bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of endotoxin and leukocytic pyrogen pyrogenicity in newborn guinea pigs
Authors: Blatteis C. M.
Published: December 2017

Guinea pigs under 8 days of age generally are unable to develop fever (viz., deltaTre greater than 0.5 degrees C) in response to a standardized dose of endotoxin (2 mug/kg iv of Salmonella enteritidis [SE]). This study was undertaken to determine whether this lack of responsiveness might be due to an incapacity of leukocytes from young neonates to produce sufficient leukocytic pyrogen (LP). Three series of experiments were performed at Ta = 27 degrees C: guinea pigs aged 0–2, 4, and 8 days were injected iv with: a) 2, 4, 8, or 16 mug/kg of SE, b) 0.1, 0.5, or 1.0 ml of LP generated by 8 mug of SE/25 X 10(6) leukocytes from adult guinea pigs (LPa), or c) 0.1 or 1.0 ml of LP generated by 8 mug of SE/25 X 10(6) leukocytes from 0-5-, 6-12-, and 13-16-day-old guinea pigs (LPn). Adult guinea pigs received iv 1.0 ml of LPa or LPn. The results revealed that fever could be induced in these animals from birth, but the required doses of SE, LPa and LPn were greater the younger the guinea pigs. Under these conditions, LPn, regardless of the donors' ages, produced fever in all the recipients. It is concluded that the pyrogenic unresponsiveness of newborn guinea pigs to endotoxin may be related not to an inability of leukocytes from these neonates to elaborate LP, but rather to an insensitivity of, presumably, their hypothalamic febrogenic mechanisms to low levels of LP.
Effects of hyperoxia on leg blood flow and metabolism during exercise
Authors: Welch H. G. , Bonde-Petersen F. , Graham T. , Klausen K. , Secher N.
Published: December 2017

These experiments were designed to investigate the effects of O2 breathing on limb blood flow and metabolism during exercise. Six subjects took part in the study. Four subjects breathed air or 100% O2 while pedaling a Krogh bicycle at 150 W (55–70% of maximal aerobic capacity). Two subjects breathed either 60% or 100% O2 while working at a power output at or slightly in excess of their maximal aerobic capacities. The major findings of the study were 1) leg blood flow is reduced during exercise when comparing hyperoxia with normoxia; 2) VO2 of the exercising limb is not different during hyperoxia; 3) O2 delivery to the leg (the product of blood flow and arteriovenous O2 difference) is not significantly different in the two conditions; and 4) blood pressure is not markedly affected in the experiments at 150 W. Since BP was not different during hyperoxia, at a time when flow was reduced by 11%, this suggests an increased resistance to flow in the exercising limb. In general, these findings are consistent with those reported for the in situ dog muscle but are at variance with results of experiments with humans, especially the reports indicating substantial increases in O2 uptake during hypertoxic conditions.
Temperature and force-velocity relationship of human muscles
Authors: Binkhorst R. A. , Hoofd L. , Vissers A. C.
Published: December 2017

The force-velocity relationship of maximal contractions with the handgrip muscles is established in a group of subjects. The effect of different muscle temperatures is studied. The parameters vo (maximal velocity), Fo (maximal force), Pmax (maximal power), a/Fo and H (both parameters describing the shape of the curve), and Ft/Fo (the value of the force at which power is maximal) are established. It is shown that 1) in repeated measurements the coefficient of variation in general is less than 10% for all the parameters except a/Fo; 2) the parameter a/Fo should be discarded in comparative measurements since it is not linearly related to the course of the curve. A parameter called H should be used instead to describe the curvature; 3) an increase in muscle temperature is accompanied by an increase in magnitude of all parameters except Fo. The temperature effect expressed as Q10 in the range 22–38 degrees C is in the order of 1.2.
Effects of body temperature on ventilatory response to hypoxia and breathing pattern in man
Authors: Petersen E. S. , Vejby-Christensen H.
Published: December 2017

The ventilatory response to hypoxia (PAO2 55 and 45 Torr) at each of four levels of PACO2 was studied in five healthy subjects before and after a rise in rectal temperature of 1.4 degrees C had been induced by means of a heated flying suit. At a given level of chemical drive both ventilation and mean inspiratory flow increased after heating, frequency relatively more than tidal volume. In isoventilation comparisons mean inspiratory flow was identical in normo- and hyperthermia, whereas the durations of inspiration (TI) and expiration (TE) were proportionately shortened. It is suggested that a rise in temperature shortens TI by affecting a central “clock” and that TE changes are secondary to changes in end-inspiratory volume. The euoxic CO2 response in hyperthermia was suggestive of multiplication between CO2 and temperature. Hypoxic sensitivity was significantly increased, indicating a temperature effect on the arterial chemoreceptors. The breathing pattern was in either temperature condition identical in euoxia and in hypoxia.
Panting in small mammals: a comparison of two marsupials and the laboratory rabbit
Authors: Nicol S. C. , Maskrey M.
Published: December 2017

By use of a barometric technique, tidal volume (VT), minute volume (VE), respiratory frequency (f), and respiratory evaporative heat loss (Eex) were measured from conscious unrestrained potoroos (Potorous tridactylus), barred bandicoots (Perameles gunnii), and New Zealand white rabbits (Oryctolagus cuniculus) at temperatures in and above the thermoneutral zone (TNZ). Rectal temperature (Tre) and oxygen consumption were also measured. VT initially decreased with rising Ta, but in the potoroo and rabbit it then increased past the resting level. VE increased much more in the marsupials than in the rabbit, and higher Eex maxima were also found for the marsupials. The marsupials had high Q10's above the TNZ, and had a panting efficiency of 80%. The rabbits had a Q10 of 1.9 above the TNZ and 100% panting efficiency. The high VE and Eex and low panting efficiency of the marsupials may be due to their lower Tre which allows transfer of heat from the environment to the animal.
Oxygen storage in beavers
Authors: McKean T. , Carlton C.
Published: December 2017

