bluuebunny/crossref_metadata_2025 huggingface dataset:
Lower limb skeletal muscle function after 6 wk of bed rest
Authors: Berg H. E. , Larsson L. , Tesch P. A.
Published: December 2017

Berg, H. E., L. Larsson, and P. A. Tesch. Lower limb skeletal muscle function after 6 wk of bed rest. J. Appl. Physiol. 82(1): 182–188, 1997.—Force, electromyographic (EMG) activity, muscle mass, and fiber characteristics were studied in seven healthy men before and after 6 wk of bed rest. Maximum voluntary isometric and concentric knee extensor torque decreased ( P < 0.05) uniformly across angular velocities by 25–30% after bed rest. Maximum quadricep rectified EMG decreased by 19 ± 23%, whereas submaximum (100-Nm isometric action) EMG increased by 44 ± 28%. Knee extensor muscle cross-sectional area (CSA), assessed by using magnetic resonance imaging, decreased by 14 ± 4%. Maximum torque per knee extensor CSA decreased by 13 ± 9%. Vastus lateralis fiber CSA decreased 18 ± 14%. Neither type I, IIA, and IIB fiber percentages nor their relative proportions of myosin heavy chain (MHC) isoforms were altered after bed rest. Because the decline in strength could not be entirely accounted for by decreased muscle CSA, it is suggested that the strength loss is also due to factors resulting in decreased neural input to muscle and/or reduced specific tension of muscle, as evidenced by a decreased torque/EMG ratio. Additionally, it is concluded that muscle unloading in humans does not induce important changes in fiber type or MHC composition or in vivo muscle contractile properties.
Phosphorylation of rat muscle acetyl-CoA carboxylase by AMP-activated protein kinase and protein kinase A
Authors: Winder W. W. , Wilson H. A. , Hardie D. G. , Rasmussen B. B. , Hutber C. A. , Call G. B. , Clayton R. D. , Conley L. M. , Yoon S. , Zhou B.
Published: December 2017

Winder, W. W., H. A. Wilson, D. G. Hardie, B. B. Rasmussen, C. A. Hutber, G. B. Call, R. D. Clayton, L. M. Conley, S. Yoon, and B. Zhou. Phosphorylation of rat muscle acetyl-CoA carboxylase by AMP-activated protein kinase and protein kinase A. J. Appl. Physiol. 82(1): 219–225, 1997—This study was designed to compare functional effects of phosphorylation of muscle acetyl-CoA carboxylase (ACC) by adenosine 3′,5′-cyclic monophosphate-dependent protein kinase (PKA) and by AMP-activated protein kinase (AMPK). Muscle ACC (272 kDa) was phosphorylated and then subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. Functional effects of phosphorylation were determined by measuring ACC activity at different concentrations of each of the substrates and of citrate, an activator of the enzyme. The maximal velocity ( Vmax) and the Michaelis constants ( Km) for ATP, acetyl-CoA, and bicarbonate were unaffected by phosphorylation by PKA. Phosphorylation by AMPK increased the Kmfor ATP and acetyl-CoA. Sequential phosphorylation by PKA and AMPK, first without label and second with label, appeared to reduce the extent of label incorporation, regardless of the order. The activation constant ( Ka) for citrate activation was increased to the same extent by AMPK phosphorylation, regardless of previous or subsequent phosphorylation by PKA. Thus muscle ACC can be phosphorylated by PKA but with no apparent functional effects on the enzyme. AMPK appears to be the more important regulator of muscle ACC.
Determination of fascicle length and pennation in a contracting human muscle in vivo
Authors: Fukunaga Tetsuo , Ichinose Yoshiho , Ito Masamitsu , Kawakami Yasuo , Fukashiro Senshi
Published: December 2017

Fukunaga, Tetsuo, Yoshiho Ichinose, Masamitsu Ito, Yasuo Kawakami, and Senshi Fukashiro. Determination of fascicle length and pennation in a contracting human muscle in vivo. J. Appl. Physiol. 82(1): 354–358, 1997.—We have developed a technique to determine fascicle length in human vastus lateralis muscle in vivo by using ultrasonography. When the subjects had the knee fully extended passively from a position of 110° flexion (relaxed condition), the fascicle length decreased from 133 to 97 mm on average. During static contractions at 10% of maximal voluntary contraction strength (tensed condition), fascicle shortening was more pronounced (from 126 to 67 mm), especially when the knee was closer to full extension. Similarly, as the knee was extended, the angle of pennation (fascicle angle, defined as the angle between fascicles and aponeurosis) increased (relaxed, from 14 to 18°; tensed, from 14 to 21°), and a greater increase in the pennation angle was observed in the tensed than in the relaxed condition when the knee was close to extension (<40°). We conclude that there are differences in fascicle lengths and pennation angles when the muscle is in a relaxed and isometrically tensed conditions and that the differences are affected by joint angles, at least at the submaximal contraction level.
Alignment of microvascular units along skeletal muscle fibers of hamster retractor
Authors: Emerson Geoffrey G. , Segal Steven S.
Published: December 2017

