bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo measurement of variations in the oxygen 18 content of water in rat brain
Authors: Mayevsky A. , Samuel D. , Ortega C. , Amsel G.
Published: December 2017

A method of analysis for oxygen 18 is described, based on the anodic oxidation of specially prepared tantalum wires implanted through cannulas into the tissue of living animals. The thin anodic oxide layer formed on these wires is then analyzed by the 18O(p,alpha)15N reaction. The isotopic oxygen concentration of water in the brain obtained by this method compares very well with the values obtained by conventional analysis using mass spectrometry. This in vivo method of nuclear microanalysis has been used in both metabolic and equilibration experiments involving oxygen 18. The half-life for the turnover of 18O in body water was found to be about 3 days. A simple three-pool model is presented which can account for the experimental results obtained from the dilution by body water of interperitoneally injected water highly enriched in 18O.
Effect of lactate on FFA and glycerol turnover in resting and exercising dogs
Authors: Issekutz B. , Shaw W. A. , Issekutz T. B.
Published: December 2017

The rates of appearance of FFA (RaFFA) and that of glycerol (RaGLY) were measured simultaneously with [1–14 C]palmitate and [2-3H]-glycerol, in dogs with indwelling arterial and venous catheters. Lipolysis was stimulated by exercise (treadmill run on 10% slope) or by the infusion of norepinephrine (0.5 mug/kg-min). Na-L(+)-lactate (L), Na-pyruvate (Py), or Na-nicotinate (N) were infused. All three components decreased RaFFA. RaGLY was increased by L, unaltered by Py, and decreased by N. There was an inverse correlation (P less than 0.001) between the logarithms of RaFFA and plasma lactate. A linear correlation was obtained between RaGLY and plasma lactate when this latter was increased by the infusion of L. It is suggested that a) lactate in physiological concentrations inhibits the release of FFA stimulated by exercise and b) the increase of the NADH/NAD ratio leads to the formation of alpha-glycerophosphate which in turn yields glycerol. Therefore changes in plasma glycerol do not reflect lipolysis when blood lactate increases. c) The effect of lactate on RaFFA can be explained by an enhanced reesterification, although a direct inhibition on lipase could not be excluded.
Effect of hypoxia on immediate ventilatory load response in dogs
Authors: Lynne-Davies P. , Bowden J. A. , Giles W.
Published: December 2017

The effective elastance of the respiratory system (which has been previously shown to provide an index of the ability of the respiratory musculature to compensate rapidly for transient mechanical ventilatory loads) was measured in six hypoxic dogs to determine whether hypoxia hindered immediate load-compensatory mechanisms. The effective elastance value was computed from measurements of control tidal volume and the pressure developed at the airway opening during the first inspiratory effort following airway occlusion at FRC. The mean effective elastance was 197 cmH2O/l while the animals were breathing room air and did not change significantly when the animals were rendered hypoxic by reducing the inspired oxygen concentration, in five dogs, or by controlled hemorrhage, in two dogs. It was concluded that inasmuch as effective elastance measurements remain constant during hypoxia, the stability of ventilation is not significantly impaired in this situation.
Relationship of phase IV to closing volume in lateral body positions
Authors: Don H. F. , Ingram R. H. , Green M.
Published: December 2017

We studied the effect of body position in humans on the relationship between exhaled vital capacity (VC) and both helium (He) and nitrogen (N2) concentrations after delivery of an He bolus at residual volume (RV) followed by 100% oxygen to total lung capacity. Phase IV, defined as the % VC at the first sharp and permanent increase in N2 and He, occurred at a mean of 15.7% VC while seated, 60.0% VC in right lateral and 59.6% VC in left lateral positions. He bolus delivery above RV but well below 60% VC resulted in the disappearance of phase IV. Lung pressure-volume (PV) curves had inflections at the volume of phase IV in the seated position: but the inflections were well below phase IV in lateral positions. Phase IV increased to higher volumes at higher mouth pressures. The relationship between phase IV and mouth pressure fell near the respiratory system relaxation PV curves. The findings suggest the higher phase IV in lateral positions is due to sequence of emptying without airway closure and is influenced by active expiration.
Awake baboon's ventilatory response to venous and inhaled CO2 loading
Authors: Lewis S. M.
Published: December 2017

Steady-state ventilatory responses to CO2 in trained awake baboons were studied to determine the response to a venous CO2 load. CO2 was loaded either directly into the venous blood through an arteriovenous shunt or by addition to the inhaled air. The two modes of loading were adjusted to produce the same increase in minute volume. Minute volume, tidal volume respiratory frequency, end-tidal PCO2, PaCO2, and pHa were measured. PaCO2 and PETCO2 increased the same amount during the two modes of CO2 loading; thus, the response to changes in arterial PCO2, deltaVE/deltaPaCO2, was the same. I conclude that the ventilatory response to venous CO2 loading occurs only through the change in mean arterial PCO2 and thus it is unlikely that there are any important venous CO2 receptors.
Left ventricular dynamics during recovery from exercise
Authors: Horwitz L. D. , Atkins J. M. , Dunbar S. A.
Published: December 2017

