bluuebunny/crossref_metadata_2025 huggingface dataset:
Human alveolar macrophages: antigen-independent binding of lymphocytes
Authors: Lussier L. M. , Chandler D. K. , Sybert A. , Yeager H.
Published: December 2017

To characterize the initial step in alveolar macrophage (AM)-lymphocyte (L) interaction in the human lung, we studied the ability of human AM to bind autologous blood L in vitro in the absence of antigen. AM were obtained by saline bronchial lavage through a fiberoptic bronchoscope. Monolayers of AM attached to glass bound autologous blood L prepared by Ficoll-Hypaque and nylon wool column separation. The AM-L binding increased from zero time to a maximum at 2 h and then declined to a zero time value at 18 h. The binding was dependent on the number of L added to the AM monolayers, with greatest binding at an AM:L ratio of 1:50. AM:L binding required viability of AM, but not of L, and was temperature dependent. Pretreatment of AM with iodoacetic acid, trypsin, neuraminidase, or colchicine diminished attachment of L at 2 h. Neuraminidase pretreatment of L resulted in increased binding to nontreated AM. Thus, a physical interaction between human AM and autologous peripheral blood L can occur in vitro in the absence of known antigen; similar interaction in vivo may play a role in the generation of cell-mediated immune responses in the lung.
Effect of an inhaled atropinelike agent on normal airway function
Authors: Douglas N. J. , Sudlow M. F. , Flenley D. C.
Published: December 2017

Ten normal subjects inhaled 80 microgram ipratropium or placebo. Body plethysmograph studies showed that ipratropium increased specific conductance (0.14–0.21 s-1.cmH2O–1) and increased flow rates during both maximal and partial forced expiratory maneuvers at all volumes from 50 to 10% vital capacity (P less than 0.01). Ipratropium produced no change in quasi-static or dynamic compliance, closing volume, or the slope of phase III of the closing volume trace, but there was an increase in the height of phase IV (P less than 0.01). Specific conductance reflects central airways caliber, whereas flow rates at low lung volumes in the absence of alteration in static recoil pressure may reflect the caliber of more peripheral airways. We conclude that inhibition of vagal tone results in dilatation of large and small airways. Analysis of the flow volume results on the equal pressure point model suggests that the bronchodilatation normally resulting from the inhalation to total lung capacity is not solely due to inhibition of vagal tone.
Respiratory mechanics in recumbent dogs anesthetized with thiopental sodium
Authors: Lai Y. L. , Rodarte J. R. , Hyatt R. E.
Published: December 2017

Pressure-volume (PV) and conductance-volume (GV) curves were obtained in trained dogs awake and then anesthetized with thiopental sodium, in the prone left lateral decubitus, and supine positions. By paired analyses, induction of anesthesia had no significant effect on lung volumes, static PV curves of the lung or chest wall, or static compliance of the lung or chest wall. In addition, change of posture had little effect on these variables in either the awake or the anesthetized state. Frequently, however, individual dogs showed changes in lung PV curves after induction of anesthesia or change of posture. These PV curve shifts were not accompanied by predictable changes in GV relations. Therefore, we concluded that such changes in the lung PV curve reflect either local artifacts or local deformation of the respiratory system.
Acute hypertrophic response of skeletal muscle to removal of synergists
Authors: Armstrong R. B. , Marum P. , Tullson P. , Saubert C. W.
Published: December 2017

The purpose of this project was to study the initial rapid enlargement phase of skeletal muscle in response to ablation of synergistic muscles. The first experiment tested the hypothesis that this initial phase is due to inflammation in the enlarging muscle. The wet weight of the plantaris muscle increased significantly (14%) within 1 h after removal of the ipsilateral gastrocnemius muscle. This increase was due to inflammation, as evidenced initially by edema, and within the next few hours, by leukocyte invasion of the interstitium and enhanced hexose monophosphate shunt-reducing capacity. In the second experiment we followed the time course of this inflammatory reaction. The response peaked at 1–5 days following surgery, after which it subsided to control levels by 16 days postsurgery. The final experiments were designed to uncover the factor(s) causing the inflammatory response. Two possible mechanisms were hypothesized: 1) trauma resulting from surgical manipulation of the tissue, and 2) trauma due to elevated stretch and/or tension on the muscle following removal of the synergists. The data indicate that surgical trauma is the causative factor of the inflammatory response in this hypertrophy model.
Factors affecting the physical performance of the rat in hyperbaric environments
Authors: Lin Y. C. , Chen L. H. , Baker D. G.
Published: December 2017

Experiments were designed to partition the effect of inspired oxygen tension (PIO2), gas density (rho), and ambient pressure (P) at rest and during exercise in rats. At rest oxygen uptake (VO2) was reduced by 19.5% (P less than 0.01) in 3 ATA air and by 32.1% (P less than 0.01) in 10 ATA air from 1 ATA air control of 29.3 +/- 1.21 (SE) ml/min.kg; there was no difference in VO2 between 1, 3, and 10 ATA He mixtures containing 20% O2. During exercise, VO2 was depressed by 36.2% (P less than 0.01) in 3 ATA air from 1 ATA air value of 55.3 +/- 3.23 ml/min.kg; VO2 was unaffected in 3 ATA He containing 20% O2 as compared to that of 46.5 +/- 2.43 ml/min.kg at 1 ATA He-O2 ambient. These VO2 values were compared to that obtained from normoxic ambients for separation of effects of elevated PIO2, P, and rho on VO2 at rest and during exercise. The effect of PIO2 was deduced by comparing VO2 in normoxic and hyperoxic He and N2 at a given P and rho. The density effect was obtained by comparing the VO2 in various densities at a given P and PIO2. The P effect was obtained by comparing the VO2 in various ambient pressures at a given rho and PIO2. Summation of the effects of P, rho, and PIO2 sufficiently approximates the changes in VO2 at rest. The same procedure underestimates the actually measured VO2 in all N2 ambients.
Effects of training on postexercise limb muscle EMG synchronous to respiration
Authors: Kisselkova H. , Georgiev V.
Published: December 2017

