Are acute effects of maximal dynamic contractions on upper-body ballistic performance load specific?

This study investigated the acute effects of upper-body maximal dynamic contractions on maximal throwing speed with 0.55- and 4-kg medicine balls. It was hypothesized that heavy preloading would transiently improve throwing performance only when overcoming the heavier of the two loads. Twenty-three male volunteers were randomly allocated into experimental (n = 11) and control (n = 12) groups. Both groups performed initial and final seated medicine ball throws from the chest, and the maximal medicine ball speed was measured by means of a radar gun. Between the two measurements, the control group rested passively for 15 minutes, and the experimental group performed three sets of three-repetition maximum bench presses. For the 0.55-kg load, a 2 x 2 repeated-measures analysis of variance revealed no significant effect of time x group interaction (p = 0.22), as well as no significant time (p = 0.22) or group (p = 0.72) effects. In contrast, for the 4-kg load, a significant time x group interaction (p = 0.004) and a significant time (p = 0.035) but not group (p = 0.77) effect were observed. Analysis of simple main effects revealed that the experimental group significantly (8.3%; p < 0.01) improved maximal throwing speed with the 4-kg load. These results support our research hypothesis and suggest that the acute effects of heavy preloading on upper-body ballistic performance might be load specific. In a practical sense, our findings suggest that the use of upper-body heavy resistance exercise before ballistic throwing movements against moderate external loads might be an efficient training strategy for improving an athlete's upper-body explosive performance.     

γ-Aminobutyric acid modulation of acetylcholine-induced contractions of a smooth muscle from an echinoderm (Sclerodactyla briareus)

This study provides pharmacological evidence for the presence of GABAergic neurons innervating the longitudinal muscle of the body wall (LMBW) of holothurians. γ-Aminobutyric acid (GABA) A and B receptor subtypes were both present in this system and regulated spontaneous contractions as well as responses to acetylcholine (ACh) that stimulated contraction of the LMBW. GABA dose-dependently relaxed the resting tone of the LMBW. GABA (10⁻⁵ M) inhibited ACh-induced (10⁻⁴ M) contractions by 20%. The GABA B agonist, baclofen, relaxed the LMBW, an effect potentiated by GABA. Pretreatment with baclofen (10⁻⁴ M) inhibited ACh (10⁻⁴ M) contractions of the LMBW by 50%. Phaclofen, a GABA receptor B antagonist, caused a dose-dependent increase in resting tension. Phaclofen-induced (10⁻⁵ M) contractions were reversed by the addition of GABA or baclofen (10⁻⁴ M) and potentiated by the addition of another GABA B receptor antagonist, 2-hydroxy-saclofen (10⁻⁵ M). Pretreatment with phaclofen (10⁻⁵ M) caused a marked potentiation of ACh-induced (10⁻⁴ M) contractions by 101%. 2-Hydroxy-saclofen (10⁻⁵ M) had a toxic effect on the LMBW, rendering it completely unresponsive either to ACh or to a second exposure to GABA, and so exhibiting cross-desensitization. Muscimol, a GABA A receptor agonist, had no effect on the resting tension of the LMBW. Curiously, pretreatment of the muscle with muscimol (10⁻⁵ M) potentiated ACh-evoked (10⁻⁴ M) contractions by nearly 20%. Bicuculline (10⁻⁵ M), a GABA A receptor antagonist, generated large, sustained contractions and partially blocked GABA-induced (10⁻⁴ M) relaxation. Like 2-hydroxy-saclofen, bicuculline (10⁻⁵ M) had a profound cross-desensitizing effect on the LMBW to subsequent exposures to GABA and ACh. ACh was unable to potentiate the sustained contractions induced by bicuculline. Accepted: 17 September 1998     

Causes of excitation-induced muscle cell damage in isometric contractions: mechanical stress or calcium overload?

