Selections from the RESEARCH HIGHLIGHTS scientific literature PHARMACOLOGY Painkiller kills the bad effects of pot Marijuana’s undesirable effects NICK CALOYIANIS on the brain can be overcome by using painkillers similar to ibuprofen, at least in mice. Chu Chen and his colleagues at Louisiana State University Health Sciences Center in New Orleans treated mice with THC, marijuana’s main active ingredient. They found that THC impaired the animals’ memory and the efficiency of their neuronal signalling, probably by stimulating the enzyme COX-2. The authors reversed these negative effects — and were able to maintain marijuana’s benefits, such as reducing CLIMATE SCIENCES neurodegeneration — when they also treated the mice with a drug, similar to ibuprofen, Crusty alga uncovers sea-ice loss that inhibits COX-2. The authors suggest that the Like tree rings, layers of growth in a long-lived marine alga Clathromorphum compactum benefits of medical marijuana Arctic alga may preserve a temperature record (pictured). It can live for hundreds of years and could be enhanced with the use of past climate. Specimens from the Canadian builds a fresh layer of crust each year. of such inhibitors. Arctic indicate that sea-ice cover has shrunk The thickness of each layer, and the ratio of Cell 155, 1154–1165 (2013) drastically in the past 150 years — to the lowest magnesium to calcium within it, are linked to levels in the 646 years of the algal record. water temperature and the amount of sunlight PALAEOECOLOGY Satellite records of the Arctic’s shrinking the organism receives. The discovery suggests sea-ice cover date back only to the late 1970s. a new way to calculate how much polar sea ice Dung reveals Jochen Halfar of the University of Toronto at existed hundreds of years ago. goats’ last days Mississauga, Canada, and his colleagues have Proc. Natl Acad. Sci. USA http://doi.org/p6g found a new palaeoclimate proxy in the coralline (2013) Climate change, rather than human actions, probably drove the Balearic mountain goat humans arrived on the islands, declined sharply 4,000–5,000 the gut as a satiety signal to the (Myotragus balearicus) extinct. about 5,000 years ago. Some years ago because of a drier brain. When it is injected into This small goat, unique researchers have proposed that climate. This is likely to have humans, however, it causes to Spain’s Balearic Islands in disease or hunting by humans contributed greatly to the nausea and ruins the taste of the western Mediterranean, killed off the goats. goats’ extinction. food. Sergei Zolotukhin at disappeared soon after Frido Welker and Barbara Quat. Res. http://doi.org/p6b the University of Florida in Gravendeel of the Naturalis (2013) Gainesville and his colleagues Biodiversity Center in Leiden, sprayed PYY into the mouths the Netherlands, and their NEUROSCIENCE of mice and found that colleagues analysed plant although the animals stopped DNA found in the goats’ Satiety signal eating, as expected, they did fossilized faeces (pictured). from the mouth not become nauseous. The results suggest that the PYY in saliva seems to use goats were dependent on A human hormone might be a different signalling pathway Buxus balearica, a local species a potent treatment for obesity, from gut PYY to tell the brain of shrub. Further analysis but only if it is taken orally. when it is time to stop eating. indicated that the shrub’s The peptide hormone PYY Targeting molecules in this abundance on the islands is made primarily by cells in pathway with oral PYY or BIODIVERSITY CENTER ALINE NIEMAN/NATURALIS 440 | NATURE | VOL 503 | 28 NOVEMBER 2013 | CORRECTED 29 NOVEMBER 2013 © 2013 Macmillan Publishers Limited. All rights reserved RESEARCH HIGHLIGHTS THIS WEEK other compounds could them to eat, tadpole alkaloid reduce overeating without concentrations rose. Adult inducing nausea. frogs obtain the alkaloids from COMMUNITY The most viewed J. Neurosci. 33, 18368–18380 ants and mites in their diet. CHOICE papers in science (2013) Hand-reared O. pumilio that were fed nutritive eggs from PHYSICS VIROLOGY another frog species lacking chemical defences remained Pinch of salt makes for bumpy icicles A more alkaloid-free. predictable flu Ecology http://doi.org/p59 ✪ HIGHLY READ Impurities in water are behind the ripples (2013) on iopscience. seen around an icicle’s circumference. Influenza viruses may have iop.org Ripples or ribs form naturally in fewer routes for escaping PHYSIOLOGY 20 Oct–19 Nov icicles, an effect that previous theories vaccines than previously attributed to surface tension in the thin thought. Smells maintain film of water that flows over the ice. Antony