bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue oxygen tension in rabbits measured with a galvanic electrode
Authors: Towell M. E. , Lysak I. , Layne E. C. , Bessman S. P.
Published: December 2017

A galvanic electrode which generates current in response to oxygen was used to measure tissue PO2 in 10 rabbits. Sixteen electrodes were calibratedin vitro at PO2 = 0 mmHg and PO2 = 100 mmHg before implantation into muscleand peritoneal cavity. Electrode calibration was checked after removal 7–20days later; mean +/- SE reading at PO2 = 0 was 1.5 +/- 1.83 mmHg and at PO2 = 100 was 98.1 +/- 6.49 mmHg. Continuous recordings of tissue PO2 showed little fluctuation in unanesthetized rabbits resting quietly. Tissue PO2 was lower than arterial or venous PO2 during air breathing but frequently exceeded venous PO2 during O2 breathing. Highly significant correlations(P less than 0.001) were found between blood and tissue PO2 over a wide range of values obtained during air breathing and during 10%, 50%, and 100% O2breathing. Thus, the galvanic electrode provided a reliable measure of tissue PO2 and maintained its stability in vivo for periods as long as 20 days.
Effects of intermittent hyperbaric oxygen on guinea pig lung elastin and collagen
Authors: Richmond V. , D'Aoust B. G.
Published: December 2017

The effect of high oxygen pressure on collagen and elastin turnover in lung parenchyma tissue was studied in guinea pigs. Three groups of animals was used. One group (I) was given a clinically excessive exposure of 3 h daily for 9 days of 3 ATA oxygen. A second group (II) was given 3 ATA compressed air on the same schedule, and a third (III), a control, was given the same handling conditions only. Collagen and elastin which amounted to 10.45 and 4.62 mg, respectively, per 100 mg dry defatted parenchymal tissue was labeled with [14C]proline injected ip. Connective tissue protein turnover wasestimated by labeling half of each group before exposure (a); effects on biosynthesis were determined by labeling the other half postexposure (b). No differences in hydroxyproline specific activity of collagen fractions or elastin were found with respect to either biosynthesis or turnover. Alveolarwall length-tension measurements were not changed. Since exposures were in excess of those used for treatment of gas gangrene, ischemic burns or woundhealing, these results suggest that the metabolism of lung connective tissueis unaffected by the short-term exposure to hyperbaric oxygen.
Quantitation of right-to-left shunting by double indicator and oxygen techniques
Authors: Copley D. P. , Klocke R. A. , Klocke F. J.
Published: December 2017

An improved double indicator technique for quantitating right-to-left shunting has been validated in a canine right-heart bypass shunt model and compared to standard O2 shunt measurements in the same preparation. A bolus of dissolved sulfur hexafluoride (SF6) and indocyanine green dye (ICG) is injected into systemic venous return and a single, time-averaged arterial blood sample is collected during the initial circulation of indicators. Because of its low solubility, SF6 is eliminated essentially quantitatively from blood traversing gas-filled alveoli; correction for volatile tracer in arterial blood derived from nonshunt pathways in therefore unnecessary. ICG remains confined to the vascular space and SF6 is not lost in shunt pathways. Ratios of SF6-ICG shunt to directly measured shunt averaged 0.99 +/- 0.27 (SD) in 55 comparisons of shunts ranging from 2 to 25% of cardiac output; differences between actual and measured shunt averaged 0.5 +/- 2.9% of cardiac output. Simultaneously determined ratios of O2 shunt to directly measured shunt averaged 0.98 +/- 0.48 in 34 comparisons; differences between actual and measured shunt were 0.7 +/- 3.4% of cardiac output.
Mechanical apparatus for rigid suspension of the spinal column in mammals
Authors: Eick H. , Kostreva D. R. , Hosko M. , Kampine J. P.
Published: December 2017

An apparatus is described for rigid suspension of the spinal columns of mammals ranging in size from large dogs to small rabbits. This apparatus isunique in that the animal is suspended on its side, allowing free access tothe entire spinal column for spinal cord studies and free access to the thoracic and abdominal regions for heart, lung, and visceral studies that may require simultaneous surgical procedures in both ventral and dorsal regions.
Growth hormone in exercise: comparison of physiological and pharmacological stimuli
Authors: Sutton J. , Lazarus L.
Published: December 2017

This study was designed to compare the serum growth hormone (GH) response with quantified exercise to that obtained with other stimuli. In eight normal males, aged 21–24 yr, we studied the serum GH response to 20 min cycle ergometer exercise at 300, 600, and 900 kpm/min on three separate occasions and compared the results with those found during sleep, insulin hypoglycemia, arginine infusion, and L-DOPA. Exercise at 900 kpm/min and insulin hypoglycemia resulted in the greatest elevations in serum GH which weresignificantly greater than those found with sleep, arginine or L-DOPA. The 20-min exercise at 900 kpm/min represented 75–90% of the subjects' maximal oxygen uptake and is a suitable provocative test for GH secretion. As a screening test for pituitary GH reserve, exercise compares favorably with insulin hypoglycemia and is superior to sleep, arginine, and L-DOPA.
Lack of humanlike active vasodilation in skin of heat-stressed baboons
Authors: Wyss C. R. , Rowell L. B.
Published: December 2017

