bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of myosin heavy chain mRNA expression by RT-PCR
Authors: Wright Carola , Haddad Fadia , Qin Anqi X. , Baldwin Kenneth M.
Published: December 2017

Wright, Carola, Fadia Haddad, Anqi X. Qin, and Kenneth M. Baldwin. Analysis of myosin heavy chain mRNA expression by RT-PCR. J. Appl. Physiol. 83(4): 1389–1396, 1997.—An assay was developed for rapid and sensitive analysis of myosin heavy chain (MHC) mRNA expression in rodent skeletal muscle. Only 2 μg of total RNA were necessary for the simultaneous analysis of relative mRNA expression of six different MHC genes. We designed synthetic DNA fragments as internal standards, which contained the relevant primer sequences for the adult MHC mRNAs type I, IIa, IIx, IIb as well as the embryonic and neonatal MHC mRNAs. A known amount of the synthetic fragment was added to each polymerase chain reaction (PCR) and yielded a product of different size than the amplified MHC mRNA fragment. The ratio of amplified MHC fragment to synthetic fragment allowed us to calculate percentages of the gene expression of the different MHC genes in a given muscle sample. Comparison with the traditional Northern blot analysis demonstrated that our reverse transcriptase-PCR-based assay was reliable, fast, and quantitative over a wide range of relative MHC mRNA expression in a spectrum of adult and neonatal rat skeletal muscles. Furthermore, the high sensitivity of the assay made it very useful when only small quantities of tissue were available. Statistical analysis of the signals for each MHC isoform across the analyzed samples showed a highly significant correlation between the PCR and the Northern signals as Pearson correlation coefficients ranged between 0.77 and 0.96 ( P < 0.005). This assay has potential use in analyzing small muscle samples such as biopsies and samples from pre- and/or neonatal stages of development.
Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats
Authors: Sadamoto Tomoko , Matsukawa Kanji
Published: December 2017

Sadamoto, Tomoko, and Kanji Matsukawa. Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats. J. Appl. Physiol.83(5): 1454–1460, 1997.—To examine whether the cerebrum is essential for producing the rapid cardiovascular adjustment at the beginning of overground locomotion, we examined heart rate (HR), mean arterial blood pressure (MAP), and integrated electromyogram (iEMG) of the forelimb triceps brachialis muscle in freely moving decerebrate cats during locomotion. Two to four days after decerebration surgery performed at the level of the precollicular-premammillary body, the animals spontaneously produced coordinated overground locomotion, supporting body weight. HR began to increase immediately before the onset of iEMG, and MAP began to rise almost simultaneously with the iEMG onset. Their increases in HR and MAP (24 ± 3 beats/min and 22 ± 4 mmHg) were sustained during locomotion. Sinoaortic denervation (SAD) did not affect the abrupt changes in HR and MAP at the beginning of locomotion (0–4 s from the onset of iEMG), whereas SAD had a contrasting effect during the subsequent period, a decrease in the HR response (9 ± 1 beats/min) and an increase in the MAP response (30 ± 3 mmHg). These results suggest that the cerebrum and the rostral part of the diencephalon are not essential for producing the rapid cardiovascular adjustment at the beginning of spontaneous overground locomotion. The arterial baroreflex does not contribute to this rapid adjustment but plays an important role in regulating the cardiovascular responses during the later period of spontaneous locomotion.
Effect of particles on sheep lung hemodynamics parallels depletion and recovery of intravascular macrophages
Authors: Sone Yasuyuki , Nicolaysen Anne , Staub Norman C.
Published: December 2017

Sone, Yasuyuki, Anne Nicolaysen, and Norman C. Staub, Sr.Effect of particles on sheep lung hemodynamics parallels depletion and recovery of intravascular macrophages. J. Appl. Physiol. 83(5): 1499–1507, 1997.—We previously showed in newborn lambs that the pulmonary hemodynamic responses to foreign particulate matter (liposomes; Monastral blue) developed in parallel with the maturation of the pulmonary intravascular macrophage system. We now report our use of the liposome-encapsulated heavy-metal-chelating agent dichloromethylene diphosphonate to deplete the intravascular macrophages of small lambs. Functionally and by quantitative histology, we depleted the vast majority of the intravascular macrophages (71% by Monastral blue particle retention, n = 22; 77% by histology; n = 2). Depletion success increased to >90% as we optimized the liposome-depletion regime. Recovery of the lung hemodynamic response began within 3 days. By 2 wk, the functional responses had fully recovered ( n = 8), and, according to quantitative histology, the macrophage population ( n = 2) had recovered 65%. Macrophage depletion in lambs is relatively inexpensive and easy to achieve. It is a safe procedure and is followed by full recovery in ∼2 wk, provided that an aseptic technique is used to prevent bacteremia.
Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans
Authors: Vøllestad N. K. , Sejersted I. , Saugen E.
Published: December 2017

Vøllestad, N. K., I. Sejersted, and E. Saugen. Mechanical behavior of skeletal muscle during intermittent voluntary isometric contractions in humans. J. Appl. Physiol. 83(5): 1557–1565, 1997.—Changes in contractile speed and force-fusion properties were examined during repetitive isometric contractions with the knee extensors at three different target force levels. Seven healthy subjects were studied at target force levels of 30, 45, and 60% of their maximal voluntary contraction (MVC) force. Repeated 6-s contractions followed by 4-s rest were continued until exhaustion. Contractile speed was determined for contractions elicited by electrical stimulation at 1–50 Hz given during exercise and a subsequent 27-min recovery period. Contraction time remained unchanged during exercise and recovery, except for an initial rapid shift in the twitch properties. Half relaxation time (RT1/2) decreased gradually by 20–40% during exercise at 30 and 45% of MVC. In the recovery period, RT1/2 values were not fully restored to preexercise levels. During exercise at 60% MVC, the RT1/2 decreased for twitches and increased for the 50-Hz stimulation. In the recovery period after 60% MVC, RT1/2 values declined toward those seen after the 30 and 45% MVC exercise. The force oscillation amplitude in unfused tetani relative to the mean force increased during exercise at 30 and 45% MVC but remained unaltered during the 60% MVC exercise. This altered force-fusion was closely associated with the changes in RT1/2. The faster relaxation may at least partly explain the increased energy cost of contraction reported previously for the same type of exercise.
Efficacy of forced-air and inhalation rewarming by using a human model for severe hypothermia
Authors: Goheen M. S. L. , Ducharme M. B. , Kenny G. P. , Johnston C. E. , Frim John , Bristow Gerald K. , Giesbrecht Gordon G.
Published: December 2017

