Velocity fields and turbulent stresses downstream of biological and mechanical aortic valve prostheses implanted in pigs

Since detailed knowledge about velocity fields downstream of heart valve prostheses obtained from in vitro studies has not been followed up by similar detailed studies in vivo a pig model for acute velocity field studies downstream of aortic valve prostheses was established. Two mechanical and two bioprosthetic valves were studied and a dynamic three dimensional visualisation of velocity fields one diameter downstream performed under different haemodynamic conditions in a total of 22 pigs. The Ionescu-Shiley pericardial valve had velocity fields very similar to the normal native porcine aortic valve. The Edwards-Carpentier porcine valve caused a jet type flow, and the valve design of the St Jude Medical and Bj?rk-Shiley Monostrut valves was reflected in the velocity profile. Normalised (mean(SEM] systolic Reynolds normal stresses in the total cross sectional area were: native porcine 15(1.5) Nm-2; St Jude Medical 24(3.4) Nm-2; Bj?rk-Shiley Monostrut 25(1.6) Nm-2; Edwards-Carpentier Supra-annular 51(6.6) Nm-2; Ionescu-Shiley Pericardial 19(2.0) Nm-2. Reynolds normal stresses were higher in areas of rapidly changing or constantly high velocity gradients.     

Positron emission tomography of cortical centers of tinnitus.

Tinnitus is associated with a wide variety of disorders in the auditory system. Whether generated peripherally or centrally, tinnitus is believed to be associated with activity in specific cortical regions. The present study tested the hypothesis that these cortical centers subserve the generation, perception and processing of the tinnitus stimulus and that these processes are suppressed by lidocaine and masking. Positron emission tomography was used to map the tinnitus-specific central activity. By subtracting positron emission tomography images of regional cerebral blood flow distribution obtained during suppression of the tinnitus from positron emission tomography images obtained during the habitual tinnitus sensation, we were able to identify brain areas concerned with the cerebral representation of tinnitus. Increased neuronal activity caused by tinnitus occurred predominantly in the right hemisphere with significant foci in the middle frontal and middle temporal gyri, in addition to lateral and mesial posterior sites. The results are consistent with the hypothesis that the sensation of tinnitus is associated with activity in cortical regions functionally linked to subserve attention, emotion and memory. For the first time, the functional anatomy of conditions with and without the habitual tinnitus sensation was obtained and compared in the same subjects.     

Cerebral blood-flow changes evoked by two levels of painful heat stimulation: A positron emission tomography study in humans

Positron emission tomography (PET) and accumulation of H₂ ¹⁵O as a marker of neuronal activity were used to create maps of cerebral blood-flow changes evoked by painful heat stimulation in 10 subjects. Two levels of painful tonic and phasic heat stimuli were applied with use of a newly developed contact heat thermode on the volar surface of the dominant (right) arm. The subjects participated in two separate PET sessions. Maps reflecting low and high levels of painful tonic heat were obtained in the first session, and low and high levels of painful phasic heat in the second session. The subjects scored their peak pain intensity and unpleasantness on 10-cm visual analogue scales. For each subject, PET images were aligned to nuclear magnetic resonance (NMR) images and remapped into the standardized co-ordinate system of Talairach. After normalization of the PET volumes, subtraction images were formed voxel-by-voxel and converted to a t-statistic volume. The perceived pain intensity and unpleasantness were identical with painful tonic and phasic heat stimulation. Directed searches revealed significant blood-flow increases in the contralateral primary sensorimotor cortex (MI/SI), SII, insular cortex and cingulate cortex when the low tonic heat map was subtracted from the high. A similar, but not identical, pain-processing network was observed for the maps representing the subtraction of low and high phasic heat. In this subtraction, the blood-flow increases in MSI/SI did not reach statistical significance, and significant blood flow decreases were found in the contralateral middle temporal gyrus. Finally, the location of the activation site in the cingulate cortex was different from that observed during tonic heat pain. This study has provided more evidence for the existence of a common pain-processing network engaged during the perception of different levels of toxic and phasic heat pain.     

Simultaneous determination of β-hydroxybutyrate and β-hydroxy-β-methylbutyrate in human whole blood using hydrophilic interaction liquid chromatography electrospray tandem mass spectrometry

Objectives

For the quantification of β-hydroxybutyrate (BHB) and β-hydroxy-β-methylbutyrate (HMB) in human whole blood, a method using hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC–MS/MS) was developed, which does not require chemical modification of the analytes.