To discover whether humanlike active skin vasodilation occurs in a sweating, subhuman primate, four unanesthetized male baboons (Papio anubis) were heated (blood temp = 39–39.5 degrees C) before and after arterial administration of the alpha-adrenergic blocking agent phenoxybenzamine HCl. Hcat stress alone increased common iliac vascular conductance (CIVC) from 1.2 to 3.7 ml-min-1-mmHg-1 (averages). alpha-Blockade alone increased CIVC from 1.2 to 3.3 ml-min-1-mmHg-1. Heat stress subsequent to alpha-blockade further increased CIVC by only 0.4 ml-min-1-mmHg-1. Thus, most of the rise in CIVC caused by heat stress could be mimicked by alpha-blockade. If, as in man, the dominant means of raising skin blood flow were nonadrenergic active vasodilation, the response of CIVC to heating would far exceed that due to alpha-blockade. We conclude that, in baboons, humanlike active vasodilation of skin plays no significant role in CIVC response to heat stress. Thus, the baboon is not an appropriate model for investigation of control of human skin circulation during hyperthermia.
Phrenic nerve activity and occlusion pressure changes during CO2 rebreathing in cats
Authors: Evanich M. J. , Lopata M. , Lourenco R. V.
Published: December 2017

Changes in phrenic nerve activity, quantified as a moving time average, PNG(t), were characterized during complete airway occlusion at functional residual capacity (FRC) and compared to simultaneously occurring changes in intratracheal pressure. In anesthetized cats breathing room air and during CO2 breathing, PNG(t) during occlusion was the same as that found during unobstructed breathing until it reached a value approximately corresponding to that at peak inspiration in the preceding unoccluded breath, the rate of change of PNG(t) usually remained the same but in a few cases (2 out of 11)increased. When intratracheal occlusion pressure was plotted as a function of PNG(t), both while breathing room air and during CO2 rebreathing, an approximately linear relationship was obtained. Thus, changes in intratracheasocclusion pressure obtained at FRC parallel changes in phrenic motor nerve activity. Quantification of electrical activity of respiratory nerves as a moving time average provides a means of characterizing changes in the average level of electrical activity during an inspiratory effort.
Anaerobic threshold and maximal aerobic power for three modes of exercise
Authors: Davis J. A. , Vodak P. , Wilmore J. H. , Vodak J. , Kurtz P.
Published: December 2017

Alterations in selected respiratory gas exchange parameters have been proposed as sensitive, noninvasive indices of the onset of metabolic acidosis(anaerobic threshold (AT) during incremental exercise. Our purposes were toinvestigate the validity and feasibility of AT detection using routine laboratory measures of gas exchange, i.e., nonlinear increases in VE and VCO2 and abrupt increases in FEO2. Additionally, we examined the comparability ofthe AT and VO2 max among three modes of exercise (arm cranking, leg cycling, and treadmill walk-running) with double determinations obtained from 30 college-age, male volunteer subjects. The AT's for arm cranking, leg cycling, and treadmill walk-running occurred at 46.5 +/- 8.9 (means +/- SD), 63.8 +/- 9.0, and 58.6 +/- 5.8% of VO2 max, respectively. No significant difference was found between the leg exercise modes (cycling and walk-running) forthe AT while all pairwise arm versus leg comparisons were significantly different. Using nine additional subjects performing leg cycling tests, a significant correlation of r = 0.95 was found between gas exchange AT measurements (expressed as % VO2 max) and venous blood lactate AT measurements (% VO2 max). We conclude that the gas exchange AT is a valid and valuable indirect method for the detection of the development of lactic acidosis during incremental exercise.
Effects of arterial versus venous sampling on analysis of glucose kinetics in man
Authors: McGuire E. A. , Helderman J. H. , Tobin J. D. , Andres R. , Berman M.
Published: December 2017

A compartmental model is presented to account for transient and steady-state changes in blood glucose concentration which result from transit through the forearm and hand in man. This model permits the inter-conversion of arterial and venous data and the derivation of arterial equivalent total body glucose models from venous data. Data were obtained from subjects in thebasal state following a pulse injection of [1–14C]glucose tracer. An artery, an antecubital vein, and a dorsal vein of a heated hand (68 degrees C environment) were sampled. Blood transit time is shorter 0.3 vs. 1.0 min) and irreversible glucose loss is reduced (1.9 vs. 2.9%) in the heated hand preparation when compared to the antecubital vein preparation. Because of the smaller correction required and the smaller variation among individuals whenheated hand rather than antecubital vein data are obtained, we suggest thatfor analysis of whole-body kinetics such data should be used along with thecompartmental model correction when arterial data cannot be obtained.
Effect of vagal tone on airway diameters and on lung volume in anesthetized dogs
Authors: Hahn H. L. , Graf P. D. , Nadel J. A.
Published: December 2017

In 18 open-chest dogs we obtained pressure-diameter (P-D) curves from tantalum bronchograms and pressure-volume (P-V) curves by plethysmography. After vagotomy most of the decrease in diameter with decreasing transpulmonary pressure (Ptp) occured below 10 cmH2O and there was no P-D hysteresis. Smaller airways narrowed more with decreasing Ptp than larger ones. Bronchodilators did not increase diameters after vagotomy (P less than 0.2). With vagi intact, diameters were smaller at all Ptp (P less than 0.01) and exhibited hysteresis, but the lung P-V curve was unchanged. Vagal stimulation narrowed airways further at all Ptp and hysteresis was marked. Smaller airways narrowed more with vagal stimulation than larger ones. Vagal stimulation did not change the deflation limb of the P-V curve but decreased inflation volumes slightly at all Ptp (P less than 0.01). We conclude that in vivo toneis vagal and that it affects the physical properties of airways, but not oflungs, making the airways remarkably independent from lung parenchyma.
Endotracheal tube as a factor in measurement of respiratory mechanics
Authors: Sullivan M. , Paliotta J. , Saklad M.
Published: December 2017

