bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracheal dimensions at full inflation and deflation in adolescent twins
Authors: Kawakami Y. , Nishimura M. , Kusaka H.
Published: December 2017

Tracheal dimensions at total lung capacity (TLC) and residual volume (RV) were analyzed roentgenographically in 17 pairs of male adolescent twins (mean age 16.3 yr; 12 monozygotic pairs and 5 dizygotic pairs). Genetic factors dominated environmental traits in intra- as well as extrathoracic tracheal width at RV. Extrathoracic tracheal width at TLC was also governed by genetic components. Intrathoracic tracheal depth (anteroposterior diameter), length, and cross-sectional area did not seem to be genetically controlled at TLC and RV. Intrathoracic tracheal cross-sectional area increased by 14.4% and became more elliptical from RV to TLC, owing mainly to an increase in tracheal depth (16.7%). Increments from RV to TLC in tracheal depth but not width correlated with increases in lung width, depth, and height. Intrathoracic trachea was elongated 14% in association with increase in lung height from RV to TLC. At TLC, extrathoracic tracheal width was larger than intrathoracic tracheal width, but this dimension did not differ at RV. These results indicate that genetic factors influence, at least at RV, the tracheal rings more strongly than membranous parts. Intrathoracic tracheal depth but not width increases during inspiration in accordance with increase in lung volume. Extrathoracic tracheal width widens more than intrathoracic trachea from RV to TLC.
Effects of lower limb unloading on skeletal muscle mass and function in humans
Authors: Berg H. E. , Dudley G. A. , Haggmark T. , Ohlsen H. , Tesch P. A.
Published: December 2017

A model to simulate effects of microgravity on skeletal muscle mass and function in humans has been developed. Unilateral lower limb unloading that allowed ankle, knee, and hip joint mobility was conducted in six healthy men by suspending one lower limb and having the subjects walk on crutches. They performed maximal unilateral concentric or eccentric quadriceps actions at different angular velocities before and after 4 wk of suspension and after 4 days and after 7 wk of uncontrolled recovery. Peak torque (PT) and angle-specific torque (AST) were measured. Muscle cross-sectional area (CSA) and radiological density (RD) of the thigh were assessed by means of computerized tomography. Concentric and eccentric PT and AST across speeds decreased (P less than 0.05) by 22 and 16%, respectively, in response to unloading. At 4 days of recovery PT (-11%) and AST (-7%) were still lower (P less than 0.05) than before. Muscle CSA and RD decreased (P less than 0.05) by 7 and 6%, respectively. After 7 wk of recovery PT, AST, CSA, and RD had returned to normal. The control limb showed no changes over the experimental period except for a 6% decrease (P less than 0.05) in RD. It is suggested that this human model of unloading could serve to simulate effects of microgravity on skeletal muscle mass and function because reductions in muscle mass and strength were of similar magnitude to those produced by bed rest.
Renal O2 consumption during progressive hemorrhage
Authors: Schlichtig R. , Kramer D. J. , Boston J. R. , Pinsky M. R.
Published: December 2017

Most mammalian tissues regulate O2 utilization such that O2 consumption (VO2) is relatively constant at O2 delivery (DO2) higher than a critical value (DO2c). We studied the relationship between VO2 and DO2 of kidney and whole body during graded progressive exsanguination. The relationship between whole body VO2 and DO2 was biphasic, and whole body VO2 decreased by 5.6 +/- 14.4% (P = NS) from the initial value to the value nearest whole body DO2c. Kidney DO2 decreased in direct proportion to whole body DO2 such that the average R2 value describing the linear regression of kidney DO2 vs. whole body DO2 was 0.94 +/- 0.02. The relationship between kidney, like whole body, VO2 and DO2 appeared biphasic; however, kidney VO2 decreased by 63.3 +/- 10.4% (P less than 0.0001) from the initial value to the value nearest kidney DO2c. Renal O2 extraction ratio was relatively constant over a wide range of kidney DO2, whereas whole body O2 extraction ratio increased progressively at all whole body DO2 values as whole body DO2 decreased. However, final values of O2 extraction ratio were indistinguishable for whole body (0.86 +/- 0.1) and kidney (0.86 +/- 0.06) (P = NS). We conclude that the pattern of kidney and whole body VO2 response to decreasing DO2 differs during hemorrhage, particularly in the range of DO2 normally associated with tissue wellness.
Respiratory epithelium-dependent inhibition of protein kinase C of airway smooth muscle cells
Authors: Souhrada M. , Souhrada J. F.
Published: December 2017

We have examined the effect of phorbol myristate acetate (PMA) on airway smooth muscle (ASM) in the presence and absence of respiratory epithelium (RE) and analyzed the dependence of this response on extracellular sodium, Na+/H+ exchange, calcium, and cyclooxygenase products; we determined both the resting membrane potential and isometric force developed by ASM preparations. Removal of RE had no effect on the values of the resting membrane potential of ASM cells. In the presence of RE in the preparation, both electrical and contractile responses to PMA (10(-5) M) were significantly different compared with the response of ASM to PMA without RE. When the RE was present, stimulation of protein kinase C caused only a biphasic response in both membrane potential and isometric force. In either the presence or absence of RE, amiloride (10(-5) M) and a low-sodium solution inhibited both electrical and contractile changes of ASM cells caused by PMA. In the presence or absence of RE, verapamil (10(-5) M) attenuated (P less than 0.05) both electrical and contractile responses of ASM cells as induced by PMA. Verapamil, however, had no effect on the last phase of PMA-induced response. Pretreatment of preparations with indomethacin (10(-6) M) changed the PMA-induced response of ASM with RE to a response usually observed in ASM without RE. Finally, the incubation of tracheal preparations without RE with prostaglandin E2 (10(-8) M) altered the response of these preparations in such a way that their electrical and contractile response to PMA was essentially identical to the PMA response observed in preparations with an intact RE.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal neurohormonal and vascular responses to dynamic exercise in humans
Authors: Tidgren B. , Hjemdahl P. , Theodorsson E. , Nussberger J.
Published: December 2017

