How astrocytes change with age

 Salk researchers have discovered that genes that are switched on early in brain development to sever connections between neurons as the brain fine-tunes, are again activated in aging neuronal support cells called astrocytes. Astrocytes may be good therapeutic targets to prevent or reverse the effects of normal aging.

Neuroscientists know that in the young, developing brain, synapses are being activated and deactivated, while in the adult brain they are mostly stable. But in aging brains, neurons start to lose connections and don't communicate as well. Allen and graduate student Matthew Boisvert wondered whether the changes to synapses and neuronal communication during aging might be related to changes in astrocytes.

To find out, the duo decided to compare gene expression in astrocytes in the adult brain versus the aged brain in mice. This would give them an idea of which genes are active at the two stages.o Researchers compare four-month-old mice, who in mouse years are adults, to two-year-old mice, who are quite elderly. They used a molecular technology called ribo-tag that allowed him to find out which genes were being made into proteins by astrocytes. It works by isolating the protein-making machines of cells (called ribosomes), which turn mRNA copies of DNA (genes) into proteins.

By taking a sort of molecular snapshot of an astrocyte's ribosomes, it's possible to see all the mRNA copies in progress and thus know which genes are active. To develop a comprehensive view of astrocyte gene expression, the duo used the technique in four very different areas of the mouse brain: two regions of the cortex and the hypothalamus and cerebellum.

To their surprise, they found that most of the properties that make an astrocyte an astrocyte didn't change much with age-gene expression was fairly consistent with time. But what did change: genes that during development would normally cause the loss of connections between neurons were switched on again in the aging astrocytes.

This suggests that there's some sort of genetic program that's being reactivated in these astrocytes as they age that's causing neurons to lose their connections with each other. Interestingly, the areas in which astrocytes looked the most different were brain areas where neurons are known to function notably less well with age or even to die-the cerebellum and the hypothalamus. This may explain why metabolism decreases and coordination gets worse with age, because these are functions that are coordinated by the hypothalamus and cerebellum.
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Anger causes untimely death

Researchers have discovered that angry men aged 20 to 40 were one-and-a-half times more likely to be dead 35 years later than those who were calmer. They believe this is due to a number of factors linking stress to physiological damage. The frequent release of adrenaline during periods of stress damages DNA, which could lead to life-threatening illnesses such as multiple sclerosis.

Feelings of anger produce a heightened response in the amygdala, the part of the brain associated with survival instincts. Angry emotions prompt the amygdala to signal a heightened state of anxiety to the rest of the brain and the body, increasing blood flow to the limbs and heart, which makes relaxation impossible.

Those exposed to anger-inducing stimuli without discussing how it made them feel are more likely to experience insomnia than those who engage in an emotional ‘debrief’, according to neuroscientists. Writing the cause of anger frees up the space in the head, dampening the fear response and encouraging relaxation.

 Emotions such as excitement or anger result in the release of stress hormones cortisol, adrenaline and testosterone, which put the body into flight-or-flight mode. The chemical surge increases blood flow to the brain and triggers the swelling of both blood vessels and nerves surrounding the brain. The pressure can result in tension and headaches.

Highly hostile individuals performed significantly worse on a simple inhalation task than those who were rated less hostile. When you are angry, neurotransmitters and hormones are sent through the bloodstream which, in turn, increase both the heart rate and muscle tension. Frequent occurrence of this reaction puts a strain on neurons in the hypothalamus, the brain’s ‘stress control centre’, meaning that it becomes harder for the neurons to switch off. And the ‘happy hormone’ serotonin is significantly depleted in some aggressive individuals.

Too much cortisol in the body – released by adrenal glands during angry outbursts can cause an imbalance in blood sugar, repress the thyroid and even decrease bone density. When released initially, cortisol triggers an anti-inflammatory response by the immune system, but prolonged increase of the hormone makes the body more susceptible to viruses. As blood pressure rises thanks to a surge in adrenaline, the heart beats faster, increasing the risk of potentially fatal abnormal heart rhythms. Adrenaline also signals for the release of platelets, which can trigger blood clots or block arteries – particularly dangerous if arteries are restricted by a build-up of cholesterol.

