LanI-Mediated Lantibiotic Immunity in Bacillus subtilis: Functional Analysis.

Lantibiotics subtilin and nisin are produced by Bacillus subtilis and Lactococcus lactis, respectively. To prevent toxicity of their own lantibiotic, both bacteria express specific immunity proteins, called SpaI and NisI. In addition, ABC transporters SpaFEG and NisFEG prevent lantibiotic toxicity by transporting the respective peptides to the extracellular space. Although the three-dimensional structures of SpaI and NisI have been solved, very little is known about the molecular function of either lipoprotein. Using laser-induced liquid bead ion desorption (LILBID)-mass spectrometry, we show here that subtilin interacts with SpaI monomers. The expression of either SpaI or NisI in a subtilin-nonproducing B. subtilis strain resulted in the respective strain being more resistant against either subtilin or nisin. Furthermore, pore formation provided by subtilin and nisin was prevented specifically upon the expression of either SpaI or NisI. As shown with a nisin-subtilin hybrid molecule, the C-terminal part of subtilin but not any particular lanthionine ring was needed for SpaI-mediated immunity. With respect to growth, SpaI provided less immunity against subtilin than is provided by the ABC transporter SpaFEG. However, SpaI prevented pore formation much more efficiently than SpaFEG. Taken together, our data show the physiological function of SpaI as a fast immune response to protect the cellular membrane.IMPORTANCE The two lantibiotics nisin and subtilin are produced by Lactococcus lactis and Bacillus subtilis, respectively. Both peptides have strong antimicrobial activity against Gram-positive bacteria, and therefore, appropriate protection mechanisms are required for the producing strains. To prevent toxicity of their own lantibiotic, both bacteria express immunity proteins, called SpaI and NisI, and in addition, ABC transporters SpaFEG and NisFEG. Whereas it has been shown that the ABC transporters protect the producing strains by transporting the toxic peptides to the extracellular space, the exact mode of action and the physiological function of the lipoproteins during immunity are still unknown. Understanding the exact role of lantibiotic immunity proteins is of major importance for improving production rates and for the design of newly engineered peptide antibiotics. Here, we show (i) the specificity of each lipoprotein for its own lantibiotic, (ii) the specific physical interaction of subtilin with its lipoprotein SpaI, (iii) the physiological function of SpaI in protecting the cellular membrane, and (iv) the importance of the C-terminal part of subtilin for its interaction with SpaI.

On the measurement of ski boot viscoelasticity.

OBJECTIVES: Since the polymeric materials commonly used for ski boots feature viscoelastic properties, the results of ski boot flexion tests are expected to be influenced by flexion velocity. Devices testing at all skiing specific ankle angular velocities are currently not available. Therefore, the aims of this study were to (i) develop a system allowing the testing of ski boots at high ankle angular velocities, (ii) quantify the effect of ankle angular velocity on viscoelasticity and (iii) determine the repeatability of the system. DESIGN AND METHOD: A test bench and a lower limb prosthesis were developed to determine tibia angle and applied torque. To assess the effect of angular velocity, two pairs of ski boots were tested at 5°/s, 50°/s, 75°/s and 100°/s. To assess stiffness variation and measurement repeatability, ten different used ski boots of different manufacturers were tested twice. RESULTS: Four ski boot flexion stiffness parameters and two energy dissipation factors were reported. The repeatability of the stiffness and the energy dissipation parameters was better than 4% and 3%, respectively. Stiffnesses and dissipation factors increased with increasing angular velocity. CONCLUSION: In the present study a reliable system facilitating the testing of ski boots at velocities of up to 100°/s was developed. To comprehensively characterise the viscoelastic properties of ski boots, we propose to report four ski boot stiffness parameters and two energy dissipation factors. An ankle angular velocity above 50°/s was recommended to perform mechanical tests of ski boots if employed in slalom-like skiing.

Does Kinesiology tape counter exercise-related impairments of balance in the elderly?

BACKGROUND: Maintaining balance is an essential requirement for the performance of daily tasks and sporting activities, particularly in older adults to prevent falls and associated injuries. Kinesiology tape has gained great popularity in sports and is frequently used as a tool for performance enhancement. However, there is little research investigating its influence on balance. RESEARCH QUESTION: The purpose of this study was to evaluate the effect of Kinesiology tape on dynamic balance, postural stability and knee proprioception after physical activity in healthy, older adults. METHODS: Twelve physically active, healthy men aged 63-77 years performed the test on two separate days, with and without Kinesiology tape at the knee joint (prospective intervention with cross-over design). Dynamic balance during an obstacle-crossing task, postural stability in a single-leg stance test, and knee joint position sense as a measure of proprioception were examined before and after 30 min of downhill walking on a treadmill. The influences of taping condition and physical activity on all parameters were statistically tested using factorial ANOVAs. RESULTS: Factorial ANOVA revealed significant time × taping condition interaction effects on all performance parameters (p < 0.05), indicating that the exercise-related changes in dynamic balance, postural stability and knee proprioception differed between the two taping conditions. The deterioration of performance was always greater when no tape was used. SIGNIFICANCE: This study demonstrated that physical exercise significantly deteriorated dynamic balance, postural stability and knee proprioception in older men. These effects can be attenuated through the usage of Kinesiology tape. By preventing exercise-related impairments of balance, Kinesiology tape might help reduce the risk of sports-associated falls and associated injuries.

