Showing papers in "Journal of Applied Physiology in 1978"
TL;DR: Ten patients with daytime somnolence and obesity were found to have periodic airway occlusion (AO) during nocturnal sleep, and it is speculated that genioglossal force act,s to open the oropharynx and that negative pharyngeal pressure promotes pharynGEal closure.
Abstract: .. sleep. J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44ftik 931-938, 1978. -Ten patients with daytime somnolence and obesity were found to have periodic airway occlusion (AO) during nocturnal sleep. The cyclical ventilatory pattern consisted of a series of regular inspiratory efforts against an occluded airway (occlusive phase) alternating with a period of regular breathing (ventilatory phase). Significant periods of central respiratory apnea were observed only in one case. The effects of pharyngeal intubation and pharyngeal pressure recordings showed that the locus of airway closure lay in the oropharynx. The genioglossal electromyogram (EMG) consistently revealed periodicity: low level activity at the onset of occlusion and prominent discharge at the instant of pharyngeal opening. In one case, this activity was closely related to pharyngeal patency, whereas in other cases there was considerable overlap between EMG values recorded during occluded and ventilatory phases. In these cases, the relationship of genioglossal discharge to pharyngeal pressure correlated with the presence or absence of pharyngeal occlusion. We speculate that genioglossal force act,s to open the oropharynx and that negative pharyngeal pressure promotes pharyngeal closure. The results are consistent with the idea that, once the pharvnx has collapsed, relative recruitment of genioglossal and inspiratory muscle act.ivity is such that the latter influence outstrips the former, so that pharyngeal transmural pressure increases more than genioglossal force. Pharyngeal opening occurs coincident with arousal and preferential activation of the genioglossus muscle of the tongue.
1,670 citations
TL;DR: It was concluded that lipid peroxidation occurs during exercise and that it is attenuated by vitamin E.
Abstract: Expired pentane, an index of lipid peroxidation, and pulmonary function were measured as a function of exercise for 1 h with and without exposure to 0.3 ppm ozone. In experiment 1, 10 subjects who exercised on a bicycle ergometer at 50% of maximal oxygen consumption while being exposed to 0.3 ppm ozone had increased lung residual volume and decreased vital capacity, maximal midexpiratory flow rate, and forced expiratory volume in 1 s. In experiment 2, breath collected into a spirometer filled with hydrocarbon-scrubbed air showed increased pentane from the stress of exercise but no effect of ozone. During rest and exercise in experiment 3, two of six subjects had higher pentane levels than the other subjects. Following daily supplementation with 1,200 IU dl-alpha-tocopherol for 2 wk, the mean production of pentane during rest and exercise was significantly lowered, and there was no difference in pentane production among the subjects. It was concluded that lipid peroxidation occurs during exercise and that it is attenuated by vitamin E.
506 citations
TL;DR: A rapid-flow, open-circuit, indirect calorimeter was developed and used to study metabolic rates of rats at rest and in response to three running speeds and five grades and Electrocardiogram connections were available within the apparatus for simultaneous determination of heart rate.
Abstract: BROOKS, GEORGE A., AND TIMOTHY P. WHITE. Determination of metabolic and heart rate responses of rats to treadmill exercise. J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 45(6): 1009-1015, 1978. -A rapid-flow, open-circuit, indirect calorimeter was developed and used to study metabolic rates of rats at rest and in response to three running speeds (14.3, 28.7, and 43.1 m/min) and five grades (1, 5, 10, 15, and 20%). Electrocardiogram connections were available within the apparatus for simultaneous determination of heart rate (f,>. Validity of the calorimeter was established by observing responses to the addition of mixed gases including 14C02, and by comparing oxygen consumptions when anesthetized rats were placed in the openor a closed-circuit system. Halfresponse time of the system was 27 t 3 s (mean t SE). With one rat in each system values for O2 consumption (Vo,) were 15.86 t 0.91 and 15.77 ~fr 0.90 ml/kg per min for the open and closed systems, respectively. Highest Vo,. values observed were 80.86 t 2.48 ml/kg per min for rats running at 43.1 m/ min on a 20% grade. The corresponding heart rates were 595 t 5 beats/min. Correlations between Vo, and running speed ranged from 0.83 on 1% and 15% grades, to 0.90 on a 10% grade. Correlations between frl and speed ranged from 0.70 on a 1% grade, to 0.79 on a 10% grade. Steady-rate values for Vo, and V@O~ were 51.1. and 45.3 ml/kg per min during running at 14.3 m/min on 1% grade, and 69.0 and 65.1 ml/kg per min during running at 28.7 m/min on 15% grade.