Twenty university students (10 trained and 10 untrained) participated in 60 sessions testing the effect of training on postexercise electromyogram synchronous to respiration. The latter was recorded for m. biceps brachii dextra, m. quadriceps femoris dextra, and m. gastrocnemium dextra. The respiration rate was taken before and after three levels of functional effort performed on a bicycle ergometer. The first (2 X 30 s with a 20-s interval at 100 rpm and 245 W) and the second (5 X 1 min with a 30-s interval after each min, at 90 rpm and 200 W) were of speed-developing nature; the third (20 min at 60 rpm and 117 W with 1-min interval every 5 min) was to develop endurance. Our observations show that the greatest percentage of a synchronous-to-respiration muscle bioelectric activity can be observed after the first two types of effort. In the third type the percentage is smaller and the duration of the activity is shorter. On the other hand, the percentage of biopotential occurrence is greater for untrained persons, with a considerable longer disappearance time. The phenomenon can be used as a criterion in the athlete's functional diagnosis.
Effects of carotid body denervation on respiratory pattern of awake cats
Authors: Gautier H. , Bonora M.
Published: December 2017

Eight awake cats have been studied before and after carotid denervation during air and oxygen breathing, and during hypercapnia. Analysis of the variables that characterize the spirogram shows that carotid denervation consistently results in a decrease of the mean inspiratory flow (VT/TI), causing a decrease in tidal volume (VT) and ventilation with a relative alveolar hypercapnia. In carotid-denervated animals, inhalation of oxygen results in an increase in ventilation due to an augmentation of VT/TI and VT and a relative hypocapnia. TI does not significantly change in the different conditions whereas TE is significantly affected. TE seems therefore to be more closely related to the rate of rise of inspiratory activity than to inspiratory duration.
Inert gas transport in the microcirculation: risk of isobaric supersaturation
Authors: Tepper R. S. , Lightfoot E. N. , Baz A. , Lanphier E. H.
Published: December 2017

This paper is concerned with the theretical background and implications of isobaric supersaturation and bubble formation in the microcirculation following an abrupt shift from one inspired inert gas to another. The use of more than one inert gas, simultaneously or sequentially, has become common in diving and presents risks as well as potential benefits. A review of microcirculatory model useds, theoretical approaches to decompression, and order of magnitude calculations indicates that present empiricisms are inadequate for predicting such supersaturation phenomena. This is true whether based on the familiar assumption of perfusion-limited behavior or its diffusion-limited counterpart. The “chromatographic” model used here, which considers both perfusion and axial diffusion in tissue cylinders, shows that these combined effects can produce unexpectedly high local supersaturation. The implications include new possibilities for the experimental evaluation of gas transport models as well as practical risks of inert gas shifts in diving and certain diagnostic procedures.
Orthostatic fluid-electrolyte and endocrine responses in fainters and nonfainters
Authors: Shvartz E. , Convertino V. A. , Keil L. C. , Haines R. F.
Published: December 2017

A tilt-table test was administered to five young men before (test 1) and after (test 2) 8 days of heat acclimation (2-h daily exercise at 50% VO2max at 40 degrees db, 30 degrees C wb) and to five other young men before and after the same exercise at 24 degrees C to determine fluid-electrolyte and endocrine responses in orthostasis in fainters and nonfainters. Half of the 10 subjects showed improved orthostatic reactions from test 1 to test 2 (disappearance of nausea and dizziness and improved heart rate and blood pressure), and the other 5 subjects showed no improvement. The improvement, especially in the nonfainters, was related to increases in posttilt plasma volume (PV) and plasma concentration of potassium. During test 1, plasma renin activity (PRA) increased five times from supine to orthostatis, with a corresponding increase in plasma vasopressin (ADH) of 50 times. The corresponding increases in test 2 were lower by 50 and 75% compared with those occurring in test 1 for PRA and ADH, respectively. PRA was five times higher in nonfainters than in fainters in test 1, whereas ADH showed an opposite trend. The orthostatic-induced increase in ADH seems to be related to volume control independent of PRA. This increase is reduced with improvement in orthostatic reactions, probably because of an increase in PV.
Basenji-greyhound dog model of asthma: pulmonary responses after beta-adrenergic blockade
Authors: Hirshman C. A. , Downes H. , Leon D. A. , Peters J. E.
Published: December 2017