Studies have shown that men in particular who score highly on trait anger scales are three times more likely to suffer from general heart disease. Once the ‘fight or flight’ signal has been issued by the brain, blood supply is directed to areas needed for action such as the limbs. That means blood supply to the digestive system is reduced, with a reduced amount of oxygen provided to keep vital ‘good’ bacteria in the gut alive. A dampened immune system can lead to a weakened gut lining, increasing vulnerability to harmful bacteria entering the area.

Heightened stress reduces the amount of available glucocorticoids -the hormone involved in the synthesis of the skin-plumping compound collagen. Lack of collagen contributes towards saggy, wrinkled skin. The weakened immune system caused by stress responses increases inflammatory reactions to pathogens underneath the skin.

Enhanced periods of anger disrupt the skin-barrier function, making it easier for allergens to penetrate and resulting in skin conditions such as dermatitis and psoriasis. Repressing, rather than expressing anger puts you at an higher risk of developing health problems. This increased risk of hypertension for angry individuals who tended to keep their anger below a level of consciousness. By repressing emotion, excess stress hormones remain in the emotion-processing areas of the brain for longer period making physical reactions chronic.
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Long term use of electronics gadgets hinders brain development

According to neuroscientists, long term use of smartphones can hinders brain development, the use of technology is reducing hard work and accumulation of knowledge.

Human brain has a ‘use it or lose it policy’, the ability to store facts may become diminished through lack of regular practice to recall information without checking the internet.

Time spent in a screen-based world displaced time spent ‘learning, playing and socialising in the real world’.
Outsource thinking to smartphones and other digital devices will leads to loss of brain muscles.

 Technological dependence on internet for information could have profound effects on how we routinely make sense of complex arguments, logical reasoning and creativity.

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Cell can makes or breaks your habits

Some habits are useful and healthy like drinking enough water everyday, eating of fruits and vegetables while habits like eating a cookie every day after work, smoking after meal and excess consumption of alcohol are not healthy.

Neuroscientists have identified a single type of neuron in the brain that serves as a master controller of habits. The team found that habit formation increases the activity of this influential cell, and that shutting it down with a drug is enough to break habits in sugar-seeking mice.

This cell exerts its control through a web of connections to more populous cells that are known to drive habitual behavior. This cell is a relatively rare cell but heavily connected to the main neurons that relay the outgoing message for this brain region. We find that this cell is a master controller of habitual behavior, and it appears to do this by re-arranging the message sent by the outgoing neurons.

The scientists trained healthy mice to receive a tasty treat every time they pressed a lever. Many mice developed a lever-pressing habit, continuing to press the lever even when it no longer dispensed treats. The team compared the brain activity of mice who had developed a lever-pressing habit with those who hadn't. They focused on an area deep within the brain called the striatum, which contains two sets of neural pathways: a "go" pathway, which incites an action, and a "stop" pathway, which inhibits action.

They discovered that the go and stop pathways were stronger in habit-driven mice. Habit formation also shifted the relative timing of the two pathways, making the go pathway fire before the stop. The fast-spiking interneuron in striatum FSI might serve as master conductor of the widespread changes in the outgoing neurons activity. The FSI belongs to a class of neurons responsible for relaying messages located between other types of neurons in a particular brain region.

Though FSIs make up about only one percent of the cells in the striatum, they grow long branch-like tendrils that link them up to the 95 percent of neurons that trigger the stop and go pathways. Forming a habit appeared to make the FSIs more excitable. After giving the mice a drug that decreases the firing of FSIs, they discovered that the stop and go pathways reverted to their previous brain activity patterns, and the habit behavior disappeared. Harmful behaviors like compulsion and addiction in humans might involve corruption of the normally adaptive habit -learning mechanisms.
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