Effects of graded supine dynamic exercise (30, 60, and 80-90% of maximal physical capacity, i.e., work loads of 69, 132, and 188 W) on renal vascular resistance (RVR); renal sympathetic nerve activity [assessed by the renal venous overflow of norepinephrine (NE)]; renal overflows of dopamine (DA), immunoreactive neuropeptide Y (NPY-LI), and renin; as well as plasma concentrations of angiotensin-(1-8)-octapeptide (ANG II) were evaluated in eight healthy male volunteers. Exercise evoked stimulus-dependent and marked elevations of RVR, arterial NE, epinephrine (Epi), and DA. RVR increased by 140% and the renal overflows of NE and DA increased by 1,331 and 179%, respectively, at 188 W. A net removal of NPY-LI at rest turned into a small net renal overflow, which correlated with increases in RVR at 188 W. Increases in renin release (+1,200% at 188 W) correlated with increases in renal NE and DA overflows and with arterial Epi levels. Arterial ANG II levels increased stimulus dependently (by 264% at 188 W) and correlated more closely with increases in RVR than did other variables. Thus dynamic exercise is a potent stimulus for renal nerve activation in humans, and renal sympathetic nerve activity may contribute to increased RVR both directly (NE and, at exhaustive work loads, possibly NPY) and indirectly (via renin-mediated ANG II formation).
Interaction between CO2 concentration and flow rate on peripheral airway resistance
Authors: Kaise A. , Freed A. N. , Mitzner W.
Published: December 2017

In the present study, we investigated the interaction between CO2 concentration and rate of delivered flow on peripheral airway resistance (Rp) in the intact canine lung. Dogs were anesthetized, intubated, paralyzed, and mechanically ventilated with room air to maintain end-tidal CO2 between 4.8 and 5.2%. Using a wedged bronchoscope technique, we measured Rp at functional residual capacity. The relationship between CO2 concentration and Rp was measured at flow rates of 100 and 400 ml/min with 5, 3, 2, 1, and 0% CO2 in air. Measurements were made at the end of a 3-min exposure to each gas. At low flow rates (100 ml/min) responses to hypocapnia were small, whereas at high flow rates (400 ml/min) responses were large. The PC50 (defined as the CO2 concentration required to produce a 50% increase in Rp above baseline Rp established on 5% CO2) at 400 ml/min (1.73%) was significantly larger than that at 100 ml/min (0.38%). We also directly measured the relationship between Rp and flow rate with 5% CO2 (normocapnia) or 1% CO2 (hypocapnia) delivered into the wedged segment. Increases in normocapnic flow caused small but significant decreases in Rp. In contrast, increases in hypocapnic flow from 100 to 400 ml/min caused a 108% increase in Rp. Thus the response to hypocapnia is augmented by increasing flow rate. This interaction can be explained by a simple model that considers the effect of local ventilation-perfusion ratio and gas mixing on the local CO2 concentration at the site of peripheral airway contraction.
EMG patterns of rat ankle extensors and flexors during treadmill locomotion and swimming
Authors: Roy R. R. , Hutchison D. L. , Pierotti D. J. , Hodgson J. A. , Edgerton V. R.
Published: December 2017

Intramuscular electromyography (EMG) was used to determine and compare the recruitment patterns of the rat soleus (Sol), tibialis anterior (TA), and a deep and a superficial portion of the medial gastrocnemius (MG) during treadmill locomotion at various speeds and inclines and during swimming. Raw EMG signals for 10-20 step or stroke cycles were rectified, averaged, and processed to determine cycle period (EMG onset of one cycle to EMG onset of the next cycle), EMG burst duration, and integrated area of the rectified burst (IEMG). Mean EMG per burst was calculated as IEMG/burst duration. IEMG/min was calculated as IEMG times the number of bursts (cycles) per minute. Cycle period and burst duration of the extensors decreased hyperbolically, while the TA burst duration was unchanged, with increased treadmill speed. With increased treadmill speed, IEMG was decreased in the Sol and unchanged in the MG and TA, whereas IEMG/min decreased in the Sol and increased in the MG and TA. An elevation in treadmill incline resulted in an increase in the activation levels of the MG but not in the Sol or TA. These data indicate that the additional power required at increased speeds and/or inclines of treadmill locomotion is derived from the recruitment of the fast extensors, e.g., the MG. The mean cycle period during swimming was similar to that observed during the fastest treadmill locomotion. EMG burst durations and amplitudes, however, were higher in the TA, relatively similar in the MG, and lower in the Sol during swimming than treadmill locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)
Mitogenic response of T-lymphocytes to exercise training and stress
Authors: Tharp G. D. , Preuss T. L.
Published: December 2017