Emerson, Geoffrey G., and Steven S. Segal. Alignment of microvascular units along skeletal muscle fibers of hamster retractor. J. Appl. Physiol. 82(1): 42–48, 1997.—When muscle fibers contract, blood flow requirements increase along their entire length. However, the organization of capillary perfusion along muscle fibers is unclear. The microvascular unit (MVU) is defined as a terminal arteriole and the group of capillaries it supplies. We investigated whether neighboring MVUs along the fiber axis perfused the same group of muscle fibers by using the parallel-fibered retractor muscle. Hamsters were anesthetized and perfused with Microfil to visualize MVUs relative to muscle fibers. Fields of study, which encompassed five to seven neighboring MVUs along a muscle fiber, were chosen from the interior of muscles and along muscle edges. On average, MVUs were 1 mm in length, 0.50 mm in width, and 0.1 mm deep; segments of ∼30 fibers were contained in this tissue volume of 0.05 mm3 (20 MVUs/mg muscle). The total distance across muscle fibers encompassed by a pair of MVUs is designated “union” (U); the fraction of this distance common to both MVUs is designated “intersection” (I). The ratio of I to U for the widths of neighboring MVUs provides an index of MVU alignment along muscle fibers (e.g., I/U = 1.0 indicates complete alignment, where the fibers perfused by one MVU are the same as those perfused by the neighboring MVU). We found that I/U along muscle edges (0.71 ± 0.02) was greater ( P < 0.05) than the ratio measured within muscles (0.66 ± 0.02). A model predicted a maximum I/U of 0.58 with random MVU alignment. Thus measured values were closer to random than to complete alignment. These findings indicate that an increase in blood flow along muscle fibers requires the perfusion of many MVUs and imply that vasodilation is coordinated among the parent arterioles from which corresponding MVUs arise.
Temporal dynamics of acute isovolume bronchoconstriction in the rat
Authors: Bates Jason H. T. , Schuessler Thomas F. , Dolman Carrie , Eidelman David H.
Published: December 2017

Bates, Jason H. T., Thomas F. Schuessler, Carrie Dolman, and David H. Eidelman. Temporal dynamics of acute isovolume bronchoconstriction in the rat. J. Appl. Physiol. 82(1): 55–62, 1997.—The time course of lung impedance changes after intravenous injection of bronchial agonist have produced significant insights into the mechanisms of bronchoconstriction in the dog (J. H. T. Bates, A.-M. Lauzon, G. S. Dechman, G. N. Maksym, and T. F. Shuessler. J. Appl. Physiol. 76: 616–626, 1994). We studied the time course of acute induced bronchoconstriction in five anesthetized paralyzed open-chest rats injected intravenously with a bolus of methacholine. For the 16 s immediately after injection, we held the lung volume constant while applying small-amplitude flow oscillations at 1.48, 5.45, and 19.69 Hz simultaneously, which provided us with continuous estimates of lung resistance (Rl) and elastance (El) at each frequency. This procedure was repeated at initial lung inflation pressures of 0.2, 0.4, and 0.6 kPa. Both Rl and El increased progressively after methacholine administration; however, the rate of change of El increased dramatically as frequency was increased, whereas Rl remained relatively independent of frequency. We interpret these findings in terms of a three-compartment model of the rat lung, featuring two parallel alveolar compartments feeding into a central airway compartment. Model simulations support the notions that both central airway shunting and regional ventilation inhomogeneity developed to a significant degree in our constricted rats. We also found that the rates of increase in both Rl and El were greatly enhanced as the initial lung inflation pressure was reduced, in accord with the notion that parenchymal tethering is an important mechanism limiting the extent to which airways can narrow when their smooth muscle is stimulated to contract.
Myoglobin oxygen dissociation by multiwavelength spectroscopy
Authors: Schenkman Kenneth A. , Marble David R. , Burns David H. , Feigl Eric O.
Published: December 2017

Schenkman, Kenneth A., David R. Marble, David H. Burns, and Eric O. Feigl. Myoglobin oxygen dissociation by multiwavelength spectroscopy. J. Appl. Physiol. 82(1): 86–92, 1997.—Multiwavelength optical spectroscopy was used to determine the oxygen-binding characteristics for equine myoglobin. Oxygen-binding relationships as a function of oxygen tension were determined for temperatures of 10, 25, 35, 37, and 40°C, at pH 7.0. In addition, dissociation curves were determined at 37°C for pH 6.5, 7.0, and 7.5. Equilibration was achieved with a myoglobin solution, at the desired temperature and pH, and 16 oxygen-nitrogen gas mixtures of known oxygen fraction. Correction for the inevitable presence of metmyoglobin was made by using a three-component least squares analysis and by correcting the end point oxymyoglobin spectra for the presence of metmyoglobin. The[Formula: see text] at which myoglobin is half-saturated with O2(P50) was determined to be 2.39 Torr at pH 7.0 and 37°C. The myoglobin dissociation curve was well fit by the Hill equation [saturation =[Formula: see text]/([Formula: see text]+ P50)].
Instantaneous force-velocity-length relationship in diaphragmatic sarcomere
Authors: Coirault Catherine , Chemla Denis , Pourny Jean-Claude , Lambert Francine , Lecarpentier Yves
Published: December 2017

Coirault, Catherine, Denis Chemla, Jean-Claude Pourny, Francine Lambert, and Yves Lecarpentier. Instantaneous force-velocity-length relationship in diaphragmatic sarcomere. J. Appl. Physiol. 82(2): 404–412, 1997.—The simultaneous analysis of muscle force, length, velocity, and time has been shown to precisely characterize the mechanical performance of isolated striated muscle. We tested the hypothesis that the three-dimensional force-velocity-length relationship reflects mechanical properties of sarcomeres. In hamster diaphragm strips, instantaneous sarcomere length (S L) and muscle length were simultaneously measured during afterloaded twitches. S L was measured by means of laser diffraction. We also studied the influence of initial S L, abrupt changes in total load, and 2 × 10−7 M dantrolene. Baseline resting S L at the apex of the length-active tension curve was 2.2 ± 0.1 μm, whereas S L at peak shortening was 1.6 ± 0.1 μm in the preloaded twitch and 2.1 ± 0.1 μm in the “isometric” twitch. Over the whole load continuum and at any given level of isotonic load, there was a unique relationship between instantaneous sarcomere velocity and instantaneous S L. Part of this relationship was time independent and initial S L independent and was markedly downshifted after dantrolene. When five different muscle regions were considered, there were no significant variations of S L and sarcomere kinetics along the muscle. These results indicate that the time- and initial length-independent part of the instantaneous force-velocity-length relationship previously described in muscle strips reflects intrinsic sarcomere mechanical properties.
Contractile properties of clenbuterol-treatedmdx muscle are enhanced by low-intensity swimming
Authors: Hayes Alan , Williams David A.
Published: December 2017

