Changes in leg spring behaviour, plantar loading and foot mobility magnitude induced by an exhaustive treadmill run in adolescent middle-distance runners.

OBJECTIVES: This study aimed to determine adjustments in spring-mass model characteristics, plantar loading and foot mobility induced by an exhaustive run. DESIGN: Within-participants repeated measures. METHODS: Eleven highly-trained adolescent middle-distance runners ran to exhaustion on a treadmill at a constant velocity corresponding to 95% of velocity associated with VO₂max (17.8 ± 1.4 kmh(-1), time to exhaustion=8.8 ± 3.4 min). Contact time obtained from plantar pressure sensors was used to estimate spring-mass model characteristics, which were recorded (during 30 s) 1 min after the start and prior to exhaustion using pressure insoles. Foot mobility magnitude (a composite measure of vertical and medial-lateral mobility of the midfoot) was measured before and after the run. RESULTS: Mean contact area (foot to ground), contact time, peak vertical ground reaction force, centre of mass vertical displacement and leg compression increased significantly with fatigue, while flight time, leg stiffness and mean pressure decreased. Leg stiffness decreased because leg compression increased to a larger extent than peak vertical ground reaction forces. Step length, step frequency and foot mobility magnitude did not change at exhaustion. CONCLUSIONS: The stride pattern of adolescents when running on a treadmill at high constant velocity deteriorates near exhaustion, as evidenced by impaired leg-spring behaviour (leg stiffness) and altered plantar loading.

New synthetic strategies to tethered bilayer lipid membranes

Tethered bilayer lipid membranes provide an efficient, stable and versatile platform for the investigation of integrated membrane proteins. However, the incorporation of large proteins, as well as of proteins with a large submembrane part is still a very critical issue and therefore, further optimisation of the system is necessary. The central element of a tBLM is a lipid bilayer. Its proximal leaflet is, at least to some extend, covalently attached to a solid support via a spacer group. The anchor lipid consists of three distinct parts, a lipid headgroup, a spacer group and an anchor. All parts together influence the final bilayer properties. In the frame of this work, the synthesis of new thiolipids for tBLMs on gold has been investigated. The aim was to obtain molecules with longer spacers in order to increase the submembrane space. The systems obtained have been characterized using SPR and EIS. The results obtained during this study are multiple. First, the synthesis of a previously synthesized architecture was successfully scaled up in an industrial lab using a new synthetic approach. The synthesis of large amounts is now feasible. Then, the synthesis of the new thiolipids was carried out taking into account the following requirements: the increase of the submembrane space by having longer ethyleneglycol spacers, the attachment of the molecules to a gold substrate via a thiol bond, and the tunability of the lateral mobility by changing the lipid headgroup. Three different synthetic strategies have been investigated. The polymeric approach did not prove to be successful, merely because of the broad molecular weight distribution. The synthesis of heterofunctionally protected oligoethyleneglycols allowed to obtain ethyleneglycol moieties with 6 and 8 units, but the tedious purification steps gave very low yields. Finally, the block by block synthesis using ethyleneglycol precursors proved to be an efficient and fast method to synthesize the target molecules. Indeed, these were obtained with very high yields, and the separation was very efficient. A whole family of new compounds was obtained, having 6, 8 and 14 ethyleneglycol units and with mono- or diphytanyl lipid headgroups. This new pathway is a very promising synthetic strategy that can be used further in the development of new compounds of the tether system. The formation of bilayers was investigated for the different thiolipids mainly by using EIS. The electrical properties of a bilayer define the quality of the membrane and allow the study of the functionality of proteins embedded in such a system. Despite multiple trials to improve the system using self assembly, Langmuir Blodgett transfer, and detergent mixed vesicles, the new polymer thiolipids did not show as high electrical properties as tBLMs reported in the literature. Nevertheless, it was possible to show that a bilayer could be obtained for the different spacer lengths. These bilayers could be formed using self assembly for the first monolayer, and two different methods for bilayer formation, namely vesicle fusion and solvent exchange. We could furthermore show functional incorporation of the ion carrier valinomycin: the selective transport of K+ ions could be demonstrated. For DPHL, it was even possible to show the functional incorporation of the ion channel gramicidin. The influence of the spacer length is translated into an increase of the spacer capacitance, which could correspond to an increase in the capacity of charge accumulation in the submembrane space. The different systems need to be further optimised to improve the electrical properties of the bilayer. Moreover, the incorporation of larger proteins, and proteins bearing submembrane parts needs to be investigated.

