bluuebunny/crossref_metadata_2025 huggingface dataset:
The orientation specificity of two visual after‐effects
Authors: Blakemore Colin , Nachmias Jacob
Published: December 2014

1. Inspection of a high‐contrast adapting grating produces two visual after‐effects: (a) the contrast threshold is raised for test gratings of similar spatial frequency to that of the adapting pattern and (b) the apparent spatial frequency of test gratings shifts away from that of the adapting grating—higher frequencies seem higher and lower ones lower than they really are.

2. Both after‐effects are orientation‐specific. A horizontal adapting grating influences neither the threshold nor the apparent spatial frequency of vertical test gratings.

3. The magnitude of the two after‐effects was measured with vertical test gratings as a function of (a) tilt of a high‐contrast adapting grating and (b) contrast of a vertical adapting grating.

4. At all frequencies of the test grating, the decline of both after‐effects produced by an increase in tilt of approximately 6¾° could be matched by a reduction in contrast by a factor of 2.

5. We take this as evidence for a common neural origin for these two visual phenomena.
Cholinergic regulation of hepatic tyrosine transaminase activity
Authors: Black Ira B. , Reis Donald J.
Published: December 2014

1. The cholinergic agent carbachol (0·5 mg/kg) produces within 2 hr a two‐ to threefold increase in the activity of hepatic tyrosine transaminase in the adrenalectomized fasted rat.

2. The carbachol‐evoked rise in enzyme activity is prevented by pretreatment with atropine.

3. Cycloheximide, an inhibitor of protein synthesis, prevents the carbachol‐evoked rise of enzyme activity; actinomycin D, an inhibitor of RNA synthesis, partially reduces it.

4. Atropine or unilateral (right or left) vagotomy suppresses the daily rhythm of tyrosine transaminase by attenuating the normal evening peak but not the normal lower daily levels of the enzyme.

5. Electrical stimulation of the right vagus results in a significant elevation of tyrosine transaminase activity within 2 hr.

6. The observations suggest that activity of vagal cholinergic nerves produces an RNA‐dependent induction of hepatic tyrosine transaminase through a process requiring cholinergic‐receptor stimulation. Intermittent activity of this vagal cholinergic system may contribute to the regulation of the daily rhythm in this enzyme.
Evidence for central timing of rhythmical mastication
Authors: Dellow P. G. , Lund J. P.
Published: December 2014

1. The origin of the co‐ordination and rhythm of mastication provoked by electrical stimulation of the putamen and corticobulbar pathways was studied in the rabbit.

2. Bursts of activity were recorded from the mandibular and hypoglossal nerves and the hypoglossal nucleus, which were in phase with the observed masticatory movements. Discharges occurred alternately in nerves to jaw‐opening and jaw‐closing muscles.

3. The rate of burst discharges was not altered by paralysis, or by large variations in the stimulation frequency.

4. Regularly recurring bursts of activity continued to occur in the hypoglossal nucleus in response to random frequency stimulation after severing branchial nerves, cervical nerves and the spinal cord of paralysed rabbits.

5. Mechanical deformation of the brain of vascular or respiratory origin was discounted as the origin of the rhythm.

6. It is concluded that mastication is controlled by a brain‐stem pattern generator which can be activated by adequate inputs from certain higher centres and, as concluded in other studies, from the oral cavity itself.
Cardiovascular responses to tilting in tetraplegic man
Authors: Corbett J. L. , Frankel H. L. , Harris P. J.
Published: December 2014

1. A study has been made of the effect of head‐up tilt on blood pressure, heart rate, forearm blood flow and occluded vein pressure in the hand and foot in non‐bedridden patients with chronic, closed, complete, localized traumatic transection of the cervical spinal cord.

2. In typical responses the blood pressure fell and the heart rate rose progressively for about 2 min, tending to plateau thereafter. The average falls in mean blood pressure for tilts of +30, +45 and +60° were from 68 to 44, 74 to 36 and 70 to 44 mm Hg respectively, and the corresponding heart rate increases were from 67 to 85, 62 to 97 and 62 to 103 beats/min respectively. One patient lost consciousness when his blood pressure was 29/19 mm Hg and one other patient experienced symptoms suggesting cerebral ischaemia.

3. Following the return to horizontal, the blood pressure and heart rate usually returned to their previous values within 1 min and the blood pressure tended to overshoot slightly in the following few minutes. No immediate blood pressure overshoot occurred after the tilt except in association with a spasm of skeletal muscles.

4. There was consistently a decrease in forearm blood flow, sometimes to unrecordably low levels and a venoconstriction with postural change and it is argued that these changes are the result of spinal cardiovascular reflexes to peripheral vessels. Following the return to the horizontal position, there was occasionally a large immediate increase in forearm blood flow.

5. Following the intravenous administration of 3 mg atropine on two occasions, head‐up tilting produced further small heart rate increases.