Hayes, Alan, and David A. Williams. Contractile properties of clenbuterol-treated mdxmuscle are enhanced by low-intensity swimming. J. Appl. Physiol. 82(2): 435–439, 1997.—The β2-agonist clenbuterol has potent anabolic properties in normal and denervated muscle and, as such, may be of use in muscle wasting diseases such as muscular dystrophy. However, potential side effects such as the transformation of the fiber type pool toward increased proportions of fast-twitch fibers must be balanced with the beneficial anabolic properties. In the present report, we clearly show that extensor digitorum longus and soleus muscles from dystrophic mdxmice exposed to a combination of clenbuterol and low-intensity endurance swimming exercise did not undergo the slow- to fast-twitch fiber transformations caused by clenbuterol administration alone, yet increases in the force-generating capacity of the soleus (30–40%) that resulted from the clenbuterol treatment were maintained after the swimming program. The increased sensitivity of dystrophin-deficient dystrophic muscle to clenbuterol and low-intensity exercise that is evident in this study may have therapeutic implications in the treatment of muscle wasting diseases.
Effects of the combination of skin cooling and hyperpnea of frigid air in asthmatic and normal subjects
Authors: McDonald James S. , Nelson Joann , Lenner K. A. , McLane Melissa L. , McFadden E. R.
Published: December 2017

McDonald, James S., Joann Nelson, K. A. Lenner, Melissa L. McLane, and E. R. McFadden, Jr. Effects of the combination of skin cooling and hyperpnea of frigid air in asthmatic and normal subjects. J. Appl. Physiol. 82(2): 453–459, 1997.—To investigate whether reducing integumental temperatures influences pulmonary mechanics and interacts with inhaling cold air, 10 normal and 10 asthmatic subjects participated in a three-part trial in which cooling the skin of the head and thorax and isocapnic hyperventilation of frigid air were undertaken as isolated challenges and then administered in combination. Integumental cooling for 30 min caused airway obstruction to develop in both populations [change in 1-s forced expiratory volume (ΔFEV1) asthmatic subjects = 10%; normal subjects = 6%)]. Hyperventilation, however, only affected the asthmatic subjects (ΔFEV1 asthmatic subjects = 18%; normal subjects = 3%). In contrast to expectations, the combined challenge did not produce a summation effect (ΔFEV1 asthmatic subjects = 21%; normal subjects = 7%). These data demonstrate that the skin of the trunk and head is cold sensitive and when stimulated causes similar degrees of bronchial narrowing in both normal subjects and patients with airway disease independent of any ventilatory effect. They also indicate that cooling of the skin does not add to the obstructive consequences of hyperpnea.
Time- and order-dependent changes in functional and NO-mediated dilation during exercise training
Authors: Lash Julia M. , Bohlen H. Glenn
Published: December 2017

Lash, Julia M., and H. Glenn Bohlen. Time- and order-dependent changes in functional and NO-mediated dilation during exercise training. J. Appl. Physiol.82(2): 460–468, 1997.—Arterial vessel responses to sodium nitroprusside (SNP) and acetylcholine (ACh) were measured in the spinotrapezius muscle of sedentary (Sed) and treadmill-trained (Tr) rats to determine whether these endothelium-dependent (ACh) and -independent (SNP) mechanisms contribute to the training-induced increase in functional vasodilation previously observed. Control and maximal vessel diameters were similar between Sed and Tr. After 8 wk of training, functional dilation (2-, 4-, and 8-Hz contractions) was enhanced in all orders of vessels studied [terminal feed artery (FA), largest arterioles (1A), and intermediate-sized arterioles (2A)], but responses to SNP were increased only in FA. Responses to ACh were not significantly increased in any vessel order. After 16 wk of training, functional dilation had regressed in Tr such that only the FA response to 4 Hz was significantly elevated relative to Sed. However, the FA and 1A responses to SNP were significantly greater in Tr than in Sed, as were the 1A and 2A responses to ACh. These results show a dissociation of functional dilation and SNP- or ACh-mediated responses, as well as age-dependent interactions, a time-dependent progression, and vessel order specificity in the adaptations to training.
Putative projection of phrenic afferents to the limbic cortex in humans studied with cerebral-evoked potentials
Authors: Straus Christian , Zelter Marc , Derenne Jean-Philippe , Pidoux Bernard , Willer Jean-Claude , Similowski Thomas
Published: December 2017

Straus, Christian, Marc Zelter, Jean-Philippe Derenne, Bernard Pidoux, Jean-Claude Willer, and Thomas Similowski.Putative projection of phrenic afferents to the limbic cortex in humans studied with cerebral-evoked potentials. J. Appl. Physiol. 82(2): 480–490, 1997.—Respiratory sensations may rely in part on cortical integration of respiratory afferent information. In an attempt to study such projections, we recorded evoked potentials at scalp and cervical sites in 10 normal volunteers undergoing transcutaneous phrenic stimulation (0.1-ms square pulses, intensity liminal for diaphragmatic activation, series of 600 shocks at 2 Hz). A negative cerebral component of peak latency (12.79 ± 0.54 ms; N13) was constant, and a negative spinal component (7.09 ± 1.04 ms; N7) could also be recorded, all results being reproducible over time. Monitoring of cardiac frequency, skin anesthesia, and stimulation adjacent to the phrenic nerve made the phrenic origin of N7 and N13 the foremost hypothesis. Increasing stimulation frequency and comparison with median nerve stimulation provided arguments for the neural nature of the signals and their cerebral origin. Recordings from intracerebral electrodes in a patient showed a polarity reversal of the evoked potentials at the level of the cingulate gyrus. In conclusion, phrenic stimulation could allow one to study projections of phrenic afferents to the central nervous system in humans. Their exact site and physiological meaning remain to be clarified.
Hyperpnea-induced bronchoconstriction is dependent on tachykinin-induced cysteinyl leukotriene synthesis
Authors: Yang X. X. , Powell W. S. , Hojo M. , Martin J. G.
Published: December 2017

