'Darwinian' test uncovers an antidepressant's hidden toxicity

A University of Utah test detects hidden toxic effects by subjecting mice to competition for resources. Biology professor Wayne K. Potts and biologist Shannon M. Gaukler, who recently completed a doctoral degree at the U, stand in front of the test enclosure, illuminated in red light that mice perceive as nightfall. Credit: Andy Brimhall / University of Utah

Because of undetected toxicity problems, about a third of prescription drugs approved in the U.S. are withdrawn from the market or require added warning labels limiting their use. An exceptionally sensitive toxicity test invented at the University of Utah could make it possible to uncover more of these dangerous side effects early in pharmaceutical development so that fewer patients are given unsafe drugs.

To prove the point, the U researchers ran their test on Paxil, an antidepressant that thousands of pregnant women used in the years before it was linked to an increased risk of birth defects. The U.S. Food and Drug Administration now requires a warning about use in the first trimester of pregnancy. In the U study, mice exposed during development experienced multiple problems: males weighed less, had fewer offspring, dominated fewer territories and died at a higher rate. Females took longer to produce their first litters, had fewer pups and pups that were underweight. The drug doses were relatively close to those prescribed for people. In the conventional animal safety testing reported by the drug's manufacturer, no reproductive side effects emerged until rodents took doses multiple times higher than those given to treat depression.

"We are seeing effects at a dose that is close to human levels. And we are doing it exactly the way we need to determine if it presents a risk of harm to a developing fetus," says University of Utah biologist Shannon M. Gaukler, the study's lead author who recently completed a doctoral degree at the U. The study will be published in the January-February issue of Neurotoxicology and Teratology, which has posted a preprint online.

University of Utah biology professor Wayne K. Potts, the study's senior author, says that detecting toxicity problems early in preclinical testing would not only protect patients from exposure to unsafe drugs, but also help pharmaceutical companies avoid wasting billions of dollars bringing drugs to market only to have them fail.

"If we can find these health problems early on in preclinical testing, it has the potential of saving them a lot of money," Potts says.

Survival-of-the-fittest test

The key to the test's sensitivity is the way it uses untamed house mice -- rather than docile, inbred laboratory strains -- and subjects them to a relentless, Darwinian competition for food, shelter and mates much like they would face in the wild. Mice jostle and race for a place in a roughly 300-square-foot pen divided into six territories by wire fencing that individuals must climb to invade or flee neighboring turf. Four of the territories are prime real estate with multiple hidden nesting sites and direct access to feeders. Two territories are poor, offering only open nesting sites and indirect feeder access. The test is called the organismal performance assay, or OPA.

Potts first came up with the idea as a way to explore the impact of inbreeding. Those studies revealed harmful effects of cousin-level inbreeding that had gone unnoticed for decades of research on mouse genetics. Laboratory mice that are only slightly less healthy may not appear so when given ample food and living space. But if there is a defect in any physiological system, it is likely to stand out during intense competition.

"When they really have to compete directly, males are constantly testing each other and fighting over territories," Potts says. "If they don't win a territory, females won't consider them when it comes time to choose a mate."

In a study published last year, the performance assay revealed that doses of sugar that people regularly consume -- and deemed safe by regulators -- may in fact be toxic. When mice ate a diet of 25 percent extra sugar (the mouse equivalent of drinking three cans of soda daily) females died at twice the normal rate and males were a quarter less likely to hold territory and reproduce.

Testing Paxil

In the Paxil study, the researchers gave food laced with the antidepressant to 20 breeding pairs of mice for several weeks, until all had produced up to four litters. Doses were equivalent to about 1.8 times the level typically prescribed for people. The offspring also ate Paxil-laced chow until they reached breeding age. The researchers then released the exposed offspring into the competitive arena with the offspring of a control group of mice never exposed to Paxil. Groups consisted of eight males and 14 to 16 females, creating population densities comparable to those seen in the wild. The researchers started five such populations and kept them going for six months.

Males exposed to Paxil were about half as likely to control a territory. They also lagged behind control males in body weight throughout the weeks of competition and were more likely to die. Exposed males produced 44 percent fewer offspring. Exposed females showed no significant weight or mortality differences, but they produced half as many offspring as control females at the initial assessment. Their fecundity rebounded at later time points.

