Explosions can tear apart buildings, send shrapnel flying, and hurtle humans into the air. But explosions also cause damage in ways that aren’t as visually apparent. Scientists say the force of a blast can cause brain damage, but questions linger about how the symptoms that emerge after a blast-induced traumatic brain injury are connected to the initial trauma.
In their quest to learn more about how symptoms emerge after a traumatic blast, researchers at the Ludwig-Maximilians University of Munich, in Munich, Germany have developed an animal model of blast-related mild traumatic brain injury (br-mTBI) using C. elegans – a popular model organism alternative to vertebrate animals.
In their study, published in Frontiers in Behavioral Neuroscience, the research team used WormLab to analyze thousands of worms. They found that shockwaves either slowed the worms’ movements or rendered them paralyzed. Symptoms played out in a dose-dependent manner, meaning that worms exposed to a higher number of shockwaves displayed a higher severity of symptoms.
To create their model, the scientists set up a system where C. elegans contained in a liquid medium were exposed to shock waves from a therapeutic shock wave device. These shock waves share characteristics with the types of shock waves that might induce mTBI in humans – the types of shock waves soldiers experience in war zones.
Each sample of worms was exposed to a certain number of shock waves ranging from zero to 500, then transferred to agar plates for analysis with WormLab, MBF Bioscience’s system for imaging, tracking, and analyzing C. elegans. Using a dissecting microscope equipped with a digital camera and WormLab’s built-in video capture function, the researchers captured a series of one-minute videos of the worms in motion. By analyzing these videos with WormLab, the scientists were able to calculate each worm’s average speed, and count the number of paralyzed worms.
“Given the high variability in C. elegans behavior we observed, generating a large sample size was crucial to our study,” said first author Nicholas Angstman. “WormLab made this easy, allowing us to capture hundreds of videos and generate useful behavioral data on thousands of worms in the quick manner we needed.”
When mTBI occurs from the shock waves of a blast (as opposed to a blunt force injury sustained from impact from other objects because of the blast), there are two parts of the blast that could cause injury – the high positive pressure from the first part of the blast wave, and the cavitation that occurs as a result of the vacuum that forms from the initial force of the blast.
Since cavitation is thought to be a substantial factor in blast-induced mTBI, the researchers set up an experimental group of C. elegans in polyvinyl alcohol – a liquid solution known to reduce cavitation. This allowed them to study the effects of a blast on C. elegans in the absence of cavitation.
What they saw was that these worms, though slowed, demonstrated a higher average speed than the control worms, which were exposed to shock waves in the liquid medium in which they were bred, as well as a decreased amount of paralyzed worms compared to controls. These observations led the researchers to conclude that while cavitation contributes significantly to the damaging effects of shock waves on C. elegans, primary blast waves are also injurious.
The scientists also observed that worms exposed to the same conditions displayed a large variability between individuals. They also saw that worms were able to recover from paralysis and reduced speed after a certain amount of time.
“The possibility to investigate br-mTBI at a simple, high-throughput level makes C. elegans a useful model organism in the attempt to connect the bridge between cause and effect in br-mTBI.,” the authors say in their paper.
Angstman, N., Kiessling, M., Frank, H.G., and Schmitz, C. (2015) High interindividual variability in dose-dependent reduction in speed of movement after exposing C. elegans to shock waves. Front Behav Neurosci. 2015; 9: 12. doi: 10.3389/fnbeh.2015.00012