bluuebunny/crossref_metadata_2025 huggingface dataset:
Exercise causes tissue-specific enhancement of endothelin-1 mRNA expression in internal organs
Authors: Maeda Seiji , Miyauchi Takashi , Kobayashi Tsutomu , Goto Katsutoshi , Matsuda Mitsuo
Published: December 2017

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide, which also potentiates contractions to norepinephrine in human internal mammary and coronary vessels. Exercise causes a redistribution of blood flow, i.e., the increase in working muscles that is partly attributable to a decrease in visceral blood flow. We hypothesized that exercise causes a tissue-specific increase in ET-1 expression in internal organs. We studied whether exercise affects expression of preproET-1 mRNA in the kidneys and lungs. The rats performed treadmill running (0% grade) for 45 min at a speed of 25 m/min. The plasma concentrations of ET-1, epinephrine, and norepinephrine were greater in the exercise rats than in the sedentary control rats. The expression of preproET-1 mRNA in the kidneys was markedly higher in the exercise rats than in the sedentary control rats, whereas that in the lungs did not differ between the two groups. Therefore, the present study provides a possibility that the exercise-induced increase in production of ET-1 in the kidneys causes vasoconstriction and hence decreases blood flow in the kidneys through its direct vasoconstrictive action and/or its indirect effect of enhancing vasoconstrictions to norepinephrine.
Dynamics of segmental extracellular volumes during changes in body position by bioimpedance analysis
Authors: Zhu Fansan , Schneditz Daniel , Wang Erjun , Levin Nathan W.
Published: December 2017

Extracellular volume (ECV) of arms, trunk, and legs determined from segmental bioimpedance data in 11 healthy men (31.6 ± 7 yr) obtained at the end of a 30-min equilibration phase in the supine body position was compared with ECV determined from whole body measurements (ECVWB). ECV was calculated from extracellular resistance ( R ECV) identified from the bioimpedance spectrum for a range of 10 frequencies. Whole body R ECV (527.6 ± 55.6 Ω) was equal to the sum of R ECV in the arms, trunk, and legs (241.6 ± 36.3, 49.2 ± 5.1, and 236.3 ± 25.5 Ω, respectively). The sum of equilibrated ECV in arms (1.31 ± 0.25 liters), trunk (10.08 ± 1.65 liters), and legs (2.80 ± 0.82 liters) was smaller than ECVWB (20.90 ± 2.59 liters). In six subjects who changed from a standing to a supine body position, ECV decreased in arms (−2.59 ± 2.51%, P = NS) and legs (−10.96 ± 3.02%, P < 0.05) but increased in the trunk (+4.2 ± 3.2%, P< 0.05). ECVWB also decreased (−4.98 ± 1.41%, P < 0.05). However, the sum of segmental extracellular volumes remained unchanged (−0.06 ± 0.07%, P= NS). The sum of segmental ECVs is not sensitive to changes in body position, which otherwise interferes with the estimation of ECV in bioimpedance analysis when ECVWBis used.
Transit time dispersion in the pulmonary arterial tree
Authors: Clough Anne V. , Haworth Steven T. , Hanger Christopher C. , Wang Jerri , Roerig David L. , Linehan John H. , Dawson Christopher A.
Published: December 2017

Knowledge of the contributions of arterial and venous transit time dispersion to the pulmonary vascular transit time distribution is important for understanding lung function and for interpreting various kinds of data containing information about pulmonary function. Thus, to determine the dispersion of blood transit times occurring within the pulmonary arterial and venous trees, images of a bolus of contrast medium passing through the vasculature of pump-perfused dog lung lobes were acquired by using an X-ray microfocal angiography system. Time-absorbance curves from the lobar artery and vein and from selected locations within the intrapulmonary arterial tree were measured from the images. Overall dispersion within the lung lobe was determined from the difference in the first and second moments (mean transit time and variance, respectively) of the inlet arterial and outlet venous time-absorbance curves. Moments at selected locations within the arterial tree were also calculated and compared with those of the lobar artery curve. Transit times for the arterial pathways upstream from the smallest measured arteries (200-μm diameter) were less than ∼20% of the total lung lobe mean transit time. Transit time variance among these arterial pathways (interpathway dispersion) was less than ∼5% of the total variance imparted on the bolus as it passed through the lung lobe. On average, the dispersion that occurred along a given pathway (intrapathway dispersion) was negligible. Similar results were obtained for the venous tree. Taken together, the results suggest that most of the variation in transit time in the intrapulmonary vasculature occurs within the pulmonary capillary bed rather than in conducting arteries or veins.
Visual system maldevelopment disrupts extraocular muscle-specific myosin expression
Authors: Brueckner Jennifer K. , Porter John D.
Published: December 2017

The genetic and epigenetic influences that are responsible for the establishment and maintenance of the unique phenotype of the extraocular muscles (EOMs) are poorly understood. A role for visual cues in shaping EOM maturation was assessed in rats by using two visual deprivation paradigms, dark rearing and monocular deprivation. Isoforms of the contractile protein myosin heavy chain (MHC) were used as an index of phenotypic change in developing and adult EOMs after these visual insults. In rats that were dark reared during the visual critical period, the proportion of EOM fibers expressing either fast or slow MHCs was decreased significantly. EOM-specific myosin was also sensitive to dark rearing during the critical period, as evidenced by a significant decrease in its mRNA in EOMs from these rats. EOM-specific MHC did not change in either dark-reared rats returned to normally illuminated conditions or in adult rats denied visual experience for a similar time period. These data suggest that there may be a critical period during development when alterations in visual activity have significant consequences for the eye muscle phenotype. In contrast to dark rearing, monocular deprivation had a minimal effect on expression of the typical myosin isoforms and no effect on EOM-specific myosin expression. Collectively, these data confirm the hypothesis that visual input to the oculomotor system during development modulates EOM-specific MHC expression.
ATP-sensitive K+channel blocker glibenclamide and diaphragm fatigue during normoxia and hypoxia
Authors: Van Lunteren Erik , Moyer Michelle , Torres Augusto
Published: December 2017