Goheen, M. S. L., M. B. Ducharme, G. P. Kenny, C. E. Johnston, John Frim, Gerald K. Bristow, and Gordon G. Giesbrecht.Efficacy of forced-air and inhalation rewarming by using a human model for severe hypothermia. J. Appl. Physiol. 83(5): 1635–1640, 1997.—We recently developed a nonshivering human model for severe hypothermia by using meperidine to inhibit shivering in mildly hypothermic subjects. This thermal model was used to evaluate warming techniques. On three occasions, eight subjects were immersed for ∼25 min in 9°C water. Meperidine (1.5 mg/kg) was injected before the subjects exited the water. Subjects were then removed, insulated, and rewarmed in an ambient temperature of −20°C with either 1) spontaneous rewarming (control), 2) inhalation rewarming with saturated air at ∼43°C, or 3) forced-air warming. Additional meperidine (to a maximum cumulative dose of 2.5 mg/kg) was given to maintain shivering inhibition. The core temperature afterdrop was 30–40% less during forced-air warming (0.9°C) than during control (1.4°C) and inhalation rewarming (1.2°C) ( P< 0.05). Rewarming rate was 6- to 10-fold greater during forced-air warming (2.40°C/h) than during control (0.41°C/h) and inhalation rewarming (0.23°C/h) ( P< 0.05). In nonshivering hypothermic subjects, forced-air warming provided a rewarming advantage, but inhalation rewarming did not.
Stimulation of vagal pulmonary C fibers by inhaled wood smoke in rats
Authors: Lai C. J. , Kou Y. R.
Published: December 2017

Lai, C. J., and Y. R. Kou. Stimulation of vagal pulmonary C fibers by inhaled wood smoke in rats. J. Appl. Physiol. 84(1): 30–36, 1998.—This study investigated the stimulation of vagal pulmonary C fibers (PCs) by wood smoke. We recorded impulses from PCs in 58 anesthetized, open-chest, and artificially ventilated rats and delivered 6 ml of wood smoke into the lungs. Within 1 or 2 s after the smoke delivery, an intense and nonphasic burst of discharge [Δ = +7.4 ± 0.7 (SE) impulses/s, n = 68] was evoked in 60 of the 68 PCs studied and lasted for 4–8 s. This immediate stimulation was usually followed by a delayed and more sustained increase in C-fiber activity (Δ = +2.0 ± 0.4 impulses/s). The overall stimulation was not influenced by removal of smoke particulates ( n = 15) or by pretreatment with vehicle ( n = 8) for dimethylthiourea (DMTU; a hydroxyl radical scavenger) or indomethacin (Indo; a cyclooxygenase inhibitor). The immediate-phase stimulation was not affected by pretreatment with Indo ( n= 8) but was largely attenuated by pretreatment with DMTU ( n = 12) or by a combined treatment with DMTU and Indo (DMTU+Indo; n = 8). Conversely, the delayed-phase stimulation was partially suppressed either by DMTU or by Indo but was totally abolished by DMTU+Indo. These results suggest that 1) the stimulation of PCs is linked to the gas phase of wood smoke and 2) hydroxyl radical, but not cyclooxygenase products, is involved in the immediate-phase stimulation, whereas both metabolites are responsible for evoking the delayed-phase stimulation.
A comprehensive equation for the pulmonary pressure-volume curve
Authors: Venegas José G. , Harris R. Scott , Simon Brett A.
Published: December 2017

Venegas, José G., R. Scott Harris, and Brett A. Simon.A comprehensive equation for the pulmonary pressure-volume curve. J. Appl. Physiol. 84(1): 389–395, 1998.—Quantification of pulmonary pressure-volume (P-V) curves is often limited to calculation of specific compliance at a given pressure or the recoil pressure (P) at a given volume (V). These parameters can be substantially different depending on the arbitrary pressure or volume used in the comparison and may lead to erroneous conclusions. We evaluated a sigmoidal equation of the form, V = a + b[1 +[Formula: see text]]−1, for its ability to characterize lung and respiratory system P-V curves obtained under a variety of conditions including normal and hypocapnic pneumoconstricted dog lungs ( n = 9), oleic acid-induced acute respiratory distress syndrome ( n = 2), and mechanically ventilated patients with acute respiratory distress syndrome ( n = 10). In this equation, a corresponds to the V of a lower asymptote, b to the V difference between upper and lower asymptotes, cto the P at the true inflection point of the curve, and d to a width parameter proportional to the P range within which most of the V change occurs. The equation fitted equally well inflation and deflation limbs of P-V curves with a mean goodness-of-fit coefficient ( R2) of 0.997 ± 0.02 (SD). When the data from all analyzed P-V curves were normalized by the best-fit parameters and plotted as (V − a)/ bvs. (P − c)/ d, they collapsed into a single and tight relationship ( R2= 0.997). These results demonstrate that this sigmoidal equation can fit with excellent precision inflation and deflation P-V curves of normal lungs and of lungs with alveolar derecruitment and/or a region of gas trapping while yielding robust and physiologically useful parameters.
Laryngeal and abdominal muscle electrical activity during periodic breathing in nonsedated lambs
Authors: Kianicka Irenej , Diaz Véronique , Renolleau Sylvain , Canet Emmanuel , Praud Jean-Paul ,   (With the Technical Assistance of Bruno Gagné)
Published: December 2017

