Spin Fluctuations in Sr_{2}RuO_{4} from Polarized Neutron Scattering: Implications for Superconductivity.

Triplet pairing in Sr_{2}RuO_{4} was initially suggested based on the hypothesis of strong ferromagnetic spin fluctuations. Using polarized inelastic neutron scattering, we accurately determine the full spectrum of spin fluctuations in Sr_{2}RuO_{4}. Besides the well-studied incommensurate magnetic fluctuations, we do find a sizable quasiferromagnetic signal, quantitatively consistent with all macroscopic and microscopic probes. We use this result to address the possibility of magnetically driven triplet superconductivity in Sr_{2}RuO_{4}. We conclude that, even though the quasiferromagnetic signal is stronger and sharper than previously anticipated, spin fluctuations alone are not enough to generate a triplet state strengthening the need for additional interactions or an alternative pairing scenario.

Dynamic Displacement Disorder of Cubic BaTiO_{3}.

The three-dimensional distribution of the x-ray diffuse scattering intensity of BaTiO_{3} has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO_{3} to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material. The presented methodology allows one to go beyond the harmonic approximation in the analysis of phonons and phonon-related scattering.

Dynamics of nanoscale polarization fluctuations in a uniaxial relaxor.

We have studied neutron diffuse scattering in a Sr(0.61)Ba(0.39)Nb(2)O(6) single crystal by neutron backscattering at sub-µeV energy resolution. We can identify two response components with transverse polarization: an elastic (resolution limited) central peak, which monotonically increases with decreasing temperature, and a quasielastic central peak, having a maximum intensity around the ferroelectric phase transition close to 350 K. In contrast to previous neutron experiments on this and other relaxor materials, we were able to observe a temperature dependence of the characteristic frequency of these fluctuations, obeying the same Vogel-Fulcher law as the dynamic part of the dielectric permittivity of this material. In this way our findings provide a first direct link between the Vogel-Fulcher-type frequency dependence of dielectric permittivity and dynamic nanoscale lattice modulations with a transverse correlation length of about 5-10 unit cells.

[Secondary peritonitis prognosis assessment]. / Hodnocení prognózy tezké sekundární peritonitidy.

INTRODUCTION: Secondary peritonitis is a severe disease with high mortality and morbidity. In the last 20 years the results of treatment of this disease have improved markedly. AIM OF THE STUDY: To determine statistically significant risk factors for mortality in patients with severe secondary peritonitis. MATERIAL AND METHODS: We studied in retrospective analysis the cohort of patients treated at our clinic in the period 2005-2010. 65 patients (38 men and 27 women) with an average age of 60.7 years were included. 27 patients died (41.5%). The average age of the died patients was 72 years. The average value of APACHE II was 20.77, which corresponds to the prediction of lethality 41.8%. The average value of the SOFA score was 11.87. RESULTS: The performed statistical analysis showed age over 65 years, bronchopneumonia, obesity, ischemic heart disease, artificial ventilation over 6 days and circulatory support over 10 days as statistically significant independent factors for mortality. Patients older than 65 years had 8.9 times greater risk of death. In the case of bronchopneumonia was the risk 4.8 times higher. Obesity increased the risk of death 3.1 times and ischemic heart disease 2.4 times. In the case of mechanical ventilation for more than 6 days and circulatory support for more than 10 days, these increased the risk of death 4.1 times respectively 4.3 times. DISCUSSION: The benefit for determining the prognosis secondary peritonitis is the use of scoring systems. It was also shown that the basic clinical data may have the same benefit for predicting the prognosis of patients as a sophisticated scoring systems. CONCLUSION: The performed retrospective analysis age over 65 years, bronchopneumonia, obesity, artificial ventilation and circulatory support as statistically significant independent factors for prediction of poor survival. These basic clinical factors correlated with scoring systems APACHE II a SOFA.

[Treatment of upper gastrointestinal tract fistules in the surgical intensive care unit]. / Lécba pístelí orální cásti gastrointestinálního traktu na chirurgické jednotce intenzivní péce.

