Scientists Use a CT Scanner to Give Whales a Hearing Test

Ted Cranford
Ted Cranford

It's hard to study how whales hear. You can't just give the largest animals in the world a standard hearing test. But it's important to know, because noise pollution is a huge problem underwater. Loud sounds generated by human activity like shipping and drilling now permeate the ocean, subjecting animals like whales and dolphins to an unnatural din that interferes with their ability to sense and communicate.

New research presented at the 2018 Experimental Biology meeting in San Diego, California suggests that the answer lies in a CT scanner designed to image rockets. Scientists in San Diego recently used a CT scanner to scan an entire minke whale, allowing them to model how it and other whales hear.

Many whales rely on their hearing more than any other sense. Whales use sonar to detect the environment around them. Sound travels fast underwater and can carry across long distances, and it allows whales to sense both predators and potential prey over the vast territories these animals inhabit. It’s key to communicating with other whales, too.

A CT scan of two halves of a dead whale
Ted Cranford, San Diego State University

Human technology, meanwhile, has made the ocean a noisy place. The propellers and engines of commercial ships create chronic, low-frequency noise that’s within the hearing range of many marine species, including baleen whales like the minke. The oil and gas industry is a major contributor, not only because of offshore drilling, but due to seismic testing for potential drilling sites, which involves blasting air at the ocean floor and measuring the (loud) sound that comes back. Military sonar operations can also have a profound impact; so much so that several years ago, environmental groups filed lawsuits against the U.S. Navy over its sonar testing off the coasts of California and Hawaii. (The environmentalists won, but the new rules may not be much better.)

Using the CT scans and computer modeling, San Diego State University biologist Ted Cranford predicted the ranges of audible sounds for the fin whale and the minke. To do so, he and his team scanned the body of an 11-foot-long minke whale calf (euthanized after being stranded on a Maryland beach in 2012 and preserved) with a CT scanner built to detect flaws in solid-fuel rocket engines. Cranford and his colleague Peter Krysl had previously used the same technique to scan the heads of a Cuvier’s beaked whale and a sperm whale to generate computer simulations of their auditory systems [PDF].

To save time scanning the minke calf, Cranford and the team ended up cutting the whale in half and scanning both parts. Then they digitally reconstructed it for the purposes of the model.

The scans, which assessed tissue density and elasticity, helped them visualize how sound waves vibrate through the skull and soft tissue of a whale’s head. According to models created with that data, minke whales’ hearing is sensitive to a larger range of sound frequencies than previously thought. The whales are sensitive to higher frequencies beyond those of each other’s vocalizations, leading the researchers to believe that they may be trying to hear the higher-frequency sounds of orcas, one of their main predators. (Toothed whales and dolphins communicate at higher frequencies than baleen whales do.)

Knowing the exact frequencies whales can hear is an important part of figuring out just how much human-created noise pollution affects them. By some estimates, according to Cranford, the low-frequency noise underwater created by human activity has doubled every 10 years for the past half-century. "Understanding how various marine vertebrates receive and process low-frequency sound is crucial for assessing the potential impacts" of that noise, he said in a press statement.

How to Relieve a Tension Headache in 10 Seconds, According to a Physical Therapist

iStock.com/SIphotography
iStock.com/SIphotography

The source of a pounding headache isn't always straightforward. Sometimes over-the-counter painkillers have no effect, and in other cases all you need is a glass of water to ease the pain. When it comes to a specific type of a headache, Prevention recommends a treatment that takes about 10 seconds—no fancy medications or equipment required.

If you're experiencing pain throughout your head and neck, you may have a tension headache. This type of headache can happen when you tense the muscles in your jaw—something many people do when stressed. This tightening triggers a chain reaction where the surrounding muscles in the head and neck become tense, which results in a painful, stiff feeling.

Fortunately, there's a way to treat tension headaches that's even easier than popping an Advil. David Reavy, a physical therapist known for his work with NFL and NBA athletes, recently suggested a solution to Prevention writer Christine Mattheis called the masseter release. To practice it yourself, look for the masseter muscle—the thick tissue that connects your jawbone to your cheekbone on either side of your face—with your fingers. Once you've found them, press the spots gently, open your mouth as wide as you can, close it, and repeat until you feel the muscle relax. Doing this a few times a day helps combat whatever tension is caused by clenching your jaw.

If that doesn't work, it's possible that the masseter muscle isn't the source of your headache after all. In that case, read up on the differences among popular pain killers to determine which one is the best match for your pain.

[h/t Prevention]

Why Do Hangovers Get Worse As You Get Older?

iStock/OcusFocus
iStock/OcusFocus

“I just can’t drink like I used to” is a common refrain among people pushing 30 and beyond. This is roughly the age when it starts getting harder to bounce back from a night of partying, and unfortunately, it keeps getting harder from there on out.

Even if you were the keg flip king or queen in college, consuming the same amount of beer at 29 that you consumed at 21 will likely have you guzzling Gatorade in bed the next day. It’s true that hangovers tend to worsen with age, and it’s not just because you have a lower alcohol tolerance from going out less. Age affects your body in various ways, and the way you process alcohol is one of them.

Because your body interprets alcohol as poison, your liver steps in to convert it into different chemicals that are easier to break down and eliminate from your body. As you get older, though, your liver produces less of the enzymes and antioxidants that help metabolize alcohol, according to a study from South Korea. One of these enzymes—called alcohol dehydrogenase (ADH)— has been called the “primary defense” against alcohol. It kicks off the multi-step process of alcohol metabolization by turning the beer or booze—or whatever you imbibed—into a chemical compound called acetaldehyde. Ironically, this substance is even more toxic than your tipple of choice, and a build-up of acetaldehyde can cause nausea, palpitations, and face flushing. It usually isn’t left in this state for long, though.

Another enzyme called aldehyde dehydrogenase (ALDH) helps convert the bad toxin into a new substance called acetate, which is a little like vinegar. Lastly, it’s converted into carbon dioxide or water and expelled from your body. You’ve probably heard the one-drink-per-hour recommendation, which is roughly how long it takes for your liver to complete this whole process.

So what does this mean for occasional drinkers whose mid-20s have come and gone? To summarize: As your liver enzymes diminish with age, your body becomes less efficient at metabolizing alcohol. The alcohol lingers longer in your body, leading to prolonged hangover symptoms like headaches and nausea.

This phenomenon can also partly be explained by the fact that our bodies tend to lose muscle and water over time. People with more body fat don’t break down alcohol as well, and less water in your body means that the booze stays concentrated in your system longer, The Cut reports. This is one of the reasons why women, who tend to have a higher body fat percentage than men, often suffer worse hangovers than their male counterparts. (Additionally, women have fewer ADH enzymes.)

More depressingly, as you get older, your immune system deteriorates through a process called immunosenescence. This means that recovering from anything—hangovers included—is more challenging with age. "When we get older, our whole recovery process for everything we do is harder, longer, and slower," gastroenterologist Mark Welton told Men’s Health.

This may seem like a buzzkill, but we're not telling you to put down the pint. However, if you're going to drink, just be aware of your body’s limitations. Shots of cotton candy-flavored vodka were a bad idea in college, and they’re an especially bad idea now. Trust us.

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