Merge (IMAGE) Princeton University Caption The researchers also found that MHCI proteins may resume pruning nerve-muscle synapses in older organisms, an age when there are no longer any extra synapses. Instead, muscle fibers become completely 'denervated', or detached from nervous system control, which could lead to weakness and instability in older people. This image from a 2-year-old (elderly) normal mouse shows denervation in the upper-right synapse, which is apparent as very little overlap of the red and green fluorescent markers used to indicate places where the neuron and muscle fiber connect. At lower left, a healthy-looking synapse displays good overlap. Credit Image by Lisa Boulanger, Princeton Neuroscience Institute, and Mazell Tetruashvily, Department of Molecular Biology Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.