Biomimetic bilayer membranes made from polymers and lipids

Amphiphile Blockcopolymere sind in der Lage in Wasser Morphologien auszubilden, die analog sind zur hydrophil-hydrophob-hydrophil-Struktur von natürlichen Lipiddoppelschichten. In dieser Arbeit wird zum ersten Mal die Präparation und Charakterisierung von oberflächengestützten Polymerdoppelschichten aus Polybutadien-b-Polyethylenoxid (PB-PEO) beschrieben. Für die Herstellung dieser Strukturen wurden zwei unterschiedliche Präparationsstrategien verfolgt. Der erste Weg besteht aus einer zweistufigen Methode, bei der im ersten Schritt organisierte Monoschichten mittels Langmuir-Blodgett-Transfer auf Gold übertragen und kovalent angebunden werden. Im zweiten Schritt werden hydrophobe Wechselwirkungen ausgenutzt, um über Langmuir-Schaefer-Transfer eine weitere Schicht aufzubringen. Somit wurden homogene Architekturen erzeugt, die oberflächengestützten Lipiddoppelschichten gleichen. Als alternativer, einstufiger Ansatz zur Herstellung von Polymerdoppelschichten wurde das Spreiten von Polymervesikeln auf Gold verfolgt. Auch hierdurch ließen sich Doppelschichtstrukturen mit einer vollständigen Oberflächenbedeckung erzeugen. Die hergestellten Polymerdoppelschichten besitzen eine Dicke von 11-14 nm, die von der Präparationsmethode abhängt. Die Polymerstrukturen weisen bei Trocknung für 1.5 h eine Stabilität gegenüber Luft auf. Bei längeren Trocknungszeiten von ca. 12 h kommt es zu einer Reorganisation der Oberfläche. Dies deutet darauf hin, dass Wasser dazu notwendig ist die Strukturen auf lange Sicht zu stabilisieren. Um die Biokompatibilität der Polymerschichten nachzuweisen, wurden die Wechselwirkungen mit dem membranaktiven Peptid Polymyxin B und dem Transmembranprotein α-Haemolysin gezeigt. Mobilität ist ein wichtiger Faktor für die korrekte Funktion vieler Transmembranproteine. Um die laterale Diffusionsdynamik innerhalb der künstlichen Strukturen zu untersuchen, wurde die Mobilität eines integralen Modellpeptids und von fluoreszierenden Membransonden gemessen. Es konnte mit einzelmolekülempfindlichen Techniken gezeigt werden, dass das α-helikale Peptid und die kleinen Fluoreszenzfarbstoffe frei im hydrophoben Kern der Polymerdoppelschicht diffundieren können. Die Diffusion von beiden Spezies scheint stark von der Fluidität der Polymermatrix beeinflusst zu sein. Ein weiterer Teil dieser Arbeit widmet sich der Entwicklung eines angemessenen, lipidbasierten Referenzsystems für zukünftige Proteinuntersuchungen. Hierzu wurde eine neue Methode zu Herstellung von peptidgestützten Lipiddoppelschichtmembranen entwickelt. Dies wurde durch kovalente Befestigung eines Thiopeptids an einen Goldfilm und darauffolgende Anbindung eines Lipids erreicht. Zur Ausbildung der Lipiddoppelschicht auf dem Lipopeptidunterbau wurder der Rapid Solvent Exchange verwendet. Die Ausbildung der Lipiddoppelschicht wurde sowohl auf microskopischer als auch auf makroskopischer Ebene nachgewiesen. Im letzten Schritt wurde die Anwendbarkeit des Modelsystems für elektrochemische Messungen durch den funktionalen Einbau des Ionentransporters Valinomycin unter Beweis gestellt.

