Activity Of GM Research Articles

Photosynthetic plasticity aggravates the susceptibility of magnesium-deficient leaf to high light in rapeseed plants: the importance of Rubisco and mesophyll conductance.

Plants grown under low magnesium (Mg) soils are highly susceptible to encountering light intensities that exceed the capacity of photosynthesis (A), leading to a depression of photosynthetic efficiency and eventually to photooxidation (i.e., leaf chlorosis). Yet, it remains unclear which processes play a key role in limiting the photosynthetic energy utilization of Mg-deficient leaves, and whether the plasticity of A in acclimation to irradiance could have cross-talk with Mg, hence accelerating or mitigating the photodamage. We investigated the light acclimation responses of rapeseed (Brassica napus) grown under low- and adequate-Mg conditions. Magnesium deficiency considerably decreased rapeseed growth and leaf A, to a greater extent under high than under low light, which is associated with higher level of superoxide anion radical and more severe leaf chlorosis. This difference was mainly attributable to a greater depression in dark reaction under high light, with a higher Rubisco fallover and a more limited mesophyll conductance to CO2 (gm ). Plants grown under high irradiance enhanced the content and activity of Rubisco and gm to optimally utilize more light energy absorbed. However, Mg deficiency could not fulfill the need to activate the higher level of Rubisco and Rubisco activase in leaves of high-light-grown plants, leading to lower Rubisco activation and carboxylation rate. Additionally, Mg-deficient leaves under high light invested more carbon per leaf area to construct a compact leaf structure with smaller intercellular airspaces, lower surface area of chloroplast exposed to intercellular airspaces, and CO2 diffusion conductance through cytosol. These caused a more severe decrease in within-leaf CO2 diffusion rate and substrate availability. Taken together, plant plasticity helps to improve photosynthetic energy utilization under high light but aggravates the photooxidative damage once the Mg nutrition becomes insufficient.

A Novel Wall Touch-Single Limb Stance Exercise for Dynamic Activation o f Gluteus Maximus - A Cross Sectional Study

ObjectiveGluteus maximus (GM) dysfunction is associated with spinal/lower extremity musculoskeletal conditions. Studies on weightbearing GM exercises that can be used earlier in rehabilitation is limited. Utilizing GM isometric contraction and load transmission to thoracolumbar fascia during trunk straightening under unilateral stance, we for the first time describe Wall Touch Single Limb Stance (WT-SLS) exercise. Specific exercise prescription may be rationalised using knowledge of how upper and lower fibres of GM (UGM, LGM) respond during novel WT-SLS. MethodologySurface EMG signals from UGM and LGM were compared among WT-SLS, Step up (SU) and Unilateral wall squat (UWS) in healthy subjects (N = 24). Raw data was normalized and expressed as percentage of maximum voluntary isometric contraction (%MVIC). Relative easiness in performing the exercises was scored using Borg's CR10 scale. Statistical significance was defined as p < 0.05. ResultsWT-SLS had the highest %MVIC for both UGM and LGM (p < 0.0001), suggesting maximum activation of GM in healthy adults by our novel exercise. WT-SLS generated more motor unit action potentials, and had significantly greater activity for UGM than LGM (p = 0.0429). Remaining exercises had no differential activation of UGM and LGM. WT-SLS was perceived as only ‘slight’ exertion. ConclusionsWT-SLS depicted the greatest muscle activation, suggesting possible better clinical and functional outcomes considering GM activation and strengthening. UGM was preferentially activated during WT-SLS, but not during SU and UWS. Therefore, targeting GM with our novel exercise may improve gluteal weakness and dysfunction in lumbar radiculopathy, knee ligament injuries; as preventive measure for injury; or for postural correction.

