bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary mechanics during the ventilatory response to hypoxemia in the newborn monkey
Authors: LaFramboise W. A. , Guthrie R. D. , Standaert T. A. , Woodrum D. E.
Published: December 2017

Dynamic lung compliance (CL), inspiratory pulmonary resistance (RL), and functional residual capacity (FRC) were measured in 10 unanesthetized 48 h-old newborn monkeys and seven 21-day-old infant monkeys during acute exposures to an equivalent level of hypoxemia. End-expiratory airway occlusions were performed and the pressure developed by 200 ms (P0.2) was utilized as an index of central respiratory drive. P0.2 demonstrated a sustained increase throughout the period of hypoxemia on day 2 despite the fact that minute ventilation (VI) initially increased but then fell back to base-line levels. Dynamic lung compliance fell and FRC increased by 5 min of hypoxemia in the newborns. The 21-day-old monkeys exhibited a sustained increase in both VI and P0.2 throughout the hypoxic period with no change in CL and FRC. RL did not change at either postnatal age during hypoxemia. These data indicate that the neonatal monkey is subject to changes in pulmonary mechanics (decreased CL and increased FRC) during hypoxemia and that these changes are eliminated with maturation.
Single-position calibration of the respiratory inductance plethysmograph
Authors: Loveridge B. , West P. , Anthonisen N. R. , Kryger M. H.
Published: December 2017

Since we intended to use the respiratory inductance plethysmograph (RIP) to study breathing patterns in a single body position, we developed a method to calibrate the RIP in one position (seated) and verified the stability of this calibration procedure during a 60-min period. The subject breathed spontaneously through a pneumotachograph for 1 min during all calibration and verification runs. All inspiratory data from the abdomen and rib cage RIP transducers was analyzed using multiple linear regression analysis to calculate calibration factors for the transducers. Eight normal subjects were studied, and the stability of calibration at 20, 40, and 60 min was determined. The correlation coefficients were all greater than 0.94. The mean slope and mean intercept describing the relationship of the RIP volume to the pneumotachograph volume for all calibration and verification runs were 0.995 +/- 0.074 and 0.012 +/- 0.018 liter, respectively. This calibration method allows a spirogram to be generated from the RIP signals. Therefore, this technique may be valuable in further investigating resting breathing patterns in humans.
Site and sensitivity for stimulation of hypoxic pulmonary vasoconstriction
Authors: Marshall C. , Marshall B.
Published: December 2017

Rat lungs were perfused in an in vitro circuit with separate control of alveolar and pulmonary arterial O2 tension. With perfusion flow constant, the hypoxic pulmonary vasoconstrictor (HPV) response was measured as changes of perfusion pressure. HPV was a function of both alveolar O2 tension (PvO2) and was described by a double sigmoid response surface. Where RA-v is this pressure response expressed as a percent of the maximum, the linearized form of the response surface is given by log [RA-v/(100-RA-v)] = 3.93 - 1.029 (log PvO2) - 1.623 (log PAO2). From this relationship it was concluded that 1) HPV is determined by PAO2 and PvO2; 2) the fundamental stimulus-response relationship is a sigmoid with a 50% response when both PAO2 and PvO2 are 30.3 Torr; 3) PAO2 has a greater effect than PvO2 due in part to the geometry of the vascular wall but principally due to O2 exchange between alveolar gas and blood in small pulmonary arteries; 4) there is not a localized sensor for HPV (the response is accounted for by each smooth muscle cell in the pulmonary arterial wall responding to the O2 tension in its vicinity); and 5) the characteristics of the response suggest that the cell sensor resembles a cytochrome.
Duration of mucociliary dysfunction following antigen challenge
Authors: Allegra L. , Abraham W. M. , Chapman G. A. , Wanner A.
Published: December 2017

Antigen-induced bronchospasm is associated with an impairment of airway mucociliary clearance, but the duration of this defect has not been examined. In the present study, we determined the time course of mucociliary dysfunction following inhalation challenge with Ascaris suum extract in conscious sheep with hypersensitivity to this antigen. Tracheal mucous velocity (TMV) as an index of mucociliary function, pulmonary resistance (RL), and arterial oxygen tension (Pao2) were measured prior to, immediately after, and serially for 8 h after inhalation challenge. TMV and Pao2 were then measured periodically for at least 2 wk. Immediately after A. suum challenge, mean RL increased to 264% of base line (P less than 0.05), and mean Pao2 decreased to 61% of base line (P less than 0.05). By 2 h postchallenge, mean RL and Pao2 had returned to base line but mean TMV had fallen to 61% of base line (P less than 0.05). Mean TMV reached a minimum of 35% of base line after 5 h (P less than 0.05) and remained significantly depressed between 37% and 54% of base line for 7 days; by day 9, mean TMV had returned to base line. Inhalation challenge with a control antigen (ragweed) failed to alter mean TMV, RL, and Pao2 during the first 8 h and TMV and Pao2 at any time throughout the 2-wk observation period.(ABSTRACT TRUNCATED AT 250 WORDS)
Influence of body CO2 stores on ventilatory dynamics during exercise
Authors: Ward S. A. , Whipp B. J. , Koyal S. , Wasserman K.
Published: December 2017

