bluuebunny/crossref_metadata_2025 huggingface dataset:
Instantaneous venous return curves in an intact canine preparation
Authors: Pinsky M. R.
Published: December 2017

The relationship between right atrial pressure (Pra) and venous return describes a venous return curve. Because changes in venous return and right ventricular stroke volume (SVRV) are similar during small tidal volume (VT) breathing, we compared the relationship of SVRV and Pra during positive-pressure ventilation (VT less than 10 ml/kg) in 17 pentobarbital-anesthetized, closed-chest, canine preparations. The SVRV-Pra relationship describes a straight line with a negative slope and a positive mean systemic pressure (Pms)-zero flow intercept (instantaneous Pms). Instantaneous Pms is similar to ventricular fibrillation-induced (stop-flow) Pms (8.1 +/- 0.8 vs. 8.4 +/- 0.7 mmHg, mean +/- SE). With volume infusion, both instantaneous and stop-flow Pms increase to a similar degree (R = 0.9014, P less than 0.001). The effect of opening an arteriovenous fistula is time dependent and variable between dogs, but by 30 s it is associated with an increase in instantaneous Pms (5.2 +/- 3.2 mmHg). Vascular compliance determined by adding and removing blood from the intravascular space displays a curvilinear hysteresis. The instantaneous venous return curve is affected by intravascular blood volume, vasomotor tone, and resistance to venous return. The relationship between SVRV and Pra during small VT breathing define instantaneous venous return curves similar to those described using right-heart bypass preparations.
Energy cost of and energy sources for alpine skiing in top athletes
Authors: Veicsteinas A. , Ferretti G. , Margonato V. , Rosa G. , Tagliabue D.
Published: December 2017

O2 uptake (VO2) during exercise and at 2 min of the recovery along with blood lactate concentration 5 min after exercise were measured in an all-out special slalom (SS) and giant slalom (GS) performed by eight top male athletes and five controls in a field study. Heart rate (HR) was continuously monitored before, during, and after each task. On the basis of an energy equivalent of 3.15 ml O2 X kg body wt-1 for 1 mmol X 1–1 lactate accumulation and the assumption that the amount of O2 consumed in recovery is used to reconstitute approximately phosphates used during the exercise, the total energy cost (delta VO2 tot) could be calculated and subdivided into aerobic, lactic, and alactic fractions. In top athletes, delta VO2 tot was equal during SS and GS [7.28 +/- 1.14 (SD) and 7.47 +/- 0.89 liters for about 55- and 70-s performances, respectively]. When referred to time, the O2 expenditure rate was 2 and 1.6 times VO2max in SS and GS, respectively. In SS and GS, the energy sources were about 40% aerobic, 20% alactic , and 40% lactic metabolism. In control skiers, delta VO2 tot of GS was 6.12 +/- 1.45 liters for 77 s, amounting to about 1.3 VO2max, with the contribution of the different energy sources being roughly the same as in top skiers. HR reached maximal values in 30–40 s in all subjects for all conditions.
Determinants of pulmonary arterial flow variation during respiration
Authors: Pinsky M. R.
Published: December 2017

We characterize the determinants of pulmonary arterial flow ( Qpa ) variation during spontaneous breathing ( SPONT ) and matched tidal volume intermittent positive-pressure breathing (IPPB) in 14 pentobarbital-anesthetized closed-chest canine preparations in which Qpa is measured by an electromagnetic flow probe around the pulmonary artery. Pressures are recorded from the juxtacardiac pleural space (Ppl), right atrium (Pra), and pulmonary artery. Spontaneous inspiratory efforts increase transmural Pra (Pra - Ppl) and right ventricular stroke volume ( SVRV ) but decreases Pra, whereas IPPB inspiration has the opposite effect. However, the relationship between instantaneous changes in SVRV and transmural Pra during SPONT and IPPB define a common “instantaneous” right ventricular (RV) function curve independent of mode of ventilation or phase or respiratory cycle, and this curve is similar to one generated by volume infusion measured at end expiration. Pulmonary vascular resistance changes during ventilation are small (less than 15%) and do not affect RV performance as noted by similar instantaneous RV function curves for SPONT and IPPB with Mueller and Valsalva maneuvers, respectively. Thus variations in Qpa during ventilation represent matched changes in RV filling pressure induced by phasic changes in venous return.
Pleural liquid pressure measured by micropipettes in rabbits
Authors: Lai-Fook S. J. , Beck K. C. , Southorn P. A.
Published: December 2017

Pleural liquid pressure (Ppl) was measured by the micropipette servo-nulling method. In anesthetized, paralyzed, and mechanically ventilated rabbits, windows were made by dissecting away the intercostal muscle layers, exposing the parietal pleura over the right caudal lung lobe. Repeated measurements of Ppl were made at the windows by puncturing the parietal pleura with micropipettes during apnea at functional residual capacity. In five supine rabbits, Ppl relative to atmospheric pressure averaged -3.32 +/- 1.22 (SD) cmH2O at a distance of 5.64 +/- 0.34 (SD) cm above the lung base and -1.64 +/- 0.79 cmH2O at a distance of 2.35 +/- 0.64 cm above the lung base; the vertical Ppl gradient was 0.51 cmH2O/cm height. Ppl interpolated to midlung height was equal in absolute magnitude to mean lung static recoil (Pst) of 2.00 cmH2O. In prone rabbits, Ppl measured near the dorsal surface, 3.9 cm above the lung base, averaged -1.32 +/- 0.46 cmH2O on the costal surface, not statistically different in magnitude from mean Pst of 1.59 +/- 0.09. In contrast, Ppl measured at the same vertical height off the edge of the caudal lung in the costo-diaphragmatic recess was -4.64 +/- 0.65 cmH2O. We concluded from these data that Ppl was equal to pleural surface pressure over the costal surface and that the vertical gradient in Ppl was not hydrostatic, except in large fluid spaces off the sharp edges of the lung.
Applicability of echocardiography in volume determinations in experimental animals
Authors: Lust R. M. , Lutherer L. O. , Cooper M. W.
Published: December 2017