The role of ATP-sensitive K+channels in skeletal muscle contractile performance is controversial: blockers of these channels have been found to not alter, accelerate, or attenuate fatigue. The present study reexamined whether glibenclamide affects contractile performance during repetitive contraction. Experiments systematically assessed the effects of stimulation paradigm, temperature, and presence of hypoxia and in addition compared intertrain with intratrain fatigue. Adult rat diaphragm muscle strips were studied in vitro. At 37°C and normoxia, glibenclamide did not significantly affect any measure of fatigue during continuous 5- or 100-Hz or intermittent 20-Hz stimulation but progressively prolonged relaxation time during 20-Hz stimulation. At 20°C and normoxia, neither force nor relaxation rate was affected significantly by glibenclamide during 20-Hz stimulation. At 37°C and hypoxia, glibenclamide did not significantly affect fatigue at 5-Hz or intertrain fatigue during 20-Hz stimulation but reduced intratrain fatigue and prolonged relaxation time during 20-Hz stimulation. These findings indicate that, although ATP-sensitive K+channels may be activated during repetitive contraction, their activation has only a modest effect on the rate of fatigue development.
Oral [13C]glucose oxidation during prolonged exercise after high- and low-carbohydrate diets
Authors: Péronnet F. , Rhéaume N. , Lavoie C. , Hillaire-Marcel C. , Massicotte D.
Published: December 2017

The effect of a diet either high or low in carbohydrates (CHO) on exogenous 13C-labeled glucose oxidation (200 g) during exercise (ergocycle: 120 min at 64.0 ± 0.5% maximal oxygen uptake) was studied in six subjects. Between 40 and 80 min, exogenous glucose oxidation was significantly higher after the diet low in CHO (0.63 ± 0.05 vs. 0.52 ± 0.04 g/min), but this difference disappeared between 80 and 120 min (0.71 ± 0.03 vs. 0.69 ± 0.04 g/min). The oxidation rate of plasma glucose, computed from the volume of13CO2produced the13C-to-12C ratio in plasma glucose at 80 min, and of glucose released from the liver, computed from the difference between plasma glucose and exogenous glucose oxidation, was higher after the diet low in CHO (1.68 ± 0.26 vs. 1.41 ± 0.17 and 1.02 ± 0.20 vs. 0.81 ± 0.14 g/min, respectively). In contrast the oxidation rate of glucose plus lactate from muscle glycogen (computed from the difference between total CHO oxidation and plasma glucose oxidation) was lower (0.31 ± 0.35 vs. 1.59 ± 0.20 g/min). After a diet low in CHO, the oxidation of exogenous glucose and of glucose released from the liver is increased and partly compensates for the reduction in muscle glycogen availability and oxidation.
Leak measurements in spontaneously breathing premature newborns by using the flow-through technique
Authors: Foitzik B. , Schmidt M. , Windstetter D. , Wauer R. R. , Schmalisch G.
Published: December 2017

A new method for measuring and correcting air leaks during lung-function testing in infants has been validated in vitro and in vivo by using a flow-through system that measured the inflow and outflow of a face mask. An adjustable leak was quantified by using suction flow to validate the accuracy of leak measurements. To validate the leak correction, the volume of a pump was measured with different air leaks (0–30%). The method developed was tested in 67 infants breathing spontaneously. There was good agreement between measured and simulated leaks ( r = 0.998, P < 0.001; 95% limits of agreement were −0.3 and 0.1%, respectively). The volume was generally underestimated because of leaks, and the volume error was up to 94% compared with the maximum error of 5% after leak correction. With continuous leak measurements in vivo, there were <4% actual leaks (median 2.6%), and we did not observe any leaks in >7% of cases. The leak correction improved the accuracy of ventilatory measurements. The monitoring of leaks is helpful for airtight placement of the face mask and for prevention of serious measurement errors caused by leaks.
Irregularities and power law distributions in the breathing pattern in preterm and term infants
Authors: Frey U. , Silverman M. , Barabási A. L. , Suki B.
Published: December 2017

Unlike older children, young infants are prone to develop unstable respiratory patterns, suggesting important differences in their control of breathing. We examined the irregular breathing pattern in infants by measuring the time interval between breaths (“interbreath interval”; IBI) assessed from abdominal movement during 2 h of sleep in 25 preterm infants at a postconceptional age of 40.5 ± 5.2 (SD) wk and in 14 term healthy infants at a postnatal age of 8.2 ± 4 wk. In 10 infants we performed longitudinal measurements on two occasions. We developed a threshold algorithm for the detection of a breath so that an IBI included an apneic period and potentially some periods of insufficient tidal breathing excursions (hypopneas). The probability density distribution ( P ) of IBIs follows a power law, P (IBI)∼IBI−α, with the exponent α providing a statistical measurement of the relative risk of insufficient breathing. With maturation, α increased from 2.62 ± 0.4 at 41.2 ± 3.6 wk to 3.22 ± 0.4 at 47.3 ± 6.4 wk postconceptional age, indicating a decrease in long hypopneas (for paired data P = 0.002). The statistical properties of IBI were well reproduced in a model of the respiratory oscillator on the basis of two hypotheses: 1) tonic neural inputs to the respiratory oscillator are noisy; and 2) the noise explores a critical region where IBI diverges with decreasing tonic inputs. Accordingly, maturation of infant respiratory control can be explained by the tonic inputs moving away from this critical region. We conclude that breathing irregularities in infants can be characterized by α, which provides a link between clinically accessible data and the neurophysiology of the respiratory oscillator.
Effects of 5-day hypoxia on cardiac adrenergic neurotransmission in rats
Authors: Mardon Karine , Merlet Pascal , Syrota André , Mazière Bernard
Published: December 2017