Ten wild beavers were anesthetized with pentobarbital and total lung capacity (60.5 +/- 4.8 ml/kg), hemoglobin (12.4 +/- 1.5 g/100 ml), blood volume (6.5 +/- 0.8% body mass), and myoglobin (1.2 +/- 0.3 g/100 mg) were determined. These measured values were used to calculate total oxygen storage capacity. Even though the beaver is a good diver (15-min submersion time), its oxygen stores are not large and are about one-third the stores of a good marine diver, the harbor seal.
Kidney structure and function of desert kangaroos
Authors: Denny M. J. , Dawson T. J.
Published: December 2017

The structure and function of the kidneys of two species of desert kangaroos, the red kangaroo (Megaleia rufa) and the euro (Macropus robustus), were examined. Both kangaroos had glomerular filtration rates (GFR), renal plasma flows, and urine flow rates, when hydrated and dehydrated, which were lower than those of similarly sized eutherian mammals. The differences observed between the two species of marsupials were both structural and functional. The GFR of the red kangaroo was higher than that of the euro, under hydrated and dehydrated conditions, and this was correlated with the occurrence of larger and more numerous glomeruli, particularly juxtamedullary glomeruli, in the red kangaroo. Although the kidney of the euro had a greater relative medullary thickness than that of the red kangaroo, the latter had better urine-concentrating abilities. As opposed to this the euros reabsorbed significantly more urea from the filtrate when dehydrated (89.0%) than did the red kangaroos (69.2%). This ability of the euro to resorb more urea may be related to their tendency to overgraze their restricted home ranges during drought.
Respiratory movements in the fetal guinea pig in utero
Authors: Kendall J. Z.
Published: December 2017

Intrauterine respiratory movements in the fetal guinea pig were detected from about 0.6 of term by the use of chronically implanted tracheal and amniotic catheters. Three distinct patterns were seen: 1) “slow” breathing recurring at a rate of 1–8/min; 2) “rapid irregular” breathing in which episodes last a few seconds to 40 min and the frequency of breathing is high (greater than 0.5 HZ) (the respiratory movements are associated with negative tracheal pressures of of 0.5–20 Torr); and 3) “rapid regular” breathing which recurs in bursts lasting 0.6–6.8 min with a maximum incidence of 3/h. Inspiratory efforts in the range of 10–20 Torr were uniform during a single episode. All three types of respiratory activity were continued into first stage labor, both during and between contractions, but were absent during second stage labor.
Influence of lung parenchyma on dynamic bronchial collapsibility of excised dog lungs
Authors: Sasaki H. , Takishima T. , Sasaki T.
Published: December 2017

The main bronchi of excised dog lobes were obstructed 5–6 cm from their origin with beads, so that they did not communicate with the peripheral air spaces. With the lobe held at constant transpulmonary pressure, bronchial pressure-volume curves were recorded during both static and dynamic bronchial deflations. This was done both before and after dissecting the obstructed bronchus free of parenchymal attachments. The parenchymal contribution on dynamic deflation was much larger than the airway contribution: dynamic bronchial compliances in intact bronchi were 58 +- 8% and 65 +- 8% of the static at dynamic rates of bronchial deflation of 14 and 8 ml/s, respectively, whereas in dissected bronchi they were 72 +- 9% and 78 +- 9%. These relationships were not influenced by changes of transpulmonary pressure applied to the lobar parenchyma. The parenchymal effect on dynamic bronchial compliance was analyzed in terms of parenchymal interdependence and bronchial stress adaptation. We concluded that the presence of lung parenchymal attachments significantly reduced dynamic bronchial collapsibility as compared to static collapsibility.
Effects of Valsalva and Mueller maneuvers on breath-holding time
Authors: Bartlett D.
Published: December 2017

Breath holding to the breaking point was studied at FRC in six healthy subjects in the sitting position. Breath-holding time increased with successive trials within experimental sessions in all subjects. To study the influence of Valsalva and Mueller maneuvers on breath-holding performance, sustained inspiratory or expiratory effort against an occluded mouthpiece was initiated 5 s before the anticipated breaking point, determined in previous trials. The subject tried to maintain a target mouth pressure of +20 or -20 cmH2O, displayed on an oscilloscope, for the remainder of the breath hold. Both types of maneuver consistently prolonged breath-holding time in all subjects. However, a control maneuver, in which the subjects squeezed rubber bulbs with their hands, was equally effective in prolonging breath-holding time. The results demonstrate the important influence of psychological factors on breath-holding performance and emphasize the need for caution in the interpretation of effects of “relieving maneuvers” on breath-holding time.
Diet and starvation on the composition and calculated density of fat-free body mass
Authors: Mendez J. , Kollias J.
Published: December 2017

