bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic adenosine 3′,5′‐monophosphate concentration in the pancreas following stimulation by secretin, cholecystokinin‐pancreozymin and acetylcholine*
Authors: Case R. M. , Johnson M. , Scratcherd T. , Sherratt H. S. A.
Published: December 2014

1. Following an
I.V. injection of secretin into anaesthetized cats, the pancreatic cyclic AMP concentration rose within 30 sec and reached near‐maximal values within 1 min. Pancreatic secretion began only after 45 sec. As secretion declined, the cyclic AMP concentration also fell. However, after 40 min, when secretion had ceased, the concentration again rose, reaching a maximum after about 80 min and returned to basal values within 140 min.

2. During secretin infusion the pattern of cyclic AMP changes was the same, except that the initial rise was maintained as long as secretin was infused.

3. Following either pancreozymin or acetylcholine, alone or super‐imposed on secretin stimulation, similar changes in cyclic AMP concentration were observed. However, the initial rise lasted only 30 sec, basal concentrations being approached within 1 min, and was accompanied by enzyme secretion. The concentration of cyclic AMP subsequently rose and fell again, in the absence of enzyme secretion, exactly as after secretin stimulation.

4. Similar observations were made using an isolated, saline‐perfused preparation of the cat's pancreas.

5. By using very low doses of pancreozymin it was possible to observe the first rise in cyclic AMP concentration in the absence of enzyme secretion. Similarly atropine, while blocking enzyme secretion, did not affect the rise in cyclic AMP concentration after acetylcholine. The second increase in concentration was never associated with secretion (it may have been connected with the synthesis of exportable enzymes by the gland).

6. While these observations suggest that cyclic AMP may be involved in the response of the pancreas to secretin, pancreozymin and acetylcholine, no simple relation exists between cyclic AMP concentration and secretion.
Quantal components of the inhibitory synaptic potential in spinal motoneurones of the cat
Authors: Kuno M. , Weakly J. N.
Published: December 2014

1. Monosynaptic i.p.s.p.s were produced in spinal motoneurones of the cat by stimulation of a pool of interneurones following chronic degeneration of descending tracts and primary afferent fibres in the lumbosacral cord.

2. Monosynaptic i.p.s.p.s so evoked by supramaximal stimuli often showed a fluctuation in amplitude with occasional failures of response.

3. When two successive stimuli were applied at a short interval, the mean amplitude of the second i.p.s.p.s was greater than that of the first. This facilitation was associated with a decrease in the number of failures, a decrease in the coefficient of variation of the amplitude distribution and an increase in the probability of occurrences of large i.p.s.p.s.

4. A statistical analysis of the i.p.s.p. amplitude fluctuation showed that the monosynaptic i.p.s.p. is composed of discrete unit potentials evoked with a certain probability in a manner described by a binomial law.

5. The application of strychnine decreased the mean amplitude of i.p.s.p.s with little change in the coefficient of variation of the i.p.s.p. amplitude distribution.

6. It is concluded that the release of inhibitory transmitter occurs in quantal steps and that strychnine blocks primarily the post‐synaptic receptors for the inhibitory transmitter.
An attempt at an analysis of the factors determining the time course of the end‐plate current
Authors: Kordaš M. , Gabrovec I. , Kordaš M. , Popovič B.
Published: December 2014

1. An attempt was made to analyse the factors which might determine the time course of the falling phase of the end‐plate current.

2. The end‐plate current was measured by ‘clamping’ the membrane potential during neuromuscular transmission.

3. The falling phase of the end‐plate current was found to consist of a non‐exponential, and an exponential portion, the duration of both of which varies under different experimental conditions.

4. The results suggest that the rate constants determining the dissociation of the receptor—mediator complex seem greatly to influence the time course of the end‐plate current.
The influence of deep body and skin temperatures on thermoregulatory responses to heating of the scrotum in pigs
Authors: Ingram D. L. , Legge K. F.
Published: December 2014

1. The temperature on the surface of the pig's scrotum was increased by circulating water through a pad held over the scrotal surface while the animal was lightly restrained.

2. At an ambient temperature of 25° C there was no change in respiratory frequency even when the scrotum was heated to 42° C, but peripheral blood flow did increase and body temperature fell. At 30° C ambient temperature, respiratory frequency increased when the scrotum was warmed to 42° C. At an ambient temperature of 32° C, the frequency increased at a scrotal temperature of 40° C and was even higher when the scrotum was 42° C, but body temperature did not fall.

3. At a constant ambient temperature the effect on respiratory frequency of heating the scrotum to a given temperature depended on the skin temperature of the trunk which was modified by means of a coat through which water was circulated.

4. In a cold environment, heating the scrotum was accompanied by a fall in body temperature, the arrest of shivering and a decline in oxygen consumption.

5. Cooling a thermode in the hypothalamus or over the spinal cord inhibited the increase in respiratory frequency and peripheral blood flow caused by heating the scrotum. Warming either thermode potentiates the effect of heating the scrotum.
Changes in axon light scattering that accompany the action potential: current‐dependent components
Authors: Cohen L. B. , Keynes R. D. , Landowne D.
Published: December 2014

1. When light scattering was measured during hyperpolarizing and depolarizing voltage‐clamp steps, relatively large scattering changes were found during the depolarizing steps. These large changes were found to depend on the time integral of the ionic current and not on the changes in conductance or potential.

