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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.

Treatments for Depression, Part 2

Posted January 20, 2016 12:00 AM by Chelsey H

Stress has been discussed many times on this blog. The dangers and benefits of stress are widely discussed in the scientific community as well as in the lifestyle industry concerning productivity and behavior. In part 1, we talked about early research on mental health issues and some current treatment options for those suffering with depression.

The stress hormone cortisol cycles daily to help when we need to pay attention to what's going on around us. Many studies find that in rodents and humans a mild increase in stress is good for the brain, particularly for memory. For example, students who get stressed while studying are more alert and remember more than those who feel no urgency - up to a point. Stress becomes a problem when there is too much at one moment such as in a rape or violent attack or too sustained as in long-term poverty, neglect, or abuse.

Stress changes the brain's architecture and the effect of hormones on the brain. For example, in a case of chronic stress, neurons in the hippocampus and the prefrontal cortex (mood and impulse control) start to shrink, while those in the amygdala (fear and anxiety) expand. However, everyone has different levels of vulnerability depending on genes and prior life experience. According to Maurizio Popoli, a professor of pharmacology at University of Milan, "it is because they perceive the stress differently." Image Credit

The role of the stress hormone is to flood parts of the brain with glutamate, the brain's "go" signal. Glutamate triggers neurons to generate sudden bursts of electricity that release more glutamate, which can trigger electrical bursts in nearby neurons. This function is called excitation and is fundamental to how information is processed in the brain. It ebbs and flows, meaning there is a "refractory period" following each neural firing during which the neuron cannot be excited.

Other neurotransmitters, like serotonin, are called "modulatory," because they change the sensitivity of neurons that secrete glutamate. As Popoli puts it, these modulators are "very important for fine-tuning the machine. But the machine itself is an excitatory machine," driven by glutamate.

Stress hormones affect the glutamate system along its journey through the brain. Stress causes more glutamate to be released, then block glial cells from removing the glutamate from the synapse, and block the glutamate from reaching its destination on the other side of the synapse. All of these changes increase the amount of glutamate in the synapse, flooding the cell with aberrant signals. A depressed person's brain, or at least animal models of depression, shows that all three of these problems lead to long-lasting excess glutamate in key portions of the brain. This makes a neuron fire sooner than it should and triggers a cascade of signals inside the cell damaging its structure. An overdose of glutamate causes the neurons and their dendrites (branches of the neuron) to shrink and after a time whole branches recede.

This dangerous process, called excitotoxicity, is thought to be involved in bipolar disorder, depression, epilepsy, and neurodegenerative diseases like Alzheimer's, Huntington's, and Parkinson's. In depressed brains, many area are shrunken and underactive.

Usually the brain's ability to adapt is considered a good thing; however in the case of mental disorders the human brain's flexibility allows regeneration, but also renders it vulnerable to being altered by stress. A traumatic event or a time of homelessness could cause a person with a genetic predisposition to find his mind stuck in a loop of chronic fear or depression.

In part 3 we'll discuss how drugs can be used to modify the effect of stress.

5 comments; last comment on 01/29/2016
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Treatments for Depression, Part 1

Posted January 05, 2016 12:00 AM by Chelsey H

Did you know that nearly half of Americans are affected by some sort of mental disorder at some point in their life? Suicides, 90 percent of them among the mentally ill, take 40,000 Americans every year and since 2005, the suicide rate among U.S. war veterans has nearly doubled.

At the same time, treatment for mental disorders can be woefully ineffective. Thirty-three percent of patients don't respond to any drugs at all. And when they do work, they are slow - a dangerous risk, given the number of suicides each year.

The treatments don't work well because scientists don't really understand what they do. Serotonin, the most common target for current antidepressants, is a neurotransmitter, a chemical that carries messages in the brain. In early studies of serotonin, researchers thought a lack of serotonin was the cause for many disorders. Iproniazid was the first of a class of medicines (called monoamine oxidase inhibitors (MAOIs)) that block an enzyme from breaking down serotonin as well as dopamine and norepinephrine, two other neurotransmitters. The chief downside of these drugs is that they require a strict diet which often causes patients to not take the drug. Deviating from the diet can cause deadly spikes in blood pressure. Tricyclic antidepressants work by blocking the re-absorption of serotonin and norepinephrine but they come with side effects including, dry mouth, weight gain, erectile dysfunction, and loss of libido.

Research today is starting to find that just adding or subtracting serotonin in a person doesn't change his or her mood. For example, Prozac raises serotonin levels within hours yet doesn't change mood for weeks, and when a healthy person's brain is depleted of serotonin it doesn't make him or her sad. Serotonin is not just a feel-good chemical. As it falls short of explaining depression, a most likely candidate is emerging.

The next article will discuss the effect of stress on the brain and how it relates to depression.

