The Acute Effects of Ischemic Preconditioning on Short-Duration Cycling: A Randomized Crossover Study

International Journal of Exercise Science 16(6): 148-158, 2023. There is recent interest from coaches and athletes regarding IPC as an effective way to generate better competitive outcomes. Regarding cycling specifically, the impact of IPC remains unclear. This study aimed to assess the effectiveness of IPC treatment for improving athletic performance during short-duration cycling. After the exclusion and inclusion criteria, there were 11 volunteers for the 3-minute cycling TT and 13 volunteers for the 6-minute cycling TT. All volunteers were competitive athletes of aerobic sports. The IPC treatment consisted of three alternating cycles of 5 minutes of 100% occlusion followed by 5 minutes of reperfusion to each leg. The sham treatment consisted of three alternating cycles of 1 minute of 100% occlusion followed by 1 minute of reperfusion to each leg. The main finding was that IPC significantly improved (p\u3c0.05) power output during 3-minute (4.22%) and 6-minute (2.29%) cycling TT relative to a sham. Additionally, about one-third of our participants required a tourniquet pressure higher than 220 mmHg to achieve 100% occlusion. These findings indicate ischemic preconditioning, administered bilaterally as three rounds of 5 minutes of total occlusion and ensuing reperfusion 20 minutes before a cycling TT, significantly enhanced average power output

Crystal structures of a halophilic archaeal malate synthase from Haloferax volcanii and comparisons with isoforms A and G

<p>Abstract</p> <p>Background</p> <p>Malate synthase, one of the two enzymes unique to the glyoxylate cycle, is found in all three domains of life, and is crucial to the utilization of two-carbon compounds for net biosynthetic pathways such as gluconeogenesis. In addition to the main isoforms A and G, so named because of their differential expression in <it>E. coli </it>grown on either acetate or glycolate respectively, a third distinct isoform has been identified. These three isoforms differ considerably in size and sequence conservation. The A isoform (MSA) comprises ~530 residues, the G isoform (MSG) is ~730 residues, and this third isoform (MSH-halophilic) is ~430 residues in length. Both isoforms A and G have been structurally characterized in detail, but no structures have been reported for the H isoform which has been found thus far only in members of the halophilic Archaea.</p> <p>Results</p> <p>We have solved the structure of a malate synthase H (MSH) isoform member from <it>Haloferax volcanii </it>in complex with glyoxylate at 2.51 Å resolution, and also as a ternary complex with acetyl-coenzyme A and pyruvate at 1.95 Å. Like the A and G isoforms, MSH is based on a β8/α8 (TIM) barrel. Unlike previously solved malate synthase structures which are all monomeric, this enzyme is found in the native state as a trimer/hexamer equilibrium. Compared to isoforms A and G, MSH displays deletion of an N-terminal domain and a smaller deletion at the C-terminus. The MSH active site is closely superimposable with those of MSA and MSG, with the ternary complex indicating a nucleophilic attack on pyruvate by the enolate intermediate of acetyl-coenzyme A.</p> <p>Conclusions</p> <p>The reported structures of MSH from <it>Haloferax volcanii </it>allow a detailed analysis and comparison with previously solved structures of isoforms A and G. These structural comparisons provide insight into evolutionary relationships among these isoforms, and also indicate that despite the size and sequence variation, and the truncated C-terminal domain of the H isoform, the catalytic mechanism is conserved. Sequence analysis in light of the structure indicates that additional members of isoform H likely exist in the databases but have been misannotated.</p

15th Annual Environmental Law Institute

Materials from the 15th Annual Environmental Law Institute held by UK/CLE in March 1999

Reliability and validity of the Adolescent Stress Questionnaire in a sample of European adolescents--the HELENA study

BACKGROUND: Since stress is hypothesized to play a role in the etiology of obesity during adolescence, research on associations between adolescent stress and obesity-related parameters and behaviours is essential. Due to lack of a well-established recent stress checklist for use in European adolescents, the study investigated the reliability and validity of the Adolescent Stress Questionnaire (ASQ) for assessing perceived stress in European adolescents. METHODS: The ASQ was translated into the languages of the participating cities (Ghent, Stockholm, Vienna, Zaragoza, Pecs and Athens) and was implemented within the HELENA cross-sectional study. A total of 1140 European adolescents provided a valid ASQ, comprising 10 component scales, used for internal reliability (Cronbach α) and construct validity (confirmatory factor analysis or CFA). Contributions of socio-demographic (gender, age, pubertal stage, socio-economic status) characteristics to the ASQ score variances were investigated. Two-hundred adolescents also provided valid saliva samples for cortisol analysis to compare with the ASQ scores (criterion validity). Test-retest reliability was investigated using two ASQ assessments from 37 adolescents. RESULTS: Cronbach α-values of the ASQ scales (0.57 to 0.88) demonstrated a moderate internal reliability of the ASQ, and intraclass correlation coefficients (0.45 to 0.84) established an insufficient test-retest reliability of the ASQ. The adolescents' gender (girls had higher stress scores than boys) and pubertal stage (those in a post-pubertal development had higher stress scores than others) significantly contributed to the variance in ASQ scores, while their age and socio-economic status did not. CFA results showed that the original scale construct fitted moderately with the data in our European adolescent population. Only in boys, four out of 10 ASQ scale scores were a significant positive predictor for baseline wake-up salivary cortisol, suggesting a rather poor criterion validity of the ASQ, especially in girls. CONCLUSIONS: In our European adolescent sample, the ASQ had an acceptable internal reliability and construct validity and the adolescents' gender and pubertal stage systematically contributed to the ASQ variance, but its test-retest reliability and criterion validity were rather poor. Overall, the utility of the ASQ for assessing perceived stress in adolescents across Europe is uncertain and some aspects require further examination.The HELENA Study takes place with the financial support of the European Community Sixth RTD Framework Programme (Contract FOOD-CT-2005-007034)