bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of calcium and magnesium on statistical release parameters at the crayfish neuromuscular junction
Authors: Wernig A. 
Published: December 2014

1. Transmitter release at excitatory neuromuscular junctions of crayfish muscle was studied at low temperature by recording synaptic potentials with extracellular micro‐electrodes.2. Increasing the Ca concentration in the bathing solution produced an increase in the average number of quanta released per nerve stimulus (m). Increasing the Mg concentration resulted in a decrease in m.3. Statistical analysis of fluctuations in the quantal release from trial to trial, assuming binomial statistics, indicated that both the changes in m were due to changes in the average quantal release probability (p).
Renal handling of phenol red. I. A comparative study on the accumulation of phenol red and p‐aminohippurate in rabbit kidney tubules in vitro
Authors: Sheikh M. Iqbal 
Published: December 2014

1. The characteristics of renal accumulation of phenol red and p‐aminohippurate (PAH) by slices of rabbit kidney cortex suspended in an electrolyte medium have been compared.2. It has been found that at low medium concentrations the accumulation of phenol red is about 4–5 times as high as that of PAH. Furthermore, phenol red is accumulated by the renal tissue under anaerobic conditions, in contrast to PAH.3. Experiments involving incubation of slices at low temperatures and addition of various metabolic inhibitors to the medium, indicate that the anaerobic accumulation of phenol red is due to binding to cellular constituents. This conclusion is corroborated by studies on renal homogenates from which it appears that phenol red is bound predominantly to the microsomal and mitochondrial fraction.4. The aerobic accumulation of phenol red is less susceptible to inhibition by probenecid, 2,4‐dinitrophenol (DNP), and octanoate than is that of PAH. Besides, probenecid, DNP, and octanoate inhibit phenol red binding to the microsomal fraction, whereas mitochondrial binding of phenol red is unaffected by the presence of these substances.5. Fumarate and succinate affect the aerobic accumulation of phenol red and PAH to the same degree. Furthermore, fumarate, succinate, and PAH do not alter anaerobic accumulation of phenol red.6. It is concluded that probenecid, DNP, and octanoate cause more inhibition of organic anion transport than fumarate, succinate, and PAH because of lipophilic interaction with the membrane. The pronounced resistance of phenol red accumulation to inhibition by lipophilic inhibitors is probably due to the ability of the indicator dye to displace these substances from binding sites on the transporting membranes.
Bile salt and non‐bile salt components in bile affecting micellar cholesterol uptake by rat intestine in vitro
Authors: Rampone Alfred J. 
Published: December 2014

1. The uptake of micellar cholesterol was measured in sacs of the upper half of everted rat intestine. Sacs of 20 cm length were incubated 1 hr in 25 ml. phosphate buffer containing fatty acid, monoglyceride and 3H‐labelled cholesterol in micellar form with the bile salt, sodium taurocholate, as the dispersing agent.2. Sacs obtained from bile fistula rats (bile duct cannulated 48 hr previously) took up more than twice as much cholesterol as did sacs obtained from untreated control rats.3. In experiments utilizing bile‐deficient sacs increasing the sodium taurocholate concentration caused an increase in cholesterol uptake. Conversely, adding a small amount of whole bile caused a decrease in cholesterol uptake.4. The inhibitory effects of the bile were greatly enhanced if the bile was pre‐treated with cholestyramine to remove the bile salts.5. It is concluded that bile has a variable effect on intestinal cholesterol absorption depending upon its relative concentration of bile salt and a non‐bile salt component having opposite actions.6. It is suggested that the variable effect may be related to the physico‐chemical dispersion of cholesterol and that the non‐bile salt component may be lecithin.
Central projections of gastric afferent vagal inputs
Authors: Harding R. , Leek B. F. 
Published: December 2014

