bluuebunny/crossref_metadata_2025 huggingface dataset:
Human tactile detection thresholds: modification by inputs from specific tactile receptor classes
Authors: Ferrington D. G. , Nail B. S. , Rowe Mark
Published: December 2014

1. Human detection thresholds for a vibratory stimulus applied to the volar surface of the index finger were examined under conditions where afferents from specific tactile receptor classes were simultaneously activated from the thenar eminence. The experiments were designed to test whether stimuli which have been shown previously to induce afferent inhibition of ‘tactile’ neurones in the cuneate nucleus of the cat could modify human subjective performance in a tactile detection task. Conditioning stimuli to the thenar eminence were usually of three forms; steady indentation to engage slowly adapting tactile receptors; 300 Hz vibration to engage Pacinian corpuscles; and 30 Hz vibration to engage the intradermal, rapidly adapting tactile receptors which are thought to be Meissner's corpuscles.

2. In ten subjects the mean detection threshold for a 30 Hz test stimulus in the absence of conditioning stimulation was 8·6 ± 1·0 μm (
S.E.). Detection thresholds were increased substantially in the presence of a 300 Hz, 100 μm conditioning stimulus (mean increase 11·1 ± 2·0 μm), whereas minor or insignificant effects were seen with conditioning stimuli consisting of (a) 30 Hz, 100 μm (mean increase 1·4 ± 0·8 μm), (b) steady indentation, 1·5 mm in amplitude (mean increase 1·3 ± 0·7 μm) or (c) 300 Hz, 100 μm to the contralateral thenar eminence (mean increase 0·4 ± 0·5 μm).

3. The 300 Hz conditioning stimulus to the ipsilateral thenar eminence caused a marked increase in detection thresholds at all test stimulus frequencies over the range 10‐450 Hz. The effects of the conditioning stimulation therefore operated on inputs from Pacinian corpuscles, which are responsible for vibration detection at 80‐450 Hz, and on inputs from the intradermal, rapidly adapting receptors which are responsible for vibration detection at 10‐80 Hz.

4. The band width of conditioning vibratory frequencies which was effective at amplitudes of 100 μm in bringing about increases in detection threshold extended from 50‐80 Hz to 300 Hz, the maximum tested.

5. Whereas amplitudes of 1‐2 μm produced clear increases in detection thresholds with conditioning stimuli of 300 Hz, amplitudes of > 200 μm were needed at 30 Hz.

6. The observed elevations in detection threshold are consistent with an afferent‐induced inhibitory action exerted at synaptic relays of the sensory pathway by tactile inputs arising exclusively or predominantly from Pacinian corpuscles.
A radiological study of gastric (abomasal) emptying in calves before and after vagotomy.
Authors: Bell F R , Holbrooke S E , Titchen D A
Published: December 2014

1. Gastric emptying has been studied in the conscious, standing calf by lateral radiography and fluoroscopy of radiopaque meals instilled into the abomasum before and after vagotomy. 2. Bilateral cervical vagotomy proved to be the only certain way of achieving total vagal transection. By instillation of milk into the abomasum through a cannula calves were maintained in normal, healthy condition for up to 36 days after vagotomy. 3. Motility of the antrum was not impaired by vagotomy so that some movement of gastric chyme to the duodenum occurred within minutes of instillation into the abomasum. Complete transference of the test meal was, however, delayed after vagotomy. 4. The greatest effect of vagotomy appeared to be on the abomasal body so that inadequate amounts of chyme were transferred to the antrum for pumping to the duodenum. 5. Delay in passage of contrast material through the intestine was related to delay in gastric emptying although vagotomy may have affected the intestine directly. 6. Following vagotomy the abomasum showed a resumption of normal motility and emptying after 7‐29 days. This effect of vagotomy is similar to that seen in the simple stomach and is probably due to the establishment of intrinsic gastric control.
The entrainment of breathing frequency by exercise rhythm.
Authors: Bechbache R R , Duffin J
Published: December 2014

1. The incidence of entrainment of breathing frequency by the rhythm of exercise was detected by a cross‐correlation of the two frequencies. 2. During moderate, steady‐state exercise on a bicycle ergometer at 50 rev/min, eight of fifteen volunteers (53%) showed entrainment when pedalling speed was kept constant with a metronome, and three of fifteen volunteers (20%) showed entrainment when pedalling speed was kept constant with a speedometer. 3. At 70 rev/min, in a second group of fifteen volunteers, the results were nine of fifteen (60%) and five of fifteen (33%) respectively. 4. During moderate, steady state exercise on a treadmill, in a third group of fifteen volunteers, eight of 15 volunteers (53%) showed entrainment while walking, and twelve of fifteen volunteers (80%) showed entrainment while running. 5. It is concluded that the rhythm of exercise is likely to affect the rhythm of breathing and that this controlling factor must be considered during studies of breathing pattern in exercise.
Reflexes in cat ankle muscles after landing from falls.
Authors: Prochazka A , Schofield P , Westerman R A , Ziccone S P
Published: December 2014

