bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanism of peripherally evoked responses in retinal ganglion cells.
Authors: Derrington A M , Lennie P , Wright M J
Published: December 2014

1. Responses to stimulation of retinal regions remote from the classical receptive field were recorded from optic tract fibres in lightly anaesthetized cats. 2. X‐ and Y‐cells gave reliably different responses to the sudden reversal of the phase of a high contrast grating that fell on the retina more than 15 deg from the centre of the receptive field. 3. The mechanism that generates these responses ('shift effect' or 'periphery effect') in Y‐cells is insensitive to the spatial phase of the stimulating grating. It can resolve gratings of higher spatial frequency than can be resolved by the classical receptive field mechanisms of Y‐cells but its temporal resolution is poorer. 4. Signals that contribute to peripherally evoked responses are accumulated over a region that extends to at least 35 deg from the centre of the receptive field. Although this region is not uniformly sensitive, regions in the periphery of the visual field are as effective as regions around the area centralis in eliciting the responses, and do not require coarser gratings. 5. In some Y‐cells the response to peripheral stimulation was amplified by increasing (on‐centre units) or decreasing (off‐centre units) the steady illumination of the centre of the receptive field. This confirms Krüger & Fisher (1973), but the effect is only found in a proportion of cells. 6. The mechanism that generates peripherally evoked responses is tentatively identified with the 'rectifying subunits' postulated by Hochstein & Shapley (1976b) to account for the spatial non‐linearity in the receptive fields of Y‐cells. Transient (bistratified) amacrine cells are known to have many of the properties attributed to these mechanisms (Chan & Naka, 1976).
The effect of ouabain on amino acid and orthophosphate influxes in squid giant axons.
Authors: Caldwell P C , Lea T J
Published: December 2014

1. Some effects of ouabain on the uptake of 14C‐labelled amino acids and 32P‐labelled orthophosphate into squid axons have been investigated. 2. Ouabain in artificial sea water reduced the uptake of glycine, L‐alanine, L‐arginine, L‐aspartate and L‐glutamate. After a period of 3 hr in ouabain the inhibition of glycine and L‐glutamate uptake was appreciable. 3. After 3 hr in ouabain the axoplasmic Na concentration had increased by only about 14% and the K concentration had fallen by only about 9%. It therefore seems unlikely that changes in the Na and K gradients across the membrane due to ouabain are the reason for the inhibition of amino acid uptake. This was confirmed when the axons were made to conduct impulses at 200/sec for 40 min. There was no subsequent inhibition of glycine and L‐glutamate uptake, even though the axoplasmic Na increased by about 42% and the K decreased by about 37%. 4. A detailed investigation of the time course of the inhibition of amino acid uptake by ouabain in which intracellular scintillator techniques were used, showed that there was no inhibition for 30‐‐100 min, and then it occurred fairly quickly. This course of events was not affected by the protein synthesis inhibitor cycloheximide. It is unlikely that the inhibition of orthophosphate uptake is subject to a similar delay since this had reached a maximum after 40 min. 5. It is concluded that the inhibitory effects of ouabain on amino acid uptake in squid axons are not due to effects on the Na and K gradients brought about by inhibition of the Na‐K pump. The delay in the inhibiton may reflect the operation of an intracellular regulatory mechanis, which is initiated when ouabain inhibits the pump but which takes time to operate. If the formation of an inhibitory second messenger molecule is involved this is unlikely to be a protein.
Dependence of phrenic motoneurone output on the oscillatory component of arterial blood gas composition.
Authors: Cross B A , Grant B J , Guz A , Jones P W , Semple S J , Stidwill R P
Published: December 2014

1. The hypothesis that respiratory oscillations of arterial blood gas composition influence ventilation has been examined. 2. Phrenic motoneurone output recorded in the C5 root of the left phrenic nerve and the respiratory oscillations of arterial pH in the right common carotid artery were measured in vagotomized anaesthetized dogs which had been paralysed and artificially ventilated. 3. The effect of a change in tidal volume for one or two breaths on phrenic motoneurone output was measured with the inspiratory pump set at a constant frequency similar to, and in phase with, the animal's own respiratory frequency. A reduction of tidal volume to zero or an increase by 30% led to a corresponding change of mean carotid artery pH level. The changes of carotid artery pH resulted in a change of phrenic motoneurone output, predominantly of expiratory time (Te) but to a lesser extent of inspiratory time (T1) and also peak amplitude of 'integrated' phrenic motoneurone output (Phr). Denervation of the carotid bifurcation blocked this response. 4. The onset of movement of the inspiratory pump was triggered by the onset of phrenic motoneurone output. When a time delay was interposed between them, the phase relationship between respiratory oscillations of arterial pH and phrenic motoneurone output altered. The dominant effect was to alter Te; smaller and less consistent changes of Phr and T1 were observed. 5. When the inspiratory pump was maintained at a constant frequency but independent of and slightly different from the animal's own respiratory frequency (as judged by phrenic motoneurone output), the phase relationship between phrenic motoneurone output and the respiratory oscillations of pH changed breath by breath over a sequence of 100‐200 breaths, without change of the mean level of arterial blood gas composition. Te varied by up to 30% about its mean value depending on the phase relationship. Ti and Phr were also dependent on the phase relationship but varied to a lesser extent. The changes were comparable to the results obtained in paragraph 4. 6. It was concluded that phrenic motoneurone output is dependent in part on its relationship to the respiratory oscillations of arterial blood gas composition. 7. Information concerning a transient ventilatory disturbance is stored in the arterial blood in the form of an altered pattern of the respiratory oscillations of blood gas composition; this in turn can change breathing by an effect on the carotid bodies.
Hormones, feeding and temperature in sheep following cerebroventricular injections of neurotransmitters and carbachol.
Authors: Driver P M , Forbes J M , Scanes C G
Published: December 2014

