Myasthenia Gravis May Be (Literally) All Greek to You

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Myasthenia gravis is a disease that affects the way that muscles receive signals from nerves. Myasthenia is Greek for “muscle weakness,” which is a good description of this disease’s symptoms. Muscle weakness, which worsens after physical activity but gets better with rest, is the primary symptom of the condition.

Weakness may occur in any skeletal muscle, but smaller muscles in the face are commonly affected. This leads to symptoms that may include:

  • difficulty chewing or swallowing,
  • speech impairment,
  • altered facial expression,
  • drooping eyelids, and
  • blurred vision.

Weakness in the limbs is often a symptom when larger muscles are affected. One of the most serious consequences of myasthenia gravis is a myasthenic crisis, which occurs when the respiratory muscles that allow us to breathe are affected. Someone in myasthenic crisis may need a machine (ventilator) to help them breathe if they have trouble on their own.

An understanding of how nerves work with muscles is important to understanding the effects of myasthenia gravis. The brain sends signals through the nerves, telling them which direct body parts to move. The signals travel down nerves to nerve endings, which are located very close to—but not touching—muscle fibers. Nerves release chemicals called neurotransmitters to send signals that bridge the gap between the nerves and muscles. Neurotransmitters bind to molecules on the surface of the muscle cells (receptors) that send a signal inside the cell. Acetylcholine is a neurotransmitter that causes muscle movement when it binds to its receptor. The normal interaction between a neurotransmitter and receptor doesn’t always work as smoothly as it should. In some cases, the immune system interferes, producing proteins called antibodies that are meant to protect the body from substances that might harm it. In the case of myasthenia gravis, the immune system makes antibodies that bind to acetylcholine receptors, which prevents the interaction between the neurotransmitters and receptors.

The disease typically occurs in women under 40 and men over 60, but it can develop at any age. Myasthenia gravis may be debilitating, but the good news is that symptoms can usually be controlled with medication. Steroids can help limit the production of antibodies that target acetylcholine receptors. Drugs called acetylcholinesterase inhibitors increase muscle strength by slowing the breakdown of acetylcholine. When neurotransmitters remain for longer periods of time, signals to the muscles are more likely to go through.

As you enjoy the outdoors and weather during Myasthenia Gravis Awareness Month, keep in mind all the things your muscles and nerves are doing without you even thinking about it.

 

Rebekah Morrow 3Rebekah Morrow, PhD, is an assistant professor of immunology and microbiology at the Alabama College of Osteopathic Medicine.

Like Father, Like Son (and Daughter): How Your Dad’s Past Affects Your Future

Happy daughter playing with dad

Credit: iStock

What makes your father the best dad in the world? Maybe it’s his sense of humor or the times he has taken you to the movies or played catch in the yard. Or maybe it’s the fact that he made healthy lifestyle choices before you were born. Recent research suggests that your father’s health before you were conceived (preconception) may change the way your genes behave to affect your future health. It almost sounds like something out of a science fiction movie, but it’s real.

Studies tend to focus on the mother’s preconception health and the risks her baby might face later in life if she’s overweight. But a dad’s weight and early eating habits can also play a role, according to research published in the American Journal of Stem Cells. Researchers found that offspring of men who were obese before reproducing were more likely to have diabetes and be overweight. On the other hand, the researchers also found that fathers who had limited food resources in their early life caused genetic changes that protected their children—and even grandchildren—against cardiovascular disease.

Most people know that exercise is one of the healthiest lifestyle choices you can make to maintain your weight and keep your heart and even your brain healthy. However, research presented at the APS Integrative Biology of Exercise 7 meeting showed that offspring of men who exercised long term before conceiving had a higher likelihood of being obese and developing diabetes. This result was a huge surprise to the research team, but is it a reason to stop exercising? Not really. The study focused on how efficiently the body used energy on a high-fat diet. Limiting dietary fat and being active is still the way to go for most people.

Keeping stress levels low is also a good plan for dads-to-be. One study suggests that a man’s preconception stress may program his kids for mood disorders. Researchers found a pathway in the brain that transmits signals about stress hormones, and it may be passed down to the next generation.  If the signal is passed on to you, then your father’s stress levels could affect your predisposition for anxiety and depression.

These studies represent clues to learning how genetic material is transformed as it passes through generations. It’s also a reminder that following a healthy diet, staying active and maintaining mental health is important for everyone at every age.

Happy Father’s Day!

– Erica Roth

Putting Out Fires Hurts Firefighters’ Hearts

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As the temperature outside rises, our bodies make adjustments to keep our internal temperature constant to prevent us from overheating through a process called thermoregulation. This includes bodily functions such as sweating and widening of the blood vessels (vasodilation). When we sweat, perspiration evaporates from our skin to cool us down. When the blood vessels under our skin widen, our heart pumps more blood to our skin, which releases more heat from our inner body.

Our bodies are constantly working to hold a steady core temperature around 98-100 degrees Fahrenheit (F). This allows our organs to function properly. But when the temperature outside is extremely hot, our temperature can start to rise. A person with a body temperature above 104 degrees can develop heat stroke. This can cause dizziness, difficulty breathing, confusion, seizures or loss of consciousness. Brain and heart damage—sometimes permanent—can occur when body temperature climbs above 107 degrees F.

Too much summer heat can be unhealthy for everyone, but it can be especially dangerous to firefighters. The incidence of fires increases in the U. S. during the summer months. Firefighters fight almost twice as many fires in the summer compared to the rest of the year. On top of dealing with the extreme heat (sometimes over 700 degrees F!), these first responders face extreme physical exertion, mental stress and smoke inhalation on the job. All of these factors together can place firefighters in immediate danger of heat exhaustion, heatstroke and heart problems. In fact, firefighters are up to 136 times more likely to die from coronary artery or heart disease during or soon after they suppress a fire.

In a study published in Circulation last month, researchers may have uncovered several reasons why putting out fires puts firefighters at risk for heart disease. They discovered that a single, 20-minute session of fire simulation training—where healthy firefighters were exposed to physical activity in the extreme heat (about 755 degrees F)—was enough to injure their blood vessels, even though the firefighters’ core body temperature never reached above 101 degrees F. The problem: Although the firefighters’ bodies did keep their core temperature within a healthy range, their blood vessels did not relax properly immediately after the training. Also, as a result of the training, the firefighters’ blood clotted more easily. Damaged blood vessels and increased clotting of the blood can be very harmful to the heart and sometimes can lead to a heart attack.

This research shows us that even when we are able to keep our body temperature from getting too high, there are hidden dangers of being physically active in extremely hot temperatures. So keep your heart healthy this summer and don’t overexert yourself while outdoors!

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.