The measurement of respiratory mechanics is frequently performed on intubated patients. This study shows the effect which the turbulent and inertial characteristics of an endotracheal tube have on the accuracy of the measurement. Two techniques are examined utilizing a mechanical model: the least-squares and the phasor technique. It is concluded that both techniques will give erroneous results if the characteristics of the tube are not accounted for. The error is markedly reduced if the turbulent and inertial terms are accounted for in the analysis.
Pyrenebutyric acid as an optical oxygen probe in the intact cerebral cortex
Authors: Mitnick M. H. , Jobsis F. F.
Published: December 2017

The application of the fluorochrome pyrenebutyric acid (PBA) as an in vivo quantitative probe for intracellular oxygen tension (iPO2) is reported.PBA is nontoxic, noninvasive, nonconsumptive, and allows optical monitoringof iPO2 on line. Cats were anesthetized with ether and lesioned midcollicularly to produce cerveau isole preparations with optical monitoring via a compensated microfluorometer. The “normal” iPO2 was determined to be 42.8 /-8.6 (SD) mmHg. Decrease in cerebral perfusion results in observing a decreased iPO2. This method of monitoring iPO2 was found to overcome drawbacks inherent in the polarographic technique and to posess additional advantages.
Integration of chemoreceptor stimuli by caudal pontile and rostral medullary sites
Authors: St John W. M. , Wang S. C.
Published: December 2017

Ventilatory regulation by pontile pneumotaxic and apneustic centers and by rostral medullary sites was evaluated in intercollicular decerebrate cats. Following pneumotaxic center ablation, PAco2 was significantly elevated.Moreover, in response to hypercapina or hypoxia, frequency responses were significantly diminished whereas tidal volume responses were unchanged or elevated. Interruption of apneustic center function by caudal pontile transection or radiofrequency lesions in the caudal pons and/or rostral medulla resulted in significant decreases of tidal volume responses and significant elevations of frequency responses to both hypercapnia and hypoxia. Neither minute volume responses nor the PAco2 level was altered. It is concluded that the apneustic center exercises a primary role in the brainstem definitionof tidal volume responses for both peripheral and central chemoreceptor afferent stimuli. The apneustic center is also considered to exert an impoetant function in the definition of respiratory frequency. A medially placed pathway in the rostral medulla is proposed to interconnect the apneustic center with the medullary respiratory nuclei.
Urinary catecholamine excretion on acute induction to high altitide (3,658 m)
Authors: Hoon R. S. , Sharma S. C. , Balasubramanian V. , Chadha K. S. , Mathew O. P.
Published: December 2017

Fifty healthy male volunteers, 21–34 yr of age, normally residentat altitudes less than 1,000 m, were airlifted to 3,658 m. Urinary excretion of catecholamines was measured at sea level (198 m) and on the 1st, 2nd, 4th, and 10th day of a stay at high altitude. The symptoms observed on exposure to high altitude were assigned arbitrary scores. The volunteers could,on this basis, be divided into “symptomatic” and “asymptomatic” groups. Thetwo groups showed a markedly different pattern of urinary catecholamines excretion on exposure to high altitude and on return to sea level. Significant increase in the catecholamine excretion was observed in thesymptomatic grouponly. A possible role for enhanced sympathoadrenal activity in the etiopathogenesis of high-altitude illnesses is postulated.
Lung mechanics following antigen challenge of Ascaris suum-sensitive rhesus monkeys
Authors: Pare P. D. , Michound M. C. , Hogg J. C.
Published: December 2017

Pulmonary resistance (RL) breathing air and a helium-oxygen mixture (He-O2) dynamic compliance (Cdyn), respiratory frequency (f), subdivisions of lung volume, and static deflation pressure-volume (PV) curves were measured before and after bronchial challenge with Ascaris suum antigen in six rhesus monkeys with varying skin reactivity to this antigen. The animals were lightly anesthetized with pentobarbital sodium, intubated, and studied in a volume displacement body plethysmograph, transpulmonary pressure being measured with an esophageal balloon technique. With the animals breathing spontaneously antigen was delivered with a De Vilbiss ultrasonic nebulizer and RL was determined by the method of electrical subtraction. With challenge, three monkeys showed no response and three persistently demonstrated significant bronchonconstriction (peak RL 700+/-100% control) with a decreased response to He-O2 suggesting combined central and peripheral airway narrowing. Responding monkeys also developed tachypnea (f 210+/-8% control) and a fall in Cdyn (18+/-6% control) but no significant changes in total lung capacity and its subdivisions, or in static PV curves were seen. We conclude that this primate model shows important similarities to and differences from human asthma.
Effect of carbon monoxide exposures on erythrocytic 2,3-DPG in rabbits
Authors: Ramsey J. M. , Casper P. W.
Published: December 2017

To determine if an exposure to lower levels of carbon monoxide (CO) produces quantitative changes in erythrocytic 2,3-diphosphoglycerate (2,3-DPG), eight rabbits were exposed to 100 ppm CO for 5 h resulting in approximately 20% carboxyhemoglobin (HbCO). 2,3-DPG was determined before exposure and immediately after exposure as well as every 3 h during the 24 h following exposure. To determine if intermittent CO exposures over a prolonged period of time affect 2,3-DPG, an additional 12 rabbits were exposed to 250 ppm CO for three intermittent periods totaling 300 min daily for 14 days (30% HbCO). 2,3-DPG was determined once per animal at the end of each day's exposure period. All animals served as their own controls in both experiments. Neither the results of the 24-h time course nor those of the 14-day time course showed significant differences in mean 2,3-DPG between controls and exposed animals at any sampling time. Apparently erythrocytic 2,3-DPG plays neither a compensating nor aggravating role in respect to the hypoxia induced by these levels of HbCO in the rabbit.
Alterations in the coronary circulation of man following ascent to 3,100 m altitude
Authors: Grover R. F. , Lufschanowski R. , Alexander J. K.
Published: December 2017

