bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of heat stress on cutaneous vascular responses to the initiation of exercise
Authors: Johnson J. M. , Park M. K.
Published: December 2017

To explore further the competition between vasoconstrictor and vasodilator reflexes in the regulation of skin blood flow, responses in forearm blood flow (FBF) to the initiation of supine leg exercise were measured by plethysmography against a background of rising internal temperature. In 17 studies involving six men, skin temperature (Tsk) was controlled with water-perfused suits first at normothermic levels, followed by a 40- to 50-min period during which Tsk was held at 3813;38.5 degrees C. Supine leg exercise at a moderate intensity (100–150 W) was performed for 5–6 min of each 15 min throughout, yielding one period of exercise performed during normothermic conditions and three periods of exercise performed during the period of elevated Tsk. On the average, FBF fell significantly with the beginning of each period of exercise (P less than 0.05). Furthermore, the amount by which FBF fell tended to increase with increasing levels of preexercise FBF. Thus the average fall in FBF associated with the onset of the last period of exercise, 2.45 ml X 100 ml-1 X min-1, significantly exceeded the 1.12 ml X 100 ml-1 X min-1 fall in FBF seen with onset of work in normothermic conditions. These responses were not due to changes in internal temperature as reflected by esophageal temperatures. However, individual studies occasionally revealed a reduction or abolition of the vasoconstrictor response with the last period of exercise. These findings are in agreement with earlier studies showing a cutaneous participation in the vasoconstrictor responses to exercise but also indicate that sufficient hyperthermia can attenuate or even abolish this response.
Analysis of volume displacement and length changes of the diaphragm during breathing
Authors: Mead J. , Loring S. H.
Published: December 2017

Diaphragmatic volume displacements cause equal displacements of abdominal contents. Since the rib cage forms a variable part of the abdominal container (the variable part being its area of apposition with the diaphragm) the rib cage and ventral abdominal wall share in abdominal displacements. The fraction of total rib cage volume displacement (delta Vrc) contributing to abdominal displacement is predicted from anatomic considerations and measurements. During quiet inspirations it is estimated that more than half of delta Vrc goes into abdominal expansion. This displacement plus the outward displacement of the anterolateral abdominal wall constitute the diaphragmatic displacement. In a typical inspiration in which delta Vrc accounts for 3/4 of the lung volume change, the diaphragm displaces nearly the same volume. Associated changes in diaphragm length are estimated with a model. Diaphragm shortening during an inspiration in which only the rib cage expands is estimated to be only 11% less than during a normal inspiration. We conclude that the direct rib cage contribution to lung volume change is much less, and that diaphragmatic contribution is much more than was previously thought.
Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle
Authors: Dudley G. A. , Abraham W. M. , Terjung R. L.
Published: December 2017

The influence of intensity and daily duration of exercise on cytochrome c concentration in the three muscle fiber types was assessed in rats that were treadmill trained for 8 wk (5 days/wk) by 1 of 19 protocols. The importance of exercise duration was determined at six running intensities (10, 20, 30, 40, 50, and 60 m/min). Daily run times resulted in a maximal adaptive change for each running intensity. The general pattern of cytochrome c change, caused by increasing daily run times, followed a first-order manner in all fiber types. The final time-independent asymptotic values were dependent on the intensity of running. In addition, as running intensity was increased, the length of daily run time required to achieve the peak adaptive response was shortened. The intensity influence was very different between fiber types. In the fast-twitch red fiber, the maximal time-independent response at each work intensity was altered by exercise intensity at only submaximal work loads (i.e., the adaptation from 19 to 29 nmol/g was not further increased at 50 and 60 m/min). In contrast, the adaptive response in the fast-twitch white fiber began at 30 m/min (approx 80% VO2max) and increased exponentially as intensity was increased (200% increase at 60 m/min). Whether this different adaptive response between fiber types is due solely to the ordered recruitment of motor units remains to be determined.
Reflex tracheal gland secretion evoked by stimulation of bronchial C-fibers in dogs
Authors: Davis B. , Roberts A. M. , Coleridge H. M. , Coleridge J. C.
Published: December 2017

We examined the effect of stimulating bronchial C-fibers on tracheal submucosal gland secretion in anesthetized dogs with open chest and lungs ventilated through the lower trachea. We opened the upper trachea in the midline, retracted the cut edges, and sprayed powdered tantalum onto the exposed mucosa. Secretions from the ducts of submucosal glands caused elevations (hillocks) in the tantalum layer, which were viewed through a microscope and recorded on videotape with a television camera. We counted the hillocks (greater than 0.2 mm diam) in an area of mucosa (1.2 cm2) before and after injecting capsaicin (3 micrograms) into a bronchial artery to stimulate bronchial C-fibers. In the minute before capsaicin was injected 7 +/- 2 (mean +/- SE; n = 20) hillocks appeared and in the minute after 40 +/- 2 hillocks. Bradykinin (1.5 micrograms) had similar effects. Secretion was accompanied by contraction of the trachealis muscle. Effects were abolished by cooling (0 degree C) or cutting the vagus nerves. Since capsaicin and bradykinin stimulate bronchial C-fibers selectively when injected in these small doses, we conclude that bronchial C-fibers furnish the afferent arm of an airway secretory reflex.
Effect of lung inflation on pulmonary vascular resistance by arterial and venous occlusion
Authors: Hakim T. S. , Michel R. P. , Chang H. K.
Published: December 2017