To understand the mechanism underlying bronchial hyperreactivity in the Basenji-Greyhound (BG) dog, the effects of propranolol (2 mg/kg) and hexamethonium (5 mg/kg) on base-line pulmonary mechanics and on the bronchial response to aerosol challenges of citric acid and methacholine were studied in five BG dogs. Both propranolol and hexamethonium increased base-line pulmonary resistance (RL) from 0.69 +/- 0.05 (means +/- SE) cmH2O.l-1.s to 1.67 +/- 0.10 (P less than 0.05) and 2.22 +/- 0.45 cmH2O.1–1.s (P less than 0.05) and decreased dynamic compliance (Cdyn) from 190 +/- 10 ml/cmH2O to 154 +/- 9 (P less than 0.05) and 140 +/- 9 (P less than 0.05) ml/cmH2O, respectively. Both propranolol and hexamethonium potentiated the pulmonary response to 10% citric acid given for 5 min (P less than 0.05). RL postchallenge was 4.4 +/- 0.23, 8.1 +/- 0.81, and 7.8 +/- 0.31 cmH2O.l-1.s, and Cdyn was 78 +/- 5, 58 +/- 6, and 51 +/- 3 ml/cmH2O in untreated, propranolol-pretreated, and hexamethonium-pretreated animals. In untreated BG dogs, methacholine (0.075 mg/ml) increased RL from 0.94 +/- 0.25 to 2.2 +/- 0.21 cmH2O.l-1.s (234%) and decreased Cdyn from 223 +/- 39 to 141 +/- 14 ml/cmH2O (63%). In the same animals pretreated with propranolol, methacholine (0.075 mg/ml) increased RL from 1.9 +/- 0.66 to 4.8 +/- 1.37 cmH2O.l-1.s (253%) and decreased Cdyn from 144 +/- 35 to 81 +/- 15 ml/cmH2O (56%). We conclude that propranolol produces airway constriction in BG dogs, as in asthmatic humans and that the effects of propranolol on airways in BG dogs are not due to parasympathetic or alpha-adrenergic predominance.
Intrapulmonary gas transport and perfusion during high-frequency oscillation
Authors: Schmid E. R. , Knopp T. J. , Rehder K.
Published: December 2017

The effects of high-frequency oscillation (HFO) on 1) regional pulmonary 133Xe clearance after equilibration, 2) regional distribution and subsequent clearance of 133Xe after right atrial bolus injection, and 3) pulmonary gas exchange were examined in anesthetized supine dogs. After equilibration 133Xe cleared similarly from all lung regions with HFO at 16 and 30 Hz and a stroke volume of 2.6 ml/kg. Pulmonary gas exchange was adequate. 133Xe, injected as a bolus into the right atrium, was preferentially distributed to dependent lung regions during both HFO and apnea, indicating vertical gradients in pulmonary perfusion. During the subsequent pulmonary clearance of 133Xe, regional 133Xe concentrations (CrXe) increased initially in nondependent regions. By contrast, CrXe decreased immediately in the dependent lung region; after CrXe's became similar in dependent and nondependent regions, all lung regions started to clear at similar rates. The initial increases of CrXe in nondependent regions were attributed to interregional mixing, which may contribute to the uniformity in regional pulmonary 133Xe clearance after equilibration.
Dependence of visible spectrum [epsilon (lambda)] of fully oxygenated hemoglobin on concentration of hemoglobin
Authors: Burkhard O. , Barnikol W. K.
Published: December 2017

Lambert-Beer's law assumes that the extinction coefficient of a dye is not influenced by its concentration. Some experiments of Barnikol (Proc. Int. Congr. Physiol. Sci. 27th Paris 1977; Respiration 36: 86–95, 1978) led to the presumption that especially at highly concentrated hemoglobin (Hb) solutions Lambert-Beer's law does not hold. To further elucidate this problem we have measured the extinction coefficient of completely oxygenated hemoglobin (epsilon HbO2) over a wide range of Hb concentrations (CHbO2). Our results prove clearly that epsilon HbO2 in visible range as well as in the Soret region depends on CHbO2. In our opinion the invalidity of Lambert-Beer's law is caused by the self-association of the Hb molecules. This concept is a powerful tool to explain the high n values (n greater than 4) which were obtained by some authors in animal blood (bird, frog, trout, earthworm). Furthermore the influence of the self-association on the physicochemical properties of concentrated solutions of human hemoglobin is discussed.
Cardiac output increase and gas exchange at start of exercise
Authors: Weissman M. L. , Jones P. W. , Oren A. , Lamarra N. , Whipp B. J. , Wasserman K.
Published: December 2017

To determine the rapidity of increased gas exchange resulting from increased cardiac output (Q) following exercise onset, subjects performed multiple rest-exercise transitions on a cycle ergometer: the early dynamics of pulmonary gas exchange were measured during 1) rhythmic breathing with ventilation kept constant at the resting level (controlled ventilation) and 2) prolonged constant airflow exhalation. With controlled ventilation, PACO2 increased and PAO2 decreased, typically beginning in the first exercise breath. After 15 s, PACO2 had increased and PAO2 decreased by 4.5–6.2 and 8.7–12.1 Torr, respectively, graded within these narrow ranges as functions of work rate (0–100 W). Exercise starting during a prolonged exhalation caused the slopes of the alveolar phases for O2 and CO2 to increase immediately or within 2–5 s following exercise onset. Work rate had little effect on the delay or the change of alveolar gas tension slope during the subsequent 10–15 s. Thus, increased gas exchange due to increasing Q occurred very rapidly following exercise onset so that it would coincide with the first or second breath of exercise in free-breathing subjects.
Critical assessment of jacket plethysmographs for use in young children
Authors: Helms P. , Taylor B. W. , Milner A. D. , Hatch D. J.
Published: December 2017

