rowe highlighted
the studies.
Superelastic Aerogel Muscles
New materials that can convert electrical, chemical, thermal, or
photonic energy into mechanical energy are being investigated with
growing vigor, as these materials could be used to generate force, move
objects, and accomplish work. In a Research Article in the 20 Mar 2009 Science, Aliev
et al. described
the development of artificial muscles that have the strength and
stiffness of steel by weight in one direction and are more compliant
than rubber in the other two directions. The new materials consist of
sheets of multi-walled carbon nanotubes formed into aerogels that are
only slightly denser than air. When electrically charged, the nanotube
sheets can reversibly stretch to 220% of their original width or
thickness within milliseconds. They can also be frozen in place. The
aerogel muscles are capable of handling dozens of times more stress
than natural skeletal muscle and could be useful in medical devices,
robots, and aerospace applications requiring specialized materials with
very low mass. An accompanying Perspective
by J. D. W. Madden noted that
the discovery "should inspire the development of new nanostructured
materials whose stiff, long, and carefully arranged elements enable
exquisite tailoring of material properties."
Earliest Horse Harnessing
The domestication of wild horses changed the course of human history,
revolutionizing transport, communications, and specialized forms of
warfare. Genetic studies of modern domestic horse breeds have implied
either multiple domestication events or domestic stallions from a
single original lineage being bred with captured local wild mares, but
have failed to clearly identify when and where horse domestication
first took place. In a Report in the 6 Mar 2009 Science, Outram
et
al.
presented three independent lines of evidence that point to early horse
domestication in the Botai culture, located in what is now northern
Kazakhstan from 5700 to 5100 years ago. First, bone measurements
indicate that Botai horses more closely resembled slender Bronze Age
domestic horses than the sturdier wild horses in the region. Second,
several skulls of Botai horses showed damage to the skeletal tissues of
the mouth that typically occurs when a horse is ridden or driven with a
bit/bridle. Finally, isotope data from fragments of Botai pottery
revealed the presence of horse fat residues, including milk fats, which
suggests that the vessels were used for the processing of mare's milk
and carcass products and thus that the animals were used as a dietary
staple.
Stealthy Transmission
Intracellular bacterial pathogens have evolved a variety of strategies
to exploit host cell resources in order to replicate while staying out
of reach of the host's immune system. In the 27 March 2009 Science,
Hagedorn
et al. reported
that in the social amoeba Dictyostelium
discoideum, a model system
for cellular infection, mycobacterial pathogens can slip undetected
from host cell to host cell via specialized exit structures called
ejectosomes. The ejectosome is a barrel-shaped actin structure
surrounding a mycobacterium that is rupturing through the host cell
plasma membrane. It is generated by mycobacteria that have escaped from
phagosomes (pathogen-containing vacuoles) into the cytoplasm and
requires a cytoskeleton regulator from the host and the mycobacterial
virulence locus RD1. The tuberculosis-causing pathogen Mycobacterium
tuberculosis might use a similar type of structure to spread
between
human macrophages during infection, which might point to new avenues of
drug discovery research. An accompanying Perspective
by F. Carlsson and
E. J. Brown highlighted the Report.
Heating the Solar
Atmosphere
The temperature of the Sun increases markedly as one moves from its
surface to the outer layers of its atmosphere (the corona) -- from
about 6000 degrees to a million degrees Celsius. Curiously, although a
variety of magnetic waves flow through the solar atmosphere, they do
not carry enough energy to generate the corona's extreme heat. In a
Report in the 20 Mar 2009 Science
Jess et al. reported
the detection of Alfvén waves -- high-velocity, twisting
magnetic waves that have long been hypothesized to heat the solar
atmosphere, but have not before been unambiguously detected (listen to
the related podcast
interview with lead author David Jess). Using
the Swedish Solar Telescope in the Canary Islands and optic techniques
to remove the blurring due to Earth's turbulent atmosphere, the team
was able to obtain high-resolution images of the solar surface and
observe oscillations coming from a large group of magnetic bright
points about 430,000 square kilometers in area that bear the signatures
of Alfvén waves. The team surmises that the waves are driven
upward from the sun's photosphere (its visible surface) in the form of
a flaring tube to the bottom of the corona 5000 kilometers above. As
noted in an accompanying News
story by R. A. Kerr, the team
calculates that there are enough bright point groups on the surface of
the sun for the Alfvén waves to heat the corona to its observed
million degrees.
In Science Signaling
Intrinsically Responsive
Signaling through the mitogen-activated protein kinase (MAPK) pathway
is important for mediating the response to osmotic stress in yeast
cells. Upon exposure to high osmolarity, the MAPK pathway is activated
and culminates in the transcription of genes that help the cell avoid
physiological damage. In a Research Article in the 24 March 2009 issue,
Macia
et al. reported that
inhibiting the kinase activity of the MAPK Hog1 does not prevent the
accumulation of its phosphorylated form, suggesting that signaling
through this pathway occurs even in the absence of osmotic stress. The
researchers found that this basal signaling is held in check by a
negative feedback loop that requires the kinase activity of Hog1. A
mathematical model that includes the basal signaling and negative
feedback recapitulates the experimental data and suggests that
intrinsic basal signaling poises the system to respond rapidly even to
small changes in osmolarity. A similar basal activity was also detected
for two additional yeast MAPKs involved in the pheromone response,
suggesting that high basal signaling may be a common property of MAPK
pathways.
Also in Science Signaling
this month:
-- Levy
et al. discussed the
evolutionary reasons for why all protein-protein interactions need not
be functional (3 March 2009)
-- Roy
et al. highlighted
recent research on a bacterial protein that posttranslationally
modifies and inactivates GTPases in host cells (17 March 2009)
-- Depoil
et al. presented a
slideshow illustrating morphological events during B cell activation in
response to antigen-presenting cells (24 March 2009)
-- Takei
described a phosphorylation event that enables neurite outgrowth, a
prerequisite for axonal regeneration, in the central nervous system (31
March 2009)
This month’s Science Roundup is sponsored by
Qiagen
NEW:
QIAgility Rotor-Gene Q
Automated solutions for quantitative PCR
www.qiagen.com/goto/QIAgilityS
Image credits (in order of appearance): Alex Aravanis and Karl
Deisseroth/Stanford; Nicholas Makris; Stephen Ausmus/Agricultural
Research Service, USDA; Alan K. Outram; D.B. Jess
