bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of glycogen depletion and pedaling speed on "anaerobic threshold"
Authors: Hughes E. F. , Turner S. C. , Brooks G. A.
Published: December 2017

Nine male subjects performed continuous incremental exercise on a bicycle ergometer pedaling at 50 and 90 rpm in a normal glycogen state (NG) and at 50 rpm in a glycogen-depleted state (GD) to determine if alterations in pedaling frequency and muscle glycogen content would affect their “anaerobic thresholds.” Ventilatory [T(vent)] and lactate [T(lac)] thresholds were identified as the points after which expired minute volume and blood lactate began to increase nonlinearly as a function of work rate. The GD protocol elicited a significant divergence between the two thresholds shifting the T(vent) to a lesser and the T(lac) to a greater work rate relative to the NG state. When the pedaling frequency was increased to 90 rpm in the NG condition, the T(lac) was shifted to a lesser work rate relative to the 50-rpm NG condition. A correlation of only 0.71 was obtained between subjects' T(vent) and T(lac). In subjects of less than 70 kg body wt, the T(lac) came at a work rate 400 kg.m.min-1 less than in subjects of greater than 80 kg body wt despite equivalent O2 uptake. The observation that the T(vent) and T(lac) could be manipulated independently of each other reveals limitations in using the T(vent) to estimate the so-called anaerobic threshold.
Attenuation of blood pressure increases in Dahl salt-sensitive rats by exercise
Authors: Shepherd R. E. , Kuehne M. L. , Kenno K. A. , Durstine J. L. , Balon T. W. , Rapp J. P.
Published: December 2017

Systolic blood pressure was determined weekly to assess the development of hypertension in sedentary and active Dahl salt-sensitive (S) rats that were exercised by running at 20 m/min, 60 min/day, 5 days/wk. The marked rise in blood pressure that occurred with feeding 8% NaCl (wt/wt) diet in Dahl S rats could be attenuated by chronically practiced endurance running, but only if exercise at 20 m/min was started at the beginning of salt feeding. Under the same dietary feeding conditions, running at 27 m/min resulted in incomplete attenuation of hypertension. Further, running for 30 min/day was not as beneficial as running 60 min/day at 20 m/min. Delaying the start of exercise for 6 wk after the beginning of salt feeding did not result in reduction of hypertension in the S rat. These experiments indicate that increases in blood pressure can be prevented in Dahl S rats for 12 wk if running is initiated concomitantly with salt feeding. Blood pressure is not reduced if hypertension due to salt feeding has been continued for 6 wk. The results also indicate that there is an optimal exercise intensity, duration, or both, for controlling hypertension in Dahl rats.
Ventilatory response to inspired CO2 in normal and carotid body-denervated ponies
Authors: Klein J. P. , Forster H. V. , Bisgard G. E. , Kaminski R. P. , Pan L. G. , Hamilton L. H.
Published: December 2017

The purpose of these studies was to gain insight into mechanisms regulating pulmonary ventilation (VE), arterial CO2 partial pressure (PaCO2), and arterial pH (pHa) in ponies when inspired CO2 partial pressure (PICO2) is above normal. Ponies were studied four times daily each weekday for 2 wk in an environmental chamber. Each study consisted of a 15-min control period (PICO2 = 0.7 Torr) followed by a 15- to 30-min experimental period during which PICO2 in the chamber was 0.7, 7, 14, 21, 28, or 42 Torr (PIO2 = 147 Torr throughout). Between 11 and 15 min of each period, four 3-ml samples of arterial blood were drawn, each over 45 s. In 12 normal ponies, elevation of PICO2 to 7 Torr caused PaCO2 to increase approximately 0.4 Torr (P less than 0.01) and pHa to decrease approximately 0.003 (P less than 0.02) relative to control. The hypercapnia and acidosis increased progressively as PICO2 was increased in 7- to 14-Torr increments to 42 Torr (P less than 0.02). Accordingly, the hyperpnea in these ponies during CO2 inhalation could have been mediated by carotid and intracranial chemoreceptors. One month after carotid body denervation (CBD) in nine ponies, PaCO2 during control conditions was 6 Torr above normal, but during CO2 inhalation, PaCO2 changed less from control than during CO2 inhalation before CBD (P less than 0.01). The delta VE/ delta PaCO2 near eupneic PaCO2 appeared to be above normal 1 mo after CBD (P less than 0.01). The mechanism of this increase was not discernible from our data. Finally, our data indicated that the magnitude of the hypercapnia and acidosis during CO2 inhalation was inversely related to PaCO2 and breathing frequency during control conditions.
Use of microwave oven for determination of postmortem water volume of lungs
Authors: Peterson B. T. , Brooks J. A. , Zack A. G.
Published: December 2017

To determine if a microwave oven could be used to obtain accurate values of postmortem lung and blood water contents, we compared measurements made with a microwave oven to those obtained by drying the tissue in a vacuum oven set at room temperature. Tissue samples were obtained from 9 dogs and 10 sheep used for a variety of experiments resulting in a wide biological range of water fractions (0.74–0.88). The ratio of the values obtained by these two methods was 1.00 +/- 0.06 for dog tissues and 1.00 +/- 0.02 for sheep tissues. The use of a microwave oven for drying lung tissue and blood provides a measurement of lung water content that is not significantly different from values obtained by vacuum drying, but the microwave method requires only 1 h vs. several days or weeks.
A modification for preparing the chronic lung-lymph fistula in sheep
Authors: Brown M. J. , Erichsen D. F. , Helgerson R. , Will J. A.
Published: December 2017