A method is described for the use of echocardiography in volume determinations in the experimental animal. Suitability of the technique in both acute and chronically implanted animals was tested. Stroke volumes derived from calculations based on echo data were compared with those obtained by an electromagnetic flow probe placed around the aorta. High correlation was found in both the acute (r = 0.96, P less than 0.001) and the chronic (r = 0.89, P less than 0.001) preparations. Cardiac output computed from echocardiographic data and compared with those based on either flow probe or indicator-dilution techniques also showed a high degree of correlation in both the acute (r = 0.91 and 0.95, respectively; P less than 0.001) and chronic (r = 0.98 and 0.94, respectively, P less than 0.001) preparations. It is suggested that echocardiography, because of the potential to measure many indicators of myocardial function in addition to volume, represents a significant improvement in the techniques available for basic cardiovascular experimentation.
Glucose turnover and hormonal changes during insulin-induced hypoglycemia in trained humans
Authors: Kjaer M. , Mikines K. J. , Christensen N. J. , Tronier B. , Vinten J. , Sonne B. , Richter E. A. , Galbo H.
Published: December 2017

Eight athletes (T), studied the third morning after the last exercise session, and seven sedentary males (C) (maximal O2 consumption 65 +/- 4 vs. 49 +/- 4 (SE) ml X kg-1 X min-1, for T and C men, respectively) had insulin infused until plasma glucose, at an insulin level of 1,600 pmol X l–1, was 1.9 mmol X l–1. Glucose turnover was determined by primed constant rate infusion of 3-[3H]glucose. Basal C-peptide (0.46 +/- 0.04 vs. 0.73 +/- 0.06 pmol X ml–1) and glucagon (4 +/- 0.4 vs. 10 +/- 2 pmol X l–1) were lower (P less than 0.05) and epinephrine higher (0.30 +/- 0.06 vs. 0.09 +/- 0.03 nmol X l–1) in T than in C subjects. During and after insulin infusion production, disappearance and clearance of glucose changed identically in T and C subjects. However, in spite of identical plasma glucose concentrations, epinephrine (7.88 +/- 0.99 vs. 3.97 +/- 0.40 nmol X l–1), growth hormone (97 +/- 17 vs. 64 +/- 6 mU X l–1), and pancreatic polypeptide (361 +/- 84 vs. 180 +/- 29 pmol X l–1) reached higher levels (P less than 0.05) and glucagon (28 +/- 3 vs. 47 +/- 10 pmol X l–1) lower levels in T than in C subjects. Blood pressures changed earlier in athletes during insulin infusion, and early recovery of heart rate, free fatty acid, and glycerol was faster. Responses of norepinephrine, cortisol, C-peptide, and lactate were similar in the two groups. Training radically changes hormonal responses but not glucose kinetics in insulin hypoglycemia.
Central hemodynamics during progressive upper- and lower-body exercise and recovery
Authors: Miles D. S. , Sawka M. N. , Hanpeter D. E. , Foster J. E. , Doerr B. M. , Frey M. A.
Published: December 2017

The purpose of this study was to compare stroke volume (SV) and myocardial contractility responses during and immediately after upper- and lower-body exercise. Nine men (mean 28 yr, 78 kg) completed progressive intensity discontinuous tests on both an arm crank and cycle ergometer. Exercise for each power output (PO) was 7 min with 20-min rest periods interspersed. Impedance cardiography was used to measure cardiac output (Q), SV, and contractility on a beat-by-beat basis during exercise and a 15-s recovery period. Q increased linearly, and total peripheral resistance decreased exponentially with increasing PO levels. During recovery from exercise, the Q and heart rate (HR) values decreased immediately at all PO levels. When the exercise VO2 exceeded 1.0 1 X min-1, SV fell significantly during recovery for both exercise modes. In general, the recovery myocardial contractility indices remained similar to exercise values. It was concluded that immediately after low intensities of exercise, Q decreases because of a fall in HR. After moderate- and high-intensity exercise, Q decreases because of a fall in both HR and SV.
Upper airway closing pressures in obstructive sleep apnea
Authors: Issa F. G. , Sullivan C. E.
Published: December 2017

We studied 18 patients with obstructive sleep apnea (OSA). Each subject slept while breathing through the nose with a specially designed valveless breathing circuit. Low levels of continuous positive airway pressure (CPAP) applied through the nose (2.5–15.0 cmH2O) prevented OSA and allowed long periods of stable stage III/IV sleep and rapid-eye-movement (REM) sleep. Externally applied complete nasal occlusion while the upper airway was patent resulted in upper airway closure during inspiration which was identified by a sudden deviation of nasal pressure from tracheal or esophageal pressure. The level of upper airway closing pressure (UACP) did not change throughout the occlusion test, suggesting that upper airway dilator muscles do not respond to asphyxia during sleep. The upper airway was more collapsible during stage I/II non-rapid-eye-movement (NREM) and REM sleep compared with stage III/IV NREM sleep. The pooled mean UACP was 3.1 +/- 0.4 cmH2O in stage I/II NREM, 4.2 +/- 0.2 cmH2O in stage III/IV NREM, and 2.4 +/- 0.2 cmH2O in REM sleep. Nasal occlusion at successively higher levels of CPAP did not alter the level of UACP in stage I/II NREM and REM sleep but resulted in the upper airway becoming more stable in stage III/IV NREM sleep, suggesting a reflex which augments the tone of upper airway dilator muscles.
Effect of ischemia on responses of group III and IV afferents to contraction
Authors: Kaufman M. P. , Rybicki K. J. , Waldrop T. G. , Ordway G. A.
Published: December 2017