Yang, X. X., W. S. Powell, M. Hojo, and J. G. Martin.Hyperpnea-induced bronchoconstriction is dependent on tachykinin-induced cysteinyl leukotriene synthesis. J. Appl. Physiol. 82(2): 538–544, 1997.—The purpose of the study was to test the hypothesis that tachykinins mediate hyperpnea-induced bronchoconstriction indirectly by triggering cysteinyl leukotriene (LT) synthesis in the airways. Guinea pigs (350–600 g) were anesthetized with xylazine and pentobarbital sodium and received hyperpnea challenge (tidal volume 3.5–4.0 ml, frequency 150 breaths/min) with either humidified isocapnic gas ( n = 6) or dry gas ( n = 7). Dry gas challenge was performed on animals that received MK-571 (LTD4 antagonist; 2 mg/kg iv; n = 5), capsaicin ( n = 4), neurokinin (NK) antagonists [NK1 (CP-99994) + NK2 (SR-48968) (1 mg/kg iv); n = 6], or the H1 antihistamine pyrilamine (2 mg/kg iv; n = 5). We measured the tracheal pressure and collected bile for 1 h before and 2 h after hyperpnea challenge. We examined the biliary excretion of cysteinyl LTs; the recovery of radioactivity in bile after instillation of 1 μCi [3H]LTC4intratracheally averaged 24% within 4 h ( n = 2). The major cysteinyl LT identified was LTD4 (32% recovery of radioactivity). Cysteinyl LTs were purified from bile of animals undergoing hyperpnea challenge by using reverse-phase high-pressure liquid chromatography and quantified by radioimmunoassay. There was a significant increase in the peak value of tracheal pressure after challenge, indicating bronchoconstriction in dry gas-challenged animals but not after humidified gas challenge. MK-571, capsaicin, and NK antagonists prevented the bronchoconstriction; pyrilamine did not. Cysteinyl LT levels in the bile after challenge were significantly increased from baseline in dry gas-challenged animals ( P < 0.05) and were higher than in the animals challenged with humidified gas or dry gas-challenged animals treated with capsaicin or NK antagonists ( P < 0.01). The results indicate that isocapnic dry gas hyperpnea-induced bronchoconstriction is LT mediated and the role of tachykinins in the response is indirect through release of LTs. Endogenous histamine does not contribute to the response.
Respiratory function of velopharyngeal constrictor muscles during wakefulness in normal adults
Authors: Launois Sandrine H. , Tsui Judy , Weiss J. Woodrow
Published: December 2017

Launois, Sandrine H., Judy Tsui, and J. Woodrow Weiss.Respiratory function of velopharyngeal constrictor muscles during wakefulness in normal adults. J. Appl. Physiol. 82(2): 584–591, 1997.—The levator veli palatini (LVP) and the superior pharyngeal constrictor (SPC) influence velopharyngeal patency and soft palate position, but their behavior during respiration is incompletely characterized. To further clarify their respiratory function, we recorded electromyographic activity (EMG) in the LVP and the SPC in awake normal subjects breathing orally. EMG data were obtained in six subjects for the LVP and in nine subjects for the SPC. EMG activity and timing and ventilation were measured during isocapnic hypoxia and hyperoxic hypercapnia. Phasic EMG activity was inconsistently present during unstimulated oral breathing. Timing of EMG phasic activity was variable for both muscles. Peak LVP activity was mainly or exclusively expiratory in three of six subjects. Peak SPC activity was mainly or exclusively expiratory in five of nine subjects. With chemostimulation, recruitment of phasic activity was observed in the LVP in four of six subjects and in the SPC in five of nine subjects. Tonic activity increased in four of six subjects for the LVP and in three of nine subjects for the SPC. However, the response was alinear, and intersubject as well as breath-to-breath variability was substantial. In conclusion, LVP and SPC are characterized by the high inter- and intrasubject variability of EMG activity, timing of activation, and response to chemostimulation.
Protective role of synthetic sialylated oligosaccharide in sepsis-induced acute lung injury
Authors: Ridings Philip C. , Holloway Sharon , Bloomfield Geoffrey L. , Phillips M. L. , Fisher Bernard J. , Blocher Charles R. , Sugerman Harvey J. , Fowler Alpha A.
Published: December 2017

Ridings, Philip C., Sharon Holloway, Geoffrey L. Bloomfield, M. L. Phillips, Bernard J. Fisher, Charles R. Blocher, Harvey J. Sugerman, and Alpha A. Fowler III. Protective role of synthetic sialylated oligosaccharide in sepsis-induced acute lung injury. J. Appl. Physiol. 82(2): 644–651, 1997.—Proper engagement of leukocyte and endothelial cell selectins with their counterreceptors is an initial step in neutrophil trafficking to sites of inflammation. Certain fucosylated carbohydrate determinants such as sialyl Lewis-x are proposed to act as these counterreceptors. We studied the effects of a synthetic sialyl Lewis-x analog, CY-1503, on the course of hemodynamic derangements and acute lung injury during experimental gram-negative sepsis. Anesthetized ventilated swine were made septic with an infusion of live Pseudomonas aeruginosa. A treatment group received an initial bolus of CY-1503 (60 mg/kg) before sepsis, followed by continuous infusion of CY-1503 (12 mg ⋅ kg−1⋅ h−1). Treatment with CY-1503 did not prevent the development of pulmonary hypertension, systemic hypotension, decline in cardiac output, or severe neutropenia. However, CY-1503 significantly attenuated lung injury, demonstrated by decreased bronchoalveolar lavage protein content and neutrophil influx, lowered lung myeloperoxidase activity, and improved arterial oxygenation. Neutrophils from septic and CY-1503 animals showed significant activation, reflected by upregulated CD18 expression and priming for oxidant burst compared with control animals. This study suggests blockade of selectin interactions as a potential therapeutic intervention in sepsis-induced lung injury.
Performance of the AM-5600 blood pressure monitor: comparison with ambulatory intra-arterial pressure
Authors: Omboni Stefano , Parati Gianfranco , Groppelli Antonella , Ulian Luisa , Mancia Giuseppe
Published: December 2017

