Correct performance Dotaz Zobrazit nápovědu
OBJECTIVE: To identify intracerebral sites activated after correct motor response during cognitive task and to assess associations of this activity with mental processes. METHODS: Intracerebral EEG was recorded from 205 sites of frontal, temporal and parietal lobes in 18 epileptic patients, who responded by button pressing together with mental counting to target stimuli in visual oddball task. RESULTS: Post-movement event-related potentials (ERPs) with mean latency 295 ± 184 ms after movement were found in all subjects in 64% of sites investigated. Generators were consistently observed in mesiotemporal structures, anterior midcingulate, prefrontal, and temporal cortices. Task-variant nonspecific and target specific post-movement ERPs were identified, displaying no significant differences in distribution among generating structures. Both after correct and incorrect performances the post-performance ERPs were observed in frontal and temporal cortices with latency sensitive to error commission in several frontal regions. CONCLUSION: Mesiotemporal structures and regions in anterior midcingulate, prefrontal and temporal cortices seem to represent integral parts of network activated after correct motor response in visual oddball task with mental counting. Our results imply equivalent involvement of these structures in task-variant nonspecific and target specific processes, and suggest existence of common nodes for correct and incorrect responses. SIGNIFICANCE: Our results contribute to better understanding of neural mechanisms underlying goal-directed behavior.
- Klíčová slova
- Correct performance, ERP, Error, Intracerebral EEG, Monitoring, Movement,
- MeSH
- dospělí MeSH
- elektroencefalografie metody MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- mozek fyziologie MeSH
- pohyb fyziologie MeSH
- psychomotorický výkon fyziologie MeSH
- světelná stimulace metody MeSH
- zrakové evokované potenciály fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Gradient elution is widely used for separation of complex samples in reversed-phase HPLC systems, but is less frequently applied in normal-phase HPLC, where it has a notoriously bad reputation for poor reproducibility and unpredictable retention. This behaviour is caused by preferential adsorption of polar solvents used in mixed mobile phases, which may cause significant deviations of the actual gradient profile from the pre-set program. Another important source of irreproducible retention behaviour is gradual deactivation of the adsorbent by adsorption of even traces of water during normal-phase gradient elution. To avoid this phenomenon, carefully dried solvents should be used. Finally, column temperature should be carefully controlled during normal-phase gradient elution if reproducible results are to be obtained. Working with dry solvents at a controlled constant temperature and using a sophisticated gradient-elution chromatograph, reproducibility of the retention data in normal-phase gradient elution better than 2% may be achieved even over several months of column use. The retention data in gradient elution can be calculated accurately if appropriate corrections are adopted for the gradient dwell volume and for the preferential adsorption of the polar solvents using experimental adsorption isotherms. The average error of prediction for the corrected calculated gradient retention data was lower than 2% for a silica gel column and lower than 3% for a bonded nitrile column, which may be suitable for the optimization of separation. Further, a simple approach is suggested for rapid estimation of changes in the retention induced by a change in the gradient profile in normal-phase HPLC. For such a rough estimation, it is not necessary to know the parameters of the dependence of the solute retention factors on the composition of the mobile phase.
- MeSH
- pesticidy analýza MeSH
- spektrofotometrie ultrafialová MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- pesticidy MeSH
The composition of plant membrane lipids was investigated by reversed-phase high performance liquid chromatography mass spectrometry with accurate mass measurement. The data dependent methods for the analysis of monogalactosyldiacylglycerols (MGDGs) and digalactosyldiacylglycerols (DGDGs) have been developed. The optimised chromatographic systems were based on a 2.0 mm i.d. Nucleosil C18 column with methanol/water (MGDGs) or acetonitrile/methanol/water (DGDGs) gradients. The galactolipids were ionised by electrospray operated in the positive ion mode and identified based on their MS/MS spectra. High resolution spectra with accurate masses were found to be essential for correct interpretation of the MS data. The elution order of non-oxidised MGDGs and DGDGs followed the equivalent carbon numbers. The methods were applied for detailed characterisation of the MGDGs and DGDGs in the leaves of Arabidopsis thaliana and Melissa officinalis.
