Thursday, August 11, 2022

Testosterone promotes 'cuddling,' not just aggression, animal study finds

The research used the experimental model of Mongolian gerbils, rodents that form lasting pair bonds and raise their pups together. In addition to demonstrating testosterone's effects on prosocial behavior, the work also revealed how testosterone influences the neural activity of oxytocin cells — the so-called "love hormone" associated with social bonding. (Photo by Aubrey Kelly)

By Carol Clark

Testosterone can foster friendly, prosocial behavior in males, a new animal study finds. The Proceedings of the Royal Society B published the research on Mongolian gerbils conducted by neuroscientists at Emory University. 

“For what we believe is the first time, we’ve demonstrated that testosterone can directly promote nonsexual, prosocial behavior, in addition to aggression, in the same individual,” says Aubrey Kelly, Emory assistant professor of psychology and first author of the study. “It’s surprising because normally we think of testosterone as increasing sexual behaviors and aggression. But we’ve shown that it can have more nuanced effects, depending on the social context.”

The work also revealed how testosterone influences the neural activity of oxytocin cells — the so-called “love hormone” associated with social bonding. 

Richmond Thompson, a neuroscientist at Oxford College of Emory University, is co-author of the study. 

Kelly’s lab has recently focused on the neural effects of oxytocin using rodent experimental models. Thompson’s lab investigates the neural effects of steroids in fish. Both scientists are trying to get at the question of how hormones work in the brain to allow an animal to rapidly change its behavior, depending on the social context. 

In addition to sharing this research interest, Kelly and Thompson share a home as a married couple.

“The idea for this paper was borne out of us talking together over a glass of wine,” Kelly says. “It blends our two research worlds.” 

Testing new questions 

The majority of human studies show that testosterone enhances aggressive behavior. Kelly and Thompson wondered if maybe testosterone might, in lockstep with being able to increase aggression toward intruders, also generally dampen prosocial behaviors. However, they also hypothesized that it might do something more radical — actually enhance positive social responses in contexts in which acting prosocially is appropriate. 

To test this question, the Kelly lab conducted experiments on Mongolian gerbils, rodents that form lasting pair bonds and raise their pups together. While males can become aggressive during mating and in defense of their territory, they also exhibit cuddling behavior after a female becomes pregnant, and they demonstrate protective behavior toward their pups. 

In one experiment, a male gerbil was introduced to a female gerbil. After they formed a pair bond and the female became pregnant, the males displayed the usual cuddling behaviors toward their partners. The researchers then gave the male subjects an injection of testosterone. They expected that the resulting acute rise in a male’s testosterone level would lessen his cuddling behaviors if testosterone generally acts as an antisocial molecule. 

“Instead, we were surprised that a male gerbil became even more cuddly and prosocial with his partner,” Kelly says. “He became like ‘super partner.’” 

Switching contexts 

In a follow-up experiment a week later, the researchers conducted a resident-intruder test. The females were removed from the cages so that each male gerbil that had previously received a testosterone injection was alone in his home cage. An unknown male was then introduced into the cage. 

“Normally, a male would chase another male that came into its cage, or try to avoid it,” Kelly says. “Instead, the resident males that had previously been injected with testosterone were more friendly to the intruder.” 

The friendly behavior abruptly changed, however, when the original male subjects were given another injection of testosterone. They then began exhibiting normal chasing and/or avoidance behaviors with the intruder. “It was like they suddenly woke up and realized they weren’t supposed to be friendly in that context,” Kelly says. 

The researchers theorize that because the male subjects experienced a surge in testosterone while they were with their partners, it not only rapidly increased positive social responses toward them but also primed the males to act more prosocially in the future, even when the context changed and they were in the presence of another male. However, the second testosterone injection then rapidly prompted them to switch their behavior to become more aggressive, as appropriate to the context of a male intruder. 

“It appears that testosterone enhances context-appropriate behavior,” Kelly says. “It seems to play a role in amplifying the tendency to be cuddly and protective or aggressive.” 

The laboratory experiments, in a sense, slowed down what the males might experience almost simultaneously in the wild. In their natural habitat, Kelly explains, mating with a partner elevates testosterone, which primes them to act cuddly in the moment and in the near future while living with their partner, even if the testosterone levels decline. If a rival entered its burrow the gerbil would likely experience another surge of testosterone that would immediately help adjust his behavior so he can fend off the rival and protect his pups. Testosterone, then appears to help animals rapidly pivot between pro- and antisocial responses as the social world changes. 

