bluuebunny/crossref_metadata_2025_split huggingface dataset:
The release of acetylcholine from carotid body tissues. Further study on the effects of acetylcholine and cholinergic blocking agents on the chemosensory discharge
Authors: Eyzaguirre C. , Zapata P. 
Published: December 2014

1. Both carotid bodies were removed from cats and placed in a small Perspex channel through which Locke solution was allowed to flow under a layer of paraffin oil. Stimulation of the upstream (‘donor’) organ elicited an increased sensory discharge in the downstream (‘detector’) preparation (Loewi effect).2. This effect was enhanced by eserine, depressed by hexamethonium and blocked by either mecamylamine or acetylcholinesterase. The Loewi effect did not disappear when chronically denervated (4 days) ‘donor’ carotid bodies were stimulated.3. These experiments led to the conclusion that ACh is released by the carotid body tissues (probably from the glomus cells) during stimulation and that this substance is responsible for the initiation of the chemosensory discharges.4. In single preparations the chemosensory endings proved to be very sensitive to ACh especially in the presence of eserine which, in all probability, inactivated the tissue cholinesterase. Curarizing agents such as mecamylamine, hexamethonium, (+)‐tubocurarine and atropine blocked the response of the sensory endings to applied ACh in what appeared to be ‘surmountable’ antagonism.
Renal excretion of potassium in the sheep
Authors: Dewhurst J. K. , Harrison F. A. , Keynes R. D. 
Published: December 2014

1. Observations were made on the daily intake and excretion of potassium and sodium in sheep housed in metabolism cages and fed once daily.2. The diet of chaffed hay and crushed oats provided 400‐600 m‐moles K and 50‐60 m‐moles Na daily. About 90% of the K was excreted in the urine, and over 90% of the Na was found in the faeces.3. In two groups of three experiments on each of three sheep, the urinary responses to intra‐ruminal dosing just before feeding of (i) 1 l. distilled water, (ii) 1 l. 0·25
N‐KCl, and (iii) 1 l. 0·125
N‐NaCl, were studied. In the first group, urine was collected via the urine/faeces separator of the metabolism cage, whereas for part of the experiments in the second group it was collected by an indwelling bladder catheter.4. In a third group of experiments with the same sheep, the effects on urinary excretion of K and Na of intra‐ruminal dosing with (i) 1 l. distilled water, (ii) 1 l. 0·25
N‐K acetate, and (iii) 1 l. 0·25
N‐Na acetate were investigated. During part of these experiments urine was again collected via an indwelling bladder catheter. With chloride, 82% of the additional potassium was excreted in urine in the 24 hr after dosing, but with acetate only 65%. For sodium, the corresponding figures were 12‐40% with chloride and 43% with acetate.5. In most experiments, the administration of K salts produced a marked kaliuresis and, in spite of the low sodium intake, a natriuresis as well, which did not usually coincide with maximum K excretion. No adequately tested explanation appears to exist for the natriuresis observed in response to treatment with K salts.
The effect of catecholamines on unit activity in afferent nerves from the adrenal glands
Authors: Niijima A. , Winter D. L. 
Published: December 2014

1. Afferent discharges were observed in dissected filaments of nerves to the adrenal gland in the rabbit and cat.2. Systemic intravenous and close intra‐arterial injections of (‐)‐adrenaline and (‐)‐noradrenaline caused cessation or depression of the spontaneous firing rate.3. Intravenous injection of acetylcholine and electrical stimulation of the splanchnic nerve also depressed the afferent discharge rate.4. Modification of blood pressure levels by chemical and mechanical means did not modify the afferent discharge.5. Alpha blocking agents (ergotamine and phenoxybenzamine) blocked the effect of (‐)‐adrenaline on the firing rate. Beta blocking agents (dichloroisoprenaline and propranolol) were without effect.6. It is suggested that an afferent system is present in the adrenal gland. Within this system are chemosensitive receptors which may constitute the afferent limb of a local feed‐back loop involved in adrenal catecholamine release.
The identification of four prostaglandins in dog brain and their regional distribution in the central nervous system
Authors: Holmes S. W. , Horton E. W. 
Published: December 2014