2. The current‐dependent changes were examined at several scattering angles, and three distinct time courses were found. At 30–120°, the main change occurred after the current when steps of 2–5 msec duration were used. This change was called I‐90°. At 15–30°, the change occurred with the same time course as the time integral of the current. This change was called I‐25°. At 5–15° the scattering change occurred with a time course intermediate between that of I‐90° and I‐25°. This change was called I‐10°.

3. In all experiments, outward potassium and outward sodium currents led to similar light scattering changes indicating that specific effects of the cation carrying the current across the membrane were not involved.

4. The size of I‐90° was reduced by 29% when an isethionate artificial sea water was substituted for the normal chloride artificial sea water. This reduction equalled the reduction predicted for a transport number effect at the membrane‐solution interface. The time course of I‐90° was similar to the predicted time course for a volume change in the periaxonal space, and such volume changes were tentatively identified as the origin of I‐90°.

5. Because of difficulties in measuring the time course of I‐25°, it was not possible to distinguish between a water of hydration effect and a transport number effect as the cause of this change. Similarly, the origins of I‐10° were not identified. Only I‐10° was altered in size and time course when the external refractive index was increased with bovine albumin.

6. When the scattering changes during the action potential were examined in light of the voltage‐clamp experiments, we concluded that the forward‐angle change was potential‐dependent and that the long‐lasting change at right angles probably represented a swelling of the periaxonal space resulting from the fact that chloride carried a significant fraction of the outward current during the action potential.
Ionic mechanism of a two‐component cholinergic inhibition in Aplysia neurones
Authors: Kehoe Jacsue
Published: December 2014

1. A two‐component inhibition, consisting of a rapid and slow i.p.s.p., has been observed in the medial cells of the pleural ganglion of Aplysia. Each i.p.s.p. has been shown to be mediated by a distinct cholinergic receptor. The ionic mechanisms of the two components of the inhibitory response (whether elicited synaptically or by ACh injection) are analysed in this paper.

2. The inversion potential (typically −60 mV) of the rapid i.p.s.p. and of the rapid response to ACh injection is selectively altered by an intracellular injection of chloride or by partial substitution of the external chloride by impermeant anions. The shift caused by this last procedure is similar to that predicted for the chloride equilibrium potential (ECl) by the Nernst equation.

3. The slow i.p.s.p. and the slow response to ACh injection (both of which invert around −80 mV) are insensitive to changes in either internal or external chloride concentrations; on the contrary, with alterations of the concentration of potassium in the external medium, the inversion potential of the slow responses is altered in a way similar to that expected for the potassium equilibrium potential (EK).

4. It is concluded that the rapid i.p.s.p. and the corresponding ACh potential are due to a change in chloride permeability of the post‐synaptic membrane, whereas the slow responses are due to a selective change in potassium permeability.

5. Additional data suggest that the fast, ‘chloride’ channel is impermeable to sulphate and methylsulphate, but slightly permeable to propionate and isethionate. The slow, ‘potassium’ channel is impermeable to caesium ions, whereas its permeability to rubidium ions is half that to potassium.

6. The potassium permeability of both the non‐synaptic and synaptic membrane is markedly reduced by an intracellular injection of either tetraethylammonium (TEA) or caesium. These ions not only block the cholinergic potassium currents (whether inward or outward) but likewise block the potassium currents activated in the same cells by an iontophoretic injection of dopamine.

7. The potassium dependent synaptic potentials are also selectively affected by manipulations known to block the electrogenic sodium pump. In the presence of ouabain or in sea water in which sodium has been replaced by lithium, there is an apparent reduction of these potentials which was shown to be simply a reflexion of the movement of EK towards a less polarized level. This shift in inversion potential was not seen for the potassium dependent response to ACh iontophoretic injection. These results are interpreted in terms of accumulation of potassium ions assumed to occur in the extracellular spaces of the neuropile, but not in the thoroughly dissected somatic region.

8. Cooling was shown to eliminate, selectively, the synaptic and ACh potential changes caused by an increase in potassium permeability.
Separation of the pace‐maker and plateau components of delayed rectification in cardiac Purkinje fibres
Authors: Hauswirth O. , Noble D. , Tsien R. W.
Published: December 2014

1. Experiments on sheep Purkinje fibres were designed to determine whether the current mechanisms responsible for delayed rectification at the pace‐maker (negative to −50 mV) and plateau (positive to −50 mV) ranges of potential are kinetically separable and independent.

2. Hyperpolarizations from the plateau range were shown to produce decay of a single component of outward current within the plateau range, but two components were evident when the hyperpolarizations entered the pace‐maker range.

3. The time courses of recovery of the two components were too similar at −25 mV to allow temporal resolution at this potential. Clear temporal resolution was, however, possible at potentials between −55 and −95 mV. An indirect method of resolving the two components at −25 mV was used.

4. The kinetic properties of the two components correspond to those previously described for the pace‐maker potassium current, iK2, and the outward plateau current, ix1 (Noble & Tsien, 1968, 1969a).