To explain the changes in pulmonary vascular resistance (PVR) with positive- and negative-pressure inflation (PPI and NPI, respectively), we studied their effects in isolated canine left lower lobes perfused at constant flow rate. The venous pressure was kept constant relative to atmospheric pressure during lung inflation. The total arteriovenous pressure drop (delta Pt) was partitioned with the arterial and venous occlusion technique into pressure drops across arterial and venous segments (large indistensible extra-alveolar vessels) and a middle segment (small distensible extra-alveolar and alveolar vessels). PPI caused a curvilinear increase in delta Pt due to a large Starling resistance effect in the alveolar vessels associated with a small volume-dependent increase in the resistance of alveolar and extra-alveolar vessels. NPI caused an initial decrease in delta Pt due to reduction in the resistance of extra-alveolar vessels followed by an increase in delta Pt due to a volume-dependent increase in the resistance of all vessels. In conclusion, we provided for the first time evidence that lung inflation results in a volume-dependent increase in the resistance of both alveolar and extra-alveolar vessels. The data suggest that while the volume-related changes in PVR are identical with PPI and NPI, there are pressure-related changes that can be different between the two modes of inflation.
Noninvasive cardiac output determination using inhaled oxygen-15-labeled carbon dioxide
Authors: Braslow N. M. , Hales C. A. , Hoop B. , Kanarek D. J. , Kazemi H.
Published: December 2017

Inhaled oxygen-15-labeled carbon dioxide (CO2*) is hydrated in the alveolar capillary blood to produce oxygen-15-labeled water (H2O*). This allows noninvasive delivery of a traceable indicator into the pulmonary circulation. Removal of oxygen-15 marker from the lung is a function of pulmonary perfusion. Two techniques were evaluated for computing cardiac output (CO) following single bolus inhalation of CO2*: 1) continuous monitoring of arterial blood activity through an external detector and 2) noninvasive positron imaging of oxygen-15-label washout from the chest and simultaneous emergence of activity in arterial blood. In seven mongrel dogs studied using technique 1, 46 determinations of CO were made from 1.2 to 8.0 l/min and compared with simultaneous indocyanine green dye-dilution determination. Correlation coefficient was 0.90 with slope of linear regression of 1.05. In 12 mongrel dogs studied using technique 2, 23 determinations of CO were made from 0.9 to 9.2 l/min and compared with simultaneous indocyanine green dye determination. Correlation coefficient was 0.985 (P less than 0.001) with slope of linear regression of 0.898. This noninvasive technique (2) for determination of CO is independent of assumptions regarding regional ventilation or perfusion of the lung and appears valid in animal studies.
Upper airway and diaphragm muscle responses to chemical stimulation and loading
Authors: Patrick G. B. , Strohl K. P. , Rubin S. B. , Altose M. D.
Published: December 2017

Previous studies suggest that upper airway muscles in humans respond to changes in chemical respiratory drive in a fashion similar to the diaphragm. To test this hypothesis, in nine seated healthy subjects we monitored electromyographic (EMG) activity from the alae nasi (AN), genioglossus (GG), and diaphragm (DI) not only in response to progressive isocapnic hypoxia and hyperoxic hypercapnia but also to hyperoxic hypercapnia with and without an external inspiratory resistance (15 cmH2O X 1(-1) X s). There were linear increases in DI, GG, and AN in response to increasing chemical drive, but the AN in one subject and the GG in another subject did not respond to hypoxia or hypercapnia. In response to an inspiratory load, subjects decreased ventilation (P less than 0.01) and increased AN, GG, and DI EMG activity (P less than 0.05); however, one subject did not show an AN response to either increased chemical drive or ventilatory loading. We conclude that muscles of the upper airway and the diaphragm are generally activated in a parallel fashion as respiration is stimulated by hypoxia, hypercapnia, and increased inspiratory resistance.
A comparison of gas exchange indices used to detect the anaerobic threshold
Authors: Caiozzo V. J. , Davis J. A. , Ellis J. F. , Azus J. L. , Vandagriff R. , Prietto C. A. , McMaster W. C.
Published: December 2017

This study was undertaken to determine which of four commonly used ventilatory or gas exchange indices provides the most accurate and reliable detection of the anaerobic threshold (AT). Sixteen subjects performed two cycle ergometer tests to volitional fatigue. After 4 min of unloaded cycling, the work rate was increased 20 W/min. Ventilatory and gas exchange measurements were made every 30 s throughout each test. During one of the two tests (randomly assigned), venous blood was also sampled every 30 s for subsequent determinations of blood lactate (HLa) concentration. Four ventilatory and gas exchange indices (VE, VCO2, R, VE/VO2) were used separately to detect the AT. The AT determined from systematic increases in HLa concentration was used as the criterion measure. AT values (means +/- SE) (VO2, l/min) using VE, VCO2, R, VE/VO2, and HLa were 1.79 +/- 0.11, 1.74 +/- 0.11, 1.58 +/- 0.06, 1.84 +/- 0.11, and 1.85 +/- 0.11 l/min, respectively. The highest correlation between a ventilatory or gas exchange AT and ATHLa (i.e., criterion measure) was found for VE/VO2 (r=0.93, P less than 0.001). The VE/VO2 also provided the highest test-retest correlation for detection of the AT (r = 0.93, P less than 0.001). Multiple correlational analyses did not significantly enhance detection of the AT. These results favor the use of VE/VO2 for noninvasive detection of the AT because it proved to be the most sensitive and reliable ventilatory or gas exchange index studied.
Effects of tumor necrosis factor and interleukin-1 on the constriction induced by angiotensin II in rat aorta
Authors: Vicaut E. , Rasetti C. , Baudry N.
Published: December 2017

