AFM and Fluorescence Microscopy of Single Cells with Simultaneous Mechanical Stimulation via Electrically Stretchable Substrates

We have developed a novel experimental set-up that simultaneously, (i) applies static and dynamic deformations to adherent cells in culture, (ii) allows the visualization of cells under fluorescence microscopy, and (iii) allows atomic force microscopy nanoindentation measurements of the mechanical properties of the cells. The cell stretcher device relies on a dielectric elastomer film that can be electro-actuated and acts as the cell culture substrate. The shape and position of the electrodes actuating the film can be controlled by design in order to obtain specific deformations across the cell culture chamber. By using optical markers we characterized the strain fields under different electrode configurations and applied potentials. The combined setup, which includes the cell stretcher device, an atomic force microscope, and an inverted optical microscope, can assess in situ and with sub-micron spatial resolution single cell topography and elasticity, as well as ion fluxes, during the application of static deformations. Proof of performance on fibroblasts shows a reproducible increase in the average cell elastic modulus as a response to applied uniaxial stretch of just 4%. Additionally, high resolution topography and elasticity maps on a single fibroblast can be acquired while the cell is deformed, providing evidence of long-term instrumental stability. This study provides a proof-of-concept of a novel platform that allows in situ and real time investigation of single cell mechano-transduction phenomena with sub-cellular spatial resolution.     

Simultaneous single-molecule measurements of phage T7 replisome composition and function reveal the mechanism of polymerase exchange

A complete understanding of the molecular mechanisms underlying the functioning of large, multiprotein complexes requires experimental tools capable of simultaneously visualizing molecular architecture and enzymatic activity in real time. We developed a novel single-molecule assay that combines the flow-stretching of individual DNA molecules to measure the activity of the DNA-replication machinery with the visualization of fluorescently labeled DNA polymerases at the replication fork. By correlating polymerase stoichiometry with DNA synthesis of T7 bacteriophage replisomes, we are able to quantitatively describe the mechanism of polymerase exchange. We find that even at relatively modest polymerase concentration (∼2 nM), soluble polymerases are recruited to an actively synthesizing replisome, dramatically increasing local polymerase concentration. These excess polymerases remain passively associated with the replisome through electrostatic interactions with the T7 helicase for ∼50 s until a stochastic and transient dissociation of the synthesizing polymerase from the primer-template allows for a polymerase exchange event to occur.     

Congenital muscular torticollis: Early and intensive treatment is critical. A prospective study

BACKGROUND: Although the success of conservative management of congenital muscular torticollis has been well documented, relatively little is known about the determinants of this outcome, such as treatment duration and exercise frequency. The aim of the present study was to define factors related to treatment duration, to compare different frequencies and intensities of home treatment programs and their effect on the speed of recovery. METHODS: The present study was a prospective study of 45 infants (26 male, 19 female) with congenital muscular torticollis referred to the pediatric surgical outpatient during a I year period. Following a standardized initial assessment, parents were taught our intensive home treatment protocol, consisting of passive stretching exercises repeated every 3 h. RESULTS: The mean age at initial assessment was 38.6 days (range 15-120 days). Mean treatment duration was found to be 3.2 +/- 1.3 months. All patients were treated by use of our intensive protocol of passive stretching exercises (100% success). No surgery was necessary. CONCLUSIONS: In patients with early treated congenital muscular torticollis, there is no place for surgical treatment. This group of patients can be successfully treated using an intensive protocol of passive stretching exercises. In addition, this treatment protocol has a very short treatment duration compared with other standardized protocols. A successful outcome depends primarily on good cooperation with the parents, especially in developing countries.     

Stretching position can affect levator scapular muscle activity,length, and cervical range of motion in people with a shortened levator scapulae

ObjectivesLevator scapulae (LS) muscle stretching exercises are a common method of lengthening a shortened muscle; however, the appropriate stretching position for lengthening the LS in people with a shortened LS remains unclear. The purpose of this study was to compare the effects of different stretching exercise positions on the LS and introduce effective stretching exercise methods to clinicians.ParticipantsTwenty-four university students (12 men, 12 women) with a shortened LS were recruited.MethodsLS muscle activity, LS index (LSI), and cervical range of motion (ROM) were measured pre (baseline) and post three different stretching exercise positions (sitting, quadruped, and prone).ResultsThe LSI and cervical ROM exceeded the minimal detectable change and had significant changes. The LSI was greater in the sitting position than at the baseline (p = 0.01), quadruped position (p < 0.01); the LSI in the prone position presented a higher increase than the quadruped position (p = 0.01). The cervical ROM increased in the sitting position when compared to the baseline (p < 0.01) and quadruped position (p < 0.01).ConclusionsStretching the LS in the sitting position was the most effective exercise for improving LS muscle length and cervical ROM.     