The sheep lung-lymph model has proven to be a valuable research tool. Preparing this model can be time consuming and may cause considerable trauma to the animal. The standard procedure of Staub et al., the only other published technique, requires three thoracotomies performed on three separate occasions. The objective of this study is to develop and evaluate a less traumatic and time-consuming surgical protocol for preparing the lung-lymph model. This technique enables us to cannulate the efferent lymph duct draining the lung, divide the caudal mediastinal lymph node, and catheterize the left atrium with one thoracotomy. The modified approach, along with some minor changes in aftercare, enables us to have a success rate of over 70% with an average patent flow of 8 days (range 3–21 days) and saves time and surgical trauma to the animal.
Relationship between stroke volume and pneumocardiogram
Authors: Heckman J. L. , Stewart G. H. , Tremblay G. , Lynch P. R.
Published: December 2017

The intratracheal pressure oscillations produced by the heartbeat, called the pneumocardiogram, were recorded in 15 dogs. It was found that a linear relationship existed between the amplitude of the major negative deflection of the pneumocardiogram and the cardiac stroke volume, the latter determined either by indicator dilution (avg r = 0.94) or by use of an electromagnetic flow probe (avg r = 0.95). This relationship existed in animals with both an open and a closed chest. The vector of left ventricular wall motion directed toward the lungs, determined by high-speed cineradiography of the motion of a tantalum marker inserted in the wall of the left ventricle, looked very similar to the pneumocardiogram. This study showed that the pneumocardiogram can be used as a noninvasive technique to measure changes in stroke volume and is caused primarily by the motion of the cardiac walls.
Selective effect of general anesthetics on reflex bronchoconstrictor responses in dogs
Authors: Holtzman M. J. , Hahn H. L. , Sasaki K. , Skoogh B. E. , Graf P. D. , Fabbri L. M. , Nadel J. A.
Published: December 2017

To determine which part of the parasympathetic bronchoconstrictor pathway is most sensitive to depression by general anesthetics, we stimulated different parts of the pathway in dogs after initial anesthesia with chloralose and urethan and then after additional anesthetic drugs. We stimulated the entire reflex pathway by producing apnea or hypoventilation, the sensory pathway by electrically stimulating the proximal end of cut superior laryngeal nerves, and the motor pathway by stimulating the distal end of a cut cervical vagus nerve. Bronchoconstrictor responses to all stimuli were assessed with a bypassed tracheal segment. When no additional anesthetic was administered, responses to all stimuli increased with time. Small additional doses of anesthetics (thiopental, 113;5 mg/kg; pentobarbital, 1–2 mg/kg; amobarbital, 1–2 mg/kg; or chloralose, 10 mg/kg) decreased responses to reflex and sensory stimulation markedly and reversibly, but they did not affect responses to motor stimulation. Increased doses decreased responses to motor stimulation as well. Our previous study (Skoogh et al., Am. Rev. Respir. Dis. 123: 202, 1981) showed that barbiturates depress parasympathetic ganglionic synapses; the present study suggests that central nervous system synapses may be even more sensitive to depression by general anesthetics.
Characterization of H1- and H2-receptor function in pulmonary and systemic circulations of sheep
Authors: Ahmed T. , Mirbahar K. B. , Oliver W. , Eyre P. , Wanner A.
Published: December 2017

We investigated the histamine H1- and H2-receptor function in the pulmonary and systemic circulations of sheep by in vivo and in vitro techniques. Combined H1 and H2 stimulation (by intravenous histamine) in vivo increased pulmonary vascular resistance (PVR) to 435% of base line and decreased systemic vascular resistance (SVR) to 49% of base line. Selective H2 stimulation (histamine after chlorpheniramine pretreatment) decreased PVR and SVR to 86 and 82% at base line, respectively, while selective H1 stimulation (histamine after metiamide pretreatment) increased PVR to 424% of base line and decreased SVR to 64% of base line. Combined H1- and H2-antagonist pretreatment completely blocked the effects of histamine on SVR, while PVR still decreased to 85% of base line, suggesting a mild “atypical” H2-receptor response in the pulmonary circulation under conditions of resting vascular tone. With increased pulmonary vascular tone (hypoxia), histamine decreased PVR to 55% (H1-antagonist pretreatment) and to 58% (combined H1- and H2-antagonist pretreatment) of posthypoxia values, respectively, demonstrating a marked atypical H2-receptor response. In vitro, both pulmonary arterial and venous strips showed a contractile dose-response to histamine, which was blocked by the H1-antagonist pyrilamine (mepyramine). In precontracted strips, both histamine and the H2-agonists (dimaprit and impromidine) elicited a relaxant response, which was neither blocked by H1-antagonist alone nor by combined H1- and H2-antagonists. We conclude that in sheep the histamine-induced pulmonary vasoconstrictor response is mediated by H1-receptors, while the pulmonary vasodepressor response is mediated by atypical H2-receptors. The systemic vasodepressor response is mediated by both H1- and typical H2-receptors.
Myocardial blood flow during acute isovolumic anemia and treadmill exercise in dogs
Authors: Abendschein D. R. , Fewell J. E. , Carlson C. J. , Rapaport E.
Published: December 2017