To better understand the different steps in the changes occurring in vascular reactivity during sepsis, we studied the effects of a short exposure to tumor necrosis factor (TNF) and interleukin-1 (IL-1) on the contraction in response to angiotensin II (ANG II). The contraction elicited by ANG II was studied by using standard isometric tension techniques in aortic rings exposed for 1 h to 25 ng/ml TNF or to 5 or 20 ng/ml IL-1. This contraction was not significantly changed by TNF but was 109 +/- 23 and 190 +/- 38% greater than in control rings after 5 and 20 ng/ml IL-1, respectively. Because the contraction induced by ANG II is modulated by the simultaneous release of prostaglandins, we tested the hypothesis that IL-1 interferes with this modulation. We found that the IL-1-induced increase in contraction in response to ANG II was completely inhibited by 10(-5) M of the cyclooxygenase inhibitor indomethacin and also by 10(-5) M of the prostaglandin H2/thromboxane A2-receptor antagonist SQ-29548. Note, however, that in rings exposed to IL-1 the contraction in response to the thromboxane A2-receptor agonist U-46619 was not significantly different from the contraction in unexposed rings. Furthermore, no loss was observed in either the vasodilator response to 10(-9)-10(-4) M of the endothelium-dependent-receptor agonist acetylcholine or in the receptor-independent contraction induced by 60 mM K+. We conclude that short exposure to IL-1, but not to TNF, produces a specific increase in the vasoconstrictor response to ANG II via mechanisms mediated by prostaglandin H2/thromboxane A2. This increase might result from an IL-1-induced shift in favor of constrictor prostanoids in the balance of the dilator/constrictor prostanoids, the release of which is associated with stimulation by ANG II.
Central and regional hemodynamic effects during infusion of Big endothelin-1 in healthy humans
Authors: Ahlborg G. , Ottosson-Seeberger A. , Hemsen A. , Lundberg J. M.
Published: December 2017

Big endothelin-1 (Big ET-1) was given intravenously to six healthy men to study uptakes and vascular effects. Blood samples were taken from systemic and pulmonary arterial and internal jugular and deep forearm venous catheters. Arterial Big ET-1-like immunoreactivity (Big ET-1-LI) increased from 5.43 +/- 0.60 to 756 +/- 27 pmol/l, and ET-1-LI increased from 4.67 +/- 0.08 to 6.67 +/- 0.52 pmol/l (P < 0.001). Skeletal muscle fractional extraction of Big ET-1-LI was 15 +/- 4%. ET-1-LI release did not increase in the studied vascular beds. Heart rate fell by 17% (P < 0.001), cardiac output fell by 26% (P < 0.001), and stroke volume fell by 11% (P < 0.05). Mean arterial blood pressure increased 18%, systemic vascular resistance increased 65%, and pulmonary vascular resistance increased 57% (P < 0.01-0.001). Pulmonary blood pressures, forearm blood flow, arterial pH, arterial PCO2, and systemic arterial-internal jugular venous O2 difference remained unchanged. No specific Big ET-1 receptors were found in human pulmonary membranes. The half-maximal inhibitory concentration for the receptor antagonist bosentan was 181 nM. In summary, circulating Big ET-1 elicits greater increases in mean arterial blood pressure and systemic vascular resistance and decreases in heart rate and cardiac output compared with an equimolar ET-1 infusion (26).
Exercise training prevents maturation-induced decrease in insulin sensitivity
Authors: Nakai N. , Shimomura Y. , Ohsaki N. , Sato J. , Oshida Y. , Ohsawa I. , Fujitsuka N. , Sato Y.
Published: December 2017