Effects of acute static,ballistic, and PNF stretching exercise on the muscle and tendon tissue properties

The purpose of this study was to investigate the influence of a single static, ballistic, or proprioceptive neuromuscular facilitation (PNF) stretching exercise on the various muscle‐tendon parameters of the lower leg and to detect possible differences in the effects between the methods. Volunteers (n = 122) were randomly divided into static, ballistic, and PNF stretching groups and a control group. Before and after the 4 × 30 s stretching intervention, we determined the maximum dorsiflexion range of motion (RoM) with the corresponding fascicle length and pennation angle of the gastrocnemius medialis. Passive resistive torque (PRT) and maximum voluntary contraction (MVC) were measured with a dynamometer. Observation of muscle‐tendon junction (MTJ) displacement with ultrasound allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate stiffness. Although RoM increased (static: +4.3%, ballistic: +4.5%, PNF: +3.5%), PRT (static: ?11.4%, ballistic: ?11.5%, PNF: ?13,7%), muscle stiffness (static: ?13.1%, ballistic: ?20.3%, PNF: ?20.2%), and muscle‐tendon stiffness (static: ?11.3%, ballistic: ?10.5%, PNF: ?13.7%) decreased significantly in all the stretching groups. Only in the PNF stretching group, the pennation angle in the stretched position (?4.2%) and plantar flexor MVC (?4.6%) decreased significantly. Multivariate analysis showed no clinically relevant difference between the stretching groups. The increase in RoM and the decrease in PRT and muscle‐tendon stiffness could be explained by more compliant muscle tissue following a single static, ballistic, or PNF stretching exercise.     

Comparison of 3 different methods to analyze ankle plantarflexor stiffness in children with spastic diplegia cerebral palsy

Ross SA, Foreman M, Engsberg JR. Comparison of 3 different methods to analyze ankle plantarflexor stiffness in children with spastic diplegia cerebral palsy.

Objective

To compare 3 different methods of measuring plantarflexor stiffness in children with spastic diplegia cerebral palsy (CP) and children without disability.

Design

Case-control study.

Setting

Human performance laboratory.

Participants

A retrospective analysis was conducted with children with spastic diplegia (n=121; mean age, 8.4y) and children with typical development (TD) (n=48; mean age, 9.7y).

Interventions

Not applicable.

Main Outcome Measures

An isokinetic dynamometer was used to measure ankle plantarflexor stiffness at 10°/s using 3 methods: (1) end-range method, which applied a linear slope to the end of the torque-angle curve; (2) set-range method, which applied a linear slope from 30° to 10° plantarflexion; and (3) a linear method, which applied a slope only to the linear portion of the curve.

Results

Two-way analysis of variance revealed significant main effects for group and stiffness method. The end-range method showed no significant difference between groups for plantarflexor stiffness (P=.62), the set-range method showed the CP group with 120% greater stiffness than the TD group (P<.046), and the linear method showed the CP group with 35% greater stiffness than the TD group (P<.001).

Conclusions

The linear method appeared to resolve the issues with the previous methods; applying a linear slope to a nonlinear curve or applying a linear slope to the same range of motion for each child regardless of their range limitations. It is clear that children with CP have limited range of motion; therefore, stiffness occurs earlier in the range than would be expected for a typically developing child. Using the linear method, children with CP were 35% stiffer in the ankle plantarflexors than typically developing peers.     