We examined whether submaximal treadmill exercise during acute isovolumic anemia altered the distribution of myocardial blood flow and thus caused subendocardial ischemia in unsedated dogs. Myocardial blood flow (determined by the microsphere method) and left ventricular function (indicated by pressures, volumes, and contractile indices) were measured in five dogs at rest and during exercise before and after equal volume exchange of blood and 6% dextran 70, which lowered hematocrit from 36 +/- 4 to 18 +/- 2% (SD). Total myocardial blood flow increased from 175 +/- 65 to 296 +/- 151 ml . min-1 . 100 g-1 (69%) during exercise before anemia and from 329 +/- 61 to 599 +/- 126 (82%) during exercise after anemia. The distribution of blood flow to the left and right ventricles and interventricular septum as well as the subendothelial-to-subepicardial blood flow ratio in these areas did not change during exercise either before or after anemia. Left ventricular function was not impaired during exercise after anemia. We conclude that subendocardial ischemia does not occur when dogs exercise during acute isovolumic anemia.
Brain hypoxia and control of breathing: role of the vagi
Authors: Chapman R. W. , Santiago T. V. , Edelman N. H.
Published: December 2017

Vagally mediated reflexes play an important role in the generation of respiratory responses to various stimuli. This study examined the role of vagally mediated mechanisms in the generation of the respiratory responses to progressive brain hypoxia secondary to carboxyhemoglobinemia (HbCO 013;55%) in six unanesthetized goats. Ventilation, respiratory cycle timing, and the lung inflation reflex were measured before and during CO inhalation in intact and bilaterally vagotomized animals. Our results indicate that vagal reflexes contribute a small magnitude of the hyperpnea caused by carboxyhemoglobinemia. Furthermore, in contrast to that reported for CO2 inhalation, the tachypneic nature of the ventilatory response to CO is not a vagally mediated phenomenon. CO inhalation had a biphasic influence on the strength of the lung inflation reflex measured as the ratio of inspiratory time during occlusion (TIoccl) to inspiratory time of the preceding spontaneous breath (TIspont). At HbCO levels of 35%, TIoccl/TIspont was enhanced, whereas at HbCO levels of 55% of ratio fell to unity, indicating abolition of the reflex. After vagotomy, this ratio was unity at all levels of carboxyhemoglobinemia.
Barbiturates depress vagal motor pathway to ferret trachea at ganglia
Authors: Skoogh B. E. , Holtzman M. J. , Sheller J. R. , Nadel J. A.
Published: December 2017

To determine which site in the vagal motor pathway to airway smooth muscle is most sensitive to depression by barbiturates, we recorded isometric muscle tension in vitro and stimulated the vagal motor pathway at four different sites before and after exposure to barbiturates. In isolated tracheal rings from ferrets, we stimulated muscarinic receptors in the neuromuscular junction by exogenous acetylcholine, postganglionic nerve fibers by electrical fluid stimulation, and the postsynaptic membrane in ganglia by 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP). We also developed a tracheal nerve-muscle preparation to stimulate preganglionic fibers in the vagus nerve electrically. Activation of ganglia by DMPP or by vagus nerve stimulation was depressed by barbiturates at 10-fold lower concentrations than those depressing the activation of postganglionic nerves or the neuromuscular junction. These findings suggest that the postsynaptic membrane in parasympathetic ganglia is the site in the vagal motor pathway most sensitive to depression by barbiturates.
Respiratory system compliance as seen from the cardiac fossa
Authors: Lloyd T. C.
Published: December 2017

Changes in cardiac size and shape should impose stresses on the surrounding lung and chest wall. To examine pressure-volume relationships of the cardiac fossa we measured pressures required to increase the pericardial volume of freshly killed dogs at different levels of lung inflation, first by expanding the pericardium uniformly and then by expanding only the left ventricle. In both cases we obtained linear pressure-volume relationships, the slopes of which expressed an apparent compliance. Compliance decreased as lung volumes were increased by raising end-expiratory pressure, and compliance with symmetrical pericardial filling exceeded that with asymmetrical (left ventricular) distension. These compliances were compared with the total respiratory system compliance measured during tidal ventilation, and we found that the compliance of the cardiac fossa was significantly less than would be predicted from lung and chest wall compliances as classically measured. We concluded that the respiratory system imposes a finite compliance load on cardiac filling that raises local epicardial pressure above ambient pleural pressure. This respiratory system load depends upon lung volume and the cardiac shape change.
Inhibition of aortic chemoreceptor responses by metabolic alkalosis in the cat
Authors: Pokorski M. , Lahiri S.
Published: December 2017

The responses of the same aortic chemoreceptor afferents to steady-state isocapnic hypoxia and to hypercapnia on hyperoxia, before and after the induction of metabolic alkalosis, were investigated in 12 anesthetized cats. Metabolic alkalosis was achieved by intravenous administration of sodium bicarbonate in the average dose of 7 mmol . kg-1. On the average, arterial pH (pHa) increased from 7.383 to 7.650 at an arterial CO2 partial pressure (PaCO2) of 30 Torr. The increase in pHa resulted in a decrease in chemoreceptor activity, the effect being greater at a lower arterial O2 partial pressure. Increases in PaCO2 during hyperoxia resulted in an increased activity of the chemoreceptors both before and after NaHCO3 injection. The stimulatory effect of hypercapnia, however, was attenuated by metabolic alkalosis. At a constant PaCO2, decreases in arterial [H+] by the NaHCO3 administration caused an approximately linear decrease in the chemoreceptor activity. At a constant arterial [H+], higher PaCO2 was associated with a slightly greater activity of the chemoreceptors. These results indicate that the major effect of CO2 is mediated by [H+], but there appears to be another mechanism, albeit small, for the effect of CO2.
Differential liquid and protein clearance from the alveoli of anesthetized sheep
Authors: Matthay M. A. , Landolt C. C. , Staub N. C.
Published: December 2017