Pulmonary CO2 flow (the product of cardiac output and mixed venous CO2 content) is purported to be an important determinant of ventilatory dynamics in moderate exercise. Depletion of body CO2 stores prior to exercise should thus slow these dynamics. We investigated, therefore, the effects of reducing the CO2 stores by controlled volitional hyperventilation on cardiorespiratory and gas exchange response dynamics to 100 W cycling in six healthy adults. The control responses of ventilation (VE), CO2 output (VCO2), O2 uptake (VO2), and heart rate were comprised of an abrupt increase at exercise onset, followed by a slower rise to the new steady state (t1/2 = 48, 43, 31, and 33 s, respectively). Following volitional hyperventilation (9 min, PETCO2 = 25 Torr), the steady-state exercise responses were unchanged. However, VE and VCO2 dynamics were slowed considerably (t1/2 = 76, 71 s) as PETCO2 rose to achieve the control exercise value. VO2 dynamics were slowed only slightly (t1/2 = 39 s), and heart rate dynamics were unaffected. We conclude that pulmonary CO2 flow provides a significant stimulus to the dynamics of the exercise hyperpnea in man.
Effects of hypoxia on norepinephrine release and metabolism in dog pulmonary artery
Authors: Rorie D. K. , Tyce G. M.
Published: December 2017

The effect of low O2 tensions on the release and metabolism of norepinephrine during resting conditions and in response to electrical stimulation was studied in isolated superfused segments of dog pulmonary artery. Liquid chromatography with electrochemical detection was used to measure the release and overflow of endogenous norepinephrine and the content of norepinephrine remaining in the tissue after stimulation. In other preparations, norepinephrine stores were labeled with [3H]norepinephrine, and measurements were made of [3H]norepinephrine and its metabolites (separated by column chromatography) in superfusates. Radiolabeled metabolites of norepinephrine produced intraneuronally (3,4-dihydroxyphenylglycol) and extraneuronally (O-methylated) were quantitated by liquid scintillation spectrometry and the relative importance of neuronal uptake, extraneuronal uptake and of norepinephrine overflow in the disposition of norepinephrine calculated. Hypoxia increased the release and overflow of endogenous norepinephrine. In hypoxic conditions 41% of released norepinephrine was disposed of by overflow from the cleft compared with 27% during normoxia. Neuronal uptake of released norepinephrine was reduced during hypoxia and the intraneuronal metabolism of norepinephrine by monoamine oxidase was almost eliminated.
Exercise and nasal patency
Authors: Forsyth R. D. , Cole P. , Shephard R. J.
Published: December 2017

Nasal airflow resistances were studied in 20 healthy subjects at rest, with exercise, and during recovery from exercise. Resistances were first measured under resting conditions. As a basis for comparison 0.1% xylometazoline was applied by insufflation; it reduced nasal resistance by an average of 49%. On a subsequent occasion, the degree and time course of changes in resistance were measured 1) during 5-min exercise bouts at rest 25, 50, and 75% of predicted maximum O2 intake (VO2max), 2) during 5-, 10-, and 15-min exercise bouts at 50% of VO2max, and 3) during recovery from exercise. Resistance decreased with intensity but not duration of exercise; an initial sudden decrease was followed by a more gradual but progressive decrease, which continued for several minutes following vigorous short duration exercise. Thus following 5 min of effort at 75% of VO2max, resistance reached a nadir (46% fall) 5 min after cessation of exercise. Recovery of preexercise values required 5 min after 5 min of exercise at 25% of VO2max and 10 min after 5 min of exercise at 50% of VO2max. Some decrease persisted 15 min after 5 min of exercise at 75% of VO2max.
Pulmonary microvascular permeability after coronary arterial ligation in dogs
Authors: Gabel J. C. , Butler B. D. , Scott R. L. , Drake R. E.
Published: December 2017

Recent studies have indicated that pulmonary microvascular permeability may be increased after coronary arterial ligation. We tested this by estimating the pulmonary microvascular reflection coefficient (delta) in six anesthetized control dogs and in six dogs in which we ligated the left anterior descending coronary artery. We cannulated lung lymph vessels and measured the lymph and plasma protein concentrations (CL and CP, respectively). The left atrial pressure was increased to decrease CL to a minimum. We used the minimum CL to estimate delta as 1 -CL/CP. delta for the control [0.70 +/- 0.03 (SD)] and coronary artery ligated groups (0.70 +/- 0.04) were almost identical. This data indicates that coronary artery ligation does not increase pulmonary microvascular permeability.
Chronic low-sodium diet in rats: hormonal and physiological effects during exercise in the heat
Authors: Francesconi R. P. , Hubbard R. W. , Mager M.
Published: December 2017

To elucidate the effects of sodium (Na+) deficiency on the ability to work in the heat, immature rats were fed a diet deficient in Na+ for approximately 2 mo. Rates of weight gain were severely affected (P less than 0.01) in the Na+-deficient rats (1.7 vs. 7.2 g/day in controls), although fluid consumption was unaffected. The low-Na+ diet effected no alterations in endurance or weight loss during exercise in the heat to hyperthermic exhaustion, but final core and skin temperatures were significantly reduced in the low-Na+ group (P less than 0.02) and hematocrit ratios were significantly (P less than 0.001) increased. Circulating Na+ and potassium (K+) concentrations were significantly (P less than 0.05) increased in both groups after hyperthermic exhaustion. In the Na+-deficient groups, plasma levels of both aldosterone and cortisol/corticosterone were significantly (P less than 0.05) increased, and these increments were exacerbated following exercise to hyperthermic exhaustion. Consumption of the low-Na+ diet elicited significant increments in circulating levels of lactate (P less than 0.01) and creatinine (P less than 0.01), both of which were increased further after exercise. We concluded that hormonal adaptations prevented circulatory hyponatremia and decrements in physical performance, but other clinical and metabolic effects of the low-Na+ diet were noted.
A three-compartment model of the pulmonary vasculature: effects of vasoconstriction
Authors: Linehan J. H. , Dawson C. A.
Published: December 2017

