Quantum wires as Luttinger liquids: experiment

The low-temperature ballistic transport properties of quantum wires prepared by the cleaved edge overgrowth method in the GaAs/AlGaAs material system are presented. As the Fermi energy in these one-dimensional (1D) systems is varied by application of a gate voltage a series of quantized conductance plateaus is observed. The plateau values significantly deviate from integer multiples of 2·e 2 /h and show a power law increase with increasing temperature as predicted by Luttinger liquid (LL) theory. The characteristic power law scaling exponent is obtained as a function of the Fermi energy and the number of occupied 1D subbands. From nonlinear current-voltage characteristics across the quantum wires independent LL power law scaling exponents can be deduced. The latter are found to be consistent with those obtained from temperature dependent measurements. In order to rule out contact effects as the only origin of the observed deviations we have investigated a series of quantum wires of different lengths and find quenching of the Luttinger liquid behavior as the wire length is increased. This observation is in agreement with a detailed analysis of reproducable conductance fluctuations which are superimposed on the conductance plateaus

High affinity agonists of the neuropeptide Y (NPY) Y4 receptor derived from the C-terminal pentapeptide of human pancreatic polypeptide (hPP): synthesis, stereochemical discrimination and radiolabeling

The diastereomeric mixture of D/L-2,7-diaminooctanedioyl-bis(YRLRY-NH2) (BVD-74D, 2) was described in the literature as a high affinity Y-4 receptor agonist. Here we report on the synthesis and pharmacological characterization of the pure diastereomers (2R,7R)- and (2S,7S)-2 and a series of homo- and heterodimeric analogues in which octanedioic acid was used as an achiral linker. To investigate the role of the Arg residues, one or two arginines were replaced by Ala. Moreover, N-omega-(6-aminohexylaminocarbonyl)Arg was introduced as an arginine replacement (17) (2R,7R)-2 was superior to (2S,7S)-2 in binding and functional cellular assays and equipotent with 17. [H-3]Propionylation of one amino group in the linker of (2R,7R)-2 or at the primary amino group in 17 resulted in high affinity Y4R radioligands ([H-3]-(2R,7R)-10, [H-3]18) with subnanomolar K-d values

COVID-19-related cancellation of elective orthopaedic surgery caused increased pain and psychosocial distress levels

Purpose!#!Health care systems in most European countries were temporarily restructured to provide as much capacity as possible for the treatment of coronavirus disease 2019 (COVID-19) patients. Subsequently, all elective surgeries had to be cancelled and postponed for months. The aim of the present study was to assess the pretreatment health status before and after COVID-19-related cancellation and the psychosocial distress caused by the cancellation.!##!Methods!#!For this study, a questionnaire was developed collecting sociodemographic data and information on health status before and after the cancellation. To assess psychosocial distress, the validated depression module of the Patient Health Questionnaire (PHQ-9), was implemented. PHQ-9-Scores of 10 and above were considered to indicate moderate or severe depressive symptoms. In total, 119 patients whose elective orthopaedic surgery was postponed due to the COVID-19 pandemic were surveyed once at least 8 weeks after the cancellation.!##!Results!#!Seventy-seven patients (65%; 34 female, 43 male) completed the questionnaire and were included. The predominant procedures were total knee arthroplasty (TKA), hip arthroscopy and foot and ankle surgery. The mean pain level significantly increased from 5.5 ± 2.2 at the time of the initially scheduled surgery to 6.2 ± 2.5 at the time of the survey (p < 0.0001). The pain level before cancellation of the surgery was significantly higher in female patients (p = 0.029). An increased analgetic consumption was identified in 46% of all patients. A mean PHQ-9 score of 6.1 ± 4.9 was found after cancellation. PHQ-9 scores of 10 or above were found in 14% of patients, and 8% exhibited scores of 15 points or above. Significantly higher PHQ-9 scores were seen in female patients (p = 0.046). No significant differences in PHQ-9 scores were found among age groups, procedures or reasons for cancellation.!##!Conclusion!#!Cancellation of elective orthopaedic surgery resulted in pain levels that were significantly higher than when the surgery was scheduled, leading to increased analgesic use. Additionally, significant psychosocial distress due to the cancellation was identified in some patients, particularly middle-aged women. Despite these results, confidence in the national health care system and in the treating orthopaedic surgeons was not affected.!##!Level of evidence!#!Level III