The impact of exercise training and stress on the immune response was examined by measuring the mitogenic response of spleen lymphocytes to the T-cell mitogen concanavalin A (Con-A). Male Sprague-Dawley rats were divided into four groups: sedentary controls (n = 11), handled controls (n = 12), treadmill runners (n = 10), and voluntary runners (n = 11) housed in running wheels. The treadmill group ran at 22 m/min (0.8 mph) for 45 min, 5 days/wk for 8 wk. After the training period, spleen lymphocytes isolated from each rat were incubated with Con-A for 54 h, pulsed with radiolabeled thymidine for 18 h, and counted for tritium activity. Counts per minute per group (means +/- SE) were as follows: sedentary, 6,839 +/- 1,461; handled, 8,959 +/- 1,576; voluntary runners, 13,126 +/- 2,069; and treadmill runners, 18,950 +/- 5,975. One-way analysis of variance and Tukey's highly significant difference test found the counts per minute of the treadmill runners to be significantly different from the counts per minute of the sedentary animals. These results indicate that the responsiveness of spleen lymphocytes to Con-A increases as the level of stress and exercise increases.
Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo
Authors: Mutoh T. , Lamm W. J. , Embree L. J. , Hildebrandt J. , Albert R. K.
Published: December 2017

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.
Endotoxemia and release of tumor necrosis factor and interleukin 1 alpha in acute heatstroke
Authors: Bouchama A. , Parhar R. S. , el-Yazigi A. , Sheth K. , al-Sedairy S.
Published: December 2017

To determine whether endotoxemia and release of tumor necrosis factor (TNF-alpha) and/or interleukin 1 alpha (IL-1 alpha) are involved in the pathogenesis of heatstroke, 17 adult patients with a mean rectal temperature of 42.1 +/- 0.2 degrees C were studied. Blood samples were taken on admission and after cooling was completed. TNF-alpha and IL-1 alpha levels were measured by enzyme-linked immunosorbent assay, and lipopolysaccharide (LPS) content was measured by the chromogenic substrate modification of the Limulus amebocyte lysate. TNF-alpha, IL-1 alpha, and LPS were elevated in all patients [199 +/- 25 (SE) pg/ml, 480.5 +/- 68.3 pg/ml, and 8.60 +/- 1.19 ng/ml, respectively, compared with normal control values of 31.4 +/- 8.4 pg/ml, 53.7 +/- 5.32 pg/ml, and less than 9 pg/ml]. There was no significant correlation between temperature and the circulating concentration of TNF-alpha, IL-1 alpha, and LPS. Postcooling TNF-alpha, IL-1 alpha, and LPS concentrations were significantly decreased but still above normal control values. The findings suggest that these mediators may have a role in the pathogenesis of heatstroke that could change the strategy of management.
Developmental changes in neuromuscular transmission in the rat diaphragm
Authors: Feldman J. D. , Bazzy A. R. , Cummins T. R. , Haddad G. G.
Published: December 2017

Neuromuscular transmission was studied in diaphragms from rats of three ages, 4–7 days old, 11–12 days old, and adults with the use of an in vitro phrenic nerve-hemidiaphragm preparation. Each hemidiaphragm was stimulated via either muscle or nerve with 1-s stimulus trains at frequencies from 10 to 100 Hz. The patterns of force development obtained in response to the two routes of stimulation were compared for each group. Diaphragms from adults developed maximum force in response to stimulation of approximately 40 Hz with no significant decrease in force at higher frequencies. Within each stimulus train, once peak force was achieved, it was maintained for the remainder of the stimulus and responses to nerve and muscle stimulation were almost identical. In contrast, diaphragms from 4- to 7-day-old rats developed maximum force at approximately 20 Hz; stimulation at greater than or equal to 60 Hz induced significantly less peak force. This decrease in peak force at higher frequencies was significantly larger for nerve than for muscle stimulation. In addition, during each nerve stimulus train diaphragms from 4- to 7-day-old rats were unable to maintain peak force, which decreased at frequencies greater than 20 Hz. The decrease in force reached approximately 50% of peak at stimulation frequencies greater than or equal to 60 Hz. Diaphragms from 11- to 12-day-old rats showed intermediate responses. Based on the responses to phrenic nerve stimulation, we conclude that the neonatal rat diaphragm shows marked neuromuscular transmission failure that is not seen in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)
Respiratory stimulation by female hormones in awake male rats
Authors: Tatsumi K. , Mikami M. , Kuriyama T. , Fukuda Y.
Published: December 2017

The respiratory effect of progestin differs among various animal species and humans. The rat does not hyperventilate in response to exogenous progestin. The present study was conducted to determine whether administration of combined progestin and estrogen prompts ventilatory stimulation in the male rat. Ventilation, blood gases, and metabolic rates (O2 consumption and CO2 production) were measured in the awake and unrestrained male Wistar rat. The combined administration of a synthetic potent progestin (TZP4238) and estradiol for 5 days significantly increased tidal volume and minute expiratory ventilation (VE), reduced arterial PCO2, and enhanced the ventilatory response to CO2 inhalation (delta VE/delta PCO2). On the other hand, respiratory frequency, O2 consumption, CO2 production, and body temperature were not affected. The arterial pH increased slightly, with a concomitant decrease in plasma [HCO3-]. Administration of either TZP4238 or estradiol alone or vehicle (Tween 80) had no effect on respiration, blood gases, and ventilatory response to CO2. The results indicated that respiratory stimulation following combined progestin plus estradiol treatment in the male rat involves activation of process(es) that regulate tidal volume and its augmentation during CO2 stimulus.
Short-term effect of tidal pleural pressure swings on pulmonary blood flow during rest and exercise
Authors: Giesbrecht G. G. , Ali F. , Younes M.
Published: December 2017

