Effect of rat soleus muscle overload on neuromuscular transmission efficacy during continuous and intermittent activation

Increased neuromuscular activity is known to provoke morphological and functional adaptations at the neuromuscular synapse. Most of these changes have been documented following endurance exercise training programmes. In this study, the effect of rat soleus muscle overload produced by tenotomy plus voluntary wheel-cage activity on neuromuscular transmission efficacy was investigated. The overload protocol increased miniature endplate potential (MEPP) and endplate potential (EPP) amplitudes by 17 and 19%, respectively (both P < 0.01), and increased MEPP frequency by 86% (P < 0.01). EPP amplitude rundown during continuous trains of activation was attenuated by approximately 10% in the overloaded group (P < 0.01). Also, during intermittent activation, the overload protocol attenuated EPP amplitude rundown, mainly by enhancing EPP amplitude recovery by approximately 10% during the quiescent periods (P < 0.01). Although the present results show that both the degree and direction of adaptation are similar to what has been observed at rat soleus neuromuscular junctions following an endurance training protocol, there are important nuances between the results, suggesting different mechanisms through which these changes may occur.     

Primary infection of C57BL/6 mice with Plasmodium yoelii induces a heterogeneous response of NKT cells

NKT cells are a population of innate-like lymphocytes that display effector functions and immunoregulatory properties. We characterized the NKT cell response induced in C57BL/6 mice during a primary infection with Plasmodium yoelii sporozoites. We observed a heterogeneous NKT cell response that differed between liver and spleen. Hepatic NKT cells found in infected livers consisted mainly of CD1d-dependent CD4+ and double-negative (DN) NKT cells, whereas CD1d-independent NKT cells exhibiting a TCR(high) CD4(high) phenotype were prominent among splenic NKT cells during the infection. Hepatic and splenic NKT cells isolated from infected mice were activated and secreted mainly gamma interferon and tumor necrosis factor alpha in response to stimulation. Finally, P. yoelii-activated hepatic DN NKT cells inhibited the parasite's liver stage in a CD1d-dependent manner in vitro. However, experiments using B6.CD1d-deficient mice showed that CD1d and CD1d-restricted NKT cells are not necessary to control the parasite's development in vivo during neither the preerythrocytic stage nor the erythrocytic stage. Thus, our results show that a primary P. yoelii infection induces a heterogeneous and organ-specific response of NKT cells and that CD1d-dependent NKT cells play a minor role in the control of the development of Plasmodium in vivo in our model.     

Association of interleukin-4 and interleukin-1B gene variants with Larsen score progression in rheumatoid arthritis

OBJECTIVE: To perform a genetic association study using markers in the interleukin-1 (IL-1) gene cluster and the IL-4/IL-4 receptor system genes, seeking evidence for involvement in the onset or the erosive outcome of rheumatoid arthritis (RA).METHODS: We tested the allelic distribution of IL-1A (+4845), IL-1B (-511), IL-1B (+3954), IL-1RN (+2018), IL-4 variable number of tandem repeat (VNTR), and IL-4R (+1902) in 233 patients with RA, 99 with polymyalgia rheumatica, and 148 ethnically matched controls. We analyzed the frequency of these gene variants in respect to presence of disease, but also to the degree of radiologic erosions (Larsen score) as a function of disease duration in 157 patients who had available radiographs of both hands.RESULTS: None of the 6 genetic polymorphisms was significantly different in frequency between RA patients and healthy controls or patients with polymyalgia rheumatica. Among RA patients, the rarer (#2) alleles of IL-4 VNTR and IL-1B (-511) were both associated with a milder Larsen score progression: The slope of Larsen progression in the rare allele groups diverged significantly from those of the frequent allele groups after approximately 20 years of disease duration (P < 0.001).CONCLUSION: None of the markers tested were shown to be associated with increased or decreased risk of RA. The rarer alleles of IL-4 VNTR and IL-1B (-511) appear to be associated with a less severe course in RA of long duration.     

Repeated Nitrogen Dioxide Exposures and Eosinophilic Airway Inflammation in Asthmatics: A Randomized Crossover Study

Background: Nitrogen dioxide (NO₂), a ubiquitous atmospheric pollutant, may enhance the asthmatic response to allergens through eosinophilic activation in the airways. However, the effect of NO₂ on inflammation without allergen exposure is poorly studied.Objectives: We investigated whether repeated peaks of NO₂, at various realistic concentrations, induce changes in airway inflammation in asthmatics.Methods: Nineteen nonsmokers with asthma were exposed at rest in a double-blind, crossover study, in randomized order, to 200 ppb NO₂, 600 ppb NO₂, or clean air once for 30 min on day 1 and twice for 30 min on day 2. The three series of exposures were separated by 2 weeks. The inflammatory response in sputum was measured 6 hr (day 1), 32 hr (day 2), and 48 hr (day 3) after the first exposure, and compared with baseline values measured twice 10–30 days before the first exposure.Results: Compared with baseline measurements, the percentage of eosinophils in sputum increased by 57% after exposure to 600 ppb NO₂ (p = 0.003) but did not change significantly after exposure to 200 ppb. The slope of the association between the percentage of eosinophils and NO₂ exposure level was significant (p = 0.04). Eosinophil cationic protein in sputum was highly correlated with eosinophil count and increased significantly after exposure to 600 ppb NO₂ (p = 0.001). Lung function, which was assessed daily, was not affected by NO₂ exposure.Conclusions: We observed that repeated peak exposures of NO₂ performed without allergen exposure were associated with airway eosinophilic inflammation in asthmatics in a dose-related manner.Citation: Ezratty V, Guillossou G, Neukirch C, Dehoux M, Koscielny S, Bonay M, Cabanes PA, Samet JM, Mure P, Ropert L, Tokarek S, Lambrozo J, Aubier M. 2014. Repeated nitrogen dioxide exposures and eosinophilic airway inflammation in asthmatics: a randomized crossover study. Environ Health Perspect 122:850–855; http://dx.doi.org/10.1289/ehp.1307240     