Danger signals

The test can provide an early warning of possible toxic effects, but it does not identify causal pathways. In the case of Paxil, the test might have alerted the drug's developers to the risk of birth defects when taken during pregnancy at prescribed doses, not just at the high levels used in conventional safety testing. Other selective serotonin reuptake inhibitors, or SSRIs, don't appear to pose the same level of risk as Paxil, but their safety for use during pregnancy remains unclear.

"It's unknown how Paxil causes birth defects and why Paxil has a stronger correlation with birth defects than other SSRIs," Gaukler says. "We think most of our results are driven by endocrine disruption."

Previous studies have shown that Paxil can lower the level of several reproductive hormones in female rats. In male rats, doses comparable to those prescribed for people can lower testosterone and boost estradiol. Other animal studies have shown that Paxil can lower sperm count and degrade sperm quality.

Potts says the performance assay may be even more important for identifying the toxic effects of agricultural chemicals, industrial pollutants, and other manufactured chemicals released into the environment.

"We don't really have a sensitive, broad toxicity assessment system," Potts says. "That's why these things slip through the cracks and we often don't discover harmful effects until after 10 or 20 years of epidemiology studies using the public as the experimental guinea pigs."

Source:  University of Utah

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WHACK! Study measures head blows in girls' lacrosse

Trey Crisco invited lacrosse-playing girls to the lab to measure the impact of their blows as they whacked the head of a laboratory dummy — and to evaluate the performance of protective headgear. Credit: Mike Cohea/Brown University

Lacrosse players swing hard, which is why errant stick blows are the leading cause of concussion in girls' and women's lacrosse. In a new study, researchers measured how much the worst blows accelerate the head and how much different kinds of headgear could reduce those accelerations.

Girls' and women's lacrosse is a different game from the version played by males, said Joseph Crisco, the Henry Frederick Lippitt Professor of Orthopaedic Research in the Alpert Medical School of Brown University and a researcher at Rhode Island Hospital. Females wear far less protective equipment than males do, and injuries -- especially severe head injuries -- are comparatively rare. But recently the debate about whether female players should wear headgear has gained prominence.

Coming to blows

The girls delivered peak performance averaging 60 times the acceleration of Earth's gravity (60g) when they struck the headforms with their lacrosse sticks.

"The goal of our study was to answer the question of what types of head accelerations would you see if you were hit in the head with a stick," said Crisco, who used to coach his daughters in girls lacrosse and also sits on the Sports Science and Safety Committee of US Lacrosse, the national governing body of lacrosse.

To conduct the study, published online in the Journal of Applied Biomechanics, Crisco's team asked seven female lacrosse players aged 12 to 14 to deliver at least 36 whacks each, as hard as they possibly could, to various places on two dummy headforms in the lab.

"The kinds of hits recorded were basically aggressive street fights," Crisco said. "They were really whacking at it, every shaft was broken by the end of the study, which would never happen in a game. The goal was just to give US Lacrosse and the manufacturers some baseline information on the types of accelerations they could expect to see in a worst-case scenario."

They used six different sticks, each outfitted with motion capture markers. The headforms had embedded accelerometers. In a second set of experiments the headforms donned one of four different kinds of protective headgear.

On average across 508 successful blows in the first experiment, the girls swung their sticks about 18 miles an hour, enough to complete two revolutions in less than a second. (One of Crisco's prior studies showed, perhaps not surprisingly, that high school and college players swung their sticks even faster). The peak acceleration the girls delivered to the headforms when they struck them with the shafts of their sticks averaged 60 times the acceleration of Earth's gravity (60g).

That's about three times more force than, say, football players with the kind of celebratory head butt that teammates exchange after a big play, Crisco said.

Headgear dampens blows

The second set of experiments examined what effect headgear might have on the girls' harder whacks (those with speeds around 23 miles an hour). Crisco's team measured the accelerations delivered by 20 whacks from the shaft of each volunteer's stick on both the back and the side of each headform. The headforms wore either nothing, a hard-sided men's lacrosse helmet, a rugby scrum cap, mixed martial arts headgear, or soft headgear designed for girls' and women's field hockey and lacrosse.

