bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure outside the extrapulmonary airway in dogs
Authors: Spiro S. G. , Culver B. H. , Butler J.
Published: December 2017

We have measured the static and dynamic transmural pressures of extrapulmonary airways during positive pressure lung inflation in anesthetized dogs suspended in the standing position. Thin, fluid-filled catheters measured pressures within and on the anterior surface of the airways in the mediastinum and neck. The change from mediastinal to cervical static extra-airway pressures (Pea) was not abrupt but occurred through the thoracic outlet and the root of the neck. The static Pea in the mediastinum was more positive than pleural pressure when lung volume was increased with positive pressures. During forced deflation equal pressure points (EPP) were in labor bronchi from which airway narrowing extended towards the mouth. Under these conditions, the dynamic mediastinal Pea mouthward of the EPP remained close to pleural pressures even at high volumes. This suggested that forces of restitution generated in the surrounding tissues by the narrowing of the airways did have a small effect in reducing the pressure affecting their anterior surface.
An electromagnetic valve for inspiratory occlusion pressures
Authors: Camporesi E. M. , Feezor M. , Fortune J. , Salzano J.
Published: December 2017

An electromagnetically powered respiratory valve to occlude a respiratory circuit for short (30--300ms) periods of the respiratory cycle may be inexpensively constructed from available laboratory instruments and controlled by an electronic circuit. Occlusion of the inspiratory breathing circuit may be repeated at different levels of ventilation without altering slopes or intercepts of CO2 rebreathing curves. The early phases of airway occlusion (P0.1) may therefore be studied in conscious unanesthetized human subjects.
A technique for multiple, high-rate blood samplings via an external cannula in rats
Authors: Staub J. F. , Coutris G.
Published: December 2017

A method for obtaining multiple, high-rate blood sample collections from rats without the use of anesthesia and anticoagulant is described. The surgical procedure consists of a bypass of the carotid via a cannula; this cannula forms a loop above the rat's head and is available for blood sampling. The method permits the investigation of high-frequency oscillations in blood components of rat.
Hemodynamics in teenagers and asthmatic children during exercise
Authors: Friedman M. , Kovitz K. L. , Miller S. D. , Marks M. , Sackner M. A.
Published: December 2017

Seventeen normal teenagers and eight asthmatic children were studied during submaximal exercise on a bicycle ergometer. A modification of a noninvasive multiple gas rebreathing method was utilized for the estimation of pulmonary capillary blood flow (Qc), diffusing capacity (DL), oxygen consumption (VO2), functional residual capacity (FRC), and pulmonary tissue plus capillary blood volume (VTPC). Significant increases in Qc, DL, VO2, and heart rate occurred in both groups of subjects. Regression equation of Qc equaled 6.0 + 0.0078 VO2 (ml/min) in the teenagers and 3.39 + 0.0082 X VO2 (ml/min) in the asthmatic children. The values of DL as a function of VO2 in both groups were similar to previously reported data. No significant changes in FRC or VTPC occurred in either group during exercise. This method appears to be an acceptable noninvasive way of studying exercise physiology in healthy or sick children.
Effects of methacholine and hypocapnia on airways and collateral ventilation in dogs
Authors: Smith L. J. , Inners C. R. , Terry P. B. , Menkes H. A. , Traystman R. J.
Published: December 2017

We studied the effects of hypocapnia and methacholine on small airways resistance (Rsaw) and collateral ventilation in anesthetized paralyzed dogs. The animals were ventilated with air while either 10% CO2 or air (hypocapnia) was infused through a segment obstructed with a fiber-optic bronchoscope. Measurements were made before and after instillation of methacholine into the obstructed segment. Collateral resistance (Rcoll) and Rsaw increased with hypocapnia and methacholine. The time constant for collateral ventilation increased with hypocapnia, but did not change with methacholine because of decreases in the compliance of the obstructed segment. We conclude that collateral channels respond to methacholine and hypocapnia in a manner similar to small airways and that local parasympathomimetic stimulation, unlike lung deflation does not increase the time constant for collateral ventilation.
A method for measurement of oxygen uptake in neonates
Authors: Raemer D. B. , Westenskow D. R. , Gehmlich D. K. , Richardson C. P. , Jordan W. S.
Published: December 2017

The frequent use of continuous positive airway pressure and positive end-expiratory pressure in newborn infants with pulmonary disease has prevented the use of conventional methods for measuring oxygen uptake (VO2) in intensive-care units. A feed-back replenishment technique for the determination of the oxygen uptake of these newborn infants has been developed. An instrument utilizing this method has been designed and built permitting continuous VO2 monitoring without interfering in the routine ventilatory therapy of the critically ill infant. Theoretical, bench, and animal experiments using room air as an inspired gas indicate instrument accuracies as a percentage of full scale of 2.4, 2.8, and 7.3, respectively. Preliminary trials on infants demonstrate that the instrument functions satisfactorily in the newborn intensive-care unit.
Time-constant histograms from the forced expired volume signal
Authors: Pimmel R. L. , Miller T. K. , Fouke J. M. , Eyles J. G.
Published: December 2017