The density of the fat-free body mass (FFM) was calculated from carcass composition and density of body components in 148 growing rats under different dietary conditions. These conditions were controlled feeding with 20% and 5% casein diets during 6 and 9 wk, followed by 5 days of starvation, and after starvation with 2 wk refeeding with 20 and 5% casein diets. The results showed that the density of FFM was fairly constant. The means and standard deviations for all conditions were 1.0965 +/- 0.0057 and 1.0956 +/- 0.0075, for the 20% and 5% casein groups, respectively, with a grand mean of 1.0960 +/- 0.0066. It was concluded that the assumption of a constant density of FFM holds very well for many dietary and experimental conditions.
Cardiac function and exercise training in conscious dogs
Authors: Stone H. L.
Published: December 2017

Exercise training (T) was accomplished in 21 mongrel dogs. The animals were instrumented to measure ascending aortic flow, left ventricular pressure, and left atrial pressure. They were allowed to recover for 4 wk following surgery before accomplishing a standardized submaximal test (SMT). The exercise program alternated daily between sprint and endurance training. During T, the animals were tested while lying quietly on a laboratory table as well as during the SMT. In six animals, ventricular function curves (VFC) were obtained by rapid volume loading at similar time intervals as the SMT. Heart rate increased during the SMT but was found to be reduced in the T animals by an average of 20 beats/min. The maximum derivative of left ventricular pressure (P) increased during the SMT in T animals by an average of 2,200 Torr/s above the untrained animals. The VFC was lower in T animals than untrained animals because of a reduction in heart rate response. Results indicate a reflex adaptation of the nervous system with training to improve cardiac function.
Effect of osmolality on red blood cell viscosity and transit through the lung
Authors: Effros R. M. , Chang R. S. , Silverman P.
Published: December 2017

The mean transit times of labeled red blood cells and albumin were compared in eight isolated rabbit lungs perfused with physiological albumin solutions. The osmolality of these solutions was adjusted by altering the concentration of sodium chloride. The ratios of the mean transit times of injected red blood cells to those of albumin increased as perfusion osmolality increased from hypotonic to isotonic and from isotonic to hypertonic levels. This change occurred despite a decline in pulmonary vascular resistance and red blood cell size as osmolality was increased. Red blood cell viscosity (determined with a cone-plate viscometer) increased with osmolality and it was concluded that this change of viscosity impaired the relative rate of red blood cell transit through the lungs. Passage of red blood cells through rigid homoporous membranes appeared to be related primarily to red cell size rather than vascosity. These observations suggest that both red blood cell viscosity and capillary distensibility play an important role in determining the velocity of red blood cells through the capillaries.
Computer-based system for analysis of respiratory responses to exercise
Authors: Pearce D. H. , Milhorn H. T. , Holloman G. H. , Reynolds W. J.
Published: December 2017

A computer-based system for the determination of tidal volume, respiratory frequency, minute ventilation, oxygen transfer, carbon dioxide transfer, respiratory exchange ratio, end-tidal oxygen, end-tidal carbon dioxide, and heart rate is presented. These variables are first determined on a breath-by-breath basis from data (expired carbon dioxide and oxygen fractions, airflow, and ECG) prerecorded on an FM magnetic type system. The breath-by-breath data are then averaged for each experimental run in 5-s increments. The 5-s increment data from a group of subjects can then be averaged and the SEM determined at prescribed periods of time. For the study of individual respiratory transient we found the 5-s increment data to be more useful than the breath-by-breath data because it has a lesser degree of fluctuation. The system is especially adapted to careful observation of the responses within the first few seconds of a change in work load. Appropriate computer programs are discussed. The results of several experiments are compared with data from other sources and found to be in good agreement.
Effect of cold exposure on water requirements on three species of small mammals
Authors: Deavers D. R. , Hudson J. W.
Published: December 2017

Water turnover rate (WTR) was determined from tritiated water (3H2O) loss in the short-tailed shrew (Blarina brevicauda), red-backed vole (Clethrionomys gapperi), and white-footed mouse (Peromyscus leucopus). When given ad libitum water at Ta of 20 degrees, B. brevicauda, C. gapperi, and P. leucopus turned over 16.2, 13.8, and 6.2 ml/day, respectively; minimum WTR was 9.9, 7.8, and 3.5 ml/day, respectively. When they were given ad libitum water at 5 degrees C, WTR was 1.4 to 1.6 times higher than at 20 degrees C. On minimum water rations, WTR at 5 degrees C was 1.7 to 1.9 times higher than at 20 degrees C. Since increases in VO2 at 5 degrees C and at 20 degrees C were of about the same magnitude, increased metabolic rates may have caused increased water requirements. Total body water (TBW) was calculated from 3H2O dilution. On minimum water rations, the three species at both Ta's showed decreases in TBW and body weight, but percent body H2O increased.
Lung recoil and gas trapping during oxygen breathing at low lung volumes
Authors: Rodarte J. R. , Burgher L. W. , Hyatt R. E. , Rehder K.
Published: December 2017

If airways are closed at lung volumes less than the closing volume (CV), there should be correlations among 1) the volume of trapped N2 (VTN) during N2-washout performed below CV, 2) the increase in static lung recoil pressure (delta P) while breathing below CV after denitrogenation compared with breathing air (due to absorption atelectasis distal to closed airways), and 3) the CV. Static inspiratory pressure-volume (PV) curves and CV were measured in 18 seated normal volunteers (ages 24–48 yr). Subjects then breathed air for 30 s and O2 for 2.5 min at RV + 0.6 liter (LVB-air), and an inspiratory PV curve and VTN were determined. While still breathing O2, the subjects repeated the 3 min of low-volume breathing (LVB-O2). There was a significant (P less than 0.001) delta P with LVB but no difference between delta P (LVB-air) and delta P (LVB-O2). CV was not related to VTN or to either delta P. VTN was not related to delta P (LVB-O2)--delta P (LVB-air) nor to delta P (LVB-air), but was related to delta P (LVB-O2). Evidence of airway closure could not be demonstrated in all subjects by LVB and when present showed no correlation with CV.
Plasma norepinephrine responses of man in cold water
Authors: Johnson D. G. , Hayward J. S. , Jacobs T. P. , Collis M. L. , Eckerson J. D. , Williams R. H.
Published: December 2017

