bluuebunny/crossref_metadata_2025 huggingface dataset:
A morphometric study of the carotid body in chronically hypoxic rats
Authors: McGregor K. H. , Gil J. , Lahiri S.
Published: December 2017

We performed morphometric studies of carotid body in acutely and chronically hypoxic rats (inspired PO2 = 70 Torr, at sea level). Acute exposure was for the duration of about 10 min, and chronic exposure lasted for 28 days. We confirmed that the total volume of the organ increased by severalfold. At the light-microscopy level we found an enlargement of the volume density of the blood sinuses from 14 to 31% due to chronic hypoxia. The morphometric hematocrit increased from 39 to 70% paralleling changes in the conventionally measured venous hematocrit. These data do not show any specific plasma skimming in the carotid body blood vessels. With the electron microscope we found that the mean average volume of type I cells increased from 320 micron3 in controls to 1,120 micron3 in the chronically hypoxic rats without hyperplasia, whereas type II cells had increased in number without alteration in size. Qualitative observations revealed that the normal appearance of clusters of ovoid type I cells interspersed by capillaries had been transformed into a pattern of individual cells forming plates between expanded blood vessels with a large increase of contact area between the cells and vessels. Type II cells appeared to have proliferated without changes in individual size to cover the enlarged periphery of type I cells. The observed structural changes in the carotid body parenchyma and vasculature appear to be physiologically adaptive and provide further support for the idea that various elements in the organ are particularly sensitive to hypoxia.
Pulmonary resistance and compliance by auto- and cross-correlation functions of transpulmonary pressure and flow
Authors: Clement J. , Bobbaers H. , Schepers R. , Van de Woestijne K. P.
Published: December 2017

A technique is described on how to calculate the pulmonary resistance and compliance from the higher order harmonics present in mouth flow and transpulmonary pressure signals during spontaneous breathing. The estimates of resistance and compliance (or rather reactance) obtained from these harmonics following a conventional Fourier transform are not reliable because of a lack of reproducibility. This is obviated by a preliminary smoothing of the signals by means of auto- and cross-correlation functions. Both the conventional and the modified technique yield identical results for the fundamental component of breathing.
Effect of a single breath of 100% oxygen on respiration in neonates during sleep
Authors: Aizad T. , Bodani J. , Cates D. , Horvath L. , Rigatto H.
Published: December 2017

To determine the effect of a single breath of 100% O2 on ventilation, 10 full-term [body wt 3,360 +/- 110 (SE) g, gestational age 39 +/- 0.4 wk, postnatal age 3 +/- 0.6 days] and 10 preterm neonates (body wt 2,020 +/- 60 g, gestational age 34 +/- 2 wk, postnatal age 9 +/- 2 days) were studied during active and quiet sleep states. The single-breath method was used to measure peripheral chemoreceptor response. To enhance response and standardize the control period for all infants, fractional inspired O2 concentration was adjusted to 16 +/- 0.6% for a control O2 saturation of 83 +/- 1%. After 1 min of control in each sleep state, each infant was given a single breath of O2 followed by 21% O2. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), alveolar O2 and CO2 tension, O2 saturation (ear oximeter), and transcutaneous O2 tension were measured. VE always decreased with inhalation of O2 (P less than 0.01). In quiet sleep, the decrease in VE was less in full-term (14%) than in preterm (40%) infants (P less than 0.001). Decrease in VE was due primarily to a drop in VT in full-term infants as opposed to a fall in f and VT in preterm infants (P less than 0.05). Apnea, as part of the response, was more prevalent in preterm than in full-term infants. In active sleep the decrease in VE was similar both among full-term (19%) and preterm (21%) infants (P greater than 0.5). These results suggest greater peripheral chemoreceptor response in preterm than in full-term infants, reflected by a more pronounced decrease in VE with O2. The results are compatible with a more powerful peripheral chemoreceptor contribution to breathing in preterm than in full-term infants.
Surrounding structures affect pressure-diameter behavior of excised dog bronchi
Authors: Nakamura M. , Luchtel D. L. , Ikeda Y. , Sasaki H. , Okubo T. , Takishima T. , Hildebrandt J.
Published: December 2017

The effects of adjacent large blood vessels, fibroelastic membrane, and parenchyma on pressure-diameter (P-D) behavior of intrapulmonary bronchi were studied in five dog lung lobes. Central lobar airways were inflated separately by blocking all branches with beads and inflating the distal lobar air spaces via pleural capsules. After bronchial P-D curves were obtained at fixed pleural pressures (Ppl) of -30, -10, and -5 cmH2O, the P-D properties of the isolated bronchi were measured in each of four stages of dissection: 1) lobar artery and vein were left attached to the bronchus, but parenchyma was removed to within 1-2 mm of the limiting membranes; 2) all remaining parenchyma was carefully removed; 3) the large vessels were removed, leaving the bronchial fibroelastic membrane intact; and 4) the fibroelastic membrane was peeled from the bronchus. From stage 1 it was deduced that in the intact lobes, peak peribronchial parenchymal stress (Px) averaged -29.2 cmH2O at Ppl = -30 cmH2O). In stage 2 bronchial recoil was reduced only approximately 5%. The major decrease (approximately 35%) occurred in stage 3, indicating that interaction between vessels and bronchi contributed significantly to bronchial stiffness. A final decrease of approximately 10% was seen in stage 4. We conclude that Px in the intact state is similar to Ppl at a transpulmonary pressure of 30 cmH2O and that stages 1 or 2 may provide a better basis for estimating Px than the commonly employed bronchus free of vessels and tissue.
Circulation and acid-base balance in exercising goats at different body temperatures
Authors: Feistkorn G. , Nagel A. , Jessen C.
Published: December 2017

