Laundering your nanoparticle-coated socks: dangerous to fish?

ResearchBlogging.orgYour expensive new workout socks may be toxic—at least, if you are a tiny fish* downstream from the washing machines used to wash those socks! Researchers from Purdue University found that the silver nanoparticles added to socks to prevent bacterial growth (and resulting stink) leach out of the socks when washed. Disturbingly, this wash water killed the embryos of zebrafish, a small freshwater fish commonly used in experiments. Even when the researchers diluted the wash water, the surviving zebrafish developed abnormalities like curved spines and fluid around their hearts. But were the fish being poisoned by the nanoparticles—or by silver leached from the nanoparticles? To finger the culprit, the researchers tried growing the zebrafish embryos in the wash water; in wash water from which they’d removed the nanoparticles; and in water with dissolved silver but no nanoparticles. Even when the nanoparticles were removed from the wash water, it still killed the zebrafish embryos and caused deformities in the survivors. Surprisingly, the water with just dissolved silver didn’t cause deformities. While the researchers claimed that the nanoparticles and silver were likely innocent of poisoning the zebrafish—that another chemical leached from the socks is guilty—I’m not convinced.  I would need to see what happens to zebrafish grown in fresh water with just silver nanoparticles. If the zebrafish grow up healthy, then I’d agree with their conclusions about the culprit. If not, I’d be more suspicious of the silver nanoparticles—and I would wonder if the researchers did a thorough job at removing the nanoparticles from the wash water in their experiments! However, I do agree with the researchers about this conclusion: we need for more studies of wash water toxicity to determine its effects on wild fish and animals—effects which may already be happening, given that over 400 consumer products (and not all of them socks!) contain silver nanoparticles.

* A tiny fish owning a pair of silver nanoparticle-coated socks, that is.


Citation: Gao J, Sepúlveda MS, Klinkhamer C, Wei A, Gao Y, & Mahapatra CT (2014). Nanosilver-coated socks and their toxicity to zebrafish (Danio rerio) embryos. Chemosphere, 119C, 948-952 PMID: 25303653

How to make xkcd-style plots in R

The webcomic xkcd hits a lot of sweet notes for me, from comedic science communication with Up Goer Five to the importance of labeling your axes.  Fortunately, we live in an age where it is now possible to make xkcd-style plots in R:

fuelefficiencyxkcdWith help from andrew and fibosworld’s posts on R-bloggers, here’s how I did it in Windows:

First, I installed the xkcd font from this site.

Second, in R, I installed and loaded the packages ggplot2 and xkcd.

# Ensuring packages ggplot2 and xkcd installed and loaded

Third, I checked that the xkcd font was indeed listed in my system fonts, and imported it into R.  Because I’m using Windows, I also had to load my fonts to the Windows device, so that I could display it graphically.

# Checking xkcd.tff listed among system fonts

# Importing the xkcd font into R and confirming it should be imported
font_import(pattern = "[X/x]kcd")

# Loading fonts to the Windows device to display graphs on-screen
loadfonts(device = "win")

Finally, I was able to use xkcd-style font and axes to make the plot above!

# Using R's built-in dataset, mtcars, to plot car weight vs. mpg
carPlot geom_point() +
ggtitle("Fuel Efficiency of Cars") +
xlab("Car Weight in Thousands of Pounds") +
ylab("Miles per Gallon") +
xkcdaxis(xrange = range(mtcars$wt), yrange = range(mtcars$mpg)) +
theme(text = element_text(size = 20, family = "xkcd"))

# Plotting, xkcd-style!

Lead and Alzheimer’s disease: a dangerous combination

Health vs Alzheimers brain

Alzheimer’s disease (AD) causes memory loss and dementia as the brain atrophies. Image from NIH Medline Plus.

Like my grandmother, about 5.4 million Americans suffer from Alzheimer’s disease–a terrible illness that inflicts memory loss and dementia on people as their brains accumulate microscopic plaques and tangles of protein. Despite decades of research, we still don’t know what causes most cases of Alzheimer’s. However, American and Emirati researchers are using mice to investigate a potential cause: exposure during infancy to lead, a toxic element banned from gasoline since 1995. By better understanding how lead causes the microscopic tangles of protein in mouse brains, the researchers hope to identify future drug targets for treating Alzheimer’s disease.