5. The instantaneous (fully activated) current—voltage relation for iK2 was reconstructed from the analysed current records. It was found that this relation shows a negative slope conductance at all potentials positive to −75 mV and that the current tends towards zero at zero membrane potential.

6. The results are compared with those predicted by two reaction models of the iK2 and ix1 mechanisms. It is concluded that iK2 and ix1 are kinetically separable but that it is not possible with present techniques to decide whether they are controlled by the same or completely independent membrane structures. It is also shown that the instantaneous current—voltage relation calculated for iK2 does not depend on whether the controlling mechanisms are assumed to be independent or linked.
Synaptic potentials in nerve cells of the stellate ganglion of the squid
Authors: Miledi R.
Published: December 2014

1. Intracellular recordings were made from nerve cells in the stellate ganglion of the squid.

2. Stimulation of the preganglionic nerve evoked excitatory or inhibitory synaptic potentials, or a combination of both. Antidromic stimulation of the stellar nerves also evoked excitatory and inhibitory potentials in the cells. With both types of stimulation the synaptic potentials were built up of contributions from several axons indicating considerable convergence of excitatory and inhibitory inputs on the cells.

3. Inhibitory, as well as excitatory, miniature synaptic potentials were recorded from the cells even after impulse activity had been blocked by tetrodotoxin.

4. Glutamate applied iontophoretically to some cells produced a depolarization of their membranes. In other cases glutamate evoked a hyperpolarizing potential. Application of glutamate caused a decrease in the amplitude of excitatory synaptic potentials.
The resting potential of moth muscle fibre
Authors: Rheuben Mary B.
Published: December 2014

1. The membrane of the moth muscle fibre was tested for resting permeability to various ions: it is not permeable to Mg2+ or Ca2+; it is slightly permeable to Na+ and NH4+; it is appreciably permeable to Cl−, but Cl− is passively distributed; it is apparently permeable to H+ but effects of HCO3− are not ruled out; and it is primarily permeable to K+.

2. Measurement of the internal K+ activity showed that EK is less negative than the resting potential.

3. In the presence of DNP, or under anoxia, the membrane potential approaches, EK; there is a small concomitant decrease in effective membrane resistance.

4. An increase in external Ca2+ concentration is accompanied by increased effective membrane resistance and an increase in amplitude of the negative resting potential.

5. Cooling the membrane (below room temperature) decreased the amplitude of the resting potential by 4–16 mV per 10° C, and was accompanied by a large increase in effective membrane resistance.

6. The experimental results most readily fit the hypothesis that the resting potential of the moth muscle fibre, although the membrane is highly permeable to K+, Cl− and apparently to H+, is primarily maintained by an electrogenic transport process which generates an ionic current across the membrane. The possibility that the concentration gradient of H+ ions is metabolically maintained at a level sufficient to explain the resting potential was considered to be unlikely but could not be directly excluded.
Effect of renal nerve stimulation, renal blood flow and adrenergic blockade on plasma renin activity in the cat
Authors: Coote J. H. , Johns E. J. , Macleod Valerie H. , Singer Bertha
Published: December 2014

1. The effect of electrical stimulation of the distal cut ends of the renal nerves of unilaterally nephrectomized, anaesthetized cats was studied. Using stimulation parameters of 15 pulses per second (pps), 15 V and 0·2 msec duration, there was an immediate sharp drop in renal blood flow, as determined by an electromagnetic flowmeter, which was maintained for about 2 min. Flow gradually returned to control values over approximately the next 10 min in spite of continued stimulation for up to 30 min.

2. Plasma renin activity (PRA) increased markedly after 10 min of stimulation but 20 min later fell towards pre‐stimulation values whether stimulation was maintained or not.

3. Phentolamine, an α‐adrenergic‐receptor antagonist, abolished both the blood flow and PRA responses to a 10 min period of renal nerve stimulation.

4. When the renal artery was constricted in order to produce blood flow changes similar to those found with renal nerve stimulation, the rise in PRA was similar to that observed with renal stimulation.

5. In phentolamine‐blocked animals, renal artery constriction, as described, produced the same effect on PRA as was observed with renal nerve stimulation.

6. Propranolol, a β‐adrenergic‐receptor antagonist, did not block the blood flow response to renal nerve stimulation, but did block the rise in PRA normally associated with renal nerve stimulation.

7. It is suggested that the effect of renal nerve stimulation on PRA is mediated, primarily, by changes in renal blood flow and that one of the steps leading to renin release following stimulation is sensitive to propranolol. This step must be distal to the effect on vascular smooth muscle.
Reflex firing in the lumbar sympathetic outflow to activation of vesical afferent fibres*
Authors: de Groat William C. , Lalley Peter M.
Published: December 2014

1. Activation of vesical afferent fibres in the Aγδ range by electrical stimulation of the pelvic nerve or by bladder distension elicited reflex firing in hypogastric nerves and in preganglionic nerves to the inferior mesenteric ganglion.

2. The multisynaptic reflex was present in cats with an intact spinal cord and in acute and chronic spinal animals (transections at T10—T12). The reflex pathway was partially crossed in the sacral cord, and in the periphery at the level of the inferior mesenteric ganglia. In contrast, an inhibitory response to raised intravesical pressure was mediated by a supraspinal inhibitory mechanism which was activated in parallel with the micturition reflex.