Prolonged or unaccustomed exercise leads to muscle cell membrane damage, detectable as release of the intracellular enzyme lactic acid dehydrogenase (LDH). This is correlated to excitation-induced influx of Ca2+, but it cannot be excluded that mechanical stress contributes to the damage. We here explore this question using N-benzyl-p-toluene sulfonamide (BTS), which specifically blocks muscle contraction. Extensor digitorum longus muscles were prepared from 4-wk-old rats and mounted on holders for isometric contractions. Muscles were stimulated intermittently at 40 Hz for 15-60 min or exposed to the Ca2+ ionophore A23187. Electrical stimulation increased 45Ca influx 3-5 fold. This was followed by a progressive release of LDH, which was correlated to the influx of Ca2+. BTS (50 microM) caused a 90% inhibition of contractile force but had no effect on the excitation-induced 45Ca influx. After stimulation, ATP and creatine phosphate levels were higher in BTS-treated muscles, most likely due to the cessation of ATP-utilization for cross-bridge cycling, indicating a better energy status of these muscles. No release of LDH was observed in BTS-treated muscles. However, when exposed to anoxia, electrical stimulation caused a marked increase in LDH release that was not suppressed by BTS but associated with a decrease in the content of ATP. Dynamic passive stretching caused no increase in muscle Ca2+ content and only a minor release of LDH, whereas treatment with A23187 markedly increased LDH release both in control and BTS-treated muscles. In conclusion, after isometric contractions, muscle cell membrane damage depends on Ca2+ influx and energy status and not on mechanical stress.     

Which factors influence the ability of a computational model to predict the in vivo deformation behaviour of skeletal muscle?

Deep tissue injury (DTI) is a severe form of pressure ulcer where tissue damage starts in deep tissues underneath intact skin. Tissue deformation may play an important role in the aetiology, which can be investigated using an experimental–numerical approach. Recently, an animal-specific finite element model has been developed to simulate experiments in which muscle tissue was compressed with an indenter. In this study, the material behaviour and boundary conditions were adapted to improve the agreement between model and experiment and to investigate the influence of these adaptations on the predicted strain distribution. The use of a highly nonlinear material law and including friction between the indenter and the muscle both improved the quality of the model and considerably influenced the estimated strain distribution. With the improved model, the required sample size to detect significant differences between loading conditions can be diminished, which is clearly relevant in experiments involving animals.     

Mild cognitive impairment: a prodromal phase of dementia?

Cognitive decline without dementia is common among older persons. A variety of clinical concepts have been introduced in the past 30 years, in order to describe these cognitive deficits arising in older persons. The most frequently used concept is Mild Cognitive Impairment (MCI). MCI is generally seen as a prodromal phase of Alzheimer disease (AD). Several concepts are described, with the neuropsychiatric features and predictors of conversion to dementia c.q. AD. Finally, consequences of preclinically diagnoses for health care are clarified.     

Phylloxera and the grapevine: a sense of common purpose?

The purpose of life is its continuation: survival is the reason things live. Here we explore this 'basic' of biology, by reference to the extraordinary life-cycle of the aphid-like pest phylloxera, and the complexity of its relationship with its host the grapevine. The effort and ingenuity that phylloxera employs to continue itself leads to a doubt that survival alone is sufficient reason. It has frequently been suggested that the reduction of life to a catalogue of facts (by science) creates this doubt, because it robs existence of its essence (which is something other than its mechanics). The part that science is said to steal is what Robert Pirsig calls Quality-the harmonious balance of things. Pirsig seems to imply that this is something inherent in things-and independent from us. A more mundane explanation is that the difference between facts and the complete reality is us-the tendency of mind to connect freely between different kinds of information. This possibility is briefly illustrated here by a myth based on the facts of phylloxera.     

Airway smooth muscle electrophysiology in a state of flux?

Activation of chloride currents and release of internally sequestered Ca(2+) in airway smooth muscle have long been associated with excitation and contraction. Surprisingly, however, two recent publications (Deshpande DA, Wang WC, McIlmoyle EL, Robinett KS, Schillinger RM, An SS, Sham JS, Liggett SB. Nat Med 16: 1299-1304, 2010; Gallos G, Yim P, Chang S, Zhang Y, Xu D, Cook JM, Gerthoffer WT, Emala CW Sr. Am J Physiol Lung Cell Mol Physiol 302: L248-L256, 2012) have linked both events to relaxation. This begs a closer look at our understanding of airway smooth muscle electrophysiology and its contribution to excitation-contraction coupling. This Editorial Focus highlights those two aforementioned studies and several other equally paradoxical findings and proposes some possible reinterpretations of the data and/or new directions of research in which the answers might be found.     