The authors performed a retrospective analysis in a group of consecutively treated patients with upper GIT fistules (ie. fistules with internal orifices in the esophageal, gastric and proximal small intestine region), hospitalized in the Plzen hospital Surgical Clinic Septic Intensive Care Unit, from January 1, 2006 to December 31, 2008. The author assessed the results using statistical methods and he studied any causative relationship between the characteristics of the fistules, the treatment methods and the patients morbidity/mortality rates.

Localization of gamma-tubulin in interphase and mitotic cells of a unicellular eukaryote, Giardia intestinalis.

Giardia intestinalis, a bi-nucleated amitochondrial flagellate, possesses a complex cytoskeleton based on several microtubular systems (flagella, adhesive disk, median body, funis, mitotic spindles). MTOCs of the individual systems have not been fully defined. By using monoclonal antibodies against a conserved synthetic peptide from the C-terminus of human gamma-tubulin we investigated occurrence and distribution of gamma-tubulin in interphase and mitotic Giardia cells. On the immunoblots of Giardia cytoskeletal extracts the antibodies bound to a single polypeptide of approximately 50 kDa. Immunostaining of the interphase cell demonstrated gamma-tubulin as four bright spots at the basis of four out of eight flagella. Gamma-tubulin label was associated with perikinetosomal areas of the ventral and posterolateral pairs of flagella which are formed de novo during cell division. Basal body regions of the anterolateral and caudal pairs of flagella which persist during the division and are integrated into the flagellar systems of the daughter cells did not show gamma-tubulin staining. At early mitosis, gamma-tubulin spots disappeared reappearing again at late mitosis in accord with reorientation of parent flagella and reorganization of flagellar apparatus during cell division. The antibody-detectable gamma-tubulin epitope was absent at the poles of both mitotic spindles. Albendazole-treated Giardia, in which spindle assembly was completely inhibited, showed the same gamma-tubulin staining pattern thus confirming that the fluorescent label is exclusively located in the basal body regions. Our results point to a role of gamma-tubulin in nucleation of microtubules of newly formed flagella and indicate unusual mitotic spindle assembly. Moreover, the demonstration of gamma-tubulin in Giardia shows ubiquity of this protein through the evolutionary history of eukaryotes.

Concordance between genetic relatedness and phenotypic similarities of Trichomonas vaginalis strains.

BACKGROUND: Despite the medical importance of trichomoniasis, little is known about the genetic relatedness of Trichomonas vaginalis strains with similar biological characteristics. Furthermore, the distribution of endobionts such as mycoplasmas or Trichomonas vaginalis virus (TVV) in the T. vaginalis metapopulation is poorly characterised. RESULTS: We assayed the relationship between 20 strains of T. vaginalis from 8 countries using the Random Amplified Polymorphic DNA (RAPD) analysis with 27 random primers. The genealogical tree was constructed and its bootstrap values were computed using the program FreeTree. Using the permutation tail probability tests we found that the topology of the tree reflected both the pattern of resistance to metronidazole (the major anti-trichomonal drug) (p < 0.01) and the pattern of infection of strains by mycoplasmas (p < 0.05). However, the tree did not reflect pattern of virulence, geographic origin or infection by TVV. Despite low bootstrap support for many branches, the significant clustering of strains with similar drug susceptibility suggests that the tree approaches the true genealogy of strains. The clustering of mycoplasma positive strains may be an experimental artifact, caused by shared RAPD characters which are dependent on the presence of mycoplasma DNA. CONCLUSIONS: Our results confirmed both the suitability of the RAPD technique for genealogical studies in T. vaginalis and previous conclusions on the relatedness of metronidazol resistant strains. However, our studies indicate that testing analysed strains for the presence of endobionts and assessment of the robustness of tree topologies by bootstrap analysis seem to be obligatory steps in such analyses.

Metabolic differences between metronidazole resistant and susceptible strains of Tritrichomonas foetus.