The hypothermic stress of immersion in cold water stimulates release of norepinephrine from the sympathetic nervous system. The speed and pattern of this response was studied in six healthy men by serial measurements of plasma norepinephrine concentrations before, during, and after 60 min of immersion in 10 degrees C water. After immersion for 2 min, the mean norepinephrine concentration was increased from 359+/-32 (basal) to 642+/-138 pg/ml and rose gradually to a maximum of 1.171+/-226 pg/ml after 45 min of immersion. Metabolic rate increased approximately threefold during the immersion period. After rewarming in warm water (40 degrees C), the subjects showed a transient peak in plasma norepinephrine followed by a rapid decrease to basal levels after 30 min. The fall in plasma norepinephrine after approximately 8 min of rewarming occurred despite persistent depression of the core temperature and coincided with a sudden decrease in metabolic rate and cessation of body shivering. These results suggest that the sympathetic nervous response to cold can be activated or suppressed very quickly and is dependent on the skin temperature.
Effect of hyperbaric oxygen exposure on pulmonary clearance of 5-hydroxytryptamine
Authors: Block E. R. , Fisher A. B.
Published: December 2017

Clearance of 5-hydroxytryptamine (5-HT) by the lungs of normal and vitamin E-deficient rats was evaluated following a 60-min exposure to 100% oxygen (O2) at 4 ATA (HBO). After exposure, lungs were isolated, ventilated, and perfused, with a recirculating system used for measurement of 5-HT clearance. Control lungs were obtained from rats exposed to air at 1 ATA. In control normal rats, fractional clearance of 5-HT was 0.78+/-0.03 (mean+/-SE). Following HBO 5-HT clearance was 0.55+/-0.04 (P less than 0.01). In control vitamin E-deficient rats. 5-HT clearance was 0.85+/-0.05 and was decreased to 0.46+/-0.03 (P less than 0.001) following HBO. To evaluate the effect of recovery time after HBO on 5-HT clearance, separate groups of rats were killed at varying intervals post-HBO. In normal rats, 5-HT clearance had returned to control levels by 3–4 after HBO; in vitamin E-deficient rats, clearance remained unchanged 4 h after HBO and was only 74% (P less than 0.001) of control values 24 h post-HBO. These results indicate that depression of pulmonary 5-HT clearance occurs in rats due to hyperoxia and is potentiated by vitamin E deficiency. This represents a reversible alteration of lung function which requires vitamin E for complete recovery.
Measurement of evaporative water loss in small animals by dew-point hygrometry
Authors: Bernstein M. H. , Hudson D. M. , Stearns J. M. , Hoyt R. W.
Published: December 2017

This paper presents the procedures and equations to be utilized for measurement of evaporative water loss (mw), by use of the dew-point hygrometer, in small animals exposed to air containing water vapor in an open-flow system. The system accounted accurately for the water evaporated from a bubble flask. In addition, hygrometric measurements of pulmocutaneous mw in pigeons (Columba livia, mean mass 0.31 kg) agreed closely with simultaneous gravimetric measurements, utilizing a desiccant in the sample stream, in a manner independently of air temperature (Ta, 20 or 40 degrees C), ambient water vapor pressure (PW, 4–16 10(2) Pa), or mw (5–66 mg-min-1). Evaporation in pigeons was independent of PW at 20 degrees C, but increased with decreasing PW at 40 degrees C, suggesting differences in ventilatory adjustments to changes in PW at the two temperatures.
In vivo gas trapping induced by nitrous oxide
Authors: Sergysels R. , Amyot R. , Macklem P. T. , Martin R. R.
Published: December 2017

Repeated vital capacity (VC) breaths in 17 anesthetized and curarized dogs induced a small but significant increase in residual volume (RV). This trapping was greatly enhanced when a mixture of 80% N2O and 20% O2 (N2O-O2) was used instead of air. VC breaths with N2O-O2 also increased closing volume, closing capacity and closing pressure determined with 133Xe. Successive quasi-static pressure volume (PV) curves of the lung showed a shift to the right at high lung volume and to the left at low lung volume. Again these changes were more impressive with N2O-O2). The PV curve of the chest wall was unchanged. Insufflations from RV were necessary to produce the gas trapping. Increase in RV was positively related to the size of the inspired volume, to N2O concentration, and inversely related to the inspiratory flow rate. Vagotomy, intravenous isoproterenol, and intravenous propanolol did not alter the phenomena. We propose that these observations can be explained by the presence of foam in the airways and that N2O leads to an increase of foam by osmotic liquid shift into the bronchioli, and/or to an increase in bubble's size by gas diffusion.
Protein metabolism by rat lung: influence of fasting, glucose, and insulin
Authors: Thet L. A. , Delaney M. D. , Gregorio C. A. , Massaro D.
Published: December 2017