Left ventricular dynamics during recovery were measured in dogs, 3 min after brief periods of mild, moderate, and severe treadmill exercise. As compared with resting values, stroke volume was unchanged, and the maximum first derivative of the left ventricular pressure was either unchanged or slightly elevated. Increases in heart rate of 20, 26, and 46 beats/min for mild, moderate, and severe exercise appear to be the major factor in augmenting cardiac output during recovery. With moderate and severe exercise, left ventricular end-diastolic diameter increased and continued to be elevated during recovery, whereas end-systolic diameter decreased during exercise but was elevated above resting values during recovery. Therefore, with strenuous exercise, a sympathetic-mediated increase in contractility recedes promptly during the postexercise period but the Frank-Starling mechanism continues to be a factor.
Salicylate hypothermia in rats exposed to hyperbaric air and helium
Authors: Hart J. L.
Published: December 2017

Rectal temperatures of salicylate-treated and untreated rats were observed in 21–23 degrees C air at 1, 3, 6, and 8 ATA, in 21–23 degrees C helium at 1 and 6 ATA, and in 1 ATA thermal neutral air (28 degrees C). Significant dose-related temperature decreases occurred in 21–23 degrees C 1 ATA air with 180 and 300 mg/kg of salicylate; 60 mg/kg had no effect. However, in thermal neutral air, 300 mg/kg significantly elevated temperatures. Hyperbaric air and helium had temperature-lowering effects which were correlated with thermal properties of these environments, and in them the hypothermic effects of salicylate were similar to those in 1 ATA air, the total temperature decreases being the sum of the salicylate hypothermia and that caused by the hyperbaric air or helium. These additive temperature effects are unlike previously reported results in which the temperature lowering effects of 5 degrees C cold exposure and salicylate together were greater than the sum of the two individual effects.
Using body size to understand the structural design of animals: quadrupedal locomotion
Authors: McMahon T. A.
Published: December 2017

Many parameters of gait and performance, including stride frequency, stride length, maximum speed, and rate of O2 uptake are experimentally found to be power-law functions of body weight in running quadrupeds. All of these parameters are reasonably easy to measure except maximum speed, where the question arises whether one means top sprinting speed or top speed for sustained running. Moreover, differences in training and motivation make comparisons of top speed difficult. The problem is circumvented by comparing animals running at the transition between trotting and galloping, a physiologically similar speed. Theoretical models are proposed which preserve either geometric similarity, elastic similarity, or static stress similarity between animals of large and small body weights. The model postulating elastic similarity provides the best correlation with published data on body and bone proportions, body surface area, resting metabolic rate, and basal heart and lung frequencies. It also makes the most successful prediction of stride frequency, stride length, limb excursion angles, and the metabolic power required for running at the trot-gallop transition in quadrupeds ranging in size from mice to horses.
Effect of altitude exposure on platelets
Authors: Gray G. W. , Bryan A. C. , Freedman M. H. , Houston C. S. , Lewis W. F. , McFadden D. M. , Newell G.
Published: December 2017

Since decompression from depth is known to produce a fall in platelet count, the effect of altitude decompression and high-altitude exposure on platelets was investigated. Sixteen subjects decompressed without hypoxia to 20,000 ft simulated altitude for two hours showed a significant (P less than 0.01) drop in circulating platelet count of approximately 10% for three days following decompression. Four of five subjects similarly exposed had a shortened autologous platelet survival compared to that prior to exposure. Subjects exposed to 9,800 ft and then 17,600 ft in a mountain environment showed a significant mean decrease in platelet count on day 2 of 7% and 25% respectively, which had returned to control by day 5. Nonhypoxic and hypoxic decompressed rabbits which received homologous chromium-51-labeled platelets had an increase in lung radioactivity compared with sea-level controls. It is postulated that altitude decompression produces platelet reductions similar to these seen after decompression from depth, and that platelets sequester in the pulmonary vascular bed.
Similarity of blood flows using indocyanine prepared in saline or distilled water
Authors: Aarhus L. L. , Donald D. E.
Published: December 2017

Directly measured blood flow pumped through a mixer circuit was compared to estimates of flow from indicator dilution curves derived from bolus injections of indocyanine green dye prepared in 0.9% saline (saline dye) and in triple-distilled water (3 D dye). At flows whose mean appearance time was 1.6 s, the mean error of estimate +/-SD of 2.3 +/- 5.1% using 3 D dye was significantly different (P less than 0.05) from that of 5.6 +/- 7.0% using saline dye. Essentially, there was no difference in estimates of blood flow with each dye solution when mean appearance time was increased to 3.8 s. Thus, the error, which was perhaps due to electrolyte in the concentrated indocyanine green dye (saline dye) and subsequent slowed rate of optical stabilization after dilution in plasma, is small and does not explain the overestimation by indocyanine dilution curves of blood flow in intact dogs.
Tetanic force development of adductor pollicis muscle in anesthetized man
Authors: Sugai N. , Worsley R. , Payne J. P.
Published: December 2017

The tetanic force development of the human adductor pollicis muscle was studied under light anesthesia with nitrous oxide, oxygen, and Demerol, by the use of tetanic stimulation of the ulnar nerve at frequencies ranging from 10 to 100 Hz. The time necessary for the tetanic contraction to reach a plateau was longest at frequencies between 15 and 20 Hz. Fusion of tetanus occurred between 40 and 45 Hz. The mean maximal force of 6.92 kg was developed at a mean frequency of approximately 75 Hz. The maximal force was well maintained up to a stimulation frequency of 100 Hz. The results indicate that in lightly anesthetized man, the maximal force is developed at higher stimulation frequencies than those observed in conscious man and that it is well sustained at higher frequencies.
Cellular distribution and clearance of aerosolized dipalmitoyl lecithin
Authors: Geiger K. , Gallagher M. L. , Hedley-Whyte J.
Published: December 2017

