From organic farming to off-label drugs to insect sex

The latest in McGill research news.


Navin Ramankutty

Study points toward “hybrid” approach to sustainable food security

Can organic agriculture feed the world?

Although organic techniques may not be able to do the job alone, they do have an important role to play in feeding a growing global population while minimizing environmental damage, according to Department of Geography researchers who have just published a study in Nature comparing the yields of organic and conventional agriculture.

Crop yields from organic farming are generally lower than from conventional agriculture – and that is particularly true for cereals, staples of the human diet. But the yield gap is much less significant for certain crops, and under certain growing conditions, according to the study co-authored by doctoral student Verena Seufert, Prof. Navin Ramankutty and University of Minnesota Prof. Jonathan Foley.

The study, a comprehensive analysis of the current scientific literature on organic-to-conventional yield comparisons, aims to shed light on the often heated debate over organic versus conventional farming. Some people point to conventional agriculture as a big environmental threat that undercuts biodiversity and water resources, while releasing greenhouse gases. Others argue that large-scale organic farming would take up more land and make food unaffordable for most of the world’s poor and hungry.

Overall, organic yields are 25 per cent lower than conventional, the study finds. But yields of legumes and perennials (such as soybeans and fruits) are much closer to those of conventional crops. And when best management practices are used for organic crops, overall yields are just 13 per cent lower than conventional levels

“To achieve sustainable food security we will likely need many different techniques – including organic, conventional and possible ‘hybrid’ systems – to produce more food at affordable prices, ensure livelihoods to farmers, and reduce the environmental costs of agriculture,” the researchers conclude.

The paper is already having an influence: its findings were covered by major international media outlets including the New York Times, Los Angeles Times, BBC News, Agence France-Presse and Scientific American.

 Taking it all in: Study reveals how we sense the world around us

We rely on our senses in all aspects of our lives. Unfortunately, many of us suffer from some kind of impaired sensory

Maurice Chacron

function. In Canada alone, 600,000 people are visually impaired while almost three million suffer from partial or total hearing loss. In a paper published this week in The Journal of Neuroscience, researchers from McGill have demonstrated for the first time that there are specific neurons that respond selectively to first- and second-order sensory attributes. In the visual system, for example, luminance is a first-order attribute, whereas contrast is second-order. These findings could pave the way for the development of novel therapies and improved prosthetics for those with sensory deficiencies.

The research team, led by Physiology student Patrick McGillivray and Prof. Maurice Chacron, principal investigator at McGill’s Computational Systems Neuroscience Lab, recorded the responses to stimuli of midbrain electro-sensory neurons in the weakly electric fish. Based on these responses, the researchers were able to demonstrate that there are specific neurons that respond selectively to different attributes at the same time. Moreover, they uncovered the simple and generic neural circuits that enable this selectivity. These findings provide important clues about how the brain processes first- and second-order sensory attributes in audition (like pitch and timbre) and vision (like luminance and contrast).

How common is off-label drug prescription?

A new McGill study evaluating off-label prescribing of medications by primary care physicians in Quebec suggests the practice is common, although it varies by medication, patient and physician characteristics. The paper was published in the Archives of Internal Medicine.

Off-label prescribing is the practice of prescribing medications for indications that have not received regulatory approval by Health Canada. The practice is suspected to be a factor of preventable adverse drug events, the authors write in their study background.

“Perhaps one of the most well-known issues around off-label use occurred in the ‘90s when fen-phen – the unapproved combination of fenfluramine and phentermine as an obesity treatment – was shown to cause cardiac valve damage,” explained Dr. Tewodros Eguale, the study’s lead author.

Eguale, a researcher in the Dept. of Epidemiology, Biostatistics & Occupational Health, and his team used the Medical Office of the XXI Century (MOXXI) electronic health record network in Quebec to examine off-label use. MOXXI’s novel feature allows documentation and linking of treatment indication to the prescribed drug. A total of 113 primary care physicians from Montreal and Quebec City wrote 253,347 electronic prescriptions for 50,823 patients from January 2005 through December 2009.

“Our findings indicate that off-label prescribing is common in primary care and varies by drug class, the number of approved indications for the drug, the age of the drug, patients’ sex and physicians’ attitude toward evidence-based medicine,” the authors conclude. “Electronic health records can be used to document treatment indication at the time of prescribing and may pave the way for enhanced, post-marketing evaluation of drugs if linked to treatment outcomes.”

Andrew Gonzalez

Ecosystem effects of biodiversity loss could rival impacts of climate change and pollution

The effects of species extinctions on ecosystems are on par with many other global environmental changes, according to David Hooper of Western Washington University and McGill professor Andrew Gonzalez, Department of Biology. As reported in Nature, the team of researchers found that although loss of species is known to cause reductions in ecosystem function, how the sizes of these effects compare with the effects of environmental changes has been unclear. The latest findings highlight a major role for species loss in driving ecosystem changes.

The team analysed data from nearly two hundred studies to assess the effects of changing biodiversity and different types of environmental change on productivity and decomposition, two processes fundamental to all ecosystems. They found that losing up to 40 per cent of species from an ecosystem has effects comparable to those of climate warming. The ecosystem effects of higher levels of extinction (up to 60 per cent) rival those of acidification, elevated CO2 and nutrient pollution. The strength of these findings suggests that policy makers searching for solutions to environmental problems, such as climate warming, should also address the adverse effects of biodiversity loss.

 Biologists turn back the clock to understand evolution of sex differences

Sex differences account for some of the most spectacular traits in nature, including the wild colours of male guppies, the plumage of peacocks, tusks on walruses and antlers on moose. However, neither the genetic processes responsible for producing such traits nor how they evolved from their simpler less elaborate ancestral forms are well understood. We tend to assume that each tiny step in evolution is an advantage. But are they really?

In a study recently published in Science, Prof. Ehab Abouheif of McGill’s Biology Dept. and a team of researchers found a way to recreate some of the incremental steps in evolution by studying the transformation of simple antennae in male water striders, Rheumatobates rileyi, into more elaborate ones. The antennae are used to grasp females during mating. By modifying the expression of a particular gene associated with the development of the male antennae, the researchers were able to measure the antennae’s increasing utility in grasping females. They found that as the antennae became more elaborate, mating success increased. The study is unusual in that it applies the tools of genetic modeling to a natural system where much is already known about the selective forces involved in shaping the traits under study.