18 comments; last comment on 01/08/2016
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New Year New Habits

Posted December 23, 2015 12:00 AM by Chelsey H

As the end of 2015 approaches the obligatory New Year's resolutions start to be written down, taped by the mirror, and shared with accountability buddies. The most popular New Year's resolutions tend to be health related and involve heading to the gym X number of days a week, or eating a salad every day or giving up candy. But what many people may not consider is that the worst things for your health you may not even consider unhealthy. As you list your goals consider changing your habits on these three terrible things you do to your body every day.

  • Getting Stressed Out: Stress is an important physiological response to the dangers of the world. It kept our ancestors from being attacked by wild animals and gave them the energy to run after prey. It's less helpful in an office job. A 2013 survey by the American Psychological Association found that 45% of adults felt that their stress levels had increased over the last five years. Chronic stress can have major, long-term effects on your health such as muscle tension, pain, increase heart rate and blood pressure, increased risk of heart disease and Type 2 diabetes, as well as a host of problems in the gastrointestinal system. In 2016, make sure that you relax a little bit each day; laugh, hang out with your pet, get some vitamin C, or go for a walk outside to help you beat the stress.
  • No "Sleep Hygiene": Now, while you should wash yourself and your sheets regularly, sleep hygiene is about the activities that contribute to better sleep quality. Many people fail to prioritize sleep and end up with fewer hours than they need to feel rested and productive. To have good sleep hygiene avoid stimulants like caffeine and alcohol in the evenings, establish a regular bedtime, keep your room dark, cool, and free of distractions. Avoiding electronic devices is also a good practice before bed. If you have trouble falling asleep here are some techniques you can try: take a warm shower before bed (also good for personal hygiene), scent your bedroom with lavender, practice progressive relaxation, or visualize your favorite place.
  • Eating Packaged Foods: It's 3 PM and you make your daily commute to the vending machine for a bag of chips. Or maybe you're feeling healthy so you grab a granola bar instead. Packaged foods are so convenient but they can be loaded with trans fats, high-fructose corn syrup, salt, and all kinds of preservatives and additives. All of these are shown to have negative health impacts including known carcinogens, obesity, diabetes, and headaches. To avoid adding chemicals to your body opt for homemade and natural snacks. Homemade granola is a delicious healthy treat, oil and vinegar is good as salad dressing, and fruit makes an energizing snack instead of chips.

With everyone focusing on big goals and full diet overhauls, it's important to remember that our day-to-day actions have an enormous impact on our overall health. In addition to exercising more and making healthy choices, make sure that you're taking time to relax, get enough sleep, and choose natural snacks to ensure you have an awesome 2016!

3 comments; last comment on 12/23/2015
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What We Don’t Know About Tylenol

Posted December 17, 2015 7:00 AM by cheme_wordsmithy

Many theories and principles in science & engineering begin with observation and experiment. We observe that something happens, develop a hypothesis about what we think is happening, and then run experiments to test our theory. Sometimes we don't have much understanding of the science and math behind our observations until after all these steps. That's the beauty of the scientific method (aaah, brings me back to 6th grade science).

This is all well and good when looking at science history (gravity… the light bulb…), but what about modern medicine? Certainly we would only use pharmaceuticals that we fully understand all the science behind… right? Well, take it as you like, but there are actually still some big unknowns surrounding one of the world's most common over-the-counter pain-reliever: acetaminophen.

Acetaminophen, better known by the brand name Tylenol®, is a drug that falls under a class of painkillers called non-opiod analgesics (let's call them NOAs). Unlike opiod analgesics (which suppress the brains perception and response to pain), NOAs (which also include ibuprofen, aspirin, naproxen, and others) work largely by suppressing the creation of prostaglandins, which cause pain and inflammation in nerves when cells are damaged. They do this by inhibiting the cyclooxygenase (COX) enzyme which helps make prostaglandins molecules. To sum up, NOAs block COX to prevent the formation of prostaglandins, thus limiting the pain you feel from an injury.

What makes acetaminophen different from other NOAs, however, is that it doesn't appear to block COX in the peripheral nervous system (nerves near the site of your injury) very much, which is why it isn't considered an anti-inflammatory like Ibuprofen (better known as Advil®). It instead blocks COX mainly in the central nervous system (the brain and the spinal cord), which is why you may choose acetaminophen more for headaches and ibuprofen more for physical injuries to redcue inflammation. However, the mechanism(s) behind how acetaminophen affects the central nervous system are still up for debate among scientists.

You can read more about the different theories that exist in this ACS article - they are fascinating. You can also check out a short video about it here. What intrigues me most, though, is how much uncertainty has surrounded such a well-used and well-accepted medicine. What does this say about our caution when it comes to the use of pharmaceuticals? Is it enough that we have billions upon billions of case studies of Tylenol® to look at? Should we be concerned about the unknowns when we think about cancers, or the known relationship between acetaminophen and liver damage?