Because pleural pressure (Ppl) has important effects on venous return and left ventricular function, it is possible that the magnitude of respiratory fluctuations in Ppl importantly influences cardiac output (pulmonary blood flow, QL) during exercise. To examine this question, we increased (+15 cmH2O) and decreased (-11 cmH2O) the amplitude of fluctuations in Ppl by elastic loading and unloading, respectively, during steady-state exercise (50 W) and estimated the corresponding changes in QL from measurement of breath-by-breath alveolar O2 consumption [(Vo2)A] by a modification of the technique of Beaver et al. (J. Appl. Physiol. 51: 1662–1675, 1981). Load changes were applied for three breaths. Using oscilloscopic volume feedback, subjects maintained constant breathing pattern and end-expiratory volume during control and experimental breaths. This procedure minimized errors in computing (Vo2)A. Furthermore, because over the brief period of load change (especially the first 1 or 2 breaths) mixed venous and arterial O2 contents were not likely to have changed, changes in (Vo2)A reflected changes in QL according to the Fick principle. In six normal subjects, neither loading nor unloading had any effect on (Vo2)A in the first, second, or third breath (P greater than 0.5). Additional studies at rest produced equally negative results. We conclude that the magnitude of respiratory fluctuations in Ppl has no short-term effect on pulmonary blood flow at rest or during mild exercise.
Net lactate uptake during progressive steady-level contractions in canine skeletal muscle
Authors: Gladden L. B.
Published: December 2017

The purpose of this study was to determine the changes in net lactate uptake (L) by skeletal muscle with a constant elevated blood lactate concentration during steady-level contractions of increasing intensity. The gastrocnemius-plantaris muscle group was isolated in situ in 11 anesthetized dogs. An infusion of lactate/lactic acid at a pH of 3.5–3.7 established a blood lactate concentration of approximately 9 mM while maintaining normal blood gas/pH status. L was measured during three consecutive 30-min periods during which the muscles 1) rested, 2) contracted at 1 Hz, and 3) contracted at 4 Hz. L was always positive, indicating net uptake throughout the lactate/lactic acid infusion. Steady-level O2 uptake averaged 10.9 +/- 2.2 ml.kg-1.min-1 (0.49 +/- 0.10 mmol.kg-1.min-1) at rest, 39.3 +/- 2.1 (1.75 +/- 0.09) at 1 Hz, and 127.8 +/- 9.2 (5.70 +/- 0.41) at 4 Hz. Steady-level L increased with the metabolic rate from 0.113 +/- 0.058 mmol.kg-1.min-1 at rest to 0.329 +/- 0.026 at 1 Hz and 0.715 +/- 0.108 at 4 Hz. The increase in L from rest to 1 Hz was accomplished mainly by an increase in arteriovenous lactate difference, whereas the increase from 1 to 4 Hz was entirely due to a large increase in blood flow. These results support the idea that skeletal muscle is not simply a producer of lactate but can be a significant consumer of lactate even during contractions with a large elevation in metabolic rate.
Interleukin 1 protects rats against oxygen toxicity
Authors: Tsan M. F. , Lee C. Y. , White J. E.
Published: December 2017

We studied the effect of interleukin 1 alpha (IL-1) in the protection against O2 toxicity. Tracheal insufflation of IL-1 resulted in a dose-dependent protection against O2 toxicity. All control rats died within 3 days of O2 exposure. In contrast, 84, 71, and 20% of rats insufflated with 5, 1, and 0.2 microgram(s) IL-1 (150, 30, and 6 x 10(4) U), respectively, survived 100% O2 exposure for greater than 11 days. At 2.3 days after O2 exposure, control rats showed severe pulmonary injury, which insufflation of 5 microgram(s) IL-1 markedly attenuated. The protection against O2 toxicity was associated with a selective enhancement of pulmonary Mn-superoxide dismutase (Mn-SOD) activity in IL-1-insufflated rats. In rats insufflated with IL-1 that survived exposure to 100% O2 for 7 days, the activities of pulmonary Mn-SOD, Cu,Zn-SOD, catalase, and glutathione peroxidase were all increased. The increased pulmonary Mn-SOD activity demonstrated in IL-1-insufflated rats at 2.3 days after O2 exposure may contribute to the protection against acute O2 toxicity, and the markedly increased activities of all pulmonary antioxidant enzymes shown in rats insufflated with IL-1 that survived O2 exposure for 7 days may in part be responsible for the chronic adaptation of these rats to a 100% O2 environment.
Lung to blood passage of different-sized molecules during lung inflammation in the rat
Authors: Folkesson H. G. , Westrom B. R. , Pierzynowski S. G. , Karlsson B. W.
Published: December 2017