‘A complicated dashboard’ 

The current study also looked at how testosterone and oxytocin interact biologically. The results showed that the male subjects receiving injections of testosterone exhibited more oxytocin activity in their brains during interactions with a partner compared to males that did not receive the injections. 

“We know that systems of oxytocin and testosterone overlap in the brain but we don’t really understand why,” Kelly says. “Taken together, our results suggest that one of the reasons for this overlap may be so they can work together to promote prosocial behavior.” 

Rather than just flipping an “on” or “off” button to modulate behaviors, hormones seem to play a more nuanced role, Kelly says. “It‘s like a complicated dashboard where one dial may need to move up a bit while another one moves down.” 

Human behaviors are far more complex than those of Mongolian gerbils, but the researchers hope that their findings provide a basis for complementary studies in other species, including humans. 

“Our hormones are the same, and the parts of the brain they act upon are even the same,” Thompson says. “So, learning how hormones like testosterone help other animals adjust to rapidly changing social contexts will not only help us understand the biological nuts and bolts that affect their behavior, but also predict and ultimately understand how the same molecules in human brains help shape our own responses to the social world around us.” 

Jose Gonzalez Abreu, a former research specialist in the Kelly lab, is a co-author of the study. The work was supported by the National Science Foundation. 

Related:

Study shows how a single gene drives aggression in wild songbirds

Athletes' testosterone surges not tied to winning, study finds

 

Monday, July 11, 2022

Chemists crack complete quantum nature of water

"Now that we have a good template for understanding how water molecules interact among themselves, we have a basis to deepen our understanding of the role of water in biochemical processes essential to life," says Joel Bowman,  Emory professor of theoretical chemistry.


Chemists have produced the first full quantum mechanical model of water — one of the key ingredients of life. The Journal of Physical Chemistry Letters published the breakthrough, which used machine learning to develop a model that gives a detailed, accurate description for how large groups of water molecules interact with one another. 

“We believe we have found the missing piece to a complete, microscopic understanding of water,” says Joel Bowman, professor of theoretical chemistry at Emory University and senior author of the study. “It appears that we now have all that we need to know to describe water molecules under any conditions, including ice, liquid or vapor over a range of temperature and pressure.” 

The researchers developed free, open-source software for the model, which they dubbed “q-AQUA.” The q-AQUA software provides a universal tool for studying water. 

“We anticipate researchers using it for everything from predicting whether an exoplanet may have water to deepening our understanding of the role of water in cellular function,” Bowman says. 

Read more about the discovery here

Related:

Chemists map cascade of reactions for producing atmosphere's 'detergent'

Joel Bowman's view from the top of theoretical chemistry

Behaviors of tiniest water droplets revealed

Soil quality critical to help some U.S. crops weather heat stress from climate change

"Keeping soil healthy is a key component needed to adapt to the climate crisis," says Debjani Sihi, assistant professor in Emory's Department of Environmental Sciences.

By Carol Clark

The capacity of soil to hold water will be critical to determine how well farms in some regions of the United States manage the problem of prolonged heat stress due to climate change, a new study suggests. The journal Frontiers in Sustainable Food Systems published the finding, based on analyses of 30 years of data on four major U.S. crops — corn, soybeans, cotton and wheat. 

“At the same time that farmers are facing more extreme weather events caused by climate change they are dealing with the growing problem of soil degradation,” says Debjani Sihi, first author of the study and assistant professor in Emory University’s Department of Environmental Sciences

Sihi is a biogeochemist who studies environmental and sustainability issues at the nexus of soil, climate, health and policy. 

Globally, according to Sihi and her co-authors, 750 million people were undernourished in 2019 due to the effects of climate change, including a decline in food production, hikes in food prices and increased competition for land and water. And the problem of global food security is expected to intensify. World crop yields are projected to decrease by 25% overall within the next 25 years due to climate change, and yet global food production would need to double by 2050 to feed the projected growth in human population. 

How soil impacts climate 

“Keeping soil healthy is a key component needed to adapt to the climate crisis,” Sihi says. Healthy soil contains microbes that provide the nutrients needed for healthy plants to grow, she explains, while also helping make the plant foods that we eat more nutritious. 