1. The neural mechanisms involved in the control of prolactin and growth hormone secretion, body temperature and feeding in castrated male sheep were investigated by the lateral cerebroventricular injection of several putative neurotransmitters and carbachol. 2. Feeding was inhibited by 10 and 20 microgram carbachol and by 400 microgram histamine. 100 microgram Noradrenaline stimulated, but 200 microgram inhibited, feeding; however, both results were non‐significant compared with controls. 3. 20 microgram Carbachol elicited a highly significant rise in plasma growth hormone, suggesting a cholinergic component in the neural control of growth hormone in sheep. Noradrenaline, dopamine and 5‐hydroxytryptamine, but not melatonin, significantly depressed plasma prolactin concentration indicating a similar neural control for the hormone's release in sheep as in other species. 4. Deep body temperature appeared unaffected by any ofthe injected drugs. 5. The possible interrelationships between feeding behaviour and the circulating levels of growth hormone in ruminants is discussed. 6. A method for the radioimmunoassay of ovine growth hormone is described and validated.
Hypothalamic receptors influencing the secretion of corticotrophin releasing hormone in the rat
Authors: Buckingham Julia C. , Hodges J. R.
Published: December 2014

1. The production of corticotrophin releasing hormone (CRH) by the rat hypothalamus in vitro was studied in the presence and absence of various neurotransmitter substances and drugs which mimic or antagonize their actions.

2. Acetylcholine, nicotine and bethanechol increased, in a dose‐related manner, hypothalamic CRH release and content but the maximal responses to bethanechol or nicotine were less than those to acetylcholine.

3. The actions of acetylcholine were antagonized by atropine, pempidine and hexamethonium but were completely inhibited only when atropine and pempidine were given together. The effects of nicotine were abolished by pempidine but not by atropine while those of bethanechol were abolished by atropine but not by pempidine.

4. Acetylcholine‐induced hypothalamic CRH activity was also antagonized by cyproheptadine but not by methysergide.

5. 5‐Hydroxytryptamine caused dose‐related increases in hypothalamic CRH release and content. Its effects were antagonized by cyproheptadine and methysergide but not by atropine, pempidine or hexamethonium.

6. Acetylcholine‐induced increases in hypothalamic CRH production were reduced by GABA, noradrenaline, adrenaline, methoxamine and phenylephrine but not by isoprenaline. The actions of GABA were antagonized by bicuculline and those of noradrenaline by phentolamine but not by atenolol.

7. The results suggest the presence of nicotinic and muscarinic cholinoceptors, 5‐hydroxytryptamine receptors, α‐adrenoceptors and GABA‐receptors within the hypothalamus all of which may be important in the control of CRH secretion.
The role of circulating renin in drinking in response to isoprenaline
Authors: Atkinson J. , Kaesermann H.‐P. , Lambelet Josette , Peters G. , Peters‐Haefeli Lise
Published: December 2014

1. In nephrectomized rats,
S.C. (0·12 mg. kg body wt.−1) or intracerebroventricular (
I.C.V.: 0·03 mg. kg−1), isoprenaline failed to elicit drinking. However, when preceded (5‐20 min) by a non‐dipsogenic dose of
I.V. pig renin,
S.C. isoprenaline induced a marked, and
I.C.V. isoprenaline a smaller drinking response. 2 hr after
I.V. renin,
S.C. isoprenaline no longer caused drinking.

2. Pig renin did not enhance drinking in response to 0·12 mg. kg−1 isoprenaline
S.C. in intact or sham‐operated rats.

3. Isoprenaline (0·12 mg. kg body wt.−1,
S.C.) caused a larger fall of blood pressure in unanaesthetized nephrectomized than in intact unanaesthetized rats, but it was not the resulting hypotension that interfered with the nephrectomized rats’ ability to drink, since intact rats with similar falls in blood pressure drank avidly in response to large doses of isoprenaline.

4. Since the rate of inactivation of pig renin in nephrectomized rats was not modified by isoprenaline, drinking in nephrectomized animals in response to renin+isoprenaline was not attributable to increased plasma renin levels.

