bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic actions of individual vestibular neurones on cat neck motoneurones
Authors: Rapoport S. , Susswein A. , Uchino Y. , Wilson V. J. 
Published: December 2014

1. Unitary synaptic potentials evoked by the activity of single vestibulocollic neurones were recorded by means of spike‐triggered signal averaging in neck extensor motoneurones of decerebrate cats. Properties of the vestibulocollic neurones which produced the potentials were examined.2. Vestibulocollic neurones were first identified as projecting to the C3 grey matter by antidromic microstimulation within the C3 extensor motoneurone pool. The spontaneous or glutamate‐driven activity of the vestibulocollic neurones was then used to trigger the averaging computer. In this way ten inhibitory and two excitatory neurones were identified (20% of neurones tested).3. Action potentials in local branches of vestibulocollic neurones were usually recorded in the vicinity of motoneurones. Mean orthodromic conduction time from the foot of the extracellular spike, recorded in the vestibular nuclei, that triggered the averager was 0·72 msec. Mean synaptic delay was 0·4 msec.4. I.p.s.p.s had a mean time to peak of 0·81 msec and were readily reversed by injection of hyperpolarizing current. These data, together with the shape indices of i.p.s.p.s indicate that they are generated proximally on motoneurones.5. All vestibulocollic neurones making synapses with motoneurones were monosynaptically driven by stimulation of the ipsilateral vestibular nerve. Four out of seven tested were inhibited by stimulation of the contralateral vestibular nerve (commissural inhibition).6. Two excitatory neurones were located in Deiters' nucleus or on the Deiters'‐descending border. Inhibitory neurones were found relatively medially in the vestibular complex in the medial, descending and Deiters' nuclei.7. Vestibulocollic neurones acting on motoneurones were tested for axon branching to more caudal levels of the spinal cord with electrodes placed at C5‐7. Both of the excitatory and two out of nine inhibitory neurones branched.
Some electrical properties of the rabbit anococcygeus muscle and a comparison of the effects of inhibitory nerve stimulation in the rat and rabbit
Authors: Creed Kate E. , Gillespie J. S. 
Published: December 2014

1. Simultaneous recordings of mechanical activity and membrane potential of individual smooth muscle cells have been made in the rabbit anococcygeus muscle and the effect of field stimulation on these examined.2. In the absence of tone the mean resting membrane potential was ‐ 48 mV. In the stretched muscle spontaneous tone and rhythmic activity quite frequently appeared and this was associated with depolarization of the muscle cells.3. The response to field stimulation depended on the frequency of stimulation, the level of membrane potential and the presence of myogenic tone. The usual response to single pulses or low frequency stimulation was a hyperpolarization of up to 30 mV (mean 14±6·8 mV) after a latency of 185 msec and accompanied by muscle relaxation. Higher frequencies (over 8 Hz) produced an initial depolarization often with a spike potential and followed by hyperpolarization. The mechanical response in these instances was contraction or contraction followed by relaxation. At all frequencies rebound depolarization and an associated contraction followed the end of stimulation).4. Phentolamine (5×10−6
M) and guanethidine (10−6
M) blocked the initial depolarization and contraction but had no effect on hyperpolarization, muscle relaxation or rebound depolarization and contraction.5. The effect of field stimulation in the presence of guanethidine (4×10−5
M) was re‐examined in the rat anococcygeus. Single pulses were ineffective, repetitive stimulation produced muscle relaxation but no hyperpolarization comparable to the rabbit. Any oscillations in membrane potential were damped during field stimulation and sometimes a small hyperpolarization was produced with a maximum amplitude of 13 mV and a mean of 1·9±1·2 mV.6. The transmembrane potential at the peak of hyperpolarization in the rabbit was rarely more than ‐70 mV. Passive displacement of the membrane potential by current pulses altered the amplitude of the hyperpolarization and suggested that there was a reversal potential at between ‐80 and ‐90 mV.7. No change in input resistance could be measured during inhibitory nerve stimulation in either the rabbit or the rat but measurements based on electrotonic potentials indicated a reducation in membrane resistance, small in the rat but greater in the rabbit.8. These experiments suggest that in both species muscle relaxation is associated with an increase in ionic permeability and a move, at least in the rabbit muscle, towards an equilibrium potential of ‐80 to ‐90 mV. In view of the much smaller effect in the rat it is not clear whether this is the cause or at least the sole cause of the muscle relaxation.
Voltage sensitive calcium channels in the presynaptic terminals of a decrementally conducting photoreceptor
Authors: Ross W. N. , Stuart Ann E. 
Published: December 2014