The passage of different-sized marker molecules over the lower respiratory tract into the blood circulation during pulmonary inflammation induced by dextran, endotoxin [i.e., lipopolysaccharide from Escherichia coli (LPS)], or ferritin was assessed in the rat. Bovine immunoglobulin G (BIgG, mol wt = 150,000 Da), bovine serum albumin (BSA, mol wt = 67,000 Da), and the nonapeptide 1-deaminocysteine-8-D-arginine vasopressin (dDAVP, mol wt = 1,067 Da) were used as permeability markers after intratracheal instillation. The pathophysiological indexes of a proceeding lung inflammation were increased total cell number, changed leukocyte proportions and increased total protein content obtained in bronchoalveolar lavage, and lung edema formation shown as an increased lung wet-dry weight difference. Intratracheal instillation of dextran induced a moderate neutrophil invasion into the lungs but had no effect on the passage of the different markers over the lungs (BIgG 1.8 +/- 0.6%, BSA 3.5 +/- 1.2%, dDAVP 26.1 +/- 20.7%) compared with control rats instilled with the markers alone (1.8 +/- 0.4%, 4.1 +/- 1.3%, 20.0 +/- 3.8%, respectively). Endotoxin administration resulted in markedly higher lavage cell counts and lung edema concomitantly with an increased lung passage of the markers (3.2 +/- 0.9%, 22.0 +/- 6.1%, 33.3 +/- 12.0%, respectively; P less than 0.01-P less than 0.001). The highest marker passage was obtained when the inflammation was most severe, i.e., after ferritin administration (17.6 +/- 2.3%, 60.0 +/- 6.7%, 41.6 +/- 6.9%, respectively; P less than 0.001), which resulted in markedly elevated lavage cell numbers and protein content as well as edema formation.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanics of running under simulated low gravity
Authors: He J. P. , Kram R. , McMahon T. A.
Published: December 2017

Using a linear mass-spring model of the body and leg (T. A. McMahon and G. C. Cheng. J. Biomech. 23: 65–78, 1990), we present experimental observations of human running under simulated low gravity and an analysis of these experiments. The purpose of the study was to investigate how the spring properties of the leg are adjusted to different levels of gravity. We hypothesized that leg spring stiffness would not change under simulated low-gravity conditions. To simulate low gravity, a nearly constant vertical force was applied to human subjects via a bicycle seat. The force was obtained by stretching long steel springs via a hand-operated winch. Subjects ran on a motorized treadmill that had been modified to include a force platform under the tread. Four subjects ran at one speed (3.0 m/s) under conditions of normal gravity and six simulated fractions of normal gravity from 0.2 to 0.7 G. For comparison, subjects also ran under normal gravity at five speeds from 2.0 to 6.0 m/s. Two basic principles emerged from all comparisons: both the stiffness of the leg, considered as a linear spring, and the vertical excursion of the center of mass during the flight phase did not change with forward speed or gravity. With these results as inputs, the mathematical model is able to account correctly for many of the changes in dynamic parameters that do take place, including the increasing vertical stiffness with speed at normal gravity and the decreasing peak force observed under conditions simulating low gravity.
Relationship between exercise-induced muscle damage and enzyme release in rats
Authors: Van der Meulen J. H. , Kuipers H. , Drukker J.
Published: December 2017

The relationship between the amount of exercise-induced muscle damage and the release of creatine kinase (CK), aspartate aminotransferase (AST), and lactate dehydrogenase (LD) was studied. Gender differences in enzyme release and histological damage were also studied. Serial pre- and postexercise blood samples were drawn from untrained male and female catheterized Wistar rats that ran 1.5 or 2.5 h on a treadmill (incline 10 degrees). Three days postexercise, muscle damage was quantified morphometrically in five different hindlimb and forearm muscles. The 1.5 and 2.5 h of exercise elicited histological damage only in the soleus muscle. Significant plasma CK, AST, and LD elevations were found immediately postexercise both in male and female rats. However, the enzyme release was significantly greater in males than in females. Part of this could be explained by differences in clearance rates between males and females. No gender difference in amount of histological damage was found. The actual volume of histological muscle damage was significantly less than the calculated muscle damage based on enzyme release. An increase in the exercise duration from 1.5 to 2.5 h resulted in a disproportional increase in both histological muscle damage and muscle enzyme release. From the present study it is concluded that muscle enzyme release is not clearly reflected in histological muscle damage.
Cerebral regional capillary perfusion and blood flow after carbon monoxide exposure
Authors: Sinha A. K. , Klein J. , Schultze P. , Weiss J. , Weiss H. R.
Published: December 2017

Alterations in regional cerebral blood flow (rCBF) and percent perfused capillaries (indicative of functional intercapillary distance) were determined in conscious male Long-Evans rats after reducing their blood O2-carrying capacity by exposing them to 1% CO for 12 min. rCBF was determined by the iodoantipyrine method. rCBF increased from a mean of 106 +/- 8 (SE) ml.min-1.100 g-1 before CO exposure to 173 +/- 14 ml.min-1.100 g-1 after CO exposure. There was a greater flow increase (126%) in the cerebral cortex than in the lower brain stem [pons (45%), medulla (39%)]. Presence of fluorescein isothiocyanate-labeled dextran identified the perfused capillaries before and after CO exposure. The volume fraction (Vv) and number/mm2 (Na) of all capillaries (perfused and nonperfused) in a given area of brain were determined after staining for alkaline phosphatase. The percent Vv and percent Na of perfused capillaries increased uniformly (from approximately 50% to approximately 80%) in all parts of the brain after CO exposure. In the presence of tissue hypoxia with undiminished plasma PO2, the brain vasculature allowed greater flow of blood while the microvasculature adjusted to reduce the diffusion distance for O2.
Intracranial self-stimulation motivates treadmill running in rats
Authors: Burgess M. L. , Davis J. M. , Borg T. K. , Buggy J.
Published: December 2017

