EMG activity normalization for trunk muscles in subjects with and without back pain

Purpose: The aims of the present study were to examine electromyographic (EMG) activity of six bilateral trunk muscles during maximal contraction in three cardinal planes, and to determine the direction of contraction that gives maximal activation for each muscle. both for healthy subjects and back-pain patients. Methods: Twenty-eight healthy subjects and 15 back-pain patients performed maximum voluntary contractions in three cardinal planes, Surface EMG signals were recorded from rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum, and multifidus bilaterally. Root mean square values of the EMG data were calculated to quantify I the amplitude of EMG signals. Results: For both healthy subjects and back-pain patients. one single direction of contraction was found to give the maximum EMG signals for most muscles. Rectus abdominis demonstrated maximal activity in trunk flexion, external oblique in lateral flexion. internal oblique in axial rotation, and multifidus in extension. For the latissimus dorsi and iliocostalis lumborum. maximal activity was demonstrated in more than one cardinal plane. Conclusion: This study has implications for future research involving normalization of muscle activity to maximal levels required in many trunk EMG studies. As the latissimus dorsi and iliocostalis lumborum demonstrate individual differences in the plane that gives maximal activity, these muscles may require testing in more than one plane.

Activation of ion secretion via proteinase-activated receptor-2 in human colon

Proteinase-activated receptor (PAR) type 2 (PAR-2) has been shown to mediate ion secretion in cultured epithelial cells and rat jejunum. With the use of a microUssing chamber, we demonstrate the role of PAR-2 for ion transport in native human colonic mucosa obtained from 30 normal individuals and 11 cystic fibrosis (CF) patients. Trypsin induced Cl- secretion when added to the basolateral but not luminal side of normal epithelia. Activation of Cl- secretion by trypsin was inhibited by indomethacin and was further increased by cAMP in normal tissues but was not present in CF colon, indicating the requirement of luminal CF transmembrane conductance regulator. Effects of trypsin were largely reduced by low Cl-,by basolateral bumetanide, and in the presence of barium or clotrimazole, but not by tetrodotoxin. Furthermore, trypsin-induced secretion was inhibited by the Ca2+-ATPase inhibitor cyclopiazonic acid and in low-Ca2+ buffer. The effects of trypsin were almost abolished by trypsin inhibitor. Thrombin, an activator of PAR types 1, 3, and 4, had no effects on equivalent short-circuit currents. The presence of PAR-2 in human colon epithelium was confirmed by RT-PCR and additional experiments with PAR-2-activating peptide. PAR-2-mediated intestinal electrolyte secretion by release of mast cell tryptase and potentiation of PAR-2 expression by tumor necrosis factor-alpha may contribute to the hypersecretion observed in inflammatory processes such as chronic inflammatory bowel disease.

Mechanism of mitosis-specific activation of MEK1

Activation of cyclin B-Cdc2 is an absolute requirement for entry into mitosis, but other protein kinase pathways that also have mitotic functions are activated during G(2)/M progression. The MAPK cascade has well established roles in entry and exit from mitosis in Xenopus, but relatively little is known about the regulation and function of this pathway in mammalian mitosis. Here we report a detailed analysis of the activity of all components of the Ras/Raf/MEK/ERK pathway in HeLa cells during normal G(2)/M. The focus of this pathway is the dramatic activation of an endomembrane-associated MEK1 without the corresponding activation of the MEK substrate ERK. This is because of the uncoupling of MEK1 activation from ERK activation. The mechanism of this uncoupling involves the cyclin B-Cdc2-dependent proteolytic cleavage of the N-terminal ERK-binding domain of MEK1 and the phosphorylation of Thr(286). These results demonstrate that cyclin B-Cdc2 activity regulates signaling through the MAPK pathway in mitosis.

Life transitions and changing physical activity patterns in young women

Background: Physical activity (PA) patterns are likely to change in young adulthood in line with changes in lifestyle that occur in the transition from adolescence to adulthood. The aim of this study was to ascertain whether key life events experienced by young women in their early twenties are associated with increasing levels of inactivity. Methods: This was a 4-year follow-up of 7281 participants (aged 18 to 23 years at baseline) in the Australian Longitudinal Study of Women's Health, with self-reported measures of PA, life events, body mass index (BMI), and sociodemographic variables. Results: The cross-sectional data indicated no change in PA between baseline (57% active) and follow-up (56% active). However, for almost 40% of the sample, PA category changed between baseline and follow-up, with approximately 20% of the women changing from being active to inactive, and another 20% changing from being inactive to active. After adjustment for age, other sociodemographic variables, BMI, and PA at baseline, women who reported getting married, having a first or subsequent child, or beginning paid work were more likely to be inactive at follow-up than those who did not report these events. Conclusions: The results suggest that life events such as getting married, having children, and starting work are associated with decreased levels of PA in young adult women. Strategies are needed to promote maintenance of activity at the time when most women experience these key life-stage transitions.

