bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary evidence that DEXA provides an accurate assessment of body composition
Authors: Kohrt Wendy M.
Published: December 2017

Kohrt, Wendy M. Preliminary evidence that DEXA provides an accurate assessment of body composition. J. Appl. Physiol. 84(1): 372–377, 1998.—It was previously found that dual-energy X-ray absorptiometry (DEXA) underestimated central body fat. The purposes of this study were to determine whether an updated version (enhanced version 5.64) of the analysis program corrected this problem ( experiment 1) and to compare body composition assessed by DEXA and hydrodensitometry (HD) in women ( n= 225) and men ( n = 110) across a 21- to 81-yr age range ( experiment 2). For experiment 1, 10 subjects underwent DEXA procedures in a control condition and with packets of lard positioned over either the thighs or the truncal region. DEXA accurately quantified the additional mass as ∼96% fat, regardless of position. For experiment 2, DEXA yielded higher ( P < 0.001) estimates of fatness than did HD (32.1 ± 12.0 vs. 31.2 ± 10.1%). The mean difference between the two methods was similar in young, middle-aged, and older subjects, but was different in men (HD − DEXA, 1.6 ± 3.4% of body wt) than in women (−2.1 ± 3.8% of body wt). Correcting the density of fat-free mass for variance in the bone mineral fraction of fat-free mass reduced the difference between the methods in men from 1.6 ± 3.4 to −0.7 ± 2.9% but widened it in women from −2.1 ± 3.8 to −3.5 ± 3.4%. A second correction procedure that adjusted for variance in water, protein, and mineral fractions of fat-free mass eliminated the differences in estimates of fat content by DEXA and HD in both men (21.1 ± 9.3 vs. 20.6 ± 8.4%, respectively) and women (37.5 ± 9.3 vs. 36.8 ± 8.0%, respectively). These results provide encouraging, but not definitive, evidence that the assessment of body composition by DEXA is accurate under the specified conditions.
Letters to the Editor
Authors: Mazess Richard B.
Published: December 2017

The following is the abstract of the article discussed in the subsequent letter:

Bracco, David, Daniel Thiébaud, René L. Chioléro, Michel Landry, Peter Burckhardt, and Yves Schutz.Segmental body composition assessed by bioelectrical impedance analysis and DEXA in humans. J. Appl. Physiol. 81(6): 2580–2587, 1996.—The present study assessed the relative contribution of each body segment to whole body fat-free mass (FFM) and impedance and explored the use of segmental bioelectrical impedance analysis to estimate segmental tissue composition. Multiple frequencies of whole body and segmental impedances were measured in 51 normal and overweight women. Segmental tissue composition was independently assessed by dual-energy X-ray absorptiometry. The sum of the segmental impedance values corresponded to the whole body value (100.5 ± 1.9% at 50 kHz). The arms and legs contributed to 47.6 and 43.0%, respectively, of whole body impedance at 50 kHz, whereas they represented only 10.6 and 34.8% of total FFM, as determined by dual-energy X-ray absorptiometry. The trunk averaged 10.0% of total impedance but represented 48.2% of FFM. For each segment, there was an excellent correlation between the specific impedance index (length2/impedance) and FFM ( r = 0.55, 0.62, and 0.64 for arm, trunk, and leg, respectively). The specific resistivity was in a similar range for the limbs (159 ± 23 cm for the arm and 193 ± 39 cm for the leg at 50 kHz) but was higher for the trunk (457 ± 71 cm). This study shows the potential interest of segmental body composition by bioelectrical impedance analysis and provides specific segmental body composition equations for use in normal and overweight women.
Stop-flow studies of distribution of filtration in rat lungs
Authors: Lin W. , Jacobs E. , Schapira R. M. , Presberg K. , Effros R. M.
Published: December 2017

Lin, W., E. Jacobs, R. M. Schapira, K. Presberg, and R. M. Effros. Stop-flow studies of distribution of filtration in rat lungs. J. Appl. Physiol. 84(1): 47–52, 1998.—The stop-flow approach was used to investigate where filtration occurs in the pulmonary vasculature after elevation of left atrial pressure and aspiration of HCl. Rat lungs were perfused for 11 min at zero left atrial pressures, and then flow was stopped for 10 min and left atrial pressures were increased to 20 cmH2O. Thereafter,3HOH was instilled into the air spaces, and the pulmonary vasculature was flushed by perfusing it from the pulmonary artery to left atrium (anterograde flush) or in the opposite direction (retrograde flush). Increases in fluorescein isothiocyanate (FITC)-dextran (molecular weight 2,000,000) indicated filtration, and these preceded increases in3HOH after anterograde but not retrograde flushes. This suggests that some filtration occurred through vessels that were relatively venous compared with those through which3HOH exchange had occurred. Filtration increased fivefold after instillation of 0.1 N HCl in isotonic saline into the air spaces before perfusion. Increases in Evans blue-labeled albumin concentrations were <40% those of FITC-dextran, indicating loss from the vasculature, but increases in unlabeled albumin and FITC-albumin were comparable.
Skeletal muscle ECF pH error signal for exercise ventilatory control
Authors: Evans Allison B. , Tsai Larry W. , Oelberg David A. , Kazemi Homayoun , Systrom David M.
Published: December 2017

