bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of umbilical blood flow in fetal lambs in utero
Authors: Berman W. , Goodlin R. C. , Heymann M. A. , Rudolph A. M.
Published: December 2017

We continuously measured umbilical blood flow in fetal lambs in utero by placing an electromagnetic flow transducer around the common umbilical artery. Umbilical arteries originate from a short common segment as the terminal branches of the descending aorta. This segment was isolated by a retroperitoneal surgical approach and encircled with a specially constructed electromagnetic flow transducer. Catheters were also placed in fetal vessles to monitor pressure and derive flow values by the radionuclide-labeled microsphere technique. The fetus and ewe were allowed to recover for two days before studies were performed. Average umbilical blood flow obtained in 11 animals with the transducer was 199 ml/kg per min. In seven animals flow measurements obtained with the transducer were compared with those derived from microsphere injections. Paired measurements varied by an average of only 5.3%. This technique makes possible the accurate and instantaneous measurement of umbilical blood flow in fetal lambs in utero over a prolonged period.
Peripheral body temperature and thermogenic drinking in cold-treated rats
Authors: Nelson E. L. , Fregly M. J. , Tyler P. E.
Published: December 2017

Transfer of rats abruptly from air at 5 degrees C to air at 26 degrees C was accompanied by a significant increase in water intake (thermogenic drinking) during the first hour after transfer. A possibility existed that the increased water intake observed under these conditions was attributable to the rapid change in skin temperature. Thus, the objective of this study was to determine the effect on thermogenic drinking of a slow, as opposed to an abrupt, change in ambient temperature. The results indicated that warming room air rates of either 0.5 or 1.0 centigrade deg/min had no effect on thermogenic drinking when compared with the water intake of rats removed abruptly from cold. Thermogenic drinking does not appear to be initiated by a specific pattern of changes in peripheral temperature relative to colonic temperature.
Cerebrospinal fluid sampling technique and Astrup pH and PCO2 values
Authors: Davies D. G.
Published: December 2017

The pH and PCO2 values measured by the Astrup technique were compared in cerebrospinal fluid (CSF) obtained using two different sampling techniques: 1) a direct or in vivo technique and 2) the widely accepted syringe sampling technique. In 65 pairs of measurements in 9 dogs it was found that the pH was always overestimated and the PCO2 always underestimated in the syringe sample when compared to the in vivo sample. The equations describing the relationships are as follows: 1) pH (syringe = 0.995 pH (in vivo) + 0.084 and 2) PCO2 (syringe) = 0.873 PCO2 (in vivo) + 0.2. The amount by which the syringe sample underestimated the true PCO2 value increased with the absolute PCO2 value, consistent with the possibility of there being a diffusional loss of CO2 during the transfer of CSF from the syringe to the pH electrode (PCO2 (in vivo)- PCO2 (syringe) = 2.4, 4.9, 7.5, and 10.0 mmHg at in vivo PCO2's of 20, 40, 60, and 80 mmHg). This study indicates that the technique used for sampling CSF is crucial to the expected accuracy of the results and that the number of transfers of CSF during the sampling and measurement procedures should be minimized in order to obtain reliable results.
Interactions of human cord dorsum potential
Authors: Shimoji K. , Matsuki M. , Ito Y. , Masuko K. , Maruyama M. , Iwane T. , Aida S.
Published: December 2017

The slow positive wave (P2 wave) of the evoked spinal electrogram was recorded from the posterior epidural space in wakeful man, and studied by applying several modes of peripheral nerve stimulation. With graded stimulation the P2 wave amplitude rapidly reached the maximum at weaker stimulation than that required for the initially positive spikes (P1) and the preceding negative (N1) wave. The “second” component of the P2 appeared during stronger stimulation or during excitemenpt of the subjects. With prolonged repetitive stimulation the P2 wave increased its duration with several summits on the decaying phase. Two interactions were observed between the P2 waves produced by conditioning and testing stimulations in the same or different nerves: inhibition or occlusion by strong stimulation and faciliation by weak stimulation. Thus, the characteristic of the P2 wave in man was similar in part to that of the positive wave observed in decerebrate animals, and differnt in other ways presumably due to influences from supraspinal structures or species differences.
Effects of temperature and wind on facial temperature, heart rate, and sensation
Authors: LeBlanc J. , Blais B. , Barabe B. , Cote J.
Published: December 2017

Skin temperature measurements of the face have shown that the cheek cools faster than the nose and the nose faster than the forehead. The cooling effect of wind is maximum at wind speeds between 4.5 and 6.7 m/s. Cold winds produce significant bradycardia, which is, however, much more pronounced during the expiratory phase of respiration. A significant correlation was noted between cooling of face and the reflex bradycardia observed. Similarly, a very significant correlation was noted between drop in skin temperature and subjective evaluation of cold discomfort. Consequently, the drop in skin temperature, reflex bradycardia, and subjective evaluation are parameters which are directly affected by cold wind and can be used as adequate indicators of the degree of discomfort. When comparing the present results with the windchill index, it was found that in the zone described as “dangerously cold” the index fits well with the physiological measurements. In the zone described as “bitterly cold,” the index by comparison with actual skin temperature measurements and subjective evaluation underestimates the cooling effects of combined temperature and wind by approximately 10 degrees C.
Fibrinolytic and hemostatic changes during and after maximal exercise in males
Authors: Davis G. L. , Abildgaard C. F. , Bernauer E. M. , Britton M.
Published: December 2017