To investigate the link between lead and Alzheimer’s, the researchers exposed mice to lead at different life stages. Some mice consumed lead during infancy, while others drank lead-contaminated water as adults. Still others were exposed as both infants and adults.  Two years later, when the mice were elderly, the researchers compared the brains of the lead-exposed mice to others never exposed to lead. They found that the mice exposed in infancy had more of the tangled protein, tau, compared with the unexposed mice and those only exposed as adults. But there wasn’t simply more tau: a greater proportion of tau was attached to phosphate, an important chemical used by the body.

People with Alzheimer’s also have too much phosphate-covered tau–and the more phosphate-covered tau a person has, the worse their dementia. The researchers suggest that investigating how the body controls the amount of tau in the brain, and how much phosphate attaches to it, will be important for understanding Alzheimer’s and identifying new areas for drug development.

Although my grandmother died several years ago from Alzheimer’s, new research like this makes me hopeful for myself and others at risk of Alzheimer’s–and very, very glad that lead has been banned from gasoline in the United States.

Elsewhere: Misdiagnosing mummies, finding ancient stone tools in London, using built-in R functions, and darn good science writing

Who needs an osteologist? (Installment 20): Archaeologist Kristina Killgrove dissects how doctors misdiagnosed the cause of death for an Ancient Egyptian mummy.

Liquid prehistory: The Urban Prehistorian discovers old Pepsi bottles (unsurprising) and much older knapped flint tools (very surprising!) along the banks of the River Thames in London.

Using apply, sapply, lapply in R: Pete from R-bloggers reviews several built-in R functions which improve the run speed of your R code by avoiding looping.  As someone with a background in Java/C++ who loves me some loops, this is Highly Recommended.

Bound for Pluto, Carrying Memories of Triton: Dennis Overbye at the New York Times covers recent findings about the shared parentage of Pluto and Triton, one of Neptune’s moons.  Watch the video for a fantastic example of science communication done right – Overbye uses the most marvelous analogies (“cantaloupe surface” and “egg-shaped orbit”) to effectively describe Pluto and Triton.

Unintended consequences: Arsenic, iron, and your gut bacteria


Francesco de Medici, a possible victim of arsenic poisoning, may have something in common with the human gut microbiome.  Image via Wikipedia.

Arsenic—the infamous “king of poisons” used by the murderous Borgias—can poison humans and bacteria alike.  But it doesn’t just poison bad bacteria–arsenic hurts the helpful bacteria that make up our gut microbiome, which protects us from E. coli and helps digest our food.  Even worse, the microbiome may be harmed by a common method of mixing iron into water to remove the arsenic.  Chinese researchers reported recently that mice which consumed arsenic-contaminated water with iron had healthier intestines than mice which drank only the water without iron.  However, the healthier mice still had unhealthy microbiomes.  Their gut bacteria had evolved methods for protecting themselves against the toxic metals—methods, unfortunately, which also protected them against antibiotics.  The researchers cautioned that people drinking iron-treated water to avoid arsenic poisoning may develop antibiotic-resistant bacteria, making them vulnerable to dangerous infections.

What pregnant rats can tell us about polycystic ovary syndrome

Rat photograph

Rats like these are helping researchers understand polycystic ovary syndrome. Image courtesy of Jason Snyder via Wikipedia.

A diabetes drug and popular health supplement, taken together, may improve the health of women with a common gynecological disorder.  Polycystic ovary syndrome affects one in fifty American women, and can damage a woman’s ovaries and liver.  However, Brazilian researchers reported earlier this year that pregnant rats had healthier livers when given metformin, a diabetes drug, along with melatonin, an over-the-counter supplement.  This study may aide research into treating pregnant women with liver damage, thereby improving the health of both women and babies.

To test the drugs, researchers first altered the hormone levels of female rats to mimic symptoms of polycystic ovary syndrome, such as ovarian cysts and irregular periods.  The researchers then gave metformin, melatonin, or metformin and melatonin together to the symptomatic rats.  After the rats became pregnant, researchers monitored their cholesterol levels and examined their livers for inflammation and damage.

The researchers found that both drugs together best protected the rats against liver inflammation.  Intriguingly, each drug alone restored the rats’ cholesterol to normal levels.  However, researchers would have missed the improved health of the rats treated with both drugs if they had only examined blood–indicating that pregnant women receiving only one drug may suffer from liver damage undetectable by blood tests.

Hello, hello!

Hello and welcome!  As a Ph.D. Candidate in Toxicology and freelance biomedical writer and editor, I’ll be using this blog as a platform to share my love of science and good writing.  Check back regularly for tips and tricks for better communicating science, as well as posts sharing some of the many fascinating developments in biomedical science!