6. Spasms of skeletal muscle occur frequently in these patients and greatly modify the effects of postural stimuli. Bladder percussion also modifies the normal response.
Relative contribution from different nerves to recurrent depression of Ia IPSPs in motoneurones
Authors: Hultborn H. , Jankowska Elẓbieta , Lindström S.
Published: December 2014

1. The pattern of depression of Ia IPSPs by volleys in recurrent motor axon collaterals was investigated in motoneurones supplying hind‐limb muscles in the cat. The test IPSPs were evoked by stimulation of dorsal roots and the conditioning antidromic volleys by stimulation of motor fibres in different peripheral muscle nerves.

2. In all motor nuclei investigated the strongest depression of Ia IPSPs is evoked from motor fibres to muscles whose Ia afferents produce the IPSPs. For example, the Ia IPSP from the knee extensor recorded in motoneurones to a knee flexor is most effectively depressed by antidromic stimulation of motor fibres to the knee extensor.

3. The origin of recurrent inhibition of α‐motoneurones and of Ia inhibitory interneurones with the same Ia input display a striking similarity. This suggests that the same population of Renshaw cells mediates effects to motoneurones and to Ia inhibitory interneurones.

4. The functional significance of impulses in motor axon collaterals was discussed and it was suggested that they have an important role in the control of the excitatory as well as inhibitory Ia actions to motoneurones. The recurrent inhibition may limit the Ia effects to excitation of homonymous motoneurones, which would provide optimal conditions for control of individual muscles via the γ‐loop.
The significance of changes in the temperature of the skin and body core of the chicken in the regulation of heat loss
Authors: Richards S. A.
Published: December 2014

1. The relationship between the temperatures of the hypothalamus, colon and skin and the control of heat loss mechanisms at ambient temperatures from 20 to 40° C has been studied in unanaesthetized chickens.

2. The temperatures of the core and feathered skin varied by not more than 5° C throughout the full range of ambient temperature but the comb, shank and toe varied by up to 20° C and exhibited wide fluctuations in constant environmental conditions.

3. At an ambient temperature of 26–27° C, the fluctuations ceased at all of the naked skin sites and there was evidence of a concurrent decrease in the tissue insulation of the extremities. No such change could be detected in the feathered skin.

4. Analysis of the various body temperatures suggested that the onset of thermal panting was consistently related to the increment in hypothalamic temperature and that this relationship was influenced both by the peripheral and extra‐cranial deep body temperatures.
The paramedian reticular nucleus: a site of inhibitory interaction between projections from fastigial nucleus and carotid sinus nerve acting on blood pressure
Authors: Miura Mitsuhiko , Reis Donald J.
Published: December 2014

1. The interaction between the pressor response to electrical stimulation of the fastigial nucleus (FN), the fastigial pressor response (FPR), and the depressor response to electrical stimulation of the carotid sinus nerve (CSN) was examined in paralysed anaesthetized cats.

2. Blood pressure responses evoked by electrical stimulation of the FN and the CSN were mutually inhibitory and summed algebraically.

3. The FPR was augmented after denervation of buffer nerves. Lesions of the FN did not alter the depressor response to stimulation of the CSN.

4. Bilateral electrolytic lesions of the paramedian reticular nucleus abolished both the FPR and the CSN depressor response without altering base line pressure.

5. With micro‐electrode recording neurones were discovered within the paramedian reticular nucleus which responded to electrical stimulation of the FN or the CSN. These neurones were polysynaptically excited by stimulation of either the FN or the CSN but rarely from both, and could be further subdivided into cells responding with either a single spike or a burst discharge.

6. The interaction between the FN and the CSN projections to the paramedian reticular nucleus was examined by conditioning‐test studies. Eleven per cent of FN‐ and CSN‐units were inhibited by conditioning stimulation of the heteronymous input. The interaction was exclusively inhibitory and observed only in units with latencies > 4 msec and having burst responses. The latency for inhibition was > 20 msec, peaked around 100 msec and lasted up to 300 msec.

7. We conclude that the FRP is buffered by baroreceptors and that there is a mutually inhibitory interaction between projections from the FN and the CSN acting on sympathetic vasomotor neurones. The paramedian reticular nucleus appears to be an important site for the interaction.

8. The findings support the view that interneurones mediating pressor and depressor responses are intermixed within the medial reticular formation of the medulla.
The effect of prolonged depolarization on synaptic transfer in the stellate ganglion of the squid
Authors: Katz B. , Miledi R.
Published: December 2014

1. Depolarization of the giant axon terminal of the squid causes local calcium influx which gives rise to transmitter release and post‐synaptic response, and which under certain experimental conditions leads to a regenerative action potential in the presynaptic terminal itself.

2. There has been conflicting evidence in the literature on the question whether the calcium permeability change in the terminal is rapidly inactivated, or whether it can persist with little diminution for hundreds of milliseconds during a depolarizing voltage step.

3. Results are presented which show that there is little ‘calcium inactivation’, even when very large depolarizing steps are imposed on the terminal and maintained for periods of 1‐2 sec.

4. Contrary indications are examined and found to be attributable to an increase of potassium conductance, rather than direct inactivation of calcium conductance.
Factors in cerebrospinal fluid from goats that affect sleep and activity in rats*
Authors: Fencl V. , Koski G. , Pappenheimer J. R.
Published: December 2014

1. Intraventricular infusion in the rat of 0·1 ml. cerebrospinal fluid (c.s.f.) from sleep‐deprived goats increases the duration of sleep (measured by e.e.g.) and decreases locomotor activity (measured photo‐electrically) for at least 6 hr subsequent to the infusion. Subarachnoid infusions are ineffective.