We examined the effects of exercise training initiated before maturation or after maturation on insulin sensitivity and glucose transporter GLUT-4 content in membrane fractions of skeletal muscle. Female Wistar rats (4 wk of age) were divided into sedentary and exercise-trained groups. At 12 wk of age, a subset of the trained animals (Tr) was killed along with a subset of sedentary controls (Sed). One-half of the remaining sedentary animals remained sedentary (Sed-Sed) while the other half began exercise training (Sed-Tr). The remaining rats in the original trained group continued to train (Tr-Tr). Euglycemic clamp (insulin infusion rate at 6 mU.kg body wt-1. min-1) was performed at 4, 12, and 27 wk. After euglycemic clamp in all animals except the 4-wk-old, hindlimb (gastrocnemius and part of quadriceps) muscles were removed for preparation of membrane fractions. In sedentary rats, glucose infusion rate (GIR) during euglycemic clamp was decreased from 15.9 mg.kg-1.min-1 at 4 wk of age to 9.8 mg.kg-1.min-1 at 12 wk of age and 9.1 mg.kg-1.min-1 at 27 wk of age. In exercise-trained rats, the GIR was not significantly decreased by maturation (at 12 wk) and further aging (at 27 wk). Initiation of exercise after maturation restored the GIR at 27 wk of age to the same levels as these for the corresponding exercise-trained rats. GLUT-4 content in plasma and intracellular membrane fractions of hindlimb muscle obtained just after euglycemic clamp showed the same trend as the results of GIR. These results suggest that exercise training prevented the maturation-induced decrease in insulin sensitivity. Improvement of insulin sensitivity caused by exercise training was attributed, at least in part, to the increase in insulin-sensitive GLUT-4 on the plasma membrane in skeletal muscle.
Controlled trials of rG-CSF and CD11b-directed MAb during hyperoxia and E. coli pneumonia in rats
Authors: Freeman B. D. , Correa R. , Karzai W. , Natanson C. , Patterson M. , Banks S. , Fitz Y. , Danner R. L. , Wilson L. , Eichacker P. Q.
Published: December 2017

We studied the effects of inhibiting and augmenting neutrophil function by using an immunocompetent rat model of infectious and hyperoxic lung injury. After intrabronchial Escherichia coli challenge at all fractional inspired O2 (FIO2) values studied (FIO2 = 0.21, 0.60, and 0.95) and after lethal O2 exposure alone (FIO2 = 0.90), lung injury, as measured by histological and physiological changes, was reduced by a CD11b/CD18-directed monoclonal antibody (MAb 1B6, P < 0.05 vs. controls) but was increased by recombinant granulocyte colony-stimulating factor (rG-CSF; P < 0.05 vs. control; MAb 1B6 vs. rG-CSF, P < 0.004). Pulmonary neutrophil counts were reduced by MAb 1B6 (P < 0.04) and increased by rG-CSF (P < 0.0004) compared with control animals. However, despite antibiotics, MAb 1B6 and rG-CSF both significantly increased the relative risk of death, independent of O2 concentration, during E. coli pneumonia (1.74 [symbol: see text] 1.20 and 2.39 [symbol: see text] 1.19, respectively, each P < 0.01). During lethal hyperoxia, MAb 1B6 increased the relative risk of death (1.76 [symbol: see text] 1.28, P < 0.16), whereas rG-CSF had no effect on survival (0.97 [symbol: see text] 1.28, P = 0.89). Thus inhibition of neutrophil function attenuated and enhancement worsened lung injury in response to infectious and hyperoxic challenges, supporting a pathophysiological role of the neutrophil in these processes. However, it is problematic that MAb 1B6 therapy, despite preventing lung damage, ultimately worsened host defenses and survival. Furthermore, rG-CSF also adversely affected survival during infectious lung injury, demonstrating the inherent risks of inhibiting or augmenting neutrophil function in an immunocompetent host during infection.
Effects of neonatal immunization and repeated allergen exposure on airway responsiveness in the rabbit
Authors: Minshall E. , Spina D. , Page C. P.
Published: December 2017

Neonatal immunization of rabbits has previously been shown to enhance airway responsiveness to inhaled histamine. We investigated the influence of this immunization protocol on pulmonary parameters after inhalation of histamine in littermate allergen-immunized, sham-immunized, and saline-injected rabbits. In spontaneously breathing rabbits, inhalation of histamine caused a concentration-dependent increase in total lung resistance (RL) and respiratory rate (RR) and a reduction in dynamic compliance (Cdyn). Allergen-immunized rabbits were significantly more responsive to histamine than their control littermates and saline-injected animals when the concentration-effect curves were analyzed in terms of changes in RL (P < 0.05), Cdyn (P < 0.05), and RR (P < 0.05) among these groups. The production of allergen-specific immunoglobulins in this model was not correlated to indexes of airway responsiveness (P > 0.05). The effect of inhaled AMP on pulmonary function in allergen-immunized and native animals was also examined. Inhalation of AMP failed to influence Cdyn but elicited significant non-concentration-dependent increases in total RL in allergen-immunized but not naive animals (P < 0.05). Inhalation of AMP also caused a concentration-dependent increase in RR in both allergen-immunized and naive rabbits that was not significantly different (P > 0.05). The influence of biweekly exposure to inhaled or systemic allergen in allergen-immunized rabbits was also examined. Neither repeated systemic nor aerosolized allergen exposure of neonatally immunized rabbits from 3 to 7 mo of age resulted in a further enhancement of airway responsiveness to inhaled histamine. These results suggest that neonatal immunization with Alternaria allergens enhances airway responsiveness to inhaled histamine and AMP. This airway hyperresponsiveness at 3 mo of age could not be enhanced further after chronic exposure to allergen.
Effect of three different warm-up regimens on heat balance and oxygen consumption of thoroughbred horses
Authors: Lund R. J. , Guthrie A. J. , Mostert H. J. , Travers C. W. , Nurton J. P. , Adamson D. J.
Published: December 2017

