A new database of nucleic acid base trimers has been developed that includes 141 geometries and stabilization energies obtained at the RI-MP2 level of theory with the TZVPP basis set. Compared to previously compiled biologically oriented databases, this new construct includes considerably more complicated structures; the various intermolecular interactions in the trimers are quite heterogeneous and in particular include simultaneous hydrogen bonding and stacking interactions, which is similar to the situation in actual biopolymers. Validation against these benchmark data is therefore a more demanding task for approximate models, since correct descriptions of all energy terms are unlikely to be accomplished by fortuitous cancellations of systematic errors. The density functionals TPSS (both with and without an empirical dispersion term), PWB6K, M05-2X, and BH&H, and the self-consistent charge density functional tight binding method augmented with an empirical dispersion term (SCC-DFTB-D) were assessed for their abilities accurately to compute structures and energies. The best reproduction of the BSSE corrected RI-MP2 stabilization energies was achieved by the TPSS functional (TZVPP basis set) combined with empirical dispersion; removal of the dispersion correction leads to significantly degraded performance. The M05-2X and PWB6K functionals performed very well in reproducing the RI-MP2 geometries, but showed a systematic moderate underestimation of the magnitude of base stacking interactions. The SCC-DFTB-D method predicts geometries in fair agreement with RI-MP2; given its computational efficiency it represents a good option for initial scanning of analogous biopolymeric potential energy surfaces. BH&H gives geometries of comparable quality to the other functionals but significantly overestimates interaction energies other than stacking.

• MeSH
• databáze nukleových kyselin MeSH
• financování organizované MeSH
• konformace nukleové kyseliny MeSH
• oligonukleotidy chemie   MeSH
• termodynamika MeSH

Correlated ab initio calculations on large systems, such as the popular MP2 (or RI-MP2) method, suffer from the intramolecular basis set superposition error (BSSE). This error is typically manifested in molecules with folded structures, characterized by intramolecular dispersion interactions. It can dramatically affect the energy differences between various conformers as well as intramolecular stabilities, and it can even impair the accuracy of the predictions of the equilibrium molecular structures. In this study, we will present two extreme cases of intramolecular BSSE, the internal stability of [n]helicene molecules and the relative energies of various conformers of phenylalanyl-glycyl-phenylalanine tripeptide (Phe-Gly-Phe), and compare the calculated data with benchmark values (experimental or high-level theoretical data). As a practical and cheap solution to the accurate treatment of the systems with large anticipated value of intramolecular BSSE, the recently developed density functional method augmented with an empirical dispersion term (DFT-D) is proposed and shown to provide very good results in both of the above described representative cases. (c) 2007 Wiley Periodicals, Inc.

• MeSH
• chemické modely MeSH
• fenylalanin chemie   MeSH
• financování organizované MeSH
• glycin chemie   MeSH
• kvantová teorie MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• peptidy chemie   MeSH
• polycyklické sloučeniny chemie   MeSH
• termodynamika MeSH
• Publikační typ
• srovnávací studie MeSH

PURPOSE: To evaluate the impact of MR gradient system imperfections and limitations for the quantitative mapping of short T2* signals performed by ultrashort echo time (UTE) acquisition approach. MATERIALS AND METHODS: The measurement of short T2* signals from a phantom and a healthy volunteer study (8 subjects of average age 28 ± 4 years) were performed on a 3T scanner. The characteristics of the gradient system were obtained using calibration method performed directly on the measured subject or phantom. This information was used to calculate the actual sampling trajectory with the help of a parametric eddy current model. The actual sample positions were used to reconstruct corrected images and compared with uncorrected data. RESULTS: Comparison of both approaches, i.e., without and with correction of k-space sampling trajectories revealed substantial improvement when correction was applied. The phantom experiments demonstrate substantial in-plane signal intensity variations for uncorrected sampling trajectories. In the case of the volunteer study, this led to significant differences in relative proton density (RPD) estimation between the uncorrected and corrected data (P = 0.0117 by Wilcoxon matched-pairs test) and provides for about ~15% higher values for short T2* components of white matter (WM) in the case of uncorrected images. CONCLUSION: The imperfection of the applied gradients could induce errors in k-space data sampling which further propagates into the fidelity of the UTE images and jeopardizes precision of quantification. However, the study proved that measurement of gradient errors together with correction of sample positions can contribute to increased accuracy and unbiased characterization of short T2* signals.

