Scalp electrical recording during paralysis: quantitative evidence that EEG frequencies above 20 Hz are contaminated by EMG.

OBJECTIVE: To identify the possible contribution of electromyogram (EMG) to scalp electroencephalogram (EEG) rhythms at rest and induced or evoked by cognitive tasks. METHODS: Scalp EEG recordings were made on two subjects in presence and absence of complete neuromuscular blockade, sparing the dominant arm. The subjects undertook cognitive tasks in both states to allow direct comparison of electrical recordings. RESULTS: EEG rhythms in the paralysed state differed significantly compared with the unparalysed state, with 10- to 200-fold differences in the power of frequencies above 20 Hz during paralysis. CONCLUSIONS: Most of the scalp EEG recording above 20 Hz is of EMG origin. Previous studies measuring gamma EEG need to be re-evaluated. SIGNIFICANCE: This has a significant impact on measurements of gamma rhythms from the scalp EEG in unparalysed humans. It is to be hoped that signal separation methods will be able to rectify this situation.     

Partial N-terminal amino acid sequences of three nonstructural proteins of two flaviviruses

Partial N-terminal amino acid sequences for the three largest nonstructural proteins of two flaviviruses, yellow fever virus and St. Louis encephalitis virus, have been obtained. The determined sequences of these proteins exhibit significant amino acid sequence homology, and allow the positioning of these three nonstructural proteins in the polyprotein sequence deduced from the nucleotide sequence of yellow fever virus (C. M. Rice, E. M. Lenches, S. R. Eddy, S. J. Shin, R. L. Sheets, and J. H. Strauss, 1985, Science 229, 726-733.) The deduced start points support the hypothesis that the N terminus of nonstructural glycoprotein NS1 results from cleavage by signalase, whereas the N termini of NS3 and NS5 result from cleavages following double basic residues that are flanked by amino acids with short side chains.     

Research letter: How should abridged scientific articles be presented in journals? A survey of readers and authors

SEVERAL SCIENTIFIC AND GENERAL MEDICAL JOURNALS publish full-length articles on their Web sites and abridged versions in their print journals. We surveyed a stratified random sample of BMJ readers and authors to elicit their preferred format for the abridged print version. Each participant received a research paper abridged in 3 different formats: conventional abridged version, journalistic version and enhanced-abstract version. Overall, 45% (95% confidence interval [CI] 42%–48%) of the respondents said they liked the conventional version most, 31% (95% CI 28%–34%) preferred the journalistic version and 25% (95% CI 22%–27%) preferred the enhanced-abstract version. Twenty-eight percent (95% CI 25%–32%) indicated that use of the journalistic format for abridged articles would very likely stop them from submitting papers to BMJ, and 13% (95% CI 11%–16%) said the use of the enhanced-abstract version would stop them from submitting to BMJ. Publishers of general medical journals who publish shortened articles should consider that authors and readers prefer a more conventional style of abridged papers.     

Molecular genetics and cytogenetics--a glossary and list of abbreviations.

A glossary of terms commonly used in molecular genetics and cytogenetics has been prepared to assist pathologists. The emphasis is on clinically relevant examples.     

Different mechanisms of decreased drug accumulation in doxorubicin and mitoxantrone resistant variants of the MCF7 human breast cancer cell line.

We selected two drug resistant variants of the MCF7 human breast cancer cell line by chronic in vitro exposure to doxorubicin (MCF7/D40 cell line) and mitoxantrone (MCF7/Mitox cell line), respectively. The cell lines are similar in growth characteristics including doubling time, DNA synthetic phase and cell size. Resistance to mitoxantrone conferred only partial resistance to doxorubicin; whereas resistance selected for doxorubicin appeared to confer complete resistance to mitoxantrone. Both agents selected for cross resistance to the Vinca alkaloids. MCF7/D40 cells display a classic-multi-drug resistance phenotype with expression of P-glycoprotein, decreased drug accumulation relative to the parental line and reversal of drug accumulation and drug resistance by verapamil. MCF7/Mitox cells likewise display resistance to multiple drugs, but in contrast to MCF7/D40 cells do not express P-glycoprotein by immunoblot or RNA blot analysis. Net drug accumulation in MCF7/Mitox cells was decreased relative to the parental cells but there was no selective modulation of drug accumulation or in vitro drug resistance by the addition of verapamil. Efflux of mitoxantrone was enhanced in both the MCF7/D40 and MCF7/Mitox cell lines relative to the MCF7/S cell line. We conclude that the two drug resistant cell lines have different mechanisms of decreased drug accumulation.     

Alcohol inhibition of NMDA-stimulated catecholamine efflux in aging brain.

The influence of aging on the ability of ethanol to inhibit N-methyl-D-aspartate-stimulated catecholamine overflow in rat brain was examined. Alcohol effects on N-methyl-D-aspartate stimulated [3H]norepinephrine or [3H]dopamine overflow from the cortex, hippocampus, and striatum of aged (24-28 months) middle aged (12-14 months), and young (3-5 months) rats were examined. N-methyl-D-aspartate (500 microM) stimulated catecholamine overflow in all brain regions, with aged rats showing declines in overflow of 33% in the hippocampus and 41% in the striatum. Alcohol (30-200 mM) produced a concentration-dependent inhibition of overflow at all ages and brain regions tested. The IC50 for alcohol inhibition of NMDA-stimulated catecholamine release was not significantly different in aged brain or across brain regions. These results indicate that alcohol's ability to inhibit NMDA-stimulated catecholamine release is not significantly altered with aging.