We determined the clearance rates of 50 ml of isosmotic fluids from the lungs of anesthetized, ventilated sheep with lung lymph fistulas. The removal of the liquid volume followed a monoexponential process over 4 h for both Ringer lactate [half time (t 1/2) = 3 h] and autologous serum (t 1/2 = 6 h). Lymph flow did not increase with Ringer lactate, indicating that the alveolar fluid was cleared via the circulation. With serum, however, lymph flow increased 40%. In both groups the lymph-to-plasma protein concentration ratio fell slightly. Using protein tracers in the alveolar instillate, we found that less than 2% of the protein entered the lymph and plasma. Almost all of the protein remained in the air spaces and was concentrated in proportion to the amount of liquid volume that was cleared. Clearance of liquid volume from alveoli to interstitium could be due to subatmospheric interstitial fluid pressure or to active metabolic processes that cause small molecules to leave the alveolar fluid, or both. The results of the serum experiments tend to favor a metabolic process, but passive mechanisms are possible. The difference in lymph flow response between the two fluids must be due to the protein in the alveolar fluid. We believe Ringer lactate dilutes the alveolar wall interstitial protein concentration thereby decreasing local filtration, whereas serum concentrates alveolar wall interstitial fluids proteins thereby increasing local filtration.
Altitude-induced changes in plasma thyroxine, 3,5,3'-triiodothyronine, and thyrotropin in rats
Authors: Connors J. M. , Martin L. G.
Published: December 2017

We have studied the thyroid function of high-altitude-acclimated (6,900 m for 5 wk) and nonaltitude-acclimated control (198 m) rats. After 5 wk of high-altitude exposure the plasma concentrations of both thyroxine (T4) and triiodothyronine (T3) were lower than those in control rats (4.7 +/- 0.3 vs. 3.3 +/- 0.2 microgram/dl and 96 +/- 5 vs. 74 +/- 6 ng/dl, respectively). The plasma thyrotropin (TSH) concentration was elevated in the high-altitude-acclimated rats compared with controls (52 +/- 4 vs. 29 +/- 3 micrograms/dl, respectively). Gross anatomical (thyroid wt/body wt) and histological observations of thyroid tissue were consistent with elevated plasma TSH concentrations. These results suggest that the fall in the plasma concentrations of T4 and T3 during acclimation to severe hypoxia is due to a primary block of thyroid secretion and not to a fall in plasma TSH levels.
Oral contraceptives and fibrinolysis among female cyclists before and after exercise
Authors: Huisveld I. A. , Hospers A. J. , Bernink M. J. , Biersteker M. W. , Erich W. B. , Bouma B. N.
Published: December 2017

The effect of oral contraceptives on a number of plasma fibrinolytic variables and antithrombin III was studied in 20 highly trained women before and immediately after exhaustive exercise on a bicycle ergometer. Two groups were studied, 11 women using an oral contraceptive agent (OCA group) and 9 women not using an oral contraceptive (control group). Factor XII, prekallikrein, plasminogen, alpha 2-antiplasmin, and antithrombin III activities were determined in plasma as well as a number of cardiovascular, respiratory, and metabolic components. Resting values showed a significantly higher level of prekallikrein and plasminogen in the OCA group compared with the control group. Exercise plasma values of components of the fibrinolytic system were significantly higher than resting values in both groups. However, when corrected for plasma volume changes, the exercise levels of prekallikrein and antithrombin III were significantly decreased in the OCA group only, whereas alpha 2-antiplasmin exercise level was significantly lower in both groups. Our results indicate that use of OCA even with an estrogen dosage as low as 30 micrograms has an effect on resting and exercise fibrinolytic variables; an effect, however, which does not seem to interfere with maximal performance in trained women.
Response to external inspiratory resistive loading and bronchospasm in anesthetized dogs
Authors: Savoy J. , Arnup M. E. , Anthonisen N. R.
Published: December 2017

Mouth occlusion pressure (P0.1) and breathing-pattern responses to external inspiratory resistive loading and methacholine chloride-induced bronchospasm were assessed in six dogs under pentobarbital sodium anesthesia. There was no change in P0.1 with external loading, but, in response to bronchospasm, we observed a P0.1 increase proportional to the change in lung resistance. These results indicate that, unlike external loading, the ventilatory-drive adaptation to bronchospasm does not require consciousness of the animal. The breathing-pattern response to bronchospasm consisted of tachypnea associated with decreased tidal volume (VT), decreased inspiratory duration (TI), and unchanged mean inspiratory flow (VT/TI). In response to resistive loading there was no tachypnea, VT decreased, TI was unchanged, and VT/TI decreased. We suggest that in response to resistive loading there was no modification of vagal activity, whereas in bronchospasm there was an increase of vagal activity, which was responsible for the changes in breathing pattern and, at least in part, for the changes in P0.1.
Acid-base, metabolic, and ventilatory responses to repeated bouts of exercise
Authors: Buono M. J. , Roby F. B.
Published: December 2017