The forced expired volume signal was analyzed using a parallel compartment model in which each compartment emptied exponentially. With this model the forced expired volume signal was represented by a histogram showing the fraction of the vital capacity as a functional of compartmental time constants. We developed an algorithm to compute this histogram from the volume signal. The algorithm used the least-squares criterion function with both smoothness and nonnegativity constraints. In a stimulation study reasonable histograms were obtained even in the presence of realistic random error. Three dependent forced expired volume signals from 16 subjects were analyzed, and the histograms were reproducible. Most histograms were bimodal with fast time constants of 0.12–0.55 s and slow time constants of 1.3–2.7 s. In all normal subjects and patients with restrictive disease more than 75% of the vital capacity was in the fast time-constant mode. Subjects with obstructive disease had more than 40% of the vital capacity in the slow time-constant mode.
Elevated pulmonary lymph flow and protein content during status epilepticus in sheep
Authors: Simon R. P. , Bayne L. L. , Tranbaugh R. F. , Lewis F. R.
Published: December 2017

The pathophysiology of postictal pulmonary edema was investigated by inducing seizures with bicuculline in nine paralyzed, halothane-anesthetized sheep and measuring of pulmonary lymphatic flow, pulmonary arterial and left atrial pressures, and lymph and plasma albumin concentration. Pulmonary microvascular pressure and transcapillary albumin conductance were calculated. Seizures transiently (less than 15 min) elevated microvascular pressure in all animals; lymph flow increased greater than twofold in response to the increased hydrostatic driving force. However, the elevation in lymph flow, with a stable lymph-to-plasma protein ratio and doubled transcapillary albumin conductance, persisted for the duration of the experiment, more than 3 h after microvascular pressure returned to base line. These changes were neurally mediated because they were blocked by cervical spinal cord transection in four additional animals.
Influence of upper airway pressure changes on genioglossus muscle respiratory activity
Authors: Mathew O. P. , Abu-Osba Y. K. , Thach B. T.
Published: December 2017

The effects of change in pharyngeal airway pressure on electromyographic (EMG) activity of a pharyngeal dilating muscle (genioglossus) were investigated in 20 anesthetized rabbits. In vagotomized animals, upper airway loading maneuvers (nasal occlusion) increased the peak inspiratory activity of the genioglossus (GG) muscle on the first occluded breath. In contrast, “unloading” maneuvers (switching from nose to tracheostomy breathing) decreased GG activity. To further characterize the GG response, sustained pressure changes were produced within the isolated upper airway. Negative pressure increased GG activity; positive pressure decreased it. A poststimulus effect consisting of increased GG activity compared with control was seen following both negative- and positive-pressure stimuli. Cyclical pressure changes applied to the isolated upper airway increased the GG activity. These observations indicate the presence of reflex pathways that regulate GG muscle activity in response to upper airway pressure loads. This reflex system appears to play a role in regulating GG activity during tidal breathing and could be important in ensuring pharyngeal airway patency.
Arterial CO2 response to low levels of inspired CO2 in awake beagle dogs
Authors: Reischl P. , Stavert D. M.
Published: December 2017

We have previously shown, using a repeated-measures experimental design, that 1% inspired CO2 with a partial pressure of 7 Torr at sea level results in an increased end-tidal CO2 pressure (PETCO2) in awake beagle dogs (22), suggesting hypercapnia rather than the isocapnia found by some investigators in human and nonhuman subjects. Because PETCO2 may, not equal arterial PCO2 (PaCO2), we examined the steady-state PaCO2 during air and 1% CO2 inhalation periods in three awake beagle dogs having exteriorized carotid arterial loops and an intact airway, and breathing through a low dead-space respiratory mask. Six low-level CO2 inhalation experiments were performed in three dogs with two experimental sequences in each dog on separate days. An experimental session consisted of alternating control and CO2 inhalation states for up to 10 low-CO2 and 11 control conditions, resulting in a total of 75 control and 57 low-level CO2 inhalation observations. Ten minutes were allowed to reach steady state in each condition. Blood samples (1.5 ml) drawn anaerobically over a 0.5-min time period from an indwelling arterial catheter were immediately analyzed with a radiometer blood gas system. The 1% inhaled CO2 produced a significant increase of 0.88 Torr in the steady-state PaCO2, compared with bracketing controls (t = 5.82, P less than 0.05, df = 2). We conclude that 1% inhaled CO2 results in hypercapnia detectable by a repeated-measures experimental design.
Improved method in the computer determination of plethysmographic thoracic gas volume
Authors: Harf A. , Lorino H. , Atlan G. , Lorino A. M. , Laurent D.
Published: December 2017

To improve the computer determination of thoracic gas volume (TGV), two new approaches were worked out. 1) A new program was designed, which overcomes the difficulties encountered in the time recognition of the panting maneuver and rules out the artifacts. Such a procedure is based on the data analysis in the pressure-volume time derivatives plane. 2) A hyperbolic fitting of the signals recorded during the panting maneuver was introduced. This last procedure, lying on Boyle's law, has proved to be useful in case of large mouth pressure changes. In fact the error induced by the conventional linear fitting may reach 500 ml (9% of the TGV value).
Determination of the anaerobic threshold by a noninvasive field test in runners
Authors: Conconi F. , Ferrari M. , Ziglio P. G. , Droghetti P. , Codeca L.
Published: December 2017