433 citations
TL;DR: In this paper, both infants and adults were exposed to 95+% O2 and showed significant changes in lung antioxidant enzyme activity (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPE), and GPE).
Abstract: Neonatal and adult animals of five species were exposed to 95+% O2. Survival time and changes in lung antioxidant enzyme activity (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase...
346 citations
TL;DR: Findings suggest the ventilatory muscles of newborn infants are more susceptible to fatigue than those of older subjects, which may contribute significantly to respiratory problems in the neonate.
Abstract: Premature infants tolerate respiratory loads poorly This may reflect incomplete development of the ventilatory muscles (VM) causing poor resistance to fatigue To study the developmental pattern of human VM, 31 postmortem specimens of diaphragm and intercostal muscles were obtained Individual muscle fibers were classified as type I (slow-twitch, high-oxidative) or type II (fast-twich, low-oxidative) using histochemical staining methods for myofibrillar adenosine triphosphatase (M-ATPase) (pH 1030) and nicotinamide adenine dinucleotide (NADH) tetrazolium reductase In the diaphragm, premature infants (less than 37 wk gestation) had only 97 +/- 13% type I fibers, full-term newborns 250 +/- 11%, and older subjects (greater than 2 yr of age) 549 +/- 13% There was no further increase after 8 mo postpartum In the intercostal muscles, premature infants had only 190 +/- 48% type I fibers, full-term newborns 457 +/- 13%, and older subjects 652 +/- 26% There was no further increase after 2 mo postpartum These findings suggest the ventilatory muscles of newborn infants are more susceptible to fatigue than those of older subjects This may contribute significantly to respiratory problems in the neonate
285 citations
TL;DR: It is concluded that [H+] in plasma and CSF is a function rather than a cause of ventilator acclimatization to MPA, and MPA-related materials are capable of crossing the blood-brain barrier and could potentially exert their ventilatory stimulant effect by some central mechanism.
Abstract: The time course of ventilatory adaptation to medroxyprogesterone acetate (MPA) and potential mediators of this response in plasma and lumbar CSF were determined in five healthy adult males. A significant decrease in arterial PCO2 (PACO2) at rest and exercise was noted within 48 h of drug administration with the maximum effect reached within 7 days and amounting to a 5-Torr decrement in PACO2. Blood and lumbar cerebrospinal fluid pH because significantly alkaline to control as soon as the ventilatory resporse was noted and remained alkaline during the treatment period. The ventilatory and dP/dt max response to exogenous CO2 was unchanged but their response to moderate exercise was increased after MPA. MPA-rlated materials were detected in both the plasma and CSF as soon as the ventilatory response was noted. The increase in CSF MPA-related materials approximated the unbound fraction determined in plasma. We conclude that [H+] in plasma and CSF is a function rather than a cause of ventilator acclimatization to MPA. MPA-related materials are capable of crossing the blood-brain barrier and could potentially exert their ventilatory stimulant effect by some central mechanism.
256 citations
TL;DR: A pressure-flow analogue of the force-velocity relationship for the diaphragm is constructed and it is concluded that the velocity of shortening of the diphragm increases directly as the rate of abdominal displacement.
Abstract: We determined the static, isometric relationship between diaphragmatic EMG (Edi) and transdiaphragmatic pressure (Pdi) in man at specified abdominothoracic configurations, assessed with magnetometers. During inspiratory airflow, measurements of Edi and Pdi were taken as the respiratory system passed through the same configuration as obtained during the static isometric contractions, allowing a comparison of static and dynamic contractions of the diaphragm at a given length and curvature. When voluntary inspiratory maneuvers are performed with no associated outward displacement of the abdominal wall, or with slight inward displacement, the Pdi developed dynamically is the same as that developed statically at a given Edi. When outward movement of the abdominal wall occurs during inspiratory airflow, the Pdi developed dynamically depends on the rate of abdominal displacement, not on overall inspiratory airflow rate. We conclude that the velocity of shortening of the diaphragm increases directly as the rate of abdominal displacement. We construct a pressure-flow analogue of the force-velocity relationship for the diaphragm and discuss the functional implications of these observations in relation to spontaneous breathing.
