Ankle kinematics,center of pressure progression,and lower extremity muscle activity during a side-cutting task in participants with and without chronic ankle instability

This study assessed ankle kinematics, surface electromyography, and center-of-pressure (COP) progression relative to the medial border of the foot during a side-cutting task in individuals with and without chronic ankle instability (CAI). Thirty participants (CAI = 15; Controls = 15) performed a side-cutting task on a force platform while 3-dimentional ankle kinematics, COP position, and surface electromyography from the tibialis anterior, medial gastrocnemius, fibularis longus, fibularis brevis, vastus medialis, and semitendinosus were recorded on the testing leg. Ankle kinematics, root-mean-square muscle activity and COP position relative to the medial boarder of the foot were compared between CAI and healthy controls (p < 0.05). Significantly greater ankle internal rotation from 35–54% of the stance phase (p = 0.032) was found for the CAI group compared to controls. Furthermore, significantly greater tibialis anterior muscle activity from 86–94% of the stance phase (p = 0.022) and a more medial COP position from 81–100% (p < 0.05) and of the stance phase was also observed in the CAI group. Less lateral COP progression and increased tibialis anterior activation in the CAI group could reflect a protective movement strategy during anticipated side-cutting to avoid recurrent injury. However, greater ankle internal rotation during mid-stance highlights a potential ‘giving way’ mechanism in individuals with CAI.     

Foot center of pressure manipulation and gait therapy influence lower limb muscle activation in patients with osteoarthritis of the knee

Background

Foot center of pressure (COP) manipulation has been associated with improved gait patterns. The purpose of this study was to determine lower limb muscle activation changes in knee osteoarthritis patients, both immediately after COP manipulation and when COP manipulation was combined with continuous gait therapy (AposTherapy).

Methods

Fourteen females with medial compartment knee osteoarthritis underwent EMG analyzes of key muscles of the leg. In the initial stage, trials were carried out at four COP positions. Following this, gait therapy was initiated for 3 months. The barefoot EMG was compared before and after therapy.

Results

The average EMG varied significantly with COP in at least one phase of stance in all examined muscles of the less symptomatic leg and in three muscles of the more symptomatic leg. After training, a significant increase in average EMG was observed in most muscles. Most muscles of the less symptomatic leg showed significantly increased peak EMG. Activity duration was shorter for all muscles of the less symptomatic leg (significant in the lateral gastrocnemius) and three muscles of the more symptomatic leg (significant in the biceps femoris). These results were associated with reduced pain, increased function and improved spatiotemporal parameters.

Conclusions

COP manipulation influences the muscle activation patterns of the leg in patients with knee osteoarthritis. When combined with a therapy program, muscle activity increases and activity duration decreases.     

Alterations in cholesterol absorption/synthesis markers characterize Framingham Offspring Study participants with CHD

Data is limited on measures influencing cholesterol homeostasis in subjects at high risk of developing cardiovascular disease (CVD) relative to established risk factors. To address this, we quantified circulating indicators of cholesterol homeostasis (plasma phytosterols and cholesterol precursor concentrations as surrogate measures of cholesterol absorption and synthesis, respectively) in Framingham Offspring Study Cycle-6 participants diagnosed with established CVD and/or ≥50% carotid stenosis not taking lipid lowering medication (cases, N = 155) and matched controls (N = 414). Cases and controls had similar plasma LDL-cholesterol; HDL-cholesterol was significantly lower in males, while triglyceride concentrations were significantly higher in female cases relative to their respective controls. Cholesterol absorption markers were significantly higher (229 ± 7 vs. 196 ± 4, 169 ± 6 vs. 149 ± 3 and 144 ± 5 vs. 135 ± 3 for campesterol, sitosterol, and cholestanol, respectively), whereas cholesterol synthesis markers were significantly lower (116 ± 4 vs. 138 ± 3, 73 ± 3 vs. 75 ± 2 for lathosterol and desmosterol, respectively) in cases compared with controls, irrespective of sex. After controlling for standard risk factors, campesterol (2.47 [1.71-3.56]; P < 0.0001), sitosterol (1.86 [1.38-2.50]; P < 0.0001), cholestanol (1.57 [1.09-2.27]; P = 0.02), desmosterol (0.59 [0.42-0.84]; P = 0.003), and lathosterol (0.58 [0.43-0.77]; P = 0.0002) were significantly associated with CVD (odds ratio [95% confidence interval]). These data suggest that impaired cholesterol homeostasis, reflected by lower synthesis and higher absorption marker concentrations, are highly significant independent predictors of prevalent CVD in this study population.     