• MeSH
• bílá hmota anatomie a histologie   MeSH
• dospělí MeSH
• fantomy radiodiagnostické MeSH
• kalibrace MeSH
• lidé MeSH
• magnetická rezonanční tomografie metody   MeSH
• mladý dospělý MeSH
• počítačové zpracování obrazu metody   MeSH
• protony MeSH
• referenční hodnoty MeSH
• zdraví dobrovolníci pro lékařské studie MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Standard spectral density mapping protocols, well suited for the analysis of (15)N relaxation rates, introduce significant systematic errors when applied to (13)C relaxation data, especially if the dynamics is dominated by motions with short correlation times (small molecules, dynamic residues of macromolecules). A possibility to improve the accuracy by employing cross-correlated relaxation rates and on measurements taken at several magnetic fields has been examined. A suite of protocols for analyzing such data has been developed and their performance tested. Applicability of the proposed protocols is documented in two case studies, spectral density mapping of a uniformly labeled RNA hairpin and of a selectively labeled disaccharide exhibiting highly anisotropic tumbling. Combination of auto- and cross-correlated relaxation data acquired at three magnetic fields was applied in the former case in order to separate effects of fast motions and conformational or chemical exchange. An approach using auto-correlated relaxation rates acquired at five magnetic fields, applicable to anisotropically moving molecules, was used in the latter case. The results were compared with a more advanced analysis of data obtained by interpolation of auto-correlated relaxation rates measured at seven magnetic fields, and with the spectral density mapping of cross-correlated relaxation rates. The results showed that sufficiently accurate values of auto- and cross-correlated spectral density functions at zero and (13)C frequencies can be obtained from data acquired at three magnetic fields for uniformly (13)C-labeled molecules with a moderate anisotropy of the rotational diffusion tensor. Analysis of auto-correlated relaxation rates at five magnetic fields represents an alternative for molecules undergoing highly anisotropic motions.

• MeSH
• algoritmy * MeSH
• interpretace statistických dat * MeSH
• magnetická rezonanční spektroskopie s uhlíkem 13C metody   MeSH
• magnetické pole MeSH
• malá interferující RNA analýza   chemie   MeSH
• počítačové zpracování signálu * MeSH
• reprodukovatelnost výsledků MeSH
• senzitivita a specificita MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Hypercalciuria is defined as urinary calcium excretion ≥0.1 mmol/kg/24 h, and can be a result of various disease states. The most frequent clinical signs of hypercalciuria include hematuria, abdominal pain, urolithiasis, nephrocalcinosis, dysuria, enuresis, and urinary tract infection. 3 case reports of children with hypercalciuria of different origin are presented, with final diagnoses of (1)idiopathic hypercalciuria, (2)familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), and (3)metabolic bone disease of prematurity, respectively. Assessment of hypercalciuria is essential in all children with urolithiasis and nephrocalcinosis, or demineralization of bone. It should be also a part of differential diagnostic procedure in hematuria, recurrent abdominal pain, urinary tract infection and enuresis in childhood.

• MeSH
• alely MeSH
• detekce genetických nosičů MeSH
• diferenciální diagnóza MeSH
• dítě MeSH
• fosfáty aplikace a dávkování   krev   MeSH
• hyperkalciurie diagnóza   etiologie   genetika   MeSH
• klaudiny genetika   MeSH
• kojenec MeSH
• lidé MeSH
• metabolické nemoci kostí diagnóza   MeSH
• mutační analýza DNA MeSH
• následné studie MeSH
• nefrokalcinóza diagnóza   genetika   MeSH
• nemoci nedonošenců diagnóza   terapie   MeSH
• novorozenec s nízkou porodní hmotností MeSH
• novorozenec MeSH
• předškolní dítě MeSH
• sekundární hyperparatyreóza diagnóza   terapie   MeSH
• vápník moč   MeSH
• vrozené poruchy tubulárního transportu diagnóza   genetika   MeSH
• vyšetření funkce ledvin MeSH
• Check Tag
• dítě MeSH
• kojenec MeSH
• lidé MeSH
• mužské pohlaví MeSH
• novorozenec MeSH
• předškolní dítě MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH

Stereoelectroencephalography (SEEG) records electrical brain activity with intracerebral electrodes. However, it has an inherently limited spatial coverage. Electrical source imaging (ESI) infers the position of the neural generators from the recorded electric potentials, and thus, could overcome this spatial undersampling problem. Here, we aimed to quantify the accuracy of SEEG ESI under clinical conditions. We measured the somatosensory evoked potential (SEP) in SEEG and in high-density EEG (HD-EEG) in 20 epilepsy surgery patients. To localize the source of the SEP, we employed standardized low resolution brain electromagnetic tomography (sLORETA) and equivalent current dipole (ECD) algorithms. Both sLORETA and ECD converged to similar solutions. Reflecting the large differences in the SEEG implantations, the localization error also varied in a wide range from 0.4 to 10 cm. The SEEG ESI localization error was linearly correlated with the distance from the putative neural source to the most activated contact. We show that it is possible to obtain reliable source reconstructions from SEEG under realistic clinical conditions, provided that the high signal fidelity recording contacts are sufficiently close to the source of the brain activity.