Szu-Han Chen Flu vaccines target a viral blood cells and Stephen Morris at the University of Toronto, Canada, protein called haemagglutinin, analysed 67 icicles grown under a broad range of conditions which mutates frequently, Fruitfly larvae need to sense in the laboratory. They found that whereas icicles made rendering vaccines ineffective. odours to maintain a pool of from pure water were ripple-free, even small amounts of Derek Smith of the University the cells that give rise to blood salt dissolved in the water — less than is found in most tap of Cambridge, UK, and cells. water — caused ripples to emerge. The ribs also grew faster Ron Fouchier of Erasmus A team led by Utpal Banerjee in saltier water. Medical Center in Rotterdam, at the University of California, Existing theories do not account for the effects of impurities the Netherlands, and their Los Angeles, studied mutants in ripple formation, leaving salt’s role in the process a mystery. colleagues studied how the of Drosophila melanogaster New J. Phys. 15, 103012 (2013) haemagglutinin protein has to identify molecular signals mutated to evade vaccines — a connecting odour sensing to process called antigenic drift blood progenitor cells. They GLACIOLOGY caused its sudden demise, the — over a 35-year period from found that smells prevent the authors suggest. 1968 to 2003. cells from specializing, or Anatomy of an ice Geophys. Res. Lett. http://doi. They found that seven of the differentiating, before they are shelf’s demise org/p6c (2013) ten antigenic drift events in the required. past three decades were caused When the team activated The sudden drainage of ORGANIC CHEMISTRY by a change in just one amino olfactory neurons in the fly’s thousands of small lakes acid in the protein. These brain, the neurons secreted a on the surface of Antarctic Fast and easy changes occurred at only seven chemical called GABA into glaciers seems to have fluorine fix places in the protein, all of the blood, triggering blood triggered the spectacular which cluster near a region that progenitors to let in calcium collapse of the Larsen B ice Many drug compounds and binds to host cells. The results ions. Calcium maintains shelf in March 2012. agrochemicals are fluorinated, could one day lead to more- the cells as undifferentiated Some 3,000 small but adding fluorine atoms effective flu vaccines. progenitors. Larvae raised in ponds of liquid water had to organic molecules can be Science 342, 976–979 (2013) environments with few odours emerged over the course of dangerous and expensive. had low levels of GABA, and a decade on top of glaciers Patrick Fier and John ECOLOGY their blood progenitor cells surrounding the ice shelf Hartwig at the University of differentiated earlier. on the Antarctic Peninsula. California, Berkeley, report Mother frogs arm Whether similar links exist These ponds disappeared a way to fluorinate one their tadpoles between sensory perception in striking synchronicity a class of molecules at room and progenitor cells in more few days before the shelf’s temperature and without the Some animals make chemical complex organisms is not clear. collapse. need for harsh reagents. defences against predators; Cell 155, 1141–1153 (2013) When recreating the They showed that silver(II) others obtain them from their events in a computer fluoride can swap a hydrogen food. Researchers have now simulation, Alison Banwell atom for a fluorine atom on found the first example of of the University of Chicago molecules containing nitrogen parents chemically arming in Illinois and her colleagues as part of a ring of carbon their young after birth. found that the initial atoms. The reaction replaces Ralph Saporito of John drainage of a single lake only the hydrogen attached to Carroll University in University would have produced carbons next to the nitrogen Heights, Ohio, and his fractures in the ice that in the ring. It occurs quickly colleagues analysed specimens were capable of sucking and uses only commercially of the strawberry poison frog dry neighbouring available reagents. Oophaga pumilio (pictured) lakes, kicking off a Science 342, 956–960 (2013) GREGORY BASCO/VISUALS UNLIMITED/GETTY BASCO/VISUALS GREGORY from all stages of the life cycle. catastrophic chain Newly hatched tadpoles had no reaction. NATURE.COM defensive alkaloids, but after The spread of For the latest research published by their mothers began producing fractures across the ice Nature visit: unfertilized ‘nutritive eggs’ for shelf may have ultimately www.nature.com/latestresearch 28 NOVEMBER 2013 | VOL 503 | NATURE | 441 © 2013 Macmillan Publishers Limited. All rights reserved.