Wistar-Lewis rats were anesthetized anc connected to a 3-MHz nebulizer which aerosolized 250 muCi l-alpha-1-palmitoyl-2palmitoyl-[9–10-3H]phosphatidylcholine ([3H]DPL) for 3 min. Appleton frozen-section autoradiographs showed greater than 4 times background radioactivity in approximately 30% of alveoli at 1 min and 2 h after aerosol. As tritium content in the lung decreased, it increased in liver, spleen, kidney, blood, and urine. Percentage of radioactivity from [3H]phosphatidylcholine in the liver declined with time, while [3H]phosphatidylethanolamine doubled between 2 and 12 h. One minute postaerosol 2,500 +/- 500 (SE) type I cells/mm3 lung and 2,500 +/- 750 type II cells/mm3 lung had greater than 20 times background radioactivity; 2 h later only 950 +/- 250 type I cells/-m3 lung still had levels of radioactivity greater than 20 times background while 3,150 +/- 600 type II cells/mm3 lumg now had this level of 3HIDPL. Corresponding numbers of alveolar macrophages were 450 +/- 250 1 min postaerosol and 1,100 +/- 200 after 2 h. Aerosolized DPL as a synthetic surfactant is hampered by significantly faster clearance from the alveolar surface as compared with normal in vivo DPL.
Localization of the medullary respiratory neurons in rats by microelectrode recording
Authors: Howard B. R. , Tabatabai M.
Published: December 2017

Neuronal activity has been recorded extracellularly from the medulla of anesthetized rats. Units whose discharge frequency varied in phase with respiratory airflow were located bilaterally between 1.5 and 2 mm lateral to midline, extending from 1 mm caudal to 1.5 mm rostral to the obex, in the ventral two-thirds of the medulla. Expiratory units predominated and were intermingled with inspiratory units. Ten different patterns of discharge were distinguished, varying from a short burst at the beginning of expiration to a resting discharge which increased in frequency during either inspiration or expiration. Evidence was also obtained that fiber tracts from other areas of the brain cross midline just caudally to the obex and pass to the respiratory centers on which they apparently exert and excitatory action.
Rapid estimation of pulmonary extravascular water with an instream catheter
Authors: Anderson W. P. , Dunegan L. J. , Knight D. C. , Fitzpatrick G. F. , O'Connor N. E. , Morgan A. P.
Published: December 2017

An arterial catheter-bearing external conductivity electrodes and a thermistor was used for measurement of lung thermal volume (LTV) by the double-indicator method. Ten milliliters of 3% saline at room temperature were injected, dilution curves measured, and LTV calculated as mean transit time difference, less thermistor time constant, times cardiac output (CO). Comparisons were made, in dogs, between LTV, pulmonary extravascular lung water with Evans blue and tritiated water (PEVWtho), and weighed lung water (WLW). Pulmonary edema was induced with dextran and epinephrine. CO was measured by thermodilution in both the pulmonary artery (PA) and aorta (AO) and dye dilution in the AO. CO from dye dilution was compared with thermodilution (aortic detection) to detect irreversible loss of thermal indicator. Comparisons showed good correspondence of dye and thermal curves (Y = 0.91X - 0.16 1/min; r = 0.93). LTV is about 120% of WLW in near normal lungs, 90% of WLW in extreme edema. PEVWtho was 60–70% WLW.
An automatic, closed-circuit oxygen consumption apparatus for small animals
Authors: Stock M. J.
Published: December 2017

An apparatus suitable for the continuous measurement of oxygen consumption of rats and mice is described. The system uses a motorized syringe dispenser to deliver fixed volumes of oxygen to a closed animal chamber. The dispenser is controlled by a micro-differential pressure switch to maintain chamber pressure slightly above ambient. The rate of oxygen consumption is determined by timing the interval between successive operations of the dispenser. The system has proved suitable for a range of experimental conditions and treatments.
Purified postheparin plasma lipoprotein lipase in primary hyperlipoproteinemias
Authors: Ganesan D. , Bradford R. H. , Ganesan G. , McConathy W. J. , Alaupovic P. , Bass H. B.
Published: December 2017

Purified postheparin plasma lipoprotein lipase (LPL) of normolipidemic and primary hyperlipoproteinemic subjects was characterized by lipoprotein C polypeptide activation and specificity for triglycerides in chylomicrons and VLDL. Chromatography of normal LPL on Sephadex G-100 resulted in two protein peaks, LPLC-1 (activated by C-I but not C-II) and LPLC-II (activated by C-II but not C-I). LPL from type I hyperlipoproteinemic subjects was not activated by C-I and C-II activation was reduced to 40% of control. Hydrolysis of chylomicron and VLDL triglycerides was severely impaired. Although chromatography of type I LPL resulted in two protein peaks, the protein peak corresponding to LPLC-I did not exhibit lipolytic activity and LPLC-II was reduced to 50% of control in protein and enzyme specific activity. Type III LPL was normal in respect to LPLC-I while LPLC-II averaged 40% of control. Hydrolysis of chylomicron and VLDL was reduced to 50% and 10% of control, respectively. An etiological implication for LPLC-I and/or LPLC-II in type I and III hyperlipoproteinemias is suggested.
Hematological alterations and response to acute hypobaric stress
Authors: Penney D. , Thomas M.
Published: December 2017