1. Experiments were carried out to determine whether the prostaglandins, which have been identified as natural constituents of the brain, are widely distributed or concentrated in special regions of the central nervous system.2. Prostaglandins E1, E2, F1α and F2α have been identified in dog brain using solvent partition, column and thin layer chromatographic and bio‐assay techniques.3. Each of these prostaglandins is distributed throughout all regions of the central nervous system investigated (cortex, hippocampus, caudate nucleus, hypothalamus, cerebellum, medulla and pons, cortical white matter and spinal cord).4. This distribution suggests that the role of prostaglandins in the central nervous system is not confined to any specific region.
A method of analysing the responses of spindle primary endings to fusimotor stimulation
Authors: Bessou P. , Laporte Y. , Pagès B. 
Published: December 2014

1. The superposition of records of ‘instantaneous’ frequency of discharge of spindle primary endings after stimulation of single fusimotor fibres leads to the construction of graphs called ‘frequencygrams’.2. The superposition is made on the screen of a storage oscilloscope, the time base of which is synchronized with the stimulus. It is essential that the stimulus be delivered at all possible intervals with respect to the impulse of the resting discharge which precedes it.3. Frequencygrams obtained by stimulating some static fusimotor fibres by single stimuli display a response with a fast rising phase, a pause, and a slower decreasing phase.4. Frequencygrams may give some information on the time course of the contraction of intrafusal muscle fibres elicited by stimulating their motor axons.
Termination and functional organization of the ventral spino‐olivocerebellar path
Authors: Oscarsson Olov 
Published: December 2014

1. The spino‐olivocerebellar path ascending through the ventral funiculus (VF‐SOCP) was investigated in decerebrate cats with the cord transected in the third cervical segment except for the left ventral funiculus. The climbing fibre responses evoked in Purkinje cells were studied by recording from single cells and by recording the mass activity at the cerebellar surface or in the molecular layer.2. In the spinal cord the forelimb component of the VF‐SOCP occupies a medial part and the hind limb component a lateral part of the ventral funiculus.3. The main projection of the limb nerves through the VF‐SOCP is to the lateral two thirds of the vermis of the anterior lobe. The projection area consists of three sagittally arranged bands: a lateral band receiving olivary axons activated exclusively from the ipsilateral hind limb, an intermediate band receiving olivary axons activated bilaterally from the hind limbs, and a medial band receiving olivary axons activated bilaterally from the forelimbs. Some olivary neurones are activated from all four limbs.4. The latency of the climbing fibre responses was about 22 msec on stimulation of ipsilateral hind limb nerves and about 20 msec on stimulation of ipsilateral forelimb nerves. The responses evoked from contralateral nerves had a latency which was about 3 msec longer than the latency of the corresponding ipsilateral responses.5. The olivary neurones were usually activated from all tested muscle and skin nerves in the limb(s) constituting the receptive field. Cutaneous afferents and groups II and III muscle afferents were responsible for the excitation elicited by single shock stimulation of the nerves. Brief repetitive stimulation revealed additional activation from mainly Ib, but also Ia, afferents in ipsilateral hind limb nerves.6. Natural stimulation of receptors evoked responses in about half of the olivary neurones tested. The responses were elicited by strong pressure against deep structures. Inhibitory effects were seldom observed.
The identification and characteristics of sacral parasympathetic preganglionic neurones
Authors: de Groat W. C. , Ryall R. W. 
Published: December 2014

1. Sacral parasympathetic preganglionic neurones were identified by intracellular and extracellular micro‐electrode recording of antidromic potentials in response to stimulation of the pelvic nerve or the second or third sacral ventral roots.2. The segmental distribution of autonomic neurones varied in different cats. In some cats they were mainly in S2 segment, in others in S3 and in the remainder, in both S2 and S3.3. The antidromic potentials showed initial segment‐somadendritic (IS‐SD) inflexions and delayed depolarizations and were slightly less prolonged than those of sympathetic neurones but more prolonged than those of spinal motoneurones. After‐hyperpolarization was observed after the antidromic spike potential.4. The conduction velocities for sacral parasympathetic preganglionic fibres were less than 12·5 m/sec and thus were similar to those of sympathetic preganglionic fibres.5. Parasympathetic neurones were not excited by micro‐electro‐phoretically applied 5‐hydroxytryptamine, noradrenaline or acetylcholine.
Factors controlling the washout of the interstitial space of the isolated, perfused rat heart
Authors: Young D. A. B. 
Published: December 2014