Chronic hypoxia induces an overall sympathetic hyperactivation associated with a myocardial β-receptor desensitization. The mechanisms involved in this desensitization were evaluated in 32 male Wistar rats kept in a hypobaric pressure chamber ([Formula: see text] = 40 Torr, atmospheric pressure = 450 Torr) for 5 days. In hypoxic compared with normoxic conditions, plasma norepinephrine (NE) levels were higher (2.1 ± 0.7 vs. 0.6 ± 0.2 ng/ml) with no difference in the plasma epinephrine levels (2.2 ± 0.7 vs. 1.8 ± 0.3 ng/ml). In hypoxia neuronal NE uptake measured by [3H]NE was decreased by 32% in the right ventricle (RV) and by 35% in the left ventricle (LV), and [3H]mazindol in vitro binding showed a decrease in uptake-1 carrier protein density by 38% in the RV and by 41% in the LV. In vitro binding assays with [3H]CGP-12177 indicate β-adrenoceptor density reduced by 40% in the RV and by 32% in the LV, and this was due to reduced β1-subtype fraction (competition binding experiments with practolol). Hypoxia reduced the production of cAMP induced by isoproterenol (36% decrease in the RV and 41% decrease in the LV), 5′-guanylylimododiphosphate (40% decrease in the RV and 42% decrease in the LV), and forskolin (39% decrease in the RV and 41% decrease in the LV) but did not alter the effect of MnCl2and NaF. Quantitation of inhibitory G-protein α-subunit by immunochemical analysis showed a 46% increase in the cardiac-specific isoform[Formula: see text] in hypoxic hearts. The present data demonstrate that in rats 5-day hypoxia leads to changes in pre- and postsynaptic myocardial adrenergic function. The myocardial desensitization associated with both a reduction in externalized β1-adrenoceptor and an increase in inhibitory G-protein subunit may be caused by increased synaptic NE levels due to impaired uptake-1 system.
Continuous measurement of tympanic temperature with a new infrared method using an optical fiber
Authors: Shibasaki Manabu , Kondo Narihiko , Tominaga Hirotaka , Aoki Ken , Hasegawa Eiichi , Idota Yoshiyuki , Moriwaki Toshimichi
Published: December 2017

The purpose of this study was to investigate the utility of an infrared tympanic thermometry by using an optical fiber for measuring tympanic temperature (Tty). In the head cooling and facial fanning tests during normothermia, right Tty measured by this method (infrared-Tty) and esophageal temperature (Tes) were not affected by decreased temple and forehead skin temperatures, suggesting that the infrared sensor in this system measured the infrared radiation from the tympanic membrane selectively. Eight male subjects took part in passive-heat-stress and progressive-exercise tests. No significant differences among infrared-Tty, the left Tty measured by thermistor (contact-Tty), and Tes were observed at rest or at the end of each experiment, and there was no significant difference in the increase in these core temperatures from rest to the end. Furthermore, there were no significant differences in the core temperature threshold at the onset of sweating and slope (the relationship of sweating rate vs. infrared-Tty and vs. contact-Tty). These results suggest that this method makes it possible to measure Tty accurately, continuously, and more safely.
Exertional fatigue, sleep loss, and negative energy balance increase susceptibility to hypothermia
Authors: Young Andrew J. , Castellani John W. , O’Brien Catherine , Shippee Ronald L. , Tikuisis Peter , Meyer Lloyd G. , Blanchard Laurie A. , Kain James E. , Cadarette Bruce S. , Sawka Michael N.
Published: December 2017

The purpose of this study was to determine how chronic exertional fatigue and sleep deprivation coupled with negative energy balance affect thermoregulation during cold exposure. Eight men wearing only shorts and socks sat quietly during 4-h cold air exposure (10°C) immediately after (<2 h, A) they completed 61 days of strenuous military training (energy expenditure ∼4,150 kcal/day, energy intake ∼3,300 kcal/day, sleep ∼4 h/day) and again after short (48 h, SR) and long (109 days, LR) recovery. Body weight decreased 7.4 kg from before training to A, then increased 6.4 kg by SR, with an additional 6.4 kg increase by LR. Body fat averaged 12% during A and SR and increased to 21% during LR. Rectal temperature (Tre) was lower before and during cold air exposure for A than for SR and LR. Tre declined during cold exposure in A and SR but not LR. Mean weighted skin temperature (T sk) during cold exposure was higher in A and SR than in LR. Metabolic rate increased during all cold exposures, but it was lower during A and LR than SR. The mean body temperature (0.67 Tre + 0.33T sk) threshold for increasing metabolism was lower during A than SR and LR. Thus chronic exertional fatigue and sleep loss, combined with underfeeding, reduced tissue insulation and blunted metabolic heat production, which compromised maintenance of body temperature. A short period of rest, sleep, and refeeding restored the thermogenic response to cold, but thermal balance in the cold remained compromised until after several weeks of recovery when tissue insulation had been restored.
Expiratory flow limitation and intrinsic positive end-expiratory pressure in obesity
Authors: Pankow W. , Podszus T. , Gutheil T. , Penzel T. , Peter J.-H. , Von Wichert P.
Published: December 2017