We studied protein metabolism by rat lung slices. We found that phenylalanine is not metabolized to other substances by the lung and that the rate of incorporation of L-[U-14C]phenylalanine into protein, calculated using its intracellular specific radioactivity, reached a maximum within 20 min and remained stable for the rest of a 3-h incubation. The rate of protein degradation, determined using [12C]phenylalanine as a marker, was linear over a 3-h incubation. Fasting for 3 days slowed the increase in lung protein content of fasted compared to nonfasted rats; there was also a decrease in protein synthesis and an increase in proteolysis. In fed rats, glucose, insulin, and glucose plus insulin did not alter protein synthesis. Glucose, insulin alone, and glucose plus insulin decreased proteolysis. We conclude that the in vitro system reflected changes in the in vivo protein content of the lung. Fasting decreases protein synthesis and increases proteolysis. Glucose and insulin alone modulate protein metabolism in the lung by acting on the degradative rather than the synthetic process.
Maximum expiratory flow changes induced by longitudinal tension on trachea in normal subjects
Authors: Melissinos C. G. , Mead J.
Published: December 2017

Maximal expiratory flow (Vmax) was noticed to increase in some subjects during neck hypertension. Maximal expiratory flow volume (MEFV) curves were obtained in 15 normal young subjects at regular and hyperextended neck posture. Eleven of the subjects had consistently higher Vmax during neck hyperextension at high lung volumes, accompanied by MEFV configuration changes in the form of the obliteration of a concavity towards the volume axis that existed in the curve at regular neck posture. Effort independency was documented at lung volumes where the changes occurred. Radiographic studies indicate tracheal elongation with a relatively fixed carina during neck hyperextension. We propose that at high lung volumes in normal young subjects, the flow-limiting mechanism resides in the trachea and that the increased Vmax with neck hyperextension. We propose that at high lung volumes in normal young subjects, the flow-limiting mechanism resides in the trachea and that the increased Vmax with neck hyperextension reflects the effect of tracheal elongation which stiffens the trachea under dynamic conditions and increases its tube-wave speed. This concept was confirmed by MEFV curves obtained from anesthetized tracheostomized dogs when increased tracheal longitudinal tension resulted in an increase of Vmax.
Increase in sweating sensitivity by endurance conditioning in man
Authors: Henane R. , Flandrois R. , Charbonnier J. P.
Published: December 2017

Sweating sensitivity has been evaluated at rest in 10 competitive athletes (cross-country skiers and swimmers). Three sedentary men underwent a 3-mo period of endurance training in a temperate climate, (dry bulb temperature (Tdb): 18 degrees C) and had their sweating sensitivity measured before and after the training period. Mean maximum oxygen uptake (Vo2max, ml.min(-1).kg(-1)) was: skiers: 66.5; swimmers 65.8; sedentary men, pretraining 40.9; posttraining: 48.3 (+18%). Sweat output of athletes under a given stress (passive heating) was markedly higher than that of sedentary men. Skiers exhibited a high level of heat tolerance and were better acclimatized than swimmers, although they had never experienced exposure to heat. The increase in Vo2max of sedentary men was accompanied by 1) an increase in sweating sensitivity with a decrease of body heat storage at steady state (pretraining: 5.4 kJ.kg(-1); posttraining: 3.5 kJ.kg(-1); P less than 0.05); 2) significant shift down the temperature scale with reduced rectal temperature (Tre) for sweat onset; 3) an increase of gain constants of sweating (W.m-2 degrees C(-1) (pretraining: 168; posttraining: 269; gain constant of swimmers: 222). It was suggested that endurance training in cold or temperate conditions with significant increase of Vo2max could act on the thermoregulatory function in a way similar to body heating procedures, such as work in heat, and could contribute to heat acclimatization.
Phosphagen and lactate contents of m. quadriceps femoris of man after exercise
Authors: Harris R. C. , Sahlin K. , Hultman E.
Published: December 2017

Muscle biopsies were taken from the m. quadriceps femoris of man immediately after termination of dynamic and isometric exercise. These were analyzed for adenosine triphosphate (ATP), adenosine 5′-diphosphate (ADP), adenosine 5′-phosphate (AMP), phosphorylcreatine (PC), creatine, pyruvate and lactate. Regardless of type, intensity, and duration of the preceding exercise, a general pattern of the relation between high-energy phosphates and lactate content could be observed. PG showed a nonlinear relationship to the muscle lactate content. The ratio of ATP to ADP appeared to decrease linearly when lactate content increased. The relationships are believed to be the consequence of a steady-state condition where muscle pH is one of the major determining factors.
Measurement of body temperature in neonatal mice
Authors: Goodrich C. A.
Published: December 2017

A simple method is described for obtaining repeated measurements of body temperature in young mice with minimal error introduced through stress. Temperatures are measured by an external thermocouple attached to the thorax in the region of the heart. A sling around the animal's thorax provides insulation for the thermocouple from surrounding air and mild restraint of the animal during measurement. Comparison with temperatures obtained in other locations indicates that external thoracic temperature as described gives a reliable estimate of true body temperature in mice up to 21 days old. Typical results with normal mice aged 1 day to 6 wk postpartum are included, together with a brief discussion of the technique's applicability.
Ovarian hormonal responses to exercise
Authors: Jurkowski J. E. , Jones N. L. , Walker C. , Younglai E. V. , Sutton J. R.
Published: December 2017