To evaluate changes in fibrinolytic activity, factor VIII and other hematological variables during and after a progressive step increment in work load, 10 healthy male subjects (22–27 yr of age) were exercised to exhaustion on an electromagnetic bicycle ergometer. Blood samples were drawn serially throughout the experiment. Little change in fibrinolytic activity was observed before 70–80% maximum heart rate (MHR) was achieved. Major changes occurred after 80% MHR. Peak values coincided with maximum exercise. In contrast major changes in factor VIII were observed between 95 and 100% MHR with peak values occurring 5–10 min postexercise. An increase in white blood cell count, platelet count, and retention was observed at maximum exercise. One individual failed to demonstrate an increase in either fibrinolytic or factor VIII activity. Relating the data to either the percent maximal oxygen uptake or percent maximal heart rate demonstrates the importance of the exercise protocol and exerting all subjects to the same relative level of physiological work.
A sensitive five-breath N2 washout test of distribution of ventilation
Authors: Weygandt G. R.
Published: December 2017

The amount of nitrogen eliminated in the first five breaths after start of oxygen breathing was compared with the amount that would be removed in these breaths, if alveolar mixing were uniform. The ratio of these two amounts is a measure of the degree of unevenness of ventilation; it was determined in 41 nonsmokers, 22 heavy smokers, and 6 patients with chronic obstructive pulmonary disease. The “five-breath index” (ratio x 100) in the nonsmokers ranged between 90 and 100. In 16 of the smokers, it was less than 87.5 (95% confidence limit of normals), although in only 5 of these, spirometric tests (MMEF) were considered abnormal. The index in the 6 patients ranged between 51 and 83. The test is highly reproducible, simple to perform, and might be of value in the detection of early lung disease.
Trapped air in ventilated excised rat lungs
Authors: Frazer D. G. , Weber K. C.
Published: December 2017

Degassed excised rat lungs were ventilated in a water-filled plethysmograph with the carina as the zero pressure reference. Pressure-volume curves were recorded from a minimum transpulmonary pressure (Pmin) of -5 cmH2O to a maximum pressure (Pmin) of 30 cmH2O. An index of the minimun volume for the lung (Vm) divided by the maximum lung volume for the same cycle (Vmax) was used as an index of the amount of air trapped within the lung. As the flow rate was decreased from 38.2 to 1.9 ml/min, there were significant increases in the amount of air trapped in the lung. As the maximum pressure was decreased to 25 and 20 cmH2O, or the minimum pressure was increased to 6 and 11 cmH2O, the amount of trapped air in the lung significantly decreased. The rate of lung inflation had a much greater influence on the amount of trapped air than either the deflation rate or stress relaxation. The results are consistent with the theory that bubbles are formed during inflation and are the main cause of air trapped in the excised lung.
VO2max during horizontal and inclined treadmill running
Authors: Kasch F. W. , Wallace J. P. , Huhn R. R. , Krogh L. A. , Hurl P. M.
Published: December 2017

The VO2max response of 12 well-trained and highly motivated college males was measured using two treadmill protocols: horizontal (H) and inclined (I). The duration of each test averaged 10 min. In the H test the treadmill bed was horizontal with the running rate held constant for the first 6 min, after which time it was increased at 1-min intervals to near maximal subject running speed, according to the HR response, until exhaustion. The I method simulated the protocol of Costill and Fox, with the treadmill speed at about 80–90% of mean maximal running rate established from 12- and 15-min track runs. The treadmill bed was held horizontal during the first 4 min, after which time it was elevated to 4% and elevated 2% each 2 min thereafter until exhaustion. No significant differences were found in VO2max, 4.267 1/min (I), and 4.192 1/min (H), average max HR, 190.4/MIN (I), and 188.9/min (H); respiratory rate, 56.4/min (I), and 62.0/min (H); and VEBTPS, 145.2 1/min (I), and 143.3 1/min (H). It was concluded that the intensities of both treadmill methods, H and I, were sufficient to produce a nonsignificant difference in maximal VO2 values with the type subjects employed.
Platelet antiserum inhibits hypoxic pulmonary vasoconstriction in the dog
Authors: Weir E. K. , Mlczoch J. , Seavy J. , Cohen J. J. , Grover R. F.
Published: December 2017

The literature suggests that platelets might help mediate the pulmonary vascular pressor response to hypoxia. This study evaluated the hypoxic response in dogs rendered acutely thrombocytopenic by the administration of platelet antiserum. Between 30 and 90 min after the antiserum the pulmonary vasoconstrictor response to hypoxia was virtually abolished, but subsequently returned at a time when the number of circulating platelets remained very low. The prior administration of meclofenamate completely preserved the hypoxic response, though the platelet count still fell precipitously. We conclude that circulating platelets are not necessary for hypoxic vasoconstriction. It is possible that the reaction between platelets and antiserum evokes the synthesis of a dilator prostaglandin which might be responsible for the temporary inhibition of the pressor response to hypoxia but this remains to be proven.
Esophageal elastance in awake and anesthetized recumbent dogs
Authors: Lai Y. L. , Rodarte J. R. , Hyatt R. E.
Published: December 2017