Eccentric Exercise, Kinesiology Tape, and Balance in Healthy Men.

CONTEXT: Deficits in balance have been identified as a possible risk factor for knee injuries in athletes. Despite a lack of evidence for its effectiveness, kinesiology tape (KT) is widely used to prevent knee injuries. OBJECTIVE: To investigate the influence of KT at the knee joint on balance ability in healthy men after eccentric exercise. DESIGN: Crossover study. SETTING: University laboratory. PATIENTS OR OTHER PARTICIPANTS: Twelve young men with no history of lower limb injury volunteered for the study (age = 23.3 ± 2.6 years). All participants were students enrolled in a sports science program. INTERVENTION(S): Participants performed the balance test with and without KT at the knee joint on 2 separate days. MAIN OUTCOME MEASURE(S): The ability to maintain balance was assessed during a single-legged-stance test using a computerized balance-stability test system. The test was performed before and after 30 minutes of downhill walking on a treadmill. RESULTS: Eccentric exercise resulted in a deterioration of balance ability, which was attenuated by the use of KT. Further analyses revealed that the effectiveness of KT depended on the participant's balance status, with the preventive effect being greater in participants presenting with poorer baseline balance ability. CONCLUSIONS: Applied to the knee joint, KT counteracted the exercise-related deterioration of balance ability observed when no tape was used. Participants presenting with below-average balance ability received more benefit from KT. By preventing exercise-related impairment of balance ability, KT might help to reduce the risk of sport-associated knee injuries.

Why do we suffer more ACL injuries in the cold? A pilot study into potential risk factors.

OBJECTIVES: This study aimed to investigate temperature-related changes in different neuro-muscular parameters, to elucidate the reasons for the increased likeliness of injuries of the anterior cruciate ligament under cold environmental conditions. DESIGN: Repeated measures study design. METHODS: To induce peripheral cooling of the knee joint and thigh muscles, ten healthy, female subjects underwent 30 min of exposure to a cold environment. Both knee extensor and flexor muscles were examined for electromyographic activity, maximum voluntary contraction strength, rate of force development and force sense. Measures of knee laxity were obtained by computerized arthrometry. RESULTS: Following cold exposure, rate of force development of the knee flexor muscles was significantly reduced (p = 0.016). Left-shifts of electromyography power spectra indicated changes in neural drive to the medial and lateral head of the vastus muscle. Maximum strength, force sense and knee laxity were not affected by the intervention. CONCLUSION: The reduced capacity of cold knee flexor muscles to explosively generate force may limit the hamstrings' capability to counter strong and fast contractions of the knee extensor muscles that cause anterior shear force on the tibia and, thus, strain the anterior cruciate ligament.

Does knee joint cooling change in vivo patellar tendon mechanical properties?

PURPOSE: This study aimed to assess the influence of knee joint cooling on the in vivo mechanical properties of the patellar tendon. METHODS: Twenty young, healthy women volunteered for the study. B-mode ultrasonography was used to record patellar tendon elongation during isometric ramp contraction of the knee extensors (5-7 s, 90° knee angle) and calculate tendon stiffness. Skin temperature was measured by infrared thermometry. Data were acquired before and after 30 min of local icing of the knee joint and compared by paired samples t-tests. RESULTS: After cold exposure, skin temperature as measured over the patellar tendon dropped by 16.8 ± 2.0 °C. Tendon stiffness increased from 2189 ± 551 to 2705 ± 902 N mm(-1) (+25 %, p = 0.007). Tendon strain decreased by 9 % (p = 0.004). A small, albeit significant reduction in maximum tendon force was observed (-3.3 %, p = 0.03). CONCLUSIONS: Knee cooling is associated with a significant increase in patellar tendon stiffness. The observed tendon stiffening may influence the operating range of sarcomeres, possibly limiting the maximal force generation capacity of knee extensor muscles. In addition, a stiffer tendon might benefit rate of force development, thus countering the loss in explosiveness typically described for cold muscles.

Effect of Different Bearing Ratios on the Friction between Ultrahigh Molecular Weight Polyethylene Ski Bases and Snow.