247 citations
TL;DR: The chronology of hemoconcentration and hemodilution associated with changes in posture, and the reliability of venous hematocrit, hemoglobin, and plasma proteins as indicators in evaluating changes in plasma volume were determined in seven male subjects.
Abstract: The chronology of hemoconcentration and hemodilution associated with changes in posture, and the reliability of venous hematocrit (Hct), hemoglobin (Hb), and plasma proteins (PP) as indicators in evaluating changes in plasma volume were determined in seven male subjects. Red cell mass was also measured by the CO method at the termination of the erect and supine positions. Movement to and from supine and erect positions produced consistent, rapid, and progressive changes in Hct, Hb, and PP. Thirty-five minutes in a supine position resulted in a 440-ml expansion of plasma volume. Resumption of the standing position resulted in an increase of 10.3 and 10.8% for Hct and Hb, respectively, and an increase in PP of 20.8%. A fluid efflux of 593 ml reduced blood and plasma volume by 9.5 and 16.2%, respectively. Red cell mass was unaffected by changes in posture. The significance of these postures on the reported alterations in plasma volumes consequent to the imposition of stresses on man are discussed.
242 citations
TL;DR: Heart rate during exercise continued to decrease even after the catecholamine response had plateaued, implying that the reduced sympathetic response is not solely responsible for the reduced exercise heart rate.
Abstract: One possible reason for the lower exercise heart rate after endurance exercise training is that the sympathetic drive to the heart is reduced. We have studied the relationship between plasma catech...
224 citations
TL;DR: The runners showed less rapid eye-movement activity during sleep than the nonrunners under both experimental conditions, indicating a strong and unexpected effect of physical fitness on this measure.
Abstract: We tested the hypothesis that EEG sleep stages 3 and 4 (slow-wave sleep, SWS) would be increased as a function of either acute of chronic exercise. Ten distance runners were matched with 10 nonrunners, and their sleep was recorded under both habitual (runners running and nonrunners not running, 3 night) and abruptly changed (runners not running and nonrunners running, 1 night) conditions. Analyses of both visually scored SWS and computer measures of delta activity during non-rapid eye-movement (NREM) sleep failed to support the SWS-exercise hypothesis. The runners showed a significantly higher proportion and a greater absolute amount of NREM sleep than the nonrunners. The runners showed less rapid eye-movement activity during sleep than the nonrunners under both experimental conditions, indicating a strong and unexpected effect of physical fitness on this measure. Modest afternoon exercise in nonrunners was associated with a strong trend toward elevated heart rate during sleep. Mood tests and personality profiles revealed few differences, either between groups or within groups, as a function of exercise.
222 citations
TL;DR: A technique whereby the time necessary to reach an equilibrium enrichment of expired CO2 during a primed-constant infusion of [U-13C]glucose was shortened from 7 to 8 h to 1 hour or less was described.
Abstract: We have described a technique whereby the time necessary to reach an equilibrium enrichment of expired CO2 during a primed-constant infusion of [U-13C]glucose was shortened from 7 to 8 h to 1 hour or less. We applied the theory of the primed-constant infusion technique to the bicarbonate pool, with the “constant infusion” of labeled carbon dioxide originating from oxidation of the infused [13C]glucose rather than from a labeled infusion of bicarbonate.
TL;DR: A maximal level for the lactate release from the exercising muscles with a translocation hindrance for lactate within the muscles is indicated.
Abstract: In four healthy volunteers, muscle lactate concentration and the release of lactate from the leg were determined at rest and at 4 and 12 min of sitting bicycle exercise at four intensities (30, 50, 70, and 90% of maximal oxygen uptake). The muscle biopsies were obtained by needle biopsy technique from m. vastus lateralis. The rate of lactate release was calculated from the femoral venous-arterial differences of lactate and the leg blood flow was determined by constant rate dye infusion. Both leg blood flow and leg oxygen consumption increased linearly with work intensity. The release of lactate rose approximately linearly with the muscle lactate concentration up to about 4–5 mmol/min but then the relationship revealed a clear leveling off. These results indicate a maximal level for the lactate release from the exercising muscles with a translocation hindrance for lactate within the muscles.