5. Since isoprenaline induces drinking in the presence of circulating renin, but in the absence of renin release from kidneys, renin plays a permissive role in isoprenaline‐induced drinking. Angiotensin and isoprenaline may interact at the level of intracranial receptors.
Electrical coupling between cones in turtle retina.
Authors: Detwiler P B , Hodgkin A L
Published: December 2014

1. The electrical coupling between cones of known spectral sensitivity in the peripheral part of the turtle's retina was studied by passing current through a micro‐electrode inserted into one cone and recording with a second micro‐electrode inserted into a neighbouring cone. 2. Spatial sensitivity profiles were determined by recording flash responses to a long narrow strip of light which was moved across the impaled cones in orthogonal directions. These measurements gave both the length constant lambda of electrical spread in the cone network and the separation of the two cones. 3. The cone separation determined from the spatial profiles agreed closely with that measured directly by injecting a fluorescent dye into two cones. 4. The length constant lambda varied from 18 to 39 micron with a mean of 25 micron for red‐sensitive cones and 26 micron for green‐sensitive cones. 5. The majority of cone pairs studied were electrically coupled provided they had the same spectral sensitivity and were separated by less than 60 micron: thirty‐two out of thirty‐six red‐red pairs, two out of two green‐green pairs, none out of eight red‐green pairs: no blue cones were observed. 6. The strength of electrical coupling was expressed as a mutual resistance defined as the voltage in one cell divided by the current flowing into the other. Mutual resistances decreased from a maximum value of about 30 M omega at separations close to zero to 0.2 M omega, the lower limit of detectable coupling at separations of about 60 micron. Mutual resistances were always positive and were independent of which cell was directly polarized. The coupling seemed to be ohmic and any rectification or non‐linearity probably arose in the cone membranes rather than in the coupling resistances. 7. The results were analysed in terms of the Lamb & Simon (1977) theories of square and hexagonal lattices, which approximate to the continuous sheet model except in the case of the cone to which current is applied. 8. The total membrane resistance of a single cone was estimated as 100‐‐300 M omega and the connecting resistances as 100 M omega for a square array and 170 M omega for a hexagonal array. The input resistance of a cone in the network was 25‐‐50 M omega. Lower values were often obtained but may be due to injury by the micro‐electrodes. 9. The time constant of an isolated cone was estimated as about 20 msec and the capacity as about 100 pF. 10. Discrepancies between experimental findings and theoretical predictions of the hexagonal or square array models were tentatively attributed to an overestimate of lambda resulting from light scattering.
Size, scatter and coverage of ganglion cell receptive field centres in the cat retina.
Authors: Peichl L , Wässle H
Published: December 2014

1. Receptive field centre sizes of brisk‐sustained (X) and brisk‐transient (Y) ganglion cells of the cat retina were assessed by three different methods: small spot mapping, area threshold method and spatial resolution. 2. Centre sizes of brisk‐sustained (X) cells increased from 20' in the central area to about 70' at an eccentricity of 4.5 mm, centre sizes of brisk‐transient (Y) cells from 50' in the central area to about 140' at 5 mm eccentricity. 3. The scatter of centre sizes at one retinal location was measured by recording as many ganglion cells as possible in one cat in a small field of retina. The centre sizes of the individual classes were homogeneous and exhibited only a small amount of scatter. 4. The coverage of the retina by the different ganglion cell classes was assessed from their density and their receptive field centre area. At every retinal location the receptive field centres of seven to twenty brisk‐sustained (X) cells and of three to six brisk‐transient (Y) cells were found to overlap. Sluggish concentric and non‐concentric cells taken together have a coverage factor of about 60.
Micro‐electrode measurement of skin pH in humans during ischaemia, hypoxia and local hypothermia.
Authors: Harrison D K , Walker W F
Published: December 2014

1. The extracellular pH value in the dermis of human skin (skin pH) was measured in vivo using glass micro‐electrodes. They were found to be both reliable and accurate. 2. The mean value of skin pH measured in the legs of forty different volunteers was found to be pH 7.54 +/‐ 0.09 (S.D.). No difference in skin pH was observed between males and females, or in different regions of the limb. 3. Local reductions in skin surface temperature in ten subjects caused an increase of pH 0.023 +/‐ 0.007 per degree C fall. 4. A 20 min period of tourniquet ischaemia in twenty volunteers induced a fall in skin pH of 0.13 +/‐ 0.05 units. 5. Hyperventilation during a 10 min period of breathing 10% O2 in N2 caused an increase of pH 0.04 +/‐ 0.02 in the skin of healthy subjects. 6. Skin pH fell to a value 0.02 +/‐ 0.02 units below normal 10 min after the hypoxic period, suggesting the presence of excess lactate. 7. Skin pH results compared well with blood gases and pH values of arterialized samples taken during hypoxia. 8. It was concluded that the system was suitable for clinical trials.
Neural connexions between the medial forebrain bundle, the preoptic area and the basal hypothalamus in the rat: an electrophysiological study
Authors: Perkins M. N. , Whitehead Saffron A.
Published: December 2014

1. Electrophysiological experiments have been performed on intact cycling female rats to investigate the neural connexions that exist between the medial forebrain bundle, the anterior hypothalamic region, which included the preoptic area, and the basal hypothalamus. Recordings have been made from a total of 351 neurones in the anterior hypothalamus of which 216 were responsive to stimulation of either or both the medial forebrain bundle and basal hypothalamus (arcuate and ventromedial nuclei).

