bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetylcholine and related enzymes in the neural lobe and anterior hypothalamus of the rabbit
Authors: Lederis K. , Livingston A.
Published: December 2014

1. Acetylcholine (ACh), cholinesterases and choline acetyltransferase (choline acetylase) were estimated in the neural lobe and hypothalamus of the adult male rabbit. Acetylcholine was also estimated in the neural lobes and hypothalami of some other mammals.

2. Acetylcholine‐like activity was measured by bio‐assay using the leech dorsal muscle preparation.

3. Characterization experiments indicated that about 90% of the activity measured was due to acetylcholine.

4. Mean acetylcholine content in the neural lobe of the rabbit, after extraction with perchloric acid, was 4·38 ± 0·98 μg/g fresh tissue, and 4·87 ± 1·53 μg/g in the hypothalamus.

5. Acetylcholine was also found to be present, in comparable concentrations, in the neural lobe of man and in the neural lobes and hypothalami of ox, rat and hedgehog.

6. Acetylcholinesterase, present in the neural lobe and hypothalamus of the rabbit, hydrolysed 1·74 ± 0·11 μ‐moles of substrate/min/g and 3·78 ± 0·60 μ‐moles substrate/min/g fresh tissue respectively.

7. The concentration of butyrylcholinesterase was about one tenth that of acetylcholinesterase in both tissues.

8. Choline acetyltransferase present in the neural lobe and in the hypothalamus synthesized 87 ± 22 μg ACh/hr/g fresh tissue and 378 ± 149 μg respectively.
Electrical activity in the supraoptic and paraventricular nuclei associated with neurohypophysial hormone release
Authors: Dyball R. E. J. , Koizumi Kiyomi
Published: December 2014

1. Unit recordings were made from the hypothalamus in anaesthetized male rats using steel or glass micro‐electrodes.

2. Stimuli which are known to release vasopressin and oxytocin (electrical stimulation of the central end of the severed right vagus nerve and intracarotid injection of CaCl2 solution) also excite units in the supraoptic and paraventricular nuclei. In addition, these units are excited by intracarotid injections of carbachol, acetylcholine and NaCl (5%) which are less effective stimuli for vasopressin release.

3. These stimuli also excite units from which potentials can be evoked by stimulation of the pituitary stalk and which are likely to be neurosecretory neurones. Neurosecretory neurones can conduct electrical impulses like other less specialized nerve cells. Estimations of conduction velocity range between 0·4 and 1·3 m/sec.

4. The proportion of units in the supraoptic and paraventricular nuclei which are excited and the degree of excitation corresponds approximately to the amount of vasopressin released by the stimuli. In addition, excitation of the supraoptic nucleus seems to be more directly associated with vasopressin release and excitation of the paraventricular nucleus with oxytocin release.
The kidneys and arterial pressure in immature and adult rabbits
Authors: Mott Joan C.
Published: December 2014

1. The effect of stepwise haemorrhage on arterial pressure in adult and immature (9–15 days old) rabbits lightly anaesthetized with sodium pentobarbitone is described.

2. Bethanidine (1 or 3 mg/kg) lowered initial arterial pressure but did not impair the maintenance of arterial pressure in immature or adult rabbits during stepwise haemorrhage.

3. Arterial pressure was only slightly lower in nephrectomized than in intact adult rabbits; in some immature rabbits nephrectomy caused a substantial fall of resting arterial pressure. This fall was largest in animals of low body weight and low haematocrit. Nephrectomy reduced the ability of both immature and adult rabbits to maintain arterial pressure during haemorrhage.

4. Arterial pressure fell more precipitately on stepwise haemorrhage in adult rabbits in which the carotid sinus and depressor nerves had been cut than in intact rabbits. No such difference was seen in immature rabbits despite the fact that initial arterial pressure was higher in denervated animals at all ages.

5. The responses to stepwise haemorrhage were compared in dummy operated and nephrectomized immature and adult rabbits with carotid sinus and depressor nerves cut to minimize changes of sympathetic tone. Under these conditions the presence or absence of kidneys made no significant difference in the response to stepwise bleeding in adult rabbits. In immature rabbits maintenance of arterial pressure was greatly impaired in the absence of the kidneys.

6. The results suggest that a pressor mechanism of renal origin may be relatively more important in the maintenance of arterial pressure in the face of haemorrhage in immature than in adult rabbits.

7. Resting arterial pressure in small and anaemic immature rabbits may partly depend on the presence of the kidneys. At birth arterial pressure is higher in rabbits of higher haematocrit but this relationship reverses in the second week of life when the haematocrit level is falling.
Ion movements in human red cells independent of the sodium pump
Authors: Lubowitz H. , Whittam R.
Published: December 2014

1. A study was made of the dependence on external Na of the movements of Na and K in human red cells. Special attention was given to ouabain‐insensitive movements. The effect of internal Na on Na influx, and the influence of some sulphydryl inhibitors on ion movements and metabolism was also investigated.

2. External Na stimulated ouabain‐insensitive Na efflux and K influx. There was also a ouabain‐insensitive component of Na influx that was raised on increasing the internal Na concentration. Exchange diffusion of Na appears to occur in the presence of ouabain and external K.