Thirty experiments were performed in two goats at an air temperature of +35 degrees C and a relative humidity of 33%. By means of heat exchangers, body core temperature (Tpaor) was adjusted to 39, 40.5, or 42 degrees C and maintained at these levels for 120 min. During the last 60 min the animals worked at a rate of 1.2 W/kg (treadmill, 3 km/h, 15%). Blood gases (arteriovenous O2 difference, Po2, Pco2), hemoglobin (Hb), blood lactate (LA), cardiac output (CO), blood pressure (MAP), heart rate (HR), metabolic rate (M), and respiratory evaporative heat loss (REHL) were determined. M, CO, HR, and Hb increased with exercise and were independent of Tpaor. At rest and exercise, REHL increased and Pco2 decreased at higher levels of Tpaor resulting in a respiratory alkalosis. During exercise this was accompanied by an increase in LA. At all instants, the concentrations of LA were higher at higher Tpaor. It is concluded that in a virtually nonsweating species like the goat the overall stress on the circulatory system caused by hyperthermia during exercise is relatively small while the behavior of blood LA is indicative of a temperature-dependent accumulation of LA also in the exercising muscle.
Respiratory responses to noxious and nonnoxious heating of skin in cats
Authors: Waldrop T. G. , Millhorn D. E. , Eldridge F. L. , Klingler L. E.
Published: December 2017

Respiratory responses to increased skin temperatures were recorded in anesthetized cerebrate and in unanesthetized decerebrate cats. All were vagotomized, glomectomized, and paralyzed. Core body temperature and end-tidal Pco2 were kept constant with servoncontrollers. Stimulation of cutaneous nociceptors by heating the skin to 46 degrees C caused respiration to increase in both cerebrate and decerebrate cats. An even larger facilitation of respiration occurred when the skin temperature was elevated to 51 degrees C. However, respiration did not increase in either group of cats when the skin was heated to 41 degrees C to activate cutaneous warm receptors. The phenomenon of sensitization of nociceptors was observed. Spinal transection prevented all the respiratory responses to cutaneous heating. We conclude that noxious, but not nonnoxious, increases in skin temperature cause increases in respiratory output.
Increased microvascular permeability in dog lungs due to high peak airway pressures
Authors: Parker J. C. , Townsley M. I. , Rippe B. , Taylor A. E. , Thigpen J.
Published: December 2017

The effect of peak airway pressure (Paw) on vascular permeability and the "safety factor" against edema formation was determined in isolated blood-perfused lower lobes of dog lungs. Microvascular permeability was evaluated using the measured filtration coefficient (Kf,C), isogravimetric capillary pressure (Pc,i), and critical capillary pressure (Pcrit) for exhaustion of tissue safety factors. Airway pressure was maintained constant at -3 cmH2O except for the test period of 20 min when the lungs were ventilated at 6/min with sufficient volume to generate a peak inflation pressure ranging from 5 to 60 cmH2O. Mean Kf,C (in ml X min-1 X cmH2O X 100 g-1) were measured before and immediately after the period of peak airway pressures. Kf,C was significantly increased in all lungs where Paw exceeded 42 cmH2O, but in only two experiments at a lower Paw. Mean Pc,i was significantly reduced from control in the 45-55 and 55-65 cmH2O Paw groups, and both Pc,i and Pcrit were found to be inversely related to Kf,C measured after Paw ventilation. These data indicate that ventilation with Paw above 42 cmH2O (30.9 Torr) and in some cases lower pressures for 20 min significantly increased capillary hydraulic conductivity, reduced the effective osmotic effect of plasma proteins at the capillary wall, and reduced the total tissue safety factor against edema formation.
Time course of loss of adaptations after stopping prolonged intense endurance training
Authors: Coyle E. F. , Martin W. H. , Sinacore D. R. , Joyner M. J. , Hagberg J. M. , Holloszy J. O.
Published: December 2017

Seven endurance exercise-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Maximal O2 uptake (VO2 max) declined 7% (P less than 0.05) during the first 21 days of inactivity and stabilized after 56 days at a level 16% (P less than 0.05) below the initial trained value. After 84 days of detraining the experimental subjects still had a higher VO2 max than did eight sedentary control subjects who had never trained (50.8 vs. 43.3 ml X kg-1 X min-1), due primarily to a larger arterial-mixed venous O2 (a-vO2) difference. Stroke volume (SV) during exercise was high initially and declined during the early detraining period to a level not different from control. Skeletal muscle capillarization did not decline with inactivity and remained 50% above (P less than 0.05) sedentary control. Citrate synthase and succinate dehydrogenase activities in muscle declined with a half-time of 12 days and stabilized at levels 50% above sedentary control (P less than 0.05). The initial decline in VO2 max was related to a reduced SV and the later decline to a reduced a-vO2 difference. Muscle capillarization and oxidative enzyme activity remained above sedentary levels and this may help explain why a-vO2 difference and VO2 max after 84 days of detraining were still higher than in untrained subjects.
High surface tension pulmonary edema induced by detergent aerosol
Authors: Nieman G. F. , Bredenberg C. E.
Published: December 2017