TL;DR: With both acute and extablished anemia maximal exercise capacity and maximal VO2 (VO2 max) decreased in proportion to the Hb reduction, and PVO2 was further decreased.
Abstract: Effects of acute and maintained isovolemic anemia on oxygen transport was studied during rest and exercise in normal males. Following 34% reduction in hemoglobin concentration (Hb), supine and stan...
TL;DR: It is found that cardiac output fell approximately 50% and blood pressure fell 20% during 15 cmH2OPEEP in spite of well maintained transmural right atrial and left atrial pressures suggesting a primary or reflex depression of atrial or ventricular function.
Abstract: Our purpose was to reexamine the relationship of the fall in cardiac output and blood pressure which occurs during positive end-expiratory pressure (PEEP) to changes in transmural right atrial and left atrial filling pressures. Closed-chest dogs, half with pulmonary edema, were studied during spontaneous breathing and inspiratory positive-pressure breathing (IPPB) with 0–15 cmH2O PEEP. Mean esophageal pressure accurately reflected changes in pericardial pressure and was used to estimate extracardiac pressure. We found that cardiac output fell approximately 50% and blood pressure fell 20% during 15 cmH2OPEEP in spite of well maintained transmural right atrial and left atrial (or pulmonary artery wedge) pressures suggesting a primary or reflex depression of atrial or ventricular function.
TL;DR: It is concluded that during REM sleep arousal responses to laryngeal stimulation are depressed, but ventilatory and cardiac responses are intact.
Abstract: We studied waking and ventilatory responses to laryngeal stimulation during sleep in three dogs. The dogs breathed through an endotracheal tube inserted caudally into the trachea through a tracheostomy. Laryngeal stimulation was produced either by inflating a small balloon that was positioned in the rostral tracheal segment, or by squirting water onto the larynx through a catheter inserted through the tracheostomy. Airflow was measured with a pneumotachograph, and sleep state was determined by behavioral, electroencephalographic, and electromyographic criteria. We found that the degree of laryngeal stimulation required to produce arousal and coughing was higher in rapid-eye-movement (REM) sleep than in slow-wave sleep (SWS). Stimuli that failed to cause arousal from SWS often produced a single expiratory effort, or brief apnea (1--2 s) and bradycardia. In contrast, during REM sleep subarousal stimuli often resulted in prolonged apnea (greater than 10 s) and marked bradycardia. We conclude that during REM sleep arousal responses to laryngeal stimulation are depressed, but ventilatory and cardiac responses are intact.
TL;DR: The rat's marked ventilatory response and changing VO2 during acute hypoxia clearly differs from the human response to sojourn at 4,300 m, and the progressive and sustained hypocapnia during hypoxic exposure and the continued hyperventilation with acute normoxia in the rat provided essential, perhaps unique characteristics for an animal model of human Ventilatory acclimatization.
Abstract: Oxygen uptake (VO2), expired volume (VE), and arterial blood gases were studied in awake, unrestrained rats over 14 days of hypobaric hypoxia (4,300 m altitude) and upon return to acute normoxia. C...
TL;DR: The finding that O2 uptake rises to meet O2 demand more rapidly in the trained than in the untrained state provides evidence that the working muscles become less hypoxic at the onset of exercise of the same intensity after training.
Abstract: The purpose of this study was to determine the effect of endurance exercise training on the time course of the increase in VO2 toward steady state in response to submaximal constant load work. Seven men participated in a strenuous program of endurance exercise for 40 min/day, 6 days/wk for 10 wk. Their average VO2max increased from 3.29 liters before training to 4.53 liters at the end of the training program. VO2 was measured continuously on a breath-by-breath basis at work rates requiring 40%, 50%, 60%, or 70% of VO2max before training. After training the subjects were retested both at the same absolute and the same relative work rates. The increases in VO2 toward steady state occurred more rapidly in the trained than in the untrained state both at the same absolute and at the same relative work rates. The finding that O2 uptake rises to meet O2 demand more rapidly in the trained than in the untrained state provides evidence that the working muscles become less hypoxic at the onset of exercise of the same intensity after training.
TL;DR: A remarkable increase in aerobic power was not observed in trained boys before the age of peak height growth velocity (PHV), and thereafter, training effectively increased aerobic power above the normal increase attributable to age and growth.
