Do habitual foot-strike patterns in running influence functional Achilles tendon properties during gait?

The capacity of foot-strike running patterns to influence the functional properties of the Achilles tendon is controversial. This study used transmission-mode ultrasound to investigate the influence of habitual running foot-strike pattern on Achilles tendon properties during barefoot walking and running. Fifteen runners with rearfoot (RFS) and 10 with a forefoot (FFS) foot-strike running pattern had ultrasound transmission velocity measured in the right Achilles tendon during barefoot walking (≈1.1 ms-1) and running (≈2.0 ms-1). Temporospatial gait parameters, ankle kinematics and vertical ground reaction force were simultaneously recorded. Statistical comparisons between foot-strike patterns were made using repeated measure ANOVAs. FFS was characterised by a significantly shorter stance duration (-4%), greater ankle dorsiflexion (+2°), and higher peak vertical ground reaction force (+20% bodyweight) than RFS running (P < .05). Both groups adopted a RFS pattern during walking, with only the relative timing of peak dorsiflexion (3%), ground reaction force (1-2%) and peak vertical force loading rates (22-23%) differing between groups (P < .05). Peak ultrasound transmission velocity in the Achilles tendon was significantly higher in FFS during walking (≈100 ms-1) and running (≈130 ms-1) than RFS (P < .05). Functional Achilles tendon properties differ with habitual footfall patterns in recreational runners.

Tendinopathy alters ultrasound transmission in the patellar tendon during squatting.

Measurement of loading patterns of the patellar tendon during activity is important in understanding tendon injury. We used transmission-mode ultrasonography to investigate patellar tendon loading during squatting in adults with and without tendinopathy. It was hypothesized that axial ultrasonic velocity, a surrogate measure of the elastic modulus of tendon, would be lower in tendinopathy. Ultrasound velocity was measured in both patellar tendons of adults with unilateral patellar tendinopathy (n = 9) and in healthy controls (n = 16) during a bilateral squat maneuver. Sagittal knee movement was measured simultaneously with an electrogoniometer. Statistical comparisons between healthy and injured tendons were made using two-way mixed-design ANOVAs. Axial ultrasound velocity in both symptomatic and asymptomatic patellar tendons in tendinopathy was approximately 15% higher than in healthy tendons at the commencement (F1,23  = 5.2, P < 0.05) and completion (F1,23  = 4.5, P < 0.05) of the squat. While peak velocity was ≈5% higher during both flexion (F1,23  = 5.4, P < 0.05) and extension (F1,23  = 5.3, P < 0.05) phases, there was no significant between-group difference at the midpoint of the movement. There were no significant differences in the rate and magnitude of knee movement between groups. Although further research is required, these findings suggest enhanced baseline muscle activity in patellar tendinopathy and highlight fresh avenues for its clinical management.

Magneto-optics of massive dirac fermions in bulk Bi2Se3.

We report on magneto-optical studies of Bi2Se3, a representative member of the 3D topological insulator family. Its electronic states in bulk are shown to be well described by a simple Dirac-type Hamiltonian for massive particles with only two parameters: the fundamental band gap and the band velocity. In a magnetic field, this model implies a unique property-spin splitting equal to twice the cyclotron energy: Es=2Ec. This explains the extensive magnetotransport studies concluding a fortuitous degeneracy of the spin and orbital split Landau levels in this material. The Es=2Ec match differentiates the massive Dirac electrons in bulk Bi2Se3 from those in quantum electrodynamics, for which Es=Ec always holds.

Achilles tendon loading patterns during barefoot walking and slow running on a treadmill: An ultrasonic propagation study.

Measurement of tendon loading patterns during gait is important for understanding the pathogenesis of tendon "overuse" injury. Given that the speed of propagation of ultrasound in tendon is proportional to the applied load, this study used a noninvasive ultrasonic transmission technique to measure axial ultrasonic velocity in the right Achilles tendon of 27 healthy adults (11 females and 16 males; age, 26 ± 9 years; height, 1.73 ± 0.07 m; weight, 70.6 ± 21.2 kg), walking at self-selected speed (1.1 ± 0.1 m/s), and running at fixed slow speed (2 m/s) on a treadmill. Synchronous measures of ankle kinematics, spatiotemporal gait parameters, and vertical ground reaction forces were simultaneously measured. Slow running was associated with significantly higher cadence, shorter step length, but greater range of ankle movement, higher magnitude and rate of vertical ground reaction force, and higher ultrasonic velocity in the tendon than walking (P < 0.05). Ultrasonic velocity in the Achilles tendon was highly reproducible during walking and slow running (mean within-subject coefficient of variation < 2%). Ultrasonic maxima (P1, P2) and minima (M1, M2) were significantly higher and occurred earlier in the gait cycle (P1, M1, and M2) during running than walking (P < 0.05). Slow running was associated with higher and earlier peaks in loading of the Achilles tendon than walking.

Deficits 10-years after Achilles tendon repair.