Alterations of nPKC distribution,but normal Akt/PKB activation in denervated rat soleus muscle

Denervation has been shown to impair the ability of insulin to stimulate glycogen synthesis and, to a lesser extent, glucose transport in rat skeletal muscle. Insulin binding to its receptor, activation of the receptor tyrosine kinase and phosphatidylinositol 3'-kinase do not appear to be involved. On the other hand, it has been shown that denervation causes an increase in the total diacylglycerol (DAG) content and membrane-associated protein kinase C (PKC) activity. In this study, we further characterize these changes in PKC and assess other possible signaling abnormalities that might be related to the decrease of glycogen synthesis. The results reveal that PKC-epsilon and -theta;, but not -alpha or -zeta, are increased in the membrane fraction 24 h after denervation and that the timing of these changes parallels the impaired ability of insulin to stimulate glycogen synthesis. At 24 h, these changes were associated with a 65% decrease in glycogen synthase (GS) activity ratio and decreased electrophoretic mobility, indicative of phosphorylation in GS in muscles incubated in the absence of insulin. Incubation of the denervated soleus with insulin for 30 min minimally increased glucose incorporation into glycogen; however, it increased GS activity threefold, to a value still less than that of control muscle, and it eliminated the gel shift. In addition, insulin increased the apparent abundance of GS kinase (GSK)-3 and protein phosphatase (PP)1 alpha in the supernatant fraction of muscle homogenate to control values, and it caused the same increases in GSK-3 and Akt/protein kinase B (PKB) phosphorylation and Akt/PKB activity that it did in nondenervated muscle. No alterations in hexokinase I or II activity were observed after denervation; however, in agreement with a previous report, glucose 6-phosphate levels were diminished in 24-h-denervated soleus, and they did not increase after insulin stimulation. These results indicate that alterations in the distribution of PKC-epsilon and -theta; accompany the impairment of glycogen synthesis in the 24-h-denervated soleus. They also indicate that the basal rate of glycogen synthesis and its stimulation by insulin in these muscles are diminished despite a normal activation of Akt/PKB and phosphorylation of GSK-3. The significance of the observed alterations to GSK-3 and PP1 alpha distribution remain to be determined.     

Effect of six weeks of dura disc and mini-trampoline balance training on postural sway in athletes with functional ankle instability

Lateral ankle sprain (LAS) is one of the most common injuries incurred during sporting activities, and effective rehabilitation programs for this condition are challenging to develop. The purpose of this research was to compare the effect of 6 weeks of balance training on either a mini-trampoline or a dura disc on postural sway and to determine if the mini-trampoline or the dura disc is more effective in improving postural sway. Twenty subjects (11 men, 9 women) with a mean age of 25.4 +/- 4.2 years were randomly allocated into a control group, a dura disc training (DT) group, or a mini-trampoline (MT) group. Subjects completed 6 weeks of balance training. Postural sway was measured by subjects performing a single limb stance on a force plate. The disbursement of the center of pressure was obtained from the force plate in the medial-lateral and the anterior-posterior sway path and was subsequently used for pretest and posttest analysis. After the 6-week training intervention, there was a significant (p < 0.05) difference in postural sway between pre- and posttesting for both the MT (pretest = 56.8 +/- 20.5 mm, posttest = 33.3 +/- 8.5 mm) and DT (pretest = 41.3 +/- 2.6 mm, posttest = 27.2 +/- 4.8 mm) groups. There was no significant (p > 0.05) difference detected for improvements between the MT and DT groups. These results indicate that not only is the mini-trampoline an effective tool for improving balance after LAS, but it is equally as effective as the dura disc.     