Alteration of 11β-hydroxysteroid dehydrogenase type 1 in skeletal muscle in a rat model of type 2 diabetes

Recent investigations have demonstrated that activation of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in liver and adipose tissue is closely related to the pathogenesis of obesity and diabetes. However, the relationship between alteration of 11β-HSD1 and the pathogenesis of type 2 diabetes in skeletal muscle is still unclear. A rat model of Type 2 diabetes was developed by high fat diet feeding combined with multiple low dose streptozotocin injection (30 mg/kg, i.p. twice). Intraperitoneal glucose tolerance test, insulin tolerance test were performed. Fasting blood glucose, fasting insulin, total cholesterol, triglyceride were measured. The protein and mRNA level of 11β-HSD1 and glucocorticoid receptor in gastrocnemius muscle were determined. The alteration of insulin signaling pathway related protein was investigated. We found that the protein levels of 11β-HSD1 and glucocorticoid receptor were significantly increased (P < 0.05); the mRNA level of 11β-HSD1 was also elevated (P < 0.05); the mRNA level of glucocorticoid receptor was decreased (P < 0.05). After insulin stimulation, diabetic rats had no significant changes in the level of the insulin receptor β-subunit (IR-β), AKT, as in phosphorylated AKT in the gastrocnemius muscle compared to its basal state. Similar results were observed in the protein expression level of glucose transporter 4 (GLUT4). Our data indicate that the alteration of 11β-HSD1 at protein and mRNA level may be related to the abnormality of insulin signal pathway in skeletal muscle, this effect may be mediated by glucocorticoid receptor.     

Which place for stem cell therapy in the treatment of acute radiation syndrome?

Radiation-induced (RI) tissue injuries can be caused by radiation therapy, nuclear accidents or radiological terrorism. Notwithstanding the complexity of RI pathophysiology, there are some effective approaches to treatment of both acute and chronic radiation damages. Cytokine therapy is the main strategy capable of preventing or reducing the acute radiation syndrome (ARS), and hematopoietic growth factors (GF) are particularly effective in mitigating bone marrow (BM) aplasia and stimulating hematopoietic recovery. However, first, as a consequence of RI stem and progenitor cell death, use of cytokines should be restricted to a range of intermediate radiation doses (3 to 7 Gy total body irradiation). Second, ARS is a global illness that requires treatment of damages to other tissues (epithelial, endothelial, glial, etc.), which could be achieved using pleiotropic or tissue-specific cytokines. Stem cell therapy (SCT) is a promising approach developed in the laboratory that could expand the ability to treat severe radiation injuries. Allogeneic hematopoietic stem cell transplantation (BM, mobilized peripheral blood and cord blood) transplantation has been used in radiation casualties with variable success due to limiting toxicity related to the degree of graft histocompatibility and combined injuries. Ex vivo expansion should be used to augment cord blood graft size and/or promote very immature stem cells. Autologous SCT might also be applied to radiation casualties from residual hematopoietic stem and progenitor cells (HSPC). Stem cell plasticity of different tissues such as liver or skeletal muscle, may also be used as a source of hematopoietic stem cells. Finally, other types of stem cells such as mesenchymal, endothelial stem cells or other tissue committed stem cells (TCSC), could be used for treating damages to nonhematopoietic organs.     

Finally,a sense of closure? Animal models of human ventral body wall defects

Malformations concerning the ventral body wall constitute one of the leading categories of human birth defects and are present in about one out of every 2000 live births. Although the occurrence of these defects is relatively common, few detailed experimental studies exist on the development and closure of the ventral body wall in mouse and human. This field is further complicated by the array of theories on the pathogenesis of body wall defects and the likelihood that there is no single cause for these abnormalities. In this review, we summarize what is known concerning the mechanisms of normal ventral body wall closure in humans and mice. We then outline the theories that have been proposed concerning human body wall closure abnormalities and examine the growing number of mouse mutations that impact normal ventral body wall closure. Finally, we speculate how studies in animal models such as mouse and Drosophila are beginning to provide a much-needed mechanistic framework with which to identify and characterize the genes and tissues required for this vital aspect of human embryogenesis.     

Genomic studies of mood disorders - the brain as a muscle?

Recent genomic studies showing abnormalities in the fibroblast growth factor system in the postmortem brains of people with major depressive disorder support previous indications of a role for growth factors in mood disorders. Similar molecular pathways, volumetric changes, and the effects of exercise on mood suggest a superficial analogy, and perhaps a deeper relationship, between muscle and brain functioning.     

Which Dimensions of Patient-Centeredness Matter? - Results of a Web-Based Expert Delphi Survey

Background

Present models and definitions of patient-centeredness revealed a lack of conceptual clarity. Based on a prior systematic literature review, we developed an integrative model with 15 dimensions of patient-centeredness. The aims of this study were to 1) validate, and 2) prioritize these dimensions.

Method

A two-round web-based Delphi study was conducted. 297 international experts were invited to participate. In round one they were asked to 1) give an individual rating on a nine-point-scale on relevance and clarity of the dimensions, 2) add missing dimensions, and 3) prioritize the dimensions. In round two, experts received feedback about the results of round one and were asked to reflect and re-rate their own results. The cut-off for the validation of a dimension was a median < 7 on one of the criteria.