The relationship between running speed (RS) and heart rate (HR) was determined in 210 runners. On a 400-m track the athletes ran continuously from an initial velocity of 12–14 km/h to submaximal velocities varying according to the athlete's capability. The HRs were determined through ECG. In all athletes examined, a deflection from the expected linearity of the RS-HR relationship was observed at submaximal RS. The test-retest correlation for the velocities at which this deflection from linearity occurred (Vd) determined in 26 athletes was 0.99. The velocity at the anaerobic threshold (AT), established by means of blood lactate measurements, and Vd were coincident in 10 runners. The correlation between Vd and average running speed (mean RS) in competition was 0.93 in the 5,000 m (mean Vd = 19.13 +/- 1.08 km/h; mean RS = 20.25 +/- 1.15 km/h), 0.95 in the marathon (mean Vd = 18.85 +/- 1.15 km/h; mean RS = 17.40 +/- 1.14 km/h), and 0.99 in the 1-h race (mean Vd = 18.70 +/- 0.98 km/h; mean RS = 18.65 +/- 0.92 km/h), thus showing that AT is critical in determining the running pace in aerobic competitive events.
Increased pulmonary microvasuclar permeability induced by alpha-naphthylthiourea
Authors: Rutili G. , Kvietys P. , Martin D. , Parker J. C. , Taylor A. E.
Published: December 2017

The effects of alpha-naphthylthiourea (ANTU) on lung microvascular permeability to plasma proteins were studied in anesthetized open-chest dogs. Lymph flow (Jv) was recorded, and total protein in plasma and lymph was analyzed after cannulating a small prenodal lung lymphatic. The protocol involved four experimental periods. Period 1. During this base-line period the preparation stabilized and steady states were reached in Jv, lymph total protein, pulmonary arterial pressure (Ppa), and left atrial pressure (Pla). Period 2. Pla was increased to approximately 20 cmH2O and maintained at that level until Jv and protein measurements attained a new steady state. Period 3. After Pla was lowered to control levels, ANTU (5 mg/kg body wt) was infused intravenously and parameters were measured for 3 h. Period 4 Pla was again raised to the pre-ANTU levels of period 2 and maintained for an additional 2–3 h. The lymphatic total protein clearance increased 8.6-fold for an equivalent increase in pulmonary capillary pressure after ANTU. Vascular permeability was assessed by estimating the osmotic reflection coefficient (sigma d) for total protein at the pulmonary capillary membrane. Sigma d decreased from 0.65 to 0.40 following ANTU. From plasma protein fractions in four experiments, equivalent pore radii for the capillary membrane of 95 and 280 A were calculated after ANTU compared with 80 and 200 A for normal lung capillaries. In addition, extravascular lung water increased from 3.8 +/- 0.16 to 5.87 +/- 0.25 following ANTU and to 7.55 +/- 0.55 (g/g blood-free dry wt) when Pla was elevated with ANTU. The experimental design allowed quantitative assessment of the vascular permeability increase after ANTU by use of lymph protein fluxes that had minimal errors due to changes in surface area or lymph contamination from nonpulmonary structures.
Exercise and cardiac performance capacity in rats with partial sympathectomy
Authors: Ernst S. B. , Mullin W. J. , Herrick R. E. , Baldwin K. M.
Published: December 2017

This study was undertaken to examine maximal oxygen uptake (VO2 max) and heart rate (HR) during exercise, in situ derived cardiac contractile capacity, and Ca2+ regulation of cardiac myofibril ATPase in normal female rats and in rats with partial sympathectomy (SYMX) induced by chronic injections of guanethidine. Also, normal control (NC) rats were studied during exercise with and without the beta 1-blocking drug atenolol. The results show that SYMX did not have any effect on Ca2+-regulated cardiac myofibril ATPase activity. Also similar cardiac functional capacity, as reflected in left ventricular pressure development and +dP/dtmax, was observed for both groups when the heart was stressed by either exogenous norepinephrine or maximal afterload (aortic constriction). Exercise VO2 max was reduced by 15% (P less than 0.05) in the SYMX compared to the NC group. Although this reduction in VO2 max corresponded to a parallel reduction in HRmax, NC rats with cardiac beta-blockade attained normal VO2 max even though their exercise HRmax was below the SYMX group. These findings suggest that normal rats with attenuated HR and contractility have a better capacity to acutely maintain VO2 max during exercise than rats with chemical sympathectomy.
Left atrial pressure elevation recreates the altered lung lymph flow of seizures
Authors: Simon R. P. , Bayne L. L. , Naughton M. P.
Published: December 2017

We compared the effects of elevated left atrial pressure of central nervous system origin (bicuculline-induced seizures) with an identical pulmonary vascular pressure elevation induced in six sheep by inflation of a balloon in the left atrium. The degree and duration of the consequent elevation in pulmonary lymph flow and the alteration in protein movement in the two groups was identical. Alterations in pulmonary fluid and protein flux resulting from generalized seizures can be explained by the pressor response alone; specific brain-lung neural interactions need not be postulated.
Aortic body chemoreceptor responses to dopamine, haloperidol, and pargyline
Authors: Smatresk N. J. , Lahiri S.
Published: December 2017

