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Biomedical Engineering

The Biomedical Engineering blog is the place for conversation and discussion about topics related to engineering principles of the medical field. Here, you'll find everything from discussions about emerging medical technologies to advances in medical research. The blog's owner, Chelsey H, is a graduate of Rensselaer Polytechnic Institute (RPI) with a degree in Biomedical Engineering.

Toothpaste Debunked

Posted August 30, 2014 12:00 AM by Chelsey H

Most of us can go through our morning routines without thinking. (I guess that's the point of having a routine). But as you brush away your morning breath, have you ever stopped to think about what toothpaste actually is or why we use it?

Toothpaste has a technical term - dentifrice. And modern toothpaste ingredients sound like they should be boiling in a beaker somewhere, but it shows the long way that humans have come in dental hygiene. The first toothpastes were also used to clean the teeth and gums while freshening breath and preventing decay. The ingredients consisted of powdered ashes of ox's hoof with carbonized eggshells and pumice (ew!). Combined, it created a potent abrasive capable of scrubbing teeth without the need for a toothbrush. Many counties added their own "special ingredient" too. Greeks and Romans added crushed bone and seashells, and the Chinese added ginseng, herbs, and salt.

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The tooth powder wasn't developed until the 19th century by a British inventor. It started out of homemade poultices contrived out of chalk, charcoal, brink, dust, salt, burnt bread, and cinnamon (just for good measure). Many of the early mixtures ended up being too abrasive and taking out bits of enamel in addition to plaque, but they stayed popular until WWI.

By the turn of the 20th Century, a paste-like mixture became available made with hydrogen peroxide and baking soda. Dr. Washington Sheffield invented the collapsible toothpaste tube (made out of lead) and tubed toothpaste quickly usurped tooth powders. Crest was the first American toothpaste to include fluoride after more than a decade of privately-funded research. The ADA endorses the use of fluoride saying, "Crest has been shown to be an effective anti-cavity (decay preventative) dentifrice that can be of significant value when used in a conscientiously applied program of oral hygiene and regular professional care."

While the toothpaste tube may have a laundry list of strange ingredients, all toothpastes have a common set of active ingredient classes - abrasives, fluorides, and surfactants.

· Abrasives can make up as much as half of a tube of toothpaste and they serve to scrub the enamel of plaque. This minimizes the formation of cavities and other forms of tooth decay. Aluminum hydroxide, calcium carbonate, calcium phosphate, silicas-even household baking soda-can be employed for this role.

· Fluorides act to strengthen tooth enamel and counter the formation of cavities and gingivitis. Sodium fluoride is the most commonly used and it makes up about 1000 ppm a tube.

· Surfactants are a class of detergents employed as foaming agents. The foam makes sure the toothpaste gets all over the sink and mirror - OK, it actually makes sure the other two components are evenly distributed across the entire tooth.

The rest of the stuff includes stabilizers to keep the toothpaste from drying out, antibacterial agents to kill germs that cause gingivitis, and flavorants for the minty-freshness.

Toothpaste isn't going to be going anywhere anytime soon since a 2013 study by the University of Leeds found that people with white, evenly-spaced teeth are consistently viewed as more attractive than their snaggle-toothed peers. So brush up! It will keep you healthy and may help you get a date.

Adapted from What the Heck Is Toothpaste Anyway?

32 comments; last comment on 09/04/2014
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Don't Rush to Natural Sweetners

Posted August 23, 2014 12:00 AM by Chelsey H

"I'll have the pink one." That's what my mom always says when she is making her coffee. Of course she is referring to Sweet 'N Low, one of several brands of artificial sweeteners. I have never liked the weird tangy after-taste of artificial sweeteners, which has led to me using Stevia or agave in my coffee.

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These new low-cal sweeteners are derived from natural substances but their newness on the market means they haven't been well-studied for safety. According to Barry Popkin, a professor of nutrition at the school of public health at the University of North Carolina at Chapel Hill, even though the base comes from a nature, some sweeteners may have undergone chemical processing to extract them from their original sources. This process may affect their healthfulness.

Few details about the extraction process are provided by manufacturers, but the FDA has reviewed data and considers most of them to be generally safe. And the Center for Science in Public Interest (CSPI) believes the natural sweeteners are safer than aspartame and saccharin (the chemicals found in artificial sweeteners). The exception is Nectresse, a monk fruit extract. CSPI says it has been poorly tested for safety but since it's derived from a fruit, it is probably safe.

