bluuebunny/crossref_metadata_2025_split huggingface dataset:
The movement of optically detectable organelles in myelinated axons of Xenopus laevis
Authors: Cooper Paul D. , Smith Richard S. 
Published: December 2014

1. Intra‐axonal organelles were detected by darkfield and Nomarski microscopy in isolated myelinated nerve fibres from Xenopus laevis. Nerve fibres from the 8th spinal roots, the sciatic nerve, and identified motor and sensory axons from other hind limb nerves were used. The movement of the organelles was recorded either on motion picture film or by noting the times at which they crossed the lines of an ocular grid.2. Three groups of organelles were detected in all fibres. A group of particles with round profiles 0·2–0·5 μm in diameter moved somatopetally. Another group of round particles moved somatofugally. The ratio of the number of somatopetally travelling particles to the number of somatofugally travelling particles was about 10:1. The third group of organelles consisted of rod‐shaped bodies about 0·2–0·3 μm in diameter and 1‐8 μm in length; these were usually stationary.3. All the round particles appeared to move independently of each other with a saltatory motion. The somatopetally and somatofugally travelling particles had statistically different mean velocities of 0·98 and 1·32 μm/sec respectively.4. Round particles often crossed the node of Ranvier with no appreciable change in velocity. Some, however, were temporarily arrested at the entrance to the node.5. While the rod‐shaped organelles were usually stationary, they occasionally moved rapidly lengthwise for distances of up to 10 μm. Rarely a rod‐shaped organelle exhibited a continuous saltatory motion.6. Round particles often travelled in either direction along the edge of rod‐shaped organelles. One rod was observed to move along the path previously taken by a round particle.7. The findings are discussed with respect to (a) the normality of the preparations, (b) the numbers of particles travelling in each direction, (c) the nature of the organelles, and (d) the mechanisms underlying the motion.8. We suggest that particles move along microtubules which have specific directionalities and particle affinities. The microtubules are in bundles and are closely associated with rod‐shaped mitochondria.
Secretion and electrogenesis of the supporting cell in the olfactory epithelium
Authors: Okano Masaomi , Takagi Sadayuki F. 
Published: December 2014

1. Electrophysiological study disclosed that chloroform and some other odours generate long‐lasting positive potentials in the olfactory epithelium of the bullfrog, while electron microscopical study showed that they elicit vigorous protrusion of the distal cytoplasmic portion of the supporting cell containing the secretory granules.2. The secretory process of the supporting cell is as follows: The first detectable indication is the protrusion of the apical portion of the supporting cell (Pls. 3 and 4); the protruded part detaches from its maternal supporting cell (Pl. 7 B), floats as a droplet in the mucus (Pl. 5), and finally the secretory granules inside the droplet disintegrate into the mucus (Pls. 6 and 7 A).3. The secretion was not elicited by the odours which elicit the negative potentials.4. In Cl−‐free Ringer solution, neither the positive potential nor the protrusion and secretion occurred.5. When 1‐2 m
M‐Ba2+ in Ringer solution was dripped on the epithelium, both the positive potential and the protrusion and secretion resulted. Subsequent application of chloroform vapour only advanced further disintegration of the secretory granules, but it elicited neither a new protrusion of the granules nor the positive potential.6. In the olfactory epithelium in which the olfactory cells had degenerated but the supporting cells survived, both the positive potential and the protrusion and secretion occurred, but the negative potential did not.7. It is concluded that Cl− entry which mainly generates the longlasting positive potential triggers the secretion of the supporting cell.
Cardiac responses to snout immersion in trained dogs
Authors: Gooden B. A. , Stone H. L. , Young S. 
Published: December 2014