Surface patterning with colloidal monolayers

This thesis focuses on the controlled assembly of monodisperse polymer colloids into ordered two-dimensional arrangements. These assemblies, commonly referred to as colloidal monolayers, are subsequently used as masks for the generation of arrays of complex metal nanostructures on solid substrates.rnThe motivation of the research presented here is twofold. First, monolayer crystallization methods were developed to simplify the assembly of colloids and to produce more complex arrangements of colloids in a precise way. Second, various approaches to colloidal lithography are designed with the aim to include novel features or functions to arrays of metal nanostructures.rnThe air/water interface was exploited for the crystallization of colloidal monolayer architectures as it combines a two-dimensional confinement with a high lateral mobility of the colloids that is beneficial for the creation of high long range order. A direct assembly of colloids is presented that provides a cheap, fast and conceptually simple methodology for the preparation of ordered colloidal monolayers. The produced two-dimensional crystals can be transformed into non-close-packed architectures by a plasma-induced size reduction step, thus providing valuable masks for more sophisticated lithographic processes. Finally, the controlled co-assembly of binary colloidal crystals with defined stoichiometries on a Langmuir trough is introduced and characterized with respect to accessible configurations and size ratios. rnSeveral approaches to lithography are presented that aim at introducing different features to colloidal lithography. First, using metal-complex containing latex particles, the synthesis of which is described as well, symmetric arrays of metal nanoparticles can be created by controlled combustion of the organic material of the colloids. The process does not feature an inherent limit in nanoparticle size and is able to produce complex materials as will be demonstrated for FePt alloy particles. Precise control over both size and spacing of the particle array is presented. rnSecond, two lithographic processes are introduced to create sophisticated nanoparticle dimer units consisting of two crescent shaped nanostructures in close proximity; essentially by using a single colloid as mask to generate two structures simultaneously. Strong coupling processes of the parental plasmon resonances of the two objects are observed that are accompanied by high near-field enhancements. A plasmon hybridization model is elaborated to explain all polarization dependent shifts of the resonance positions. Last, a technique to produce laterally patterned, ultra-flat substrates without surface topographies by embedding gold nanoparticles in a silicon dioxide matrix is applied to construct robust and re-usable sensing architectures and to introduce an approach for the nanoscale patterning of solid supported lipid bilayer membranes. rn

Three separable domains regulate GTP-dependent association of H-ras with the plasma membrane

The microlocalization of Ras proteins to different microdomains of the plasma membrane is critical for signaling specificity. Here we examine the complex membrane interactions of H-ras with a combination of FRAP on live cells to measure membrane affinity and electron microscopy of intact plasma membrane sheets to spatially map microdomains. We show that three separable forces operate on H-ras at the plasma membrane. The lipid anchor, comprising a processed CAAX motif and two palmitic acid residues, generates one attractive force that provides a high-affinity interaction with lipid rafts. The adjacent hypervariable linker domain provides a second attractive force but for nonraft plasma membrane microdomains. Operating against the attractive interaction of the lipid anchor for lipid rafts is a repulsive force generated by the N-terminal catalytic domain that increases when H-ras is GTP loaded. These observations lead directly to a novel mechanism that explains how H-ras lateral segregation is regulated by activation state: GTP loading decreases H-ras affinity for lipid rafts and allows the hypervariable linker domain to target to nonraft microdomains, the primary site of H-ras signaling.

Individual Palmitoyl Residues Serve Distinct Roles in H-ras Trafficking, Microlocalization, and Signaling

H-ras is anchored to the plasma membrane by two palmitoylated cysteine residues, Cys181 and Cys184, operating in concert with a C-terminal S-farnesyl cysteine carboxymethylester. Here we demonstrate that the two palmitates serve distinct biological roles. Monopalmitoylation of Cys181 is required and sufficient for efficient trafficking of H-ras to the plasma membrane, whereas monopallmitoylation of Cys184 does not permit efficient trafficking beyond the Golgi apparatus. However, once at the plasma membrane, monopalmitoylation of Cys184 supports correct GTP-regulated lateral segregation of H-ras between cbolesterol-dependent and cholesterol-independent microdomains. In contrast, monopallmitoylation of Cys181 dramatically reverses H-ras lateral segregation, driving GTP-loaded H-ras into cholesterol-dependent microdomains. Intriguingly, the Cys181 monopalmitoylated H-ras anchor emulates the GTP-regulated microdomain interactions of N-ras. These results identify N-ras as the Ras isoform that normally signals from lipid rafts but also reveal that spacing between palmitate and prenyl groups influences anchor interactions with the lipid bilayer. This concept is further supported by the different plasma membrane affinities of the monopalmitoylated anchors: Cys181-palmitate is equivalent to the dually palmitoylated wild-type anchor, whereas Cys184-pahnitate is weaker. Thus, membrane affinity of a pallmitoylated anchor is a function both of the hydrophobicity of the lipid moieties and their spatial organization. Finally we show that the plasma membrane affinity of monopahnitoylated anchors is absolutely dependent on cholesterol, identifying a new role for cholesterol in promoting interactions with the raft and nonraft plasma membrane.