Exposure of rats to simulated altitude (15,000 ft) for 1 day and 3 and 9 wk produced progressive polycythemia, elevated 2,3-diphosphoglycerate levels and raised P50 values; the latter two parameters decreased toward control values after 9 wk. Carbon monoxide (38–43% HbCO) exposure produced polycythemia after 3- and 9-wk exposure, no change in 2,3-DPG and a fall in P50 value. Ten days' treatment with sodium cyanate produced a large decrease in 2,3-DPG and P50. Survival during 90 min of acute hypobaria (0.3 atm) under Nembutal anesthesia was highest with NaOCN (75%), intermediate with 3- and 9-wk exposure to altitude and CO (56–58%) lower in 1-day altitude exposure (44%) and lowest in controls (5%). Heart and ventilation rate was monitored during this hypobaric test and response patterns established for each exposure/treatment. In states of extreme oxygen deprivation the results suggest, in order of importance, the survival value of 1) increased oxygen-hemoglobin affinity, and 2) polycythemia.
Pulmonary shunt: a comparison between oxygen and inert gas infusion methods
Authors: Hlastala M. P. , Colley P. S. , Cheney F. W.
Published: December 2017

Pulmonary shunt measurement was compared using the standard oxygen (Berggren) technique and a new multiple inert gas infusion (Wagner et al.) technique in 11 mongrel dogs with either regional atelectasis or diffuse pulmonary edema. Relative retentions of sulfur hexafluoride, ethane, cyclopropane, halothane, diethyl ether, and acetone were used to calculate intrapulmonary shunt. Relative dilution of oxygen (Berggren method) was used to calculate total right to left shunt. The two methods gave similar results in the range of 20–80%. At low shunts the oxygen method measured higher values. This is because of the greater relative importance of fixed extrapulmonary shunts at this level and, as well, error in the measurement of PO2. Both techniques are suitable for normal clinical use.
Effect of alveolar liquid on distribution of blood flow in dog lungs
Authors: Muir A. L. , Hogg J. C. , Naimark A. , Hall D. L. , Chernecki W.
Published: December 2017

Previous studies have shown that a shift in blood flow away from edematous regions does not occur until the alveoli contain liquid. The present experiments were designed to examine the separate effect of air space liquid, air space plus interstitial liquid, and reduced lung volume on blood flow. We found that reduced lung volume was not associated with significant changes in blood flow and that no systematic change in blood flow occurred when alveoli were filled with isosmotic liquid (autologous plasma). However, when hyposmotic liquid (dilute plasma) was instilled so that both the air space and the alveolar wall interstitial space were filled, blood flow was systematically reduced. This suggested that interstitial liquid was responsible raising vascular resistance in these experiments and that it might also be important in raising local vascular resistance in pulmonary edema. This latter hypothesis was tested in isolated perfused lobes where rapid freezing and quantitative histology showed that the number of open capillaries was significantly reduced in the liquid-filled alveoli (P less than 0.001). These observations suggest that interstitial pressure rises in pulmonary edema with the result that the transmural pressure of the alveolar vessels falls and vascular resistance is increased.
Recruitment in networks of pulmonary capillaries
Authors: West J. B. , Schneider A. M. , Mitchell M. M.
Published: December 2017

To improve our understanding of the pressure-flow characteristics of pulmonary capillaries, we analyzed by means of computer stimulation a theoretical model composed of 50 interconnected nonlinear elements. Each element required a critical pressure across it before flow occurred and there was a subsequent linear pressure-flow region whose slope, or resistance, could be related to the transmural pressure of the element (“distensibility”). The critical pressures and resistances of each element of the network were randomly chosen from distributions. We found that recruitment (i.e., onset of flow) occurred over a large range of network upstream or “arterial” pressures, and that relatively high arterial pressures were required before all elements had no distensibility. Intermittent and reverse flow were commonly seen in some elements as the arterial pressure was raised in steps. These flow reversals were particularly common when the critical pressures and resistances of the elements were inversely related. The critical pressures required for such behavior in the capillary segments of the pulmonary microcirculation were calculated to be extremely small, of the order of 0.02 cmH2O. Pressures of this magnitude might result from sticking of red cells to capillary walls or to each other. The properties of such a network may explain the patchiness of flow in the pulmonary microcirculation and the large range of arterial pressures over which recruitment is observed to occur.
Voluntary changes of thoracoabdominal shape and regional lung volumes in humans
Authors: Grassino A. E. , Bake B. , Martin R. R. , Anthonisen R.
Published: December 2017

We measured regional lung volumes from apex to base in humans during changes in thoracoabdominal shape which we monitored with magnetometers. In erect subjects, voluntary changes of shape at FRC did not change regional volume distribution. In supine subjects, the effect of negative pressure applied to the abdomen and a similar thoracoabdominal configuration achieved by voluntary means were studied. The distribution of regional volumes in both situations was the same as that measured during relaxation at the same overall lung volumes. We concluded that neither voluntary changes in shape nor negative abdominal pressure influenced the human pleural pressure gradient. This result, which differed from findings in animals, was probably because the human chest was relatively stiff and behaved with one degree of freedom; all parts of the human rib cage changed dimensions proportionally while negative abdominal pressure distorted the rib cage of animals.
Determination of body surface area in the rhesus monkey
Authors: Liu C. T. , Higbee G. A.
Published: December 2017