The effects of exercise on estradiol, progesterone, follicle-stimulating hormones (FSH), and luteinizing hormone (LH) were studied in nine healthy females. Subjects were studied during light, heavy, and exhaustive exercise in the midfollicular and midluteal portions of their menstrual cycles. Resting hormone levels followed the expected pattern. Increases in estradiol and progesterone occurred at all intensities of exercise in the luteal phase but only in estradiol at exhaustion in the follicular phase. LH was unchanged with exercise in either phase and FSH increased in the follicular phase but not in the luteal phase. We conclude that exercise is a physiological stimulus to elevations in plasma estradiol, progesterone, and FSH, but not LH. The elevations are more marked in the luteal phase for the steroids and in the follicular phase for FSH. Increases in estradiol and progesterone are related to the intensity of exercise and appear to be independent of pituitary control.
Wheel running of kangaroo rats, Dipodomys merriami, as related to food deprivation and body composition
Authors: Dill D. B. , Soholt L. F. , Morris J. D.
Published: December 2017

Kangaroo rats deprived of food ran themselves to death in 48 h in wheel cages. Despite the loss of 14.5% of body weight the ratio of water to protein was the same after the run as it was in control rats. Metabolic measurements at rest and in the running wheel and weight loss in the 48-h run were used to estimate fuels used and water expended. Two-thirds of the initial amount of fat and 9% of the protein were metabolized. The terminal mean percentage of body fat was about twice that observed in rats trapped in the spring of 1967, when seed production was low: death in the 48-h run could not have been due to depletion of body fat alone. The powerful activity drive seen in hungary kangaroo rats presumably is intensified in dry years when food is scarce and may deplete their reserves enough to result in death from starvation.
Physical training and connective tissues in young mice: biochemistry of long bones
Authors: Kiiskinen A. , Heikkinen E.
Published: December 2017

The effect of physical training on collagen, ground substance, and nucleic acid concentrations in long bones was studied in male mice of NMRI strain. The mice to be trained and their controls were about 2 wk old at the beginning of training, which took place on a 5 degrees inclined treadmill 5 days/wk for 3–22 wk. The duration of daily exercise was increased progressively over 3 wk. The final daily exercise bouts were 50 and 80 min for moderate programs and 180 min for the intensive program at a speed of 30 cm/s. Increased concentrations of nitrogen and hexosamines were found at both training intensities, especially after prolonged training. No conclusive changes in nucleic acid concentrations were observed after training. The hexosamine-hydroxyproline ratio was higher and the hydroxyproline-nitrogen ratio lower in the long bones of trained animals compared to the controls. In conclusion these data suggest that prolonged physical activity affects the organic matrix of long bones by maintaining above average concentrations of glycosaminoglycans in matured bones.
Exercise ventilatory mechanics at increased ambient pressure
Authors: Wood L. D. , Bryan A. C.
Published: December 2017

Transpulmonary pressure, lung volume, and flow rate were recorded in two healthy subjects performing graded exercise between 1 and 10 ATA. At simulated depths greater than 4 ATA, exercise was terminated by severe choking dyspnea at levels of work, oxygen consumption, heart rate, and ventilation significantly lower than during maximum exercise at 1 ATA. Comparison of exercise ventilatory mechanics with corresponding maximum expiratory flow-volume and expiratory isovolume pressure-flow (IVPV) curves demonstrated that the reduced aerobic capacity was associated with expiratory flow limitation. We conclude that dynamic airways compression limited aerobic capacity at these depths by causing a persistent cough making it seem difficult to continue exercise. Analysis of the IVPV curves suggested that maximum expiratory flow was reduced at depth below the rate allowing adequate exercise ventilation because increased gas density raised the resistance downstream from equal pressure points. At each level of sumbaximal exercise, end-expiratory position and alveolar CO2 tension increased with ambient pressure due primarily to the density dependence of airways resistance. In these respects, healthy subjects breathing dense gas resemble patients with obstructive lung disease.
Colloid osmotic pressure changes of dog's blood exposed to different mixtures of CO2 and air
Authors: Kakiuchi Y. , DuBois A. B. , Gorenberg D.
Published: December 2017

Hansen's membrane manometer method for measuring plasma colloid osmotic pressure was used to obtain the osmolality changes of dogs breathing different levels of CO2. Osmotic pressure was converted to osmolality by calibration of the manometer with saline and plasma, using freezing point depression osmometry. The addition of 10 vol% of CO2 to tonometered blood caused about a 2.0 mosmol/kg H2O increase of osmolality, or 1.2% increase of red blood cell volume. The swelling of the red blood cells was probably due to osmosis caused by Cl- exchanged for the HCO3- which was produced rapidly by carbonic anhydrase present in the red blood cells. The change in colloid osmotic pressure accompanying a change in co2 tension was measured on blood obtained from dogs breathing different CO2 mixtures. It was approximately 0.14 mosmol/kg H2O per Torr Pco2. The corresponding change in red cell volume could not be calculated from this because water can exchange between the plasma and tissues.
Correction for loss of CO2 from blood during measurement of osmotic pressure
Authors: Khosla S. S. , DuBois A. B.
Published: December 2017

During osmolality measurement by the vapor pressure method, exposure of the blood sample to air lowers the blood CO2 content and hence osmolality. A modification of the sample holder of a vapor pressure osmometer is described allowing exposure of the blood sample to a gas mixture with known concentration of CO2 and O2 while inside the closed sample chamber. This restores its CO2 content and hence osmolality. Data are presented comparing the unmodified and modified vapor pressure method with the freezing point depression method. A table was prepared for further correction of osmolality in case the blood's PCO2 differs from that of the gas mixture.
Respiratory mechanics in conscious sheep: response to methacholine
Authors: Wanner A. , Reinhart M. E.
Published: December 2017