External rotation of the foot position during plantarflexion increases non-uniform motions of the Achilles tendon

The medial (GM) and lateral gastrocnemius (GL) muscles enroll to different subparts of the Achilles tendon to form their respective subtendons. The relative gastrocnemii activations during submaximal plantarflexion contraction depend on the position of the foot in the horizontal plane: with toes-in, GL activation increases and GM activation decreases, compared to toes-out. The aim of the current study was to investigate whether horizontal foot position during submaximal isometric plantarflexion contraction differently affects the subtendons within the Achilles tendon in terms of their (i) length at rest, and (ii) elongations and distal motions. Twenty healthy subjects (12 females/8 males) participated in the study. Three-dimensional ultrasound images were taken to capture subtendon lengths at rest and during isometric contraction. Ultrasound images were recorded at the distal end of Achilles tendon (sagittal plane) during ramped contractions and analyzed using a speckle tracking algorithm. All tasks were conducted twice, ones with toes-in and ones with toes-out. At rest, subtendons were shorter with toes-out compared to toes-in. During contraction, the GM subtendon lengthened more in toes-out, compared to the GL, and vice versa (all p <.01). The relative motions within the Achilles tendon (middle minus top layers displacements) were smaller in toes-in compared to toes-out (p =.05) for higher contraction intensity. Our results demonstrated that the horizontal foot position during plantarflexion contraction impacts Achilles tendon motions. Such findings may be relevant in a clinical context, for example in pathologies affecting Achilles tendon motions such as Achilles tendinopathy.

Myoelectric activity of the gastrocnemius during plantar flexion in a standing versus seated position and with a neutral or dorsiflexed ankle: A pilot study

ObjectiveThe purpose of this study was to investigate the surface electromyographic (EMG) activity of the medial (GM) and lateral (GL) heads of the gastrocnemius muscle during plantar flexion performed in standing or seated positions, and with a neutral or dorsiflexed ankle. IntroductionThe tríceps surae (gastrocnemius and soleus) is an essential muscle group that promotes propulsion during walking, running and tasks of daily living. MethodsTen male volunteers (24.5 ± 3.6 years, weight: 75.8 ± 10 kg; height: 1.74 ± 0.07 m) performed ten repetitions of plantar flexion under four different conditions: a) standing position (SP); b) standing position with passive stretch of the gastrocnemius muscle (SPS); c) seated with the knee flexed (KF); d) seated with the knee flexed and a passive stretch of the gastrocnemius (KFS). ResultsThe muscle activity expressed as the root mean square (RMS) was significantly higher for the GL in the SPS versus the SP condition, while there was no difference for the GM between conditions. However, for the KF condition, GM activity was significantly higher versus the KFS condition, which was not verified for the GL. ConclusionsTherefore, the standing position with passive stretching of the triceps surae may be more efficient in increasing the myoelectric activity of the GL. However, the sitting position without passive stretching promoted greater GM muscle recruitment. The length/tension relationship of gastrocnemius could be used as a prescription variable during rehabilitation or conditioning programs.

Antiepileptic geissoschizine methyl ether is an inhibitor of multiple neuronal channels.

Geissoschizine methyl ether (GM) is an indole alkaloid isolated from Uncaria rhynchophyll (UR) that has been used for the treatment of epilepsy in traditional Chinese medicine. An early study in a glutamate-induced mouse seizure model demonstrated that GM was one of the active ingredients of UR. In this study, electrophysiological technique was used to explore the mechanism underlying the antiepileptic activity of GM. We first showed that GM (1−30 μmol/L) dose-dependently suppressed the spontaneous firing and prolonged the action potential duration in cultured mouse and rat hippocampal neurons. Given the pivotal roles of ion channels in regulating neuronal excitability, we then examined the effects of GM on both voltage-gated and ligand-gated channels in rat hippocampal neurons. We found that GM is an inhibitor of multiple neuronal channels: GM potently inhibited the voltage-gated sodium (NaV), calcium (CaV), and delayed rectifier potassium (IK) currents, and the ligand-gated nicotinic acetylcholine (nACh) currents with IC50 values in the range of 1.3−13.3 μmol/L. In contrast, GM had little effect on the voltage-gated transient outward potassium currents (IA) and four types of ligand-gated channels (γ-amino butyric acid (GABA), N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainite (AMPA/KA receptors)). The in vivo antiepileptic activity of GM was validated in two electricity-induced seizure models. In the maximal electroshock (MES)-induced mouse seizure model, oral administration of GM (50−100 mg/kg) dose-dependently suppressed generalized tonic-clonic seizures. In 6-Hz-induced mouse seizure model, oral administration of GM (100 mg/kg) reduced treatment-resistant seizures. Thus, we conclude that GM is a promising antiepileptic candidate that inhibits multiple neuronal channels.