Body surface areas (BSA) of 31 apparently normal rhesus monkeys of both sexes weighing 3.2–5.3 kg were determined by the direct skinning technique. The range of measured BSA was 1,940–3,020 cm2 (mean = 2,430 cm2). The BSA values of male and female monkeys were not significantly different. The K value, calculated as the ratio of BSA (cm2)/body wt2/3 (kg), was 969 +/- 15 (SE). Based on the principle of least squares for goodness of fit between the measured and calculated BSA, the best equation was determined to be (see article). A nomogram was constructed for rapid determination of the BSA of rhesus monkeys with known body weight and lengths (head to anus). Monkey BSA could also be computed by multiplying the DuBois human BSA equation by a factor of 1.147 for the head-to-anus measure of length or by 0.891 for the head-to-heel measurement.
Semiautomated processing of systolic time intervals
Authors: Frey M. A. , Kenney R. A.
Published: December 2017

Systolic time intervals are commonly used to identify changes in ventricular function. The method described facilitates measurement and calculation of many such intervals. This method utilizes a printed polygraph recording of electrocardiogram, phonocardiogram, and carotid pulse contour; a digitizing device for reading the necessary coordinates from the record; and a minicomputer for calculation of the intervals and for data analysis. Intervals related to approximately 100 pulse beats can be read, calculated, printed in chart and graph form, and subjected to some analyses in about an hour.
Transcapillary exchange of strontium and sucrose in canine tibia
Authors: Davies D. R. , Bassingthwaighte J. B. , Kelly P. J.
Published: December 2017

The walls of haversian capillaries have been proposed as a physiologic membrane controlling flux of solute between blood and bone. In this study, capillary permeability to 85Sr and [14C]sucrose was estimated in the dog tibia by using indicator dilution techniques. Sucrose was chosen as a tracer because it is inert and has no known transport system. The mean (+/-SD) observed ratio of permeabilities of 85Sr and sucrose was 2.36 +/- 0.46 (N = 14) which is not substantially different from the ratio of their free diffusion coefficients, 2.55. This ratio was not influenced when the dogs were made hyperparathyroid by injection of parathyroid hormone (2.16 +/- 0.55; N = 11). This suggests that free diffusion is the principal mechanism for moving 85Sr across the bone capillary wall.
Effects of exercise on excretion rates of urinary free cortisol
Authors: Bonen A.
Published: December 2017

Excretion rates of urinary free cortisol were studied in 20 men assigned to four treadmill exercise groups: walking at 3 mph for 10 min or 30 min, or running at 7.5 mph for 10 min or 30 min. Free cortisol in urine was measured before and 30, 60, and 90 min after exercise, and again on a control day. Patterns of free-cortisol excretions after exercise at 7.5 mph for 10 and 30 min were significantly different from the control day (P less than 0.05) with the largest changes occurring in the 30-min group. Exercise and control patterns were not different for the other two conditions (P greater than 0.05). Within the 7.5 mph-30 min group the postexercise cortisol excretion rates were directly related to the relative intensity of exercise (%VO2max) and the respiratory exchange ratio. It is concluded that changes in free cortisol excretion rates depend on the duration as well as the intensity of exercise.
An ultrasensitive isometric force transducer for single smooth muscle cell mechanics
Authors: Canaday P. G. , Fay F. S.
Published: December 2017

The principles of operation, design, and performance of a differential photooptical transducer of very high sensitivity are described. Useful range is 10–2,000 mugf with sufficiently low drift to allow recordings of contractile responses of isolated single smooth muscle cells. Comparison with several previous designs is presented.
Nonobstructive chronic cannulation of the left circumflex coronary artery of the dog
Authors: Rankin J. S. , McHale P. A. , Greenfield J. C.
Published: December 2017

A cannulation technique for creating a nonobstructive port in a proximal coronary artery is described. The use of this technique in awake animals allows the blood pressure to be measured in a coronary artery distal to an experimentally produced stenosis. This port can also be used to inject drugs directly into the coronary bed.
Application of the hot-wire anemometer to respiratory measurements in small animal
Authors: Godal A. , Belenky D. A. , Standaert T. A. , Woodrum D. E. , Grimsrud L. , Hodson W. A.
Published: December 2017

A hot-wire anemometer was evaluated to determine its suitability for measurement of small tidal volumes. Used with a constant background flow of gas, the output of the hot-wire anemometer was linear and independent of respiratory frequency, temperature, and humidity. The change in output with CO2 concentration was negligible within the physiologic range. The use of a background flow eliminates the need for one-way valves, minimizes dead space, and maintains the flow velocity past the hot wire within its range of linear response.
A simple electrolytic method for cutting small-diameter stainless steel tubing
Authors: Lewis V. A. , Gebhart G. F.
Published: December 2017

An electrolytic approach to cutting small-diameter stainless steel tubing is described. The method is superior to abrasion or manual methods because it produces a clear lumen in the smallest diameter tubing available. The method is simple, quick, and inexpensive and has been found valuable for making small injection needles, small tissue punches, and for repairing broken or occluded microliter syringes.
Chronic carbon monoxide poisoning: effects on performance of the isolated right ventricle
Authors: Bugaisky L. B. , Penney D. G.
Published: December 2017