Alterations in coronary blood flow associated with adaptation to high altitude were examined. Three normal men native to low altitude were studied,first at sea level, and again after 10 days' sojourn at 3,100 m altitude. During rest at high altitude, a 32% decrease in coronary blood flow was largely offset by a 28% increase in coronary arterial O2 extraction to maintainmyocardial O2 delivery. The increase in O2 extraction resulted mainly from a decrease in coronary sinus blood O2 content and saturation. However, coronary sinus O2 tension remained constant, implying a decrease in the affinity of hemoglobin for O2. These observations are consistent with the hypothesis that coronary blood flow is regulated to maintain constant myocardial tissue O2 tension (as reflected here by coronary sinus blood O2 tension). Theabsence of a decrease in coronary sinus O2 tension or a decrease in myocardial lactate extraction imply that myocardial hypoxia did not develop. Therefore, myocardial hypoxia is not the basis for the decrease in cardiac stroke volume at high altitude reported previously and also observed in the present study.
Carbohydrate metabolism of heat-acclimated hamsters. V. Control of gluconeogenesis
Authors: Chayoth R.
Published: December 2017

The rate of gluconeogenesis was similar in liver of both fed heat-acclimated and control hamsters. Twenty-four hours of fasting calsed 6 times elevation in hepatic gluconeogenesis of the control animals whereas only 4 times enhancement of this pathway was found in heat-acclimated animals. Thus, significant difference existed between the two experimental groups in fasting. Triiodothyronine stimulated the rate of gluconeogenesis only in fed heat-acclimated hamsters whereas dibutyryl cyclic AMP caused elevation of this pathway in liver slices of fed control hamsters only. The results suggest that a decrease in hepatic gluconeogenesis in heat acclimation occurs only in fasted animals and it is controlled by thyroid hormones.
Thermal effects of reproductive hormones on the sheep udder
Authors: Smith R. E. , Ingram D. L. , Heath M. E.
Published: December 2017

The thermal effect of reproductive hormones on the sheep udder was tested in five ewes at the end of their breeding season. Radiotelemetry was used to provide continuous recordings of deep body temperature (Tb), udder skin temperature (Tud), and back skin temperature (Tbk) while the animals were held in a controlled-environment isolation chamber. Injections of estradiol (1.0 and 2.5 mg, im) resulted in an increase in Tud, but not in Tb, and only occasionally in Tbk. The amplitude of the rise in Tud varied from 0.4 to 3.8 degrees C and the rise persisted over 48 h following injection. Injections of saline, prostaglandin (PGF2alpha), or progesterone did not affect Tud, and injections of pyrogen (typhoid vaccine) elicited only an insignificant change in Tud concurrent with substantial increases in Tb and Tbk.
End-respiratory pressure ventilation and sulfobromophthalein sodium excretion in dogs
Authors: Johnson E. E. , Hedley-Whyte J. , Hall S. V.
Published: December 2017

Sulfobromophthalein sodium (BSP) 25 mg/kg body wt was given as a single iv injection to 32 fasted dogs. Serum samples at 3, 5, 10, 20, 30, 45, 60, 80, and 120 min postinjection were analyzed for total concentration of BSP and from 30 to 120 min for percent conjugated BSP. Four groups were compared: spontaneous ventilation; intermittent positive-pressure ventilation (IPPV) and continuous positive-pressure ventilation (CPPV) (2 groups). During CPPV, one group of dogs was given a continuous infusion of cholecystokinin octapeptide (CCK-8, 1 ng/kg per min). Central venous pressure averaged 11.3 +/- 0.7 (SE) cmH2O in dogs with CPPV + CCK-8 and 11.8 +/- 0.8 (SE) cmH2O in dogs with CPPV alone. At 3, 5, and 10 min postinjection serum BSP levels were similar in all groups. From 30 to 120 min postinjection serum levels of both free and conjugated BSP were higher in dogs ventilated with CPPV alone than in any other group (P less than 0.01). Dogs given CCK-8 during CPPV had serum BSP levels that were statistically similar to dogs breathing spontaneously or ventilated with IPPV. We conclude that CPPV impairs BSP excretion. This effect is counteracted by CCK-8.
Renal vascular response to heat stress in baboons--role of renin-angiotensin
Authors: Eisman M. M. , Rowell L. B.
Published: December 2017

To determine if hyperthermia in the baboon caused a reduction of renal blood flow (RBF) similar to that reported in man, we repeatedly exposed six unanesthetized male baboons (Papio cynocephalus) to ambient temperatures of 42.5–49.0 degrees C for 55–175 min. Internal temperatures rose 1.0–2.0 degrees C. On the average, RBF fell 23.7% per degrees C, renal vascular resistance (RVR) rose 34.0% per degrees C, and mean arterial pressure (MAP) fell by only 2.9 Torr. Plasma renin activity (PRA), measured in four baboons, rose 97.5% per degrees C. To investigate the role of the renin-angiotensin system in this renal response, we infused propranolol or saralasin (1-sar-8-ala-angiotensin II), an angiotensin II antagonist, systemically in 14 experiments on three baboons. Both propranolol and saralasin infusions prevented most of the reduction in RBF during hyperthermia. Propranolol prevented the increase in PRA. We conclude that renal vasoconstriction accompanies moderate hyperthermia in the awake baboon, and much of this response is mediated by a beta-adrenergic release of renin.
Response of medullary respiratory neurons to hypercapnia and isocapnic hypoxia
Authors: John W. M. , Wang S. C.
Published: December 2017