2. C.s.f. from control and sleep‐deprived goats was fractionated by ultrafiltration through molecular sieves. The sleep‐promoting Factor S is found in the low molecular weight fraction (mol. wt. < 500) of c.s.f. from sleep‐deprived but not from control goats.

3. The concentration of Factor S in c.s.f. increases progressively during the first 48 hr of sleep deprivation.

4. The sleep promoting effects of Factor S cannot be duplicated by serotonin, 4‐OH‐butyrate, butyrolactone, GABA (γ‐amino butyric acid), glutamic acid or 3′,5′‐cyclic AMP when these substances are added to control fluids in concentrations up to 10 times greater than those found in normal c.s.f.

5. Intraventricular or subarchnoid infusion in the rat of 0·1 ml. proteinfree c.s.f. containing molecules in the mol. wt. range of 500–10,000 at 10–30 × normal concentration causes hyperactivity which persists for several days and nights following the infusion. The excitatory material, probably a peptide, is present in c.s.f. from both control and sleep‐deprived goats.

6. The properties of Factor S suggest that it may play a role in the normal regulation of sleep and wakefulness.
The hypothalamic neurosecretory pathways for the release of oxytocin and vasopressin in the cat
Authors: Bisset G. W. , Clark Barbara J. , Errington M. L.
Published: December 2014

1. The neurones of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) were stimulated electrically in lactating cats under chloralose anaesthesia. Milk‐ejection responses were used to monitor the release of oxytocin and vasopressin and both hormones were assayed in samples of blood collected during stimulation. The position of the tip of the stimulating electrode was confirmed from brain sections stained selectively for cystine‐rich neurosecretory material.

2. A previous finding that stimulation of the SON in the cat releases vasopressin without oxytocin was confirmed.

3. Stimulation of the PVN caused both hormones to be released. The ratio of their concentrations in blood was variable; this suggests release from separate neurones.

4. Both hormones were also released on stimulation of the median eminence but not of the zone lying vertically between this structure and the PVN. No neurosecretory material was detected in this zone. These findings argue against the existence of a direct or medial paraventriculo‐hypophysial pathway running downwards along the wall of the third ventricle.

5. Study of sections from unstimulated brains confirmed that the tractus paraventricularis cinereus of Greving which runs ventro‐laterally from the PVN towards the SON, represents the principal efferent pathway for neurosecretory fibres from the PVN.

6. The results are discussed in relation to the problem of the independent release of oxytocin and vasopressin in response to physiological stimulation of the neurohypophysis.
Spontaneous and evoked activity of neurones in the somatosensory thalamus of the waking cat
Authors: Baker M. A.
Published: December 2014

1. Adult cats were prepared for chronic micro‐electrode recording in the nucleus ventralis posterolateralis (VPL) of the ventrobasal complex (VB) of the thalamus. Spontaneous and evoked activity of single neurones was recorded extracellularly while the animal stood in a hammock. The behavioural state of the animal and the electroencephalogram (e.e.g.) were observed and recorded.

2. Three hundred and twenty‐five single neurones sensitive to movement of hairs, depression of skin or movement of claws were isolated and studied. Peripheral receptive fields were on the contralateral surface of the body. They remained constant in size and location over long periods of time and despite changes in the behavioural state of the animal. Most of the receptive fields covered a cutaneous area at least as large as an entire paw and many covered an entire limb and extended on to the trunk. These fields are larger than those described by other investigators using natural stimulation in anaesthetized or paralysed animals.

3. Moving hairs or touching skin in the peripheral receptive field elicited a burst of spikes at frequencies between 100 and 150/sec. Repeated stimulation did not result in obvious alteration or habituation of the response. There was no apparent change in responsiveness of neurones to peripheral stimulation when the animal was asleep.

4. Except for claw‐sensitive units, all neurones were active in the absence of intentional stimulation of the receptive field. When the animals were awake, VPL neurones fired more regularly than during sleeping. In slow sleep, with e.e.g. slow waves and spindles, firing patterns were characterized by the presence of more high‐frequency bursts of spikes and more long interspike intervals than in waking. Claw‐sensitive units, silent during waking, fired in bursts during sleep. When small doses of barbiturate were injected intravenously while recording the activity of neurones, the firing pattern changed to one in which all of the activity occurred in the form of high‐frequency bursts. Interburst intervals were variable.

5. The level of spontaneous activity in VB in conscious cats is greater than in sensory and sensorimotor cortex to which it projects. The pronounced effect of behavioural state on spontaneous activity of these neurones suggests that the background activity in somatosensory systems may play some role in the processing of afferent input.
Fever produced by prostaglandin E1
Authors: Feldberg W. , Saxena P. N.
Published: December 2014

Prostaglandin E1 (PGE1) produces a rise in rectal temperature when injected into the cerebral ventricles of unanaesthetized cats, rabbits and rats. An effect is obtained with as little as 20, and sometimes even with 10 ng.
Analysis of the potential‐dependent changes in optical retardation in the squid giant axon
Authors: Cohen L. B. , Hille B. , Keynes R. D. , Landowne D. , Rojas E.
Published: December 2014

1. An analysis has been made of the change in optical retradation of the membrane elicited by the application of voltage—clamp pulses in squid giant axons.

