What’s the News: Trouble sticking to your diet? It may not be entirely your fault. Scientists, reporting in the journal Cell Metabolism, have now learned that when you starve yourself of calories, your brain cells also starve, causing your neurons to begin eating parts of themselves for energy. The self-cannibalism, in turn, cranks up hunger signals. This mouse study may lead to better treatments for human obesity and diabetes.
In recent weeks we’ve covered new experimental treatments that involve injecting stem cells into patients to treat conditions like stroke and spinal injury. But in a new study, British researchers have pinpointed the possibility—in rats at least—of stimulating the body’s own stem cells to repair the chronic damage brought on by multiple sclerosis.
In MS patients, the immune system mistakenly attacks what’s called the myelin sheath, the protective layer around the axons of nerve cells.
The loss of myelin in MS sufferers leads to damage to the nerve fibres in the brain that send messages to other parts of the body, leading to symptoms ranging from mild numbness to crippling paralysis. [AFP]
Astrocytes, it was long believed, were little more than the scaffolding of the brain—they provided a support structure for the stars of the show, the neurons. But a study out in this week’s Science is the latest to suggest that this is far from the whole story. The study says that astrocytes (whose “astro” name come from their star-shape) may in fact play a critical role in the process of breathing.
Astrocytes are a type of glial cell — the most common type of brain cell, and far more abundant than neurons. “Historically, glial cells were only thought to ‘glue’ the brain together, providing neuronal structure and nutritional support but not more,” explains physiologist Alexander Gourine of University College London, one of the authors of the study. “This old dogma is now changing dramatically; a few recent studies have shown that astrocytes can actually help neurons to process information” [Nature].
Gourine’s team peeked into the brains of rats to figure out the connection between astrocytes and breathing. In humans and in rodents, the level of carbon dioxide in the blood rises after physical activity. The brain has to adjust to this, setting the lungs breathing harder to expel that CO2.
The human brain is packed with star-shaped cells called astrocytes; they make up about 50 percent of cells in the cerebral cortex, and far outnumber the neurons that process and transmit information. Yet until recently, researchers thought these ubiquitous brain cells were fairly unimportant to the brain’s functioning. Now a new study rebuts that theory, and indicates that astrocytes play a major role in sending blood to areas of brain activity.
In the study, a team of MIT researchers peered into the visual cortex of live ferrets with an advanced microscope to watch how the brain cells responded to visual stimuli. “Electrically, astrocytes are pretty silent,” study co-author James Schummers said…. “A lot of what we know about neurons is from sticking electrodes in them. We couldn’t record from astrocytes, so we ignored them.” The researchers changed this perception by imaging astrocytes with two-photon microscopy. “The first thing we noticed was that the astrocytes were responding to visual stimuli. That took us completely by surprise,” Schummers said. “We didn’t expect them to do anything at all. Yet there they were, blinking just like neurons were blinking” [HealthDay News].