Omboni, Stefano, Gianfranco Parati, Antonella Groppelli, Luisa Ulian, and Giuseppe Mancia. Performance of the AM-5600 blood pressure monitor: comparison with ambulatory intra-arterial pressure. J. Appl. Physiol. 82(2): 698–703, 1997.—The AM-5600 is a new device that simultaneously monitors electrocardiogram (ECG) and noninvasive blood pressure (BP) over a 24-h period. BP readings (Korotkoff sounds and cuff air pressure) are stored into the recorder, allowing the removal of BP artifacts after a visual check. In 12 subjects with essential hypertension, we compared BP values simultaneously provided by the AM-5600 and intra-arterial recordings. At rest, noninvasive systolic BP (SBP) values were lower (5.4 ± 4.9 mmHg) and diastolic BP (DBP) values were higher (7.3 ± 7.3 mmHg) than were intra-arterial values. In ambulatory conditions (9 subjects), between-method discrepancies were +0.8 ± 6.1 and +12.2 ± 7.4 mmHg for 24-h SBP and DBP, respectively. AM-5600 underestimated 24-h intra-arterial SBP and DBP SD, but it accurately tracked intra-arterial SBP and DBP changes. Editing removed 22.1% of total readings, slightly reducing between-method discrepancies. Thus the AM-5600 provides an accurate average estimate of resting and ambulatory SBP and, for DBP, a less accurate estimate that is slightly improved by editing. The AM-5600 allows accurate description of SBP and DBP profiles and thus may be suitable to describe the abrupt BP changes accompanying a number of clinical events.
Dew-point hygrometry system for measurement of evaporative water loss in infants
Authors: Ariagno Ronald L. , Glotzbach Steven F. , Baldwin Roger B. , Rector David M. , Bowley Susan M. , Moffat Robert J.
Published: December 2017

Ariagno, Ronald L., Steven F. Glotzbach, Roger B. Baldwin, David M. Rector, Susan M. Bowley, and Robert J. Moffat.Dew-point hygrometry system for measurement of evaporative water loss in infants. J. Appl. Physiol.82(3): 1008–1017, 1997.—Evaporation of water from the skin is an important mechanism in thermal homeostasis. Resistance hygrometry, in which the water vapor pressure gradient above the skin surface is calculated, has been the measurement method of choice in the majority of pediatric investigations. However, resistance hygrometry is influenced by changes in ambient conditions such as relative humidity, surface temperature, and convection currents. We have developed a ventilated capsule method that minimized these potential sources of measurement error and that allowed second-by-second, long-term, continuous measurements of evaporative water loss in sleeping infants. Air with a controlled reference humidity (dew-point temperature = 0°C) is delivered to a small, lightweight skin capsule and mixed with the vapor on the surface of the skin. The dew point of the resulting mixture is measured by using a chilled mirror dew-point hygrometer. The system indicates leaks, is mobile, and is accurate within 2%, as determined by gravimetric calibration. Examples from a recording of a 13-wk-old full-term infant obtained by using the system give evaporative water loss rates of ∼0.02 mgH2O ⋅ cm−2⋅ min−1for normothermic baseline conditions and values up to 0.4 mgH2O ⋅ cm−2⋅ min−1when the subject was being warmed. The system is effective for clinical investigations that require dynamic measurements of water loss.
O2availability modulates transmembrane Ca2+flux via second-messenger pathways in anoxia-tolerant hepatocytes
Authors: Land S. C. , Sanger R. H. , Smith P. J. S.
Published: December 2017

Land, S. C., R. H. Sanger, and P. J. S. Smith.O2availability modulates transmembrane Ca2+flux via second-messenger pathways in anoxia-tolerant hepatocytes. J. Appl. Physiol. 82(3): 776–783, 1997.—Transmembrane Ca2+-flux was studied from single isolated turtle hepatocytes by using a noninvasive Ca2+-selective self-referencing microelectrode. Cells in Ca2+-reduced culture medium demonstrated a vanadate-and lanthanum-inhibitable Ca2+-efflux of 4 × 10−17mol Ca2+⋅ μm−2⋅ s−1continuously over 170 h. This flux diminished with 50 nM phorbol 12-myristate 13-acetate, a protein kinase C (PKC) activator, and was reinstated on PKC deactivation with sphingosine. Progressive hypoxia resulted in a reversible suppression of Ca2+efflux to 90% of normoxic controls with an apparent Michaelis constant for oxygen of 145 μM. PKC activation was critical in this suppression, as anaerobic administration of sphingosine caused a Ca2+influx and cell rupture. Hypoxia was also associated with an altered pattern of adenosine-mediated control over Ca2+efflux. Adenosine (100 μM) elevated Ca2+efflux twofold in normoxia, but neither adenosine nor the A1-purinoreceptor antagonist 8-phenyltheophylline altered the observed anaerobic suppression. Aerobic administration of 2–10 mM KCN failed to reproduce the anaerobic suppression; however, in conjunction with 10 mM iodoacetate, complete metabolic blockade caused a Ca2+influx and cell rupture. These observations suggest modulatory control by oxygen over transmembrane Ca2+efflux involving second-messenger systems in the hypoxic transition.
Exercise training increases sarcolemmal GLUT-4 protein and mRNA content in diabetic heart
Authors: Osborn Brett A. , Daar June T. , Laddaga Richard A. , Romano Fred D. , Paulson Dennis J.
Published: December 2017

