Hunting increases phosphorylation of calcium/calmodulin-dependent protein kinase type II in adult barn owls.

Juvenile barn owls readily adapt to prismatic spectacles, whereas adult owls living under standard aviary conditions do not. We previously demonstrated that phosphorylation of the cyclic-AMP response element-binding protein (CREB) provides a readout of the instructive signals that guide plasticity in juveniles. Here we investigated phosphorylation of calcium/calmodulin-dependent protein kinase II (pCaMKII) in both juveniles and adults. In contrast to CREB, we found no differences in pCaMKII expression between prism-wearing and control juveniles within the external nucleus of the inferior colliculus (ICX), the major site of plasticity. For prism-wearing adults that hunted live mice and are capable of adaptation, expression of pCaMKII was increased relative to prism-wearing adults that fed passively on dead mice and are not capable of adaptation. This effect did not bear the hallmarks of instructive information: it was not localized to rostral ICX and did not exhibit a patchy distribution reflecting discrete bimodal stimuli. These data are consistent with a role for CaMKII as a permissive rather than an instructive factor. In addition, the paucity of pCaMKII expression in passively fed adults suggests that the permissive default setting is "off" in adults.

Input clustering and the microscale structure of local circuits.

The recent development of powerful tools for high-throughput mapping of synaptic networks promises major advances in understanding brain function. One open question is how circuits integrate and store information. Competing models based on random vs. structured connectivity make distinct predictions regarding the dendritic addressing of synaptic inputs. In this article we review recent experimental tests of one of these models, the input clustering hypothesis. Across circuits, brain regions and species, there is growing evidence of a link between synaptic co-activation and dendritic location, although this finding is not universal. The functional implications of input clustering and future challenges are discussed.

Utility of electromyography for nerve root monitoring during spinal surgery.

In addition to potential spinal cord injury, spinal surgery carries a risk of damage to spinal nerve roots, which could result in sensory or motor deficit. Both spontaneous and triggered electromyography (sEMG and tEMG, respectively) have been employed to reduce the risk of these deficits. This article reviews the theory and best practice of electromyographic monitoring for spinal surgery, the evidence supporting its use for various types of spine surgery, and finally, suggestions for future directions to improve knowledge and advance electromyographic monitoring of spinal nerves.

Bidirectional regulation of the cAMP response element binding protein encodes spatial map alignment in prism-adapting barn owls.

The barn owl midbrain contains mutually aligned maps of auditory and visual space. Throughout life, map alignment is maintained through the actions of an instructive signal that encodes the magnitude of auditory-visual mismatch. The intracellular signaling pathways activated by this signal are unknown. Here we tested the hypothesis that CREB (cAMP response element-binding protein) provides a cell-specific readout of instructive information. Owls were fitted with prismatic or control spectacles and provided rich auditory-visual experience: hunting live mice. CREB activation was analyzed within 30 min of hunting using phosphorylation state-specific CREB (pCREB) and CREB antibodies, confocal imaging, and immunofluorescence measurements at individual cell nuclei. In control owls or prism-adapted owls, which experience small instructive signals, the frequency distributions of pCREB/CREB values obtained for cell nuclei within the external nucleus of the inferior colliculus (ICX) were unimodal. In contrast, in owls adapting to prisms or readapting to normal conditions, the distributions were bimodal: certain cells had received a signal that positively regulated CREB and, by extension, transcription of CREB-dependent genes, whereas others received a signal that negatively regulated it. These changes were restricted to the subregion of the inferior colliculus that received optically displaced input, the rostral ICX, and were not evident in the caudal ICX or central nucleus. Finally, the topographic pattern of CREB regulation was patchy, not continuous, as expected from the actions of a topographically precise signal encoding discrete events. These results support a model in which the magnitude of CREB activation within individual cells provides a readout of the instructive signal that guides plasticity and learning.

A one-carbon modification of protein lysine associated with elevated oxidative stress in human substantia nigra.

We describe for the first time a naturally occurring lysine modification that is converted to methyllysine by reduction with sodium borohydride. This modification is approximately 1.7 times as abundant in soluble proteins from human substantia nigra pars compacta as in proteins from other brain regions, possibly as a result of elevated oxidative stress in the nigra. Proteins from cultured PC12 cells exposed to oxidative stress conditions also contain elevated levels of this lysine modification. The abundance of the naturally occurring modification is roughly 0.08 nmoles/mg protein in either unstressed brain or PC12 cells. Modification levels remain stable in isolated proteins incubated for 2 h at 37 degrees C in pH 7 buffer. We propose that the endogenous modification is the lysine Schiff base, epsilon-N-methylenelysine, and that lysine modifications may result from a reaction with formaldehyde in vivo. Rat brain contains approximately 60 nmoles/g wet weight of formaldehyde, which probably includes both free and reversibly bound forms. Adding approximately 35 microm HCHO to PC12 cell growth medium introduces methylenelysine modifications in cell proteins and impairs cell viability. The existence of this post-translational modification suggests new mechanisms of oxidative stress that may contribute to tissue degeneration, including loss of nigral dopamine neurons during normal aging and in Parkinson's disease.

DARPP-32-like immunoreactivity in AII amacrine cells of rat retina.

Previous studies demonstrated that the dopamine- and adenosine 3',5'-monophosphate-regulated phosphatase inhibitor known as "DARPP-32" is present in rat, cat, monkey, and human retinas. We have followed up these studies by asking what specific cell subtypes contain DARPP-32. Using a polyclonal antibody directed against a peptide sequence of human DARPP-32, we immunostained adult rat retinas that were either transretinally sectioned or flat mounted and found DARPP-32-like immunoreactivity in some cells of the amacrine cell layer across the entire retinal surface. We report here, based on the shape and spatial distribution of these cells, their staining by an anti-parvalbumin antibody, and their juxtaposition with processes containing tyrosine hydroxylase, that DARPP-32-like immunoreactivity is present in AII amacrine cells of rat retina. These results suggest that the response of AII amacrine cells to dopamine is not mediated as simply as previously supposed.