Acid-base, metabolic, and ventilatory responses to repeated bouts of exercise were examined. Ten male subjects performed two (T1, T2) 5-min work tests, on a cycle ergometer, separated by a 25-min rest. The results indicate the following. 1) T2 appears to have a larger aerobic energy component than T1, due to the fact that cumulative O2 uptake (Vo2) was significantly larger for T2 and that the immediate postexercise lactic acid (HLa) and delta HLa values were both significantly smaller for T2.2) CO2 production (Vco2) and the respiratory exchange ratio were both significantly lower for T2. This is probably due to greater fat metabolism and less nonmetabolic CO2 being produced from bicarbonate (HCO-3) buffering of HLa during T2.3) Even though Vco2 was significantly lower during T2, minute ventilation (VE) was not significantly different between T1 and T2. This suggests that the ventilatory response during exercise cannot be solely mediated via CO2 flux to the lungs. 4) HLa removal and (HCO-3) regeneration appear to be sequentially linked together as indicated by the almost identical mirror image and significant -0.93 correlation. In conclusion, it appears that a bout of high-intensity exercise (T1) can alter the acid-base and metabolic responses seen during subsequent performance (T2).
Histamine and pulmonary responses to cigarette smoke in periphery of the lung
Authors: Gertner A. , Bromberger B. , Traystman R. , Menkes H.
Published: December 2017

An animal model for studying responses of the lung periphery to controlled levels of environmental agents has been used to assess the role of histamine in pulmonary responses to cigarette smoke. A fiber-optic bronchoscope was wedged in a peripheral airway of anesthetized dogs. Measurements of collateral resistance (Rcoll) were used to monitor responses to histamine and cigarette smoke. Responses to an aerosol containing histamine (1.5 X 10(-4) mg) and cigarette smoke (420 ml) were measured before and after the administration of an aerosol containing 1.0 mg chlorpheniramine. Prior to the administration of chlorpheniramine, the histamine challenge produced a 75 +/- 26% increase in Rcoll and cigarette smoke produced a 74 +/- 26% increase. Following the administration of chlorpheniramine, the peak responses to histamine and cigarette smoke were reduced by 82 +/- 9 and 61 +/- 8%, respectively. Administration of the same dose of chlorpheniramine prior to challenge with methacholine did not reduce the response to that agent. These results indicate that acute local responses to cigarette smoke in the periphery of the lung are mediated in part through the release of histamine.
Vesicular lung sound amplitude mapping by automated flow-gated phonopneumography
Authors: O'Donnell D. M. , Kraman S. S.
Published: December 2017

A recently developed automated apparatus capable of determining vesicular lung sound amplitude rapidly and accurately was used to construct detailed inspiratory vesicular sound amplitude maps in eight healthy male subjects to determine the normal amplitude patterns on the chest wall. The sounds were recorded in 2-cm steps along the following lines bilaterally: A, vertically, clavicle to abdomen, 6 cm from the sternal border; B, vertically, from the level of T1 to the lung bases, 6 cm from the spine; and C, horizontally, from the sternal border to the spine at the level of the nipple. Sound amplitude was measured at an airflow rate of 1.3 l/s. The resulting amplitude maps revealed considerable intra- and intersubject variation with frequent amplitude heterophony. Th patterns for the subjects as a group were as follows: series A, amplitude decreasing with distance from the clavicle; series B, amplitude increasing with distance from T1 with a peak at the bases; and series C, approximately equal amplitude at all positions. The findings in series B and C are, in general, consistent with an explanation of ventilation following hydrostatic gradients. The series A pattern and the intersubject variability in amplitude are inconsistent with this explanation and suggest that the inspiratory vesicular sound amplitude is not simply a result of ventilation distribution but involves other as yet undefined factors.
Hormone response of normal and intermittent cold-preadapted humans to continuous cold
Authors: Radomski M. W. , Boutelier C.
Published: December 2017

This study examined the hormonal and thermal responses of two groups of subjects during 16 days in the Arctic (mean temperature -26.8 degrees C). One group (NPA) received no prior cold exposure, whereas the second group (PA) was subjected to nine daily immersions (20–40 min) in cold water (15 degrees C) 20 days before the Arctic exposure. Nude cold tolerance tests (cold air at 10 degrees C) were administered to both groups before and after the Arctic exposure. The NPA group showed an increase in metabolism and rectal temperature, whereas the PA group showed no elevation in metabolism and a decrease in rectal temperature. In the Arctic significant daily increases over the control period of urine volume (+86%), urinary norepinephrine (+48%), epinephrine (+84%), and 17-hydroxycorticosteroids (+34%) occurred in the NPA group. Only epinephrine (+65%) increased in the PA group. The hormonal and thermal responses of the NPA group in the Arctic were characteristic of metabolic adaption, whereas those in the PA group were suggestive of a hypothermic type of adaptation or habituation with no evidence of sympathetic or adrenocortical stimulation. The hormonal and thermal responses observed in this study indicate that a degree of cold resistance can be induced rapidly in humans by short intermittent exposures to an intense cold stress, which persists for a significant period of time after the last exposure.
Parasympathetic innervation of the cervical trachealis muscle in living dogs
Authors: Brown J. K. , Shields R. , Gold W. M.
Published: December 2017