1. Intracellular recordings were made from the presynaptic regions of the photoreceptors of the median ocellus of the giant barnacle, Balanus nubilus.2. Millivolt changes in membrane potential near the dark resting level in the terminals elicit post‐synaptic activity and consequently must be sufficient to modulate transmitter release from these endings.3. In normal saline the terminal voltage usually changes in a graded manner to increasing intensities of illumination of the cell. When the terminal region is superfused with saline containing TEA, 3‐AP or high concentrations of K, an all‐or‐none action potential can be elicited consistently by light or injected current.4. The peak value of this action potential depends on the Ca concentration in the saline. The action potential can be generated if Sr or Ba ions replace Ca, but is reduced or blocked if Mg, Co, or Mn ions are added to the saline. It is virtually unaffected by TTX or replacement of Na with TMA ions in the saline. These results suggest that Ca carries most or all of the inward current during the action potential.5. The action potential is followed by a large undershoot which can last several seconds. The amplitude and duration of the action potential and the duration of the undershoot all grow in increasing concentrations of TEA up to 400 m
M, the highest concentration tested. The threshold for the action potential decreases as the concentration of TEA is increased to 10 m
M; increasing the concentration further has no effect on the threshold. These observations suggest that TEA blocks a voltage‐sensitive potassium conductance at low concentrations but has less effect on the current responsible for the undershoot.6. Electrophysiological and pharmacological evidence suggests that the Ca channels are concentrated in the presynaptic terminals of this photoreceptor.
Formation and elimination of foreign synapses on adult salamander muscle
Authors: Dennis M. J. , Yip J. W. 
Published: December 2014

1. Synapses by flexor nerve were induced on denervated extensor muscle in adult salamander forelimbs. Excitatory potentials evoked by these ‘foreign’ synapses were at first small but increased to normal amplitude within several weeks, in the absence of correct nerve reinnervation.2. Upon return of the correct nerve the efficacy of foreign synaptic transmission began to decline. The time of initiation of this decline correlated well with the resumption of correct nerve transmission. The suppression of foreign transmission involved a reduction in mean quantal content of transmitter release.3. Suppression of foreign synapses was sufficiently thorough that most ceased transmitting entirely. Before reinnervation by the correct nerve 97% of the extensor muscle fibres received functional foreign synapses while 4‐6 months after correct nerve return only 35% of the fibres retained foreign synapses, with weak transmission.4. Two lines of evidence indicate that suppressed foreign synapses are lost from the muscle: (a) a second correct nerve lesion 6‐8 months after the initial denervation produced no significant increase in the proportion of fibres with foreign transmission and (b) four muscles which showed complete suppression of foreign transmission were bathed in medium containing horseradish peroxidase (h.r.p.) and the correct nerve was stimulated repetitively. Subsequent histochemical staining for h.r.p. and examination of synapses by electron microscopy revealed that 94% of the axon terminals had h.r.p. incorporated in vesicles. Thus at least that percentage of all identifiable synapses were from the correct nerve.5. This ability to eliminate incorrect synapses in favour of correct ones is speculated to be a general characteristic of embryonic nervous systems, which in adulthood is retained by salamanders but lost by most other animals.
Plasma adrenaline, noradrenaline and dopamine in man and different animal species
Authors: Bühler H. U. , Prada M. Da , Haefely W. , Picotti G. B. 
Published: December 2014