Kianicka, Irenej, Véronique Diaz, Sylvain Renolleau, Emmanuel Canet, and Jean-Paul Praud. Laryngeal and abdominal muscle electrical activity during periodic breathing in nonsedated lambs. J. Appl. Physiol. 84(2): 669–675, 1998.—We recently reported that glottic closure was present throughout central apneas in awake lambs. The present study tested whether glottic closure was also observed during periodic breathing (PB). We attempted to induce PB in 21 nonsedated lambs on return from hypocapnic hypoxia to room air. Airflow and thyroarytenoid (a laryngeal constrictor, n = 16), cricothyroid (a laryngeal dilator, n = 10), and abdominal ( n = 9) muscle electrical activity (EMG) were monitored continuously. PB was observed in 16 lambs, with apneic phases in 8 lambs. Thyroarytenoid muscle EMG was observed at the nadir of PB, either throughout apnea or with prolonged expiration during the lowest respiratory efforts. Phasic inspiratory cricothyroid muscle EMG and phasic expiratory abdominal EMG disappeared at the nadir of PB. Active glottic closure at the nadir of PB, without abdominal muscle contraction, could be a beneficial mechanism, preserving alveolar gas stores for continuing gas exchange during the apneic/hypopneic phase of PB. However, consequences of active glottic closure on ventilatory instability, either enhancing or reducing, are unknown.
Effects of pulmonary embolism on pulmonary vascular impedance in dogs and minipigs
Authors: Maggiorini Marco , Brimioulle Serge , De Canniere Didier , Delcroix Marion , Naeije Robert
Published: December 2017

Pigs have been reported to present with a stronger pulmonary vascular reactivity than many other species, including dogs. We investigated the pulmonary vascular impedance response to autologous blood clot embolic pulmonary hypertension in anesthetized and ventilated minipigs ( n = 6) and dogs ( n = 6). Before embolization, minipigs, compared with dogs, presented with higher mean pulmonary arterial pressure (Ppa; by an average of 9 mmHg), a steeper slope of Ppa-flow (Q˙) relationships, and higher 0-Hz impedance (Z0) and first-harmonic impedance (Z1), without significant differences in characteristic impedance (Zc), and a lower ratio of pulsatile hydraulic power to total hydraulic power. Embolic pulmonary hypertension (mean Ppa: 40–55 mmHg) was associated with increased Z0 and Z1 in both species, but the minipigs had a steeper slope of Ppa/Q˙ plots and an increased Zc. At identical Q˙ and Ppa, minipigs still presented with higher Z1 and Zc and a lower ratio of pulsatile hydraulic power to total hydraulic power. The energy transmission ratio, defined as the hydraulic power in the measured waves divided by the hydraulic power in the forward waves, was better preserved after embolism in minipigs. No differences in wave reflection indexes were found before and after embolism. We conclude that minipigs, compared with dogs, present with a higher pulmonary vascular resistance and reactivity and adapt to embolic pulmonary hypertension by an increased Zc without earlier wave reflection. These differences allow for a reduced pulsatile component of hydraulic power and, therefore, a better energy transfer from the right ventricle to the pulmonary circulation.
NMDA receptors mediate peripheral chemoreceptor afferent input in the conscious rat
Authors: Ohtake Patricia J. , Torres José E. , Gozal Yair M. , Graff Gavin R. , Gozal David
Published: December 2017

N-methyl-d-aspartate (NMDA) glutamate receptors mediate critical components of cardiorespiratory control in anesthetized animals. The role of NMDA receptors in the ventilatory responses to peripheral and central chemoreceptor stimulation was investigated in conscious, freely behaving rats. Minute ventilation (V˙e) responses to 10% O2, 5% CO2, and increasing intravenous doses of sodium cyanide were measured in intact rats before and after intravenous administration of the NMDA receptor antagonist MK-801 (3 mg/kg). After MK-801, eupcapnic tidal volume (Vt) decreased while frequency increased, resulting in a modest reduction inV˙e. Inspiratory time (Ti) decreased, whereas expiratory time remained unchanged. TheV˙e responses to hypercapnia were qualitatively similar in control and MK-801 conditions, with slight reductions in respiratory drive (Vt/Ti) after MK-801. In contrast, responses to hypoxia were markedly attenuated after MK-801 and were primarily due to reduced frequency changes, whereas Vt was unaffected. Sodium cyanide doses associated with significantV˙eincreases were 5 and 50 μg/kg before and after MK-801, respectively. Thus 1-log shift to the right of individual dose-response curves occurred with MK-801. Selective carotid body denervation reducedV˙e during hypoxia by 70%, and residual hypoxic ventilatory responses were abolished after MK-801. These findings suggest that, in conscious rats, carotid and other peripheral chemoreceptor-mediated hypoxic ventilatory responses are critically dependent on NMDA receptor activation and that NMDA receptor mechanisms are only modestly involved during hypercapnia.
Evaluation of a forced oscillation method to measure thoracic gas volume
Authors: Peslin R. , Duvivier C.
Published: December 2017