Physical Activity and Bone Mineral Accrual During Childhood and Adolescence

The epidemic that is osteoporosis has led to an increasing interest in bone mineral, and the factors that influence the levels of bone mineral, in recent years. While it is unrealistic to try and turn back the clock, a return to an increased level of physical activity may be an important consideration in terms of skeletal health. Peak bone mass is largely determined by heredity, but lifestyle and dietary patterns also influence the level of bone mineral accrued during the growing years. In this review, we summarize the evidence that vigorous weight-bearing physical activity and adequate calcium intake represent the best possibility for enhancing the attainment of an optimal level of bone mineral, within genetic limits.

The t-SNARE syntaxin 4 is regulated during macrophage activation to function in membrane traffic and cytokine secretion

Activation of macrophages with lipopolysaccharide (LPS) induces the rapid synthesis and secretion of proinflammatory cytokines, such as tumor necrosis factor (TNFalpha), for priming the immune response [1, 2]. TNFalpha plays a key role in inflammatory disease [3]; yet, little is known of the intracellular trafficking events leading to its secretion. In order to identify molecules involved in this secretory pathway, we asked whether any of the known trafficking proteins are regulated by LPS. We found that the levels of SNARE proteins were rapidly and significantly up- or downregulated during macrophage activation. A subset of t-SNAREs (Syntaxin 4/SNAP23/Munc18c) known to control regulated exocytosis in other cell types [4, 5] was substantially increased by LPS in a temporal pattern coinciding with peak TNFalpha secretion. Syntaxin 4 formed a complex with Munc18c at the cell surface of macrophages. Functional studies involving the introduction of Syntaxin 4 cDNA or peptides into macrophages implicate this t-SNARE in a rate-limiting step of TNFalpha secretion and in membrane ruffling during macrophage activation. We conclude that in macrophages, SNAREs are regulated in order to accommodate the rapid onset of cytokine secretion and for membrane traffic associated with the phenotypic changes of immune activation. This represents a novel regulatory role for SNAREs in regulated secretion and in macrophage-mediated host defense.

Effects of physical activity on emotional well-being among older Australian women - Cross-sectional and longitudinal analyses

Objective: To explore relationships between physical activity and mental health cross-sectionally and longitudinally in a large cohort of older Australian women. Method: Women in their 70s participating in the Australian Longitudinal Study on Women's Health responded in 1996 (aged 70-75) and in 1999 (aged 73-78). Cross-sectional data were analyzed for 10,063 women and longitudinal data for 6472. Self-reports were used to categorize women into four categories of physical activity at each time point as well as to define four physical activity transition categories across the 3-year period. Outcome variables for the cross-sectional analyses were the mental health component score (MCS) and mental health subscales of the Medical Outcomes Study Short Form (SF-36). The longitudinal analyses focused on changes in these variables. Confounders included the physical health component scale (PCS) of the SF-36, marital status, body mass index (BMI) and life events. Adjustment for baseline scores was included for the longitudinal analyses. Results: Cross-sectionally, higher levels of physical activity were associated with higher scores on all dependent variables, both with and without adjustment for confounders. Longitudinally, the effects were weaker, but women who had made a transition from some physical activity to none generally showed more negative changes in emotional well-being than those who had always been sedentary, while those who maintained or adopted physical activity had better outcomes. Conclusion: Physical activity is associated with emotional well-being among a population cohort of older women both cross-sectionally and longitudinally, supporting the need for the promotion of appropriate physical activity in this age group. (C) 2003 Elsevier Science Inc. All rights reserved.

Asymmetric contribution of α and β subunits to the activation of αβ heteromeric glycine receptors

This study investigated the role of beta subunits in the activation of alphabeta heteromeric glycine receptor (GlyR) chloride channels recombinantly expressed in HEK293 cells. The approach involved incorporating mutations into corresponding positions in alpha and beta subunits and comparing their effects on receptor function. Although cysteine-substitution mutations to residues in the N-terminal half of the alpha subunit M2-M3 loop dramatically impaired the gating efficacy, the same mutations exerted little effect when incorporated into corresponding positions of the beta subunit. Furthermore, although the alpha subunit M2-M3 loop cysteines were modified by a cysteine-specific reagent, the corresponding beta subunit cysteines showed no evidence of reactivity. These observations suggest structural or functional differences between alpha and beta subunit M2-M3 loops. In addition, a threonine-->leucine mutation at the 9' position in the beta subunit M2 pore-lining domain dramatically increased the glycine sensitivity. By analogy with the effects of the same mutation in other ligand-gated ion channels, it was concluded that the mutation affected the GlyR activation mechanism. This supports the idea that the GlyR beta subunit is involved in receptor gating. In conclusion, this study demonstrates that beta subunits contribute to the activation of the GlyR, but that their involvement in this process is significantly different to that of the alpha subunit.