1. The catecholamines adrenaline (A), noradrenaline (NA) and dopamine (DA) were determined in plasma samples of man and various animal species using a highly sensitive radioenzymatic method.2. Basal values were determined under conditions producing virtually no physical or psychic stress in blood obtained through acutely inserted venous catheters in human volunteers, rabbits and cows, through chronic indwelling catheters in cats and rats, and by cubital venipuncture in trained dogs.3. Basal values (pg/ml.) for A, NA, and DA were respectively 64, 203 and 98 in man, 73, 609 and 276 in cats, 166, 392 and 216 in rabbits, 56, 152 and 91 in cows, 204, 376 and 173 in dogs, and 175, 509, and 84 in SPF rats. The NA concentrations were always higher than those of A and DA.4. Gentle handling of rats for 30 sec greatly increased the levels of all catecholamines, especially of A. Even more marked rises were observed during and up to 5 min after restraint stress.5. Blood from the trunk of decapitated rats contained about 20 times more A and 3‐4 times more DA and NA than venous blood from catheters in the absence of handling.6. Basal values of plasma catecholamines in small animals can only be obtained through indwelling catheters and in the absence of handling. Most of the previously reported values are too high and are experimental artifacts.
Properties of twitch motor units in snake costocutaneous muscle
Authors: Hammond G. R. , Ridge R. M. A. P. 
Published: December 2014

1. Single motor units of twitch muscle fibres were studied in isolated nerve—muscle preparations of m. costocutanei inferiores from grass and garter snakes. Preparations were superfused with Ringer solution at a controlled temperature of 22 °C.2. The peak and time‐to‐peak tension (contraction time) were measured for isometric twitches of forty‐seven whole muscles and 83 motor units. The sample of motor units was drawn from an estimated total population of 213‐355 twitch units. Peak tetanic tensions were also measured. The measurements were made at muscle lengths at which the twitch tension was maximal, and this length was not always the same for whole muscle and unit twitches. In fifty‐nine cases 1 and in twelve cases 2 motor units were isolated from each muscle.3. Whole muscle contraction times ranged from 22‐61 msec (mean ±
S.D. = 40·3 ± 9·8 msec) and those for units from 18‐92 msec (mean ±
S.D. = 46·9 ± 15·9 msec). The wide range for whole muscles is discussed.4. The percentage of the whole muscle tetanic tension contributed by each unit (unit size) was calculated. Contraction time was inversely related to unit size.5. Twitch—tetanus ratios were calculated and found not to be related to unit contraction time.6. The conduction velocities of axons innervating 23 motor units were calculated from latency measurements at two points along the length of the nerve. They ranged from 1·9 to 10·4 m/sec. Axon conduction velocity was inversely related to unit contraction time, and directly related to unit size.
The effect of intravenous infusion of angiotensin II on drinking in the Australian marsupial Trichosurus vulpecula
Authors: Young C. E. , McDonald I. R. 
Published: December 2014

1. When marsupial brush‐tailed possums were maintained on a normal fruit and vegetable diet with access to water ad libitum,
I.V. infusion of synthetic angiotensin II at rates of 0·035‐3·5 μg/kg. min caused short‐latency drinking in up to seven of eleven animals tested. These rates also had significant pressor effects.2. There was a positive correlation between the rate of angiotensin infusion and the percentage of tested animals which responded by drinking, as well as the amount of water drunk by such animals. The amount drunk during a second infusion 1 hr later was reduced. There was a negative correlation between the rate of infusion and the latency to drinking.3. Of six animals given access to both water and 1·8% sodium chloride solutions, five drank some saline during maintenance and control periods and all responded with short‐latency drinking of water to infusion of angiotensin II at 0·35 μg/kg. min.4. Withdrawal of 10% of blood volume, known to stimulate renin production in the possum, caused an increase in water intake in only one of six possums.5. Infusion of isoprenaline
I.V. at 20 μg/kg. min, which caused a profound fall in
B.P., had no effect on drinking by all six possums.6. It is concluded that these marsupials share with eutherian mammals responsiveness to a dipsogenic action of angiotensin II, which appears to be inhibited by preceding ingestion of water and potentiated by preceding ingestion of hypertonic saline. The physiological significance of this effect is uncertain.
Studies on neurotrophic regulation of murine skeletal muscle
Authors: Mathers D. A. , Thesleff S. 
Published: December 2014