Esophageal elastance was measured in trained dogs placed in the prone, supine, and left lateral postures before and during sodium thiopental anesthesia. Esophageal elastance was measured from static pressure-volume curves and during spontaneous breathing at functional residual capacity. There was a significant decrease in esophageal elastance, estimated from the pressure-volume curves, during anesthesia in both prone and lateral positions but not in the supine posture. Changes in vagal tone produced by stimulation of the vagal nerves did not alter esophageal elastance. Therefore, underlying mechanisms for these changes in esophageal elastance are not fully understood. There was an increase in esophageal elastance when lung volumes increased from 55 to 80% total lung capacity. However, we did not find a significant change in esophageal elastance between awake and anesthetized conditions or between positions during spontaneous breathing at functional residual capacity.
Drug modification of hypothermia induced by CNS glucopenia in the mouse
Authors: Mager M. , Robinson S. , Freinkel N.
Published: December 2017

2-Deoxy-D-glucose (2-DG), insulin, or norepinephrine (NE), when injectedinto the cerebral ventricles of conscious mice, produce decreased rates of O2 consumption and hypothermia. These changes are accompanied by hyperglycemia with 2-DG, hypoglycemia with insulin, and normoglycemia with NE. Desipramine blocks the reduction in body temperature and O2 consumption produced by each of these agents, but does not modify significantly their effects onplasma glucose. The latter suggests that the thermal and oxidative responses to central glucopenia can be dissociated from concurrent alterations in circulating glucose. Propranolol enhances the hypothermic response produced by administered 2-DG, insulin, or NE. Phentolamine, however, antagonizes the hypothermia only with NE, indicating the 2-DG and insulin are probably not acting through the release of endogenous NE.
Method for continuous measurement of carbon dioxide output
Authors: Newell J. P. , Kappagoda C. T. , Linden R. J.
Published: December 2017

An open-circut flow-through technique for the continous measurement of carbon dioxide output in man has been described. A stream of room air is drawn past the subject who respires freely from it. The difference in the concentration of carbon dioxide between room air from which the subject inspires and the expired gas/room air mixture is measured and expressed as a voltage. This voltage is amplified by a factor proportional to the rate of flow of room air to yield a continous measurement of carbon dioxide output. This technique has no systematic error and a random error (95% tolerance limits) of +/-3.4, +/-1.7, and +/-1.4% at mean carbon dioxide outputs of 254, 846, and 1,906 ml/min, respectively.
Left ventricular effects on right ventricular developed pressure
Authors: Santamore W. P. , Lynch P. R. , Heckman J. L. , Bove A. A. , Meier G. D.
Published: December 2017

The possibility that left ventricular (LV) performance might affect right ventricular (RV) function through the myocardium was examined by using isolated, flow-perfused, paced rabbit hearts beating isovolumically. ReducingLV volume from its optimal volume to zero caused a 5.7% decrease (N = 10, Pless than 0.001) in right ventricular developed pressure (RVDP). Ligatingthe anterior ventricular branches of the left coronary artery which in the rabbit supply the LV free wall resulted in an additional 9.3% decrease in RVDP (N = 5, P = 0.05) within 3 min of ligation. Finally, cutting the LV free wall from the atrioventricular orifice to the apex (thereby preventing any developed LV free wall force during systole) caused a 45% further decrease in RVDP (N = 2, P less than 0.02). Cineradiographic study showed that the alterations in RVDP resulting from changes in LV volume and coronary occlusion correlated significantly (N = 5, P less than 0.01) with the magnitude ofseptal bulging into the RV cavity during systole. The results indicate thatalteration in LV free wall function and changes in LV volume can directly effect RVDP through the myocardium.
Influence of pericardial fluid on cardiogenic gas mixing in the lung
Authors: Fukuchi Y. , Cosio M. , Kelly S. , Engel L. A.
Published: December 2017

Respirat. Environ. Exercise Physiol. 42(1): 5–12, 1977. -In eight open-chested dogs we measured the end-inspiratory N2 concentration within 12 airways, 2.5–8.3 mm in diameter during constant flow inflations with 0.5 liter of O2 before and after the introduction of saline into the pericardial sac. The critical flow rate necessary to achieve a given end-inspiratory FN2, as well as the maximal amplitude of cardiogenic N2 fluctuations, became smaller in the presence of pericardial fluid (PF). In the presence of only 25–50 ml of saline in the pericardium the effective diffusion coefficient, incorporating cardiogenic gas mixing, decreased by as much as 50–66%, respectively. Studies in two dogs with the chest intact showed that PF caused a qualitatively similar impairment of gas mixing during breath holding. Multiple-breath N2 washouts did not reflect the decreases in gas mixing produced by PF. We believe that PF decreases cardiogenic gas mixing mainly by protecting the lung from the rotational thrust of the heart during myocardial contraction.
Lung lipid metabolism after 7 days of hydrocortisone administration to adult rats
Authors: Abe M. , Tierney D. F.
Published: December 2017

Pathogen-free rats were given either hydrocortisone (4 mg) or saline by intraperitoneal injection twice daily for 7 consecutive days. Lung weight, body weight, DNA, and total phosphatidylcholine content in lungs were equal in the saline and hydrocortisone groups. Lungs of rats receiving hydrocortisone had 23% more saturated phosphatidylcholine (P less than 0.001) and 7% less unsaturated phosphatidylcholine (P greater than 0.05). When tissue slices of these lungs were incubated with radioactive glycerol and palmitate, the incorporation of radioactivity into saturated phosphatidylcholine from animals given hydrocortisone was significantly higher (P less than 0.001 and P less than 0.05, respectively). Incorporation of radioactivity from lysophosphatidylcholine into phosphatidylcholine was 10 times greater than from glycerol or palmitate, but hydrocortisone had no effect. These results suggest that lysophosphatidylcholine may be an important precursor for phosphatidylcholine synthesis, especially saturated phosphatidylcholine, and hydrocortisone may lead to increased de novo synthesis of phosphatidylcholine.
Lung elasticity and airway dynamics in Peruvian natives to high altitude
Authors: Brody J. S. , Lahiri S. , Simpser M. , Motoyama E. K. , Velasquez T.
Published: December 2017