theta-defensins prevent HIV-1 Env-mediated fusion by binding gp41 and blocking 6-helix bundle formation

Retrocyclin-1, a 0-defensin, protects target cells from human immunodeficiency virus, type 1 (HIV-1) by preventing viral entry. To delineate its mechanism, we conducted fusion assays between susceptible target cells and effector cells that expressed HIV-1 Env. Retrocyclin-1 (4 mu M) completely blocked fusion mediated by HIV-1 Envs that used CXCR4 or CCR5 but had little effect on cell fusion mediated by HIV-2 and simian immunodeficiency virus Envs. Retrocyclin-1 inhibited HIV-1 Env-mediated fusion without impairing the lateral mobility of CD4, and it inhibited the fusion of CD4-deficient cells with cells bearing CD4-independent HIV-1 Env. Thus, it could act without cross-linking membrane proteins or inhibiting gp120-CD4 interactions. Retrocyclin-1 acted late in the HIV-1 Env fusion cascade but prior to 6-helix bundle formation. Surface plasmon resonance experiments revealed that retrocyclin bound the ectodomain of gp41 with high affinity in a glycan-independent manner and that it bound selectively to the gp41 C-terminal heptad repeat. Native-PAGE, enzyme-linked immunosorbent assay, and CD spectroscopic analyses all revealed that retrocyclin-1 prevented 6-helix bundle formation. This mode of action, although novel for an innate effector molecule, resembles the mechanism of peptidic entry inhibitors based on portions of the gp41 sequence.

Occupational mobility chains and the role of job opportunities for upward, lateral and downward mobility in Switzerland

This paper addresses the rarely studied relationship between job vacancies and inter-firm upward, lateral, and downward status mobility in an occupationally segmented labor market, taking Switzerland as the example. To conceptualize mobility mechanisms in this type of labor market, we introduce the concept of “occupational mobility chains” and test its validity. This concept provides the backdrop for developing time-dependent measures of individual job opportunities based on Swiss Job Monitor data. We link these measures with career data taken from the Swiss Life History Study and employ event history analysis to test different propositions of the ways in which status mobility is contingent on the number and the status of vacant positions. Results support our assumption that in occupationally segmented labor markets vacant positions affect status mobility only to the degree that they are located within workers’ occupational mobility chains.

Cervical Mobility in Women With Migraine

Objective.-To contrast the cervical range of motion (CROM) in women with episodic migraine (EM), transformed migraine (TM), and controls without migraine headaches. Background.-Migraineurs often complain about neck pain. Furthermore, neck problems can worsen the headaches in individuals with migraine. Individuals with neck pain usually have reduced CROM. Nonetheless, studies assessing the CROM in migraineurs are scarce. Methods.-Our sample was selected in an outpatient headache clinic, and consisted of 45 women aged 20-54 years old, 15 per group. Cervical mobility was evaluated in movements of flexion, extension, right lateral flexion, left lateral flexion, right rotation, and left rotation using the CROM technique, and was contrasted among the groups. Migraine clinical patterns were also evaluated ( frequency, duration of migraine, pain in the moment of evaluation, pain in movement, and pain localization) as a function of CROM. Results.-Compared with controls, individuals with TM had numerically inferior CROM in all parameters, and significant reduction in 3 of them: extension (59.3 vs 68.1, P = .02), left lateral flexion (44.5 vs 49.1, P = .03), and right rotation (62.2 vs 69.6, P = .02). Compared with individuals with migraine, the TM group presented significantly reduced mobility only for extension ( 59.3 vs 68.4, P = .02). Migraineurs also had numerically inferior ROM, contrasted to controls, in 5 of the 6 parameters, although significance was seen just for right rotation (60.8 vs 68.6 P < .01). There was no correlation between cervical mobility and migraine parameters. The CROM was not reduced for the symptomatic side of migraine, in cases of unilateral pain. Conclusion.-Contrasted to controls, individuals with episodic and TM have decreased cervical range of motion.