Aortic chemoreceptor activity, from single- or few-fiber afferent nerve preparations, was measured in response to dopamine and a dopaminergic blocker, haloperidol, in 18 anesthetized cats. In six of these cats the effect of dopamine was assessed before and after inhibiting monoamine oxidase (MAO) by pargyline. Intravenous dopamine infusion (713;14 microgram X kg-1 X min-1) had a generally inhibitory effect on aortic chemoreceptor activity, but the magnitude of this effect varied with arterial partial pressure of O2 (Pao2) levels. The inhibitory effect of dopamine increased as Pao2 levels fell, and at severely hypoxic Pao2 levels (below 30 Torr) exogenous dopamine had no significant effect. The inhibitory effect of dopamine also increased during hyperoxic hypercapnia. Blockade of dopamine receptors in the aortic body by haloperidol-stimulated chemoreceptor activity significantly during hypoxia, suggesting an O2-dependent release of dopamine from the aortic body as Pao2 falls. Inhibition of MAO by pargyline had no significant effect on the control rate of activity at any level of Pao2 but augmented the inhibitory effect of exogenously administered dopamine. These data indicate that MAO is not significantly involved in the degradation of endogenous dopamine at the aortic receptor sites, but may participate in the degradation of exogenous dopamine.
Cerebrovascular responses to CO2 after inhibition of sympathetic activity
Authors: Lopez de Pablo A. L. , Gonzalez M. C. , Dieguez G. , Gomez B. , Lluch S.
Published: December 2017

The effects of inhalation of 10% CO2 in air on cerebral blood flow (CBF) and cerebrovascular resistance (CVR) were examined in 13 unanesthetized goats before and after impairment of the sympathetic activity present in cerebral vessels. Under control conditions, inhalation of CO2 increased CBF from 112 +/- 10.2 (SE) to 191 +/- 17.2 ml X min-1 X 100 g-1 and decreased CVR from 0.91 +/- 0.02 to 0.55 +/- 0.03 Torr X ml-1 X min X 100 g. After treatment with reserpine CO2 increased CBF to levels similar to those before treatment, but values for CVR were significantly lower. Inhalation of CO2 1–2 days after removal of both superior cervical sympathetic ganglia produced a larger increase in CBF and a greater drop in CVR, whereas at 6–20 days after ganglionectomy the effects of CO2 were analogous to those measured before the operation. The results suggest that the existence of an intact tonic adrenergic activity is a factor in the level of CVR achieved in hypercapnic acidosis.
Postnatal maturation of peripheral chemoreceptor ventilatory response to O2 and CO2 in newborn lambs
Authors: Canet E. , Kianicka I. , Praud J. P.
Published: December 2017

Although studies on lambs have shown that carotid body sensitivity to O2 is reset postnatally, it is still unknown whether O2 and CO2 peripheral chemoreflexes undergo parallel postnatal maturation. The present study was designed to analyze maturation of O2 and CO2 peripheral chemoreflexes in 10 lambs at < 24 h and at 12 days of age. We measured the ventilatory (VE) response to three tidal breaths of pure N2 or 13% CO2 in air. Overall, the N2 peripheral chemoreflex increased significantly with maturation [VE/end-tidal O2 (ml.min-1.kg-1.Torr-1) = 2.94 +/- 0.91 at < 24 h vs. 5.13 +/- 0.59 at 12 days, P < 0.05], whereas the CO2 peripheral chemoreflex did not change (VE/end-tidal CO2 = 7.04 +/- 0.98 at < 24 h vs. 7.75 +/- 1.07 at 12 days, not significant). We conclude that the CO2 peripheral chemoreflex does not change in awake lambs within the time frame studied, in contrast to a marked postnatal maturation of the O2 peripheral chemoreflex. The different time courses of O2 and CO2 peripheral chemoreflex maturation support the concept that carotid body sensitivities to O2 and CO2 do not depend on the same basic mechanisms.
Effect of thromboxane A2-receptor antagonist on bradykinin-induced bronchoconstriction in asthma
Authors: Rajakulasingam K. , Johnston S. L. , Ducey J. , Ritter W. , Howarth P. H. , Holgate S. T.
Published: December 2017

The role of the thromboxane A2 (TxA2) receptor in bradykinin-induced bronchial responses was investigated in this study by using a selective and potent TxA2-receptor antagonist BAY u 3405. Eleven asthmatic subjects were randomized to receive 50 mg of BAY u 3405 or matched placebo in a crossover and double-blind fashion. Ninety minutes after dosing, serum was taken for drug assay, and subjects underwent provocation with bradykinin or prostaglandin D2 (PGD2) to determine bronchial responsiveness [provocative concentration of agonist required to produce a 20% fall in forced expiratory volume in 1 s from the postdiluent baseline (PC20)]. Pretreatment with BAY u 3405 caused a twofold doubling-dilution reduction in bronchial reactivity to PGD2; the geometric mean PC20 values were 0.132 (0.015-0.871) and 0.034 (0.008-0.095) mg/ml, respectively, for active and placebo days (P = 0.001). There was, however, no significant difference in PC20 values for bradykinin between active and placebo treatment days. We have demonstrated that BAY u 3405 caused a significant inhibition of bronchconstriction induced by inhaled PGD2 but had no influence on bronchial responsiveness to inhaled bradykinin. This study suggests therefore that TxA2 receptors do not play a role in bradykinin-induced bronchoconstriction in asthma.
Does the disease state influence the responsiveness of human airways studied in vitro?
Authors: Armour C. L. , McKay K. O. , Johnson P. R. , Glanville A. R. , Black J. L.
Published: December 2017