The venous occlusion experiments provide sufficient data to permit the vascular bed of a dog lung lobe to be mathematically modeled as three serial compartments, each containing a quantifiable resistance separated by equal parallel compliances. To determine how these compartments are related to the sites of vasomotion in the pulmonary vascular bed we investigated the effects of various pulmonary vasomotor stimuli. We found that serotonin, sympathetic nerve stimulation, hypoxia, and prostaglandin F2 alpha increased the pressure drop upstream (arterial) from the site of major lobar compliance. On the other hand, histamine, norepinephrine, epinephrine, and elevation of the cerebrospinal fluid pressure increased the pressure drop downstream (venous) from the site of major lobar compliance. These stimuli either did not affect the pressure drop across the middle compartment or increased it slightly. Thus we conclude that the middle compartment represents vessels located between the muscular arteries and veins including the capillary bed and possibly other small nonmuscular vessels. Further, the average preocclusion pressure in the middle compartment is a microvascular pressure that can be used to evaluate the impact of vasoconstriction on the lobar microcirculation.
Ventilatory response of intact cats to carbon monoxide hypoxia
Authors: Gautier H. , Bonora M.
Published: December 2017

Adult intact conscious or anesthetized cats have been exposed to either hypoxia or low concentrations of CO in air. In addition, the ventilatory response to CO2 was studied in air, hypoxic hypoxia, and CO hypoxia. The results show that 1) in conscious cats, low concentrations of CO (0.15%) induce a slight decrease in ventilation and higher concentrations of CO (0.20%) induce first a small decrease in ventilation and then a characteristic tachypnea similar to the hypoxic tachypnea described in carotid-denervated cats; 2) in anesthetized cats, CO hypoxia induces only mild changes in ventilation; and 3) the ventilatory response to CO2 is increased in CO hypoxia in both conscious and anesthetized animals but differs from the increase observed during hypoxia. It is concluded that the initial decrease in ventilation may be caused by some brain stem depression of the respiratory centers with CO hypoxia, whereas the tachypnea originates probably at some suprapontine level. Conversely, the possible central acidosis may account for the potentiation of the ventilatory response to CO2 observed in either conscious or anesthetized animals.
Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans
Authors: Behrakis P. K. , Higgs B. D. , Baydur A. , Zin W. A. , Milic-Emili J.
Published: December 2017

In six spontaneously breathing anesthetized subjects [halothane approximately 1 maximum anesthetic concentration (MAC), 70% N2O-30% O2], we measured flow (V), volume (V), and tracheal pressure (Ptr). With airway occluded at end-inspiration tidal volume (VT), we measured Ptr when the subjects relaxed the respiratory muscles. Dividing relaxed Ptr by VT, total respiratory system elastance (Ers) was obtained. With the subject still relaxed, the occlusion was released to obtain the V-V relationship during the ensuing relaxed expiration. Under these conditions, the expiratory driving pressure is V X Ers, and thus the pressure-flow relationship of the system can be obtained. By subtracting the flow resistance of equipment, the intrinsic respiratory flow resistance (Rrs) is obtained. Similar measurements were repeated during anesthesia-paralysis (succinylcholine). Ers averaged 23.9 +/- 4 (+/- SD) during anesthesia and 21 +/- 1.8 cmH2O X 1(-1) during anesthesia-paralysis. The corresponding values of intrinsic Rrs were 1.6 +/- 0.7 and 1.9 +/- 0.9 cmH2O X 1(-1) X s, respectively. These results indicate that Ers increases substantially during anesthesia, whereas Rrs remains within the normal limits. Muscle paralysis has no significant effect on Ers and Rrs. We also provide the first measurements of inspiratory muscle activity and related negative work during spontaneous expiration in anesthetized humans. These show that 36-74% of the elastic energy stored during inspiration is wasted in terms of negative inspiratory muscle work.
Alveolar pressure in fluid-filled occluded lung segments during permeability edema
Authors: Kohler J. P. , Rice C. L. , Moss G. S. , Szidon J. P.
Published: December 2017

In a model of increased hydrostatic pressure pulmonary edema Parker et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 267-276, 1978) demonstrated that alveolar pressure in occluded fluid-filled lung segments was determined primarily by interstitial fluid pressure. Alveolar pressure was subatmospheric at base line and rose with time as hydrostatic pressure was increased and pulmonary edema developed. To further test the hypothesis that fluid-filled alveolar pressure is determined by interstitial pressure we produced permeability pulmonary edema-constant hydrostatic pressure. After intravenous injection of oleic acid in dogs (0.01 mg/kg) the alveolar pressure rose from -6.85 +/- 0.8 to +4.60 +/- 2.28 Torr (P less than 0.001) after 1 h and +6.68 +/- 2.67 Torr (P less than 0.01) after 3 h. This rise in alveolar fluid pressure coincided with the onset of pulmonary edema. Our experiments demonstrate that during permeability pulmonary edema with constant capillary hydrostatic pressures, as with hemodynamic edema, alveolar pressure of fluid-filled segments seems to be determined by interstitial pressures.
Renin, angiotensin-converting enzyme, and aldosterone in humans on Mount Everest
Authors: Milledge J. S. , Catley D. M. , Blume F. D. , West J. B.
Published: December 2017