1. Electrical activity and length of ankle muscles were recorded by telemetry during free fall and landing in cats. 2. After foot contact, there was a delay in onset of stretch of ankle extensors of between 8 and 11 ms. High‐speed cinematography showed the delay to be associated with rapid initial dorsiflexion of the toes. 3. Electromyograms (e.m.g.) from lateral gastrocnemius increased in amplitude prior to landing. An early depression of lateral gastrocnemius e.m.g. commenced at 8 ms after foot contact, and was followed by a large peak of activity commencing some 8 ms after the first increase in lateral gastrocnemius length. 4. Local anaesthesia of the plantar cushion did not alter this pattern of response. 5. The early inhibition of lateral gastrocnemius was attributed to the action on lateral gastrocnemius motoneurones of non‐cutaneous afferents responding to the initial toe dorsiflexion. Additional autogenetic inhibition may also have contributed. 6. The subsequent peak of e.m.g. was at a latenty consistent with a rapid stretch reflex, and occurred soon enough for the resulting active tension to contribute significantly to the extensor force during body deceleration.
Direct excitatory interactions between spinal motoneurones of the cat.
Authors: Gogan P , Gueritaud J P , Horcholle-Bossavit G , Tyc-Dumont S
Published: December 2014

1. Ninety‐seven spinal motoneurones were identified by their antidromic invasion following stimulation of the muscle nerve and submitted to a series of four tests to reveal a possible direct excitation between motoneurones. 2. Threshold differentiation, refractoriness, hyperpolarization and collision revealed antidromically induced depolarizations in fourteen of the ninety‐seven tested motoneurones. 3. The parameters of the antidromically induced depolarizations indicate a short latency, a low amplitude and independence with regard to the membrane polarization. 4. It is concluded that the antidromically induced depolarizations reached the impaled motoneurone via a route other than its own axon. 5. The mechanism may involve either electrotonic interactions between neighbouring motoneurones or excitatory recurrent collaterals between synergist motoneurones.
Fatigue of long duration in human skeletal muscle after exercise.
Authors: Edwards R H , Hill D K , Jones D A , Merton P A
Published: December 2014

1. After severe muscular contraction in man recovery of force is largely complete in a few minutes, but is not wholly so for many hours. The long‐lasting element of fatigue is found to occur primarily for low frequencies of stimulation (e.g. 20/sec), and is much less pronounced, or absent, at high frequencies (80/sec). The twitch force is an unreliable measure of the state of fatigue. 2. The long‐lasting element of fatigue is not due to depletion of high‐energy phosphate nor is it due to failure of electrical activity as recorded from surface electrodes. It is probably the result of an impairment of the process of excitation‐contraction coupling. Its practical importance for man could be significant as an explanation of the subjective feelings of weakness following exercise.
The response to distension of the pulmonary vein‐left atrial junctions in anaesthetized dogs after section of the rostral medulla.
Authors: Burkhart S M , Ledsome J R
Published: December 2014

1. Distension of the pulmonary vein‐left atrial junctions caused an increase in heart rate and a transient decrease in mean arterial pressure. 2. Section of the brain stem at the level of the inferior cerebellar peduncle (rostral medulla) caused a decrease in mean arterial pressure. 3. Section of the rostral medulla had no effect on either the magnitude or the time course of the reflex response to pulmonary vein distension. 4. Administration of propranolol after section in the rostral medulla reduced the reflex increase in heart rate in response to pulmonary vein distension by an amount similar to that previously described in intact and decerebrate animals. 5. Bilateral cervial vagotomy prevented the reflex response to pulmonary vein distension.
Effects of medullary lesions on arterial baroreceptor reflexes and responses to distension of pulmonary vein‐left atrial junctions in anaesthetized dog.
Authors: Burkhart S M , Funnell L , Ledsome J R
Published: December 2014

1. In anaesthetized dogs lesions of 4 mm diameter centred on the obex were placed in the medulla dorsal to the hypoglossal nucleus. 2. Placing of the lesions almost totally abolished the reflex responses to distension of the pulmonary vein‐left atrial junctions and to low intensity stimulation of the aortic nerv. The reflex response to high intensity stimulation of the aortic nerve was reduced and the reflex response to carotid artery occlusion remained unaltered. 3. Mid‐collicular decerebration did not affect the results. 4. The results are consistent with a hypothesis that afferents from the carotid sinus baroreceptors synapse in the nucleus of the tractus solitarius rostral to the obex, whereas afferent fibres from the aortic baroreceptors and atrial receptors synapse in the intermediate portion of the nucleus of the tractus solitarius close to the obex.
Selective Activation of peripheral nerve fibre groups of different diameter by triangular shaped stimulus pulses.
Authors: Accornero N , Bini G , Lenzi G L , Manfredi M
Published: December 2014

1. The differential block of cutaneous nerve fibres has been achieved with a simple method of electrical stimulation, employing a single pair of active electrodes. 2. The method allows the selective activation of 95% of small myelinated (delta) axons, without activation of the larger (beta) ones; and activation of unmyelinated (C) fibres, without A fibre activation. Asynchronous firing of myelinated axons was absent in the majority of the experiments. 3. The method employs triangularly shaped electrical pulses, with a steep rise front and a slow exponential decay. The outward flow of current at the cathode fires conducted impulses in both larger and smaller axons, and the inward flow inactivates differentially the conduction in the smaller ones. 4. The differential effect of anodal currents rests upon the greater internal conductance and greater conduction velocity of larger fibres. 5. The method has the advantage over the conventional polarization block of simpler surgical preparation, longer nerve survival and minimal latency distortion. However, it cannot be applied in experiments requiring physiological stimulation of peripheral receptors.
The effect of an increase in aortic pressure upon the inotropic state of eat and dog left ventricles
Authors: Elzinga G. , Noble M. I. M. , Stubbs J.
Published: December 2014

1. The effect of increased aortic pressure on the inotropic state of the left ventricle was studied in isolated cat hearts, perfused with bovine red cells in Tyrode solution, ejecting into a hydraulic model with the same input impedance as that of the cat aorta.