Most currently used animal models of allergic airway diseases differ from human asthma in that induced bronchospasm in the former is not accompanied by pulmonary hyperinflation. In the present investigation, we chose unsedated, restrained sheep to determine the effect of cholinergic bronchial provocation on respiratory mechanics, functional residual capacity (FRC), and arterial blood gases. Seven animals had been actively sensitized by intramuscular injections of Ascaris suum extract, and four untreated animals served as controls. After inhalation of nebulized 1% methacholine solution, mean pulmonary resistance increased significantly in the sensitized sheep from a base line of 2.4 +/- 0.7 (SD) cmH2O/(l/s) to a peak value after 5 min of 7.9 +/- 4.0 cmH2O/(l/s). This was accompanied by a significant increase of mean FRC from 0.99 +/- 0.14 liters to 1.31 +/- 0.24 liters. The observed changes were transient, and after 60 min, pulmonary resistance and FRC had returned to base-line values. No significant changes occurred in static lung compliance, PaO2, PaCO2, and pH. In the control animals, methacholine provocation did not produce changes in pulmonary function. These results indicate that, in sensitized conscious sheep, induced bronchospasm is associated with pulmonary hyperinflation.
Static lung mechanics of intact and excised rhesus monkey lungs and lobes
Authors: Pare P. D. , Boucher R. , Michoud M. C. , Hogg J. C.
Published: December 2017

Subdivisions of lung volume and pressure-volume (PV) curves of the lung and chest wall (CW) were measured in 12 rhesus monkeys (Macacca mulatta) under pentobarbital anesthesia. In addition, volumes and PV curves were obtained on the excised lungs and lobes of 12 cynomolgus monkeys (M. fasicularis). Boyle's law was used to determine functional residual capacity (FRC) in the intact animals and water displacement to determine minimal volume (MV) in the excised lungs. Total lung capacity (TLC = lung volume at a transpulmonary pressure of 30 cmH2O) was similar in vivo and in vitro (90 + 83 ml/kg) but residual volume (RV = volume at airway pressure of -50 cmH2O) and MV differed markedly (16.5 + 5.9 ml/kg). In the intact animals a very stiff CW appeared to determine RV, whereas airway closure determined MV in excised lungs. PV curves of upper and lower lobes were not different when expressed as %TLC but when expressed as milliliters of gas per gram of lung, the upper lobes contained significantly more gas per unit weight.
A simple ventilator suitable for respiratory gas studies
Authors: Heneghan C. P. , Martindale D. D. , Blackburn J. P.
Published: December 2017

A simple ventilator is described where a spring-loaded bellows is filled from a compressed gas supply. The outflow from the bellows to the subjects is controlled by solenoid valves. The device is a minute volume divider and the durations of inspiration and expiration are set by timers that operate the solenoid valves. The valves are positioned near the subject to minimize dead space and gas compression effects. Precise valve timing ensures separation of inspirate and expirate. The ventilator is suitable for respiratory gas studies on animals and may be modified for human use if required.
Effects of hydrostatic pressure on conduction and excitability in rabbit atria
Authors: Doubt T. J. , Hogan P. M.
Published: December 2017

The effects of hydrostatic pressure on cardiac conduction and excitability were studied in 39 rabbit right atrial preparations. Increases in pressure significantly increased atrial conduction time, i.e., 41% at 150 ATA. Excitability, determined from strength-duration (S-D) curves, was depressed by pressure. The slope constant of the S-D curve increased 64% at 150 ATA. Rheobase and the X-asymptote were not affected significantly. The depression of excitability partially accounted for the slowed conduction. Frequency stress and pressure had an additive effect to produce even greater decreases in excitability and increases in conduction time. Atrial refractoriness to premature stimuli also increased as a function of pressure. Nitrous oxide (2.5 ATA) partially reversed the effects of 150 ATA of pressure on conduction time and excitability. The results suggest that pressure acts by altering basic functional components of the myocardial cell membrane. Some of these changes, particularly when combined with frequency stress, i.e., rapid heart rate, may pose a serious threat to humans exposed to hyperbaric environments.
Determinants of oxygen uptake during sodium bicarbonate infusion
Authors: Patterson R. W. , Sullivan S. F.
Published: December 2017

Steady-state passive hyperventilation alkalosis produces a predictable increase in oxygen uptake (VO2) proportional to the change in arterial pH (pHa) while variable changes in VO2 have been reported during alkali infusion. To compare metabolic with respiratory alkalosis 17 dogs were anesthetized with halothane and their VO2 response to respiratory alkalosis evaluated by hyperventilation. The pHa measured during this phase was duplicated during the later continuous infusion of NaHCO3 at which time either 1) ventilation was held constant at the control level, allowing arterial carbon dioxide tension (PaCO2) to rise as a consequence of the bicarbonate dissociation, or 2) PaCO2 was held constant by servo control of ventilation. Hyperventilation (pHa 7.6, PaCO2 13 Torr) produced an average increase in VO2 of 24%. During the bicarbonate infusion at constant ventilation (pHa 7.6, PaCO2 45 Torr) VO2 increased only 7%; however, when PACO2 was held constant by servo ventilation VO2 increased 21% above control. We conclude that respiratory and metabolic alkalosis produce similar increases in VO2 when steady-state acid-base conditions are achieved.
Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed prone man
Authors: Rehder K. , Knopp T. J. , Sessler A. D.
Published: December 2017

