The connective tissue of the adductor canal - a morphological study in fetal and adult specimens

The adductor canal is a conical or pyramid-shaped pathway that contains the femoral vessels, saphenous nerve and a varying amount of fibrous tissue. It is involved in adductor canal syndrome, a claudication syndrome involving young individuals. Our objective was to study modifications induced by aging on the connective tissue and to correlate them to the proposed pathophysiological mechanism. The bilateral adductor canals and femoral vessels of four adult and five fetal specimens were removed en bloc and analyzed. Sections 12 mu m thick were obtained and the connective tissue studied with Sirius Red, Verhoeff, Weigert and Azo stains. Scanning electron microscopy (SEM) photomicrographs of the surfaces of each adductor canal were also analyzed. Findings were homogeneous inside each group. The connective tissue of the canal was continuous with the outer layer of the vessels in both groups. The pattern of concentric, thick collagen type I bundles in fetal specimens was replaced by a diffuse network of compact collagen bundles with several transversal fibers and an impressive content of collagen III fibers. Elastic fibers in adults were not concentrated in the thick bundles but dispersed in line with the transversal fiber system. A dynamic compression mechanism with or without an evident constricting fibrous band has been proposed previously for adductor canal syndrome, possibly involving the connective tissue inside the canal. The vessels may not slide freely during movement. These age-related modifications in normal individuals may represent necessary conditions for this syndrome to develop.

CHANGES OF GENE EXPRESSION IN ELECTRICALLY STIMULATED AND CONTRALATERAL RAT SOLEUS MUSCLES

In this study we investigate the effect of a single session of high-intensity contractions on expression of pleiotropic genes and, in particular, those genes associated with metabolism in soleus muscle from electrically stimulated (ES) and contralateral (CL) limbs. The right limbs of male Wistar rats were submitted to contractions by 200-ms trains of electrical stimulation at 100-Hz frequency with pulses of 0.1 ms (voltage 24 3 V) delivered each second for 1 hour. Soleus muscles were isolated 1 hour after contraction, and gene expression was analyzed by a macroarray technique (Atlas Toxicology 1.2 Array; Clontech Laboratories). Electrical stimulation increased expression in 92 genes (16% of the genes present in the membrane). Sixty-six genes were upregulated in both ES and CL soleus muscles, and expression of 26 genes was upregulated in the ES muscle only. The most altered genes were those related to stress response and metabolism. Electrical stimulation also raised expression of transcription factors, translation and posttranslational modification of proteins, ribosomal proteins, and intracellular transducers/effectors/modulators. The results indicate that a single session of electrical stimulation upregulated expression of genes related to metabolism and oxidative stress in soleus muscle from both ES and CL limbs. These findings may indicate an association with tissue hypertrophy and metabolic adaptations induced by physical exercise training not only in the ES but also in the CL non-stimulated muscle, suggesting a cross-education phenomenon. Muscle Nerve 40: 838-846, 2009

Effect of neuromuscular electrical stimulation and isotonic exercises in flexor and extensor muscles of knee of hemiplegic patients

Aim. To verify the muscular force and resistance to the movement of the flexor and extensor muscles of the knee of patients with spasticity after treatment with neuromuscular electrical stimulation (NMES) and isotonic exercises. Patients and methods. The patients this study were divided into group I (NMES) and group 2 (isotonic exercises). Their muscular torque and resistance to the movement of the flexor and extensor knee muscles were measured by the isokinetic dynamometer and the degree of spasticity by the modified Ashworth scale before and after ten sessions. Results. Alterations in the scores of the modified Ashworth scale were not observed. An increase in the flexor torque in group 1 (p = 0.041) and in group 2 (p = 0.001) was verified. In the passive mode, group 1 presented a reduction of resistance to the flexion movement (p = 0.026), while in group 2, a reduction of resistance to both the flexion (p = 0,029) and extension movements (p = 0.019) was verified. Conclusions. The two therapeutical resources had their efficiency proven only for the increase of the force of the flexor muscles. The resistance to movement, the isotonic exercises were more effective because they promoted a reduction in the resistance of the flexor and extensor knee muscles.

