The brain tumours represent a complex tissue that has its own characteristic metabolic features and is interfaced with the whole organism. We investigated changes in basal blood plasma metabolites in the presence of primary brain tumour, their correlation with tumour grade, as well as the feasibility of statistical discrimination based on plasma metabolites. Together 60 plasma samples from patients with clinically defined glioblastoma, meningioma, oligodendrioglioma, astrocytoma, and non-specific glial tumour and plasma samples from 28 healthy volunteers without any cancer history were measured by NMR spectroscopy. In blood plasma of primary brain tumour patients, we found significantly increased levels of glycolytic metabolites glucose and pyruvate, and significantly decreased level of glutamine and also metabolites participating in tricarboxylic acid (TCA) cycle, citrate and succinate, when compared with controls. Further, plasma metabolites levels: tyrosine, phenylalanine, glucose, creatine and creatinine correlated significantly with tumour grade. In general, observed changes are parallel to the biochemistry expected for tumourous tissue and metabolic changes in plasma seem to follow the similar rules in all primary brain tumours, with very subtle variations among tumour types. Only two plasma metabolites tyrosine and phenylalanine were increased exclusively in

Amyloid beta peptide is recognized as the main constituent of the extracellular amyloid plaques, the major neuropathological hallmark of Alzheimer's disease. Abeta is a small peptide constitutively expressed in normal cells, not toxic in the monomeric form but aggregated Abeta is assumed to be the main if not the only factor causing Alzheimer's disease. Interestingly, the new reports suggest neurotoxicity of soluble Abeta oligomers rather than amyloid fibrils. Because of the fact that fibrils were thought to be the main toxic species in AD, early structural studies focused on fibrils themselves and Abeta monomers, as their building blocks while there is practically no data on oligomer structure and mechanism of neurotoxicity. Using a model peptide spanning residues 10-30 of Abeta, obtained by overexpression in bacteria, we have employed mass spectrometry of noncovalent complexes and disulfide rearrangement assay to gain new insight into structure and dynamics of a prenucleation step of Abeta peptide oligomerisation. PS3-02The study of the creatine kinase in rat brain during ischemia by magnetization transfer and biochemical analysis D. Dobrota,* K. Likavčanová,* S. Kašparová, T. Liptaj, N. Pró nayová, V. Mlynárikà and V. Belanà *Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin; NMR Laboratory, STU, Bratislava; àDerer Faculty Hospital, Bratislava, Slovakia, dobrota@jfmed.uniba.skVarious methods are used to study the biochemical changes in the central nervous system under normal and pathological conditions. The magnetization transfer 31 P magnetic resonance technique was used here to measure the creatine kinase (CK) reaction rate constant in vivo in rats with cerebral ischemia. The measurements indicated that the rate constant of the CK reaction was significantly reduced in the case of chronic brain ischemia in aged rats. The similar reduction of the creatine kinase activity was found in the ischemic rat brain homogenate measured by biochemical analysis. At the same time, corresponding conventional phosphorus magnetic resonance spectra showed negligible or no change in signal intensities of compounds containing macroergic phosphates. PS3-03In vitro 1 H magnetic resonance spectroscopy differences between meningeoma and astrocytoma K. Likavčanová,* D. Dobrota,* T. Liptaj, N. H spectra of meningeoma we detected high signal from lactate but were unable to detect any signal of NAA and creatine. In contrast, astrocytoma samples revealed significantly higher level of inositol and glycine and significant decrease in glutamate and glutamine compared with meningeoma but no presence of taurine. Our results suggest that 1 H MRS can provide useful information about biochemical changes in different types of brain tumors.

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