Most animal running models have traditionally used aversive motivators to induce exercise tasks. This study demonstrates treadmill running motivated by reinforcement of intracranial self-stimulation (ICSS), providing an alternative model with which to study physiological responses to exercise. Twenty-nine male Sprague-Dawley rats were stereotaxically implanted with bipolar electrodes aimed at the ventral tegmental area of the brain. After 7 days of operant lever-press training for ICSS, rats that pressed at least 50 presses/min were randomly divided into three conditions: exercise-reinforcing brain stimulation (Ex-St), exercise-aversive shock (Ex-Sh), and sedentary controls (C). Ex-St and Ex-Sh ran for 30 min at 25 m/min at 5% grade for 2 wk with ICSS and electric shock as the motivator, respectively, while C did not run. At the end of 2 wk, Ex-St and Ex-Sh performed an endurance run. Results show that Ex-St ran longer than Ex-Sh [63 +/- 10 vs. 42 +/- 10 (SD) min; P less than 0.05]. HR was higher in Ex-St than in C (P less than 0.05). Rectal temperature increased similarly in both exercise groups. This model provides a highly effective method to motivate treadmill running in rats and as such can be used to characterize physiological responses to exercise without the potentially confounding influence of stress associated with an aversive shock motivator.
Extra-alveolar veins are contiguous with, and leak fluid into, periarterial cuffs in rabbit lungs
Authors: Luchtel D. L. , Embree L. , Guest R. , Albert R. K.
Published: December 2017

We previously observed physiological evidence that arterial and venous extra-alveolar vessels shared a common interstitial space. The purpose of the present investigation was to determine the site of this continuity to improve our understanding of interstitial fluid movement in the lung. Orange G and Evans blue dyes were added to the arterial and venous reservoirs, respectively, of excised rabbit lungs as they were placed 20 cmH2O into zone 1 (pulmonary arterial and venous pressures = 5 cmH2O, alveolar pressure = 25 cmH2O). After 10 s or 4 h the lungs were fixed by immersion in liquid N2, freeze-dried, cut into 5-mm serial slices, and examined by light macroscopy. Serial sections of 0.25–0.5 mm were subsequently examined by scanning electron microscopy. In the animals subjected to the zone 1 stress for 4 h, arterial and venous extra-alveolar vessels were surrounded by cuffs of edema. The edema ratio (cuff area divided by vessel lumen area) was greater around arteries than veins and decreased with increasing vessel size. Periarterial cuffs usually contained orange dye and frequently contained both orange and blue dye. Lymphatics containing orange or blue dye were frequently seen in periarterial cuffs. Scanning electron microscopy demonstrated that extra-alveolar veins of approximately 100 microns diameter were anatomically contiguous with arterial extra-alveolar vessel cuffs. In rabbit lungs, both arterial and venous extra-alveolar vessels (and/or alveolar corner vessels) leak fluid into perivascular cuffs surrounding arterial extra-alveolar vessels, and lymphatics located in the periarterial cuff contain fluid that originates from both the arterial and venous extra-alveolar vessels.
Time domain analysis of oxygen uptake during pseudorandom binary sequence exercise tests
Authors: Hughson R. L. , Cuervo L. A. , Patla A. E. , Winter D. A. , Xing H. C. , Dietrich B. H. , Swanson G. D.
Published: December 2017

Pseudorandom binary sequence (PRBS) exercise tests involve repeated switching between two work rates (WR) according to a computer-generated pattern. This paper presents an approach to analysis of O2 uptake (VO2) in the time domain. First, the autocorrelation function (ACF) of the input WR was recognized to be a triangular-shaped pulse that can be taken to be equivalent to a ramp increase followed by a ramp decrease in WR. Then the cross-correlation function of the input (WR) and the output (VO2) was treated as if it were the response to a triangular-shaped pulse. The cross-correlation function was analyzed by fitting a linear summation of the ramp form of a two-component exponential function to this triangular pulse. VO2 responses of eight subjects were obtained from two different PRBS tests, as well as step changes in WR. The first PRBS test consisted of 15 units, each 30 s in duration. Its ACF had a base width of 60 s. The ramp increase-ramp decrease model fit the data throughout the range of response. The second PRBS test had 63 units, each 5 s in duration; thus its ACF base width was 10 s. Again, the ramp model fit adequately. The data from the second PRBS test could be fit by the impulse form of the two-component exponential equation, although the fit in the first 30 s tended to be poorer. The time constants of VO2 dynamics estimated from step and PRBS tests were not significantly different. PRBS tests can be analyzed in the time domain, and the indicators of system dynamics reflect physiological properties similar to those investigated during step changes in WR.
High rates of exogenous carbohydrate oxidation from starch ingested during prolonged exercise
Authors: Hawley J. A. , Dennis S. C. , Laidler B. J. , Bosch A. N. , Noakes T. D. , Brouns F.
Published: December 2017