Plasma renin activity (PRA), serum angiotensin-converting enzyme (ACE) activity, and plasma aldosterone concentration (PAC) were measured in 15 subjects at sea level and at high altitude. Previous work has shown that on first ascent to altitude PAC and ACE are reduced, whereas PRA may be raised or reduced. After 2-4 wk at 6,300 m all hormones had returned to within +/- 10% of sea-level values. In seven subjects PRA and PAC were measured when exercise stopped. PRA and PAC were both elevated, PRA more than PAC; i.e., the PAC response to PRA was markedly blunted. Since ACE activity was normal, it is suggested that there may be down regulation, i.e., reduction in density of angiotensin II receptors on the adrenal cortex and/or induction of enzymes which degrade angiotensin II. This mechanism apparently protects the subjects from very high levels of PAC and sodium retention when hypoxia and exercise raise PRA to very high levels.
Gas mixing in the airways of dog lungs during high-frequency ventilation
Authors: Knopp T. J. , Kaethner T. , Meyer M. , Rehder K. , Scheid P.
Published: December 2017

Washout of insoluble inert test gases of different diffusivity (He and SF6 or He and Ar) from dog lungs was studied during high-frequency ventilation (HFV). Test gas equilibrium and subsequent washout were performed with HFV, succeeding measurements being performed at different stroke volumes (1.5-2.5 ml/kg body wt), oscillation frequencies (10-30 Hz), and with different lung volumes (32-74 ml X kg-1). Test gas concentrations were continuously measured by a mass spectrometer. The time course of washout could be described as the sum of two exponentials. There were no consistent differences in the time courses of washout between He and SF6 or between He and Ar. It is concluded that gas mixing in the airways during HFV is not significantly limited by diffusion, and this is suggested to apply during HFV to steady-state transport of respiratory gases (e.g., O2 and CO2) as well as to the transient state of inert gas washout.
Ventilatory adjustments during sustained mechanical loading in conscious humans
Authors: Axen K. , Haas S. S. , Haas F. , Gaudino D. , Haas A.
Published: December 2017

Ventilatory responses to inspiratory elastic and resistive loads of 67 men were analyzed. During the 1st, 5th, and 10th consecutively loaded breaths 1) individual responses ranged from a rapid-shallow to a slow-deep breathing pattern; 2) strong tidal volume (VT) defenders employed longer inspirations than did weak VT defenders; and 3) individual frequency responses were mediated by changes in inspiratory and/or expiratory timing. Thus the group response was qualitatively similar on the 1st, 5th, and 10th loaded breaths. Quantitatively, however, the group's mean minute ventilation increased throughout each episode owing to progressively larger tidal volumes coupled with equal breathing frequencies. During elastic loading this amplified VT defense was achieved by stronger inspirations with no systematic changes in timing, whereas during resistive loading it was achieved both by stronger and longer inspirations. Inspiring 5% CO2 induced a degree of hypercapnia exceeding that accompanying mechanical loading and yet elicited a comparatively modest enhancement of respiratory output. These findings suggest that in conscious humans 1) repeated mechanical loading activates neural load-compensating mechanisms; 2) the range of these neural adjustments varies with both load size and type; and 3) the stimulus to initiate this behavior is largely nonchemical.
Flow of edema fluid into pulmonary airways
Authors: Mason G. R. , Effros R. M.
Published: December 2017

An in situ rabbit preparation was used to characterize the manner in which edema fluid enters the airways when left atrial pressures are elevated. The airways were initially filled with fluid to minimize retrograde flow of edema fluid into the alveoli. The airway solution contained 125I-albumin and in some studies [14C]sucrose, and the lungs were perfused with a comparable solution which contained albumin labeled with Evans blue dye and 99mTc-diethylenetriaminepentaacetate (DTPA) or 99mTc-sulfur-colloid particles (0.4-1.7 micron diam). After 30 min of perfusion, fluid was pumped from the airways into serial tubes. When left atrial pressures were low, there was very little transfer of labels detectable between the airway and perfusate solutions. However when left atrial pressures were increased to either 15 or 22 cmH2O, fluid entered the airways containing approximately the same concentrations of Evans blue dye and 99mTc-DTPA as those present in the perfusate. In contrast, the concentration of colloid particles averaged less than 5% perfusate concentrations, indicating that the fluid had not escaped through a tear in the barriers separating the vascular and airway compartments. Concentrations of the perfusate fluid and indicators were highest in the initial samples pumped from the airways. These observations suggest that some of the fluid entering the airways may be derived from peribronchial cuffs or that there are marked regional differences in edema formation from alveoli.
Carbonic anhydrase activity of intact erythrocytes from seven mammals
Authors: Dodgson S. J. , Forster R. E.
Published: December 2017