Single-unit activity was monitored extracellularly from medullary respiratory neurons and nonspecified neurons of decerebrate cats which were paralyzed, vagotomized, and artificially ventilated. Hypercapnia consistently resulted in increased discharge frequencies and decreased modal interspike intervals for respiratory units; peak integrated phrenic discharge heights increased concomitantly. Although isocapnic hypoxia usually resulted in comparable changes, the firing frequency of some respiratory units was depressed. Moreover, this depression was frequently observed simultaneously with a hypoxia-induced increase in phrenic discharge. Nonrespiratory unit discharge was mainly unaltered by hypercapnia or hypoxia. Following bilateral carotid sinus nerve section, hypercapnia-induced increases in respiratory neuronal and phrenic activities were still obtained; hypoxia depressed these activities. It is concluded that central chemoreceptor afferent influences are ubiquitously distributed to the medullary respiratory complex whereas peripheral chemoreceptor afferents produce only a discrete and unequal excitation of respiratory units. Hypoxia-induced ventilatory changes are further concluded to be the net result of peripheral chemoreceptor excitation of respiratory units and a direct depression of the brain stem respiratory complex by hypoxia.
Proportions of dog lung lymph in the thoracic and right lymph ducts
Authors: Vreim C. E. , Ohkuda K. , Staub N. C.
Published: December 2017

We studied the external lymphatic drainage of the lung in anesthetized dogs, by simultaneously measuring lymph flows from the thoracic duct (TD) and right lymph duct (RLD) during base line and during pulmonary edema. We measured lymph flow for a 2-h base-line period, for 2 h after tying off the thoracic duct above the diaphragm to eliminate nonthoracic lymph contributions, and after giving alloxan. Following alloxan, all dogs developed moderately severe pulmonary edema. In eight dogs the average TD flows were 24.0, 0.9, and 8.2 ml/h and RLD flows were 1.1, 1.3, and 8.4 ml/h, respectively. If we assume that all increases in lymph flow after giving alloxan are due to increased lung lymph flow, then, on the average, 50% of lung lymph drains into the TD and 50% into the RLD. However, among the eight dogs, four had significant increases in TD flow after alloxan (8.9–24.6 ml/h), and four did not. RLD flow increased in all dogs following alloxan. It appears the fraction of lung lymph draining into the TD and RLD can vary greatly amone individual dogs but, on the average, the TD and RLD receive about equal fractions of the pulmonary lymph. In shamoperated control animals TD and RLD lymph flows did not change over a 5-h period.
Lipolysis in brown adipose tissue of cold- and heat-acclimated hamsters
Authors: Rabi T. , Cassuto Y. , Gutman A.
Published: December 2017

Rates of release of free fatty acids (FFA) and glycerol to the incubation medium by brown adipose tissue (BAT) slices isolated from heat-acclimated (H), cold-acclimated (C), and control (N) hamsters in the absence or presence of epinephrine (E) were studied. Rates of FFA and glycerol release by tissue slices isolated from H and N animals were similar. In tissue slices isolated from C animals rate of release of FFA and glycerol was three times as high. Addition of E to the incubation medium (200 microgram/ml) had no effect on the rate of FFA and glycerol release of slices from C animals, but tripled the rates of slices from N, resulting in similar values for the two groups. In slices from H animals the rate of release was lower than in the other two groups, increasing only 1.5-fold. Pretreatment of N animals with triiodothyronine (T3; 0.8 microgram/100 g daily for 7 days) doubled the rates of FFA and glycerol release. Addition of E to the medium affected both pretreated and nontreated slices similarly. Two possible mechanisms by which temperature acclimation controls the lipolytic rate of BAT are suggested by 1) the concentration of specific enzymes and 2) cellular metabolites and hormones which activate existing systems. It seems that both operate in temperature-acclimated hamsters.
Estimating Va/Q distributions from inert gas data with an enforced smoothing algorithm
Authors: Pimmel R. L. , Tsai M. J. , Bromberg P. A.
Published: December 2017

The accuracy of a noniterative smoothing algorithm without a nonnegativity constraint for estimating continuous Va/Q distributions from inert gas retentions was evaluated. Simulated retention measurements computed from three assumed distributions were processed by the algorithm. Original and recovered distributions were compared with the root-mean-square (rms) difference. With noise-free retentions, the rms differences were minimum with zeta = 0 (no smoothing). With simulated 3% noise, the minima occurred when 0.01 less than zeta less than 0.10. Seven trials with independent simulated errors showed a large variation in the recovered distribution and the rms difference. All recovered distributions were qualitatively different from the originals especially at low and high Va/Q values. Negative fractional flows existed in all distributions that were not grossly different from the originals. We believe that this method which did not include a nonnegativity constraint, is inappropriate for processing inert gas retentions.
Cellular dynamics of rats' submaxillary gland during heat acclimatization
Authors: Horowitz M. , Soskolne W. A.
Published: December 2017