In 34 anesthetized dogs, we characterized the pathways by which parasympathetic fibers were carried to the cervical trachealis muscle. Nerves were stimulated electrically, and tracheal tension was monitored in segments of the posterior membrane in vivo as described previously (J.K. Brown et al.; J. Appl. Physiol: Respirat. Environ. Exercise Physiol. 49: 8413;94, 1980). Stimulation of superior laryngeal nerves contracted 34 of 34 cranial cervical segments and 2 of 4 caudal cervical segments. Recurrent laryngeal nerves contributed to innervation of 34 of 34 cranial, as well as 4 of 4 caudal, segments. Stimulation of pararecurrent nerves contracted 11 of 34 cranial and 4 of 4 caudal segments. Mechanical effects of esophageal contraction, induced by stimulating pararecurrent nerves, did not alter tension in tracheal segments. Tracheal contractions induced by stimulation of all three pathways simultaneously were significantly less than the sum of contractions produced by stimulating each set individually; this was probably due to anastomoses between terminal neurons, overlap in their anatomic distribution, or intercellular nexuses in trachealis muscle. We conclude that parasympathetic innervation of the canine trachea is by three different neuroanatomic pathways.
Protein kinase activity in liver of heat-acclimated hamsters
Authors: Chayoth R. , Aharon M. , Graziani Y.
Published: December 2017

Protein kinase activity in incubated liver slices from 35 degrees C heat-acclimated (HA) hamsters was 70% higher than in similar slices from 23 degrees C control (C) hamsters. Adding glucagon to the incubation medium increased protein kinase activity by 65% in slices from C animals, but by only 30% in slices from HA animals. Binding of [3H]cAMP to proteins of a low-speed supernatant fraction of incubated and homogenized slices was 30% lower for HA than for C hamsters. For each acclimation group this binding was reduced 30% by incubation of the slices with glucagon. The activities of phosphorylase kinase, phosphorylase phosphatase, and phosphorylase alpha in slices incubated with or without glucagon did not differ between groups. Addition of glucagon increased phosphorylase kinase by 30% and phosphorylase alpha by 40% but caused no change in phosphorylase phosphatase activity. These results suggest that heat acclimation of the hamster increases the amount of a species of liver protein kinase that is different from the one that mediates the effect of glucagon on glycogenolysis.
Rat lung cholinergic receptor: characterization and regulation by corticosteroids
Authors: Marquardt D. L. , Motulsky H. J. , Wasserman S. I.
Published: December 2017

Muscarinic cholinergic receptors have been implicated in the regulation of bronchomotor tone, bronchial mucus secretion, and lung mast-cell mediator release. Rat lung membranes prepared by homogenization, sonication, and sedimentation of 37,000 g in sucrose have been demonstrated to possess muscarinic cholinergic receptors as assessed by radioligand binding employing l-quinuclidinyl[phenyl-413;3H]benzilate ([3H]QNB). QNB binding was saturable, stereoselective, and reversible in the presence of 1 microM atropine. The rat lung muscarinic receptor demonstrated a Kd of 0.268 +/- 0.126 (+/- SD) nM and a density of 35.4 +/- 4.6 fmol/mg protein by Scatchard analysis. The Hill coefficient was 1.015 +/- 0.085, indicating noncooperative binding. Muscarinic cholinergic receptors in the rat lung were equal in number to alpha 1-adrenergic receptors, but beta-adrenergic receptors are 14 times more prevalent as defined by [3H]prazosin and l-[propyl-2, 3–3H]dihydroalprenolol ([3H]DNA) binding. Dexamethasone (140 micrograms) administration in vivo caused an increase in all three receptor types by 24–48 h, suggesting steroids regulate not only the number of beta-receptors but also that of alpha- and cholinergic receptors. These data suggest new avenues by which steroids may regulate lung function.
Ventilation-perfusion ratio distributions by mass spectrometry with membrane catheters
Authors: Mastenbrook S. M. , Dempsey J. A. , Massaro T. A.
Published: December 2017

We previously developed a quadrupole mass spectrometer system for measuring gas phase concentrations of multiple inert gases at trace levels. A new inlet with two silicone rubber membrane catheters now allows quantitative analysis of the inert gas concentrations in both blood and gas phase samples. We have determined the sensitivity, linearity, and reproducibility of this system by measuring blood-to-gas phase calibration curves for the following inert gases: sulfur hexafluoride, krypton, Freon 12, enflurane, diethyl ether, and acetone. We have used our mass spectrometer system to obtain multiple inert gas elimination data from three anesthetized, spontaneously breathing dogs. We conclude that our dual-membrane mass spectrometer system provides useful measurements of trace multiple inert gas concentrations in both blood and gas phase samples. Furthermore, the inert gases in blood can be measured directly without having to extract them into a gas phase, and the multiple inert gas elimination data acquired with our system can be used to provide estimates of ventilation-perfusion ratio distributions. Our mass spectrometer technique provides an alternative to the gas chromatographic approach for these measurements.
A statistical analysis of the spectral moments used in EMG tests of endurance
Authors: Hary D. , Belman M. J. , Propst J. , Lewis S.
Published: December 2017

EMG and bandlimited noise (BLN) signals of comparable spectra were processed to compute the centroid and median frequencies and the high/low ratio for different record lengths, signal amplitudes, and noise bandwidths. The spectral moments of EMG and BLN showed similar statistical properties, independent of record length and amplitude. The signal-to-noise ratios of the moments increased with record length. Relatively short records were sufficient to obtain low coefficients of variations especially for the centroid, which was the most stable and sensitive to changes in the underlying spectra. The high/low ratio was the least stable moment. A change of 10 and 3.9% in the centroid over successive records of overall duration of 8 and 10 s, respectively, was just sufficient to detect a spectral shift at the P less than 0.05 level. The equivalent percents for the high/low ratio were 66 and 32.5, respectively. These thresholds of significance were related to time constants of equivalent exponential trends in the spectra used to study fatigue. This relationship makes the results of the present study applicable to a wide variety of EMG tests of endurance.
Physiological effects of hypervolemic polycythemia in newborn dogs
Authors: LeBlanc M. H. , Kotagal U. R. , Kleinman L. I.
Published: December 2017

