Mind Alive Blog
Monday, January 16, 2012
I was asked to post the an article about Glia cells in the brain. Because I decided to take chemistry instead of neuroscience my knowledge of glia cells is practically non-existent; however, thanks to the Internet I have found a site called Neuroscience for kids.
Types and Functions of Glia
Astrocyte (Astroglia): Star-shaped cells that provide physical and nutritional support for neurons: 1) clean up brain "debris"; 2) transport nutrients to neurons; 3) hold neurons in place; 4) digest parts of dead neurons; 5) regulate content of extracellular space
Microglia: Like astrocytes, microglia digest parts of dead neurons.
Oligodendroglia: Provide the insulation (myelin) to neurons in the central nervous system.
Satellite Cells: Physical support to neurons in the peripheral nervous system.
Schwann Cells: Provide the insulation (myelin) to neurons in the peripheral nervous system.
By Melissa Lee Phillips
Neuroscience for Kids Consultant
May 21, 2002 Nerve cells (neurons) and glial cells (glia) are the two major types of cells present in the nervous system. For many years, glial cells were thought to only support the activities of neurons. Researchers thought that astrocytes -- glial cells named for their star-like appearance -- had only a supportive role in the central nervous system. It is well established that astrocytes help form a network on which neurons grow. Astrocytes fill in the space between neurons, take up neurotransmitters that are released by neurons, and help maintain the correct chemical concentrations around neurons.
Image courtesy of Biodidac
Within the past few years, however, attention has focused on the role of astrocytes in adult neurogenesis. Neurogenesis, the growth of new neurons from neural stem cells, has recently been shown to occur in adult mammals. In adults -- including humans -- neurogenesis has been observed in two specific areas: the subventricular zone (the area immediately surrounding the brain's ventricles) and the hippocampus. A study by researchers at the Salk Institute in California shows that astrocytes play a more important and active role in neurogenesis than previously thought. The researchers took stem cells from the hippocampus of adult rats and engineered these cells so that they would express a green fluorescent protein (GFP). The GFP makes it easy to see these cells and all of the cells' offspring...it's a bit like making the cells wear a glow-in-the-dark shirt. The stem cells were cultured with astrocytes from the hippocampus of newborn rats. The scientists found that neurogenesis was about eight times higher in cells that were cultured with astrocytes compared to those that were cultured without astrocytes. This increase in neurogenesis is consistent with previous studies. In those studies, however, it was unclear whether the astrocytes simply provided an environment that encouraged the survival and division of neural stem cells or if the astrocytes actually caused cells to become neurons. In this experiment, the researchers found that not only were more stem cells growing and maturing, but that the cells actually became neurons (instead of glia) about six times as often when they were in an astrocyte-enriched environment.
Research involving stem cells is promising because it has the potential to develop new treatments for neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. If scientists can engineer stem cells to grow into neurons -- perhaps involving signals from astrocytes -- they might be able to repair or even prevent damage caused by these diseases.
Reference: Song, H., Stevens, C.F., and Gage, F.H., "Astroglia induce neurogenesis from adult neural stem cells," Nature, Vol. 417, May 2, 2002, pp. 39-44.
Svendsen, C.N., "The amazing astrocyte," Nature, Vol. 417, May 2, 2002, pp. 39-44.
Now that you and I have refreshed our understanding of what Glia are here's the article:
"The Glia (glue) cells of the brain have been mistakenly overlooked by neurophysiology. New studies are finding glial cells work with neurons, control them and work alongside them. They provide nourishment, maintain myelin and remove waste. Microglia are the first responders to injury and repair. They are also the brain’s immune system and attack foreign invaders. Glia also handle global communication in the brain. Whereas neurons transmit their signals across chains of synapses, glia can broadcast their signals like radio transmitters. The glia is also thought to actually be “The Mind,” as they show a response on DC brain maps in response to intention and attention and direct the neurons what to do. For instance, if you move your finger, it’s the glia that responds first and then instructs the motor-strip to activate the movement.
Glia play an important part in Electro-Convulsive Therapy. Back in the 1930s, it was found that astrocytes, a type of glial cell, were high in the brains of epileptics (who rarely had depression), and low in depressives. This spawned the use of ECTs as a way to induce glial cell activation in hopes of treating depression. Of course, these days, we do know that there are epileptics who do have depression, so the theory may not be a perfect one.
Read an excellent article by Douglas Fields on glia in: ScientificAmerican Mind May/June 2011, pages 53-59."
I posted on our facebook page an article from a 2009 edition of ScientificAmerican Mind an interview with Andrew Koob, who wrote a book about Glia cells. The interview gives a lot of good background on glia cells. Douglas Fields has a great blog post which goes through why glia cells have been neglected in research. He is a frequent contributor to SciAM.
by Sima Chowdhury - January 16, 2012