This study compared the gastric emptying and oxidation of two 15% carbohydrate (CHO) solutions: a 22-chain-length glucose polymer (GP) and soluble starch (SS). Six endurance-trained subjects ingested 1,200 ml of either GP or SS while cycling for 90 min at 70% of maximal oxygen consumption (VO2max). Whereas the calculated total CHO oxidation (GP 266.8 +/- 41.9 g; SS 263.6 +/- 28.9 g) and the volume emptied from the stomach (GP 813 +/- 130 ml; SS 919 +/- 116 ml) were similar, the appearance of the 14C label in plasma occurred more rapidly from ingested SS than from GP (P less than 0.001). This resulted in a significantly greater rate of SS oxidation than that from GP (SS 105.9 +/- 21.9 g, GP 49.6 +/- 10.2 g; P less than 0.001). Exogenous CHO oxidation from GP accounted for 19% of total CHO oxidation, whereas the corresponding value for SS was 40%. This study suggests that the oxidation of SS and GP solutions ingested during exercise at 70% VO2max is not limited by gastric emptying. Rather, it appears to be either the rate of digestion or absorption of these solutions that determines their utilization.
Intramuscular accumulation of prostaglandins during static contraction of the cat triceps surae
Authors: Symons J. D. , Theodossy S. J. , Longhurst J. C. , Stebbins C. L.
Published: December 2017

We previously demonstrated that muscle afferent endings are sensitized by exogenous prostaglandins during static contraction of skeletal muscle. The purpose of this study was to determine whether 30 s of static hindlimb contraction, induced by electrical stimulation of the cat sciatic nerve, increases the concentration of immunoreactive prostaglandin E2 (iPGE2) and 6-ketoprostaglandin F1 alpha (i6-keto-PGF1 alpha, the stable metabolite of prostaglandin I2) in muscle tissue. In addition, the role of ischemia in augmenting prostanoid production was examined. Gastrocnemius muscle was obtained by freeze-clamping tissue, and prostaglandins were extracted from muscle homogenates and measured by radioimmunoassay. Compared with precontraction values, high-intensity (68% of maximal tension) static contraction elevated gastrocnemius iPGE2 and i6-keto-PGF1 alpha by 45 and 53%, respectively (P less than 0.01). Likewise, when blood flow to the gastrocnemius was attenuated by arterial occlusion during and 2 min before low-intensity contraction (29% maximal tension), the intramuscular iPGE2 concentration was increased by 71% (P less than 0.01). Conversely, low-intensity contraction (30% of maximal tension) and arterial occlusion without contraction did not alter the concentration of either prostanoid. Our findings demonstrate that prostaglandins accumulate in muscle during static contraction. We believe that local muscle ischemia may provide a stimulus for this phenomenon. These prostaglandins therefore are available to sensitize afferent endings responsible for reflex adjustments during static muscle contraction.
Physiological effects of hydrogen sulfide inhalation during exercise in healthy men
Authors: Bhambhani Y. , Singh M.
Published: December 2017

Occupational exposure to hydrogen sulfide (H2S) is prevalent in a variety of industries. H2S when inhaled 1) is oxidized into a sulfate or a thiosulfate by oxygen bound to hemoglobin and 2) suppresses aerobic metabolism by inhibiting cytochrome oxidase (c and aa3) activity in the electron transport chain. The purpose of this study was to examine the acute effects of oral inhalation of H2S on the physiological responses during graded cycle exercise performed to exhaustion in healthy male subjects. Sixteen volunteers were randomly exposed to 0 (control), 0.5, 2.0, and 5.0 ppm H2S on four separate occasions. Compared with the control values, the results indicated that the heart rate and expired ventilation were unaffected as a result of the H2S exposures during submaximal and maximal exercise. The oxygen uptake had a tendency to increase, whereas carbon dioxide output had a tendency to decrease as a result of the H2S exposures, but only the 5.0 ppm exposure resulted in a significantly higher maximum oxygen uptake. Blood lactate concentrations increased significantly during submaximal and maximal exercise as a result of the 5.0 ppm exposure. Despite these large increases in lactate concentration, the maximal power output of the subjects was not significantly altered as a result of the 5.0 ppm H2S exposure. It was concluded that healthy young male subjects could safely exercise at their maximum metabolic rates while breathing 5.0 ppm H2S without experiencing a significant reduction in their maximum physical work capacity during short-term incremental exercise.
Relationship between inspiratory effort and breathlessness in pregnancy
Authors: Field S. K. , Bell S. G. , Cenaiko D. F. , Whitelaw W. A.
Published: December 2017

Using open-magnitude scaling, we compared the relationships between breathlessness, inspiratory esophageal pressure swing (delta Pes), and ventilation in pregnancy and postpartum. Thirteen healthy women performed progressive cycle exercise tests at 33 +/- 2 wk gestation and 12 +/- 3 wk postpartum. Pulmonary function and maximal transdiaphragmatic pressure did not change. Minute ventilation (VE) was greater in the third trimester. This increase was entirely due to the increase in tidal volume (VT; 0.74 +/- 0.18 vs. 0.54 +/- 0.18 liters at rest, P less than 0.01; 1.56 +/- 0.3 vs. 1.24 +/- 0.24 liters at 48 W, P less than 0.001). delta Pes (15.3 +/- 3.0 vs. 11.9 +/- 3.5 cmH2O at 48 W, P less than 0.01) and breathlessness (1.8 +/- 1.4 vs. 1.0 +/- 0.9 at 48 W, P less than 0.05) were greater in the third trimester. However, the relationships between VT and delta Pes and between delta Pes and breathlessness were identical in the two conditions. The VT-tidal abdominal volume (Vab) and Vab-tidal gastric pressure swing (delta Pga) relationships were similar in the two conditions. In conclusion, the relationship between delta Pes and breathlessness is the same in the third trimester and postpartum. The increased VE is responsible for the breathlessness in the third trimester. Despite progressive abdominal distension by the gravid uterus, the VT-Vab and Vab-delta Pga relationships were the same in the two conditions.
Plasma volume expansion in humans after a single intense exercise protocol
Authors: Gillen C. M. , Lee R. , Mack G. W. , Tomaselli C. M. , Nishiyasu T. , Nadel E. R.
Published: December 2017