3. Net transport of Na and K in the presence of ouabain was independent of external Na, as was also lactate production.

4. Ethacrynic acid partially inhibited the Na pump; the Na‐dependent components of Na efflux and K influx in the presence of ouabain were completely inhibited by ethacrynic acid. Both ouabain‐sensitive and ouabain‐insensitive adenosinetriphosphatase activities were inhibited by ethacrynic acid indicating a non‐specific effect of this compound. Iodoacetamide decreased only the ouabain‐insensitive ATPase activity.

5. The results suggest that when the Na pump is blocked by ouabain, part of the residual ion movements can be attributed to exchange diffusion.
A reappraisal of reflex stepping in the cat
Authors: Egger M. David , Wyman Robert J.
Published: December 2014

1. In re‐evaluating Sherrington's experiment in which deafferented muscles in decerebrated cats ‘stepped’, we recorded from L5 ventral roots, a chief supplier of the major extensors of the hind legs, during stimulation of the common peroneal nerves. The extensor muscles had been denervated by appropriate dorsal root sections; the cats had been paralysed with a neuromuscular blocking agent.

2. Response versus interval curves were constructed using 1 Hz stimulation. When stimulation of one peroneal preceded another, the responses ipsilateral to the second stimulation were facilitated at testing intervals of −2 to 10 msec, and inhibited at intervals of 30–400 msec.

3. Responses from the L5 ventral roots mimicked ‘stepping’, waxing and waning at 1 Hz, only when 1 Hz was the best frequency for stimuli delivered to the two common peroneals (e.g. 24 and 25 Hz). When both sides were stimulated at the same frequency, no periodic changes in response amplitudes were seen.

4. It was concluded that the apparent ‘stepping’ in deafferented muscles seen by Sherrington may have been due to differences in frequency of the two inductoria he used to stimulate the peroneals. We found no evidence of central timing of a pattern corresponding to walking.
The release of vasopressin in response to haemorrhage and its role in the mechanism of blood pressure regulation
Authors: e Silva M. Rocha , Rosenberg Manuela
Published: December 2014

1. The release of vasopressin in response to haemorrhage and the effects of vasopressin infusions on blood pressure and heart rate have been investigated in anaesthetized dogs. Haemorrhage was produced by the method of Lamson & de Türk (1945), which allows for a precise control of the changes in arterial blood pressure.

2. Blood samples were collected from an external jugular vein, from a femoral vein or from a femoral artery and extracted with alcohol; blood extracts were assayed for antidiuretic activity.

3. Haemorrhage experiments showed that vasopressin secretion is increased when the fall in diastolic blood pressure (diastolic ΔP) is 25 mm Hg or more. Mild hypotensions (diastolic ΔP ranging from 21 to 30 mm Hg) produce an average fourfold increase in the concentration of vasopressin in blood. Such increase is maintained throughout the oligaemic period. Severe hypotensions produce, in most cases, a biphasic secretory response, with an initial high peak followed by a lower, constant, secretory plateau. In all experiments, the retransfusion of blood restored vasopressin to control levels.

4. Vasopressin infusion experiments showed that the amounts of hormone secreted in response to haemorrhage are sufficient to cause vasopressor response, provided that the buffering action of blood pressure regulation mechanisms is suppressed. It was also found that the amounts of vasopressin secreted in response to haemorrhage are apparently adequate, if the function of such secretion is to combat the hypotension which follows haemorrhage.

5. The effect of hypophysectomy on the blood pressure of animals previously submitted to bilateral division of the vagi and sinus nerves (deafferented animals) was also investigated. It was found that hypophysectomy is followed by a fall in arterial blood pressure which is positively correlated to the previous existing amounts of vasopressin. The time course of this hypotension is similar to that following the stopping of an infusion in a deafferented hypophysectomized animal. In some experiments it was shown that, following hypophysectomy, blood pressure can be restored to its pre‐hypophysectomy level by an adequate infusion of vasopressin.

6. It is proposed that the release of vasopressin in response to stimuli arising from cardiovascular sensory receptors plays a part in the mechanism of blood pressure regulation.
The redistribution of cardiac output on cold exposure in new‐born rabbits
Authors: Járai I.
Published: December 2014

1. In anaesthetized new‐born rabbits isotope‐labelled microspheres were injected into the left ventricle to investigate the distribution of cardiac output.

2. On cold exposure the proportion of radioactivity (and hence of cardiac output) distributed to brown adipose tissue rose from 6 to 19%. Similar results were obtained in ten rabbits in which the distribution of microspheres labelled with two different isotopes was examined both in a neutral thermal and cold environment.

3. The perirenal, inguinal, pectoral and axillary adipose tissue deposits showed a trivial increase in the proportion of cardiac output (from 1·2 to 1·9%) on cold exposure as compared with the cervical and interscapular deposits.

4. The small intestine of new‐born rabbits received 24% of the cardiac output while renal flow was only 8%. There were large changes in the proportions of body weight and in the distribution of cardiac output with age from 1 to 6 days from birth.

5. The results support the contention that brown adipose tissue is the principal site of additional thermogenesis in anaesthetized new‐born rabbits exposed to cold.
Changes in the maintained discharge with adaptation level in the cat retina
Authors: Barlow H. B. , Levick W. R.
Published: December 2014

1. The mean rate, impulse interval distribution, and pulse number distribution of the maintained discharge of ganglion cells in the retina of the cat have been studied after prolonged adaptation at different luminance levels.