To evaluate the role of genetic and environmental factors in the genesis of large lungs in high-altitude natives, we measured forced vital capacity (FVC), static lung pressure-volume characteristics and maximum expiratory flow-volume loops in 17- to 20-yr-old Peruvian natives to 3,850 m (highlanders) and 800 m (lowlanders). Forced vital capacity was 5.11 +/- 0.64 liters in highlanders, 116 +/- 11% of predicted; and 3.73 +/- 0.32 liters in lowlanders, 84 +/- 7% of predicted. Lung elastic recoil at functional residual capacity and at total lung capacity, and size-corrected pressure volume curves were similar in the two groups. Despite the larger volumes in highlanders, density-corrected maximum flow rates were similar in highlanders and lowlanders, and flow expressed in FVC'S-S-1 was less in highlanders. Upstream conductance at 50% FVC expressed in fvc's-s-1-cmH2O was 0.094 +/- 0.023 in highlanders vs. 0.147 +/- 0.050 in lowlanders. Flow rates did not change in sojourners to altitude, suggesting that the lower values of highlanders were due to anatomic factors. These findings suggest that airways, which form in fetal life, do not participate in adaptation to altitude, and that the large lungs of highlanders result from postnatal environmental hypoxic stimulation of lung growth. Our results illustrate the importance of “dysynaptic” lung growth in determining patterns of adult lung function.
Air embolism with positive-pressure ventilation of rats
Authors: Kao D. K. , Tierney D. F.
Published: December 2017

Although air embolism is known to occur in humans and animals when the lung is overdistended, very few cases have been reported to be associated with positive-pressure ventilation. We have observed that air embolism occurs in rats ventilated with high inspiratory pressures (70 cmH2O) associated with high end-expiratory pressures (10 cmH2O). However, it does not occur in normal rats if the end-expiratory pressure is less than 5 cmH2O or the peak inspiratory pressure is below 60 cmH2O when the frequency of ventilation is 30. Hemorrhagic shock predisposes to air embolism, whereas conditions with pulmonary edema (fluid overloading, lung injury from ventilation with high inspiratory and low expiratory pressures, or oxygen toxicity) decrease the probability of its occurrence.
Effect of respiratory acidosis and activity on airway smooth muscle intracellular pH
Authors: Stephens N. L. , Mitchell R. W.
Published: December 2017

Previous work in our laboratory has shown that respiratory acidosis (RA) impaired mechanical function in canine tracheal smooth muscle (TSM). Since an intracellular acidosis could be brought on by the increased CO2 content of the bathing medium and alter the Km's of rate-limiting glycolytic enzymes in the pathway of energy production for contractile function, we have investigated the effects of RA on the intracellular pH (pHi) of TSM. Using the DMO method, paired unstimulated or resting TSM strips were incubated under normocapnic conditions (PO2 600 Torr, PCO2 40 Torr, pH 7.40) and RA (PO2 550 Torr, PCO2 110 Torr, pH 6.95) with 14C-labeled DMO and 3H-labeled inulin or PEG-4000. In another set of paired experiments, TSM strips were tetanized electrically every 5 min or pharmacologically throughout the incubation period (“active” muscle strips). The tissue and an aliquot of bathing medium were counted for 3H and 14C content and the values entered into the Wadell and Butler equation. The pHi's of “resting” normocapnic and acidotic strips were 7.041 +/- 0.017 (SE) and 6.752 +/- 0.012, respectively. However, the pHi's of “active” normocapnic and acidotic strips were 7.275 +/- 0.017 and 7.017 +/- 0.015, respectively. We conclude that respiratory acidosis lowers intracellular pH in both resting and mechanically active TSM's; however, “active” preparations whether exposed to normocapnia or acidosis were unexpectedly more alkaline than their “resting” counterparts.
Functions of selected biochemical systems from the exercised-trained dog heart
Authors: Sordahl L. A. , Asimakis G. K. , Dowell R. T. , Stone H. L.
Published: December 2017

Mitochondria and sarcoplasmic reticulum (SR) fractions were isolated from exercised-trained (E-T) and sedentary control dog hearts. Measurements of mitochondrial respiratory functions indicated no changes in energy-producing (ATP synthesis) capacity in mitochondria from E-T compared to control dog hearts. However, the ability of isolated mitochondria from E-T hearts to retain accumulated calcium was markedly decreased compared to controls. Inhibition of mitochondrial rates of calcium uptake with the inhibitor, ruthenium red, revealed fewer binding and/or transport sites in mitochondrial membranes from exercised-trained heart preparations. ATP-dependent binding (- oxalate) and uptake (+ oxalate) of calcium by SR preparations from E-T hearts were unchanged compared to controls. In contrast, significant differences in the rates of release of bound calcium were found in SR isolated from E-T hearts. Total myocardial protein, nucleic acids, and connective tissue levels were unchanged in E-T hearts compared to controls. The results suggest subtle changes are occurring in the energy-utilizing mechanism(s) involving calcium transport of the myocardial cell during exercise training. These changes may be related to alterations in the performance of the exercised-trained heart.
Critical size of newborn homeotherms
Authors: Balmer R. T. , Strobusch A. D.
Published: December 2017

