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October 23, 2011

Z is for Zinc


Zinc. Metal. Number 30 on the periodic table. Twenty-fourth most abundant element on Earth. Common oxidation state of 2+.

Did you take your multivitamin today? Did it have zinc in it? Zinc is used to treat a wide variety of ailments from acne to the common cold, but did you also know it's important in memory formation? A new study lead by James McNamara M.D. of Duke University Medical Center shows that zinc can enhance communication between cells, particularly in the hippocampus, a center of memory formation. This data leads to the hypothesis that excessive enhancement mediated by zinc might occur in epilepsy and play a part in the severity of seizures. These findings could lead to developing new drugs for epilepsy.

High concentrations of zinc in synaptic vesicles was discovered in the 1950s and has perplexed neurobiologist ever since. These vesicles are colocalized with glutamatergic neurons of the hippocampus suggesting that zinc might be released and play a role in the plasticity of excitatory synapses. Efforts to determine zinc's function in these synapses has been difficult to determine because of previously available zinc chelators which were not specific for zinc and did not bind fast enough to remove zinc in the time scale of synaptic transmission. In the September issue of Neuron, a collaboration between Steve Lippard from MIT's Department of Chemistry and Duke University Medical Center has synthesized a novel zinc chelator. By using the chelator in mice, they found that zinc promotes presynaptic and inhibits postsynaptic long-term potentiaion in the mossy fiber-CA3 synapse.

The group began by creating a new zinc chelator, called ZX1, that binds zinc fast and has a higher specificity for zinc versus calcium or magnesium than other chelators. By using ZX1 to remove zinc from the synapse as soon as it was released, they were able to look at what happens to long-term potentiation without zinc. Using ZX1 in the hippocampus of mice, the data found that ZX1 inhibited mossy fiber-LTP. Mossy fiber LTP is NMDA independent, working by other mechanisms based in the presynaptic cell. The group also did experiments on ZnT3 null mutant mice, which lack the transporter that packages zinc into vesicles. These experiments were surprising because they saw that, as previously seen in wild type mice, zinc enhanced the presynaptic mf-LTP, but zinc actually inhibited postsynaptic mf-LTP.

Overall, zinc seems to modify the circuits related to learning and memory, but don't start gobbling down zinc supplements just yet. Zinc is a trace metal in biology, and certainly too much can be toxic. Knowing the molecular mechanisms of synaptic plasticity and excitability is an important step in treating diseases such as epilepsy, but as of yet there is no established beneficial level of zinc. In fact, too much zinc might increase the enhancement of these synapses, leading to more severe seizures. A new drug might act like ZX1 to bind zinc and remove it from the synapse, in order to reduce the enhancement of the excitatory synapse.


Source:
Enhui Pan, Xiao-an Zhang, Zhen Huang, Artur Krezel, Min Zhao, Christine E. Tinberg, Stephen J. Lippard, James O. McNamara, Vesicular Zinc Promotes Presynaptic and Inhibits Postsynaptic Long-Term Potentiation of Mossy Fiber-CA3 Synapse, Neuron, Volume 71, Issue 6, 22 September 2011, Pages 1116-1126, ISSN 0896-6273, 10.1016/j.neuron.2011.07.019.
http://www.sciencedirect.com/science/article/pii/S0896627311006465

Less in depth summary of paper:
http://www.sciencedaily.com/releases/2011/09/110921132334.htm
Posted by      Amanda W. at 1:35 PM MDT
displaying most recent comments (1 ommitted) | Comments (4)
  Amanda Weaver  says:
No, the study was focused on mouse hippocampal slices and was not advocating zinc supplements in humans, nor exploring the possible benefits or dangers inherent in changing zinc levels. In fact zinc can definitely be harmful. Here is a very interesting case study that was printed in the New York Times: http://www.nytimes.com/2009/09/06/magazine/06fob-diagnosis-t.html
Posted on Mon, 24 Oct 2011 12:37 PM MDT by Amanda W.
  Christina Uhlir  says:
That article was certainly illuminating. I guess I am glad that my vitamins do not contain even trace amounts of zinc.
Posted on Mon, 24 Oct 2011 3:27 PM MDT by Christina U.
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July 31, 2011

Look Ma, No Hands


Have you ever wondered what it would be like to actually control something, using just the power of thought? Of course you have! The best thing is, scientists are putting this awesome Sci-Fi superpower to the test. With the help of neroscientist Christof Koch of Caltech and neurosurgeon Itzhak Fried of UCLA one can start controlling a computer based on harnessing the power of a certain neuron in the human brain.

This neuron functions similarly to how a computer functions allowing it to "recognize people, landmarks, and objects." These scientists have been working with persons diagnosed with epilepsy and with the help of Moran Cerf (a postdoctoral fellow) they have found that individuals have been able to "consciously control the firing of these single neurons...and in doing so manipulate the behavior of an image on a computer screen."

It is already amazing what the brain can do, but the truly remarkable thing is that there is so much more to it that we don't know. This is truly the beginning of the brain era where we will start to unravel and discover more than we ever have about the human race. Unlocking the secrets of our full potential is on the horizon as we dig deeper for an understanding of how our brain functions.

These scientists were able to find one neuron amongst billions, and this neuron can be controlled by the patient and turned into a controller for a computer. In around 70 percent of the trials the subjects were successful in separating two images on a screen by focusing on the target image and fading out the "distractor" image. This breakthrough is so fascinating it is almost to good to be true, but the study stands and the patients felt the task to be "incredibly fun as they started to feel that they control things in the environment purely with their thought."

So surely these types of studies should be continued in a lab setting so that it can be tweaked and perfected. The discovery of this neuron can be used for a greater purpose than the sole entertainment of bringing out our childhood fantasies of controlling things with our minds; but how could it not be one of the coolest things ever? Yes, it can be used to play a new type of videogame, but it can also be expanded and used as a built-in controller for any electronic devise that can be synced to your brain. One may no longer need the use of a keyboard as they write an article, just by thinking. They are not at all shocked to see their thoughts written out on the screen in front of them with no more of an effort than to will it.

Though this is just the baby stage of what can one day be a great and dependent part of everyday life the questions of the consequences are always lingering. What the brain fully has to offer once mixed with technology is still unknown. The fact of the matter is, are we ready for this great responsibility as a race?


http://www.sciencedaily.com/releases/2010/10/101027133158.htm
Posted by      David M. at 9:10 PM MDT
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