- MeSH
- Arabidopsis chemie MeSH
- chromatografie s reverzní fází MeSH
- galaktolipidy chemie MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
- meduňka chemie MeSH
- oxidace-redukce MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- galaktolipidy MeSH
- monogalactosyldiacylglycerol MeSH Prohlížeč
Lipids are important components in all biological tissues having many essential roles associated with the proper function of the organism. Their analysis in the biological tissues and body fluids is a challenging task due to the extreme sample complexity of polar lipids and to their amphiphilic character. In this work, we describe a new method for the characterization of the lipid composition in various tissues, using off-line two-dimensional coupling of hydrophilic interaction liquid chromatography (HILIC) and reversed-phase (RP) high-performance liquid chromatography coupled to electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectrometry. In the first dimension the total lipid extracts are fractioned using HILIC into individual lipid classes. In total, 19 lipid classes (+3 regioisomeric pairs) that cover a wide range of polarities are separated in one analytical run, which is the highest number of analyzed lipid classes reported so far. The lysophospholipid regioisomers are also separated in HILIC mode followed by the identification based on the characteristic ESI mass spectra. The collected fractions of the various lipid classes are further separated in the RP mode, which offers an excellent resolution of the individual lipid species. Their ESI or APCI mass spectra give correct information on the fatty acid composition and on the individual regioisomeric positions on the glycerol skeleton. Off-line coupling of both modes enables the comprehensive analysis of plant and animal samples as illustrated on the analysis of egg yolk, soya and porcine brain tissues.
- MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací metody MeSH
- hydrofobní a hydrofilní interakce MeSH
- isomerie MeSH
- kur domácí MeSH
- lipidy chemie MeSH
- mozek - chemie * MeSH
- prasata MeSH
- vaječný žloutek chemie MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
- Názvy látek
- lipidy MeSH
Chromatographic behavior of block (co)oligomers of oxyethylene (EO) and oxypropylene (PO) surfactants in reversed-phase HPLC (RP-HPLC) was investigated. The retention of EO/PO block (co)oligomers depends on the distribution of the individual monomer repeat units, but the sequence of the individual blocks also plays a (less significant) role. The enthalpic and entropic contributions of the EO and PO repeat units to the retention were determined from the data measured at changing temperature. In RP-HPLC, the effect of the repeat PO units on separation is higher than the influence of the repeat EO units. In addition to the enthalpic contributions, the retention is significantly influenced by the entropy (possibly by the change of conformation and solvation of adsorbed molecules); dual molar mass distribution according to the number of EO and PO units complicates correct assignment of the chromatographic peaks to the individual (co)oligomers in complex samples based only on the chromatographic retention data. In spite of imperfect chromatographic separation, HPLC coupled with positive ion mode atmospheric pressure chemical ionization mass spectrometry allow identifying unambiguously the dual monomer distribution in the samples of EO-PO block (co)oligomers.
- MeSH
- epoxidové sloučeniny chemie MeSH
- ethylenoxid chemie MeSH
- hmotnostní spektrometrie metody MeSH
- polyethylenglykoly chemie MeSH
- termodynamika MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- epoxidové sloučeniny MeSH
- ethylenoxid MeSH
- polyethylenglykoly MeSH
- propylene oxide MeSH Prohlížeč
OBJECTIVES: We analyzed primary school performance of girls with Turner syndrome (TS) in two distinct countries to ascertain if the cognitive phenotype of TS causes selective learning difficulties. METHODS: The cohort comprised of 44 Czech and 50 Egyptian girls with TS who attended public schools. School reports from grades 1 to 9 were obtained retrospectively from Czech participants with TS. Only recent school reports were obtained from Egyptian participants. Two controls per participant were requested - biological sisters and/or female classmates. The results were converted into a 5-point scale (1-excellent; 5-unsatisfactory). RESULTS: Analysis of longitudinal Czech data displayed a strong time component in both subjects and controls. Showing better points in lower grades with its gradual worsening as the education complexity increased. In contrast, there was a strong statistically significant difference between groups in Mathematics (p=0.0041, p=0.0205 after Bonferroni correction) and this difference increased over time. The points for Mathematics did not differ in grades 1+2 (0.05 difference in mean grade between the two groups), however, they differed by 0.28 in grades 6+7 and by 0.32 in grades 8+9. While slightly different in character (cross-sectional vs. longitudinal), the Egyptian cohort data confirmed our findings, showing no difference in general school performance but having similar trends in Mathematics (grades 1+2: 0.11, grades 6+7: 0.54, grades 8+9: 0.68; p=0.0058, p=0.029 after Bonferroni correction). CONCLUSION: Excluding results in Mathematics, which showed pronounced worsening in relation to age in comparison with unaffected controls, girls with TS performed similarly to their controls.