Influence of low muscle activation levels on the ankle torque and muscle shear modulus during plantar flexor stretching

During stretching studies, surface electromyography (sEMG) is used to ensure the passive state of the muscle, for the characterization of passive muscle mechanical properties. Different thresholds (1%, 2% or 5% of maximal) are indifferently used to set “passive state”. This study aimed to investigate the effects of a slight activity on the joint and muscle mechanical properties during stretching.The joint torque and muscle shear modulus of the triceps surae muscles were measured in fifteen healthy volunteers during ankle dorsiflexions: (i) in a “fully relaxed” state, (ii) during active conditions where participants were asked to produce an sEMG amplitude of 1%, 2% or 5% of their maximal sEMG amplitude of the triceps surae. The 1% condition was the only that did not result in significant differences in joint torque or shear modulus compared to the relaxed condition. In the 2% condition, increases in joint torque were found at 80% of the maximal angle in dorsiflexion, and in the shear modulus of gastrocnemius medialis and gastrocnemius lateralis at the maximal angle in dorsiflexion. During the 5% condition, joint torque and the shear modulus of gastrocnemius medialis were higher than during relaxed condition at angles larger than 40% of maximal angle in dorsiflexion. The results provide new insights on the thresholds that should be considered for the design of stretching studies. A threshold of 1% seems much more appropriate than a 2% or 5% threshold in healthy participants. Further studies are required to define similar thresholds for patients.     

The role of internal pressure and muscle activation during locust oviposition

The oviposition of female locusts is a complex behaviour that includes a dramatic extension of the abdomen. The role of internal pressure during oviposition was investigated by monitoring the intra-tracheal pressure and the activity of selected longitudinal muscles, while movements of the abdomen were visualised with a video imaging system. Locust oviposition consists of a sequence of four distinct phases: (i) probing the substrate and digging without elongation of the abdomen, (ii) longitudinal extension of the abdomen up to four times its normal length, (iii) laying packages of eggs while (iv) gradually withdrawing the abdomen. During extension, neurograms and myograms of selected longitudinal muscles revealed a decreased level of activity. When the abdomen retracted to its normal length, muscle activity re-appeared. In phases two and three, rising internal pressure prevented the abdomen from slipping back when the valves released their lateral grip from the substrate. Locking the genital segments in the hole by relative bending kept the abdomen in place when producing foam or laying eggs. Intra-abdominal pressure, therefore, is not the main cause of abdominal extension, but rather maintains extension when no mechanical locking in the hole prevents the abdomen from elastic retraction.     

The functional role of the binuclear metal center in D-aminoacylase: one-metal activation and second-metal attenuation

Our structural comparison of the TIM barrel metal-dependent hydrolase(-like) superfamily suggests a classification of their divergent active sites into four types: alphabeta-binuclear, alpha-mononuclear, beta-mononuclear, and metal-independent subsets. The d-aminoacylase from Alcaligenes faecalis DA1 belongs to the beta-mononuclear subset due to the fact that the catalytically essential Zn(2+) is tightly bound at the beta site with coordination by Cys(96), His(220), and His(250), even though it possesses a binuclear active site with a weak alpha binding site. Additional Zn(2+), Cd(2+), and Cu(2+), but not Ni(2+), Co(2+), Mg(2+), Mn(2+), and Ca(2+), can inhibit enzyme activity. Crystal structures of these metal derivatives show that Zn(2+) and Cd(2+) bind at the alpha(1) subsite ligated by His(67), His(69), and Asp(366), while Cu(2+) at the alpha(2) subsite is chelated by His(67), His(69) and Cys(96). Unexpectedly, the crystal structure of the inactive H220A mutant displays that the endogenous Zn(2+) shifts to the alpha(3) subsite coordinated by His(67), His(69), Cys(96), and Asp(366), revealing that elimination of the beta site changes the coordination geometry of the alpha ion with an enhanced affinity. Kinetic studies of the metal ligand mutants such as C96D indicate the uniqueness of the unusual bridging cysteine and its involvement in catalysis. Therefore, the two metal-binding sites in the d-aminoacylase are interactive with partially mutual exclusion, thus resulting in widely different affinities for the activation/attenuation mechanism, in which the enzyme is activated by the metal ion at the beta site, but inhibited by the subsequent binding of the second ion at the alpha site.     