The purpose of this study was to analyze the effect of surfaces with different bearing ratios, but similar roughness heights, on the friction between ultrahigh molecular weight polyethylene (UHMWPE) and snow. On a linear tribometer positioned inside a cold chamber, the different samples were tested over a wide range of velocities and snow temperatures. The surface roughness was measured with a focus variation microscope and analyzed using the bearing ratio curve and its parameters. The surface energy was investigated by measuring the contact angles of a polar (water) and nonpolar (diiodmethane) liquid. The friction tests showed that the bearing ratio had a major effect on the friction between UHMWPE and snow. For temperatures close to the melting point a surface with wide grooves and narrow plateaus (nonbearing surface) performed well. For cold conditions, the friction was less for a surface with narrow grooves and wide plateaus (bearing surface). Interpretations of the results are given on the basis of mixed friction, with lubricated friction being dominant at higher snow temperatures and solid-solid interaction at lower ones.

MglC, a Paralog of Myxococcus xanthus GTPase-Activating Protein MglB, Plays a Divergent Role in Motility Regulation.

UNLABELLED: In order to optimize interactions with their environment and one another, bacteria regulate their motility. In the case of the rod-shaped cells of Myxococcus xanthus, regulated motility is essential for social behaviors. M. xanthus moves over surfaces using type IV pilus-dependent motility and gliding motility. These two motility systems are coordinated by a protein module that controls cell polarity and consists of three polarly localized proteins, the small G protein MglA, the cognate MglA GTPase-activating protein MglB, and the response regulator RomR. Cellular reversals are induced by the Frz chemosensory system, and the output response regulator of this system, FrzZ, interfaces with the MglA/MglB/RomR module to invert cell polarity. Using a computational approach, we identify a paralog of MglB, MXAN_5770 (MglC). Genetic epistasis experiments demonstrate that MglC functions in the same pathway as MglA, MglB, RomR, and FrzZ and is important for regulating cellular reversals. Like MglB, MglC localizes to the cell poles asymmetrically and with a large cluster at the lagging pole. Correct polar localization of MglC depends on RomR and MglB. Consistently, MglC interacts directly with MglB and the C-terminal output domain of RomR, and we identified a surface of MglC that is necessary for the interaction with MglB and for MglC function. Together, our findings identify an additional member of the M. xanthus polarity module involved in regulating motility and demonstrate how gene duplication followed by functional divergence can add a layer of control to the complex cellular processes of motility and motility regulation. IMPORTANCE: Gene duplication and the subsequent divergence of the duplicated genes are important evolutionary mechanisms for increasing both biological complexity and regulation of biological processes. The bacterium Myxococcus xanthus is a soil bacterium with an unusually large genome that carries out several social processes, including predation of other bacterial species and formation of multicellular, spore-filled fruiting bodies. One feature of the large M. xanthus genome is that it contains many gene duplications. Here, we compare the products of one example of gene duplication and divergence, in which a paralog of the cognate MglA GTPase-activating protein MglB has acquired a different and opposing role in the regulation of cellular polarity and motility, processes critical to the bacterium's social behaviors.

Performance limitation and the role of core temperature when wearing light-weight workwear under moderate thermal conditions.

The objective of this investigation was to achieve an understanding about the relationship between heat stress and performance limitation when wearing a two-layerfire-resistant light-weight workwear (full-clothed ensemble) compared to an one-layer short sports gear (semi-clothed ensemble) in an exhaustive, stressful situation under moderate thermal condition (25°C). Ten well trained male subjects performed a strenuous walking protocol with both clothing ensembles until exhaustion occurred in a climatic chamber. Wearing workwear reduced the endurance performance by 10% (p=0.007) and the evaporation by 21% (p=0.003), caused a more pronounced rise in core temperature during submaximal walking (0.7±0.3 vs. 1.2±0.4°C; p≤0.001) and from start till exhaustion (1.4±0.3 vs. 1.8±0.5°C; p=0.008), accelerated sweat loss (13±2 vs. 15±3gmin(-1); p=0.007), and led to a significant higher heart rate at the end of cool down (103±6 vs. 111±7bpm; p=0.004). Correlation analysis revealed that core temperature development during submaximal walking and evaporation may play important roles for endurance performance. However, a critical core temperature of 40°C, which is stated to be a crucial factor for central fatigue and performance limitation, was not reached either with the semi-clothed or the full-clothed ensemble (38.3±0.4 vs. 38.4±0.5°C). Additionally, perceived exertion did not increase to a higher extent parallel with the rising core temperature with workwear which would substantiate the critical core temperature theory. In conclusion, increased heat stress led to cardiovascular exercise limitation rather than central fatigue.

The Effect of Uphill and Downhill Walking on Joint-Position Sense: A Study on Healthy Knees.