Evans, Allison B., Larry W. Tsai, David A. Oelberg, Homayoun Kazemi, and David M. Systrom. Skeletal muscle ECF pH error signal for exercise ventilatory control. J. Appl. Physiol. 84(1): 90–96, 1998.—An autonomic reflex linking exercising skeletal muscle metabolism to central ventilatory control is thought to be mediated by neural afferents having free endings that terminate in the interstitial fluid of muscle. To determine whether changes in muscle extracellular fluid pH (pHe) can provide an error signal for exercise ventilatory control, pHewas measured during electrically induced contraction by31P-magnetic resonance spectroscopy and the chemical shift of a phosphorylated, pH-sensitive marker that distributes to the extracellular fluid (phenylphosphonic acid). Seven lightly anesthetized rats underwent unilateral continuous 5-Hz sciatic nerve stimulation in an 8.45-T nuclear magnetic resonance magnet, which resulted in a mixed lactic acidosis and respiratory alkalosis, with no net change in arterial pH. Skeletal muscle intracellular pH fell from 7.30 ± 0.03 units at rest to 6.72 ± 0.05 units at 2.4 min of stimulation and then rose to 7.05 ± 0.01 units ( P < 0.05), despite ongoing stimulation and muscle contraction. Despite arterial hypocapnia, pHeshowed an immediate drop from its resting baseline of 7.40 ± 0.01 to 7.16 ± 0.04 units ( P < 0.05) and remained acidic throughout the stimulation protocol. During the on- and off-transients for 5-Hz stimulation, changes in the pH gradient between intracellular and extracellular compartments suggested time-dependent recruitment of sarcolemmal ion-transport mechanisms. pHeof exercising skeletal muscle meets temporal and qualitative criteria necessary for a ventilatory metaboreflex mediator in a setting where arterial pH does not.
Hypochlorous acid inhibits Ca2+-ATPase from skeletal muscle sarcoplasmic reticulum
Authors: Favero Terence G. , Colter David , Hooper Paul F. , Abramson Jonathan J.
Published: December 2017

Favero, Terence G., David Colter, Paul F. Hooper, and Jonathan J. Abramson. Hypochlorous acid inhibits Ca2+-ATPase from skeletal muscle sarcoplasmic reticulum. J. Appl. Physiol. 84(2): 425–430, 1998.—Hypochlorous acid (HOCl) is produced by polymorphonuclear leukocytes that migrate and adhere to endothelial cells as part of the inflammatory response to tissue injury. HOCl is an extremely toxic oxidant that can react with a variety of cellular components, and concentrations reaching 200 μM have been reported in some tissues. In this study, we show that HOCl interacts with the skeletal sarcoplasmic reticulum Ca2+-adenosinetriphosphatase (ATPase), inhibiting transport function. HOCl inhibits sarcoplasmic reticulum Ca2+-ATPase activity in a concentration-dependent manner with a concentration required to inhibit ATPase activity by 50% of 170 μM and with complete inhibition of activity at 3 mM. A concomitant reduction in free sulfhydryl groups after HOCl treatment was observed, paralleling the inhibition of ATPase activity. It was also observed that HOCl inhibited the binding of the fluorescent probe fluorescein isothiocyanate to the ATPase protein, indicating some structural damage may have occurred. These findings suggest that the reactive oxygen species HOCl inhibits ATPase activity via a modification of sulfhydryl groups on the protein, supporting the contention that reactive oxygen species disrupt the normal Ca2+-handling kinetics in muscle cells.
Reflex responses to regional venous pooling during lower body negative pressure in humans
Authors: Halliwill John R. , Lawler Lori A. , Eickhoff Tamara J. , Joyner Michael J. , Mulvagh Sharon L.
Published: December 2017

Halliwill, John R., Lori A. Lawler, Tamara J. Eickhoff, Michael J. Joyner, and Sharon L. Mulvagh. Reflex responses to regional venous pooling during lower body negative pressure in humans. J. Appl. Physiol. 84(2): 454–458, 1998.—Lower body negative pressure is frequently used to simulate orthostasis. Prior data suggest that venous pooling in abdominal or pelvic regions may have major hemodynamic consequences. Therefore, we developed a simple paradigm for assessing regional contributions to venous pooling during lower body negative pressure. Sixteen healthy men and women underwent graded lower body negative pressure protocols to 60 mmHg while wearing medical antishock trousers to prevent venous pooling under three randomized conditions: 1) no trouser inflation (control), 2) only the trouser legs inflated, and 3) the trouser legs and abdominopelvic region inflated. Without trouser inflation, heart rate increased 28 ± 4 beats/min, mean arterial pressure fell −3 ± 2 mmHg, and forearm vascular resistance increased 51 ± 9 units at 60 mmHg lower body negative pressure. With inflation of either the trouser legs or the trouser legs and abdominopelvic region, heart rate and mean arterial pressure did not change during lower body negative pressure. By contrast, although the forearm vasoconstrictor response to lower body negative pressure was attenuated by inflation of the trouser legs (Δforearm vascular resistance 33 ± 10 units, P < 0.05 vs. control), attenuation was greater with the inflation of the trouser legs and abdominopelvic region (Δforearm vascular resistance 16 ± 5 units, P < 0.05 vs. control and trouser legs-only inflation). Thus the hemodynamic consequences of pooling in the abdominal and pelvic regions during lower body negative pressure appear to be less than in the legs in healthy individuals.
Kinetic analysis and comparison of uptake, distribution, and excretion of48V-labeled compounds in rats
Authors: Setyawati I. A. , Thompson K. H. , Yuen V. G. , Sun Y. , Battell M. , Lyster D. M. , Vo C. , Ruth T. J. , Zeisler S. , McNeill J. H. , Orvig C.
Published: December 2017