Accuracy of Positioning and Risk Factors for Malpositioning Custom-Made Femoral Stems in Total Hip Arthroplasty—A Retrospective Multicenter Analysis

Total hip arthroplasty (THA) is commonly performed using off-the-shelf implants. In the case of a severe mismatch between the anatomy of the proximal femur and the geometry of the stem, the use of custom-made stems might become necessary. The goal of this study was to investigate the precision of the implantation of custom-made stems of one manufacturer (CTX stem, AQ Implants) and to determine risk factors for malpositioning. All patients receiving a custom-made CTX stem between 2014 and 2020 at six high-volume academic centers were retrospectively recruited. The achieved position of the stem, as determined by stem version, stem coronal angle, and implantation depth on radiographs, was compared to the plan. The influence of radiographic and demographic parameters on the position was investigated. The results revealed a high variability of the achieved implant position in relation to the preoperative plan. While the stem coronal angle only differed slightly from the intended position, the stem version and the implantation depth showed a high frequency and amount of deviation. Right stems showed significantly higher positions than planned. Surgeons must be aware of this potential problem when implanting custom-made stems

High Affinity Agonists of the Neuropeptide Y (NPY) Y₄ Receptor Derived from the C‑Terminal Pentapeptide of Human Pancreatic Polypeptide (hPP): Synthesis, Stereochemical Discrimination, and Radiolabeling

The diastereomeric mixture of d/l-2,7-diaminooctanedioyl-bis­(YRLRY-NH₂) (BVD-74D, <b>2</b>) was described in the literature as a high affinity Y₄ receptor agonist. Here we report on the synthesis and pharmacological characterization of the pure diastereomers (2<i>R</i>,7<i>R</i>)- and (2<i>S</i>,7<i>S</i>)-<b>2</b> and a series of homo- and heterodimeric analogues in which octanedioic acid was used as an achiral linker. To investigate the role of the Arg residues, one or two arginines were replaced by Ala. Moreover, <i>N</i>^ω-(6-aminohexylaminocarbonyl)­Arg was introduced as an arginine replacement (<b>17</b>). (2<i>R</i>,7<i>R</i>)-<b>2</b> was superior to (2<i>S</i>,7<i>S</i>)-<b>2</b> in binding and functional cellular assays and equipotent with <b>17</b>. [³H]­Propionylation of one amino group in the linker of (2<i>R</i>,7<i>R</i>)-<b>2</b> or at the primary amino group in <b>17</b> resulted in high affinity Y₄R radioligands ([³H]-(2<i>R</i>,7<i>R</i>)-<b>10</b>, [³H]<b>18</b>) with subnanomolar <i>K</i>_d values

Non-specific alterations of craniocervical venous drainage in multiple sclerosis revealed by cardiac-gated phase-contrast MRI

Objective: There is an on-going controversy about venous drainage abnormalities in multiple sclerosis (MS). We applied cardiac-gated phase-contrast and venographic magnetic resonance (MR) techniques to compare venous drainage patterns in patients with MS, healthy controls, and subjects with migraine. Methods: A total of 27 patients with MS (21 female, age 12–59 years, mean disease duration 8.4 ± 8.5 years) and 27 age- and gender-matched healthy controls (21 female, age 12–60 years) were investigated with velocity-encoded cine-phase contrast MR sequences and a 2D time-of-flight MR venography of the cervicocranial region on a 3-T MRI. The data were compared with 26 patients with chronic migraine headaches (19 female, age 17–62 years), previously investigated with the same protocol. The degree of primary and secondary venous outflow in relation to the total cerebral blood flow (tCBF) was compared both quantitatively and qualitatively. Statistical analyses were performed using linear regression models. Results: Secondary venous outflow was significantly increased in patients with MS compared with healthy controls, both qualitatively ( p < 0.001) and quantitatively ( p < 0.013). The observed changes were independent of age and disease duration. Very similar alterations of venous drainage were detectable with the same approach in patients with migraine, without significant differences between MS and migraine patients ( p = 0.65). Conclusion: Our MRI-based study suggests that patients with MS have alterations of cerebral venous drainage similar to subjects with chronic migraine. These non-disease-specific changes seem to a secondary phenomenon rather than being of primary pathogenic importance