Rats were exposed continuously for 21–35 days to 500 ppm carbon monoxide (37.4–39.2% HbCO). Aerobic resting force (RF)-active isometric twitch force (AF) curves of isolated right ventricle preparations were constructed at 27 degrees C. CO and control groups are nearly identical when expressed as percent of maximal AF over the range of RF used. There are no significant differences in AF either at the peak of the curve or at RF = 1 g. During 15 min of anoxia AF declines at both RF‣s used. Increased anoxic tolerance is apparent in all CO preparations when anoxic AF is plotted as percent of preanoxic AF. The effect is most marked at RF = 1 g, where time to one-half preanoxic AF is 12.6 +/- 0.9 vs.9.3 +/- 0.8 min for CO-exposed and controls, respectively. However, no significant differences in “absolute” AF are seen between the groups at either level of RF at any minute during anoxia. Aerobic recovery of CO preparations is markedly enhanced at 1 g RF. Anoxic tolerance and aerobic recovery differences, however, are smaller at the peak of the RF-AF curve. Effects on time to peak AF and maximal rate of rise of AF are not marked at either level of RF in CO preparations.
Effects of hypercapnia on mouth pressure during airway occlusion in conscious man
Authors: Altose M. D. , Kelsen S. G. , Stanley N. N. , Levinson R. S. , Cherniack N. S. , Fishman A. P.
Published: December 2017

The effects of hypercapnia and inspiratory flow-resistive loading on mouth pressure during periods of arrested airflow were studied in conscious human subjects to determine the usefulness of inspiratory muscle force in the assessment of respiratory neural efferent activity. Hypercapnia increased the peak end-inspiratory mouth pressure (Ppeak) during complete airway occlusion and the pressures at 100, 200, and 300 ms after the onset of inspiration (P100, P200, P300). During rebreathing without added mechanical loads, P100 and Ppeak increased linearly with the electrical activity of the diaphragm and changes in P100 and Ppeak during hypercapnia correlated well with ventilatory responses to PCO2 (DELTA V/DELTA PCO2) suggesting that occluded mouth pressures are reliable measures of respiratory activity. In individuals with the greatest reduction in delta V/DELTA PCO2 during inspiratory flow-resistive loading, changes in P100 and Ppeak with PCO2 increased only minimally. In contrast, there was a much greater increase in occluded mouth pressures with hypercapnia in the presence of mechanical loading when inspiratory flow-resistive loading failed to depress delta V/DELTA PCO2. In all subjects, occluded mouth pressures were greater at any given PCO2 during mechanical loading than during free breathing. Mechanical loading resulted in augmented respiratory neural efferent activity unexplained by alterations in chemical stimulation.
Heat storage regulation in exercise during thermal transients
Authors: Chappuis P. , Pittet P. , Jequier E.
Published: December 2017

Rate of heat storage (S) was measured by using direct and indirect calorimetry simultaneously in 11 subjects during rest and exercise at three ambient temperatures (Ta of 20, 25, and 30 degrees C), and at two work intensities (40 and 90 W). At rest, the mean value of S was -64.9 W at 20 degrees C, -26.1 W at 25 degrees C, and +9.9 W at 30 degrees C. After 50 min of exercise at 40 or 90 W, S tended toward zero at the three ambient temperatures. This indicates that thermal equilibrium was reached. In addition, at the end of the exercise periods total heat losses (R + C + E) measured at a Ta of 20, 25, and 30 degrees C were similar, i.e., independent of Ta. During the thermal transients and the steady state of exercise, the calorimetric method allows immediate measurement of S to be made, since all the physical terms of the body heat balance equation are determined. The changes in mean body temperature (delta Tb) measured by thermometry showed a delay of 5–10 min when compared with delta Tb measured by calorimetry. Thus, determination of delta Tb by thermometry is not directly applicable during thermal transients, unless the observed delay is taken into account. Our results also support the concept that Tb may be the regulated variable of the thermoregulatory system, since we obtained a very significant and uniform correlation between Esk and delta Tb at the three Ta and the two work intensities which were studied.
Oxygen dissociation curve for chorioallantoic capillary blood of chicken embryo
Authors: Tazawa H. , Ono T. , Mochizuki M.
Published: December 2017

Oxygen dissociation curves for blood in the chorioallantoic capillary of chicken embryos were determined using a microphotometric apparatus made for measuring the reaction velocity of a red blood cell with oxygen and carbon monoxide. The modified Hill's equations expressing the dissociation curve during development were calculated by two methods. P50's at pH of 7.4 were found to be 60.0, 54.4, 46.2, 33.1, and 28.6 mmHg for 10, 12, 14, 16 and 18 days of incubation, respectively. Although the Bohr factor did not show a clear relation to age, the oxygen affinity and the oxygen capacity tended to increase with the lapse of days, and the power of heme-to-heme interaction, to decrease with age. The findings imply that there is a respiratory adaptation of embryos during development.
Oxygenation and deoxygenation velocity factors of chorioallantoic capillary blood
Authors: Tazawa H. , Ono T. , Mochizuki M.
Published: December 2017

The oxygenation and deoxygenation rates of capillary blood of chicken embryo were measured precisely with a microphotometric reaction apparatus. The velocity factors expressed as Fcox and Fcdeox in ml O2-ml RBC-1-S-1-mmHg-1 were calculated as functions of oxygen saturation. They were similar to results previously obtained in human blood using the rapid flow apparatus. The continuous registration of the reaction with oxygen enables us to estimate the equilibrium time of blood when passing through the chorioallantoic capillary. The value obtained was almost identical to the contact time indirectly assessed from the CO reaction. The diffusing capacity of the chorioallantoic capillary plexus of the 16-day-old embryos was estimated as 7.3 x 10(-3) ml-min-1mmHg-1 by using the values of the Fcox and the equilibrium time determined here together with the values of the blood flow and hematocrit which had been obtained in the previous experiments.
Adaptive modifications in the thermoregulatory system of long-distance runners
Authors: Baum E. , Bruck K. , Schwennicke H. P.
Published: December 2017