Osborn, Brett A., June T. Daar, Richard A. Laddaga, Fred D. Romano, and Dennis J. Paulson. Exercise training increases sarcolemmal GLUT-4 protein and mRNA content in diabetic heart. J. Appl. Physiol. 82(3): 828–834, 1997.—This study determined whether dynamic exercise training of diabetic rats would increase the expression of the GLUT-4 glucose transport protein in prepared cardiac sarcolemmal membranes. Four groups were compared: sedentary control, sedentary diabetic, trained control, and trained diabetic. Diabetes was induced by intravenous streptozotocin (60 mg/kg). Trained control and diabetic rats were run on a treadmill for 60 min, 27 m/min, 10% grade, 6 days/wk for 10 wk. Sarcolemmal membranes were isolated by using differential centrifugation, and the activity of sarcolemmal K+- p-nitrophenylphosphatase ( pNPPase; an indicator of Na+-K+-adenosinetriphosphatase activity) was quantified. Hearts from the sedentary diabetic group exhibited a significant depression of sarcolemmal pNPPase activity. Exercise training did not significantly alter pNPPase activity. Sedentary diabetic rats exhibited an 84 and 58% decrease in GLUT-4 protein and mRNA, respectively, relative to control rats. In the trained diabetic animals, sarcolemmal GLUT-4 protein levels were only reduced by 50% relative to control values, whereas GLUT-4 mRNA were returned to control levels. The increase in myocardial sarcolemmal GLUT-4 may be beneficial to the diabetic heart by enhancing myocardial glucose oxidation and cardiac performance
Paradoxical helium and sulfur hexafluoride single-breath washouts in short-term vs. sustained microgravity
Authors: Lauzon Anne-Marie , Prisk G. Kim , Elliott Ann R. , Verbanck Sylvia , Paiva Manuel , West John B.
Published: December 2017

Lauzon, Anne-Marie, G. Kim Prisk, Ann R. Elliott, Sylvia Verbanck, Manuel Paiva, and John B. West. Paradoxical helium and sulfur hexafluoride single-breath washouts in short-term vs. sustained microgravity. J. Appl. Physiol. 82(3): 859–865, 1997.—During single-breath washouts in normal gravity (1 G), the phase III slope of sulfur hexafluoride (SF6) is steeper than that of helium (He). Two mechanisms can account for this: 1) the higher diffusivity of He enhances its homogeneous distribution; and 2) the lower diffusivity of SF6 results in a more peripheral location of the diffusion front, where airway asymmetry is larger. These mechanisms were thought to be gravity independent. However, we showed during the Spacelab Life Sciences-2 spaceflight that in sustained microgravity (μG) the SF6-to-He slope difference is abolished. We repeated the protocol during short periods (27 s) of μG (parabolic flights). The subjects performed a vital-capacity inspiration and expiration of a gas containing 5% He-1.25% SF6-balance O2. As in sustained μG, the phase III slopes of He and SF6decreased. However, during short-term μG, the SF6-to-He slope difference increased from 0.17 ± 0.03%/l in 1 G to 0.29 ± 0.06%/l in μG, respectively. This is contrary to sustained μG, in which the SF6-to-He slope difference decreased from 0.25 ± 0.03%/l in 1 G to −0.01 ± 0.06%/l in μG. The increase in phase III slope difference in short-term μG was caused by a larger decrease of He phase III slope compared with that in sustained μG. This suggests that changes in peripheral gas mixing seen in sustained μG are mainly due to alterations in the diffusive-convective inhomogeneity of He that require >27 s of μG to occur. Changes in pulmonary blood volume distribution or cardiogenic mixing may explain the differences between the results found in short-term and sustained μG.
Conservation of bronchiolar wall area during constriction and dilation of human airways
Authors: Mitchell R. W. , Rühlmann E. , Magnussen H. , Muñoz N. M. , Leff A. R. , Rabe K. F.
Published: December 2017

Mitchell, R. W., E. Rühlmann, H. Magnussen, N. M. Muñoz, A. R. Leff, and K. F. Rabe. Conservation of bronchiolar wall area during constriction and dilation of human airways. J. Appl. Physiol. 82(3): 954–958, 1997.—We assessed the effect of smooth muscle contraction and relaxation on airway lumen subtended by the internal perimeter ( A i) and total cross-sectional area ( A o) of human bronchial explants in the absence of the potential lung tethering forces of alveolar tissue to test the hypothesis that bronchoconstriction results in a comparable change of A iand A o. Luminal area (i.e., A i) and A owere measured by using computerized videomicrometry, and bronchial wall area was calculated accordingly. Images on videotape were captured; areas were outlined, and data were expressed as internal pixel number by using imaging software. Bronchial rings were dissected in 1.0- to 1.5-mm sections from macroscopically unaffected areas of lungs from patients undergoing resection for carcinoma, placed in microplate wells containing buffered saline, and allowed to equilibrate for 1 h. Baseline, A o[5.21 ± 0.354 (SE) mm2], and A i(0.604 ± 0.057 mm2) were measured before contraction of the airway smooth muscle (ASM) with carbachol. Mean A inarrowed by 0.257 ± 0.052 mm2in response to 10 μM carbachol ( P = 0.001 vs. baseline). Similarly, A onarrowed by 0.272 ± 0.110 mm2in response to carbachol ( P = 0.038 vs. baseline; P = 0.849 vs. change in A i). Similar parallel changes in cross-sectional area for A iand A owere observed for relaxation of ASM from inherent tone of other bronchial rings in response to 10 μM isoproterenol. We demonstrate a unique characteristic of human ASM; i.e., both luminal and total cross-sectional area of human airways change similarly on contraction and relaxation in vitro, resulting in a conservation of bronchiolar wall area with bronchoconstriction and dilation.
K+supplementation increases muscle [Na+-K+-ATPase] and improves extrarenal K+homeostasis in rats
Authors: Bundgaard Henning , Schmidt Thomas A. , Larsen Jim S. , Kjeldsen Keld
Published: December 2017

