Faculty Bibliography

IMPORTANCE/OBJECTIVE:The increasing use of continuous electroencephalography (EEG) monitoring in the intensive care unit has led to recognition of new EEG patterns that are of unclear or unknown significance. OBJECTIVE:To describe an EEG pattern, lateralized rhythmic delta activity (LRDA), encountered in critically ill subjects and determine its clinical significance in this setting. DESIGN, SETTING, AND PARTICIPANTS Retrospective review at an academic medical center of EEG recordings, medical records, and imaging studies of critically ill patients with LRDA and comparison with subjects with lateralized periodic discharges (also known as periodic lateralized epileptiform discharges), subjects with focal nonrhythmic slowing, and controls. INTERVENTION/METHODS:Electroencephalography or continuous electroencephalography. MAIN OUTCOMES AND MEASURES/METHODS:Cross-sectional prevalence of lateralized rhythmic delta activity; EEG characteristics; etiology, clinical, and radiological correlates; and risk of early seizures. RESULTS:We identified LRDA in 4.7%of acutely ill subjects undergoing EEG or continuous EEG monitoring. It was often associated with other focal EEG abnormalities, including lateralized periodic discharges in 44%of cases. The most common conditions associated with LRDA were intracranial hemorrhage and subarachnoid hemorrhage. Lateralized rhythmic delta activity was an independent predictor of acute seizures, with 63%of subjects having seizures during their acute illness, a proportion similar to subjects with lateralized periodic discharges (57%) and significantly higher than associated with focal nonrhythmic slowing (20%) or in control subjects (16%). Most patients (80%-90%) in the LRDA and lateralized periodic discharges groups who had seizures while undergoing continuous EEG monitoring had only nonconvulsive seizures, whereas this was the case for only 17%of patients in the other groups. Lateralized rhythmic delta activity and lateralized periodic discharges were both associated with lesions involving the cortex or juxtacortical white matter. CONCLUSIONS AND RELEVANCE/CONCLUSIONS:Lateralized rhythmic delta activity in critically ill patients has a similar clinical significance as lateralized periodic discharges. It reflects the presence of a focal lesion and is associated with a high risk of acute seizures, especially nonconvulsive.

Impaired consciousness in epilepsy has a significant negative impact on patients' quality of life yet is difficult to study objectively. Here, we develop an improved prospective Responsiveness in Epilepsy Scale-II (RES-II) and report initial results compared with the earlier version of the scale (RES). The RES-II is simpler to administer and includes both verbal and non-verbal test items. We evaluated 75 seizures (24 patients) with RES and 34 seizures (11 patients) with RES-II based on video-EEG review. The error rate per seizure by test administrators improved markedly from a mean of 2.01 ± 0.04 with RES to 0.24 ± 0.11 with RES-II. Performance during focal seizures showed a bimodal distribution, corresponding to the traditional complex partial vs. simple partial seizure classification. We conclude that RES-II has improved accuracy and testing efficiency compared with the original RES. Prospective objective testing will ultimately lead to a better understanding of the mechanisms of impaired consciousness in epilepsy.

Finding biomarkers of human neurological diseases is one of the most pressing goals of modern medicine. Most neurological disorders are recognized too late because of the lack of biomarkers that can identify early pathological processes in the living brain. Late diagnosis leads to late therapy and poor prognosis. Therefore, during the past decade, a major endeavor of clinical investigations in neurology has been the search for diagnostic and prognostic biomarkers of brain disease. Recently, a new field of metabolomics has emerged, aiming to investigate metabolites within the cell/tissue/ organism as possible biomarkers. Similarly to other "omics" fields, metabolomics offers substantial information about the status of the organism at a given time point. However, metabolomics also provides functional insight into the biochemical status of a tissue, which results from the environmental effects on its genome background. Recently, we have adopted metabolomics techniques to develop an approach that combines both in vitro analysis of cellular samples and in vivo analysis of the mammalian brain. Using proton magnetic resonance spectroscopy, we have discovered a metabolic biomarker of neural stem/progenitor cells (NPCs) that allows the analysis of these cells in the live human brain. We have developed signal-processing algorithms that can detect metabolites present at very low concentration in the live human brain and can indicate possible pathways impaired in specific diseases. Herein, we present our strategy for both cellular and systems metabolomics, based on an integrative processing of the spectroscopy data that uses analytical tools from both metabolomic and spectroscopy fields. As an example of biomarker discovery using our approach, we present new data and discuss our previous findings on the NPC biomarker. Our studies link systems and cellular neuroscience through the functions of specific metabolites. Therefore, they provide a functional insight into the brain, which might eventually lead to discoveries of clinically useful biomarkers of the disease.