2. Inotropic state was assessed at a controlled left ventricular end‐diastolic pressure by interpolating single isovolumic beats by means of an occluder in the aortic cannula.

3. When such isovolumic beats during periods of raised aortic pressure were compared with those during control periods, the difference in peak isovolumic pressure ranged from ‐0·3 to +0·5 kPa indicating differences in inotropic state which were small and inconsistent in direction.

4. The maximum rate of rise of left ventricular pressure (dP/dtmax.) of ejecting beats was little affected by a rise of aortic pressure and the direction of changes was inconsistent.

5. The effect of increased aortic pressure was studied in intact dogs after cardiac denervation; left ventricular end‐diastolic pressure was uncontrolled and therefore rose to a higher steady level.

6. No consistent change of dP/dtmax. was found during the period of increased aortic pressure.

7. All flow and pressure variables remained steady during the period of increased aortic pressure after the higher level of left ventricular end‐diastolic pressure had been established.

8. These results demonstrate that neither the positive inotropic effect nor the negative inotropic effect of increased load dominates in these preparations. This may be the result of a balance between the two effects, or they may be of unimportant magnitude under physiological conditions.
Studies on the mechanism of renin release from isolated superfused rat glomeruli: effects of calcium, calcium ionophore and lanthanum
Authors: Baumbach L. , Leyssac P. P.
Published: December 2014

1. The effects of external medium calcium concentration, the ionophore A23187 and lanthanum on the rate of renin release in vitro were studied with particular emphasis on results obtained from isolated superfused glomeruli of rat kidneys.

2. The response to reduction in superfusate calcium concentration from 2 m
M was a graded and reversible increase in the rate of renin release. An increase in release was detectable at 0.2 m
M calcium; a threefold increase was found 36 min after a change from 2 m
M calcium to calcium‐free superfusate. A similar relative increase in release resulted from reductions from 0.1 m
M to zero calcium, but the absolute amounts of renin released were greater in this latter series. Renin release from kidney cortical slices similarly increased in response to calcium‐free incubation medium.

3. The effects of A23187 on renin release were modest. Changing from 2 m
M calcium during control periods to calcium‐free Ringer with A23187 added caused an attenuated and more delayed increase in release than the change to calcium‐free Ringer without ionophore. This difference in response was abolished when glomeruli were superfused with 0.1 m
M calcium during the preceding 1 hr control period. There was no significant difference in renin release from glomeruli exposed to calcium‐free EGTA‐Ringer with and without A23187 in the 2 m
M calcium series; in the 0.1 m
M calcium series the increase in release following a shift to calcium‐free EGTA‐containing superfusate with A23187 added was significantly greater than in the absence of the ionophore.

4. Addition of lanthanum (1 or 0.05 m
M) to calcium‐containing as well as calcium‐free superfusate resulted in a significant depression of renin release. Subsequent removal of the lanthanum did not restore the rate of release unless EGTA was added; in the latter case a massive increase in renin release occurred resulting in a marked depletion of the remaining renin content of the glomeruli.

5. It is concluded that calcium influences renin release by a direct action on the juxtaglomerular cells. The data support the previous suggestion that basal renin release is a function of active, calcium‐dependent cell volume regulation — swelling causing an increase in the release; and further suggest that membrane‐bound calcium has a direct effect on the cell membrane permeability to renin.

6. The results exclude that calcium‐stimulated exocytosis is responsible for basal renin release from the juxtaglomerular cells adhering to isolated glomeruli.
Effects of vascular perfusion on the accumulation, distribution and transfer of 3‐O‐methyl‐D‐glucose within and across the small intestine
Authors: Boyd C. A. R. , Parsons D. S.
Published: December 2014

1. Factors affecting the transfer of the non‐metabolized, ‘actively transported’ sugar, 3‐O‐methyl‐
D‐glucose (3MG) across the small intestinal epithelium have been examined in vascularly perfused anuran intestine. Transfer has been studied during absorption in the steady state, and also during the period of transition from one steady state to another.

2. During the steady state, the rate of absorption of 3MG from the intestinal lumen is equal to the rate of appearance in the portal venous effluent; this rate of transfer is to a small, but significant, extent directly related to the rate of arterial perfusion. With phlorizin in the intestinal lumen, transfer across the epithelium is reduced to very low rates which are independent of the rate of vascular perfusion.

3. The apparent size of the tissue pool(s) of 3MG that have to be loaded to achieve the steady state rate of transfer are less than those that unload into the vascular bed after 3MG is removed from the intestinal lumen. This ‘up—down asymmetry’ is abolished when phlorizin is present in the intestinal lumen during the unloading phase.