Male laboratory rats (Rattus norvegicus) ranging between 130 and 160 g were subjected to ambient temperatures of 34.5 degrees C from 0 to 28 days. The submaxillary gland, liver, spleen, and kidney were weighed. The acini size and the mitotic index of the acinar cells after intraperitoneal injection of vinblastine sulfate and colchicine were recorded for the submaxillary and parotid glands. The submaxillary glands showed increased growth rate over the initial 5 days, whereas the growth rate of the other organs decreased. The submaxillary gland enlargement was due to an initial hyperplasia of the acini cells reaching a maximum on the 2nd day. This was followed by hypertrophy of the Acini reaching a maximum on the l0th day. The parotid acini at control values throughout the experiment. It is postulated that the gland enlargement is effected to increase evaporative heat loss during the early stages of acclimatization prior to the lowering of heat production resulting from biochemical adaptation.
Thermally induced peripheral blood flow changes in chickens
Authors: Nolan W. F. , Weathers W. W. , Sturkie P. D.
Published: December 2017

Changes in wattle blood flow (Q) and vascular resistance (R) were examined during both local heating of the wattle and/or general body heating of unanesthetized, male White Leghorn chickens. Q increased and R decreased during both local and general heating. Termination of heating reversed the response. Beta stimulation with isoproterenol markedly reduced R and increased Q in normothermic birds, suggesting the presence of beta receptors in the wattle vasculature. Alpha blockade with phenoxybenzamine also resulted in pronounced vasodilatation, suggesting tonic alpha-sympathetic tone in the wattle vasculature under normothermic conditions. Neither cholinergic blockade with atropine sulfate nor beta-adrenergic blockade with propranolol altered the vascular response to general heating when administered near its peak. Release of alpha-sympathetic tone is believed to subserve the response to general heating.
Changes in arterial blood gas tensions during unsteady-state exercise
Authors: Young I. H. , Woolcock A. J.
Published: December 2017

Arterial oxygen (Pao2) and carbon dioxide (Paco2) tensions and inspired minute ventilation were measured during the first 2 min of stair-climbing exercise in nine normal subjects. The subjects climbed a staircase at a rate of approximately 9 m vertical height every minute and arterial blood was drawn from an indwelling cannula at 15-s intervals. Large falls in Pao2 from a resting value of 92 +/- 2.0 (mean +/- SE) Torr to a lowest value of 65 +/- 3.4 Torr were recorded in the first 50 s of exercise while Paco2 oscillated around the resting value. Most subjects demonstrated an initial plateau of Pao2 for at least 7 s followed by a rapid fall and subsequent rise toward the resting level after 1 min. The falls in Pao2 measured were larger than those reported for laboratory exercise. The possible reasons for this discrepancy are discussed.
Anemia as a stimulus to aortic and carotid chemoreceptors in the cat
Authors: Hatcher J. D. , Chiu L. K. , Jennings D. B.
Published: December 2017

In cats anesthetized with alpha-chloralose, the activities of aortic and carotid chemoreceptor nerves were measured during a control period and during anemia where the hematocrit was lowered in steps by dextran-for-blood exchange. With anemia there was a sustained nonlinear increase in firing of aortic chemoreceptors. There was a greater firing of aortic chemoreceptors for a given lowering of hematocrit from an initial low blood hematocrit than for a similar decrease in hematocrit from an initial high blood hematocrit. Tonic carotid chemoreceptor firing was independent of blood hematocrit and was only transiently increased at the time of dextran-for-blood exchange. The lack of effect of anemia on carotid chemoreceptor activity appeared to be due to sympathetic nerve activity. Section of the sympathetic nerves to the carotid chemoreceptors resulted in an increase in carotid chemoreceptor afferent activity during anemia in a manner similar to the increase in aortic chemoreceptor activity.
Respiratory inhibition with sympathetic afferent stimulation in the canine and primate
Authors: Kostreva D. R. , Hopp F. A. , Zuperku E. J. , Igler F. O. , Coon R. L. , Kampine J. P.
Published: December 2017

Inhibition of phrenic efferent nerve activity, diaphragm electromyogram (EMG), and external intercostal EMG was observed in halothane- and pentobarbital-anesthetized mongrel dogs and pentobarbital-anesthetized monkeys with stimulation of sympathetic afferents. The central end of the transected ventral limb of the left ansa subclavia, the sympathetic chain, or individual white rami were stimulated while simultaneously recording phrenic efferent nerve activity, diaphragm EMG, or the external intercostal EMG. Averaged phrenic efferent bursts or MEG were used to trigger an electronic respirator. In all of the dogs and monkeys, electrical stimulation of sympathetic afferent pathways resulted in inhibition of phrenic efferent nerve activity, diaphragm EMG, or external intercostal EMG. Although the exact origin of these fibers was not determined, the conduction velocities of these afferents were 4–7 m/s, which places them in the Adelta fiber-type range. The importance of these afferents in the regulation of respiration in the awake animal remains unknown.
Distribution of pulmonary responsiveness to aerosol histamine in dogs
Authors: Snapper J. R. , Drazen J. M. , Loring S. H. , Schneider W. , Ingram R. H.
Published: December 2017

Dose-response curves to aerosol histamine in 102 anesthetized, intubated, spontaneously breathing dogs revealed a spectrum of airway responsiveness with a greater than 40-fold difference between the most and the least sensitive animals. The frequency distribution of responses fits a log normal distribution. No correlation was found between sex, age, or control values of dynamic compliance (Cdyn) and lung resistance (RL) and the dose of histamine required to cause a response. Repetitive studies in 17 dogs observed for up to 20 mo showed that the dose at which an individual dog would respond was reproducible within a narrow range and that the differences between dogs were highly significant (P greater than 0.001). The long-term reproducibility of the response to aerosol histamine in individual dogs suggests that short-term reversible airway insults are not responsible for the range in responses noted between animals.
Measurement of blood O2 and CO2 concentrations using PO2 and PCO2 electrodes
Authors: Harabin A. L. , Farhi L. E.
Published: December 2017