Carbonic anhydrase activity of intact erythrocytes from seven mammalian species was determined at 25 degrees C, pH 7.4, by mass spectrometry using the 18O-exchange technique. The seven species were Cavia porcellus, Mustela putorius furo, Felis domesticus, Canis familiaris, Homo sapiens, Equus caballus, and Bos taurus. Carbonic anhydrase activities determined as a function of hemoglobin concentration (std kcat) for intact erythrocytes at pH 7.4 were not significantly different from those determined for lysed erythrocytes at pH 7.20 for each species. The carbonic anhydrase activity of intact erythrocytes was not changed by a concentration of acetazolamide that inhibited it 85% in lysate (10(-7) M) in the 5-10 min needed for the assay. However, ethoxzolamide, another carbonic anhydrase inhibitor, produced the same fractional inhibition of enzyme activity in erythrocyte suspensions as in lysate in 1-2 min. Thus the inhibition constant, Ki, was approximately the same in both intact and lysed cells from each species, and it was possible to measure the apparent molar enzyme concentration inside the erythrocytes from the concentration of bound inhibitor. Intracellular enzyme concentrations were greater in those species with larger cells, but the specific activity of the carbonic anhydrase per molecule was less so that the overall enzyme activity, std kcat, was not related to mean cell volume. The effective permeability of the cells to the self-exchange of bicarbonate ion, P(HCO3-), averaged 2 X 10(-4) cm x s-1 and did not vary among the species.
Muscle fiber type distribution and architecture of the cat diaphragm
Authors: Sieck G. C. , Roy R. R. , Powell P. , Blanco C. , Edgerton V. R. , Harper R. M.
Published: December 2017

Three types of diaphragmatic muscle fibers were identified histochemically in the sternal, costal, and crural regions of the cat diaphragm. Differences in the proportion of each muscle fiber type were observed between the abdominal and thoracic surfaces of the diaphragm but not among the different regions. A higher percentage of slow-twitch oxidative fibers was noted on the abdominal surface, whereas more fast-twitch fibers (fast-twitch oxidative-glycolytic and fast-twitch glycolytic) were found on the thoracic surface. Differences in muscle architecture were observed between diaphragmatic regions, but not between abdominal and thoracic sides. Overall, muscle fibers were longer in the crural regions, with the longest fibers being found in the crossing-band area of the crura. In the costal regions, fibers were longest in the center and became shorter toward the ventral and dorsal extent of these regions. Fiber lengths were similar throughout the sternal region. In each diaphragmatic region, the length of fibers extended from the origin of the muscle to its insertion. We conclude that functional differences between diaphragmatic regions could be attributed to fiber length and/or orientation, but not to differences in fiber-type composition.
Age-related responses to mild restraint in the rat
Authors: Rattner B. A. , Michael S. D. , Altland P. D.
Published: December 2017

Immature, postpubertal, young adult, and middle-aged rats were lightly restrained for 4 h. Relative to untreated controls, restraint uniformly reduced body weight and plasma luteinizing hormone concentration and elevated plasma corticosterone concentration in all age groups. However, restraint increased activities of plasma alanine and aspartate aminotransferase, creatine phosphokinase, and fructose-diphosphate aldolase in only immature and middle-aged animals. This age-related release of tissue enzymes is hypothesized to reflect enhanced responsiveness to catecholamines in immature rats, and possible ischemia related to diminished vasodilatory activity in middle-aged rats. On the basis of these changes, tolerance to restraint in postpubertal and young adults appears to be slightly greater than that of immature and middle-aged rats.
Effects of menstrual cycle on metabolic responses to exercise
Authors: Bonen A. , Haynes F. J. , Watson-Wright W. , Sopper M. M. , Pierce G. N. , Low M. P. , Graham T. E.
Published: December 2017

Selected substrate and hormonal responses to exercise were compared in two phases of the menstrual cycle. Exercise-induced changes in substrate [glucose, lactate, free fatty acids (FFA), glycerol] and hormonal patterns [luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin, progesterone (P), growth hormone (GH), cortisol] were compared in the follicular and luteal phases of the menstrual cycle in 24-h-fasted (n = 5), glucose-loaded (n = 6; 1.50 g/kg, 20% solution), and control subjects (n = 8). A treadmill walk was maintained for 60 min (30 min, 40% VO2 max; 30 min, 80% VO2 max). Blood samples were obtained 5 min before, 15, 30, 45, and 60 min during, and 30 min after exercise. In the glucose group a blood sample was also taken 20 min before exercise, and glucose was ingested 15 min before exercise. Within each nutritional group the metabolic and endocrine responses to exercise were similar in the two phases for glucose, lactate, glycerol, LH, FSH, and cortisol (P greater than 0.05). In the glucose group the FFA response was lower in the luteal phase (P less than 0.05). In the fasted subjects insulin and GH responses were elevated in the luteal phase (P less than 0.05). P responses in the control and glucose groups were markedly greater in the luteal phase (P less than 0.05). In the fasted subjects no alteration in P occurred in either phase (P less than 0.05), and the LH concentration was lower in these subjects relative to the control groups (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Overall "gain" of the respiratory control system in normoxic humans awake and asleep
Authors: Honda Y. , Hayashi F. , Yoshida A. , Ohyabu Y. , Nishibayashi Y. , Kimura H.
Published: December 2017