We used intense intermittent exercise to produce a 10% expansion of plasma volume (PV) within 24 h and tested the hypothesis that PV expansion is associated with an increase in plasma albumin content. The protocol consisted of eight 4-min bouts of exercise at 85% maximal O2 uptake with 5-min recovery periods between bouts. PV, plasma concentrations of albumin and total protein (TP), and plasma osmolality were measured before and during exercise and at 1, 2, and 24 h of recovery from exercise. During exercise, PV decreased by 15%, while plasma TP and albumin content remained at control levels. At 1 h of recovery, plasma albumin content was elevated by 0.17 +/- 0.04 g/kg body wt, accounting for the entire increase in plasma TP content. PV returned to control level at 1 h of recovery without fluid intake by the subjects, despite a 820 +/- 120-g reduction in body weight. At 2 h of recovery, plasma TP content remained significantly elevated, and plasma TP and albumin concentration were significantly elevated. At 24 h of recovery, PV was expanded by 4.5 +/- 0.7 ml/kg body wt (10 +/- 1%), estimated from hematocrit and hemoglobin changes, and by 3.8 +/- 1.3 ml/kg body wt (8 +/- 3%), measured by Evans blue dye dilution. Plasma albumin content was increased by 0.19 +/- 0.05 g/kg body wt at 24 h of recovery. If 1 g of albumin holds 18 ml of water, this increase in plasma albumin content can account for a 3.4-ml/kg body wt expansion of the PV. No significant changes in plasma osmolality occurred during recovery, but total plasma osmotic content increased in proportion to PV.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine prevents phorbol ester injury in rabbit lungs: role of leukotrienes and TNF
Authors: Bradley J. D. , Zanaboni P. B. , Webster R. O. , Baudendistel L. J. , Dahms T. E.
Published: December 2017

The objective of this study was to determine whether adenosine (ADO) prevents phorbol myristate acetate- (PMA) induced lung injury by modulating peptidoleukotrienes (LT) and/or tumor necrosis factor (TNF) production. PMA significantly increased pulmonary vascular resistance (PVR, 275 +/- 4 to 447 +/- 30 cmH2O.1–1.min) and microvascular filtration coefficient.(Kf, 0.024 +/- 0.002 to 0.040 +/- 0.006 g.min-1.cmH2O-1) in isolated blood-perfused rabbit lungs. ADO (5 mumol/min) blocked the increases in PVR (257 +/- 9 to 283 +/- 26) and Kf (0.028 +/- 0.005 to 0.018 +/- 0.002). After PMA (30 min), perfusate levels of LTC4 + LTD4 increased by 15.3 +/- 2.1 pg/ml; LTE4 increased by 15.1 +/- 4.1 pg/ml. ADO reduced the increase in LTC4 + LTD4 to 2.7 +/- 6.1 pg/ml, but total LT increased by 31.9 +/- 16.6 pg/ml, implying that ADO enhanced the conversion of LTC4 and LTD4 to LTE4. MK-886 (L663,536), an LT synthesis inhibitor, blocked the increase in total LT (6.1 +/- 13.9 pg/ml) but did not reduce the PMA-induced increase in Kf (0.022 +/- 0.003 to 0.035 +/- 0.005) or PVR (238 +/- 11 to 495 +/- 21). After PMA administration, perfusate TNF levels were not different from the 10-fold increase observed in control experiments and were not reduced by ADO or MK-886. TNF production was independent of perfusate blood components and presumably due to low levels of endotoxin in the perfusate (70–90 ng/ml). These results indicate that ADO does not protect against PMA-induced acute lung injury by altering circulating levels of LT or TNF.
Tissue temperature profile in the human forearm during thermal stress at thermal stability
Authors: Ducharme M. B. , VanHelder W. P. , Radomski M. W.
Published: December 2017

The purpose of the present study was to investigate the effect of a range of water temperatures (Tw from 15 to 36 degrees C) on the tissue temperature profile of the resting human forearm at thermal stability. Tissue temperature (Tti) was continuously monitored by a calibrated multicouple probe during 3 h of immersion of the forearm. The probe was implanted approximately 9 cm distal from the olecranon process along the ulnar ridge. Tti was measured every 5 mm, from the longitudinal axis of the forearm (determined from computed tomography scanning) to the skin surface. Along with Tti, skin temperature (Tsk), rectal temperature (Tre), and blood flow were measured during the immersions. For all temperature conditions, the temperature profile inside the limb was linear as a function of the radial distance from the forearm axis (P less than 0.001). Temperature gradient measured in the forearm ranged from 0.2 +/- 0.1 degrees C C cm (Tw = 36 degrees C) to 2.3 +/- 0.5 degrees C cm (Tw = 15 degrees C). The maximal Tti was measured in all cases at the longitudinal axis of the forearm and was in all experimental conditions lower than Tre. On immersion at Tw less than 36 degrees C, the whole forearm can be considered to be part of the shell of the body. With these experimental data, mathematical equations were developed to predict, with an accuracy of at least 0.6 degrees C, the Tti at any depth inside the forearm at steady state during thermal stress.(ABSTRACT TRUNCATED AT 250 WORDS)