In infants and very young children changes in thoracic gas volume (Vtg) during tidal breathing and during intermittent positive-pressure lung inflations have been estimated from pressure changes within double-layered rubber jackets covering the thorax and abdomen. In vitro and in vivo assessments demonstrated the linearity of these jackets over the range of volume changes found in these young subjects during respiratory function tests, and the small intrajacket background pressure (2.5 cmH2O) had minimal effects on resting lung volume and lung mechanics. These jackets can be used to monitor tidal volume in quiet subjects, and if an intermittent positive-pressure inflation technique is used static compliance can be accurately measured. The hysteresis of natural rubber and the direct contact of the recording system with the subject renders it unsuitable for the measurement of lung mechanics during tidal breathing and for the estimation of Vtg during airway occlusions.
Effect of muscle glycogen content on glucose uptake following exercise
Authors: Fell R. D. , Terblanche S. E. , Ivy J. L. , Young J. C. , Holloszy J. O.
Published: December 2017

This study examined the effects of raising muscle glycogen by carbohydrate feeding and of keeping muscle glycogen low by carbohydrate restriction following exhausting exercise on the ability of perfused skeletal muscle to take up glucose and to synthesize glycogen. Muscle glycogen concentration was more than twice as high in the rats fed carbohydrate as in those not given carbohydrate. Muscle glycogen synthesis during a 30-min perfusion with glucose and insulin was significantly greater in the animals with low muscle glycogen. Furthermore the muscles with low glycogen content converted a greater proportion of the glucose taken up to glycogen and less to lactate than did the muscles with high glycogen content. In rats subjected to exhausting exercise on the preceding day, the rate of glucose uptake by perfused skeletal muscle was significantly higher (60–80%) at the same insulin concentration in animals in which muscle glycogen was kept low than in those in which glycogen was raised by carbohydrate feeding.
Exercise capacity and cardiac function of rats with drug-induced cardiac enlargement
Authors: Baldwin K. M. , Ernst S. B. , Mullin W. J. , Schrader L. F. , Herrick R. E.
Published: December 2017

A study was undertaken to determine if sustained administration of isoproterenol (ISO) alters biochemical and functional properties of hearts and the submaximal and maximal exercise capacity of rodents. Compared with sham-treated controls of the same age, sex, and body weight, 4 wk of ISO (0.2--0.4 mg/kg sc) produced an approximate 30% increase in combined ventricle wet weight (P less than 0.001). Respiratory capacity of homogenates, total muscle protein concentration, and actomyosin and myofibril ATPase of heart muscle of the ISO-treated group were the same as in the control group. Various cardiac function parameters in situ, obtained under control conditions and in response to tyramine-induced norepinephrine release, were similar for the two groups. ISO-treated rats had slightly greater endurance for running submaximally on a treadmill than the control rats (P less than 0.10), but their maximal capacity to utilize oxygen (VO2max) was not different from controls. These findings suggest that rodent hearts moderately enlarged by relatively low doses of isoproterenol possess normal metabolic and functional capacity. However, this cardiac enlargement had no apparent effect on maximal exercise performance of the whole animal.
Diffusion barriers to passive lipid uptake of canine posterior tracheal epithelium
Authors: Man S. F. , Thomson A. B.
Published: December 2017

In studies of passive uptake of canine posterior tracheal epithelium in vitro, we examined the effective resistance of the unstirred water layer (UWL) when the bulk phase of the preparation was stirred and unstirred. Rates of uptake of fatty acids were corrected for unstirred layer effects. The incremental change in free energy, derived from the linear relationship between uptake and chain length of lipids, was -271 cal/mol. Measurement of the effective thickness (d) and surface area (SW) of the UWL showed that d fell and SW rose as the rate of stirring increased. SW was less than 15% of the tracheal epithelial cell membrane's surface area. It is concluded that 1) lipid membrane of the tracheal epithelium and the overlying UWL represent the major diffusion barriers for lipid uptake across the tracheal epithelium; 2) failure to correct for the UWL resistance leads to serious errors in the estimates of permeability properties of the epithelium to lipids; and 3) the unstirred layer severely limits the proportion of cell membrane available for transport in vitro.
Central integration of pulmonary stretch receptor input in the control of expiration
Authors: Zuperku E. J. , Hopp F. A. , Kampine J. P.
Published: December 2017

The dynamics of the central processing of the discharge pattern from vagal pulmonary afferents that mediate the expiratory facilitatory reflex have been investigated. These studies involved the development of mathematical models based on analogs of neurophysiological principles such as temporal summation and threshold crossing. These models, which are capable of predicting the expiratory duration for arbitrary discharge patterns, were verified through comparison of their prediction with experimentally obtained relationships between expiratory duration (TE) and waveform parameters of various input patterns. These relationships were obtained by electrical activation of the largest vagal afferent fibers in bilaterally vagotomized, pentobarbital-anesthetized dogs. A parallel two-component model with long time constants (ca. 0.8 and 18 s) was best able to describe the experimental responses. This model suggests that 1) central integration of pulmonary stretch receptor (PSR) input is similar to long time-constant temporal summation; 2) central inspiratory inhibition (no vagal input) may share a common mechanism with vagal processing; 3) PSR-induced inhibition is a linear function of discharge frequency; and 4) TE depends on both the trajectory of lung deflation and the tonic activity at functional residual capacity. These characteristics embody information regarding specific neural arrangements and properties within the respiratory centers.
Automated nitrogen-washout methods for infants: evaluated using cats and a mechanical lung
Authors: Richardson R. , Anderson M.
Published: December 2017