It is shown that for cylindrical and spherical bodies there is a critical radius below which the addition of any form of insulation to the body will increase rather than decrease the cooling of the body. It is proposed, therefore, that it would be thermally detrimental to newborn homeotherms to be born with a protective covering (fur or down) if their body size were less than this critical size, and consequently that the degree of natal covering is not necessarily related to the overall development of the species when the birth size is less than this critical size. A critical weight is derived from the critical radius for basically spherical animals which compares favorably with typical birth weights of various altricial homeotherms. The effect of the overall conductive-convective heat transfer caused by a basically cylindrical animal rolling up into a ball is also discussed.
Inversion of Fahraeus effect and effect of mainstream flow on capillary hematocrit
Authors: Yen R. T. , Fung Y. C.
Published: December 2017

The well known Fahraeus effect (1929) states that if whole blood is allowed to flow from a large reservoir into a small circular cylindrical tube, the hematocrit in the tube is smaller than that in the reservoir, and the smaller the tube, the smaller will be the tube hematocrit. This is interpreted as a feature of particulate flow. We find that this relationship is not monotonic in a model experiment in which gelatin particles (circular disks) are suspended in a silicone fluid to simulate blood. When the diameter of the underformed cell is equal to or greater than the tube diameter, the volume fraction of the cells in the tubes increases to a value equal to or greater than that in the reservoir. Thus the Fahraeus effect has a point of inversion. Additional experiments show that the hematocrit in the tube could be greatly influenced by the flow condition outside the entrance of the tube. If the tube is perpendicular to the main direction of flow in the reservoir (as is the case of Barbee and Cokelet's experiment, or in most arteriole-capillary junctions), the velocity gradient and the velocity of flow in the reservoir just outside the entrance to the tube affects the hematocrit in the tube.
Correction of water content and solute concentration in blood during hemoconcentration
Authors: Ohira Y. , Ito A. , Ikawa S.
Published: December 2017

Eleven, healthy male students were subjected to an exhaustive bicyle ergometer exercise. Many parameters of hemoconcentration were examined in blood and urine samples which were collected before and after exercise. In an exercise lasting approximately 10 min, it was found that serum total protein (STP) would be a suitable parameter that could be used to calculate water content and actual decrease in water volume in blood due to exercise. Further, it is described how STP values before and during hemoconcentration can be used to eliminate the effect of plasma water loss from the determined values of various solute levels in blood.
Predominant site of flow limitation and mechanisms of postexertional asthma
Authors: McFadden E. R. , Ingram R. H. , Haynes R. L. , Wellman J. J.
Published: December 2017

To determine if a relationship existed between the site of airway obstruction and the mechanisms of exercise-induced asthma, we studied the predominant site of flow limitation, as determined by the mid-vital capacity ratios of maximal expiratory flow with air (Vmax air) and 80% helium-20% oxygen (Vmax He-O2), before and after physical exertion in 12 asthmatics. These observations were then related to the effects seen after vagal blockade and inhibition of mediator release. Five subjects increased Vmax He-O2/Vmax air ratios suggesting that the predominant site of flow limitation was in large airways. This group had their postexercise bronchospasm abolished by pretreatment with an anticholinergic agent. Seven subjects decreased their flow ratios indicating predominant small airway obstruction. Anticholinergic agents, although producing bronchodilation, did not alter their bronchospastic response to exercise. However, pretreatment with disodium cromoglycate did significantly diminish the response of this group. Thus the airway response to exercise in asthmatics is heterogeneous in terms of predominant site of flow limitation and this factor appears to relate to mechanisms.
Limits on VA/Q distributions from analysis of experimental inert gas elimination
Authors: Evans J. W. , Wagner P. D.
Published: December 2017

Distributions of ventilation-perfusion ratios (VA/Q) actually present in the lung cannot be exactly recovered using current inert gas elimination methods, principally because of the limited number of gases and errors in their measurement. The amount of information that can be gained is studied here. When six gases are used the results are difficult to visualize so that a graphical analysis is first given for only two gases. Methods are proposed for 1) the probabilistic description of retentions compatible with a set of measured values of all six gases, and 2) the placing of limits on the associated VA/Q distributions. It is found that the variability among distributions with compatible retentions depends greatly on the particular set of data. Distributions consisting of a single or of two separated narrow modes can be identified reliably.
Effect of breathing helium-oxygen on static lung volumes and lung recoil in normal man
Authors: Hutcheon M. A. , Rodarte J. R. , Hyatt R. E.
Published: December 2017

Static lung volumes and static elastic recoil pressure (Pel) were measured in normal subjects breathing air and 80% helium plus 20% oxygen (He+O2). In 22 subjects, He+O2 produced small but significant increases in total lung capacity (TLC) (mean 0.11 liter, P less than 0.001) and residual volume (mean 0.10 liter, P less than 0.01) without change in vital capacity or functional residual capacity. The mechanisms for this change are obscure. In 10 subjects, breathing He+O2 had no significant effect on Pel (paired t-test) at any lung volume measured (50–80% TLC). In one subject, Pel at 70 and 80% TLC was significantly higher on air than on He+O2 (unpaired t-test, P less than 0.05). Because changes in lung volumes and lung recoil were small, we concluded that these effects do not negate the clinical utility of He+O2 flow-volume curves.
Immersion diuresis in dogs
Authors: Davis J. T. , DuBois A. B.
Published: December 2017