3. Since enhancement as well as depression of sympathetic firing accompanied reflex micturition, it is concluded that at least two distinct populations of lumbar preganglionic neurones are responsive to vesical afferent activity: one population being excited, the other depressed, during micturition. The latter population may be involved in an inhibitory feed‐back mechanism on to the bladder.
Gastric secretion and its facilitation as related to gastric mucosal histamine
Authors: Johansson Irene , Lundell L. , Rosengren Elsa , Svensson S. E.
Published: December 2014

1. In conscious rats provided with Pavlov or Heidenhain pouches the acid and pepsin responses to vagal stimulation, or infusions of gastrin, histamine, methacholine, and to various combinations of these stimulants have been established. The concomitant mobilization and increased formation of gastric mucosal histamine have also been examined.

2. Histamine evoked graded acid responses in the Pavlov and Heidenhain pouches. The innervated pouch was more sensitive to histamine than the denervated. Stimulation of pepsin secretion was apparent only in the Heidenhain pouch.

3. The acid response to vagal stimulation evoked by 2‐deoxy‐
D‐glucose was facilitated by infusion of histamine, but not that of pepsin, the secretion of which was depressed.

4. Acid secretion in response to graded infusion of methacholine was enhanced by background infusions of histamine in subthreshold, sub‐maximal and maximal dosages.

5. The acid response to vagal stimulation was enhanced by a background infusion of gastrin, but not that of pepsin, the secretion of which was depressed.

6. A background infusion of a large dose of histamine depressed the maximal acid response to gastrin in both types of pouches.

7. Administration of histamine restrained the accelerating effect of gastrin on histidine decarboxylase activity, probably by a feed‐back coupling.

8. The increase in gastric mucosal histamine, as reflected in its urinary excretion, in response to gastrin infusion was enhanced by vagal stimulation.

9. The amounts of histamine that can be mobilized and newly formed in the gastric mucosa have been evaluated and found to be fully adequate for efficient stimulation of the parietal cell.
An experimental analysis of the tachycardia that follows vagal stimulation
Authors: Burke G. H. , Calaresu F. R.
Published: December 2014

1. Postvagal tachycardia, the transient increase in heart rate that follows the sinus bradycardia elicited by vagal stimulation, was investigated in thirty chloralosed cats. Maximum postvagal tachycardia was elicited by stimulation at frequencies of 20–60 Hz with train durations of 30–90 sec. A positive correlation was demonstrated between the magnitudes of postvagal tachycardia and of the preceding sinus bradycardia.

2. Postvagal tachycardia was not affected by either spinal transection at C7 or by administration of propranolol (1·5 mg/kg
I.V.), but was abolished by the administration of atropine (2·0 mg/kg
I.V.).

3. Postvagal tachycardia was observed to follow the vagal bradycardia induced reflexly either by administration of phenyldiguanide (100–300 μg
I.V.) or by stimulation of the aortic depressor nerve.

4. In the isolated atria‐vagus preparations from six rabbits a positive correlation was demonstrated between the magnitude of postvagal tachycardia and of the preceding bradycardia elicited by vagal stimulation.

5. Continuous intracellular recordings were obtained from four sinuatrial node pace‐maker cells in the isolated atria‐vagus preparation of the rabbit before, during and after vagal stimulation. During postvagal tachycardia the slope of the diastolic prepotential, the maximum diastolic potential, threshold potential and the overshoot were found to be increased; these changes are different from those found in pace‐maker cells during adrenergic activation.

6. These findings demonstrate that postvagal tachycardia is not mediated by sympathetic adrenergic mechanisms, but suggest that it is dependent upon the preceding vagal bradycardia and may be related to an increase in net sodium influx into pace‐maker cells initiated by the hyperpolarization of the pace‐maker cell membrane during and immediately after vagal stimulation.
Inhibition of post‐ganglionic motor transmission in vas deferens by indirectly acting sympathomimetic drugs
Authors: Ambache N. , Dunk Linda P. , Verney J. , Zar M. Aboo
Published: December 2014

1. Using field stimulation with short trains of pulses (< 10 per train), the post‐ganglionic motor transmission in the mammalian vas deferens has been further analysed pharmacologically.

2. In preparations taken from guinea‐pigs, rats and rabbits the effects of the indirectly sympathomimetic drugs, tyramine and cocaine, could be explained entirely on the basis of the actions of released, endogenous noradrenaline.

3. Tyramine produced a contraction in vasa taken from normal rats but not from normal guinea‐pigs. The tyramine contraction was due to release of endogenous noradrenaline because it was not seen in preparations taken from reserpinized rats and because it was abolished in normal vasa by phenoxybenzamine or phentolamine, thus denying the supposed inaccessibility, to α‐blockers, of the motor α‐adrenoceptors activated by endogenous noradrenaline.

4. Phenoxybenzamine or phentolamine failed to block post‐ganglionic motor transmission in rat and in guinea‐pig vasa.

5. Tyramine strongly inhibited motor transmission in vasa taken from normal but not from reserpinized guinea‐pigs.

6. Tyramine produced inhibition of motor transmission in phenoxybenzamine‐treated preparations taken from normal but not from reserpinized rats.