Horses were exercised at 105% of their maximal O2 uptake until fatigued after three different warm-up regimens (no warm-up, a light warm-up, and a warm-up until the central venous temperature was > 39.5 degrees C) to assess the effect of the warm-up on the various avenues of heat loss. Approximately 12.79, 15.10, and 18.40 MJ of heat were generated in response to the warm-up and exercise after the three different warm-up regimens, respectively. Of the heat generated, 17.5, 17.2, and 17.4% remained as stored heat after 20 min of active recovery. Heat loss from the respiratory system was 63.6, 33.7, and 40.3% of the heat produced during and after the three warm-up intensities, respectively. The balance of the heat loss was assumed to be via the evaporation of sweat. On this basis, the heat loss by sweating was 14.9, 49.1, and 42.3% of the heat produced during and after the three warm-up intensities, which represented evaporation of 0.8, 3.1, and 3.0 liters of sweat, respectively. O2 consumption during exercise and heart rates 20 min postexercise, after two of the warm-up regimens, was significantly lower than that after no prior warm-up.
Load, length, and velocity of load-moving tibialis anterior muscle of the cat
Authors: Baratta R. V. , Solomonow M. , Nguyen G. , D'Ambrosia R.
Published: December 2017

Three-dimensional relationships of load, length, and velocity of shortening of the tibialis anterior muscle in the cat were derived experimentally and fitted with an analytic model. Gravitational loads were applied to the isolated muscle, which arrived at an equilibrium with the passive forces before supramaximal tetanic stimulation was delivered to its nerve. Recordings of initial passive muscle length at equilibrium and length changes throughout the shortening phase up to the final length at active equilibrium were taken and numerically differentiated to obtain each load's instantaneous velocity. A three-dimensional surface was constructed by using instantaneous length and the corresponding velocity for each of several loads. Maximal velocity of shortening was shown to gradually decrease, occurring earlier in the shortening phase (at larger muscle lengths) as loads increased. Whereas load-velocity curves were hyperbolic for middle and short muscle lengths, they were nonmonotonic during shortening above the optimal length. The model was found to correlate well with the experimental data (R = 0.98) and allowed for prediction of both muscle performance boundaries and instantaneous shortening velocity for a given length across the physiological load spectrum, thus offering a realistic estimation of the contractile properties exhibited by the tibialis anterior muscle in functions similar to naturally occurring movements against gravitational loads, which are accelerated and decelerated during the movement.
Representation of cochlea within primary auditory cortex in the cat
Authors: Merzenich M. M. , Knight P. L. , Roth G. L.
Published: December 2017

The representation of sound frequency (and of the cochlear partition) within primary auditory cortex has been investigated with use of microelectrode-mapping techniques in a series of 25 anesthetized cats. Among the results were the following: 1) Within vertical penetrations into AI, best frequency and remarkably constant for successively studied neurons across the active middle and deep cortical layers. 2) There is an orderly representation of frequency (and of represented cochlear place) within AI. Frequency is rerepresented across the mediolateral dimension of the field. On an axis perpendicular to this plane of rerepresentation, best-frequency (represented cochlear place) changes as a simple function of cortical location. 3) Any given frequency band (or sector of the cochlear partition) is represented across a belt of cortex of nearly constant width that runs on a nearly straight axis across AI. 4) There is a disproportionately large cortical surface representation of the highest-frequency octaves (basal cochlea) within AI. 5) The primary and secondary field locations were somewhat variable, when referenced to cortical surface landmarks. 6) Data from long penetrations passing down the rostral bank of the posterior ectosylvian sulcus were consistent with the existence of a vertical unit of organization in AI, akin to cortical columns described in primary visual and somatosensory cortex. 7) Responses to tonal stimuli were encountered in fields dorsocaudal, caudal, ventral, and rostral to AI. There is an orderly representation of the cochlea within the field rostal to AI, with a reversal in best frequencies across its border with AI. 8) Physiological definitions of AI boundaries are consistent with their cytoarchitectonic definition. Some of the implications of these findings are discussed.
Receptive fields of cerebellar cells receiving exteroceptive input in a Gymnotid fish
Authors: Bastian J.
Published: December 2017

Single neurons in the caudal lobe of the cerebellum of the weakly electric fish Apteronotus albifrons respond to distortions in the normal electric field produced by the animal. Moving plastic or metal objects as well as a simpler stimulus, a moving electrical dipole, produce adequate distortions of the fish's field to cause the cerebellar cells to respond. The moving dipole stimulated small enough areas of the fish's skin, as determined by the responses of single electroreceptors, to allow maps of the receptive fields of single cerebellar cells to be produced. The receptive fields seen varied widely in complexity from relatively small excitatory or inhibitory areas to larger fields containing multiple excitatory and inhibitory areas usually bordering one another. Most cells studied displayed directional responses. Usually qualitatively different responses resulted from opposite directions of movement, and less frequently units were seen in which no response resulted from movement opposite the direction which caused responses; Varying the rate of stimulus movement caused only small changes in the responses of cerebellar cells; however, motionless stimuli applied over areas of skin known to respond to moving stimuli produced weaker responses of the appropriate sign for that area. Movement seems to be an important component of the stimulus for these cells. Cells were also seen which responded to visual as well as to electroreceptive input. Responses to each of these two modalities presented above were quite different. The cells recorded from frequently displayed burst discharges similar to those produced by Purkinje cells in other lower vertebrates, and most of the cells studied are believed to be Purkinje cells. A somatotopic relationship was found between the position of the center of a receptive field on the fish's body and the position of the cell in the brain. All of the results obtained are compatible with the hypothesis that the caudal lobe of the cerebellum is processing electroreceptive information related to object detection.
Theory of current source-density analysis and determination of conductivity tensor for anuran cerebellum
Authors: Nicholson C. , Freeman J. A.
Published: December 2017