Human airway tissue has been used in vitro to study mechanisms of airway disease. However, there has never been a comprehensive study that has looked at the influence of disease on the subsequent in vitro responsiveness of human airways. In this study, we obtained airway tissue from patients who were undergoing resection of the lung for carcinoma. We then compared the airway responsiveness in these tissues and in tissues from patients who had undergone lung transplantation for alpha-1-antitrypsin deficiency, emphysema, or cystic fibrosis with the responsiveness in tissues obtained from donor lungs, i.e., nondiseased. When the relationships between concentration and response were compared, we found that for histamine, electrical field stimulation, levcromakalim, and isoproterenol similar responses could be expected in tissues obtained from all the sources studied. This was not true for acetylcholine in that there were significantly lower responses in tissues from patients with alpha-1-antitrypsin deficiency (P = 0.02; n = 9) or from patients having a lung resected for carcinoma (P = 0.01; n = 6) compared with that of the nondiseased group (n = 6). Similarly, for carbachol, the responses were significantly lower in the alpha-1-antitrypsin deficiency group (P = 0.001; n = 10) and in specimens resected for carcinoma (P = 0.001; n = 6) than in the nondiseased group (n = 9). We conclude that, apart from acetylcholine and carbachol, contractile and relaxant agonists give similar responses when used in human airway tissues from various sources. Our results highlight the importance of stating the source of tissue when human airways are to be studied.
Somatotopic representation of hindlimb skin in cat dorsal horn
Authors: Brown P. B. , Fuchs J. L.
Published: December 2017

Single-unit exploration of the dorsal horn of segments L4-S2 of unanesthetized cats with the neuraxis transected at lower thoracic levels reveals a somototopic organization in the horizontal plane. The dorsal horn dermatomes correspond closely to the dermatomes of the corresponding dorsal roots, and the ML gradient is equally well described by two different projection schemes: a distoproximal gradient and a ventrodorsal one (5, 33). There is no evidence of segmental discontinuity of the map. As is the case in other nuclear regions of the CNS, the relative area devoted to projections from the foot is disproportionately large relative to the area devoted to skin regions of similar size which are located more proximally on the limb. From our data, and from the close correspondence to anatomical data obtained by others, we suggest that at least some cutaneous afferent fibers from a given skin area project directly to any dorsal horn region where that skin area is represented. This assumption, together with the organization of the dorsal horn map, yields a model which predicts a precise somatotopic organization of presynaptic neuropil in the substantia gelatinosa.
An electrically evoked slow potential of the frog's retina. I. Properties of response
Authors: Knighton R. W.
Published: December 2017

1. Brief pulses of electrical current passed through the frog's eye cup from sclera to vitreous (inward current) evoked large, vitreous positive slow potentials of retinal origin. Brief pulses of outward current evoke no response. 2. This electrically evoked retinal response (EERG) increased sharply in amplitude as the strength of the stimulus was increased. 3. Strength-duration curves showed that the stimulating pulse was integrated with a time constant ranging from 14 to 36 ms. The time constant was a function of the amplitude chosen as a criterion. 4. The EERG was abolished by chemical agents which abolish the PII component of the ERG (KCl, NH3, aspartate). 5. The waveform of the EERG returned to the base line with exactly the same time course as the PII component of the ERG, both when the PII was evoked by flashes of light and when it was evoked by flashes of darkness. 6. These results can be explained in terms of the hypothesis that electrical stimuli act on the synaptic terminals of the photoreceptor cells.
Morphological and functional identifications of catfish retinal neurons. I. Classical morphology
Authors: Naka K. , Garraway N. R.
Published: December 2017

The morphology of the catfish horizontal cells is comparable to that in other fish retinas. The external horizontal cells contact cone receptors and are stellate in shape; the intermediate horizontal cells are even more so and contact rod receptors. The internal horizontal cells constitute the most proximal layer of the inner nuclear layer and may possibly be, in reality, extended processes from the other two horizontal cell types. Bipolar cells resemble those in other teleost retinas: the size and shape of their dendritic tree encompass a continuous spectrum ranging from what is known as the small to the large bipolar cells. The accepted definition of amacrine cells is sufficiently vague to justify our originating a more descriptive and less inferential name for the (axonless) neurons in the inner nuclear layer which radiate processes throughout the inner synaptic layer. These starbust and spaghetti cells vary considerably in the character and extent of their dendritic spread, but correlates exist in other vertebrate retinas. Ganglion cells are found not only in the classical ganglion layer but displaced into the inner nuclear layer as well. Several types can be distinguished on the basis of cell geometry and by the properties of their dendritic tree. Not all of the categorization corresponds with previous descriptions; our findings suggest that some reorganization may be necessary in the accepted classification of cells in the proximal areas of the vertebrate retina. A subtle yet remarkable pattern underlies the entire structure of the catfish retina; there exists a definite gradient of size within a particular class of cells, and of configuration among the subclasses of a specific cell type. It remains to be seen if these morphological spectra bear any functional consequences. The fact that the structure of the catfish retina most closely resembles those of other phylogenetically ancient animals, such as the skate and the dogfish shark, testifies to its primitive organization; morphological and functional mechanisms discernible in this simple system may, therefore, be applicable to the retinas of higher ordered vertebrates.
NADH fluorescence and [K+]o changes during hippocampal electrical stimulation
Authors: Lewis D. V. , Schuette W. H.
Published: December 2017