1. The medulla oblongata of thirteen halothane‐anaesthetized, decerebellate sheep was explored systematically with recording micro‐electrodes.2. The nervous activity recorded was designated either ‘cyclical’, if it was related to the periodic vagal outflow responsible for primary cycle movements of the reticulo‐rumen, or ‘afferent‐like’, if it was directly related to mechanical stimulation of the reticulum or the abomasum.3. Forms of mechanical stimulation were used which were known (from earlier ‘single afferent fibre’ studies) to evoke characteristic and distinguishable responses from four receptor types, i.e. reticular tension receptors, reticular epithelial receptors, abomasal tension receptors and abomasal mucosal receptors.4. Micro‐electrode penetrations were made within a zone 4 mm lateral to the mid line, 6 mm rostral to and 2·5 mm caudal to the obex. In certain regions, ‘afferent‐like activity’ was recorded, which corresponded to the discharge properties of one or more of the above receptor types.5. Units were sometimes excited or inhibited by more than one kind of receptor excitation, thus demonstrating the possibilities of a convergence of afferent projections and either a direct or a reciprocal relationship between receptor activity and central nervous ‘afferent‐like activity’.6. It is concluded that most, if not all, of the ‘afferent‐like activity’ was recorded from the vicinity of interneurones.7. There was a partially overlapping viscerotopic organization of ‘afferent‐like activity’ derived from abomasal and from reticular receptors.8. Regions showing ‘afferent‐like activity’ were located dorso‐laterally to regions showing ‘cyclical activity’ although there was some overlap between the two regions.9. ‘Afferent‐like activity’ was recorded from regions which included the dorso‐lateral part of the dorsal vagal motor nucleus, the adjacent reticular formation and the nucleus of the solitary tract between transverse planes 3 mm rostral to the obex and 1 mm caudal to the obex.10. Some of the gastric afferent vagal inputs were projected to contralateral locations via unidentified commissural connexions.
Contrasts in spatial organization of receptive fields at geniculate and retinal levels: centre surround and outer surround
Authors: Hammond P. 
Published: December 2014

1. The organization of receptive fields of retinal ganglion cells and A‐laminae cells from the dorsal lateral geniculate nucleus (LGN) of the cat are compared under identical conditions. Some aspects of the geniculate data have been given elsewhere (Hammond, 1972b).2. The receptive fields of geniculate cells consist of three zones — centre, antagonistic surround and synergistic outer surround — compared with only two for retinal cells. This result further supports the theory that the centre and surround of geniculate cell receptive fields derive from convergent, but discrete, retinal inputs.3. The surrounds of geniculate receptive fields are known to be more powerfully antagonistic on their centres than is true of retinal cells. This relationship is re‐examined.4. Unlike geniculate fields, the locus of maximum sensitivity for the receptive field surround of retinal cells is not invariant either to stimulus geometry or adaptational state.5. The latter result strongly suggests that the surround mechanism for retinal cells extends through the centre of the field. It establishes unequivocally that the overlap between receptive field centre and surround mechanisms, only marginal in geniculate, is very extensive indeed in retina.
The contractile properties of human motor units during voluntary isometric contractions
Authors: Milner‐Brown H. S. , Stein R. B. , Yemm R. 
Published: December 2014

1. The electrical activity of single motor units has been recorded from the first dorsal interosseus muscle of normal human subjects during voluntary, isometric contractions, together with the force generated by the muscle.2. By averaging the force correlated with the impulses from a single motor unit, the contraction time and twitch tension generated by that motor unit could be measured. When the rate of discharge was limited, either voluntarily or by automatic selection of intervals for analysis, the time for the tension to decline to half its maximum value (half‐relaxation time) could also be measured for some motor units.3. Under our experimental conditions the trains of impulses from different motor units in most subjects were generated quite independently as tested by (a) measuring the correlation between activity in single units and that in the whole muscle as recorded by the surface electromyogram (e.m.g.), (b) measuring the cross‐correlations between pairs of single units and (c) comparing the tension generated by stimulating single motor units with the average tension correlated in time with voluntary activity of single units in the same location.4. In one normal subject evidence of synchronization between separate motor units was obtained. Cross‐correlation studies suggested that the cause of the synchronization was the presence of substantial common excitation received by the various motor units in the muscle.5. The frequency response for the contractions of single motor units was well fitted by that for a linear, second‐order system with nearly critical damping. However, when stimulation of a few motor units was superimposed on a voluntary contraction, underdamped (oscillatory) responses were seen which were probably of reflex origin.6. The significance of these results in relation to the normal postural tremor in hand muscles is discussed.
Cumulative and persistent effects of nerve terminal depolarization on transmitter release
Authors: Cooke J. D. , Quastel D. M. J. 
Published: December 2014