The purpose of this study was to test a plethysmographic method of measuring thoracic gas volume (TGV) that, contrary to the usual panting method, would not require any active cooperation from the subject. It is based on the assumption that the out-of-phase component of airway impedance varies linearly with frequency. By using that assumption, TGV may be computed by combining measurements of total respiratory impedance (Zrs) and of the relationship between the plethysmographic signal (Vpl) and airway flow (V˙) during forced oscillations at several frequencies. Zrs and Vpl/V˙were measured at 10 noninteger multiple frequencies ranging from 4 to 29 Hz in 15 subjects breathing gas in nearlybtps conditions. Forced oscillation measurements were immediately followed by determination of TGV by the standard method. The data were analyzed on different frequency ranges, and the best agreement was seen in the 6- to 29-Hz range. Within that range, forced oscillation TGV and standard TGV differed little (3.92 ± 0.66 vs. 3.83 ± 0.73 liters, n = 77, P < 0.05) and were strongly correlated ( r = 0.875); the differences were not correlated to the mean of the two estimates, and their SD was 0.35 liter. In seven subjects the differences were significantly different from zero, which may, in part, be due to imperfect gas conditioning. We conclude that the method is not highly accurate but could prove useful when, for lack of sufficient cooperation, the panting method cannot be used. The results of computer simulation, however, suggest that the method would be unreliable in the presence of severe airway inhomogeneity or peripheral airway obstruction.
Effects of emphysema on diaphragm blood flow during exercise
Authors: Sexton William L. , Poole David C.
Published: December 2017

Chronic hyperinflation of the lung in emphysema displaces the diaphragm caudally, thereby placing it in a mechanically disadvantageous position and contributing to the increased work of breathing. We tested the hypothesis that total and regional diaphragm blood flows are increased in emphysema, presumably reflecting an increased diaphragm energetic demand. Male Syrian Golden hamsters were randomly divided into emphysema (E; intratracheal elastase 25 units/100 g body wt) and control (C; saline) groups, and experiments were performed 16–20 wk later. The regional distribution of blood flow within the diaphragm was determined by using radiolabeled microspheres in hamsters at rest and during treadmill exercise (walking at 20 feet/min, 20% grade). Consistent with pronounced emphysema, lung volume per unit body weight was greater in E hamsters (C, 59.3 ± 1.8; E, 84.5 ± 5.0 ml/kg; P < 0.001) and arterial[Formula: see text] was lower both at rest (C, 74 ± 3; E, 59 ± 2 Torr; P < 0.001) and during exercise (C, 93 ± 3; E, 69 ± 4 Torr; P < 0.001). At rest, total diaphragm blood flow was not different between C and E hamsters (C, 47 ± 4; E, 38 ± 4 ml ⋅ min−1 ⋅ 100 g−1; P = 0.18). In both C and E hamsters, blood flow at rest was lower in the ventral costal region of the diaphragm than in the dorsal and medial costal regions and the crural diaphragm. During exercise in both C and E hamsters, blood flows increased more in the dorsal and medial costal regions and in the crural diaphragm than in the ventral costal region. Total diaphragm blood flow was greater in E hamsters during exercise (C, 58 ± 7; E, 90 ± 14 ml ⋅ min−1 ⋅ 100 g−1; P = 0.03), as a consequence of significantly higher blood flows in the medial and ventral costal regions and crural diaphragm. In addition, exercise-induced increases in intercostal ( P < 0.005) and abdominal ( P < 0.05) muscle blood flows were greater in E hamsters. The finding that diaphragm blood flow was greater in E hamsters during exercise supports the contention that emphysema increases the energetic requirements of the diaphragm.
Mechanisms of ventilatory inhibition by exogenous dopamine in cats
Authors: Loos N. , Haouzi P. , Marchal F.
Published: December 2017

Intravenous injection of dopamine (DA) has consistently been shown to depress minute ventilation (V˙e). Whereas at low dosage (≤10 μg/kg) this effect may be accounted for by inhibition of the carotid sinus nerve chemosensory discharge (CSNCD), other mechanisms appear to be involved with large dosage (≥50 μg/kg). The purpose of this study was to elucidate the mechanisms of DA-inducedV˙e depression. The effects of intravenous injection of DA doses ranging from 1 to 200 μg/kg were studied in 18 anesthetized cats. DA was injected during air and O2 breathing, after α-adrenergic blockade by phenoxybenzamine and after baro- and chemodenervation.V˙e and CSNCD were also simultaneously recorded on four occasions. In contrast to that with use of low-dose DA, V˙e depression induced by high-dose DA was dissociated from CSNCD, persisted during 100% O2 breathing, and was significantly correlated with the rise in arterial blood pressure. Although blunted, V˙e depression was still present after complete chemo- and barodenervation but was suppressed by blocking of the concomitant vasoconstriction with phenoxybenzamine. It is concluded that reflexes of circulatory origin contribute to the V˙e depression induced by large-dose DA, in addition to its effects on arterial chemoreceptors. The contribution of baroreceptor stimulation and peripheral vasoconstriction is discussed.
Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people
Authors: Häkkinen K. , Kallinen M. , Izquierdo M. , Jokelainen K. , Lassila H. , Mälkiä E. , Kraemer W. J. , Newton R. U. , Alen M.
Published: December 2017