1. Short (2 s) trains of stimuli were applied to the dorsal hippocampal surface of cats, producing an increase in [K+]o and a decrease in NADH fluorescence (the latter being indicative of an increase in tissue oxygen utilization). 2. The [K+]o rose rapidly during stimulation (delta[K+]o values from 1 to 6 mM) with larger stimulus currents producing larger changes. The time course of the poststimulus decline of [K+]o was an exponential decay function, with T 1/2 values varying from 1.3 to 6.9s, and independent of the magnitude of the delta[K+]o. Consistent undershoots of [K+]o occurred following stimuli causing less than 1 mM change in [K+]o. 3. The maximum depression of fluorescence and the time integral of the fluorescence changes following each stimulus train were both highly correlated with the total increase of [K+]o occurring during the stimulus train. 4. Application of several stimulus trains in close succession resulted in more rapid potassium reuptake following the later trains and an unusually large undershoot after the last train. Concomitantly, there was a progressive decrease in the fluorescence level. 5. When afterdischarges were induced by prolonged (less than 2 s) stimulation, larger and more sustained increases in [K+]o and decreases of fluorescence were observed, and there was some indication that afterdischarges were followed by accelerated reuptake of extracellular potassium.
Medial recticular neurons projecting Rostrally
Authors: Eccles J. C. , Nicoll R. A. , Taborikova H. , Willey T. J.
Published: December 2017

1. In the latter part of investigations on the medial reticular neurons, stimulation was applied to the ipsilateral tegmental tract in the upper pontine level. Of the 426 neurons in this series, 56 had rostrally projecting axons as evidenced by their antidromic responses. 2. Of these 56 neurons, 41 were activated by limb nerve stimulation, usually very strongly, and so qualify as units in the reticular activating system. Fastigial stimulation monosynaptically excited 14 of these reticular activating neurons, so providing and ascending pathway from the cerebellar vermis. 3. Axonal branching has been demonstrated by antidromic testing in four reticular neurons with ascending axons. In two there were branches to the fastigial nucleus and in two, down the spinal cord. 4. The latency histograms of the excitatory and inhibitory responses resembled those for reticular neurons with descending axons except for the poverty of inhibitory responses in neurons not receiving a fastigial projection.
Single-unit responses to natural vestibular stimuli and eye movements in deep cerebellar nuclei of the alert rhesus monkey
Authors: Gardner E. P. , Fuchs A. F.
Published: December 2017

To study the possible role of the cerebellum in the vestibular-ocular reflex, extracellular responses of cerebellar nuclear neurons were recorded in awake monkeys during natural vestibular stimulation; 115 neurons in the fastigial nucleus responded to horizontal sinusoidal accelerations applied to the head by means of whole-body rotation. More than 75% of these cells were located in a distinct layer, 500 mum thick, in the rostral part of the fastigial nucleus; they were excited by contralateral horizontal angular acceleration and inhibited by ipsilateral rotation (type IIf neurons). The remaining 25% of the population were scattered more caudally in the nucleus, and were excited by ipsilateral rotation and inhibited by contralateral rotation (type If). All showed fairly high resting discharges, averaging 50 spikes/s. Sinusoidal horizontal rotation (0.2--4.8 HZ) produced clear periodic modulation of the firing rate of fastigial neurons, which was approximately sinusoidal about the resting rate at low frequencies. As the frequency of oscillation (and the applied acceleration) increased, the sinusoidal modulation of unit firing increased in amplitude; at high stimulus frequencies the firing rate was usually driven to zero during the inhibitory part of stimulus cycle, but did not saturate in the excitatory half leading to an increase in the mean firing rate. The maximum firing rates of fastigial neurons were related to the peak acceleration by a power function. At all stimulus frequencies, the peak firing frequency of fastigial neurons lagged the input angular acceleration. Maximum firing of most units occurred just prior to the maximum velocity of the head. The gain and phase lag of the averaged unit discharge relative to head acceleration were calculated by Fourier analysis, using the fundamental as a first approximation of the response. Over a 20-fold stimulus range (0.2--4.0 HZ), mean phage lags of type IIf unit responses with respect to the applied acceleration remained relatively constant; the phase lag at 0.9 HZ measured 62 plus or minus 13 degrees. This phase lag is very similar to that recorded from vestibular nerve fibers (15), suggesting that type IIf fastigial neurons provide an excitatory signal to the ipsilateral vestibular nuclei which is in phase with direct vestibular afferent input, although functionally opposite in sign. Over the same frequency range, the gain decreased at minus- 18 dB/decade. Our data suggests that the majority of fastigial neurons work in parallel with flocculus Purkinje cells to functionally inhibit type Iv neurons in the ipsilateral vestibular nuclei.
Transition in sensitivity of spindle receptors that occurs when muscle is stretched more than a fraction of a millimeter
Authors: Hasan Z. , Houk J. C.
Published: December 2017