1. Four dogs were trained to immerse their snout voluntarily for durations up to 30 sec. Indwelling instrumentation was implanted to measure blood flow velocity in the circumflex branch of the left coronary artery, to sample blood from the left atrium and coronary sinus for the determination of PO2, PCO2, pH, oxygen saturation and haemoglobin concentration, and to pace the heart. An index of myocardial oxygen consumption was calculated by multiplying the mean flow velocity by the arteriovenous difference in oxygen content.2. Mean coronary flow velocity decreased significantly during simulated diving by 26 ± 27% (±
S.D.). The range of decrease in seventeen out of twenty experiments was from −5 to −81%. Heart rate decreased by 48 ± 7% and this bradycardia was abolished by
I.V. atropine.3. Coronary sinus oxygen saturation increased significantly with snout immersion (three dogs) and arteriovenous difference decreased from 67 ± 10 to 47 ± 5%. The index of myocardial oxygen consumption decreased by 42 ± 19%. This decrease was attenuated slightly by β‐blockade but was abolished by cardiac pacing in three out of four experiments.4. The present study indicates that the heart consumes oxygen at a considerably reduced rate during simulated diving and therefore plays a direct role in the overall conservation of oxygen. This response appears to result primarily from a negative chronotropic effect induced by increased vagal tone.
Regulation of the cell magnesium in vascular smooth muscle
Authors: Palatý Vladimír 
Published: December 2014

1. The relation between [Mg]o and the Mg content of the rat tail artery incubated in Ca‐free solutions was studied.2. Variation of [Mg]o in Ca‐free Krebs solution between 0·6 and 2·4 m
m did not affect the cell Mg. In ATP‐depleted arteries, a sizeable fraction of the cell Mg was found to be proportional to [Mg]o.3. An even larger fraction of the cell Mg became proportional to [Mg]o in metabolically active arteries in which the transmembrane gradient of Na had been dissipated as a result of inhibition of the Na pump. In contrast to the extracellular Mg, the fraction responded to a change in [Mg]o at a very slow rate. The size of the fraction was reflected in net uptake of Mg if [Mg]o was higher than 1·2 m
m. The rate of the uptake was lowered markedly by external Ca. All the Mg taken up by the cells was extruded again after restoration of the Na gradient.4. The uptake of Mg in Ca‐free, ouabain‐containing solution took place even if the concomitant swelling of cells was prevented by substitution of isethionate for external Cl.5. Under steady‐state conditions and at const. [Mg]o and [Na]o, [Mg]i increased with increasing [Na]i.6. The results are consistent with the hypothesis that the outwardly directed Mg pump in rat vascular smooth muscle utilizes the energy released in the course of spontaneous influx of Na.
Cells responding to changing image size and disparity in the cortex of the rhesus monkey
Authors: Zeki S. M. 
Published: December 2014

1. The cells of the cortex of the posterior bank of the superior temporal sulcus of the monkey appear to be specialized to signal motion in the visual field. In this paper, cells in this cortical area capable of signalling motion towards or away from the animal are described.2. Two such types of cell were encountered. One type, the opposed movement complex and opposed movement hypercomplex cells, responded to two edges at a given orientation moving towards or away from each other within the receptive fields. These cells were driven either monocularly or binocularly, but when binocularly driven the cells responded in an identical manner to stimulation of each eye, thus suggesting that such cells must receive a double, and opposed, input from each eye. The other type of cell, always binocularly driven, responded to movement in opposite directions on the two retinas, thus suggesting that such cells must receive diametrically opposite connexions from the two eyes.3. Long penetrations made to study the manner in which such cells were grouped together in the cortex revealed that they were arranged in small groups or clusters, separated from each other by the common directionally selective cells so prominently present in this area. Thus, cells with one type of wiring mechanism were separated from each other by cells receiving another, and more common, type of anatomical wiring.
The internal anal sphincter in the cat: a study of nervous mechanisms affecting tone and reflex activity
Authors: Garrett J. R. , Howard E. R. , Jones W. 
Published: December 2014