The effect of the detergent dioctyl sodium sulfosuccinate on pulmonary extravascular water volume (PEWV) was studied in adult anesthetized mongrel dogs. The detergent was dissolved as a 1% solution in a vehicle of equal volumes of 95% ethanol and normal saline and administered by ultrasonic nebulizer attached to the inspiratory tubing of a piston ventilator. Two hours following detergent aerosol PEWV measured gravimetrically was increased compared with either animals receiving no aerosol or those receiving an aerosol of vehicle alone. Loss of surfactant activity and increased alveolar surface tension were demonstrated by Wilhelmy balance studies of minced lung extracts, by a fall in static compliance, and by evidence of atelectasis and instability noted by gross observation and by in vivo microscopy. No significant changes in colloid oncotic pressure or pulmonary microvascular hydrostatic pressure were observed. These data suggest that pulmonary edema can be induced by increased alveolar surface tension and support the concept that one of the major roles of pulmonary surfactant is to prevent pulmonary edema.
Cardiovascular reactions to cold exposures differ with age and gender
Authors: Wagner J. A. , Horvath S. M.
Published: December 2017

This study was conducted since virtually no information was available concerning age- and gender-related differences in cardiovascular adjustments to cold exposure. Men and women between the ages of 20 and 30 and 51 and 72 yr, wearing swim suits, rested for 2 h in 28, 20, 15, and 10 degrees C ambient temperatures (Ta), with 40% relative humidity. Cardiac output (Qc) and stroke volumes (Qs) were higher in younger than older subjects regardless of Ta. Cardiac output was not influenced by gender, but all cold exposures resulted in increased Qs and decreased heart rate in men but not women. Regardless of age or gender, Qc increased about 10% only during exposure to 10 degrees C. Cold exposure resulted in minimal increases in the mean systolic and diastolic pressures (Pa) of the younger subjects. The Pa of older subjects were higher than in the young during 28 degrees C exposures and increased during all cold exposures. Total peripheral resistance and forearm blood flows were higher in older than young subjects exposed to cold. Total peripheral resistance, systolic and diastolic Pa, and finger and forearm blood flows were not affected by gender, but hand plus forearm blood flows were higher in men than women exposed to 28 degrees C. Although Qc appeared adequate to meet increased oxygen demands of shivering in the older subjects, rising Pa may become limiting in extended exposures. A similar response in hypertensive or angina-prone individuals may result in some untoward responses.
Effect of cold exposure on liver and muscle cAMP content and cAMP phosphodiesterase activity
Authors: Palmer W. K. , Kane T. A. , Bach F. , Doukas S.
Published: December 2017

Adenosine 3′,5′-cyclic monophosphate (cAMP) concentration and 3′,5′-cyclic-nucleotide phosphodiesterase (PDE) activity were measured in skeletal muscle, heart, and liver of rats exposed to 1, 3, 5, and 7 days of cold. Cyclic nucleotide concentration increased in fast-twitch red muscle at the same time that PDE activity was decreasing. Nucleotide concentration and enzyme activity of slow-twitch red muscle were not altered by the cold exposure. The PDE activity of fast-twitch white muscle was elevated approximately 50% above control after 1 and 3 days of cold exposure. By the 5th day in the cold, white muscle PDE activity had returned to control levels and remained there through the 7th day of experimentation. cAMP concentration in hearts of cold-exposed rats was significantly (P less than 0.01) elevated above control at all time points measured. Myocardial PDE activity was elevated above control (P less than 0.05) at 1 and 3 days of cold exposure but returned to control levels by the 5th day in the cold. Hepatic cAMP and PDE activity were elevated above control at all time points analyzed. These data suggest that changes in cyclic nucleotide metabolism play a role in attaining homeostasis during acute cold exposure.
Dexamethasone and indomethacin modify endotoxin-induced respiratory failure in pigs
Authors: Olson N. C. , Brown T. T. , Anderson D. L.
Published: December 2017

We studied the porcine pulmonary response to endotoxemia before and after administration of nonsteroidal antiinflammatory drugs (NSAID, i.e., indomethacin or flunixin meglumine) or dexamethasone (DEX). Escherichia coli endotoxin was infused intravenously into anesthetized 10- to 12-wk old pigs for 4.5 h. In endotoxemic pigs, the phase 1 (i.e., 0–2 h) increases in pulmonary arterial pressure, pulmonary vascular resistance (PVR), and alveolar-arterial O2 gradient and the decreases in cardiac index (CI) and lung dynamic compliance (Cdyn) were blocked by NSAID. Thus phase 1 changes were cyclooxygenase dependent. Furthermore, these effects were blocked or greatly attenuated by DEX. During phase 2 of endotoxemia (i.e., 2–4.5 h), the increased PVR and decreased CI and Cdyn were not blocked by NSAID but were attenuated by DEX, suggesting the presence of cyclooxygenase-independent metabolites. Both NSAID and DEX blocked the endotoxin-induced increases in lung water, bronchoalveolar lavage (BAL) neutrophil, and BAL albumin content. The fall in plasma proteins persisted in NSAID but not DEX-treated pigs. We conclude that endotoxemia in the pig causes severe acute respiratory failure largely mediated by cyclooxygenase and possibly lipoxygenase products of arachidonic acid metabolism.
Assessment of pharyngeal airway stability in normal and micrognathic infants
Authors: Roberts J. L. , Reed W. R. , Mathew O. P. , Menon A. A. , Thach B. T.
Published: December 2017