The effect of hypervolemic polycythemia (Hct 62–77) on O2 transport and O2 consumption (Vo2) was studied in 16 unanesthetized newborn dogs (age 3–10 days). A control group of 10 newborn dogs (3–10 days old) was made hypervolemic but not polycythemic in an otherwise identical experiment. Hypervolemia was attained by infusing 33 ml/kg of either packed red blood cells (polycythemia) or whole blood (controls). In the polycythemic group as a result of the transfusion, cardiac output (CO) decreased by 50% (P less than 0.001), peripheral vascular resistance (PVR) increased by 170% (P less than 0.001), but O2 transport did not change significantly, and Vo2 decreased only slightly by 13% (P less than 0.01). In the 10 control animals there were no significant changes in CO, PVR, O2 transport, or Vo2 as a result of the transfusion. Blood lactate increased only slightly in experimental (35%, P less than 0.04) and control animals (23%, NS). The ability of the animals to increase their O2 transport and Vo2 was tested by measuring the changes induced by cold stress. Cold stress produced a 20% increase in Vo2 (P less than 0.05) in both the polycythemic and the control animals. Thus in spite of a decreased CO in the nonstressed state the polycythemic animals were still able to increase O2 transport and Vo2 in response to cold stress. These results suggest that the newborn animal is capable of regulating CO to maintain O2 transport appropriate to uptake under conditions of hypervolemic, polycythemic hyperviscosity, and environmental cold stress.
Right ventricular pressure response to +GZ acceleration stress
Authors: Whinnery J. E. , Laughlin M. H.
Published: December 2017

Measurements of right ventricular pressure in miniature swine were made at +Gz levels from +1 through +9 Gz. Polyethylene catheters were chronically placed in the cranial vena cava of five 2-yr-old female miniature swine (35–50 kg). The catheters were large enough to allow the introduction of a Millar pressure transducer into the venous system for placement in the right heart. The animals were fitted with an abdominal anti-G suit, restrained in a fiberglass couch, and exposed to the various +Gz levels on a centrifuge while fully conscious and unanesthetized. Right ventricular pressure and heart rate were measured during and for 2 min following 30-s exposures to each level of +Gz stress. The maximum right ventricular systolic pressure observed during +Gz was 200 Torr at +5 Gz with the maximum diastolic pressure being 88 Torr observed at +5 Gz. Mean heart rates were 200–210 beats/min at all levels of +Gz greater than or equal to +3 Gz when the animal remained stable. Mean maximum right ventricular pressures during +Gz stress were observed to increase through +5 Gz (85 Torr) and to decrease at higher levels of +Gz, indicating that through +5 Gz there is at least a partial compensation during acceleration stress. Decompensation in response to the stress began to occur during acceleration above +5 Gz with all animals decompensating during +9 Gz.
Effects of salicylate and 2,4-dinitrophenol on respiration and metabolism
Authors: Millhorn D. E. , Eldridge F. L. , Waldrop T. G.
Published: December 2017

The respiratory and metabolic responses to intravenous administration of sodium salicylate (240 mg/kg0.75) and 2,4-dinitrophenol (5.7 mg/kg0.75), uncouplers of oxidative phosphorylation, were studied in anesthetized, paralyzed, vagotomized, and glomectomized cats. During the initial 10 min after administration of salicylate, metabolic rate (VCO2) increased 70% and did not increase further during the experiment. Respiration, on the other hand, increased progressively at the same rate over the entire 60-min course of the experiment. The total increase in respiration was greater than 300%. Thus neither the time course nor the magnitude of the metabolic and respiratory responses were related. Similar findings were also obtained following administration of 2,4-dinitrophenol. We conclude that these agents stimulate respiration by a mechanism other than one related to the ability to uncouple oxidative phosphorylation and cause an increase in whole-body metabolism.
Control of human airway smooth muscle: in vitro studies
Authors: Davis C. , Kannan M. S. , Jones T. R. , Daniel E. E.
Published: December 2017

An in vitro study of neural and myogenic control of human tracheal smooth muscle was undertaken. Over 80% of these had active tension and 13% had phasic contractile activity. Tonic and phasic activities were not reversed by indomethacin, 5,8,11,14-eicosatetraynoic acid, methysergide, mepyramine, atropine, or tetrodotoxin (TTX) but were blocked by the calcium antagonist verapamil. In some quiescent strips, tonic and/or phasic activity was induced by exposure to potassium-conductance blockers such as 4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA). Electrical (field) stimulation resulted in frequency-dependent biphasic responses: an initial atropine-sensitive cholinergic contraction followed by a nonadrenergic relaxation. This biphasic response to low stimulus parameters (less than 0.5 ms, less than 15 Hz) was blocked by TTX and scorpion venom and enhanced by 4-AP and TEA, consistent with a neural mechanism. Relaxation responses to longer pulse durations (0.5–1 ms) were not blocked by TTX despite abolition of contraction nor were they enhanced by 4-AP and TEA, suggesting a nonneural mechanism. ATP, adenosine, arachidonate metabolites, histamine, 5-hydroxytryptamine, neurotensin, or vasoactive intestinal polypeptide were ruled out as possible nonadrenergic mediators. The nature and physiological significance of the nonneural inhibitory response remains unknown.
Effect of local pulmonary blood flow control on gas exchange: theory
Authors: Grant B. J.
Published: December 2017