Which of the five classical ballet positions is the most demanding for the dancer’s body? An electromyography-based study to determine muscular activity

The study aimed to determine which of the five classical ballet positions is the most demanding regarding muscular activity, values of external rotation in the hip joints, angular values of foot progression as well as the inclination (tilt) of the pelvis in the sagittal plane. In this cross-sectional study, 14 female pre-professional ballet dancers (aged 11-16) participated. Participants were tasked with the sequential adoption of five classical ballet positions (CP1-CP5). The electromyographic activity of the muscles of the trunk and the lower limb was recorded with surface electrodes. Kinematic data including hip and knee external rotation, foot progression angle and pelvic tilt were collected using a motion capture system. Symmetric positions CP1 and CP2 were not as demanding as asymmetric CP3-CP5. Higher values of hip and foot external rotation without greater muscular effort in CP2 than CP1 was noticed. Considering asymmetric positions, CP3 did not trigger a greater activity of hip or foot muscular groups than CP4 and CP5. CP4 was characterised by the greatest pelvic anterior tilt and the lowest activity of GM in the forward lower limb. In CP5, forward lower limb entailed a higher activity of muscles supporting the foot than in the remaining positions. In terms of biomechanics, the most demanding classical ballet position in pre-professional dancers is CP4, followed by CP5, CP3, CP1 and CP2. This finding can be applied in educational methodology of dancers, figure skaters, synchronized swimmers, acrobatic gymnasts, rhythmic gymnasts or cheerleaders.

Neuromechanical coupling within the human triceps surae and its consequence on individual force-sharing strategies.

Little is known about the factors that influence the coordination of synergist muscles that act across the same joint, even during single-joint isometric tasks. The overall aim of this study was to determine the nature of the relationship between the distribution of activation and the distribution of force-generating capacity among the three heads of the triceps surae [soleus (SOL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL)]. Twenty volunteers performed isometric plantarflexions, during which the activation of GM, GL and SOL was estimated using electromyography (EMG). Functional muscle physiological cross-sectional area (PCSA) was estimated using imaging techniques and was considered as an index of muscle force-generating capacity. The distribution of activation and PCSA among the three muscles varied greatly between participants. A significant positive correlation between the distribution of activation and the distribution of PCSA was observed when considering the two bi-articular muscles at intensities ≤50% of the maximal contraction (0.51<r<0.62). Specifically, the greater the PCSA of GM compared with GL, the stronger bias of activation to the GM. There was no significant correlation between monoarticular and biarticular muscles. A higher contribution of GM activation compared with GL activation was associated with lower triceps surae activation (-0.66<r<-0.42) and metabolic cost (-0.74<r<-0.52) for intensities ≥30% of the maximal contraction. Considered together, an imbalance of force between the three heads was observed, the magnitude of which varied greatly between participants. The origin and consequences of these individual force-sharing strategies remain to be determined.

Comparative study of the mechanism of action of the antimicrobial peptide gomesin and its linear analogue: The role of the β-hairpin structure

Gomesin (Gm) is an antimicrobial peptide first isolated from the hemolymph of a Brazilian spider. Its powerful antimicrobial activity is, however, accompanied by hemolysis. As an alternative to this issue, a linear analogue (named GmL) lacking the disulfide bonds was designed. Here, CD spectroscopy, a fluorescence-based leakage assay, isothermal titration calorimetry (ITC) and light scattering are used to study the interaction of both Gm and GmL with large unilamellar vesicles (LUVs) composed of POPC (palmitoyl oleoyl phosphatidylcholine) with 25 and 50mol% POPG (palmitoyl oleoyl phosphatidylglycerol). The activities of Gm and GmL in respect to their binding affinity/enthalpy, ability to permeabilize membranes and to induce vesicle aggregation are correlated with peptide secondary structure. Whereas Gm displays a quite stable β-hairpin motif irrespective of the environment, GmL assumes a random conformation in aqueous solution and in the presence of 25mol% POPG but adopts a β-like structure in the presence of 50mol% POPG. Gm exhibited high lytic activity against both surface charge densities. Instead, the activity of GmL was found to be negligible in the presence of 25mol% POPG LUVs, but comparable to that of the native peptide against 50mol% POPG as a consequence of peptide structuring. We conclude that the activity of Gm and its linear analogue is intimately related to the formation of a β-turn motif, in which the hydrophobic residues form a hydrophobic face able to insert into the membrane and disrupt it.