Effects of 6 mo of heavy-resistance training combined with explosive exercises on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, as well as maximal and explosive strength were examined in 10 middle-aged men (M40; 42 ± 2 yr), 11 middle-aged women (W40; 39 ± 3 yr), 11 elderly men (M70; 72 ± 3 yr) and 10 elderly women (W70; 67 ± 3 yr). Maximal and explosive strength remained unaltered during a 1-mo control period with no strength training. After the 6 mo of training, maximal isometric and dynamic leg-extension strength increased by 36 ± 4 and 22 ± 2% ( P < 0.001) in M40, by 36 ± 3 and 21 ± 3% ( P < 0.001) in M70, by 66 ± 9 and 34 ± 4% ( P < 0.001) in W40, and by 57 ± 10 and 30 ± 3% ( P < 0.001) in W70, respectively. All groups showed large increases ( P< 0.05–0.001) in the maximum integrated EMGs (iEMGs) of the agonist vastus lateralis and medialis. Significant ( P < 0.05–0.001) increases occurred in the maximal rate of isometric force production and in a squat jump that were accompanied with increased ( P < 0.05–0.01) iEMGs of the leg extensors. The iEMG of the antagonist biceps femoris muscle during the maximal isometric leg extension decreased in both M70 (from 24 ± 6 to 21 ± 6%; P < 0.05) and in W70 (from 31 ± 9 to 24 ± 4%; P < 0.05) to the same level as recorded for M40 and W40. The CSA of the quadriceps femoris increased in M40 by 5% ( P < 0.05), in W40 by 9% ( P < 0.01), in W70 by 6% ( P < 0.05), and in M70 by 2% (not significant). Great training-induced gains in maximal and explosive strength in both middle-aged and elderly subjects were accompanied by large increases in the voluntary activation of the agonists, with significant reductions in the antagonist coactivation in the elderly subjects. Because the enlargements in the muscle CSAs in both middle-aged and elderly subjects were much smaller in magnitude, neural adaptations seem to play a greater role in explaining strength and power gains during the present strength-training protocol.
Leukocyte adhesion molecule expression during intense resistance exercise
Authors: Miles Mary P. , Leach Sharyn K. , Kraemer William J. , Dohi Keiichiro , Bush Jill A. , Mastro Andrea M.
Published: December 2017

We hypothesized that expression of L-selectin and very late antigen-4 (VLA-4) integrin adhesion molecules would influence cell type-specific redistribution during exercise. Women subjects performed six sets of 10-repetition maximum squats. L-selectin and VLA-4 integrin were measured by using flow cytometry pre- and postexercise on peripheral blood neutrophils and lymphocytes ( n = 29 subjects) and lymphocyte subsets ( n = 70 subjects), respectively. Neutrophil concentration increased 41.8% ( P < 0.001), whereas the percent expressing L-selectin was unchanged (79%). Lymphocyte concentration increased 61.8% ( P < 0.001). The percent of T cells expressing L-selectin decreased from 73.5 ± 8.9 to 68.2 ± 11.4% ( P < 0.001); the combined population of natural killer and B cells expressing L-selectin decreased from 80.4 ± 22.5 to 62.7 ± 25.8% ( P < 0.001). VLA-4 integrin was expressed by nearly all lymphocytes both pre- and postexercise. The proportional decrease in L-selectin positive cells could have resulted from 1) shedding of L-selectin, 2) selective entry of L-selectin-negative subsets, or 3) selective removal of L-selectin-positive subsets.
Effect of creatine supplementation on sprint exercise performance and muscle metabolism
Authors: Snow R. J. , McKenna M. J. , Selig S. E. , Kemp J. , Stathis C. G. , Zhao S.
Published: December 2017

The aim of the present study was to examine the effect of creatine supplementation (CrS) on sprint exercise performance and skeletal muscle anaerobic metabolism during and after sprint exercise. Eight active, untrained men performed a 20-s maximal sprint on an air-braked cycle ergometer after 5 days of CrS [30 g creatine (Cr) + 30 g dextrose per day] or placebo (30 g dextrose per day). The trials were separated by 4 wk, and a double-blind crossover design was used. Muscle and blood samples were obtained at rest, immediately after exercise, and after 2 min of passive recovery. CrS increased the muscle total Cr content (9.5 ± 2.0%, P < 0.05, mean ± SE); however, 20-s sprint performance was not improved by CrS. Similarly, the magnitude of the degradation or accumulation of muscle (e.g., adenine nucleotides, phosphocreatine, inosine 5′-monophosphate, lactate, and glycogen) and plasma metabolites (e.g., lactate, hypoxanthine, and ammonia/ammonium) were also unaffected by CrS during exercise or recovery. These data demonstrated that CrS increased muscle total Cr content, but the increase did not induce an improved sprint exercise performance or alterations in anaerobic muscle metabolism.
Mechanical and metabolic determination ofV˙o2and fatigue during repetitive isometric contractions in situ
Authors: Ameredes Bill T. , Brechue William F. , Stainsby Wendell N.
Published: December 2017

Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length ( Lo) or short length ( Ls; ∼0.9 ⋅ Lo), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were ( Lovs. Ls, all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (Po) = 544 vs. 174 (0.38 ⋅ Po) g/g, maximal blood flow (Q˙) = 2.0 vs. 1.4 ml ⋅ min−1⋅ g−1, and maximal oxygen uptake (V˙o2) = 12 vs. 9 μmol ⋅ min−1⋅ g−1. Tension at Lodecreased to 0.64 ⋅ Poover 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at Ls. In separate muscles contracting at Lo,Q˙ was set to that measured at Ls(1.1 ml ⋅ min−1⋅ g−1), resulting in decreased V˙o2(7 μmol ⋅ min−1⋅ g−1), and rapid fatigue, to 0.44 ⋅ Po. These data demonstrate that 1) muscles at Lohave higher Q˙ andV˙o2values than those at Ls; 2) fatigue occurs at Lowith highV˙o2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at Lswith lower tension, Q˙, andV˙o2suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension andV˙o2between Loand Lsgroups indicate that muscles contracting isometrically at initial lengths shorter than Loare working under submaximal conditions.
Leg intramuscular pressures during locomotion in humans
Authors: Ballard Richard E. , Watenpaugh Donald E. , Breit Gregory A. , Murthy Gita , Holley Daniel C. , Hargens Alan R.
Published: December 2017