The mechanism of diuresis during the 1st h of immersion was investigated using anesthetized dogs. Four different experiments were carried out. First, left atrial transmural pressure was measured before, during, and after immersion. The data suggest that, although the left atrium may or may not be stretched depending on the conditions of immersion, the amount of diuresis is independent of the amount of left atrial stretch, and therefore a causal relationship between diuresis and left atrial stretch could not be established. Second, bilateral cervical vagotomy was carried out. Immersion diuresis sometimes occurred despite this vagotomy, suggesting that the left atrial stretch reflex was not participating in those cases. Third, negative-pressure breathing was carried out to simulate the negative transthoracic pressure associated with uncompensated immersion. The average left atrial transmural pressure did not change. A slight hemodilution and a moderate diuresis occurred. There was no correlation between changes in left atrial transmural pressure and changes in urine ouput. Fourth, blood studies were done on splenectomized dogs subjected to immersion. Hemodilution occurred and was most marked in dogs which had had their kidneys removed. The hemodilution is sufficient to explain the early phase of the immersion diuresis. The data suggest that, in anesthetized dogs, hemodilution is the probable initiator of diuresis upon immersion and that, in dogs, left atrial stretch is unrelated to diuresis during immersion or negative-pressure breathing.
Response of immunosympathectomized rats to training
Authors: Paynter D. E. , Tipton C. M. , Tcheng T. K.
Published: December 2017

The influence of chronic exercise was investigated with male rats assigned to normal (N) and sympathectomized (IS) groups. Animals in the latter group were injected daily for 5 days with the antiserum to the nerve growth factor beginning 24 h after birth. Training was introduced when the animals were 35--45 days old and lasted for 12 wk. The exercise program used by both groups was progressive in nature and modified in accordance with the performance capability of the IS animals. When IS and N rats performed a standardized treadmill test, the IS rats had significantly higher rectal temperatures than normal animals. Significant training differences were observed in resting heart rate and in mean blood pressures, but only in the N animals. However, both trained groups exhibited significantly less vasoconstricting ability to conditions of lower body negative pressure than their nontrained controls. Varied doses of epinephrine and norepinephrine were injected into both groups and training per se had no significant influence on the responses recorded. However, both IS group had changes which indicated that a supersensitivity to catecholamines had occurred. Although selective training adaptations can occur without sympathetic nerves, it was concluded that an intact nervous system was essential for maximal training effects to occur.
Preparation of matched reagents for use with the Scholander gas analyzer
Authors: Collins R. G. , Musasche V. W. , Howley E. T.
Published: December 2017

Scholander's method of gas analysis requires that the solutions for CO2 absorber, O2 absorber, and acid-rinse be matched in terms of water vapor tension throughout the analysis. Any difference in vapor pressure between either or both of the absorbing solutions and the indicator drop (composed of acid-rinse) will produce a measurable volume change which cannot be attributed to the presence of absorbable gases. This paper describes a practical and quantitative method for preparing reagents whose vapor pressures are matched. A fixed acid-rinse formulation was used throughout. A CO2 absorber prepared from 1.35 N KOH and an O2 absorber prepared from 0.76 N KOH were both matched in terms of vapor pressure with Scholander's acid-rinse solution. Analysis of atmospheric air provided a check on the accuracy of the technique. The values obtained were O2 20.94%, CO2 0.03%, and N2 (balance) 79.04%.
Changes in airway mast cells and histamine caused by antigen aerosol in allergic dogs
Authors: Gold W. M. , Meyers G. L. , Dain D. S. , Miller R. L. , Bourne H. R.
Published: December 2017

We studied the effect of inhaled specific antigen on airflow resistance, histamine concentration, and mast cell numbers in airway tissues in allergic dogs. In each of six allergic dogs with open chests, inhalation of specific antigen aerosol (Ascaris suum) increased airflow resistance from 0.30+/-0.40 (mean+/-SE) to 2.8+/-0.41 cmH2O/1 per s (P less than 0.05); decreased mast cell number from 38.6+/-3.2 to 24.3+/-4.5 mast cells/mm2 (P less than 0.05); decreased histamine (per mg airway tissue) from 5.3+/-0.4 to 3.5+/-0.2 ng (P less than 0.05) in lobar bronchi 5–7 mm in diam; and released histamine into the blood perfusing the lung, control arterial plasma histamine; 2.8+/-0.64 ng/ml; antigen: 154+/-1.7 ng/ml (P less than 0.005). Specific antigen caused no significant changes in mast cells or histamine in bronchi 1–2 mm in diam. Control aerosols of nonspecific antigen or methacholine did not change levels of mast cells or histamine in airway tissues. These results suggest that experimental canine asthma involves local airway reactions with degranulation of mast cells and histamine release, as well as vagally mediated reflex bronchoconstriction.
Diaphragmatic function during immersion
Authors: Minh V. D. , Dolan G. F. , Linaweaver P. G. , Friedman P. J. , Konopka R. G. , Brach B. B.
Published: December 2017