Setyawati, I. A., K. H. Thompson, V. G. Yuen, Y. Sun, M. Battell, D. M. Lyster, C. Vo, T. J. Ruth, S. Zeisler, J. H. McNeill, and C. Orvig. Kinetic analysis and comparison of uptake, distribution, and excretion of48V-labeled compounds in rats. J. Appl. Physiol. 84(2): 569–575, 1998.—Vanadium has been found to be orally active in lowering plasma glucose levels; thus it provides a potential treatment for diabetes mellitus. Bis(maltolato)oxovanadium(IV) (BMOV) is a well-characterized organovanadium compound that has been shown in preliminary studies to have a potentially useful absorption profile. Tissue distributions of BMOV compared with those of vanadyl sulfate (VS) were studied in Wistar rats by using48V as a tracer. In this study, the compounds were administered in carrier-added forms by either oral gavage or intraperitoneal injection. Data analyzed by a compartmental model, by using simulation, analysis, and modeling (i.e., SAAM II) software, showed a pattern of increased tissue uptake with use of48V-BMOV compared with48VS. The highest48V concentrations at 24 h after gavage were in bone, followed by kidney and liver. Most ingested48V was eliminated unabsorbed by fecal excretion. On average,48V concentrations in bone, kidney, and liver 24 h after oral administration of48V-BMOV were two to three times higher than those of48VS, which is consistent with the increased glucose-lowering potency of BMOV in acute glucose lowering compared with VS.
Albumin synthesis after intense intermittent exercise in human subjects
Authors: Yang Roger C. , Mack Gary W. , Wolfe Robert R. , Nadel Ethan R.
Published: December 2017

Yang, Roger C., Gary W. Mack, Robert R. Wolfe, and Ethan R. Nadel. Albumin synthesis after intense intermittent exercise in human subjects. J. Appl. Physiol.84(2): 584–592, 1998.—We measured hepatic albumin synthesis in five volunteers (4 men and 1 woman) at 3 and 6 h after recovery from intense exercise. A primed-constant infusion of a stable isotopic tracer of phenylalanine was used to determine hepatic fractional synthetic rate (FSR) and absolute synthetic rate (ASR) of albumin from the enrichment of phenylalanine in albumin. The infusion of the stable isotope tracer began 2 h after upright exercise or upright rest. Albumin FSR and ASR were 6.39 ± 0.48%/day and 120 ± 9 mg ⋅ kg body wt−1 ⋅ day−1, respectively, 3–6 h after recovery from exercise; the FSR and ASR on the time control study day were 5.94 ± 0.47%/day and 104 ± 9 mg ⋅ kg body wt−1 ⋅ day−1, respectively. The 6 and 16% increases ( P < 0.05) in FSR and ASR after exercise were associated with an elevated plasma albumin content at 5 and 6 h of recovery ( P < 0.05), an increased total protein content throughout recovery ( P < 0.05), and a negative free water clearance ( P < 0.05) at 2, 3, and 6.5 h of recovery compared with baseline values; these variables were unchanged from their baselines on the time control study day. Increased albumin content and reduced free water clearance contribute to a retention of fluid within the circulation after intense exercise. The measured increase in albumin synthesis could not account for the entire increase in albumin content at 6 h of recovery from exercise. However, we estimate that if the increased activity was maintained for the next 18 h, it could account for the expected increase in albumin content at 24 h of recovery.
A miniature mechanical ventilator for newborn mice
Authors: Kolandaivelu Kumaran , Poon Chi-Sang
Published: December 2017

Kolandaivelu, Kumaran, and Chi-Sang Poon.A miniature mechanical ventilator for newborn mice. J. Appl. Physiol. 84(2): 733–739, 1998.—Transgenic/knockout mice with predefined mutations have become increasingly popular in biomedical research as models of human diseases. In some instances, the resulting mutation may cause cardiorespiratory distress in the neonatal or adult animals and may necessitate resuscitation. Here we describe the design and testing of a miniature and versatile ventilator that can deliver varying ventilatory support modes, including conventional mechanical ventilation and high-frequency ventilation, to animals as small as the newborn mouse. With a double-piston body chamber design, the device circumvents the problem of air leakage and obviates the need for invasive procedures such as endotracheal intubation, which are particularly important in ventilating small animals. Preliminary tests on newborn mice as early as postnatal day 0 demonstrated satisfactory restoration of pulmonary ventilation and the prevention of respiratory failure in mutant mice that are prone to respiratory depression. This device may prove useful in the postnatal management of transgenic/knockout mice with genetically inflicted respiratory disorders.
Perfusion technique determines alveolar fluid resorption rate in the isolated perfused rat lung
Authors: Lasnier Joseph M. , Ingbar David H. , Carter Ethan P. , Wilson Kirk , McKnite Scott , Lurie Keith G. , Wangensteen O. Douglas
Published: December 2017

Lasnier, Joseph M., David H. Ingbar, Ethan P. Carter, Kirk Wilson, Scott McKnite, Keith G. Lurie, and O. Douglas Wangensteen.Perfusion technique determines alveolar fluid resorption rate in the isolated perfused rat lung. J. Appl. Physiol. 84(2): 740–745, 1998.—The isolated perfused lung (IPL) preparation is a well-established model for the study of alveolar epithelial sodium transport. We noted that preparations of normal fluid-filled rat lungs with recirculated perfusate reproducibly lost weight, whereas preparations in which the perfusate was discarded after a single pass through the lungs had a variable and lesser weight change. To confirm this, we performed IPL experiments by using male Sprague-Dawley specific-pathogen-free rats (175–225 g). In 10 IPLs, perfusate initially was discarded after passing through the lungs and then was recirculated continuously. During the single-pass period, the rate of weight change was +0.7 ± 2.0 mg/min compared with −9.0 ± 1.3 mg/min for the recirculating period. Adenosine 3′,5′-cyclic monophosphate (cAMP) accumulated during recirculation. The weight loss induced by recirculation was reproduced by perfusion with 8-bromoadenosine 3′,5′-cyclic monophosphate or terbutaline in single-pass fashion and blocked when the kinase inhibitor H-8 or phosphodiesterase was present in the recirculating perfusate. In summary, perfusate recirculation in the IPL stimulates fluid resorption at least partially via cAMP. This should be factored into the design and interpretation of IPL experiments.
Application of negative expiratory pressure during expiration and activity of genioglossus in humans
Authors: Tantucci Claudio , Mehiri Selma , Duguet Alexandre , Similowski Thomas , Arnulf Isabelle , Zelter Marc , Derenne Jean-Philippe , Milic-Emili Joseph
Published: December 2017