Design and methods

Samples were deproteinised by a mixture of methanol and acetonitrile, and the extracts were cleaned-up using both polymeric strong cation exchange and strong anion exchange sorbents. The analytes and their structural isomers were separated using a column with a zwitterionic stationary phase. Isotope dilution of both analytes was used for quantitative analysis.

Results

Separation of BHB from isobaric interferences was achieved through chromatography. The relative intra-laboratory reproducibility standard deviations were better than 10% for blood samples at concentration levels of 10–20 μM BHB and 1 μM HMB and better than 5% at concentration levels 10 times higher. The mean true extraction recoveries were close to 100%. The trueness expressed as the relative bias of test results was within ± 5% at concentration levels of 10–1000 μM BHB and 1–20 μM HMB. The lower limits of quantification were estimated to be 3 μM for BHB and 0.4 μM for HMB.

Conclusions

A simple and highly sensitive and selective HILIC–MS/MS method was developed that is suitable for the quantification of BHB and HMB in whole blood.     

Associations between active commuting to school, fat mass and lifestyle factors in adolescents: the Kiel Obesity Prevention Study (KOPS)

OBJECTIVE: To examine possible associations between active commuting (walking or cycling) to school, parameters of adiposity and lifestyle factors in 14-year-old adolescents of the Kiel Obesity Prevention Study. SUBJECTS: A total of 626 14-year-old adolescents. METHODS: Measured body mass index (BMI), fat mass (FM), distance to school as well as self-reported modes and duration of commuting to school, time spent in structured and unstructured physical activities (PAs), media use, nutrition, alcohol consumption and smoking. RESULTS: Parameters of adiposity did not differ between different commuting modes after stratifying by gender. Active commuters reported higher overall PA, which was caused by commuting activity and time spent in unstructured PA in girls and just by commuting activity in boys. In active commuters, 28.4% of overall PA was explained by commuting activity. Additionally, TV viewing was lower in active commuters. Compared to their inactively commuting counterparts, actively commuting boys were less likely to smoke. After controlling for potential confounders the interaction term 'active commuting by distance to school' and 'time spent in structured PA' were independent predictors of FM, whereas active commuting by itself showed no effect. CONCLUSION: The present data suggest that active commuting to school per se does not affect FM or BMI until considering distance to school. Increasing walking or cycling distance results in decreasing FM. However, the everyday need to get to and from school may enhance adolescents' overall PA.     

Vagusnervstimulation bei epileptischen Enzephalopathien

Epileptic encephalopathies encompass a heterogeneous group of childhood epilepsies with poor prognosis, and treatment is a special challenge considering the possible impairments in neurocognitive development. Early diagnosis and successful treatment are, therefore, crucial for this patient group. Four patients with progressive epilepsies, who responded outstandingly well to vagus nerve stimulation (VNS), are presented. The epilepsies of all patients were drug-resistant and surgical treatment was not an option. VNS, not as a first-line therapy but considered early after delineation of a progressive epilepsy course, represents an important therapeutic option in patients with epileptic encephalopathies.     

Synthesis and biological evaluation of technetium(III) mixed-ligand complexes with high affinity for the cerebral 5-HT(1A) receptor and the alpha1-adrenergic receptor

Tc(III) and Re(III) complexes [M(NS(3))(CNR)] (M = Re, 99mTc, NS(3) = 2,2',2"-nitrilotris(ethanethiol), CNR = functionalized isocyanide bearing a derivative of WAY 100635) have been synthesized and characterized. Re was used as Tc surrogate for chemical characterization and in vitro receptor-binding studies. For two representatives subnanomolar affinities for the 5-HT(1A) as well as for the alpha1-adrenergic receptor were reached. Biodistribution studies in rats of the 99mTc complexes showed brain uptakes between 0.3 and 0.5% ID/organ (5 min p.i.). In vitro autoradiography of one 99mTc representative in sections of post mortem human brain indicate its accumulation in 5-HT(1A) receptor-rich brain regions. However, addition of the specific 5-HT(1A) receptor agonist 8-OH-DPAT as well as the alpha1-adrenoceptor antagonist prazosin could not substantially block this tracer accumulation. A preliminary SPET study in a monkey showed negligible brain uptake.