2. From a state of complete dark adaptation up to a luminance of about 5 × 10−3 cd/m2 (viewed through a 7 mm2 pupil) the mean rate of on‐centre units increases. From darkness up to a somewhat higher luminance the mean rate of some off‐centre units decreases, but others show little change.

3. Above 10−2 cd/m2 the mean rate ceases to show a regular relation with adaptation level. On units often decrease and then increase again at a higher level. Rhythmical fluctuations are common near 10−2 cd/m2, especially if the retina is not in first class condition. Mean rates above 70/sec and below 1/sec are very rare at any adaptation level.

4. Over the range where mean rate increases monotonically with adaptation level, it is shown that the surround of on‐centre units does not inhibit and off responses cannot be elicited. When the monotonic increase is slowed or reversed it becomes possible to elicit responses from the surround. We suspect that the surround exerts a sustained, tonic, inhibiting effect at higher adaptation levels, thus holding down the maintained discharge.

5. There are rare units, forming less than 1% of those isolated, that show a regularly increasing frequency with increase of adaptation level above 10−2 cd/m2. These units have concentric ‘on’ and ‘off’ zones in their receptive fields, but the responses to rapidly changing stimuli are sluggish and they have an unusually regular maintained discharge. They have been tentatively called ‘luminance units’.

6. The impulse‐interval and pulse‐number distributions of on‐centre units change predictably with adaptation level; the variance of the pulse number distribution is usually several times the mean at very low adaptation levels, but only a fraction of the mean at high levels. Off‐centre units do not show predictable changes. Luminance units fire more regularly, and have narrower pulse‐number and impulse interval distributions than other concentric units.

7. A simple model is proposed to account for the statistical characteristics of the maintained discharge of on‐centre units.
A comparison of sweat gland activity in eight species of East African bovids
Authors: Robertshaw D. , Taylor C. R.
Published: December 2014

1. The pattern and control of the sweat glands of eight species of wild bovids has been studied.

2. Heat exposure resulted in changes in cutaneous moisture loss which showed considerable species variation. Duiker, Grant's gazelle, Thomson's gazelle and oryx all demonstrated periodic discharges of moisture on to the surface of the skin. Defassa waterbuck and eland exhibited discharges which were accompanied by a gradual rise in basal level. Buffalo showed an immediate large increase which was sustained during the period of heat exposure. Three wildebeest displayed small fluctuations whilst a fourth animal showed a step‐wise increment in cutaneous moisture loss.

3. The intravenous infusion of adrenaline into the buffalo and one wildebeest caused an increase in cutaneous moisture loss, the magnitude of which was directly related to the size of the dose administered. In three other wildebeest, and all other animals tested, a single injection of adrenaline was necessary to cause a discharge of moisture on to the surface of the skin. Noradrenaline was without effect.

4. Heat‐induced but not adrenaline‐induced sweating was inhibited by the intravenous administration of an adrenergic neurone blocking agent, bethanidine.

5. It is concluded that the sweat glands of the wild bovids studied are under adrenergic neurone control, in common with the domestic bovids previously studied, and that there is no correlation between the pattern of sweating and the phylogenetic position of the species.
The yellow colour of the lens of the grey squirrel (Sciurus carolinensis leucotis)
Authors: Cooper G. F. , Robson J. G.
Published: December 2014

1. The absorption spectrum of the lens of the grey squirrel (Sciurus carolinensis leucotis) has been measured, revealing an absorption maximum at 370 nm. Peak densities in the intact lens ranged from 12 to 20.

2. This peak is not present in the lenses of horse, cow, pig, dog, cat, ferret (Mustelo furo), or guinea‐pig (Cavia porcellus).

3. The pigment responsible for this absorption is water‐soluble and aqueous extracts have been examined. Protein‐free aqueous extracts show an additional maximum at 265 nm, which can only partially be accounted for by the presence of ascorbic acid.

4. The absorption spectrum of extracts of lens material from the ground squirrel (Citellus mexicanus) also had maxima at 265 and 370 nm.

5. Chromatography of the protein‐free solution separated two yellow components, both of which had a yellow fluorescence. The faster component had a very similar absorption spectrum to the original protein‐free solution.

6. Possible functions of the yellow pigment are discussed.
Light scattering and birefringence changes during activity in the electric organ of Electrophorus electricus
Authors: Cohen L. B. , Hille B. , Keynes R. D.
Published: December 2014

1. In an attempt to obtain information about structural changes related to electrical activity in Electrophorus electroplates, we have determined the size and time course of the changes in light scattering and in bire‐fringence that occur during and after the discharge of the electric organ.

2. The changes in light intensity detected with a photomultiplier were never greater than 0·2% for a single discharge, and were often much smaller than this, but records with an acceptable ratio of signal to noise could be obtained by signal‐averaging techniques.

3. A single stimulus led to a decrease, then an increase, and finally another decrease in the light scattered by slices of the main electric organ. These three phases were designated E1, E2 and E3.

4. E1 started at the beginning of the action potential, and its peak was reached at the same time as the completion of repolarization, even when the repolarization was delayed by cooling or hastened by drawing larger currents from the tissue.