A current hypothesis for obstructive sleep apnea states that 1) negative airway pressure during inspiration can collapse the pharyngeal airway, and 2) neural control of pharyngeal airway-dilating muscles is important in preventing this collapse. To test this hypothesis we performed nasal mask occlusions to increase negative pharyngeal airway pressures during inspiration in eight normal and five micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by-breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. These findings suggest that nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midinspiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. These findings imply a similar pathophysiology for snoring, spontaneous airway obstruction, and obstruction during snoring.
Fatigue and contraction of slow and fast muscles in hypokinetic/hypodynamic rats
Authors: Fell R. D. , Gladden L. B. , Steffen J. M. , Musacchia X. J.
Published: December 2017

This investigation examined the effects of hypokinesia/hypodynamia (H/H) on fatigability and contractile properties of rat soleus (S) and gastrocnemius (G) muscles. Whole-body suspension for 1 wk was used to eliminate hindlimb load-bearing functions and simultaneously permit voluntary isotonic contractions. Train stimulations (45/min, 16 min) resulted in significantly (P less than 0.05) faster rates of fatigue to lower asymptotes in G from H/H rats. Fatigue in the S was minimal at this stimulation frequency and differences between H/H and control animals were not significant. Contractile properties (twitch and tetanic) were measured before and after train stimulations. H/H suspension resulted in an increased twitch tension in G. However, H/H did not change train or tetanic tensions per gram or other G contractile properties. Peak twitch, train, and tetanic tensions, time to peak tension, one-half relaxation time, and twitch and tetanic peak rates of tension development and decline were unchanged by H/H in S muscles. These results indicate that 1 wk of H/H-induced muscle atrophy significantly increases fatigability in G but does not effect contractile properties of fast-twitch (G) or slow-twitch (S) muscles.
Lower body positive pressure vs. dopamine during PEEP in humans
Authors: Payen D. M. , Carli P. A. , Brun-Buisson C. J. , Huet Y. J. , Teisseire B. P. , Chiron-Payen B. , Lemaire F. L.
Published: December 2017

The application of lower body positive pressure (LBPP) of approximately 40 Torr was used to increase cardiac index (CI) in eight patients with acute respiratory failure (ARF) during positive end-expiratory pressure (PEEP) ventilation. The effects of LBPP on hemodynamics and gas exchange were compared with those of dopamine at the same level of CI without blood volume expansion. LBPP increased CI via an increase in stroke index without associated tachycardia, whereas dopamine combined both effects. A positive linear relationship (r = 0.82) was evidenced between CI and right atrial pressure (Pra) during application of LBPP according to the Frank-Starling mechanism, whereas dopamine did not increase Pra. The increase in CI with dopamine was associated with a significant rise in venous admixture (r = 0.84, P less than 0.001), whereas no such effect was observed with LBPP (r = 0.088). Changes in venous admixture were directly related to changes in mixed venous O2 pressure (PVO2) in both situations (r = 0.733, P less than 0.01), but the increase in PVO2 was more pronounced with dopamine than with LBPP (P less than 0.04). We conclude that LBPP can effectively counterbalance peripheral venous blood pooling during PEEP ventilation in humans with ARF and that changes in PVO2 appear as a major determinant of venous admixture in this setting.
Ventilation and acid-base balance in awake dogs exposed to heat and CO2
Authors: Maskrey M. , Jennings D. B.
Published: December 2017

Some awake quiet dogs pant at cool ambient temperature (Ta) and some do not pant even when acutely exposed to heat. The purpose of the study was to determine whether this puzzling variability in respiratory behavior diminished during prolonged heat. The contributions of thermal and CO2 drives to respiratory adaptations were also examined. Five awake dogs acclimated to 20 degrees C were studied before and 2 and 48 h following exposure to 30–31 degrees C. Rectal temperature did not change; the important thermal stimulus, even at 48 h, appeared to be the increase in peripheral temperature. Variability between nonpanting and panting persisted over 48 h. On the average, ventilation (VE) doubled during heat, largely due to increased dead space ventilation. Nonpanting dogs at cool Ta decreased the threshold of the ventilatory response to CO2. A panting dog at cool Ta changed its slope of the ventilatory response from negative to positive. During hypercapnia in acute heat, ventilatory pattern changed so that frequency increased and tidal volume decreased for a given VE. By 48 h of heat, the ventilatory response to CO2 returned to control in only two dogs, but the ventilatory pattern during hypercapnia returned to control in four dogs. Since thermal stimuli remained unchanged at 48 h, adaptations of respiratory control may have been related to progressive adjustments of strong ions and acid-base balance.
A model for determining alveolar and small airway dimensions from aerosol recovery data
Authors: Rosenthal F. S.
Published: December 2017