Evaluation of trace element levels in muscles, liver and gonad of fish species from Sao Francisco River of the Parana Brazilian state by using SR-TXRF technique

This study is focused on the analysis of an accumulation of inorganic elements in muscles, liver and gonad of seven fish species from Sao Francisco River located in the Parana state of Brazil. Concentrations of the elements were determined using the SR-TXRF technique. In the muscles of fish species, negative length dependent relationships were observed for chromium and zinc ion absorption. The obtained results showed that accumulated Cr ions values are above the limits defined in the Brazilian legislative norm on food. (C) 2010 Elsevier Ltd All rights reserved.

Self-esteem and negative affect as moderators of sociocultural influences on body dissatisfaction, strategies to decrease weight and strategies to increase muscles among adolescent boys and girls

The study was conducted to examine the impact of sociocultural influences and the moderating role of self-esteem and negative affect on body dissatisfaction and body change strategies for both adolescent boys and girls. Surveys designed to assess body dissatisfaction, body change strategies to decrease weight and increase muscles, perceived sociocultural pressures to lose weight and increase muscles, self-esteem and negative affect were administered to 587 boys and 598 girls aged between 11 and 15 years. The majority of respondents were from Anglo-Australian backgrounds (83%) with the remainder being from Asian and European non-English-speaking backgrounds. The sociocultural influences were found to significantly predict body dissatisfaction and body change strategies for both boys and girls. However, in the case of boys, self-esteem was found to moderate the impact of the sociocultural influences in predicting body change strategies. It was primarily the boys with low self-esteem who were more affected by the sociocultural pressures whereas the girls were affected independently of their self-esteem. Negative affect was also found to play a moderating role on some of the sociocultural influences in predicting strategies to increase muscles. Both boys and girls with higher levels of negative affect were more likely to be affected by sociocultural messages directed at increasing muscles. The results from the present study demonstrate that as well as examining the direct influence of sociocultural pressures, it is also important to examine how these may be moderated by self-esteem and negative affect.

Body image, strategies to change muscles and weight, and puberty. Do they impact on positive and negative affect among adolescent boys and girls?

The purpose of this study was to examine the impact of strategies to both decrease weight and increase muscle tone on negative (depression, anxiety) and positive affect among adolescent males and females. The respondents were 1185 adolescents (587 males, 598 females) who were enrolled in grades 7 and 9 (mean age for MALES=13.22 years; mean age for FEMALES=13.21 years). Respondents completed the Body Image and Body Change Inventory that assessed body image satisfaction, body image importance, body change strategies to decrease weight, body change strategies to increase muscle tone, and food supplements. Respondents also completed the Pubertal Development Scale, the depression and anxiety scales of the Depression Anxiety and Stress Scale, and the positive affect items from the Positive and Negative Affect Scale. Structural equation modelling was used to determine how body satisfaction and importance, body change strategies, and puberty impacted on depression, anxiety, and positive affect. The results demonstrated that for both boys and girls, there was a strong association between body change strategies and negative affect. For boys, body dissatisfaction did not predict negative affect, although this was a strong predictor for girls. Body change strategies did not strongly predict positive affect for either boys or girls, although body image satisfaction was a strong predictor for both genders. The implications of these findings for obtaining a better understanding of the role of pubertal development, body image, and body change strategies in predicting positive and negative affect among adolescent males and females are discussed.

A longitudinal study of body image and strategies to lose weight and increase muscles in children

A longitudinal study was used to examine age differences in the role of body mass index (BMI) and sociocultural pressures in predicting changes in body image and strategies to both lose weight and increase muscles among 443 children aged between 8 and 12 years (207 boys, 236 girls) over a 16-month period. The strongest predictors of body image and these strategies were BMI, the media and mothers, and to a lesser extent fathers and best friends. Girls were focused on losing weight, whereas boys were focused on both increasing muscle and losing weight. Surprisingly, there was a reduction in strategies both to lose weight and increase muscles as children approached adolescence. The implications of these findings for preventative educational programs for boys and girls are discussed.

