EEG abnormalities with and without relation to severe hypoglycaemia in adolescents with type 1 diabetes.

AIMS/HYPOTHESIS: The aim of the present study was to identify whether adolescents with type 1 diabetes receiving modern multiple insulin injection therapy (MIT) have abnormal EEGs, and to elucidate possible correlations with a history of severe hypoglycaemia, poor metabolic control and nerve conduction defects. METHODS: We investigated 35 patients (age 14-19 years) with disease duration 7.6+/-4.6 years, and 45 healthy control subjects. EEG spectral components were obtained from 15-min recordings in resting, awake subjects. Nerve conduction was measured bilaterally in motor and sensory fibres in the median, peroneal and sural nerves. RESULTS: The EEGs of patients showed an increase in slow activity (delta and theta) and a reduction in alpha peak frequency, both of which were most pronounced in the frontal regions (p<0.001). They also showed a decrease in fast activity, which was most pronounced bilaterally in the posterior temporal regions (alpha p<0.001, beta p<0.01, gamma p<0.001). A history of severe hypoglycaemia was correlated with a global increase in theta activity (p<0.01-0.05). Poor metabolic control, measured as acute and long-term HbA1c levels, was correlated with an increase in delta activity and a decrease in alpha peak frequency. The decrease in fast activity in the temporal regions was a separate type of abnormality because it had a different distribution, and was not correlated with the increase in delta/theta power, poor metabolic control or with hypoglycaemia. CONCLUSIONS/INTERPRETATION: Recurrent severe hypoglycaemia and poor metabolic control are risk factors for EEG abnormalities in adolescents with type 1 diabetes receiving MIT treatment. In addition, we found pronounced abnormalities in the temporal regions that were not related to these risk factors.

Evaluation of L1 and L2 minimum norm performances on EEG localizations.

OBJECTIVE: In this work we study the performance of minimum norm methods to estimate the localization of brain electrical activity. These methods are based on the simplest forms of L(1) and L(2) norm estimates and are applied to simulated EEG data. The influence of several factors like the number of electrodes, grid density, head model, the number and depth of the sources and noise levels was taken into account. The main objective of the study is to give information about the dependence, on these factors, of the localization sources, to allow for proper interpretation of the data obtained in real EEG records. METHODS: For the tests we used simulated dipoles and compared the localizations predicted by the L(1) and L(2) norms with the location of these point-like sources. We varied each parameter separately and evaluated the results. RESULTS: From this work we conclude that, the grid should be constructed with approximately 650 points, so that the information about the orientation of the sources is preserved, especially for L(2) norm estimates; in favorable noise conditions, both L(1) and L(2) norm approaches are able to distinguish between more than one point-like sources. CONCLUSIONS: The critical dependence of the results on the noise level and source depth indicates that regularized and weighted solutions should be used. Finally, all these results are valid both for spherical and for realistic head models.

Expression of a pilin subunit BfpA of the bundle-forming pilus of enteropathogenic Escherichia coli in an aroA live salmonella vaccine strain.

Enteropathogenic Escherichia coli (EPEC) is a major cause of childhood diarrhea in developing countries and is a leading cause of severe diarrheal illness among Brazilian infants. As one approach to constructing a vaccine candidate against diarrhea caused by EPEC, we evaluated whether the pilin subunit (BfpA) of the bundle-forming pilus (BFP) could be expressed by a live Salmonella vaccine strain. Several copies of the coding region of BfpA (bfpA) were amplified by PCR from a preparation of the EAF plasmid of EPEC strain B171 and cloned into plasmid vectors. An intact copy of bfpA was subcloned into the heat inducible prokaryotic expression vector pCYTEXP1, and the resulting pBfpA was used to transform the aroA S. typhimurium strain SL3261, generating SL3261(pBfpA). The recombinant vaccine strain was able to express, but not to process, rBfpA as evidenced by a prominent 21 kDa protein that crossreacted with anti-BFP antiserum found only in extracts of heat-treated SL3261(pBfpA), but not in strains of untreated SL3261(pBfpA) or SL3261 not carrying the plasmid. Furthermore, rBfpA accumulation was not toxic to the Salmonella host, as evidenced by similar plating efficiencies between induced and uninduced strains of SL3261(pBfpA). Finally, SL3261(pBfpA) orally administered to BALB/c mice was capable of eliciting a sustained and vigorous humoral immune response to BfpA, achievable even with a single oral dose of approximately 10(9) organisms. Therefore, this pilin product may serve as a potential immunogen as part of a live combined vaccine strategy to prevent two of the major public health problems in Brazil--salmonellosis and EPEC childhood diahrrea.