1. The time course of the washout of the extracellular markers, inulin, raffinose, sucrose and sorbitol, has been determined for the isolated rat heart perfused for 20 min with Krebs bicarbonate medium containing the marker, and washed out with marker‐free perfusate.2. The filtration problem for the perfused rat heart was found to be due to omission of the gassing of the concentrated sodium bicarbonate solution with CO2 in the preparation of the perfusate. This probably caused calcium phosphate to be precipitated. The reduced contractility of the heart was reflected in the washout of the extracellular markers.3. The logarithmic plot of the heart content of the marker against time showed two components. The slower was an exponential process, the rate of which was linearly related to the diffusion coefficient for the various markers.4. The faster component was absent in the quiescent heart, and in the beating heart its contribution to the washout of the interstitial space was related to the strength of contraction.5. Similar washout curves were obtained for Evans Blue‐albumin conjugate, which readily penetrates the interstitial space of the isolated rat heart.6. It is suggested that the two components of efflux are a diffusion process limited by perfusate flow, and bulk movements of fluid.
Fine structure of tortoise skeletal muscle
Authors: Page Sally G. 
Published: December 2014

1. The fine structure of tortoise skeletal muscle has been studied with the electron microscope.2. The packing of the A filaments (1·6 μ long) and the I filaments (2·35 μ long) within the myofibril is similar to that in frog twitch fibres.3. The position of the N line within the I band is found to vary with the sarcomere length.4. The T‐system tubules in these muscles form a three‐dimensional network across the fibre at the level of the I band. On either side of the Z line it forms triad relationships with the other network of tubules of the sarco‐plasmic reticulum.
Conduction failure in myelinated and non‐myelinated axons at low temperatures
Authors: Franz D. N. , Iggo A. 
Published: December 2014

1. The effects of low temperature on conduction in single myelinated and non‐myelinated axons of the feline saphenous nerve were examined and compared. Nerves were cooled by a conventional thermode, but thermal gradients were minimized by an insulating layer of agar‐saline gel over the nerve and the face of the thermode.2. The mean blocking temperature of thirty‐one non‐myelinated axons, 2·7° C, was significantly lower than that of 111 myelinated axons, 7·2° C. No evidence for a differential block of myelinated axons according to their normal conduction velocity could be demonstrated.3. Reductions in the proportional conduction velocities of both myelinated and non‐myelinated axons were nearly identical between 17 and 37° C. However, below 17° C the rate at which the proportional conduction velocity of the non‐myelinated axons fell during cooling was significantly less than for the myelinated axons and was sufficient to account for their lower blocking temperatures. As a result, critical minimum conduction velocities were reached at higher temperatures in myelinated axons than in non‐myelinated axons.4. The conduction velocity of successive impulses in a train slowed progressively to a constant value which depended on the frequency of stimulation. Consequently, the early impulses were separated by intervals that exceeded those between stimuli and were not affected by temperatures that blocked later impulses. The pattern of block was consistent with an increasing refractoriness of the axons as the temperature fell.5. The maximal frequency of discharge that myelinated axons could carry at temperatures between normal and 12° C was related directly to fibre size. Non‐myelinated axons could conduct low frequency trains of impulses at temperatures that blocked such activity in myelinated axons. In all axons, high frequency trains of impulses could be completely blocked at temperatures which permitted lower frequency trains to pass uninterrupted.6. Hysteresis in the blocking temperatures of axons was related to the hysteresis in their conduction velocities.
Depolarizing and hyperpolarizing receptor potentials in the non‐myelinated nerve terminal in Pacinian corpuscles
Authors: Nishi K. , Sato M. 
Published: December 2014