Don't get too excited about them being low calorie. There has been very little research done about how these sweeteners affect weight loss.

"Our research shows that artificial sweeteners do appear to reduce the risk for weight gain when combined with a healthy, well-balanced diet," Popkin says. The risk for weight gain and diabetes with artificial sweeteners is because they may interfere with the physiological responses that help regulate body weight and control sugar.

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When we taste something sweet, our bodies expect actual calories to hit our stomachs and we release insulin to prepare. But in the absence of actual calories, the insulin and other hormones cause your blood sugar to plunge and make you crave more sweets (i.e. overeat).

Experts think natural low-calorie sweeteners will have the same effect since the sweetness will jump-start the chain reaction. They may not be the best tool for weight management.

There is one tip - the overeating effect can be countered if you consume food that contains fiber. The fiber keeps insulin levels steady so blood sugar doesn't plunge.

33 comments; last comment on 09/02/2014
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Why Do People Get Goosebumps?

Posted July 27, 2014 3:44 PM by Chelsey H

Goosebumps, goosepimples, goose flesh…there are many words for the little bumps that form on your skin and many reasons why they form. Medically, they are called cutis anserine and they are a physiological phenomenon that has evolutionary significance. It was useful to our ancestors, but it's not much help to us.

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Speaking of ancestors, no one is 100% sure why they are called goosebumps. Many assume it's because when plucked, a goose leaves a bumpy flesh behind, but so do most birds. Additionally, numerous languages use the bird to describe the bumps; it's a mystery as to why goose is used in German, Italian, Russian, Polish and many other languages.

Goosebumps are caused by a contraction of miniature muscles called arrector pili muscles that are attached to each hair. The reflex of producing goose bumps is known as arasing, piloerection, or the pilomotor reflex. The contraction creates a shallow depression on the skin surface, causing the surrounding area to protrude (bump). The same contraction also causes the hair to stand up whenever the body feels cold. This adaption is useful for animals with thick hair. The rising hair expands the layer of air that serves as insulation to retain more heat. During the formation of goosebumps, the body is warmed from the muscle's tension in piloprection. In people this reaction is useless because we (well most of us) don't have a hair coat.

Goosebumps also signify an emotional response. For animals, the expanded hair makes them appear bigger when threatened in an attempt to scare off the threatening animal. People get goosebumps during emotional situations such as watching horror movies, listening to a song that brings back memories, or events such as winning in sports. This reaction is caused by a release of the stress hormone adrenaline. Adrenaline causes the contraction of skin muscles as well as tears, sweaty palms, racing heart, and trembling hands. Check out the video for more info.

In more recent news, a goosebump detector is being developed that could track such hair-raising moments in life. This could be used to detect a person's reaction to a new movie or online advertisement. It's made using a conductive polymer and a type of flexible silicon that is also biocompatible to create a postage stamp-sized sensor that could help monitor the physical and emotional states of consumers in real time. Not the noblest use of goosebumps, but it has potential.

So when a beautiful piece of music gives you chills or makes your hair stand on end, know that it's just your body's way of saying that something awesome is happening.

9 comments; last comment on 07/31/2014
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Brain Games

Posted July 26, 2014 12:00 AM by Chelsey H

I may be late to the party (or late to getting cable) but last weekend I discovered one of the most entertaining and mind-blowing shows I've seen in a long time. Brain Games on The National Geographic Channel is a 30 minute workout for your brain.

Image Credit: Natgeotv

Hosted by Jason Silva (who is very cool and I'll talk about soon), the Emmy-nominated series gets inside your head and shows you the inner-workings of your brain. Every episode has a theme which prompts interactive experiments designed to mess with your mind and show you what's really going on.

The show uses experts in cognitive science, neuroscience, and psychology. Apollo Robbins, a deception specialist (aka pick-pocket extraordinaire) helps carry out some of the experiments to prove that what the brain thinks it sees and what is actually there can be very different.

Jason Silva, has a poetic, impassioned, and inspirational take on scientific and technological advancements. Silva has been featured in CBS News, The Atlantic, The Economist, Vanity Fair, Forbes, Wired,, IO9, Huffington Post, BigThink, and BrainPickings, just to name a few. Silva was also featured as part of the Gap "Icons" campaign. More of his videos, and those from before Brain Games, can be found here.

The show's website is full of articles and video clips which support the science and lessons in each episode such as, How to Have a Winning Brain and How to Improve Your Sense of Direction. It also has some very entertaining games that test your brain.