Accurate dilution of a small blood volume with a carbon monoxide-saturated solution allows measurement of the whole blood O2 concentration as an increase in O2 tension in the solution. We have improved the method by simplifying both equipment and procedure. We also suggest an additional step in which the mixture is acidified, thereby allowing the measurement of CO2 concentration in the same solution with a CO2 electrode. The accuracy of both the O2 and CO2 determinations compares favorably with that obtained with other micromethods.
Elastic constants of trapped lung parenchyma
Authors: Lai-Fook S. J. , Hyatt R. E. , Rodarte J. R.
Published: December 2017

Isolated dog lobes were maximally trapped with air, and their parenchymal elastic properties were measured at the trapped volume. Indentation tests were performed on the surface of the lobes, followed by uniaxial and torsion tests on excised pieces of parenchyma. Similar values for Young's modulus were obtained from the indentation and uniaxial tests. The values for the shear modulus from the torison tests also were consistent with Young's modulus measured by the other procedures. The indentation test provided an accurate estimate of Young's modulus or the shear modulus for trapped lobes, and the results suggest that it is a valid method for estimating these constants in nontrapped lobes.
Effect of parenchymal shear modulus and lung volume on bronchial pressure-diameter behavior
Authors: Lai-Fook S. J. , Hyatt R. E. , Rodarte J. R.
Published: December 2017

A method that interrelates lung pressure-volume behavior, bronchial pressure-diameter behavior, and parenchymal shear modulus is presented. The method was used to predict changes in intraparenchymal bronchial diameter that occurred when lobe pressure-volume behavior and parenchymal shear modulus were markedly changed by inducing air trapping in isolated dog lobes. Predictions agreed with measurements, thereby supporting the general method. Measured values for the shear modulus were approximately 0.7 times the transpulmonary pressure for the control state. Estimated values for the peribronchial pressure difference from pleural pressure during a deflation pressure-volume maneuver for transpulmonary pressures below 12 cmH2O were small, approximately +/- 1 cmH2O, its sign being positive or negative, depending on whether the bronchus was dilated or contricted.
Faster adjustment of O2 uptake to the energy requirement of exercise in the trained state
Authors: Hickson R. C. , Bomze H. A. , Hollozy J. O.
Published: December 2017

The purpose of this study was to determine the effect of endurance exercise training on the time course of the increase in VO2 toward steady state in response to submaximal constant load work. Seven men participated in a strenuous program of endurance exercise for 40 min/day, 6 days/wk for 10 wk. Their average VO2max increased from 3.29 liters before training to 4.53 liters at the end of the training program. VO2 was measured continuously on a breath-by-breath basis at work rates requiring 40%, 50%, 60%, or 70% of VO2max before training. After training the subjects were retested both at the same absolute and the same relative work rates. The increases in VO2 toward steady state occurred more rapidly in the trained than in the untrained state both at the same absolute and at the same relative work rates. The finding that O2 uptake rises to meet O2 demand more rapidly in the trained than in the untrained state provides evidence that the working muscles become less hypoxic at the onset of exercise of the same intensity after training.
A gas-stream heater to control local skin temperature under evaporative sweat capsules
Authors: Kraning K. K. , Schibli E. G. , Momii S. T. , Merrick E. A.
Published: December 2017

A compact 4-W gas-stream heater for use with ventilated sweating capsules is described. The heating element is constructed from two modified 75-omega power resistors connected in parallel and contained in the capsule gas inlet tube. Heater power is controlled with integrated circuits which compare the output of a thermocouple, measuring either capsule skin or air temperature, with a predetermined target temperature. The unit responds fairly slowly to sudden large changes in target temperature, but once a steady state is achieved, maintains target temperature levels despite changes in evaporative heat loss. The device is well suited for studies in which local skin temperature or capsule air temperature must be elevated and clamped while the effects of other local stimuli or central thermoregulatory activity are studied, and in studies where the skin temperature effect on transepidermal water loss must be controlled.
Primary role of respiratory afferents in sustaining breathing rhythm
Authors: Sullivan C. E. , Kozar L. F. , Murphy E. , Phillipson E. A.
Published: December 2017

We studied the effects on breathing rhythm of suppressing the major respiratory stimuli (wakefulness, vagal, peripheral and central chemoreceptors) in healthy, unanesthetized dogs. Respiratory frequency (f) was obtained with a pneumotachograph; the state of wakefulness (W) or sleep was determined by EEG and behavioral criteria. During quiet W, f averaged 17 breaths/min and minute volume of ventilation (VI), 8.4 l/min. In slow-wave sleep (SWS), f slowed to 14 breaths/min, and VI decreased to 6.8 l/min. Afferent vagal blockade during SWS slowed f to 4 breaths/min, due primarily to prolongation of expiratory duration (Te) to 13.3 s, and decreased VI to 4.8 l/min. One breath of 100% O2 prolonged Te further to 27.4 s. Central chemoreceptor sensitivity was then reduced by inducting a metabolic alkalosis that combined with SWS, vagal blockade, and hyperoxia prolonged Te to as long as 57 s and reduced f to as low as 1 breath/min. The results demonstrate that afferent respiratory stimuli are essential for sustaining adequate ventilation.
Effect of pulmonary vascular engorgement on respiratory mechanics in the dog
Authors: Gray B. A. , McCaffree D. R. , Sivak E. D. , McCurdy H. T.
Published: December 2017