Static contraction of the hindlimb muscles of cats reflexly increases cardiovascular function, an effect that is potentiated by occlusion of the arterial supply to the working muscles. Although group III and IV afferents are known to be stimulated by and to cause the reflex cardiovascular responses to static muscular contraction, little is known about the responses of these afferents to static contraction when the arterial supply to a working muscle is occluded. We therefore recorded the impulse activity of 24 group III afferents and 30 group IV afferents with endings in the triceps surae while we statically contracted this muscle group, both when the abdominal aorta was occluded and when it was patent. A chi 2 analysis revealed that ischemia increased the responses to static contractions of a significantly higher percentage of group IV afferents than group III afferents (46.7% vs. 12.5%, respectively; P less than 0.02). In addition, two patterns of responses to ischemic contraction were observed. The first pattern was displayed by afferents (n = 10) that were stimulated by nonischemic contraction but were stimulated more by ischemic contraction. The second pattern was displayed by afferents (n = 7) that were not stimulated by nonischemic contraction but were stimulated by ischemic contraction. We conclude that afferents displaying both patterns are likely to contribute to the reflex cardiovascular responses to ischemic contraction.
Effects of naloxone on exercise performance
Authors: Surbey G. D. , Andrew G. M. , Cervenko F. W. , Hamilton P. P.
Published: December 2017

This study was designed to investigate the effects of naloxone on athletic performance in humans. Two groups of elite middle-distance runners performed a maximal or a submaximal exercise protocol following the double-blind intravenous injection of either naloxone (0.15 mg X kg body wt-1) or saline. The maximal test (group M) was comprised of a short-duration treadmill run to maximal intensity; the submaximal test (group S), a prolonged submaximal treadmill run to exhaustion. O2 uptake, heart rate, ventilation, and perceived exertion were determined during each test. Perception of pain was assessed after exercise by use of a modified McGill pain questionnaire. No significant differences between placebo and naloxone treatments were found in any of the measured variables at the usually accepted 5% (P = 0.05) confidence level; however, evidence suggesting differences (i.e., P = 0.1 to 0.05) in these important respects was observed. In group M, maximal exercise performance measured by maximal O2 consumption was not different between placebo and naloxone; results suggest that VE was increased (P = 0.08) following naloxone, but only at the final work stage. In group S, exercise performance time was reduced following naloxone (P = 0.09), whereas the affective component of pain was increased (P = 0.06); no differences in the measured physiological variables were observed. These results suggest the following: 1) the opiate receptor-endorphin system may alter the perception of pain associated with prolonged high-intensity submaximal exercise with a resultant significant effect on performance; and 2) it may play a role in the control of ventilation during maximal exercise.
Cardiodynamic variables and ventilation during treadmill exercise in ponies
Authors: Pan L. G. , Forster H. V. , Bisgard G. E. , Dorsey S. M. , Busch M. A.
Published: December 2017

We assessed the relationship of ventilation (VE) to cardiodynamic variables and CO2 transport in seven normal ponies during treadmill exercise. At 1.8, 3, and 6 mph, respectively, VE increased from 15 l/min at rest to 43, 51, and 86 l/min by 1 min and 48, 68, and 125 l/min by 8 min. In three ponies at the same work loads, cardiac output (Qc) increased from approximately 12 l/min at rest to 19.7, 28.1, and 40.3 l/min between 30–60 s (P less than 0.05) and then decreased by about 20% to a steady state by 3–4 min. Heart rate (HR) shows a similar biphasic response during exercise. Mean right ventricular pressure (MRVBP) increased from 9.9 to 15.9 Torr at 1.8 mph, 15.2 Torr at 3 mph, and 23.5 Torr at 6 mph by 1 min (P less than 0.05) and then decreased to 11.8, 12.2, and 15.8 Torr by 8 min of the three respective work intensities. At all work loads, VE increased proportionately faster than these cardiovascular variables in the 1st min. For example, at 6 mph VE increased 470%, whereas Qc and HR increased only 230%. Thereafter, VE generally continued to increase at 3 and 6 mph, whereas MRVBP, Qc, and HR decreased. Therefore, the basic assumption of a cardiodynamic hyperpnea that VE and Qc are equivalently coupled at the exercise onset is rejected for this species. Mixed venous CO2 content (C-vCO2) at 3 and 6 mph, respectively, decreased slightly from 61.6 and 62.3 vol% at rest to 59.6 and 61.9 vol% by 45 s and then increased to 63.3 and 63.5 vol% by 7 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Thromboxane and prostacyclin synthesis following whole body irradiation in rats
Authors: Schneidkraut M. J. , Kot P. A. , Ramwell P. W. , Rose J. C.
Published: December 2017