The application of negative expiratory pressure (NEP) at end expiration has been shown to cause reflex-mediated activation of the genioglossus muscle in awake humans. To test whether a reflex contraction of pharyngeal dilator muscles also occurs in response to NEP applied in early expiration, the effect on genioglossus muscle reflex activity of NEP pulses of 500 ms, given 0.2 s after the onset of expiration and during the end-expiratory pause, was assessed in 10 normal awake subjects at rest. The raw and integrated surface electromyogram of the genioglossus (EMGgg) was recorded with airflow and mouth pressure under control conditions and with NEP ranging from −3 to −10 cmH2O. Intraoral EMGgg was also recorded under the same experimental conditions in two subjects. The application of NEP at the end-expiratory pause elicited a consistent reflex response of EMGgg in seven subjects with a mean latency of 68 ± 5 ms. In contrast, when NEP was applied at the onset of expiration, EMGgg reflex activity was invariably observed in only one subject. No relationship was found between steady increase or abrupt fall in expiratory flow and the presence or the absence of a reflex activity of genioglossus during sudden application of NEP at the beginning of expiration. Our results show that a reflex activity of genioglossus is elicited much more commonly during application of NEP at the end rather than at the onset of expiration. These findings also suggest that when NEP is applied in early expiration to detect intrathoracic flow limitation the absence of upper airways narrowing does not imply the occurrence of a reflex-mediated activation of genioglossus and vice versa.
Rapid reversal of adaptive increases in muscle GLUT-4 and glucose transport capacity after training cessation
Authors: Host Helen H. , Hansen Polly A. , Nolte Lorraine A. , Chen May M. , Holloszy John O.
Published: December 2017

Previous studies have shown that when exercise is stopped there is a rapid reversal of the training-induced adaptive increase in muscle glucose transport capacity. Endurance exercise training brings about an increase in GLUT-4 in skeletal muscle. The primary purpose of this study was to determine whether the rapid reversal of the increase in maximally insulin-stimulated glucose transport after cessation of training can be explained by a similarly rapid decrease in GLUT-4. A second purpose was to evaluate the possibility, suggested by previous studies, that the magnitude of the adaptive increase in muscle GLUT-4 decreases when exercise training is extended beyond a few days. We found that both GLUT-4 and maximally insulin-stimulated glucose transport were increased approximately twofold in epitrochlearis muscles of rats trained by swimming for 6 h/day for 5 days or 5 wk. GLUT-4 was 90% higher, citrate synthase activity was 23% higher, and hexokinase activity was 28% higher in triceps muscle of the 5-day trained animals compared with the controls. The increases in GLUT-4 protein and in insulin-stimulated glucose transport were completely reversed within 40 h after the last exercise bout, after both 5 days and 5 wk of training. In contrast, the increases in citrate synthase and hexokinase activities were unchanged 40 h after 5 days of exercise. These results support the conclusion that the rapid reversal of the increase in the insulin responsiveness of muscle glucose transport after cessation of training is explained by the short half-life of the GLUT-4 protein.
Physiological control of a total artificial heart: conductance- and  arterial pressure-based control
Authors: Abe Y. , Chinzei T. , Mabuchi K. , Snyder A. J. , Isoyama T. , Imanishi K. , Yonezawa T. , Matsuura H. , Kouno A. , Ono T. , Atsumi K. , Fujimasa I. , Imachi K.
Published: December 2017

To obtain a physiological response by a total artificial heart (TAH), while eliminating the hemodynamic abnormalities commonly observed with its use, we proposed the use of a conductance- and arterial pressure-based method (1/R control) to determine TAH cardiac output. In this study, we endeavored to make use of a variable more closely tied to central nervous system (CNS) efferents, systemic conductance, to provide the CNS with more direct control over the output of the TAH. The control equation that calculates the target cardiac output of the TAH was constructed on the basis of measurement of blood pressures and TAH flow. The 1/R control method was tested in TAH-recipient goats with an automatic method by using a microcomputer. In 1/R control animals, the typical TAH pathologies, such as mild arterial hypertension and substantial systemic venous hypertension, did not occur. Cardiac output varied according to daily activity level and exercise in a manner similar to that observed in natural heart goats. These results indicate that we have determined a control method for the TAH that avoids hemodynamic abnormalities exhibited by other TAH control systems and that exhibits physiological responses to exercise and daily activities under the conditions tested. The stability of the control and the complete lack of inappropriate excursions in cardiac output is suggestive of CNS involvement in stabilizing the system.
Perfusion heterogeneity in the pulmonary acinus
Authors: Tanabe Nobuhiro , Todoran Thomas M. , Zenk Gerald M. , Bunton Brenda R. , Wagner Wiltz W. , Presson Robert G.
Published: December 2017