Diaphragmatic function during immersion to midneck level was studied in upright mongrel dogs, using constant electrophrenic stimulation. Effectiveness of diaphragmatic contraction was analyzed in terms of inspired volume (VT) (with airways open), and change in intrathoracic pressure (Pmus) (with the respiratory system occluded). Hydrostatic compression of the immersed body decreased functional residual capacity (FRC) to 55% base-line value (FRCO), resulting in a 2.8-fold increase in Pmus. In spite of this Pmus increase, VT often decreased during immersion, averaging only 83% VTO (base-line value in air). Hence, immersion was associated with a marked stiffening of the respiratory system. The Pmus increase during immersion persisted after restoration of FRC to FRCO, and was related to diaphragmatic length being greater in water than in air under condition of iso-lung volume. In all, there were three factors affecting diaphragmatic function during immersion: FRC reduction, change in thoracic configuration, and stiffening of the respiratory system.
Recurrent heat exposure: enzymatic responses in resting and exercising men
Authors: Francesconi R. P. , Maher J. T. , Bynum G. D. , Mason J. W.
Published: December 2017

Heat acclimatization was induced in a group of healthy male test subjects by repetitive treadmill walking (5.6 km-h-1, 49 degrees/27 degrees C dry/wet bulb, 90 min-day-1, 7 days). A second group of men, paired for maximal O2 consumption and body weight, remained sedentary under identical environmental conditions. Total plasma protein increased significantly after 45 (P less than 0.05) and 90 (P less than 0.025) min of exercise on the first day of heat exposure, yet after 7 days no increments occurred. Even after heat acclimatization was achieved (day 7), plasma levels of creatine phosphokinase increased during the 90-min walk in the heat (time O vs. 90, P less than 0.025), as was also the case on day 1 (P less than 0.05). Levels of lactate dehydrogenase, glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase were not significantly affected by exercise in the heat either before or after heat acclimatization. No correlations could be drawn between base-line enzyme levels and state of physical conditioning.
Relationship of thoracic volume and airway occlusion pressure: muscular effects
Authors: Eldridge F. L. , Vaughn K. Z.
Published: December 2017

The occluded airway pressure generated by contraction of inspiratory muscles was measured in spontaneously breathing, anesthetized, vagotomized cats at thoracic volumes below, at, and above true FRC (range, -8 to +28 ml/kg). A relatively constant neural drive at all volumes was shown by recordings of integrated phrenic nerve and external intercostal muscle activities. Peak occlusion pressure declined progressively with increasing thoracic volume and increased with occlusion volumes below FRC. Occlusion pressures measured early in inspiration (0.3 and 0.5 s) decreased similarly. Since occluded airway pressure was a satisfactory index of muscle force output of all inspiratory muscles, the study demonstrates that inspiratory muscle performance decreases with increasing thoracic volume throughout the range studied. Analysis of all occluded breaths shows that, quantitatively, the decline in muscle performance from that occurring at true FRC was -1.9% per ml/kg volume change from FRC. Zero effective muscle pressure generation occurred at 52 ml/kg above FRC, or 2.8 times FRC. These findings have important implications for the use of occlusion pressures and ventilatory responses in respiratory control system studies, since changes in FRC may affect muscle performance.
Influence of exercise and heat stress on pulmonary function during ozone exposure
Authors: Folinsbee L. J. , Horvath S. M. , Raven P. B. , Bedi J. F. , Morton A. R. , Drinkwater B. L. , Bolduan N. W. , Gliner J. A.
Published: December 2017

We studied the effects of a 2-h exposure to ozone (0.5 ppm) in 14 nonsmoking males under four environmental conditions (WBGT (wet bulb-globe temperature index) = 64.4, 80.0, 85.2, and 92.0 degrees F). The subjects were divided into two groups, A (n = 8) and B (n = 6). Thirty minutes of exercise at 40% Vo2 max was performed from 60 to 90 min for group A and 30 to 60 min for group B. Pulmonary function changes, determined throughout exposure, were greatest immediately after exercise in both groups. Few changes occurred before the exercise period. However, the decrease in FVC (826 ml) and FEV1.0 (937 ml) following exercise was more than twice as large as the decrement seen at end exosure (388 and 423 ml, respectively). Measures of maximum expiratory flow (FEF 25–75%, FEF 50% FEF 75%) showed similar reductions. In many cases, reversal of these changes occurred during the remainder of the exposure period. The greatest decrease in FVC occurred when heat and ozone exposures were combined (WBGT = 92.0 degrees F). We conclude that the effects of ozone are most severe immediately after exercise and that heat stress may modify the overall effect of ozone on pulmonary function.
Respiratory patterns during progressive asphyxia in newborn rabbits
Authors: Lawson E. E. , Thach B. T.
Published: December 2017

During acute progressive asphyxia an abrupt transition occurs from regular respiratory efforts to primary apnea and gasping. To study this transition we measured inspiratory duration (TI), expiratory duration (TE), maximal inspiratory tracheal pressure (Pmax), electromyographic activity (EMG) of different muscle groups, and the electrocorticogram (ECoG) of 3- to 5-day-old rabbits following airway occlusion at functional residual capacity (FRC). The onset of primary apnea was associated with other central nervous system events as indicated by decerebrate posture and maximal EMG activity which were followed by relaxation, loss of EMG activity, and an isoelectric ECoG. Indices of inspiratory drive (Pmax and Pmax/TI) were preserved or accentuated following primary apnea despite a reduction of overall respiratory activity (frequency X Pmax). The onset of primary apnea appears to be due to interruption of the respiratory cycling controls rather than failure of the respiratory center which regulates inspiratory force. Gasping appears to be linked with progressive changes in respiratory patterns which are observed prior to primary apnea. These findings do not support the concept of a “gasping” center.
Effect of SO2 on control of breathing in anesthetized cats
Authors: Grunstein M. M. , Hazucha M. , Sorli M. H. , Milic-Emili J.
Published: December 2017