The effect of radiation on the mechanism and source of in vivo thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) synthesis was evaluated. Rats were irradiated with 2, 10, or 20 gray (Gy) whole-body gamma irradiation and showed an increase in urine TxB2 after either 10 or 20 Gy. Urine 6-keto-PGF1 alpha was elevated only after exposure to 20 Gy. Irradiation did not alter urine volume or osmolarity, nor was there a correlation between urine osmolarity and the urinary concentration of TxB2 r 6-keto-PGF1 alpha. Rats were pretreated with indomethacin to determine if radiation-induced alterations in urine TxB2 and 6-keto-PGF1 alpha could be suppressed. Pretreatment with indomethacin significantly decreased urine TxB2 and 6-keto-PGF1 alpha in both irradiated and nonirradiated animals. Finally, the sources of urinary cyclooxygenase products were investigated using an isogravitometric cross-perfusion system. These experiments demonstrated that urine TxB2 is derived from extrarenal sources, whereas 6-keto-PGF1 alpha is synthesized primarily by the kidney. It may be concluded that radiation exposure increases in vivo cyclooxygenase pathway activity by both renal and extrarenal tissues.
Accessory muscle activity during sleep in chronic obstructive pulmonary disease
Authors: Johnson M. W. , Remmers J. E.
Published: December 2017

Hypoventilation contributes to oxyhemoglobin desaturation during rapid-eye-movement (REM) sleep in patients with severe chronic obstructive pulmonary disease (COPD). Due to hyperinflated lungs these patients have mechanically impaired diaphragms and increased activity of other inspiratory muscles while awake. We speculated that rib cage (RC) inspiratory muscles might lose activity during REM, thereby contributing to hypoventilation. We therefore recorded scalene (SCA) and sternocleidomastoid (SCM) electromyorgrams in six subjects with severe COPD. SCA activity decreased 76% (P less than 0.001), from non-REM (NREM) to tonic REM and decreased an additional 17% during phasic REM. SCM activity was much more variable during NREM but when present also decreased during REM. SCA activity correlated strongly with RC excursion. SCA and SCM activity, RC excursion, estimates of minute ventilation, and oxyhemoglobin saturation all decreased in parallel. Expiratory activity of the SCA and SCM, present during wakefulness and NREM, disappeared during REM. We conclude that loss of inspiratory activity of rib cage muscles during REM causes chest wall distortion and hypoventilation in patients with severe COPD. Loss of expiratory activity of these muscles may contribute to a decrease in end-expiratory volume and thereby to a deterioration of pulmonary gas exchange.
Endurance training in older men and women. I. Cardiovascular responses to exercise
Authors: Seals D. R. , Hagberg J. M. , Hurley B. F. , Ehsani A. A. , Holloszy J. O.
Published: December 2017

The effects of prolonged endurance training on maximal O2 uptake capacity (VO2max) and its determinants were studied in 11 older individuals (63 +/- 2 yr). The subjects were evaluated before training, after 6 mo of low-intensity (LI) training, and after an additional 6 mo of higher intensity (HI) training. VO2max was 25.4 +/- 4.6 ml X kg-1 X min-1 before training, 28.2 +/- 5.2 ml X kg-1 X min-1 after LI training (P less than 0.05), and 32.9 +/- 7.6 ml X kg-1 X min-1 after HI training (P less than 0.01), with an overall increase of 30%. The increase in VO2max in response to training appeared to be mediated primarily through an increase in maximal arteriovenous O2 difference (P less than 0.01), with little augmentation of maximal cardiac output (Q) (P greater than 0.05). At the same absolute work rates, stroke volume was higher (P less than 0.05); heart rate (HR), blood pressure (BP), and systemic vascular resistance were lower (P less than 0.05); and Q and arteriovenous O2 difference were unchanged after training. At the same relative work rates, arteriovenous O2 difference was higher (P less than 0.01); BP and systemic vascular resistance were lower (P less than 0.05); and HR, Q, and stroke volume did not change significantly. These findings show that older individuals can adapt to prolonged endurance training with a large increase in aerobic power.
Inspiratory flow pattern in humans
Authors: Lafortuna C. L. , Minetti A. E. , Mognoni P.
Published: December 2017

The theoretical estimation of the mechanical work of breathing during inspiration at rest is based on the common assumption that the inspiratory airflow wave is a sine function of time. Different analytical studies have pointed out that from an energetic point of view a rectangular wave is more economical than a sine wave. Visual inspection of inspiratory flow waves recorded during exercise in humans and various animals suggests that a trend toward a rectangular flow wave may be a possible systematic response of the respiratory system. To test this hypothesis, the harmonic content of inspiratory flow waves that were recorded in six healthy subjects at rest, during exercise hyperventilation, and during a maximum voluntary ventilation (MVV) maneuver were evaluated by a Fourier analysis, and the results were compared with those obtained on sinusoidal and rectangular models. The dynamic work inherent in the experimental waves and in the sine-wave model was practically the same at rest; during exercise hyperventilation and MVV, the experimental wave was approximately 16–20% more economical than the sinusoidal one. It was concluded that even though at rest the sinusoidal model is a reasonably good approximation of inspiratory flow, during exercise and MVV, a physiological controller is probably operating in humans that can select a more economical inspiratory pattern. Other peculiarities of airflow wave during hyperventilation and some optimization criteria are also discussed.
A protein from airways of premature lambs that inhibits surfactant function
Authors: Ikegami M. , Jobe A. , Jacobs H. , Lam R.
Published: December 2017

