ANTHROPOLOGY
Wine trade in medieval Islamic Sicily
An amphora produced in Palermo between 900 and 1100 CE.
Wine was a popular good traded amid the Roman Empire. However, it is unclear whether wine trade in Sicily continued during the Byzantine–Islamic transition. To distinguish remnants of grapevine products from other fruit-based products in ancient ceramics, Léa Drieu et al. analyzed organic acids found in 109 amphorae produced or imported in Sicily between approximately 400 and 1100 CE. Amphorae were excavated in Italy and North Africa and may have stored grapevine products, as indicated by the presence of residue composed of more than 35% tartaric acid with respect to the sum of malic and tartaric acids; in ripening grapes, the proportion of malic acid decreases while the proportion of tartaric acid increases, and this effect is stronger in grapes than in other ripening fruits. Traces of grapevine products were found in local amphorae, suggesting that local trade in wine continued in Sicily. However, these amphorae might have stored grape syrup or wine vinegar, which were used as preservatives for medicinal purposes and in Islamic cuisine. However, the detection of grapevine products in Palermitan amphorae found as far away as Christian Sardinia and mainland Italy suggests that, despite wine being prohibited by Islamic hadiths, Early Medieval Sicilian merchants may have continued trading wine across the Mediterranean, according to the authors. — M.S.
PNAS e2017983118 (2021)
BIOPHYSICS AND COMPUTATIONAL BIOLOGY
Tetracycline combinations inhibit neuropathic pain in mice
Schematic showing Ephrin and EphB1 intracellular kinase domain with chlortetracycline cocrystalized with the ATP binding pocket.
Dubbed “the silent epidemic” by the NIH, chronic pain is responsible for hundreds of billions of dollars in lost wages and medical expenses and an exponential increase in opioid use. Despite the large scale of the epidemic, effective nonopioid alternatives for managing chronic pain remain scarce, hampered in part by the decades-long process of bringing new pain medications to market. Mahmoud Ahmed, Ping Wang, et al. describe a platform for repositioning FDA-approved drugs that inhibit the activity of EphB1, a synaptic receptor implicated in neuropathic pain. Using a structure-based in silico screen to identify drug targets, as well as an in vitro assay, X-ray crystallography, and an in vivo mouse model, the study demonstrates that drug cocktails of three FDA-approved tetracyclines—demeclocycline, chlortetracycline, and minocycline—can inhibit EphB1 phosphorylation in the brain, spinal cord, and dorsal root ganglion to block neuropathic pain in mice. In addition to offering an easily applicable treatment for neuropathic pain, the platform can be expanded to identify other novel therapies that target Eph/Ephrin-mediated illnesses, according to the authors. — T.J.
PNAS e2016265118 (2021)
PHYSICS
How giant unicellular slime molds encode memories
The giant unicellular slime mold can make rapid decisions and solve complex problems, despite not having a nervous system. How a nonneuronal eukaryote encodes memories about the environment is unclear. Mirna Kramar and Karen Alim collected a time series of bright-field images to observe the foraging behavior of the giant unicellular slime mold, which has a network-like body consisting of interlaced tubes of varying diameters. Approximately 15 minutes after a single, local nutrient source was applied nearby, tubes throughout the network changed their diameter, imprinting the nutrient location in the hierarchy of thinner and thicker tubes. This reorganized network persisted for 30 minutes, until the organism started to migrate toward the nutrient source. A theoretical model combined with experimental data suggests that the nutrient source releases a soluble chemical that enters the network and locally softens the tube wall. The chemical triggers the dilation of tubes reached by flow-based transport, at the expense of other tubes that shrink due to conservation of fluid volume. The findings suggest that a softening agent imprints nutrient location into the network by changing tube diameters. According to the authors, this mechanism may underlie memory formation in other living flow networks and could be harnessed to design biomimetic materials and soft robots. — J.W.
PNAS e2007815118 (2021)
EVOLUTION
Reconstructing early evolution of bird biodiversity
Independent approaches to analyze crown and stem birds have made it challenging to reconstruct the evolution of bird biodiversity within a unified framework. Yilun Yu et al. analyzed lineage diversification rates through time of three supertrees that combined the published phylogenies of both stem and crown birds. The analysis revealed three distinct large-scale increases in the diversification rate across bird evolutionary history. The first increase, which began between 160 and 170 million years ago and reached its peak between 130 and 135 million years ago, corresponded to the accelerated morphological evolution of key structures for flight among early stem birds. This first radiation of early stem birds from their close dinosaurian relatives is thus likely related to their occupation of a new ecospace—the aerial space. The second increase, which began around 90 million years ago and reached its peak between 65 and 55 million years ago, was associated with cranial modifications among early crown birds that were likely related to diversification in diet and foraging behavior. The third increase, which occurred after around 40–45 million years ago, lacks support from morphological data but has some support from the fossil record. According to the authors, bird biodiversity has been mainly influenced by long-term climatic changes and changes related to the Cretaceous–Paleogene mass extinction event. — S.R.
PNAS e2019865118 (2021)
BIOPHYSICS AND COMPUTATIONAL BIOLOGY
Sound propagation velocity in katydid ears
Katydid alongside 3D reconstruction showing mathematically modeled sound in the ear canal.
Katydids use hearing for social communication and to detect predators, requiring precise auditory perception and orientation. Katydid ears have outer, middle, and inner ear components analogous to mammalian ears, but, unlike mammals, they receive sounds both externally, via two tympanic membranes, and internally, through a narrow ear canal (EC), which connects to the tympana. The two inputs show differences in sound velocity for accurate sound localization. Daniel Veitch, Emine Celiker, et al. investigated whether the EC geometry is the primary cause of changes in sound velocity in the katydid Copiphora gorgonensis. The authors experimentally determined the velocity of sound propagation inside the EC and found that it was always reduced in comparison to the expected velocity in free air. This reduction in sound velocity occurred regardless of the gas composition in the EC, suggesting that it was mainly caused by the small dimensions of the EC. In addition, numerical simulations of sound propagation in the precise geometry of ECs obtained through microcomputed tomography revealed decreasing sound propagation velocity in ECs with computationally reduced diameters. According to the authors, even though gas composition contributes to the rate of velocity reduction, narrow EC radius is the primary cause of sound velocity reduction within the outer ears of katydids. — S.R.
PNAS e2017281118 (2021)
ANTHROPOLOGY
In Mesopotamia, early cities may have faltered before climate-driven collapse
A mounded archaeological site in northern Syria. Image credit: Andrea Ricci.
Posted on February 26, 2021
Amy McDermott
Some of the earliest cities, now buried in the soil of Syria, Iraq, Turkey, and Lebanon, are thought to have collapsed because of rapid climatic change. Drought along with lower temperatures descended on these settlements some 4,200 years ago, forcing residents to adapt, move away, or starve. A recent study in PLOS One suggests these cities may also have been overpopulated before the drought. “It was unsustainable in its own right,” says lead author Dan Lawrence, a landscape archaeologist at Durham University in the United Kingdom. “Climate might have pushed it over the cliff, but it was already teetering on the edge.” Continue Reading⇒