Herpes Simplex Virus 1 gN Partners with gM To Modulate the Viral Fusion Machinery

Herpes simplex virus 1 (HSV-1) capsids are assembled in the nucleus, where they incorporate the viral genome. They then transit through the two nuclear membranes and are wrapped by a host-derived envelope. In the process, several HSV-1 proteins are targeted to the nuclear membranes, but their roles in viral nuclear egress are unclear. Among them, glycoprotein M (gM), a known modulator of virus-induced membrane fusion, is distributed on both the inner and outer nuclear membranes at the early stages of the infection, when no other viral glycoproteins are yet present there. Later on, it is found on perinuclear virions and ultimately redirected to the trans-Golgi network (TGN), where it cycles with the cell surface. In contrast, transfected gM is found only at the TGN and cell surface, hinting at an interaction with other viral proteins. Interestingly, many herpesvirus gM analogs interact with their gN counterparts, which typically alters their intracellular localization. To better understand how HSV-1 gM localization is regulated, we evaluated its ability to bind gN and discovered it does so in both transfected and infected cells, an interaction strongly weakened by the deletion of the gM amino terminus. Functionally, while gN had no impact on gM localization, gM redirected gN from the endoplasmic reticulum (ER) to the TGN. Most interestingly, gN overexpression stimulated the formation of syncytia in the context of an infection by a nonsyncytial strain, indicating that gM and gN not only physically but also functionally interact and that gN modulates gM's activity on membrane fusion. HSV-1 gM is an important modulator of virally induced cell-cell fusion and viral entry, a process that is likely finely modulated in time and space. Until now, little was known of the proteins that regulate gM's activity. In parallel, gM is found in various intracellular locations at different moments, ranging from nuclear membranes, perinuclear virions, the TGN, cell surface, and mature extracellular virions. In transfected cells, however, it is found only on the TGN and cell surface, hinting that its localization is modulated by other viral proteins. The present study identifies HSV-1 gN as a binding partner for gM, in agreement with their analogs in other herpesviruses, but most excitingly shows that gN modulates gM's impact on HSV-1-induced membrane fusion. These findings open up new research avenues on the viral fusion machinery.

Voxel-based comparison of state-of-the-art reconstruction algorithms for 18F-FDG PET brain imaging using simulated and clinical data

The resolution of a PET scanner (2.5–4.5mm for brain imaging) is similar to the thickness of the cortex in the (human) brain (2.5mm on average), hampering accurate activity distribution reconstruction. Many techniques to compensate for the limited resolution during or post-reconstruction have been proposed in the past and have been shown to improve the quantitative accuracy. In this study, state-of-the-art reconstruction techniques are compared on a voxel-basis for quantification accuracy and group analysis using both simulated and measured data of healthy volunteers and patients with epilepsy. MethodsMaximum a posteriori (MAP) reconstructions using either a segmentation-based or a segmentation-less anatomical prior were compared to maximum likelihood expectation maximization (MLEM) reconstruction with resolution recovery. As anatomical information, a spatially aligned 3D T1-weighted magnetic resonance image was used. Firstly, the algorithms were compared using normal brain images to detect systematic bias with respect to the true activity distribution, as well as systematic differences between two methods. Secondly, it was verified whether the algorithms yielded similar results in a group comparison study. ResultsSignificant differences were observed between the reconstructed and the true activity, with the largest errors when using (post-smoothed) MLEM. Only 5–10% underestimation in cortical gray matter voxel activity was found for both MAP reconstructions. Higher errors were observed at GM edges. MAP with the segmentation-based prior also resulted in a significant bias in the subcortical regions due to segmentation inaccuracies, while MAP with the anatomical prior which does not need segmentation did not. Significant differences in reconstructed activity were also found between the algorithms at similar locations (mainly in gray matter edge voxels and in cerebrospinal fluid voxels) in the simulated as well as in the clinical data sets. Nevertheless, when comparing two groups, very similar regions of significant hypometabolism were detected by all algorithms. ConclusionIncluding anatomical a priori information during reconstruction in combination with resolution modeling yielded accurate gray matter activity estimates, and a significant improvement in quantification accuracy was found when compared to post-smoothed MLEM reconstruction with resolution modeling. AsymBowsher provided the most accurate subcortical GM activity estimates. It is also reassuring that the differences found between the algorithms did not hamper the detection of hypometabolic regions in the gray matter when performing a voxel-based group comparison. Nevertheless, the size of the detected clusters differed. More elaborated and application-specific studies are required to decide which algorithm is best for a group analysis.

