bluuebunny/crossref_metadata_2025 huggingface dataset:
Noninvasive measurement of the tension-time index in children with neuromuscular disease
Authors: Mulreany Laura T. , Weiner Daniel J. , McDonough Joseph M. , Panitch Howard B. , Allen Julian L.
Published: March 2015

Respiratory muscle weakness is common in children with neuromuscular disease (NMD). We hypothesized that weakness puts them at risk for respiratory muscle fatigue, a harbinger of chronic respiratory failure. We therefore measured a noninvasive index of respiratory muscle fatigue, the tension-time index of the respiratory muscles (TTmus), in 11 children with NMD and 13 control subjects. Spirometric flow rates and maximal inspiratory pressure were significantly lower in the NMD group than in controls (43 ± 23 vs. 99 ± 21 cmH2O, P < 0.001). The mean TTmus was significantly higher in the NMD group than in controls (0.205 ± 0.117 vs. 0.054 ± 0.021, P < 0.001). The increase in TTmus was primarily due to an increase in the ratio of average mean inspiratory pressure to maximal inspiratory pressure, indicating decreased respiratory muscle strength reserve. We found a significant correlation between TTmus and the residual volume-to-total lung capacity ratio ( r = 0.504, P = 0.03) and a negative correlation between TTmus and forced expiratory volume in 1 s ( r = -0.704, P < 0.001). In conclusion, children with NMD are prone to respiratory muscle fatigue. TTmus may be useful in assessing tolerance during weaning from mechanical ventilation, identifying impending respiratory failure, and aiding in the decision to institute therapies.
Acoustic rhinometry in dog and cat compared with a fluid-displacement method and magnetic resonance imaging
Authors: Straszek Sune P. , Taagehøj Finn , Graff Søren , Pedersen Ole F.
Published: March 2015

An increasing number of studies have used acoustic rhinometry (AR) for study of pharmacological interventions on nasal cavity dimensions in dogs and cats, but there have been no attempts to validate AR in these species. This is done in the present study. We compared area-distance relationships of nasal cavities from five decapitated dogs (3.5–41 kg) and cats (3.8–6 kg). AR was compared with magnetic resonance (MR) imaging and a fluid-displacement method (FDM) using perfluorocarbon. AR measured 88% (98–79%) (mean and 95% confidence interval) of nasal cavity volume in dogs determined by FDM and 71% (83–59%) in cats. AR markedly underestimated nasal cavity dimensions when minimum areas were below 0.1 cm2 in dogs and 0.05 cm2 in cats. AR underestimation increased with the severity of the constriction and with distance. Cross-sectional areas in the deeper parts of the cavity measured 76% (99–54%) of FDM in dogs and 52% (66–39%) in cats. AR agreed well with MR, especially in the deeper part of the cavity. MR images showed that the nasal cavities had a very complex structure not expected to be reproduced by AR. MR could not be considered a “gold standard” because definition of the cross-sectional area of the lumen depended critically on subjective choices. FDM produced repeatable measurements and possibly offers the most adequate reference in future evaluation of AR. AR underestimated what we believed were the most correct cross-sectional areas determined by FDM, especially in the deeper part of the dog and cat nasal cavities. Despite these difficulties, AR has been shown to be useful to describe qualitative changes in cross-sectional area.
Effects of sleep pressure on endogenous cardiac autonomic activity and body temperature
Authors: Holmes Alexandra L. , Burgess Helen J. , Dawson Drew
Published: March 2015

This study investigated the effects of variations in sleep pressure on cardiac autonomic activity and body temperature. In a counterbalanced design, 12 healthy, young subjects (6 men and 6 women) remained recumbent during 30 h of wakefulness (high sleep pressure) and 6 h of wakefulness (low sleep pressure). Both periods of wakefulness were immediately followed by a sleep opportunity, and the first 2 h of sleep were analyzed. During extended hours of wakefulness, a reduction in heart rate was mediated by a decline in cardiac sympathetic activity (measured via preejection period) and the maintenance of cardiac parasympathetic activity (measured via respiratory sinus arrhythmia). In subsequent high-pressure sleep, parasympathetic activity was amplified and sympathetic activity was negatively associated with electroencephalographic slow-wave activity. Sleep deprivation had no impact on foot temperature, but it did alter the pattern of change in core body temperature. A downregulation of cardiac autonomic activity during both extended hours of wakefulness and subsequent sleep may respectively provide “protection” and “recovery” from the temporal extension of cardiac demand.
Strength training reduces arterial blood pressure but not sympathetic neural activity in young normotensive subjects
Authors: Carter Jason R. , Ray Chester A. , Downs Emily M. , Cooke William H.
Published: March 2015

The effects of resistance training on arterial blood pressure and muscle sympathetic nerve activity (MSNA) at rest have not been established. Although endurance training is commonly recommended to lower arterial blood pressure, it is not known whether similar adaptations occur with resistance training. Therefore, we tested the hypothesis that whole body resistance training reduces arterial blood pressure at rest, with concomitant reductions in MSNA. Twelve young [21 ± 0.3 (SE) yr] subjects underwent a program of whole body resistance training 3 days/wk for 8 wk. Resting arterial blood pressure ( n = 12; automated sphygmomanometer) and MSNA ( n = 8; peroneal nerve microneurography) were measured during a 5-min period of supine rest before and after exercise training. Thirteen additional young (21 ± 0.8 yr) subjects served as controls. Resistance training significantly increased one-repetition maximum values in all trained muscle groups ( P < 0.001), and it significantly decreased systolic (130 ± 3 to 121 ± 2 mmHg; P = 0.01), diastolic (69 ± 3 to 61 ± 2 mmHg; P = 0.04), and mean (89 ± 2 to 81 ± 2 mmHg; P = 0.01) arterial blood pressures at rest. Resistance training did not affect MSNA or heart rate. Arterial blood pressures and MSNA were unchanged, but heart rate increased after 8 wk of relative inactivity for subjects in the control group (61 ± 2 to 67 ± 3 beats/min; P = 0.01). These results indicate that whole body resistance exercise training might decrease the risk for development of cardiovascular disease by lowering arterial blood pressure but that reductions of pressure are not coupled to resistance exercise-induced decreases of sympathetic tone.
Aged men display blunted biorhythmic variation of muscle performance and physiological responses
Authors: Deschenes Michael R. , Bronson Laurie L. , Cadorette Meredith P. , Powers Julia E. , Weinlein John C.
Published: March 2015

Aging is known to disrupt the “biological clock” that governs physiological variables at rest. This study sought to determine whether aged men demonstrated biorhythmic variation in muscle performance during resistance exercise and physiological responses to that stimulus. Ten aged (75.6 ± 1.6 yr; mean ± SE) men completed an isokinetic testing protocol of knee extensors and flexors at 0800, 1200, 1600, and 2000 h. Although time of day variation in peak torque was detectable, significant ( P ≤ 0.05) oscillation was established only in the knee flexors at 3.14 rad/s. Heart rate, blood pressure, and rectal temperature displayed no significant variation, but trends ( P < 0.10) in oscillation of postexercise blood pressure and rectal temperature were noted. Temporal patterns in biorhythmic variation of muscle performance, as well as thermal and cardiovascular measures, emulated those observed in a previous study involving young men where the magnitude of variation was sufficient to achieve statistical significance. Similar to our earlier findings in young men, however, pre- and postexercise testosterone and cortisol concentrations demonstrated significant variation among aged men. These data confirm the blunting of biorhythmic variation in muscle performance and physiological variables, except for circulating hormones, in aged men.