1. Pacinian corpuscles or non‐myelinated nerve terminals in Pacinian corpuscles, from which lamellae had been removed, were stimulated with linearly increasing compression of varying rate, which decayed linearly after a maximum compression.2. An impulse was initiated with a compression having a rate of increase greater than a critical slope. The critical slope was 1·1‐1·2 rheobase/msec in both intact corpuscles and decapsulated terminals.3. The receptor potential of the terminal increased in magnitude and rate of rise with an increase in the rate of compression. Its rate of rise was linearly related to the rate of compression.4. Hyperpolarization was observed on removal of compression, and an impulse was initiated upon recovery of the hyperpolarized membrane potential.5. In some corpuscles or decapsulated terminals hyperpolarization was produced on compression and a depolarizing response was produced upon removal of compression. After rotation by 90° along their long axis, they produced depolarization on compression.6. Difference in the directional sensitivity of corpuscles and decapsulated terminals was confirmed and was explained on the basis of the shape of the terminal.7. On‐ and off‐responses of variable latency recorded from a central portion of the axon to Pacinian corpuscles were explained by the depolarizing and hyperpolarizing responses in the terminal.
The dynamics of small saccadic eye movements
Authors: Thomas J. G. 
Published: December 2014

1. The mechanical characteristics of the system comprising the eyeball and its attachments have been determined, by applying rotational forces to the eyeball, and using an accelerometer on a contact lens to measure the resulting movement.2. The angular acceleration‐versus‐time curves of small saccades have been recorded. Some of these saccades are made whilst the eye is being vibrated by external forces.3. A mechanical model of the orbital system has been formulated. This is considered to bear a relationship to the structures in the orbit.4. The model has been used to deduce the force pattern of the active component in the extraocular muscles during the execution of a saccade. It is concluded that a saccade is initiated by a rapid rise of tension. After a short time, the tension falls to a lower level, which is the new steady‐state level. The present findings are therefore basically different from those of previous workers, in that we deduce a change in the force pattern during the course of the movement.5. In the execution of saccades of various sizes, both the strength and duration of the brief heightened tension are found to vary. For a 4 degree saccade, the transient tension is approximately 36 g, lasting for approximately half of the duration of the saccade.6. Characteristic features of saccades are interpreted in terms of variations in the duration of the transient excess tension.7. Differences in the time course of horizontal and vertical saccades are attributed to differences in the elasticity of the muscles involved in the movements.8. It is suggested that, in view of the similarity of the acceleration‐versus‐time wave forms, the muscular force pattern which is responsible for rapid head movements is of a similar type to that which has been deduced for saccades.
The mechanism of oscillatory activity at low membrane potentials in cardiac Purkinje fibres
Authors: Hauswirth O. , Noble D. , Tsien R. W. 
Published: December 2014

1. The mechanism of oscillations at low membrane potentials in Purkinje fibres has been investigated using voltage clamp experiments.2. The oscillations are generated by time‐dependent variations in an outward current component, ix1, that is activated over the voltage range ‐40 to 10 mV. During normal activity, this current is responsible for initiating full repolarization to the resting potential (Noble & Tsien, 1969b) so that the oscillations represent a failure of the normal repolarization process, probably as a consequence of a small change in background (leakage) current.3. These oscillations are distinct from the normal pacemaker activity of Purkinje fibres which is generated by a separate time‐dependent current, iK2 (Noble & Tsien, 1968). iK2 shows no time‐dependence when the membrane potential variations are entirely positive to ‐65 mV and cannot, therefore, be involved in the oscillatory activity apart from contributing a background outward current.4. The amplitude and frequency of the oscillations are very sensitive to applied currents less than 1 μA/cm2. Larger currents abolish the oscillatory activity.5. The mechanism of the oscillations is discussed in relation to the possible mechanisms underlying the natural pacemaker activity of the sino‐atrial (SA) node.
The occurrence, structure and innervation of slow and twitch muscle fibres in the tensor tympani and stapedius of the cat
Authors: Fernand V. S. V. , Hess A. 
Published: December 2014

