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Article Highlights


Also of Interest


Article Highlights

Retracing the emergence of H7N9 in humans

A study pieces together the evolutionary events leading up to the first human case of avian-derived H7N9 influenza. Since the virus’s 2013 emergence in humans, it has been linked to two outbreaks and at least 115 deaths. Phylogenetic analysis suggests the virus is a triple reassortment of H7, N9, and H9N2 avian influenza viruses, but it remains unclear how the prevalence and evolution of these three viruses gave rise to novel H7N9. Jinhua Liu and colleagues investigated the prevalence and evolution of H9N2 viruses mainly in farm chickens in China. The authors’ findings reveal that multiple H9N2 genotypes circulated in chickens for more than 10 years, finally yielding a G57 viral genotype with markedly different antigenicity and enhanced adaptability. The G57 viruses, the authors report, rose in prevalence and sparked widespread outbreaks in chickens from 2010 to 2013. Before long, the viruses contributed a complete set of genetic information to the novel H7N9 viruses, which emerged in humans in 2013. The prevalence and variation of H9N2 influenza virus in farmed poultry could provide an important early warning that novel reassortants with pandemic potential are on the rise, according to the authors.

“Evolution of the H9N2 influenza genotype that facilitated the genesis of the novel H7N9 virus,” by Juan Pu, et al.
10.1073/pnas.1422456112

abstract

Warfare and reproduction

A study finds that male members of the Nyangatom population who participated in livestock raids in their youth may experience greater reproductive success in the long term than non-raiders. The high personal risk of engaging in warfare has led researchers to investigate the benefits that may drive raiding behavior. To determine whether raiding afforded a reproductive advantage, Luke Glowacki and Richard Wrangham traced the number of wives and children of 120 male members of the pastoralist Nyangatom people of Ethiopia and South Sudan. The authors found that, in the short term, men who engaged in livestock raids did not have a greater number of wives or children than non-raiders, suggesting that captured livestock are distributed to family members and not used as bridewealth by raiders over the short term. Elders who gained reputations as successful raiders in their youth, however, had more wives and children than other elders. Although the number of a man’s older siblings may affect the amount of bridewealth his family has access to, the authors found that the number of older siblings did not affect whether a man became a raider or how frequently he raided. The results suggest a link between successful raiding in youth, delayed access to bridewealth, and improved reproductive success, according to the authors.

“Warfare and reproductive success in a tribal population,” by Luke Glowacki and Richard Wrangham
10.1073/pnas.1412287112

abstract

Stickiness of gecko feet and adaptive simplification

Evolution can remove previously acquired morphological adaptations to confer survival advantages to a species, a study finds. Morphological adaptations such as the prehensile tail allowed species to rapidly diversify and thrive, but some innovations can impose functional constraints on behaviors such as locomotion. To study how and why complex adaptations are often subsequently simplified or lost altogether, Timothy E. Higham and colleagues examined the adhesive system that allows geckos to cling to surfaces, a functional innovation whose complexity fluctuated as this diverse group of lizards adapted to a variety of microhabitats. According to the researchers, species in which the adhesive system was either lost or simplified experienced elevated rates of evolution related to morphology and locomotion, suggesting that the removal of the constraints associated with adhesion allowed those species to either run fast or burrow. This association between habitat and the loss or reduction of adhesion also points to a link between morphology, biomechanics, and ecology, according to the authors.

“Adaptive simplification and the evolution of gecko locomotion: Morphological and biomechanical consequences of losing adhesion,” by Timothy E. Higham, Aleksandra V. Birn-Jeffery, Clint E. Collins, C. Darrin Hulsey, and Anthony P. Russell
10.1073/pnas.1418979112

abstract

Seismic signals and major earthquakes

Regional monitoring of seismic signals may help localize the possible epicenter of an impending major earthquake, a study suggests. Major earthquakes such as the March 2011 Tohoku earthquake in Japan highlight the need for advance earthquake prediction and warning. Seiya Uyeda and colleagues examined seismic signals preceding major earthquakes in the Japan region to find possible predictive signals. Previously, the authors had determined that fluctuations of a seismic parameter called κ1 on a time domain called Natural Time revealed distinct fluctuation minima across the Japan region a few months before major earthquakes. The authors further refined the finding by dividing the Japan region into small areas and re-examining seismic records for each area preceding six shallow earthquakes with magnitudes greater than 7.6 over a period of 27 years, including the March 2011 Tohoku earthquake. Fluctuations in κ1 reached a minimum in some small areas, clustered within a few hundred kilometers from the epicenter of the next major earthquake, within two days of the same time that the fluctuations reached a minimum across the overall Japan region. The results suggest that monitoring of fluctuations in κ1 may help localize the possible epicenter area of the forthcoming shock of a future major earthquake, according to the authors.