There is little information on the distribution of acinar perfusion because it is difficult to resolve blood flow within such small regions. We hypothesized that the known heterogeneity of arteriolar blood flow and capillary blood flow would result in heterogeneous acinar perfusion. To test this hypothesis, the passage of fluorescent dye boluses through the subpleural microcirculation of isolated dog lobes was videotaped by using fluorescence microscopy. As the videotapes were replayed, dye-dilution curves were recorded from each of the tributary branches of Y-shaped venules that drained an acinus. From the dye curves, we calculated the mean appearance time of each curve. The difference in mean appearance times between venular tributary branches was small in most cases. In 43% of the observed venular branch pairs, the dye curves were essentially superimposable (the mean appearance-time difference was <5%); and in another 42%, the mean appearance-time difference between curves was 5–10%. From these results, we conclude that acinar perfusion is unexpectedly homogeneous.
Absence of myofibrillar creatine kinase and diaphragm isometric function during repetitive activation
Authors: Labella John J. , Daood Monica J. , Koretsky A. P. , Roman Brian B. , Sieck Gary C. , Wieringa Be , Watchko Jon F.
Published: December 2017

Creatine kinase (CK) provides ATP buffering in skeletal muscle and is expressed as 1) cytosolic myofibrillar CK (M-CK) and 2) sarcomeric mitochondrial CK (ScCKmit) isoforms that differ in their subcellular localization. We compared the isometric contractile and fatigue properties of 1) control CK-sufficient (Ctl), 2) M-CK-deficient (M-CK[−/−]), and 3) combined M-CK/ScCKmit-deficient null mutant (CK[−/−]) diaphragm (Dia) to determine the effect of the absence of M-CK activity on Dia performance in vitro. Baseline contractile properties were comparable across groups except for specific force, which was ∼16% lower in CK[−/−] Dia compared with M-CK[−/−] and Ctl Dia. During repetitive activation (40 Hz, [Formula: see text] duty cycle), force declined in all three groups. This decline was significantly greater in CK[−/−] Dia compared with Ctl and M-CK[−/−] Dia. The pattern of force decline did not differ between M-CK[−/−] and Ctl Dia. We conclude that Dia isometric muscle function is not absolutely dependent on the presence of M-CK, whereas the complete absence of CK acutely impairs isometric force generation during repetitive activation.
Effects of mode and carbohydrate on the granulocyte and monocyte response to intensive, prolonged exercise
Authors: Nieman David C. , Nehlsen-Cannarella Sandra L. , Fagoaga Omar R. , Henson Dru A. , Utter Alan , Davis J. Mark , Williams Franklin , Butterworth Diane E.
Published: December 2017

The influence of exercise mode and 6% carbohydrate (C) vs. placebo (P) beverage ingestion on granulocyte and monocyte phagocytosis and oxidative burst activity (GMPOB) after prolonged and intensive exertion was measured in 10 triathletes. The triathletes acted as their own controls and ran or cycled for 2.5 h at ∼75% maximal O2uptake, ingesting C or P (4 total sessions, random order, with beverages administered in double-blind fashion). During the 2.5-h exercise bouts, C or P (4 ml/kg) was ingested every 15 min. Five blood samples were collected (15 min before exercise, immediately after exercise, and 1.5, 3, and 6 h after exercise). The pattern of change over time for GMPOB was significantly different between C and P conditions ( P ≤ 0.05), with postexercise values lower during the C trials. Little difference was measured between running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin, lower plasma levels of cortisol and growth hormone, and lower blood neutrophil and monocyte cell counts. These data indicate that C vs. P ingestion is associated with higher plasma glucose levels, an attenuated cortisol response, and lower GMPOB.
Apnea and periodic breathing in bed-sharing and solitary sleeping infants
Authors: Richard Christopher A. , Mosko Sarah S. , McKenna James J.
Published: December 2017

Mother-infant bed sharing, compared with the solitary sleeping condition, has recently been associated with several physiological and behavioral effects. Because the physiological effects of bed sharing may also include respiratory changes, we compared the incidence of central and obstructive apneas and periodic breathing in bed-sharing and solitary sleeping infants. Twenty routinely bed-sharing mother-infant pairs and fifteen routinely solitary sleeping pairs slept for 3 nights in a sleep laboratory. After an initial adaptation night, each pair spent 1 night bed sharing and 1 night in solitary sleep in random order. Apnea and periodic breathing were scored from polysomnographic recordings. The frequency of central apnea was significantly increased on the bed-sharing night, compared with the solitary night, regardless of routine sleeping arrangement. There were significantly fewer obstructive apneas on the bed-sharing night than on the solitary night, but only in routinely solitary sleeping infants. In both groups, there was a significantly higher frequency of periodic breathing events on the bed-sharing night than on the solitary night. These findings demonstrate that the bed-sharing environment can have a significant impact on respiratory control in the infant. Evidence is also presented to suggest that routine bed sharing may result in subtle neurophysiological and/or developmental differences in infants.
Effects of chest wall vibration on breathlessness during hypercapnic ventilatory response
Authors: Edo Hidenori , Kimura Hiroshi , Niijima Mafumi , Sakabe Hideo , Shibuya Masato , Kanamaru Arata , Homma Ikuo , Kuriyama Takayuki
Published: December 2017