1. Smooth muscle activities in rectum and internal anal sphincter have been recorded using intraluminal balloons.2. Reflex activation of the sphincter, caused by distension of the rectum, has been assessed before and after various combinations of blocking drugs.3. Responses to stimulation of hypogastric or sacral nerves, or to the administration of drugs with autonomic actions have been tested before and after various combinations of blocking drugs.4. Results indicate that the tone of the internal anal sphincter is influenced by a number of neural mechanisms. These include motor pathways involving both α‐adrenergic and cholinergic mechanisms and inhibitory pathways involving both β‐adrenergic and non‐adrenergic non‐cholinergic mechanisms.5. Cholinergic contractions of the sphincter were converted to relaxations after α‐adrenergic blockade. This indicates that the contractions are an indirect effect operating through an adrenergic reflex. Cholinergic relaxations may also be indirect and operate through reflex inhibition secondary to rectal contractions.6. Sphincteric motor activity is controlled largely through α‐adrenergic mechanisms by adrenergic nerves acting directly on the muscle. β‐Adrenergic inhibitory mechanisms are thought to operate indirectly via ganglia.7. The over‐all control of the sphincter is by complex reflex mechanisms involving numerous pathways and the activity of the sphincter at any one time is determined by the net balance between motor and inhibitory influences.8. Sacral nerve stimulation indicated that it contains cholinergic nerves to the rectum, non‐adrenergic non‐cholinergic inhibitory axons to the sphincter and variable numbers of adrenergic axons to the sphincter.9. Responses of the sphincter to drugs and nerve stimulation were often variable, as has been described many times in the literature. It is considered that this is due to complex combinations of indirect reflex effects, secondary to activation of structures outside the sphincter, operating with or against direct effects on the sphincter itself.
On the transmitter function of 5‐hydroxytryptamine at excitatory and inhibitory monosynaptic junctions
Authors: Gerschenfeld H. M. , Tritsch Danièle Paupardin 
Published: December 2014

1. Two symmetrical giant neurones located in the cerebral ganglion of Aplysia californica contain 4–6 p‐mole 5‐hydroxytryptamine (5‐HT) and are able to synthesize it (Weinreich, McCaman, McCaman & Vaughn, 1973; Eisenstadt, Goldman, Kandel, Koike, Koester & Schwartz, 1973). Stimulation of each of these neurones evokes excitatory and inhibitory potentials in various cells of the ipsilateral buccal ganglion. In nine buccal neurones it evokes excitatory potentials, in other three, ‘classical’ inhibitory potentials and in one neurone an ‘atypical’ inhibitory potential.2. The connexion between the giant cerebral neurone and the cells receiving either an excitatory or a ‘classical’ inhibitory input from it are monosynaptic. TEA injection into the cerebral giant neurone, which prolongs the presynaptic spike, causes a gradual increase of both the excitatory and the inhibitory potentials. On the other hand, high Ca2+ media, which block polysynaptic pathways, do not suppress these synaptic potentials.3. The iontophoretic application of 5‐HT to the buccal neurones receiving excitatory input from the giant cerebral neurones evokes depolarizations showing the pharmacological properties of both A‐ and A′‐responses to 5‐HT (see preceding paper). Antagonists which block only the A‐receptors (curare, 7‐methyltryptamine, LSD 25) block partially the synaptic depolarizing potentials. Bufotenine, which blocks both the A‐ and A′‐receptors, completely blocks the excitatory potentials. Thus, the post‐synaptic membrane of these buccal neurones appears to be endowed with both A‐ and A′‐receptors to 5‐HT.4. The ‘classical’ inhibitory potentials elicited in three buccal neurones are hyperpolarizations which reverse at — 80 mV and are due to an increase in K+‐conductance. The iontophoretic application of 5‐HT to these post‐synaptic neurones evokes hyperpolarizing B‐responses which are also generated by an increase in K+‐conductance. Antagonists which block the B‐responses (bufotenine, methoxygramine) also block the inhibitory potentials.5. The ‘atypical’ inhibitory potential evoked in one buccal neurone consists in an hyperpolarization which increases in amplitude with cell hyperpolarization. Iontophoretic application of 5‐HT to this buccal cell evokes an hyperpolarizing β‐response which also increases in amplitude with cell polarization and results from a decrease in both Na+‐ and K+‐ conductances. The monosynaptic character of the ‘atypical’ inhibitory potential is not yet fully proven.6. It can be concluded that the excitatory and inhibitory synaptic effects evoked in the buccal neurones by the stimulation of the 5‐HT‐containing‐giant cerebral neurones are very likely mediated by 5‐HT.
Evidence on the origin of impulses recorded from dentine in the cat
Authors: Horiuchi H. , Matthews B. 
Published: December 2014