Tritrichomonas foetus mutants resistant to metronidazole lack the hydrogenosomal enzymes pyruvate: ferredoxin oxidoreductase and hydrogenase. Hydrogenosomes of these organisms did not oxidize pyruvate or produce ATP in its presence. Elimination of hydrogenosomal metabolism of pyruvate was compensated by an increased rate of glycolysis. The resistant mutants excreted no organic acids and H2 as metabolic end products. Glycolysis of the resistant T. foetus KV1-1MR-100 can be summarized as 1 mol glucose----2 mol ethanol + 2 mol CO2. The parent strain KV1, excreting H2, CO2 and acidic end products, converted about 10% of glucose to ethanol. Both strains produced ethanol from pyruvate through the action of two cytoplasmic enzymes: pyruvate decarboxylase and alcohol dehydrogenase. The specific activity of the former enzyme, catalyzing nonoxidative decarboxylation of pyruvate to acetaldehyde, was nearly seven times higher in the resistant than in the parent strain. Alcohol dehydrogenase reducing acetaldehyde to ethanol was specific to NADPH; it catalyzed the reverse reaction only slowly, and displayed similar activities in both resistant and sensitive trichomonads. Development of anaerobic metronidazole resistance in T. foetus depended on the loss of pyruvate:ferredoxin oxidoreductase as well as on the ability to increase alcoholic fermentation.

Iron-ascorbate cleavable malic enzyme from hydrogenosomes of Trichomonas vaginalis: purification and characterization.

Two isoforms of NAD(P)(+)-dependent malic enzyme (EC 1.1.1.39) were isolated from hydrogenosomes of Trichomonas vaginalis. A positively charged isoform at pH 7 was obtained in a single purification step using cation-exchange chromatography. The second isoform, negatively charged at pH 7.5, was partially purified using a combination of anion-exchange and affinity chromatography. Both isoforms displayed similar physical and kinetic properties. Molecular weight determination of the native enzyme suggested a homotetrameric arrangement of the 60 kDa subunits. The enzyme utilized NAD+ (Km, 6-6.3 microM) preferentially to NADP+ (Km, 125-145 microM). The NAD(+)-dependent activity showed a broad pH optimum with maximum under alkaline conditions (pH 9) likely to be present inside hydrogenosomes. Immunocytochemical studies using a polyclonal rabbit antibody raised against purified T. vaginalis malic enzyme proved hydrogenosomal localization of the enzyme. Subfractionation of hydrogenosomes suggested an association of the malic enzyme with the hydrogenosomal membranes. The 60 kDa malic enzyme subunit was highly sensitive to non-enzymatic cleavage by an iron-ascorbate system resulting in two enzymatically inactive fragments of about 31 kDa. Microsequencing of the fragments revealed that the 60 kDa subunit was cleaved at the metal-binding site between Asp279-Ile280. The enzyme inactivation was inhibited by an excess of manganese. Iron-dependent posttranslational modification might contribute to the regulation of malic enzyme activity in vivo.

Trichomonads, hydrogenosomes and drug resistance.

Trichomonas vaginalis and Tritrichomonas foetus are sexually transmitted pathogens of the genito-urinary tract of humans and cattle, respectively. These organisms are amitochondrial anaerobes possessing hydrogenosomes, double membrane-bound organelles involved in catabolic processes extending glycolysis. The oxidative decarboxylation of pyruvate in hydrogenosomes is coupled to ATP synthesis and linked to ferredoxin-mediated electron transport. This pathway is responsible for metabolic activation of 5-nitroimidazole drugs, such as metronidazole, used in chemotherapy of trichomoniasis. Prolonged cultivation of trichomonads under sublethal pressure of metronidazole results in development of drug resistance. In both pathogenic species the resistance develops in a multistep process involving a sequence of stages that differ in drug susceptibility and metabolic activities. Aerobic resistance, similar to that occurring in clinical isolates of T. vaginalis from treatment-refractory patients, appears as the earliest stage. The terminal stage is characterised by stable anaerobic resistance at which the parasites show very high levels of minimal lethal concentration for metronidazole under anaerobic conditions (approximately 1000 microg ml(-1)). The key event in the development of resistance is progressive decrease and eventual loss of the pyruvate:ferredoxin oxidoreductase so that the drug-activating process is averted. In T. vaginalis at least, the development of resistance is also accompanied by decreased expression of ferredoxin. The pyruvate:ferredoxin oxidoreductase deficiency completely precludes metronidazole activation in T. foetus, while T. vaginalis possesses an additional drug-activating system which must be eliminated before the full resistance is acquired. This alternative pathway involves the hydrogenosomal malic enzyme and NAD:ferredoxin oxidoreductase. Metronidazole-resistant trichomonads compensate for the hydrogenosomal deficiency by an increased rate of glycolysis and by changes in their cytosolic pathways. Trichomonas vaginalis enhances lactate fermentation while T. foetus activates pyruvate conversion to ethanol. Drug-resistant T. foetus also increases activity of the cytosolic NADP-dependent malic enzyme, to enhance the pyruvate producing bypass and provide NADPH required by alcohol dehydrogenase. Production of succinate by this species is abolished. Metabolic changes accompanying in-vitro development of metronidazole resistance demonstrate the versatility of trichomonad metabolism and provide an interesting example of how unicellular eukaryotes can adjust their metabolism in response to the pressure of an unfavorable environment.