2. The retardation response consists of three separate voltage—dependent components. For freshly mounted axons, defined as being in state 1, hyperpolarizing pulses give a rapid increase in the light intensity measured with crossed polarizers which has been termed the fast phase. This is followed by a rather slow return towards the base line termed the rebound. On treatment of the axon with certain agents that include tetrodotoxin, high calcium and terbium, the rebound disappears and the fast phase slows down, increases in size, and has a new slow component added to it. This transition from state 1 to a second state, 2, appears to be irreversible.

3. In state 1, the time constant of the fast phase is 20–40 μsec at 13° C; it has a very large negative temperature coefficient (Q10 = Ca.⅛). The size of the retardation change is independent of temperature and varies as the square of the applied voltage, but the voltage—retardation curve is symmetrical about a point well beyond zero membrane potential, at an internal potential of around + 70 mV. In state 2, the time constant is about five times larger, and varies much less markedly with temperature; the apex of the voltage—retardation curve is shifted to + 200 mV.

4. The rebound has a time constant of the order of 20 msec at 13° C. A 10° rise in temperature more than halves the time constant and roughly doubles the amplitude of the rebound. The voltage dependence of the rebound differed from that of the fast phase.

5. The slow component of state 2 has a time constant of about 2 msec which does not change noticeably between 10 and 25° C. The size of this component seems to be linearly dependent on the applied voltage, rather than obeying a square law.

6. A tenfold increase in external calcium concentration had no discernible effect on the fast and slow phases, but reversibly reduced the amplitude of the rebound nearly to half.

7. In experiments on perfused axons, the retardation response was not measurably altered by any of the modifications made to the composition of the perfusing fluid.

8. There was some indication of the possible existence of a small current‐ or conductance‐dependent component of the retardation response.

9. These phenomena seem likely to originate either from molecular relaxation processes analogous with the Kerr effect, or from changes in membrane thickness under the influence of the pressure exerted by the electric field. However, the specific molecules involved in the retardation response cannot yet be identified.
The effect of different ionic levels on the electrical response of toad skin to noradrenaline
Authors: House C. R.
Published: December 2014

1. After the addition of noradrenaline (final concentration 4 × 10−5
M) to the inner medium of isolated toad skins, they underwent a depolarization (inner surface becoming less positive) followed by a hyperpolarization.

2. The dependence of the minimal and maximal levels of the depolarizing and hyperpolarizing phases of the response upon the external concentrations of sodium and chloride ions was examined.

3. The experimental data were considered to support the view that the hyperpolarization was generated by an increase in the sodium to chloride permeability ratio for the outer barrier of the skin and that the depolarization resulted from a transient increase in the conductance of transient shunt pathways in the skin.

4. When the external sodium and chloride ions were replaced by magnesium (or potassium) and sulphate ions, noradrenaline initiated a transient hyperpolarization. During this hyperpolarizing response the time course of the change in the skin's conductance resembled that of the skin potential. The polarity of the response was changed by reversing the chloride concentration gradient across the skin.

5. The dependence of the maximal level of the hyperpolarizing response upon the internal potassium concentration was examined.

6. It was concluded that the hyperpolarizing response was generated partially by an increase in the potassium to chloride permeability ratio for the inner barrier of the skin and predominantly by the movement of chloride and accompanying cations through a transient shunt pathway, probably the active glands.
Effects on body temperature of prostaglandins of the A, E and F series on injection into the third ventricle of unanaesthetized cats and rabbits
Authors: Milton A. S. , Wendlandt Sabine
Published: December 2014

1. Prostaglandins were injected into the third ventricle of unanaesthetized cats and rabbits whilst rectal temperature was recorded.

2. In cats prostaglandin E1 and E2 (PGE1 and PGE2) produced hyperthermia which mostly began within a minute of injection and lasted 1 or more hours. With PGE1 the hyperthermia was shown to be dose dependent between 10 ng and 10 μg (2·8 × 10μ11 and 2·8 × 10−8
M). The hyperthermia was associated with vigorous shivering, skin vasoconstriction and piloerection. In several experiments a secondary rise in temperature occurred a few hours after the injection but such an effect was sometimes observed with control injections of 0·9% NaCl solution as well.

3. None of the other prostaglandins (A1, F1α, F2α) examined in cats had an immediate or strong effect on temperature comparable to the hyperthermia produced by PGE1 and PGE2.

4. In rabbits PGE1 (2 μg) also caused hyperthermia which began shortly after the injection and lasted for hours. PGF2α and PGA1, did not affect temperature.

5. In cats it was seen that an intraperitoneal injection of 4‐acetamidophenol (paracetamol 50 mg/kg) did not affect the initial strong hyperthermia produced by PGE1 and PGE2 but abolished the secondary rise.