Bundgaard, Henning, Thomas A. Schmidt, Jim S. Larsen, and Keld Kjeldsen. K+supplementation increases muscle [Na+-K+-ATPase] and improves extrarenal K+homeostasis in rats. J. Appl. Physiol.82(4): 1136–1144, 1997.—Effects of K+supplementation (∼200 mmol KCl/100 g chow) on plasma K+, K+content, and Na+-K+-adeonsinetriphosphatase (ATPase) concentration ([Na+-K+-ATPase]) in skeletal muscles as well as on extrarenal K+clearance were evaluated in rats. After 2 days of K+supplementation, hyperkalemia prevailed (K+-supplemented vs. weight-matched control animals) [5.1 ± 0.2 (SE) vs. 3.2 ± 0.1 mmol/l, P < 0.05, n = 5–6], and after 4 days a significant increase in K+content was observed in gastrocnemius muscle (104 ± 2 vs. 97 ± 1 μmol/g wet wt, P < 0.05, n = 5–6). After 7 days of K+supplementation, a significant increase in [3H]ouabain binding site concentration (344 ± 5 vs. 239 ± 8 pmol/g wet wt, P < 0.05, n = 4) was observed in gastrocnemius muscle. After 2 wk, increases in plasma K+, K+content, and [3H]ouabain binding site concentration in gastrocnemius muscle amounted to 40, 8, and 68% ( P < 0.05) above values observed in weight-matched control animals, respectively. The latter change was confirmed by K+-dependent p-nitrophenyl phosphatase activity measurements. Fasting for 1 day reduced plasma K+and K+content in gastrocnemius muscle in rats that had been K+supplemented for 2 wk by 3.1 ± 0.3 mmol/l ( P < 0.05, n = 5) and 15 ± 2 μmol/g wet wt ( P < 0.05, n = 5), respectively. After induction of anesthesia, arterial plasma K+was measured during intravenous KCl infusion (0.75 mmol KCl ⋅ 100 g body wt−1⋅ h−1). The K+-supplemented fasted group demonstrated a 42% ( P < 0.05) lower plasma K+rise, associated with a significantly higher increase in K+content in gastrocnemius muscle of 7 μmol/g wet wt ( P < 0.05, n = 5) compared with their control animals. In conclusion, K+supplementation increases plasma K+, K+content, and [Na+-K+-ATPase] in skeletal muscles and improves extrarenal K+clearance capacity.
Metabolic and phenotypic adaptations of diaphragm muscle fibers with inactivation
Authors: Zhan Wen-Zhi , Miyata Hirofumi , Prakash Y. S. , Sieck Gary C.
Published: December 2017

Zhan, Wen-Zhi, Hirofumi Miyata, Y. S. Prakash, and Gary C. Sieck. Metabolic and phenotypic adaptations of diaphragm muscle fibers with inactivation. J. Appl. Physiol. 82(4):1145–1153, 1997.—We hypothesized that metabolic adaptations to muscle inactivity are most pronounced when neurotrophic influence is disrupted. In rat diaphragm muscle (Diam), 2 wk of unilateral denervation or tetrodotoxin nerve blockade resulted in a reduction in succinate dehydrogenase (SDH) activity of type I, IIa, and IIx fibers (∼50, 70, and 24%, respectively) and a decrease in SDH variability among fibers (∼63%). In contrast, inactivity induced by spinal cord hemisection at C2(ST) resulted in much less change in SDH activity of type I and IIa fibers (∼27 and 24%, respectively) and only an ∼30% reduction in SDH variability among fibers. Actomyosin adenosinetriphosphatase (ATPase) activities of type I, IIx, and IIb fibers in denervated and tetrodotoxin-treated Diamwere reduced by ∼20, 45, and 60%, respectively, and actomyosin ATPase variability among fibers was ∼60% lower. In contrast, only actomyosin ATPase activity of type IIb fibers was reduced (∼20%) in ST Diam. These results suggest that disruption of neurotrophic influence has a greater impact on muscle fiber metabolic properties than inactivity per se.
Sympathetic outflow to the skeletal muscle in humans increases during prolonged light exercise
Authors: Saito Mitsuru , Sone Ryoko , Ikeda Masao , Mano Tadaaki
Published: December 2017

Saito, Mitsuru, Ryoko Sone, Masao Ikeda, and Tadaaki Mano.Sympathetic outflow to the skeletal muscle in humans increases during prolonged light exercise. J. Appl. Physiol. 82(4): 1237 – 1243, 1997.—To investigate the effects of exercise duration on muscle sympathetic nerve activity (MSNA), heart rate, blood pressure (BP), tympanic temperature, blood lactate concentration, and thigh electromyogram were measured in eight volunteers during 30 min of cycling in the sitting position at an intensity of 40% of maximal oxygen uptake. MSNA burst frequency increased 18 min after exercise was begun (25 ± 4 bursts/min at baseline and 36 ± 5 bursts/min at 21 min of exercise), reaching 41 ± 5 bursts/min at the end of exercise. Heart rate and systolic BP increased during exercise. Twenty minutes after commencement of exercise, however, both systolic and diastolic BP values tended to drop compared with the initial period of exercise. Tympanic temperature increased in a time-dependent manner, and the increment was significant 12 min after exercise was begun. Blood lactate concentration and integrated electromyogram showed no significant changes during exercise. The increased MSNA during prolonged light-intensity exercise may be a secondary effect of the drop in BP as a result of blood redistribution caused by thermoregulation rather than by metaboreflex.
Nitric oxide response in exhaled air during an incremental exhaustive exercise
Authors: Chirpaz-Oddou M. F. , Favre-Juvin A. , Flore P. , Eterradossi J. , Delaire M. , Grimbert F. , Therminarias A.
Published: December 2017