Chiral critical exponents of the triangular-lattice antiferromagnet CsMnBr3 as determined by polarized neutron scattering

The critical exponents gamma(c) = 0.84(7) of the chiral susceptibility above the Neel temperature, T(N), and beta(c) = 0. 44(2) of the average chirality below T(N) have been determined for the triangular-lattice antiferromagnet CsMnBr3 by means of polarized neutron scattering. These first experimental values of chiral critical exponents are in line with theoretical predictions and fulfill their scaling relation. The temperature at which the average chirality appears coincides with the spin-order transition temperature, T(N).

Growth and transformation of Trypanosoma danilewskyi in a liquid medium.

The complex liquid medium L4NHS has proved suitable for obtaining trypomastigote-rich suspensions of the fish parasite Trypanosoma danilewskyi. Growth of T. danilewskyi strains in the medium has been characterized in test tube cultures at 25 degrees C. The cultures with an initial cell density of 1 x 10(5) x ml01 grew exponentially for 3 days with an average generation time of 15 h 17 min (strain BD) and 14 h 25 min (strain BZ). Both strains remained in the stationary phase for another 7-10 days. Total growth amounted to 1.3-1.6 x 10(7) cells x ml-1. The trypanosomes in culture were polymorphic (epimastigotes, broad trypomastigotes, slender trypomastigotes). The succession of the epimastigote and trypomastigote stages was dependent on the growth phase. The trypomastigotes of the strain BD from 300 ml Erlenmeyer flasks containing 40 ml of medium. Suspensions of trypanosomes from these cultures proved to be useful antigenic substrate in a determination of anti-ds-DNA antibodies by the kinetoplast immunofluorescence assay.

Isolation and characterization of cytosolic malate dehydrogenase from Trichomonas vaginalis.

Malate dehydrogenase (EC 1.1.1.37.) (MDH) was purified to apparent homogeneity from the cytosolic fraction of the protozoan Trichomonas vaginalis Donné. The four step purification included ion-exchange chromatography (DEAE-Sephacel and Q-Sepharose, elution with NaCl) and affinity chromatography (Reactive Red Agarose, elution with NADH and NaCl). The enzyme was purified about 132-fold (30.6% yield) to a specific activity of 352 units mg-1. The Km values determined at pH 7.8 (pH optimum from 7.5 to 8.3) for oxaloacetate and NADH were 16.2 microM and 10.6 microM, respectively. The MDH activity was inhibited by the substrate, decreasing to 50% at about 1 microM concentration of oxaloacetate. The reverse reaction from malate to oxaloacetate showed a pH optimum around pH 9.5. The Km for malate and NAD+ (determined at pH 7.8) were 1220 microM and 69.9 microM, respectively. SDS-PAGE analysis of the purified MDH revealed a single band with an apparent size of 34.5 kDa. The native molecular weight was estimated by HPLC gel filtration to be 60 kDa, which indicates that the T. vaginalis MDH exists as a dimer.

Circular DNA and cardiolipin in hydrogenosomes, microbody-like organelles of trichomonads.

Circular molecules of DNA approximately 3 mum in length were revealed by electron microscopy in deproteinized extracts prepared from purified hydrogenosomal fraction of a protozoan Tritrichomonae foetus. This fraction contained also cardiolipin amounting to approximately 14.4% of its total phospholipids, as detected by thin-layer chromatography and quantitative phosphorus measurement. These characteristics extend a number of biochemical properties of hydrogenosome shared also by mitochondria and by prokaryotic cells.