The presence of these microbes also improves the ability of soil to sequester carbon. The top 30 centimeters of the world’s soil contains about twice as much carbon as the entire atmosphere, making soil the second-largest natural carbon sink after oceans, according to the United Nations’ Food and Agriculture Organization. 

The rise in average temperatures, however, is contributing to declines in soil moisture in some areas, which can impact crop production while also degrading the soil over the long term. 

For the current paper, the researchers sought to quantify the long-term impact of climate and soil properties on yields of corn, soybeans, cotton and wheat across the mainland United States. They drew on county-level data of the U.S. Department of Agriculture from 1981 to 2015. Their dataset contained precipitation rates and accumulation of average daily temperatures over a crop’s growing season, known as growing-degree days. The data also factored in soil variations, including water-holding capacity, organic matter texture (the percentage of sand, silt and clay), pH, slope, erodibility and soil-loss tolerance. 

How farmers can adapt 

The researchers used an explainable machine-learning approach to evaluate the impact on crop yields of each of these climate and soil variables. The results singled out growing-degree days as the most important climatic factor and water holding capacity as the most influential soil property for crop-yield variability. 

“The take-home message,” Sihi says, “is that farmers in regions facing added heat stress for their crops may want to proactively focus on the water-holding capacity of their soil.” 

Clay soil and soil rich in organic material holds water better than sandy soil, she explains. So farms with sandy soil, or with soils containing less organic material, may want to add more amendments to improve the water-holding capacity of the land. Another possible adaptation is to use more mulch to reduce evaporation. 

The researchers hope that their findings will help farmers, land-management specialists and policy makers in decision-making related to sustainable and long-term soil-, water- and crop- management practices. 

Co-authors of the study include Kanad Basu and Abraham Peedikayil Kuruvila from the University of Texas at Dallas; Biswanath Dari from North Carolina Agricultural and Technical State University and Gaurav Jha from Montana State University. 

Funding for the work was provided by Emory University, North Carolina Agricultural and Technical State University and Montana State University. 

Related:

Climate change on course to hit U.S. corn belt especially hard 

Paint color-matcher quantifies iron levels in soil

Diverse landcover boosts yields for major U.S. crops, study finds

Tuesday, May 24, 2022

Climate change on course to hit U.S. Corn Belt especially hard, study finds

"It's important to begin thinking about how to transition out of our current damaging monoculture paradigm toward systems that are environmentally sustainable, economically viable for farmers and climate-smart," says Emily Burchfield, assistant professor in Emory's Department of Environmental Sciences.

By Carol Clark

Climate change will make the U.S. Corn Belt unsuitable for cultivating corn by 2100 without major technological advances in agricultural practices, an Emory University study finds. 

Environmental Research Letters published the research, which adds to the evidence that significant agricultural adaptation will be necessary and inevitable in the Central and Eastern United States. It is critical that this adaptation includes diversification beyond the major commodity crops that now make up the bulk of U.S. agriculture, says Emily Burchfield, author of the study and assistant professor in Emory’s Department of Environmental Sciences. 

“Climate change is happening, and it will continue to shift U.S. cultivation geographies strongly north,” Burchfield says. “It’s not enough to simply depend on technological innovations to save the day. Now is the time to envision big shifts in what and how we grow our food to create more sustainable and resilient forms of agriculture.” 

Burchfield’s research combines spatial-temporal social and environmental data to understand the future of food security in the United States, including the consequences of a changing climate. 

More than two-thirds of the land in the U.S. mainland is currently devoted to growing food, fuel or fiber. And about 80 percent of these agricultural lands are cultivated with just five commodity crops: Corn, soy, wheat, hay and alfalfa. Previous research based on biophysical data has established that climate change will adversely affect the yields of these crops. 

Building predictive models

For the current paper, Burchfield wanted to investigate the potential impacts of climate change on cultivation geographies. She focused on the six major U.S. crops that cover 80 percent of cultivated land in the United States: Alfalfa, corn, cotton, hay, soy and wheat. She drew from historical land-use data classifying where these crops are grown and publicly available data from the U.S. Department of Agriculture, the U.S. Geographical Survey, the WorldClim Project, the Harmonized World Soil Database and other public sources. 

Using these data, she built models to predict where each crop has been grown during the 20 years spanning 2008 to 2019. She first ran models using only climate and soil data. These models accurately predicted — by between 85 and 95 percent — of where these major crops are currently cultivated. 