The identification of neural stem and progenitor cells (NPCs) by in vivo brain imaging could have important implications for diagnostic, prognostic, and therapeutic purposes. We describe a metabolic biomarker for the detection and quantification of NPCs in the human brain in vivo. We used proton nuclear magnetic resonance spectroscopy to identify and characterize a biomarker in which NPCs are enriched and demonstrated its use as a reference for monitoring neurogenesis. To detect low concentrations of NPCs in vivo, we developed a signal processing method that enabled the use of magnetic resonance spectroscopy for the analysis of the NPC biomarker in both the rodent brain and the hippocampus of live humans. Our findings thus open the possibility of investigating the role of NPCs and neurogenesis in a wide variety of human brain disorders.

The bulge region of the hair follicle serves as a repository for epithelial stem cells that can regenerate the follicle in each hair growth cycle and contribute to epidermis regeneration upon injury. Here we describe a population of multipotential stem cells in the hair follicle bulge region; these cells can be identified by fluorescence in transgenic nestin-GFP mice. The morphological features of these cells suggest that they maintain close associations with each other and with the surrounding niche. Upon explantation, these cells can give rise to neurosphere-like structures in vitro. When these cells are permitted to differentiate, they produce several cell types, including cells with neuronal, astrocytic, oligodendrocytic, smooth muscle, adipocytic, and other phenotypes. Furthermore, upon implantation into the developing nervous system of chick, these cells generate neuronal cells in vivo. We used transcriptional profiling to assess the relationship between these cells and embryonic and postnatal neural stem cells and to compare them with other stem cell populations of the bulge. Our results show that nestin-expressing cells in the bulge region of the hair follicle have stem cell-like properties, are multipotent, and can effectively generate cells of neural lineage in vitro and in vivo.

The present study examined whether nestin+ neural-like stem cells detected in the scar tissue of rats 1 week after myocardial infarction (MI) were derived from bone marrow and/or were resident cells of the normal myocardium. Irradiated male Wistar rats transplanted with beta-actin promoter-driven, green fluorescent protein (GFP)-labeled, unfractionated bone marrow cells were subjected to coronary artery ligation. Three weeks after MI, GFP-labeled bone marrow cells were detected in the infarct region, and a modest number were associated with nestin immunoreactivity. The paucity of GFP+/nestin+ cells in the scar tissue provided the impetus to explore whether neural-like stem cells were derived from cardiac tissue. Nestin mRNA and immunoreactivity were detected in normal rat myocardium, and transcript levels were increased in the damaged heart after MI. In primary-passage, cardiac tissue-derived neural cells, filamentous nestin staining was associated with a diffuse, cytoplasmic glial fibrillary acidic protein signal. Unexpectedly, in viable myocardium, numerous nestin+/glial fibrillary acidic protein+ fiberlike structures of varying length were detected and observed in close proximity to neurofilament-M+ fibers. The infarct region was likewise innervated, and the preponderance of neurofilament-M+ fibers appeared to be physically associated with nestin+ fiberlike structures. These data highlight the novel observation that the normal rat heart contained resident nestin+/glial fibrillary acidic protein+ neural-like stem cells, fiberlike structures, and nestin mRNA levels that were increased in response to myocardial ischemia. Cardiac tissue-derived neural stem cell migration to the infarct region and concomitant nestin+ fiberlike innervation represent obligatory events of reparative fibrosis in the damaged rat myocardium.