1. The muscle fibres of the tensor tympani and stapedius of the cat have been examined in the light microscope in teased preparations after cholinesterase staining and in the electron microscope.2. In both muscles, two kinds of fibre have been found: those with an individual end‐plate and those with multiple nerve terminals.3. The stapedius fibres with an end‐plate have fibrils regularly separated from each other by sarcoplasmic reticulum, a straight Z line, transverse tubular T system elements regularly occurring at the junction of A and I bands, an M line, an extensive sole plate area, and numerous post‐junctional sarcolemmal infoldings under the nerve terminal. This type of muscle fibre in the tensor tympani has all of these features except that the fibrils are not well separated from each other, T system elements are absent in some sarcomeres, and a typical M line is absent.4. Compared to the individually innervated fibres, the fibres with multiple endings have fibrils poorly separated from each other by sarcoplasmic reticulum, a jagged Z line, very few T system elements, a less extensive sole plate area, and essentially no folds under the nerve terminal. These fibres in both muscles have M lines.5. Muscle fibres have thus been found in both the tensor tympani and stapedius of the cat which conform in their innervation, the structure of their motor nerve endings, and their internal structure to many of the morphological characteristics which are exhibited by slow muscle fibres elsewhere.
The relation between environmental temperature and oxygen consumption in the new‐born baby
Authors: Hey E. N. 
Published: December 2014

1. Oxygen consumption (V̇O2) has been measured serially in sixty‐eight infants during the first 10‐35 days of life, when naked in a Perspex metabolic chamber, by recording the changes in circulating gas volume. Air speed in the chamber was 4‐5 cm/sec, and absolute humidity ∼ 18 mm Hg.2. When environmental temperature (TE) was 35‐38° C minimal V̇O2 rose from 5 to 7 ml.O2/kg.min during the first 2 days of life in infants weighing over 2·5 kg, and more slowly in the first 7‐10 days in infants under 2 kg at birth.3. Physical activity and V̇O2 both increased when TE fell below 33° C: the increase appeared to be linearly and inversely related to TE, but the rise in heat production was seldom enough to prevent a fall in rectal temperature. In infants over 2·5 kg at birth the mean increase amounted to 0·56 ml.O2/kg.min for each 1° C fall in TE when 4‐12 hours old, and 1·27 ml.O2/kg.min when between 4 and 20 days old. In infants weighing 1–2 kg at birth the mean increase was similar in the first 12 hr, but the coefficient rose more gradually with age.4. The maximum V̇O2 in infants over 2·5 kg at birth and over 2 days old was about 2½ times the minimum V̇O2; the maximum was rather lower in most infants of low birth weight.5. In seven infants who were motionless and apparently asleep after sedation with chloral hydrate, the increase in V̇O2 at low TE was reduced but still significant.6. It is concluded that the new‐born baby responds to a cool environment with a considerable immediate increase in heat production; visible muscular activity appears to account for only part of this increase.
Elastic constants of the human lens capsule
Authors: Fisher R. F. 
Published: December 2014

1. A technique is described whereby the elasticity of the human lens capsule has been determined at birth and throughout life. This technique requires three separate determinations: (a) thickness; (b) stress and strain; (c) Poisson's ratio; (a) the capsule was clamped between accurately perforated ground glass plates and its thickness determined by noting the change in depth of focus between Latex spherules adhering to its upper and lower surfaces; (b) the undisturbed capsule was then placed in a specially designed glass distension apparatus and the relationship between volume and pressure recorded when it was distended with isotonic saline. The permeability of the capsule was also measured; (c) in some cases Poisson's ratio was determined by measuring the change of thickness of the capsule and the height to which it rose when distended with isotonic saline at different pressures. An apparatus was designed for this purpose.2. The average thickness of the anterior capsule increases from birth until about the 60th year but thereafter it decreases slightly.3. Poisson's ratio was about 0·47 for both cat and human capsule, and no significant variations with age in human capsule could be detected.4. Corrected volume pressure curves obeyed Hook's law almost to the point of capsule rupture.5. In childhood Young's Modulus of elasticity is about 6 × 107 dyn/cm2 and decreases to 3 × 107 dyn/cm2 at 60 and 1·5 × 107 dyn/cm2 in extreme old age.6. The ultimate tensile stress was 2·3 × 107 dyn/cm2 in young capsules and 0·7 × 107 dyn/cm2 in old ones. The maximum percentage elongation was 29 per cent and independent of age.7. The implications of these findings are discussed in relation to(a) the mechanical properties of the lens capsule;(b) the ageing of the lens capsule and basement membranes; and(c) the decrease in elasticity of the lens capsule as a cause of presbyopia.