We studied the responses of 34 deefferented spindle receptors to slowly applied ramp stretches (0.01-1 mm/s) of small (0.02-0.2 mm) and intermediate (0.2-1 mm) amplitudes. The afferent discharge from primary and secondary endings was recorded from filaments of dorsal root in anesthetized cats. 1. Responses of most endings to ramps of intermediate amplitude showed abrupt changes in slope (discontinuities) which were highly repeatable. Discontinuities occurred more nearly at constant stretch (in the range 50-400 mum for different receptors) than at constant discharge rate. They were less pronounced in the case of secondary endings. 2. Changes in sensitivity occurred when the degree of stretch exceeded a transitional amplitude which ranged from 50 to 200 mum. These changes were studied by constructing plots based on a family of responses to a family of ramps which were scaled versions of each other. The plots indicated that reductions in sensitivity occurred both during stretch and during adaptation; the reductions were more marked for primary than for secondary endings. 3. Responses were modified considerably by preceding changes in muscle length. When the last change was an increase of a few millimeters, discontinuities became more pronounced and other changes in the appearance of the dynamic response occurred, particularly in the case of primary endings. These changes could last for several minutes, but were abolished by a single test stretch of intermediate amplitude. 4. The resetting of high sensitivity that occurs when muscle length is changed, the discontinuities, the transitions in sensitivity, nonlinear adaptation, and the effects of previous length change appeared to be related phenomena. They can all be accounted for by the hypothesis that polar zones of intrafusal muscle fibers possess a frictionlike property, one analogous to that which has been described for whole muscle. A simple nonlinear model which shows these features is presented. 5. The adequate stimulus for a change in primary ending discharge is a small change in muscle length, relatively independently of its velocity. The dynamic response arises mainly from a changing sensitivity to length itself, which is a nonlinear property.
Sustained and transient cells in monkey lateral geniculate nucleus: conduction velocites and response properties
Authors: Marrocco R. T.
Published: December 2017

The receptive-field properties of units in the macaque LGN were studied with extracellular microelectrodes. Analysis of responses of opponent and nonopponent cells to stationary spots, moving spots, and grating revealed transient and sustained varieties of both spectral groups as well as cells with mixed properties. The cell's temporal discharge pattern was not correlated with its color sensitivity. Cells that ere classified as sustained responders did so under all stimulus conditions tested. Most transient cells responded in a transient fashion to each stimulus tested. In a few cells, a sustained response could be shortened into a transient response by activating the cell's surroun mechanism. The conduction velocities of sustained and transient cells were determined by shocking optic chiasm and striate cortex. Among nonopponent cells, transient types conducted significantly faster than the sustained type. No such difference was found among opponent cells. Among all cells, the fastest conducting were transient nonopponent (14 m/s), while the slowest were +B-Y opponent cells (4 m/s). Intermediate were sustained nonopponent (11 m/s) and the remainder of opponent cells types (about 7 m/s). There was a significant positive correlation between a cell's shock-evoked spike latency and its visually evoked latency. These results suggest that there are at least three independent information channels in monkey geniculostriate pathway. Further characterization of these channels is in progress.
Analysis of afferent responses from isolated semicircular canal of the guitarfish using rotational acceleration white-noise inputs. I. Correlation of response dynamics with receptor innervation
Authors: O'Leary D. P. , Dunn R. F.
Published: December 2017

The small-signal linear characteristics of afferent responses from the isolated semicircular canal were described by the use of white-noise rotational acceleration inputs. The results, based on cross-correlation analysis, showed a striking and systematic variation in linear system impulse response characteristics from afferents which innervated different regions of the receptor. Afferents from centrally located nerve bundles innervating the crest region of the crista exhibited an initial maximum response amplitude followed by a rapid decay. In contrast, afferents from extreme rostral and caudal nerve bundles innervating the crista slopes exhibited an initial rise up to a low-amplitude maximum followed by a slower decay.These results imply that the afferents innervating a single canal do not merely carry redundant information concerning current head acceleration, but could be considered an ensemble of specific classes of filters that are tuned individually to specific classes of head movements. On the basis of these considerations, a new hypothesis of matched filter detection was proposed as relevant to information processing and dynamic control in central vestibular pathways.
Interaction of electrosensory and electromotor signals in lateral line lobe of a mormyrid fish
Authors: Zipser B. , Bennett M. V.
Published: December 2017

A signal associated with the neural command to discharge the electric organ is recorded in cells of the lateral line lobe. Responses of cells activated by medium receptor inputs are facilitated or less frequently inhibited during this command-associated signal. Only responses to disynaptic inputs are affected, the monosynaptic response is not altered. The periods of facilitation and inhibition occur at times at which electroreceptor activity evoked by organ discharge reaches the lateral line lobe. Presumably the command-associated signal is important in electrolocation. Cells responding to large receptor inputs are inhibited by the command-associated signal. Activity evoked by large receptors is transmitted in a mesencephalic fiber tract. The tract response is also inhibited by the command-associated signal. Since each organ discharge would excite all the large receptors at short latency, there would be little information contained in their responses. Inhibiting discharge-evoked activity may allow the system to return to maximum sensitivity most rapidly.
Physiology of peripheral neurons innervating otolith organs of the squirrel monkey. II. Directional selectivity and force-response relations
Authors: Fernandez C. , Goldberg J. M.
Published: December 2017