In seven anesthetized tracheotomized cats we studied the acute respiratory effects of SO2 inhalation at different steady-state levels of arterial CO2 tension (Paco2). During room air breathing, SO2 (0.05%) addition caused a progressive reduction in tidal volume (VT) and increases in both respiratory frequency (f) and pulmonary resistance (RL). Atropine sulfate abolished the bronchoconstriction response to SO2 and thus permitted the study of the influence of SO2 on VT and f in the absence of constricted airways. Despite marked reductions in the VT VS. PaCO2 relationships with SO2 exposure after atropine, the relationship between pulmonary ventilation (VE) and PaCO2 was not signifcantly altered. This was the case since SO2 caused solely a reduction in inspiratory duration (Ti), affecting neither the mean rate of rise of inspiratory activity (i.e., VT/Ti) nor the relationship between Ti and breath duration. Thus, airways irritation with SO2 produced rapid, shallow breathing characterized by a shortening of inspiratory and total respiratory cycle times with no change in the rate of development of inspiratory activity. The findings suggest an influence exclusively concerned with the timing of inspiration. Perhaps premature onset of inspiratory activity accounts for the observed effects.
Effect of aging alone on mechanical properties of the normal adult human lung
Authors: Knudson R. J. , Clark D. F. , Kennedy T. C. , Knudson D. E.
Published: December 2017

For plethysmographic studies of respiratory mechanics, we selected, from a general population, 51 subjects, aged 25–75 yr, who had never smoked, had no present or past cardiorespiratory symptoms or disease, were alpha1-antitrypsin MM phenotypes, and were normal by physical examination, vectorcardiography, and chest roentgenography. Approximately equal numbers of men and women were represented in each of three age groups; 25–35, 36–64, and 65–75. Both sexes demonstrated loss of lung elastic recoil with age, most significant at high lung volumes, but the rate of loss was less than previously reported. Males had higher lung recoil than females of comparable age, but if lung size was taken into account, there were no sex differences in bulk elastic properties. Maximum expiratory flow diminished with age only at low volumes, suggesting that equal pressure points are more centrally located at low lung volumes in the elderly.
Contribution of a net transmembrane HCO3- flux to intracellular acid-base regulation
Authors: Strome D. R. , Clancy R. L. , Gonzalez N. C.
Published: December 2017

Experiments were performed to determine the relative effects of a net extracellular-to-intracellular HCO3- flux and of elevated carbon dioxide tension (PCO2) on cellular acid-base regulation. Isolated rabbit hearts were perfused by recirculating a small volume of Ringer solution in which the PCO2 and the HCO3- concentration could be independently altered. Net HCO3- flux was assessed by the disappearance of HCO3- from perfusate. Between 40 and 100 Torr PCO2, a HCO3- flux into the cell occurs only when perfusate HCO3- concentration is increased. Therefore, by selective manipulation of perfusate HCO3- and PCO2 it is possible to induce hypercapnia with or without an accompanying HCO3- flux. When perfusate HCO3- concentration was increased from 20 to 36 mM, cellular HCO3- concentration increased from 22.5 +/- 0.8 to 26.1 +/- 1.0 mM at 40 Torr PCO2 and from 27.8 +/- 0.7 to 34.1 +/- 1.4 mM at 98 Torr PCO2. These increases can be accounted for by the amount of HCO3- that disappeared from the perfusate. The results suggest that most of the initial cell CO2 buffering is provided by the net HCO3- flux in addition to the passive physicochemical buffering.
Autonomic blockade and coronary catecholamines and cyclic AMP in exercising man
Authors: Robson R. H. , Fluck D. C.
Published: December 2017

To assess in man the effects of autonomic blockade on the response of catecholamines in the coronary circulation to dynamic exercise, arterial and coronary sinus catecholamine concentrations were measured in six patients during supine cycling exercise, following atropine 1.8 mg and oxprenolol 0.2 mg/kg iv. Although arterial concentrations did not increase significantly, coronary sinus catecholamine concentrations increased from 2.54 +/- 0.59 nmol/1 at rest 4.44 +/- 1.3 nmol/1 during exercise (P less than 0.05; one-tailed test) and were associated with a small increase in heart rate and coronary sinus cyclic AMP concentrations from 9.4 +/- 0.7 nmol/1 (rest) to 11.6 +/- 1.1 nmol/1 (exercise) (0.05 greater than P greater than 0.01). Although autonomic blockade may have increased catecholamine release, this was not reflected in an increased efflux of catecholamines from the heart, because similar increases in coronary sinus catecholamine concentrations occurred in the absence of autonomic blockade.
Effect of positive end-expiratory pressure on intracranial pressure in dogs
Authors: Huseby J. S. , Pavlin E. G. , Butler J.
Published: December 2017

Application of positive end-expiratory pressure to dogs with noncardiogenic pulmonary edema increased intracranial pressure (measured as cerebrospinal fluid pressure) and decreased cerebral perfusion pressure. The magnitude of these changes depended on the amount of end-expiratory pressure applied and the lung compliance.