CONTEXT: During sport activity, knee proprioception might worsen. This decrease in proprioceptive acuity negatively influences motor control and therefore may increase injury risk. Hiking is a common activity characterized by a higher-intensity-exercise phase during uphill walking and a lower-intensity-exercise phase during downhill walking. Pain and injuries are reported in hiking, especially during the downhill phase. OBJECTIVE: To examine the effect of a hiking-fatigue protocol on joint-position sense. DESIGN: Repeated measures. SETTING: University research laboratory. PARTICIPANTS: 24 nonprofessional sportswomen without knee injuries. MAIN OUTCOME MEASURES: Joint-position sense was tested at the beginning, after 30 min uphill walking, and after 30 min downhill walking on a treadmill (continuous protocol). RESULTS: After downhill walking, joint-position sense was significantly worse than in the test at the beginning (P = .035, α = .05). After uphill walking, no differences were observed in comparison with the test at the beginning (P = .172, α = .05) or the test after downhill walking (P = .165, α = .05). CONCLUSION: Downhill walking causes impairment in knee-joint-position sense. Considering these results, injury-prevention protocols for hiking should focus on maintaining and improving knee proprioception during the descending phase.

A pilot study of the effect of Kinesiology tape on knee proprioception after physical activity in healthy women.

OBJECTIVES: Kinesiology tape has gained significant popularity in recent years and is widely used as an adjunct for treatment and prevention of musculoskeletal injuries. However, evidence regarding its influence on knee proprioception is scarce. The purpose of this study was to evaluate the effect of Kinesiology tape on knee proprioception after physical activity in healthy women. It was hypothesized that Kinesiology tape enhances knee proprioception. DESIGN: Longitudinal analysis, pretest-posttest design. METHODS: Twelve young women with healthy knees were tested for knee proprioception without the use of Kinesiology tape and wearing Kinesiology tape at the knee. The joint position sense was measured at the start and after a 30-min uphill walking protocol on a treadmill. Outcome was the knee angle deviation. RESULTS: No significant difference of proprioceptive performance between the application with Kinesiology tape and without Kinesiology tape was found after uphill walking (p > 0.05). However, when the participants' results for knee angle deviation were graded into good (< 6.1°) and poor ( > 6.1°), Kinesiology tape significantly enhanced those with poor proprioceptive ability after uphill walking, compared to the untaped knee (p = 0.002). CONCLUSIONS: This study has shown that the application of Kinesiology tape did not improve knee proprioception in a group of healthy young women. However, it also has demonstrated that Kinesiology tape provided significant proprioceptive enhancement at the knee joint after uphill walking in healthy women with poor proprioceptive ability. This may support its use in sports medicine for preventing knee injuries.

Microclimate in ski boots--temperature, relative humidity, and water absorption.

Ski boot quality is determined by mechanical properties and comfort. Comfort is strongly affected by cold feet. The purpose of this study was to determine the microclimate in ski boots. Climate chamber tests with five male subjects and field tests with two male subjects were conducted. Temperature and relative humidity were measured using four sensors placed on the foot and one on the liner. Absorbed water in liners and socks was measured with a precision balance. The subjects gave subjective ratings for comfort. The toe sensor temperature dropped below 20 °C at an ambient temperature of 0 °C, -10 °C, and -20 °C. Relative humidity values at the foot were as high as 78% in the climate chamber and 93% in the field. Water absorption in socks and liners ranged from 4 to 10 g in the climate chamber and 19 to 45.5 g in the field. The results reveal the importance of keeping the feet and in particular the toes warm during skiing. One possible improvement may be to construct the liner so that sweat and melted snow are kept as far away as possible from the foot. Liner material with high water absorption capacity and hydrophobic socks were suggested to prevent wet feet.

An approximate simulation model for initial luge track design.

Competitive and recreational sport on artificial ice tracks has grown in popularity. For track design one needs knowledge of the expected speed and acceleration of the luge on the ice track. The purpose of this study was to develop an approximate simulation model for luge in order to support the initial design of new ice tracks. Forces considered were weight, drag, friction, and surface reaction force. The trajectory of the luge on the ice track was estimated using a quasi-static force balance and a 1d equation of motion was solved along that trajectory. The drag area and the coefficient of friction for two runs were determined by parameter identification using split times of five sections of the Whistler Olympic ice track. The values obtained agreed with experimental data from ice friction and wind tunnel measurements. To validate the ability of the model to predict speed and accelerations normal to the track surface, a luge was equipped with an accelerometer to record the normal acceleration during the entire run. Simulated and measured normal accelerations agreed well. In a parameter study the vertical drop and the individual turn radii turned out to be the main variables that determine speed and acceleration. Thus the safety of a new ice track is mainly ensured in the planning phase, in which the use of a simulation model similar to this is essential.