Breathing at very low lung volumes might be affected by decreased expiratory airflow and air trapping. Our purpose was to detect expiratory flow limitation (EFL) and, as a consequence, intrinsic positive end-expiratory pressure (PEEPi) in grossly obese subjects (OS). Eight OS with a mean body mass index (BMI) of 44 ± 5 kg/m2 and six age-matched normal-weight control subjects (CS) were studied in different body positions. Negative expiratory pressure (NEP) was used to determine EFL. In contrast to CS, EFL was found in two of eight OS in the upright position and in seven of eight OS in the supine position. Dynamic PEEPi and mean transdiaphragmatic pressure (mean Pdi) were measured in all six CS and in six of eight OS. In OS, PEEPi increased from 0.14 ± 0.06 (SD) kPa in the upright position to 0.41 ± 0.11 kPa in the supine position ( P < 0.05) and decreased to 0.20 ± 0.08 kPa in the right lateral position ( P < 0.05, compared with supine), whereas, in CS, PEEPi was significantly smaller (<0.05 kPa) in each position. In OS, mean Pdi in each position was significantly larger compared with CS. Mean Pdi increased from 1.02 ± 0.32 kPa in the upright position to 1.26 ± 0.17 kPa in the supine position (not significant) and decreased to 1.06 ± 0.26 kPa in the right lateral position ( P < 0.05, compared with supine), whereas there were no significant changes in CS. We conclude that in OS 1) tidal breathing can be affected by EFL and PEEPi; 2) EFL and PEEPi are promoted by the supine posture; and 3) the increased diaphragmatic load in the supine position is, in part, related to PEEPi.
Influence of acute lung volume change on contractile properties of human diaphragm
Authors: Polkey Michael I. , Hamnegård Carl-Hugo , Hughes Philip D. , Rafferty Gerrard F. , Green Malcolm , Moxham John
Published: December 2017

The effect of stimulus frequency on the in vivo pressure generating capacity of the human diaphragm is unknown at lung volumes other than functional residual capacity. The transdiaphragmatic pressure (Pdi) produced by a pair of phrenic nerve stimuli may be viewed as the sum of the Pdi elicited by the first (T1 Pdi) and second (T2 Pdi) stimuli. We used bilateral anterior supramaximal magnetic phrenic nerve stimulation and a digital subtraction technique to obtain the T2 Pdi at interstimulus intervals of 999, 100, 50, 33, and 10 ms in eight normal subjects at lung volumes between residual volume and total lung capacity. The reduction in T2 Pdi that we observed as lung volume increased was greatest at long interstimulus intervals, whereas the T2 Pdi obtained with short interstimulus intervals remained relatively stable over the 50% of vital capacity around functional residual capacity. For all interstimulus intervals, the total pressure produced by the pair decreased as a function of increasing lung volume. These data demonstrate that, in the human diaphragm, hyperinflation has a disproportionately severe effect on the summation of pressure responses elicited by low-frequency stimulations; this effect is distinct from and additional to the known length-tension relationship.
Effect of endurance training on cardiac morphology in Alaskan sled dogs
Authors: Stepien R. L. , Hinchcliff K. W. , Constable P. D. , Olson J.
Published: December 2017

The cardiac morphology of 77 conscious Alaskan sled dogs before and after 5 mo of endurance training (20 km/day team pulling a sled and musher) was studied using two-dimensional and M-mode echocardiography. Subgroups included dogs with at least one season of previous training (“veterans”) and dogs undergoing their first season of training (“rookies”). Training resulted in a significant ( P< 0.05) decrease in resting heart rate (−15%) and significant increases in interventricular septal thickness (systole, 15%; diastole, 13%), left ventricular (LV) internal dimension in diastole (LVIDd, 4%), LV free wall thickness in systole (9%) and diastole (LVWd, 9%), and left atrial diameter (5%) in all dogs, but the increase in LVWd was greater in rookies (16%) than in veterans (7%). Training increased end-diastolic volume index (8%), LV mass index (24%), and heart weight index (24%) and decreased the LVIDd-to-LVWd ratio (−6%) but did not alter cardiac index. We conclude that increased LV mass attributable to LV dilation and hypertrophy is associated with endurance training in Alaskan sled dogs. Disproportionate LV wall thickening accompanying LV dilation suggests that cardiac morphological changes are due to volume and pressure loading. These training-induced changes are similar to those documented in human athletes undergoing combined isometric and isotonic training and differ from studies of dogs trained on treadmills.
Individual variation in response to altitude training
Authors: Chapman Robert F. , Stray-Gundersen James , Levine Benjamin D.
Published: December 2017