4. When 3MG is abruptly removed from the intestinal lumen after the tissue has been previously loaded with the sugar, the rate of washout into the vascular bed can be described by the sum of two exponential terms. The two terms differ in that the rate constant of the earlier ‘fast’ term is sensitive to the rate of vascular perfusion, while the later, ‘slow’, rate constant is insensitive to flow rate. The total quantity of 3MG that can be unloaded from the tissue into the portal venous effluent is decreased when phlorizin is present in the intestinal lumen during the unloading phase.

5. Absorption from the lumen of the anuran intestine continues while the mesenteric circulation is interrupted. An estimate of the concentration of 3MG during the period of vascular stoppage can be made from the quantity recovered in the portal venous effluent when vascular perfusion is reinstituted (‘vascular stop‐flow’). The extent of the accumulation depends upon the duration of the vascular stoppage and the presence of Na ions in the intestinal lumen is essential for accumulation to occur.

6. The findings are discussed in relation to the transfer of 3MG between various possible compartments in the tissue during absorption. Evidence is presented that a re‐uptake of previously absorbed 3MG may occur across the brush border membrane. Such a recycling of 3MG across the epithelium implies that the apparent unidirectional fluxes measured across the epithelium between the bulk phase of the lumen and the blood may underestimate the size of fluxes across the epithelium at the cellular level.
The effect of membrane cholesterol on the sodium pump in red blood cells.
Authors: Claret M , Garay R , Giraud F
Published: December 2014

1. Human red blood cells (R.B.C.) were incubated with phosphatidylcholine vesicles to obtain partial depletion of their membrane cholesterol. The kinetic parameters of the Na pump (affinities and maximal fluxes) were determined in these cells and compared with controls. 2. In the presence of internal K, progressive cholesterol depletion induces gradually (i) an increase of the maximal flux (ii) a reduction of the apparent affinity for internal Na. 3. In the absence of internal K, cholesterol depletion has no apparent effect, indicating that the observed changes were mediated by the internal K. Cholesterol depletion acts by increasing these two K effects: (i) activation of the maximal fluxes, and (ii) reduction of the internal Na affinity. 4. The cholesterol effect (on the K‐pump interaction) is specific; it occurs without any change (i) in the affinities for internal Na and inorganic phosphate and for external Na and K, and (ii) in the number of pumping sites. 5. Under physiological conditions, cholesterol reduces the cation translocation rate and increases the selectivity of the pump for internal Na.
The dynamic behaviour of photoreceptor cells in the fly in response to random (white noise) stimulation at a range of temperatures.
Authors: French A S , Järvilehto M
Published: December 2014

1. Photoreceptor cells in Calliphora stygia were stimulated with randomly fluctuating green light while the resulting fluctuations in membrane potential were recorded with intracellular micro‐electrodes. 2. Fourier analysis was used to obtain the frequency response functions between the light intensity fluctuations and the membrane potential fluctuations at a range of different temperatures. 3. The results show that for small light fluctuations the transducer function can be modelled by a cascade of five identical linear exponential filters whose time constants decrease as the temperature of the cell is increased. 4. The time constants of the linear filters and their rate of change with temperature are similar to the electrical behaviour of cell membranes. However, a series of chemical reactions with similar activation energies could also explain the observed behaviour. 5. Evidence is presented that the total light response is a linear summation of discrete waves of depolarization (bumps), which become longer in duration but of constant area as the temperature is reduced.
The effects of artificial lung inflation on reflexly induced bradycardia associated with apnoea in the dog
Authors: Angell‐James Jennifer E. , Daly M. De Burgh
Published: December 2014

1. The cardiac effects of artificial inflation of the lungs were studied during reflexly induced apnoea and bradycardia in anaesthetized dogs.

2. Reflex apnoea and bradycardia were induced (a) by stimulation of the larynx with water or by electrical stimulation of afferent fibres in the superior laryngeal nerve, or (b) by combined stimulation of the superior laryngeal nerve and carotid body chemoreceptors.

3. During combined stimulation of the laryngeal and carotid body inputs, the activation of respiration normally evoked by chemoreceptor stimulation was inhibited whereas the chemoreceptor cardio‐inhibitory reflex was facilitated leading to periods of temporary cardiac arrest.

4. In spontaneously breathing animals and in those artificially ventilated, lung inflation invariably caused tachycardia.

5. Rhythmic artificial inflation of the lungs during the apnoeic period produced by the laryngeal input or by a combination of the laryngeal and chemoreceptor inputs wholly or partly reversed the bradycardia. This occurred using lung inflation volumes within the range of the normal tidal volume and inflation pressures of less than 12 mmHg; the response was independent of the composition of the gas used for inflating the lungs, and occurred at constant Pa, O2 and Pa, CO2. Lung inflation carried out during a reflexly induced arrest of the heart immediately restarted the heart and was accompanied by an exaggerated sinus arrhythmia.

6. Evidence is presented that the observed effects of artificial lung inflation are reflex in origin with the vagus nerves as the main afferent and efferent pathways.

7. Electrical stimulation of the central end of the cut pulmonary branches of the thoracic vagosympathetic nerves also caused tachycardia and had the same effects as lung inflation in modifying the reflexly induced bradycardia.