Vibratory stimulation applied to the chest wall during inspiration reduces the intensity of breathlessness, whereas the same stimulation during expiration has no effect or may increase breathlessness. The purpose of the present study was to determine whether vibration reduced the intensity of breathlessness during progressive hypercapnia with and without the addition of an external resistive load. A second objective was to see whether the mouth occlusion pressure at 0.2 s (P0.2) was reduced by the vibratory stimulation. Hypercapnic ventilatory response was conducted in 10 healthy male volunteers with simultaneous measurement of visual analog scale, P0.2, and minute ventilation. Hypercapnic ventilatory response was performed and randomly combined with or without vibratory stimulation (100 Hz) as well as with or without inspiratory load. With inspiratory load, in-phase vibration did not cause any significant changes in the slopes of P0.2 and minute ventilation to CO2, whereas the slope of visual analog scale to CO2 significantly decreased from 0.47 ± 0.15 to 0.34 ± 0.11 (SE) cm/Torr ( P < 0.05). We conclude that in-phase vibration could decrease the slope of breathlessness elicited by inspiratory load combined with hypercapnia without changing motor output.
Rapid reversibility of the allergen-induced pulmonary late-phase reaction by an intravenous β2-agonist
Authors: Peebles R. Stokes , Permutt Solbert , Togias Alkis
Published: December 2017

This study was performed to determine the degree to which β2-adrenergic receptor agonists can reverse the allergen-induced late reduction in lung function. On two occasions, seven asthmatic subjects were administered terbutaline or its vehicle by intravenous infusion 7 h after inhaled allergen, at which point the forced expiratory volume in 1 s was 57% of baseline. On another occasion, terbutaline was infused at baseline to determine maximal attainable bronchodilation. After allergen challenge, terbutaline rapidly improved lung function. At the end of terbutaline infusion, the forced expiratory volume in 1 s reached 100 ± 1.3% of baseline and 84.2 ± 4.3% of maximal attainable value, but the bronchodilating effect of the β-agonist did not plateau. The values for forced vital capacity were 102 ± 1.3% of baseline and 95.1 ± 3% of maximal attainable value. The kinetics of the terbutaline effect, when it was infused at baseline, were similar to those in the late phase. Because the late-phase reduction in lung function is rapidly reversible by β2-adrenergic agonists, we conclude that it is caused mainly by bronchial smooth muscle spasm.
Coordination between glottic adductor muscle and diaphragm EMG activity in fetal lambs in utero
Authors: Kianicka Irenej , Diaz Véronique , Dorion Dominique , Praud Jean-Paul ,   (With the Technical Assistance of Bruno Gagné and Jocelyn Labbé)
Published: December 2017

It has previously been reported that active glottic adduction is present during prolonged apneas but absent during periods of breathing movements in fetal lambs in utero. The present study was aimed at examining the precise coordination between fetal breathing movements [diaphragm electromyographic (EMG) activity (Di EMG)] and glottic adduction [thyroarytenoid muscle EMG activity (TA EMG)]. Electrodes for electroencephalogram, eye movements, TA EMG, and Di EMG and an arterial catheter were surgically implanted in fetal lambs 123–142 days postconception. Polygraphic recordings were performed without sedation while the ewe breathed room air ( n = 11) or various gas mixtures (hypoxia, n = 5; hyperoxia, n = 4; hypercapnia, n = 5; hypercapnia+hyperoxia, n = 5). Tonic TA EMG was observed throughout >90% of apneas (>6 s) in both non-rapid-eye-movement and rapid-eye-movement sleep, and when Di EMG frequency decreased in rapid-eye-movement sleep. In all but two fetuses, TA EMG was immediately inhibited when Di EMG appeared. Altering blood gases did not modify these results. In conclusion, Di EMG and TA EMG are well coordinated in late gestation in fetal lambs, except in a few cases. These findings may have consequences for understanding the pathogenesis of mixed/obstructive apneas of prematurity.
Metabolic and hemodynamic responses of lower limb during exercise in patients with COPD
Authors: Maltais François , Jobin Jean , Sullivan Martin J. , Bernard Sarah , Whittom François , Killian Kieran J. , Desmeules Marc , Bélanger Marthe , LeBlanc Pierre
Published: December 2017

Premature lactic acidosis during exercise in patients with chronic obstructive pulmonary disease (COPD) may play a role in exercise intolerance. In this study, we evaluated whether the early exercise-induced lactic acidosis in these individuals can be explained by changes in peripheral O2delivery (D˙o2). Measurements of leg blood flow by thermodilution and of arterial and femoral venous blood gases, pH, and lactate were obtained during a standard incremental exercise test to capacity in eight patients with severe COPD and in eight age-matched controls. No significant difference was found between the two groups in leg blood flow at rest or during exercise at the same power outputs. Blood lactate concentrations and lactate release from the lower limb were greater in COPD patients at all submaximal exercise levels (all P < 0.05). LegD˙o2at a given power output was not significantly different between the two groups, and no significant correlation was found between this parameter and blood lactate concentrations. COPD patients had lower arterial and venous pH at submaximal exercise, and there was a significant positive correlation between venous pH at 40 W and the peak O2uptake ( r = 0.91, P < 0.0001). The correlation between venous pH and peak O2uptake suggests that early muscle acidosis may be involved in early exercise termination in COPD patients. The early lactate release from the lower limb during exercise could not be accounted for by changes in peripheralD˙o2. The present results point to skeletal muscle dysfunction as being responsible for the early onset of lactic acidosis in COPD.
Intramuscular fatty acid metabolism evaluated with stable isotopic tracers
Authors: Guo Zengkui , Jensen Michael D.
Published: December 2017