1. Following focal depolarization of rat motor nerve terminals there could often be observed an ‘after‐discharge’ of m.e.p.p.s with transient frequencies of up to 1000/sec. This after‐discharge was graded with intensity and duration of the previous depolarization.2. Following pulses which were relatively short (about 1 sec) and not too large (< —100 mV local extracellular potential field) the logarithm of m.e.p.p. frequency fell exponentially. With larger or longer pulses there was a tail to the after‐discharge which could persist for several minutes.3. M.e.p.p. frequency during an after‐discharge was not inhibited appreciably by nerve terminal hyperpolarization, raised [Ca] (8 m
M) or lowered pH.4. Measured as a multiplication of spontaneous m.e.p.p. frequency after‐discharge was depressed in solution containing no Ca2+ and added 1 m
M‐MgEDTA but equal in 0·125 m
M‐Ca2+ or 2 m
M‐Sr2+ to that in 2 m
M‐Ca2+ or 8 m
M‐Ca2+.5. During an after‐discharge the multiplication of m.e.p.p. frequency by focal nerve terminal depolarization or raised K+ was reduced. This phenomenon was termed ‘uncoupling’.6. It was concluded that the after‐discharge is not caused by a persistent rise of K+ concentration in the synaptic cleft, nor by a maintained nerve terminal depolarization.7. In preparations depolarized by raised K+ m.e.p.p. frequency during a relatively small focal depolarizing pulse rose continuously, after an initial rapid rise, and after the pulse there was a tail of increased m.e.p.p. frequency. The magnitude of the rise during the pulse and the tail after it were similar on, a logarithmic basis; during both processes the logarithm of m.e.p.p. frequency usually followed (approximately) an exponential time course.8. The relative magnitude of the slow effect of depolarization, as compared with the fast effect, was increased by lowering [Ca] or increasing [Mg], and the slow effect of depolarization in contrast to the fast effect was found to exist in the presence of Ca reduced to about 10−7
M, but only during pulses. At this [Ca] there was no rapid response to depolarization. At [Ca] about 10−10
M, there was no response at all of m.e.p.p. frequency to nerve terminal depolarization.9. The results are discussed, and compared with similar data referring to ‘facilitation’ and ‘post‐tetanic potentiation’. It is concluded that these and the slow effect of depolarization represent the same phenomenon, a response of the transmitter release system which can be distinguished from the fast response in terms of ionic requirement as well as time course.
The responses of cells in the rat thalamus to mechanical movements of the whiskers
Authors: Waite Phil M. E. 
Published: December 2014

1. The responses of single cells to mechanical movements of individual whiskers have been recorded from the ventro‐basal complex of the thalamus, in rats under urethane or barbiturate anaesthesia.2. With ramp‐shaped displacements of a whisker above a critical velocity, the cells gave a short latency response of 1–5 impulses, while with sinusoidal movement (1–35 Hz) they usually responded with 1–2 impulses per cycle.3. The cells did not respond to maintained deflexions of a whisker. Small static displacements did not modify the response to a superimposed movement; larger static displacements reduced or abolished the response.4. Three‐quarters of the cells were found to be particularly sensitive to movements in one quadrant (90° or less). For any one cell, there was no obvious relationship between the most sensitive direction and the position of the whisker on the face.5. The ramp amplitude appeared to have little effect on the response. However, increases in ramp velocity decreased the response latency and, in some cells, increased the number of impulses per ramp.6. Other studies have shown that most afferent nerve fibres from whiskers give slowly adapting responses and the possible modification of these thalamic responses, by anaesthesia, is discussed.
Properties of sustained and transient ganglion cells in the cat retina
Authors: Cleland B. G. , Levick W. R. , Sanderson K. J. 
Published: December 2014