8. Some clinical implications of these results are discussed.
The action of acetylcholine on background conductance in frog atrial trabeculae.
Authors: Garnier D , Nargeot J , Ojeda C , Rougier O
Published: December 2014

The action of acetylcholine (ACh) on membrane potential and currents in frog atrial muscle has been studied with a double sucrose gap technique. The results show the following. 1. ACh induces the development of an extra current, outward at the resting potential, which is dependent on the ACh concentration. 2. The preparation does not show any sign of desensitization. 3. The reversal potential of the current induced by ACh is between 0 and 20 mV more negative than the resting potential and behaves as a K electrode. 4. The mechanism of ACh‐induced K conductance presents inward going rectification properties. 5. The delayed outward current is not affected by ACh. However the evolution of its tail current seems to indicate a process of K accumulation related to the ACh‐induced current.
Osmotic behaviour of human red blood cells: an interpretation in terms of negative intracellular fluid pressure
Authors: Hladky S. B. , Rink T. J.
Published: December 2014

1. The observation that human red blood cells do not shrink in hypertonic media as much as expected for ideal osmometers has previously been explained in terms of either a marked increase in the osmotic coefficient of the cell contents or an increase in the chloride content of the cells.

2. Changes in suspension pH and haematocrit have been observed when the concentration of the unbuffered NaCl medium was doubled. The small increases in external pH, and the size of the volume decreases, are inconsistent with variations in the Cl content as a significant factor in the non‐ideal osmotic responses.

3. Membrane potentials of red cells in buffered media were followed using the fluorescent dye, diS‐C3‐(5). On shrinking at pH 7·4, the cells hyperpolarized ca. 5 mV as predicted if changes in the osmotic coefficient rather than in Cl content explained the osmotic behaviour.

4. Regarding haemoglobin in concentrated solution as a solute with high osmotic coefficient is formally correct but is little help in understanding the properties of the solution. We have found it useful to consider separately haemoglobin and the rest of the contents of the cell. The haemoglobin then supports part of the total hydrostatic pressure on the cell leaving the crystalloid solution to experience a reduced fluid pressure. In greatly shrunken cells the contents act like a gel with the matrix of haemoglobin under compression and the fluid which fills the spaces within the matrix under tension.
Carbon dioxide and venous return and their interaction as stimuli to ventilation in the cat
Authors: Ponte J. , Purves M. J.
Published: December 2014

1. Respiratory responses were measured in forty‐seven cats, made decerebrate or anaesthetized with pentobarbitone or chloralose‐urethane, to changes in the level of CO2 infused into the inferior vena cava via an external oxygenator circuit or to changes in the volume of venous return or to the inhalation of CO2.

2. No consistent difference was found between the respiratory response to the increase in the level of CO2 infused or CO2 inhaled provided that the volume of venous return during both sets of tests was held constant at normal levels.

3. If the volume of venous return was increased and the level of CO2 infused maintained at levels such that V̇CO2 did not increase, ventilation increased with a fall in Pa, CO2, a response lying approximately on the isometabolic curve.

4. If the volume of venous return and the level of CO2 infusion were raised together, a spectrum of intermediate respiratory responses was obtained which reproduced all those seen in earlier papers, in muscular exercise or other hypermetabolic states.

5. None of the steady‐state respiratory responses was significantly affected by bilateral vagotomy or section of the sinus nerves, though sinus nerve section slowed the responses to infused or inhaled CO2 and they were then less precisely controlled.

6. Additional experiments indicated that where CO2 was infused or inhaled, the effective stimulus to respiration was an increase in mean Pa, CO2 in proportion to the CO2 added and that the respiratory response to CO2 was enhanced by reduced blood volume. How the changes in venous return were sensed and affected respiration, remains unclear.

7. These results may explain why previous workers have obtained exaggerated respiratory responses to the infusion of CO2 and why respiration increases rapidly at the start of exercise and is then maintained at high levels without discernible change in the chemical stimulus in arterial blood.
Neurones in cat parastriate cortex sensitive to the direction of motion in three‐dimensional space
Authors: Cynader Max , Regan D.
Published: December 2014

1. On psychophysical grounds, Beverley & Regan suggested that in man different neural mechanisms mediate the binocular perception of movement in depth and the binocular perception of positional (static) depth. They proposed that the human visual pathway contains several neural mechanisms, each sensitive to a different direction of motion in space. These mechanisms compute the direction of motion from the relative speeds and directions of movement of the left and right retinal images.

2. We have recorded from 101 units in area 18 of cat visual cortex, searching for neurones tuned to the direction of motion in three dimensions, with properties that could account for the proposed directionally tuned binocular motion detectors in man. The cat's left eye viewed one bar, while its right eye simultaneously viewed a second bar. Single units were stimulated by independently oscillating the bars from side to side. The apparent direction of movement in three dimensions was altered by varying the relative speeds of the bars and their relative directions of motion. The mean (positional) disparity of the bars could also be varied.