With the addition of external dead space in normoxia, PCO2-ventilation response and CO2 production were determined in 10 healthy male subjects. Overall “gain” (G) of the respiratory control system was calculated from the slope of the CO2-response curve (S) and that of the metabolic hyperbola (SL) at alveolar partial pressure of CO2 (PACO2) of the respective experimental run. We found that 1) despite the depression of ventilation during non-rapid-eye-movement (NREM) sleep, G was generally not changed due to decreased SL, although considerable individual variations were seen; 2) effects of external dead space on PACO2 change during sleep and wakefulness were similar in magnitude; and 3) the above PACO2 changes experimentally induced agreed well with the predicted values estimated from G. Contrary to general opinion, these results demonstrated that overall gain of the respiratory control system is generally not depressed during NREM sleep in normal healthy subjects.
Model analysis of respiratory responses to inspiratory resistive loads
Authors: Zin W. A. , Rossi A. , Milic-Emili J.
Published: December 2017

Based on experimental inspiratory driving pressure waveforms and active respiratory impedance data of anesthetized cats, we made model predictions of the factors that determine the immediate (first loaded breath) intrinsic (i.e., nonneural) tidal volume compensation to added inspiratory resistive loads. The time course of driving pressure (P) was given by P = atb, where a is the pressure at 1 s from onset of inspiration and represents the intensity of neuromuscular drive, t is time, and b is a dimensionless index of the shape of the driving pressure wave. For a given value of active respiratory impedance, tidal volume compensation to added resistive loads increases with increasing inspiratory duration and decreasing value of b but is independent of a. Model predictions of load compensation are compared to experimental results.
Cardiopulmonary control during exercise in the duck
Authors: Kiley J. P. , Fedde M. R.
Published: December 2017

To determine the importance of nonhumoral drives to exercise hyperpnea in birds, we exercised adult White Pekin ducks on a treadmill (3 degrees incline) at 1.44 km X h-1 for 15 min during unidirectional artificial ventilation. Intrapulmonary gas concentrations and arterial blood gases could be regulated with this ventilation procedure while allowing ventilatory effort to be measured during both rest and exercise. Ducks were ventilated with gases containing either 4.0 or 5.0% CO2 in 19% O2 (balance N2) at a flow rate of 12 l X min-1. At that flow rate, arterial CO2 partial pressure (PaCO2) could be maintained within +/- 2 Torr of resting values throughout exercise. Arterial O2 partial pressure did not change significantly with exercise. Heart rate, mean arterial blood pressure, and mean right ventricular pressure increased significantly during exercise. On the average, minute ventilation (used as an indicator of the output from the central nervous system) increased approximately 400% over resting levels because of an increase in both tidal volume and respiratory frequency. CO2-sensitivity curves were obtained for each bird during rest. If the CO2 sensitivity remained unchanged during exercise, then the observed 1.5 Torr increase in PaCO2 during exercise would account for only about 6% of the total increase in ventilation over resting levels. During exercise, arterial [H+] increased approximately 4 nmol X l-1; this increase could account for about 18% of the total rise in ventilation. We conclude that only a minor component of the exercise hyperpnea in birds can be accounted for by a humoral mechanism; other factors, possibly from muscle afferents, appear responsible for most of the hyperpnea observed in the running duck.
Antigen stimulates glycoprotein secretion and alters ion fluxes in sheep trachea
Authors: Phipps R. J. , Denas S. M. , Wanner A.
Published: December 2017

We studied the effects of in vitro challenge with specific antigen (Ascaris suum antigen) on glycoprotein secretion and ion fluxes in tracheal tissues from allergic sheep. We mounted tissues in Perspex chambers and measured secretion of 35S- and 3H-labeled glycoproteins and fluxes of Cl- and Na+. In tissues from allergic sheep, A. suum antigen (25 micrograms protein X ml-1) increased glycoprotein secretion. A. suum antigen initially reversed net Cl- flux, causing net absorption of Cl- and of Na+. This was followed 15-30 min later by net secretion of Cl- and of Na+. Pretreatment of tissues with cromolyn (10(-4) M) greatly reduced the effects of A. suum antigen but did not abolish them. The cromolyn-resistant effects were nonspecific, because they were similar to those of in vitro challenges with nonspecific proteins, ovalbumin and ragweed in allergic sheep, and A. suum antigen in nonallergic sheep. We conclude that challenge with A. suum antigen results in mucus hypersecretion in airways of allergic sheep, by both specific and smaller nonspecific effects. Specific effects (cromolyn sensitive) are produced by mediators which are released from airway cells in response to A. suum challenge.
Effects of hypercapnia and hypoxia on abdominal expiratory nerve activity
Authors: Ledlie J. F. , Pack A. I. , Fishman A. P.
Published: December 2017

We examined the effects of progressive hypercapnia and hypoxia on the efferent neural activity in a whole abdominal expiratory nerve (medial branch of the cranial iliohypogastric nerve (L1) in anesthetized, paralyzed dogs. To eliminate effects of phasic lung and chest-wall movements on expiratory activity, studies were performed in the absence of breathing movements. Progressive hyperoxic hypercapnia and isocapnic hypoxia were produced in the paralyzed animals by allowing 3-5 min of apnea to follow mechanical ventilation with 100% O2 or 35% O2 in N2, respectively; during hypoxia, isocapnia was maintained by intravenous infusion of tris(hydroxymethyl)aminomethane buffer at a predetermined rate. To quantify abdominal expiratory activity, mean abdominal nerve activity in a nerve burst was computed by integrating the abdominal neurogram and dividing by the duration of the nerve burst. Hypercapnia and hypoxia both increased mean abdominal nerve activity and decreased expiratory duration. In contrast to the ramplike phrenic neurogram, the abdominal neurogram consisted of three phases: an initial rising phase, a plateau phase in which abdominal nerve activity was approximately constant, and a terminal declining phase in which the activity returned to the base-line level. The height of this plateau phase and the rates of rise and decline of abdominal nerve activity all increased with increasing hypercapnia and hypoxia. We conclude that, with proprioceptive inputs constant, both hypercapnia and hypoxia are excitatory to abdominal expiratory neural activity.
Effects of aging and Parkinson’s disease on motor unit remodeling: influence of resistance exercise training
Authors: Kelly Neil A. , Hammond Kelley G. , Bickel C. Scott , Windham Samuel T. , Tuggle S. Craig , Bamman Marcas M.
Published: December 2017