We evaluated the applicability of stable isotopic tracers to the study of intramuscular fatty acid metabolism by infusing both [U-13C]palmitate and [1-13C]oleate intravenously for 4 h into fasted conscious rats. Skeletal muscles were sequentially biopsied, and the concentration and13C enrichment of fatty acids were measured by gas chromatography/combustion/isotope ratio mass spectrometry. Throughout the study, the13C enrichment of plasma palmitate and oleate remained substantially greater than intramuscular nonesterified palmitate and oleate enrichment, which in turn was greater than intramuscular triglyceride palmitate and oleate enrichment. Fractional synthesis rates of intramuscular triglycerides in gastrocnemius and soleus were 0.267 ± 0.075 and 0.100 ± 0.030/h ( P = 0.04), respectively, as determined by using [U-13C]palmitate, and were 0.278 ± 0.049 and 0.075 ± 0.013/h ( P = 0.02), respectively, by using [1-13C]oleate. We conclude that plasma free fatty acids are a source for intramuscular triglycerides and nonesterified fatty acids; the latter are likely the synthetic precursors of the former. Uniformly and singly labeled [13C]fatty acid tracers will provide an important tool to study intramuscular fatty acid and triglyceride metabolism.
Muscle metabolites and performance during high-intensity, intermittent exercise
Authors: Hargreaves Mark , McKenna Michael J. , Jenkins David G. , Warmington Stuart A. , Li Jia L. , Snow Rodney J. , Febbraio Mark A.
Published: December 2017

Six men were studied during four 30-s “all-out” exercise bouts on an air-braked cycle ergometer. The first three exercise bouts were separated by 4 min of passive recovery; after the third bout, subjects rested for 4 min, exercised for 30 min at 30–35% peak O2 consumption, and rested for a further 60 min before completing the fourth exercise bout. Peak power and total work were reduced ( P < 0.05) during bout 3 [765 ± 60 (SE) W; 15.8 ± 1.0 kJ] compared with bout 1 (1,168 ± 55 W, 23.8 ± 1.2 kJ), but no difference in exercise performance was observed between bouts 1 and 4 (1,094 ± 64 W, 23.2 ± 1.4 kJ). Before bout 3, muscle ATP, creatine phosphate (CP), glycogen, pH, and sarcoplasmic reticulum (SR) Ca2+ uptake were reduced, while muscle lactate and inosine 5′-monophosphate were increased. Muscle ATP and glycogen before bout 4 remained lower than values before bout 1( P < 0.05), but there were no differences in muscle inosine 5′-monophosphate, lactate, pH, and SR Ca2+ uptake. Muscle CP levels before bout 4 had increased above resting levels. Consistent with the decline in muscle ATP were increases in hypoxanthine and inosine before bouts 3 and 4. The decline in exercise performance does not appear to be related to a reduction in muscle glycogen. Instead, it may be caused by reduced CP availability, increased H+ concentration, impairment in SR function, or some other fatigue-inducing agent.
Breathing route dependence of upper airway muscle activity during hyperpnea
Authors: Shi Yong-Xin , Seto-Poon Margaret , Wheatley John R.
Published: December 2017

Exercise (Ex) and hypercapnia (HC) both lead to increases in ventilation and upper airway muscle (UAM) activity. To determine whether different breathing routes (nasal vs. oral) or stimuli produced differential UAM activation, electromyographic (EMG) activity of the alae nasi (AN) and genioglossus (GG) were measured in seven normal subjects seated on a bicycle ergometer. Subjects performed paired runs during both progressive Ex and HC while breathing through the nose alone (N) or the mouth alone (O). During hyperpnea, AN EMG was greater when the subjects were breathing via N [81 ± 6% maximum (HC) and 69 ± 7% maximum (Ex)] than when they were breathing via O [30 ± 5% maximum (HC) and 27 ± 5% maximum (Ex); both P < 0.01], whereas the GG EMG did not differ between N and O. Both AN and GG EMG were similar for Ex and HC when the subjects were breathing via the same route. We conclude that UAM activation was independent of the nature of the stimulus. However, the AN muscle but not the GG muscle demonstrated breathing-route dependence of activity.
Effect of prolonged heavy exercise on pulmonary gas exchange in horses
Authors: Hopkins S. R. , Bayly W. M. , Slocombe R. F. , Wagner H. , Wagner P. D.
Published: December 2017

During short-term maximal exercise, horses have impaired pulmonary gas exchange, manifested by diffusion limitation and arterial hypoxemia, without marked ventilation-perfusion (V˙a/Q˙) inequality. Whether gas exchange deteriorates progressively during prolonged submaximal exercise has not been investigated. Six thoroughbred horses performed treadmill exercise at ∼60% of maximal oxygen uptake until exhaustion (28–39 min). Multiple inert gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained at rest and 5-min intervals during exercise. Oxygen uptake, cardiac output, and alveolar-arterial[Formula: see text] gradient were unchanged after the first 5 min of exercise. Alveolar ventilation increased progressively during exercise, from increased tidal volume and respiratory frequency, resulting in an increase in arterial[Formula: see text] and decrease in arterial[Formula: see text]. At rest there was minimalV˙a/Q˙inequality, log SD of the perfusion distribution (log SDQ˙) = 0.20. This doubled by 5 min of exercise (log SDQ˙= 0.40) but did not increase further. There was no evidence of alveolar-end-capillary diffusion limitation during exercise. However, there was evidence for gas-phase diffusion limitation at all time points, and enflurane was preferentially overretained. Horses maintain excellent pulmonary gas exchange during exhaustive, submaximal exercise. AlthoughV˙a/Q˙inequality is greater than at rest, it is less than observed in most mammals and the effect on gas exchange is minimal.
Adherent neutrophils activate endothelial myosin light chain kinase: role in transendothelial migration
Authors: Garcia Joe G. N. , Verin Alexander D. , Herenyiova Maria , English Denis
Published: December 2017