3. For one class of neurone (twenty cells), binocular stimulation inhibited firing for trajectories parallel to the frontoparallel plane over a large volume of space. Strong firing was produced by oppositely directed bar movements. Some of these neurones were especially narrowly tuned to the direction of movement in depth, responding only to a range of 2‐3°, i.e. to moving bodies that would hit or only narrowly miss the cat. These cells emphasized the direction of movement at the expense of positional information.

3. These units occurred in clusters. On the perpendicular penetrations in which they were found, they comprised a substantial majority of all cells encountered.

5. For a second class of neurone (nine cells), binocular facilitation produced selective responses to objects moving along trajectories that missed the head.

6. The two classes of neurone provide a basis for four proposed directionally tuned binocular motion detectors.

7. A third class of neurone (seventeen cells) was selectively sensitive to movements parallel to the frontoparallel plane. There was strong binocular facilitation when the bars moved at the same speeds in the same directions: oppositely directed movements might be more than 100 times less effective. These neurones may signal positional disparity.

8. These three classes of neurone cut across established categories. Only when both eyes were stimulated simultaneously with targets moving in different speeds and directions was it possible to demonstrate the binocular interactions described here.
Chloride/bicarbonate exchange in human erythrocytes.
Authors: Lambert A , Lowe A G
Published: December 2014

1. The exchange of chloride and bicarbonate across the human erythrocyte membrane has been followed by measuring the changes in extracellular pH which occur when chloride‐rich erythrocytes are added to chloride‐free media containing varying concentrations of bicarbonate and carbonic anhydrase. 2. The dependence of the rate of chloride/bicarbonate exchange on the extracellular concentration of bicarbonate was consistent with the existence of a saturable membrane anion transporter exhibiting Michaelis‐‐Menten kinetics. In a medium containing sodium gluconate buffered to pH 7.0 with imidazole‐‐malate the Km for bicarbonate activation of transport was 0.39 (+/‐ 0.03) mM and the Vmax was 2033 (+/‐ 80 m‐mole anions exchanged/3 X 10(13) cells. min, at 10 degrees C. 3. Chloride/bicarbonate exchange was temperature‐dependent with an Arrhenius activation energy of 19.4 kcal/mole in the temperature range 2‐‐10 degrees C. 4. Exchange of intracellular chloride for extracellular bicarbonate was inhibited by the presence of extracellular halides. Inhibition by chloride, bromide and fluoride was competitive and the affinity of the transport system decreased in the order HCO‐3 greater than Cl‐ greater than Br‐ greater than F‐. The kinetics of inhibition by iodide were complex, but inhibitory effects of low concentrations of iodide were less than those of chloride and bromide.
The effect of external pH on osmotic permeability, ion and fluid transport across isolated frog skin.
Authors: Fischbarg J , Whittembury G
Published: December 2014

1. The rate of volume flow across frog skin induced by an osmotic gradient was measured when normal (7.4) and low pH (2.28) solutions bathed the outside. The osmotic permeabilities (Pos) were 2.4 +/‐ 0.4 and 4.8 +/‐ 1.0 micrometer/sec, respectively. The change in Pos induced by low pH was reversible. 2. Volume flow in the absence of an osmotic gradient was measured at normal and low pH. Values were 0.69 +/‐ 0.13 and 1.1 +/‐ 0.2 microliter/hr. cm2, respectively; the paired differences were significant (P less than 0.0025). This change in rate was partially reversible upon return to normal pH. 3. The potential difference (V) and short‐circuit current (Is) across skins were measured under several conditions and the following equivalent parameters in a simplified electrical model were computed: total resistance (Rt); shunt resistance (Rs); electromotive force of the pump (ENa); and salt transport at open circuit (JNaCl). Representative figures were (a), at pH 7.4: Is = 14 +/‐ 1.6 microampere/cm2; Rt = 3.3 +/‐ 0.4 komega.cm2; Rs = 7.2 +/‐ 1.0 komega.cm2; ENA = 103 +/‐ 38 mV; JNaCl = 7.2 +/‐ 1.2 microampere/cm2; (b) at pH 2.28: Is = 8.3 +/‐ 2.1 microampere/cm2; Rt = 0.46 +/‐ 0.12 komega. cm2; Rs = 0.65 +/‐ 0.06 komega.cm2; ENa = 59 +/‐ 25 mV; JNaCl = 9.4 +/‐ 3.3 microampere/cm2. 4. From the electrical parameters measured concomitantly with the rate of fluid transport in given experiments, the expected salt concentration of the transported fluid was 0.30 +/‐ 0.08 and 0.38 +/‐ 0.08 mole/l. at normal and low pH, respectively, or some 3‐4 times hyperosmotic with respect to the medium. 5. Treatment with low pH on the outside has been found to open the intercellular junctions in previous studies. The present results suggest that, if such an effect occurs, it is localized only to a small fraction of the cell perimeter. Making certain assumptions that fraction could be as low as 0.003. 6. Low pH on the outside reversibly changes the electrical parameters of a 'tight' epithelium like the frog skin into values more typical of 'intermediate' epithelia; both the total and shunt resistances decrease to about 0.1 of their normal values. These changes do not apparently affect the osmolarity of the transported fluid.
New properties of rabbit retinal ganglion cells.
Authors: Caldwell J H , Daw N W
Published: December 2014