Evaluation of a modified Broström-Gould procedure for treatment of chronic lateral ankle instability: A retrospective study with critical analysis of outcome scoring.

BACKGROUND: Chronic lateral ankle instability accounts for 20% of the ankle injuries. This study evaluates functional outcome of the modified Broström-Gould technique using suture anchors, with 4 different clinical scores. METHODS: A consecutive series of 41 patients were included with a minimum follow-up of one year. The function was assessed using 4 clinical scores including: the AOFAS for hind foot; the FAAM; the CAIT and the CAIS. RESULTS: Out of 41 patients; 27 patients were very satisfied, 11 satisfied and 3 were not satisfied. Ankle mobility returned to normal in 93% of patients. At follow-up the AOFAS was 89/100 (37-100), the FAAM 85/100% (35-100%), the CAIT 20/30 (5-30), and the CAIS 74/100% (27-100%). CONCLUSION: Outcome of modified Broström-Gould procedure is good with high satisfaction rate in terms of ankle mobility. The disparity in outcome of scores, signals towards the need of a standard evaluation system.

Donor-site morbidity of the sensate extended lateral arm flap.

The free extended lateral arm flap (ELAF) has gained increasing popularity thank to its slimness and versatility, longer neurovascular pedicle, and greater flap size when compared with the original flap design. The aim of this study was to assess the donor-site morbidity associated with this extended procedure. A retrospective study of 25 consecutive patients analyzing postoperative complications using a visual analogue scale questionnaire revealed high patients satisfaction and negligible donor-site morbidity of the ELAF. Scar visibility was the commonest negative outcome. Impaired mobility of the elbow had the highest correlation with patient dissatisfaction. Sensory deficits or paresthetic disorders did not affect patient satisfaction. The extension of the lateral arm flap and positioning over the lateral humeral epicondyle is a safe and well-accepted procedure with minimal donor-site morbidity. To optimize outcomes, a maximal flap width of 6 or 7 cm and intensive postoperative mobilization therapy is advisable.

Effect of the Glenosphere Position and Size on Reverse Shoulder Prostheses Mobility

Introduction: Several methods have already been proposed to improve the mobility of reversed prostheses (lateral or inferior displacement, increase of the glenosphere size). However, the effect of these design changes have only been evaluated on the maximal range of motion and were not related to activities of daily living (ADL). Our aim was thus to measure the effect of these design changes and to relate it to 4 typical ADL. Methods: CT data were used to reconstruct a accurate geometric model of the scapula and humerus. The Aequalis reversed prosthesis (Tornier) was used. The mobility of a healthy shoulder was compared to the mobility of 4 different reversed designs: 36 and 42 mm glenospheres diameters, inferior (4 mm) and lateral (3.2 mm) glenospheres displacements. The complete mobility map of the prosthesis was compared to kinematics measurement on healthy subjects for 4 ADL: 1) hand to contra lateral shoulder, 2) hand to mouth, 3) combing hair, 4) hand to back pocket. The results are presented as percentage of the allowed movement of the prosthestic shouder relative to the healthy shoulder, considered as the control group. Results: None of the tested designs allowed to recover a full mobility. The differences of allowed range of motion among each prosthetic designs appeared mainly in two of the 4 movements: hand to back pocket and hand to contra lateral shoulder. For the hand to back pocket, the 36 had the lowest mobility range, particularly for the last third of the movement. The 42 appeared to be a good compromise for all ADL activities. Conclusion: Reverse shoulder prostheses does not allow to recover a full range of motion compared to healthy shoulders, even for ADL. The present study allowed to obtain a complete 3D mobility map for several glenosphere positions and sizes, and to relate it to typical ADL. We mainly observed an improved mobility with inferior displacement and increased glenosphere size. We would suggest to use larger glenosphere, whenever it is possible.