7. Cocaine inhibited motor transmission in guinea‐pig and in rat vasa. This effect was not due to a local anaesthetic or to a smooth‐muscle depressant action because it did not occur in preparations taken from reserpinized animals.

8. The inhibitory effect of tyramine or cocaine was not abolished by β‐adrenoceptor blockade with propranolol.

9. Whereas reserpinization abolished the tyramine‐ and cocaine‐inhibitions, it did not affect the inhibitory actions of noradrenaline or of PGE2.

10. Indomethacin and sodium meclofenamate, which suppress prostaglandin synthesis, did not affect the twitch‐inhibiting actions of noradrenaline, tyramine or cocaine.

11. These results provide further support for the conclusion that post‐ganglionic motor transmission to the vas deferens is non‐adrenergic in these species and assign to endogenously released noradrenaline an inhibitory role upon motor transmission.
The propagation of segmental contractions along the small intestine*
Authors: Grivel M‐L. , Ruckebusch Y.
Published: December 2014

1. The electrical activity of the small intestine of conscious dogs, rabbits and sheep was recorded by means of chronically implanted electrodes and was related to mechanical changes in the bowel.

2. A pattern of activity characteristic of segmental contractions (a prolonged series of bursts of spike activity superimposed on the basic electrical rhythm) was recorded successively at consecutive sites along the small intestine. This activity was as pronounced in the rabbits and sheep which were fed ad lib. as in the dogs which were fasted for 12 hr.

3. The segmental contractions began in the duodenum and had a frequency of 15–20/24 hr. As they passed along the intestine, their velocity diminished and in the rabbits and sheep this was associated with an increased duration of activity. Most of the contractions reached the terminal ileum taking 1·5‐2 hr in each of the species despite the differences in the length of the small intestine.

4. The propagation of segmental contractions appears to be a normal and common activity of the intact bowel and it may have a propulsive as well as a mixing function.
The role of circulating catecholamines in sweat production in man
Authors: Allen Judith A. , Roddie I. C.
Published: December 2014

1. The effects of intravenous infusions of adrenaline, isoprenaline and noradrenaline on human sweating were assessed by continuous measurement of total body weight loss in normal subjects.

2. All three catecholamines increased the rate of weight loss but isoprenaline was effective in a much smaller dosage than either adrenaline or noradrenaline.

3. β‐adrenoceptor blockade with propranolol reduced the response.

4. The response was not abolished by collecting expired air in a Douglas bag suggesting that it was not due to an increase in respiratory water loss.

5. The response was not abolished by atropine infusions suggesting that it was not mediated through cholinergic sudomotor nerves.

6. It is concluded that intravenous infusions of catecholamines may elicit a small, non‐cholinergically mediated sweat response in man.
The effects of tetanus toxin on neuromuscular transmission and on the morphology of motor end‐plates in slow and fast skeletal muscle of the mouse
Authors: Duchen L. W. , Tonge D. A.
Published: December 2014

1. A sublethal dose of tetanus toxin was injected into the muscles of one hind leg of the mouse and caused local tetanus which persisted for 4 weeks.

2. Neuromuscular transmission was studied in vitro in nerve—muscle preparations of soleus, a slow muscle, and extensor digitorum longus (EDL), a fast muscle, from 1 day to 6 months after the injection of toxin.

3. Soleus failed to respond to nerve stimulation, became supersensitive to acetylcholine and showed spontaneous fibrillations for several weeks before returning to normal. EDL did not show these changes. A higher dose of tetanus toxin, lethal within 24 hr, caused paralysis of EDL as well as soleus.

4. In muscle fibres in which neuromuscular transmission was blocked spontaneous miniature end‐plate potentials (m.e.p.p.s) were recorded. The frequency of m.e.p.p.s was increased by repetitive nerve stimulation but not by raising the external potassium concentration.

5. The amplitude of spontaneous m.e.p.p.s showed a skew distribution because of a disproportionate number of potentials of less than 0·2 mV.

6. Raising the external calcium concentration did not restore neuromuscular transmission.

7. Histological examination of soleus showed atrophy of muscle fibres with normal preterminal axons. There was sprouting from motor nerve terminals and subsequently new motor end‐plates were formed. These changes were not found in EDL.

8. The results indicate that, in the mouse, tetanus toxin causes a presynaptic block of neuromuscular transmission and ‘functional denervation’ of muscle. Slow muscle is more sensitive to the effects of the toxin than fast.
Input from muscle and cutaneous nerves of the hand and forearm to neurones of the precentral gyrus of baboons and monkeys
Authors: Wiesendanger M.
Published: December 2014

1. The precentral bank of the Rolandic fissure of the cortical arm area has been explored with extracellular micro‐electrodes in primates (baboons and monkeys) under nitrous oxide and oxygen anaesthesia, supplemented by small doses of Parkesernyl® and chloralose. The results in baboons and monkeys were the same.

2. Single units were classified as pyramidal tract neurones or non‐pyramidal tract neurones according to their antidromic responsiveness to stimuli applied in the dorsolateral funiculus at C1–2.