Moderate-altitude living (2,500 m), combined with low-altitude training (1,250 m) (i.e., live high-train low), results in a significantly greater improvement in maximal O2 uptake (V˙o 2 max) and performance over equivalent sea-level training. Although the mean improvement in group response with this “high-low” training model is clear, the individual response displays a wide variability. To determine the factors that contribute to this variability, 39 collegiate runners (27 men, 12 women) were retrospectively divided into responders ( n = 17) and nonresponders ( n = 15) to altitude training on the basis of the change in sea-level 5,000-m run time determined before and after 28 days of living at moderate altitude and training at either low or moderate altitude. In addition, 22 elite runners were examined prospectively to confirm the significance of these factors in a separate population. In the retrospective analysis, responders displayed a significantly larger increase in erythropoietin (Epo) concentration after 30 h at altitude compared with nonresponders. After 14 days at altitude, Epo was still elevated in responders but was not significantly different from sea-level values in nonresponders. The Epo response led to a significant increase in total red cell volume andV˙o 2 max in responders; in contrast, nonresponders did not show a difference in total red cell volume or V˙o 2 maxafter altitude training. Nonresponders demonstrated a significant slowing of interval-training velocity at altitude and thus achieved a smaller O2 consumption during those intervals, compared with responders. The acute increases in Epo and V˙o 2 maxwere significantly higher in the prospective cohort of responders, compared with nonresponders, to altitude training. In conclusion, after a 28-day altitude training camp, a significant improvement in 5,000-m run performance is, in part, dependent on 1) living at a high enough altitude to achieve a large acute increase in Epo, sufficient to increase the total red cell volume andV˙o 2 max, and 2) training at a low enough altitude to maintain interval training velocity and O2 flux near sea-level values.
Caffeine, performance, and metabolism during repeated Wingate exercise tests
Authors: Greer F. , McLean C. , Graham T. E.
Published: December 2017

Investigations examining the ergogenic and metabolic influence of caffeine during short-term high-intensity exercise are few in number and have produced inconsistent results. This study examined the effects of caffeine on repeated bouts of high-intensity exercise in recreationally active men. Subjects ( n = 9) completed four 30-s Wingate (WG) sprints with 4 min of rest between each exercise bout on two separate occasions. One hour before exercise, either placebo (Pl; dextrose) or caffeine (Caf; 6 mg/kg) capsules were ingested. Caf ingestion did not have any effect on power output (peak or average) in the first two WG tests and had a negative effect in the latter two exercise bouts. Plasma epinephrine concentration was significantly increased 60 min after Caf ingestion compared with Pl; however, this treatment effect disappeared once exercise began. Caf ingestion had no significant effect on blood lactate, O2 consumption, or aerobic contribution at any time during the protocol. After the second Wingate test, plasma NH3concentration increased significantly from the previous WG test and was significantly higher in the Caf trial compared with Pl. These data demonstrate no ergogenic effect of caffeine on power output during repeated bouts of short-term, intense exercise. Furthermore, there was no indication of increased anaerobic metabolism after Caf ingestion with the exception of an increase in NH3 concentration.
Recovery from mild hypothermia can be accelerated by mechanically distending blood vessels in the hand
Authors: Grahn Dennis , Brock-Utne John G. , Watenpaugh Donald E. , Heller H. Craig
Published: December 2017

Peripheral vasoconstriction decreases thermal conductance of hypothermic individuals, making it difficult to transfer externally applied heat to the body core. We hypothesized that increasing blood flow to the skin of a hypothermic individual would enhance the transfer of exogenous heat to the body core, thereby increasing the rate of rewarming. External auditory meatus temperature (TEAM) was monitored in hypothermic subjects during recovery from general anesthesia. In 10 subjects, heat (45–46°C, water-perfused blanket) was applied to a single forearm and hand that had been placed in a subatmospheric pressure environment (−30 to −40 mmHg) to distend the blood vessels. Heat alone was applied to control subjects ( n = 6). The application of subatmospheric pressure resulted in a 10-fold increase in rewarming rates as determined by changes in TEAM[13.6 ± 2.1 (SE) °C/h in the experimental group vs. 1.4 ± 0.1°C/h in the control group; P < 0.001]. In the experimental subjects, the rate of change of TEAMdecreased sharply as TEAMneared the normothermic range.
Pulmonary vasoconstriction induced by mitral valve obstruction in sheep
Authors: Hermo-Weiler Casilda I. , Koizumi Tomonobu , Parker Richard , Newman John H.
Published: December 2017

We hypothesized that left atrial hypertension results in pulmonary vasoconstriction, which is obscured by the expected passive decrease in pulmonary vascular resistance. The objectives of this study were to demonstrate and quantify the vasoconstrictive changes that occur in the pulmonary circulation during experimental left atrial hypertension, to determine the site of vasoconstriction, and to explore its mechanism. Sheep were instrumented for measurement of pulmonary arterial (Ppa), left atrial (Pla), and systemic arterial pressures (Psa) with a Foley balloon catheter to variably obstruct the mitral valve. Distal pulmonary arterial wedge pressure (Ppaw) was determined by using a 5-Fr Swan-Ganz catheter that was advanced until it wedged with the balloon deflated. Cardiac output (CO) was estimated by thermodilution; pulmonary vascular resistances (PVR) were calculated as mean (Ppa − Pla)/CO = total PVR, (Ppa − Ppaw)/CO = upstream PVR, and (Ppaw − Pla)/CO = downstream PVR. We studied 15 awake sheep at baseline and during increases in Pla of 10 and 20 cmH2O, with and without inhalation of ∼36 parts per million of nitric oxide. Left atrial hypertension resulted in elevation of Ppa. CO decreased only slightly at both levels of Pla elevation. Nitric oxide inhalation caused a significant decrease in PVR, which was greater as Pla increased. This vasodilator effect was most striking in downstream vessels. Experiments with phentolamine, atropine, and ibuprofen failed to reveal the mechanism of the reactive pulmonary vasoconstriction.
Inspiratory and expiratory patterns of the pectoralis major muscle during pulmonary defensive reflexes
Authors: Bolser Donald C. , Reier Paul J.
Published: December 2017

