The Genetic of Autism

July 17, 2015

By Medical Discovery News

The Genetics of Autism

In the past decade, autism has garnered a lot of media attention. Lately much of the focus has been on finding the cause. Much is still a mystery, despite confirming that vaccines and parenting are not responsible. Now a new study of twins has given us another clue, revealing that the influence of genetics on the development of autism may be between 56 and 95 percent.

According to the Centers for Disease Control, one in 68 children have autism, a neurodegenerative disorder that exists on a spectrum, meaning its symptoms and their severity varies tremendously. A hallmark feature of autism is impaired social interaction, noticeable even in babies. Those with autism find it difficult to interpret what others are thinking or feeling because they miss the social clues most take for granted. Other symptoms can include repetitive movements such as spinning or rocking, speech delays, and self-destructive behaviors. Children with autism can also have a variety of other conditions including epilepsy, Tourette’s syndrome, learning disabilities, and attention deficit disorder (ADD).

The cause of autism is probably rooted in genetics and environment. Comparing sets of twins is a well-established way of clarifying the extent of both these influences. Scientists in London studied over 6,400 pairs of twins in England and Wales between 1994 and 1996, all raised by their parents in the same environments. The data they collected revealed that the chance of identical twins having autism was 77-99 percent, whereas the chance of non-identical twins having autism was 22-65 percent. This suggests that additive genetic factors contribute to 56-95 percent of autism cases. This is far higher than previous estimates, which assumed environmental influences were more of a factor.

While no one gene has been attributed to autism, the majority of the genes that are associated seem to be linked to one specific symptom. For example, the gene EN2 is often studied for its role in autism because it is critical to midbrain and cerebellum development. Reelin, a protein found mainly in the brain, also plays an important role in autism development. In adults, reelin is important to learning and memory and is critical to inducing and maintaining long-term neuronal connections. Autistic individuals consistently show elevated levels of serotonin, otherwise known as the feel-good hormone. This has led researchers to examine the role of genes involved in serotonin regulation as potential causes of autism. Another hormone system called arginine-vasopressin affects social behavior, so one of the genes that regulates it is a candidate for autism as well. These are just a few of the many genes being studied.

As more people become aware of autism and more children are diagnosed, the pressure is building to further understand this disorder. Discovering the causes might translate to better diagnostics and treatment for autism.

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Thinking with your Stomach

May 31, 2013

By Medical Discovery News

“The way to a man’s heart is through his stomach.” New research might amend this common proverb to “the way to a man’s brain is through his stomach.” An article in the “New Scientist” argues that the enteric nervous system (ENS), found in the tissues of the gastrointestinal (GI) tract, functions as a second brain of sorts.

Spanning the mouth to anus, the GI system is approximately 30 feet long and can be divided into the upper (esophagus, stomach, and duodenum) and lower (large and small intestine) tracts. This is where digestion occurs, providing metabolic functions and energy to the body. With this complex role, it is not hard to imagine why it needs its own nervous system.

Like the brain, the ENS consists of different types of neurons as well as glial cells, which provide support and protection for the neurons. The human ENS contains upward of 500 million neurons and an equal number of glial cells, more than all of those in a rodent’s brain. However, the human brain contains 90 billion neurons. The ENS communicates with the brain to control unconscious or autonomic processes, like peristalsis, the wave-like motions that push food through the GI tract. 

To accomplish this, the ENS produces hormones and neurotransmitters much like the brain. In fact, the ENS produces as much dopamine (which triggers feelings of reward and pleasure) as the brain and most of the serotonin (which controls mood, appetite, and sleep) within the body.

So, if the ENS truly acts as a second brain, then the GI system can affect a person’s moods and sense of wellbeing. The ENS causes this by transmitting signals to the brain through the vagus nerve. This makes sense, since people typically feel good after enjoying a meal. For example, when rich foods are digested they release fatty acids. The gut detects this, prompting the ENS to send certain signals to the brain. According to brain imaging studies, the brain then releases pleasurable sensations, altering a person’s mood. So it’s no wonder that people crave rich, fatty foods!

On the other hand, people usually eat differently when stressed. Stress can lead to the production of a GI hormone called ghrelin, which causes feelings of hunger and leads to a reduction of anxiety and depression. In experiments, mice subjected to stress sought out fatty foods, which elevated the production of ghrelin. The link between chronic stress and obesity is then a no-brainer.

The main function of the ENS is to monitor the digestion of food and identify threats in what is eaten, such as toxins or infections. So, perhaps listening to the stomach when it comes to choosing meals isn’t all bad. After all, that’s the second brain at work.

Zombies? Not Quite

By Medical Discovery News

Nov. 31, 2012

When a nude Miami man chewing on another man’s face made headlines and sparked fears of “zombie” attacks, the public became acutely aware of a designer drug with the street name “bath salts.” Authorities speculated the man was high on bath salts since similar bizarre events were reported in other cities. Toxicology reports have since shown the man only had marijuana in his system. Yet the case highlights the growth of designer drugs and the violent highs they create while skirting the law.

Bath salts’ innocuous name is meant to make them appear safe and legal. They resemble bath crystals but are synthetic drugs sold under innocent names such as “Ivory Wave,” “Purple Wave,” “Vanilla Sky,” and “Bliss,” and are widely available on the Internet, head shops and some convenience stores. To confuse the public even further, they’re also sold as glass cleaners or plant food, which again is an attempt at avoiding drug laws.

Sold in small packets, these stimulants can be smoked, swallowed, snorted, or put into a solution and injected. They’re far cheaper and easier to get than cocaine or ecstasy, yet like those, they act on the central nervous system with far less predictable effects. Since “street chemists” produce bath salts, no one knows exactly what’s in them.

The main compounds in bath salts are synthetic stimulants including MDPV, mephedrone, and methylone, but there are many others. These compounds are synthetic derivatives of cathinones, which are naturally found in the Catha edulis plant. The North African shrub known as khat is a hallucinogenic stimulant and illegal in the U.S. But the synthetic derivatives are far more concentrated and acutely toxic.

Bath salts affect behavior by altering levels of the neurotransmitters dopamine, norepinephrine, and serotonin. Dopamine controls movement, emotional responses, and the ability to experience pleasure and reward. Norepinephrine regulates heart rate, blood pressure, and sugar levels, and is part of the fight or flight response. Serotonin modulates mood, emotion, sleep, and appetite, and is implicated in the control of numerous behavioral and physiological functions.

Bath salts raise the concentration of these neurotransmitters in two ways. First, they block the reuptake of neurotransmitters, leaving extra dopamine, norepinephrine, and serotonin to react with other receptors instead of being stored safely inside neurons. Second, the drug stimulates the release of additional internal stores of neurotransmitters.

The results are increased heart rate and blood pressure, agitation, anxiety, hallucinations, extreme paranoia, and even full-blown psychosis. There also have been cases of suicide days after the more obvious effects of the drugs have worn off.

In October 2011, the US Drug Enforcement Agency banned three of the key ingredients used to make bath salts for at least a year, and 40 states have outlawed the drug. But producers can make small chemical adjustments in the molecules to stay ahead of the law, which challenges the legal system’s ability to crack down on drug use. The drug is mostly being made in China and imported through other countries, but that’s expected to change as dealers learn to manufacture it here in the United States.

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