Abstract: Maximal aerobic power was measured for 5–6 successive years in 50 Japanese schoolboys starting from the age of 9 or 13 yr. and for 2–3 yr in 6 superior junior runners from the age of 14 yr. A large increase in aerobic power was observed during the adolescent growth spurt for 7 schoolboys who trained between the ages of 9 and 14 yr. Aerobic power for 43 average schoolboys increased from 45.0 to 52.2 ml/kg.min between the ages of 13 and 17 yr. The aerobic power of 6 superior junior runners increased from 63.4 to 73.4 ml/kg.min between the ages of 14 and 17 yr. A remarkable increase in aerobic power was not observed in trained boys before the age of peak height growth velocity (PHV). Beginning approximately 1 yr prior to the age of PHV and thereafter, training effectively increased aerobic power above the normal increase attributable to age and growth. The highly developed aerobic power found in superior junior runners may have been derived from strenuous training and partially by genetically superior endowment.
TL;DR: It is concluded that exercise is a physiological stimulus to elevations in plasma estradiol, progesterone, and FSH, but not LH, and the elevations are more marked in the luteal phase for the steroids and in the follicular phase for FSH.
Abstract: The effects of exercise on estradiol, progesterone, follicle-stimulating hormones (FSH), and luteinizing hormone (LH) were studied in nine healthy females. Subjects were studied during light, heavy, and exhaustive exercise in the midfollicular and midluteal portions of their menstrual cycles. Resting hormone levels followed the expected pattern. Increases in estradiol and progesterone occurred at all intensities of exercise in the luteal phase but only in estradiol at exhaustion in the follicular phase. LH was unchanged with exercise in either phase and FSH increased in the follicular phase but not in the luteal phase. We conclude that exercise is a physiological stimulus to elevations in plasma estradiol, progesterone, and FSH, but not LH. The elevations are more marked in the luteal phase for the steroids and in the follicular phase for FSH. Increases in estradiol and progesterone are related to the intensity of exercise and appear to be independent of pituitary control.
TL;DR: Intracellular pH (pHi) and bicarbonate concentration ([HCO3-]i) in muscle have been calculated and the changes are the greatest so far reported for an in vivo situation.
Abstract: Eight subjects exercised on an ergometer until exhaustion. Femoral venous blood was analyzed for lactate, pyruvate, protein, electrolytes, and acid-base parameters. Muscle samples taken during the recovery period from m. quadriceps femoris were analyzed for water, electrolytes, lactate, and acid-labile CO2. Water content in the muscle biopsy sample was increased after exercise to 78.7 +/- 0.5% compared with the normal 76.7 +/- 0.8% at rest. The distribution of water between the extra- and intracellular space was calculated by the chloride method. In spite of elevated PCO2 in femoral venous blood the content of acid-labile CO2 was decreased in muscle after exercise. One minute after termination of exercise muscle CO2 was about half of the normal content at rest. During the recovery period muscle CO2 increased but was 20 min after termination of exercise still significantly below the value at rest. Intracellular pH (pHi) and bicarbonate concentration ([HCO3-]i) in muscle have been calculated. The validity of the assumptions underlying the calculations are thoroughly discussed. pHi decreased from the normal value at rest, 7.00 +/- 0.06 (mean +/- SD), to about 6.4 after exercise. [HCO3-] decreased from 10.2 +/- 1.2 mmol/l at rest to about 3 mmol/l after exercise. The changes are the greatest so far reported for an in vivo situation. After 20 min recovery pHi was almost the same as at rest, whereas bicarbonate was still well below.
TL;DR: In anesthetized dogs, an increase in left ventricular filling pressure (LVFP) with both constant and increasing lung volume during an inspiratory effort is found consistent with the hypothesis that a fall in pleural pressure afterloads the left ventricle.
Abstract: The conventional explanation for the fall in left ventricular stroke volume (LVSV) with inspiration is that blood pools in the lungs, thereby decreasing pulmonary venous return. In anesthetized dogs, we have found an increase in left ventricular filling pressure (LVFP) with both constant and increasing lung volume during an inspiratory effort. Transmural aortic diastolic pressure rises as LVSV falls and LVFP rises consistent with the hypothesis that a fall in pleural pressure afterloads the left ventricle. Additionally the increase found in right ventricular filling pressure with inspiration may adversely affect LV performance by decreasing LV compliance and/or contractility. Our findings are incompatible with pooling of blood in the lungs being the primary determinant of the fall in LVSV with inspiration.