Experiments were conducted to determine the discharge pattern of the pectoralis major muscle during pulmonary defensive reflexes in anesthetized cats ( n = 15). Coughs and expiration reflexes were elicited by mechanical stimulation of the intrathoracic trachea or larynx. Augmented breaths occurred spontaneously or were evoked by the same mechanical stimuli. Electromyograms (EMGs) were recorded from the diaphragm, rectus abdominis, and pectoralis major muscles. During augmented breaths, the pectoralis major had inspiratory EMG activity similar to that of the diaphragm, but during expiration reflexes the pectoralis major also had purely expiratory EMG activity similar to the rectus abdominis. During tracheobronchial cough, the pectoralis major had an inspiratory pattern similar to that of the diaphragm in 10 animals, an expiratory pattern similar to that of the rectus abdominis in 3 animals, and a biphasic pattern in 2 animals. The pectoralis major was active during both the inspiratory and expiratory phases during laryngeal cough. We conclude that, in contrast to the diaphragm or rectus abdominis muscles, the pectoralis major is active during both inspiratory and expiratory pulmonary defensive reflexes.
Experimental and theoretical comparison of NIR spectroscopy measurements of cerebral hemoglobin changes
Authors: Firbank Michael , Elwell Clare E. , Cooper Chris E. , Delpy David T.
Published: December 2017

Two near-infrared spectroscopy (NIRS) methods are available for measuring changes (Δ) in total cerebral hemoglobin concentration (CHC): 1) a continuous measurement of the changes in total hemoglobin concentration (Δ[Hb]tot) and 2) the difference between two absolute measurements of CHC, each derived from a small, controlled change in inspired O2fraction. This paper investigates the internal consistency of these two methods by using an experimental and theoretical comparison. NIRS was used to measure [Hb]totin five newborn piglets before and after a change in arterial[Formula: see text]. Δ[Hb]totdemonstrated a low coefficient of variation of 2.8 ± 2.8 (SD) % which allowed changes in CO2-cerebral blood volume reactivity to be clearly discriminated. However, a high coefficient of variation of 22.8 ± 3.5% on the ΔCHC measurements obscured any CO2reactivity changes. A theoretical analysis demonstrates the effects of optical pathlength, background absorption, scatter, and blood vessel diameter on both methods. For more accurate monitoring of CHC, individual measurements of optical pathlength and more accurate pulse oximetry are required.
Analysis of forced expiratory maneuvers from raised lung volumes in preterm infants
Authors: Henschen Matthias , Stocks Janet , Hoo Ah-Fong , Dixon Paul
Published: December 2017

During recent years it has been suggested that forced expiratory measurements, derived from a lung volume set by a standardized inflation pressure, are more reproducible than those attained during tidal breathing when the rapid thoracoabdominal compression technique is used in infants. The aim of this study was to evaluate the feasibility of obtaining measurements from raised lung volumes in unsedated preterm infants. Measurements were made in 18 infants (gestational age 26–35 wk, postnatal age 1–10 wk, test weight 1.4–3.5 kg). Several inflations [1.5–2.5 kPa (15–25 cmH2O)] were used to briefly inhibit respiratory effort before the rapid thoracoabdominal compression was performed. Conventional analysis of flows and volumes at fixed times and percentages of the forced expiration resulted in a relatively high variability in this population. However, by using the elastic equilibrium point (i.e., the passively determined lung volume, derived from passive expirations before the forced expiration) as a volume landmark, it was feasible to achieve reproducible results in unsedated preterm infants, despite their strong respiratory reflexes and rapid respiratory rates. Because this approach is independent of changes in expiratory time, expired volume, or applied pressures, it may facilitate investigation of the effects of growth, development, and disease on airway function in infants, particularly during the first weeks of life, when conventional analysis of forced expirations may be inappropriate.
Diaphragm EMG measured by cervical magnetic and electrical phrenic nerve stimulation
Authors: Luo Y. M. , Polkey M. I. , Johnson L. C. , Lyall R. A. , Harris M. L. , Green M. , Moxham J.
Published: December 2017

The purpose of the study was to compare electrical stimulation (ES) and cervical magnetic stimulation (CMS) of the phrenic nerves for the measurement of the diaphragm compound muscle action potential (CMAP) and phrenic nerve conduction time. A specially designed esophageal catheter with three pairs of electrodes was used, with control of electrode positioning in 10 normal subjects. Pair A and pair B were close to the diaphragm ( pair A lower than pair B); pair C was positioned 10 cm above the diaphragm to detect the electromyogram from extradiaphragmatic muscles. Electromyograms were also recorded from upper and lower chest wall surface electrodes. The shape of the CMAP measured with CMS (CMS-CMAP) usually differed from that of the CMAP measured with ES (ES-CMAP). Moreover, the latency of the CMS-CMAP from pair B (5.3 ± 0.4 ms) was significantly shorter than that from pair A (7.1 ± 0.7 ms). The amplitude of the CMS-CMAP (1.00 ± 0.15 mV) was much higher than that of ES-CMAP (0.26 ± 0.15 mV) when recorded from pair C. Good-quality CMS-CMAPs could be recorded in some subjects from an electrode positioned very low in the esophagus. The differences between ES-CMAP and CMS-CMAP recorded either from esophageal or chest wall electrodes make CMS unreliable for the measurement of phrenic nerve conduction time.
Enhanced brain natriuretic peptide response to peak exercise in heart transplant recipients
Authors: Geny Bernard , Charloux Anne , Lampert Eliane , Lonsdorfer Jean , Haberey Pascal , Piquard François
Published: December 2017