The average peak accelerations measured on bare headgear were 81.6g for blows to the side and 150.7g for blows to the back. The men's lacrosse helmet brought the average peak acceleration all the way down to 28.2g on the side and 23.1g on the back. The martial arts and girls lacrosse/field hockey headgear each reduced the accelerations significantly as well, but not nearly as much as the men's helmet. The rugby cap failed to reduce acceleration for blows to the side but dampened blows to the back a little better than the martial arts or lacrosse/field hockey gear.

Headgear, therefore, significantly reduced head accelerations. But Crisco cautioned against a run on headgear at the sporting goods store based on the study.

Generally research has shown that helmets do not protect against concussion -- only against skull fractures and traumatic brain injury. Indeed very little data connects accelerations to concussion risk, and individual susceptibility varies widely. Though some research hints at a figure around 100g, only the hard-sided men's helmet brought accelerations for blows to the back significantly below that figure. And in many game situations, given how little other protective equipment female players wear, Crisco said, a hard-sided helmet could easily cause more injuries that it prevents.

"It could actually make the game more aggressive," Crisco said.

Source: Brown University

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Digging for answers: Gender inequality in archeology?

Dana Bardolph.
Credit: Image courtesy of University of California - Santa Barbara

On an archaeology field trip in New Mexico as an undergraduate in 2006, Dana Bardolph noticed something that struck her as an odd gender imbalance: The professor leading the dig was a men, while the graduate assistant and all but two of the 14 undergrads were women.

"And it just got me thinking," Bardolph recalled. "Is this reflective of the profession as a whole, or is it an anomaly?"

The question stayed with her, and four years ago she decided to search for an answer. Her findings -- generated after digging through more than 4,500 peer-reviewed papers in 11 archaeology journals covering a 23-year period -- are published in a recent issue of the archaeology journal American Antiquity.

Bardolph, a Ph.D. student in UC Santa Barbara's Department of Anthropology, found that female authors are significantly and consistently underrepresented in American archaeology journals. Indeed, although the gender ratio among researchers is roughly equal, in the journals Bardolph surveyed, female authors account for slightly less than 29 percent of articles published.

"I found that there was no significant difference between any of the regions, any of the journals, so it was really a ubiquitous pattern across the study samples," Bardolph said.

The results, she and researchers familiar with the paper said, have deep implications not just for women in the field but for the direction and substance of archaeology itself. Bardolph argues, based on feminist theory, that the low rates of publication perpetuate a marginalization of female researchers in academia and demonstrate what she called "a pernicious historical bias with regards to the visibility, recognition, presentation and circulation of women's writing."

Bardolph's adviser, Amber VanDerwarker, associate professor of anthropology and director of UCSB's Integrative Subsistence Laboratory, said the paper has the potential to catalyze a movement toward greater gender equity in publishing and academia. "It is hugely significant because there have been articles here and there that talk about this issue of gender equity in the field," she said, "and none of the studies has done this much data collection and analysis; this is the first study of this scale looking at publication rates."

Among the articles surveyed in the major journals, Bardolph found 71.4 percent were lead-authored by men and 28.6 percent by women. The regional journals revealed nearly identical numbers. In addition, the data were consistent over time.

While the data demonstrated a clear gender bias, what they didn't show is the source, said Bardolph, whose specialty is paleoethnobotany, a study of the relationship between humans and plants in the past.

The journals don't track submissions by gender, so there's no way to tell if men are being favored explicitly, she said. Other studies, however, have found that men submit papers far more often than women do, with equal rejection rates among the genders.

Based on her research, Bardolph said she suspects the bias is likely a result of authorial behavior rather than editorial or reviewer bias. Women, she noted, are more likely to take on "nurturing" roles in academia and accept positions in smaller teaching colleges as opposed to large research universities with their more abundant resources.

"When you have grad students you can collaborate with, you publish more than you would if you were doing everything by yourself," VanDerwarker said. "I spent a few years at a teaching college just struggling to keep up with the publication record."