The intrapulmonary distribution of inspired gas (ventilation/unit lung volume, VI), functional residual capacity (FRC), closing capacity (CC), and the slope of phase III were determined in five awake and five anesthetized-paralyzed volunteers who were in the prone position with the abdomen unsupported. After induction of anesthesia-paralysis, FRC was less in four of five subjects and CC was consistently less. At FRC there was no difference in the vertical gradient of regional lung volumes between the awake and anesthetized-paralyzed prone subjects. Also, there was no difference in VI between the two states. The normalized slope of phase III decreased consistently with induction of anesthesia-paralysis, but the vertical distribution of a 133Xe bolus inhaled from residual volume was not different between the two states. The data of the study are compatible with 1) a pattern of expansion of the respiratory system during anesthesia-paralysis and mechanical ventilation different than that during spontaneous breathing and 2) a more uniform intraregional distribution of inspired gas and/or a different sequence of emptying during anesthesia-paralysis.
Slow postcapillary changes in blood pH in vivo: titration with acetazolamide
Authors: Bidani A. , Crandall E. D.
Published: December 2017

A stopped-flow pH electrode apparatus was used to investigate the mechanisms underlying slow changes in plasma pH (pHO) after blood leaves the pulmonary capillaries in carbonic anhydrase-inhibited animals. After acetazolamide was administered to an anesthetized dog or cat, arterial blood was withdrawn through the electrode apparatus into a syringe. Syringe movement was then suddenly stopped. Temperature and pHO of the blood in the electrode chamber were monitored both before and after blood withdrawal ceased. After stopping flow, pHO of the blood in the electrode chamber a) rose 0.02 after a dose of about 1 mg/kg acetazolamide; b) did not change after a dose of about 2 mg/kg acetazolamide; and c) fell 0.10 after a dose greater than about 5 mg/kg acetazolamide. With reasonable red cell and plasma carbonic anhydrase activities assumed for each dose level of acetazolamide, a computer model of the reaction and transport processes occurring in blood after gas exchange in the lung yielded predicted time courses of pHo that were in good agreement with the experimental results. The observed slow pHo changes are largely a result of disequilibrium of [H+] between red blood cells and plasma as blood leaves the pulmonary capillaries.
Myocardial metabolism and performance in hypoxia: effect of epinephrine
Authors: Kypson J. , Hait G.
Published: December 2017

Effects of epinephrine (10(-5) M) on mechanical performance, glycolysis, glycogenolysis, lipolysis, and metabolism of adenine nucleotides were studied in isolated hypoxic rabbit hearts. The exposure of hearts to hypoxia decreased their mechanical performance and heart rate, but increased their utilization of glucose by 50% and the release of lactate by 139%. Myocardial stores of glycogen and ATP declined by 53 and 84%, respectively, but their breakdown products such as lactate, pyruvate, AMP, and inosine accumulated in these hearts. Myocardial content of free fatty acids decreased, and the amount of glycerol increased in hypoxic hearts. Epinephrine stimulated mechanical performance and heart rate of hypoxic hearts, but decreased myocardial glycogen and ATP even more by 62 and 33%, respectively. Though glucose utilization remained unchanged, the release of lactate increased by 66% from hypoxic hearts treated with epinephrine. However, epinephrine failed to stimulate myocardial lipolysis in hypoxic hearts. These metabolic changes due to epinephrine would lead to accelerated depletion of energetic reserves in hypoxic heart and its earlier deterioration.
Maximum expiratory flow and transpulmonary pressure in the hamster
Authors: Lucey E. C. , Celli B. R. , Snider G. L.
Published: December 2017

Maximum expiratory flow was measured in 19 normal, anesthetized, tracheostomized, supine hamsters from records of forced deflation produced by the application of varying degrees of negative pressure to the tracheostomies of animals whose lungs had been previously inflated to a transpulmonary pressure (PL) of 25 cmH2O. Flow was measured with a pneumotachograph, volume with a constant-volume pressure plethysmograph and pleural surface pressure (Ppl) with a water-filled esophageal catheter. The esophageal pressure measurement overestimated Ppl and a simple technique was based on an estimate of the resting volume of the chest wall. This volume, at which the Ppl is zero, was calculated for anesthetized supine hamsters from the measurement of respiratory-system pressure and PL made independently of esophageal pressure and was found to be about 30% of vital capacity (VC). Flow limitation was present below 70% of VC with a tracheal deflation pressure of -30cmH2O. Negative effort dependence of flow was seen in small segments of the flow-volume curves. Mean +/- SD maximum expiratory flow at 50% VC was 52 +/- 9.5 ml/s or 9.1 VC/s. Upstream resistance was 0.09 +/- 0.03 cmH2O/ml per s.
Effects of fatigue and recovery on contractile properties of frog muscle
Authors: Fitts R. H. , Holloszy J. O.
Published: December 2017

The contractile properties of frog sartorius muscles were evaluated during development of fatigue and recovery. Muscles were stimulated under anaerobic conditions at a rate of 30 stimuli/min. Twitch tension (Pt) decreased 59% and tetanic tension (Po) decreased 52% during 15 min of stimulation. Contraction time and one-half relaxation time increased markedly during the first 6 min and then leveld off. The peak rate of twitch tension development (dP/dt) progressively declined to 33% of its initial value. Maximum shortening velocity did not change significantly. Large increases in Pt and twitch dP/dt occurred during the first 15 s of recovery while Po did not increase significantly in this time. Thereafter, Pt, Po, and, dP/dt all progressively returned towards normal over 30 min. These results show that the initial rapid recovery in Pt is not due to an increase in the capacity to generate force. Po is a better indicator of the force-generating capacity of a muscle because, unlike Pt, it is not affected by changes in the rate of tension development.