Using a 14C-labeled DMO, 36Cl and 3H method, we have determined the in vivo buffering capacity of lung, kidney, heart, skeletal muscle, and extracellular fluid (ECF) of guinea pigs during hypercapnia (FICO2 = 0.15). After 1 days' exposureto 15% CO2, both the relative CO2 buffer values (delta HCO3/deltapH) and the “%pH regulation” were lung greater than kidney greater than heart greater than ECF greater than skeletal muscle. For lung tissue the intracellular pH was significantly decreased only during acute (8 h) hypercapnia and had completely returned to control values after 7 days with arterial PCO2 congruent to 122 Torr. Kidney and cardiac muscle also showed ca. 100% regulation of pH at 7 days, whereas skeletal muscle and ECF showed only 80 and 70% pH regulation, respectively. The results are discussed with respect to the important (and pH-dependent) metabolic functions of the lung and kidney.
Oxygen electrode design criteria and performance characteristics: recessed cathode
Authors: Schneiderman G. , Goldstick T. K.
Published: December 2017

A computer simulation of the steady-state operation of recessed (Whalen-type) polarographic oxygen electrodes has been developed to give the design factors important for performance optimization. The simulation makes use of a specially formulated three-dimensional orthogonal coordinate system with the geometry identical to the actual recessed cathode and gives the oxygen concentration field induced by it in the surrounding medium. Equations are presented which allow one to calculate, for any recessed cathode, the current sensitivity, maximum stirring artifact, measurement error, and time constant. Comparisons with analytically obtained expressions for the corresponding quantities for idealized, spherosymmetric cathodes demonstrate the unique aspects of recessed-cathode performance. For commonly used electrodes, a recess length-to-cathode diameter ratio of greater than 10 is found to give a negligible stirring artifact, a negligible measurement error, and a rapid response.
Tracheobronchial secretions collected from intact dogs. I. Protein and mucous glycoprotein composition
Authors: Reasor M. J. , Adams G. K. , Proctor D. F. , Rubin R. J.
Published: December 2017

Tracheobronchial secretions (TBS) were collected in situ from intact, anesthetized dogs, and the protein composition and distribution were studied. TBS were separated into supernatant and pellet phases by centrifugation. The supernatant phase comprised 85%, by weight, of the secretory mixture; yet it contained only 58% of the total protein. Peptides of apparent molecular weights ranging from 16,000 to 154,000 daltons were present in the supernatant phase. Electrophoretic and immunochemical comparisons with canine serum suggested that certain of the peptides were of plasma origin including albumin, IgG, IgA, and IgM. Albumin and IgG comprised approximately 70% of the supernatant phase protein. Three percent of the total TBS protein was contributed by the peptide portion of mucous glycoproteins (mucins), and 97% of the mucin protein separated into the pellet phase. When compared to mucus collected from a canine tracheal pouch, TBS was less concentrated in mucins, and differences were observed in electrophoretic profiles between the two samples.
Tracheobronchial secretions collected from intact dogs. II. Effects of cholinomimetic stimulation
Authors: Reasor M. J. , Cohen D. , Proctor D. F. , Rubin R. J.
Published: December 2017

The effect of cholinomimetic stimulation on the quantity and composition of tracheobronchial secretions (TBS) collected from intact dogs was studied. After the administration of methacholine chloride, the collection rate of TBS increased over threefold within 10 min and returned to the control level by 50 min. Even though there was an increase in the total amount of protein collected, the protein concentration of the secretions decreased initially by 40%, returning to normal by 30 min. This was the result of an apparent dilution of the secretions by nonproteinaceous components. In addition, at 10 min, there was an increase in the protein associated with mucins. These responses were blocked by the preadministration of atropine. When TBS was separated into supernatant and pellet phases by centrifugation, we found that, following methacholine, there was a 35% increase in the ratio of albumin to IgG in the supernatant phase. These results suggest that the increased secretion due to methacholine may result, in part, by a selective filtration of fluid from the interstitial and/or vascular compartment(s) with proteins appearing in the secretory mixture based partially on their size.
Reflex effects of lung inflation and inhalation of halothane, ether, and ammonia
Authors: Lloyd T. C.
Published: December 2017

Anesthetized dogs were perfused at constant pressure from an external oxygenator after removing their hearts. Systemic vascular resistance (SVR) and spontaneous breathing effors were monitored while the lungs were ventilated briefly at a low frequency with several tidal volumes and at a low volume with several frequencies. Inflation depressed respiratory activity and transiently lowered SVR to a minimum from which it spontaneously partially recovered. The transient and sustained SVR changes were directly related to peak inflating pressure, independent of the mode of ventilation. Pressurization of the sublaryngeal extrapulmonary airways and addition of ammonia to lung inspirate were without effect. Ventilation with 7% ether had no effect, but at 13% it occasionally increased respiratory activity. Ventilation with 7% halothane depressed SVR and stimulated respiration, whereas 13% caused vasodilation and apnea. The magnitudes of SVR responses to halothane and to inflation were uncorrelated. All effects of inflation and inhalants were eliminated by vagotomy. We condluded that the systemic vessels appear to respond to changes in respiratory minute volume; that this is brought about by intrapulmonary receptors, perhaps of more than one type; that two classical –irritants” have little effect in dogs; and that halothane has effects on breathing and SVR consistent with stimulation of J-receptors.