- Klíčová slova
- Cognitive phenotype, Learning disability, Primary school, School performance, Turner syndrome,
- MeSH
- dítě MeSH
- kohortové studie MeSH
- lidé MeSH
- matematika MeSH
- mladiství MeSH
- průřezové studie MeSH
- retrospektivní studie MeSH
- Turnerův syndrom * MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- mladiství MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
This work describes the intricacies of the determination of the trimethylselenonium ion (TMSe) in human urine via high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS). By definition, this technique requires that the separated TMSe can be online converted into a volatile compound. Literature data for the determination of TMSe via the hydride generation technique are contradictory; i.e., some authors claim that direct formation of volatile compounds is possible under reduction with NaBH4, whereas others reported that a digestion step is mandatory prior to conversion. We studied and optimized the conditions for online conversion by varying the mobile phase composition (pyridine, phosphate, and acetate), testing different reaction coils, and optimizing the hydride generation conditions, although technically no hydride (H2Se) is formed but a dimethylselenide (DMSe). The optimized conditions were used for the analysis of 64 urine samples of 16 (unexposed) volunteers and the determination of low amounts of TMSe (LOD = 0.2 ng mL-1). Total (specific gravity-corrected) selenium concentrations in the urine samples ranged from 7.9 ± 0.7 to 29.7 ± 5.0 ng mL-1 for individual volunteers. Four volunteers were characterized as TMSe producers (hINMT genotype GA) and 12 were non-producers (hINMT genotype GG). Urine of TMSe producers contained 2.5 ± 1.7 ng mL-1 of TMSe, compared to 0.2 ± 0.2 ng mL-1 for non-producers.
- Klíčová slova
- Hydride generation, Reaction coil, TMSe, Trimethylselenonium ion, Urine,
- MeSH
- fluorescenční spektrometrie MeSH
- lidé MeSH
- selen * moč MeSH
- sloučeniny selenu * MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- selen * MeSH
- sloučeniny selenu * MeSH
- trimethylselenonium MeSH Prohlížeč
In this study, the potential of high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) for metabolomic profiling of red wine samples was examined. Fifty one wines representing three varieties (Cabernet Sauvignon, Merlot, and Pinot Noir) of various geographical origins were sourced from the European and US retail market. To find compounds detected in analyzed samples, an automated compound (feature) extraction algorithm was employed for processing background subtracted single MS data. Stepwise reduction of the data dimensionality was followed by principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA) which were employed to explore the structure of the data and construct classification models. The validated PLS-DA model based on data recorded in positive ionization mode enabled correct classification of 96% of samples. Determination of molecular formula and tentative identification of marker compound was carried out using accurate mass measurement of full single MS spectra. Additional information was obtained by correlating the fragments obtained by MS/MS accurate mass spectra using the QTOF with collision induced dissociation (CID) of precursor ions.
The retention (migration) behaviour of various barbiturates, phenylurea and triazine herbicides in micellar electrokinetic chromatography (MEKC) with uncoated fused-silica capillaries was compared with the behaviour in micellar electrokinetic chromatography with reduced electroosmotic flow (RF-MEKC) using capillaries modified with linear polyacrylamide. The error in the values of the retention factors caused by the neglection of the contribution of the electroosmotic flow in RF-MEKC was investigated and a method for correcting this error was suggested. The retention was characterised using the lipophilic and polar indices to characterise and to predict the retention as a function of the concentration of the surfactant (sodium dodecylsulphate) in the running buffer in MEKC and in RF-MEKC. Homologous series of n-alkylbenzenes and of n-alkan-2-ones were compared as the standard sets for the calibration of the retention (migration) index scale. The values of the lipophilic indices of a given solute measured in reversed-phase HPLC, MEKC and RF-MEKC are close to each other. Under ideal MEKC conditions, the values of the polarity indices are close to one for various sample solutes. However, for partially ionised compounds such as weakly acidic barbiturates, where the contribution of the electrophoretic migration is significant, the values of the polarity indices are significantly lower than one. Optimum conditions for separations of mixtures of triazine and phenylurea herbicides and of barbiturates using various techniques tested were compared.
A novel, highly specific, simple and rapid method for the determination of malondialdehyde (MDA), the routinely used marker for free radical generation in body fluids has been developed and evaluated. Serum samples from 30 healthy volunteers in heparin and 1,4-dithiothreitol-containing tubes stored at -80 degrees C were analyzed. The MDA-thiobarbituric acid complex was separated from interfering substances using HPLC. For the separation, reverse phase column MAC (4 x 250 mm, Biospher SI 120 PSI C18, particle size 7 microm) was used. The mixture of methanol and 8.3 mmol/l phosphate buffer, pH= 7.2, (35:65, v/v) was used as mobile phase. The volume of serum samples injected on the column was 50 microl. The analyte was detected at 532 nm. Retention time of MDA-thiobarbituric acid complex was 4.9+/-0.1 min at the flow rate 0.7 ml/min. Excellent linearity was achieved. The intra- and interassay coefficient of variation was 7.3% and 8.8%, respectively. The recovery was 95.6% and the detection limit was 0.1 micromol/l. The validity of this method was proved by comparison with the spectrophotometric determination of MDA-thiobarbituric acid complex by the method of Yagi at three different wavelengths (485, 532 and 560 nm) with Allen's correction.
- MeSH
- chelátory chemie MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- malondialdehyd krev MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chelátory MeSH
- malondialdehyd MeSH