6. The possibility is discussed that PGE1 plays a role as a central transmitter or modulator in temperature regulation.
The permeation of several materials into the fluids of the rabbit's brain
Authors: Davson Hugh , Welch Keasley
Published: December 2014

1. 24Na, 36Cl and 35S thiourea were infused
I.V. in rabbits according to schedules designed to yield approximately level activity in plasma for periods up to 5 hr. Cerebrospinal fluid was sampled before ending the experiment by decapitation and the radioactivities in cerebrospinal fluid and in homogenized brain were compared in each case to a time weighted mean value for plasma.

2. The results are considered in terms of a simplified model which specifically acknowledges the continuity of the extracellular and cerebrospinal fluids and thus the coupling between processes which occur at the interfaces bordering those fluids.

3. From the rate constants for exchange across the blood—brain interface that were necessary for simulation of the observed behaviours, permeability coefficients for that interface were estimated for the materials studied and, from experiments of others, for 42K.
Depolarization of the tooth pulp afferent terminals in the brain stem of the cat
Authors: Davies W. I. R. , Scott D. , Vesterstrøm K. , Vyklický L.
Published: December 2014

1. Tooth pulp afferent fibres belonging exclusively to the Aδ group were stimulated bi‐polarly with electrical pulses applied to the dentine and the central effects of the stimulation were examined in the nucleus of the spinal trigeminal complex of anaesthetized cats.

2. Field potentials evoked by single pulses to the upper or lower canine tooth pulp were explored over the nucleus of the spinal trigeminal tract in the region 5 mm caudally to the obex up to 8·5 mm rostrally to the obex. They were found to be restricted to a region of 5·5–8·5 mm rostrally to the obex, 4‐5 mm laterally from the mid line, with a maximum amplitude at a depth of 5 ± 0·5 mm.

3. Antidromic action potentials were recorded from the tooth pulp afferents. The stimulating micro‐electrode was inserted in the region of the medulla from which distinct field potentials could be recorded by orthodromic stimulation.

4. Excitability of the central terminals of the tooth pulp primary afferents was increased when the test stimulus was preceded either by a conditioning volley in low threshold afferent fibres of the infraorbital nerve or in Aδ fibres of another tooth.

5. Single pulses applied to the afferent fibres of the tooth pulp produced changes in the excitability of central terminals of the fast conducting afferent fibres of the infraorbital nerve.

6. The greatly increased excitability of central terminals of tooth pulp primary afferent fibres was accompanied by a small decrease in their synaptic efficiency as estimated from the changes of the post‐synaptic component of the field potential evoked by their stimulation.

7. It is concluded that an analogous presynaptic control mechanism is present at the central terminals of the tooth pulp primary afferent fibres as is known for the fast conducting cutaneous system. But a difference in the specifity of the action from this afferent system is suggested. While activity from Aα fibres is very effective in evoking primary afferent depolarization at both fast conducting trigeminal fibres and slow conducting Aδ system, the Aδ fibre activity is effective only at the latter, and not at the former.
The action of carbon dioxide on synaptic transmission in the cuneate nucleus
Authors: Morris Mary E.
Published: December 2014

1. The excitability of synaptic structures in the cuneate nucleus was studied in eighteen decerebrate, unanaesthetized cats during acute changes in inspired PCO2.

2. Micro‐electrode stimulation in the caudal half of the cuneate nucleus evoked antidromic and orthodromic responses which were recorded simultaneously from a forelimb nerve and from the medial lemniscus at the transected mid‐brain surface.

3. Increases in the concentration of inspired CO2 (2–20%) progressively decreased the direct excitability of both the afferent fibre terminals (reflected in the antidromic potentials) and the cuneate relay neurones (reflected in the α wave of the orthodromic lemniscal response). Synaptically mediated responses, recorded as the β component of the lemniscal potentials, were also depressed.

4. The relation between input and output at the cuneate was determined by plotting antidromic against trans‐synaptic (β lemniscal) responses for different intensities of stimulation. The mean slope for logarithmic values of control potential amplitudes was 1·17 (±
S.E. 0·13). It therefore appears that the transfer function for the cuneate is linear over a wide range.

5. In the majority of experiments the input—output relation was unchanged or increased by raising PCO2. It was concluded that the efficiency of synaptic transmission and release of transmitter appeared to be well maintained or possibly increased at individual active synapses during hypercarbia.

6. The depressant action of CO2 on afferent transmission can therefore be attributed largely to a block of impulse conduction in the primary afferent fibres.
Myoepithelial cell activation in the submaxillary salivary gland
Authors: Darke A. C. , Smaje L. H.
Published: December 2014

1. Pressure in the duct of the submaxillary gland of the cat was recorded under chloralose anaesthesia. Single pulses applied to the parasympathetic nerve caused a pressure rise.

2. Salivation was just detectable in about half of the animals when an open tube was connected to the duct and single pulses applied to the nerve. Applying a back pressure of 1‐4 mm Hg renders the duct less distensible and under these circumstances secretion of 1‐3 μl. fluid was always seen. An alternative method of detecting salivation based on the pressure record itself also showed that salivation occurred in response to the stimulus and that salivation was responsible for the pressure rise observed.

3. Single pulses applied to the cervical sympathetic trunk produced a small fall in pressure. In a short series of pulses this was followed by a slow rise which then slowly decayed. It was tentatively concluded that the initial fall was secondary to the accompanying vasoconstriction but the subsequent effects were due to myoepithelial cell contraction.

