Image post 6: spinal cord cell reaches for its neighbor

While many posts from The Mix feature a science story, we also share images coming out of UAB research. Below is a description of what we are looking at and related hints about how the brain forms in the womb. 

Pictured here is one star-shaped astrocyte "reaching out" to another in a dish. The most abundant cell type in the brain and spinal cord, astrocytes are not nerve cells, but instead provide support, nutrients and protection to nerve cells. Recent work has shown that astrocytes help to shape the messages being passed from nerve cell to nerve cell, and that problems with astrocyte function may throw off nerve cell performance.

In her research, Michelle Olsen, Ph.D., assistant professor in the UAB Department of Cell, Developmental and Integrative Biology, seeks to determine how the overlap between nerve cells and astrocytes contributes to normal brain development, and to brain abnormalities when something goes wrong.

Dr. Olsen's experiments with isolated cells seek to model processes underway in the brain as it forms during development. Nerve cells are known to put out "roots" that reach out, find nearby cells and link up to form signaling networks. The above picture suggests that astrocytes do something similar.

Named for their star shape, astrocytes put out extensions that wrap around synapses, the gaps between nerve cells in signaling pathways. Each nerve cell in a pathway sends an electric pulse down itself until it reaches a synapse, a gap between itself and the next cell in line. When it reaches the cell's end, the pulse triggers the release of chemicals called neurotransmitters that float across the gap. Arriving at the other side, they cause the downstream nerve cell to “fire” and, depending on the synapse type, to either pass on or stop the message.

In this way, each synapse between nerve cells “decides” whether or not a message continues down that pathway. The balance of messages passed on (excitation) and messages halted (inhibition) is crucial to brain function. One theory has it that astrocytes influence that balance at synapses with their own set of extensions and transmitters.

Dr. Olson captured the image using an inverted Zeiss Observer microscope. 

Image post 5: eye nerves shed light on memory disorders

While most posts from The Mix feature a science story, we have also begun sharing images coming out of UAB research. Below is a brief description of what we are looking at and how related work may contribute to a better understanding of Alzheimer's disease.

Pictured here is a retinal ganglion (center), a kind of nerve cell near the eye’s retina that helps to process light into the images we perceive. It had been injected with a fluorescent dye, which made it glow green along with the cells connected to it electrically. In each of our eyes, 125 million photoreceptors capture light. They then trigger nerve messages in 1.5 million retinal ganglion cells, long extensions of which bundle together to form the optic nerve.

Captured by Christianne Strang, Ph.D., research instructor in the Department of Vision Sciences within the UAB School of Optometry, this image represents signaling mechanisms between the retina and surrounding nerve cells. Strang's lab seeks to understand how photoreceptors connect to surrounding nerve pathways, as well as the degree to which they signal using the neurotransmitter acetylcholine.

Within nerve pathways, each nerve cell sends an electric pulse down an extension of itself called an axon until it reaches a synapse, a gap between itself and the next cell in line. When it reaches an axon’s end, the pulse triggers the release of chemicals called neurotransmitters that float across the gap. Upon reaching the other side, they either cause the downstream nerve cell to “fire” and pass on the message, or stop the message. Certain neurological diseases, including Alzheimer’s, have been linked to a decrease in acetylcholine signals in nerve pathways related to vision and memory.

As for rest of the color scheme, the pictured eye tissue has also been treated with dyes that interact with choline acetyltransferase (blue), which helps to produce acetylcholine, and synaptophysin (red), which reveals the location of synapses. The work was done in the lab of Kent Keyser, Ph.D., professor in the School of Optometry.

Image post 1: brain message superhighways

While most posts from The Mix feature a science story, we also wanted a forum to share powerful images coming out of UAB research. Regular image posts will be accompanied by a brief description, including how the image depicted might soon be important to science or medicine. The post will also link to the creator of the image.

Above is a face view of a brain’s white matter created by UAB graduate student Meredith Reid using an MRI technology called diffusion tensor imaging (DTI). The strands running through the image are axons, long extensions of nerve cells that form pathways carrying messages between the parts of the brain. The colors represent the spatial orientation of the axons, with one color for those running left to right, another for those running back to front, etc. Certain qualities of such images give researchers a measure of the integrity of white matter axon fibers, which promises to improve understanding of neurological disorders like schizophrenia. The work was done in the lab of Adrienne Lahti, M.D., professor in the Department of Psychiatry and Behavioral Neurobiology within the UAB School of Medicine. On a final, related note, it's also worth checking out the Human Connectome Project run by the National Institutes of Health.  

Note: if you have an amazing UAB research image you would like to share, please email mwindsor@uab.edu.