Assessment of physical activity with a pedometer and its relationship with VO2max among adolescents in Switzerland

Summary Objectives: In the absence of a gold standard, the assessment of physical activity in children remains difficult. To record physical activity with a pedometer and to examine to what extent it is correlated with VO₂max.Methods: Survey on physical activity and fitness; 233 Swiss adolescents aged 11 to 15 carried a pedometer (Pedoboy^®) during seven consecutive days. VO₂max was estimated through an endurance shuttle run test.Results: The physical activity recorded by the pedometer did not vary from one day to the other (p>0.05). The physical activity was higher among boys than among girls (p<0.001) and higher among younger adolescents (6^th versus 8^th grade; p<0.001). The correlation between physical activity and estimated VO₂max was 0.30 (p<0.01).Conclusions: The use of a pedometer to assess physical activity over one entire week is feasible among adolescents. The record provided by the pedometer gives an objective measure of the usual physical activity and, as such, is relatively well correlated with aerobic capacity.

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Zusammenfassung Fragestellung: Mangels einer allgemein akzeptierten Wertskala verbleibt die Schätzung der physischen Aktivität der Kinder schwierig. Physische Aktivität mittels eines Pedometers zu messen und feststellen, in welchem Ausmass diese Aktivität mit VO₂max in Zusammenhang steht.Methoden: Untersuchung über physische Aktivität und körperliche Verfassung; 233 schweizerische Jugendliche im Alter von 11 bis 15 Jahren trugen einen Pedometer (Pedoboy^®) während sieben aufeinanderfolgenden Tagen. VO₂max wurde durch einen Dauerlauftest bewertet.Resultate: Die vom Pedometer registrierte physische Aktivität änderte sich nicht von einem Tag zum anderen (p>0.05). Die physische Aktivität war bei den jungen Männern höher als bei den jungen Frauen (p<0.001) und höher je jünger die Jugendlichen waren (6. Klassenstufe versus 8. Klassenstufe; p<0.01). Der Zusammenhang zwischen physischer Aktivität und geschätzte VO₂max war 0.30 (p<0.01).Schlussfolgerungen: Der Gebrauch eines Pedometers, um während einer ganzen Woche die physische Aktivität Jugendlicher zu schätzen, ist durchaus möglich. Die vom Pedometer registrierten Daten geben einen objektiven Anhaltspunkt für die normale physische Aktivität und stimmen mit der Aerobic-Kapazität einigermassen überein.

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Résumé Objectifs: En l'absence d'une méthode de référence acceptée par tous, l'évaluation de l'activité physique chez les enfants est difficile. Evaluer l'activité physique à l'aide d'un pédomètre et analyser la corrélation entre activité physique et VO₂max.Méthodes: Enquête sur l'activité et la condition physique; 233 adolescents suisses de 11 à 15 ans ont porté un pédomètre (Pedoboy^®) pendant sept jours consécutifs. La VO₂max a été calculée grâce au test d'endurance de course navette.Résultats: L'activité physique enregistrée par le pédomètre ne varie pas d'un jour à l'autre (p>0.05). Le niveau d'activité physique est plus élevé chez les garçons que chez les filles (p<0.001) et parmi les adolescents les plus jeunes (comparaison entre la 6ème année et la 8ème année; p<0.001). Le coefficient de corrélation entre l'activité physique mesurée par le pédomètre et la VO₂max est de 0.30 (p<0.01).Conclusions: Il est possible d'utiliser le pédomètre chez les adolescents pour évaluer l'activité physique sur une durée d'une semaine entière. Les données enregistrées par le pédomètre donnent une mesure objective du niveau d'activité et sont relativement bien corrélées avec la capacité aérobie.

     

Unintentional injuries among 16 to 20 year old students in Switzerland

In our society, accidents constitute a major public health problem, especially among youth. The objective of this paper was to describe the incidence of nonfatal injuries that required medical care among 16 to 20 year-old in Switzerland, its distribution by type of injury and whether there were differences by gender or by academic track and whether these injuries had sequels (hospitalisation, physical and psychological sequels). Overall, 28.3% of the sample reported at least one accident needing medical care in the previous 12 months, with males having more accidents than females and apprentices more than students. By type of accident, sports were the most frequently reported, followed by traffic, leisure time and work accidents. Half of males and one-third of females reported more than one accident, and 16% and 8% of them, respectively, reported four or more. Both physical and psychological sequels were more frequent among females, while hospitalisation was more frequent among males. Accident prevalence rates remain high among adolescents. Safety counselling and environmental measures need to be implemented.