Changes in intra-abdominal pressure, trunk muscle activation and force during isokinetic lifting and lowering

Intra-abdominal pressure (IAP), force and electromyographic (EMG) activity from the abdominal (intra-muscular) and trunk extensor (surface) muscles were measured in seven male subjects during maximal and sub-maximal sagittal lifting and lowering with straight arms and legs. An isokinetic dynamometer was used to provide five constant velocities (0.12–0.96 m·s^–1) of lifting (pulling against the resistance of the motor) and lowering (resisting the downward pull of the motor). For the maximal efforts, position-specific lowering force was greater than lifting force at each respective velocity. In contrast, corresponding IAPs during lowering were less than those during lifting. Highest mean force occurred during slow lowering (1547 N at 0.24 m·s^–1) while highest IAP occurred during the fastest lifts (17.8 kPa at 0.48–0.96 m·s^–1). Among the abdominal muscles, the highest level of activity and the best correlation to variations in IAP (r=0.970 over velocities) was demonstrated by the transversus abdominis muscle. At each velocity the EMG activity of the primary trunk and hip extensors was less during lowering (eccentric muscle action) than lifting (concentric muscle action) despite higher levels of force (r between –0.896 and –0.851). Sub-maximal efforts resulted in IAP increasing linearly with increasing lifting or lowering force (r=0.918 and 0.882, respectively). However, at any given force IAP was less during lowering than lifting. This difference was negated if force and IAP were expressed relative to their respective lifting and lowering maxima. It appears that the IAP increase primarily accomplished by the activation of the transversus abdominis muscle can have the dual function of stabilising the trunk and reducing compression forces in the lumbar spine via its extensor moment. The neural mechanisms involved in sensing and regulating both IAP and trunk extensor activity in relation to the type of muscle action, velocity and effort during the maximal and sub-maximal loading tasks are unknown.     

Altered postural modulation of Hoffmann reflex in the soleus and fibularis longus associated with chronic ankle instability

Our purpose was to assess Hoffmann (H) reflex modulations of the soleus and fibularis longus in three body positions (prone, bipedal and unipedal stances) in subjects with and without chronic ankle instability (CAI). Sixteen subjects with unilateral CAI and 15 healthy controls participated. Maximum H-reflexes and motor (M) waves were recorded bilaterally from the soleus and fibularis longus while subjects lied prone and then stood in quiet bipedal and unipedal stances. Maximum H-reflexes were normalized to maximum M waves to obtain H_max:M_max ratios for the three positions. H-reflex modulations, for each muscle, were quantified as the percent change scores in H_max:M_max ratios between each pair of positions: prone to bipedal, bipedal to unipedal, and prone to unipedal. There were significant group by limb interactions found for all three modulations (P < 0.05) for the soleus. In the CAI group, soleus modulations in involved limbs were significantly lower than in uninvolved limbs and both limbs in the controls. For the fibularis longus, similar results were found for the bipedal to unipedal and prone to unipedal modulations. Constrained ability of the sensorimotor system to down regulate H-reflex in more demanding postures may represent a potential mechanism of postural control deficits associated with CAI.     

Alterations in plasma membrane proteins associated with the proteolytic activation of adenylate cyclase

Treatment of intact normal rat kidney fibroblasts, or of purified NRK plasma membranes, with trypsin or papain markedly enhances adenylate cyclase activity [ATP pyrophosphatelyase (cyclizing) EC 4.6.1.1]. Limited proteolysis (25 μg/ml trypsin for 7 min) of confluent cells grown with unheated calf serum significantly increases cyclase activity, whereas similar treatment of sparse cells causes only a marginal increase in cyclic AMP formation. To determine which membrane protein(s) is altered under conditions which result in proteolytic activation of adenylate cyclase, purified plasma membranes and intact normal rat kidney cells were subjected to limited proteolysis and membrane proteins analyzed by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis. Membranes prepared from intact confluent normal rat kidney cells exposed to mild trypsinization showed a decrease in proteins of 56,000, 46,000, 37,000, and 32,000 daltons. Trypsin treatment of intact, sparse cells does not activate the cyclase system and does not lead to modification of the 46,000-dalton membrane protein. Treatment of purified normal rat kidney plasma membranes results in the loss of numerous bands in the high molecular mass region (>150,000 daltons) as well as decreases membrane proteins of 56,000, 49,000, 46,000, and 23,000 daltons. Compared with trypsin, the proteolytic action of papain appears to be quite specific, causing a discernible decrease in only the 46,000-dalton protein. The correlation between modification of the 46,000-dalton membrane component and the activation of the cyclase system suggests that perhaps this protein is proteolytically modified to elicit activation of adenylate cyclase.     

