Continuous intrathecal baclofen infusions induced a marked increase of the transcranially evoked silent period in a patient with generalized dystonia

We observed a marked prolongation of the transcranially evoked silent period during continuous intrathecal administration of high doses of the gamma-aminobutyric acid (GABA)_B receptor agonist baclofen in a patient with generalized dystonia. Size of motor evoked potentials and central conduction time remained unchanged during intrathecal baclofen administration. The selective prolongation of the silent period during high-dose continuous intrathecal baclofen therapy supports the notion that GABA_B-ergic intracortical interneurons play a part in the generation of the transcranially evoked silent period. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:1209–1212, 1998.     

Identification of enterococci and determination of their glycopeptide resistance in German and Austrian clinical microbiology laboratories

Objectives: To determine exactly how German and Austrian routine laboratories perform tests for the identification of enterococci and determination of their glycopoptide resistance.
Methods: Six enterococcal test strains with different types of glycopeptide resistance ( Enterococcus faecium , VanA; E. faecalis , VanA; E. faecium , VanB; E. faecalis , VanB; E. gallinarum , VanC₁; E. casseliflavus , VanC₂) were sent as anonymous isolates to 73 clinical microbiology laboratories (65 in Germany; eight in Austria). The participating laboratories had to identify the strains up to the species level and to determine their antibiotic susceptibilities to the glycopeptides vancomycin and teicoplanin by the test method(s) that are used daily in the corresponding laboratories.
Results: The analysis of the results received from 62 laboratories (56 from Germany, six from Austria) demonstrated that the most used routine method in susceptibility testing was the agar diffusion test, followed by the Etest, and the microbroth dilution procedure. The majority of participants had no difficulties in susceptibility testing with the VanA-type strains. However, the agar diffusion test was often not able to recognize clearly the VanB and VanC strains; some problems also arose with VanB isolates in the Etest. With the microbroth dilution method, the corresponding type of glycopeptide resistance was correctly determined in the majority of enterococcal test strains. Difficulties also arose in identification, especially with the VanC strains ( E. gallinarum and E. casseliflavus ), which were often falsely identified as E. faecium. The reasons for these errors are obviously based on the lack of important tests (such as motility and presence of a yellow pigment) in some commercially available identification test kits.     

Lateralized auditory spatial perception and the contralaterality of cortical processing as studied with functional magnetic resonance imaging and magnetoencephalography

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were used to study the relationships between lateralized auditory perception in humans and the contralaterality of processing in auditory cortex. Subjects listened to rapidly presented streams of short FM‐sweep tone bursts to detect infrequent, slightly deviant tone bursts. The stimulus streams consisted of either monaural stimuli to one ear or the other or binaural stimuli with brief interaural onset delays. The onset delay gives the binaural sounds a lateralized auditory perception and is thought to be a key component of how our brains localize sounds in space. For the monaural stimuli, fMRI revealed a clear contralaterality in auditory cortex, with a contralaterality index (contralateral activity divided by the sum of contralateral and ipsilateral activity) of 67%. In contrast, the fMRI activations from the laterally perceived binaural stimuli indicated little or no contralaterality (index of 51%). The MEG recordings from the same subjects performing the same task converged qualitatively with the fMRI data, confirming a clear monaural contralaterality, with no contralaterality for the laterally perceived binaurals. However, the MEG monaural contralaterality (55%) was less than the fMRI and decreased across the several hundred millisecond poststimulus time period, going from 57% in the M50 latency range (20–70 ms) to 53% in the M200 range (170–250 ms). These data sets provide both quantification of the degree of contralaterality in the auditory pathways and insight into the locus and mechanism of the lateralized perception of spatially lateralized sounds. Hum. Brain Mapping 7:49–66, 1999. © 1999 Wiley‐Liss, Inc.     

Cholesterol and synaptic compensatory mechanisms in Alzheimer's disease mice brain during aging

Research into the development of Alzheimer's disease (AD) provides increasing evidence that vascular risk factors, including high serum cholesterol, might influence the progression of cognitive impairment and neural degeneration. In this study, we investigated the effects of high dietary cholesterol intake and the cholesterol-lowering liver X receptor-agonist T0901317 on capillary density, amyloid-β deposition, and presynaptic boutons in the hippocampus of adult (8 months) and aged (15 months) AβPPswe-PS1dE9 and wild-type mice to elucidate how cholesterol may affect neurodegenerative processes in aging and AD. Our results show increased number of presynaptic boutons in 15-month-old AβPP-PS1 mice compared to age-matched wild-type animals, but no difference at 8 months of age. High cholesterol intake accelerated this response by increasing the amount of presynaptic boutons at 8 and 15 months of age, while T0901317 intake decreased the amount of presynaptic boutons in 15-month-old AβPP-PS1 mice. These findings suggest a synaptic compensatory response to maintain connectivity during aging. We hypothesize that high cholesterol intake may cause impaired cerebral blood flow inducing ischemia, fortifying the above mentioned hypothesis of a compensatory mechanism. Contrarily, cholesterol-lowering agents may positively influence cerebral circulation, thereby diminishing aggravation of AD-like pathology.