A mathematical model is presented that allows the determination of alveolar and small airway dimensions from a series of aerosol recovery measurements performed at different inspiration volumes. The model assumes 1) a symmetric dichotomous lung, 2) representation of airway and alveoli as ensembles of straight tubes, and 3) Gaussian dispersion of the aerosol bolus. Calculations with this model using dimensions given by Weibel show general agreement with experimental data on six human subjects obtained by Palmes et al. (J. Appl. Physiol. 34: 356–360, 1973). Close agreement is found by varying two parameters describing alveolar size and airway size to obtain the best fit. The resulting estimates of size are almost independent of the choice of the dispersion coefficient; however, the estimate of alveolar size is quite dependent on the form of settling assumed during breath holding. The values of alveolar diameter in the six subjects, determined under the assumption of stirred settling, ranged from 0.13 to 0.33 mm, whereas under the assumption of still settling the range was 0.24–0.65 mm. Small airway (generations 18–24) dimensions ranged from 0.41 to 0.66 mm under the still-settling assumption and 0.39 to 0.63 mm under the stirred-settling assumption. With the assumption of an intermediate (partially stirred) form of settling, the alveolar diameter in the six subjects is 0.28 +/- 0.02 mm, in close agreement with morphometric measurements by other investigators. A partially stirred form of settling is also consistent with model predictions of recovery vs. breath-holding time and with cardiogenic gas mixing in the lung.
A rodent treadmill for inhalation toxicological studies and respirometry
Authors: Mautz W. J. , Phalen R. F. , McClure T. R. , Bufalino C.
Published: December 2017

A 10-runway treadmill was enclosed for inhalation toxicological studies of rodents under exercise exposure to environmental pollutants. The exposure system was lined with sheet stainless steel to minimize scrubbing of charged particles and reactive gases. Average metabolic gas exchange of exercising animals was derived from measurements of inlet or outlet airflow and data from an O2 analyzer in conjunction with either a CO2 or N2 analyzer. An airflow rate of 400 l X min-1 ensured a response time of 1 min to reach 95% of a step change in metabolic rate and held scrubbing losses of an O3 test atmosphere to less than 2% of treadmill inlet concentration. Gas exchange averaged for 10 rats during incremental exercise up to their highest collective performance was similar to published data for rats tested individually.
Effect of hematocrit on vascular pressure profile in dog lungs
Authors: Julien M. , Hakim T. S. , Vahi R. , Chang H. K.
Published: December 2017

We studied the effect of blood hematocrit (Hct) on the longitudinal distribution of pulmonary vascular pressure profile in an in situ isolated left lower lobe preparation of dog lung using the arterial and venous occlusion technique. The total arteriovenous pressure drop (delta PT) across the lobe was partitioned into pressure drops across an arterial (delta Pa), a venous (delta Pv), and a middle segment (delta Pm). Three levels of Hct were studied: low (18 +/- 5%), normal (41 +/- 4%), and high (66 +/- 5%). Arterial and venous occlusions were performed under constant-flow or constant-pressure perfusion. When flow was maintained constant, the increase in delta PT between low and normal Hct was due to increases in delta Pa, delta Pm, and delta Pv; however, between normal and high Hct, the increase in delta PT was primarily due to an increase in delta Pm. When delta PT was kept constant by adjusting flow, changes in delta Pa and delta Pv were in the same direction as changes in blood flow rate but in opposite direction to changes in Hct. In contrast, changes in delta Pm were in the same direction as changes in Hct. The results showed that the vascular resistance of the middle segment ranged from 7% of total pulmonary vascular resistance at low Hct to 53% at high Hct, suggesting that the vessels within this segment offer the greatest impairment to the transit of blood cells.
Effects of transfusion-induced polycythemia on O2 transport during exercise in the dog
Authors: Schumacker P. T. , Guth B. , Suggett A. J. , Wagner P. D. , West J. B.
Published: December 2017

An increased hematocrit could enhance peripheral O2 transport during exercise by improving arterial O2 content. Conversely, it could reduce maximal delivery of O2 by limiting cardiac output during exercise or by limiting the distribution of blood flow to peripheral capillaries with high O2 extractions. We studied O2 transport at rest and during graded treadmill exercise in splenectomized tracheostomized dogs at normal hematocrit (38 +/- 3%), and 48 h after transfusion of type-matched donor cells. This procedure increased hematocrit (60 +/- 3%) but also increased blood volume (P less than 0.05). Following transfusion, resting cardiac output (QT) and heart rate were not different. During exercise, QT was significantly lower at each level of O2 consumption (VO2) at high hematocrit (P less than 0.01). A reduction in QT was also seen during polycythemic exercise with hypoxemia produced by breathing 12 or 10% O2 in N2. Despite the reduction in QT, mixed venous PO2 was not lower at high hematocrit, and the increase in base deficit with VO2 was not different from control measurements. O2 delivery (QT X arterial content) was similar at each level of VO2 at both levels of hematocrit, during both normoxic and hypoxic studies. Both systemic and pulmonary arterial pressures were increased at rest after transfusion (P less than 0.05). However, pulmonary and systemic pressures were not higher than control during exercise at high hematocrit. We conclude that a hematocrit of 60% with increased blood volume is not associated with a cardiac limitation of O2 delivery, nor does it interfere with peripheral O2 extraction during exercise in the dog.
Heat exchanges in wet suits
Authors: Wolff A. H. , Coleshaw S. R. , Newstead C. G. , Keatinge W. R.
Published: December 2017