4. Close arterial injection of bradykinin caused a pressure rise which could best be explained by myoepithelial cell contraction.

5. It is concluded that the myoepithelial cells of the submaxillary gland of the cat do not receive a parasympathetic motor innervation but it is probable that they are innervated by the sympathetic nervous system and contract in the presence of bradykinin.
The detection of gratings in narrow‐band visual noise*
Authors: Carter Barbara E. , Henning G. Bruce
Published: December 2014

1. The detectability of sinusoidal gratings comprised of either one or many cycles was measured in veiling luminances the spatial frequencies of which were either narrow‐ or broad‐band.

2. In narrow‐band noise, the single‐cycle grating was detected with approximately 0·6 log units less contrast than the many‐cycle grating. On the other hand when both broad‐band and narrow‐band noise were present, there was no measurable difference in the detectability of the two types of grating.

3. The results are interpreted as supporting the hypothesis of Campbell & Robson (1968) that spatially varying luminance patterns are processed by mechanisms selectively sensitive to limited ranges of spatial frequencies.
Chloride conductance in normal and myotonic muscle fibres and the action of monocarboxylic aromatic acids
Authors: Bryant S. H. , Morales-Aguilera A.
Published: December 2014

1. Cable parameters, component conductances, excitability and membrane potentials in isolated external intercostal fibre bundles at 38° C from normal and myotonic goats were measured in normal and low‐chloride Ringer, and in the presence of monocarboxylic aromatic acids that produce myotonic responses in mammalian muscle.

2. The mean resting chloride conductance in μmho/cm2 of myotonic fibres (range 0–147) was significantly less than that of normal fibres (range 376–951). The mean resting potassium conductance was higher in myotonic fibres (range 123–285) than in normal fibres (range 44–132). Potassium conductance increased about 10 μmho/cm2 per mV increase in absolute resting potential.

3. In normal fibres in normal Ringer 3‐chloro‐2,5,6‐trimethylbenzoic acid; 5,6‐dihydro‐5,5‐dimethyl‐7‐carboxybenz[c]acridine; phenanthrene‐9‐carboxylic acid; and anthracene‐9‐carboxylic acid at 10−5‐10−4
M decreased membrane conductance without consistently changing diameter or capacitance. In low‐chloride Ringer 3‐chloro‐2,5,6‐trimethylbenzoic acid (5 × 10−5
M) increased potassium conductance in myotonic and normal fibres. It is concluded that these compounds block chloride conductance.

4. The carboxylic acids produced myotonia in normal fibres similar to that in untreated myotonic fibres.

5. Anthracene‐9‐carboxylic acid intravenously (8 mg/kg) in normal goats produced acutely a condition resembling myotonia congenita. The carboxylic acids produced no myotonic effects in frog muscle.
Stimulation of tubero‐infundibular dopamine neurones and gonadotrophin secretion
Authors: Keller P. J. , Lichtensteiger W.
Published: December 2014

1. In ovariectomized rats pre‐treated with oestrogen and progesterone, the intensity of the catecholamine fluorescence was determined by micro‐fluorimetry in the cell bodies of the tubero‐infundibular dopamine neurones (situated in the arcuate and periventricular hypothalamic nuclei). The concentrations of follicle‐stimulating (FSH) and luteinizing hormone (LH) in serum and pituitary were estimated by bio‐assay.

2. The characteristic changes in fluorescence intensity of the tuberal catecholamine‐containing nerve cell group that are induced by unilateral intermittent electrical stimulation of the arcuate nucleus or of the medial preoptic area during 5‐60 min, were accompanied by a marked rise in serum LH concentration. With arcuate stimulation, the rise in serum LH paralleled the increase in the fluorescence intensity of the nerve cell bodies, whereas with preoptic stimulation, the initial increase in cellular fluorescence intensity preceded the rise in serum LH. Preoptic stimulation also caused a moderate fall in pituitary LH which was simultaneous with the increase in fluorescence intensity. No systematic changes in FSH concentration were observed during the time interval studied.

3. Pre‐treatment with the tyrosine hydroxylase inhibitor α‐methyltyrosine completely blocked the increase in fluorescence intensity caused by electrical stimulation of the arcuate nucleus but did not prevent the rise in serum LH.

4. It is concluded that the tubero‐infundibular dopamine neurones serve as an intermediary between the medial preoptic area (and possibly other forebrain structures) and neurones containing releasing factors. Under the present experimental conditions, stimulation of the tuberoinfundibular dopamine neurones increased the release of LH, probably by promoting the release of LH‐releasing factor.
The independence of the temporal integration properties of individual chromatic mechanisms in the human eye
Authors: Krauskopf J. , Mollon J. D.
Published: December 2014

1. Since it has been shown by Stiles that the adaptive states of the primary chromatic (π) mechanisms of the human eye vary independently and since recent theories of visual function have postulated an intimate relation between sensitivity and the temporal characteristics of the retinal response, it is asked whether the temporal integration properties of the eye depend upon the state of adaptation of the retina as a whole or vary independently for each of the chromatic mechanisms.