The effect of local pulmonary blood flow control by local alveolar O2 tension on steady-state pulmonary gas exchange is analyzed with techniques derived from control theory. In a single homogeneous lung unit with normal inspired and mixed venous blood gas composition, the homeostatic effect on local ventilation-perfusion ratios (VA/Q) regulation occurs over a restricted range of VA/Q. The homeostatic effect is maximal at a moderately low VA/Q (about 0.4) due to the slope of the O2 dissociation curve. In a multicompartment lung with a lognormal distribution of VA/Q, regulation of arterial O2 tension varies with the extent of inhomogeneity. At mild degrees of inhomogeneity where local pulmonary blood flow (Q) control acts predominantly on the lower VA/Q of the Q distribution, the regulatory effect is best. At severe degrees of inhomogeneity where local Q control acts mainly on the higher VA/Q of the Q distribution, the regulatory effect is worse, and positive-feedback behavior may occur. Local Q control has the potential of reducing the deleterious effects of lung disease on pulmonary gas exchange particularly when it operates in association with other regulatory mechanisms.
Kinetics of erythrocyte penetration by aliphatic acids
Authors: Klocke R. A. , Flasterstein F.
Published: December 2017

The rate of entry of aliphatic acids into human red blood cells was studied using a new stopped-flow technique. Solutions of aliphatic acids and erythrocyte suspensions were rapidly mixed in a stopped-flow reaction apparatus. The change in extracellular pH resulting from entry of acid into the cell was monitored using chlorophenol red as an extracellular indicator. Extracellular pH of the mixture was linearly related to differential light transmission at 480 and 560 nm. Values of membrane permeability were fitted to data using a model of passive exchange with flux proportional to the transmembrane concentration gradient. At all temperatures the permeabilities were in the order: valeric acid greater than butyric acid greater than propionic acid. Permeabilities were highly temperature dependent and the activation energy (10.5 kcal/mol) remained constant between 7 and 37 degrees C. Despite rapid rates of exchange, permeability measurements did not exhibit evidence of artifact secondary to an unstirred solvent layer on the cell surface. The data are compatible with the hypothesis that aliphatic acid transport across the erythrocyte membrane is passive in nature and proportional to the transmembrane concentration gradient.
Exercise-induced morphological and biochemical changes in skeletal muscles of the rat
Authors: Watt P. W. , Kelly F. J. , Goldspink D. F. , Goldspink G.
Published: December 2017

Morphological and biochemical changes have been studied in two forelimb (i.e., brachialis and extensor carpi radialis) and two hindlimb (i.e., soleus and extensor digitorum longus) muscles of rats subjected to short bursts of high-intensity exercise over 2 wk. Regardless of muscle type, all four muscles grew significantly, accumulating protein, RNA, and DNA at faster rates than in the growing control tissues. Of the intrinsic fiber types within the individual muscles all increased their cross-sectional areas, but the fast-oxidative, glycolytic fibers (type IIa) showed marginally more hypertrophy than the slow-oxidative (I) or fast-glycolytic fibers (IIb). Induced changes in protein turnover were consistent with the additional growth of the exercised muscles. However, the precise alterations in the rates of protein synthesis and protein breakdown varied according to the fiber type composition of the muscle. The increased growth rate of the two principally fast-twitch muscles (i.e., brachialis and extensor digitorum longus) correlated solely with an enhancement of protein synthesis (measured in vivo). In contrast, the hypertrophy of the slow-twitch soleus appeared to relate only to a decrease in protein breakdown (a calculated value). In a more intermediate type of muscle (i.e., extensor carpi radialis) a complementary combination of an increase in synthesis and a decrease in breakdown was found.
Determinants of forced expiratory flows in newborn infants
Authors: Taussig L. M. , Landau L. I. , Godfrey S. , Arad I.
Published: December 2017

Maximal flows at functional residual capacity (VmaxFRC) from partial expiratory flow-volume (PEFV) curves (achieved with rapid compression of the chest) were obtained on 11 healthy newborn babies. Mean VmaxFRC, size corrected by dividing absolute values by measured thoracic gas volume, was 1.90 TGV's/s. Specific upstream conductances were high, and the cross-sectional area of the flow-limiting segment was estimated to be approximately 0.30 cm2 in the three infants on whom recoil pressures at FRC were also measured. The cross-sectional area of the major bronchi in the neonate is approximately 0.26–0.30 cm2. PEFV curves were convex to the volume axis. Many of the neonates increased their flows while breathing a helium-oxygen gas mixture. These results suggest 1) size-corrected flows are higher in the neonate than in older children or adults; 2) the site of the flow-limiting segment at FRC during maximal expiratory maneuvers is in large proximal airways, similar to the adult; and 3) the relationship of airway size to parenchymal size may be similar in neonates and adults or, in fact, airways may be larger, relative to parenchyma, in neonates. These physiological data do not support the hypothesis, based on pathological studies, that peripheral airways are disproportionately smaller (when compared with central airways) in infants than in adults.