Infants with respiratory distress syndrome are treated with constant distending pressures to counter atelectasis and increase the functional residual capacity (FRC). However, FRCs are not monitored in these severely ill infants because present methods are impractical. We computerized N2-washout techniques for estimating the lung volume in these infants. The system has been evaluated using 1) a mechanical lung model and 2) small cats with normal and edematous lungs. Comparing the results of measured lung volumes with the fixed mechanical lung volumes yielded a correlation coefficient 0.996 (n=50). Decreasing the N2 gradient between initial N2 concentration and the washout medium from 0.79 to 0.10 did not affect the accuracy or reproducibility of measurements in the mechanical lung. For normal cats, comparing the results of N2-washout measurements of FRC with He-dilution values yielded a correlation coefficient of 0.921 (n=128); results from cats with pulmonary edema yielded a correlation coefficient 0.989 (n=80). We conclude that this computerized system is accurate, reproducible, and clinically acceptable for monitoring infants.
Effect of gaseous interaction between lung units on the expired concentration of nitrogen
Authors: Nixon W. , Pack A. I.
Published: December 2017

There is debate over the mechanisms that produce the alveolar slope, with theories relating to both series and parallel inhomogeneity being proposed. We use a mathematical model of pulmonary gas transport, which incorporates both series and parallel effects, to investigate the relevance of each in the production of this alveolar slope. Interaction between lung units is specifically studied by simulating mixing at both proximal- and distal-branch points in the bronchial tree. During expiration mixing of the gas from inhomogeneous parallel lung units leads to concentration gradients within each unit. The resultant effect on the concentration of the expirate depends on the position in the bronchial tree at which this mixing takes place; proximal interaction alters the initial phase of the expired concentration profile, whereas distal interaction changes the magnitude of the alveolar slope. The net effect of distal interaction is to produce a greater alveolar slope for gases with low molecular diffusivity. These effects are present even in the absence of asynchronous emptying of lung units but may be enhanced by it. These results help to clarify controversies about the mechanisms underlying production of the alveolar slope.
Exercise-induced amplitude modification of physiological action tremor of the ankle
Authors: Iaizzo P. A. , Pozos R. S.
Published: December 2017

To determine whether exercise would affect physiological action tremor (PAT), normal male and female subjects exercised either by running or lifting weights. Surface electromyograms and acceleration recordings were analyzed using power spectral techniques to quantitate variations in amplitude and/or frequency of PAT. The results of this study show that running causes an increase in the amplitude of PAT. By having subjects run successively longer distances, a graded increase in amplitude of PAT was observed. After the subjects ran for long periods of time, PAT continued as an overt continuous oscillation. This oscillation did not greatly differ from pathological clonus. Furthermore, exercising the upper body alone by lifting weights increased the amplitude of PAT of the ankle. The results suggest that the exercise may cause alterations in the gain of the spinal reflexes which may lead to an underdamping of PAT. As the gain of the reflexes controlling PAT increases, this may lead to overt continuous oscillations, such as physiological or pathological clonus.
Effect of phase of stimulation on acute damage caused by eccentric contractions in mouse soleus muscle
Authors: Stevens E. D.
Published: December 2017

Eccentric contractions (activation during muscle lengthening) can cause muscle damage. The effect of phase of stimulation on the extent of muscle damage was studied by using the work-loop method. For the work-loop method, the muscle was subjected to sinusoidal length changes at 2 Hz. The muscle was activated at different times during the imposed length-change cycle; this time is called the phase of stimulation. Work was calculated from the loop formed when force was plotted against length. Work done was positive when the muscle was shortening and was negative when the muscle was lengthening; net work was the difference. One complete length-change cycle was 100 (i.e., given as a percentage of the cycle); shortening occurred from 25 to 75. The muscle did the most net work when stimulated at phase 20, that is, when activation started just before shortening. Damage was defined as a decrease in work. Significant damage occurred after a single trial of three consecutive eccentric contractions; the muscle did less positive and less net work because of the damage. Maximal damage occurred at phases 90 and 0, the center of the lengthening part of the length-change cycle (work decreased 10%). Negligible damage occurred at phases 20-40. Negative work (work required to lengthen the muscle) also decreased because of the damage. Eccentric contractions caused much more damage than concentric contractions during oscillatory work.
Compartmental analysis of Ca2+ kinetics in long-lasting diaphragm fatigue: loss of t-tubular membrane Ca2+
Authors: Howell S.
Published: December 2017