Burchfield ran a second set of models that incorporated indicators of human interventions — such as input use and crop insurance — that alter biophysical conditions to support cultivation. These models performed even better and highlighted the ways in which agricultural interventions expand and amplify the cultivation geographies supported only by climate and soil. 

Burchfield then used these historical models to project biophysically driven shifts in cultivation to 2100 under low-, moderate- and high-emission scenarios. The results suggest that even under moderate-emission scenarios, the cultivation geographies of corn, soy, alfalfa and wheat will all shift strongly north, with the Corn Belt of the upper Midwest becoming unsuitable to the cultivation of corn by 2100. More severe emissions scenarios exacerbate these changes. 

“These projections may be pessimistic because they don’t account for all of the ways that technology may help farmers adapt and rise to the challenge,” Burchfield concedes. She notes that heavy investment is already going into studying the genetic modification of corn and soy plants to help them adapt to climate change. 

“But relying on technology alone is a really risky way to approach the problem,” Burchfield adds. “If we continue to push against biophysical realities, we will eventually reach ecological collapse.” 

The need for diverse landscapes

She stresses the need for U.S. agricultural systems to diversify beyond the major commodity crops, most of which are processed into animal feed. 

“One of the basic laws of ecology is that more diverse ecosystems are more resilient,” Burchfield says. “A landscape covered with a single plant is a fragile, brittle landscape. And there is also growing evidence that more diverse agricultural landscapes are more productive.” 

U.S. agricultural systems incentivize “monoculture farming” of a handful of commodity crops, largely through crop insurance and government subsidies. These systems take an enormous toll on the environment, Burchfield says, while also supporting a meat-heavy U.S. diet that is not conducive to human health. 

“We need to switch from incentivizing intensive cultivation of five or six crops to supporting farmers’ ability to experiment and adopt the crops that work best in their particular landscape,” she says. “It’s important to begin thinking about how to transition out of our current damaging monoculture paradigm toward systems that are environmentally sustainable, economically viable for farmers and climate-smart.” 

Burchfield plans to expand the modeling in the current paper by integrating interviews with agricultural policy experts, agricultural extension agents and famers. “I’d especially like to better understand what a diverse range of farmers in different parts of the country envision for their operations over the long term, and any obstacles that they feel are preventing them from getting there,” she says. 

Related:

Data-driven study digs into the state of U.S. farm livelihoods

Diverse landcover boosts yields for major U.S. crops, study finds 

Monday, May 23, 2022

Paint color-matcher quantifies iron levels in soil

Debjani Sihi, right, demonstrates using the Nix Pro to measure iron content in soil with colleagues Gaurav Jha (left) and Biswanath Dari. Iron is a vital micronutrient to grow plants and "a fundamental mineral species that dictates many other soil functions, like carbon storage, greenhouse gas emissions and nitrogen and phosphorous recycling," says Sihi, a biogeochemist in Emory's Department of Environmental Sciences.  (Photo by Aneesh Chandel)
 

By Carol Clark

A handheld color-sensing tool, commonly used to match paint shades, is also effective at quantifying the iron content in soil by analyzing its color, a study finds. Agricultural & Environmental Letters published the research showing that the inexpensive color sensor, known as the Nix Pro, can rapidly and accurately quantify soil iron. 

“We found that the Nix Pro is easy to use in the field on soil samples and can give an accurate estimate for iron content within seconds using a technique that we developed,” says Debjani Sihi, corresponding author of the paper and assistant professor in Emory’s Department of Environmental Sciences. “We think that this device holds the potential to become a really handy, cost-effective tool for farmers.” 

Gaurav Jha, who did the work as a post-doctoral researcher at the University of California, Davis, is first author of the study. 

Iron is a vital micronutrient, explain Sihi, a biogeochemist who studies environmental and sustainability issues at the nexus of soil, climate, health and policy. Just as people need iron to make a protein in red blood cells that carries oxygen through the body, plants need iron to move oxygen through their systems and produce the chlorophyll that makes them a healthy, green color. 

Soil iron levels are also a key factor in climate change. “It’s a fundamental mineral species that dictates many other soil functions, like carbon storage, greenhouse gas emissions and nitrogen and phosphorus cycling,” Sihi says. 

And yet, iron is often deficient in soil, especially in agricultural lands. “If a farmer knows that their soil does not contain the right amount of iron for their crops, they can amend the soil before planting,” she says. 