What is your favorite educational show? Did Brain Games trip you up?

3 comments; last comment on 07/26/2014
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The Deal with DEET

Posted July 05, 2014 12:00 AM by Chelsey H

One of the worst things about summertime is the increase in mosquitos and other biting, buzzing, and annoying insects. Image Credit

Many of us turn to insect repellent sprays, candles, or lotions to keep the bugs from making us their dinners, but do you know if those products are safe? DEET, a popular insect repellent, is used by an estimated 30 percent of Americans every year, and researchers estimate people around the world put on DEET 200 million times a year.

DEET (N,N-diethyl-meta-toluamide) has been sold to US consumers since the 1950s and was originally developed by the US Army. Here is a great video about DEET.

The Good

DEET has been the focus of dozens of studies, all of which show the product is generally safe and, contrary to many internet reports, does not cause nervous system damage and very rarely causes skin reactions. One study followed women in Thailand who used DEET during pregnancy and found that, not only did the women have less incidences of malaria, but the babies born were healthy and of the same weight, length, and head circumference as babies born to women not using DEET.

British experts say more harm occurs when people use too little DEET and put themselves at risk of harmful insect-borne diseases.

The Bad

As with any chemical there are risks. In concentrations of 50 percent and above (which does not act as a better repellent) DEET has been shown to cause allergic skin reactions and eye irritation. In 2013, 4,000 DEET-related calls were made to poison control centers. Most serious symptoms, such as seizures, slurred speech, coma, and death, occurred in people who ingested DEET, applied it for three or more days in a row, or used products with 95 percent DEET or more.

To Sum It Up

Doctors in countries where people are at a greater risk of insect-borne diseases, such as malaria or West Nile virus, recommend using DEET in concentrations between 20 and 50 percent. They also recommend that in children, seniors, and those with weakened immunity use extra caution when handling DEET.

And there are plenty of ways to avoid mosquitos while also avoiding DEET.

- When you're sitting on a deck or patio, plug in a fan to blow away mosquitoes.

- If you need a repellent, first try plant-based products. If you opt for DEET, use products with appropriate concentrations, such as Off Family-Care Smooth & Dry spray.

- Don't drink as much beer (outside)

What's your solution to keeping the bugs away?

14 comments; last comment on 07/31/2014
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Genome Editing

Posted May 31, 2014 12:00 AM by Chelsey H

Genome editing could provide a powerful new way to study complex brain disorders. The breakthrough use of a genome-tool to create two monkeys with specific genetic mutations demonstrates that the ability to modify targeted genes in primates is a valuable tool in the study of human diseases.

This breakthrough took place last November in Kunming, the capital of China's southwestern Yunnan province. Scientists used a new method of DNA engineering known as CRISPR, to modify fertilized macaque monkey eggs by editing three different genes. The eggs were then implanted into a surrogate macaque mother. Twin females were born in the Yunnan Key Laboratory of Primate Biomedical Research and it was the first time that CRISPR has been used to target genetic modification in primates.

Credits: illustrations by John Macneill

CRISPR was originally developed by researchers in California and Boston over the last several years. It is a breakthrough technology because it allows scientists to make changes to the genome precisely and relatively easily. "The idea that we can modify primates easily with this technology is powerful," says Jennifer Doudna, a professor of molecular and cell biology at the University of California, Berkeley, and a developer of CRISPR.

This breakthrough could lead to powerful new ways to study complex human diseases; however is also poses new ethical dilemmas since the technology could ultimately alter fertilized human eggs to create genetically modified babies (aka "designer babies").

This thought is far removed from the minds of scientists working on CRISPR. They see the potential opportunities to create animals with mutations linked to human disorders, including brain disorders. Many brain disorders, such as autism, schizophrenia, and Alzheimer's disease, are difficult to study in mice. Often times, the psychiatric drugs that appear to work well in mice have not proved successful in human trails and many pharmaceutical companies have scaled back efforts to develop treatments. Therefore, using primates as models for such diseases could be helpful to researchers as a way to identify mutations.

Weizhi Ji, who helped lead the effort -, says the Chinese researchers responsible for the birth of the genetically engineered monkeys are still focusing on developing the technology. He goes on to say that considering the dangers, there would be a long way to go before creating humans with CRISPR-edited genomes is possible. Right now, they hope to use the technology to create "efficient animal models for human diseases to improve human health in the future."

Genome Editing

This story is part of a series of 10 Breakthrough Technologies 2014 on MIT Technology Review.

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