2. Forty‐six of these cells were responsive to a stimulus applied both to the medial forebrain bundle and the basal hypothalamus with a variety of response combinations. The majority of neurones were orthodromically activated by stimulation in both sites. Inhibition by stimulation of the medial forebrain bundle coupled with orthodromic excitation from the basal hypothalamus, or the reverse situation, was also encountered frequently.

3. A few cells were antidromically invaded by the stimulation of the medial forebrain bundle and these received orthodromic or inhibitory inputs from the basal hypothalamus, although one unit outside the anterior hypothalamus was antidromically activated by both stimuli.

4. Ninety per cent of all the doubly responsive units that could be antidromically activated by stimulation of the basal hypothalamus received an orthodromic input from the medial forebrain bundle, and no cells in the anterior hypothalamus that projected to the basal hypothalamus were found to receive an inhibitory input from the medial forebrain bundle.

5. These results provide electrophysiological evidence for inhibitory and excitatory inputs from the medial forebrain bundle to the preoptic and anterior hypothalamic cells that either project to, or receive connexions from, the basal hypothalamus. Neurones in the preoptic area which project to the basal hypothalamus are implicated in the control of anterior pituitary function, particularly gonadotrophin secretion. These experiments, coupled with functional studies, suggest that there is an excitatory input from the medial forebrain bundle to these preoptic and anterior hypothalamic cells which may modulate adenohypophyseal secretions.
Relationship between calcium release and potassium release in rat parotid gland.
Authors: Haddas R A , Landis C A , Putney J W
Published: December 2014

1. A study was made of the role of Ca release in mediating the sustained phase of K release (86 Rb release) in the rat parotid gland due to receptor activation. 2. Sr could substitute for Ca in supporting the sustained phase of the 86Rb release due to carbachol. Sr was less effective than Ca, while Ba was ineffective. 3. Sr could also restore responsiveness of the transient phase to agonists in media lacking Ca. Again, Sr was less effective than Ca, and Ba was without effect. 4. Carbachol stimulated release of 45Ca from parotid gland slices. The amount of Ca released (about 0.2 micromole/g) was much greater than the estimated Ca influx for the same period. 5. Release of 45Ca by carbachol prevented release due to a subsequent exposure to substance P. 6. Release of 45Ca due to substance P was significantly increased if muscarinic receptors were activated during tissue labelling. 7. These results support an earlier hypothesis whereby different agonists (such as carbachol and substance P) stimulate the release of Ca from a common pool and the release of this Ca mediates the transient phase of the K release response.
Propagation of electrical spiking activity along the small intestine: intrinsic versus extrinsic neural influences.
Authors: Bueno L , Praddaude F , Ruckebusch Y
Published: December 2014

1. The electrical activity of the small intestine of conscious dog, recorded by means of chronically implanted electrodes, was related to the transit time estimated by phenol red infusion and its propagation observed after a single or double transection and following either isolation or removal of a 50 cm jejunal loop. 2. In the fasted dog, the activity was characterized by the propagation of myoelectric complexes at a velocity of 4 cm/min during which the mean transit time averaged 13 min/m. About 2/3 of these complexes were seen to pass beyond a single section and anastomosis of the jejunum with a delay of 15 min. This number was reduced to 1/3 and the delay doubled when a second section was performed 50 cm distally. 3. In dog with an isolated jejunal loop, most of the myo‐electric complexes were seen to pass from the proximal intestine to the loop and then to the intestine beyond the sit of anastomosis within 37 min. Some complexes however passed directly through the anastomosis within 30‐32 min, affecting or not the loop. Others started on the loop and/or on the intestine beyond the anastomosis. Finally, the total number of complexes recorded on the distal jejunum was greater than on the duodenum, an effect which disappeared after removal of the isolated loop. 4. The propagation of the complexes occurred at a lower velocity after denervation of a jejunal segment in situ but was arrested in the case of an isolated‐denervated jejunal loop. 5. It is concluded that continuity of structures in the bowel is essential for the propagation of a myo‐electric complex which is stopped and replaced by another complex at the level of an anastomosis, the number os complexes reorganized beyond an anastomosis and their velocity of propagation depending upon both intrinsic and extrinsic neural influences.
Tremor in the tension developed isometrically by soleus during the tonic vibration reflex in the decerebrate cat.
Authors: Cussons P D , Matthews P B , Muir R B
Published: December 2014