3. Responses to electrical stimulation of the deep (motor) radial nerve, the deep palmar (motor) branch of the ulnar nerve, and the superficial (cutaneous) radial nerve could be recorded in the majority of neurones of the motor cortex provided that short trains of strong stimuli were used. Minimal responses to muscle nerve stimulation were observed in a few neurones at 1·4 × group I threshold, but most units reacted only with higher stimulus intensities (2–3 × group I threshold).

4. The latencies to peripheral nerve stimulation were measured from the first peak of the incoming volley recorded at the root entry zone. The mean response latencies of pyramidal tract cells were between 20 and 25 msec; non‐pyramidal tract cells were activated at slightly shorter mean latencies, the difference being significant for superficial radial nerve stimulation only (4 msec). These latencies are more than twice as long as those recorded in the postcentral gyrus, and the probability of discharge is lower than for postcentral neurones.

5. A further difference between neurones of the postcentral and precentral gyrus is the pronounced convergence from different nerves and also from different modalities (cutaneous and muscle afferents) in units of the precentral cortex in contrast to units of the postcentral cortex.

6. The high thresholds, necessary to activate precentral neurones by muscle nerve stimulation, make it unlikely that group I muscle afferents are involved. This is, furthermore, indicated by the lack of responsiveness to intravenous injection of succinylcholine which was, however, effective for driving neurones of the specific projection area for group I afferents, area 3a. The present experiments are consistent with the view that sensitivity of precentral neurones to muscle stretch (described in previous studies) is due to activation of secondary muscle spindle endings and their ascending pathways.

7. The original hypothesis of a load compensating ‘pyramidal reflex’ with an oligosynaptic afferent contribution from the spindle primaries can be discarded. The present findings indicate that there is a feed‐back from secondary muscle spindle afferents which, by way of a more complex pathway, can modulate the firing frequency of neurones in the motor cortex.
Somatotopic organization of vibrissal responses in the ventro‐basal complex of the rat thalamus
Authors: Waite Phil M. E.
Published: December 2014

1. The region of the ventro‐basal complex (VB) of the thalamus responding to movements of the whiskers has been mapped electrophysiologically in rats under either urethane or barbiturate anaesthesia.

2. Whisker responses were found in the dorso‐medial part of VB throughout its rostro‐caudal extent; they occupied one third to one half of the total VB region.

3. Most cells responded to movements of only one whisker and the responses were somatotopically organized. The different horizontal lines of whiskers were represented at different rostro‐caudal levels within the nucleus, the most dorsal line being represented most caudally. At each level the larger, more caudal whiskers were represented more dorsally and laterally than the smaller, more rostral whiskers.
Salt adaptation in Bufo bufo
Authors: Ferreira H. G. , Jesus C. H.
Published: December 2014

1. The capacity of adaptation of toads (Bufo bufo) to environments of high salinity was studied and the relative importance of skin, kidney and urinary bladder in controlling the balance of water and salt was assessed.

2. Toads were kept in NaCl solutions of 20, 50, 110, 150 and 220 m
M and studied in their fourth week of adaptation. A group of animals considered as ‘control’ was kept in wet soil with free access to water. Plasma, ureter urine, and bladder and colon contents were analysed for sodium, potassium, chloride and osmolality, and total body sodium and water were determined. Absorption of water and 22Na through the skin, and water flow and sodium excretion through the ureter, of intact animals was studied. Hydrosmotic water transport through the isolated urinary bladder of ‘control’ and adapted animals was determined. The effects of pitressin and aldosterone on the water and sodium balance are described.

3. The survival rates of toads kept in saline concentrations up to 150 m
M were identical to that of ‘control’ animals, but half of the animals kept in 220 m
M died within 4 weeks.

4. There is a linear correlation between the sodium concentrations and osmolality of plasma and of the external media.

5. The sodium concentration in colon contents rose with rising external concentrations, up to values higher than the values in plasma.

6. Sodium concentrations and osmolalities of ureter and bladder urine increased in adapted animals, the values for bladder urine becoming much higher than those for ureter urine in animals adapted to 110, 150 and 220 m
M.

7. Total body water, as a percentage of total weight was kept within very narrow limits, although the total body sodium increased with adaptation.

8. Absorption of water through the skin for the same osmotic gradients was smaller in adapted than in ‘control’ animals.

9. The ureteral output of water of toads adapted to 110 and 150 m
M‐NaCl was larger than the water absorption through the skin.

10. Skin absorption of sodium was lower in animals adapted to concentrated saline solutions than in ‘control’ animals.

11. Sodium output by the ureter was identical to skin absorption in ‘control’ animals adapted to 20, 50 and 110 m
M‐NaCl but was higher in animals adapted to 150 m
M‐NaCl.

12. Aldosterone increased the absorption of sodium in ‘control’ and adapted toads, but at all dose levels absorption by control was greater than by adapted animals.