“Spatiotemporal variations of seismicity before major earthquakes in the Japanese area and their relation with the epicentral locations,” by Nicholas V. Sarlis, et al.
10.1073/pnas.1422893112

abstract

Comparing climate change assessment methods

Three predominant methods for assessing future impacts of climate change on plant communities show agreement in the direction of community development but differ in the magnitude of projected climate effects, according to a study. Researchers seeking to understand the changes in plant communities in response to a warming climate typically employ one of three methods: experimental warming, monitoring under variable temperature conditions, or monitoring along a spatially variable environmental gradient. Sarah C. Elmendorf and colleagues compared the three methods using results from experiments conducted in Arctic and alpine sites in North America and Europe. The authors found that the direction of change in all three study types was the same, with each method indicating that warming may lead to an increasing abundance of plants with a warm thermal niche. The magnitude of change was significantly greater in spatial variation studies, also called space-for-time studies, than in the other two study types. The results suggest that space-for-time studies capture effects of long-term climate processes and that experimental warming or temporal temperature variability studies may provide more accurate representations of short-term climate change effects than space-for-time studies, according to the authors.

“Experiment, monitoring, and gradient methods used to infer climate change effects on plant communities yield consistent patterns,” by Sarah C. Elmendorf, et al.
10.1073/pnas.1410088112

abstract

Transport of Fukushima radioactivity across the Pacific

A study tracing the transport of radioactive material from the Fukushima Dai-ichi nuclear accident finds that cesium radionuclides Cs-134 and Cs-137 arrived on the North American Pacific continental shelf around June 2013. Damage to the Fukushima nuclear power plant following the earthquake and tsunami that struck Japan in March 2011 raised concern about transport of radioactive material across the Pacific Ocean to North American shores. John Norton Smith and colleagues measured radioactive cesium isotopes in samples of seawater collected at depths up to 1,000 m in the eastern North Pacific Ocean between June 2011 and February 2014. The authors detected early signals of elevated radioactivity 1,500 km west of British Columbia, Canada, in June 2012. A year later, the authors detected radioactivity around 2 Bq/m3 at the Canadian continental shelf, approximately double the activity of pre-Fukushima background radiation. Ocean circulation model results suggest that Cs-137 concentrations along the North American Pacific coast may peak at levels of 3-5 Bq/m3 around 2015-2016 before declining to fallout background levels. The results suggest that Fukushima inputs of radioactivity might return eastern North Pacific water concentrations of Cs-137 to the fallout levels of the 1980s, but the radioactivity likely does not represent a threat to human health or the environment, according to the authors.

“Arrival of the Fukushima radioactivity plume in North American continental waters,” by John N. Smith, et al.
10.1073/pnas.1412814112

abstract

Also of Interest

Raindrop imprints and asteroid strikes

A study of raindrop impacts on sandy surfaces finds a quantitative similarity between liquid-drop impacts and impact craters formed by asteroids, allowing planetary science models of asteroid impacts to be applied to small-scale liquid-drop craters.

“Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes,” by Runchen Zhao, Qianyun Zhang, Hendro Tjugito, and Xiang Cheng
10.1073/pnas.1419271112

abstract

Long-term memory and visual attention

Transcranial direct-current stimulation applied to a brain region associated with long-term memory in 18 individuals engaged in a visual search task increased their tuning of perceptual attention, suggesting that long-term memory storage may influence human efficiency at object recognition, according to a study.

“Enhancing long-term memory with stimulation tunes visual attention in one trial,” by Robert M. G. Reinhart and Geoffrey F. Woodman
10.1073/pnas.1417259112

abstract

Coral modification of symbiont microenvironment

A study finds that coral cells can acidify the microenvironment of their symbiotic dinoflagellate algae to assist algal production of fixed carbon through photosynthesis.