ACTIVATION PATTERN OF M.GLUTEUS MEDIUS IN PRE-PUBESCENT FEMALE AND MALE ATHLETES DURING DROP-JUMP AND CUTTING MANEUVERS

BackgroundOne of many risk factors for ACL injury may involve neuromuscular activation patterns of muscles in the lower extremities. These have been studied for some muscles in pre- and post-pubescent...

Lower Extremity Biomechanics During a Regular and Counterbalanced Squat

If the efficiency of human movement patterns could be improved using exercise, this could lead to more effective musculoskeletal disease-injury prevention and rehabilitation programs. It has been suggested that an efficient squat movement pattern emphasizes the use of the large hip extensors instead of the smaller knee extensors. The purpose of this study was to determine whether a counterbalanced squat (CBS) could produce a more hip-dominant and less knee-dominant squat movement pattern as compared with a regular squat (RS). There were 31 recreationally trained college-aged participants (15 male, 16 female) who performed 10 squats (5 CBS and 5 RS), while segment kinematics, ground reaction forces, and muscle (gluteus maximus [GM], quadriceps, hamstrings) electromyographic (EMG) activations were recorded. Peak sagittal plane net joint moments and joint ranges of motion at the hip, knee, and ankle joints along with peak and integrated EMG activation levels for all 3 muscles were compared using analysis of variance (squat type × sex). The results revealed that the CBS increased the hip joint moment and GM activation, while it decreased the knee joint moment and quadriceps activation as compared with the RS. Therefore, the CBS produces a more hip-dominant and less knee-dominant squat movement pattern and could be used in exercise programs aimed at producing more hip-dominant movement patterns.

Lower Extremity Muscle Activation and Knee Flexion During a Jump-Landing Task

Decreased sagittal-plane motion at the knee during dynamic tasks has been reported to increase impact forces during landing, potentially leading to knee injuries such as anterior cruciate ligament rupture. To describe the relationship between lower extremity muscle activity and knee-flexion angle during a jump-landing task. Cross-sectional study. Research laboratory. Thirty recreationally active volunteers (15 men, 15 women: age = 21.63 ± 2.01 years, height = 173.95 ± 11.88 cm, mass = 72.57 ± 14.25 kg). Knee-flexion angle and lower extremity muscle activity were collected during 10 trials of a jump-landing task. Simple correlation analyses were performed to determine the relationship between each knee-flexion variable (initial contact, peak, and displacement) and electromyographic amplitude of the gluteus maximus (GMAX), quadriceps (VMO and VL), hamstrings, gastrocnemius, and quadriceps : hamstring (Q : H) ratio. Separate forward stepwise multiple regressions were conducted to determine which combination of muscle activity variables predicted each knee-flexion variable. During preactivation, VMO and GMAX activity and the Q : H ratio were negatively correlated with knee-flexion angle at initial contact (VMO: r = 0.382, P = .045; GMAX: r = 0.385, P = .043; Q : H ratio: r = 0.442, P = .018). The VMO, VL, and GMAX deceleration values were negatively correlated with peak knee-flexion angle (VMO: r = 0.687, P = .001; VL: r = 0.467, P = .011; GMAX: r = 0.386, P = .043). The VMO and VL deceleration values were negatively correlated with knee-flexion displacement (VMO: r = 0.631, P = .001; VL: r = 0.453, P = .014). The Q : H ratio and GM activity predicted 34.7% of the variance in knee-flexion angle at initial contact (P = .006). The VMO activity predicted 47.1% of the variance in peak knee-flexion angle (P = .001). The VMO and VL activity predicted 49.5% of the variance in knee-flexion displacement (P = .001). Greater quadriceps and GMAX activation and less hamstrings and gastrocnemius activation were correlated with smaller knee-flexion angles. This landing strategy may predispose an individual to increased impact forces due to the negative influence on knee-flexion position.