TL;DR: VO2 increased significantly from the 5th to 20th min of exercise in 81% of the tests at both levels of work intensity, and no evidence was found to support the lactacid explanation proposed for this rise.
Abstract: Previous investigators have reported that oxygen consumption (VO2) continues to rise after the initial 2- to 3-min transient period of exercise when work exceeds approximately 60% of VO2 max. The purpose of this investigation was to examine the possible causes of this slow rise in VO2. Eighteen subjects exercised for 20 min at 65% and at 80% of VO2 max on the bicycle ergometer. VO2, ventilation (VE), and respiratory exchange ratio were monitored by a continuous computer-based system. Blood lactate concentration and rectal temperatures were measured at 2- to 3-min intervals during the exercise. VO2 increased significantly from the 5th to 20th min of exercise in 81% of the tests at both levels of work intensity. The magnitude of the rise was not different for the two work loads. No evidence was found to support the lactacid explanation proposed for this rise. Increased temperature could account for 30% of the rise; the estimated cost of increased VE could account for 30 and 81% of the rise at the two work loads. The sum of these factors could account for 60 and 111% of the rise in VO2 at the 65 and 80% of VO2 max work loads.
TL;DR: Investigation of the effects of the newly discovered bicyclic prostaglandin, prostacyclin (PGI2), in the anesthetized dog demonstrated that PGI2 has marked vasodilator activity in the pulmonary and systemic vascular beds and suggested that prostacyClin is the only known metabolite of arachidonic acid that dilates the pulmonary
Abstract: The effects of the newly discovered bicyclic prostaglandin, prostacyclin (PGI2), on the pulmonary and systemic vascular beds were investigated in the anesthetized dog. PGI2 decreased systemic and pulmonary arterial pressures in a dose-related manner when injected into the vena cava in doses of 1--30 microgram. Since left ventricular end-diastolic, left atrial, and right atrial pressures were unchanged, and since cardiac output was increased or unchanged, pulmonary and systemic vascular resistances were decreased. PGI2 was 10 times more potent than prostaglandins E1 or E2 in decreasing aortic pressure when injected intravenously, and the effects of PGI2 on the systemic vascular bed were similar when injected into the vena cava or the left atrium. These data indicate that inactivation of PGI2 is minimal in the lung. The stable prostacyclin metabolite, 6-keto-PGF1alpha, had little hemodynamic effects, suggesting that responses to PGI2 were not due to formation of this metabolite. PGI2 produced dose-dependent increases in blood flow in the mesenteric and renal vascular beds. These data demonstrate that PGI2 has marked vasodilator activity in the pulmonary and systemic vascular beds and suggest that prostacyclin is the only known metabolite of arachidonic acid that dilates the pulmonary and systemic circulations.
TL;DR: In this article, the reactions of human tracheal and bronchial smooth muscle and canine trachealis muscle to alpha-adrenergic agonists were studied and compared.
Abstract: We studied the reactions of human tracheal and bronchial smooth muscle and canine trachealis muscle to adrenergic agonists. Human tissue was obtained from recent autopsies of patients with normal lungs and patients with respiratory disorders, and canine tissue was obtained from animals used in other experiments. The muscle was mounted in tissue baths fitted with platinum wire electrodes and the mechanical activity was recorded. Norepinephrine added to the normal human or canine tissue in concentrations up to 10(-5) M caused no reaction. In the normal human and in the dog, pretreatment with histamine or KCl changed this response and when norepinephrine was added the tissue contracted. This contraction was blocked by phentolamine or N,N'-bis-(O-methoxybenzylaminohexyl)-cystamine tetrahydrochloride (BHC). In diseased tissue, the addition of norepinephrine resulted in a contraction that was blocked by phentolamine or BHC and no pretreatment with histamine or KCl was required. These findings demonstrate alpha-receptors in human and canine airway smooth muscle, and there is a difference between normal and diseased human tissue in the reaction of these tissues to alpha-adrenergic agonists.
TL;DR: An apparatus for quantitative measurement of ventilation in unrestrained small animals is described, and an electronic device also is described which automatically calculates expired minute volumes from the pressure signal obtained from the plethysmograph.