1. The functional basis for a sustained/transient classification of cat retinal ganglion cells has been strengthened by quantitative measurements of the sizes of the centre and surround components of receptive fields. Transient cells had larger surrounds than sustained; the distributions were non‐overlapping. Although the distributions of centre sizes overlapped, the transient cells had very significantly larger centres on average.2. There were characteristic differences in area‐threshold and annulus‐threshold curves and shapes of responses to brief and long flashes of light, and relative differences in the nature of surround adaptation and maintained discharge rates.3. The distinction of sustained from transient units survived over a wide range of backgrounds including the two principle reorganizations of function: relative weakening of surround components at low background; Purkinjě shift at high.4. Sustained and transient units were differentially distributed in the retina: there was an overwhelming preponderance of sustained units in the area centralis.5. It is proposed that the transient units are the so‐called multidendritedeep cells and the sustained units are the variously styled small ganglion cells.
Effects of electrogenic sodium pumping on the membrane potential of longitudinal smooth muscle from terminal ileum of guinea‐pig
Authors: Bolton T. B. 
Published: December 2014

1. The membrane potential of the separated longitudinal muscle of the guinea‐pig terminal ileum was recorded intracellularly with glass micro‐electrodes.2. In tissues kept at room temperature and then brought to 35° C for 15–30 min or about 1 hr, the fall in membrane potential upon changing to potassium‐free solution was 21.4 ± 3.5 mV and 13.4 ± 1.8 mV respectively. Ouabain (1.7 × 10−6
M) produced a fall in membrane potential of 8.1 ± 1.1 mV. Returning potassium to potassium‐free solution, or changing from ouabain‐containing to ouabain‐free solution, resulted in an increase in membrane potential which was greater than the initial fall.3. Readmitting potassium to potassium‐free solution produced an increase in membrane potential which began within 10 sec and reached a maximum within 15–30 sec. This response was reduced, abolished, or converted to a depolarization by ouabain. In chloride‐deficient (13 m
M) solution in which membrane resistance was increased, the response to readmitting potassium was increased 2½‐fold so that the membrane potential sometimes exceeded −100 mV, which was probably more negative than E
K. On the basis of these results it was assumed that the response to readmitting potassium was due to the electrogenic activity of the sodium pump.4. The response to briefly readmitting a fixed concentration of potassium increased during the first 30 min in potassium‐free solution. This increase was not due to an increase in membrane resistance as this fell with time in potassium‐free solution. It was suggested that the increase in the response resulted from the progressive rise in internal sodium concentration which is known to occur in smooth muscle in potassium‐free solution.5. Increasing the concentration of potassium over the range ∼ 0.1–20 m
M, increased the size of the electrogenic potential observed upon readmitting potassium to potassium‐free solution. There was a fall in membrane resistance upon readmitting potassium (0.6, 5.9, or 20 m
M) which was greater the larger the concentration of potassium. When allowance was made for the fall in membrane resistance, the dependency of the electrogenic response upon the concentration of potassium over the range 0.6–20 m
M was much increased.6. The results indicate that the rate of electrogenic sodium pumping in this tissue is increased by increasing the external potassium concentration, and probably by increasing the internal sodium concentration. It was suggested that a rise in the latter could sensitize the pump to an increase in the former.
Scotopic and photopic components of the rat electroretinogram
Authors: Green Daniel G. 
Published: December 2014

1. Increment thresholds were measured on the albino rat retina using the e.r.g. as an indicator of visual sensitivity.2. Light adaptation produces a change in b‐wave spectral sensitivity independently of whether brief or steady adapting backgrounds are used. This shows that the changed spectral sensitivity is not directly associated with the bleaching of visual pigment.3. Light adaptation does not appear to alter the spectral sensitivity of the ordinary a‐wave. Consequently, after light adaptation a‐ and b‐waves have different spectral sensitivities.4. B‐wave increments determined with a blue test stimulus on a red adaptive background show rod saturation. Background levels which saturate the rods cause the a‐wave mechanism to cease responding to incremental stimuli.5. A background intense enough to saturate the rods evokes a maximum a‐wave response. If a light is sufficiently bright to saturate the rods then the isolated a‐wave fails to signal the termination of the stimulus.6. Scotopically equated blue and orange stimuli produce equal early receptor potentials.
Failure of thermoregulation in the cold during hypoglycaemia induced by exercise and ethanol
Authors: Haight J. S. J. , Keatinge W. R. 
Published: December 2014