1. Recordings have been made from dentine at the tip of the canine teeth of cats using a large Ag/AgCl electrode.2. All‐or‐none action potentials with complex shapes were recorded when single nerve fibres from the dental pulp were stimulated electrically outside the tooth.3. The wave forms of these action potentials changed when the stimulation rate was increased from 1/sec to 10/sec, when the temperature of the tooth surface was changed between 17 and 42° C, when the thickness of the dentine was reduced, and when local anaesthetic was applied to the dentine. Only a small, monophasic, positive potential remained after transection of the pulp in the crown of the tooth.4. The latency of the action potentials was not affected by these same procedures.5. It is suggested that each wave form represented a compound action potential produced by impulses invading the main branches and terminals of a single nerve in the pulp. Some of the terminals may have penetrated the innermost layers of the dentine.6. There was no spontaneous discharge from pulpal nerves.7. A discharge of impulses was recorded from dentine when 2·5 mol/l. NaCl was applied beneath the electrode at the tip of the tooth. By recording simultaneously from dentine and from single fibres from the tooth pulp, it was shown that impulses recorded from dentine were associated with propagated nerve action potentials.
Multiple light‐evoked conductance changes in the photoreceptors of Hermissenda crassicornis
Authors: Detwiler P. B. 
Published: December 2014

1. Light responses were recorded from the photoreceptors of Hermissenda crassicornis. The response to a flash is a complex potential change involving an initial depolarization, a hyperpolarization, and a depolarizing tail. None of the phases of the response are due to synaptic interactions.2. Polarization of the membrane by extrinsic current indicates that three separate conductance changes are associated with the response. The initial depolarization and hyperpolarization are accompanied by conductance increases and the tail with a conductance decrease. The initial depolarization has a positive reversal potential and the hyperpolarizing and tail phase have a reversal voltage more negative than resting potential.3. The different processes that give rise to the conductance changes have similar spectral sensitivities but are affected unequally by light adaptation. Strong light adaptation reduced the depolarizing phases more than the hyperpolarizing phase, so that following an adapting stimulus the cell responded to illumination with a pure hyperpolarization (isolated hyperpolarization).4. Removal of external Na+ ions greatly reduced the initial depolarization. In Na+‐free sea water the cell responds to dim flashes with a slow depolarization (isolated tail) that involves a conductance decrease, and has the same reversal potential as the hyperpolarizing response recorded from light adapted cells.5. The amplitude of the isolated hyperpolarization and tail varied inversely with the external K+ concentration.6. It is concluded that in Hermissenda photoreceptors light initiates processes that result in three distinct permeability changes. Following a brief flash there is: a rapid and transient increase in Na+ permeability that is responsible for the initial depolarization, a less rapid increase in K+ permeability that is responsible for the hyperpolarizing phase, and a delayed decrease in K+ permeability that gives rise to the depolarizing tail.
Sucrose absorption by the rat small intestine in vivo and in vitro
Authors: Davidson Ruth E. , Leese H. J. 
Published: December 2014