An analytic method based on simulation and modeling of long-term 45Ca2+ efflux data was used to estimate Ca2+ contents (nmol Ca2+/g tissue wet wt) and exchange fluxes (nmol Ca2+.min-1.g-1) for extracellular and intracellular compartments in in vitro hamster diaphragm. Three physiological states were studied: control (n = 5), acute fatigue (after repeated tetany; n = 5), and long-lasting fatigue (1-h recovery; n = 5). Experimental muscles were loaded with 45Ca2+ for 1 h, and efflux data were collected for 8 h by use of a flow-through tissue chamber. Induction of acute diaphragm fatigue led to a uniform 200% elevation of the 8-h efflux curve (expressed as dpm.min-1.mg-1) relative to control. Conversely, in long-lasting fatigue the early component of the efflux curve was depressed compared with control, whereas the balance of the curve was restored to baseline. Analysis of control efflux data revealed that the early curve (0-2 h) contained data on two rapidly exchanging extracellular Ca2+ compartments, whereas the late curve (2-8 h) reflected information on two slowly exchanging intracellular compartments. Modeling of acute fatigue efflux data estimated a 239% increase in one extracellular Ca2+ compartment (putative t-tubular membrane) and a 546% increase in one intracellular Ca2+ compartment (putative terminal cisternae). These increase accounted for the model prediction of a twofold rise in total diaphragm Ca2+. The kinetic data were quantitatively consistent with the hypothesis that diaphragm Ca2+ overload in acute fatigue required sarcolemmal Ca2+ permeability to double and Ca2+ diffusion into the t-tubular and terminal cisternal compartments to escalate nearly threefold. Fitting of long-lasting fatigue efflux data was associated with the sole prediction that t-tubular membrane Ca2+ was reduced to less than one-half of the control value.
Ozone toxicity in the mouse: comparison and modeling of responses in susceptible and resistant strains
Authors: Watkinson W. P. , Highfill J. W. , Slade R. , Hatch G. E.
Published: December 2017

Previous studies from this laboratory have demonstrated a concentration-related hypothermia and increases in bronchoalveolar lavage (BAL) fluid indexes of toxicity in the rat after exposure to environmentally relevant levels of ozone (O3). In similar studies with C57BL/6J (B6) and C3H/HeJ (C3) mice, other investigators have reported differential effects on BAL toxicity indexes between the two strains after O3 exposure. The present study investigated the relationship between the reported strain differences in BAL parameters in B6 and C3 mice exposed to O3 and the induced hypothermic response. Male 80-day-old mice (n = 94, 47/strain) were used for these studies. Subsets (n = 8/strain) of these animals were surgically implanted with radiotelemetry transmitters that permitted continuous monitoring of core body temperature and activity. All telemetry animals and an equal number of nontelemetry animals (n = 8/strain) were exposed to filtered air for 24 h followed by a 2-h exposure to 2 parts/million 16O3. With use of a similar protocol, groups of nontelemetry mice (n = 12/strain) were exposed to either filtered air or 2 parts/million 16O3 for 2 h. At 0 or 22 h postexposure, mice were anesthetized with halothane and intubated, and their lungs were lavaged with 37 degrees C saline. Although both strains of mice exhibited significant abrupt decreases in core body temperature on exposure to O3 and both recovered rapidly after cessation of the O3 exposure, the response of the C3 mice was more dynamic than that of the B6 mice. Similarly, both strains showed characteristic changes in biomarkers of O3 toxicity; however, the increases in BAL fluid protein and cells at 22 h postexposure were significantly greater and the percentage of neutrophils was significantly less in B6 mice than in C3 mice. It is possible that the strain differences in BAL constituents may be related to the differences in the hypothermic response.
Myosin phenotype and SDH enzyme variability among motor unit fibers
Authors: Sieck G. C. , Fournier M. , Prakash Y. S. , Blanco C. E.
Published: December 2017

Motor units in cat diaphragm and tibialis posterior muscles were classified physiologically as slow-twitch, fast-twitch, fatigue-resistant, fast-twitch fatigue-intermediate, or fast-twitch fatigable. Motor unit fibers were then identified by glycogen depletion and classified as type I, IIa, IIb, or IIx on the basis of myofibrillar adenosinetriphosphatase-staining profiles and immunoreactivity for myosin heavy-chain (MHC) isoforms. In both muscles, slow-twitch and fast-twitch fatigue-resistant units comprised type I and IIa fibers expressing MHC-slow and MHC-2A isoforms, respectively. Fast-twitch fatigue-intermediate and fast-twitch fatigable units comprised type IIx fibers expressing the MHC-2X isoform. Some fast-twitch fatigue-intermediate units had a mixed composition with a few fibers (approximately 10%) expressing the MHC-2A isoform. Motor unit fiber succinate dehydrogenase (SDH) activity was quantified, and variability was estimated by the interquartile range, which was lower among motor unit fibers than in adjacent fibers of the same histochemical type but comparable to that along the length of individual fibers. We conclude that, despite the mixed-MHC phenotype of some diaphragm and tibialis posterior motor units, SDH activity is relatively uniform. This supports the hypothesis that motoneurons exert a predominant influence on muscle fiber SDH activity.
Corrigenda for Extrageniculostriate vision in the monkey: V. Role of accessory optic system.
Authors: Pasik Pedro , Pasik Tauba
Published: December 2017

Page 455: Pedro Pasik and Tauba Pasik, “Extrageniculostriate vision in the monkey. V. Role of accessory optic system.” The sentence beginning on the eighth line from the bottom of the page, right-hand column, should read: These fibers have been described in the monkey as a slender bundle of only 11 μm in diameter (1). Page 457: Reference 17 should be deleted.
Modification of the frog's electroretinogram by transretinal direct current
Authors: Knighton R. W.
Published: December 2017

