Water supply for Alberta oil sands
Upper reaches of the Athabasca River in Jasper National Park.
The Athabasca River supplies water for the exploitation of the Alberta oil sands, the world’s third largest crude oil reserve. The current water allocation for the oil sands is based on the assumption that the measured river flow record, most of which only dates from the 1950s, accurately represents long-term flow variability. David Sauchyn et al. (pp. 12621–12626) analyzed the measured river flow record for the Athabasca River Basin, while explicitly accounting for the effects of climate oscillations such as the Pacific Decadal Oscillation, the Pacific North American mode, and El Niño, which can mask long-term trends. The analysis revealed declining flows throughout the river basin. The authors also reconstructed the annual flow over the past 900 years from moisture-sensitive tree growth rings in the river basin. The reconstruction indicates considerably greater variability in flow than is apparent from the measured record, with several periods of sustained low flow far longer than the worst recorded droughts. The results suggest that the measured flow record might not adequately capture the flow variability of the Athabasca River, and that water allocations to the oil sands industry may have to account for the possibility of extended droughts in the future, according to the authors. — B.D.
Computational phylogenetics and linguistic macrofamilies
Linguists have successfully reconstructed the history of human languages, establishing over 200 language families extending back several thousand years. Some linguists have proposed macrofamilies going back more than 10,000 years, but traditional methods do not allow an exploration this far back in time. Gerhard Jäger (pp. 12752–12757) used the method of computational phylogenetics to investigate these putative macrofamilies. Unlike previous studies, the author did not rely on expert judgments about the degree to which various languages might be related, in part because the judgments are available for only a small number of languages. Instead, the author used data from the Automated Similarity Judgment Program, a database with translations of 40 basic concepts for thousands of languages. The author focused on 1,161 Eurasian languages and dialects, using sequence alignment to look first at pairwise similarities between individual words and subsequently at pairwise dissimilarities. The dissimilarity between two word lists is a good measure of whether the similarities could have arisen solely by chance. The author found support for several proposed macrofamilies, including Austro-Tai and Euroasiatic. The results contribute to continuing efforts to perform linguistic reconstruction further back in time, according to the author. — L.G.
Reconstructing the tree of life
A representation of tree of life. The colors represent the number of termini for each branch.
Assembling the tens of thousands of published evolutionary trees into a single comprehensive tree of life remains a challenge, mainly because DNA sequence data that can be compared across distantly related lineages are few and because most published trees are not available in digital format for easy integration into the tree of life. Cody Hinchliff et al. (pp. 12764–12769) assembled a comprehensive global scheme for classifying organisms, namely the Open Tree Taxonomy, to which existing trees can be mapped. The authors also developed an open database of published evolutionary trees. By mapping trees from the database to their global taxonomy, the authors assembled a draft tree of life containing 2.3 million terminal branches. Both the tree and the data used to construct it are available on the web for analysis, and can be continuously updated as new data become available. The tree reveals a significant gap between the estimated number of species and the available data for certain taxa, such as bacteria, fungi, nematodes, and insects. According to the authors, the comprehensive tree might help guide and facilitate future research in biodiversity. — B.D.
Mathematical model for synthetic cancer biomarkers
Activity-based probes amplify tumor signals for detection in urine. Image courtesy of Justin Lo.
Cancer treatment outcomes improve when the disease is detected early. However, abundance-based biomarkers produced by small tumors circulate for only short periods in blood, are diluted, and vary widely in magnitude. Thus, tumors may reach 1–2 cm in diameter and remain undetectable with blood biomarkers. Gabriel Kwong et al. (pp. 12627–12632) developed a mathematical model that can reveal nonintuitive behaviors of activity-based biomarkers, or probes, which provide an alternative to blood biomarkers. Using activity-based probes called synthetic biomarkers, which consist of nanoparticles conjugated with protease-cleavable peptides, cancer-related signals can be generated when peptides are cleaved by tumor proteases and concentrated in urine. Building on previous work on engineering synthetic biomarkers, the authors used polyethylene glycol cores to explore enzyme kinetics, dosage, organ physiology, and probe stability in a mouse model of colorectal cancer with the goal of identifying the parameters that may increase detection sensitivity. The model predicts that activity-based probes may be able to elevate signals from tumors as small as 5 mm in diameter to levels detectable in urine by a common diagnostic technique called ELISA. The model can be expanded to include multiple proteases and their inhibitors, according to the authors. — L.G.
Adiponectin and maternal obesity
Structure of adiponectin. Image courtesy of the Protein Data Bank.
Obesity in pregnancy can lead to multiple prenatal and perinatal complications for both mother and infant and is associated with low levels of circulating adiponectin in maternal blood. To investigate the connection between adiponectin, obesity, and pregnancy-related complications, Irving Aye et al. (pp. 12858–12863) compared the pregnancy and birth outcomes of obese mice fed supplemental adiponectin with those of obese mice that did not receive adiponectin supplements. During pregnancy, the obese mice exhibited high levels of the hormones leptin and insulin and low levels of adiponectin. Supplemented mice exhibited normalized insulin sensitivity, placental insulin signaling, and nutrient transport, compared with unsupplemented mice. Further, supplemented mice delivered pups of normal size and weight that did not exhibit the hyperglycemia observed in mice born to unsupplemented mice. Supplementation, however, did not affect maternal fat mass. The findings suggest that adiponectin may regulate placental function and may serve as an endocrine link between adipose tissue in the mother and growth of the fetus. The results suggest that boosting adiponectin levels in mothers who exhibit low levels of the protein may restore normal placental nutrient transport, prevent fetal overgrowth, and prevent transfer of metabolic disease from mothers to children, according to the authors. — P.G.
Stress and learning in infants
Studies have shown that stress promotes habitual behavior at the expense of flexible behavior in adults. However, it is not known if stress has similar effects on infants. Sabine Seehagen et al. (pp. 12882–12886) studied 26 15-month-old infants who were randomly assigned to a stress group or a control group. Infants in the stress group were exposed to an unfamiliar person, an unfamiliar dancing toy robot, and then briefly separated from their parents. Infants in the control group played with their parents for the equivalent length of time. Subsequently, infants in both groups were taught to push two buttons that lit up and played a sound when pushed, and were allowed to use one of the buttons until pushing that button became habitual. Each infant was then allowed to access both buttons at will for 30 seconds, though pushing the buttons had no effect. The authors found that stressed infants continued pushing the habitual button, while nonstressed infants switched to pushing the other button. The finding suggests that stress promotes habitual behavior in infants in a manner similar to that seen in adults. Because flexible behavior is important for learning, the authors suggest that frequent stress exposure might hinder infants’ knowledge acquisition. — B.D.