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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High levels of sodium in cerebrospinal fluid can cause migraine

Migraine sufferers have significantly higher sodium concentrations in their cerebrospinal fluid than people without the condition, according to the first study to use a technique called sodium MRI to look at migraine patients. Migraine is a a type of headache characterized by severe head pain, and sometimes nausea and vomiting, is one of the most common headache disorders. Some migraines are accompanied by vision changes or odd sensations in the body known as auras. Diagnosis is challenging as the characteristics of migraines and the types of attacks vary widely among
patients.

Consequently, many migraine patients are undiagnosed and untreated. Other patients, in contrast, are treated with medications for migraines even though they suffer from a different type of headache, such as the more common tension variety.  Researchers explored a magnetic resonance technique called cerebral sodium MRI as a possible means to help in the diagnosis and understanding of migraines. While MRI most often relies on protons to generate an image, sodium can be visualized as well. Research has shown that sodium plays an important role in brain chemistry.

The researchers recruited different women, mean age 34, who had been clinically evaluated for migraine. The women filled out a questionnaire regarding the length, intensity and frequency of their migraine attacks and accompanying auras. The researchers also brought in healthy women of similar ages to serve as a control group. Both groups underwent cerebral sodium MRI. Sodium concentrations of migraine patients and healthy controls were compared and statistically analyzed.

The researchers found no statistical differences between the two groups for sodium concentrations in the gray and white matter, brain stem and cerebellum. However, significant differences emerged when the researchers looked at sodium concentrations in the cerebrospinal fluid, the fluid that surrounds the brain and spinal cord, providing a cushion for the brain while also helping to ensure chemical stability for proper brain function. Sodium concentrations were significantly higher in the brain's cerebrospinal fluid in migraine patients than in the healthy control group.
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Brain stimulation may help people suffering from schizophrenia

Brain stimulation therapies involve activating or inhibiting the brain directly with electricity. It could be used to treat cognitive deficits frequently associated with schizophrenia.

Schizophrenia is a chronic mental disorder characterised by abnormal social behavior. This can make it difficult for affected people to plan, focus, pay attention and remember information.

Problems in short-term memory and decision making, which are often severely impaired in people with schizophrenia can be corrected by brain stimulation.

Researchers used neuromodulation - transcranial direct current stimulation (tDCS) - to check if they could correct some of these cognitive deficit in people with schizophrenia.

The researchers applied tDCS with tasks which specifically tapped into 'working memory' and ' executive functioning ': the principle was that 'training' the brain in regions that are typically poorly performing in schizophrenia would be enhanced by the brain stimulation technique.

An improvement in cognitive performance was discovered in those who had tDCS brain stimulation after 24 hours. This shows that changes in the
brain cells induced by neuromodulation may take some time to occur.

The researchers also ran brain imaging analyses to determine what was happening in the brain as these changes occurred. They discovered that tDCS was linked with changes in brain activity in regions associated with working memory and cerebellum.
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