Problems with testing for soil iron 

The problem farmers face is that determining iron content in soil is expensive and/or time consuming. One method is to gather soil samples from across a landscape. The samples are then sent to a laboratory for analyses via a benchtop atomic-absorption spectrometer or inductively coupled plasma. Laboratory analysis yields a precise percentage of iron content for each sample but it can be costly and often requires weeks to learn a result. 

A thick book of soil color samples, known as the Munsell charts, provides an alternative. Comparing the color of a soil sample with the swatches on the Munsell charts can guide an effort to classify the soil color. The downside to this method is that it requires practice, it is labor-intensive and the data is qualitative and imprecise. 

During a coffee break chat among Sihi, Jha and co-author Biswanath Dari, from North Carolina Agricultural and Technical State University, the idea came up of trying the Nix Pro’s color sensing on soil. 

The Nix Pro is a palm-sized light-emitting spectrometer that measures the reflectance of a surface to quantify its color composition. It’s commonly used by paint stores, printing shops and graphic design firms for color matching. A Nix Pro costs just $349 and is easy to use, with a cell phone app providing a near-instantaneous result for a sample. 

The Nix Pro soil sensor, center, is a handheld device that is more automated and user-friendly for measuring soil iron content than a book of color samples known as the Munsell charts. (Photo by Gaurav Jha)

“The color of soil can tell you a lot of stories about an environment,” Sihi says. 

Dark brown soil contains a lot of organic material while whitish soil indicates that most of the organic material has washed away. Dark red soil, including Georgia’s famous red clay, indicates strong iron-oxide content. 

If researchers want to learn about the water table in red clay soil, they can look at the colors in a cross-section of the ground. Past flooding will turn some of the soil layers from red to a grayish color because the water has washed out much of the iron. Tree roots from the past will appear as orange patches. “The orange color indicates where the tree roots borrowed oxygen from the surrounding air and oxidized the iron,” Sihi says. 

Sihi studies redox reactions involving electron receptors like oxygen and iron, which can reveal such hidden stories in an environment. Ferrous oxide, for instance, is known as iron 2 due to the number of electrons lost in the oxidation process. Ferric oxide, or iron 3, contains iron oxide that lost three electrons. 

Soil oscillating between periods of heavy rain to no rain undergoes fluctuating redux, or shifts in the levels of iron 2 and iron 3 as the water tables go up and down. “Fluctuating redox is a big threat multiplier for greenhouse gas emissions into the atmosphere,” Sihi says. 

‘An extremely strong result’ 

Due to the broad importance of iron, the researchers focused on iron content as the first soil test for the Nix Pro. They first collected data on soil samples from New Mexico using the Nix Pro app for three different color spaces: cyan, magenta, yellow and black; lightness and darkness; and red, green and blue. The Nix Pro app allowed them to export the data into an Excel document. 

Researchers from New Mexico State University helped calibrate and validate the three color models generated by the Nix Pro data by comparing them with results for total iron content generated through analysis in a NMSU laboratory. The results showed that all three of the models were significant in predicting soil iron content, with the cyan, magenta, yellow and black model (CMYB) delivering the strongest result. 

Finally, they further validated the CMYB model by using it to estimate total iron content in soil samples from an adjacent field. The results showed that the Nix Pro CMYB model was 80 percent accurate compared to laboratory results for the same samples. 

“That’s an extremely strong result,” Sihi says. “We’re comparing the power of a small, handheld tool with a really fancy lab instrument and it’s holding up.” 

The team now plans to test the Nix Pro on soils from other regions to determine if the method will work universally as an iron soil predicter. They hope other researchers will also apply their method to speed up the data-gathering process. Sihi and her colleagues plan to further expand their project by experimenting with the Nix Pro’s possible efficacy for other agricultural applications related to soil composition. And this summer, they will conduct a greenhouse gas experiment to evaluate if the Nix Pro color sensor can be used to identify nitrogen deficiency in corn plants through the characteristic symptom of yellowing leaves. 

Additional authors of the current paper include Harpreet Kaur, April Ulery and Kevin Lombard (NMSU); and Mallika Nocco (University of California, Davis). 

Related:

Climate change on course to hit U.S. Corn Belt especially hard, study finds

Data-driven study digs into the state of U.S. farm livelihoods

The growing role of farming and nitrous oxide in climate change