The theoretical basis of current source-density (CSD) analysis in the central nervous system is described. Equations relating CSD, the current flow vector, and the extracellular field potential are given. It is shown that the CSD provides superior resolution of neuronal events when compared to conventional field-potential analysis. Expressions for the CSD in rectangular Cartesian coordinates are derived, including the general case of anisotropic, inhomogeneous conductive tissue, and a coordinate system rotated with respect to the principal axes (APPENDIX). The minimum number of spatial dimensions for accurate CSD analysis is discussed. The conductivity tensor was experimentally measured in frog and toad cerebella. All three principal components of the tensor were evaluated and their spatial gradients determined to be negligible. It was also shown that the conductivity was independent of potential. Thus the anuran cerebellum is anisotropic, homogeneous, and ohmic. On the basis of these results the appropriate mathematical expression for the CSD was selected.
Experimental optimization of current source-density technique for anuran cerebellum
Authors: Freeman J. A. , Nicholson C.
Published: December 2017

This paper represents a systematic, semirigorous attempt to optimize the technique of current source-density (CSD) analysis experimentally. We compared different spatial differentiation formulas in terms of accuracy, aliasing, and smoothing, and provide experimental and theoretical rationale for their use. Sources of error have also been investigated. Expressions were derived to enable one to estimate the relative magnitude of errors due to electrical noise, uncertainty in tip position of recording electrodes, and error in the conductivity tensor. Corresponding experiments illlustrating the validity of such estimates are also presented. Methods to determine the optimum interelectrode spacing are given, based on computations of spatial energy-density spectra in the anuran cerebellum. The application of the technique of CSD analysis developed in this, and the accompanying paper, to the vestibulocerebellar input in the toad cerebellum provided significantly better temporal and spatial resolution of neuronal events than conventional field-potential analysis. Considerations germane to the optimum application of this technique to other neural structures are also discussed.
Spatial limits of epileptogenic cortex: its relationship to ectopic spike generation
Authors: Gabor A. J. , Scobey R. P.
Published: December 2017

In order to investigate if ectopic spike generation was ubiquitous in and specific generation was ubiquitous in and specific to epileptogenic cortex, a method was devised to determine the limits of such an area based on a well-accepted physiologic characteristic of epileptogenicity. The limits of the penicillin-induced epileptogenic cortex were defined in terms of a retinal activation field; this is a circumscribed area whose stimulation by light evokes a characteristic cortical epileptiform wave. All lateral geniculate nucleus (LGN) neurons manifesting ectopic spike generation during interictal epileptiform waves had receptive fields within the activation field. During organized seizures, ectopic spike generation was observed in neurons with receptive fields outside the activation field. Because of these findings it was concluded that ectopic spike generation is a characteristic and specific feature of epileptogenic cortex and that it is a characteristic of the epeleptogenic process rather than a peripheral event related entirely to the direct effect of penicillin on neurons.
An electrically mediated inhibition in goldfish medulla
Authors: Korn H. , Faber D. S.
Published: December 2017

1. Passive hyperpolarizing potentials (PHPs) have been recorded intracellularly from goldfish medullary neurons in the vicinity of the Mauthner cell (M-cell). They are evoked when this cell is activated antidromically by stimulation of the spinal cord, and orthodromically via the ipsilateral eighth nerve; when appropriately timed they block or delay spikes induced both directly and transsynaptically. 2. Since the PHPs and the M-cell spike have the same latency, time course, and all-or-none character, they cannot be generated by chemically mediated synaptic transmission. This conclusion is further supported by the evidence that PHP amplitude and time course are independent of membrane potential. 3. The analysis of the mechanism underlying PHP generation has been based on the hypothesis that they are brought about by the extracellular currents flowing to the axon cap during an M-cell action potential. Specifically, it was postulated that some of this current is channeled back to the axon cap region intracellularly through processes of PHP-exhibiting neurons, and that these cells are passively hyperpolarized by the associated inward transmembrane current flow. This model would require that PHP-exhibiting neurons send processes into the axon cap. This hypothesis is confirmed by the following: a) When the PHP is timed to occur during the conductance increase associated with a spike after hyperpolarization, it is reduced, as would be expected for a passive current flow across a membrane resistance. b) PHPs are not found in all medullary neurons in the vicinity of the M-cell, but rather in a specific neuronal population. c) PHP-exhibiting neurons have been identified following Procion yellow injections; as predicted, they issue one process, presumably the axon, which projects toward the M-cell axon cap area. d) The PHP can be stimulated by passing a cathodal current from a microelectrode located in the axon cap; it is not mimicked when the cathodal electrode is moved outside this region. The currents necessary to mimic a PHP are comparable to the estimated current flowing back to the axon cap during an M-cell action potential. 4. The input resistance of PHP-exhibiting neurons is in the range of 4 M alpha, and their estimated specific membrane resistance is in the range of 900-2,000 alpha-cm-2, which is not an unusually low value for neuronal membranes. By contrast, the intracellular channeling of current during a PHP can rather be attributed to a high extracellular tissue resistance within the axon cap, which was found to be at least 2.5 times that of the surrounding medullary tissue..
Static and dynamic responses of spinothalamic tract neurons to mechanical stimuli
Authors: Willis W. D. , Maunz R. A. , Foreman R. D. , Coulter J. D.
Published: December 2017