Flow of water under foam neoprene wet suits could halve insulation that the suits provided, even at rest in cold water. On the trunk conductance of this flow was approximately 6.6 at rest and 11.4 W . m-2 . C-1 exercising; on the limbs, it was only 3.4 at rest and 5.8 W . m-2 . degrees C-1 exercising; but during vasoconstriction in the cold, skin temperatures on distal parts of limbs were lower than were those of the trunk, allowing adequate metabolic responses. In warm water, minor postural changes and movement made flow under suits much higher, approximately 60 on trunk and 30 W . m-2 . degrees C-1 on limbs, both at rest and at work. These changes in flow allowed for a wide range of water temperatures at which people could stabilize body temperature in any given suit, neither overheating when exercising nor cooling below 35 degrees C when still. Even thin people with 4- or 7- mm suits covering the whole body could stabilize their body temperatures in water near 10 degrees C in spite of cold vasodilatation. Equations to predict limits of water temperature for stability with various suits and fat thicknesses are given.
Effects of chronic hypoxia on structure and reactivity of rat lung microvessels
Authors: Davies P. , Maddalo F. , Reid L.
Published: December 2017

The reactivity of lung microvessels is determined by a method based on planimetry of elastic laminae (EL) in vessel cross sections. Because wall structure is assessed, arteries that undergo remodeling during chronic hypertension can be identified. To study the structure and reactivity of such vessels, slices obtained from lungs of six rats exposed to hypobaric hypoxia for 14 days and from normoxic controls were incubated in culture with 10(-4) M l-epinephrine (EPI), then fixed and processed for microscopy. For muscular arteries (less than 200 microns diam), the circumferential length of internal EL (IEL) is positively correlated with length of external EL (EEL). In larger arteries, EEL is shorter than IEL and may restrict distension, but in smaller arteries the converse is true. After chronic hypoxia, the regression line shifts, indicating structural remodeling. For newly muscularized arteries found only after hypoxia the new IEL is always shorter than EEL, and a complex network of elastin connects the two. Muscular arteries constrict with EPI to the same degree after hypoxia as after normoxia. Nonmuscular vessels (arteries and veins) also constrict similarly after either exposure regimen. For newly muscularized arteries of the same size and location as the nonmuscular vessels, the response is significantly less.
Respiratory epithelium inhibits bronchial smooth muscle tone
Authors: Flavahan N. A. , Aarhus L. L. , Rimele T. J. , Vanhoutte P. M.
Published: December 2017

The aim of the present study was to determine whether or not the respiratory epithelium can modulate the responsiveness of bronchial smooth muscle. Paired rings of canine bronchi (4–6 mm OD), in some of which the epithelium had been removed mechanically (by rubbing the luminal surface), were mounted in physiological saline solution, gassed with 95% O2–5% CO2, and maintained at 37 degrees C. The presence or absence of the epithelium was confirmed by histological examination. Removal of the epithelium increased the contractile responses evoked by acetylcholine, histamine, and 5-hydroxytryptamine. Transmural nerve stimulation evoked similar peak responses in the presence and absence of epithelium. In unrubbed preparations, the peak response was followed by a gradual decrease when the stimulation was continued. This decrease, which persisted in the presence of propranolol, was not observed in epithelium-denuded preparations. In bronchial rings contracted with acetylcholine, isoproterenol produced concentration-dependent relaxations which were significantly greater in rings with epithelium compared with denuded rings. These results suggest that respiratory epithelial cells may generate an inhibitory signal to decrease the responsiveness of bronchial smooth muscle to contractile agonists and augment the effectiveness of inhibitory stimuli.
Ventilatory response to high-frequency airway oscillation in humans
Authors: DeWeese E. L. , Sullivan T. Y. , Yu P. L.
Published: December 2017

To investigate respiratory control during high-frequency oscillation (HFO), ventilation was monitored in conscious humans by respiratory inductive plethysmography during application at the mouth of high-frequency pressure oscillations. Studies were conducted before and after airway and pharyngeal anesthesia. During HFO, breathing became slow and deep with an increase in tidal volume (VT) of 37% (P less than 0.01) and inspiratory duration (TI) of 34% (P less than 0.01). Timing ratio (TI/TT) increased 14% (P less than 0.05) and respiratory frequency (f) decreased 12% (P less than 0.01). Mean inspiratory flow (VT/TI) did not change during HFO. Following airway anesthesia, VT increased only 26% during HFO (P less than 0.01), whereas significant changes in TI, TI/TT, and f were not observed. Pharyngeal anesthesia failed to diminish the effect of HFO on TI, TT, or f, although the increase in VT was reduced. These results indicate that 1) HFO presented in this manner alters inspiratory timing without affecting the level of inspiratory activity, and 2) receptors in the larynx and/or lower airways may in part mediate the response.
Laryngeal resistance immediately after panting in control and constricted airways
Authors: Sekizawa K. , Sasaki H. , Takishima T.
Published: December 2017