A protein that interfered with surfactant function was isolated from the alveolar washes of prematurely delivered and ventilated lambs. This inhibitor was recovered following sequential precipitation with polyethylene glycol, Affi-Gel Blue, and diethylaminoethyl (DEAE) cellulose chromatography as a protein of approximately 110,000 mol wt. Compared to surfactant alone or surfactant and bovine serum albumin, the purified inhibitor increased the time required for surfactant to spread, increased both maximal and minimal surface tensions, increased the percent surface area that had to be compressed to reach a minimum surface tension of less than 15 dyn/cm, and delayed the surface adsorption of surfactant. The effect of inhibitor on the minimum surface tensions of surfactant solutions was inversely related to surfactant concentration. A radioimmunoassay was used to estimate that approximately 10% of the protein from plasma of premature lambs and alveolar washes after 4 h of ventilation was inhibitory. Following the simultaneous intravascular injection of labeled inhibitor and bovine serum albumin, about 4% of the radioactivity associated with both proteins was recovered in alveolar washes and 6% was associated with lung tissue after alveolar wash. This large proportionate leakage of both proteins did not occur in other tissues. The inhibitor affected multiple measurements of surfactant function in vitro and its presence may contribute to a surfactant deficiency state in the immature lung.
Effects of age on metabolic responses to endurance training in rats
Authors: Mazzeo R. S. , Brooks G. A. , Horvath S. M.
Published: December 2017

The purpose of this investigation was to determine the age-related metabolic responses to chronic exercise. Female Fischer 344 rats 3, 12, and 24 mo of age were trained for 8 wks by treadmill running at 75% of their maximal oxygen uptake (VO2max). Values of VO2max were 74.5 +/- 3.1, 63.3 +/- 3.9, and 54.6 +/- 2.3 ml X kg-1 X min-1 in the untrained 3-, 12-, and 24-mo groups, respectively. In response to training, VO2max increased significantly (P less than 0.05) by 11.9, 18.6, and 20.4% in the three groups. The 24-mo animals also demonstrated the greatest improvement in the treadmill speed eliciting VO2max (71%) when compared with the 12-mo (64%) and 3-mo (57%) age groups. While large increases in endurance times were recorded for all trained groups (456, 806, and 324% in 3, 12, and 24 mo, respectively) relative to the controls, the older animals exhibited a diminished response, comparatively. Body weights did not differ between the trained (Tr) and sedentary controls for 3- and 12-mo animals, but the 24-mo Tr rats demonstrated a more rapid decline in body weight with age than did the age-matched controls. While no differences in absolute or relative heart weights existed for the 3- and 12-mo groups with training, both of these parameters in the 24-mo Tr animals were significantly greater than sedentary controls. It was concluded that compared with younger animals the 24-mo group demonstrated a similar relative adaptation to training in terms of aerobic power but a diminished response comparatively in endurance capacity.(ABSTRACT TRUNCATED AT 250 WORDS)
Comparison of alpha- and gamma-thrombin on lung fluid balance in anesthetized sheep
Authors: Garcia-Szabo R. R. , Kern D. F. , Bizios R. , Fenton J. W. , Minnear F. L. , Lo S. K. , Malik A. B.
Published: December 2017

We examined the effects of varying dosages of thrombin on lung fluid balance in halothane-anesthetized sheep prepared with lung lymph fistulas. A 15-min iv infusion of sublethal doses of alpha-thrombin (2.5 clotting units/micrograms), the native enzyme, at 0.6 or 1.1 nmol active enzyme/kg body wt increased the mean pulmonary arterial pressure (Ppa) and pulmonary vascular resistance (PVR) two- to threefold. Neither parameter increased in a dose-dependent manner. Platelet counts decreased 50% with both dosages. Leukocyte counts decreased 35 and 75% from base line in the low- and high-dosage groups, respectively, and reached comparable levels of 50% below base line at 60-min postinfusion in both groups. Plasma fibrinogen concentrations decreased in a dose-dependent manner preceding dose-dependent increases in pulmonary lymph flow (Qlym) and lymph protein clearance (Clym). Fibrin deposition in pulmonary vessels was greater at 30 than at 180 min postinfusion. In contrast, a 15-min iv infusion of gamma-thrombin (0.002 clotting units/micrograms), which lacks the fibrinogen recognition site, at 1.2 nmol active enzyme/kg produced no significant increases in PVR, Ppa, Qlym, or Clym. The fibrinogen concentration did not change significantly, whereas platelet and leukocyte counts decreased 25% within 15 min. Fibrin microthrombi were less prominent in pulmonary vessels. Fibrin deposition associated with intravascular coagulation may be an important factor mediating thrombin-induced increases in pulmonary transvascular fluid and protein exchange.
Atrophy and growth failure of rat hindlimb muscles in tail-cast suspension
Authors: Jaspers S. R. , Tischler M. E.
Published: December 2017

Atrophy and growth failure of muscle in a tail-cast suspension model were evaluated in hindlimbs of female Sprague-Dawley rats. Based on measurements of food consumption, animal growth rate, urinary excretion of urea and ammonia, and muscle size, 6 days seemed to be the optimum duration of suspension for studying muscle unloading. After 6 days, the soleus, plantaris, and gastrocnemius muscles from suspended animals were 27, 10, and 11% smaller (P less than 0.05), respectively, than those from tail-casted weight-bearing animals. The extensor digitorum longus and tibialis anterior muscles were unaffected by suspension (less than or equal to 6 days) while the triceps brachii hypertrophied (8%, P less than 0.05). Wet weight-to-dry weight ratios were smaller in the plantaris (-0.19, P less than 0.05) and gastrocnemius (-0.19, P less than 0.05) muscles from suspended rats. In the plantaris, this difference coincided with a higher protein concentration (+12 mg/g, P less than 0.001). In vitro measurements of protein metabolism in the soleus muscles of suspended rats showed both slower protein synthesis (P less than 0.05) and faster protein degradation (P less than 0.05), whereas these processes were unaltered in the extensor digitorum longus muscles.
Quiet-breathing vs. panting methods for determination of specific airway conductance
Authors: Krell W. S. , Agrawal K. P. , Hyatt R. E.
Published: December 2017