“Coral host cells acidify symbiotic algal microenvironment to promote photosynthesis,” by Katie L. Barott, Alexander A. Venn, Sidney O. Perez, Sylvie Tambutté, and Martin Tresguerres
10.1073/pnas.1413483112

abstract

Separating and integrating tactile signals

Although exploring an object by touch with one hand usually involves combining tactile and movement signals coming from a single hand, a study of 27 participants finds that when the tactile and movement signals are dissected, with one stationary hand feeling a tactile stimulus that changed according to the movement of the other hand, the participants were able to determine the shape and orientation of the object created by the tactile stimulus, suggesting that their brains had combined the two hands’ signals as if they had come from a single hand.

“Direct coupling of haptic signals between hands,” by Lucile Dupin, Vincent Hayward, and Mark Wexler
10.1073/pnas.1419539112

abstract

Searching for life using mechanical nanosensors

A sensor that can detect motion on a nanoscale has demonstrated the ability to detect the small movements and vibrations that result from cellular metabolism in the cells of bacteria, yeast, fungi, plants, mice, and humans, suggesting that the technique might be used to detect extraterrestrial life by mechanical means, potentially bolstering techniques that currently rely on sensors that detect chemical signatures of life, according to a study.

“Detecting nanoscale vibrations as signature of life,” by Sandor Kasas, et al.
10.1073/pnas.1415348112

abstract

Tropical carbon storage

A study finds that current tropical carbon uptake by terrestrial plants represents a significant carbon sink in response to rising atmospheric carbon dioxide concentrations, likely absorbing up to one-third of fossil fuel emissions.

“Effect of increasing CO2 on the terrestrial carbon cycle,” by David Schimel, Britton B. Stephens, and Joshua B. Fisher
10.1073/pnas.1407302112

abstract

Dopamine signaling and memory formation in the fruit fly

Sugar ingestion by fruit flies triggered dopamine release that stimulated long and short term memory formation by two separate regions of the midbrain that ultimately became a stable long term memory, suggesting that long term memory formation may depend on complementary signaling by multiple subsets of dopamine neurons rather than by a single set of neurons that sequentially transforms a short term memory into a long term memory, according to a study.

“Distinct dopamine neurons mediate reward signals for short- and long-term memories,” by Nobuhiro Yamagata, et al.
10.1073/pnas.1421930112

abstract

Birth cohort and obesity

An examination of genetic, physical, and questionnaire data collected over 30 years from more than 3,000 individuals in the Offspring Cohort of the Framingham Heart Study reveals that individuals born in the same time period share a similar degree of correlation between body mass index and a variant of the FTO gene that correlates with obesity, suggesting that genetic and environmental factors may interact differently during different time periods to influence the likelihood of obesity, according to a study.

“Cohort of birth modifies the association between FTO genotype and BMI,” by James Niels Rosenquist, et al.
10.1073/pnas.1411893111

abstract

DNA-assembled nanomaterials

A study finds that programmable DNA can guide the assembly of gold nanoparticles into superlattices and crystal structures with tunable properties allowing interaction between light and nanomaterial electrical properties.

“Plasmonic photonic crystals realized through DNA-programmable assembly,” by Daniel J. Park, et al.
10.1073/pnas.1422649112

abstract

Inflammation and red meat

Neu5Gc, a glycan shown to be enriched in red meat, can be incorporated into human tissues and, as a foreign antigen, induced systemic inflammation and promoted cancer progression in a study of mice fed orally absorbable Neu5Gc.

“A red meat-derived glycan promotes inflammation and cancer progression,” by Annie N. Samraj, et al.
10.1073/pnas.1417508112

abstract

Brainstem regions and REM sleep

Optogenetic stimulation of cholinergic neurons in two different regions of the brainstem, the pedunculopontine tegmentum and the laterodorsal tegmentum, increased the number of rapid eye movement (REM) sleep episodes in mice, suggesting a link between cholinergic neurons in the brainstem and initiation of REM sleep, according to a study.

“Optogenetic activation of cholinergic neurons in the PPT or LDT induces REM sleep,” by Christa J. Van Dort, et al.
10.1073/pnas.1423136112

abstract

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