1. Receptive fields of centre surround cells in the rabbit retina were investigated. There is a clear distinction between cells with sluggish responses, low spontaneous activity and slow conduction velocity (centre surround sluggish cells) and cells with brisk responses, higher spontaneous activity and faster conduction velocity (X and Y cells). The sluggish cells can be divided into sustained and transient types. X and Y cells can be distinguished from each other by their responses to a moving linear grating, a large rapidly moving object and whether or not there is a response to the alternation of certain stimuli. Some times the response to a rotating radial grating, the rate of spontaneous activity, and whether or not the response to spots and annuli was sustained or transient could also be used to distinguish these two types. The antidromic latency from electrical stimulation of the optic chiasm and the periphery effect did not distinguish X from Y. 2. Eleven colour coded units were investigated. They all gave on responses to blue light in the centre of their receptive field and off responses to green light in the periphery of their receptive field. The blue pigment had a spectral sensitivity peaking at about 465 nm. The other pigment peaked near 500 nm, like the rods but gave a response at high mesopic and probably photopic levels. In some cases there was evidence for excitatory input from the green receptors to the centre of the receptive field. All the colour coded cells had rapidly conducting axons and were on centre X cells by all criteria. 3. Eighty‐five cells various types other than colour coded were tested for their thresholds at 420 nm and 590 nm. In all cases the results were explained by a pigment peaking close to 500 nm, even at high mesopic and low photopic levels, which suggests the existence of cones with a cyan pigment in them. 4. Conduction latency from stimulation at the optic chiasm was measured for cells with centre surround receptive fields and cells with more complex receptive fields. Both 'on‐off' and 'on' directionally sensitive cells have short conduction latencies, overlapping X and Y cells. Orientation selective cells and local edge detectors have long conduction latencies, overlapping centre surround sluggish cells. The sample of uniformity detectors was too small to characterize...
Accumulation of amines by rabbit erythrocytes in vitro.
Authors: Blakeley A G , Nicol C J
Published: December 2014

1. Accumulation of noradrenaline (NA), 5‐hydroxytryptamine (5HT) and tyramine by rabbit erythrocytes was measured at 37 degrees C in vitro. 2. Of the amines used only NA was broken down during incubation. This was a result of intracellular catechol‐O‐methyl transferase activity. 3. NA and 5HT entered the red cells by similar processes which were temperature‐sensitive (cooling to 0 degrees C inhibited accumulation) and had saturation kinetics. The entry of NA was partially stereospecific; the (‐)‐isomer accumulated twice as fast as did (+)‐NA. 5HT and NA competed for entry. Tyramine entry was unaffected by cooling, was not saturable and did not affect the entry of either NA or 5HT. NA and 5HT entered the erythrocytes at rates which were proportional to their lipid solubilities. 4. Metabolic inhibitors had no effect on amine transport. Inhibitors of amine transport in other tissues produced only small non‐specific reductions of NA accumulation in the red cells. 5. Amine accumulation was a symmetrical process (no amine was retained by the red cells if the concentration gradient was reversed). It is concluded that NA and 5HT enter the cells by facilitated diffusion. The entry of NA and 5HT displayed countertransport, an additional feature of facilitated diffusion. 6. The relationship between the physical properties of the amines and the routes by which they entered the erythrocytes is discussed.
A study of the composition of pericardial fluid, with special reference to the probable mechanism of fluid formation.
Authors: Gibson A T , Segal M B
Published: December 2014

The composition of pericardial fluid and simultaneously withdrawn plasma have been measured in rabbits and greyhounds. 1. Sodium and chloride distributions were found to be not markedly different from the ratio predicted for a passive distribution. The small deviation found in greyhounds could be largely corrected by the in vitro dialysis of plasma against pericardial fluid. 2. Calcium and magnesium were distributed in a manner expected from a passive ultrafiltrate of plasma. 3. Pericardial fluid was found to contain between one quarter and one third of the protein of plasma. 4. Separation of the protein constituents demonstrated a far higher proportion of albumin to other proteins in the pericardial fluid. 5. The osmolality of plasma was slightly higher than that of pericardial fluid, as would be expected from a plasma ultrafiltrate. 6. The potassium concentration of pericardial fluid was higher than the plasma concentration in all animals studied. This difference could be abolished, and an expected distribution obtained in the samples from greyhounds, by the in vitro dialysis of plasma against pericardial fluid. This observation for potassium cannot be attributed to haemolysis of blood in pericardial fluid samples or to the use of any inappropriate references. It is suggested that the elevated potassium concentration of pericardial fluid may reflect the lability of the cardiac intracellular potassium during cardiac contraction. 7. The results obtained in this study do not support the concept of an active secretion of pericardial fluid as has been claimed by others. The distribution of ions would appear to be passive and to follow the values predicted by the Gibbs‐Donnan relationship.
Discrimination between descriptive models of L‐glutamate uptake by the retina using non‐linear regression analysis.
Authors: Neal M J , White R D
Published: December 2014