Specific airway conductance (sGaw) was measured during quiet breathing and during panting in 21 normal subjects and 10 patients with obstructive lung disease. The direct method used does not require measuring thoracic gas volume (TGV). Coefficients of variation were 5.5% for panting and 5.1% for quiet breathing. Interobserver variability was 4.7% in the quiet-breathing method and 6.3% in the panting method. The two methods gave equivalent results for sGaw. A slightly greater sGaw was found by the panting method in normal subjects with the highest sGaw values, probably due to widening of the oropharynx-glottis during panting. In six normal subjects studied for intrasubject variability over time, no significant diurnal or day-to-day variability was seen by either method. We conclude that the quiet-breathing method is a simple valid means of determining sGaw and utilizes a physiological respiratory maneuver. Obviation of the need to measure TGV is advantageous. Results are equivalent to those of the panting method and variability is similar.
Postpneumonectomy airway growth in the ferret
Authors: McBride J. T.
Published: December 2017

To investigate the participation of the conducting airways in compensatory growth following partial lung resection, bronchial casts of six ferrets having undergone right-sided pneumonectomy at 8 wk of age were compared with those of five sham-operated control animals. At maturity, the left lungs of the postpneumonectomy animals were 65% larger than those of the controls. Central airway cross-sectional areas at 10 specific locations in each cast were 12% larger in the postpneumonectomy animals compared with controls. To characterize the size of more peripheral airways, the size and number of the terminal bronchioles subtended by each airway in each left lower lobe cast were identified so that the fraction of the lobe served by that airway could be estimated. The characteristic cross-sectional areas of airway serving 0.7, 2.2, and 9.5% of the left lower lobe in postpneumonectomy animals were 18, 13, and 13% larger than those of controls, but this difference was statistically significant only at the two more peripheral levels. Although airway areas were larger in postpneumonectomy animals, the ratio of airway cross-sectional area to the 0.67 power of lung volume was 20–26% smaller in operated than in control animals at each of the four levels. Following pneumonectomy in the weanling ferret, central and peripheral conducting airways increase in cross-sectional area to similar degrees, but this airway growth is less than the compensatory increase in lung volume.
Effect of hypoxemia on the renin-angiotensin-aldosterone system in humans
Authors: Colice G. L. , Ramirez G.
Published: December 2017

Hypoxemia was induced in five subjects older than 40 (group 1) and five younger than 35 yr (group 2) on normal and low-salt diets by having the subjects breathe hypoxic gas. The fractional inspired O2 of the hypoxic gas was regulated so that group 1 hemoglobin saturations fell to 90% for 1 h. Group 2 subjects had desaturation to 90% for 1 h followed by desaturation to 80% for a 2nd h. Plasma renin activity (PRA), angiotensin-converting enzyme activity (ACE), and plasma cortisol levels did not change during hypoxemia. Plasma aldosterone levels fell in both groups during the 1st h of hypoxemia. Decreases were greatest during salt restriction and were significant (P less than 0.01) for the combined groups. Plasma aldosterone levels plateaued during the 2nd h of more severe hypoxemia in group 2. Hepatic blood flow, measured by indocyanine green clearance, and the adrenal response to exogenous adrenocorticotropic hormone, measured by changes in plasma cortisol and aldosterone, were not changed by hypoxemia in group 2 subjects. These results indicate that plasma aldosterone falls during hypoxemia despite unchanged PRA, ACE, hepatic blood flow, and adrenal function.
Interaction between cold and altitude exposure on pulmonary circulation of cattle
Authors: Busch M. A. , Tucker A. , Robertshaw D.
Published: December 2017

Hereford calves were exposed in a temperature-controlled hypobaric chamber to environmental temperatures of -2 to 1 degree C (cold) at altitudes of 1,524 m (resident altitude) and 3,048 m 1) to characterize the effects of cold exposure on the pulmonary circulation; 2) to examine the role of cold-induced hypoventilation on the pulmonary circulation; and 3) to examine the interaction between cold and hypoxia on the pulmonary circulation. Cold exposure produced a significant increase in pulmonary arterial pressure (Ppa), pulmonary arterial wedge pressure (Ppaw), and pulmonary vascular resistance (PVR) at both 1,524 and 3,048 m without affecting cardiac output. Concomitantly, cold exposure caused reductions in minute ventilation, respiratory rate, end-tidal O2 tension (PETO2), and arterial O2 tension (PaO2). Tidal volume, end-tidal CO2 tension, and arterial CO2 tension increased. Neither arterial pH nor O2 consumption changed during cold exposure. These results indicated that both pulmonary arterial and venous vasoconstriction were responsible for the pulmonary hypertension associated with cold exposure. Acute exposure to 3,048 m during cold exposure produced increases in Ppa and PVR that were similar to those elicited by cold exposure at 1,524. It was concluded that altitude exposure neither attenuated nor potentiated the effect of cold exposure on the pulmonary circulation; rather, altitude and cold exposure interacted additively. O2 administered during cold exposure to restore PETO2 and PaO2 to control values partially restored Ppa and PVR to control values. This suggested that a portion of the pulmonary hypertension associated with cold exposure was due to hypoxic pulmonary vasoconstriction elicited by the cold-induced alveolar hypoventilation.
Bronchoconstrictor response to inhaled capsaicin in humans
Authors: Fuller R. W. , Dixon C. M. , Barnes P. J.
Published: December 2017