1. Irregularities in the development of tension during the tonic vibration reflex of the soleus muscle of the decerebrate cat have been analysed into their frequency components. The reflex was recorded isometrically and elicited by longitudinal vibration, normally at 150 Hz. The amplitude of vibration was set so as to elicit a maximal reflex response, suggesting 1:1 driving of the majority of the Ia afferents at the frequency of vibration. 2. The resulting power spectrum regularly showed a well marked tremor peak separated by a trough from any slow irregularities. The predominant frequency of this tremor varied from 4 to 11 Hz in different preparations, with a mean of 7.4 Hz; on average, frequencies within 1.7 Hz on either side contained over half the power of the predominant frequency. Altering the frequency of vibration did not alter the distribution of tremor frequencies. 3. The root mean square value of the tension irregularities, over the range 4‐14 Hz, varied from 12 to 110 mN in different preparations (median value, 23 mN); this was superimposed on mean active reflex tensions varying from 2 to 10 N. 4. The ‘tremor’ due to a single motor unit was estimated from spectral analysis of tetanic contractions of the whole muscle and decreased with increasing frequency of activation. Comparison of the single unit values with the tremor seen during vibration in the same preparations showed that equivalent amounts of tremor to the latter could typically have been produced by the continued synchronous contraction of about five ‘average’ motor units firing at the predominant tremor frequency. 5. When a tonic stretch reflex was present its tremor frequencies did not differ consistently from those of the tonic vibration reflex. On average, the tremor was smaller for the stretch reflex than for the tonic vibration reflex; the difference was usually slight and might have been related to the stretch refex tension being smaller. 6. Evidence was obtained that the tremor was not due to any insecurity of 1:1 driving of the Ia afferents by the vibration. First, the tremor did not increase when the amplitude of vibration was decreased sufficiently to ensure that the degree of 1:1 driving must have been reduced. Secondly, the introduction of a comparable ‘artificial tremor’ by sinusoidally oscillating the muscle at low frequency did not produce the e.m.g. response that would have been expected if the applied ‘tremor’ had been modulating the firing of the Ia or any other group of afferents. 7. It is concluded that the observed tremor cannot be attributed to ‘oscillation in the stretch reflex arc', though without prejudice to the role of this mechanism under other conditions and especially when the recording is not isometric. However, the genesis of the tremor has not been established and much of it might result simply from the chance synchronization of motor units that are firing below their tetanic fusion frequency.
Numerical solution of coupled transport equations applied to corneal hydration dynamics.
Authors: Klyce S D , Russell S R
Published: December 2014

1. A quantitative basis for the currently accepted theory on the regulation of corneal hydration was derived using the technique of finite element analysis to integrate a set of coupled flow equations. The model was based on non‐equilibrium thermodynamics and incorporated the transport and permeability properties of the corneal epithelium and endothelium as well as the gel properties of the central connective tissue layer. 2. Considerable errors were introduced in the prediction of corneal hydration dynamics (unsteady‐state behaviour) unless allowance was made for the development of trans‐stromal gradients in pressure and solute concentration. 3. Thickness of in vitro rabbit corneal epithelium and stroma were measured with an automatic specular microscope during responses to changes in the osmolarity of the tear‐side bathing medium. The time course of these experiments was fitted with the mathematical model to obtain a set of membrane phenomenological coefficients and transport rates. 4. The model with the redetermined membrane parameters was tested by predicting the influence of other variations in boundary conditions with excellent match to several well‐documented experimental observations, including an explanation for the slight stromal swelling observed in hibernating mammals. 5. The regulation of corneal stromal hydration can be explained accurately by balance between the dissipative flows across the serial array of corneal layers and the active HCO3 transport by the endothelium, supporting the earlier ‘pump‐leak’ hypothesis. 6. It was found that stromal retardation of fluid flow, as well as gradients in solute concentration, significantly influences the dynamics of corneal stroma hydration. Tissue gel properties may be a more important factor in coupled transport across cell layers than generally appreciated.
Two‐carrier influx of neutral amino acids into rabbit ileal mucosa.
Authors: Paterson J Y , Sepúlveda F V , Smith M W
Published: December 2014

1. The influx of serine, alanine and methionine across the brush border membrane of the rabbit ileal mucosa has been measured during short periods of incubation. 2. A kinetic analysis of the uptake data, assuming one mediated entry mechanism or one mediated entry mechanism plus a diffusion component to be present, does not provide an adequate explanation for the results obtained. Methionine inhibition of serine uptake provided direct evidence that the diffusive entry of serine into the rabbit ileum was small or non‐existent. 3. Data taken from amino acid inhibition and substrate‐uptake experiments, fitted simultaneously to a double hyperbolic model of amino acid uptake, give good agreement between predicted and experimental results. There is also good quantitative agreement between computer‐derived kinetic constants in the present work and similar constants obtained previously using a different method of analysis. 4. Present work supports the general hypothesis that neutral amino acids use two mediated pathways to enter the rabbit ileal mucosa. The possible physiological significance of these results and their probable effect on currently held concepts of how amino acids cross the brush border membrane of the rabbit intestinal mucosa is discussed.
Effects of atropine on secretion and motility in isolated gastric mucosa and attached muscularis externa from ferret and cat
Authors: Roth S. H. , Schofield B. , Yates J. C.
Published: December 2014

1. A combined in vitro preparation of gastric mucosa and adjacent muscle from young ferrets and kittens has been used to study the effects of atropine on acid secretion and motility produced by acetylcholine (ACh) and pentagastrin.