Results

105 experts participated in round one and 71 in round two. In round one, one new dimension was suggested and included for discussion in round two. In round two, this dimension did not reach sufficient ratings to be included in the model. Eleven dimensions reached a median ≥ 7 on both criteria (relevance and clarity). Four dimensions had a median < 7 on one or both criteria. The five dimensions rated as most important were: patient as a unique person, patient involvement in care, patient information, clinician-patient communication and patient empowerment.

Discussion

11 out of the 15 dimensions have been validated through experts’ ratings. Further research on the four dimensions that received insufficient ratings is recommended. The priority order of the dimensions can help researchers and clinicians to focus on the most important dimensions of patient-centeredness. Overall, the model provides a useful framework that can be used in the development of measures, interventions, and medical education curricula, as well as the adoption of a new perspective in health policy.     

The interference of flexible working times with the utility of time: a predictor of social impairment?

Periodic components inherent in actual schedules of flexible working hours and their interference with social rhythms were measured using spectrum analysis. The resulting indicators of periodicity and interference were then related to the reported social impairments of workers. The results show that a suppression of the 24 and the 168 h (seven-day) components (absence of periodicity) in the work schedules predicts reported social impairment. However, even if there are relatively strong 24 and 168 h components left in the work schedules, their interference with the social rhythm (using the phase difference between working hours and the utility of time) further predicts impairment. The results thus indicate that the periodicity of working hours and the amount of (social) desynchronization induced by flexible work schedules can be used both for predicting the impairing effects of the specific work schedules on social well-being as well as for the design of socially acceptable flexible work hours.     

Do more complex organisms have a greater proportion of membrane proteins in their genomes?

One may speculate that higher organisms require a proportionately greater abundance of membrane proteins within their genomes in order to furnish the requirements of differentiated cell types, compartmentalization, and intercellular signalling. With the recent availability of several complete prokaryotic genome sequences and sufficient progress in many eukaryotic genome sequencing projects, we seek to test this hypothesis. Using optimized hydropathy analysis of proteins in several, diverse proteomes, we show that organisms of the three domains of life-Eukarya, Eubacteria, and Archaea-have similar proportions of alpha-helical membrane proteins within their genomes and that these are matched by the complexity of the aqueous components.     

Basic muscle protein,a third genetic locus isoenzyme of carbonic anhydrase?

Rabbit muscle cytosol extract contains a basic protein which represents about 2% of the total cytosol protein. It contains zinc in a 1:1 stoichiometric ratio, based on a molecular weight of 30,000, and it catalyzes the hydration of CO₂. It is immunochemically distinct from the high and low activity forms of rabbit blood carbonic anhydrase. It has comparatively poor activity as an esterase, and about 20% of the CO₂ hydratase activity of the rabbit blood low activity carbonic anhydrase. This CO₂ hydratase activity is not inhibited by acetazolamide at concentrations which totally inhibit the activity of the blood carbonic anhydrases. The evidence obtained to date, though circumstantial, suggests that this basic metalloprotein is a carbonic anhydrase derived from a third genetic locus with properties considerably different from those of the mammalian carbonic anhydrases heretofore identified.     

Redundancy or heterogeneity in the electric activity of the biceps brachii muscle? Added value of PCA-processed multi-channel EMG muscle activation estimates in a parallel-fibered muscle

Conventional bipolar EMG provides imprecise muscle activation estimates due to possibly heterogeneous activity within muscles and due to improper alignment of the electrodes with the muscle fibers. Principal component analysis (PCA), applied on multi-channel monopolar EMG yielded substantial improvements in muscle activation estimates in pennate muscles. We investigated the degree of heterogeneity in muscle activity and the contribution of PCA to muscle activation estimates in biceps brachii (BB), which has a relatively simply parallel-fibered architecture. EMG-based muscle activation estimates were assessed by comparison to elbow flexion forces in isometric, two-state isotonic contractions in eleven healthy male subjects. Monopolar EMG was collected over the entire surface of the BB with about 63 electrodes. Estimation quality of different combinations of EMG channels showed that heterogeneous activation was found mainly in medio-lateral direction, whereas adding channels in the longitudinal direction added largely redundant information. Multi-channel bipolar EMG amplitude improved muscle activation estimates by 5–14% as compared to a single bipolar. PCA-processed monopolar EMG amplitude yielded a further improvement of (12–22%). Thus multi-channel EMG, processed with PCA, substantially improves the quality of muscle activation estimates compared conventional bipolar EMG in BB.