Whole Body Vibration vs. Gluteal Muscle Activation: What are the Acute Effects on Explosive Power?

Peak power production is an important component of many sports including Australian Football which is a contact sport involving an array of explosive movements including kicking, tackling, sprinting and jumping. Players in the Australian Football League (AFL) are full-time professional athletes. Exercises targeting the activation of the gluteal muscle group (GM) are commonly used in the rehabilitation of injuries involving the hips and pelvis, however they may also be used in healthy athlete populations as a warm-up protocol before exercise or sport. The effects of such a protocol on peak power production are currently unknown. Studies into the influence of whole body vibration (WBV) on performance and peak power production have produced inconsistent results and have been the focus of conjecture in recent published literature. PURPOSE: To investigate the effects of WBV, an exercise protocol targeting GM activation and a control protocol on peak power production during countermovement vertical jumps (CMJ). METHODS: 22 AFL players performed three different pre-performance protocols on separate days in a randomized order. Players were then tested within 5 minutes for peak power production during CMJ. These protocols included WBV, GM activation exercise and a control protocol. The WBV protocol involved standing on the WBV platform for 45 seconds at 30 Hz. The GM activation protocol consisted of 7 exercises taking about 7 min to perform. The control protocol involved CMJ testing without any prior warm-up. CMJ peak power testing involved the player performing 5 jumps on a smith-machine while a linear transducer was used to measure peak power. Testing was conducted after football training sessions on non-consecutive days over a 10 day period. Players who were unable to perform all three pre-performance protocols were excluded from the study. An ANOVA with repeated measures was performed to determine any differences in peak power between the protocols. RESULTS: The GM activation protocol produced significantly higher peak power during CMJ testing than both the control (p = 0.03) and WBV protocols (p < 0.01) (Figure 1). There were no other significant differences between protocols, although the WBV protocol showed a trend for reduced peak power scores when compared to control (p = 0.08). Conclusion: GM activation exercises used as a pre-performance protocol generated greater peak power scores during CMJ testing than both a control and a WBV protocol in professional AFL players. The WBV protocol showed a trend for lower peak power scores than those recorded using the control protocol. Practical Application: Exercise targeted at activating the GM group should be considered as a pre-performance protocol in sports where peak power production is a key component. In contrast, the use of WBV as a pre-performance modality should be reconsidered as its use may have a deleterious effect on peak power production.

Preventing ischial pressure ulcers: II. Biomechanics

Background: Pressure ulcers PUs are common and debilitating wounds that arise when immobilized patients cannot shift their weight. Neuromuscular Electrical Stimulation NMES has been investigated for Pressure Ulcer Prevention PUP for over 20 years. Historically gluteus maximus GM has been considered an important actuator in attempting to redistribute seated pressures through NMES. Methods: Analysis of skeletal biomechanics to quantify the value of GM relative to hamstring hip extensors HS, using muscle moment models based on torques and rigid body mass estimates from the literature. Surface stimulation experiments n = 10 + 1, non-paralyzed to validate model and identify promising stimulation sites and treatment strategies that would approximate healthy biomechanics. Results: Literature values and Rigid Body Analysis estimate: ~63 Nm extensor torque requirement calculated for complete ipsilateral unloading of the buttocks. Muscle Moment Analysis: GM can provide 70% of total hip extensor torque when walking vs. 18% when seated. HS can provide 100 Nm hip extension torque when seated, exceeding 63 Nm requirement. Surface Stimulation: ipsilateral seated interface pressure mean -26% during HS stimulation vs. +16% with GM; peak pressure area -94% HS vs. +213% GM. Conclusions: GM activation reduces disuse atrophy and improves circulation, but appears neither required, nor desired, for unloading when seated. HS stimulation alone should be capable of sufficient unloading. This new proposed approach is explored clinically in companion paper III.