1. A quantitative comparison was made of the effects of the paralysis caused by botulinum toxin (BoTx) type A with those of surgical denervation on the development of tetrodotoxin (TTX) resistant action potentials and of extrajunctional acetylcholine (ACh) receptors in rat and mouse skeletal muscle.2. After surgical denervation, TTX resistant action potentials were present in all fibres on the third day and their rate of rise and amount of overshoot reached peak values at the fifth day. BoTx poisoning failed, despite causing complete paralysis, to induce TTX resistant action potentials in all fibres and their average rate of rise was at all times (4‐12 days) only about half that in denervated fibres. Similarly BoTx poisoning induced a smaller increase than surgical denervation in the number of extrajunctional ACh receptors, measured as 3H‐labelled Naja naja siamensis α‐neurotoxin binding sites.3. Surgical denervation of BoTx poisoned muscles induced TTX resistant action potentials in all fibres and their rate of rise and amount of overshoot were 2‐3 times those in BoTx poisoned muscles only. Denervation also significantly increased the binding of labelled α‐neurotoxin. These effects of denervation were prevented by the administration of actinomycin D, a blocker of protein synthesis.4. Administration of the α‐neurotoxin to BoTx poisoned animals resulted in the appearance of TTX resistant action potentials in all fibres and in a significant increase in their rate of rise and overshoot.5. The results show that, despite causing complete paralysis, BoTx is less effective than surgical denervation in inducing denervatory changes in skeletal muscle. This suggests that the BoTx poisoned nerve has an influence which suppresses the appearance of denervation signs. Since the α‐neurotoxin blocked this influence remaining release of ACh, quantal or non‐quantal, may be responsible for this neurotrophic action.
Control of water content of respiring kidney slices by sodium chloride and polyethylene glycol
Authors: Robinson J. R. 
Published: December 2014

1. Cortical slices from kidneys of adult rats were incubated for 1 and 2 hr at 25 °C in oxygenated solutions containing 5 m
M‐K, 2·5 m
M‐Ca and Mg, 0·007
M‐phosphate buffer (pH 7·4) and 5 m
M‐glucose, together with 1, 2, 4 and 6% polyethylene glycol (PEG 6000) and 46, 92, 123, 154 and 231 m
M‐NaCl.2. There were no significant differences in water content between slices incubated for 1 and for 2 hr.3. The slices contained more water when the concentration either of NaCl or of PEG 6000 was lower.4. Larger increases in the contribution of NaCl to total osmolarity were required to prevent increases in water content accompanying relatively small reductions in the contribution of PEG 6000. At a physiological salt concentration around 300 m‐osmole/l., it took 10 m‐osmole/l. of additional NaCl to compensate for the loss of 1 m‐osmole/l. PEG 6000 and keep the volume of cell water normal.5. The much greater contribution, osmole for osmole, which PEG 6000 made to tonicity suggests that metabolic activity failed to make the cell membranes effectively semipermeable; they were still substantially permeable to NaCl.6. Comparison with earlier results suggested that ionic strength affected colloid osmolarity similarly in respiring and in non‐metabolizing cells; and that respiration at 25 °C somehow kept the concentration of diffusible solutes in the cells sufficiently lower than outside to compensate for a swelling effect of intracellular colloid osmolarity which, in the absence of metabolism, could be balanced by 20 m‐osmole/l. PEG 6000 added to the medium.
Two types of vagal preganglionic motoneurones projecting to the heart and lungs
Authors: McAllen R. M. , Spyer K. M. 
Published: December 2014