1. After young men had exercised for approximately 2 hr at 70% maximum O2 uptake, and taken 28 ml. ethanol by mouth, their mean blood glucose fell to 2·17 m
M. It fell further to 1·77 m
M during a 30 min exposure to air at 14·5° C. Plasma lactate, glycerol, β‐hydroxybutyrate and free fatty acid concentrations increased.2. Rectal temperature fell to reach a mean level of 34·49° C by the end of the cold exposure; oesophageal temperature fell to as low as 33·00° C in one case.3. Virtually no increase in metabolic rate and no visible shivering occurred during the cold exposure.4. Administration of glucose (mean 60·4 g) prevented the falls in temperature, and restored metabolic response to the cold to the size found in control experiments without exercise or ethanol.5. Neither exercise without ethanol or ethanol without exercise significantly lowered the blood glucose or impaired the maintenance of body temperature in the cold.6. One obese subject showed almost as great a fall in blood glucose and depression of metabolic response to cold as the thinner men, but no fall in body temperature.
Edge detectors in human vision
Authors: Shapley R. M. , Tolhurst D. J. 
Published: December 2014

1. The spatial properties of edge detectors were measured psychophysically with the technique of subthreshold addition. Subthreshold patterns used to add to an edge were lines, sine gratings, Gaussian edges, and ramps.2. The sensitivity profile, determined from experiments on subthreshold addition of lines to an edge was an antisymmetric function, with peak sensitivity approximately ± 1·5′ from its midpoint. Its total extent was about ± 6′.3. The spatial frequency response of edge detectors was measured in experiments on subthreshold addition of sine gratings to an edge. The spatial frequency response was peaked at about 3 c/deg, and was broadly tuned in frequency. It was approximately equal to the Fourier transform of the sensitivity profile, implying linearity of edge detectors.4. The visibility of Gaussian edges and ramps could be explained largely in terms of the activation of edge detector neurones.5. The role of edge detectors in perception, in creating apparent brightness, and as an explanation of contour illusions, is discussed.
The organization of primary afferent depolarization in the isolated spinal cord of the frog
Authors: Carpenter D. O. , Rudomin P. 
Published: December 2014

1. The organization of primary afferent depolarization (PAD) produced by excitation of peripheral sensory and motor nerves was studied in the frog cord isolated with hind limb nerves.2. Dorsal root potentials from sensory fibres (DR‐DRPs) were evoked on stimulation of most sensory nerves, but were largest from cutaneous, joint and flexor muscle afferents. With single shock stimulation the largest cutaneous and joint afferent fibres gave DR‐DRPs, but potentials from muscle nerves resulted from activation of sensory fibres with thresholds to electrical stimulation higher than 1·2–1·5 times the threshold of the most excitable fibres in the nerve. This suggests that PAD from muscle afferents is probably due to excitation of extrafusal receptors.3. Dorsal root potentials produced by antidromic activation of motor fibres (VR‐DRPs) were larger from extensor muscles and smaller or absent from flexor muscles. The VR‐DRPs were produced by activation of the lowest threshold motor fibres.4. Three types of interactions were found between test and conditioning DRPs from the same or different nerves. With maximal responses occlusion was usually pronounced. At submaximal levels linear summation occurred. Near threshold the conditioning stimulus frequently resulted in a large facilitation of the test DRP. All three types of interactions were found with two DR‐DRPs, two VR‐DRPs or one DR‐DRP and one VR‐DRP.5. The excitability of sensory nerve terminals from most peripheral nerves was increased during the DR‐DRP. The magnitude of the excitability increase varied roughly with the magnitude of the DR‐DRP evoked by the conditioning stimulus.6. There was a marked excitability increase of cutaneous and extensor muscle afferent terminals during the VR‐DRP. Flexor muscle afferent terminals often showed no excitability changes to ventral root stimulation. In those experiments where afferent terminals from flexor muscles did show an excitability increase, the effects were smaller than those of cutaneous and extensor terminals.7. The VR‐DRPs appear to reflect activity of a negative feed‐back loop from extensor motoneurones on to sensory fibres from cutaneous and extensor muscles. This system may have a role in modulating the ballistic movement of the frog. DR‐DRPs, on the contrary, are widespread in origin and distribution. PAD from sensory fibres may function to sharpen contrast between incoming afferent information.