The dsRNA of Trichomonas vaginalis is associated with virus-like particles and does not correlate with metronidazole resistance.

Twelve metronidazole-resistant and twelve metronidazole-susceptible strains of Trichomonas vaginalis were tested for the presence of dsRNA. Three resistant and five susceptible strains were found to contain dsRNA which indicated that metronidazole resistance does not correlate with the absence of dsRNA. Electron microscopy showed the homogenates of all dsRNA-positive strains to contain virus-like particles 32-38 nm in diameter, while no such particles were found in the dsRNA-negative strains. A mutual relationship between the dsRNA and virus-like particles seems to exist.

The temperature dependence of the phononic band gap of NaI.

The position and size of the energy gap in the phonon density of states of NaI single crystal have been investigated by inelastic neutron scattering in a wide range of temperatures from 10 to 700 K. The results reveal a pronounced temperature effect which effectively leads to closure of the phonon gap at temperatures in the range of 700-800 K. The results are discussed in the context of studies of possible intrinsic localized modes in the phonon gap of alkali halides.

Tetratrichomonads from the oral cavity and respiratory tract of humans.

To clarify the taxonomy of trichomonads associated with human respiratory diseases, we examined a collection of axenic trichomonad strains isolated from the oral cavity and bronchi of patients from pulmonary diseases clinics in Tallin, Estonia. The oral and bronchial strains were compared mutually as well as with a reference strain of Trichomonas tenax, a common inhabitant of the human oral cavity, and other trichomonad species from humans and animals. Unexpectedly, the morphological studies, as well as DNA sequencing of ITS1-5.8S rRNA-ITS2 regions revealed that the Estonian strains belong to the genus Tetratrichomonas, with a high similarity to the avian species Tetratrichomonas gallinarum. None of the strains belonged to Trichomonas tenax. DNA fingerprinting using the RAPD method separated Estonian strains into 2 distinct groups: 'bronchial' consisting of 5 and 2 strains isolated from bronchi and 'oral' cavity, respectively, and oral consisting of 3 oral strains. Consistent differences between 'bronchial' and 'oral' groups were confirmed by analysis of ITS1-5.8S rRNA-ITS2 sequences. Our results have revealed novel trichomonad species of the human oral cavity and bronchi.

Three-dimensional spin fluctuations in Na0.75CoO2.

We report polarized- and unpolarized-neutron scattering measurements of magnetic excitations in single-crystal Na0.75CoO2. The data confirm ferromagnetic correlations within the cobalt layers and reveal antiferromagnetic correlations perpendicular to the layers, consistent with an A-type antiferromagnetic ordering. The magnetic modes propagating perpendicular to the layers are sharp, and reach a maximum energy of approximately 12 meV. From a minimal spin-wave model, containing only nearest-neighbor Heisenberg exchange interactions, we estimate the interlayer and intralayer exchange constants to be 12.2+/-0.5 meV and -6+/-2 meV, respectively. We conclude that the magnetic fluctuations in Na0.75CoO2 are highly three dimensional.

[Metronidazole resistance test in vitro in strains of Trichomonas vaginalis isolated from clinical material. 1. Test conditions]. / Testování rezistence k metronidazolu in vitro u kmenu Trichomonas vaginalis izolovaných z klinického materiálu. 1. Podmínky testu.

Metronidazole-resistant clinical isolates of Trichomonas vaginalis display an aerobic type of resistance detectable in vitro only if some oxygen is present. Consequently, adjustment of the optimal concentration of O2 in assay system is of critical importance for dependable determination of minimal lethal concentration (MLC) of the drug. The authors demonstrated that decrease of oxygen content in assay media (from 191.2 nM to 49.5 nM O2.ml-1) resulted in increased susceptibility of the drug-resistant strain IR-78 to metronidazole (from MLC 100 micrograms.ml-1 to MLC 25 micrograms.ml-1). Different MLCs were obtained in media of different reducing capacity. Oxygen dependent variations in MLC were also observed in assay systems containing different volumes of medium. The authors discuss effect of these and other variables in methodology of susceptibility assays in order to define conditions of standard procedure.