To assess the usefulness of intramuscular pressure (IMP) measurement for studying muscle function during gait, IMP was recorded in the soleus and tibialis anterior muscles of 10 volunteers during treadmill walking and running by using transducer-tipped catheters. Soleus IMP exhibited single peaks during late-stance phase of walking [181 ± 69 (SE) mmHg] and running (269 ± 95 mmHg). Tibialis anterior IMP showed a biphasic response, with the largest peak (90 ± 15 mmHg during walking and 151 ± 25 mmHg during running) occurring shortly after heel strike. IMP magnitude increased with gait speed in both muscles. Linear regression of soleus IMP against ankle joint torque obtained by a dynamometer produced linear relationships ( n = 2, r = 0.97 for both). Application of these relationships to IMP data yielded estimated peak soleus moment contributions of 0.95–1.65 N ⋅ m/kg during walking, and 1.43–2.70 N ⋅ m/kg during running. Phasic elevations of IMP during exercise are probably generated by local muscle tissue deformations due to muscle force development. Thus profiles of IMP provide a direct, reproducible index of muscle function during locomotion in humans.
Identical responses of fast muscle to sustained activity by low-frequency stimulation in young and aging rats
Authors: Škorjanc Dejan , Traub Irmtrud , Pette Dirk
Published: December 2017

To investigate effects of sustained activity on major phenotypic properties, the left extensor digitorum longus muscle of young (15 wk) and aging (101 wk) male Brown Norway rats was subjected to 50 days of chronic low-frequency stimulation (CLFS; 10 Hz, 10 h/day). The contralateral muscle served as control. Changes in metabolic enzymes were analyzed by using glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase as reference enzymes of glycolysis and by using citrate synthase and 3-hydroxyacyl-CoA dehydrogenase as mitochondrial enzymes representative of aerobic-oxidative metabolism. Myosin heavy chain (MHC) isoforms were analyzed by SDS-PAGE. No differences existed between the enzyme activity profiles of control muscles from young and aging rats. CLFS induced similar increases in mitochondrial enzymes, as well as similar decreases in glycolytic enzymes. Although the MHC composition of the control muscles in the aging rats displayed a shift toward slower isoforms, the ultimate changes induced by CLFS led to nearly identical MHC phenotypes in both young and aging rats. These results demonstrate an unaltered adaptability of skeletal muscle to increased neuromuscular activity in the aging rat.
Diffusional permeability of rabbit mesothelium
Authors: Zocchi L. , Raffaini A. , Agostoni E. , Cremaschi D.
Published: December 2017

Diffusional permeability ( P) to sucrose ( P suc) and Na+([Formula: see text]) was determined in specimens of rabbit sternal parietal pericardium, which may be obtained without stripping. Specimens were mounted in an Ussing apparatus with 3H-labeled sucrose and22Na+in a luminal (L) or interstitial (I) chamber. P suc was 2.16 ± 0.44 for L→I and 2.63 ± 0.45 (SE) × 10−5 cm/s for I→L, i.e., ∼10 times smaller than that previously obtained in stripped specimens of pleura despite the similarity of intercellular junctions in pericardium and pleural mesothelium of various species. These findings suggest that previous P suc was overestimated because stripping damages the mesothelium.[Formula: see text](×10−5 cm/s) was 7.07 ± 0.71 for L→I and 7.37 ± 0.69 × 10−5 cm/s for I→L. Measurements were also done with phospholipids, which are adsorbed on the luminal side of mesothelium in vivo. With phospholipids in L, P suc was 0.75 ± 0.10 and 0.65 ± 0.08 and[Formula: see text]was 3.80 ± 0.32 and 3.76 ± 0.15 × 10−5 cm/s for L→I and I→L, respectively, i.e., smaller than without phospholipids. With phospholipids in I (where they are not adsorbed), P suc (2.33 ± 0.42 × 10−5 cm/s) and[Formula: see text](7.01 ± 0.45 × 10−5 cm/s) were similar to those values without phospholipids. Hence, adsorbed phospholipids decrease P of mesothelium. If the mesothelium were scraped away from the specimen, P suc of the connective tissue would be 13.2 ± 0.76 × 10−5 cm/s. P suc of the mesothelium, computed from P suc of the unscraped and scraped specimens, corrected for the effect of unstirred layers (2.54 and 19.4 × 10−5 cm/s, respectively), was 2.92 and 0.74 × 10−5 cm/s without and with phospholipids, respectively. Hence, most of the resistance to diffusion of the pericardium is provided by the mesothelium.
Catecholamines, heart rate, and oxygen uptake during exercise in persons with spinal cord injury
Authors: Schmid Andreas , Huonker Martin , Barturen Jose-Miguel , Stahl Fabian , Schmidt-Trucksäss Arno , König Daniel , Grathwohl Dominik , Lehmann Manfred , Keul Joseph
Published: December 2017

The purpose of this study was to investigate the influence of different injury levels in persons with spinal cord injury (SCI) on epinephrine (Epi) and norepinephrine (NE) at rest and during graded wheelchair exercise and the related changes in heart rate and O2 uptake (V˙o 2). Twenty tetraplegics (Tetra), 10 high-lesion paraplegics (HLPara), 20 paraplegics with SCI below T5 (MLPara), and 18 able-bodied, nonhandicapped persons (AB) were examined. Because of the higher level of interruption of the sympathetic pathways, Tetra persons showed lower Epi and NE at rest and only slight increases during exercise compared with all other groups; the Tetra subjects’ impaired cardiac sympathetic innervation caused restricted cardioacceleration and strongly reduced maximalV˙o 2. When compared with AB persons, HLPara had comparable NE but lower Epi levels as a result of partial innervation of the noradrenergic system and denervation of the adrenal medulla. MLPara subjects showed an augmented basal and exercise-induced upper spinal thoracic sympathetic activity compared with AB subjects. The increase in heart rate in relation toV˙o 2 was higher in HLPara because of a smaller stroke volume as a result of venous blood pooling. The different exercise response in persons with SCI is a result of the interruption of pathways in the spinal cord to the peripheral sympathetic nervous system in addition to the motor paralysis.
Angiotensin II mediates systemic rebound hypertension after cessation of prostacyclin infusion in sheep
Authors: Robbins Ivan M. , Cuiper Leslie L. , Stein C. Michael , Wood Alastair J. J. , He Huai B. , Parker Richard , Christman Brian W.
Published: December 2017