5. E2 was proportional to the integral of the current flowing through the slice of electric organ, and may arise from the swelling and shrinking of the tubules that stud the faces of the electroplates. It developed within a millisecond or two of the start of an applied current, and lasted for about 100 msec.

6. E3 was a variable decrease in scattering that lasted for some seconds.

7. A stimulus also led to a transient increase in the birefringence of the electric organ. The optical change followed the change in electrical potential across the innervated faces of the electroplates with a delay of somewhat under 50 μsec.

8. This voltage‐dependent change in birefringence may arise from a Kerr effect (electric birefringence) in the membrane or from compression of the membrane.
Kinetics of potassium in colonic mucosa of normal and sodium‐depleted rats
Authors: Edmonds C. J.
Published: December 2014

1. The transport of K across the mucosal epithelium of the colon of normal and Na‐depleted rats has been investigated in vivo by methods involving
I.V. administration of solutions containing 42K and by labelling the mucosa with 42K from the lumen and observing the ‘soaking‐out’ rates into radionucleide‐free solutions.

2. During the infusions, the specific activity of the mucosal K was always less than the simultaneous specific activity of the secreted K. On stopping the infusion the specific activity of the mucosal K fell although the plasma specific activity remained at all times greater than that of the mucosa. The blood flow rate to the mucosa estimated from these results was 0·95 ml./min.g wet wt.

3. Experiments with 42K in the lumen showed that the steady‐state specific activity of the mucosal K was considerably less than expected if the K had been in a single compartment. The 42K efflux curves were also consistent in showing two components. The curves were analysed on the basis of a model having two compartments in the mucosa with half‐times of 6 and 33 min.

4. Na depletion produced two significant changes, (a) K secretion rate doubled, (b) the steady‐state specific activity of the mucosal K after luminal exposure to 42K was increased. The half‐times of the compartments were unaffected.

5. The results were discussed in terms of a working hypothesis which represented the mucosal K in two compartments. Most of the K exchanges across the mucosa took place through the smaller compartment which probably contained 5% or less of the mucosal K, but which had a rapid turnover rate. The change of K permeability of the luminal face produced by Na depletion and probably due to increased aldosterone action, may well be an important factor in producing the rise of K secretion rate.
After‐effects of nerve impulses on signalling in the central nervous system of the leech
Authors: Baylor D. A. , Nicholls J. G.
Published: December 2014

A long‐lasting hyperpolarization has been observed in sensory neurones of the
C.N.S. of the leech following natural stimulation applied to their receptive fields. The underlying mechanism of this hyperpolarization and its effects on signalling were investigated by intracellular recording.

1. The amplitude and duration of the hyperpolarization depended on the number of action potentials. Whereas a brief burst of impulses had little effect, a prolonged sensory discharge was followed by a hyperpolarization of up to 30 mV that gradually declined over a period of several minutes.

2. The hyperpolarization was abolished by ouabain, reversibly inhibited by strophanthidin or cooling, unaffected by Mg and accompanied by an increase in membrane resistance. These observations suggest that the hyperpolarization is the result of membrane current generated by an electrogenic pump.

3. A hyperpolarization similar to that recorded in the cell body also occurred in the neuronal processes within the neuropile, where synaptic contacts are made. This led to significant changes in integrative activity, such as an increase in the amplitude of excitatory synaptic potentials, a reversal of inhibitory synaptic potentials or a conduction block in parts of the neurones. All of these effects could be mimicked by injecting hyperpolarizing currents into resting cells, or abolished by injecting a depolarizing current into a cell hyperpolarized by previous impulses.

4. During neuronal hyperpolarization the sensitivity of the membrane potential to small increments of external K was enhanced by a factor of about three. This effect varied with the magnitude of the hyperpolarization produced by preceding impulses and could not be mimicked by applying K to a neurone hyperpolarized by the injection of current into its cell body.

5. These findings are discussed in relation to possible effects that changes in the intracellular and extracellular concentrations of ions produced by activity might have on integration in the
C.N.S.
Dynamic properties of fast and slow skeletal muscles of the rat after nerve cross‐union
Authors: Close R.
Published: December 2014

1. The properties of self‐innervated (S‐EDL, S‐SOL) and cross‐innervated (X‐EDL, X‐SOL) extensor digitorum longus (EDL) and soleus (SOL) muscles have been determined at various times between 25 and 490 days after operations, and these are compared with the properties of normal muscles from unoperated animals of about the same age.

2. The muscle fibres of X‐SOL were 1·15 times longer than fibres of N‐SOL and S‐SOL at about 480 days after operations but the diameter of fibres was the same in the three muscles.

3. The length of muscle fibres was the same in X‐EDL, N‐EDL and S‐EDL 480 days after operations but the fibres of X‐EDL failed to grow in cross‐sectional area after innervation by soleus nerve fibres.

4. The twitch: tetanus ratio was altered transitorily in both X‐EDL and X‐SOL but returned to near normal values within about 300 days after operations.