We investigated the atrial (ANP) and brain natriuretic peptides (BNP), catecholamines, heart rate, and blood pressure responses to graded upright maximal cycling exercise of eight matched healthy subjects and cardiac-denervated heart transplant recipients (HTR). Baseline heart rate and diastolic blood pressure, together with ANP (15.2 ± 3.7 vs. 4.4 ± 0.8 pmol/l; P < 0.01) and BNP (14.3 ± 2.6 vs. 7.4 ± 0.6 pmol/l; P< 0.01), were elevated in HTR, but catecholamine levels were similar in both groups. Peak exercise O2uptake and heart rate were lower in HTR. Exercise-induced maximal ANP increase was similar in both groups (167 ± 34 vs. 216 ± 47%). Enhanced BNP increase was significant only in HTR (37 ± 8 vs. 16 ± 8%; P < 0.05). Similar norepinephrine but lower peak epinephrine levels were observed in HTR. ANP and heart rate changes from rest to 75% peak exercise were negatively correlated ( r = −0.76, P < 0.05), and BNP increase was correlated with left ventricular mass index ( r = 0.83, P < 0.01) after heart transplantation. Although ANP increase was not exaggerated, these data support the idea that the chronotropic limitation secondary to sinus node denervation might stimulate ANP release during early exercise in HTR. Furthermore, the BNP response to maximal exercise, which is related to the left ventricular mass index of HTR, is enhanced after heart transplantation.
Mechanical advantage of the canine diaphragm
Authors: Wilson Theodore A. , Boriek Aladin M. , Rodarte Joseph R.
Published: December 2017

The mechanical advantage (μ) of a respiratory muscle is defined as the respiratory pressure generated per unit muscle mass and per unit active stress. The value of μ can be obtained by measuring the change in the length of the muscle during inflation of the passive lung and chest wall. We report values of μ for the muscles of the canine diaphragm that were obtained by measuring the lengths of the muscles during a passive quasistatic vital capacity maneuver. Radiopaque markers were attached along six muscle bundles of the costal and two muscle bundles of the crural left hemidiaphragms of four bred-for-research beagle dogs. The three-dimensional locations of the markers were obtained from biplane video-fluoroscopic images taken at four volumes during a passive relaxation maneuver from total lung capacity to functional residual capacity in the prone and supine postures. Muscle lengths were determined as a function of lung volume, and from these data, values of μ were obtained. Values of μ are fairly uniform around the ventral midcostal and crural diaphragm but significantly lower at the dorsal end of the costal diaphragm. The average values of μ are −0.35 ± 0.18 and −0.27 ± 0.16 cmH2O ⋅ g−1 ⋅ kg−1 ⋅ cm−2in the prone and supine dog, respectively. These values are 1.5–2 times larger than the largest values of μ of the intercostal muscles in the supine dog. From these data we estimate that during spontaneous breathing the diaphragm contributes ∼40% of inspiratory pressure in the prone posture and ∼30% in the supine posture. Passive shortening, and hence μ, in the upper one-third of inspiratory capacity is less than one-half of that at lower lung volume. The lower μ is attributed primarily to a lower abdominal compliance at high lung volume.
Decreases in organ blood flows associated with increases in sublingual P CO 2 during hemorrhagic shock
Authors: Jin Xiaohua , Weil Max Harry , Sun Shijie , Tang Wanchun , Bisera Joe , Mason Earl J.
Published: December 2017

Earlier studies demonstrated that not only the stomach but also the esophageal wall served as an appropriate site for estimating the severity of circulatory shock by using tonometric methods. We then conceived of the option of sublingual tonometry. In the present study, we tested the hypothesis that the changes in sublingual [Formula: see text] serve as indicators of decreases in blood flow to sublingual and visceral tissue. In Sprague-Dawley rats, sublingual[Formula: see text] increased from 50 to 127 Torr and arterial blood lactate increased from 0.9 to 11.2 mmol/l during bleeding. Sublingual blood flow simultaneously decreased to ∼32% of preshock values. After reinfusion of shed blood, organ blood flows and sublingual [Formula: see text] were promptly restored to near-baseline values. There were corresponding decreases in blood flows in the tongue, stomach, jejunum, colon, and kidneys during hemorrhagic shock. Increases in sublingual[Formula: see text] were highly correlated with decreases in sublingual blood flow ( r= 0.80), tongue blood flow ( r = 0.81), gastric blood flow ( r = 0.74), jejunal blood flow ( r = 0.65), colon blood flow ( r = 0.80), and renal blood flow ( r = 0.75). Unbled control animals demonstrated no significant changes. Therefore, we anticipate that sublingual tonometry will provide a useful, noninvasive alternative for monitoring visceral [Formula: see text].
Regional deposition and retention of particles in shallow, inhaled boluses: effect of lung volume
Authors: Bennett William D. , Scheuch Gerhard , Zeman Kirby L. , Brown James S. , Kim Chong , Heyder Joachim , Stahlhofen Willi
Published: December 2017

The regional deposition of particles in boluses delivered to shallow lung depths and their subsequent retention in the airways may depend on the lung volume at which the boluses are delivered. To evaluate the effect of end-inspiratory lung volume on aerosol bolus delivery, we had healthy subjects inhale radiolabeled, monodisperse aerosol (99mTc-iron oxide, 3.5-μm mass median aerodynamic diameter) boluses (40 ml) to a volumetric front depth of 70 ml into the lung at lung volumes of 50, 70, and 85% of total lung capacity (TLC) end inhalation. By gamma camera analysis, we found significantly greater deposition in the left (L) vs. right (R) lungs at the 70 and 85% TLC end inhalation; ratio of deposition in L to R lung, normalized to L-to-R ratio of lung volume (mean L/R), was 1.60 ± 0.45 (SD) and 1.96 ± 0.72, respectively ( P < 0.001 for comparison to 1.0) for posterior images. However, at 50% TLC, L/R was 1.23 ± 0.37, not significantly different from 1.0. These data suggest that the L and R lungs may be expanding nonuniformly at higher lung volumes. On the other hand, subsequent retention of deposited particles at 2 and 24 h postdeposition was independent of L/R at the various lung volumes. Thus asymmetric bolus ventilation for these very shallow boluses does not lead to significant increases in peripheral alveolar deposition. These data may prove useful for 1) designing aerosol delivery techniques to target bronchial airways and 2) understanding airway retention of inhaled particles.
Muscle quality. I. Age-associated differences between arm and leg muscle groups
Authors: Lynch N. A. , Metter E. J. , Lindle R. S. , Fozard J. L. , Tobin J. D. , Roy T. A. , Fleg J. L. , Hurley B. F.
Published: December 2017