Efectividad de un programa de estiramientos sobre los niveles de ansiedad de los trabajadores de una plataforma logística: un estudio controlado aleatorizado

ObjectiveTo study the influence of a short programme of stretching exercises on anxiety levels of workers in a Spanish logistic company.MethodA controlled clinical trial was carried out by means of an inter-subject design of random homogeneous blocks. Participants were assigned to the experimental group (n = 67), treated with a programme of stretching exercises of 10-minute duration after working hours for a period of 3 months, or to the untreated control group (n = 67). The primary result variable was anxiety, and the secondary variables were burnout syndrome, quality of life and flexibility. An analysis of covariance (ANCOVA) by intention to treat was performed on each of the result variables by controlling the baseline scores, the age and the practice of introjective activities outside the program, with the size effect calculated by means of the partial eta-squared value (η²).ResultsThe results of the ANCOVA showed a moderate effect of the stretching exercise programme on the levels of anxiety (η² = 0,06; P = .004). Other effects found were substantial for flexibility (η² = 0,13; P < .001); moderately high for bodily pain (η² = 0,08; P = .001), and moderate for vitality (η² = 0,05; P = .016); mental health (η² = 0,05; P = .017); general health (η² = 0,04; P = .028) and exhaustion (η² = 0,04; P = .025).ConclusionsThe implementation of a short programme of stretching exercises in the work place was effective for reducing levels of anxiety, bodily pain and exhaustion, and for raising levels of vitality, mental health, general health and flexibility. This type of intervention could be seen as a low-cost strategy for improving the well-being of workers.     

电针配合肌肉伸展练习治疗大腿后肌拉伤疗效观察

目的：观察电针配合肌肉伸展练习治疗大腿后肌拉伤的疗效。方法：阿是穴为主,用电针治疗20min,1次/d,配合肌肉伸展练习。结果：50例中治愈29例（58%）,好转21例（42%）,总有效率100%。结论：电针配合肌肉伸展练习治疗大腿后肌拉伤的疗效满意。     

机械牵张应变对人牙周膜细胞内游离钙离子浓度的影响

目的:观察机械牵张应变作用下,人牙周膜细胞(HPDLCs)内游离Ca2 浓度的变化。方法:体外培养HPDLCs,利用动态机械应变细胞加载装置,对1%、10%和20%应变组的细胞分别进行30、60和120min的动态牵张加载,通过流式细胞仪和激光共聚焦显微镜检测细胞内游离Ca2 浓度的变化,并应用SPSS13.0软件包对数据进行方差分析。结果:当HPDLCs加载30min时,各组检测到的胞内游离Ca2 浓度与对照组无显著差异(P>0.05);60min时,各个应变组的胞内Ca2 浓度明显升高,与对照组相比均有非常显著的差异(P<0.01);加载时间延长到120min时,各组Ca2 浓度又降至对照组水平(P>0.05)。结论:机械牵张应变可通过钙离子信号系统影响HPDLCs的生物学活性。     

THE EFFECTS OF A DAILY STRETCHING PROTOCOL ON PASSIVE GLENOHUMERAL INTERNAL ROTATION IN OVERHEAD THROWING COLLEGIATE ATHLETES

Introduction/Purpose:

Shoulder dysfunction and injury are common in throwing athletes. Loss of internal rotation has been correlated to shoulder pathologies. The purpose of this study was to assess the effects of a stretching protocol on passive internal rotation. The purpose of this study was assess the effects of a stretching protocol on passive internal rotation motion in the throwing shoulders of collegiate baseball players.

Study Design:

Pre-Post, intervention, using a within subjects comparison of a convenience sample.

Methods:

Glenohumeral internal rotation and external rotation of the throwing and non-throwing shoulders of NCAA Division I baseball players were measured using a universal goniometer. Determinations were made as to the degree of Glenohumeral Internal Rotation Deficit (GIRD) in the throwing shoulder. A daily (5 days per week), 12-week posterior capsule stretching program was administered. Post-stretching internal rotation and external rotation measures were again obtained. The coaches and athletic trainers of the included team monitored the players for shoulder injuries and innings of training/competition lost due to shoulder injuries during the 12 week intervention.

Results:

A significant increase in range of motion was found for dominant arm internal rotation (IR) and total range of motion (TOT) following the stretching program. No statistically significant improvement in range of motion was found for external rotation (ER), non-throwing arm internal rotation (NDIR), non-throwing arm external rotation (NDER), and non-throwing arm total motion (NDTOT).

Conclusions:

Implementation of a posterior capsule stretching program may be helpful to facilitate increased passive internal rotation range of motion at the glenohumeral joint. Further research should be performed using a control group not receiving the stretching program in order to more completely establish the impact of stretching on measures of passive glenohumeral range of motion.

Level of Evidence:

1b