Prostacyclin (or epoprostenol), an arachidonic acid metabolite, is an effective treatment for patients with primary pulmonary hypertension. Interruption of chronic prostacyclin infusion can result in recurrent symptoms of dyspnea and fatigue. The etiology of this phenomenon is unknown. We hypothesized that sympathoadrenal activation could lead to increased vascular tone after abrupt termination of the infusion. To evaluate this effect, we monitored six chronically instrumented, awake sheep during and after infusion of prostacyclin. Prostacyclin decreased mean arterial pressure (MAP) by 14% and increased cardiac output by 33%. After the infusion ceased, MAP rebounded 23% above baseline, and cardiac output decreased by 28% from peak values within 10 min. We were unable to demonstrate an increase in norepinephrine levels after cessation of prostacyclin, nor did α-adrenergic blockade affect postinfusion hemodynamics. However, plasma renin activity increased >10-fold at peak infusion and remained elevated for up to 2 h after discontinuation of prostacyclin. Coinfusion of the angiotensin II-receptor antagonist L-158,809 resulted in complete abrogation of the postcessation rise in MAP. We conclude that renin-angiotensin system activation is primarily responsible for systemic hypertension occurring after abrupt cessation of prostacyclin infusion in sheep and that angiotensin II receptor blockade prevents this response. Our data do not support a role for sympathetic nervous system activation in the systemic pressor response after prostacyclin infusion.
Budesonide affects allergic mucociliary dysfunction
Authors: O’Riordan Thomas G. , Mao Yongming , Otero Ricardo , Lopez Juan , Sabater Juan R. , Abraham William M.
Published: December 2017

Airway inflammation characterized by neutrophils and free elastase contributes to allergic mucociliary dysfunction. Glucocorticosteroids are the most important anti-inflammatory agents used in the treatment of asthma, but their effect on allergic mucociliary dysfunction is not known. Therefore, we assessed both the prophylactic and therapeutic effects of the glucocorticosteroid budesonide on antigen-induced mucociliary dysfunction in sheep. Tracheal mucus velocity (TMV), a marker of mucociliary clearance, was measured by using a roentgenographic technique. When budesonide was administered either 30 min before or 1 h after airway challenge with Ascaris suum, the antigen-induced fall in TMV at 6 h was prevented. The effects on TMV at 8 and 24 h after challenge were also determined when budesonide and, for comparative purposes, α1-protease inhibitor were given 6 h after antigen challenge. Budesonide treatment improved TMV at 8 h, but TMV was not significantly different from antigen alone at 24 h. Treatment with α1-protease inhibitor, however, caused only a significant reversal of the antigen-induced fall in TMV at 24 h after challenge; this indicates a more prolonged effect than budesonide. Our results suggest that antiproteases may have a potential role as a therapeutic approach to mucociliary dysfunction in asthma and provide evidence for another means by which glucocorticosteroids contribute to the control of the disease.
Fluorescein-labeled dextran concentration is increased in BAL fluid after ANTU-induced edema in rats
Authors: Guery Benoit P. , Nelson Steve , Viget Nathalie , Fialdes Patrice , Summer Warren R. , Dobard Elizabeth , Beaucaire Gilles , Mason Carol M.
Published: December 2017

Several methodologies have been developed to assess alveolocapillary membrane permeability in acute lung injury. The purpose of this study was to determine the reliability of FITC-dextran compared with radioactive tracers to assess lung permeability alterations. After intraperitoneal administration of α-naphthylthiourea (ANTU, 50 mg/kg) or DMSO-ANTU vehicle, the animals were euthanized and their lungs were studied in an isolated-lung preparation. FITC-dextran or radiolabeled tracers were added to the perfusate. At 2 h the bronchoalveolar lavage (BAL) fluid from the ANTU group showed a significantly greater amount of fluorescence in the supernatant after centrifugation of BAL fluid compared with the DMSO group. Consistent results were observed with the radioactive tracers: there was an increase in extravascular albumin space and extravascular lung water compared with the control group. No cleavage of the FITC from the dextran molecule was evident by chromatography comparing samples recovered from the BAL fluid to the pure FITC-dextran molecule. In conclusion, measurement of FITC-dextran in the supernatant of BAL fluid after intravascular administration is a reliable method of assessing lung permeability changes in vivo and ex vivo.
State-space models of insulin and glucose responses to diets of varying nutrient content in men and women
Authors: Holtschlag David J. , Gannon Mary C. , Nuttall Frank Q.
Published: December 2017

Discrete-time state-space models were developed to describe contemporaneous responses of plasma insulin and glucose of normal human subjects. Male and female subjects ingested three consecutive identical meals from isocaloric diets classified as high-carbohydrate, high-fat, high-protein, or standard. Distinctly different glucose and insulin responses were measured in men and women. A seven-state system of linear equations, three in insulin and four in glucose, was identified and estimated to describe responses in men. A six-state system, three in insulin and three in glucose, describes responses in women. Model simulations at 15-min intervals closely match measured concentrations over a 12-h period. Effects of diet content and meal timing on insulin and glucose concentrations were quantified. Dynamic insulin and glucose responses to isocaloric meals of pure carbohydrate, fat, and protein diets were projected on the basis of models developed from mixed diets. The symmetry of the projections indicates that positive excursions in glucose concentrations associated with carbohydrate intake may be matched with negative excursions associated with fat and protein intake to help manage postmeal glucose excursions.
Nonisometric behavior of fascicles during isometric contractions of a human muscle
Authors: Ito Masamitsu , Kawakami Yasuo , Ichinose Yoshiho , Fukashiro Senshi , Fukunaga Tetsuo
Published: December 2017