2. The minimal dose of atropine required to abolish a maximum secretory response to ACh also prevented the associated motility response. This dose of atropine also blocked the motility response to pentagastrin, but was without influence on the secretory effect of this agent. A 103 times larger dose of atropine reduced the secretory effect of pentagastrin by half, probably not by anti‐muscarinic effect. The results exclude the possibility that the acid secretory response to pentagastrin necessarily involves a cholinergic receptor.

3. The results support the view that the response of the fundic smooth muscle to pentagastrin depends on the excitation of cholinergic nerves.

4. No evidence has been found of any cholinergic component in the acid secretory response to pentagastrin. In assessing the significance of this result, however, it must be remembered that the Auerbach plexus has been removed over the major part of the mucosa, and the Meissner plexus deprived of input and probably damaged.

5. The results are compatible with the hypothesis that the depressant effect of atropine on acid secretion produced by gastrin and its derivatives is due to the elimination of a cholinergic potentiating influence arising in the intramural plexuses. The residual Meissner plexus elements in this in vitro preparation appear inadequate to sustain this effect.
Influence of potassium, sodium, perfusion pressure, and isoprenaline on renin release induced by acute calcium deprivation
Authors: Fray John C. S. , Park C. S.
Published: December 2014

1. These studies were conducted in isolated perfused rat kidneys to determine the influence of perfusion pressure, isoprenaline, K, and Na on renin release stimulated by acute Ca deprivation.

2. Removing Ca from the perfusion medium for 10 min stimulated renin release and reintroducing Ca returned it toward control values.

3. Lowering concentration of Ca in the perfusion medium from 5 to 0 m
M increased the effectiveness of low perfusion pressure (50 mmHg) and isoprenaline (2·43 μ
M) in stimulating renin release.

4. At higher perfusion pressure (150 mmHg), renin release was inhibited in perfusion medium containing 2·5 m
M‐Ca but not in medium containing no Ca. In fact, high perfusion pressure stimulated renin release when the perfusion medium was without Ca.

5. Raising concentration of K in the perfusion medium partially inhibited the renin release induced by Ca deprivation. Adding 5 m
M‐EGTA to Ca‐deprived medium stimulated a greater rate of renin release than that of Ca‐deprived medium alone. This greater renin release was also partially inhibited by raising K concentration in the perfusion medium.

6. Lowering concentration of Na in the perfusion medium from 145 to 25 m
M partially inhibited the renin release induced by Ca deprivation in the presence of low perfusion pressure or isoprenaline.

7. These findings support the hypothesis that a decreased concentration of Ca in the cytoplasm of the juxtaglomerular cell stimulates renin release and increased Ca inhibits renin release. The sequence of events which leads to changes in cytoplasmic Ca might depend on the concentration of Ca in the perfusion medium, the renal perfusion pressure, the membrane potential of the juxtaglomerular cells, and Ca—Na exchange mechanisms.
Plasma active and inactive renin in the rabbit: effect of dietary sodium depletion and repletion.
Authors: Grace S A , Munday K A , Noble A R , Richards H K
Published: December 2014

1. Active and acid‐activatable (inactive) renins were measured in rabbit plasma under control conditions and during sodium depletion with subsequent repletion. 2. Active renin increased by 97% during sodium depletion and returned to control levels on repletion. Both changes were complete within 1 day of changing the diet. 3. During dietary sodium depletion inactive renin levels initially fell to zero and then increased until, after 13 days, inactive renin was again 10% of total renin levels, a proportion comparable to the control values. 4. Sodium repletion caused plasma inactive renin to return to control levels over about 13 days, a quite different time course to active renin. Therefore, in the first phase of repletion the proportion of total renin in the inactive form rose to 19%. 5. These changes are discussed in relation to concurrent changes in sodium, potassium and water metabolism.
Inhibition of external pancreatic secretion by intracolonic and intraileal infusions in the cat.
Authors: Harper A A , Hood A J , Mushens J , Smy J R
Published: December 2014

1. Infusions of oleic acid into the colon or the distal part of the ileum in anaesthetized cats inhibits secretion of water and amylase by the pancreas, stimulated by secretin and pancreozymin. Intraileal infusions of other non‐water‐soluble substances or hypertonic solutions can also inhibit the pancreas. 2. As inhibition can be produced after extrinsic denervation of the pancreas and gut, it must in part be humorally mediated. 3. Pentagastrin‐stimulated gastric secretion of acid and pepsin is also inhibited by the intraileal infusions, but the inhibition of acid secretion is less than that of pancreatic secretion. 4. It is suggested that the physiological counterpart of the inhibitory effects induced by the infusion of non‐physiological solutions into the colon or ileum is an inhibition of pancreatic secretion brought about by the cessation of intestinal absorption, which marks the completion of the post‐prandial digestive process.
Electrophysiology and pharmacology of striated muscle fibres cultured from dissociated neonatal rat pineal glands
Authors: Freschi J. E. , Parfitt A. G. , Shain W. G.
Published: December 2014

1. Striated muscle fibres were found in each of twenty consecutive pineal glands cultured from individual neonatal rats.

2. In subsequent experiments performed with dissociated cultures of pineal organs pooled from several litters, myotubes were first visible after about 1 week in culture.