5. The time courses of isometric contractions and the force: velocity properties were virtually the same in normal and self‐innervated muscles 480 days after operations. The isometric twitch contraction time was about 13 msec for N‐EDL, 25 msec for X‐EDL, 34 msec for N‐SOL and 15 msec for X‐SOL, and the intrinsic speed of shortening of sarcomeres was about 45·1 μ/sec for N‐EDL, 22·5 μ/sec for X‐EDL, 19·8 μ/sec for N‐SOL and 33·8 μ/sec for X‐SOL; in these respects there was incomplete transformation of EDL to a slow muscle and of SOL to a fast muscle.

6. There was a high degree of correlation between the intrinsic speed of shortening of sarcomeres and the isometric twitch contraction time but there was no correlation between isometric twitch contraction time and twitch: tetanus ratio of self‐innervated and cross‐innervated muscles 200–480 days after operations, and normal muscles from unoperated animals of the same age.

7. The relation between intrinsic speed of shortening of sarcomeres and isometric twitch contraction time was approximately hyperbolic for normal, self‐innervated and cross‐innervated EDL and SOL muscles 480 days after operations.

8. The maximum speed of shortening of whole muscle fibres was the same for X‐SOL, S‐EDL and N‐EDL, and the same for X‐EDL, S‐SOL and N‐SOL. The possibility that a neural influence determines the speed of shortening of whole fibres is discussed.
Identification of adenosine triphosphate in human plasma and the concentration in the venous effluent of forearm muscles before, during and after sustained contractions
Authors: Forrester T. , Lind A. R.
Published: December 2014

1. When diluted human plasma is perfused through a frog heart, a marked augmentation of the heartbeat is produced which is very similar in action to that of low concentrations of adenosine triphosphate (ATP) on the heart.

2. It was established that the substance in the plasma responsible for the heart stimulation was ATP. The following tests were used: (a) the diluted plasma emitted light from firefly lantern extract characteristic of the light signal produced by a solution of ATP; (b) the stimulatory effect on the frog heart and luminescent effect upon the firefly extract were abolished by incubation of the plasma solution with the enzyme apyrase, which converts ATP to adenosine monophosphate (AMP); AMP does not stimulate the heart or cause light to be emitted from firefly extract; (c) the stimulatory substance in the plasma was eluted through a column of Sephadex G‐25 in the same pattern as ATP; and (d) simultaneous assay of plasma solutions on frog heart and firefly extract produced the same quantitative result as that produced by a solution of ATP.

3. The amount of ATP in plasma from the venous blood of resting subjects ranged from 0·19 to 0·95 μg/ml. (mean 0·63 μg/ml.,
S.D. ± 0·25); up to half of the ATP detected could be attributed to blood platelet damage. Simultaneous arterial and venous samples of blood from four subjects at rest had mean concentrations of 0·19 μg/ml. (0·07–0·26 μg/ml.) and 0·70 μg/ml. (0·57–0·84 μg/ml.) respectively.

4. The concentration of ATP in the venous effluent from exercising forearm muscles was measured. The venous concentration consistently increased over the resting values in response to exercise while in one subject little change occurred in the arterial blood concentration during the exercise. It was concluded that the ATP was added to the blood in its passage through the muscle bed.

5. The origin of the ATP, including erythrocytes, blood platelets and active skeletal muscle, is discussed.
Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat
Authors: Matthews P. B. C.
Published: December 2014

1. The size of the tonic stretch reflex of the soleus or gastrocnemius muscle of the decerebrate cat has been compared with the size of the reflex contraction elicited in the same muscle by high‐frequency vibration applied to its tendon.

2. On the assumption that vibration preferentially excites the primary endings of the muscle spindles it may be used to estimate the relation between the reflex response and the frequency of the Ia input to the spinal cord. On this basis, the increase in tension evoked by increasing extension is too great to be explained by the increase in Ia input with extension previously found on single fibre recording in comparable preparations.

3. When vibration was superimposed on stretch reflexes elicited by different extensions, the size of the additional contraction elicited by the vibration remained approximately constant. If the stretch and vibration reflexes both depended entirely upon the Ia pathway, then occlusion between them would have been expected instead of the simple summation which was found.

4. The absence of occlusion was not due to variation of the contractile strength of the muscle with its extension. This was shown by finding that the reflex contraction of soleus produced by stimulating the medial gastrocnemius nerve also remained the same size when elicited at different lengths of the muscle.

5. The reflex effects were studied of superimposing alternate stretches and releases of 0·2 mm, on extensions of several mm. The small stretches elicited responses which were larger than expected from the response to large stretches, and which were approximately the same size at different mean lengths of the muscle.

6. It is concluded that the tonic stretch reflex of the decerebrate cat cannot readily be explained solely by the increase in Ia discharge produced by stretching, as usually believed. Instead, it is suggested that the group II afferent fibres from the secondary endings of the muscle spindle also play an important part in its production.
Potential differences between mother and foetus at different gestational ages in the rat, rabbit and guinea‐pig
Authors: Mellor David J.
Published: December 2014

1. Potential differences associated with fluid compartments of rat, rabbit and guinea‐pig conceptuses have been measured. [Na+] and [Cl−] in maternal plasma and amniotic fluid from these three species were also determined.

2. Transplacental potential differences of about 15 mV (foetus positive) were found in the rat, of approximately 0 mV in the rabbit, and of about 18 mV (foetus negative) in the guinea‐pig.