1. Transretinal direct current modifies the amplitude and waveform of the frog's electroretinogram (ERG). Outward current (that flowing from vitreous to sclera) depresses the ERG while inward current enhances it. Outward current causes an apparent reversal of the polarity of the positive off-response (d-wave) of the ERG. 2. A true reversal does not actually occur. Rather, the outward current unmasks a negative off-response by depressing the positive off-response. 3. The positive off-response and the b-wave can be completely abolished by strong outward current, but cannot be reversed. 4. Treatment with ammonia abolishes the negative off-response, leaving a positive off-response which is affected by current in exactly the same way as the normal positive off-response. 5. Two possible mechanisms by which the current could be affecting the amplitude of the positive off-response would require that its amplitude be reversed for strong outward current. The absence of such reversal rejects these mechanisms.
Abnormal neuronal responses during evolution of a penicillin epileptic focus in cat visual cortex
Authors: Ebersole J. S. , Levine R. A.
Published: December 2017

After defining the receptive fields of single units in cortical area 17 of anesthetized cats, recurrent on-off stimulation with bars of light of optimal configuration win from a second micropipette; Progressively, three distinct alterations of neuronal activity developed. The most longlasting and usually the earliest abnormality was an increase in the number and frequency of spikes comprising a neuron's response to stimuli that were effective prior to iontophoresis. This enhanced physiologic response (EPR) could be elicited from a cell independently of the discharge activity of an induced focus, but only with stimuli appropriate for the cell's receptive field. With additional iontophoresis an entirely new response developed, which was consistent with an extracellular paroxysmal depolarization shift (PDS). This high-frequency burst of spikes appeared only in association with an ECoG interictal potential. It could be triggered, however, by stimuli which were previously effective or ineffective, as well as occur spontaneously. Characteristics which further distinguished the PDS from EPR included a longer and more-variable latency, a longer recovery period, and a different sensitivity to changes of stimulus intensity. A period of response inhibition also accompanied each interictal potential and persisted with a variable duration afterward. It was most noticeable as an interruption in the activity of tonically responding neurons and was often present before the cell began to generate PDSs. It was concluded that the EPR represents a direct effect of penicillin on the cell or its immediate synaptic connections, while the PDS appears dependent on the altered interactions within a population of such affected cells. The inhibitory phenomenon, in addition, seems a result of projected influences from cells more fully involved with the developing focus. A dynamic model of the EPR-PDS relationship is proposed.
Analysis of postural motoneuron activity in crayfish abdomen. I. Coordination by premotoneuron connections
Authors: Sokolove P. G. , Tatton W. G.
Published: December 2017

The activity of the crayfish abdominal postural motoneurons and their associated neurons (the accessory neuron(s) and the MRO(1)) were examined with the aid of techniques for the analysis of simultaneously recorded spike trains. A means of reliably identifying the spikes of the individual motoneurons based on their relative axon conduction velocities is presented. The analyses show that: 1) the large, phasically active synergist motoneurons innervating muscles producing the same movement show a marked similarity in their average responses, which is independent of the input source; 2) the small, tonically active and the middle-sized, tonicphasic synergist motoneurons innervating the same muscle and similar synergist motoneurons innervating antagonistic muscles are coordinated entirely by premotoneuron connections; 3) the accessory neuron is coordinated in its activity with the phasically active flexor excitor motoneurons and the extensor inhibitor motoneuron and thereby functions as a flexor synergist; and 4) the simultaneous presentation of flexion-producing and extension-producing inputs to the postural system results in a reciprocal oscillation in flexor-extensor motoneuron output. The functional significance of these results with respect to the operation of the postural system are discussed.
Analysis of postural motoneuron activity in crayfish abdomen. II. Coordination by excitatory and inhibitory connections between motoneurons
Authors: Tatton W. G. , Sokolove P. G.
Published: December 2017

The identified spike trains of the crayfish abdominal postural efferent neurons were recorded simultaneously from one or more segments. The efferent activity was analyzed using cross-correlation histograms, peristimulus time scatter diagrams, and specialized antidromic techniques. The analyses show that the larger, phasically active motoneurons are coordinated in their activity by cross connections made at the motoneuron level. The cross connections are both excitatory and inhibitor in nature and result in significant alterations in spike output. Further, the accessory neuron receives an inhibitory cross connection from a middle-sized extensor excitor motoneuron or motoneurons. In each case, the cross connections appear to be appropriate to the function of the postural system.
Neural implications of different profiles between treadmill and overground locomotion timings in cats
Authors: Wetzel M. C. , Atwater A. E. , Wait J. V. , Stuart D. C.
Published: December 2017

A cinematographic comparison of treadmill and overground performances by the cat revealed considerable flexibility in the neural control program for locomotion. For the single limb's step cycle, swing duration (time foot is off the surface) was approximately equal in both situations, as has been found previously. Subcomponents of the swing (flexion duration and timings between joints during the transition from flexion to extension) differed, however. Interlimb timings also responded to situation. The interval between touchdown of one hindlimb and the ipsilateral forelimb was reduced for treadmill stepping. An ipsilateral coupling interval also differed that had been previously reported to involve propriospinal activity, the time for onset of extension during the swing phase of the hindlimb to the onset of flexion at the beginning of the swing phase in the forelimb. Segmental afferent input, visual and other suprasegmental inputs, and motivational variables probably all contribute to the separation of treadmill and overground timing profiles.
Visual receptive-field properties of cells in area 18 of cat's cerebral cortex before and after acute lesions in area 17
Authors: Dreher B. , Cottee L. J.
Published: December 2017