In seven long-distance runners (42 km or more) the thermoregulatory responses to acute external cooling and heating, under resting conditions, were recorded and compared with those in physically untrained controls. Sweating as well as shivering thresholds were significantly decreased in the runners when compared either in terms of mean body temperature (Tb) or esophageal temperature (Tes); Tb and Tes were reduced in the runners at rest under thermoneutral conditions. Moreover, cold sensation in the runners occurred at lower Tb. The runners thus behaved as if the “set point” of their thermoregulatory system had been reset to a lower level. As for the sweating threshold, the shift is quantitatively comparable to that found in heat adaptation. The described modifications in long-distance runners would prolong the time period until a dangerous body temperature-one of the important limiting factors in physical endurance-is reached during heavy exercise.
Influence of bronchomotor tone on regional ventilation distribution at residual volume
Authors: Engel L. A. , Landau L. , Taussig L. , Martin R. R. , Sybrecht G.
Published: December 2017

We studied the topographical distribution of 133Xe boluses inhaled slowly from RV, as well as the distribution of regional volumes at RV (RVr) in seven seated normal subjects before and after aerosolized isoprenaline (ISO) and after aerosolized methacholine hydrochloride (Mech). After Mech the ratio of inhaled 133Xe in the upper lung regions to that in lower lung regions (U/L) decreased from 3.21 +/- .33 (mean +/- 1 SE) to 1.27 +/- 0.12 (P less than 0.001) and returned to 3.89 +/- 0.55 after Iso. Iso alone increased U/L from 3.23 +/- 0.47 to 5.49 +/- 0.85 (P less than 0.025). The height of phase IV in expired 133Xe vs. volume plots correlated with U/L, being greater after Iso and smaller after Mech in each subject. The difference in RVr between upper and lower lung regions decreased after Mech in four out of five subjects from 0.22 TLC to 0.11 TLC. Iso alone did not change the gradient of RVr. The results are consistent with the concept that increased bronchomotor tone widens the range of critical opening and closing pressures with a more patchy and extensive distribution of airway closure.
Influence of diaphragmatic contraction on ventilation distribution in horizontal man
Authors: Roussos C. S. , Fukuchi Y. , Macklem P. T. , Engel L. A.
Published: December 2017

The washout of a bolus of helium (inhaled from residual volume) during relaxed expiration (RE) through a resistance was compared with that during expiration with voluntary diaphragmatic contraction (VDCE) achieved by tensing the abdominal muscles while maintaining constant expiratory flow (less than 0.4 l/s). In six subjects in the lateral decubitus position, phase IV during RE started at 58 +/- 1.6% vital capacity (VC) (mean +/- 1 SE). During VDCE, when the transdiaphragmatic pressure (Pdi) exceeded 30 cmH2O, phase IV commenced at 8.2 +/- 0.8% VC. The expired He concentration (FEHe) at lung volumes greater than 70% VC was 1.3 +/- 0.05 times that during RE. In supine subjects VDCE flattened the slope of the alveolar plateau and decreased closing volume by 3.7 +/- 0.4% VC. Our results suggest that when the diaphragm is relaxed in the horizontal subject, the hydrostatic gradient of pressure within the abdomen enhances early emptying of dependent lung zones. Diaphragmatic contraction results in more homogeneous emptying. We conclude that diaphragmatic tone influences the vertical gradient of regional volume, and hence of pleural pressure. The latter is not constant, being less during inspiration than during expiration. Therefore, differences in the changes of applied pressure between dependent and nondependent lung regions influence ventilation distribution in subjects in the horizontal posture.
A square-pulse flow method for measuring characteristics of the arterial bed
Authors: Bottomley M. G. , Mainwood G. W.
Published: December 2017

A device was designed to provide a “square” pulse of blood flow into the arterial system. Pulses were injected into the carotid artery of the rabbit during transient cardiac arrest. Analysis of pressure response curves generated by the flow provides information as to the state of the arterial tree. With certain assumptions it is possible to estimate from these curves lumped values of peripheral resistance, critical closing pressure, and arterial compliance. In a series of 12 rabbits the mean value of peripheral resistance was found to be 0.21 +/- 0.7 mmHg-ml-1-min and critical closing pressure was estimated to be 23.6 +/- 3.8 mmHg. This method gives two possible values for arterial compliance 0.036 +/- 0.010 and 0.055 +/- 0.010 ml-mm-1 based, respectively, on the rise and decay curves of the pressure response. The theory and limitations of the method are discussed. The use of the method is illustrated in following the response to increased PCO2 and hemorrhage.
Oxygen electrode syringe as an instrument for determining oxygen-hemoglobin dissociation curves
Authors: Knight V. A.
Published: December 2017

A new instrument is described which simplifies the measurement of the oxygen-hemoglobin dissociation curve, using small volumes of blood. An oxygen electrode, as the plunger of a syringe accommodating increasing volumes of blood at predetermined levels of saturation with oxygen, measures the amount of dissolved oxygen in the plasma, which is proportional to the gas tension.
Oxygen affinity of human blood in presence of carbon monoxide
Authors: Collier C. R.
Published: December 2017