13. The stimulation of water absorption by vasopressin in vivo or in isolated bladders was not modified in animals adapted to high salinities.
Presbyopia and the changes with age in the human crystalline lens
Authors: Fisher R. F.
Published: December 2014

1. A method of determining the distribution of capsular moulding pressure is described. This includes:

(a) measuring the decrease in polar depth of the lens from photographed lens profiles before and after the capsule has been cut around the entire equator of the lens,

(b) measuring the elastic properties of the lens substance by subjecting the lens to known centrifugal forces and photographing the polar strain so produced.

2. A method of determining the relationship between capsular and lenticular strain is described. This includes (a) measuring the elastic properties of the capsule (b) measuring the elastic properties of the lens substance and (c) measuring the profiles of the photographed lens.

The ratio of the strain of lens substance to capsule is expressed as a dimensionless parameter, the lens number.

3. The decrease in the amplitude of accommodation with increasing age is proportional to the lens number divided by the square of the radius of the accommodated lens, assuming that the movement of the capsulozonular attachments of the lens remains unimpaired in the ageing eye.

4. Ageing changes in the human crystalline lens are sufficient to account for a total loss of accommodation by the age of 61 years.
Left ventricular contractility and developed tension in the intact dog submitted to an intracoronary infusion of adenosine
Authors: Lammerant J. , Becsei I.
Published: December 2014

1. The effect of adenosine on left ventricular contractility and developed tension was studied in the anaesthetized intact dog. Normal and propranolol‐treated animals were used. Adenosine was infused through a catheter into one of the two main branches of the left coronary artery, usually the circumflex branch. The rate of infusion was 150 × 10−9
M/min. The infusion was maintained during 50 min.

2. In both series of animals, no change was observed in the heart rate, aortic pressure, left ventricular end‐diastolic pressure, time from onset of left ventricular contraction to peak dP/dt, peak dP/dt and left ventricular tension—time index. It is concluded that a regional increase in adenosine concentration in the left ventricular wall has no inotropic effect when the adrenergic mechanisms are normal or depressed.

3. The myocardial blood flow response to adenosine was determined at the 10th, 30th and 50th min of the infusion by the radioactive inert gas method. At the 10th min of the infusion, the myocardial blood flow averaged three times the control value in both series of dogs. Thereafter, the flow response remained stable in the normal dogs but declined at the 50th min of the infusion in the propranolol‐treated animals. It is suggested that autoregulation of the coronary circulation in response to overperfusion of the myocardium at constant cardiac work may be enhanced at the lower myocardial oxygen requirements of the propranolol‐treated dogs while, in the normal animals, it was insufficient to overcome the potent coronary dilator action of adenosine.
The pontomedullary area integrating the defence reaction in the cat and its influence on muscle blood flow
Authors: Coote J. H. , Hilton S. M. , Zbrożyna A. W.
Published: December 2014

1. In anaesthetized cats the effects were investigated of electrical stimulation of regions in the caudal mesencephalon, pons and medulla on muscle blood flow, skin blood flow and arterial blood pressure.

2. It was found that within the dorsal part of the well known pressor area there is a narrow strip, 2·5 mm lateral from the mid line, starting ventral to the inferior colliculus and ending in the medulla close to the floor of the IV ventricle, from which vasodilatation in skeletal muscles is selectively obtained. This strip is quite separate from the more ventral, efferent pathway for active vasodilatation running from the hypothalamic and rostral mesencephalic ‘defence centre’.

3. As in the case of the hypothalamic and rostral mesencephalic ‘defence centre’, the muscle vasodilatation obtained from the caudal strip is accompanied not only by a rise of arterial blood pressure, but also by tachycardia, vasoconstriction in the skin, pupillary dilatation and piloerection.

4. Stimulation, restricted to the caudal strip, via implanted electrodes in unanaesthetized animals, produced a behavioural response resembling the defence reaction. The strip, therefore, is probably a caudal extension of the ‘defence centre’.

5. Unlike the vasodilatation elicited from the more rostral part of the ‘defence centre’ in the hypothalamus and mesencephalon, the muscle vasodilatation obtained on stimulation of the caudal strip was resistant to atropine, but was blocked by guanethidine.

6. It is suggested that during naturally occurring defence reactions in the normal animal the ponto‐medullary area is activated together with the hypothalamo‐mesencephalic area, inhibition of vasoconstrictor tone then accompanying activation of the vasodilator nerve fibres in skeletal muscle.
The maintenance of arterial constriction at different transmural pressures
Authors: Speden R. N.
Published: December 2014

1. Distensibility characteristics of the isolated, perfused rabbit ear artery were measured in the presence and absence of different concentrations of adrenaline.

2. The major effect of varying the adrenaline concentration was to vary the radius at which active tension first developed. This radius was inversely related to the adrenaline concentration.

3. Increases in radius of the constricted artery produced by pressures rising from 40 to 150 mm Hg were small relative to the increase in wall stress. Distension was opposed largely by increases in active tension. With some arteries (60%) an increase in pressure between 30 and 80 mm Hg was associated with a decrease in radius when low concentrations of adrenaline were present.

4. The ability of the constricted ear artery to resist distension at transmural pressures of 100 mm Hg was uninfluenced by the adrenaline concentration provided constriction exceeded 28% of maximal. The static, incremental, circumferential modulus of the artery wall varied little from a value of 6·5 × 106 dyn/cm2.