Increased vascular endothelial cell (EC) permeability and neutrophilic leukocyte (PMN) diapedesis through paracellular gaps are cardinal features of acute inflammation. Activation of the EC contractile apparatus is necessary and sufficient to increase vascular permeability in specific models of EC barrier dysfunction. However, it is unknown whether EC contraction with subsequent paracellular gap formation is required for PMN transendothelial migration in response to chemotactic factors. To test this possibility, we assessed migration of human PMNs across confluent bovine pulmonary arterial EC monolayers. Transendothelial PMN migration in the absence of a chemotactic gradient was minimal, whereas abluminal addition of leukotriene B4(LTB4; 5 μM) resulted in significantly increased PMN migration. Reductions in EC myosin light chain kinase (MLCK) activity by EC monolayer pretreatment with specific MLCK inhibitors (KT-5926 or ML-7) or by increases in cAMP-protein kinase A activity (cholera toxin) significantly reduced PMN transmigration (30–70% inhibition). In contrast, pretreatment with the myosin-associated phosphatase inhibitor calyculin resulted in the accumulation of phosphorylated myosin light chains, EC contraction, and significantly enhanced PMN migration. Finally, the interaction of PMNs with32P-labeled EC monolayers was shown to directly increase EC myosin phosphorylation in a time-dependent fashion. Taken together, these results are consistent with the hypothesis that the phosphorylation status of EC myosin regulates PMN migration and further indicate that EC MLCK is activated by chemoattractant-stimulated PMNs. Neutrophil-dependent activation of the EC contractile apparatus with subsequent paracellular gap formation may be a key determinant of transendothelial PMN migration responses to chemotactic agents.
Postprandial lipemia in endurance-trained people during a short interruption to training
Authors: Hardman Adrianne E. , Lawrence Janet E. M. , Herd Sara L.
Published: December 2017

This study examined changes in postprandial lipemia in endurance-trained people during a short interruption to training. Nine men and one woman (ages 18–55 yr) undertook fat tolerance tests after 15 h, 60 h, and 6.5 days without exercise. The test meal (1.2 g fat, 1.1 g carbohydrate, 66 kJ/kg body mass) was consumed after a 12-h fast. Postprandial lipemia increased rapidly with detraining (area under plasma triacylglycerol vs. time curve: 8.42 ± 1.40, 11.35 ± 1.38, and 11.97 mM × 6 h at 15 h, 60 h and 6.5 days, respectively). In the fasted state, plasma triacylglycerol concentration (0.85 ± 0.15, 1.09 ± 0.12, and 1.10 ± 0.11 mM at 15 h, 60 h and 6.5 days, respectively) and the ratio of total cholesterol to high-density-lipoprotein cholesterol increased with detraining. Values were significantly higher at 60 h and 6.5 days than values at 15 h ( P < 0.05) for each of these three variables. The serum insulin response was higher ( P < 0.05) at 6.5 days than at 15 h (81.6 ± 11.3, 87.6 ± 11.4, and 94.5 ± 9.4 μIU/ml × 6 h at 15 h, 60 h, and 6.5 days, respectively). Frequent exercise is needed to maintain a low level of postprandial lipemia and insulinemia in trained people.
Force, speed, and oxygen consumption in Thoroughbred and draft horses
Authors: Potard U. Silke Birlenbach , Leith David E. , Fedde M. Roger
Published: December 2017

Thoroughbred (TB) and draft horses (DH) have long been selected for tasks of very different intensities and force-speed relationships. To study their adaptations, we measured O2consumption and related variables in three TB and four DH during progressive exercise tests on a level treadmill. The horses exerted a draft force of 0, 5, 10, 15, or 20% of their body weight at speeds that increased by 2 m/s every 3 min until they could not maintain that speed. We found that TB could exert the same draft forces as DH and, at each force, TB achieved about twice the speed, twice the external power, and twice the O2consumption as DH; thus the two breeds had the same gross efficiencies. We also found maximal O2consumption of TB to be about twice that of DH (134 vs. 72 ml ⋅ kg−1⋅ min−1, respectively), suggesting adaptations to high-intensity exercise. Peak efficiency was reached at lower speeds in DH than in TB, suggesting adaptations to high-force, low-speed exercise. These differences between TB and DH in force-speed and aerobic capacities and in speed for peak efficiency likely reflect different contraction velocities in locomotor muscles.
Hypercapnia-induced long-term depression of respiratory activity requires α2-adrenergic receptors
Authors: Bach K. B. , Mitchell G. S.
Published: December 2017

We investigated the effects of repeated hypercapnic episodes (inspired CO2fraction = 0.10) on posthypercapnic respiratory nerve discharge. Anesthetized (urethan), vagotomized, and artificially ventilated rats were presented with three consecutive 5-min episodes of hyperoxic hypercapnia, separated by 5 min of hyperoxic normocapnia (inspired O2 fraction = 0.5). Respiratory nerve discharge and blood gases were recorded before and 30 and 60 min after the final hypercapnic episode. Posthypercapnia, arterial[Formula: see text] was maintained within 1 Torr of initial baseline values. Integrated phrenic and hypoglossal burst amplitudes decreased posthypercapnia by up to 46 ± 17 and 55 ± 13% of baseline values, respectively, and remained reduced for at least 1 h [long-term depression (LTD)]. The protocol was repeated in rats pretreated with the α2-adrenergic antagonists yohimbine HCl (0.5 mg/kg; n = 7) or 2-[2-(2-methoxy-1,4-benzodioanyl)]imidazoline (RX-821002) HCl (0.25 mg/kg; n = 3). Both drugs attenuated LTD in the phrenic and hypoglossal neurograms. Results indicate that episodic hypercapnia elicits a yohimbine- and RX-821002-sensitive LTD of respiratory nerve activity in rats, suggesting that LTD requires α2-receptor activation.