2. It is found that the critical duration, or limit of time‐intensity reciprocity, for the detection of monochromatic increments presented on monochromatic background fields depends only upon the adaptive state of the individual π mechanism mediating the detection. Our results support the hypothesis that each chromatic mechanism has its own automatic gain control.

3. At both dark‐adapted and asymptotic levels the critical durations for the short wave‐length mechanisms appear to be greater than those for π4 and π5.

4. When 500 nm test flashes are presented on 600 nm adaptation fields, critical durations increase at high background intensities. This anomaly adds further support to the hypothesis that the critical durations of different chromatic mechanisms vary independently, since 500 nm flashes are probably detected by π1, rather than by π4, when presented on long wave‐length adaptation fields of high energy.

5. Our findings provide partial support for the suggestion that the Fechner—Benham subjective colours are due to differences in the time constants of the different colour mechanisms.

6. It is concluded that the critical duration is principally determined at a very distal stage in the visual system before interactions occur between chromatic mechanisms.
Thermoregulatory effects of intrahypothalamic injections of adrenergic and cholinergic substances at different environmental temperatures
Authors: Avery David D.
Published: December 2014

1. Rats were unilaterally implanted with chronic indwelling cannulae directed towards the medial preoptic area of the hypothalamus. Carbamylcholine chloride (carbachol), noradrenaline, and saline were microinjected in volumes of 0·5 μl. at each of three environmental temperatures, 5, 24, and 35° C.

2. At an ambient temperature of 24° C injections of carbachol significantly raised core temperature, whereas injections of noradrenaline to the same sites significantly lowered temperature.

3. Injections of carbachol did not affect core temperature at 35° C, but injections of noradrenaline defended against the normal hyperthermia observed in this environment.

4. Hyperthermia resulted from hypothalamic injections of both substances at an ambient temperature of 5° C.

5. The data generally support a neurochemical model for hypothalamic thermoregulatory mechanisms proposed by Myers & Yaksh (1969).

According to their theory a cholinergically coded heat production pathway courses from the anterior to the posterior hypothalamus. This pathway is activated by 5‐HT and inhibited by noradrenaline in the anterior hypothalamus. The observation in the present experiments of hyperthermia following adrenergic stimulation at 5° C cannot be accounted for by this model and therefore an addition to the model is proposed. It is suggested that a heat loss mechanism is also located, at least partially, in the anterior hypothalamus and that this system is inhibited by noradrenaline. Thus a thermal balance is established via an interaction of the two systems.
The antagonistic actions of calcium and magnesium on the superfused ventricle of the snail Helix pomatia
Authors: Burton R. F. , Loudon J. R.
Published: December 2014

1. The isolated, superfused half‐ventricle of the snail (Helix pomatia) maintains a degree of tonic activity even when not beating, since the membrane is depolarized beyond the tension threshold. Beating may be initiated by lateral stretch of the ventricle and by 5‐hydroxytryptamine.

2. Ca and Mn each have a hyperpolarizing action, while K and to a lesser extent Na cause depolarization: the tonic activity of the ventricle is affected accordingly.

3. An increase in the extracellular concentration of Mg also causes the tension to fall, but without change in membrane potential. It can also initiate beating.

4. Contractures induced by 30 m
M‐K are steadily maintained, but start with a more‐or‐less distinct twitch‐like contraction. A contracture induced by a concentration of K above about 50 m
M is poorly sustained and is followed by a further brief contracture when the K concentration is reduced to normal.

5. Relations between contracture tension and the concentrations of Ca and Mg accord with the hypothesis that the two ions compete for attachment to a binding site on the cell surface and that tension is proportional to the amount of bound Ca. On this hypothesis, the apparent dissociation constant of the Mg complex is 11·4 m
M and that of the Ca complex 0·15 m
M or less.

6. This effect of Mg is like that of Na on frog ventricle and some of the differences in the behaviour of snail and frog ventricles are abolished by appropriate adjustment of the extracellular concentrations of these ions.
Membrane potentials recorded from the mucosa of the toad's tongue during chemical stimulation
Authors: Eyzaguirre C. , Fidone S. , Zapata P.
Published: December 2014

An isolated stretch of tongue mucosa was obtained from the Chilean toad (Callyptocephalella gayi). The preparation was observed under transmitted illumination through a binocular microscope. The surface cells were impaled with micro‐electrodes and different chemical agents were applied to the area. The following results were obtained.

1. The surface cells had resting potentials of −6 to −40 mV (mean of −17·6 mV) with the preparation bathed in Ringer solution.

2. The cells underwent depolarization by application of different salts (NaCl, NaF, KCl, Na2SO4, CaCl2 and MgCl2) in concentrations of 0·25–1·0
M. The potentials evoked by the salt solutions often overshot the zero membrane potential level by several millivolts. The positive‐going potential change produced by application of salts was increased during hyperpolarization of the membrane by inward current and was decreased by current of the opposite sign. Application of salts during depolarization of the membrane to a certain positive level produced a negative‐going potential change. The potentials evoked by different salts were about the same, qualitatively, when recordings were made from different areas of the tongue, i.e. top of the fungiform and filiform papillae, doughnut‐shaped folds at the base of the fungiform papillae, areas between papillae and from the side of the tongue totally devoid of papillary structures.