The effect of inhaled capsaicin, the irritant extract of pepper, on airway tone has been studied in humans. Inhaled capsaicin (2.4 X 10(-10) and 2.4 X 10(-9) mol) caused a dose-dependent fall in specific airways conductance (maximum fall 28 +/- 19 and 38 +/- 19%, respectively; means +/- SD, n = 17). This was maximal within 20 s of exposure and lasted for less than 60 s. There was no difference in the magnitude or duration of bronchoconstriction between normal, smoking, or asthmatic subjects. Capsaicin also caused coughing and retrosternal discomfort. On repeated exposure to capsaicin, there was no evidence for a reduced response (tachyphylaxis). Ipratropium bromide (0.25 mg by inhalation) significantly (P less than 0.05) reduced the bronchoconstriction (maximum falls 34 +/- 14 and 15 +/- 9% after saline and ipratropium bromide, respectively; means +/- SD n = 6), indicating that it was dependent on a cholinergic vagal reflex rather than on local release of substance P from nerves in the airway. Inhaled sodium cromoglycate (10 mg by nebulizer or 40 mg as a dry powder), however, had no significant effect on the bronchoconstrictor response. Capsaicin may be a useful tool for investigating nonmyelinated nerve reflexes in human airways.
Exercise-induced changes in blood zinc and related proteins in humans
Authors: Ohno H. , Yamashita K. , Doi R. , Yamamura K. , Kondo T. , Taniguchi N.
Published: December 2017

Effects of cycle ergometer exercise (approximately 75% maximum ventilatory O2 consumption for 30 min) on the concentrations of zinc and related proteins in erythrocytes and/or plasma were studied on 11 sedentary male students. Lower concentrations of total zinc and of zinc derived from carbonic anhydrase I type (CA-I) in erythrocytes were observed immediately after exercise, but they disappeared after 30 min of rest. The change in total zinc concentration in erythrocytes correlated well with that in CA-I concentration immediately after exercise, as well as after rest. The concentration of carbonic anhydrase II type (CA-II)-derived zinc did not vary substantially at any time. On the other hand, there were significant increases in the plasma concentrations of total zinc and of alpha 2-macroglobulin (alpha 2-MG)-bound zinc immediately after exercise, whereas no such effect was noted in albumin-bound zinc. A positive correlation was found between total zinc and alpha 2-MG concentrations in plasma immediately after exercise. In addition, the change in the activity of alkaline phosphatase, a zinc metalloenzyme, correlated well with that in the total zinc concentration in plasma. These results suggest that a brief physical exercise induces the movement of zinc into plasma.
Effects of plasma- and cell-free perfusates on filtration coefficient of perfused canine lungs
Authors: Rippe B. , Townsley M. I. , Taylor A. E.
Published: December 2017

The filtration coefficient (Kf,c) of the microvessels in isolated dog lungs were studied for whole and diluted blood, whole and diluted plasma, Tyrode's solution, and Tyrode's plus dextran (4%, 63,000 mol wt) perfusates. When whole blood and plasma were diluted, Kf,c increased abruptly at a plasma protein concentration between 4 and 5 g/l, an effect which was not dependent on the erythrocyte mass. Both Tyrode's and Tyrode's plus dextran produced increases in Kf,c (60 and 30%, respectively). The difference in Kf,c measured between these latter perfusates was completely abolished when Kf,c were corrected for viscosity differences. Thus the pulmonary microvasculature responds similarly to the systemic circulation in that complete removal of plasma proteins from the perfusate increases Kf,c by 50%. This effect is independent of erythrocyte mass or colloid osmotic pressure of the perfusate, since perfusion with dextran solutions alone also increased Kf,c.
Patellar tendon matrix changes associated with aging and voluntary exercise
Authors: Vailas A. C. , Pedrini V. A. , Pedrini-Mille A. , Holloszy J. O.
Published: December 2017

Male rats maintained under constant environmental conditions were randomly assigned to nonrunner (NR) and voluntary exercise (R) groups. At 9 mo, voluntary exercise significantly increased muscle cytochrome c concentration and citrate synthase activity. Also, at the same age, R animals had significantly greater glycosaminoglycan concentration than NR, but no changes in dry weight and collagen concentration were significant. By age 28 mo, the R groups had reduced daily running by 70%, and elevation of tendon glycosaminoglycans relative to NR animals was no longer statistically significant. A similar trend was noted for muscle mitochondrial markers. Aging significantly decreased tendon glycosaminoglycans and increased collagen concentration. Although aging reduced the total amount of voluntary exercise, the concentration of tendon glycosaminoglycans in 28-mo-old runners was equivalent to levels in 9-mo-old sedentary rats, suggesting that voluntary exercise slowed the decline in galactosamine-containing glycosaminoglycans with aging.
Dynamics of respiratory drive and pressure during NREM sleep in patients with occlusive apneas
Authors: Onal E. , Leech J. A. , Lopata M.
Published: December 2017

