The effects of fasting on swimming performance in juvenile qingbo (Spinibarbus sinensis) at two temperatures

We measured the following variables to investigate the effects of fasting and temperature on swimming performance in juvenile qingbo (Spinibarbus sinensis): the critical swimming speed (U_crit), resting metabolic rate ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$ and active metabolic rate ${(\dot{\mathrm{M}}O}_{2active})$ of fish fasting for 0 (control), 1, 2 and 4 weeks at low and high acclimation temperatures (15 and 25 °C). Both fasting treatment and temperature acclimation had significant effects on all parameters measured (P<0.05). Fasting at the higher temperature had a negative effect on all measured parameters after 1 week (P<0.05). However, when acclimated to the lower temperature, fasting had a negative effect on U_crit until week 2 and on ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$, ${(\dot{\mathrm{M}}O}_{\mathrm{2active}})$ and metabolic scope (MS, ${(\dot{\mathrm{M}}O}_{\mathrm{2active}})$–${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$) until week 4 (P<0.05). The values of all parameters at the lower temperature were significantly lower than those at the higher temperature in the identical fasting period groups except for ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$ of the fish that fasted for 2 weeks. The relationship between fasting time (T) and U_crit was described as U_crit(15)=−0.302T²−0.800T+35.877 (r=0.781, n=32, P<0.001) and U_crit(25)=0.471T²−3.781T+50.097 (r=0.766, n=32, P<0.001₎ at 15 and 25 °C, respectively. The swimming performance showed less decrease in the early stage of fasting but more decrease in the later stage at the low temperature compared to the high temperature, which might be related to thermal acclimation time, resting metabolism, respiratory capacity, energy stores, enzyme activity in muscle tissue and energy substrate utilization changes with fasting between low and high temperatures. The divergent response of the swimming performance to fasting in qingbo at different temperatures might be an adaptive strategy to seasonal temperature and food resource variation in their habitat.     

A Model for the Transient Subdiffusive Behavior of Particles in Mucus

In this study we have applied a model to explain the reported subdiffusion of particles in mucus, based on the measured mean squared displacements ($MSD$). The model considers Brownian diffusion of particles in a confined geometry, made from permeable membranes. The applied model predicts a normal diffusive behavior at very short and long time lags, as observed in several experiments. In between these timescales, we find that the “subdiffusive” regime is only a transient effect, $MSD\propto {\tau }^{\alpha },\alpha <1$. The only parameters in the model are the diffusion-coefficients at the limits of very short and long times, and the distance between the permeable membranes L. Our numerical results are in agreement with published experimental data for realistic assumptions of these parameters. Finally, we show that only particles with a diameter less than 40 nm are able to pass through a mucus layer by passive Brownian motion.     

Sleep Apnea Detection from Single-Lead ECG Using Features Based on ECG-Derived Respiration (EDR) Signals

Background and objective

One of the important applications of non-invasive respiration monitoring using ECG signal is the detection of obstructive sleep apnea (OSA). ECG-derived respiratory (EDR) signals, contribute to useful information about apnea occurrence. In this paper, two EDR extraction methods are proposed, and their application in automatic OSA detection using single-lead ECG is investigated.

A Comparative Study of Two Ambulatory Core Temperature Assessment Methods

Background. Given the need to identify reliable non-invasive solutions for core temperature ambulatory monitoring, the purpose of this study was to evaluate the performance of zero-heat-flux (ZHF) temperature sensor on the forehead ($T_{\mathrm{COzhf}}$) by comparing it with intestinal temperature ($T_{\mathrm{COpill}}$) in different ambient and physiological conditions.Methods. Seven trained male subjects were followed during a 45-min rest period (STA) and a 25-min self-regulated cycling exercise performed in neutral (TMP, 22.8?°C) and hot (HOT, 38.5 °C) ambient temperature.Results.$T_{\mathrm{COzhf}}$ values differed from $T_{\mathrm{COpill}}$ of ?0.23 ± 0.13 in STA, 0.15 ± 0.30 °C in TMP and $0.28\pm 0.38$?°C in HOT. The 95% limits of agreement showed an acceptable bias between $T_{\mathrm{COzhf}}$ and $T_{\mathrm{COpill}}$ in STA (±0.26?°C), but not in TMP and HOT (±0.60 and ±0.75?°C).Conclusion. The non-invasive ZHF sensor gave an accurate estimation of $T_{\mathrm{COpill}}$ in steady state but not during exercise. However, complementary results let suppose that ZHF performance is not affected by ambient conditions and could be a relevant alternative for deep body temperature measurement during whole-body heat stress.