Perhaps these are warranted reactions, perhaps they are overreactions. For me, the mystery of acetaminophen at least confirms the reality that the human body (and the biochemistry behind its workings) is incredibly complex, and there will always be more to understand and to learn.

References:

Tufts Journal

Chemical and Engineering News

29 comments; last comment on 12/24/2015
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On Pins and Needles

Posted December 04, 2015 12:00 AM by Chelsey H

We've all felt it; the sharp, tingling sensation in our forearm or legs. Most people know this sensation as "pins and needles" or they say their foot has "fallen asleep." Science calls it temporary paresthesia and it occurs when some sort of exterior pressure compresses the nerve and cuts off localized blood flow in a specific part of the body, which messes with that part's ability to send signals to the brain. Image Credit

When your legs are caught against a hard surface, such as from sitting on a chair or crossing your legs, it also puts pressure on the nerves and blood vessels. With those tiny blood vessels impaired, your nerves sense something's not right; they send the tingling sensation as a pain response, which tells you to move the extremity. The peripheral nerves send information back to the brain and spinal cord. When a sensory nerve is pressed it begins to stop working. In time, the affected extremity "falls asleep," which means the sensory messages are blocked.

Removing the pressure often results in return of function. But we all know your leg, arm, or foot keeps hurting even after adjusting your position. This is because your nerves need to restart and return to their normal state. The sensations range from feeling hot to cold to numb. The feeling depends on which nerves are affected. If it's the nerves used for sensing that are compressed, then the area will feel numb. If it's the nerves that tell your muscles to move, then you won't be able to move that part. The nerves may stop firing or fire hyperactively, and the mixed signals are interpreted as burning, prickling, or tingling. Image Credits

Since there is no rule for how quickly the extremity will fall asleep it's important to pay attention to when the sensation starts to occur. For example, if you notice that your leg starts to tingle ten minutes into a movie, start massaging, stretching or readjusting your legs just before that to bring blood to the area

People with poor circulation are more prone to having extremities fall asleep and should avoid sitting cross-legged or readjust frequently to avoid putting pressure on the blood vessels. In general, temporary paresthesia is nothing to worry about. If you have constant pins and needles it could be a sign of chronic paresthesia, which often requires medical attention.

9 comments; last comment on 12/21/2015
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The First Genetically Modified Animal to be Approved for American Consumption

Posted December 02, 2015 1:51 PM by Quasar

The Food and Drug Administration (FDA) has approved the sale of a genetically modified salmon known as AquAdvantage salmon to U.S. consumers. The fish was developed by AquaBounty Technologies, which first submitted data to the FDA twenty years ago. In 2010, the FDA determined that the fish was safe to eat and would not have a significant impact on the environment in the United States.

Many consumer and environmental groups have opposed the approval of the new salmon. The Center for Food Safety, a consumer advocacy organization, said it and other groups would file a lawsuit challenging the approval. More than 60 supermarket chains have already committed to not sell modified salmon, including Kroger, Safeway, Costco, Safeway, Trader Joe's, and Whole Foods. Walmart and Publix have not yet commented on the fish. Red Lobster said it would not serve modified salmon.

The AquAdvantage salmon is a genetically modified version of Atlantic salmon engineered for rapid growth. It has an rDNA construct composed of the growth hormone from Chinook salmon controlled by a promoter from the eel-like fish known as an ocean pout. The promoter is a sequence of DNA that turns on the expression of the growth hormone gene, leading to increased growth rate in the AquAdvantage salmon.

According to the FDA's lengthy review of the fish, the nutritional profile of AquAdvantage salmon is comparable to that of unmodified farm-raised Atlantic salmon. Fish composition was equivalent in both overall measures (such as total protein and total fat) and detailed measures (including specific amino acids, vitamins, and fatty acids including omega-3 and omega-6).

In addition, the FDA examined data on hormones in three groups of fish: unmodified Atlantic salmon from both an AquaBounty farm and a third party commercial farm, and the AquAdvantage salmon. No biologically relevant differences were found in a comparison of several key hormones (including estradiol, testosterone, 11-ketotestosterone, T3, T4 and insulin-like growth factor 1 (IGF1)).

The risks of adverse environmental impacts were found to be insignificant due to multiple physical containment measures in place. In addition, the AquAdvantage fish must be produced as all-female, triploid fish, meaning they would be effectively sterile.

It will likely be at least two years before any AquAdvantage salmon reaches consumers because it takes about two years for the salmon to reach market size. Even then, the amount reaching the market will start off small because the approved production facility in Panama has the capacity to produce only 100 tons of fish per year compared to the 200,000 tons of Atlantic salmon that the U.S. imports each year.

Would you feel safe consuming AquAdvantage salmon?

12 comments; last comment on 12/04/2015
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