Abstract: An apparatus for quantitative measurement of ventilation in unrestrained small animals is described. The subject rests in an environmental chamber, and respiration is indicated by barometric pressure oscillations proportional to tidal volume. The chamber is purged continuously at a relatively high flow rate during studies. Thus, CO2 does not accumulate and long-term measurement can proceed without interruption. Respiratory control studies are especially facilitated since different gas mixtures can be rapidly passed through the chamber. An electronic device also is described which automatically calculates expired minute volumes (VE) from the pressure signal obtained from the plethysmograph.
TL;DR: Although waking responses to hypoxia are delayed in REM sleep, ventilatory responses remain intact and therefore may be of importance in maintaining adequate ventilation during this stage of sleep.
Abstract: We examined waking and ventilatory responses to acute hypoxia in four dogs during natural sleep. Progressive hypoxia was induced by a rebreathing technique in which alveolar CO2 pressure (PACO2) was held at the eucapnic level. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Arousal from eucapnic hypoxia occurred at a SaO2 of 87.5 +/- 2.6% (mean +/- SE) during slow-wave sleep (SWS), and at a SaO2 of 70.5 +/- 3.4% during rapid-eye-movement (REM) sleep (P less than 0.005). The irregular pattern of breathing typical of REM sleep persisted during hypoxia. However linear regression analysis of breath-by-breath instantaneous minute volume of ventilation (VI) against SaO2 revealed regression coefficients in REM sleep that were similar to those found in SWS and wakefulness. This finding contrasts with earlier observations of a decreased response of VI to CO2 during REM sleep. The results indicate that although waking responses to hypoxia are delayed in REM sleep, ventilatory responses remain intact and therefore may be of importance in maintaining adequate ventilation during this stage of sleep.
TL;DR: O2 debt and lactate measurements attest to the severity of exercise and dominance of anaerobic metabolism during early stages of work.
Abstract: Metabolic function was measured by open-circuit spirometry for 310 competitive oarsmen during and following a 6-min maximal rowing ergometer exercise. Aerobic and anaerobic energy contributions to ...
TL;DR: The analysis indicates that the diaphragm can act both as a fixator, preventing transmission of Ppl to the abdomen and as an agonist, when abdominal muscles remain relaxed it only assumes the latter role to the extent that Pab increases.
Abstract: We tested the hypothesis that the inspiratory pressure swings across the rib-cage pathway are the sum of transdiaphragmatic pressure (Pdi) and the pressures developed by the intercostal/accessory muscles (Pic). If correct, Pic can only contribute to lowering pleural pressure (Ppl), to the extent that it lowers abdominal pressure (Pab). To test this we measured Pab and Ppl during during Mueller maneuvers in which deltaPab = 0. Because there was no outward displacement of the rib cage, Pic must have contributed to deltaPpl, as did Pdi. Under these conditions the total pressure developed by the inspiratory muscles across the rib-cage pathway was less than Pdi + Pic. Therefore, we rejected the hypothesis. A plot of Pab vs. Ppl during relaxation allows partitioning of the diaphragmatic and intercostal/accessory muscle contributions to inspiratory pressure swings. The analysis indicates that the diaphragm can act both as a fixator, preventing transmission of Ppl to the abdomen and as an agonist. When abdominal muscles remain relaxed it only assumes the latter role to the extent that Pab increases.
TL;DR: It is concluded that cellular adaptations are induced in the ventilatory muscles by chronic increased respiratory loads.
Abstract: It is not known whether cellular adaptations of the ventilatory muscles are induced by increased respiratory loads. A chronic respiratory load was produced in rats by tracheal banding. Five weeks after the imposition of this increased load, biochemical and histochemical analyses were performed on the diaphragm and intercostal muscles. The oxidative capacity, as indicated by succinate dehydrogenase (SDH) activity, increased 38% in the diaphragm. The capacity for beta-oxidation fatty acids, as indicated by 3-hydroxy-acyl-CoA dehydrogenase (HADH) activity, increased 29%. The glycolytic capacity, as indicated by phosphofructokinase (PFK) activity, did not change. Similar enzymatic adaptations were observed in the intercostal muscles. The proportion of slow-twitch muscle fibers, as indicated by the myofibrillar adenosine triphosphatase (ATPase) stain, increased in the diaphragm, but not in the intercostal muscles. Thus, these ventilatory muscles responded with an increase in their oxidative capacity, and the d...