Another potential factor Bardolph noted is more subjective: braving the sometimes-brutal journal submission process. The anonymity of peer reviewers occasionally engenders harsh rejections. And archaeology, which has long been dominated by men, is no exception.

"I think it's highly plausible that the issue of rejection ¾ and whether you do decide to revise and resubmit or discard the manuscript -- has a lot to do with confidence issues," Bardolph said. "I wouldn't be surprised if that was in fact the case, that perhaps women were revising and resubmitting less often than men."

For Bardolph, getting academia to acknowledge gender bias is just one step on a long road to equality. "People aren't really realizing this sort of inequality is still pervasive," she said. "My real goal is to bring awareness to the issue and to inspire people to delve more deeply into their particular subdisciplines and continue this type of research so we can continue to explore why these inequities perpetuate and think about what we can do about them."

Source: University of California - Santa Barbara

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How culture influences violence among the Amazon's ‘fierce people'

In this mid-1960s photo, men from two Yanomamo villages in the Amazon engage in nonhostile combat to determine the strength and fighting prowess of potential alliance partners. A new study from the University of Utah and University of Missouri indicates the Yanomamo -- who engaged in killing to gain status in past decades -- often formed alliances with men in different villages when they attacked and killed people in other communities, then married their allies' sisters or daughters. The idea is they fought like a 'band of brothers-in-law' more than a closely related 'band of brothers,' fathers and sons from a single community. [show less] Credit: Napoleon Chagnon

When Yanomamö men in the Amazon raided villages and killed decades ago, they formed alliances with men in other villages rather than just with close kin like chimpanzees do. And the spoils of war came from marrying their allies' sisters and daughters, rather than taking their victims' land and women.

Those findings -- which suggest how violence and cooperation can go hand-in-hand and how culture may modify any innate tendencies toward violence -- come from a new study of the so-called "fierce people" led by provocative anthropologist Napoleon Chagnon and written by his protégé, University of Utah anthropologist Shane Macfarlan.

Macfarlan says the researchers had expected to find the Yanomamö fought like "bands of brothers" and other close male kin like fathers, sons and cousins who live in the same community and fight nearby communities. That is how fights are conducted by chimpanzees -- the only other apes besides humans that form coalitions to fight and kill.

Instead, "a more apt description might be a 'band of brothers-in-law,'" in which Yanomamö men ally with similar-age men from nearby villages to attack another village, then marry their allies' female kin, Macfarlan, Chagnon and colleagues write in the study, published this week in the journal Proceedings of the National Academy of Sciences.

The study provides a mechanism to explain why Yanomamö warriors in a 1988 Chagnon study had more wives and children than those who did not kill.

"We are showing these guys individually get benefits from engaging in killing," Macfarlan says. "They're getting long-term alliance partners -- other guys they can trust to get things done. And they are getting marriage opportunities."

Since his 1968 book "Yanomamö: The Fierce People," Chagnon has been harshly criticized by some cultural anthropologists who claim he places undue emphasis on genes and biology as underpinnings of human violence, based on his 1964-1993 visits to the Yanomamö. Defenders such as Macfarlan say Chagnon takes a much more balanced view, and that "it's never a genes-versus-culture argument. They operate in tandem."

Chagnon got what was seen as vindication in 2012 when he was elected to the National Academy of Sciences. The new study, with Macfarlan as first author and Chagnon as senior author -- is Chagnon's inaugural PNAS article as a member.

Macfarlan joined the University of Utah faculty this year an assistant professor of anthropology. He worked as Chagnon's postdoctoral fellow at the University of Missouri from January 2013 to June 2014. Chagnon and Macfarlan conducted the study with two Missouri colleagues: anthropologists Robert S. Walker and Mark V. Flinn.

Models of Warfare

The Yanomamö -- hunters and farmers who live in southern Venezuela and northern Brazil -- once gained social status as "unokai" for killing.

Up to 20 Yanomamö (pronounced yah-NO-mama, but also spelled Yanomami or Yanomama) would sneak up on another village at dawn, "shoot the first person they saw and then hightail back home," Macfarlan says. Some Yanomamö men did this once, some up to 11 times and some never killed. (Data for the study, collected in the 1980s, covered somewhat earlier times when spears, bows and arrows were the primary weapons.)