Aging muscle atrophy is in part a neurodegenerative process revealed by denervation/reinnervation events leading to motor unit remodeling (i.e., myofiber type grouping). However, this process and its physiological relevance are poorly understood, as is the wide-ranging heterogeneity among aging humans. Here, we attempted to address 1) the relation between myofiber type grouping and molecular regulators of neuromuscular junction (NMJ) stability; 2) the impact of motor unit remodeling on recruitment during submaximal contractions; 3) the prevalence and impact of motor unit remodeling in Parkinson’s disease (PD), an age-related neurodegenerative disease; and 4) the influence of resistance exercise training (RT) on regulators of motor unit remodeling. We compared type I myofiber grouping, molecular regulators of NMJ stability, and the relative motor unit activation (MUA) requirement during a submaximal sit-to-stand task among untrained but otherwise healthy young (YA; 26 yr, n = 27) and older (OA; 66 yr, n = 91) adults and OA with PD (PD; 67 yr, n = 19). We tested the effects of RT on these outcomes in OA and PD. PD displayed more motor unit remodeling, alterations in NMJ stability regulation, and a higher relative MUA requirement than OA, suggesting PD-specific effects. The molecular and physiological outcomes tracked with the severity of type I myofiber grouping. Together these findings suggest that age-related motor unit remodeling, manifested by type I myofiber grouping, 1) reduces MUA efficiency to meet submaximal contraction demand, 2) is associated with disruptions in NMJ stability, 3) is further impacted by PD, and 4) may be improved by RT in severe cases.

NEW & NOTEWORTHY Because the physiological consequences of varying amounts of myofiber type grouping are unknown, the current study aims to characterize the molecular and physiological correlates of motor unit remodeling. Furthermore, because exercise training has demonstrated neuromuscular benefits in aged humans and improved innervation status and neuromuscular junction integrity in animals, we provide an exploratory analysis of the effects of high-intensity resistance training on markers of neuromuscular degeneration in both Parkinson’s disease (PD) and age-matched older adults.
Short-term menthol treatment promotes persistent thermogenesis without induction of compensatory food consumption in Wistar rats: implications for obesity control
Authors: Vizin Robson Cristiano Lillo , Motzko-Soares Anna Carolina P. , Armentano Giovana Marchini , Ishikawa Débora T. , Cruz-Neto Ariovaldo P. , Carrettiero Daniel Carneiro , Almeida Maria Camila
Published: December 2017

In this study, we aimed to evaluate the influence of daily repeated menthol treatments on body mass and thermoregulatory effectors in Wistar rats, considering that menthol is a transient receptor potential melastatin 8 channel agonist that mimics cold sensation and activates thermoregulatory cold-defense mechanisms in mammals, promoting hyperthermia and increasing energy expenditure, and has been suggested as an anti-obesity drug. Male Wistar rats were topically treated with 5% menthol for 3 or 9 consecutive days while body mass, food intake, abdominal temperature, metabolism, cutaneous vasoconstriction, and thermal preference were measured. Menthol promoted hyperthermia on all days of treatment, due to an increase in metabolism and cutaneous vasoconstriction, without affecting food intake, resulting in less mass gain in menthol-hyperthermic animals. As the treatment progressed, the menthol-induced increases in metabolism and hyperthermia were attenuated but not abolished. Moreover, cutaneous vasoconstriction was potentiated, and an increase in the warmth-seeking behavior was induced. Taken together, the results suggest that, although changes occur in thermoeffector recruitment during the course of short-term treatment, menthol is a promising drug to prevent body mass gain.

NEW & NOTEWORTHY Menthol produces a persistent increase in energy expenditure, with limited compensatory thermoregulatory adaptations and, most unexpectedly, without affecting food intake. Thus short-term treatment with menthol results in less mass gain in treated animals compared with controls. Our results suggest that menthol is a promising drug for the prevention of obesity.
A model-based approach to interpreting multibreath nitrogen washout data
Authors: Bates Jason H. T. , Peters Ubong
Published: December 2017

The multibreath nitrogen washout (MBNW) test, as it is currently practiced, provides parameters of potential physiological significance that are derived from the relationship between the volume-normalized Phase III slope of the exhaled nitrogen fraction ([Formula: see text]) vs. the cumulative change in lung volume (V). Reliable evaluation of these parameters requires, however, that the subject breathe deeply and evenly, so that Phase III can be clearly identified in every breath. This places a burden on the test subject that may prove troublesome for young children and those with lung disease. Furthermore, the determination of the slope of Phase III requires that a decision be made as to when Phase II ends and Phase III begins. In an attempt to get around these methodological limitations, we develop here an alternative method of analysis based on a multicompartment model of the lung that accounts for the entire exhaled nitrogen profile, including Phases I, II, and III. Fitting this model to [Formula: see text] and V measured during a MBNW provides an estimate of the coefficient of variation of specific ventilation, as well as functional residual capacity, dead space volume, and a parameter that reflects structural asymmetry at the acinar level in the lung. In the present study, we demonstrate the potential utility of this modeling approach to the analysis of MBNW data.

