Human taurine metabolism: fluxes and fractional extraction rates of the gut, liver, and kidneys

Taurine is involved in numerous biological processes. However, taurine plasma level decreases in response to pathological conditions, suggesting an increased need. Knowledge on human taurine metabolism is scarce and only described by arterial-venous differences across a single organ. Here we present taurine organ fluxes using arterial-venous concentration differences combined with blood flow measurements across the 3 major organ systems involved in human taurine metabolism in patients undergoing hepatic surgery. In these patients, we collected blood from an arterial line, portal vein, hepatic vein, and renal vein, and determined blood flow of the hepatic artery, portal vein, and renal vein using Doppler ultrasound. Plasma taurine was determined by high-performance liquid chromatography, and net organ fluxes and fractional extraction rates were calculated. Seventeen patients were studied. No differences were found between taurine concentrations in arterial, portal venous, hepatic venous, and renal venous plasma. The only significant finding was a release of taurine by the portally drained viscera (P = .04). Our data show a net release of taurine by the gut. This probably is explained by the enterohepatic cycle of taurine. Future studies on human taurine metabolism are required to determine whether taurine is an essential aminosulfonic acid during pathological conditions and whether it should therefore be supplemented.     

Surface roughness directed self-assembly of patchy particles into colloidal micelles

Colloidal particles with site-specific directional interactions, so called "patchy particles", are promising candidates for bottom-up assembly routes towards complex structures with rationally designed properties. Here we present an experimental realization of patchy colloidal particles based on material independent depletion interaction and surface roughness. Curved, smooth patches on rough colloids are shown to be exclusively attractive due to their different overlap volumes. We discuss in detail the case of colloids with one patch that serves as a model for molecular surfactants both with respect to their geometry and their interactions. These one-patch particles assemble into clusters that resemble surfactant micelles with the smooth and attractive sides of the colloids located at the interior. We term these clusters "colloidal micelles". Direct Monte Carlo simulations starting from a homogeneous state give rise to cluster size distributions that are in good agreement with those found in experiments. Important differences with surfactant micelles originate from the colloidal character of our model system and are investigated by simulations and addressed theoretically. Our new "patchy" model system opens up the possibility for self-assembly studies into finite-sized superstructures as well as crystals with as of yet inaccessible structures.     

Golf Performance Enhancement and Real-Life Neurofeedback Training Using Personalized Event-Locked EEG Profiles

Background. This study reports on a new method for golf performance enhancement employing personalized real-life neurofeedback during golf putting.

Method. Participants (n = 6) received an assessment and three real-life neurofeedback training sessions. In the assessment, a personal event-locked electroencephalographic (EEG) profile at FPz was determined for successful versus unsuccessful putts. Target frequency bands and amplitudes marking optimal prefrontal brain state were derived from the profile by two raters. The training sessions consisted of four series of 80 putts in an ABAB design. The feedback in the second and fourth series was administered in the form of a continuous NoGo tone, whereas in the first and third series no feedback was provided. This tone was terminated only when the participants EEG met the assessment-defined criteria. In the feedback series, participants were instructed to perform the putt only after the NoGo tone had ceased.

Results. From the personalized event-locked EEG profiles, individual training protocols were established. The interrater reliability was 91%. The overall percentage of successful putts was significantly larger in the second and fourth series (feedback) of training compared to the first and third series (no feedback). Furthermore, most participants improved their performance with feedback on their personalized EEG profile, with 25% on average.

Conclusions. This study demonstrates that the “zone” or the optimal mental state for golf putting shows clear recognizable personalized patterns. The learning effects suggest that this real-life approach to neurofeedback improves learning speed, probably by tapping into learning associated with contextual conditioning rather than operant conditioning, indicating perspectives for clinical applications.     

Non-invasive imaging of the crystalline structure within a human tooth

The internal crystalline structure of a human molar tooth has been non-destructively imaged in cross-section using X-ray diffraction computed tomography. Diffraction signals from high-energy X-rays which have large attenuation lengths for hard biomaterials have been collected in a transmission geometry. Coupling this with a computed tomography data acquisition and mathematically reconstructing their spatial origins, diffraction patterns from every voxel within the tooth can be obtained. Using this method we have observed the spatial variations of some key material parameters including nanocrystallite size, organic content, lattice parameters, crystallographic preferred orientation and degree of orientation. We have also made a link between the spatial variations of the unit cell lattice parameters and the chemical make-up of the tooth. In addition, we have determined how the onset of tooth decay occurs through clear amorphization of the hydroxyapatite crystal, and we have been able to map the extent of decay within the tooth. The described method has strong prospects for non-destructive probing of mineralized biomaterials.     

No Effect of Hole Geometry in Microfracture for Talar Osteochondral Defects

Background

Débridement and bone marrow stimulation is an effective treatment option for patients with talar osteochondral defects. However, whether surgical factors affect the success of microfracture treatment of talar osteochondral defects is not well characterized.

Questions/purposes

We hypothesized (1) holes that reach deeper into the bone marrow-filled trabecular bone allow for more hyaline-like repair; and (2) a larger number of holes with a smaller diameter result in more solid integration of the repair tissue, less need for new bone formation, and higher fill of the defect.

Methods

Talar osteochondral defects that were 6 mm in diameter were drilled bilaterally in 16 goats (32 samples). In eight goats, one defect was treated by drilling six 0.45-mm diameter holes in the defect 2 mm deep; in the remaining eight goats, six 0.45-mm diameter holes were punctured to a depth of 4 mm. All contralateral defects were treated with three 1.1-mm diameter holes 3 mm deep, mimicking the clinical situation, as internal controls. After 24 weeks, histologic analyses were performed using Masson-Goldner/Safranin-O sections scored using a modified O’Driscoll histologic score (scale, 0–22) and analyzed for osteoid deposition. Before histology, repair tissue quality and defect fill were assessed by calculating the mean attenuation repair/healthy cartilage ratio on Equilibrium Partitioning of an Ionic Contrast agent (EPIC) micro-CT (μCT) scans. Differences were analyzed by paired comparison and Mann-Whitney U tests.

Results

Significant differences were not present between the 2-mm and 4-mm deep hole groups for the median O’Driscoll score (p = 0.31) and the median of the μCT attenuation repair/healthy cartilage ratios (p = 0.61), nor between the 0.45-mm diameter and the 1.1-mm diameter holes in defect fill (p = 0.33), osteoid (p = 0.89), or structural integrity (p = 0.80).

Conclusions

The results indicate that the geometry of microfracture holes does not influence cartilage healing in the caprine talus.

Clinical Relevance

Bone marrow stimulation technique does not appear to be improved by changing the depth or diameter of the holes.