1. A study has been made of eighty‐four cells in the cat's nucleus ambiguus whose axons projected to the cardiac (seventy‐four) and pulmonary (ten) branches of the right vagus. Their axonal conduction velocities were all in the range of B fibres (2·8‐15·5 m/sec).2. Pulmonary branch projecting neurones were usually spontaneously active (nine out of ten) and fired in phase with inspiration. Their activity showed no pulse modulation.3. Ten cardiac branch projecting neurones had properties indistinguishable from those of pulmonary branch projecting neurones. Inspiratory‐firing cells projecting to either branch are believed to be bronchoconstrictor in function.4. The remaining sixty‐four cells that projected to the cardiac branch had properties expected of cardioinhibitory neurones. Most (fifty‐four) were silent until activated by ionophoresis of excitant amino acids. All showed an expiratory discharge when active, and of twenty‐seven tested twenty‐three showed a cardiac modulation of their discharge. When the aortic baroreceptors were denervated, the cardiac rhythm was always abolished reversibly by carotid occlusion.5. Ionophoretic activation of expiratory firing (presumed cardioinhibitory) cells slowed the heart (fifteen out of eighteen neurones tested). Excited inspiratory‐firing cells never had this effect (eleven tested).6. Both types of neurones were found in the nucleus ambiguus, but presumed cardioinhibitory cells tended to be found more caudally and ventrally than presumed bronchoconstrictor neurones.
A comparison of threshold and suprathreshold appearance of gratings with components in the low and high spatial frequency range
Authors: Campbell F. W. , Howell E. R. , Johnstone J. R. 
Published: December 2014

1. The appearance of square gratings with some of their Fourier components missing has been investigated for both threshold and suprathreshold contrasts.2. If high frequency components are removed from a square grating there is only a very small effect on the detection threshold, or suprathreshold appearance, unless the components are visible by themselves.3. If the fundamental frequency is removed from a square‐wave grating which has a spatial frequency lower than 1 cycle per degree (c/d) the contrast sensitivity is not altered. This is a generalisation of the Craik‐Cornsweet illusion. If the contrast is raised above the detection threshold the grating is indistinguishable from a square grating, unless the contrast is high enough to see the fundamental when it is presented alone.4. If the fundamental is removed from a square grating which has a spatial frequency higher than 1 c/d the contrast threshold and the appearance at all contrasts are changed. At threshold it appears as a sinusoidal grating of three times the fundamental frequency. The threshold is dictated solely by the amplitude of the third harmonic. If the contrast is further raised, so that the fifth harmonic also reaches threshold, the periodictiy of the fundamental is seen.5. Therefore, gratings of many different luminance profiles (including the Craik‐Cornsweet profile) all produce the perception of a square grating simply because those missing components which would be required in each case to produce a perfect square are by themselves undetectable. The visual system responds as though hardwired to detect square gratings and edges by means of quasi‐Fourier analysis.6. These results are analagous to the missing fundamental, or residue, effect in hearing.
Nucleoside and glucose transport in erythrocytes from new‐born lambs
Authors: Mooney Nuala A. , Young J. D. 
Published: December 2014

1. Glucose and inosine transport by erythrocytes from new‐born lambs and adult sheep were compared. Uptake of both permeants was considerably faster in the new‐born. Inosine uptake by erythrocytes from nucleoside‐permeable and impermeable lambs were not significantly different at birth. The difference between the two phenotypes was first apparent 30 days after birth.2. The post‐natal changes in glucose and inosine transport activity closely paralleled the progressive decrease in the percentage of fetal erythrocytes (i.e. cells containing fetal haemoglobin) in the circulation. Cell fractionation studies confirmed that the permeability changes were directly related to changes in the relative proportions of fetal and adult haemoglobin containing erythrocytes.3. The results demonstrate that fetal cells are highly permeable to both glucose and inosine. These cells are replaced by erythrocytes which contain adult haemoglobin and which have a much lower, but still significant, glucose permeability and either low or negligible inosine transport activity depending on the genotype of the animal.4. Inosine transport by fetal erythrocytes from both nucleoside‐permeable and impermeable animals was mediated by a nucleoside transport system which had similar properties to that responsible for nucleoside transport in adult nucleoside‐permeable cells. Glucose transport in both fetal and adult cells was highly stereo‐specific, indicating the presence of a selective transport system.5. It is suggested that the regulatory mechanism responsible for initiating the switch from fetal to adult haemoglobin synthesis may also be responsible for the changes in glucose and nucleoside transport activity.