5. The maximum active tension required to maintain constriction was inversely related to the degree of constriction and hence to the adrenaline concentration. The modulus for fully or near‐fully activated muscle was 18·5 × 106 dyn/cm2 of media.

6. Muscle function deteriorated following exposure of constricted arteries to pressures sufficient to overwhelm the constriction.

7. These observations may be explained by a negative feedback system where the contractile elements are arranged in parallel with a length sensor element whose setting is determined by the concentration of adrenaline. The length sensor may be the cell membrane. It is concluded that a radius increase may be a primary stimulus for blood flow auto‐regulation.
Conductance changes, an electrogenic pump and the hyperpolarization of leech neurones following impulses
Authors: Jansen J. K. S. , Nicholls J. G.
Published: December 2014

Following trains of impulses, sensory neurones in the C.N.S. of the leech show a prolonged hyperpolarization, which lasts for seconds or minutes. In the present investigation the mechanisms that underly this hyperpolarization have been studied by recording intracellularly. Two factors have been found to be responsible. One is the activity of an electrogenic pump (see Baylor & Nicholls, 1969b); the other is a long‐lasting change in K conductance.

1. Additional evidence that an electrogenic pump contributes to a slow after‐hyperpolarization of leech sensory neurones is provided by the effects of injecting Na intracellularly. This leads to an increase in membrane potential that is blocked by the cardiac glycoside strophanthidin. Furthermore, after a train of impulses, reducing the K concentration in the external fluid characteristically reduces the hyperpolarizing action of the pump.

2. The hyperpolarization following impulses is associated with a reduction of the cell membrane resistance that can persist for several minutes.

3. Several lines of evidence suggest that the reduction in input resistance during the hyperpolarization is mainly due to an increased permeability to K. Thus, when the K concentration in Ringer fluid is reduced, the peak amplitude of the hyperpolarization following a train becomes larger. Furthermore, the conductance dependent part of the after‐hyperpolarization has a reversal potential close to the equilibrium potential for K (EK). Substitution of Cl by SO4 has little effect either on the after‐hyperpolarization or on the conductance change following a train.

4. Increased external Ca concentrations lead to a marked increase in the hyperpolarization that follows impulse activity. The enhanced hyperpolarization in high Ca is associated with a corresponding reduction in input resistance. The amplitude and duration of the hyperpolarization following a brief train of impulses can be increased by a factor of 5 or more in Ringer fluid containing 10 mM‐Ca instead of the usual 1·8 mM. The hyperpolarization and resistance changes still occur in solutions containing 20 mM‐Mg.

5. To augment the hyperpolarization the increased concentration of Ca must be present during the train of impulses.

6. The relative contributions of the K conductance increase and of the electrogenic pump for generating the hyperpolarization after impulse activity are different in the three types of sensory cell responding to touch, pressure and noxious stimulation.
The influence of exogenous steroids on macromolecule uptake by the small intestine of the new‐born rat
Authors: Daniels V. G. , Hardy R. N. , Malinowska K. W. , Nathanielsz P. W.
Published: December 2014

1. Plasma concentrations of cortisol and corticosterone measured by competitive protein binding in rats between 5 and 28 days after birth have been related to the intestinal uptake of [125I]polyvinyl pyrrolidone (PVP).

2. Plasma cortisol concentration was consistently low throughout the period studied, but there was an increase in plasma corticosterone concentration at the time (18–21 days) when PVP uptake declined to zero (closure).

3. Injection of a large dose of cortisone acetate 5 days after birth resulted in precocious closure; PVP uptake declined progressively to zero during the 6 days following the injection. Injection of this steroid at 12 days of age caused closure within 4 days.

4. Precocious closure induced by cortisone acetate was closely comparable histologically with natural closure; the decline in PVP uptake was associated with the progressive displacement of vacuolated cells from the villi of the terminal intestine.

5. Injection of corticosterone at either 5 or 12 days after birth also reduced PVP uptake. However, the reduction was transient and uptake returned to control levels some days after the injection.

6. The temporary reduction in PVP uptake following corticosterone injection was not associated with any change in the histological appearance of the small intestine at the light microscope level.

7. The injection of either cortisone acetate or corticosterone was followed by a period of impaired body growth and also a reduction of adrenal weight in animals injected at 12 days but not in animals injected at 5 days.
The contrast sensitivity of the cat
Authors: Campbell F. W. , Maffei L. , Piccolino M.
Published: December 2014

1. The experiments were carried out on pretrigeminal cats.

2. By recording potentials evoked from the visual cortex by a grating stimulus, it was established that there was a linear relation between the voltage generated and the logarithm of the contrast of the grating.

3. The voltage evoked by the grating was independent of the orientation of the grating.

4. It has previously been shown in man that, if the contrast is determined by an extrapolation to the point at which a zero voltage occurs, this value corresponds to the psychophysical threshold. On the assumption that the threshold of the cat also occurs at zero voltage, thresholds for a number of spatial frequencies and orientations were determined.

5. When the threshold sensitivity function for the cat is compared with man it is found to be displaced to lower spatial frequencies by a factor of about ten. This means that while the cat cannot see such high spatial frequencies as man, it can see lower frequencies better than man.