NEW & NOTEWORTHY The multibreath nitrogen washout test potentially provides important physiological information about regional ventilation heterogeneity throughout the lung, but the conventional analysis requires the subject to breathe deeply and regularly, which is not always practical. We have developed a model-based analysis method that avoids this limitation and that also provides measures of functional residual capacity and dead space volume, thereby expanding the applicability and scope of the method.
Reinventing the wheel: comparison of two wheel cage styles for assessing mouse voluntary running activity
Authors: Seward T. , Harfmann B. D. , Esser K. A. , Schroder E. A.
Published: December 2017

Voluntary wheel cage assessment of mouse activity is commonly employed in exercise and behavioral research. Currently, no standardization for wheel cages exists resulting in an inability to compare results among data from different laboratories. The purpose of this study was to determine whether the distance run or average speed data differ depending on the use of two commonly used commercially available wheel cage systems. Two different wheel cages with structurally similar but functionally different wheels (electromechanical switch vs. magnetic switch) were compared side-by-side to measure wheel running data differences. Other variables, including enrichment and cage location, were also tested to assess potential impacts on the running wheel data. We found that cages with the electromechanical switch had greater inherent wheel resistance and consistently led to greater running distance per day and higher average running speed. Mice rapidly, within 1–2 days, adapted their running behavior to the type of experimental switch used, suggesting these running differences are more behavioral than due to intrinsic musculoskeletal, cardiovascular, or metabolic limits. The presence of enrichment or location of the cage had no detectable impact on voluntary wheel running. These results demonstrate that mice run differing amounts depending on the type of cage and switch mechanism used and thus investigators need to report wheel cage type/wheel resistance and use caution when interpreting distance/speed run across studies.

NEW & NOTEWORTHY The results of this study highlight that mice will run different distances per day and average speed based on the inherent resistance present in the switch mechanism used to record data. Rapid changes in running behavior for the same mouse in the different cages demonstrate that a strong behavioral factor contributes to classic exercise outcomes in mice. Caution needs to be taken when interpreting mouse voluntary wheel running activity to include potential behavioral input and physiological parameters.
Effect of changing feedback delay on spontaneous oscillations in smooth pursuit eye movements of monkeys
Authors: Goldreich D. , Krauzlis R. J. , Lisberger S. G.
Published: December 2017

Pages 625–638: D. Goldreich, R. J. Krauzlis, and S. G. Lisberger, ,Effect of changing feedback delay on spontaneous oscillations in smooth pursuit eye movements of monkeys.- Page 634, legend to Fig. 11, second line from bottom, ,Functions for nonlinear gain elements …,- the first equation should read:

See PDF for Equation
Organization of suppression in receptive fields of neurons in cat visual cortex
Authors: DeAngelis G. C. , Robson J. G. , Ohzawa I. , Freeman R. D.
Published: December 2017

1. The response to an optimally oriented stimulus of both simple and complex cells in the cat's striate visual cortex (area 17) can be suppressed by the superposition of an orthogonally oriented drifting grating. This effect is referred to as cross-orientation suppression. We have examined the spatial organization and tuning characteristics of this suppressive effect with the use of extracellular recording techniques. 2. For a total of 75 neurons, we have measured the size of each cell's excitatory receptive field by use of rectangular patches of drifting sinusoidal gratings presented at the optimal orientation and spatial frequency. The length and width of these grating patches are varied independently. Receptive-field length and width are determined from the dimensions of the smallest grating patch required to elicit a maximal response. 3. The extent of the area from which cross-orientation suppression originates has been measured in an analogous manner. Each neuron is excited by a patch of drifting grating the same size as the receptive field. The response to this stimulus is modulated by a superimposed patch of grating having an orthogonal orientation. After selecting the spatial frequency that produces maximal suppression, the response of each cell is examined as a function of the length and width of the orthogonal (suppressive) grating patch. Results from 29 cells show that the dimensions of the orthogonal grating patch required to elicit maximal suppression are similar to, or smaller than, the dimensions of the excitatory receptive field. Thus cross-orientation suppression originates from within the receptive field. 4. For some cells the spatial frequency tuning of the suppressive effect is much broader than the spatial frequency tuning for excitation. In these cases it is possible to find a spatial frequency that produces suppression but not excitation. With the use of a suppressive stimulus having this spatial frequency, we examined the strength of suppression as a function of orientation for 11 cells. These tests show that suppression occurs at all orientations, including the preferred orientation for excitation. In some cases, suppression is somewhat stronger at the preferred orientation for excitation than at any other orientation. 5. For 12 cells we varied the relative spatial phase between the optimally oriented and orthogonal gratings. In all cases the magnitude of suppression is largely independent of the relative spatial phase. 6. For three binocular cells we examined whether the suppressive effect of a grating oriented orthogonal to the optimum could be mediated dichoptically.(ABSTRACT TRUNCATED AT 400 WORDS)