1. Receptive-field properties of single neurons in cat's cortical area 18 were studied before and after partial bilateral lesions of area 17. 2. The majority of cells recorded from animals with intact visual cortex exhibited orientation selectivity, directional selectivity, and could be independently activated through either eye. All cells responded well to moving targets and nearly all of them exhibited broadly tuned preferences with respect to speed of the target. Over 45% of cells responded optimally or exclusively at very fast (above 50 degrees/s) speeds. 3. The majority of neurons recorded from animals with intact visual cortex responded weakly but clearly to appropriately oriented localized stationary stimuli flashed on and off. About one-third of the cells responded with mixed on-off discharges from all over their receptive field. In the receptive fields of 10% of cells, separate on- and off-discharge regions could be revealed. In the receptive fields of the remaining cells, only on- or only off-discharge regions could be revealed. 4. The majority of neurons recorded after ablation of area 17 were orientation selective; 50% of the cells were also direction selective. All neurons responded well to moving targets; about 65% of them responded optimally or exclusively at very fast target speeds. 5. Destruction of the dorsolateral part of contralaterial area 17 and most of contralateral area 18 caused significant reduction in proportion of cells in area 18 which could be activated through either eye. 6. The majority of neurons recorded after ablation responded to appropriately oriented localized stationary stimuli flashed on and off. Cells with mixed on-off discharge regions all over the receptive field with separate on- and off-discharge regions and with only on- or only off-discharge regions were found. 7. It is concluded that the processing of afferent visual information in area 18 is, to a great extent, independent of the information carried to this area by associational fibers from cells of area 17.
Discharge patterns of cat pontine brain stem neurons during desynchronized sleep
Authors: McCarley R. W. , Hobson J. A.
Published: December 2017

1. Discharge pattern has been characterized by autocorrelation analysis of stationary portions of extracellularly recorded discharge trains of cat pontine brain stem neurons during spontaneously occurring desynchronized sleep episodes. 2. Neurons localized to the area implicated in control of the desynchronized phase of sleep, the gigantocellular tegmental field (FTG), show the most phasic or clustered discharge pattern, as evinced by initial peaks in the autocorrelations. At the peak, the FTG population average discharge probability is 3 times that expected had the discharges been evenly distributed over time. The initial peak extends beyond a lag of 3 s, indicating runs of clustered discharge extending beyond this duration. Neurons in other reticular tegmental fields, the tegmental reticular nucleus and pontine gray, show a more sustained or tonic discharge pattern. 3. Discharge patterns of a given cell are consistent from one desynchronized sleep episode to the next; units with phasic discharge patterns remain phasic, and tonic patterns remain tonic. 4. There is a three-way correlation among FTG units recorded at sites with many giant cells, units with high discharge rate increases on transition to desynchronized sleep, and units with a markedly phasic discharge pattern. This implicates the giant cells as the source of both the distinctive discharge rate and pattern changes of neurons during desynchronized sleep. 5. Stereotyped, regular discharge patterns are not characteristic of FTG or other units, suggesting they are not pacemakers and that endogenous activation of pacemaker cells is unlikely to be a mechanism for generation of the marked discharge rate increases on transition to desynchronized sleep that are found in FTG units. The irregular, clustered discharge pattern of FTG is more compatible with generation of discharge rate increases through interaction with other cells. The markedly phasic discharge of FTG units is also consistent with a driving role in generation of the phasic electrophysiologic events of desynchronized sleep.
Responses of red nucleus neurons to antidromic and synaptic activation
Authors: Eccles J. C. , Scheid P. , Taborikova H.
Published: December 2017

An account is given of the responses of 432 red nucleus (RN) neurons with axons projecting down the spinal cord. Almost half were in an initial series of 18 experiments on anesthetized cats, and the remainder were in a second series of 12 experiments on decerebrate unanesthetized cats. The differences between the two series were of little significance. All recording was from single neurons using extracellular glass microelectrodes that were inserted throught the right superior colliculus and directed to the right red nucleus at a standard orientation. Identification of RN neurons was both by location, checked by subsequent histology, and by antidromic invasion from the spinal cord. The spinal stimulating electrodes were placed in proximity to the left rubrospinal tract at C2 and L2 segmental levels. Axonal conduction velocities were calculated from the latency differential between the L2 and C2 antidromic responses and were usually in the range 60-130 m/s, 97% of all neurons located in the red nucleus had axons projecting to the C2 level, and 37% projected to the L2 level. The responses of 229 RN neurons were observed with stimulation applied to the contralateral (left) interpositus nucleus. In 10 (5%) there were antidromic responses to both interpositus and C2 stimulation, a finding in good agreement with the anatomical description of rare axon collaterals from rubrospinal fibers to the interpositus nucleus. In 209 (91%), there was a clear monosynaptic excitation. The impulse generation was at a latency usually of 1.0-1.8 ms, which a modal value of 1.4 ms. The afferent inputs to RN neurons were provided by stimulation either of predominantly cutaneous nerves in all four limbs or of cutaneous mechanoreceptors of the contralateral forelimb and hindlimb...