Macfarlan says the classic debate has been, "does warfare in small-scale societies like the Yanomamö resemble chimpanzee warfare?" -- a theory known as the "fraternal interest group" model, in which bands of brothers, fathers, sons and paternal uncles all living in the same community fight other similar communities.

The new study asked whether Yanomamö killing follows that model or the "strategic alliance model," which the researchers dub the "band of brothers-in-law" model. This model -- supported by the study's findings -- indicates that Yanomamö men form alliances not with close kin from the same community, but with men from other communities. After killing together, a bond is formed and they often marry each other's daughters or sisters and move into one or the other's village or form a new village.

"When we started off this project, we all assumed it would be the chimpanzee-like model. But in human groups we have cultural rules that allow us to communicate with other communities. You certainly don't see chimpanzees doing this."

Is the study a retreat from what Chagnon's critics see as too much focus on genetic and biological underpinnings of violence? Macfarlan says no, that Chagnon "has never been as all-biology as people have painted him. Most of his published research shows how unique cultural rules make the Yanomamö an interesting group of people."

Earlier research suggested that for chimps, warfare is adaptive in an evolutionary sense, and that it also benefits small-scale human societies. The new study asked, "If warfare is adaptive, in what way do the adaptive benefits flow?" Macfarlan says.

"Some people, myself included, said, to the victor goes the spoils, because if you conquer another territory, you might take their land, food or potentially their females."

But the new study indicates "the adaptive benefits are the alliances you build by perpetrating acts of warfare," he adds. "It's not that you are taking land or females from the vanquished group, but for the Yanomamö, what you acquire is that you can exchange resources with allies, such as labor and, most importantly, female marriage partners."

The study's findings that the Yanomamö form strategic alliances to kill suggest that "our ultracoooperative tendencies tend to go hand-in-hand with our ultralethal tendencies," Macfarlan says. "We show a relationship between cooperation and violence at a level unseen in other organisms." That may seem obvious for allied nations in modern wars, but "we're saying that even in small-scale societies this is the case."

How the Study was Conducted

The new study analyzed data collected by Chagnon in the 1980s, when about 25,000 Yanomamö lived in about 250 villages ranging from 25 to 400 people.
The study examined 118 Yanomamö warriors or unokai who had killed a total of 47 people by forming raiding parties of two to 15 men. The researchers analyzed the relationships between every possible pair of men in those raiding parties. Among the 118 unokai men, there were 509 possible pairs. Macfarlan says the findings revealed surprises about the relationship between co-unokai -- pairs of men who kill together:

-- Only 22 percent of men who kill together were from the same lineage.

-- Only 34 percent of co-unokai pairs were from the same place of birth. "Guys who come from different places of birth are more likely to kill together."

-- Among co-killers known to be related, a majority were related on their mother's side rather than their father's side -- more evidence of forming alliances beyond the immediate paternal kinship group. In Yanomamö culture, true kin are viewed as being on the paternal side, while maternal relatives are seen as belonging to another social group.

-- The Yanomamö preferred forming coalitions with men within a median of age difference of 8 years. "The more similar in age, the more likely they will kill multiple times," Macfarlan says.

-- Of the 118 unokai, 102 got married in a total of 223 marriages to 206 women. Of married killers, 70 percent married at least one woman from the same paternal line as an ally in killing. And "the more times they kill together, the more likely they are going to get marriage partners from each other's family line," Macfarlan says.

-- As a result, "The more times the guys kill together, the more likely they are to move into the same village later in life, despite having come from different village."

The study found allies-in-killing often are somewhere between maternal first and second cousins, Macfarlan says. Under Yanomamö rules, a man's ideal marriage partner is a maternal first cousin, who would be the offspring of your mother's brother. He says Yanomamö rules allow marriage to a maternal first cousin, but not a paternal first cousin.

Despite debate over the biological roots of deadly coalitions in chimps and humans, the new study shows how culture can make it "uniquely human" because if Yanomamö men "kill together, they are plugged into this social scene, this marriage market," Macfarlan says. "They are playing the game of their culture."

Source: University of Utah

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