New initiatives and developments at JEB Handel, Michaela J P; Hoppeler, Hans H
Journal of experimental biology,
01/2018, Letnik:
221, Številka:
Pt 1
Journal Article
Temperature plays a critical role in determining the biology of ectotherms. Many animals have evolved mechanisms that allow them to compensate biological rates, i.e. adjust biological rates to ...overcome thermodynamic effects. For low energy-organisms, such as bivalves, the costs of thermal compensation may be greater than the benefits, and thus prohibitive. To examine this, two experiments were designed to explore thermal compensation in Unio tumidus. Experiment 1 examined seasonal changes in behaviour in U. tumidus throughout a year. Temperature had a clear effect on burrowing rate with no evidence of compensation. Valve closure duration and frequency were also strongly affected by seasonal temperature change, but there was slight evidence of partial compensation. Experiment 2 examined oxygen consumption during burrowing, immediately following valve opening and at rest in summer (24°C), autumn (14°C), winter (4°C), and spring (14°C) acclimatized U. tumidus. Again, there was little evidence of burrowing rate compensation, but some evidence of partial compensation of valve closure duration and frequency. None of the oxygen compensation rates showed any evidence of thermal compensation. Thus, in general, there was only very limited evidence of thermal compensation of behaviour and no evidence of thermal compensation of oxygen compensation rates. Based upon this evidence, we argue that there is no evolutionary pressure for these bivalves to compensate these biological rates. Any pressure may be to maintain or even lower oxygen consumption as their only defence against predation is to close their valves and wait. An increase in oxygen consumption will be detrimental in this regard so the cost of thermal compensation may outweigh the benefits.
•The freshwater mussel Unio tumidus experiences significant seasonal temperature variation.•Burrowing rate and valve closure behaviour vary directly with temperature.•Oxygen consumption also varies directly with temperature.•There is little evidence of thermal compensation in Unio tumidus.•The costs of compensation in a low-energy species like Unio tumidus must outweigh the benefits.
Skeletal muscle complaints are a common consequence of cholesterol‐lowering therapy. Transverse tubular (T‐tubular) vacuolations occur in patients having statin‐associated myopathy and, to a lesser ...extent, in statin‐treated patients without myopathy. We have investigated quantitative changes in T‐tubular morphology and looked for early indicators of T‐tubular membrane repair in skeletal muscle biopsy samples from patients receiving cholesterol‐lowering therapy who do not have myopathic side effects. Gene expression and protein levels of incipient membrane repair proteins were monitored in patients who tolerated statin treatment without myopathy and in statin‐naive subjects. In addition, morphometry of the T‐tubular system was performed. Only the gene expression for annexin A1 was up‐regulated, whereas the expression of other repair genes remained unchanged. However, annexin A1 and dysferlin protein levels were significantly increased. In statin‐treated patients, the volume fraction of the T‐tubular system was significantly increased, but the volume fraction of the sarcoplasmic reticulum remained unchanged. A complex surface structure in combination with high mechanical loads makes skeletal muscle plasma membranes susceptible to injury. Ca2+‐dependent membrane repair proteins such as dysferlin and annexin A1 are deployed at T‐tubular sites. The up‐regulation of annexin A1 gene expression and protein points to this protein as a biomarker for T‐tubular repair.—Voigt, T., Sebald, H.‐J., Schoenauer, R., Levano, L., Girard, T., Hoppeler, H.H., Babiychuk, E.B., Draeger, A. Annexin A1 is a biomarker of T‐tubular repair in skeletal muscle of nonmyopathic patients undergoing statin therapy. FASEB J. 27, 2156–2164 (2013). www.fasebj.org
Purpose. Recreational cross-country skiers can benefit from a performance diagnostic when planning a training program. The aim of this study was to establish a simple test protocol to measure ...endurance capacity and provide training recommendations. Methods. The relationship between endurance performance and cross-country skiing technique was assessed using two tests. First, a lactate threshold test whereby running speed was determined on a treadmill at 4 mmol/l blood lactate concentration. Second, participants completed a variation of the Cooper test using skating technique on flat terrain to determine the distance covered in 12 min and maximum heart rate. Results. There was a correlative (r = 0.18 respectivelly R2 = 0.43) relationship of between the distance covered in the Cooper test and treadmill running speed at 4 mmol/l blood lactate concentration. Conclusions. The two tests allow recreational athletes to rank themselves with regards to their endurance capacity within a population. The relationship between distance covered and maximum heart rate can indicate whether future training should focus on technical or physical improvement.
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