1. The uptake of labelled L‐glutamate by the isolated rat retina was measured over a large range of external concentrations (1 micron to 1 mM). 2. The results obtained from measurements of the initial velocity of L‐glutamate uptake at different concentrations did not follow simple hyperbolic kinetics. 3. The error structure of replicate velocity measurements was examined and found to be normally distributed and heteroscedastic. 4. Descriptive models were fitted directly to data, weighted by the invariance, using non‐linear regression analysis. 5. The most suitable suitable descriptive model consisted of a saturable hyperbola (Vm = 285 n‐mole.(g wet wt.)‐1.min‐1, Km = 252 micron) and a linear term (b = 0.45 min‐1).
Selective impairment of contrast sensitivity in kittens exposed to periodic gratings.
Authors: Fiorentini A , Maffei L
Published: December 2014

1. Kittens were exposed to a periodic grating orientated vertically during the critical period of their life. 2. At the end of the critical period the amplitude of the response to drifting gratings was found to be reduced at the spatial frequency of exposure in multi‐unit and in some single unit recordings at lateral geniculate level. 3. The contrast sensitivity measured with behavioural methods also showed a depression at the spatial frequency of exposure. 4. An analysis of the preferred stimulus orientation of cortical units in area 17 showed that all orientations were represented.
The influence of stimulus velocity on the responses of single neurones in the striate cortex.
Authors: Goodwin A W , Henry G H
Published: December 2014

1. Using a multi‐histogram technique forty‐seven response‐velocity curves were prepared for a variety of visual stimuli presented to twenty‐one cells in the striate cortex of the anaesthetized, paralysed cat. 2. The character of each velocity‐response curve varied according to the measurement used in assessing a response. Reasons are advanced for sampling the response over a single bin of short duration at the peak of the discharge in each average response histogram. 3. The sharpness of tuning varied markedly throughout the population of cells but it was not possible to establish any definitive class differences. 4. For simple and complex cell categories there was considerable overlap in both the range of effective stimulus velocities and the distribution of the optimal velocities. An observation not emphasized in the past was that some simple cells responded to very fast stimuli while a number of complex cells were driven by very slowly moving stimuli. 5. Generally changes in stimulus parameters such as the polarity of contrast of a moving edge, its orientation or direction of movement produced only slight modifications in the profile of the velocity‐response curve. 6. The abolition of the response of simple cells that failed to be driven by rapidly moving stimuli was shown to be due to the entry of the stimulus into the inhibitory flank distal to the discharge region. When the movement of the stimulus was confined to the discharge region there was little evidence of velocity dependence in the response. The duration over which the inhibition from the distal flank remained effective was evaluated for representative simple cells.
Factors affecting the utilization of ketone bodies and other substrates by rat jejunum: effects of fasting and of diabetes.
Authors: Hanson P J , Parsons D S
Published: December 2014

1. The utilization of some metabolic fuels has been measured in vitro in a preparation of rat jejunum to which the substrates were supplied via the perfusate flowing through the vascular bed. 2. In jejunum from 48 hr‐fasted rats, the combined rates of utilization of 1 mM‐acetoacetate and 2mM‐D‐3‐hydroxybutyrate are similar to that of 7.5 mM‐glucose. 3. The utilization of glucose is reduced in jejunum from animals fasted for 48 hr (45‐‐63% reduction) and also from animals after 3‐‐6 days of diabetes induced by streptozotocin (29% reduction). The addition of ketone bodies or of Na‐oleate to the vascular perfusate does not reduce the utilization of glucose by the jejunum of either fed or 48 hr fasted rats. 4. Ketone bodies in the vascular perfusate reduce the oxidation of glucose by the jejunum of fed rats. In the jejunum of 48 hr‐fasted rats, ketone bodies completely inhibit the oxidation of glucose so that all the glucose utilized by the tissue is converted to lactate. 5. The findings are discussed in relation to other work and it is concluded that substrates for the oxidative metabolism of the jejunum of fasted rats are likely to be ketone bodies, glutamine and fatty acids; at the same time the utilization of glucose is reduced and its oxidation completely abolished.
The response properties of the steady antagonistic surround in the mudpuppy retina.
Authors: Thibos L N , Werblin F S
Published: December 2014

1. The graded response of bipolar and ganglion cells to test flashes at the receptive field centre, spans only a limited portion of the test intensity domain: more than 90% of the graded response range can be elicited by test flashes differing by less than 100 to 1. 2. In the presence of steady illumination of the receptive field surround, the absolute levels of log test intensities required to elicit 90% of the graded response are increased (reset), but the relation in (1) still applies. 3. Each point in the receptive field surround, when illuminated, contributes to the resetting of the required centre test flash intensities by a weighing that decreases exponentially with distance from the centre. The space constant is 0.25 mm. 4. When the receptive field surround is fully covered with illumination, the centre test flash intensities required to elicit 90% of the response range must be increased by about tenfold for each tenfold increase in surround intensity over a surround intensity domain of about 1000 to 1. 5. The absolute levels of surround and required centre test intensities are inter‐related: when the receptive field surround is fully covered, a test flash with intensity equal to that of the surround elicits a half‐maximal response. Thus, in the presence of a full field background, the bipolar potential is held near its half‐maximum response potential. 6. The graded resetting of the required centre test flash intensities is well correlated with the graded increase in horizontal cell response as the surround intensity and area are varied. It is inferred that units with response and receptive field properties like those of the horizontal cells, when driven by surround illumination, act as interneurones to reset the relationship between required test flash intensity and response in bipolar and ganglion cells.