A longitudinal study to explain stratiges to change weight and muscles among normal weight and overweight children

Previous research has indicated that both boys and girls strive for a slim body, with boys having an additional focus on a muscular body build. The current study was designed to evaluate the utility of a biopsychosocial model to explain body image and body change strategies among children. The study evaluated changes over time in body image and strategies to lose weight and increase muscles among 132 normal weight and 67 overweight boys (mean age=9.23 years) and 158 normal weight and 55 overweight girls (mean age=9.33 years). The predictive role of BMI, positive and negative affect, self-esteem and perceived sociocultural pressures to lose weight or increase muscle on body image and body change strategies over a 16 month period was evaluated. All participants completed the questionnaire on both occasions. The results demonstrated that both overweight boys and girls were more likely to be dissatisfied with their weight, place more importance on their weight, engage in more strategies to lose weight as well as perceive more pressure to lose weight. Overweight boys and girls were also more likely to report lower levels of self-esteem and positive affect, and higher levels of negative affect, and reported a reduction in their self-esteem over time. Regression analyses demonstrated that among overweight boys, low self-esteem and high levels of perceived pressure to lose weight predicted weight dissatisfaction; for overweight girls, weight dissatisfaction was also predicted by low levels of self-esteem. The implication of these findings in terms of factors contributing to the adoption of health risk behaviors among children is discussed.

Stress-shielding as a cause of insertional tendinopathy: the operative technique of limited adductor tenotomy supports this theory

The aetiology of tendinopathy is poorly understood. A new hypothesis proposed argues that tendinopathy may not be purely a tensile injury, rather that altered mechanics such as compression or stress-shielding may be important. Both tendon compression and a decrease in tendon load (stress-shielding) will induce change in a tendon similar to that seen in an insertional tendinopathy.

Stress-shielding as a cause of tendinopathy is supported by the clinical success of operative release of adductor longus. This surgery releases the superficial section of the normal adductor longus tendon at a point distal to the insertion. This may have the effect of transferring stress from the superficial section of the tendon to the stress-shielded deeper portion, and the induction of normal loads in both the deeper and superficial portions of the tendon may assist in tendon recovery. This interesting hypothesis and clinical intervention require further investigation

Calcineurin-Aα alpha activation enhances the structure and function of regenerating muscles after myotoxic injury

Calcineurin signaling is essential for successful muscle regeneration. Although calcineurin inhibition compromises muscle repair, it is not known whether calcineurin activation can enhance muscle repair after injury. Tibialis anterior (TA) muscles from adult wild-type (WT) and transgenic mice overexpressing the constitutively active calcineurin-Aα transgene under the control of the mitochondrial creatine kinase promoter (MCK-CnAα*) were injected with the myotoxic snake venom Notexin to destroy all muscle fibers. The TA muscle of the contralateral limb served as the uninjured control. Muscle structure was assessed at 5 and 9 days postinjury, and muscle function was tested in situ at 9 days postinjury. Calcineurin stimulation enhanced muscle regeneration and altered levels of myoregulatory factors (MRFs). Recovery of myofiber size and force-producing capacity was hastened in injured muscles of MCK-CnAα* mice compared with control. Myogenin levels were greater 5 days postinjury and myocyte enhancer factor 2a (MEF2a) expression was greater 9 days postinjury in muscles of MCK-CnAα* mice compared with WT mice. Higher MEF2a expression in regenerating muscles of MCK-CnAα* mice 9 days postinjury may be related to an increase of slow fiber genes. Calcineurin activation in uninjured and injured TA muscles slowed muscle contractile properties, reduced fatigability, and enhanced force recovery after 4 min of intermittent maximal stimulation. Therefore, calcineurin activation can confer structural and functional benefits to regenerating skeletal muscles, which may be mediated in part by differential expression of MRFs.