Skeletal muscle myofibrillar protein metabolism in heart failure: relationship to immune activation and functional capacity

Chronic heart failure is characterized by changes in skeletal muscle that contribute to physical disability. Most studies to date have investigated defects in skeletal muscle oxidative capacity. In contrast, less is known about how heart failure affects myofibrillar protein metabolism. Thus we examined the effect of heart failure on skeletal muscle myofibrillar protein metabolism, with a specific emphasis on changes in myosin heavy chain (MHC) protein content, synthesis, and isoform distribution in 10 patients with heart failure (63 +/- 3 yr) and 11 controls (70 +/- 3 yr). In addition, we examined the relationship of MHC protein metabolism to inflammatory markers and physical function. Although MHC and actin protein content did not differ between groups, MHC protein content decreased with increasing disease severity in heart failure patients (r = -0.748, P < 0.02), whereas actin protein content was not related to disease severity. No difference in MHC protein synthesis was found between groups, and MHC protein synthesis rates were not related to disease severity. There were, however, relationships between C-reactive protein and both MHC protein synthesis (r = -0.442, P = 0.05) and the ratio of MHC to mixed muscle protein synthesis (r = -0.493, P < 0.03). Heart failure patients showed reduced relative amounts of MHC I (P < 0.05) and a trend toward increased MHC IIx (P = 0.06). In regression analyses, decreased MHC protein content was related to decreased exercise capacity and muscle strength in heart failure patients. Our results demonstrate that heart failure affects both the quantity and isoform distribution of skeletal muscle MHC protein. The fact that MHC protein content was related to both exercise capacity and muscle strength further suggests that quantitative alterations in MHC protein may have functional significance.     

Alterations of the pituitary-ovarian axis in dogs with a functional granulosa cell tumor

Information on the pituitary-ovarian axis in dogs with a granulosa cell tumor (GCT) is lacking. Therefore, we investigated the plasma concentrations of luteinizing hormone (LH) and estradiol before and after gonadotropin-releasing hormone (GnRH) administration in seven bitches with a functional GCT (GCT-total), of which three were intact (GCT-intact) and four had remnant ovarian tissue (GCT-ROT). The results of the GnRH stimulation test were compared with those in six anestrous and six ovariectomized bitches. The most noteworthy results were as follows. The basal plasma LH concentrations of the GCT-ROT bitches were higher (P < 0.05) than those of the anestrous bitches. The increment in the plasma LH concentration after GnRH administration in the GCT-total bitches was lower (P < 0.001) than the increments in both the anestrous and ovariectomized bitches. The basal plasma estradiol concentrations in the GCT-total bitches were higher (P < 0.001) than those in the anestrous and ovariectomized bitches. In conclusion, the pituitary-ovarian axis is affected in bitches with a functional GCT and is characterized by relatively high plasma LH concentrations in GCT-ROT bitches and a subnormal LH response to GnRH stimulation in all GCT bitches compared with those in anestrous and ovariectomized bitches. The relatively high proportion of dogs with remnant ovarian tissue among the GCT bitches suggests a pathogenetic role for elevated gonadotropin secretion in the pathogenesis of GCT.     