Recent advances in cell-based therapies for demyelinating central nervous system diseases have demonstrated the ability to restore damaged neuronal architecture and function. Demyelinated axons in patients with multiple sclerosis can spontaneously remyelinate over time; however, the rate and extent at which remyelination occurs is inadequate for complete recovery. Previous attempts aimed at regenerating myelin-forming cells have been successful but limited by the multifocal nature of the lesions and the inability to produce large numbers of myelin-producing cells in culture. Stem cell-based therapy can overcome these limitations to some extent and may prove useful in the future treatment of demyelinating diseases.

Nitric oxide (NO) is a free radical signaling molecule with remarkably complex biochemistry. Its involvement in multiple sclerosis (MS) had been postulated soon after the discovery of the critical role NO plays in inflammation. However, the extent of NO's contribution to MS is not yet understood, party due to the often opposing roles that NO can play in cellular processes. This review briefly covers new developments in the area of NO that may be relevant to MS. It also describes recent progress in understanding the role of NO in MS, new potential targets of the action of NO in the cell, and prospects for NO-based therapies.

Voltage-gated Kv1 channels are key factors regulating excitability in the mammalian central nervous system. Diverse posttranslational regulatory mechanisms operate to determine the density, subunit composition, and localization of Kv1 channel complexes in the neuronal plasma membrane. In this study, we investigated the role of the endoplasmic reticulum chaperone calnexin in the intracellular trafficking of Kv1 channels. We found that coexpressing calnexin with the Kv1.2alpha subunit in transfected mammalian COS-1 cells produced a dramatic dose-dependent increase in cell surface Kv1.2 channel complexes. In calnexin-transfected COS-1 cells, the proportion of Kv1.2 channels with mature N-linked oligosaccharide chains was comparable to that observed in neurons. In contrast, calnexin coexpression exerted no effects on trafficking of the intracellularly retained Kv1.1 or Kv1.6alpha subunits. We also found that calnexin and auxiliary Kvbeta2 subunit coexpression was epistatic, suggesting that they share a common pathway for promoting Kv1.2 channel surface expression. These results provide yet another component in the elaborate repertoire of determinants regulating the density of Kv1 channels in the plasma membrane.

Voltage-gated Kv1 potassium channels consist of pore-forming alpha subunits and cytoplasmic Kv beta subunits. The latter play diverse roles in modulating the gating, stability, and trafficking of Kv1 channels. The crystallographic structure of the Kv beta2 subunit revealed surprising structural homology with aldo-keto reductases, including a triosephosphate isomerase barrel structure, conservation of key catalytic residues, and a bound NADP(+) cofactor (Gulbis, J. M., Mann, S., and MacKinnon, R. (1999) Cell 90, 943-952). Each Kv1-associated Kv beta subunit (Kv beta 1.1, Kv beta 1.2, Kv beta 2, and Kv beta 3) shares striking amino acid conservation in key catalytic and cofactor binding residues. Here, by a combination of structural modeling and biochemical and cell biological analyses of structure-based mutations, we investigate the potential role for putative Kv beta subunit enzymatic activity in the trafficking of Kv1 channels. We found that all Kv beta subunits promote cell surface expression of coexpressed Kv1.2 alpha subunits in transfected COS-1 cells. Kv beta1.1 and Kv beta 2 point mutants lacking a key catalytic tyrosine residue found in the active site of all aldo-keto reductases have wild-type trafficking characteristics. However, mutations in residues within the NADP(+) binding pocket eliminated effects on Kv1.2 trafficking. In cultured hippocampal neurons, Kv beta subunit coexpression led to axonal targeting of Kv1.2, recapitulating the Kv1.2 localization observed in many brain neurons. Similar to the trafficking results in COS-1 cells, mutations within the cofactor binding pocket reduced axonal targeting of Kv1.2, whereas those in the catalytic tyrosine did not. Together, these data suggest that NADP(+) binding and/or the integrity of the binding pocket structure, but not catalytic activity, of Kv beta subunits is required for intracellular trafficking of Kv1 channel complexes in mammalian cells and for axonal targeting in neurons.