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Brain's Axons move just for a single molecule...
Neuroscience Posted by Lucifugo Rofocale on Wednesday May 26, @10:57AM
from the find-your-way-department dept.
New technology permits steering axons in the petri dish with emparalled precision. Novel way of manipulating the chemical concentration gradient in the culture allows for new forms of neuron manipulation and experimentation.
"I was curious about the physics of this wiring up process, which led our lab in a different direction than others who study axonal guidance," said Geoff Goodhill, PhD associate professor of neuroscience at Georgetown University Medical Center. "Once we had created a stable environment and could control molecular gradients, we were amazed to discover just how sensitive axons are to tiny changes in the concentration of molecular cues. We've found that a difference in concentration of a single molecule across the tip of an axon can measurably impact the direction in which the axons grow." Read More in: http://www.sciencedaily.com/releases/2004/05/040524060425.htm http://gumc.georgetown.edu/communications/releases/release.cfm?ObjectID=2670

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    Re: Brain's Axons move just for a single molecule...
    by Jamesx on Friday June 04, @05:48PM
    This is really not surprising, given that molecular gradients are one of the primary ways that cellular differentiation and organism development takes place.

    In one of the most simple models of differentiation, slim molds (dictyostelium discoideum), a set of single celled organisms will come together to form a multi-celled slug under low nutrient conditions. It was discovered a number of years ago that they follow a gradient of cyclic AMP, secreted by one of the individual cells which starts secreting it sooner than others.

    Similar gradients have been studied in developing embryos, etc.
    [ Reply to this ]
    Re: Brain's Axons move just for a single molecule.
    by James Robertson on Monday June 07, @07:20PM
    What may be surprising to most is that axonal guidance and synaptogenesis during development and the number and plasticity of synapse that are present in mature animals is a function of astrocytes. This is the most common cell in the brain (neurons consist of only 10% of the brain cell population). This was publish in Science a few years ago by Ullian and associates in Barres lab at Stanford University. They studied the develpment of axons from the retina to their synaptic terminals in the superior colliculus. Similar results were obtained when synapse in the neocortex were studied. These findings were presented by Barres at the Society of Neuroscience annual meeting in New Orleans in October. This article also details astrocyte "messengers" that were identified. I believe that cyclic AMP was a second messenger that affected the axonal response. There is overwhelming evidence that astrocytes and neurons carry on a very complicated and sophisticated dialog at each synapse and that these glial cells are of extreme importance in synaptic plasticity, the basis of learning and memory. Neurotransmitters produced and released only by astrocytes (gliotransmitters) have been identified. This includes D-serine which is required for neuronal NMDA receptor activation and homocysteine which also activates neuronal NMDA receptors. Astrocytes may, therefore, actually control synaptic activity since these transmitters are not under neural control.
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