The activity of primate spinothalamic tract neurons was investigated. Units were identified by antidromic activation from the diencephalon. Most had a spontaneous discharge. The fastest spontaneous discharge rates were from neurons activated by receptors in muscles or joints. However, such activity could be decreased by repositioning the hindlimb. Spontaneous activity was also altered by changes in anesthetic level. Time-interval histograms demonstrated the patterns of spontaneous discharge. Many units could be excited by noxious stimulation. Graded step displacements of the skin often evoked a slowly adapting discharge which was a function of pressure (or displacements above a threshold of some hundreds of microns). Responses continued to increase as pressures became noxious. Rapidly adapting responses of hair-activated and low-threshold spinothalamic tract neurons were tested with ramp stimuli and found to signal acceleration (or a higher derivative of position), velocity, or a combination of these. Responses to stimulus acceleration were prominent when hairs were displaced, while responses to stimulus velocity were seen with displacement of the skin. Possible receptor types which might account for the observations are discussed.
Analysis of response properties of deefferented mammalian spindle receptors based on frequency response
Authors: Hasan Z. , Houk J. C.
Published: December 2017

Sinusoidal responses of primary and secondary endings in deefferented spindles of anesthetized cats were studied over the low-frequency range 0.001-0.1 Hz. Stretch amplitudes were chosen conservatively small (25-100 mum peak-to-peak) so as to lie within the linear region. 1. At 0.1 Hz average sensitivity was 350 pps/mm for primary endings and 80 pps/mm for secondary endings. Sensitivity fell to lower values at lower frequencies, but even at 0.001 Hz, corresponding to 17 min/cycle, sensitivity remained elevated above static values determined with large stretches. Phase lead varied from 5 to 50 degrees and, in the case of primary endings, tended to be greater at lower frequencies. 2. Except for the different scaling factors, the only apparent difference between the frequency responses of primary and secondary endings was a tendency for primary endings to show a greater phase lead over the range 0.001-0.01 Hz. 3. Dynamic responsiveness was assessed theoretically from frequency-response data by calculating responses to ramps at various velocities. Over most of the velocity range dynamic responses were not proportional to velocity. The greater dynamic responsiveness of primary endings during large (6 mm) ramp stretches might be related to frequency response below 0.01 Hz. 4. Certain aspects of dynamic responsiveness to large ramps (6 mm) were accounted for by assuming all phases of responses were attenuated by 25 dB in the case of primary endings and 20 dB in the case of secondary endings. The nonlinearity responsible for attenuation appears to occur at an early stage in the sensory process. 5. Comparison of individual responses to slow ramps with predictions based on linear theory indicated the presence of abrupt departures from linearity for both primary and secondary endings.
Cross connections among crayfish claw efferents
Authors: Wiens T. J. , Gerein G. L.
Published: December 2017

Spontaneous and reflex spike trains in the efferent neurons to the claw opener and closer muscles of the crayfish were cross correlated. The opener inhibitor and the slow closer excitor were found to be closely synchronized under all conditions. Details of the correlation suggested an electrical synapse coordinating these neurons, possibly bidirectional, but possibly from CE to OI only. The OE-OI cross correlogram showed signs of direct central inhibition of OE to OI. Polysynaptic inhibition of OI by OE may also occur. CI and OI show signs of mutual inhibition. An unidentified closer bundle efferent was strongly and positively correlated with OE. The results are consistent with the respective muscular effects of the pairs of neurons involved; they disagree, however, with some previous findings (19).
Neural repetitive firing: a comparative study of membrane properties of crustacean walking leg axons
Authors: Connor J. A.
Published: December 2017

1. Repetitive activity and membrane conductance parameters of crab walking leg axons have been studied in the double sucrose gap. 2. The responses to constant current stimulus could be classified into three catagories; highly repetitive with wide firing frequency range, type I; highly repetitive with narrow frequency range, type II; and nonrepetitive or repetitive to only a limited degree, type III. The minimum firing frequency for type I axons was much greater than for other recording techniques. 3. Voltage-clamp currents in type III axons were qualitatively similar to those of squid or lobster axon. 4. The outward membrane currents of type I and II axons showed a transient phase in addition to the usual delayed current. The magnitude of this transient was a function of both the holding and test voltages. 5. The direction of the transient current reversed in potassium-rich saline. 6. The type I repetitive response in the walking leg axons appears to be generated by the same types of conductance changes that have been demonstrated in molluscan central neurons.
Accommodative reactions of medullary respiratory neurons of the cat
Authors: Richter D. W. , Heyde F.
Published: December 2017