1. The absorption of glucose and fructose derived from sucrose has been studied using in vitro and in vivo loops of the rat jejunum.2. At low sucrose concentrations (1 and 10 m
M) glucose appeared in the serosal compartment of the in vitro preparation at a faster rate than fructose, but at high sucrose concentrations (50 and 100 m
M) the rates of serosal transfer of the two sugars were similar. Glucose and fructose appeared in the mucosal compartment, with the rate of fructose appearance exceeding that of glucose, at all the sucrose concentrations studied.3. Phlorizin (5 × 10−5
M) added to the mucosal medium of the in vitro preparation abolished the serosal transfer of glucose derived from 50 m
M sucrose, and reduced that of fructose by 75%.4. In the absence of sodium ions, the in vitro preparation failed to transfer glucose and fructose derived from 50 m
M sucrose, into the serosal compartment.5. Glucose was actively accumulated in the whole gut wall of the in vivo preparation to concentrations higher than those in the plasma at 50 and 100 m
M, but not at 10 m
M sucrose concentrations. Fructose was also actively accumulated to about half the extent of glucose, but reached tissue concentrations greater than those in the plasma, at each sucrose concentration.6. The whole wall concentrations of glucose and fructose derived from sucrose added to the lumen continued to rise when the blood supply to the in vivo preparation was terminated.7. No increase in the in vivo whole wall concentrations of glucose and fructose were detected when sucrose was added to the lumen together with concentrations of glucose sufficient to saturate the monosaccharide transport systems.8. The results favour the view that disaccharide hydrolysis and resulting hexose transfer are sequential, separate events.
Mechanical work and efficiency in level walking and running
Authors: Cavagna G. A. , Kaneko M. 
Published: December 2014

1. The mechanical power spent to accelerate the limbs relative to the trunk in level walking and running, Ẇint, has been measured at various ‘constant’ speeds (3‐33 km/hr) with the cinematographic procedure used by Fenn (1930a) at high speeds of running.2. Ẇint increases approximately as the square of the speed of walking and running. For a given speed Ẇint is greater in walking than in running.3. In walking above 3 km/hr, Ẇint is greater than the power spent to accelerate and lift the centre of mass of the body at each step, Ẇext (measured by Cavagna, Thys & Zamboni, 1976b). In running Ẇint < Ẇext up to about 20 km/hr, whereas at higher speeds Ẇint > Ẇext.4. The total work done by the muscles was calculated as Wtot = ǀWintǀ + ǀWextǀ. Except that at the highest speeds of walking, the total work done per unit distance Wtot/km is greater in running than in walking.5. The efficiency of positive work was measured from the ratio Wtot/Net energy expenditure: this is greater than 0·25 indicating that both in walking and in running the muscles utilize, during shortening, some energy stored during a previous phase of negative work (stretching).6. In walking the efficiency reaches a maximum (0·35‐0·40) at intermediate speeds, as may be expected from the properties of the contractile component of muscle. In running the efficiency increases steadily with speed (from 0·45 to 0·70‐0·80) suggesting that positive work derives mainly from the passive recoil of muscle elastic elements and to a lesser extent from the active shortening of the contractile machinery. These findings are consistent with the different mechanics of the two exercises.
Convergence of rod and cone signals in the cat's retina
Authors: Enroth-Cugell Christina , Hertz B. Gevene , Lennie P. 
Published: December 2014

1. In an attempt to understand the convergence of rod and cone signals in the cat's retina, ganglion cells that received inputs from both rods and cones were stimulated using lights chosen to excite one or other receptor system or both together.2. If a mesopic background was chosen to allow the ganglion cell to be excited by a blue‐green test flash primarily through rods and a deep red flash primarily through cones, one light could not be alternated with the other without eliciting a response from the cell.3. This appears to be a result of the different temporal properties of the scotopic and photopic systems. On the mesopic background responses to blue‐green test flashes were transient. Responses to red test flashes arose with similar latency, but were more sustained.4. Rod and cone systems responded with similar latencies in the presence of the mesopic background that substantially light‐adapted the rod system but left the full sensitivity of the cone system undiminished. When equivalently light‐adapted, the cone system was faster.5. When brief flashes that acted through rods were presented with flashes that acted through cones the ganglion cell's response was the sum of the responses to the two flashes presented separately, as long as the flashes were weak. This linear relation ceased to hold when flashes were strong, but the breakdown appears not to be the result of mutual inhibition between rod and cone signals.6. When a background light excited both rod and cone systems it appeared to reduce sensitivity independently in each.7. The scotopic and photopic receptive fields of a given ganglion cell always were of the same type, on‐ or off‐centre, and, within the limits of measurement, the central regions of the receptive fields were concentric and both the same size.