- Vessel Formation
The heart needs blood vessels, too
- Beverly A. Purnell
For the newborn heart to grow quickly, the heart's own blood vessels must grow as well. Researchers have assumed that preexisting fetal coronary vessels expand to cause this postnatal coronary vascular growth. Instead, Tian et al. now show that, for the most part, brand-new blood vessels form within the neonatal heart (see the Perspective by Burns and Burns). This ability to produce new coronary blood vessels after birth may one day help researchers work out how to promote cardiovascular regeneration after injury or disease.
Toward safer bone marrow transplants
- Yevgeniya Nusinovich
People who receive bone marrow transplants often develop graft-versus-host disease, in which immune cells from the transplanted bone marrow attack the patient's body. To understand this serious complication, Nalle et al. mimicked common human transplantations in mice. Before a transplant, human patients—and the experimental mice—are irradiated to kill their own bone marrow. In the mice, however, this irradiation promoted gut “leakiness,” allowing immune-activating bacteria to enter the body. That made graft-versus-host disease worse. If medics can find a way around this sort of complication in humans, they should be on their way to safer transplants.
Sci. Transl. Med. 6, 243ra87 (2014).
Exploiting nervous paths already traveled
- Pamela J. Hines
The parasympathetic nervous system helps regulate the functions of many tissues and organs, including the salivary glands and the esophagus. To do so, it needs to reach throughout the body, connecting central systems to peripheral ones. Dyachuk et al. and Espinosa-Medina et al. explored how these connections are established in mice (see the Perspective by Kalcheim and Rohrer). Progenitor cells that travel along with the developing nerves can give rise to both myelin-forming Schwann cells and to parasympathetic neurons. That means the interacting nerves do not have to find each other. Instead, the beginnings of the connections are laid down as the nervous system develops.
- Social Psychology
Don't leave me alone with my thoughts
- Gilbert Chin
Nowadays, we enjoy any number of inexpensive and readily accessible stimuli, be they books, videos, or social media. We need never be alone, with no one to talk to and nothing to do. Wilson et al. explored the state of being alone with one's thoughts and found that it appears to be an unpleasant experience. In fact, many of the people studied, particularly the men, chose to give themselves a mild electric shock rather than be deprived of external sensory stimuli.
Science, this issue p. 75
Exosomes can help cancer cells hide out
- Leslie K. Ferrarelli
Some locations in the body, such as the bone marrow, can actually help cancer cells to metastasize, or spread. Chemotherapy targets rapidly dividing cells, but cancer cells that hide out in the bone marrow proliferate slowly, which protects them from chemotherapy. Ono et al. found that stem cells in the bone marrow released vesicles called exosomes. Metastatic breast cancer cells took up these exosomes, which contained various factors that blocked the cancer cell proliferation.
Sci. Signal. 7, ra63 (2014).
- Extrasolar Planets
Impolite planet ignores host's partner
- Margaret M. Moerchen
Many known exoplanets (planets outside our own solar system) are hosted by binary systems that contain two stars. These planets normally circle around both of their stars. Using microlensing data taken with a worldwide network of telescopes, Gould et al. found a planet twice the mass of Earth that circles just one of a pair of stars. The same approach has the potential to uncover other similar star systems and help to illuminate some of the mysteries of planet formation.
Science, this issue p. 46
- Bilayer Graphene
Breaking down graphene degeneracy
- Jelena Stajic
Bilayer graphene has two layers of hexagonally arranged carbon atoms stacked on top of each other in a staggered configuration. This spatial arrangement results in degenerate electronic states: distinct states that have the same energy. Interaction between electrons can cause the states to separate in energy, and so can external fields (see the Perspective by LeRoy and Yankowitz). Kou et al., Lee et al., and Maher et al. used three distinct experimental setups that clarify different parameter regimes of bilayer graphene.
- Climate Change
Strong winds, upwelling, and teeming shores
- H. Jesse Smith
Climate warming has produced stronger winds along some coasts, a result of growing differences in temperature and pressure between land and sea. These winds cause cold nutrient-rich seawater to rise to the surface, affecting climate and fueling marine productivity. Sydeman et al. examined data from the five major world regions where upwelling is occurring. Particularly in the California, Humboldt, and Benguela upwelling systems, winds have become stronger over the past 60 years. These regions represent up to a fifth of wild marine fish catches and are hot spots of biodiversity.
Science, this issue p. 77
- Cell Death
Life and death and quality control
- Stella M. Hurtley
When cells are subjected to too much stress, they curl up their toes and die. Lu et al. describe a clever strategy cells use to stay alive as long as they are not stressed for too long. The cells' quality-control machinery will activate a so-called death receptor when defective proteins accumulate within the cell, a sign of stress—but they will wait until the proteins have built up for a good long time. If stress is relieved soon enough, levels of the death receptor decay back to normal, and the cells stay alive; otherwise, R.I.P.