3. Amniotic fluid potential differences appeared to arise indirectly from the transplacental potential difference in the rat, from the foetal gastric mucosa in the rabbit, and possibly from the foetal gastric mucosa and indirectly from the placenta in the guinea‐pig.

4. The results are discussed in the context of Na+ transfer to the foetus, and on this basis tend to question the general assumption that almost all Na+ reaching the foetus passes across the placenta.
On the metabolic basis of nervous activity
Authors: den Hertog A. , Greengard P. , Ritchie J. M.
Published: December 2014

1. A study has been made of the metabolic substrates that can support the active extrusion of sodium ions from mammalian non‐myelinated nerve fibres. The post‐tetanic hyperpolarization obtained in chloride‐free Locke solution, which reflects the electrogenic component of the sodium pump, was used as the index of metabolic activity.

2. When glucose was removed from the Locke solution there was no immediate change in the size of the post‐tetanic hyperpolarization.

3. However, glucose is essential for metabolism in nerve fibres; for when a competitive inhibitor, deoxy‐
D‐glucose, was added to the Locke solution the post‐tetanic response was much reduced or abolished. Larger concentrations of deoxy‐
D‐glucose were required in the presence of glucose than in its absence.

4. This effect of deoxy‐
D‐glucose could be reversed by glucose, fructose, pyruvate and acetate.

5. The depressant effect of deoxy‐
D‐glucose was enhanced by oxaloacetate and by malate.

6. Malonate, a competitive inhibitor of the conversion of succinate to fumarate, reduced or abolished the post‐tetanic hyperpolarization.

7. This effect of malonate could be overcome by glucose and by pyruvate.
Immunohistochemical localization of protein components of catecholamine storage vesicles
Authors: Geffen L. B. , Livett B. G. , Rush R. A.
Published: December 2014

1. The distribution of specific proteins in sympathetic neurones has been examined by immunofluorescent histology using antibodies prepared against soluble protein components of the catecholamine storage vesicles of the adrenal medulla.

2. Two antigen preparations were separated by ion exchange chromatography of the soluble proteins released on osmotic lysis of catecholamine storage vesicles which had been isolated by centrifugation from homogenates of sheep adrenal medulla. One fraction (AgDH) had high dopamine‐β‐hydroxylase activity, while another (AgCB), consisting of the bulk of the protein, had some capacity to bind catecholamines. On disk gel electrophoresis the antigens ran as single bands with very different mobilities.

3. Antisera (AsDH) and (AsCB) produced in rabbits to the two antigens were shown to react specifically with their antigens by immunodiffusion and electrophoresis in agarose.

4. Indirect immunofluorescent staining of tissue sections was achieved by layering first the rabbit anti‐sera, followed by goat anti‐rabbit globulin serum which had been conjugated with fluorescein isothiocyanate.

5. The adrenal medulla and the cell bodies of sympathetic ganglia showed the most intense green fluorescence with the immune rabbit sera, and hardly stained when pre‐immune serum from the same animal was used. The reactivity of the antisera could be abolished by incubation with the corresponding antigen.

6. The preterminal and terminal axons of sympathetic nerves also stained specifically but less intensely with both antisera. When the nerves were ligated for up to 24 hr, the portion immediately proximal to the constriction showed an enhanced reaction to the antisera.

7. The results provide evidence that sympathetic neurones contain proteins immunologically identical to those involved in the synthesis and storage of noradrenaline in the adrenal medulla, and support the concept that granular vesicles are synthesized in the perikaryon of the neurone and are transported somatofugally in the axon.
Membrane currents underlying delayed rectification and pace‐maker activity in frog atrial muscle
Authors: Brown Hilary F. , Noble Susan J.
Published: December 2014

1. A double sucrose gap method has been used to polarize and voltage clamp frog atrial muscle strips.

2. In response to steady depolarizing currents, normally quiescent strips often show pace‐maker activity, and long lasting depolarization occurs when the current is terminated.

3. Voltage clamp experiments reveal the presence of two current components underlying delayed rectification.

4. The first of these components has a time constant which varies with potential and is approximately 500 msec at −90 mV. Its reversal potential usually lies between −70 and −40 mV and has always been found to be positive to the resting potential of normally quiescent fibres.

5. The time constant of the second component is extremely slow (τ [unk] 5 sec at −90 mV). Its reversal potential is much more positive than that of the faster component.

6. The results confirm the presence of a component of inward current which is insensitive to tetrodotoxin (TTX), having an activation threshold about 20 mV positive to the sodium threshold. This current differs from the two components underlying delayed rectification both in its greater speed of activation and in showing inactivation. The inactivation of this TTX‐insensitive current is also a fairly rapid process.

7. It is suggested that pace‐making in sino‐atrial muscle may depend upon the deactivation of the faster component of delayed rectification and that the TTX‐insensitive inward current is also involved.
A quantitative analysis of the slow component of delayed rectification in frog atrium
Authors: Brown Hilary F. , Noble Susan J.
Published: December 2014

1. The slow component of delayed rectification in the atrial muscle membrane of Rana ridibunda has been analysed quantitatively using a voltage‐clamp technique.

2. It is shown that the current is proportional to a variable which obeys first‐order kinetics. At negative potentials the time constant of this process is very long (τ = 3 sec at −55 mV) but it becomes faster at positive potentials (τ = 1·85 sec at +25 mV).