• MeSH
• elektroencefalografie metody   MeSH
• elektrokortikografie * metody   MeSH
• epilepsie * chirurgie   MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• mapování mozku metody   MeSH
• neurozobrazování MeSH
• somatosenzorické evokované potenciály MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• fyzikální jevy MeSH
• magnetická rezonanční tomografie MeSH

• Konspekt
• Patologie. Klinická medicína
• NLK Obory
• radiologie, nukleární medicína a zobrazovací metody
• NLK Publikační typ
• kolektivní monografie

Práce shrnuje poznatky o molekulární podstatě dědičného onemocnění lipidového metabolizmu způsobující zvýšení hladin LDL-cholesterolu. Familiární hypercholesterolemie je nejčastěji autosomálně dominantním onemocněním. Pro svého nositele přináší vysokou pravděpodobnost předčasného vzniku kardiovaskulárního onemocnění. Většina (85–90 %) případů je způsobena mutacemi snižujícími nebo zcela vyřazujícími funkčnost genu pro LDL receptor (LDLR). Menší množství případů (5–10 %) má příčinu v mutovaném genu pro apolipoprotein B (FDB mutace), který je ligandem LDL receptoru. Méně než 5 % případů je geneticky podloženo gain-of-function mutací v genu PCSK9 zvyšující aktivitu tohoto proteinu při degradaci molekul LDLR. Známe ale i extrémně vzácnou autosomálně recesivní formu onemocnění, při níž hrají roli mutace v genu pro LDLR adaptorový protein.

The review focuses on the molecular background of an inborn error of lipid metabolism -familial hypercholesterolemia. FH describes a group of genetic defects resulting in severe elevations of blood cholesterol levels and increased risk of premature coronary heart disease. Most cases are due to the mutations decreasing and/or destroying the function of the LDL receptor (85–90 % of cases), smaller portion of cases is caused by defects in the gene encoding the ligand for LDL receptor – apolipoprotein B-100 (5–10 %). Less than 5 % of cases has gain-of-function station of the PCSK9 gene that increases the rate of degradation of the LDL receptor molecules. Autosomal recessive form of the disease, caused by the mutations in LDLR adaptor protein 1 gene, is extremely rare.

• MeSH
• apolipoproteiny B genetika   MeSH
• fenotyp MeSH
• genetická heterogenita MeSH
• hyperlipoproteinemie typ II * etiologie   genetika   MeSH
• LDL-receptory fyziologie   genetika   klasifikace   MeSH
• lidé MeSH
• molekulární biologie * metody   MeSH
• mutace genetika   MeSH
• proproteinkonvertasa subtilisin/kexin typu 9 fyziologie   genetika   sekrece   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH

The article presents results of peculiarities of the hepatobiliary system in pregnant women with preeclampsia. It is set in the pregnant with preeclampsia of mild severity the frequency and combination of two and more complaints was reliably lower comparing to the frequency and combination of complaints in the pregnant with preeclampsia of mean severity. It must be mentioned that the received laboratory data positively correlated with the clinical manifestations of hepatobiliary dysfunction and the level of severity of preeclampsia that makes the further scientific researches necessary in future. Among the ultrasound signs of the dysfunction of the hepatobiliary system the following were detected: hepatomegaly, diffuse changes in the liver, increasing the density of the gallbladder against the decrease in contractility of the formation of sludge.

• MeSH
• dospělí MeSH
• hepatomegalie MeSH
• játra * patologie   MeSH
• komplikace těhotenství MeSH
• lidé MeSH
• preeklampsie * MeSH
• sběr dat MeSH
• těhotenství MeSH
• výzkumný projekt MeSH
• žlučové ústrojí * patologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• těhotenství MeSH
• ženské pohlaví MeSH

• MeSH
• gastrointestinální nemoci MeSH
• metabolismus MeSH
• nemoci jater MeSH
• nemoci žlučového ústrojí MeSH
• žlučové kyseliny a soli MeSH
• Publikační typ
• kongresy MeSH
• sborníky MeSH
• zprávy MeSH

• Konspekt
• Patologie. Klinická medicína
• NLK Obory
• gastroenterologie