In most of the bulbospinal respiratory neurons, threshold depolarization increased during the early period of their spontaneous burst discharge but decreased again at the end of a burst. In some vagal respiratory neurons, however, threshold depolarization increased steadily until the very end of their discharge period. These changes generally were accompanied by changes in the rate of depol1rization of the spikes, the amplitude of their overshoot, and their discharge frequency. For a given synaptic input, as indicated by the constancy of the interspike membrane potential trajectories, threshold depolarization of bulbospinal neurons remained constant or even decreased. Only in some vagal neurons was an increase in threshold deplarization observed under these conditions. With the exception of some vagal neurons, most of the respiratory neurons did not show a pronounced accommodative behavior when stimulated with linear rising currents. When stimulating with current pulses, all neurons discharged repetitively with only slight adaptation, which was already complete by the first few spike intervals. The current-frequency relationship was linear and revealed a primary and secondary range. The results support neither accommodation nor adaptation as important mechanisms in the genesis of the rhythmic activity of respiratory neurons.
Discrimination of odors in olfactory bulb, pyriform-amygdaloid areas, and orbitofrontal cortex of the monkey
Authors: Tanabe T. , Iino M. , Takagi S. F.
Published: December 2017

In the orbitofrontal olfactory area (LPOF) which was delineated in a previous paper, the capacity for odor discrimination was studied and compared with that in the anterior pyriform cortex (AP), the medial portion of the amygdala (MA), and the olfactory bulb (OB). Unanesthetized monkeys were used and eight odors were applied. 1. In the OB, 12.5% of the cells responded to only one odor, and the cells which responded to five odors were most numerous (25%). The total of the cells which responded to two, three, and four odors was 52%, which was less than the total of the cells responding to three, four, and five odors (67.5%). A small number oc cells responded to all eight odors (2.5%). The responses were classified as an increase (+type), a decrease (-type), or no change (no-type) in the rate of spike discharge. 2. In the AP and MA, no difference in the response patterns was found. The cells which responded to only one odor were 12.3% of the total, and the cells which responded to three different kinds of odors were most numerous (34.3%). The total of the cells responding to two, three, and four odors was 80%, much more than that in the OB. In addition, no cell responded to all eight odors. Concerning the response types, an increase followed by a decrease, or vice versa, in the rate of spike discharges (mixed-type) was observed which did not appear in the OB. Thus, an advance was found in the processing of olfactory information when compared with the OB. 3. A most striking finding in the LPOF was that 50% of the cells responded to only one odor. The cells which responded to two, three, and four odors decreased in this order, and no cell responded to more than five odors. These cells never responded to light or sound. 4. Using three very similar odors and five very different odors, it was apparent that the ability to discriminate odors of the same category is far more advanced in the LPOF than in the lower olfactory areas; and, in contrast, the lower olfactory areas also play a significant role in the discrimination of odors which belong to different categories. 5. It was concluded that the capacity for odor discrimination definitely improves along the olfactory nervous system from the lower to the higher areas. It is highly probable that a fine and sepcific discrimination of odors is performed in the LPOF.
Properties of projections from vestibular nuclei to medial reticular formation in the cat
Authors: Peterson B. W. , Abzug C.
Published: December 2017

In one series of experiments, vestibular neurons that could be activated antidromically by stimulation of the contralateral medial reticular formation were studied with extracellular recording in cats under pentobarbital anesthesia. These neurons were found in all of the four main vestibular nuclei, but were less prevalent in dorsal Deiters' nucleus and in the central region of the superior vestibular nucleus than elsewhere. Regions of the pontine and medullary reticular formation from which neurons in different vestibular nuclei were activated corresponded to the pattern of vestibuloreticular projections described by neuroanatomists. 2. Latencies of antidromic responses to stimulation of the contralateral reticular formation ranged from 0.6 to over 3 ms, indicating a relatively slow transfer of activity from vestibular nuclei to reticular formation.
Stereopsis in normal domestic cat, Siamese cat, and cat raised with alternating monocular occlusion
Authors: Packwood J. , Gordon B.
Published: December 2017

Normal cats, cats raised with alternating monocular occluders, and Siamese cats were tested for stereoscopic vision using a shadow-casting technique that produced line stereograms. Human subjects were tested with the same apparatus. 1. Normal cats had stereoscopic vision, but AO and Siamese cats did not. 2. Normal AO cats, and Siamese cats all had equal visual activity (about 6 feet of arc) and all could make accurate judgments about the depth of real objects. 3. Normal cats could fuse crossed disparities as great as 50 feet of arc and uncrossed disparities as great as 30 feet of arc. 4. Normal cats could make stereoscopic discriminations with stimulus disparities greater than 1 degree, even though they could not fuse disparities of this magnitude. 5. Both the AO and the Siamese cats exhibited a convergent squint. 6. Human subjects viewing identical stimuli could not fuse stimuli having disparities greater than 10 feet, although they could make depth judgments for crossed disparities as great as 5 degrees. 7. These results imply that animals without binocular cells in area 17 do not have stereoscopic vision, but do not determine if disparity-selective cells in the visual cortex are responsible for stereopsis.