Abnormal activation of knee and ankle flexors–extensors is related to transmission changes in ankylosing spondylitis gait pattern?

Discussion: Our preliminary data confirm the presence of delays in GM activation as in [3] but difference were found in the pattern of TA and RF. Some subjects showed the presence of co-contractions in GM and TA, with possible consequent increment in gait energy expenditure. Further evidence of these features will be obtain extending this study to a larger sample of subjects, and by including kinetic and kinematic analysis.

Comparing Three Types of Core Stabilization Exercises Using Surface Electromyography

Core stabilization has been used to strengthen trunk muscles, prevent, and treat spine injuries. There are many types of core exercises, however few studies have assessed muscle activity. PURPOSE: The purpose of this study was to compare muscle activity using surface electromyography (sEMG) of eight muscles during pilates(P), ball(B), and traditional (T) exercises during supine and prone positions. METHODS: Twenty six subjects (age=40.3 + 6.7 yrs; BMI=25.7+ 6.7 kg.m2). sEMG electrodes were placed over rectus femoris RF, rectus abdominis RA, external oblique EO, internal oblique IO, biceps femoris BF, gluteus medius GM, paraspinals PS, and latissimus dorsi LD. Subjects were randomly assigned an order for P, T, and B and asked to perform five repetitions of supine oblique crunch and prone opposite upper and lower extremity for each program. Raw EMG signals were full wave rectified, smoothed and normalized to each respective maximal isometric voluntary contraction of the 8 muscles and expressed as %MVC. Within repeated measure ANOVAs were performed for each muscle to examine within subject difference across 3 conditions, (p<0.05). RESULTS: Peak sEMG for supine for RF was higher for B (47.7+ 27.70%) and P (53.6+ 29.96%) than T (16.3+ 20.90%). Area sEMG activity during supine for GM was higher for B (58.0+ 32.39%) and P (48.5+ 20.97%) than T(35.2+ 18.85%). Peak sEMG for prone IO was higher for B (58.4+ 29.79%) versus P (42.1+ 35.08%) and T(42.7+ 28.39%), BF was higher for P (73.8+ 48.50%) and T (52.7+ 26.26%) compared to B(39.35+ 21.79%). GM was higher for P (93.6+ 36.57%) versus B (70.1+ 26.88%) and T(67.5+ 29.32%), PS was higher for P (89.4+ 35.99%) compared to B (66.3+ 20.45%) and T(64.1+ 21.40%). Area sEMG for prone for EO was higher during B (42.6+ 26.79%) than P (29.1+ 19.33%) and T(27.3+ 15.44%), IO was higher for B (34.5+ 21.56%) than P (19.8+ 18.85%) and T(22.2+ 17.58%), BF was higher for T(42.0+ 28.24%) and P (50.4+ 34.37%) compared B(25.6+ 18.37%), and PS was higher during P (68.8+ 26.53%) than B (45.7+ 24.21%) and T(47.5+ 20.02%). CONCLUSIONS: It appears that ball exercises elicit higher RF and GM activity during supine position compared to pilates and traditional floor exercises. During the prone exercises, IO and EO activity was found to be higher during ball exercises while BF, PS, and GM were more active during pilates exercises.

Impaired functional activity of alveolar macrophages from GM-CSF-deficient mice.