Outcome of a Modified Broström-Gould Procedure for Lateral Ankle Instability

Introduction: Ankle sprains affect 200'000 persons/year in Switzerland. Most incidences are successfully treated by conservative measures but 20% require reconstruction for symptomatic chronic lateral ankle instability. This study evaluates the functional outcome after a modified Broström-Gould technique as measured by different clinical scores and compares the functional outcome of this technique with other surgical treatments of ankle instability. Methods: This retrospective cohort study evaluates 47 patients who underwent a modified Broström-Gould procedure using suture anchors to refix the lateral ankle capsuloligamentary structures at our institution from 2005 to 2009 with a minimum follow-up of one year (13-72 Mo). All patients were operated by one single surgeon and evaluated by an independent examiner. The function was assessed using 4 scores including: the AOFAS (American Orthopaedic Foot and Ankle Society's Score) hindfoot score; the FAAM (Foot and Ankle Ability Measurement); the CAIT (Cumberland Ankle Instability Tool); the CAIS (Chronic Ankle Instability Scale). Results: Six patients were excluded leaving 41 patients for examination. 34 patients (83%) thought that their ankle was more stable after the surgery, 7 (17%) did not feel any difference. 27 patients were very satisfied, 11 satisfied and 3 not satisfied. Reasons for non satisfaction included persistent instability and pain. Ankle mobility returned to normal in 93% of patients. Five patients had transcient hypoesthesy in the area of the superficial peroneal nerve. One patient suffered from a superficial infection treated successfully by local measures. 80% had the perception of a normal ankle, 20% thought to be below normal. At follow-up the AOFAS was 89/100 (37-100), the FAAM 85/100% (35-100%), the CAIT 20/30 (5-30), and the CAIS 74/100% (27-100%). Conclusions: The modified Broström-Gould procedure, which belongs to the anatomic ankle stabilizations is relatively simple and offers good outcome that satisfied 93% of the patients in the present study. No active stabilisator is sacrificed. Preservation of the ankle mobility is better and the complication rate is lower than after non-anatomical procedures described in the literature. The CAIT appeared as the most severe score compared to the other scales used in our study.

Evaluation of Reducibility of Trunk Asymmetry in Lateral Bending

The value of the lateral bending test is important in the assessment of spinal curve mobility and prediction of surgical outcome in the treatment of adolescent idiopathic scoliosis (AIS). However, radiographic bending tests are unable to assess the reducibility of trunk asymmetry. This study aims to exploit surface topography measurement in order to evaluate the changes in shape of the trunk (a) between bending and neutral standing positions, and (b) between standing pre- and post-operative visits, in a cohort of adolescents with AIS having undergone surgical correction; and to correlate the differences measured in cases (a) and (b). Our cohort includes 13 patients with right thoracic AIS. Each patient had their 3D trunk surface digitized with a multi-head InSpeck system in standing posture (at the pre-op and post-op visits) and in maximum voluntary right and left bending (at the pre-op visit). We developed a novel trunk shape analysis method which produces a set of inclined trunk cross-sections allowing comparison between different postures. Two asymmetry indices, trunk rotation (TR) and back surface rotation (BSR), were computed in all cases and a statistical analysis was performed. Our correlation study (Pearson test) showed fair correlations in most cases between the changes in side-bending and those post-surgery, with the strongest relationship (p-value < 0.01) when combining the TR measurements from both bendings. These results provide evidence that the bending test can be used to assess trunk asymmetry reducibility. The proposed approach could provide a non-invasive trunk asymmetry reducibility test for routine clinical use in AIS surgery planning.

Laryngeal mobility and dysphagia

The authors studied the utility of the physical test of laryngeal movement in swallowing disorders of the oropharyngeal region. Measurement and palpation of the larynx during deglutition were performed in the neck of 14 dysphagic patients and in two normal control groups. The normal groups were used to establish the pattern of the movement and the normal values of laryngeal elevation. Control elevation ranged from 1.80 to 2.50 cm. In eight patients laryngeal motion was defective and presented values ranging from zero to 1.50 cm. Palpation during laryngeal movement also revealed unexpected anomalous displacement such as lateral shifting and lowering of the larynx. In six patients with defective laryngeal motion, pharyngeal and upper esophageal sphincter function were also impaired. Direct measurement and palpation of laryngeal mobility during deglutition is a noninvasive method that can be used to evaluate dysphagia and the risk for aspiration. Also, it allows physical assessment of the evolution of the disorder.