Activated calcineurin ameliorates contraction-induced injury to skeletal muscles of mdx dystrophic mice

Utrophin expression is regulated by calcineurin and up-regulating utrophin can decrease the susceptibility of dystrophic skeletal muscle to contraction-induced injury. We overexpressed the constitutively active calcineurin-A α in skeletal muscle of mdx dystrophic mice (mdx CnA*) and examined the tibialis anterior muscle to determine whether the presence of activated calcineurin promotes resistance to muscle damage after lengthening contractions. Two stretches (10 s apart) of 40% strain relative to muscle fibre length were initiated from the plateau of a maximal isometric tetanic contraction. Muscle damage was assessed 1, 5 and 15 min later by the deficit in maximum isometric force and by quantifying the proportion of muscle fibres staining positive for intracytoplasmic albumin. The force deficit at all time points after the lengthening contractions was approximately 80% in mdx muscles and 30% in mdxCnA* muscles. The proportion of albumin-positive fibres was significantly less in control and injured muscles from mdxCnA* mice than from mdx mice. Compared with mdx mice, mean fibre cross-sectional area was 50% less in muscles from mdxCnA* mice. Furthermore, muscles frommdxCnA* mice exhibited a higher proportion of fibres expressing the slow(er) myosin heavy chain (MyHC) I and IIa isoforms, prolonged contraction and relaxation times, lower absolute and normalized maximum forces, and a clear leftward shift of the frequency–force relationship with greater force production at lower stimulation frequencies. These are structural and functional markers of a slower muscle phenotype. Taken together, our findings show that muscles from mdxCnA* mice have a smaller mean fibre cross-sectional area, a greater sarcolemmal to cytoplasmic volume ratio, and an increase in utrophin expression, promoting an attenuated susceptibility to contraction-induced injury. We conclude that increased calcineurin activity may confer functional benefits to dystrophic skeletal muscles.

Differential calcineurin signalling activity and regeneration efficacy in diaphragm and limb muscles of dystrophic mdx mice

Calcineurin activity is essential for successful skeletal muscle regeneration in young mdx mice and in wild type mice following myotoxic injury and cryodamage. In mature myofibres of adult mdx mice, calcineurin stimulation can ameliorate the dystrophic pathology. The aim of this study was to test the hypothesis that the more severe dystrophic pathology of the diaphragm compared with hindlimb muscles of mdx mice could be attributed to aberrant calcineurin signalling and that due to ongoing regeneration calcineurin activity would be greater in muscles of adult mdx than wild type mice. Differences in markers of regeneration between tibialis anterior and diaphragm muscles were also characterised, to determine whether there was an association between regeneration efficacy and calcineurin activity in dystrophic muscles. In diaphragm muscles of adult mdx mice, the proportion of centrally nucleated fibres and developmental myosin heavy chain protein expression was lower and myogenin protein expression was higher than in tibialis anterior muscles. Calcineurin and activated NFATc1 protein content and calcineurin phosphatase activity were higher in muscles from mdx than wild type mice and calcineurin activation was greater in diaphragm than tibialis anterior muscles of mdx mice. Thus, despite greater calcineurin activity in diaphragm compared to hindlimb muscles, regeneration events downstream of myoblast differentiation and mediated by the injured myofibre were severely compromised.

Examination of EMG normalisation methods for the study of the posterior and posterolateral neck muscles in healthy controls

The purpose of this study was to examine the reliability of normalisation methods used in the study of the posterior and posterolateral neck muscles in a group of healthy controls. Six asymptomatic male subjects performed a total of 12 maximum voluntary isometric contractions (MVIC) and 60%-submaximal isometric contractions (60%-MVIC) against the torque arm of an isokinetic dynamometer whilst surface and intramuscular electromyography (EMG) was recorded unilaterally from representative posterior and posterolateral locations. Reliability was calculated using intra-class correlation coefficient (ICC), relative standard error of measurement (%SEM) and relative coefficient of variation (%CV). Maximal torque output was found to be highly reliable in the directions of extension and right lateral bending when the first of three MVIC contractions was excluded. When averaged across contraction direction, high reliability was found for both surface (MVIC: ICC = 0.986, %SEM = 7.5, %CV = 9.2; 60%-MVIC: ICC = 0.975, %SEM = 10, %CV = 13.7) and intramuscular (MVIC: ICC = 0.910, %SEM = 20, %CV = 19.1; 60%-MVIC: ICC = 0.952, %SEM = 16.5, %CV = 13.5) electrodes. Intramuscular electrodes displayed the least reliability in right lateral bending. The use of visual feedback markedly increased the reliability of 60%-MVIC contractions.