3. During the next several weeks the myotubes increased in size, developed crossstriations, and began to twitch spontaneously.

4. The resting membrane potential increased with age in culture. All myotubes studied showed delayed rectification. Action potentials either occurred spontaneously or could be evoked if the membrane were sufficiently polarized. No spontaneous end plate potentials were seen.

5. Acetylcholine (ACh) produced a brief, monophasic depolarizing response. Noradrenaline, serotonin, melatonin, dopamine, and γ‐aminobutyric acid (GABA) had no effect on the resting membrane potential when applied iontophoretically.

6. The ACh response was reversibly blocked by 10−6
M‐tubocurarine and irreversibly blocked by 10−6
M‐α‐bungarotoxin. Atropine (10−4
M) reduced the amplitude and shortened the time course of the ACh response, and 10−3
M‐atropine produced complete but reversible inhibition.

7. We conclude that pineal muscle fibres are electrophysiologically and pharmacologically similar to skeletal muscle fibres in vitro. Although the pineal gland has undetectable levels of ACh, pineal muscle develops ACh receptors but not noradrenaline, serotonin, melatonin, dopamine, or GABA receptors mediating electrophysiological responses, although these latter substances (except dopamine) are found in the pineal.
The nature of the negative endocochlear potentials produced by anoxia and ethacrynic acid in the rat and guinea‐pig.
Authors: Bosher S K
Published: December 2014

1. The alterations in the Na+ and K+ concentrations of the cochlear endolymph and in the endocochlear potential were followed simultaneously by means of ion‐sensitive and conventional micro‐electrodes during simple anoxia, during anoxia after i.v. ethacrynic acid and after i.v. ethacrynic acid alone. The endolymphatic pH changes were measured separately and the effect of perilymphatic ethacrynic acid upon the endocochlear potential was investigated. 2. The over‐all Na+:K+ permeability ratio for the endolymph system was determined in individual animals for the first time using an indirect method. The normal mean values of 0.27 (rat) and 0.38 (guinea‐pig) were increased after ethacrynic acid. Permeability changes occurred during anoxia but were delayed in onset. 3. The negative endocochlear potentials in each situation behaved quantitatively like modified K+ diffusion potentials largely dependent upon the K+ and Na+ gradients between endolymph and perilymph.
Factors affecting the movement of amino acids and small peptides across the vascularly perfused Anuran small intestine.
Authors: Cheeseman C I
Published: December 2014

1. In the vascularly perfused frog small intestine, the characteristics of the washout into the vascular bed of L‐leucine and glycine have been investigated following loading either as free amino acids or as the dipeptide glycyl‐L‐leucine. In both cases, the washout of the two amino acids was biexponential and could be ascribed a fast rate constant K1 and a slow rate constant K2. The K1 for glycine was always smaller than that for L‐leucine. 2. The K1 and K2 for L‐leucine had a Q10 of 1.71 and 2.66 respectively, while steady‐state transfer of the amino acid exhibited a Q10 of 2.45. 3. Vascular perfusion rate affected the K1 but not the K2 for L‐leucine. 4. Na+ replacement in the lumen did not affect K1 and K2 for either amino acid from the mixture or the peptide, but did reduce the pool size of both when taken up as free amino acids. Peptide uptake, as measured by pool size, was not affected by luminal Na+ replacement. 5. If Na+ in the lumen was replaced with Li+, all substitutions of Na in the vascular bed inhibited the exit of L‐leucine. 6. These results are discussed in relation to a model proposing that sodium pumping across the basolateral membranes of the epithelial cells to keep the intercellular spaces patent is an important factor in the movement of amino acids from the enterocytes to the blood stream.
Initial‐image and afterimage discrimination in the human rod and cone systems.
Authors: Geisler W S
Published: December 2014

1. The rod‐isolation technique of Aguilar & Stiles (1954) was used to obtain scotopic increment‐threshold functions in the dark‐adapted eye. Increment‐threshold functions were obtained for background durations of 50 to 500 msec, but the onset of the background and increment fields was always simultaneous. In all conditions the duration of the increment field was 50 msec. 2. The pattern of results obtained is the same as that reported earlier for the cone system (Geisler, 1978). For background durations greater than that of the increment field, the increment‐threshold functions have two distinct branches. It was shown, by measuring action spectra, that both branches reflect the sensitivity of the rod system. 3. When the increment thresholds are plotted as a function of background retinal illuminance, all the lower branches superimpose. This implies that those thresholds are dependent only on the number of background quanta absorbed during presentation of the increment field. On the other hand, when the increment thresholds are plotted as a function of background energy, all the upper branches superimpose, implying that those thresholds are determined by the total number of background quanta absorbed. 4. For the thresholds falling on the lower branches observes reported that the increment field was detected in the initital image of the background and increment fields when they were flashed. For the upper branches, the increment field was detected in a short‐term afterimage that appeared after the background was extinguished. The higher the background intensity the longer was the latency until the increment appeared in the afterimage. 5. All of the above findings appear to be consistent with the known properties of the electrical responses of vertebrate photoreceptors. A model based on Penn & Hagins' (1972) model for the photocurrent in rat rods predicts, fairly accurately, the rod and cone increment‐threshold results. The parameters estimated by fitting the model support the hypothesis that the short‐term rod and cone afterimages are due to the relatively slow decay of internal transmitter, but they suggest that post‐receptor mechanisms are responsible for the threshold saturation observed with flashed backgrounds.
Renin, antidiuretic hormone and the kidney in water restriction and rehydration.
Authors: Blair‐West J R , Brook A H , Gibson A , Morris M , Pullan P T
Published: December 2014