Fascicle length, pennation angle, and tendon elongation of the human tibialis anterior were measured in vivo by ultrasonography. Subjects ( n = 9) were requested to develop isometric dorsiflexion torque gradually up to maximal at the ankle joint angle of 20° plantarflexion from the anatomic position. Fascicle length shortened from 90 ± 7 to 76 ± 7 (SE) mm, pennation angle increased from 10 ± 1 to 12 ± 1°, and tendon elongation increased up to 15 ± 2 mm with graded force development up to maximum. The tendon stiffness increased with increasing tendon force from 10 N/mm at 0–20 N to 32 N/mm at 240–260 N. Young’s modulus increased from 157 MPa at 0–20 N to 530 MPa at 240–260 N. It can be concluded that, in isometric contractions of a human muscle, mechanical work, some of which is absorbed by the tendinous tissue, is generated by the shortening of muscle fibers and that ultrasonography can be used to determine the stiffness and Young’s modulus for human tendons.
Patterned cardiovascular responses to sleep and nonrespiratory arousals in a porcine model
Authors: Launois Sandrine H. , Abraham Joseph H. , Weiss J. Woodrow , Kirby Debra A.
Published: December 2017

Patients with obstructive sleep apnea experience marked cardiovascular changes with apnea termination. Based on this observation, we hypothesized that sudden sleep disruption is accompanied by a specific, patterned hemodynamic response, similar to the cardiovascular defense reaction. To test this hypothesis, we recorded mean arterial blood pressure, heart rate, iliac blood flow and vascular resistance, and renal blood flow and vascular resistance in five pigs instrumented with chronic sleep electrodes. Cardiovascular parameters were recorded during quiet wakefulness, during non-rapid-eye-movement and rapid-eye-movement sleep, and during spontaneous and induced arousals. Iliac vasodilation (iliac vascular resistance decreased by −29.6 ± 4.1% of baseline) associated with renal vasoconstriction (renal vascular resistance increased by 10.3 ± 4.0%), tachycardia (heart rate increase: +23.8 ± 3.1%), and minimal changes in mean arterial blood pressure were the most common pattern of arousal response, but other hemodynamic patterns were observed. Similar findings were obtained in rapid-eye-movement sleep and for acoustic and tactile arousals. In conclusion, spontaneous and induced arousals from sleep may be associated with simultaneous visceral vasoconstriction and hindlimb vasodilation, but the response is variable.
Discharge patterns in human motor units during fatiguing arm movements
Authors: Griffin L. , Garland S. J. , Ivanova T.
Published: December 2017

The purpose of this study was to determine whether short interspike intervals (ISIs of <20 ms) would occur naturally during voluntary movement and would increase in number with fatigue. Thirty-four triceps brachii motor units from nine subjects were assessed during a fatigue task consisting of fifty extension and fifty flexion elbow movements against a constant-load opposing extension. Nineteen motor units were recorded from the beginning of the fatigue task; the number of short ISIs was 7.1 ± 4.1% of the total number of ISIs in the first one-third of the task (unfatigued state). This value increased to 11.8 ± 5.9% for the last one-third of the task (fatigued state). Fifteen motor units were recruited during the fatigue task and discharged, with 16.4 ± 6.0% of short ISIs in the fatigued state. For all motor units, the number of short ISIs was positively correlated ( r 2 = 0.85) with the recruitment threshold torque. Short ISIs occurred most frequently at movement initiation but also occurred throughout the movement. These results document the presence of short ISIs during voluntary movement and their increase in number during fatigue.
Effect of estrogen supplementation on exercise thermoregulation in premenopausal women
Authors: Chang R.-T. , Lambert G. P. , Moseley P. L. , Chapler F. K. , Gisolfi C. V.
Published: December 2017

This study examined the effects of 3 days of estrogen supplementation (ES) on thermoregulation during exercise in premenopausal (20–39 yr) adult women during the follicular phase of the menstrual cycle. Subjects (11 control, 10 experimental) performed upright cycle ergometer exercise at 60% of maximal O2 consumption in a neutral environment (25°C, 30% relative humidity) for 20 min. Subjects were given placebo (P) or β-estradiol (2 mg/tablet, 3 tablets/day for 3 days). All experiments were conducted between 6:30 and 9:00 AM after ingestion of the last tablet. Heart rate, forearm blood flow (FBF), mean skin temperature, esophageal temperature (Tes), and forearm sweat rate were measured. Blood analysis for estrogen and progesterone reflected the follicular phase of the menstrual cycle. Maximal O2 consumption (37.1 ± 6.2 in P vs. 38.4 ± 6.3 ml ⋅ kg−1 ⋅ min−1in ES) and body weight-to-surface area ratio (35.58 ± 2.85 in P vs. 37.3 ± 2.7 in ES) were similar between groups. Synthesis of 70-kDa heat shock protein was not induced by 3 days of ES. Neither the threshold for sweating (36.97 ± 0.15 in P vs. 36.90 ± 0.22°C in ES), the threshold for an increase in FBF (37.09 ± 0.22 in P vs. 37.17 ± 0.26°C in ES), the slope of sweat rate-Tes relationship (0.42 ± 0.16 in P vs. 0.41 ± 0.17 in ES), nor the FBF-Tes relationship (10.04 ± 4.4 in P vs. 9.61 ± 3.46 in ES) was affected ( P > 0.05) by 3 days of ES. We conclude that 3 days of ES by young adult women in the follicular phase of their menstrual cycle have no effect on heat transfer to the skin, heat dissipation by evaporative cooling, or leukocyte synthesis of 70-kDa heat shock protein.