3. Quinine applied in concentrations of 2 × 10−2
M did not change the resting polarization of the surface epithelial cells. However, quinine applied to cells already depolarized by outward currents induced further depolarization. When it was delivered to cells hyperpolarized by inward current the substance induced further hyperpolarization.

4. Sucrose (0·5–1·0
M) did not change the membrane potential of lingual cells regardless of the level of cell polarization induced by injected currents.

5. Hydrochloric, sulphuric, nitric and acetic acids produced minimal biphasic effects: a brief hyperpolarization followed by a slower secondary depolarization.

6. Water increased the membrane potential of the surface cells. Salts applied at the peak of the water‐evoked hyperpolarization induced cell depolarization which was much larger than that evoked during application of salts to cells bathed in Ringer solution.
An electrophysiological analysis of the storage of acetylcholine in preganglionic nerve terminals
Authors: Bennett M. R. , McLachlan Elspeth M.
Published: December 2014

1. An electrophysiological analysis has been made of the storage of acetylcholine (ACh) in the preganglionic nerve terminals of the isolated superior cervical ganglion of the guinea‐pig. The mean amplitude of excitatory post‐synaptic potentials recorded intracellularly was taken as a measure of the ACh output per impulse from the terminals of a preganglionic axon.

2. Prolonged repetitive stimulation of the cervical sympathetic trunk at 10 and 20 Hz in the presence of hemicholinium No. 3 led to an exponential decline of ACh output as the transmitter formed before the beginning of stimulation was depleted.

3. The rate of decline of ACh output during stimulation at 20 Hz (τ = 0·83–1·95 min) was about twice as fast as that at 10 Hz (τ = 1·00–6·83 min).

4. The results suggest that, during prolonged stimulation, ACh is released from a single store in the preganglionic nerve terminal and that each impulse releases a constant fraction of the store of the transmitter.
The composition of foetal and maternal blood during parturition in the ewe
Authors: Comline R. S. , Silver Marian
Published: December 2014

1. Changes in the composition of foetal and maternal blood have been followed during the last 5–10 days of gestation and throughout parturition in the conscious sheep.

2. Catheters were placed in the foetal inferior vena cava through a tarsal vein and in a maternal uterine vein in ten ewes under sodium pentobarbitone anaesthesia. In four of the foetuses blood pressure and heart rates were recorded before and during parturition from an arterial catheter.

3. Foetal blood gas tensions, pH and PCV remained stable during the latter part of gestation and throughout labour until 15 min before delivery, when PO2 and pH fell while PCV and PCO2 rose in about 50% of the foetuses examined.

4. Metabolite levels were also relatively stable at the end of gestation. Plasma glucose in both maternal and foetal blood rose during the hour before birth, while foetal plasma lactate was elevated as early as 4 hr before birth and was unrelated to any maternal changes. Foetal fructose levels were maintained until after delivery.

5. Rises in foetal blood pressure before birth were associated with uterine contractions. Foetal heart rate changes during labour varied in different individuals. The heart rate either fell gradually before birth or there was little change until a sudden drop at delivery.

6. The most striking changes in the lamb occurred at, or a few minutes after, birth; pH and PO2 fell, PCO2 and PCV rose, and bradycardia at delivery was succeeded by prolonged tachycardia. There were marked increases in plasma glucose and lactic acid at this time.

7. PO2 rose rapidly once respiration was established, while pH and PCO2 levels were restored within ½–1 hr. Plasma FFA levels rose rapidly in the lambs 10–30 min after birth and remained high, while plasma glucose, lactate and fructose concentrations declined slowly in the 1–2 hr after birth, although suckling raised the plasma glucose levels. Considerable individual variation in the metabolite levels was found in both ewes and lambs.

8. In the majority of ewes delivery was associated with an abrupt maternal hyperglycaemia, with a much smaller rise in lactate and virtually no change in maternal blood gases or pH.

9. These findings are discussed in relation to existing information on new‐born lambs and the human infant during birth.
An extreme supernormal period in cerebellar parallel fibres
Authors: Gardner-Medwin A. R.
Published: December 2014

1. The electrical responses produced by stimulation at the surface of the cerebellar cortex have been studied in anaesthetized cats.

2. The propagation of the underlying activity is attributed to parallel fibres, but the mode of generation of the potential changes is less certain.

3. The threshold for a second response is up to 40% lower following a conditioning stimulus, and the responses to test stimuli less strong than the conditioning stimulus are correspondingly potentiated.

4. A second stimulus given 22 msec after the first produces a response which propagates 15–20% faster along the folium.

5. The reduction of the threshold and the increase of the propagation velocity are as large with small (but above threshold) conditioning shocks as with large shocks.

6. Both after‐effects are present from 5 to 100 msec after a conditioning stimulus, with maximal values at about 10–30 msec.

7. The fibre conduction velocity inferred from collision experiments agrees with that inferred from the propagation velocity of the responses, and shows a similar increase after conditioning.

8. A second shock does not recruit a new and faster population of parallel fibres.

9. Under the conditions of electrical stimulation the after‐effects are probably restricted to those fibres which are active during conditioning.