If carbon monoxide is present in the blood, it is necessary to quantitate its effect on apparent O2 affinity in order to properly compute venous PO2 and P50. Ways of doing this are analyzed theoretically. The classical principles of Haldane and of Roughton and Darling are reviewed and simplified. The method of computation of PO2 in the presence of CO as introduced by Forster is shown to be in considerable error. The source of this error is determined. The error produced if the presence of CO is ignored during the computation of P50 is analyzed.
Effect of substrate on hypoxic response of pulmonary artery
Authors: Souhrada J. F. , Dickey D. W.
Published: December 2017

Main pulmonary arteries (MPA) were isolated from young guinea pigs and incubated in a modified Krebs-Henseleit solution containing either glucose and sucrose, or sucrose alone. Experimental hypoxia (PO2=30 mmHg) was induced by aerating the muscle chamber with a gas mixture of 95% nitrogen and 5% carbon dioxide. In must experiments the MPA was electrically stimulated, whereas in some no electrical stimulation was used. The isometric tension of electrically stimulated MPA was analyzed by means of resting tension (RT), active tension (ATmax), and maximum rate of tension development (dT/dt). It was demonstrated that when MPA was exposed to acute hypoxia in a glucose-free medium a significant increase in resting tension was observed in both electrically stimulated and nonstimulated preparations. However, the significantly hypoxic response was inhibited by the presence of glucose in the experimental medium. This tonic response of MPA is suggestive of the in vivo hypoxic pressor response of pulmonary circulation. A lower oxygen tension (PO2=95 mmHg) exposure prior to hypoxia significantly potentiated this hypoxic response of the MPA. In a separate series of experiments, isolated aortas demonstrated a similar response when exposed to acute hypoxia in vitro. Similarly, as in experiments with MPA, the presence of glucose inhibited the hypoxic tonic response of isolated aorta.
Canine hyperthermia with cerebral protection
Authors: Carithers R. W. , Seagrave R. C.
Published: December 2017

Extreme whole-body hyperthermia was achieved without lasting side effects in canines by elevating body core temperature to 42 degrees C, using a warm water bath. Cold water irrigation of the nasal alar fold permitted an additional core temperature elevation of 0.5–1.0 degrees C above brain temperature for periods up to 1.5 h. The brain-core temperature differential was maintained by a physiological arteriovenous heat exchanger located at the base of the brain. The maximum tolerable core temperature for the 21 nonirrigated dogs was 42 degrees C for 60–90 min, whereas that for the 28 irrigated dogs was 42.5–43 degrees C for similar time intervals. A mathematical model of the total heat transfer system described the observed dynamic temperature responses. It was the solution of a differential equation which fit the normalized experimental data points and predicted reasonable values for known and unknown experimental parameters.
Posthyperventilation isocapnic hyperpnea
Authors: Swanson G. D. , Ward D. S. , Bellville J. W.
Published: December 2017

Subjects voluntarily hyperventilated for 10 breaths. A dynamic end-tidal forcing technique manipulated inspired gases to hold end-tidal CO2-O2 tensions at normal values during the voluntary ventilation period and the postvoluntary ventilation recovery period when the subjects returned to spontaneous breathing. Six of the seven subjects studied exhibited a hyperpnea during the recovery period. Although intersubject and intrasubject variations were evident, the average response for 30 experiments in the six subjects was characterized by an initial drop to 32% of the hyperventilation magnitude followed by an exponential-like decrease with a time constant of 22 s. This recovery period response is consistent with theoretical properties of neural network and physical oscillators where there is a persistence in the amplitude response after the removal of the stimulus. Thus, such oscillator properties may govern the respiratory center behavior in man. Furthermore, since isocapnic voluntary ventilation increases cardiac output, the recovery period response may be a consequence of cardiodynamic hyperpnea.
High salt intake and blood pressure in lower primates (Papio hamadryas)
Authors: Cherchovich G. M. , Capek K. , Jefremova Z. , Pohlova I. , Jelinek J.
Published: December 2017

One year of increased salt intake in monkeys elevates mean blood pressure significantly. This effect is more marked in animals exposed just after birth. In animals exposed as adults, the response in males is more pronounced than in females, mainly due to a marked increase of pulse pressure. Th hypertensive response was potentiated by reduction of renal mass, which caused GFR values (in terms of body weight) to decrease compared with intact salt-fed animals, in which GFR values were elevated above the control level. It is concluded that the mechanisms involved in the hypertensive response are similar to those in the rat and dog.
An automated system for assessing metabolic and respiratory function during exercise
Authors: Wilmore J. H. , Davis J. A. , Norton A. C.
Published: December 2017

This paper provides a brief description of a new, totally automated system for assessing metabolic and respiratory function during exercise. This system was evaluated simultaneously against two established systems, one a computer-based system and the other a semiautomated system, to determine its validity over a wide range of metabolic levels, i.e., less than 2 to greater than 16 mets. A total of 112 males and females, 12–65 yr of age, performed either arm or leg exercises on a bicycle ergometer or treadmill, starting at approximately 2 mets and progressing by approximately 1 met/min to the point of volitional fatigue. Respiratory and metabolic assessments were made each minute during the entire exercise bout. Comparisons across the three systems demonstrated remarkable agreement, particularly when all potential sources of error for each system are considered. Although several statistically significant differences between two of the systems were noted at the lowest work levels, the difference in VO2 between any two systems never exceeded 1.1 ml/kg-min.