3. In the steady state the degree of activation is a sigmoid function of potential. The activation threshold varies substantially between preparations but is usually negative to −30 mV.

4. The instantaneous current—voltage relation is nearly linear and its reversal potential most frequently lies between zero and −30 mV.

5. The properties of this current system resemble those of the current system ix2 found in mammalian Purkinje fibres.
Interaction of 28Mg with Ca and K in the smooth muscle of guinea‐pig taenia coli
Authors: Sparrow M. P.
Published: December 2014

1. The uptake of 28Mg, and the total tissue content of Mg, Ca, Na and K have been determined in the smooth muscle of the guinea‐pig taenia coli. The Mg content was 6·56 m‐mole/kg fresh wt. immediately after dissection, falling slowly to 5·11 after 6 hr immersion in Krebs solution at 37° C.

2. The Mg content rose to 15·4 m‐mole/kg fresh wt. during immersion in isotonic sucrose containing only MgCl2. It was independent of the Mg2+ concentration in this solution, but was depressed when K+ or Ca2+ ions were added.

3. 28Mg uptake showed three separate phases, extracellular, intermediate and slow. The size of the extracellular phase was proportional to the Mg2+ concentration in the solution, but the size of the slow phase was constant. The size of the intermediate phase, exchanging with a half‐time of a few minutes, was depressed when K+ or Ca2+ ions were added.

4. The results are compatible with a competition between Mg in the intermediate phase of tracer exchange, and K+ or Ca2+ ions for fixed anionic sites in the tissue.
The activities and concentrations of sodium and potassium in toad oocytes
Authors: Dick D. A. T. , McLaughlin S. G. A.
Published: December 2014

1. The activity of potassium, aK, in the cytoplasm of oocytes from the toad, Bufo bufo, as measured by potassium‐sensitive glass micro‐electrodes, was 82 m
M. The concentration of potassium, CK, in oocytes from the same ovaries, as determined by flame photometric analysis, was 113 m
M. The ratio aK/CK = 0·73 does not differ significantly from the measured activity coefficient of the normal Ringer bathing solution, which is 0·75.

2. The activity of sodium, aNa, in the cytoplasm of toad oocytes, as measured by sodium‐sensitive glass micro‐electrodes, was 9·3 m
M. The concentration of sodium, CNa, in oocytes from the same ovaries, as determined by flame photometric analysis, was 25·8 m
M. The value of the aNa/CNa ratio in the cells, 0·36, is only about half the value of either the aK/CK ratio in the cells or the activity coefficient of sodium in the normal Ringer bathing solution. This implies that about half the sodium in the cell is sequestered in some manner, such that it is unavailable to affect a cation‐sensitive micro‐electrode.

3. When the oocytes were bathed for 5 hr in a sodium‐free, lithium‐substituted, Ringer solution the aNa/CNa ratio decreased to 0·06–0·10. This drop in the aNa/CNa ratio implies that the sodium available to the cation‐sensitive micro‐electrode can leave the cell much faster than the sequestered sodium.
Sweat gland function of the donkey (Equus asinus)
Authors: Robertshaw D. , Taylor C. R.
Published: December 2014

1. Donkeys sweat on exposure to heat and in response to intravenous adrenaline infusion.

2. Thermal sweating was abolished by the adrenergic‐neurone blocking agent bethanidine but not by atropine.

3. Sympathetic decentralization (by preganglionic sympathectomy) abolished thermal sweating but adreno‐medullary denervation had no effect.

4. Exercise resulted in sweating from both sympathetically innervated and decentralized skin and from the innervated skin of animals which had previously undergone adreno‐medullary denervation.

5. Insulin‐induced hypoglycaemia resulted in sweating from sympathetically decentralized skin and from innervated skin in two out of four animals. Adreno‐medullary denervation abolished the sweat gland response to insulin administration.

6. Cold exposure inhibited the response of innervated sweat glands but not that of decentralized glands to adrenaline infusion.

7. It was concluded that heat‐induced and exercise‐induced sweating of the donkey is controlled by adrenergic nerves; adreno‐medullary secretion may contribute to sweating during exercise, and that cutaneous blood flow is important in the response of the glands to humoral stimulation.
Mechanical properties of glycerinated fibres from the tymbal muscles of a Brazilian cicada
Authors: Aidley D. J. , White D. C. S.
Published: December 2014

1. Some of the properties of glycerinated fibres from the synchronous tymbal muscles of the cicada Fidicina rana have been investigated.

2. In the presence of suitable concentrations of ATP and calcium ions, the fibres are able to perform oscillatory work when subjected to small sinusoidal length changes in the frequency range 2‐30 c/s.

3. When subjected to abrupt changes in length, active fibres show a delayed increase in tension after a stretch and a delayed decrease in tension after release.

4. The muscle fibres therefore show the mechanical properties characteristic of glycerinated fibres from asychronous insect flight muscles. Some implications of this finding in relation to the evolution of asynchronous muscles are discussed.
Influence of carotid baroreceptors on different components of the vascular system
Authors: Brender David , Webb‐Peploe Michael M.
Published: December 2014

1. Reflex changes in wall tension of the lateral saphenous vein of one hind limb, the splenic veins and capsule, and the resistance vessels of the other hind limb caused by changes in baroreceptor activity were measured in vagotomized dogs under thiopentone‐chloralose anaesthesia.