1. The effect of restricted water intake followed by voluntary rehydration with water or 10 mM‐KCl was studied in four conscious sheep with respect to plasma concentrations of renin, antidiuretic hormone (ADH), protein and electrolytes, and urine flow rate, osmolality and osmolal excretion. 2. Water restriction increased the plasma renin concentration and the plasma ADH concentration. 3. Rehydration with water caused a further rise in plasma renin, but plasma ADH returned to basal levels in less than 2 hr. 4. Rehydration with 10 mM‐KCl in order to stabilize plasma K concentration greatly attenuated the post‐drinking rise in plasma renin concentration, while plasma ADH levels fell as before. 5. Urine flow rates after rehydration with water and 10 mM‐KCl remained low for at least 6 hr in most experiments despite low plasma ADH levels. The effect on urine osmolality ranged from no change to a large drop. 6. The post‐drinking antidiuresis was associated with a reduction in solute excretion rate. However, free water clearance usually remained negative. 7. These experiments do not support the existence of a direct nexus between plasma ADH levels and plasma renin concentration.
Studies on amino acid inhibition of monosaccharide exit from anuran small intestinal epithelium.
Authors: Boyd C A
Published: December 2014

1. The effect of the addition of amino acids to the intestinal lumen upon the movement of the monosaccharide alpha‐methyl‐D‐glucopyranoside (alpha MG) from the preloaded epithelium into the blood and into the lumen of the vascularly perfused frog small intestine has been studied. 2. The neutral hydrophobic amino acids tryptophan, leucine, phenylalanine, tyrosine, isoleucine, valine, norleucine and cycloleucine all rapidly inhibit the exit of alpha MG out of the epithelium into the vascular bed. They stimulate backflux of the sugar from the epithelium into the lumen to a very much smaller extent. 3. L‐Leucine is a more effective inhibitor of alpha MG exit into the blood than is D‐leucine. Near‐maximal inhibition of alpha MG exit is seen with 10 mM‐L‐leucine in the intestinal lumen. 4. The addition of leucine (10 mM) to the lumen of the intestine preloaded with alpha MG approximately halves the rate constant for alpha MG washout into the blood from 12.6 +/‐ 1.7 (4) x 10(‐3) to 5.5 +/‐ 1.4 (4) x 10(‐3) min‐1, without appreciably altering the pool of monosaccharide in the tissue. The inhibitory effect of L‐leucine upon alpha MG exit into the blood is not abolished by the presence of phlorizin (5 x 10(‐5) M) in the intestinal lumen. 5. The complex pattern of inhibition of alpha MG transfer from the lumen to the blood observed upon the addition of L‐leucine to the lumen is consistent with the finding that the amino acid inhibits the exit of the monosaccharide out of the epithelium into the blood in addition to any inhibitory effect upon sugar entry across the brush border. 6. It is suggested that alpha MG may be a substrate for a proposed transport system for neutral hydrophobic amino acids which, it is suggested, is present in the basolateral membrane of the epithelial cell.
Renal calcium and magnesium excretion during vasopressin administration into sheep with acid or alkaline urine.
Authors: Beal A M
Published: December 2014

1. The proposition that changes in renal calcium excretion during vasopressin administration are positively correlated with concurrent changes in urine hydrogen ion concentration was tested by administration of vasopressin into twelve conscious diuresing sheep receiving either alkalinizing or acidifying infusions. 2. Vasopressin‐induced antidiuresis in sheep with alkaline urine was associated with significant increases in urinary pH and decreases in the rate of calcium excretion whereas antidiuresis in sheep with acid urine was associated with significant decreases in urinary pH and no consistent effect on calcium excretion. 3. Magnesium excretion increased during vasopressin administration in most experiments regardless of urinary pH changes. 4. Vasopressin administration did not significantly alter the rate of excretion of sodium, potassium, chloride and phosphate or the rates of sodium, potassium, chloride, inulin, para‐aminohippurate and osmolal clearance in sheep with either acid or alkaline urine. Potassium excretion and clearance in sheep with alkaline ruine was higher than that of sheep with acid urine during vasopressin infusion. 5. The results support the hypothesis that changes in renal tubular hydrogen ion concentration or bicarbonate concentration caused by water reabsorption from the collecting duct and possibly the late distal tubule could be part of the explanation for changes in renal calcium excretion which occur during vasopressin‐induced antidiuresis.