1. The directional selectivity of peripheral otolith neurons was studied in the barbiturate-anesthetized squirrel monkey (Saimiri sciureus). Each unit's most sensitive axis was characterized by a functional polarization vector. The direction of a centrifugal force was varied with respect to the vector and to the macular plane. The neurons respond in an excitatory manner to shearing forces orthogonally disposed to the vector. The sensitivity to orthogonal shears was usually 10-15% of the sensitivity to parallel shearing forces. There was no significant response to orthogonal compressions, nor did compressions modify the response to shearing forces. 2. Force-response functions were obtained in the stimulus range of +/- 4.92 g. Forces were directed parallel to each unit's polarization vector. The functions are sigmoid shaped and possess both inhibitory and excitatory plateaus. The presumed physiological range of +/-1 g is represented in the lower (concave upward) portion of the function and has a dynamic range, expressed in terms of response magnitude, amounting to 20-40% of the potential dynamic range of the neuron. 3. There was considerable variation among units in their +/- 4.92 g force-response curves. The salient features of the functions are described by three factors, tentatively identified as a transduction gain, a receptor bias, and a mechanical gain. Both the resting discharge (do) and the +/-1 g sensitivity (so) vary in the same direction with changes in the factors related to transduction gain and receptor bias. It is shown that this covariation provides a quantitatively precise explanation for the positive relation between do and so.
Sensory neurons in leech central nervous system: changes in potassium conductance an excitation threshold
Authors: Schlue W. R.
Published: December 2017

1. The sensory neurons in the leech central nervous system differ in their accommodation to linearly rising currents. Advantage was taken of these differences to study the ionic mechanism of accommodation in single pairs of N (noxious), P (pressure), and T (touch) cells. 2. Nonlinearities in membrane-potential changes and current-voltage relationships with square-wave and ramp currents are more pronounced in P and T cells than in N cells. The accommodation coefficients increase in conditions that reflect this delayed rectification. When rectification is absent, the accommodation coefficients depart from unity only slightly or not at all. 3. Accommodation coefficients remain unchanged when half of the chloride in the bathing medium is replaced by sulfate. Accommodation coefficients become greater when the extracellular potassium concentration is reduced from 4 to 0 mM, and decrease when the concentration is raised to 8 mM. The membrane potential changes by only a few millivolts. 4. As extracellular potassium concentration is increased, the action potential is lengthened and the maximal rate of fall of the action potential is reduced. With concentrations greater than 4 mM these relationships are linear, but depart from linearity at lower concentrations. The amplitude of the undershoot decreases linearly as the extracellular potassium concentration increases from 4 to 16 mM, and increases non-linearly at concentrations below 4 mM. 5. The rapid accommodation of leech neurons is based primarily on an increased potassium conductance. The possibility is considered that concentration changes like those produced experimentally may occur naturally, affecting integrative processes in the central nervous system.
Properties of relay cells in cat's lateral geniculate nucleus: a comparison of W-cells with X- and Y-cells
Authors: Wilson P. D. , Rowe M. H. , Stone J.
Published: December 2017

1. Observations are presented on the physiological properties of W-, X-, and Y-type relay cells in the cat's lateral geniculate nucleus (LGN). Emphasis is placed on the most recently recognized type, W-cells; data are presented on X- and Y-cells by way of comparison. 2. Seventy-seven W-cells were recognized on 70 microelectrode penetrations through the LGN. They resembled W-type retinal ganglion cells in their responses to visual stimuli. Tonic (on-center and off-center) W-cells, phasic (on-, off- and on-off center) W-cells, suppressed-by-contrast, and color-coded cells were recognized. 3. W-type relay cells also resembled retinal W-cells in their maintained activity and receptive field-center diameters. 4. W-type relay cells comprised 11.5% X-cells 48.4%, and Y-cells 22.3% of all LGN cells encountered on a reference sample of 62 electrode tracks. W-cells were found in laminae C, C1, and C2, comprising 36.5% of the sample in these laminae, but were not encountered in laminae A or A1. X- and Y-cells were found in laminae A, A1, and C. Within lamina C there was a tendency for X- and Y-cells to be located dorsal to W-cells. There was thus a substantial dorsoventral segregation of W-cells from X- and Y-cells. W-cells being found in the ventral parvocellular component of the dorsal LGN. 5. Cells considered to be W-type relay cells were shown to respond to electrical stimulation of the optic nerve and chiasm at latencies which were longer than those of X- and Y-cells, and were consistent with their receiving monosynaptic input from retinal W-cells. Geniculate W-cells of all subtypes were activated antidromically from the visual cortex. Their antidromic latencies were, on the average, longer than for Y- or X-cells, indicating that W-type relay cells had slower axons as well as slower retinal afferents, than X- or Y-cells. 6. The visual cortex thus appears to receive input from all three major types of retinal ganlion cells (W-, X-, and Y-cells) relayed separately, in parallel, by different groups of relay cells.
Quantitative studies of single-cell properties in monkey striate cortex. II. Orientation specificity and ocular dominance
Authors: Schiller P. H. , Finlay B. L. , Volman S. F.
Published: December 2017

1. Quantitative analyses of orientation specificity and ocular dominance were carried out in striate cortex of the rhesus monkey. 2. Sharpness of orientation selectivity was greater for simple (S type) than for complex (CX type) cells. CX-type cells became more broadly tuned in the deeper cortical layers: S-type cells were equally well tuned throughout the cortex. 3. Sharpness of orientation selectivity for S-type cells was similar at all retinal eccentricities studied (0 degrees - 20 degrees from the fovea):in CX-type cells orientation selectivity decreased slightly with increasing eccentricity. 4. The orientation tuning of binocular cells was similar when mapped separately through each eye. 5. Orientation selectivity and direction selectivity are independent of each other, suggesting that separate neural mechanisms give rise to them. 6. More CX-type cells can be binocularly activated than S-type cells (88% versus 49%). The ocular dominance of S-type cells is similar in all cortical layers: for CX-type cells there is an increase in the number of cells in ocular-dominance category 4 in layers 5 and 6.