Laryngeal resistance (Rla) in the postpanting interval (PPRla) was examined in five normal subjects in the control state and with methacholine- and histamine-induced bronchoconstriction. Respiratory resistance (Rrs) was measured by the forced oscillation technique at 10 Hz, and Rla was measured by the low-frequency sound method (Sekizawa, K., C. Shindoh, W. Hida, S. Suzuki, et al. J. Appl. Physiol. 55:591–597, 1983). Inspiratory Rrs (IRrs) was lower than expiratory Rrs (ERrs), and Rrs immediately after panting (PPRrs) was not significantly different from IRrs in the three airway conditions. Rla increased with bronchoconstriction and inspiratory Rla (IRla) was lower than expiratory Rla (ERla). PPRla was lower than IRla (P less than 0.01) by an amount corresponding to the decrease in Rrs in the control airway. However, in constricted airways, PPRla was higher than IRla and about the same as ERla. We suggest that the panting maneuver is suitable for minimizing the effect of laryngeal artifact in the control airway, but in the constricted airway the panting maneuver may fail to cause widening of the laryngeal orifice.
Vasoactive effects of substance P on isolated rabbit pulmonary artery
Authors: Tanaka D. T. , Grunstein M. M.
Published: December 2017

The vasoactive properties of substance P (SP) were studied in isolated rabbit pulmonary artery (PA) segments in vitro. In the absence of active base-line tone, noncumulative administration of SP (10(-11) to 10(-4) M) produced dose-dependent increases in PA tension. The peak isometric tension (Tmax) with SP was similar to the Tmax response to epinephrine; however, the doses of the agonist producing a threshold contraction and 25% of Tmax (ED25) were significantly lower for SP. In the presence of active base-line tone, induced by epinephrine or 5-hydroxytryptamine, SP produced transient PA relaxation which was directly related to the magnitude of the precontracted PA tension. Blockade of neurotransmission with tetrodotoxin (1 microgram/ml) and antagonists to alpha 1-adrenergic and histamine receptor binding had no effect on the contractile response to SP. On the other hand, PA contraction to an ED50 dose of SP was 1) inhibited by a mean of 33 +/- 10% (SE) following pretreatment with the cholinesterase inhibitor, neostigmine (10(-6) M) and 2) augmented by 52 +/- 21% with the cholinergic antagonist, atropine (10(-4) M). The latter also completely blocked the relaxation response to SP in precontracted PA. Similarly, removal of the PA endothelium also abolished the relaxation response to SP. In contrast, SP-induced contraction was markedly inhibited by the cyclooxygenase inhibitor, meclofenamate (1 microgram/ml), as well as the SP antagonist, D-Pro2, D-Trp7,9-SP.
Mechanisms of interaction between oxygen and granulocytes in hyperoxic lung injury
Authors: Krieger B. P. , Loomis W. H. , Czer G. T. , Spragg R. G.
Published: December 2017

Hyperoxia and infused granulocytes act synergistically in producing a nonhydrostatic high-permeability lung edema in the isolated perfused rabbit lung within 4 h, which is substantially greater than that seen with hyperoxia alone. We hypothesized that the interaction between hyperoxia and granulocytes was principally due to a direct effect of hyperoxia on the lung itself. Isolated perfused rabbit lungs that were preexposed to 2 h of hyperoxia (95% O2–5% CO2) prior to the infusion of unstimulated granulocytes (under normoxic conditions) developed significant nonhydrostatic lung edema (P = 0.008) within 2 h when compared with lungs that were preexposed to normoxia (15% O2–5% CO2) prior to granulocyte perfusion. The edema in the hyperoxic-preexposed lungs was accompanied by significant increases in bronchoalveolar lavage (BAL) protein, BAL granulocytes, BAL thromboxane and prostacyclin levels, perfusate chemotactic activity, and lung lipid peroxidation. These findings suggest that the synergistic interaction between hyperoxia and granulocytes in producing acute lung injury involves a primary effect of hyperoxia on the lung itself.
Ventilation by external high-frequency oscillation in cats
Authors: Ward H. E. , Armengol J. , Jones R. L.
Published: December 2017

Eight anesthetized tracheostomized cats were placed in an 8.2-liter airtight chamber with the trachea connected to the exterior. Thirty-two combinations of high-frequency oscillations (HFO) (0.5–30 Hz; 25–100 ml) were delivered for 10 min each in random order into the chamber. Arterial blood gas tensions during oscillation were compared with control measurements made after 10 min of spontaneous breathing without oscillation when the mean arterial PCO2 (PaCO2) was 30.1 Torr. Ventilation due to spontaneous breathing (Vs) and oscillation (Vo) were derived from the chamber pressure trace and a pneumotachograph, respectively. As the oscillation frequency increased, oscillated tidal volume (Vo) decreased from a mean of 39 (0.5 Hz) to 3.3 ml (30 Hz) when 100 ml was delivered to the chamber. From 6–25 Hz, apnea occurred with Vo less than estimated respiratory dead space (VD); the minimum effective Vo/VD ratio was 0.37 +/- 0.05. Although Vo was maximal at 10 Hz at each oscillation volume, the lowest PaCO2 occurred at 2–6 Hz, and arterial PO2 rose as expected during hypocapnia. Above 10 Hz, PaCO2 was determined by Vo and was independent of frequency, whereas at lower frequencies, PaCO2 was related to Vo; below 6 Hz, PaCO2 varied inversely with the calculated alveolar ventilation. As oscillations became more effective, both PaCO2 and Vs fell progressively and were highly correlated; apnea occurred when PaCO2 was reduced by a mean of 4.5 Torr. Mean chamber pressure remained near zero up to 15 Hz, indicating functional residual capacity did not change. We conclude that externally applied HFO can readily maintain gas exchange in vivo, with Vo less than VD at frequencies over 2 Hz.
Hypothalamic, rectal, and muscle temperatures in exercising dogs: effect of cooling
Authors: Kruk B. , Kaciuba-Uscilko H. , Nazar K. , Greenleaf J. E. , Kozlowski S.
Published: December 2017