Science, this issue p. 98
- Human Evolution
Pleistocene people and environments
- Andrew M. Sugden
In the past few decades, hundreds of hominin fossils have been recovered from well-dated sites in East Africa. In addition, early representatives from far outside Africa have been found in Asia and Europe. Recently, discoveries at Malapa in South Africa and at Dmanisi in western Asia have brought important new fossils and archaeological residues to light. Analyses of local stratigraphy, windblown dust, sea and lake cores, and stable isotopic analyses have improved the reconstruction of ancient environments inhabited by early humans. Antón et al. review recent evidence and arguments about the evolution of early Homo, arguing that habitat instability and fragmentation imposed an important selective force.
Science, this issue p. 10.1126/science.1236828
- Molecular Kinetics
Outliers dominate signaling at cell membrane
- L. Bryan Ray
SOS enzymes act at cell membranes to activate Ras, a regulatory protein often overactive in cancer cells. Iversen et al. devised a system where they could observe the activity of individual enzymes at work. The single SOS molecules occupied stable states that varied greatly in their catalytic activity. Regulation appeared to occur by altering the time spent in active states. The overall activity of SOS was determined by just a few molecules that achieved the highest catalytic activity. The methods described should allow further detailed kinetic analysis of this and other signaling events that occur at the cell membrane — properties that it is not possible to discern from bulk biochemical measurements.
Science, this issue p. 50
- Separation Membranes
High-surface-area gas separation membranes
- Marc S. Lavine
Membranes for gas separation require a combination of high surface area and selective transport pathways. Brown et al. present a potentially scalable route for making high-quality gas separation membranes in a high-surface-area configuration. Using two different solvents flowing in opposite directions, a metal-organic framework material was selectively deposited within hollow polymer fibers. The membranes showed high-performance separation capabilities when tested with mixtures of hydrocarbon gases.
Science, this issue p. 72
- Active Galaxies
Gas jets block extragalactic x-rays
- Margaret M. Moerchen
Supermassive black holes at the heart of active galaxies produce powerful gas outflows. NGC 5548 is one such source known to sustain a persistent outflow of ionized gas. However, its associated x-ray and ultraviolet (UV) emission seem to have been suppressed in recent years. Kaastra et al. conducted a multiwavelength monitoring campaign throughout 2013 to characterize the system's behavior. They suggest that an additional faster jet component has been launching clumps of gas that obscure both the x-ray and UV radiation. The timing of this phenomenon indicates a source only a few light-days away from the nucleus. This proximity suggests that the outflow could be associated with a wind from the supermassive black hole's accretion disk. Even more powerful outflows could also influence their host galaxies, and this finding demonstrates how that feedback might work.
Science, this issue p. 64
- C-H Bond Activation
Carbon-carbon bonds without byproducts
- Jake Yeston
Environmental and cost concerns are spurring development of chemical methods that minimize byproduct formation. In this vein, Mo and Dong present a catalyst that inserts olefins such as ethylene directly into the C-H bonds of ketones. Traditional methods to form such products rely on the preliminary reaction of the ketone with a base, followed by subsequent reaction with an alkyl halide. The authors used a ligand that simultaneously activates the ketone and guides the catalytic rhodium to the right location. This approach removes the need for the other reagents and eliminates the associated halide salt byproducts.
Science, this issue p. 68
- Earthquake Dynamics
Seismic noise reveals volcanic plumbing
- Nicholas S. Wigginton
Monitoring the way in which seismic noise passes through Earth's crust after a large earthquake can clarify how volcanoes erupt. Japan has the highest-density seismic network in the world. Brenguier et al. observed reductions in seismic velocity below volcanic regions of Japan from before, to the weeks and months after the 2011 Tohoku-Oki earthquake (see the Perspective by Prejean and Haney). This indicates that pressurized fluids below volcanoes can weaken in response to dynamic stress perturbations.
- Plant-Fungal Ecology
It takes two to tango in restricted environments
- Laura M. Zahn
Despite being unrelated, free-living algae and fungi can learn to help one another out. Hom and Murray raised the green alga Chlamydomonas reinhardtii in CO2-restricted environments in the presence of the yeast Saccharomyces cerevisiae (see the Perspective by Aanen and Bisseling). The experimental setup forced the two species to depend on one another for the metabolic production of CO2, which is provided by the yeast as it consumes glucose and is needed by the alga, and ammonia, which conversely can be made from nitrite by the alga and then used by the yeast. This dependence was seen under a broad range of environmental conditions. Similar tests between other Chlamydomonas and fungal species revealed the ability to create a phylogenetically broad range of mutualisms.