Alterations in recruitment and activation of Rab proteins during mycobacterial infection

At the phagosome level, Mycobacterium spp. alters activation and recruitment of several "Ras gene from rat brain" proteins, commonly known as Rab. Mycobacterial phagosomes have a greater and sustained expression of Rab5, Rab11, Rab14 and Rab22a, and lowered or no expression of Rab7, Rab9 and Rab6. This correlates with increased fusion of the phagosomes with early and recycling endosomes acquiring some features of early phagosomes, allowing the bacteria to gain access to nutrients and preventing the activation of anti-mycobacterial mechanisms. The expression of constitutively active mutants of Rab from the early stage endosomes prevents the maturation of phagosomes containing latex beads or heat-inactivated mycobacteria. Silencing of these mutants by interference RNA or dominant negative forms induces the maturation of mycobacterial phagosomes. The mechanisms have not been established by which mycobacteria alter the expression of these GTPases and thereby shift the phagolysosomal maturation. The problem can be explained by alterations in the recruitment of proteins that interact with Rab, such as phosphoinositide 3-kinases and early endosomal antigen 1. Identifying the mechanisms used by Mycobacterium spp. to disrupt the cycle of Rab activation will be essential to understand the pathophysiology of mycobacterial infections and usefully to potential drug targets.     

The effect of dry needling on gastrocnemius muscle stiffness and strength in participants with latent trigger points

Abnormal muscle stiffness is a potential complication after injury and identifying interventions that modify muscle stiffness may be useful to promote recovery. The purpose of this study was to identify the short-term effects of dry needling (DN) on resting and contracted gastrocnemius muscle stiffness and strength of the triceps surae in individuals with latent myofascial trigger points (MTrPs). In this randomized controlled trial, 52 individuals received two DN treatment sessions to latent MTrPs and 50 individuals received two sham needling sessions. Resting and contracted muscle stiffness were assessed both at the treatment site and a standardized central site in the medial gastrocnemius head immediately post-treatment and one week after the last session. There were significant group by time interactions for resting muscle stiffness at the site of the MTrP (p = .03), but not at the central site (p = .29). Post-needling between group comparison indicated that the DN group had significantly lower resting muscle stiffness at the site of the MTrP than the sham group after adjusting for baseline differences. There were no significant between group differences in contracted muscle stiffness or muscle strength. Identifying strategies that can reduce aberrant muscle stiffness may help to guide management of individuals with neuromuscular pain-related conditions.Level of evidence: Therapy, level 2.     

Alterations in cell-surface carbohydrates of rat large granular lymphocytes associated with interleukin-2 activation

The activation of large granular lymphocytes (LGLs)/natural killer (NK) cells with interleukin-2 (IL-2) has been shown to increase the ability of these cells to lyse NK-resistant tumor target cells. Activated LGLs, termed LAK (lymphokine-activated killer) cells, have been demonstrated to be of therapeutic value in vivo against metastatic tumors. The mechanism by which IL-2 induces broadened cytolytic capability, as well as the molecular basis of target recognition and killing by the activated cells has not yet been elucidated. Since carbohydrate moieties have been demonstrated to be of possible significance in the cytolytic cascade of a variety of effector cells, the current study was undertaken to determine if the activation of LGLs with IL-2 is accompanied by an alteration of cell-surface carbohydrates. Two-color flow cytometry was performed to identify LGL/NK cells in populations of nylon wool-nonadherent splenic mononuclear cells and to assess the binding of various lectins to activated as well as nonactivated LGLs. Increases were observed in the binding of four lectins to LGLs after IL-2 activation; Triticum vulgaris (wheat germ agglutinin), Phytolacca americana (pokeweed mitogen), Lycopersicon esculentum (tomato lectin), and Griffonia simplicifolia I-B4 (GSI-B4). The wheat germ, pokeweed, and tomato lectins recognize complex carbohydrates structure consisting of GlcNAc(Bl,4GlcNAc)n while GSI-B4 recognizes alpha-D-galactose terminal end groups. Lectin binding to the activated LGLs was homogenous (i.e., flow cytometry revealed only a single population of fluorescent cells). Lectin binding to LGLs prior to activation was more heterogeneous, however, the tomato lectin uniquely revealed a bimodal distribution of receptors. These data indicate that LGL/NK cells from the rat are heterogeneous in their ability to bind specific lectins, and that IL-2 activation of these cells results in altered expression of specific cell-surface carbohydrates.