Chirpaz-Oddou, M. F., A. Favre-Juvin, P. Flore, J. Eterradossi, M. Delaire, F. Grimbert, and A. Therminarias. Nitric oxide response in exhaled air during an incremental exhaustive exercise. J. Appl. Physiol. 82(4): 1311–1318, 1997.—This study examines the response of the exhaled nitric oxide (NO) concentration (Cno) and the exhaled NO output (V˙no) during incremental exercise and during recovery in six sedentary women, seven sedentary men, and eight trained men. The protocol consisted of increasing the exercise intensity by 30 W every 3 min until exhaustion, followed by 5 min of recovery. Minute ventilation (V˙e), oxygen consumption (V˙o2), carbon dioxide production, heart rate, Cno, andV˙nowere measured continuously. The Cno in exhaled air decreased significantly provided that the exercise intensity exceeded 65% of the peak V˙o2. It reached similar values, at exhaustion, in all three groups. TheV˙no increased proportionally with exercise intensity up to exhaustion and decreased rapidly during recovery. At exhaustion, the mean values were significantly higher for trained men than for sedentary men and sedentary women. During exercise,V˙nocorrelates well with V˙o2, carbon dioxide production, V˙e, and heart rate. For the same submaximal intensity, and thus a givenV˙o2and probably a similar cardiac output,V˙no appeared to be similar in all three groups, even if theV˙e was different. These results suggest that, during exercise,V˙no is mainly related to the magnitude of aerobic metabolism and that this relationship is not affected by gender differences or by noticeable differences in the level of physical training.
Effect of mechanical deformation on structure and function of polymorphonuclear leukocytes
Authors: Kitagawa Yuko , Van Eeden Stephan F. , Redenbach Darlene M. , Daya Maleki , Walker Blair A. M. , Klut Maria E. , Wiggs Barry R. , Hogg James C.
Published: December 2017

Kitagawa, Yuko, Stephan F. Van Eeden, Darlene M. Redenbach, Maleki Daya, Blair A. M. Walker, Maria E. Klut, Barry R. Wiggs, and James C. Hogg. Effect of mechanical deformation on structure and function of polymorphonuclear leukocytes. J. Appl. Physiol. 82(5): 1397–1405, 1997.—The present studies were designed to test the hypothesis that mechanical deformation of polymorphonuclear leukocytes (PMN) leads to functional changes that might influence their transit in the pulmonary capillaries. Human leukocytes were passed through 5- or 3-μm-pore polycarbonate filters under controlled conditions. Morphometric analysis showed that the majority of PMN were deformed and that this deformation persisted longer after filtration through 3-μm filters than through 5-μm filters ( P < 0.05) but did not result in the cytoskeletal polarization characteristic of migrating cells. Flow cytometric studies of the filtered PMN showed that there was a transient increase in the cytosolic free Ca2+concentration after both 3- and 5-μm filtration ( P< 0.01) with an increase in F-actin content after 3-μm filtration ( P < 0.05). AlthoughL-selectin expression on PMN was not changed by either 5- or 3-μm filtration, CD18 and CD11b were increased by 3-μm filtration ( P < 0.05). Priming of the PMN with N-formyl-methionyl-leucyl-phenylalanine (0.5 nM) before filtration resulted in an increase of CD11b by both 5 ( P < 0.05)- and 3-μm ( P < 0.01) filtration. Neither 5- nor 3-μm filtration induced hydrogen peroxide production. We conclude that mechanical deformation of PMN, similar to what occurs in the pulmonary microvessels, induces both structural and functional changes in the cells, which might influence their passage through the pulmonary capillary bed.
In vitro bronchial responsiveness in two highly inbred rat strains
Authors: Wang C. G. , Almirall J. J. , Dolman C. S. , Dandurand R. J. , Eidelman D. H.
Published: December 2017

Wang, C. G., J. J. Almirall, C. S. Dolman, R. J. Dandurand, and D. H. Eidelman. In vitro bronchial responsiveness in two highly inbred rat strains. J. Appl. Physiol. 82(5): 1445–1452, 1997.—We investigated methacholine (MCh)-induced bronchoconstriction in explanted airways from Fischer and Lewis rats. Lung explants, 0.5- to 1.0-mm thick, were prepared from agarose-inflated lungs of anesthetized 8- to 12-wk-old male rats. After overnight culture, videomicroscopy was used to record baseline images of the individual airways. Dose-response curves to MCh were then constructed by repeated administration of MCh; airways were reimaged 10 min after each MCh administration. Airway internal luminal area ( A i) was measured at successive MCh concentrations from 10−9 to 10−1 M. In addition to the effective concentration leading to 50% of the achieved maximal response, we also determined the effective concentration leading to a 40% reduction in A i. Both the effective concentration leading to 50% of the achieved maximal response and the concentration leading to a 40% reduction in A iwere significantly lower among Fischer rat airways ( P < 0.05). Airway closure was more common among Fischer rat airways (17%) than among those of Lewis rats (7.5%). Responsiveness of Fischer rat airways was more heterogeneous than among Lewis airways; a larger number of Fischer rat airways exhibited high sensitivity to MCh. There was no relationship between responsiveness and baseline A iin either strain. In a second experiment, we measured the rate of contraction of explanted airways from lungs inflated to 50, 75, and 100% of total lung capacity. The average rate of contraction in the first 15 s was higher in Fischer rat airways at each inflation volume. These data indicate that the hyperresponsiveness of the Fischer rat reflects the responsiveness of individual airways throughout the airway tree and are consistent with the notion that in this model hyperresponsiveness is an intrinsic property of airway smooth muscle.