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Quantitative markers extracted from resting-state electroencephalogram (EEG) reveal subtle neurophysiological dynamics which may provide useful information to support the diagnosis of seizure disorders. We performed a systematic review to summarize evidence on markers extracted from interictal, visually normal resting-state EEG in adults with idiopathic epilepsy or psychogenic nonepileptic seizures (PNES). Studies were selected from 5 databases and evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2. 26 studies were identified, 19 focusing on people with epilepsy, 6 on people with PNES, and one comparing epilepsy and PNES directly. Results suggest that oscillations along the theta frequency (4-8 Hz) may have a relevant role in idiopathic epilepsy, whereas in PNES there was no evident trend. However, studies were subject to a number of methodological limitations potentially introducing bias. There was often a lack of appropriate reporting and high heterogeneity. Results were not appropriate for quantitative synthesis. We identify and discuss the challenges that must be addressed for valid resting-state EEG markers of epilepsy and PNES to be developed.

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The low molecular weight polypeptide ubiquitin is commonly found conjugated to other protein species. The ubiquitin moiety has a well characterised role in targetting many of these proteins for rapid degradation [reviewed in I]. Some ubiquitin conjugates however, such as the ubiquitinated histones H2A and H2B, appear to be long-lived and formed reversibly [2]. There is limited evidence for the ubiquitination of cell-surface proteins, for instance, the lymphocyte homing receptor LECAM-1 [reviewed in 31. Moreover, anti-ubiquitin antibodies inhibit several high-affinity neurotransmitter uptake systems when incubated with intact rat synaptosomes [4]. We have therefore investigated the possible ubiquitination of plasma membrane proteins in the mammalian central nervous system. Subcellular fractions from adult rat brain were prepared by a modification of the procedure of Cotman and Taylor [5] as previously described [6]. All operations were carried out in the presence of the following cocktail of protease inhibitors; 0.2mM phenylmethylsulphonyl fluoride (PMSF), and lpglml each of leupeptin, pepstatin, chymostatin and antipain. Affinity-purified rabbit anti-ubiquitin antisera have been prepared by a modification of the method of Haas and Bright [7]. Western blotting of brain fractions was carried out by standard protocols [8] using a wet blotting system. Fig. 1. Western blot of adult rat forebrain subcellular fractions, immunodeveloped with an affinity-purified rabbit anti-ubiquitin antiserum.Samples of homogenate (lane A), cytosol (B), myelin (C), light membranes (D) and synaptic membranes (E), each loaded at 70pg of protein per track, were resolved on a 10% gel. The blot was developed with the anti-ubiquitin antiserum followed by an anti-rabbit alkaline phosphatase conjugated secondary antibody. Gels were calibrated using SDS-7B prestained molecular weight markers (Sigma). UB -Free ubiquitin.UC -Ubiquitin conjugate with molecular weight in kD.INTp-iodonitrotetrazolium violet, a dye used in the sucrose gradient separation of fractions C, D and E.We have shown that the cocktail of inhibitors did indeed protect the fractions from extensive degradation of ubiquitinated proteins and, unlike other combinations of inhibitors, did not interfere with the purity or yield of the various subcellular fractions. Aging of synaptic membrane fractions for 16 hours at room temperature showed that anti-ubiquitin conjugate immunoreactivity was preserved by the full cocktail of inhibitors, whereas control samples showed significant loss of this immunoreactivity.As shown in Fig. 1, immunodevelopment of Western blots of a range of subcellular fractions reveals a complex pattern of immunoreactive polypeptides. For example, there are at least twenty distinct bands in the homogenate (Lane A). The majority of these proteins have molecular weights greater than 55kD.Each of the fractions including the synaptic membranes (lane E), has its own characteristic pattern of immunoreactive bands, except the myelin which contains no detectable reactivity....