To investigate mechanisms that may be involved in the prolongation of exercise performance with body cooling hypothalamic (Thy), rectal (Tre), and exercising muscle (Tm) temperatures, as well as the heart rate, respiratory rate, blood lactic acid concentration ( [LA] ), and plasma osmolality (Osm) were measured in five dogs during exhaustive treadmill exercise at an ambient temperature (Ta) of 22 +/- 1 degree C without cooling (control) and with external cooling by use of ice packs. In both series of experiments, dehydration of animals was prevented. Compared with exercise with noncooling, exercise with cooling resulted in 1) increased exercise duration from 90 +/- 14 to 145 +/- 15 min (62%, P less than 0.05); 2) attenuated increases in Thy, Tre, and Tm; 3) decreased respiratory and heart rates; and 4) lowered LA. Significant negative correlations were found between both Tm and delta Tm attained at 60 min of the run and time of exercise until exhaustion (r = -0.72 and -0.74, respectively; P less than 0.02). This work failed to differentiate clearly changes or equilibrium levels of brain, core, or muscle temperature as separate factors affecting work tolerance. However, the inverse relationship between Tm reached at 60 min of the run (in both experiments) and the total duration of exercise indicates that sustained muscle hyperthermia may largely contribute to limitation of working ability.
Assessment of transdiaphragmatic pressure in humans
Authors: Laporta D. , Grassino A.
Published: December 2017

Maximal force developed by the diaphragm at functional residual capacity is a useful index to establish muscle weakness; however, great disparity in its reproducibility can be observed among reports in the literature. We evaluated five maneuvers to measure maximal transdiaphragmatic pressure (Pdimax) in order to establish best reproducibility and value. Thirty-five naive subjects, including 10 normal subjects (group 1), 12 patients with chronic obstructive pulmonary disease (group 2), and 13 patients with restrictive pulmonary disease (group 3), were studied. Each subject performed five separate maneuvers in random order that were repeated until reproducible values were obtained. The maneuvers were Mueller with (A) and without mouthpiece (B), abdominal expulsive effort with open glottis (C), two-step (maneuver C combined with Mueller effort) (D), and feedback [two-step with visual feedback of pleural (Ppl) and abdominal (Pab) pressure] (E). The greatest reproducible Pdimax values were obtained with maneuver E (P less than 0.01) (group 1: 180 +/- 14 cmH2O). The second best maneuvers were A, B, and D (group 1: 154 +/- 25 cmH2O). Maneuver C produced the lowest values. For all maneuvers, group 1 produced higher values than groups 2 and 3 (P less than 0.001), which were similar. The Ppl to Pdi ratio was 0.6 in maneuvers A and B, 0.4 in D and E, and 0.2 in C. We conclude that visual feedback of Ppl and Pab helped the subjects to elicit maximal diaphragmatic effort in a reproducible fashion. It is likely that the great variability of values in Pdimax previously reported are the result of inadequate techniques.
Role of ascorbic acid in chicks exposed to high environmental temperature
Authors: Pardue S. L. , Thaxton J. P. , Brake J.
Published: December 2017

This study was conducted to determine if ascorbic acid (AA) 1) increases resistance to high environmental temperature in young chickens and 2) alters heat-induced changes in several physiological responses. Groups of male chicks received either a standard ration containing 1,000 mg/kg (ppm) of AA or the ration without AA. Chicks were brooded for 3 wk and then maintained at 22 +/- 0.8 degrees C. At 4 wk of age, both AA-supplemented and control chicks were exposed to 30 min of heating (43 +/- 0.1 degrees C and 40 +/- 2% rh) on each of 3 consecutive h in an environmentally controlled chamber. Chicks were challenged with sheep erythrocytes (1 ml, 10(5) cells, iv) 12 h postheating. Heating reduced plasma potassium, body weight gain, relative bursa and spleen weights, and anti-sheep erythrocyte levels. Heating increased cloacal temperature, plasma protein, corticosteroid levels, and mortality. AA ameliorated many of these stress-related responses.
Gas flux through human skin: effect of temperature, stripping, and inspired tension
Authors: Baumgardner J. E. , Graves D. J. , Neufeld G. R. , Quinn J. A.
Published: December 2017

The flux of He and O2 through intact adult human skin was measured at various inspired concentrations and skin temperatures. The skin surface was then stripped with cellophane tape to alter the diffusional conductance of the stratum corneum. He flux for stripped skin was used to estimate skin perfusion as a function of local temperature, and diffusional conductance for O2 was estimated from O2 flux and perfusion. The flux of He or O2 at constant skin temperature can be related to inspired concentration by a simple linear model. Increasing surface temperature in the range 33–43 degrees C produced a much larger increase in O2 flux than in He flux for intact skin. Skin stripping greatly increased skin O2 flux. Estimated skin conductance for O2 showed a more marked temperature dependence than estimated skin perfusion. The results suggest that raising skin temperature in the range 38–43 degrees C has only a modest effect on skin perfusion and that stratum corneum conductance may have a major role in the large increase of O2 flux with temperature.