To determine the differences between arm and leg muscle quality (MQ) across the adult life span in men and women, concentric (Con) and eccentric (Ecc) peak torque (PT) were measured in 703 subjects (364 men and 339 women, age range 19–93 yr) and appendicular skeletal muscle mass (MM) was determined in the arm and leg in a subgroup of 502 of these subjects (224 men and 278 women). Regression analysis showed that MQ, defined as PT per unit of MM, was significantly higher in the arm (∼30%) than in the leg across age in both genders ( P < 0.01). Arm and leg MQ declined at a similar rate with age in men, whereas leg MQ declined ∼20% more than arm MQ with increasing age in women ( P ≤ 0.01 and P < 0.05 for Con and Ecc PT, respectively). Moreover, the age-associated decrease in arm MQ was steeper in men than in women whether Con or Ecc PT was used (both P < 0.05). Arm MQ as determined by Con PT showed a linear age-related decline in men and women (28 and 20%, respectively, P < 0.001), whereas arm MQ as determined by Ecc PT showed a linear age-related decline in men (25%, P < 0.001) but not in women (not significant). In contrast, both genders exhibited an age-related quadratic decline in leg MQ as determined by Con PT (∼40%) and Ecc PT (∼25%; both P< 0.001), and the rate of decline was similar for men and women. Thus MQ is affected by age and gender, but the magnitude of this effect depends on the muscle group studied and the type of muscle action (Con vs. Ecc) used to assess strength.
Muscle quality. II. Effects of strength training in 65- to 75-yr-old men and women
Authors: Tracy B. L. , Ivey F. M. , Hurlbut D. , Martel G. F. , Lemmer J. T. , Siegel E. L. , Metter E. J. , Fozard J. L. , Fleg J. L. , Hurley B. F.
Published: December 2017

To determine the effects of strength training (ST) on muscle quality (MQ, strength/muscle volume of the trained muscle group), 12 healthy older men (69 ± 3 yr, range 65–75 yr) and 11 healthy older women (68 ± 3 yr, range 65–73 yr) were studied before and after a unilateral leg ST program. After a warm-up set, four sets of heavy-resistance knee extensor ST exercise were performed 3 days/wk for 9 wk on the Keiser K-300 leg extension machine. The men exhibited greater absolute increases in the knee extension one-repetition maximum (1-RM) strength test (75 ± 2 and 94 ± 3 kg before and after training, respectively) and in quadriceps muscle volume measured by magnetic resonance imaging (1,753 ± 44 and 1,955 ± 43 cm3) than the women (42 ± 2 and 55 ± 3 kg for the 1-RM test and 1,125 ± 53 vs. 1,261 ± 65 cm3for quadriceps muscle volume before and after training, respectively, in women; both P < 0.05). However, percent increases were similar for men and women in the 1-RM test (27 and 29% for men and women, respectively), muscle volume (12% for both), and MQ (14 and 16% for men and women, respectively). Significant increases in MQ were observed in both groups in the trained leg (both P < 0.05) and in the 1-RM test for the untrained leg (both P < 0.05), but no significant differences were observed between groups, suggesting neuromuscular adaptations in both gender groups. Thus, although older men appear to have a greater capacity for absolute strength and muscle mass gains than older women in response to ST, the relative contribution of neuromuscular and hypertrophic factors to the increase in strength appears to be similar between genders.
Bone hyperemia precedes disuse-induced intracortical bone resorption
Authors: Gross Ted S. , Damji Ariff A. , Judex Stefan , Bray Robert C. , Zernicke Ronald F.
Published: December 2017

An in vivo model was used to determine whether bone hyperemia precedes increased intracortical porosity induced by disuse. Twenty-four adult male roosters (age 1 yr) were randomly assigned to intact-control, 7-days-sham-surgery, 7-days-disuse, and 14-days-disuse groups. Disuse was achieved by isolating the left ulna diaphysis from physical loading via parallel metaphyseal osteotomies. The right ulna served as an intact contralateral control. Colored microspheres were used to assess middiaphyseal bone blood flow. Bone blood flow was symmetric between the left and right ulnae of the intact-control and sham-surgery groups. After 7 days of disuse, median (±95% confidence interval) standardized blood flow was significantly elevated compared with the contralateral bone (6.5 ± 5.2 vs. 1.0 ± 0.8 ml ⋅ min−1 ⋅ 100 g−1; P = 0.03). After 14 days of disuse, blood flow was also elevated but to a lesser extent. Intracortical porosity in the sham-surgery and 7-days-disuse bones was not elevated compared with intact-control bones. At 14 days of disuse, the area of intracortical porosity was significantly elevated compared with intact control bones (0.015 ± 0.02 vs. 0.002 ± 0.002 mm2; P = 0.03). We conclude that disuse induces bone hyperemia before an increase in intracortical porosity. The potential interaction between bone vasoregulation and bone cell dynamics remains to be studied.