The purpose of this study was to determine the long-term impact of surgical repair and subsequent 6-week immobilization of an Achilles tendon rupture on muscle strength, muscle strength endurance and muscle activity. 63 patients participated in this study on average 10.8 ± 3.4 years after surgically repaired Achilles tendon rupture and short-term immobilization. Clinical function was assessed and muscle strength, strength endurance and muscle activity were measured using a dynamometer and electromyography. Ankle ROM, heel height during heel-raise tests and calf circumference were smaller on the injured than on the contralateral side. Ankle torques during the concentric dorsiflexion tasks at 60 °/sec and 180 °/sec and ankle torques during the eccentric plantarflexion task and during the concentric plantarflexion task at 60 °/sec for the injured leg were significantly lower than those for the contralateral leg. The total work during a plantarflexion exercise at 180 °/sec was 14.9% lower in the injured compared to the contralateral leg (p < 0.001). Muscle activity for the gastrocnemius muscle during dorsiflexion tasks was significantly higher in the injured than in the contralateral limb. Limited ankle joint ROM and increased muscle activity in the injured leg suggest compensatory mechanisms to account for differences in muscle morphology and physiology caused by the injury.

Comparative measurements of membrane potentials with microelectrodes and voltage-sensitive dyes.

The usefulness of a new voltage-sensitive fluorescent dye, the membrane permeant negatively charged oxonol dye diBA-C4-(3)-, was evaluated by measuring the membrane potentials of BICR/M1R-k and L cells with glass microelectrodes and simultaneously recording the fluorescence of the stained cells. The membrane potential of BICR/M1R-k cells was varied between -25 mV and -90 mV by changing the bicarbonate concentration in the medium or by voltage clamping. To avoid any interference by the inserted electrodes with the fluorescence measurement of the cytoplasm, the cells were fused by polyethyleneglycol to form giant cells (homokaryons). These homokaryons also allowed penetration by two glass microelectrodes without causing a serious leakage of the plasma membrane. The slow responding dye diBA-C4-(3)- had a fluorescence response of about 1% per mV. Mathematical analysis of the fluorescence changes after voltage clamping revealed a first-order reaction with a rate constant between 0.1 min-1 and 0.8 min-1, depending on the cell size which was determined by the number of nuclei per homokaryon. A model for the mechanism of the fluorescence changes is proposed.

Histopathology of shock wave treated tumor cell suspensions and multicell tumor spheroids.

L1210 mouse leukemia cell suspensions exposed to 500 shock waves (SW) in an experimental lithotripter (XL1, Dornier) revealed severe cellular damage. Apart from cell fragments and cellular debris, cells exhibited alterations of shape, vacuolization of the cytoplasm, perinuclear cisternae, swelling of mitochondria or rupture of the mitochondrial fine structure, and permeabilization of the cell membrane. Treatment of multicell tumor spheroids of both HeLa and EMT6/Ro cells in suspension with 500 SW resulted either in loss of peripheral cells and serious cellular damage in the outer regions or in a fragmentation of the spheroids. Many of the geometrically intact cells exhibited the same histopathological alterations as the suspended L1210 cells. Immobilization of the spheroids in agar or gelatine, however, prevented spheroids from being agitated and accelerated during SW-exposure. After treatment with 500 SW, spheroids immobilized in gelatine were not different from control cultures, as investigated with light- and electronmicroscopy. From our results we conclude that spheroids in suspension are subject to cavitation and liquid jet formation, causing not only acceleration and shearing forces but also collisions which account for the observed cell damage.

Effect of shock waves on suspended and immobilized L1210 cells.

L1210 mouse leukemia cells have been exposed to different doses of shock waves generated by underwater spark discharge at 18 kV in an experimental lithotripter (XL1, Dornier). Histological and flow cytometric investigations revealed severe damage and a LD50 of about 420 shock waves when the cells were treated as suspensions. Cells immobilized in gelatine, however, were unaffected, indicating that secondary effects are responsible for the cellular damage. Possible mechanisms such as cavitation, jets, and shear forces are discussed.

Tumor cell invasion and gap junctional communication. II. Normal and malignant cells confronted in multicell spheroids.

The invasive behavior of five tumor cell lines was investigated with an in vitro invasion assay developed by Mareel et al. Spheroids of all 5 cell lines readily attached to precultured heart fragments (PHF), resulting in confronting pairs. Tumor cells (BICR/M1Rk, C6, and EMT6/Ro) which communicated with the host tissue via gap junctions, rapidly invaded the PHF within 3 days. Population doubling time or migratory activities had no influence on the invasion process. The noncoupled HeLa and L cells formed a cellular capsule around the PHF and showed no invasive activities. HeLa cells, however, started to destroy the PHF after 4 days. We suggest a mechanism different from that of coupled tumor cells. Epithelioid HeLa cells are linked by numerous tight junctions and may, therefore, cut off the nutrition supply for the inner-laying PHF, resulting in a disintegration of the heart tissue.

Tumor cell invasion and gap junctional communication. I. Normal and malignant cells confronted in monolayer cultures.

Mammary tumor cells of the rat (BICR/M1Rk) and mouse (EMT6/Ro) as well as rat glioma cells (C6) are electrically coupled and show intercellular dye spreading. Monolayer cultures of synchronously beating chicken heart cells were also electrically coupled, dye spreading, however, was significantly restricted to only one or two adjacent cells. In all coupled cells, gap junctions were found in both freeze-fracture replicas and ultrathin sections. Heterologous gap junctional coupling between these tumor cells and heart cells was regularly established. The human cervix carcinoma line HeLa and the mouse L sarcoma line were electrically not coupled and did not reveal gap junctions, consequently they showed no coupling to heart cells.