To study the dynamics of respiratory drive and pressure in patients with occlusive apneas, diaphragmatic electromyogram (EMGdi), esophageal pressure (Pes), and genioglossal electromyogram (EMGge) were monitored during nocturnal sleep in five patients. Both EMGs were analyzed as peak moving time average, and Pes was quantitated as the peak inspiratory change from base line. During the ventilatory phase both EMGs decreased proportionally. The decrease in Pes was less than the decrease observed in EMGdi, and Pes generated for a given EMGdi increased during the preapneic phase in spite of the proportional decrease in EMGdi and EMGge during this period. We conclude that negative inspiratory pressures which lead to the passive collapse of oropharyngeal walls are dependent on both respiratory and upper airway muscle activity and that occlusive apneas of non-rapid-eye-movement (NREM) sleep do occur in spite of proportional changes observed in the activity of both muscle groups. The preapneic increase in negative inspiratory pressures generated for a given respiratory muscle activity is most likely due to the decrease in upper airway muscle activity that is associated with an increase in oropharyngeal resistance.
Adaptive response of hypertrophied skeletal muscle to endurance training
Authors: Riedy M. , Moore R. L. , Gollnick P. D.
Published: December 2017

The response of hypertrophied soleus and plantaris muscle of rats to endurance training was studied. Hypertrophy was produced by bilateral extirpation of the gastrocnemius muscle. A 13-wk training program of treadmill running initiated 30 days after removal of the gastrocnemius muscle accentuated (P less than 0.01) the hypertrophy. Succinate dehydrogenase activities of the enlarged muscles of sedentary rats were similar to those of normal animals, as were the increases associated with training. Phosphorylase and hexokinase activities were unaltered as a result of the experimental perturbations. Rates of glycogen depletion during exercise were lower (P less than 0.01) in the liver and soleus and plantaris muscles of endurance-trained animals. No difference existed in the rate of glycogen depletion of normal and hypertrophied muscle within the sedentary or trained groups. These data demonstrate that extensively hypertrophied muscle responds to training and exercise in a manner similar to that of normal muscle.
Function of mature coronary collateral vessels and cardiac performance in the exercising dog
Authors: Longhurst J. C. , Motohara S. , Atkins J. M. , Ordway G. A.
Published: December 2017

Formation of extensive collateral vessels after chronic constriction of a coronary artery in dogs can provide for similar increases in blood flow to native and collateralized regions of myocardium during exertion. Previous investigations have not compared myocardial blood flow and cardiac functional responses during exercise in constricted and nonconstricted (sham) animals. Thus we evaluated left ventricular performance and myocardial blood flow at rest and during mild, moderate, and severe exertion in sham-operated dogs and in dogs 2–3 mo after placement of an Ameroid occluder around the proximal left circumflex artery. Changes in double product, maximal left ventricular dP/dt, and pressure-work index were similar in both groups for each level of exertion. Despite similar increases in estimated myocardial O2 demand and similar diastolic perfusion pressures, average transmural myocardial blood flow increased less in the constrictor animals, particularly during severe exercise (2.74 +/- 0.22 vs. 1.45 +/- 0.29 ml X min-1 X g-1). The smaller increases in blood flow occurred equally in native and collateralized regions as well as in the papillary muscles and boundary areas between the native and collateralized regions. The differences in flow in the native and collateralized regions were uniform across the wall of the myocardium. We also observed smaller increases in stroke volume and cardiac output in the constrictor group, disparities which increased with increasing exertion (stroke volume, severe exercise = 0.92 +/- 0.13 vs. 0.53 +/- 0.09 ml/kg). We postulate that myocardial active hyperemia is limited either because the coronary vessels remaining after chronic circumflex occlusion cannot dilate sufficiently or that there is inappropriate active vasoconstriction during severe exertion.
Effect of exercise on plasma interferon levels
Authors: Viti A. , Muscettola M. , Paulesu L. , Bocci V. , Almi A.
Published: December 2017

The effect of exercise on plasma interferon activity was studied on eight male subjects before and after exercise on a bicycle ergometer for 1 h at 70% of their maximal O2 consumption (VO2 max). Acid-labile interferon, alpha-type according to immunological characterization, rose significantly from a preexercise value of 3 +/- 1 to 7 +/- 2 IU/ml postexercise. Negligible changes were recorded for plasma protein, lipid, and glucose concentrations, whereas blood lactate slightly increased only at the end of exercise. According to hematocrit and plasma protein values before and after exercise, hemoconcentration did not occur. These data provide evidence that plasma interferon activity increased following a bout of submaximal exercise.
Reflex compensation of voluntary inspiration when immersion changes diaphragm length
Authors: Banzett R. B. , Lansing R. W. , Reid M. B.
Published: December 2017

When immersion alters inspiratory muscle operating lengths, spontaneously breathing humans maintain a constant tidal volume by reflex adjustment of inspiratory muscle activation (Reid et al. J. Appl. Physiol. 58: 1136–1142, 1985). We term this the operational length compensation reflex. The present experiment demonstrates that similar adjustments occur during voluntary respiratory maneuvers. Each of seven naive subjects sat in a tank with water at hip level. We trained them to reproduce an inspired volume (+/- 10%) at constant inspiratory duration. They received verbal feedback during training but not during the experiment. We measured surface electromyograms (EMGs) of diaphragm and intercostal muscles and tidal volume. After the subjects were trained, we made repeated measurements of 10 trained breaths with water at the hip and then again after raising water level to the xiphoid (which decreases lung volume and increases operating length of the diaphragm). In 30 of 42 trials there was a substantial fall in peak diaphragm EMG. In 10 trials this was sufficient to prevent any change in tidal volume. Inspiratory flow was more closely regulated than tidal volume. Subjects were not aware of making adjustments in drive.