We hypothesized that pulmonary granulocyte-macrophage colony-stimulating factor (GM-CSF) is critically involved in determining the functional capabilities of alveolar macrophages (AM) for host defense. To test this hypothesis, cells were collected by lung lavage from GM-CSF mutant mice [GM(-/-)] and C57BL/6 wild-type mice. GM(-/-) mice yielded almost 4-fold more AM than wild-type mice. The percentage of cells positive for the beta(2)-integrins CD11a and CD11c was reduced significantly in GM(-/-) AM compared with wild-type cells, whereas expression of CD11b was similar in the two groups. The phagocytic activity of GM(-/-) AM for FITC-labeled microspheres was impaired significantly compared with that of wild-type AM both in vitro and in vivo (after intratracheal inoculation with FITC-labeled beads). Stimulated secretion of tumor necrosis factor-alpha (TNF-alpha) and leukotrienes by AM from the GM(-/-) mice was greatly reduced compared with wild-type AM, whereas secretion of monocyte chemoattractant protein-1 was increased. Transgenic expression of GM-CSF exclusively in the lungs of GM(-/-) mice resulted in AM with normal or supranormal expression of CD11a and CD11c, phagocytic activity, and TNF-alpha secretion. Thus, in the absence of GM-CSF, AM functional capabilities for host defense were significantly impaired but were restored by lung-specific expression of GM-CSF.

Pharmacokinetics-pharmacodynamics of a sordarin derivative (GM 237354) in a murine model of lethal candidiasis.

Sordarins are a new class of antifungal agents which selectively inhibit fungal protein synthesis (FPS) by impairing the function of elongation factor 2. The present study investigates possible correlations between sordarin pharmacokinetic (PK) properties and therapeutic efficacy, based on a murine model of invasive systemic candidiasis, and provides a rationale for dose selection in the first study of efficacy in humans. A significant correlation between PK parameters and the in vivo activity of GM 237354, taken as a representative FPS inhibitor, was demonstrated in a murine model of lethal systemic candidiasis. Area under the concentration-time curve (AUC) and maximum concentration of drug in serum (C(max)) over 24 h were determined after a single GM 237354 subcutaneous (s.c.) dose (50 mg/kg of body weight) in healthy animals (no significant PK changes with infection were observed for other sordarin derivatives). These results have been used to simulate PK profiles obtained after several doses and/or schedules in animal therapy. A PK-pharmacodynamic (PD) parameter such as the time that serum drug concentrations remain above the MIC (t > MIC) was also determined. Treatment efficacies were evaluated in terms of the area under the survival time curve (AUSTC), using Kaplan-Meier survival analysis and in terms of kidney fungal burden (log CFU/gram) after s.c. doses of 2.5, 5, 10, 20, and 40 mg/kg every 4, 8, or 12 h (corresponding to total daily doses of 5 to 240 mg/kg). The results show all treatments to significantly prolong survival versus that of infected and nontreated controls (P < 0.05). Relationships between simulated PK and PK-PD parameters and efficacy were explored. A good correlation independent of the dosing interval was observed with AUC (but not C(max) or t > MIC) and both AUSTC and kidney burden. Following repeated dosing every 8 h, AUC(50) (AUC at which 50% of the maximum therapeutic efficacy is obtained) was estimated as 21.7 and 37.1 microg. h/ml (total concentrations) for AUSTC and kidney burden using a sigmoid E(max) and an inhibitory sigmoid E(max) PK-PD model, respectively. For an efficacy target of 90% survival, AUC was predicted as 67 microg. h/ml. We conclude that the PK-PD approach is useful for evaluating relationships between PK parameters and efficacy in antifungal research. Moreover, the results obtained with this approach could be successfully applied to clinical studies.

Influence of the steric barrier activity of amphipathic poly(ethyleneglycol) and ganglioside GM 1 on the circulation time of liposomes and on the target binding of immunoliposomes in vivo

A series of dioleoyl N-(monomethoxy polyethyleneglycol succinyl)phosphatidylethanolamine (PEG-PE) of different polymer chain length was used in this study. Both the activity of PEG-PE in prolonging the circulation time of liposomes and the relative steric barrier activity of amphipathic polymer, measured by a liposome agglutination assay, were found to be directly proportional to the chain length of PEG-PE (PEG5000-PE > PEG2000-PE > PEG750-PE). However, PEG5000-PE caused a reduced target binding of immunoliposomes in mice due to its overly strong steric barrier activity. The best PEG-PE species supporting the target binding of immunoliposomes was PEG2000-PE, the activity of which was compatible to that of ganglioside GM 1. However, GM 1 only showed a weak steric barrier activity, suggesting a different mechanism for this glycolipid.