2. Three different methods were used to alter pressure in one or both carotid sinuses. (1) Both carotid sinuses were vascularly isolated and filled with fully oxygenated Krebs—Ringer bicarbonate solution (pH 7·4) from a reservoir in which the pressure could be altered at will. (2) One sinus was denervated, and the contralateral sinus was perfused with arterial blood at different flow rates. (3) One sinus was denervated, and the innervated sinus was perfused with arterial blood at constant flow, the pressure being altered by changing the outflow resistance.

3. The left saphenous vein was perfused at constant flow with autologous blood; changes in perfusion pressure were used as a measure of changes in veno‐motor activity. The right common iliac artery was perfused at constant flow to measure changes in resistance vessel activity. Blood flow through the spleen was temporarily arrested, trapping a fixed volume of blood in the organ. Under these conditions, changes in splenic vein pressure were a measure of changes in smooth‐muscle tension in the splenic capsule and veins.

4. In order to assess the responses to baroreceptor stimulation in terms of alterations in sympathetic nerve traffic to different components of the peripheral vascular system, ‘frequency—response curves’ were constructed for spleen, saphenous vein, and limb resistance vessels by electrical stimulation of the splenic nerves and lumbar sympathetic chains.

5. The saphenous vein showed no consistent response to changes in baroreceptor activity. Reduction in carotid sinus pressure from 180 to 100 mm Hg caused an increase in venous pressure in the isovolumetric spleen and in the iliac artery perfusion pressure. These results were confirmed by electrical stimulation of the carotid sinus nerve. Whereas the peak responses of the limb resistance vessels corresponded to an increase in lumbar sympathetic nerve traffic of 6–10 c/s, the maximal splenic responses were equivalent to an increase in splenic nerve traffic of 1‐4 c/s. These results are consistent with selective autonomic nervous control of different components of the peripheral vascular system.
Presynaptic inhibition of the monosynaptic reflex by vibration
Authors: Gillies J. D. , Lance J. W. , Neilson P. D. , Tassinari C. A.
Published: December 2014

In cats, the monosynaptic reflex (MSR) elicited from L7 or S1 dorsal roots, or from the tibial nerve (H reflex) was suppressed by vibration at 50–500 c/s of the hind limb with innervation intact. The MSR was not suppressed by selective vibration of cutaneous receptors, and suppression was still observed after the hind limb was skinned. In contrast, the phenomenon disappeared when all muscle nerves were crushed.

Suppression of the MSR by vibration was shown to be mediated by presynaptic inhibition by the following methods: correlation with onset of the dorsal root potential (DRP) evoked by vibration, and abolition of both DRP and reflex suppression by picrotoxin; demonstration of primary afferent depolarization and normal excitability of motoneurones to direct stimulation.

Reasons are given for deducing that the muscle afferent fibres responsible for the presynaptic inhibition induced by vibration are group Ia rather than groups Ib or II, or afferent fibres from Pacinian corpuscles.
The effect of urea loading on volume and concentration of urine in rabbits
Authors: Stanier Margaret W.
Published: December 2014

1. To find how urea contributes to the water‐conserving ability of a herbivore's kidney, groups of ten young rabbits on a low‐protein diet and at three different levels of dietary electrolyte were given 1·8 g urea by mouth daily for 3 days. Vasopressin was administered daily to half the animals in each group.

2. The urinary osmolarity and urea output of each animal was recorded daily during the urea loading and for a 3‐day control period before and after loading. The renal water requirement for non‐urea solute output (defined as daily volume/daily non‐urea solute output) was calculated. The sodium content of renal cortex and medulla was measured in some animals from each group.

3. Urea caused additional water excretion only in those rabbits which were receiving the low‐salt diet. There was invariably increased water excretion when the ratio of urea to non‐urea solute output exceeded 2.

4. In most of the rabbits on normal‐salt and high‐salt intake, urea produced little change in the volume in which non‐urea solute was excreted. Three out of the ten high‐salt animals showed significant reduction of this volume during urea‐loading.

5. Vasopressin significantly reduced the volume required for non‐urea solute output, but the effect of vasopressin was independent of urea‐loading and of dietary electrolyte level.

6. The low‐electrolyte diet significantly reduced the sodium concentration in the rabbits’ renal medullary tissue.

7. It is concluded that in rabbits urea contributes to water retention mainly by its high permeability, enhanced by vasopressin, which permits maximal water reabsorption in the renal medulla. Water retention by means of uphill transport of urea, if it occurs at all, is slight.
Secretomotor function of the dorsal motor nucleus of the vagus
Authors: Kerr F. W. L. , Preshaw R. M.
Published: December 2014

1. The effect of chronic ablation of the dorsal motor nucleus of the vagus on insulin‐induced secretion of acid by the stomach has been investigated in conscious cats.

2. Destruction of this nucleus results in a persistent profound reduction in gastric secretion of acid under these experimental conditions, while the visceromotor and cardioinhibitory effects of stimulation of the distal end of the acutely transected ipsilateral cervical vagus were unaffected.

3. It is concluded that the dorsal motor nucleus is a secretomotor centre.